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Volume 93-B, Issue SUPP_IV November 2011

JY Lazennec A Ducat H Sarialli Y Catonne

Introduction: Wear performances and fracture toughness of the alumina-matrix composite (AMC) Biolox-delta® are pointed out in the literature. Clinical and radiological studies are needed to assess the potential benefits of AMC/AMC bearing surfaces. The aim of this study is the prospective evaluation of complications and risk factors in patients implanted with AMC liners and 32–36 mm AMC femoral heads.

Methods: 323 consecutive patients were included prospectively since 2006.

243 were implanted for primary surgery with 32 or 36 mm ball heads for a 10–12, 6° tapers.

In 80 cases, we used 32 and 36 mm Delta® sleeved heads (M,L,XL) for the adaptation on 12–14,5°43 tapers or 10–12, 6° tapers (acetabular revisions in absence of stem exchange, or to increase the lenght of the femoral neck and the offset) All the clinical and radiological files were evaluated at a minimum 2 years follow-up with a special attention for the fracture risk and squeaking. Radiological data were analysed using Dicomesure® software.

Results: We did not face any significant problem in this series. No fracture occurred. No abnormal wear or implants migration could be detected. We did not observe squeaking phenomenons. 2 THP were revised for septic complications ; the retrivials were analysed for transformation studies(Xray diffraction method XRD). The phase transformation tetragonal to monoclinic was mild, in accordance with previous experimental data.

Conclusion: The limitation of this study is its short follow-up; nevertheless the clinical results are in accordance with the previously published experimental data.

M.A. Swanson C. Schwan F. Gottschalk R. Bucholz M.H. Huo

The purpose of this study was to review the clinical and radiographic outcome in THRs done following acetabular fractures (fx). All patients undergoing conversion THR after previous acetabular fx between 1990 and 2006 at a single institution were identified.

Clinical evaluation was done using the Harris hip scale. Radiographic evaluation was done using the system proposed by the Hip society. THRs as part of initial treatment for acute acetabular fx were excluded.

There were 90 THRs (90 patients) performed in patients previously treated for an acetabular fracture. At the time of their acetabular facture, 67 had been treated with ORIF, 12 were treated with closed or limited open reduction and percutaneous fixation, and 11 were treated without surgery. The mean age at injury was 43.7 years, (range, 14–79). 68 patients sustained their fx from a high-energy mechanism (MVC, MPC, or MCC).

Three patterns accounted for 52% of the fx: transverse posterior wall (20), both column (18), and T-Type (9). Associated pelvic fractures were present in 14 patients. Associated ipsilateral proximal femur fractures were present: femoral head (four), femoral neck (five), and femoral shaft (three). Among those treated with ORIF, marginal impaction was noted in 31 and osteo-chondral head damage in 32 hips.

The mean interval between injury and THR was 42 months (range, two months to 32 years). Cement-less fixation was used in 81 of the 90 cups. Similarly, cementless stems were used in 80 stems. Bone graft was necessary in 26 patients (17 autograft, nine allograft). Two cases each required pelvic augments and reinforcement cage, respectively.

Additional findings at THR included: femoral head erosion (53 hips), femoral head osteonecrosis (37 hips), osteonecrosis of the acetabulum (22 hips), and fx non-union (six hips). The average cup abduction angle was 440 (range, 28 to 60), the average cup height was 24 mm (range, 10 to 42), and the average medialization distance was 23 mm (range, 5 to 48). The mean EBL was 810 ml and mean operative time was 195 minutes. The mean F/U was 36 months (range, 6 months to 17 years). The median Harris hip score was 89 at the most recent F/U. Fifteen revisions (16%) have been done: aseptic loosening (seven hips), recurrent dislocation (six hips) and infection (two hips).

Five of the six revisions for recurrent dislocation were performed in patients who had a posterior approach for both their acetabular fracture treatment and their THR. No revision was done in those who had been initially with percutaneous fixation. There was no infection in those who had been initially with percutaneous fixation either from the fx treatment or the THR. In contrast, 14 ORIF patients were complicated by infection. One of these developed infection following THR.

Our data support the clinical efficacy and mid-term durability of THR in this patient group. Aseptic loosening and recurrent dislocation remain the primary reasons for revision surgery.

D.J. Jacofsky J.D. McCamley M. Bhowmik-Stoker M.C. Jacofsky M.W. Shrader

Previous studies (Chen et al., 2003; Kaufmann et al., 2001) have shown that persons with osteoarthritis (OA) walk more slowly with lower cadence, have lower peak ground reaction forces and load their injured limb at a lower rate than healthy age matched subjects. However, another study (Mündermann et al., 2005) found that patients with severe bilateral OA loaded their knee joint at a higher rate. They also found these patients had higher knee adduction moments and lower hip adduction moments. It has been reported (McGibbon and Krebs 2002) that when subjects with knee OA are required to walk at the same speed as healthy subjects they generate more power at the hip joint to help overcome reduced knee power and aid in the advancement of the leg prior to the swing phase of the gait cycle. Myles et al. (2002) reported that patients with knee OA have reduced knee range of motion during walking. This paper presents detailed kinematic and kinetic data collected on a large group of patients with advanced knee osteoarthritis to show the differences in the gait of these patients just prior to surgery compared with age-matched control group.

This study was approved by the Sun Health Institutional Review Board. Subjects volunteered to participate in the study and signed informed consent prior to testing. Subjects were excluded if the had significant diseases of the other joints of the lower extremity or a diagnosed disorder with gait disturbance. Motion data was captured using a ten-camera motion capture system (Motion Analysis Corp., Santa Rosa, CA). Three-dimensional force data was recorded using four floor embedded force platforms (AMTI Inc., Watertown, MA). Patients were asked to walk at a self selected speed along a 6.5 meter walkway. A minimum of five good foot strikes for each limb were recorded. Data were collected using EVaRT 5 software (Motion Analysis Corp., Santa Rosa, CA) and analyzed using OrthoTrak 6.2.8 (Motion Analysis Corp., Santa Rosa, CA) and MatLab software (The Mathworks Inc., Natick, MA). Statistical analysis was performed using SPSS 14.0 software (SPSS Inc., Chicago, Il) (α = 0.05).

Eighty-six patients (71 ± 7 years) along with sixty-four control subjects (65± 10 years) volunteered to participate in the study. All measured temporal and spatial parameters showed significant differences between the OA patients and the control group. The OA patients were found to walk at a significantly lower velocity (p< .01) and cadence (p< .01) using a wider step width (p< .01) than the control subjects. Patients had their injured knee significantly more flexed at foot strike (p< .01) but flexed the knee significantly less during swing (p< .01) when compared to the control group. Patients had significantly higher knee flexion angles as well as hip flexion and abduction angles during stance. Knee varus angles were significantly higher for the OA patients during stance (p< .01) but not during swing when compared to the control group.

Significant increases in pelvic tilt and pelvic obliquity were measured during the stance phase. Hip abduction angles during stance were significantly lower for the OA group. Patients generated significantly lower vertical ground reaction forces during stance (p< .01) while sagittal plane kinetic analysis showed significantly lower external knee flexion moments (p< .01) and knee power generation (p< .01) during this phase of the gait cycle. Analysis of frontal plane angles showed OA patients had a significantly higher maximum knee varus angle during stance as well as generating a higher external knee varus moment (p=.03) during this phase of the gait cycle.

Changes in gait measured in this study support and enhance findings from previous studies. OA patients appeared to walk with a more crouched posture with higher knee and hip flexion angles through mid stance. This along with lower velocity and cadence and a larger step width would indicate a desire for more stability while walking. Patients also flexed their knees more at foot strike in an attempt to absorb the forces generated during weight acceptance. While knee flexion angles measured for the OA group were similar to the control subjects during the initial period of stance, the OA patients did not extend their knees as much during mid stance indicating a desire to reduce the angular rotation of the knee while in single support. Changes measured in frontal plane angles of the hip and pelvis may be an attempt to compensate for the different angles generated by the knee during stance. The differences in hip and knee angles measured during stance for patients and controls allowed patients to have reduced peak external knee flexion moments during initial stance but a higher knee flexion moment at mid stance. The reduction in knee angular change during stance and the reduced cadence meant power absorption during early and late stance and generation during mid stance was much lower for the OA patients than the control group. All the changes noted appear to be designed to limit the movement of the knee joint while loaded and reduce the peak loads in an effort to reduce pain at the affected joint while at the same time increase stability during gait. These data show the differences that exist between the gait patterns of patients with advanced osteoarthritis and healthy age-matched persons and highlight the changes that are necessary following knee replacement surgery and rehabilitation to return the gait of these patients to normal.

W. L. Buford F. M. Ivey D. M. Loveland C. W. Flowers

Past work in our laboratory identified the generalized effects of TKA on muscle balance, showing a significant change in relative moment generating potential balance favoring flexion and external rotation relative to the normal (intact) knee (for both PCL sparing and posterior stabilized TKA). However, there are no reliable data descriptive of the effect of any single prosthesis. This study hypothesized that using a modern TKA (Smith Nephew Journey) and implantation by a single surgeon in five fresh cadaver specimens would result in change in muscle balance similar to the earlier results for posterior stabilized TKA.

Using the tendon excursion-angular motion method (MA = dr/dΘ, r is excursion, Θ is joint angle in radians), moment arms of all muscles at the knee were determined for each of three conditions (intact, ACL-deficient, and prosthesis). The moment arms were then multiplied by the known muscle tension fractions to generate each muscle’s relative moment potential for each specimen across the three conditions. The resultant summed total moment potential was then examined for differences in the flexion-extension (FE) and internal-external (IE) rotation components.

There was no significant difference in either FE or IE component for intact versus either the ACL deficient condition (FE, p=0.62, IE, p=0.49) or arthroplasty (FE, p=0.99, IE, p=0.82). TKA agreed more closely with the intact knee. Thus, we reject the hypothesis that a modern TKA (Journey) performs as projected by past generic results, and conclude that modern TKA effectively reconstructs the balance of the intact knee.

This improves prospects for rehabilitation following TKA.

T. Kabata T. Maeda T. Murao K. Tanaka H. Yoshida Y. Kajino T. Horii S. Yagishita K. Tomita

Objective: The treatment of osteonecrosis of the femoral head (ONFH) in young active patients remains a challenge. The purpose of this study was to determine and compare the clinical and radiographic results of the two different hip resurfacing systems, hemi-resurfacing and metal-on-metal total-resurfacing, in patients with ONFH.

Materials and Methods: We retrospectively reviewed 20 patients with 30 hips with ONFH who underwent hemi-resurfacing or total-resurfacing between November 2002 and February 2006. We mainly performed hemi-resurfacing for early stage ONFH, and total-resurfacing for advanced stage. Fifteen hips in 11 patients had a hemi-resurfacing component (Conserve, Wright Medical Co) with the mean age at operation of 50 years and the average follow-up of 5.5 years. Fifteen hips in 10 patients had a metal-on-metal total-resurfacing component (Birmingham hip resurfacing, Smith & Nephew Co.) with the mean age at operation of 40 years and the average follow-up of 5 years. Clinical and radiographic reviews were performed.

Results: The average postoperative JOA hip scores were 86 points in hemi-resurfacing, 96 points in total-resurfacing. The difference of pain score was a main factor to explain the difference of total JOA hip score in the two groups. Both implants were radiographically stable, but radiolucent lines around the metaphyseal stem were more frequent in total-resurfacing. In hemi-resurfacing patients, ten of 15 hips had groin pain or groin discomfort, three hips were revised to total hip arthroplasties (THA) because of femoral neck fracture, acetabular pro-trusio, and osteoarthritic change, respectively. On the other hand, in total-resurfacing patients, there were no revision and no groin pain.

Discussion: In the prosthetic treatment of young active patients with ONFH, it is theoretically desirable to choose an implant with conservative design in anticipation of the future revision surgery. Hemi-resurfacing hip arthroplasty is the most conservative implant for the treatment of ONFH. However, the results of hemi-resurfacing in this study have been very disappointing due to high revision rates and insufficient pain relief despite of the good implant stability. On the other hand, the pain relief and implant survivorship after total-resurfacing were superior to the results of hemi-resurfacing, although the usages of the total-resurfacing were for more advanced cases. These results suggested that total-resurfacing was a more valuable treatment option for active patients with ONFH than hemi-resurfacing

C. Manders A.M. New M. Taylor

During hip replacement surgery the hip centre may become offset from its natural position and it is important to investigate the effect of this on the musculoskeletal system. Johnston et al [1] found that medialisation of the hip centre reduced the hip joint moment, hip contact and abductor force using a musculoskeletal model with hip centre displacements in 10mm increments. More recently an in vivo study found that the range of displacement of the hip centre of rotation was from 4.4mm laterally to 19.1mm medially [2]. To investigate the hypothesis that medialisation of the hip centre reduces the hip contact force, a musculoskeletal model of a single gait cycle was analysed using three scenarios with the hip in the neutral position and with it displaced by 10mm medially and laterally.

The lower limb musculoskeletal model included 162 Hill type muscle units in each leg and uses a muscle recruitment criterion based on minimising the squared muscle activities, where the muscle activity is the muscle force divided by the muscle’s maximum potential force. The maximum potential force is affected by the length of the muscle unit and the muscle’s tendons each are calibrated to give the correct length in its neutral position. The same gait analysis data from one normal walking cycle was applied to each modelled scenario and the resultant hip joint moment, hip contact force and muscle forces were calculated. The abductor muscles forces were summed and the peak force at heel strike reported. The peak resultant hip moments and the peak hip contact forces at heel strike are also reported and compared between the different scenarios. The scenarios were each run twice, once with the muscle tendon lengths calibrated for the hip in the altered position and subsequently with the muscle tendon lengths maintained from the neutral hip position.

For the medialising of the femoral head, the hip contact force and the peak abductor force were reduced by 4% and 2% respectively compared the neutral position. However if the tendon lengths of the muscles were maintained from the neutral position, the medial displacement model had a 3% higher hip contact force and a 6% larger abductor force than calculated for the neutral position. Although the peak resultant hip joint moment increases with a lateral displacement by 3%, the peak abductor force and peak hip contact force have a reduced force of 3% compared to the neutral hip. Using the muscle tendon lengths calibrated for the hip in the original position produces a 3% increase in the hip contact and abductor force for the lateralised femoral head.

This study has shown that the hip contact force and abductor force depend on the calibration of the muscle’s tendon lengths. Using the model with muscles calibrated for the altered hip centre produced the hypothesed reduction in hip contact force. However, maintaining the tendon lengths from the neutral position had a significant effect the calculated forces. The hip contact and abductor forces increased in the models with the original tendon lengths and the effect was also found to be greater when the hip was displaced medially.

J. M. Johnson M.R. Mahfouz

Accurate segmentation of bone structures is an important step in surgical planning. Patient specific 3D bone models can be reconstructed using statistical atlases with submillimeter accuracy. By iteratively projecting noisy models onto the bone atlas, we can utilize the statistical variation present in the atlas to accurately segment patient specific distal femur and proximal tibia models from the CT data.

Our statistical atlas for the knee consists of 199 male distal femur models and 71 male proximal tibia models. We performed an initial registration between the average model from the atlas and the volume space before beginning the segmentation algorithm. Intensity profiles were linearly interpolated along the direction normal to the surface of the current model. The profiles were then smoothed via a low-pass filter. A point-tonearest peak gradient was calculated for each profile, and then weighted by a Gaussian window centered about the originating vertex. The flesh-to-bone edge locations are taken as the maximum of the weighted gradient. The detected locations were then projected onto the atlas using a subset of the available principal components (PC’s). The amount of variation is increased by projecting the edge locations onto a larger subset of PC’s. The process is repeated until 99.5% of the statistical variation is represented by the PC’s. Though our dataset is much larger, we initially performed bone segmentation on 5 male knee joints. The knee joint was considered to be the distal femur and proximal tibia. We used manually segmented models to determine ground truth. Initial results on the 5 knee joints (distal femur and proximal tibia) had a mean RMS error of 1.192 mm, with a minimum of 1.010 mm. Segmentation on the distal femur achieved a mean RMS error of 1.213 mm, and the results for the tibia had a mean RMS error of 1.264 mm.

Our results suggest that our atlas-based segmentation is capable of producing patient-specific 3D models with high accuracy, though patient-specific degeneration was often not well represented. To achieve more accurate patient-specific models, we must incorporate local deformations into the final model.

H.E. Cates R.E. Barnett S.M. Zingde M.A. Schmidt R.D. Komistek M.R. Anderle M.R. Mahfouz

Previous fluoroscopic analyses of Total Hip Arthroplasty (THA) determined that the femoral head slides within the acetabular cup, leading to separation of certain aspects of the articular geometries. Although separation has been well documented, it has not been correlated to clinical complications or a more indepth understanding of the cause and effect. Surgical technique is one of the important clinical factors when considering THA procedures, and it is hypothesized, that it could affect the magnitude and occurrence of femoral head separation (sliding) in THAs. Hence, the objective of this study was to determine and compare in-vivo THA kinematics for subjects implanted with a THA using two different surgical approaches.

Thirty seven subjects, each implanted with one of two types of THA were analysed under in vivo, weight-bearing conditions using video fluoroscopy while performing a sit-to-stand activity. Ten subjects were implanted by Surgeon 1 using a long incision postero-lateral approach (G1); while a further 10 subjects were implanted by the same surgeon using a short incision posterolateral approach (G2). The remaining 17 subjects were implanted using the anterolateral approach; 10 by Surgeon 2 (G3) and seven by Surgeon 3 (G4). All patients with excellent clinical results, without pain or functional deficits were invited to participate in the study (HHS > 90). 3D kinematics of the hip joint was determined, with the help of a previously published 2D-to-3D registration technique. From a completely seated position to the standing position, four frames of the fluoroscopy video were analysed.

Subjects in all groups experienced some degree of femoral head separation at all increments of the sit-to-stand activity that were analysed. The magnitude and frequency of separation greater than 1.0mm varied between each surgeon group, between incision types, between incision lengths and between the two types of THA that were analysed. The average maximum separation was 1.3, 1.1, 1.3 and 1.4mm for G1, G2, G3 and G4 respectively. Though there was no difference in the average maximum separation values for the 4 groups, the maimum separation varied significantly. While the maximum separation in G2 was 1.8mm, the maximum separation in G4 was 3.0mm. G1 and G3 had maximum separation values of 2.3mm and 2.4mm respectively.

This study suggests that there may be a correlation between incision lengths and surgical approach with femoral head separation in THAs. The maximum separation that was seen among all groups was a subject with a traditional long incision, while the short incision group had less incidence of separation. Results from this study may give researchers and implant developers a better understanding of kinematics around the hip joint and how they vary with respect to different surgical techniques. Further analysis is being conducted on the subjects before definitive conclusions can be made.

GA Higgins Z Morison M Olsen EH Schemitsch

Surgeons performing hip resurfacing ante-vert and translate the femoral component anterior to maximize head/neck offset and educe impingement. The anterior femoral neck is under tensile forces during gait similarly to the superior neck [6]. This study was esigned to determine the risk of femoral neck fracture after anterior or posterior notching of the femoral neck.

Method: Fortyseven 4th generation synthetic femora were implanted with Birmingham Hip Resurfacing pros-theses (Smith & Nephew Inc. emphis, USA). Implant preparation was performed using imageless computer navigation (VectorVision SR 1.0, BrainLAB, Grmany). The virtual prosthesis was initially planned for neutral version and translated anterior, or posterior, to create the notch. The femora were fixed in a single-leg stance and tested with axial compression using a mechanical testing machine. This method enabled comparison with previously published data. The synthetic femora were prepared in 8 experimental groups:2mm and 5mm anterior notches, 2mm and 5mm posterior notches, neutral alignment with no notching (control), 5mm superior notch, 5mm anterior notch tested with the femur in 25° flexion and 5mm posterior notch tested with the femur in 25° extension We tested the femora flexed at 25° flex-ion to simulate loading as seen during stair ascent. [3] The posterior 5mm notched femoral necks were tested in extension to simulate sporting activities like running. The results were compared to the control group in neutral alignment using a one-way ANOVA:

Results: Testing Group Mean load to failure Significance Neutral (Control) 4303.09 ± 911.04N Anterior 2mm 3926.62 ± 894.17N p=0.985 Anterior 5mm 3374.64 ± 345.65N p=0.379 Posterior 2mm 4208.09 ± 1079.81N p=1.0 Posterior 5mm 3988.07 ± 728.59N p=0.995 Superior 5mm 2423.07 ± 424.16N p=0.003 Anterior 5mm in 25° flexion 3048.11 ±509.24N p=0.087 Posterior 5mm in 25° extension 3104.61±592.67N p=0.117 Both the anterior 5mm notch tested in single-leg stance and anterior notch in flexion displayed lower compressive loads to failure (3374.64N and 3048.11N). The mean load to failure value for the posterior 5mm notches in extension was 3104.62N compared to 4303.09N for the control group. Our data suggests that anterior and posterior 2mm notches are not statistically significantly weaker in axial compression. The anterior 5mm notches tend towards significance in axial compression (p=0.38) and bordered significance in flexion (p=0.087). The 5mm posterior notches were not significantly weakened in axial compression (p=0.995), but tended towards significance in extension (p=0.117). The 5mm superior notch group was significantly weaker with axial compression supporting previous data published (p=0.003). We are currently assessing offset and other variables that may reduce data spread.

Conclusion: We conclude that anterior and posterior 2mm notching of the femoral neck has no clinical implications, however 5mm anterior notches may lead to fracture. The fracture is more likely to occur with stair ascent rather than normal walking. Posterior 5mm notches are not likely to fracture with normal gait, but may fracture with higher impact activities that promote weight bearing in extension. Hip resurfacing is commonly performed on active patients and ultimately 5mm notching in the anterior or posterior cortices has clinically important implications.

E. E. Abdel Fatah M. R. Mahfouz L N. Bowers

Fracture of the distal radius is one of the most common wrist fractures that orthopedic surgeons face. Quite often an injury is too severe to be repaired by supportive measures and pin or plate fixation is the subsequent alternative. In this study we present a novel method for automated 3D analysis of distal radius utilizing statistical atlases, this method can be used to design pin or plate fixation device that accurately fit the anatomy.

A set of 120 bones (60 males and 60 females) were scanned using high resolution CT. These CT scans were then segmented and the surface models of the radius were added to the statistical atlas. Global shape differences between males and females were then identified using the statistical atlas. A set of landmarks were then calculated including the tip of the lateral styloid process and centroid of the distal plateau. These landmarks were then used to calculate the width of the distal plateau, the height of the distal plateau, overall radius length and the curvature of the distal plateau. These measurements were then compared for both males and females. Three of the measurements came statistically significant with p< 0.01. Curvature of the distal plateau wasn’t found to be significant, with females having slightly higher radius of curvature than males.

This automated 3D analysis overcomes the major drawbacks of 2D x-ray measurements and manual localization methods. Thus, this analysis quantifies more accurately the anatomical differences between males and females. Statistically significant anatomical gender differences were found and quantified, which can be used for the design of trauma prosthesis that can fit normal anatomy.

A. Palermo G. Calafiore M. Rossoni R. Simonetta

The return to the use of big diameter femoral heads is now a well-established reality.

The certainty of a better result is not only for young patients with an high functional demand, but also for elderly people, who need a reduction of enticement time and an increase of intrinsic Materials optimization and “hard to hard” bearings allowed surgeons to reduce the problem of volumetric wear and to guarantee some undeniable advantages such as: -better articular stability, thanks to the off-set restore -better range of motion -reduction of dislocation risk Increasing the femoral head diameter means increasing the off-set therefore the lever arm of the gluteus medius which is a great articular stabilizer. With the old metal to polyethylene and ceramic to polyethylene bearings, the bigger contact surface between the head and the cotyle interior certainly increased the volumetric wear in the past. The introduction of bearings at “low friction coefficient” ceramic-to-ceramic and metal-to-metal solved this problem and the undeniable improvement of the polyethylene preparation made this material to be considered safe even with big diameter heads. All articular stability parameters, in primis for the off-set, can be improved by the use of those solutions which are all efficient and able to give the surgeon the right mean to solve every single case.

The eventuality to break ceramic heads is reported in literature and has fortunately reference to a low percentage, about 1.5% (“Biolox 28 mm ceramic-ceramic THR: 1.5% fractures 7 years f.u.” Toni, Alt.Bearings, NYC, 2002), but it maybe limits this kind of choice in cases of hip dysplasia, in which a bigger acetabulum uprightness increases the percentage of mistake in placing the cotyle. Nowadays, the diameter of the available heads is progressively increasing with the cotyle diameter (32, 36), so ceramic-ceramic is anyway an excellent solution for all other fatigued coxofemural articulations, above all if they are still eumorphic, and for female patients in which a worst bone quality reduces the choice of metal-metal.

The metal-metal bearing finds instead a great indication in all patients, above all male patients with a good bone quality with high functional demand. The only reasons to go back preferring the metal-metal bearing are the reduction of the average age of the prosthesized patient and the increasing performance need. New techniques of superficial finish of the chrome-cobalt allowed surgeons to optimize the clearance, the self-smoothing ability in case of “streaks” of third body.

Tests drawn in gate analysis demonstrated a reduced detachment between the two prosthesis components when the metal-metal operated patient makes the step, not only in favour of the bearing, but also of the choice of big diameters (“Metal on metal and distraction: an in vivo comparison.” Komistec et al; JBJS; October 2002). Moreover, other indications in literature show that there is no direct correlation between the cancer development and the metal-metal bearing prosthesis implant (Visuri, COOR 1996) (“The risk of cancer following total hip or knee arthroplasty” Tharani et al., JBJS May 2001), and even that there were no cobalt toxic serum levels able to justify cardio-pneumatie (Brodner, JBJS 1997). Independently by the materials choice, the bearing with big diameter heads undeniably reduces dislocation risk and accelerates the post-operative recovery even in old patients surgically treated for fracture.

The larger distance a big diameter head has to cover in order to come out of the acetabular cavity (Jump distance) certainly reduces the number of dislocation cases.

(“Large versus small femoral heads in metal on metal total hip arthroplasty” –Cucler J.M. et al., JoA, Vol 19, num 8, suppl. 3., 2004) (“Effect of femoral head diameter and operative approach on risk of dislocation after primary total hip arthroplasty” Berry DJ et al., JBJS Am. 2005 Nov; 87(11):2456–63).

All those reasons pushed us to believe in “hard to hard” bearings with big diameter, whose results could not be more satisfying. Nevertheless, there are some complications which can make us think, such as cases of pseudocancer for metal-metal bearing and the squeaking in the ceramic-ceramic bearing. The introduction of last generation polyethylene could bring the golden standard near the ceramicpolyethylene again.

Robert E. Booth

Orthographic radiography, a revelation at its inception, has been the orthopaedic standard for a century. It has facilitated osteology and empowered arthroplasty like no other parallel technology. While many new imaging modalities – nuclear scans, computerized axial tomography, magnetic resonance imaging, etc. – have advanced the art even further, plain XRays, quite frankly, remain the standard for identifying patient pathology and evaluating surgical intervention. The enlightened scrutiny of properly obtained and successfully reproduced radiographic images still yields far more information in the daily practice of orthopaedics than its more sophisticated and expensive derivatives. A detailed review of readily available diagnostic information is intended to rejuvenate/resuscitate our most valuable ally in the evolving struggle against arthritic disease.

C.S. Ranawat

The three distinct phases of design and development of total knee replacement (TKR) were:


1986–2000 and

2000 to today and beyond.

Hinge designs and early condylar designs highlight the first major period of TKR development from 1969 to 1985. These designs included but were not limited to the Waldius, Shiers, and GUEPAR hinges, Gunston’s Polycentric Knee in 1971, Freeman’s ICLH Knee in 1972, Coventry’s Geomedic Knee in 1972, St. George’s Sled Prosthesis in 1971, Marmor’s Modular Uni in 1971, Townley’s Condylar Design in 1972, Walker and Ranawat’s Duocondylar in 1971, Waugh’s UCI Knee in 1976, Eftekar’s Metal Backing in 1978, Murray and Shaw’s Metal Backed Variable Axis Knee in 1978, Insall and Burstein’s IB-1 Knee in 1978, the Kinematics in 1978, and finally Walker, Ranawat and Insall’s Total Condylar in 1978.

The Total Condylar Knee, developed by Walker, Ranawat, and Insall between 1974 and 1978, has been the benchmark for all designs through the 20th century. My personal experience of cemented TKR from 1974–2009 has shown a survivorship of 89%–98% at 15–20 years. Similar data has been presented in several 10+ year follow-up studies.

The next major phase of development gave birth to semi-constrained TKR, cruciate saving and substituting PS designs, improved instrumentation and improved cemented fixation. Other guiding principles involved improving alignment, managing soft-tissue balance for varus-valgus deformity, improving kinematics and producing superior polyethylene for reduced wear and oxidation. The advent of rotating platform mobile bearing knees with multiple sizes marked the most recent major advancement in TKR design.

With more total knee replacements being performed on younger, more active patients, improved design, better fixation (non-cemented), and more durable articulation are needed. The new standard for ROM will be 125 degrees. Non-cemented fixation, improved poly, such as E-poly, and the rotating platform design will play a major role in increasing the longevity of TKR to over 25 years.

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G.R. Scuderi

John N. Insall accomplished unparalleled success as an orthopedic surgeon, implant designer, and teacher. Over a span of 4 decades he was a pioneer in the field of knee surgery and was instrumental in evolving total knee arthroplasty to its current state of excellence. His legacy in total knee implant design began with the Duocondylar and Duopatellar prosthesis; was revolutionary with the implantation of the first Total Condylar Prosthesis -the first modern prosthesis; followed by posterior cruciate ligament substitution with the Insall – Burstein Posterior Stabilized Prosthesis; and ultimately with the Legacy Posterior Stabilized High Flexion Prosthesis – a fixed and mobile bearing high performance implant. Recognizing the importance of surgical technique with any implant design, Insall simultaneously described the surgical technique of ligament releases for restoring axial alignment and balancing the flexion and extension gaps. Over time his innovations have been embraced by the majority of surgeons and have become the foundation of what we do today. During more than 40 years of clinical practice, John N. Insall was an unselfish educator. He shared his clinical experiences with the medical community by publishing, along with his students and associates, an exhaustive array of articles and books on various afflictions of the knee. Recognized by his contemporaries as a leader in the field of total knee arthroplasty, he was elected president of the Knee Society in 1987. For the entire orthopedic community he continued to work laboriously, sharing his experiences with his fellows and colleagues until his death in 2000. The life of John N. Insall will be remembered in perpetuity for his unparalleled influence on knee surgery.

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D.J. Berry

Sir John Charnley unquestionably was the pioneer of modern joint arthroplasty. He was also an innovator in many other areas of orthopedics, including fracture care and arthrodesis, but this tribute will focus on his contributions to arthroplasty.

Charnley pioneered the use of methyl methacrylate cement and in so doing provided the first reliable means of fixing implants to bone. For the first time, this provided arthritis patients with reproducible long-term, reliable pain relief from advanced joint arthritis. Charnley also pioneered the use of a novel bearing surface, high molecular weight polyethylene. In so doing, he pioneered resurfacing of both sides of a joint with a low-friction, low-wear bearing. This provided the potential for excellent pain relief and also durable function of a hip arthroplasty.

Charnley understood the importance of reproducing joint mechanics and kinematics, and the arthroplasties he designed fully reproduced leg length and hip offset, and therefore the mechanics of the hip.

Finally, Charnley understood that technology is only a great value when it can be transferred effectively to many surgeons around the world. He created a carefully constructed educational structure to teaching the methodology in a way that would allow surgeons to practice this procedure successfully in other centers. Charnley understood the importance of minimizing complications for a procedure to be widely adopted and successful.

It is no exaggeration to state that Charnley’s contributions have helped tens of millions of patients worldwide who otherwise would have been permanently crippled by arthritis. Today’s further advances in joint arthroplasty are all dependent on the foundations of joint arthroplasty pioneered by Sir John Charnley.

P. Bergschmidt C. Lohmann R. Bader C. Lukas W. Ruether W. Mittelmeier

The objective of this prospective duo-center study was to evaluate the clinical and radiological outcome of the unconstrained Multigen Plus total knee system (Lima Lto, San Daniele, Italy) with the new BIOLOXÒ Delta ceramic femoral component.

40 patients underwent cemented total knee arthroplasty in two university hospitals. Clinical evaluations were undertaken preoperatively and at 3 as well as 12 months postoperatively using the HSS-Score, WOMAC-Score and SF-36-Score. The radiological investigations included ant-post. radiographs (whole leg in two leg stance and lateral view of the knee) and patella tangential radiographs (Merchant view).

During 12 months follow-up three patients underwent revision surgery. One patient had to be revised due to infection after postoperative opening of the knee joint due to direct trauma. One patient sustained an osteosynthetic procedure due to periprosthetic fracture after trauma. In one patient a retropatellar replacement was inserted one year postoperatively. Implant related complications were not found. The mean preoperative HSS-Score amounted to 57.8±11.7 points. At 3 and 12 month follow-up the mean HSS-Score was 76.0±12.3 and 83.3±11.9 points respectively.

Therefore HSS, as well as WOMAC and SF-36 Score improved significantly from preoperativly to both postoperative evaluations (Wilcoxon-Test p< 0.002). Radio-lucent lines around the femoral ceramic component were found in six cases.

However, subsequent long-term studies must be carried out in order to prove the good early clinical results and to clarify if progression of radiolucent lines may influence the clinical outcome of the presented newly ceramic total knee system.

A1226. TRIBUTE TO HAP PAUL Pages 403 - 403
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WL Bargar

Hap Paul was a unique individual. It is appropriate that this award should go a unique paper presented at this year’s ISTA. The name “Hap” comes from his initials Howard A. Paul. He was an outstanding veterinarian, but he was also much more than that. He had an insatiable curiosity combined with a quick mind and a surgeon’s practicality. His first love was research. After graduating from high school in Connecticut, he went to Notre Dame as a swimmer. He graduated with a degree in Microbiology and a strong desire to “cure cancer”. Acting on his dreams, as he always did, he decided to go to Paris to work with one of the pioneers of Interferon research. Never mind that he didn’t have a job and did not know a word of French. Of course he got the job and learned French playing rugby (hence his awful accent and colorful vocabulary). The funding ran out for the Interferon research, but he somehow got a shot at a spot in the veterinary school in Paris. He got married and finished his veterinary training. The veterinary thing worked out, but the marriage didn’t. He returned to the US after 9 years living in France, to attend the UC Davis School of Veterinary Science as a surgical resident in the small animal area. He met his wife, Dr. Wendy Shelton there… but that is another story.

I met Hap when I was a new attending orthopaedic surgeon at UC Davis and looking to do some animal modeling of hip replacement revision techniques. He was an imposing figure: six feet four, big curly afro and wire glasses. He dressed like a Frenchman, wore big clogs and carried a purse. Needless to say I was intimidated initially. But, he had great joi de vive and lived up to his name… he was almost always happy.

Hip replacement in dogs began in the 1970’s, but was nearly abandoned by the early 1980’s because of infections and “luxations” (dislocations). In order to develop an animal model we had to develop instruments and techniques that incorporated “third generation” cementing techniques. This we did, but Hap took these instruments and began using them clinically on working dogs. He developed quite a reputation for resurrecting hip replacements for dogs in the US and internationally. Hap and I went on to develop dog models for CT-based custom implants and later surgical robotics (eventually leading to the development of Robodoc). Despite our academic interests, both Hap and I went into private practice in the mid 1980’s… separately, of course (he as a veterinary orthpaedic surgeon and I specialized in hip and knee replacements for humans). Our research in surgical robotics took off when we landed a huge grant from IBM. But then the sky fell in when we learned that Hap had developed lymphoma. After surgery, radiation and chemotherapy, he was in remission, but temporarily couldn’t perform surgery due to a peripheral neuropathy attributed to Vincristine. So Hap went to the lab at UC Davis to work directly with the robotics team. He was a slave driver… but a pleasant one. Certainly the basic research behind Robodoc could not have been done without Hap getting lymphoma.

Over 5 years (1986–91) we both had a ball working with some of the best minds in robotics and imaging research. We presented our research on CT-based customs and robotics at many international venues, and Hap made many friends… some are in the audience today. He was one of the founders of this organization (ISTA). Hap returned to veterinary practice when he could finally work with his hands again… but this was not for long. Soon our research lead to the founding of Integrated Surgical Services (ISS) in 1991, the makers of Robodoc. Hap agreed to leave his practice to lead the company and I stayed in clinical practice to develop and utilize the device on patients. In 1992, we shocked the world by being the first to use an active robot in human surgery. It looked like the dawning of a new age. (I still believe it is, but it has been a very slow dawn).

For Hap, the joy was short-lived. He developed leukemia as a complication of his prior chemotherapy. He died while recovering from a bone marrow transplant on Feb. 10, 1993 at the young age of 44. During his short life he contributed tremendously to the benefit of others by his research and development work. But mostly he inspired others to excel in their endeavors. He was a wonderful guy. And we are all pleased to honor him with the presentation of the Hap Paul Award at each year’s meeting of ISTA.

E. Chimoto Y. Hagiwara Y. Saijo A. Ando H. Suda Y. Onoda E. Itoi

Introduction: Acoustic microscopy for medicine and biology has been developed for more than twenty years at Tohoku University [18]. Application of acoustic microscopy in medicine and biology has three major features and objectives. First, it is useful for intra-operative pathological examination because staining is not required. Second, it provides basic acoustic properties to assess the origin of lower frequency ultrasonic images. Third, it provides information on biomechanical properties at a microscopic level because ultrasound has close correlation with mechanical properties of the tissues. This paper describes the preliminary results obtained using 300 MHz ultrasound intensity microscopy for in vitro characterization of rat synovial cell cultures. The novelty of the approach lies in the fact that it allows remote, non-contact and disturbance-free imaging of cultured synovial cells and the changes in the cells’ properties due to external stimulants such as transforming growth factor beta-1 (TGFbeta1).

Materials and Methods: Ultrasound intensity microscope: An electric impulse was generated by a high speed switching semiconductor. The electric pulse was input to a transducer with sapphire rod as an acoustic lens and with the central frequency of 300 MHz. The reflections from the tissue was received by the transducer and were introduced into a Windows-based PC (Pentium D, 3.0 GHz, 2GB RAM, 250GB HDD) via a digital oscilloscope (Tektronix TDS7154B, Beaverton, USA). The frequency range was 1GHz, and the sampling rate was 20 GS/s. Four values of the time taken for a pulse response at the same point were averaged in order to reduce random noise. The transducer was mounted on an X-Y stage with a microcomputer board that was driven by the PC through RS232C. The Both X-scan and Y-scan were driven by linear servo motors. The ultrasound propagates through the thin specimen such as cultured cells and reflects at the interface between the specimen and substrate. A two-dimensional distribution of the ultrasound intensity, which is closely related to the mechanical properties, was visualized with 200 by 200 pixels.

Tissue preparation: The synovial membrane was obtained from non-operated male rats weighing from 380 to 400 g through medial parapatellar incision. The tissue was diluted and loosened 0.15% DispaseII (Boehringer, Mannheim) in DMEM for 2 hours at 37 C°. Then centrifuged at 400 g for 5 min and discard the supernatant. The cells were plated in 75 mm2 dish (Falcon) with Dulbecco’s modified Eagle’s medium (DMEM, GIBCO Laboratories) containing 10% fetal bovine serum (SIGMA Chemical Co.) at 37 C° in a CO2 incubator. To determine changes of intensity, the cells were treated with 1 ng/ml of human recombinant TGF-β1 (hTGF-β1, R& D Systems, Inc.) for 1 and 3 days after reaching confluent. The non-treated cells was harvested at 3 days after reaching confluent and defined as control. Randomized four points at each dish were measured and averaged data was defined as the representative value of each dish. The cells used for experiments were at the third passage.

Signal processing: The reflection from the tissue area contains two components. One is from the tissue surface and another from the interface between the tissue and the substrate (phosphate buffered saline). Frequency domain analysis of the reflection enables the separation of these two components and the calculation of the tissue thickness and intensity by Fourier-transforming the waveform [9].

Image analysis: Randomized point regions were determined using ultrasound intensity microscopic images. This was done by employing commercially available image analysis software (PhotoShop CS2, Adobe Systems Inc.). Ultrasound intensity microscopic images with a gradation color scale were also produced for clear visualization of the ultrasound intensity variations.

Statistics: Statistical analysis among groups was performed using one factor analysis of variance. Data were expressed as mean ± standard deviation. A value of P < 0.05 was accepted as statistically significant.

Results: The ultrasound intensity microscope can clearly visualize cells. The high intensity variations area of the reflected ultrasound energy at the central part of the cell corresponded to the nucleus and the high intensity area at the peripheral zone corresponded to the cytoskeleton mainly consisting of actin filaments. The intensity of the reflected ultrasound energy at the peripheral zone was significantly increased after stimulation with hTGF-b1.

A.S. Dickinson M. Browne A.C. Taylor

Although resurfacing hip replacement (RHR) is associated with a more demanding patient cohort, it has achieved survivorship approaching that of total hip replacement. Occasional failures from femoral neck fracture, or migration and loosening of the femoral head prosthesis have been observed, the causes of which are multifactorial, but predominately biomechanical in nature. Current surgical technique recommends valgus implant orientation and reduction of the femoral offset, reducing joint contact force and the femoral neck fracture risk. Radiographic changes including femoral neck narrowing and ‘pedestal lines’ around the implant stem are present in well performing hips, but more common in failing joints indicating that loosening may involve remodelling. The importance of prosthesis positioning on the biomechanics of the resurfaced joint was investigated using finite element analysis (FEA).

Seven FE models were generated from a CT scan of a male patient: the femur in its intact state, and the resurfaced femur with either a 50mm or 52mm prosthesis head in

neutral orientation,

10° of relative varus or

10° of relative valgus tilt.

The fracture risk during trauma was investigated for stumbling and a sideways fall onto the greater trochanter, by calculating the volume of yielding bone. Remodelling was quantified for normal gait, as the percentage volume of head and neck bone with over 75% post-operative change in strain energy density for an older patient, and 50% for a younger patient.

Resurfacing with the smaller, 50mm prosthesis reduced the femoral offset by 3.0mm, 4.3mm and 5.1mm in varus, neutral and valgus orientations. When the 52mm head was used, the natural joint centre could be recreated rrespective of orientation, without notching the femoral neck. The 50mm head reduced the volume of yielding femoral neck bone relative to the intact femur in a linear correlation with femoral offset. When the natural femoral offset was recreated with the 52mm prosthesis, the predicted neck fracture load in stumbling was decreased by 9% and 20% in neutral and varus orientations, but remained in line with the intact bone when implanted with valgus orientation. This agrees with clinical experience and justifies currently recommended techniques. In oblique falling, the neck fracture load was again improved slightly when the femoral offset was reduced, and never fell below 97% of the natural case for the larger implant in all orientations.

Predicted patterns of remodelling stimulus were consistent with radiographic clinical evidence. Stress shielding increased slightly from varus to valgus orientation, but was restricted to the superior femoral head in the older patient. Bone densification around the stem was predicted, indicating load transfer. Stress shielding only extended into the femoral neck in the young patient and where the femoral offset was reduced with the 50mm prosthesis. The increase in remodelling correlated with valgus orientation, or reduced femoral offset. The trend would become more marked if this were to reduce the joint contact force, but there was no such correlation for the 52mm prosthesis, when the natural femoral offset was recreated. Only in extreme cases would remodelling alone be sufficient to cause visible femoral neck narrowing, i.e. patients with a high metabolism and considerably reduced femoral offset, implying that other factors including damage from surgery or impingement, inflammatory response or retinacular blood supply interruption may also be involved in femoral neck adaptation.

The results of this FEA biomechanical study justify current surgical techniques, indicating improved femoral neck fracture strength in stumbling with valgus position. Fracture risk under oblique falling was less sensitive to resurfacing. Furthermore, the results imply that reduced femoral offset could be linked to narrowing of the femoral neck; however the effects of positioning alone on bone remodelling may be insufficient to account for this. The study suggests that surgical technique should attempt to recreate the natural head centre, but still aim primarily for valgus positioning of the prosthesis, to reduce the femoral neck fracture risk.

A. Speranza E. Monaco M. Vetrano C. D’Arrigo A. Ferretti

The choice of surgical technique for total hip arthroplasty (THA) can affect time and postoperative rehabilitation procedures. The aim of this prospective blinded cohort study is to determine significant differences in gait parameters in the short term between those patients who have experienced THA using a limited incision anterolateral intermuscular (MIS) approach compared with those who have experienced traditional lateral transmuscular (LTM) approach.

Thirty patients were enrolled in this study, 15 of who received the MIS technique and 15 the LTM approach. A single surgeon performed all the operations using short hip stem implants with 36mm femoral head size and all patients received a standard postoperative rehabilitation protocol. Patients, physiotherapists, and assessors were blinded to the incision used. Gait analysis was performed 30 day after surgery, when patients were able to ambulate without crutches.

Minimal differences in temporostatial parameters were shown between the MIS and LTM groups, whereas significant differences (p< 0.05) in kinematics (hip range of motion in sagittal, frontal and transverse planes), kinetics (hip flexion/extension and abduction/adduction moments) and electromiography parameters (gluteus medius activation pattern and degree of activity) between two groups.

This study demonstrates functional benefits of the minimally invasive incision over the standard lateral transmuscular approach in terms of walking ability 30 days postoperatively.

W.N. Capello

At ten years, alumina ceramic bearings are functioning well with low complication rates and a fewer number of revisions than the control cohort.

Alumina ceramic bearings have proven superior wear resistance, lubrication, and scratch resistance, without carrying the risk of metal ion release. In 1996 a U.S. IDE clinical trial was initiated utilizing newly improved alumina ceramic materials and implant design. The purpose of this multi-center, prospective, randomized study is to prove comparable safety and efficacy of alumina-alumina ceramic to a control cobalt chrome-polyethylene bearing.

Four hundred fifty two patients (475 hips) are followed in this study. Subjects include ceramic on ceramic, with either porous coated cup or arc deposited cup, or control group with metal on polyethylene with porous coated cup. Average age of subject at time of surgery was 53 years with 82% diagnosis of OA. The average Harris Hip Score was 96 and 94% of hips had little to no pain. Kaplan-Maier survivorship at 10 years, component revision for any reason, was 95.9% for ceramic bearings compared to 91.3% for metal on polyethylene control. There have been nine hips requiring revision of one or both components for any reason.

Data was recently collected on the subjects that participated in either the IDE or Continued Access arms of the ABC® and Trident® study. Data collection included revisions, complications, and noise. Out of 930 hips (848 patients) there were nine incidences of squeaking noise reported, no wear/osteolysis issues, and only two insert fractures (0.2%).

At ten years ceramic bearings show no wear, inconsequential lysis, minimal breakage, and occasion noise. Clinically, alumina ceramic bearings perform as well as the metal-on-polyethylene, with fewer revisions and less osteolysis, suggesting that they are a safe, viable option for younger, more active patients.

I. C. Clarke K. Kubo A. Lombardi E. McPherson A. Turnbull A. Gustafson D. Donaldson

Ceramic-on-ceramic alumina bearings (ALX) have demonstrated low wear with minimal biological consequences for almost four decades. An alumina-zirconia composite (BIOLOX-DELTATM) was introduced in 2000 as an alternative ceramic. This contains well-distributed zirconia grains that can undergo some surface phase transformations from tetragonal to monoclinic. We analyzed 5 cases revised at 1–7 years to compare to our simulator wear studies. For the retrieved DELTA bearings, two important questions were

how much tetragonal to monoclinic transformation was there in the zirconia phase and

how much did the articular surfaces roughen, either as a result of this transformation or from formation of stripe wear zones?

The retrieval cases were photographed and logged with respect to clinical and revision details. The DELTA balls varied from 22mm to 36mm diameters. These had been mated with liner inserts varying by UHMWPE, BIOLOX-FORTE and BIOLOX-DELTA materials. Bearing features were analyzed for roughness by white-light interferometry, for wear by SEM, for dimensions by CMM and for transfer layers by EDS technique. Surface transformations on DELTA retrievals were mapped by XRD. The four combinations of 36mm diameter BIOLOX-FORTE and BIOLOX-DELTA were studied in a hip simulator, which was run in ‘severe’ micro-separation test mode to 5 million cycles. Wear rates, wear stripes, bearing roughness and wear debris were compared to the retrieval data.

In two DELTA ball cases, there were conspicuous impingement signs, stripe wear and black metallic smears. It is to be noted that the metal transfer sites (EDS) appeared to be from the revision procedures. The retrieved balls run with alumina liners showed monoclinic phase peaking at 32% on the particular surface and internal bore. On the fracture surface of case 1, the monoclinic content had increased to 40%. Various surface roughness indices were assessed on the bearings. The polished articular surfaces averaged roughness (Sa) of the order 3 nm, representing extremely smooth surfaces. The main wear zone was only marginally rougher (5 nm). In contrast the stripe wear zones had roughness of the order 55–140 nm.

In the laboratory, the DELTA bearings provided a 3–6 fold wear reduction compared to FORTE controls. Roughness of stripes increased to maximum 113nm on controls. Roughness of wear stripes showed FORTE with the highest and DELTA with the lowest values. DELTA bearings also revealed much milder wear by SEM imaging. Phase transformations showed peaks at < 30% for both main wear zone and stripe wear sites. It is hypothesized that the concentration of monoclinic phase reached a certain level due to compression contraint imposed by the alumina matrix. With implant wear, additional tetragonal grains of zirconia are exposed and these will also transform to tetragonal. This consistency between laboratory and retrieval studies confirmed the stable nature of the bearings. The BIOLOX-DELTA combination provides optimal potential for a clinically relevant reduction in stripe wear.

TJ Blumenfeld DA Glaser WL Bargar RD Komistek GD Langston MR Mahfouz

Previous in vivo studies pertaining to THA performance have focused on the analysis of gait. Unfortunately, higher demand activities have not yet been analyzed. Therefore, the objective of the present study was to determine the in vivo kinematics for THA patients, using fluoroscopy, while they performed four higher demand activities.

The 3D in vivo kinematics of 10 THA patients were analyzed during the following activities: pivoting (PI), tying a shoe (SHOE), sitting down (SDOWN) and standing up (SUP) with and without the aid of handrails. Patients were matched for age, height, weight, body mass index, diagnosis and femoral head diameter to control for confounding variables possibly having influence on the hip performance and kinematics of the various activities.

The largest amount, incidence and variation of separation (femoral head sliding in the acetabular cup) were achieved during the PI with 1.5mm (SD 1.1) and 9 of 10 (90%) subjects experiencing separation. For the SHOE, SDOWN and SUP activities the average separation values were 1.1, 1.2 and 0.7mm, respectively. Femoral head separation was observed in 8 of 10 subjects (80%) during SHOE, in 9 (90%) during SDOWN, and in only one of 6 (60%) during SUP.

In this present study, subjects demonstrated hip separation during the high demand subjects, which could be a concern because these same activities are subjected to higher bearing surface forces. Also, the presence of hip separation leads to reduced contact area between the femoral head and the acetabular cup, possibly leading to higher contact stresses.

A771. FEMORAL COMPONENT Pages 405 - 406
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K. Kindsfater D.A. Dennis J. Politi

Introduction: Although use of modular femoral components in revision hip arthroplasty is widely accepted, many still question the need for modular versatility in primary THA. The purpose of our study was to examine in a large cohort the percentage of hips in which femoral component version was changed to optimize stability or avoid prosthetic impingement of the THA construct. We hypothesized that the percentage of hips needing version change in routine primary THA would be low.

Methods: This prospective study analyzed 1000 consecutive primary THAs using a modular S-ROM (DePuy) stem performed by 3 surgeons at 3 institutions all via a posterior approach. Mean patient age at surgery was 57.5 years; 51.6% were male. The difference in version between the femoral sleeve placed anatomically and the femoral stem was recorded intra-operatively.

Results: Femoral component version was changed in 47.9% of hips. Logistic regression analysis showed no correlation between the likelihood of changing stem version and patient age (p=0.87), gender (p=0.23), diagnosis (p=0.54), or surgeon (p=0.27). 10 hips (1%) experienced early dislocation (within 3 months post-op). With the numbers available, there was a slight trend of lower dislocation rate in hips where stem version was changed (0.6%) versus those in which it was not (1.5%, p=0.16, chi squared).

Conclusion: The incidence of femoral version change in routine primary THA was much higher than expected. It was difficult to predict the need to alter version based on clinical variables including diagnosis. Thus, we conclude it may be advantageous to routinely use a stem that allows variable version as it is not possible to pre-operatively determine when changing version will be required. In addition, we surmise our low dislocation rate compared to historical controls of THA performed using a posterior approach was aided by the ability to adjust version in almost half of our patients.

C. Colwell N. Steklov S. Patil D. D’Lima

Total knee arthroplasty (TKA) provides relatively pain-free function for patients with end-stage arthritis. However, return to recreational and athletic activities is often restricted based on the potential for long-term wear and damage to the prosthetic components. Advice regarding safe and unsafe activities is typically based on the individual surgeon’s subjective bias. We measured knee forces in vivo during downhill skiing to develop a more scientific rationale for advice on post-TKA activities A TKA patient with the tibial tray instrumented to measure tibial forces was studied at two years postoperatively. Tibial forces were measured for the various phases of downhill skiing on slopes ranging in difficulty from green to black.

Walking on skis to get to the ski lift generated peak forces of 2.1 ± 0.20 xBW (times body weight), cruising on gentle slopes 1.5 ± 0.22 xBW, skating on a flat slope 3.9 ± 0.50 xBW, snowplowing 1.7 ± 0.20 xBW, and coming to a stop 3 ± 0.12 xBW. Carving on steeper slopes generated substantially higher forces: blue slopes (range 6° to 10°), 4.4 ± 0.18 xBW; black slopes (range 15° to 20°), 4.9 ± 0.57 xBW. These forces were compared to peak forces generated by the same patient during level walking: 2.6 ± 0.4 xBW, stationary biking 1.3 ± 0.7 xBW, stair climbing 3.1 ± 0.31 xBW, and jogging 4.3 ± 0.8 xBW.

The forces generated on the knee during recreational skiing vary with activity and level of difficulty. Snow-plowing and cruising on gentle slopes generated lower forces than level walking (comparable to stationary biking). Stopping and skating generated forces comparable to stair climbing. Carving on steeper slopes (blues and blacks) generated forces as high as those seen during jogging. This study provides quantitative results to assist the surgeon in advising the patient regarding postoperative exercise.


INTRODUCTION: Many orthopaedic device companies now offer a high flexion (HF) choice within their knee Arthroplasty portfolios. Early published results are mixed between standard (STD) and HF knee devices despite claims of increased flexion with the HF offerings. The purpose of this randomized, controlled, simultaneous, bilateral study was to compare two coronally conforming rotating platform devices to determine if flexion differences were attributed to implant design.

METHODS: Ninety-three subjects underwent simultaneous bilateral TKA across 8 centers. The HF device was randomly assigned to one side and the contralateral leg received the STD device. Average age was 61 years, 99% were diagnosed with osteoarthritis, 66% were females, average BMI was 32 and range of motion was measured by subjective expectations versus satisfaction.

RESULTS: The HF design had statistically better single leg active flexion (SLAF) 12 months after surgery compared to the STD. Consistent with Gupta et. al, in a subgroup with pre-op flexion < 120 degrees in both knees, the HF device was statistically superior in passive flexion, ROM, and SLAF by between 1.8 and 4.5 degrees at 6 months, 12 months, and longitudinally over all postoperative intervals using raw degrees, improvement from pre-op, and adjusting for potentially confounding variables. 57% of subjects preferred their HF knee 6 months postoperatively, although there was no difference in preference at 12 months.

DISCUSSION: The simultaneous bilateral design of this study necessitates that subjects act as their own control eliminating most confounding variables. Gains in postoperative flexion, although small, were superior in the HF TKA group and were greater in those subjects with less than 120 degrees of preoperative flexion, suggesting the ideal candidate for a HF TKA is one with lesser preoperative flexion.

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Jonathan Garnio

Squeaking has become a more common problem following hard on hard bearings in total hip replacements. Although most squeaking is occasional and not concerning to either patient or health care practitioner, some reports of squeaking indicate high percentages (7% or higher) that can be constant and quite concerning. Much work has been done in this area, and although the exact mechanism is not yet understood, most of the data suggests a particular hip replacement system (metal alloy, taper design, cup design) significantly elevates to quantity and quality of the squeaking problem to concerning levels. Those specific details are described in depth along with future studies to improve our understanding in the nature of this acoustical phenomenon.

S. Nakamura M. Kobayashi H. Ito H. Yoshitomi R. Arai K. Nakamura T. Ueo T. Nakamura

In Far East, including Japan and the Middle East, daily activities are frequently carried out on the floor. Deep flexion of the knee joint is therefore very important in these societies. Some patients who underwent total knee arthroplasty (TKA) in these countries often perform deep flexion activity, such as squatting, cross-leg sitting and kneeling. However it is still unknown that deep flexion activity affects long term durability after TKA. The purpose of this study was to examine the correlation between deep flexion and long term durability.

Between December 1989 and May 1997, 507 total knee arthroplasties were carried out in 371 patients using the Bi-Surface Knee System (Japan Medical Material, Osaka, Japan) at two institutions and routine rehabilitation program continued for one to two months after TKA. One patient who underwent simultaneous bilateral TKA was excluded because of pulmonary embolism within one month. The other 505 knees (370 patients) were divided into two groups according to the range of flexion after our routine rehabilitation program; one group (Group A: 207 knees) consisted of more than 135 degrees flexion knees and the other group (Group B: 298 knees) consists of less than 135 degrees flexion knees. Patients whose follow-up period was less than 10 years were excluded from this clinical evaluation. Range of flexion was measured preoperatively, at the time after routine rehabilitation program, and at the latest follow-up. Knee function was evaluated on the basis of Knee Society knee score and functional score preoperatively and at the latest follow-up. Kaplan-Meier survivorship analysis was performed with revision for any operation as the end point.

In Group A, the mean preoperative range of flexion was 133.0±16.3 degrees, and at the time after routine rehabilitation program, this improved to 139.7±5.1 degrees. This angle maintained to 136.2±14.3 at the latest follow-up. In Group B, the mean preoperative range of flexion was 111.6±20.4 degrees, and at the time after routine rehabilitation program, this improved to 114.5±13.6 degrees. This angle maintained to 118.2±17.8 at the latest follow-up. The Knee Society knee score and functional score was improved from 43.0±16.9 points and 39.0±20.2 points preoperatively to 95.1±5.8 points and 51.8±21.2 points at the latest follow-up, respectively in Group A. The Knee Society knee score and functional score was improved from 37.1±16.7 points and 31.9±18.4 points preoperatively to 92.5±8.7 points and 53.1±26.1 points at the latest follow-up, respectively in Group B. Kaplan-Meier survivorship at 10-year was 95.5% in Group A and 96.2% in Group B with any operation as the end point. The survivorship between Group A and Group B was not statistically significant.

Good range of flexion was maintained and Knee society score was excellent after a long time follow-up for the patients who achieved deep flexion after TKA. Deep flexion was proved not to affect long term durability in this Bi-Surface Knee System.

J. Victor L. Labey P. Wong J. Bellemans

A comparative kinematic study was carried out on six cadaver limbs, comparing tibiofemoral kinematics in five different conditions: unloaded, under a constant 130 N ankle load with a variable quadriceps load, with and without a constant 50 N medial and lateral hamstrings load. Kinematics were described as translation of the projected centers of the medial (MFT) and lateral femoral condyles (LFT) in the horizontal plane of the tibia, and tibial axial rotation (TR) as a function of flexion angle. In passive conditions, the tibia rotated internally with increasing flexion, to an average of −16° (range −12/−20°, SD 3.0°). Between 0 – 40° flexion, the medial condyle translated forwards 4 mm (range 0.8/5.5 mm, SD 2.5 mm), followed by a gradual posterior translation, totaling −9 mm (range −5.8/−18.5 mm, SD 4.9 mm) between 40° – 140° flexion. The lateral femoral condyle translated posteriorly with increasing flexion completing −25 mm (range −22.6 – −28.2 mm, SD 2.5 mm). Dynamic, loaded measurements were carried out in a knee rig. Under a fixed ankle load of 130 N and variable quadriceps loading, tibial rotation was inverted, mean TR 4.7° (range −3.3°/11.8° SD 5.4°), MFT −0.5 mm (range = −4.3/2.4 mm, SD = 2.4 mm), LFT 3.3 mm (range = −3.6/10.6 mm, SD = 5.1 mm). As compared to the passive condition, all these excursions were significantly different: p=0.015, p=0.013, and p=0.011 for TR, MFT and LFT respectively. Adding medial and lateral hamstrings force of 50N each, reduced TR, MFT and LFT significantly as compared to the passive condition. In general, loading the knee with hamstrings and quadriceps reduces rotation and translation as compared to the passive condition. Lateral hamstring action is more influential on knee kinematics than medial hamstrings action.

S. Walker Gokce Yildirim Sally Arno

The treatment of osteoarthritis using artificial knee joints is expected to expand further over the next decade. Increasingly, patients expect quicker rehabilitation, improved performance, and high durability. However, economic limitations require a reduced cost for each procedure, as well as early intervention and even preventative measures. The major goal of implant design needs to be a restoration of normal knee mechanics, whether by maximum preservation of tissues, or by guiding surfaces which replicate their function. In this paper it is proposed that total knees should exhibit anatomic knee mechanics, namely medial stability – lateral mobility.

Many studies in the past have shown that the neutral path of motion of the anatomic knee, is that the medial side remains relatively immobile in the AP direction, which will impart a feeling of stability, while the lateral side shows posterior femoral displacement with flexion, to obtain a high range of flexion. There is considerable rotational laxity about this neutral path to accommodate a range of positions and activities. Recent studies carried out in our laboratory using an up-and-down crouching machine, and other test machines, have conformed this mechanical behaviour. To further elaborate, we tested eight young male subjects in a 7T MRI machine, where compressive and shear loads were applied. AP displacements occurred laterally but not medially. We attributed this behaviour to the medial meniscus and the tibial bearing geometry under weight-bearing conditions.

On the basis of these various studies, we developed a method for the design of Guided Motion knees, which would be implanted without the cruciates, and which would restore anatomic knee mechanics. The method started with the femoral component, where the medial side had features to provide a continuous radius anteriorly, and distally to 75 degrees flexion when a post-cam would contact. This feature would prevent paradoxical anterior femoral sliding in early flexion. Multiple femoral positions were then defined for accommodating anatomic motion, in particular limited AP motion on the medial side, but posterior displacement laterally. Tibial bearing surfaces were generated accordingly.

Tests were carried out on the crouching machine and on a Desktop TKR Test machine to compare the TKR motion with anatomic. Although not accurate in all respects, the Guided Motion designs were closer than models of standard TKR’s today. Such Guided Motion designs hold the promise for restoring anatomic knee mechanics and a normal feeling knee.

A. Fritsche C. Zietz S. Teufel W. Kolp I. Tokar C. Mauch W. Mittelmeier R. Bader

Sufficient primary stability of the acetabular cup is essential for stable osseous integration of the implant after total hip arthroplasty. By means of under-reaming the cavities press-fit cups gain their primary stability in the acetabular bone stock. These metal-backed cups are inserted intra-operatively using an impact hammer.

The aim of this experimental study was to obtain the forces exerted by the hammer both in-vivo and in-vitro as well as to determine the resulting primary stability of the cups in-vitro.

Two different artificial bone models were applied to simulate osteoporotic and sclerotic bone. Polymeth-acrylamid (PMI, ROHACELL 110 IG, Gaugler & Lutz, Germany) was used as an osteoporotic bone substitute, whereas a composite model made of a PMI-Block and a 4 mm thick (cortical) Polyvinyl chloride (PVC) layer (AIREX C70.200, Gaugler & Lutz, Germany) was deployed to simulate sclerotic bone. In all artificial bone blocks cavities were reamed for a press-fit cup (Trident PSL, Size 56mm, Stryker, USA) using the original surgical instrument. The impactor of the cup was equipped with a piezoelectric ring sensor (PCB Piezotronics, Germany). Using the standard surgical hammer (1.2kg) the acetabular cups were implanted into the bone substitute material by a male (95kg) and a female (75kg) surgeon. Subsequently, primary stability of the implant (n=5) was determined in a pull-out test setup using a universal testing machine (Z050, Ziwck/Roell, Germany).

For validation the impaction forces were recorded intra-operatively using the identical press-fit cup design.

An average impaction force of 4.5±0.6kN and 6.3±0.4kN using the PMI and the composite bone models respectively were achieved by the female surgeon in vitro.

7.4±1.5kN and 7.7±0.8kN respectively were obtained by the male surgeon who reached an average in-vivo impaction force of 7.5±1.6kN.

Using the PMI-model a pull-out force of 298±72N and 201±112N were determined for the female and male surgeons respectively. However, using the composite bone model approximately half the pull-out force was measured for the female surgeon (402±39N) compared to the male surgeon (869±208N).

Our results show that impact forces measured in-vitro correspond to the data recorded in-vivo. Using the osteoporotic bone model the pull-out test revealed that too high impaction forces affect the pull-out force negatively and hence the primary implant stability is reduced, whereas higher impact forces improve primary stability considerably in the sclerotic bone model. In conclusion, the amount of impaction force contributes to the quality of the obtained primary cup stability substantially and should be adjusted intra-operatively according to the bone quality of each individual patient.

M.T. Bah P.B. Nair M. Browne

Implant positioning is a critical factor in assuring the primary stability of cementless Total Hip Replacements (THRs). Although it is under the direct control of surgeons, finding the optimal implant position and achieving a perfect fit remain a challenge even with the advent of computer navigation. Placement of the femoral stem in an excessive ante/retroversion or varus/valgus orientation can be detrimental to the performance of THR. To determine the effect of such malalignment, finite element (FE) computer modelling is often used. However, this can be time consuming since FE meshes must be repeatedly generated and solved each time for a range of defined implant positions. In the present study, a mesh morphing technique is developed for the automatic generation of FE models of the implanted femur; in this way, many implant orientations can be investigated in a single analysis.

An average femur geometry generated from a CT scan population of 13 male and 8 female patients aged between 43 and 84 years was considered. The femur was virtually implanted with the Furlong HAC titanium alloy stem (JRI Ltd, Sheffield, UK) and placed in the medullary canal in a baseline neutral nominal position. The head of the femur was then removed and both femur and implant volumes were joined together to form a single piece that was exported into ANSYS11 ICEM CFD (ANSYS Inc., 2008) for meshing. To adequately replicate implant ante/retroversion, varus/valgus or anterior/posterior orientations, the rigid body displacement of the implant was controlled by three rotations with respect to a local coordinate system. One hundred different implant positions were analysed and the quality of the morphed meshes analysed for consistency.

To check the morphed meshes, corresponding models were generated individually by re-positioning the implant in the femur. Selected models were solved to predict the strain distribution in the bone and the boneimplant relative micromovements under joint and muscle loading. A good agreement was found for bone strains and implant micromotions between the morphed models and their individually run counterparts. In the postprocessing stage further metrics were analysed to corroborate the findings of the morphed and individually run models. These included: average and maximum strains in bone interface area and its entire volume, percentage of bone interface area and its volume strained up to and beyond 0.7%; implant average and maximum micromotions and finally percentages of implant area undergoing reported critical micromotions of 50 μm, 100 μm and 150 μm for bone in growth. Excellent correlation was observed in all cases.

In conclusion, the proposed technique allowed an automatic generation of FE meshes of the implanted femur as the implant position varies; the required computational resources were considerably reduced and the biomechanical response was evaluated. This model forms a good basis for the development of a tool for multiple statistical analyses of the effects of implant orientation in pre-clinical studies.

A.V. Lombardi K.R. Berend J.B. Adams

Lateral retinacular release (LRR) may be necessary to balance the patellofemoral articulation in primary total knee arthroplasty (TKA). However, lateral retinacular release may be associated with an increased risk of patellar necrosis, loosening, perioperative bleeding, and pain.

Additionally, the need for lateral retinacular release may herald a more significant problem with implant positioning, rotation, and balance. The purpose of this study is to report the lateral retinacular release rate with a “patella friendly” femoral TKA design, and to identify if a less invasive approach is associated with reduced need for lateral retinacular release.

A retrospective review of our database identified 4667 primary TKA performed by two surgeons between October 2002 and January 2009. Beginning in 2002, a less invasive approach has been used in over 95% of primary TKA. Also beginning in 2002, the authors began using a new TKA design with a more swept back patellofemoral articulation (Vanguard Complete Knee System; Biomet). During the first two years of the study, the authors also used the Maxim Complete Knee System (Biomet). We previously reported a lateral retinacular release rate associated with the Maxim of 22%. There were 555 Maxim and 4112 Vanguard TKA performed. Lateral retinacular release with Maxim TKA was 12.8% (71/555), significantly less than that previously reported for the same implant design using a standard approach. Lateral retinacular release for Vanguard TKA was 1.8% (72/4112), significantly less than that with the Maxim TKA using either a standard or less invasive approach (p< 0.005).

Implant design, surgical technique, and a less invasive exposure combine to significantly reduce the need for lateral retinacular release in primary TKA.

Y. Song N. J Giori H. Ito M. R. Safran

Cam type femoro-acetabular impingement is defined by a reduced femoral head-neck offset and by excessive bone at antero-lateral femoral head-neck junction.

Reconstruction of the femoral head-neck offset by removing the femoral bony prominence is a common treatment for cam type impingement. In many cases, the goal of this treatment is to make the antero-lateral head-neck offset symmetrical to the postero-lateral offset. However, guidelines for bony removal are not well established. The objective of this study is to examine if the antero-lateral and postero-lateral femoral offsets are symmetrical in normal healthy hips.

CT analyses of the anatomic geometry of the femoral head and neck were performed. Hip joints with any evidence of cartilage defects and impingement were excluded. Eight cadaveric hips (3 right and 5 left hips) were examined. The average age of the cadavers was 65.1±15.1 years. A peripheral QCT scanner was used which provided 0.2 x 0.2 x 2 mm resolution. To improve the resolution of the final result, each hip joint was scanned in three different scanning directions (sagittal, coronal, and axial scanning planes). A custom imaging fixture was built to position a joint sample in three different scanning planes and a custom irrigation system supplied saline to protect the sample from dehydration. A custom segmentation program was developed to delineate the bony contours of the femoral head and neck in a fully automated manner. The segmentation data from the three differenent imaging planes were merged and a 3D solid model of each hip joint was created. The prominence of the femoral head was determined by the distance of the 3D head from an ideal sphere fitted into the 3D model.

All the femoral heads were found to be asymmetric. Prominence of posteromedial femoral head averaged 0.105 mm more than the antero-medial femoral head.

The antero-lateral head-neck junction was also found to be more prominent than the postero-lateral head-neck junction by an average of 1.09 mm. Asymmetry in the femoral head and femoral head-neck junction was a general finding in normal hip joints. The conventional approach of symmetric reconstruction of femoral head-neck junction may result in unnecessary removal of bone at the antero-lateral head-neck junction and potentially increase the risk of femoral neck fracture.

C. M. Maguire T. M. Seyler R. H. Jinnah

Femoroacetabular impingement (FAI) has been identified as the cause of idiopathic osteoarthritis in young patients. FAI is the result of decreased femoral head/neck offset ratio due to bony deformities and causes hip pain and labral tears. Because the unique design and bone preserving nature of metal-onmetal hip resurfacing implants, it is extremely difficult to correct extensive bony deformities associated with FAI. Poor patient selection and lack of orrection/undercorrection of the underlying FAI deformity may lead to prosthetic impingement, extensive wear and metal ion release, component loosening, and subsequent implant failure. Hence, it is critical to define the patient population undergoing hip resurfacing. Because metal-on-metal hip resurfacing is performed more frequently in a younger population, we hypothesize that this patient population will have a larger proportion of femoroacetabular impingement than the general population and identification of this patient population is critical to the longevity of the implant.

A retrospective review of 153 hips undergoing metal-on-metal hip resurfacing was performed. 52 hips were excluded based on the exclusion criteria of inadequate preoperative films (6 subjects), existing hardware/history of trauma (11 subjects), or if the resurfacing was performed due to avascular necrosis secondary to trauma, steroids, etc (35 subjects). The remaining 101 hips (76 male, 25 female) had an average age of 51.8 years. Preoperative x-rays were utilized to assess impingement according to previously published methods. An acetabular index (AI) of x ≤ 0°, center edge angle (CE angle) of x > 39°, a Sharp angle of x < 33°, and a present cross-over sign were considered pathologic findings for pincer impingement. Pathologic findings for cam impingement included the triangular index (TI; pathologic with R=r+2mm) and an α angle greater than 83° in men or 57° in women. Subjects were categorized as having impingement if they had one or more pathologic finding for either cam or pincer impingement and as having mixed impingement if they had one pathologic finding for both cam and pincer measurements. Prevalence rates were compared to published data for the general population.

Fifty-five subjects had at least one pathologic finding for cam impingement (18, 7, and 30 subjects had pathologic measurements for α angle, TI, and both measurements, respectively); 24 subjects had at least one pathologic pincer measurement (4, 6, 14, and 4 pathologic measurements for AI, CE angle, cross-over sign, and Sharp angle, respectively; 3 subjects had multiple pincer findings) 13 subjects were classified as having mixed impingement (with α angle and cross-over sign as the most prevalent cam and pincer measurements). When compared to published data for the general population (M: 17%, F: 4%), we found a significantly larger proportion of cam impingement in both males (60.5%) and females (36%) in patients undergoing resurfacing at our institution (p< 0.001). There was also a significantly larger proportion of pincer impingement in our population (23.8%) than in the general population (10.7%) (p=0.01). There was no significant difference between our proportion of patients with mixed impingement (12.9%) and the general population (20.8%) (p=0.150).

The patient population for metal-on-metal hip resurfacing shows a greater prevalance of FAI than the general population. Because the femoral head/neck junction is preserved with hip resurfacing, patients undergoing this type of procedure might be at increased risk of impingement. Hence, it is important to assess the degree of FAI preoperatively. This will allow proper patient selection and careful planning of surgical correction of the underlying FAI deformity to increase implant longevity.

A.V. Lombardi M.D. Skeels K.R. Berend J.B. Adams

With increased use of alternative bearings, surgeons have moved from utilization of 22, 26, 28 and 32mm heads to larger head diameters in total hip arthroplasty (THA). Reported benefits of large heads are enhanced stability secondary to the increased range of motion prior to impingement and the increased jump distance required for subluxation from the acetabulum.

This study evaluates the use of large diameter heads in primary THA comparing the rate of dislocation to a published study from our practice as a historic control.

Between October of 2001 and October 2008, 2015 THA with large heads were performed in 1743 patients. Femoral head sizes ranged from 36 to 60mm, with articulations consisting of metal-on-poly, ceramic-on-poly, and metal-on-metal. Operative approach was 63% less invasive direct lateral, 10% anterior supine intermuscular, and 27% standard direct lateral. In 1999 (Mallory et al., Clin Orthop Relat Res) we reported a low incidence of 12 dislocations (0.8%) in 1518 primary THA done with smaller femoral heads via a standard direct lateral approach. In the current series with large heads, follow-up averaged 22 months. There has been one dislocation requiring revision (0.05%), representing a significant reduction from our earlier report (p=0.0003). Forty additional acetabular components have been revised (2.0%), with eight related to sepsis (0.4%), 23 aseptic loosening (1.1%), six metal sensitivity (0.2%), one pseudotumor (0.05%), one failure of ingrowth (0.05%), and one acute early migration (0.05%).

The use of larger diameter heads has significantly lowered our dislocation rate in primary THA with only one occurrence observed in 2015 cases, for a rate of 0.05% at two years average follow-up.

J.C. Finch L.G. Morawa R. Ramakrishnan

In patients with significant bone loss and a nonfunctioning extensor mechanism, the approach to revision is complicated. We describe a unique approach to solve this complex problem to help restore clinically satisfactory results. Our technique involves the use of a donor allograft that consists of proximal tibia along with the attached extensor mechanism (patellar tendon-patella-quadriceps tendon).

Five reconstructions utilizing bone allografts and extensor mechanisms were performed by two surgeons. Each has extensive surgical history on the affected knee and presented with gross instability, considerable bone loss, and significant extensor lag or total loss of extension. The implants used were press-fit stems with the tibial baseplate cemented into the allograft prior to implantation. In this series, either hinged or total stabilized prostheses were used.

The follow up ranged from 1 to 5 years. The only complication to date was reported in one patient who required irrigation and debridement with surgical wound closure after partial dehiscence. However the patency of the allograft was not disrupted.

All prostheses have been noted to be stable with no signs of loosening.

This procedure presented should be considered a salvage procedure for bone stock and extensor mechanism deficiency in revision total knee arthroplasty. The advantage to our allograft is the inherent stability of the proximal tibia with the tibial tubercle and associated extensor mechanism. For patients with this complex deficiency, there has been no effective method of treatment and we advocate the use of this procedure to restore function and relieve pain to an otherwise grossly unstable and functionally limited joint.

Takashi Itokawa Makoto Kondo Kazuhide Tomari Miyuki Sato Masashi Hirakawa Katsutoshi Hara Nobuhiro Kaku Y. Higuma T. Noguchi H. Tsumura

Introduction: Appropriate femoral component alignment is important for long-term survival of total knee arthroplasty (TKA). Valgus angle of femoral component is recommended as the angle between mechanical axis and anatomical axis of the femur. Intramedullary guide system is widely used for determining the valgus positioning of femoral component. Entry point of intramedullary guide is one of the key factors for determining valgus angle of femoral component. Some investigators have shown appropriate entry points of intramedullary guide, however, it is still unclear. In this study, appropriate entry point of intramedullary guide system was calculated using three-dimensional digital templating software “Athena” (Soft Cube, Osaka, Japan).

Method: Forty-one knees in 34 osteoarthritis patients except valgus deformity (30 females and 4 males, mean age 75.1 years) received TKA and were simulated using “Athena” from January 2009 to March 2009. All cases were grade III or IV in Kellgren-Lawrence index. Radiograph and CT scan image were used for determination of appropriate entry point of femur using “Athena”. The anatomical axis of femur was defined as a line connecting the midpoints of femoral AP and lateral diameter, at 60 mm and 110 mm proximal to the center of intercondylar notch. Two coordinate systems were configured as representation of entry points. One was at the center of intercondylar notch defined as the point of origin in axial view of CT image and the line parallel to the clinical epicondylar axis (cTEA) defined as X-axis. Another coordinate system was the same point of origin but parallel to the line between trochlear groove and the center of intercondylar notch (AP line) defined as Y-axis.

Result: In the coordinate system that defined the cTEA as the X-axis, the average of entry point was 0.3± 0.30 mm medial (range, −4.8~ 4.7mm) and 11.6 ± 0.52mm anterior (range, 3.1~ 16.5mm) to the center of intecondylar notch. In the other coordinate system that defined AP line as the Y-axis, the average of entry point was 2.6± 0.29 mm medial (range, −1.5~ 6.3mm) and 11.2±0.52 mm anterior (range, 2.8~ 16.0mm) to the center of intercondylar notch.

Discussion: In this study, the appropriate entry point of intramdullary guide was slightly medial and about 11mm anterior to the center of intercondylar notch on average. However, individual entry point varied considerably in distance. These data indicates that it is important to simulate the appropriate entry point of intramedullary guide in preoperative planning.

WL Walter A. Shimmin

Reasons for failure of hip resurfacing arthroplasty include femoral neck fracture, loosening, femoral head osteonecrosis, metal sensitivity or toxicity and component malpositioning.

Patient factors that influence the outcome include prior surgery, body mass index, age and gender, with female patients having two and a half times greater risk of revision by 5 years than males 14. In 2008, the Australian National Joint Replacement Registry (ANJRR) reported poorer results with small sizes, whereby component sizes 44mm or less have a five times greater risk of revision than those 55mm or greater 1. This finding is true for both males and females and after accounting for femoral head size, the effect of gender is eliminated.

We explore the relationship between component size and the factors that may influence the survivorship of this procedure, resulting in higher revision rates with smaller components.

These include femoral neck loading, edge loading, wear debris production and the effects of metal ions, cement penetration, component orientation, and femoral head vascularity. In particular the way the components are scaled from the large sizes down to the smaller sizes results in some marked changes in interactions between the implant and the patient.

Wall thickness of the acetabular and femoral component does not change between the large and small sizes in most devices. This results in a relative excessively thick component in the small sizes. This may cause more acetabular and femoral bone loss, increased risk of femoral neck notching and relative undersizing of the component where acetabular bone is a limiting factor. Stem thickness does not change throughout the size range in many of the devices leading to relatively more femoral bone loss and a greater stiffness mismatch between the femoral stem and the bone. Relatively stiffness between the femoral stem and the bone is up to six times greater in the small size compared to the large size in some designs.

The angle subtended by the articular surface (the articular arc) ranges from 170° down to as low as 144° in the small sizes of some devices. A smaller articular arc increases the risk of edge loading, especially if there is any acetabular component malpositioning. Acetabular inclination has been related to metal ion levels 5 and to the early development of pseudotumour6.

An acetabular component with a radiographic inclination of 45° will have an effective inclination anywhere from 50° to 64° depending on the type and size of the component. This corresponds to a centre-edge angle from 40° down to 26°. The effective anteversion is similarly influenced by design.

The result of a smaller articular arc is to reduce the size of the ‘safe window’ which is the target for orthopaedic surgeons.

Jean-Noel A. Argenson Sebastien Parratte Jean-Manuel Aubaniac

Improving the adaptation between the implant and the patient bone during total hip arthroplasty (THA) may improve the survival of the implant. This requires a perfect understanding of the tridimensional characteristics of the patient hip. The perfect evaluation of the tridimensional anatomy of the patient hip can be done pre-operatively using CT-scan and in case of important hip deformation, a custom implant can be used. When this solution is not available, modular necks may be a reliable alternative using standard x-rays and intraoperative adaptation. We aimed to evaluate:

The usefulness of modular neck to restore the anatomy of the hip and

the short-term clinical and radiological results of a consecutive series of THA using modular neck.

We prospectively included 209 hips treated in our institution with a modular neck total hip arthroplasty between January 2006 and December 2007. All patients underwent a standard xrays evaluation in the same center according to the same protocol. Pre-operatively, the frontal analysis of the hip geometry was performed and the optimal center of rotation, CCD angle, neck length and lever arm was analyzed to choose the optimal modular neck shape among 9 available shape. These 9 frontal shapes are available in standard, anteverted or retroverted shapes, leading to 27 potential neck combinations. The mean patient age was 68 years and the mean BMI 26 Kg/m2 All the procedures were performed supine using a Watson-Jones approach and the same anatomic stem. Intra-operatively the sagittal anatomy of the hip was analyzed and a standard, ante or retro modular necks were tested for the frontal shape defined pre-operatively.

According to the pre-operative frontal planning, nonstandard necks were required in 24 % of the cases to restore the anatomy of the hip. Intra-operatively, a sagittal correction using anteverted neck was required in 5% of the cases and retroverted necks in 18% of the cases.

Harris hip score improved from 56 to 95 points at last follow-up. No leg length discrepancy greater than 1 cm was observed. Restoration of the lever arm (mean 39.3 mm, range 30 to 49 mm) and of the neck length (55.2, range 43 to 68 mm) was adapted for 95% compared to the non operate opposite side. No loosening was observed.

According to our results modular neck combined are useful and reliable to restore optimal hip geometry and in this series 25% of the patient would have had imperfect extra-medullary hip geometry with a standard prosthesis. The good clinical and radiological short-term results should be confirmed at longer follow-up.

J.M.S. Lamvohee R. Mootanah P. Ingle J.K. Dowell K. Cheah

Cemented total hip replacements (THR) are widely used and are still recognized as the gold standard by which all other methods of hip replacements are compared. [1]. Long-term results of cemented total hip replacements show that the revision rate due to aseptic loosening could be as high as 75.4% [2]. Moreover, high stresses developed in the cement mantle of reconstructed hips can lead to premature failure of the constructs [3]. Surgical fixation techniques vary considerably [4]. The aim of this study was to investigate the performances of different surgical fixation techniques of hip implants for patients with different body mass indices, bone morphology and bone quality, using finite element (FE) methods.

Anatomically correct reconstructed hemi-pelves were created, using CT-Scan data of the Visible Human Data set, downloaded to Mimics V8.1 software, where poly-lines of cancellous and cortical bones were created, and exported to I-Deas 11.0 FE package, where the econstructed hemi-pelvis was simulated. Accurate 3D model of the hemi-pelvis was scaled up and down to create hemi-pelves of acetabular sizes of the following diameters: 46 mm, 52 mm, and 58 mm. Following sensitivity analyses, element sizes ranging from 1–3 mm were used. Material properties of the bones, implants and cement were taken from literature [57]. Bones of poor quality were simulated by a reduction in the elastic modulii of the cortical bone by 50%, the cancellous bone by 10 % and the subchondral bone by 50% [5]. The nodes at the sacro-iliac joint areas and the pubic support areas were fixed. A compressive force of 3 times body weight was simulated at the hip joint. The nodes between the cancellous and subchondral bones were merged. Contact elements were used at the subchondral bone and cement mantle interface and between the femoral head implant and acetabular component. Dynamic in vitro tests, simulating forces acting on a hip joint during a gait cycle, were carried out on reconstructed synthetic bones, positioned on an Instron 8874 hydraulic machine, to verify the FE models.

The volume of cement stressed at different levels in groups of 0–1 MPa, 1–2 MPa and up to 11 and above MPa were calculated. Results of FE analyses showed that

an increase in the body mass index from 20 to 30 generated an increase in the tensile stress level in the cement mantle;

lower tensile and shear stresses developed in thicker cement mantles. For a 46mm acetabular size, peak tensile stresses decreased from 10.32MPa to 8.14MPa and peak shear stresses decreased from 5.36MPa to 3.67MPa when cement mantle thickness increased from 1mm to 4mm.

A reduction in the bone quality would result in an increase of approximately 45% in the cement mantle stresses.

Results of in-vitro tests show that an increase in the cement mantle thickness improved fixation, corroborating with the FE results.

Performances of fixation techniques depend on the patient’s bone mass index, bone quality, bone morphology.

B. Grimm T. Boymans I.C. Heyligers

Introduction: In total hip arthroplasty (THA) an optimal fit and fill of the stem is essential for stable fixation. Thus femur morphology must be studied during pre-op planning (implant choice, sizing, positioning) or when a new stem is to be designed. Using plain AP x-ray analysis and the definition of a simple two-level parameter (canal flare index, CFI), Noble et al. identified an age related transition of the endosteal canal in AP view from a ‘champagne flute’ to a ‘stove pipe’. This reference data is 2D only, limited to the endosteal geometry and the elderly age range was defined as 60–90yrs so that the number of octogenerians > 80yrs was too low to analyze morphological features of this rapidly growing and critical THA patient population.

In this study the endosteal and periosteal femur morphology of subjects > 80yrs was studied using 3D CT analysis. It was the goal to

describe age related changes of the femur morphology in 3D,

to study the influence of gender

to investigate if the results may affect fit & fill of current stem designs.

Methods: High-resolution CT-scans (slice thickness 1mm) were made of 170 consenting volunteers (m/ f=101/69). The old group consisted of 119 subjects ≥80yrs (m/f=65/54, mean age: 84.1yrs [80–105]) and the young group of 51 subjects < 80yrs (m/f=36/15, mean age 67.8yrs [39–79]). After thresholding the bone boundaries in Mimics V12 (Materialise, B), the endos-teal and periosteal coordinates were analyzed for width, wall thickness, surface areas and various CFI’s relating dimensions at 20mm above LT and at a distal level (e.g. 60mm below LT, isthmus): Surface CFI (3D-CFI), frontal and lateral CFI based on the AP and ML projections (2D-CFI) and flaring in each of the four directions (1DCFI).

Results: The surface CFI was sign. lower in subjects ≥80yrs (5.08 ±1.23) than in subjects < 80yrs (6.61 ±1.72, p< 0.0001). This difference was sign. larger in females than in males (−32% vs. −17%), an observation valid with reference to any distal level. Equivalent age differences were found in both the frontal and lateral 2D-CFI as well as the medial, lateral and anterior 1D-CFI with changes in the anterior direction (−26.3%) being most dominant. In addition wall thickness was sign. reduced in the very elderly. E.g. at 20mm above LT, the medial wall measured 10.40mm at < 80yrs and 7.61 at ≥80yrs, a reduction of −27% (p< 0.001). In females (−35%) this difference was sign. larger (males: −23%, p< 0.001) even when corrected for height.

Discussion: The age driven transition of proximal femur morphology continues in the octogenarian population. This transition is not limited to two discrete levels in the AP plane as previously reported but it is a continuous 3D phenomenon with high directional asymmetry. In addition, this transition also affects the wall thickness and the periosteal shape. Furthermore a strong gender effect was identified with aging females showing increasingly and asymmetrically less flaring and thinner walls. An age and gender specific THA stem design seems necessary to fit the morphed femur. The asymmetric transition prohibits the effective use of current implant systems with proportionally scaled dimensions but favors a matrix sizing scheme with frontal and lateral dimensions changing independently.

T.M. Ecker C. Robbins G. van Flandern D. Patch S.D. Steppacher W. Kurtz B.E. Bierbaum S.B. Murphy

While alumina ceramic-ceramic THA has been performed in the US for more than 12 years, the phenomenon of frequent, clinically reproducible squeaking is relatively new. The current study investigates the influence of implant design on the incidence of squeaking.

We reviewed implant information on 1275 consecutive revision THAs performed from 10/2002 through 10/2007 to identify any patients who had complained of squeaking or grinding. We also identified, 2778 consecutive primary ceramicceramic THA. Of these, we reviewed the clinical records of 1,039 patients (37%) to date. Any patient complaint of squeaking or grinding at the time of an office visit or by phone interview was recorded. Hips were divided into group 1: flush mounted ceramic liner; group 2a: recessed ceramic liner mated with a stem made of TiAlV and using a 12/14 neck taper; and group 2b: recessed ceramic liner mated with a stem made of a beta titanium alloy comprised of 12% molybdenum, 6% Zirconium, and 2% Iron and using a neck taper smaller than a 12/14 taper.

Of the revision THAs, 5 hips (0.4%) were in patients who had complained of squeaking or grinding. All 5 hips had a recessed, metal-backed ceramic liner and evidence of metallosis. In primary THAs, Group 2b had statistically significantly (p=0.04) more squeaking (7.6%) than group 2a (3.2%) which had statistically significantly (p=0.002) more squeaking than group 1 (0.6%).

Squeaking following ceramic-ceramic THA is associated with use of a recessed metal-backed ceramic liner in combination with a femoral component made of a betatitanium alloy and using a relatively small head-neck taper. Since all revised hips in our study had metallosis, it is possible that metal debris is adversely affecting the bearing and that the elevated metal rim combined with a small head neck taper and the beta-titanium alloy contribute to this problem. Use of bearings with a flush-mounted ceramic liner mated with femoral components made of TiAlV and using a 12/14 taper appears to be prudent.

S.D. Stulberg T.C. Moen R. Ghate N. Salaz

Originally introduced in 1997, porous tantalum is an attractive alternative metal for orthopaedic implants because of its unique mechanical properties. Porous tantalum has been used in numerous types of orthopaedic implants, including acetabular cups in total hip arthroplasty. The early clinical results from porous tantalum acetabular cups have been promising. The purpose of this study was to evaluate the presence of bone ingrowth and the incidence of osteolytic lesions in the acetabular cup -at 10 year follow up – in patients who had a total hip arthroplasty with a monoblock porous tantalum acetabular cup.

50 consecutive patients underwent a total hip arthroplasty with a monoblock porous tantalum acetabular component. All patients had computed tomography at an average of 10 years of follow-up. The computed tomography scan used a standard, validated protocol to evaluate bony ingrowth in the cup and for the presence of osteolysis.

The computed tomographic scans showed evidence of extensive bony ingrowth, and no evidence of osteolysis.

This study reports the 10-year results of a monoblock porous tantalum acetabular cup. This is the first study to evaluate a porous tantalum acetabular cup with the use of computed tomography. These results show that a porous tantalum monoblock cup has excellent bony ingrowth and no evidence osteolysis at 10 year follow-up. These results suggest that porous tantalum is an attractive material for implantation in young, active patients.

S.C. Wollera K. Bertinc S.M. Stevensa K. Samuelson J. Hickman R. Hanseen R.S. Evans J.F. Lloyd P. Dechet C.G. Elliotta

Current orthopedic practice requires consideration of apparently contradictory recommendations regarding VTE prevention among THR/TKR patients. American College of Chest Physicians (ACCP) 8th Clinical Practice Guidelines for the Prevention of Venous Thromboembolism recommend against aspirin for VTE prophylaxis in any patient1. The American Academy of Orthopedic Surgeons (AAOS) Guideline recommends pulmonary embolism risk stratification, then implementation of one of many possible courses including the use of aspirin2.

We conducted a prospective observational study among consecutive patients presenting for total hip or knee arthroplasty. Pre-operative PE risk stratification was performed at the discretion of the surgeon. Patients identified as usual risk for PE received aspirin. Patients considered being at elevated risk for PE received warfarin. This observational study protocol called for one year of data collection. At approximately 8 months 656 patients were enrolled, and the surgeon principally implementing PE risk stratification and administration of aspirin chose to stop enrolling patients due to a high incidence of pulmonary emboli. One hundred fifty five patients received thromboprophylaxis with aspirin 600 mg PR in the PACU, then 325 mg BID for one month (reduced to 81 mg daily if GI symptoms were present). The remaining 501 patients received an ACCP-based warfarin protocol managed by a pharmacist anticoagulation management service.

Our hypothesis is the null hypothesis; that an AAOS-based approach to hromboembolism prevention is not inferior to an ACCP-based approach. The a priori primary endpoints of the AVP Study are clinically overt VTE, DVT, PE, major bleeding, and death. All patients will receive a 90 day follow-up questionnaire in person or by telephone. Additionally, the electronic medical record of Intermountain Healthcare will be interrogated for ICD-9 codes germane to the outcomes of interest.

Ninety day follow-up has been completed for approximately 140 patients. The dataset will be locked upon completion of the 90 day follow-up among those patients who last received PE risk stratification and aspirin therapy (data lock early June, 2009). We anticipate preliminary data available for report by July, 2009.

J.J. Wu Q.Q. Wang I. Khan

Orthopaedic grade ultra-high molecular weight polyethylene (UHMWPE) remains the preferred material for one of the bearing surfaces in total joint prostheses because of its high wear resistance and proven biocompatibility. Since the 1970s, UHMWPE has served as the only widely used bearing material for articulation with metallic components in total knee arthroplasty (TKA). However, polyethylene-related total knee failures have limited the lifetime of total knee joint replacements. The present study is focused on improving material integrity and reducing the probability of material failure. The hypothesis examined here is that there is a correlation between material failure of UHMWPE knee-joint components and the precise time-temperature history employed during fabrication, due to their strong effect on interparticle cohesion. The presence of fusion defects due to incomplete consolidation and incomplete polymer self-diffusion has been implicated in the failure of UHMWPE joints [1, 2]. Computer-aided methodology used in this study allowed quantitative prediction and optimisation of the extent of interparticle cohesion to ensure that inter-particle boundaries are of high integrity during moulding [3]. The current study has investigated the correlation between inter-particle cohesion governed by reputation theory and wear performance.

We have investigated the wear performance of direct compression moulded UHMWPE plates with different degree of inter-particle diffusion. Direct compression moulding was used in the present study because of its uniformly excellent surface finish which is better than machined surfaces. UHMWPE plates (44×24×3mm) were direct compression moulded using GUR1050 powder (Ticona). Various moulding temperature (e.g. 145°C, 150°C, 175°C) and dwell time (e.g. 15mins and 30mins) were investigated.

The wear tests were carried out at 37°C using a Durham four-station multidirectional pin-onplate machine, which generates both reciprocating and rotating motions simultaneously. The material combination of the flat-ended metallic indentors loaded against UHMWPE plates was constructed to mimic conformal contact conditions in knee prostheses. The articulating surfaces were lubricated using 25% diluted bovine serum. Meanwhile the experimental method was validated by evaluating the wear generation under the conventional configuration (i.e. UHMWPE pins on metal plates); results were comparable with the data in the literature [4].

For the direct compression moulded UHMWPE plates, experimental wear factors were determined and found to correlate well with numerically calculated degree of inter-particle diffusion. Increasing moulding temperature and dwell time decreased the wear factors and increased inter-particle diffusion. Surface structures were characterised before and after every 0.5 million cycles. The observed surface features on UHMWPE plates in ESEM and optical microscopy is very similar to those in retrieved knee prostheses [5] and those found in our own recent work with knee wear simulator testing.

M Odumenya M L Costa S J Krikler N Parson J Achten

Purpose of Study: To identify the functional outcome, quality of life and prosthesis survivorship in patients who have undergone the Avon patellofemoral arthroplasty at an independent centre.

Method and Results: Sixty-three patellofemoral arthroplasty (PFA) procedures were undertaken on 44 patients between May 1998 to May 2007. The primary and secondary outcome measures were knee function and quality of life, respectively. These outcomes were determined using the Oxford Knee Score (OKS) and EQ-5D and visual analogue score. Out of the forty-four patients 6 were deceased and 6 were lost to follow-up.

Therefore, thirty-two patients (50 PFAs) were included; nine males and 23 females.

Seventeen patients had bilateral PFA. The mean age of the patients was 65.8 years (SD 9.2). Follow-up averaged at 5.34years (range 2.1–10.2years) (SD2.64). The Oxford Knee Scores in this population showed a bimodal distribution. One group centred around 35 and the other around 60. The median Oxford knee score was 42.5 (IQR 34.25 to 54.25). Two sample t-test analysis of the population, divided as those above and below an OKS of 42, showed that follow-up time and age, did not differ between the groups (p=0.325, p=0.255 respectively). The quality of life outcome scores were significantly lower for bilateral compared to unilateral patients, with median scores of 50 and 72.5 respectively (p=0.03829). The cumulative survival at 5years for those with minimum 5 year follow-up (32 out of 50 PFA) was 100%. Three knees in total were revised. One patient developed bilateral tibiofemoral osteoarthritis, requiring revision to total knee replacement (TKA) at seven and 10 years. Another had persistent anterior knee pain and was converted to a TKA.

Conclusion: The Avon patellofemoral arthroplasty provides good functional outcome. The survivorship rate is promising although longer follow-up is required. Prudent patient selection is needed avoid high rates of revision to TKA.

S. Takai N. Shimazaki N. Nakachi H. Mitsuyama Y. Konaga T. Matsushita N. Yoshino

Purpose: The effect of patellar position on soft tissue balancing in total knee arthroplasty (TKA) is under debate. We developed the digital tensor system to measure the load (N) and the distance (mm) of extension and flexion gaps in medial and lateral compartment separately with setting of femoral component trial. The gap load and distance in extension and flexion position of posterior stabilized (PS) and cruciate retaining (CR) TKA in both patella everted and reset position were measured.

Materials and Methods: Thirty-four patients who underwent primary TKA for medial type osteoarthritis using medial parapatellar approach were included. The load was measured at the gap distance, which is equal to the sum of implants including polyethylene insert.

Results: In extension, there was no significant difference between the load in patella everted and reset position in both PS-TKA and CR.-TKA. In flexion, there was a significant decrease of the load, which is comparable to the increase of gap distance of approximately 2mm, by resetting the patella from eversion in PS-TKA.

There was, however, no significant difference in CR-TKA by resetting the patella.

There was no significant difference in the ratio of medial/lateral load in both PSTKA and CR.-TKA.

Conclusion & Significance: Soft tissue balancing of PS-TKA with medial parapatellar approach should be performed after resetting the patella.

M.A. Baldwin C. Clary L.P. Maletsky P.J. Rullkoetter

Design phase evaluation of potential implant designs requires verified computational and experimental models. Computational models are important where parametric evaluation of geometric features experimentally is both cost and time-prohibitive due to the need to manufacture complex parts, and provide information not easily measured experimentally, such as internal stresses/strains in the implant or bone.

However, before implementation into the design process, a thorough verification/validation is required. In this study, a finite element model of the Kansas knee simulator (KKS) was developed and a systematic verification of predicted joint kinematics was performed by comparison with experimental measurements, including evaluating the patellofemoral joint first in isolation, followed by whole joint kinematic comparisons.

Four unmatched, healthy cadaver knees (average age 63 yrs) were mounted in the KKS to reproduce a simulated gait and deep knee bend activity in their natural and implanted states. Finite element models of the KKS assembly and the four cadaver specimens in their natural and implanted states were created. Isolated patellofem-oral kinematics were initially verified during simulated deep knee bend. Average RMS differences between predicted and experimental natural patellar kinematics were less than 3.1° and 1.7 mm for rotations and translations, respectively, while differences in implanted kinematics were less than 2.1° and 1.6 mm between 10 and 110° femoral flexion. Similar agreement was found with the subsequent whole joint simulations.

Deep knee bend tibiofemoral internal-external (IE) and varus-valgus (VV) rotations had average RMS differences from experimental measurements of 1.5 ± 0.4° and 0.9 ± 0.5°, respectively. Anterior-posterior (AP), inferior-superior (IS) and medial-lateral translations matched within 1.8 ±0.8 mm, 1.2 ±0.7 mm, and 0.6 ±0.1 mm, respectively.

The experimental and verified computational tools can be used in harmony for pre-clinical assessment of implant designs; the computational model allows rapid screening of implant geometry or alignment issues and provides additional insight into joint mechanics such as implant stresses or bone strains, while the experimental simulator can subsequently be utilized to assess in cadavera only the most promising designs or features identified.

J H Lonner T John M A Conditt

Bicompartmental arthritis involving the medial and patellofemoral compartments of the knee is a common pattern that has often been treated with total knee arthroplasty.

However, the success of unicompartmental and patellofemoral arthroplasty for unicompartmental arthritis, as well as an interest in bone and ligament conservation for earlier stages of arthritis, has led to an interest in bicompartmental arthroplasty. The purpose of this study is to review the clinical, functional, and radiographic results of modular bicompartmental arthroplasty.

Twelve consecutive modular bicompartmental arthroplasties, using separate contemporary unicompartmental tibiofemoral and patellofemoral prostheses, were performed by the senior author. Clinical and functional data including range of motion (ROM), WOMAC and Knee Society (KS) scores were collected pre-operatively and post-operatively at 6 weeks, 12 weeks and annually. Radiographs were taken preoperatively and at the 6 week and annual postoperative visits. The average patient age at the time of surgery was 63 (range, 47 to 72); seven patients were women.

At most recent follow-up, the mean knee ROM improved from 100 degrees of flexion pre-operatively (range, 90 to 110) to a mean of 126 degrees of flexion (range, 115 to 130) (p < 0.0001). Improvements in WOMAC scores were statistically significant (p = 0.02). Statistically significant improvements in Knee Society scores were also observed (p = 0.03). No radiographs showed evidence of loosening, polyethylene wear or progressive lateral compartment degenerative arthritis. There were no complications in the peri-operative period.

Modular bicompartmental arthroplasty is an effective method for treating arthritis of the knee restricted to the medial and patellofemoral compartments. Early results using contemporary prostheses are encouraging and should prompt further mid-and long-term study.

Sung-Do Cho Yoon-Seok Youm Chang-Yun Jung Chang-Ho Hwang

The purpose of this double-blinded prospective study was to evaluate the effectiveness of electromyography (EMG)-guided preoperative femoral nerve block (FNB) for postoperative analgesia in total knee arthroplasty (TKA).

Forty knees of primary TKA by one surgeon were included in our study. One doctor performed a single injection FNB with an EMG guide in EMG group (23 knees) and with a blind maneuver in control group (17 knees). The same 10ml of 0.375% ropivacaine was injected in both groups. Same postoperative rehabilitation protocol was applied to all patients. Continuous passive motion was started at postoperative 1st day and weight bearing was started as soon as possible.

Intravenous patient-controlled analgesics which contained 30mg of morphine were used until postoperative 72 hours and no additional intravenous, intramuscular or oral analgesics were used. Pain was evaluated by Visual Analogue Scale (VAS) and Postoperative Pain Score (PPS) at postoperative 4, 24, 48 and 72 hours. The amount of opioid consumption and complication were compared between two groups. VAS score was 6.8 in EMG group and 8.0 in control group at postoperative 4 hours, 6.2 and 7.1 at postoperative 24 hours, 5.3 and 5.9 at postoperative 48 hours, and 4.6 and 5.7 at postoperative 72 hours, respectively. PPS was 2.2 in EMG group and 2.2 in control group at postoperative 4 hours, 2.1 and 2.1 at postoperative 24 hours, 1.6 and 1.7 at postoperative 48 hours, and 1.4 and 1.6 at postoperative 72 hours, respectively. The amount of opioid consumption was 6.0mg in EMG group and 7.2mg in control group during postoperative 24 hours, 2.7mg and 3.2mg during postoperative 24–48 hours, and 1.7mg and 3.2mg during postoperative 48–72 hours, respectively. There was no complication in either group.

Pain tended to decrease more in EMG group than control group, especially VAS at postoperative 4, 24 and 72 hours (p< 0.05). The demand of opioid was significantly smaller in EMG group during postoperative 24 hours and 48–72 hours (p< 0.05). EMG-guided single FNB before TKA allowed better postoperative pain relief and reduced the demand of pain killer.

David J. Covall Bernard Stulberg Jay Maybrey

Introduction: The Posterior Cruciate Referencing Technique (PCRT) for total knee arthroplasty (TKA) uses innovative instrumentation and tibial inserts with varying posterior slopes, and is designed to maximize motion and stability in cruciate-retaining knees, while preserving bone and ligament integrity. This study evaluated early clinical results for this technique.

Methods: An IRB-approved, retrospective, single-site, single-surgeon study was conducted in 2009. 50 patients were put into two groups: Group 1 included patients undergoing CR TKA using standard technique and implants and Group 2 included patients undergoing CR TKA using PCRT. Demographics, surgical time, length of stay (LOS), range of motion, and Oxford Knee Scores (OKS) were collected.

Results: Data sets were complete on 41 patients. Follow-up averaged 14 months for Group 1 and nine months for group 2. Both groups had a mean age of 66.4, were 51% female, and had an average BMI of 30.6. LOS was 1.25 days for Group 1 and 1 day for Group2 (p=0.011). Surgical time was 48 minutes for Group 1 and 46 minutes for Group 2 (p=0.184). Average flexion was 118° for Group 1 and 123° for Group 2 (p=0.073). OK S were 92–94% good and excellent with a mean of 20.4 for both groups.

Conclusions: The learning curve for PCRT and the associated instrumentation and implants did not adversely affect clinical results. Instead, the data indicated a small savings in surgical time and a moderate, but not statistically significant, increase in flexion. LOS, however, was significantly shortened. PCRT may allow for better PCL function while preserving bone and reducing surgical manipulation, and with tibial inserts of varying posterior slopes may improve flexion, stability, and function in CR TKA. Further study is warranted.

AS Ranawat TW Koob JH Koenig HJ Cooper LF Foo HG Potter CS Ranawat

Introduction: Computer-based wear analysis is currently the most accurate method for determining the in vivo wear rates of polyethylene liners during total hip arthroplasty. MRI of a total hip is emerging as the best method for determining the intra-articular volume of particulate debris. The purpose of this study is to determine if there is a correlation between polyethylene wear and the development of particle load in patients with highly crosslinked (HXLP) liners.

Materials and Methods: 20 well-functioning total hips (7 metal heads against HXLP liners and 13 ceramic heads against HXLP liners) in 18 young active individuals were analyzed using the following criteria: femoral head penetration of the liner was measured by Roman (ROntgen Monographic ANalysis) software and particulate load was calculated by MRI criteria as described by Potter et al. Clinical and radiographic analyses were performed using HSS, WOMAC, and criteria defined by DeLee, Charnley, and Engh. The average age of the patients was 57 (Range 45–67) and average follow-up was 1.6 y (range 1.0 – 3.0 y).

Results: All implants appeared well osteointegrated with no radiographic evidence of osteolysis. All patients had well-functioning total hips with a greater than one mile daily walking tolerance. A trend towards correlation was observed between increased polyethylene wear and increased particulate volumes. Average HXLP wear was 0.03 mm (range −0.19 to 0.27 mm) and average particle volume was 841 (range 6951 to 0). One patient in particular recorded 0.27 mm of polyethylene wear, mild particle disease and a particle disease volume of 3321 at 1.6 years follow-up. However, statistical significance could not be achieved with these data points.

Conclusions: There appears to be a relationship between polyethylene wear as measured by computer-based systems and particulate volume as measured by MRI. Limitations of the current methodology include the inability of computer-based systems to detect precise levels of minimal wear with HXLP liners, and the highly sensitive MRI images which may be detecting more than just wear debris.

Bin SHEN Jing YANG Liao WANG Zong-ke ZHOU Peng-de KANG Fu-xing PEI

Objective: Considering the high incidence and misdiag-nostic rate of developmental dysplasia of hip (DDH) in China, some patients suffer from severe pain in the hip at early age, and a total hip arthroplasty would be necessary. To our knowledge, the intermediate-term(equal to or more than five years) results of total hip arthroplasty (THA) in patients with osteoarthritis secondary to developmental dysplasia of the hip has not been studied in China previously. This study evaluated more than five-year clinical and radiographic outcomes associated with total hip arthroplasty (THA) in a consecutive series of patients with osteoarthritis secondary to developmental dysplasia of the hip.

Methods: From February 2000 to July 2002, 55 patients (69 hips) underwent THA in our hospital were involved in this study. Clinical outcomes were evaluated according to Harris evaluate score. Components migration, periprosthetic bone changes, the polyethylene wear rate were measured radiologically. Kaplan-Meier analysis was performed to evaluate the survival of the acetabular and femoral component. End point was obvious radiological loosening or revision either or both of the acetabular and femoral component for any reason.

Results: Forty-five patients (57 hips) were followed up at least 5 years. The average preoperative Harris hip score was (46.19±18.01) points, which improved to (91.78±3.52) points at final follow-up. There were 48 excellent hips (84.21%), 7 good hips (12.28%), 2 fair hips (3.51%) and no poor hip. There is no significant difference of Harris score between the dysplasia group, the low dislocation group and the high dislocation group (P> 0.05, ANOVA). The mean polyethylene liner wear rate was (0.27±0.14)mm/year. According to the statistical relevant analysis, the wear rate of the polyethylene liner had relationship with the age(r=−0.288, P=0.040), the abnormal abduction angle of the acetabular cup (r=0.317, P=0.023)and the osteolysis rate (r=0.573, P=0.026), while had no significant relationship with the thickness of the polyethylene liner (P=0.326), gender(P=0.097), DDH classification(P=0.958) and the Harris score(P=0.598). There are 5 pelvic osteolysis and 8 proximal femoral osteolysis. Using loosening or revision as the end point for failure, the survival rate of both components was 1.0 (95% confidence interval, 0.98–1.00).

Conclusions: In conclusion, improved surgical technique and design in the components provided favorable mid-term results in Chinese patients with osteoarthritis secondary to developmental dysplasia of the hip. Bulk autogenous or allografting is not needed if more than 70% of the acetabular component is covered by host bone. Although the Asia life style includes more squatting and cross-legged, the results of this series in Chinese population are comparable to the satisfactory results of other reported DDH series whose patients are mainly western people. The mid-term results of THA are equivalent in the group of patients with dysplasia, low dislocation, and high dislocation types both in ace-tabular and femoral components. However, the authors continue to be anxious about the high rate of liner wear and osteolysis, which deserve the necessary long-term follow-up.

Y-H Kim J-S Kim W-S Huh K-H Lee

Although total knee arthroplasty (TKA) has been a reliable procedure providing durable pain relief, polyethylene (PE) wear remains a major limitation of the long-term success of TKA. One potential method of lowering PE wear in TKA is to use oxidized zirconium (OxZr)-bearing surface. Although wear simulating testing of an OxZr counter surface of femoral component produced less PE wear and fewer particles than did cobalt-chrome (Co-Cr) counter surface of femoral component [1–4], this finding has not been demonstrated in vivo to our knowledge.

We measured in vivo PE wear by isolating and analyzing PE wear particles in synovial fluid from wellfunctioning TKA [5]. The purpose of the current study was to determine the size, shape, and amount of PE wear particles isolated from synovial fluid of patients who underwent a bilateral simultaneous TKA prosthesis, but different materials of femoral components.

We performed a bilateral simultaneous TKA in 100 patients (200 knees) who received an OxZr femoral component in one knee and a Co-Cr femoral component in the other. Mean age was 55.6 (44–60) years. Synovial fluid was obtained from 28 patients (56 knees) who had undergone a simultaneous bilateral TKA under completely sterile conditions at one or two years after the operation. Randomization to an OxZr or Co-Cr femoral component was accomplished with use of a sealed study number envelope, which was opened in the operating room before the skin incision had been made. After the opening the randomization envelope, the first knee received prosthesis indicated by the envelope (OxZr or Co-Cr component) and the contralateral (second TKA) knee received the other prosthesis (OxZr or Co-Cr component).

All operations were performed by one surgeon using the same design of total knee prosthesis: Genesis II (Smith and Nephew, Memphis, Tennessee). Only the material of the femoral component differed between two groups. The preoperative diagnosis was osteoarthritis in all patients. Preoperative and post operative KS and HSS knee scores, KS functional scores and UCLA activity scores were evaluated.

The amount of polyethylene wear particles in the aspirated synovial fluid sample was analyzed by thermogravimetic analysis (TGA) using a TGA instrument (TGA/SDTA 84le model, Mettler Toledo CO., Greifensee, Switzerland). The weight of the sample solution was measured before and after removing the organic content by heating the sample solution. The sample solution was casted onto petri dishes. The petri dish was covered and kept in a dry oven at 60°C for 2 days. While the sample solution was kept in a dry oven for 2 days, a small hole was made on the cover of the petri dish to allow water to evaporate slowly for 2 days. After this procedure, the cover of petri dish was removed and TGA sample was dried at 60°C for another 2 days. After the sample was completely dried out, the dried sample was measured using analytical balance.

TGA was used to determine the weight change profiles of polyethylene subject to heating under a nitrogen atmosphere. The nitrogen flow rate was kept constant at 50mL per minute. TGA data were taken at heating rate as 5°C per minute in the temperature range of 20° to 1000°C. The weight loss data were recorded as a function of time and temperature using special software in computer. When the temperature reached to the point of decomposition of the sample, the sample started to lose weight. By calculating the weight of the sample around the temperature which led to start to decomposition, real amount of polyethylene in the sample was measured. The size and shape of PE particles were examined using scanning electron microscopy (JSH-6360A model, Jeol Co., Tokyo, Japan). The samples were coated using a platinum sputtering machine for 20 sec.

ANOVA, nonparametric chi square test, nonpaired t-test and Mann-Whitney U-test were used for statistical analyses. Differences of P< 0.05 were considered statistically significant.

Mean preoperative KS (27.5 vs 27.2 points) scores, HSS (51.1 vs 51.2 points) knee scores, KS functional scores (55.4 vs 55.4 points) and UCLA activity scores (2.8 vs 2.8 point) were not significantly different between two groups. Mean postoperative KS (93 vs 92 points), HSS knee scores (90 vs 89 points), KS functional scores (78 vs 78 points), and UCLA activity scores (7.8 vs 7.8) were not significantly different. Mean weight of the polyethylene particles was 0.0219 g (SD, 0.0058) in the Co-Cr femoral component groups and it was 0.0214 g (SD, 0.005) in the OxZr group. This difference was not significant (P=0.711139, paired t-test). The size of particles was not different between the two groups. Also, shape of particles was not different between the two groups.

Under the condition and the duration of this study in this specific group of patients, TKA with OxZr or Co-CR femoral knee component had excellent clinical and radiographic outcomes with no osteolysis. While the wear simulator test in vitro demonstrated significant decrease in PE particles in the knees with an OxZr femoral component, our study in vivo revealed that total particle weight, size, and shape of PE wear particles were similar in the knees with an OxZr femoral component and in those with a Co-Cr femoral component.

William G Ward Joshua Cooper

The presence of an unremovable cemented tibial nail presents a unique challenge for limb salvage reconstructions utilizing a rotating hinge knee. All manufacturers’ designs except Link America incorporate a vertically-oriented rotational channel in the proximal tibia to provide the housing for a rotational axis stem. Such channel placement may be impossible in patients with pre-existing tibial hardware that obliterates the proximal tibial intramedullary canal. The Link America design utilizes a superiorly-projecting rotational stem that articulates with a housing located on the rotational yoke component; however it requires an intramedullary tibial stem for component stabilization. Thus all currently available rotating hinge knees require placement of a stem or a stem equivalent into the tibial intramedullary canal.

We describe a limb salvage case employing a Link America rotating hinge knee with a tibial component incorporating a custom hollow stem in a patient with an unremovable centralized, straight, cemented tibial nail. This reconstruction was required following an intra-articular fracture of a successfully incorporated massive proximal tibial osteoarticular allograft. The allograft had been implanted seven years previously following resection of a proximal tibia osteosarcoma.

This custom device allowed a relatively simple limb salvage reconstruction with good results and only a two day hospital stay.

This custom hollow-stemmed device allowed limb salvage in a situation that otherwise would have required either an amputation or resection of a healed tibial allograft that had successfully incorporated, replacing approximately 50% of the length of the tibia shaft. While rarely required, such an implant can allow a relatively simple and straight-forward functional salvage of an extremity in those patients whose only other choices for limb salvage include much more extensive bone resections and complex reconstructions. The potential for subsequent articular level failure should be considered whenever utilizing an osteoarticular allograft. A cemented, retrograde inserted, intramedullary nail can provide reliable internal fixation of such an allograft. If such fixation is selected, a straight intramedullary nail (as in this case) should be utilized, so that the intramedullary device is centered in the proximal tibia. This will allow for future revision to a total knee with a hollow stemmed tibial component should the need arise.

K. Goto H. Akiyama K. Kawanabe K. Sou T. Nakamura

Poly-L-lactic acid (PLLA) is characterized by its biocompatibility and biodegradability, and is used clinically. In our hospital, we started to use PLLA screws instead of metallic or ceramic screws in the fixation of acetabular bone grafts in total hip arthroplasty (THA) in 1990, because there were concerns about the use of rigid and nonbioabsorble screws, which might contribute to the absorption of the grafted bone and induce metallosis or third-body wear when breakage of the screws occurs. The purpose of this study was to review a series of cemented THA for dysplasia, with structural autograft fixed with PLLA screws. We focused on the survival rate of the acetabular component and radiological change of the grafted bone–socket interface.

This study included 104 consecutive cemented total hip arthroplasties (80 patients) performed between July 1990 and December 1995 in our hospital. All patients were followed over 10 years and reviewed retrospectively. The grafted bone trimmed from the excised femoral head was fixed rigidly with 1 or 2 PLLA screws (cancellous lag screws 6.5 mm in bore diameter and 4.1 mm in grove diameter) (Fixsorb; Takiron Co., Ltd., Osaka, Japan).

X-ray photographs taken just after the primary operation showed an obscure but still visible radiolu-cent region corresponding to the inserted PLLA screws in many cases.

However, X-ray photographs at the final follow-up showed an unclear radiolucent zone at the sites of the PLLA screws, and the osteosclerotic line surrounding the site where the radiolucent zone had been found was confirmed in only 4 cases. Bone union was confirmed radiologically at the grafted site in every case, and there were no cases of early collapse or extravasation of the grafted bone. No positive resorption of the grafted bone was observed in any case. Kaplan–Meier survivorship analysis of socket revision, radiological loosening of the socket, and the appearance of a radiolucent line > 1 mm in the graft–socket interface as the endpoints indicated survival rates of 99%, 97.1%, and 63.5% at 10 years, and 96.6%, 90.2%, and 56.1% at 15 years, respectively.

The results of this study indicated that PLLA screws are safe and useful for the fixation of acetabular bone graft concomitant to cemented THA with a careful rehabilitation program. However, because of concern about the mechanical insufficiency of the PLLA screws for THA with an early weight-bearing rehabilitation program, we have used mechanically stronger and bioabsorbable screws made of forged composites of hydroxyapatite and PLLA since 2003.

D.A. Dennis R.H. Kim D.R. Johnson B.D. Springer T.K Fehring P.J. Rullkoetter P.J Laz M.A. Baldwin

Introduction: Patellar crepitus (PC) has been reported in 13% of cruciatesubstituting total knee arthroplasty (TKA) patients resulting from synovial tissue impingement within the femoral component intercondylar box (IB). Patient factors, component design, and technical errors have been implicated in PC. We compared primary TKA patients with PC requiring surgery against matched controls to identify significant variables.

Methods: The databases of 2 institutions were reviewed to identify patients requiring surgery for PC. A control group matched for age, sex, and BMI was identified.

Patient charts and radiographs were reviewed. Statistical analysis was performed.

Significant variables associated with patient anatomy, implant size and alignment were subsequently investigated in a computational model to evaluate tendofemoral contact.

Results: Between 2002 and 2008, over 4000 primary TKAs were performed using the Press Fit Condylar Sigma (DePuy, Warsaw, Indiana) TKA. Of these, 59 knees developed PC requiring surgery. The mean time to presentation was 10.9 months. The incidence of PC correlated with greater number of previous surgeries (1.18 vs. 0.44, p= 0.002), decreased patellar button size (35.7 vs. 37.1mm, p=0.003), shorter patellar tendon length (54.5 vs. 57.9mm, p=0.01), and increase in posterior femoral condylar offset (1.27mm vs. 0.17mm, p=0.022). Using a patellar component of 32 or 35mm significantly increased the risk of PC compared to the use of a 38 or 41mm component (p< 0.01, RR=1.61, OR 2.63). Modeling results demonstrated decreased patellar tendon length created increased tendofemoral contact near the IB, while larger buttons increased separation between the tendon and the box edge.

Conclusion: Shortened patellar tendon length and use of smaller patellar components may expose the quadriceps tendon to increased irritation as it traverses across the femoral component IB. Increasing posterior femoral offset may increase quadriceps tendon tension, further risking synovial tissue impingement within the IB.

A. Kinbrum A. Unsworth

Particulate debris created during a fiber-filled PEEK material (MOTISTM) rubbing on a ceramic femoral head in a hip wear simulation study was characterized. The particles were cleaved from the protein lubricant with a double enzymatic protocol and then sized using two different techniques. The sizes obtained were verified using an AFM imaging technique.

Many metal-on-UHMWPE joints ultimately fail due to late aseptic loosening. This occurs due to the particulate debris built up in the periprosthetic area. The body’s natural immunological response leads to bone resorption, the prosthesis becomes loose and severe pain can then necessitate revision. It is therefore important to characterize the wear particles of novel materials in order to understand their biological impact.

Particles were generated in a Durham hip wear simulator from a MOTISTM acetabular cup articulating against a ceramic femoral head for 25 million cycles1. The samples were generated in 500 ml of bovine serum lubricant (17 g/l protein) and a 10 ml sample of this lubricant was analyzed.

A double enzymatic protein cleavage protocol was used as it was shown to be the least harmful to the particles.

A bi-modal distribution of sizes was seen with a large number of particles of 100 nm and a large number at the two micron size range. AFM results verified the size of the particle distribution and also showed that the smaller particles were round to oval and the larger particles were long and thin. No carbon fibers were evident in the AFM images. Although the wear rate over the 25 million cycles1 remained low and linear, the average particle size tended to increase over the 25 million cycles whilst the volume of the particles decreases over the period.

Howling2 studied particle debris from a pin-on-plate carbon fiber reinforce PEEK against ceramic test using a 6M KOH protocol and resin embedded TEM analysis.

This method only allowed around 100 particles to be imaged at a time, no size distribution was given. Ctyotoxicity was also tested using U937 monocytic cells indicating that MOTISTM has no cytotoxic effects such as necrosis.

J. Chouteau J.L. Lerat R. Testa B. Moyen M.H. Fessy S.A. Banks

Mobile-bearing total knee arthroplasty was developed to provide low contact stress and reasonably unrestricted joint motion. We studied the results of a cementless, posterior cruciate ligament (PCL)-retaining total knee arthroplasty (TKA), with a mobile-bearing insert in rotation and anterior-posterior (AP) translation (Innex® Anterior-Posterior Glide, Zimmer).

Kinematic analyses were performed on a series of 51 primary TKA. The patients’ mean age was 71±8 years at operation. Patients were studied at 23 months average follow-up with weight-bearing radiographs at full-extension, 30° flexion and maximum flexion (“lunge” position). Three dimensional position and orientation of the mobile-bearing relative to the femoral and the tibial component during flexion were determined using model-based shapematching techniques.

The average weight-bearing range of implant motion was 110°±14°. In flexion, the mobile-bearing was internally rotated 3°±3° with respect to the femoral component (p< 0.0001) and the tibial tray was internally rotated 5°±7° with respect to the mobile-bearing (p< 0.0001). On average, the mobile-bearing did not translate relative to the tibial base plate from full extension to 45° flexion [0±2 mm (range −5 mm to 6 mm)]. However, the mobilebearing did translate anteriorly 1±2 mm (range −2 mm to 9 mm, p< 0.0001) between 45° flexion and maximal flexion.

We conclude that the mobile-bearing insert showed a progressive increase in internal rotation during flexion. Most of this rotational mobility occurred between the mobile insert and the tibial base plate. With flexion, AP translation did occur between the femoral component and mobile-bearing, and between the mobile-bearing and tibial base plate, but mobile-bearing translation was unpredictable with this unconstrained design.

M. El Hachmi M. Penasse JP. Forthomme

The clunk syndrome is a rare complication of the posterostabilized total knee arthroplasties.

In the literature, there is a lot of aetiologies described concluding to a multifactorial disease.

The aim of our study is to analyse the risk factors described in the literature in a serie of clunk syndrome occurring in three different prosthesis.

We retrospectively analyzed all our cases of clunk syndrome. We compared radiographic values before and after the intervention: the Insall-Salvati ratio, the joint line modification, the thickness of the patella and position of the tibial tray. We compared the appearance of the clunk in three different types of new generation prosthesis: Scopio NRG (Stryker), Legacy (Zimmer) and Sigma (DePuy). The bone scan was done preoperatively to confirm diagnosis.

There are four cases of clunk in each group of prosthesis which represents an mean incidence of 0,5 %. All the clunks occurred in female patients. There is three bilateral cases and one homolateral recurrence. We find no difference in the preoperative values compared to the postoperative status. There is no difference between the three groups. The bone scan was done in eight cases and returned positive in seven cases.

All our cases of clunk syndrome occurred in female patients which is our first risk factor. Doing a clunk syndrome on one side is a great risk factor of doing a clunk on the other side if implanted. The diagnosis of the syndrome is mostly clinical but the bone scan is frequently positive.

The patellar clunk syndrome remains a rare complication of posterostabilized TKA.

Being a woman and one episode of clunk are two risk factors. In presence of symptoms, the bone scan is a reliable preoperative exam to confirm the diagnosis.

J. Kinder V. Rawlani L. Puri

Patients with a thrombotic history are thought to be at greater risk for developing blood clots following total hip arthroplasty (THA) or total knee arthroplasty (TKA). The incidence of venous thromboembolism and risk factors associated with clot development in this population of patients, however, are not well defined.

From the years 2002 to 2008, 547 patients undergoing elective joint arthroplasty with a history of thrombotic disease, defined by prior history of deep venous thrombosis (DVT) or pulmonary embolism (PE), were followed prospectively for a minimum of one month after TKA or THA. Patients received prophylactic anticoagulation with coumadin starting on POD 1 with or without bridge therapy with low molecular weight heparin (LMWH). Patients were compared for the following risk factors: advanced age (> 70 years old), inherited or acquired thrombophilia, time elapsed since prior episode, association of prior episode with surgery, and method of anticoagulation.

Of the 547 patients, 72 (13.2%) developed symptoms consistent with DVT or PE. Thirty-two thromboembolic events (5.9%, 26 DVT, 6 PE) were confirmed by lower extremity Doppler ultrasound, spiral computerized tomography or ventilation-perfusion scanning. 60% of events occurred before POD 3, and the average INR at the time of diagnosis was 1.67. The incidence of thromboembolism was 14.6% and 9.9% for unilateral TKA and THA, respectively and 27.6% and 25% for bilateral TKA and THA, respectively. The institutional rate of DVT during that same time frame is 1.9%. History of inherited or acquired thrombophilia (p< 0.01), time elapse since prior thrmoboembolic event (p=0.04), and association of prior events with surgery (p=0.02) significantly increase the risk of thromboembolism in this population. Bridge therapy with LMWH of any dose did not significantly reduce the risk of DVT or PE, however, there was a trend towards significance (p=0.17). Eight patients (1.5%) experienced bleeding complications; 6 were major in nature (gastrointestinal bleeding and joint hematoma).

Patients with a thrombotic history are at increased risk for developing DVTs after joint arthroplasty. These patients share the same risk factors for development of DVT or PE then patients without a history of prior events. Furthermore, thromboembolic events tend to occur early following surgery in these patients and treatment with LMWH may help reduce the risk of developing clots when used in combination with coumadin.

J.-L. Briard P. Witoolkollachit G. Lin

Stability in TKR is provided by the prosthesis design, weight bearing, alignment and soft tissue envelope which triggers proprioception and neuromuscular control. For long survivorship, the least constrained design are prefered whenever possible. Today there is a discussion about the best prosthetic femoro-tibial alignment as discussed widely in Europe and more recently by Pagnano.

Total knee replacements must be very stable to improve the function and the wear. We certainly performed too many releases in the past and misunderstood some of the fine tuning between posterior structures and collateral ligament frame. Technique in release tends to be more elaborated in order to address sequentially primary and secundary restraints. Release of the lateral structures often created excessive laxity in the past and can be addressed with translocation of the ligaments insertions.

In case of elongated collateral structures, preserving the posterior cruciate and reconstruction of the collateral ligament allows use of less constrained prosthesis.

In revision arthroplasty, the condition may be even more complex but usually the collateral ligaments may be identified. It is usually possible to find and reconstruct their insertions especially on the femoral side. Sometimes, augmentation will be needed but at the end, there is a good functional collateral ligament frame.

Deformities with different soft tissues conditions and with extraarticular components in primary and revision total knee arthroplasty will be reported in severe varus, valgus and stiff knees.

J.H. Yang J.G. Seo M.H. Kim Y.W. Moon J.G. Kim

We aimed to analyze the clinical results of the patients according to joint line change who underwent navigation assisted cruciate ligament retention type mobile bearing total knee arthroplasty.

From September 2004 to January 2006, cruciate ligament retention type mobile bearing total knee arthroplasties using navigation system(Orthopilot®, Aesculap) were performed for 50 knees in 45 patients (2 men, 43 women). The mean follow up period was 46(39~55) months and the mean age was 65. There was one case with rheumatoid arthritis and all other were degenerative arthritic cases. All surgeries were performed using navigation system. Proximal tibia resection was performed at the sclerotic level of medial tibial plateau. The distance from the lowest point of lateral tibial plateau (registered point) to the proximal resection plane was measured. Clinical outcome were compared between joint line elevation with more than 3 mm(20cases) and less than 3mm (30cases).

The mean joint line elevation was 1.93 mm (range −1~5mm). There were no significant difference in the clinical results according to the joint line change (p> 0.05). It may be suggested that the change of joint line in the range of −1 to 5mm in cruciate ligament retention type mobile bearing total knee arthroplasty result in satisfactory clinical outcome.

R. Nagamine D. D’Lima S. Patil W. Chen K. Kondo M. Todo T. Hara Y. Sugioka

Routinely in TKA, at least one of the cruciate ligaments are sacrificed. The cruciate ligaments excision may have an impact in the stability of the reconstructed knee by virtue of the impact on the gap kinematics. In this study, a selective cutting protocol was designed to quantify the individual contribution of ACL and PCL about the knee by means of a loaded cadaveric model.

Five fresh frozen normal cadaver specimens were used. The femur was fixed to a specially designed machine, and 3D tibial movements relative to the femur and joint gap distances were measured by means of a navigation system from full extension to 140° flexion. The joint was distracted with 10 pounds. The measurement was performed before and after ACL and PCL excision.

Medial gap distance at 90° flexion before and after cruciate ligaments excision was 4.3 ± 2.7 mm (mean ± SD) and 5.1 ± 2.8 mm (p< 0.05) respectively. Cruciate ligaments excision significantly widened the medial and lateral gaps at many flexion angles, and the effect of excision on the gap distance was different between medial and lateral sides especially at 90° knee flexion. Cruciate ligaments excision also significantly influenced knee kinematics. If this varying gap is not accounted for either through implant shape and orientation or through soft tissue adjustments, instability could be the result.

Surgeons should be made aware of the influence of cruciate excision on varus/valgus laxity throughout the range of motion. Design modification of the femoral component may also be necessary in order to obtain optimal stability in deep flexion.

P. Boesch W. Huber R. Legenstein

Objectives: To evaluate the outcome of a cementless, low carbon MOM (metal on metal) THR with a 28mm ball-head (PPF STRATEC-SYNTHES, since 2002 BIOMET) and the concentration of metal ions within the intra-articular fluid.

Methods: 173 unilateral MOM THR’s performed in 1995 were investigated. Average follow up time was 12 yrs (range 9–14yrs). During the study period there were, 11(6.4%) deaths, 2 (1.2%) lost to F.U. and 5 (2.9%) refused follow up x-rays because of lack of symptoms, and a self perceived perception that these were not necessary. 41 effusions in part of this group could be analysed for levels of Co, Cr and Ni.

Results: 112 THR’s (64.7%) were completely symptom free and did not show any signs of osteolysis. 7 THR’s had revision surgery, unrelated to metallosis (1 cup loosening, 1 early infection and 5 late infections that could be attributed to a large amount of necrotic tissue within the joint space). 36 hips (20.8%) showed over time, progressive signs of a metallosis. Clinically none or moderate complaints in the groin were reported, and massive effusions of up to 90ml were present. The osteolysis began in the majority of these cases in the periosteal region of the acetabulum and the trochanter. No loosening of the implants was seen. A quarter of these implants had late dislocations. The CRP was up to three times above normal levels. Only 26 patients (15.0%) could be convinced to undergo further surgery (synovectomy, exchange of head and liner and bone grafting as required). Typical histology showed massive necrosis within the joint and a peri-vascular infiltrate of CD-3 pos. activated T-lymphocytes and L26 pos. B-lymphocytes. These findings have been recently published as ALVAL.

In the 41 joint effusions, the mean level of Co was 595.6 μg/l (max 4802.2), Cr 481.1 μg/l (max 4602.9) and Ni 3.7 μg/l (max 14.4). The serum ion levels were up to four times the maximal permitted level (Co 3 μg/l, Cr 3 μg/l, Ni 3 μg/l).

Conclusion: High levels of toxic metal ions in the joint space over time can lead to a severe allergic reaction and tissue necrosis.

The current literature reports, that almost all MOM bearings show slightly elevated serum metal ion levels, and therefore a much higher concentration must be calculated within the joint space. In our experience, because of the serious consequences and unpredictable onset of metallosis, we no longer use MOM articulations.

R.H. Kim D.A. Dennis C.C. Yang B.D. Haas

Introduction: Common failure modes of revision total knee arthroplasty (TKA) include aseptic component loosening and damage to constraining mechanisms which are often required in revision TKA. Mobile-bearing (MB) revision TKA components have been developed in hopes of lessening these failure mechanisms. Our objective was to evaluate the early clinical outcomes for the use of MB in revision TKA with a minimum 2-year follow-up and to evaluate bearing complications.

Methods: Retrospective clinical and radiographic evaluation of 84 MB revision TKAs with minimum 2-year follow-up was performed. Revision TKAs were performed using PFC Sigma and LCS revision rotating platform implants (Depuy, Warsaw, IN).

Indications for revision include aseptic loosening (31 knees), instability (30 knees), failed unicompartmental knee replacement (8 knees), infection reimplantation (7 knees), arthrofibrosis (3 knees), chronic hemarthrosis (3 knees), failed patellofemoral replacements (1 knees), and nonunion of a supracondylar femur fracture (1 knee).

Results: At a mean follow-up of 3.7 years, the average Knee Society clinical and function scores had increased from 50.3 points preoperatively to 89.1 points and from 49.3 points to 80.1 points, respectively. Average motion improved from 99.8° preoperatively to 116.5° postoperatively. Radiographic review demonstrated excellent fixation with no evidence of component loosening upon latest follow-up. No cases of bearing instability were observed.

Conclusion: This evaluation of 84 MB revision TKAs has demonstrated favorable early results at a mean follow-up of 3.7 years with no occurrence of bearing instability. Longer follow-up is required to evaluate for potential advantages of reducing polyethylene wear, lessening fixation stresses, and protection of constraining mechanisms.

P. Zeng W.M. Rainforth B.J. Inkson T.D. Stewart

Retrieved alumina-on-alumina hip joints frequently exhibit a localised region of high wear, commonly called ‘stripe wear’. This ‘stripe wear’ can be replicated in vitro by the introduction of micro-separation, where the joint contact shifts laterally reproducing edge loading during the simulated walking cycle. While the origin of stripe wear is clearly associated with the micro-scale impact resulting from micro-separation, the wear processes leading to its formation and the wear mechanisms elsewhere on the joint are not so well understood. The purpose of this study was to compare the surface microstructure of in vivo and in vitro alumina hip prostheses, and investigate the origins of the damage accumulation mechanisms that lead to prosthetic failure.

The in vivo alumina hip prosthesis was Biolox (Ceram-Tec, AG, Plochingen, Gemany) implanted for 11 years [1]. The in vitro alumina hip prosthesis was Biolox-forte (CeramTec, AG, Plochingen, Gemany), which had been tested in a hip joint simulator under micro-separation at Leeds University using the procedures given in [2]. The worn surfaces of the alumina hip prostheses were investigated using a Scanning Electron Microscopy (SEM). Similar worn surfaces were seen for both in vivo and in vitro samples. Focused ion beam (FIB) microscopy was used to determine the sub-surface damage across the stripe wear. Samples were subsequently removed for Transmission Electron Microscopy (TEM). Sub-surface damage was found to be limited to a few μm beneath the surface; ~ 2μm for in vivo samples and ~1μm for in vitro samples. The transition from mild wear to more severe (stripe) wear was entirely triggered by intergranular fracture. The first stages of fracture lead to the liberation of surface grains which act as 3rd body abrasives. The TEM showed that abrasive grooves are associated with extensive surface dislocation activity, which leads to further grain boundary fracture.

This allows the cycle to be repeated and accelerated, thus yielding the stripe wear region.

The conclusions are: 1. In vitro hip simulation with micro-separation can produce similar microstructure to in vivo alumina hip prostheses; 2. To extend the life of the joint through the avoidance of severe wear, material and design solutions can be investigated using ceramic materials that have an increased surface inter-granular fracture toughness and component designs with reduced contact stress under edge loading.

Youn-Soo Park Young-Wan Moon Seung-Jae Lim Jin-Hong Kim

As the proximal femoral bone is generally compromised in failed hip arthroplasty, achievement of solid fixation with a new component can be technically demanding. Recent studies have demonstrated good short-term clinical results after revision total hip arthroplasty using modular distal fixation stems, but, to our knowledge, none have included clinical follow-up of greater than 5 years. The purpose of this study was to report the clinical and radiographic outcomes assessed 5 to 10 years following revision total hip arthroplasty with a modular tapered distal fixation stem.

We retrospectively evaluated 50 revision total hip arthroplasties performed using a modular tapered distal fixation stem Between December 1998 and November 2003. There were 15 men (16 hips) and 34 women (34 hips) with a mean age of 59 years (range, 36 to 80 years). The index operation was the first femoral revision for 46 hips, the second for 3 hips, and the fifth for 1 hip. According to the Paprosky classification, 5 femoral defects were Type II, 31 were Type IIIA, and 14 were Type IIIB. An extended trochanteric osteotomy was carried out in 24 (48%) of the 50 hips. Patients were followed both clinically and radiographically for a mean of 7.2 years.

The mean Harris hip score improved from 54 points preoperatively to 94 points at the time of the latest follow-up. The mean stem subsidence was 1.5mm. Three stems subsided more than 5 mm, but all have stabilized in their new positions. During follow-up, a total of 4 hips required additional surgery. One hip had two-stage re-revision due to deep infection, one had liner and head exchange for alumina ceramic head fracture, and the other two underwent isolated cup re-revision because of aseptic cup loosening and recurrent dislocation, respectively. No repeat revision was performed due to aseptic loosening of the femoral component. Complications included 6% intraoperative fractures, 4% cortical perforations, and 4% dislocations. There were no stem fractures at the modular junction.

The medium-term clinical results and mechanical stability obtained with this modular tapered distal fixation stem were excellent in these challenging revision situations with femoral bone defects.

M Kurita T Tomita K Futai T Yamazaki Y Kunugiza M Tamaki M Shimizu M Ikawa H Yoshikawa K Sugamoto

Mobile-bearing (MB) total knee prostheses have been developed to achieve lower contact stress and higher conformity than fixed-bearing total knee prostheses. However, little is known about the in vivo kinematics of MB prostheses especially about the motion of polyethylene insert (PE). And the in vivo motion of PE during squat motion has not been clarified. The objective of this study is to clarify the in vivo motion of MB total knee arthroplasty including PE during squat motion. Patients and methods: We investigated the in vivo knee kinematics of 11 knees (10 patients) implanted with PFC-Sigma RPF (DePuy). Under fluoroscopic surveillance, each patient did a wight-bearing deep knee bending motion. And motion between each component was analyzed using two-to three-dimensional registration technique, which uses computer-assisted design (CAD) models to reproduce the spatial position of the femoral, tibial components, and PE (implanted with four tantalum beads intra-operatively) from single-view fluoroscopic images. We evaluated the range of motion between the femoral and tibial components, axial rotation between the femoral component and PE, the femoral and tibial component, and the PE and tibial component, and AP translation of the nearest point between the femoral and tibial component and between the femoral component and PE.

Results: The mean range of hyper-extension was 2.1° and the mean range of flexion of 121.2°. The femoral component relative to the tibial component demonstrated 10.4° external rotation for 0–120 degrees flexion. The tibial component rotated 10.2° externally relative to the PE and the femoral component minimally rotated relative to the PE within ± 5 degrees. In upright standing position, the femoral component already rotated externally relative to the tibial component in 6.3°, and the PE also rotated on average 6.4° externally on the tibial tray. Typically the femoral component relative to the tibial component exhibited a central pivot pattern external rotation from extension to 80° knee flexion. Subsequently from 80 to 120°, bilateral condyles moved backward. In a similar fashion, the femoral component relative to the PE exhibited a central pivot pattern external rotation from extension to 70° knee flexion and subsequently bicondylar rollback from 70 to 120° knee flexion.

Discussion and Conclusion: In this study, we evaluated the in vivo motion of PE during squat motion. About this total knee prosthesis, the mobile-bearing mechanism which advantages over fixed-bearing prosthesis to reduce contact stress and keep high comformity might work well, and arc of range of motion was maintained. Furthermore, in upright standing position, the femoral component and tibial component already rotated externally relative to the PE in almost equal measure. This indicated that, self-aligning mechanism, another characteristic of the MB prosthesis might also work well.

Peter S. Walker David J Cleary Yonah Heller Gokce Yildirim

The objective was to develop a simple, rapid, and low-cost method for evaluating proposed new Total Knee (TKA) designs, and then to use the method to evaluate three different TKA models with different kinematic characteristics. In a previous study, we reported on the use of an Up-and-Down Crouching Machine, where the neutral path of motion for knee specimens were measured, and then TKR models were implanted and the tests repeated. These experiments showed that standard CR and PS designs behaved more like an ACL deficient knee, whereas Guided Motion knees produced motion similar to that of the intact specimens. However the method was time consuming, technically demanding, and expensive, and hence is suitable for designs which had already passed through a screening method. The latter was the subject of this present study, called the Desktop TKR Test Machine.

The principle of the testing protocol on the machine, called Holistic Testing, was that a spectrum of compressive, shear and torque forces were applied to a knee, to represent a complete spectrum of daily and sporting activities. The resulting femoraltibial positions were measured, both the Neutral Path of Motion and the Laxity about the neutral path. The motions were displayed as both the motion of the transverse femoral axis on the tibial surface, and by the centers of the lateral and medial contact patches.

Eight knee specimens were tested first, to act as a reference target for evaluating TKR models. Knee models were designed in the computer and made in a hard low-friction plastic using SLA and stereolithography.

A typical Posterior-Stabilized (PS) TKA did not display the normal external femoral rotation with flexion, and also showed abnormal anterior sliding on the medial side prior to cam-post engagement. Guided Motion designs included a Medial Pivot type, and a Medial Pivot with a cam-post. Both of these had a dished medial side and a shallow lateral side, to more accurately reproduce anatomic motion characteristics. The guidedmotion design with the cam-post produced a neutral path and laxity more similar to that of normal.

It was concluded that the test method satisfied the objective in terms of being a useful test method for rapid evaluation of new proposed TKR designs. The method was able to identify designs which showed motion and stability characteristics closer to the normal anatomic knee.

J.T. Moskal S.G. Capps

Many factors can negatively impact acetabular component positioning including poor visualization, increased patient size, inaccuracies of mechanical guides, and inconsistent precision of conventional instruments and techniques, and changes in patient positioning. Improper orientation contributes to increased dislocation rates, leg length discrepancies, altered hip biomechanics, component impingement, acetabular component migration, bearing surface wear, and pelvic osteolysis thus affecting revision rates and long-term survivorship. Despite the established definitions of acetabular safe zones, recent analysis of U.S. Medicare THA data found dislocation rates during the first six months to be 3.9% for primary surgeries and 14.4% for revision surgeries. Accurate and precise acetabular component orientation during initial THA is an increasingly important factor in decreasing revision THA; a recent report cites instability and dislocation as the primary cause of revision accounting for 22.5% of cases. Larger femoral heads and alternative bearing couples are less tolerant of variation in acetabular orientation and thus are poor substitutes for proper acetabular component placement.

Variability in acetabular orientation has been reported to have both an inter-surgeon and an intra-surgeon component; pre-surgical templating combined with intraop-erative measurements is subject to inconsistencies and errors. Current methods for determining acetabular orientation include preoperative imaging such as CT scans, intraoperative imaging such as plain radiographs and fluoroscopy, and intraoperative anatomical tests. Combining the concepts of patient-specific morphology (PSM) and quantitative technologies (QuanTech) such as computer-assisted navigation (CAN) has the potential to maximise range of motion and to further improve acetabular component orientation through improved accuracy and precision.

PSM refers to the practice of allowing the form and structure of the patient’s hip joint to guide surgical reconstruction and component placement thus creating an individualised and more accurate “target zone”; unlike “safe zones,” PSM does not rely on averages. Although gross anatomic changes may make it difficult to use PSM, certain structures may be used as guide-posts for orientation, alignment, and stability in most patients. At present, there are three options when considering anatomic landmarks as guides for acetabular component placement: bony landmarks, soft tissue landmarks, or a combination.

QuanTech has been shown to increase the precision of component placement by reducing intra-surgeon deviation. Some pitfalls of current CAN techniques result from maintaining camera line of sight during surgery, registration process, and pin placement. Performing THA using smaller incisions can impose additional complications as well as risks for errors in component positioning; QuanTech has the potential to provide greater visualization and precision, thus decreasing the impact of those constraints.

THA has become one of the most common and successful orthopaedic procedures; its efficacy at relieving pain and its ability to help patients have improved quality of life is without dispute yet results continue to vary with inter-surgeon and intra-surgeon differences. As the population needing THA increases, the prevalence of complications and problems will increase, even if the percentage of complications decreases. Coupling PSM with QuanTech such as CAN may allow the surgeon to decrease variability and more consistently implant THA components based on each patient’s individualized requirements. The goal of combining PSM and CAN is to further reduce inter-and intra-surgeon variation, thereby decreasing outliers, complications, and revision rates, and possibly narrowing the gap between specialist and generalist. More accurate and precise acetabular component orientation correlates with better hip biomechanics, translating into better function, fewer dislocations, fewer impingements, maximized safe range of motion, less wear, and therefore less aseptic loosening and improvements in survivorship of primary THA. Decreasing revision rates, combined with the benefits listed above, could translate into increased THA survivorship, improved patient satisfaction, and decreased economic burden on the entire healthcare system.

T. Nakamura C. Fukuda M. Imamura K. Goto T. Kokubo

Many types of bioactive bone cement have been developed to overcome the disadvantages of polymethyl-methacrylate (PMMA) bone cement, especially its lack of bone-bonding ability, which occasionally leads to aseptic loosening of prostheses used for arthroplasty. Earlier, we showed that bioactive bone cements containing either nano-sized or micron-sized titania (TiO2) particles had excellent in vivo osteoconductivity.

However, anatase phase titania particles contained in these bioactive bone cements raise concerns about their safety in vivo. We developed pure rutile micron-sized titania particles. because rutile is the only stable phase, whereas anatase is metastable.

In this study, polymethylmethacrylate (PMMA)-based bone cement containing pure rutile micron-sized titania (TiO2) particles were developed, and their mechanical properties and osteoconductivity are evaluated. The three types of bioactive bone cement were T10, T20, and T30, which contained 10, 20, and 30wt% TiO2, respectively.

Commercially available PMMA cement (PMMAc) was used as a control. Hardened cylindrical cement sample (φ2.5mm*10mm) was inserted manually on rabbit femur vertically. Push out test was performed for evaluation of bonding strength. For mechanical testing, the flexural strength, flexural modulus, and compressive strength were measured.

Results of this study revealed that polymethylmeth-acrylate (PMMA)-based bone cement containing pure rutile micron-sized titania particles has outstanding osteoconductivity in vivo, and their mechanical properties were exceeded that of commercially available PMMA cement. Interfacial shear strength of T10, T20 and T30 were 17.1~24.0MPa each at 12 weeks, and were significantly higher than PMMAc. In general, the interfacial bonding strength of bone cement depends mainly on its interdigitation with cancellous tissue, which is accomplished by the pressurized injection of the cement in paste form. On the other hand, we inserted the hardened specimens into oversized holes on rabbit femur in this study, because we intended to examine the osteoconductive and bone-bonding potentials of each material. The flexural strength, flexural modulus, and compressive strength were equivalent to or exceeded that of PMMAc.

These results show that bone cement containing pure rutile micron-sized titania particles is a promising material applied to prosthesis fixation as well as vertebroplasty.

N.P. Jain M. Granieri M. Polavarapu S.D. Stulberg

The focus of deep vein thrombosis (DVT) prophylaxis following total joint arthroplasty has shifted in recent years to the reduction of symptomatic pulmonary emboli (PE). The relative infrequency and presumed delayed occurrence of these events has led many to suggest that the risks of more frequent early postoperative complications of treatment, especially bleeding, be weighed against the benefits of thromboembolic prophylaxis. The purpose of this study was to determine the timing and risk factors associated with the development of symptomatic PE following total hip arthroplasty (THA) and total knee arthroplasty (TKA).

A retrospective analysis was performed of all patients diagnosed with a symptomatic pulmonary embolism following THA and TKA performed from January, 2004 to March, 2008. The records of 4706 patients were reviewed who were operated upon by 7 surgeons, and a total of 58 PE were identified. All patients were managed and treated by an anti-coagulation dosing service. Helical CT Scans were used to make the diagnosis of PE.

The overall incidence of PE was 1.2%, with 1.8% occurring in TKAs and 0.5% occurring in THAs. 48 of the 58 PE patients (83%) were women. 33 patients (57%) had unilateral TKA, 14 (24%) had bilateral TKA and 11 (19%) had THA. The average patient age was 65 (range: 44–88) and BMI was 33.8 (range: 24.7–51.9). There was no apparent correlation between age and BMI with incidence of PE. The PE were diagnosed an average of 4 days (range: 1–46) following surgery. 56 of the 58 patients (97%) were diagnosed by the sixth postoperative day. The average INR at the time of diagnosis was 1.7 (range: 1.0–3.0). There were two mortalities (3%), both of which occurred within the first two postoperative days.

The PE in this study occurred predominantly in women undergoing TKA. There appears to be an urgent need to develop an effective prophylaxis program aimed at preventing PE in the early post-operative period and to identify patients at risk of these PE.

M. Bercovy D. Hasdenteufel S. Delacroix N. Legrand M Zimmermann

This study aims to compare the gait pattern of patients operated with a TKA versus a normal population in order to evaluate if the excellent function of TKA reported in the literature corresponds to objectively measured parameters.

20 patients operated of TKA with a follow up > 1 year, all patients rated with a very good functional result (Knee Society Knee score > 85/100 – VAS < = 1/10) were compared with a group of 20 “ normal” persons.

The study was blind: the examiner did not know whether the person was a normal, or which knee was operated.

The test consisted in an 11 meters walk, on an AMTI force platform; the movements of the body were recorded with 6 IR cameras and analysed with the “Motion Analysis” software.

The implant was a mobile bearing AP stabilised knee.

The measured parameters were kinematic : speed, step length, flexion angle, duration of stance /WB phase and dynamic : flexion/extension, varus/valgus, internal/ external moments and resultant force direction. When matched with age and BMI, all kinematic parameters of the TKA group are equal to that of the normals.

However, dynamic parameters differ significantly between both groups: At the end of stance phase and heel strike the operated patients have a lack of extension of 10° despite a clinical measurement of full extension (0°) In the frontal plane, all patients exhibited a valgus walking pattern but the mechanical axis measured on long standing radiographs was 180°+/−1°. In the horizontal plane, all operated patients had an external rotation of +8° compared to the normals.

Despite excellent clinical scores and radiologic positioning, gait analysis demonstrates important dynamic differences between the TKA and the normal group. The extension lag at heel strike may be related to either quad weakness, or an insufficient extension gap at surgery; The valgus resultant pattern occurs despite a perfect alignment of the mechanical axis (180°) on the operated patients: this rises the question whether this alignment is the goal or if an undercorrection would be more physiologic. External rotation is superior to the normal group : it is in relation with the external rotation of the femoral and tibial components.

Conclusion. Gait analysis of the TKA group of patients compared to normal demonstrates important dynamic differences in relation with the surgical positioning of the implant.

G. Gasparini G. Maistrelli V. De Santis

Background: Poor results were observed at medium term follow-up (FU) after first and second generation cementless stems implantation in total hip arthroplasty (THA). Revision rate up to 24% is reported with anatomic stems; stress-shielding rate up to 50%, thigh pain rate up to 21%, loosening rate up to 20% and osteolysis rate up to 29% were reported with cylindrical stems. A third generation tapered stem, the Synergy stem, was introduced in 1996 to rise such weakness points.

Material and methods: A retrospective, cohort study was carried out in two academic centers (London, Toronto, Canada & Rome, Italy) on 232 primary THA in 215 patients with a 10 to 12 yrs FU. Mean age at surgery was 60 yrs (18–82), 95 patients were males and 120 females. Thirty-six patients were lost at FU (13 died before the 10 yrs mark, 22 changed residency, 1 not willing to be seen) with no problems related to the replaced hip. Remained at FU 196 THA. Patients selection: Dorr type A and B femurs suitable for receive a Synergy stem. Its characteristics are the following: Ti-6Al-4V, straight, tapered, 3D wedge cross-section, proximal antirotational fins, low-profile neck, neck angle 131°, metaphyseal part porous or HA coated, diaphyseal part grit blasted, polished tip, surgeon-friendly ancillary instruments. Clinical results of the 196 THA with more than 10 yrs of FU were assessed preoperatively and postoperatively at 5 and 10 or 11 or 12 yrs by means of standard evaluation tools: SF12, WOMAC and Harris Hip Score. Thigh pain frequency and intensity were also scored. Radiographic analysis was focused on stem alignment, bone ingrowth, radiolucent lines presence, width and progression, stress-shielding, heterotophic ossification (HTO). Student paired test and Kaplan-Meier survival analysis were used for statistical analysis.

Results: All clinical evaluation tools showed both at 5 years FU and at latest FU (10–12 years) a statistically significant (p=0,001) improvement compared to the preoperative scores. We observed a not constant thigh pain in 7 patients (5,5%). Nineteen patients (10%) underwent evision due to polyethylene wear (6 cases), late periprosthetic fracture (5 cases), subsidence (2 cases), instability (3 cases), infection (3 cases). Cumulative survival rate was 97% at 2 and 5 years, 90% at 10 years. Stem related revisions were the 2 cases of subsidence, both related to occult intraoperative calcar crack and early revised (within 1 year); cumulative stem-related survival rate at 10 years was 99%. Alignment was varus in 9 cases and valgus in 3. Bone in-growth was observed in 194 patients (98%). Radiolucent lines were uncommon, non progressive, less than 2 mm, in Gruen zones 2 and 6. Stress-shielding was present as cortical reaction in 5 femurs in Gruen zones 3 and 5. Thirty-four cases of HTO (grade I and II in 27 case and grade III in 7 cases) were observed.

Conclusions: The Synergy stem demonstrates excellent clinical and radiographic results at 10–12 yerars FU in 196 patients. Survivorship (with stem revision as end point) is 99% at 10 years. Thigh pain is uncommon and the level of activity and autonomy is excellent. Radiographically bone ingrowth is evident in all stems and radiolucent lines are “benign” with no aseptic loosening. Attention must be paid at the moment of stem press fit insertion to avoid occult proximal femoral fractures that may require revision surgery.

Kwang-Jun Oh

Background: The purpose of this prospective study was to asses the reliability of image-free navigated cup positioning and its correlation with biometrical parameters (age, sex, body mass index, soft tissue thickness overlying anterior superior iliac spine and symphysis pubis, and lumbar lordosis) and three different orientations of pelvis (tilt, obliquity, and rotation) in patients of Asian ethnicity.

Methods: Intraoperative data was obtained from 50 consecutive total hip arthroplasties in which acetabular cup implantation was done with a cementless cup (Plasma Cup SC®, Aesculap AG, Tuttlingen, Germany) using Orthopilot® image-free navigation system. The data was then compared with mathematically calculated synchronized anteversion and inclination obtained postoperatively through computed tomography and 3-dimensional processing.

Results: Mean navigated and synchronized inclination obtained were 40.1°±5.34° and 41.79°± 7.96° respectively (mean difference 1.69°±6.95°, range −20.72° ~ 18.47°), while the mean navigated and synchronized anteversion were 19.98°± 6.44° and 20.00°± 6.33° (mean difference 0.01°±6.35°, range −15.15° ~ 11.10°). A discrepancy of > 10° was observed in 5 hips in inclination and 5 hips in anteversion. No correlation was found between all of biometrical parameters and discrepancy of cup orientation. A statistically significant correlation was found between discrepancy of anteversion and pelvic tilt (1.78 + 0.55 x pelvic tilt°, r=0.493, p=0.0016).

Conclusion: In spite of variations in pelvic geometry, image-free navigation assisted acetabular cup positioning showed the significant reliability. The next generation of navigation systems must be combined with data on precision of pelvic orientation intraoperatively for complete validation.

*Index; Synchronized Inclination = arctan [tan (Operative AV) ÷ tan (Anatomic AV)] Synchronized AV = arctan[tan (Anatomic AV) x sin (synchronized Inclination)] or arctan[tan (Operative AV) x cos (Synchronized Inclination

Wooshin Cho Yoonseok Yeum Byungkwan Kim Jeho Woo Hoyoun Park

We checked intraoperative patellar tracking with both ‘towel clip technique’ and the ‘no thumb technique’ on 354 patients (571 knees) who underwent primary total knee arthroplasty to decide whether to do or not to do lateral retinacular release.

All surgical procedures consisted of medial parapatellar arthrotomy and patellar resurfacing. Patellar tracking was assessed under pneumatic tourniquette with the no thumb technique first and reevaluated with the towel clip technique. The tracking was graded as total contact, good contact, lateral contact, and subluxation. The knees graded as total or good contact with the no thumb technique were classified into group A; those graded lateral contact or subluxation by the no thumb technique but total or good contact by the towel clip technique were classified into group B; and those graded lateral contact or subluxation by both techniques were classified into group C, in which lateral releases were performed. We classified 371, 148, and 52 knees into groups A, B, and C respectively. Patellar lateral tilting in the Merchant view was reviewed preoperatively and 2 weeks, 6 weeks, 6 months, and 1 year postoperatively.

There were no statistical differences on postoperative patellar tilting among the groups. Assessment of the patellar tracking using only the no thumb technique may overestimate the need for lateral retinacular release. The use of the no thumb technique as a screening test, and reevaluation with the towel clip technique, may reduce unnecessary lateral retinacular release.

H. Oonishi H. Oonishi S.C. Kim M. Kyomoto M. Iwamoto M. Ueno

A consensus on total hip arthroplasty (THA) concluded that the major remaining issues of concern included the long-term fixation of the joint replacement, osteolysis due to poluethylene (PE) wear debris which often leads to aseptic loosening. Alumina ceramics had been extensively used in medicine, and we started using the alumina ceramic for THA bearing surface in hopes to reduce the PE debris. It was because alumina ceramics is advantageous for precision machining compared with metal materials, and its hardness is higher than that of metal materials. Also, to augment cement–bone bonding, we interposed hydroxyl apatite (HA) granules at the cement–bone interface, so called “Interface Bioactive Bone Cement (IBBC) technique”. HA granules (2–3 g) were smeared on the bone surface of the acetabulum and femur just before cementing. In this study, we evaluated 19–22 years clinical results of THA with alumina ceramic head combined with PE cup fixated IBBC technique.

Total 285 joints (212 patients) were implanted by one senior surgeon from January 1986 to December 1988, and 265 joints (192 patients) were traceable. Alumina ceramic femoral head of 28 mm in diameter and acetabular cup of the conventional PE sterilized with ethylene oxide gas were used in all patients. The PE cup and stem were fixed with IBBC technique in all cases. The presence of radiolucent line, loosening and osteolysis were observed using radiograph of the traceable cases. The locations of radiolucent lines were identified according to the zones described by DeLee and Charnley for acetabular cups and the zones described by Gruen et al. for femoral stems. The in vivo wear of 21 PE acetabular cups for 19.0–21.9 years (mean 20.3 years) was measured from the latest radiographs using computer assistant technique with Vector Works 10.5 software.

Features of the clinical radiograph images of the IBBC case were classified as follows: the radiolucent line represented “gap” between the HA layer and the cement; the loosening represented “opening” between the HA layer and the cement. For the quantitative analysis, we divided the surrounding bones of the THA into several zones as done in the previous studies. The “gap” appeared in zone 4 in three joints (1.4 %), in zone 3 in two joints (0.9 %) of acetabular cup. In femoral side, in zone 1 in four joints (1.8 %) in zone 7 in one joint (0.4 %). The “opening” appeared in three acetabular cup (1.4 %). Since no opening was appeared in zone 3 or zone 4, however, no re-operation was needed. Images of osteolysis were seen one in zone 1 (0.5 %), and one in zone 2 (0.5 %) in acetabular side and two in zone 1 (0.9 %) of the femur. The mean linear wear rate of PE acetabular cups was 0.13 mm/year.

The fixation to the bone by the IBBC technique has been maintained for long term. We think that the result was brought by the biological integration between bone and HA granules. In conclusion, this study has shown satisfactory results of the cemented THA with ceramic head combined with PE cup for 19–22 years.

W.J. Long G.R. Scuderi

Bone loss is a challenging reconstructive problem in revision total knee arthroplasty (TKA).

Uncemented porous tantalum modular components are designed to act as substitutes for allograft bone in complex revision TKA with significant bone defects.

A consecutive series of 23 revision TKAs performed by a single surgeon were reviewed at a minimum two-years following implantation. In all cases bone loss was assessed using the Anderson Orthopaedic Research Institute System, and porous tantalum components were used to augment the reconstructions when bone loss was encountered.

Twenty-one patients had 23 procedures (2 bilateral) requiring the use of porous tantalum following 18 cases of aseptic loosening, 4 cases of staged re-implantation for infection, and 1 case of a periprosthetic patellar fracture and aseptic loosening. Structural bone graft was not used during this time period. Porous tantalum uses include: 20 distal and posterior femoral augments; 2 femoral cones; 8 patellar augments; and 18 tibial cones. 20 cases required augmentation in more than one area, and one case involved an extensor mechanism allograft. There were 2 cases of recurrent sepsis requiring removal of well-fixed tantalum components. At an average 37 months (24 to 73) no patients were lost to follow-up. Clinical follow-up in the remaining 21 cases showed reconstructions were functioning well with no revisions. Radiographic imaging showed re-establishment of the joint line, neutral mechanical axis, and signs of stable fixation of the augments. There were no cases of radiographic or clinical loosening at the most recent follow-up.

Short term results with the use of porous tantalum augments and cones for bone loss in revision TKA demonstrate the versatile, and durable nature of these new reconstructive tools, at early follow-up.

S.D. Steppacher M. Tannast J. Kowal G. Zheng K.A. Siebenrock S.B. Murphy

Acetabular component malpositioning increases the risk of impingement, dislocation, and wear. The goal of computer-assisted techniques is to improve the accuracy of component positioning, in particular optimizing the orientation of the acetabular cup.

The goal of the current study was to measure accuracy of cup placement in a large clinical series of hips that underwent CT-based computer-assisted THA.

146 hips in 140 patients underwent CT-based computer-assisted THA between 2006 and 2008. In all cases cup orientation was planned according to the individual preoperative CT and the anterior pelvic plane with an inclination of 41° and anteversion of 30°. For the procedure, all patients were placed in the lateral position and the cup was implanted using angled instruments. Intra-operatively all cases were navigated using an optoelec-tronic camera and tracked instruments (Vector Vision prototype, BrainLab, Germany).

Post-operatively, cup orientation was measured using a previously validated technique of 2D/3D-matching using the preoperative CT and post-operative radiographs. This technique allows for accurate measurement of cup position from plain radiographs corrected for individual pelvic orientation.

The mean accuracy for inclination was −2.5° ± 4.0° (−12° – 10°) and for anteversion it was 0.7° ± 5.3° (−11° – 15°). In 2 hips (1.4%) a deviation of more then 10° in inclination and in 4 hips (2.7%) a deviation of more then 10° in anteversion were found.

The current study demonstrates that the acetabular component can routinely be implanted with the assistance of CT-based navigation with reasonable agreement between the navigation measurements of component orientation at the time of surgery. Nonetheless, outliers still occasionally occur. These might be due to unrecognized loosening of the pelvic reference base, inaccurate registration or the use of the ipsilateral surface-based registration algorithms which rely heavily on points near the center of rotation of the hip.

JY Lazennec MA Rousseau A Rangel Y Catonne

Introduction: Computer assisted total hip replacement (THA) usually uses the anterior pelvic plane (plane of Lewinneck, APP) for reference because the anatomical landmarks are easy to access during the surgical procedure. However, a recent study shows the lack of correlation in between the Lewinnek angle in standing position (L) and the spinal radiological parameters for sagittal balance, specifically the incidence angle and the sacral slope. The anatomical variations of the anterior superior iliac spines account for the discrepancy. The authors propose here the assessment of the Lewin-nek – sacrum angle (LS) (anterior pelvic plane to the sacral endplate) Methods: 120 asymptomatic patients with THA had low dose lateral X-rays of the lumbo-pelvic area (Definium 8000, GE Healthcare ;dose 0,6 mSivert). The measurements of the sacral slope, incidence angle, and APP were done by two independent observers.

Results: The sacral slope and incidence angles were similar to other series. The APP was no clearly identified in 78 cases. The average L angle was −3° (SD 8°) in standing position, −23° (SD 11°) in sitting postion, and −2° (SD 8°) in lying position. The average LS angle was 47° (SD 13°). The geometrical relationship between the LS a ngle, the L angle and the sacral slope is reported.

Conclusion: THA stability supposes that the orientation of the acetabular component shall remain within extreme values in standing, sitting, and lying postures. The adjustment of the acetabulum takes into account the functionnal anatomy of the lumbopelvic area. The sacral slope is a reliable radiological reference and is related to the sagittal balance of the spine. The APP presents some interindividual variability and is poorly visible on the radiographs, but it is easily accessible during surgery. The author suggest using the Lewinnek sacrum (LS) angle for radiological planification and for surgical navigation procedures.

G Suzuki S Saito T Ishii S Mori S Motojima J Ryu

Total knee arthroplasty (TKA) has been proven to be the most effective treatment for patients with severe or “end-stage” joint disease. Although infection is not a frequent complication of total knee arthroplasty, it is certainly one of the most dreaded. The purpose of this study was to identify related factors associated with septic arthritis.

2202 primary total knee arthroplasties were done in 1257 patients between 1995 and 2006. Of these knee arthroplasties, 2022 knees in 1146 patients were available for follow-up. Revision arthroplasty procedures and infected knees were excluded. 252 knees in 147 males, 1770 knees in 999 females were done. Their mean age at the time of primary TKA was 70.6 (range, 26–91) years. The mean follow-up period post primary TKA was 48 (range, 3–145) months. The medical records were reviewed to extract the following information: age, gender, body mass index, preoperative CRP, preoperative ESR, preoperative TP, duration of surgery, operative blood loss, total blood loss, duration of surgical drain, duration of antibiotic prophylaxis, primary diagnoses, smoking, diabetes mellitus, steroid or DMARDs therapy, previous operation around the knee joint, previous arthroscopic surgery, previous except arthroscopic surgery, previous operation of high tibial osteotomy (HTO) or open reduction internal fixation (ORIF), residue of internal fixation material, bone graft, patella replacement, and bone cement.

Proportions were compared using the chi-square or two-tailed Fisher’s exact test, as appropriate. Continuous variables were compared by the student’s t-test. Logistic regression analysis (stepwise) of selected variables from univariate analysis was performed to identify factors independently associated with the development of infection following total knee arthroplasty.

During the study period, 17 infected knee arthroplasties in 17 patients were identified. The infections occurred in 8 males and 9 females, with a medial age of 69.5 years.

The results of univariate analysis indicating those variables statistically associated with infection are : gender (p < 0.0001), smoking (p = 0.02), previous operation around the knee joint (p = 0.001), previous except arthroscopic surgery(p < 0.0001), previous operation of ORIF (p < 0.0001), residue of internal fixation material (p < 0.0001).

Logistic regression analysis indicated that the four predictors of infection following total knee arthroplasty were gender (odds ratio [OR], 0.2; 95% confidence interval [CI95], 0.1 to 0.6; P=0.005), previous operation of ORIF (OR, 7.9; CI95, 1.1 to 57.1; P=0.041), residue of internal fixation material (OR, 26.0; CI95, 4.5 to 151.0; P< 0.001), body mass index (OR, 1.2; CI95, 1.0 to 1.3; P=0.007).

We conclude that the risk factors of infection after TKA were previous operation of ORIF, gender, residue of internal fixation, and body mass index.

Stefan Kreuzer Jonah J Stulberg

Introduction: The Direct Anterior Approach (DAA) for hip replacement is an unfamiliar approach to most surgeons. The challenging portion of this approach is the preparation of the femur. In this study we determine factors that can assist in predicting the difficulty of femoral preparation to improve the learning curve.

Methods: Data was collected prospectively on 151 consecutive cases utilizing the DAA for hip replacement. After each case the femoral preparation was rated into one of 5 categories: very easy, easy, medium, difficult and very difficult. Clinical and demographic data were collected prospectively using web based data entry software. Post-operative x-rays were evaluated by an independent reviewer unaware of the exposure difficulty. Using multivariate regression, we examined several different x-ray based pelvic measurements as predictors for difficulty of femoral exposure.

Results: Univariate analysis demonstrated difficulty of femoral preparation was significantly (p< 0.05) correlated with height (OR=2.67, 95% CI = [1.03–6.94]), weight (OR=8.30, 95% CI=[2.35, 29.35]), male gender (OR=6.11, 95%CI=[1.97–18.97]), the distance from the greatertrochanter-to-ASIS (OR=0.30, 95%CI=[0.11–0.82]), teardrop-to-teardrop (OR=0.29, 95%CI=[0.11–0.79]), and greatertrochanter-to-greater-trochanter (OR=3.31, 95%CI=[1.23–8.95]). From this, we determined a simple pre-operative formula which allows the surgeon to predict difficult femoral preparations with an 87% sensitivity and easy preparations with > 95% specificity.

Conclusion: In MIS hip surgery, the DAA has proven difficult to learn for many surgeons. Careful patient selection can facilitate the learning curve and improve patient outcomes. We describe a simple to implement preoperative rating scale, which gives the surgeon learning DAA an algorithm for appropriate patient selection. With new advances in surgical procedures, selecting the appropriate patient can reduce the risks to the patient and minimize the cost to society of integrating new surgical techniques.

R. Patel S.D. Stulberg

Despite the clinical success of uncemented femoral stems of various types, current issues continue to require repeated examination:

proximal-distal mismatch

optimization of load transfer and preservation of femoral bone and

facilitation of MIS (minimally-invasive surgery) exposures, particularly an anterior approach.

A previous study demonstrated that a custom-made (based on CT-scan) short metaphyseal engaging femoral stem design provided stable fixation and reliable bony ingrowth at four-year follow-up. The purpose of this study is to present the minimum two-year clinical and radiographic results obtained with an off-the-shelf metaphyseal filling stem.

An uncemented, metaphyseal engaging femoral stem was inserted in 194 consecutive hips in 181 patients, whose average age was 70 years (range 32–95) and BMI of 28 (range 19–63). The implant, which averaged 94 millimeters in length (range 91–105), was made of titanium alloy with a hydroxyapatite coating on a titanium plasma-spray in the third of the stem.

The average Harris hip score (HHS) was 52 (range 10–80) preoperatively and 91 (range 70–100) postoperatively and no patients experienced thigh pain. Preoperative WOMAC scores averaged 48, compared to a postoperative average of 4. There were no fractures or other complications related to the prosthesis, no radiographic evidence of subsidence, and all stems were radiographically stable on most recent radiographs. The typical pattern of bony ingrowth was that of bone bridging and endosteal condensation at the proximal portion of the stem.

This study demonstrated that the use of an off-the-shelf short femoral stem designed to fit and fill the metaphysis provides reliable clinical and radiographic results at a minimum two-year (average 31 months) follow-up. Short stems may be particularly helpful to surgeons performing total hip arthroplasty using a MIS anterior approach.

D Parodi J Besomi J Lopez J Lara C Mella L Moya

Long-term functional and degenerative consequences of non treated slipped capital femoral epiphysis (SCFE), have been extensively demonstrated. At present, the treatment of SCFE is well described, however the treatment of the sequelae of SCFE, once osseous consolidation has happened, remains controversial.

Our aim is to describe an original technique of cuneiform osteotomy of the femoral neck through surgical hip dislocation for the treatment of sequelae of SCFE. Six hips were operated with sequelae of severe SCFE; average age of 15,2 years, whose consulting motivation was hip pain and severe limp. All of them, with bony consolidation of the femoral physis at the time of the consultation.

In all cases, it was performed a cuneiform osteotomy of femoral neck and replacement of the femoral epiphysis, through surgical hip dislocation. It was made a dissection and elevation of cervical periosteum to protect the epiphyseal vessels of the femoral head; then, the cuneiform osteotomy of the femoral neck is made with replacement of the femoral epiphysis to anatomical location and fixed.

The mean follow up was 21,2 months. We obtained consolidation in 100% of the cases, did not appear avascular necrosis nor other complications. An improvement was obtained according to Harris Hip Score from 37,6 points to 96,6. Correction of the epiphyseal-shaft angle was obtained from 62° to 12,6°.

This technique proposed in patients with sequel of SCFE is a good alternative of treatment, with good anatomical, functional, clinical and radiological results in young patients, without mid-term complications.

D.A. Heuer M. Williams R. Moss K. Butcher M. Anderson R. Milner C. Alley L. Gilmour M. Scott

This study evaluated the biologic fixation of two different titanium porous coatings: a clinically successful sintered spherical bead coating [1] and a new sintered asymmetric particle coating (STIKTITE™, Smith & Nephew). The spherical bead coating has a porosity of about 50% and an average pore size of about 220 μm, whereas the STIKTITE coating has greater porosity (about 62%) and slightly smaller average pore size (about 200 μm). Biologic fixation was assessed using a load-bearing ovine model in which coated semi-circular disc implants were inserted into a defect created in the cancellous bone parallel to and approximately 3 mm below the medial tibial plateau [2] similar to the method reported by Ignatius [3]. The implants were slightly thicker than the defect created, producing a 0.2-mm overall pressfit. Initial implant stability was assessed using mechanical push-out (n = 3) immediately after implantation into cadaveric ovine bone. Quantitative mechanical push-out testing and qualitative histology (n = 9 and n = 2, respectively, per group per time point) was performed after six and 26 weeks in vivo.

The time-zero average peak push-out load (±S.D.) of the STIKTITE group (95±3 N) was found to be significantly greater (p < 0.02) than that of the spherical bead group (36±5 N). By six weeks in vivo, the average peak push-out load for the STIKTITE group was up to 1001±362 N, and that for the spherical bead group was up to 985±425 N, both representing a significant increase compared to their time-zero results (p < 0.0005). From six to twenty-six weeks in vivo, there was again a significant increase in the peak push-out load irrespective of group (p < 0.0005), with the average peak push-out loads up to 1620±406 N and 1444±446 N for the STIK-TITE and spherical bead groups, respectively. Histology revealed bone ingrowth in both groups that confirmed the findings of the mechanical push-out testing. While the STIKTITE group showed a trend toward greater biologic fixation, overall there was insufficient evidence to support differences between the two groups (p = 0.47) irrespective of the amount of time in vivo.

The results of this study confirm the ability of the STIK-TITE coating to achieve superior initial stability. This improved initial stability reduces the reliance on adjunct fixation (such as screws) or large amounts of press-fit to prevent micromotion and create an environment suitable for long-term bone ingrowth. The results also suggest that the STIKTITE coating had a tendency to initiate and maintain bone ingrowth under load-bearing conditions to a level greater than that of a clinically successful sintered bead coating. Because loading of the implant can cause micromotion at the bone/implant interface, models like the one used in this study likely provide a more challenging and realistic representation of anticipated clinical conditions than models with minimal implant loading.

M.L. Hansen W.J. Ciccone M.C. Jacofsky A. Jaczynski A. Boyles J.C. Otis

Although reverse total shoulder arthroplasty (TSA) may restore shoulder abduction and forward flexion in the setting of a massive rotator cuff tear, the ability to use the extremity for ADL’s is often limited by external rotation weakness. Even though the reverse TSA restores abduction, the patient may be unable to bring the hand to his or her mouth because with the elbow flexed the weight of the hand causes the shoulder to fall into internal rotation. Concomitant transfer of latissimus dorsi (LDT) to the posterior greater tuberosity is a solution advocated by some surgeons. It is hypothesized that this inferiorly-directed force partially counteracts the superiorly-directed force of the deltoid, resulting in decreased shear forces on the glenoid baseplate-bone interface.

Three cadaver shoulder specimens were dissected and implanted with the reverse TSA. The rotator cuff was completely released to simulate a massive rotator cuff tear. Each shoulder was mounted in a shoulder controller that simulates neuromuscular control and replicates in vivo glenohumeral kinematics. The controller utilizes an optical, three dimensional tracking system. The humerus was weighted to simulate the full mass of the upper extremity and stepper motors were connected to the insertion points of the anterior, middle and posterior divisions of the deltoid by Spectra® cord. Simulated active abduction in the scapular plane was performed using position closed-loop feedback control. The joint reaction force at the glenosphere was measured at 5° intervals from 30°–70°. A fourth stepper motor was then connected to the greater tuberosity with 2.73kg applied to simulate a LDT and the test was repeated. Five trials were performed under each condition. Four-factor ANOVA statistical analysis with Bonferroni correction and α = 0.05 was performed.

After simulated LDT the JRF demonstrated an increase in magnitude at abduction angles between 30° and 65° inclusive (p=0.033). The superiorly-directed shear force was significantly decreased as a result of the LDT between 45° and 70° (p< 0.0001). The compressive component of the JRF was increased for all abduction angles (p=0.025). The force required to achieve abduction increased for the middle deltoid (p=0.035) and anterior deltoid (p=0.036) for the simulated LDT condition at all abduction angles. The posterior deltoid force required for abduction decreased at all abduction angles (p=0.031).

In this model of reverse total shoulder arthroplasty concomitant transfer of latissimus dorsi decreased the superiorly-directed shear force. In addition to providing improved external rotation strength, these lower shear forces may have a protective effect on baseplate fixation by reducing the risk of failure in shear. This may provide additional justification for the transfer. Although superior shear was decreased, total JRF was increased as a result of an increase in the compressive component. Further investigation is needed to determine the potential gain in joint stability and whether the glenoid bone can support such elevated compressive forces. Additionally, the force required in the anterior and middle deltoid was increased after the LDT. This indicates the need for sufficient deltoid strength and rehabilitation.

H. Ike Y. Inaba N. Kobayashi N. Iwamoto T. Ishida Y. Yukizawa C. Aoki C. Hyonmin T. Saito

Periprosthetic bone loss is one of the major concerns in total hip arthroplasty (THA). Several studies have reported that bone mineral density (BMD) decreases after THA especially in the proximal femur. The phenomenon is explained as an adaptive remodeling response of bone tissue to a significant alteration of its stress environment. The purpose of this study was to evaluate the pattern of load transfer after stem implantation, and to compare the stress of finite element (FE) studies to BMD in the proximal femur after THA.

Forty-eight consecutive patients who received a primary cementless THA with implantation of the same femoral prosthesis (VerSys, Zimmer Inc, Warsaw, Idaho) between January 2007 to December 2007 were identified. Twenty-nine patients were excluded for administration of alendronate or alfacalcidol, and four patients were lost to follow-up or had incomplete computed tomography (CT) or dual-energy X-ray absorptiometry (DEXA) data. The remaining 15 patients formed the basis of this study. The average age of the patients at the time of THA was 64 years (range, 44 to 82 years). BMD were measured with DEXA at 1 week and 12 months after THA. Regions of interest (ROIs) were defined according to Gruen’s system (ROIs 1–7). FE models of the femur and stem were obtained from pre-and postoperative CT data by “Mechanical Finder (Research Center of Computational Mechanics Inc.)” that was a software to make FE models considering individual bone shape and density distribution. FE model of the femur consisted of approximately 600,000 elements and that of the stem consisted of 200,000 elements. The shaft was restrained and force was applied to the femoral head and directed within the coronal plane at 20° to the shaft axis. Stress distribution and strain energy density were analyzed and compared to DEXA data.

BMD maintained at 1 year after THA in ROI 3,4,5, and 6, where as BMD decreased in ROI 1,2, and 7 by 17%, 16%, and 26 %, respectively. This means that BMD decreased especially in the proximal femur at 1 year after THA. FE studies revealed that the stress and the strain energy density in ROI 3,4,5, and 6 were much higher than in ROI 1,2, and 7. It was suggested that high stress and strain energy density are contributed to maintenance of BMD in the femur at 1 year after THA.

R Russo M Ciccarelli L Vernaglia Lombardi F Cautiero G. Giudice

Aim: The treatment of the fractures to three and four fragments of the humerus still represents a challenge. The authors describe the surgical technique and results with a modular prosthesis that permits an anatomical reconstruction of the proximal humerus from the calcarside, that becomes the point reference of reconstruction with the “Puzzle-Pieces” technique.

Methods: From February 2000 to February 2007 41 patients were treated with modular prosthesis. They were 8 males and 33 females aged between 56 and 79 years. In 23 cases the interested shoulder has been the right, in 18 the left. All fractures were diagnosed with X-ray and CT-scan. The type of fracture includes: 20 fractures of four fragments, 15 pluri-fragmentary fractures, and 6 fracture\dislocations. At the follow-up we evaluated 26 patients.

Results: The functional results were evaluated in 26 patients by Constant score with a mean follow-up of 4 years. All the patients reviewed have executed a X-Ray, while in 18 cases we also have evaluated the reconstruction of the tuberosities with CT-scan. In one case there has been had a complete resorption of the tuberosities with insufficiency of rotator cuff. The mean of forward elevation was 132° Conclusion: The plant of a humeral pros-thesis for fractures is a very complex intervention. The technique, for modular prostheses it’s not very codified. Moreover the results from the Literature are inconstant in particular as to function of the shoulder, not predictable and often were it accompanied by complications.

The technique we described consists in the identification and reconstruction of the medial part of calcar that becomes “the thread conductor” for restoration of the height and the retrotorsion of the humeral head.

GP. Rinaldi F. Pace D. Capitani

The Gibson and Moore postero-lateral approach is one of the most often used in hip replacement. The advantage of this approach is an easy execution but it’s criticized because of its invasivity to muscletendinous tissues especially on extrarotators muscles and because of predisposition to posterior dislocation.

Since June 2003 we executed total hip replacements using a modified postero-lateral approach which allows to preserve the piriformis and quadratus femoris muscles and to detach just the conjoint tendon (gemelli and obturator internus). Articular capsule is preserved and it will be anatomically sutured at the end of the procedure as well as the conjoint tendon with two transossesous sutures. Piriformis and quadratus femoris muscles result untouched by this approach.

We have executed 500 surgeries with this modified approach.

We have used different stems (straight, anatomical, modular and short) and press fit cetabular cup with polyethylene or ceramic insert and we have always used 36 mm femoral heads when allowed by the cup dimensions. We have used any size both of stems and cups without limitation due to the surgical approach. The mean age is 61.8 y.o., 324 females and 176 males. Obese patients, hip dysplasia Crowe 3 and 4 and post traumatic arthrosis are exclusion factors for the execution of this approach. If possible we have maintained the capsulo-tendinous less invasivity. The BMI is not an excluding factor because it’s just the gluteus region that is an important factor to decide if to execute or not a less invasive approach.

Analyzing our 500 cases we didn’t have any case of malpositioning of the stem in varus or valgus (more than 5°) and considering acetabular cup we had the tendency to position it in valgus position (not more than 40°) in the first 20 cases.

No leg discrepancies more than 1 cm were observed.

Intra-operative blood loss have been reduced of about 30 % and 50% in the post-operative. All the patients were able to active hip mobilization within the first day after surgery with a mean range of motion of 0–70°. The patients were mobilized the first day after surgery and 80% of them were able to assisted walk within second day after surgery. The mean time of stay in hospital was 6.8 days.

After 4 weeks 98% of the patients were able to walk without crutches.

One case of deep infection were evaluated and then solved with surgical debridement; no wound dehiscence. We had 1 case of anterior hip dislocation in dysplastic arthrosis due to a technical mistake. In 1 case we had femoral nerve palsy, then solved, probably because of anterior retractor malpositioning. We had 5 cases of piriformis muscle contracture without sciatic nerve palsy, then solved. We think that for total hip replacement this conservative postero-lateral approach, thanks to capsuletendinous modification we have adopted, could be considered an anatomical approach, which doesn’t present more dislocation risks compared to other approaches to the hip also thanks to the introduction of 36 mm femoral head that gives more stability and proprioceptiveness. Besides this approach gives the possibility of a shorter rehabilitation as seen above and it could be consider optimal for total hip replacement.

R. Accetta A. Meersseman L. Monti F. Anasetti G. Mineo

In this report a novel surgical treatment of proximal humerus fractures with shoulder hemiarthroplasty through an anterolateral acromial approach is presented. This access allows a drastic reduction of the risk of iatrogenic neurovascular complications and was developed to allow less invasive treatment of proximal humerus fractures with an easy control of the tuberosities which are often dislocated. Furthermore, this access allows the conservation of the anatomical integrity of the rotator cuff muscle which is fundamental in older patients. After removal of the humeral head, by this antero-lateral approach a better visibility of glenoid cavity is achieved thus allowing a more correct prosthesis components placement and a easier fixation of the tuberosity around the prosthesis using strong non-absorbable suture.

Over a 2-years period, 24 patients (age 68.9, range 53–83, 17 females and 7 males) with either displaced 4-parts fractures, according to Neer classification, or fracturedislocations of the humeral proximal third, were surgically treated trought a shoulder hemiarthroplasty with direct antero-lateral acromial approach. Clinical and functional assessments were performed at 3, 6, 12, and 18 months including the determination of the Constant Score, the radiographic assessment in an antero-posterior and axillary view of the humerus, a photographic documentation of the injured shoulder function as compared with the non-injured extremity and the assessment of the upper limb motion with a motion analysis system.

An increase in mean Constant Score and ranges of motion was observed over the follow-up-period. At 12-months follow-up the Constant Score was 62.2 points (range 41–91) out of a total of 100. Patients at 12 months showed a mean active flexion of the shoulder in the sagittal plane of 45.8 degrees (range 19.1–89.4); the mean active abduction was 49.4 degrees (range 26.1–90.8) with forearm turned down and 57.1 degrees (range 16.7–119.2) with forearm turned up; the range of rotation was 30.9 degrees (range 26.2–35.6). Nevertheless, all patients were able to perform the activity with a relatively pain-free shoulder.

The results obtained in the present study are comparable with the literature data, where other surgical approaches were used. Due to its conservative features, the presented surgical approach may represent a good alternative in shoulder hemiarthroplasty.

J.F. Cazeneuve Y. Hasssan A. Hilaneh F. Kermad A. Brunel

Synthesis and hemi-prosthesis give well known radiological results for acute proximal complex humeral fractures in elderly population. We wanted to expose the radiological outcome of the reverse concept in this indication.

From 1993 to 2008, forty four DELTA III were implanted for thirty three three-part and four-part displacements and eleven fracture-dislocations, in 3 males for 41 females, with an average age of seventy five years. The results were estimated with AP and LAMY profile Xrays.

Because of ten deceases and three moving, thirty one cases were reviewed with a mean follow-up of 6.3 years, range 1 to 15. The radiographs showed : two 2-mm thick borders on the glenoid at four and eight years with a scapular notch at 11 years and an aseptic loosening of the base plate at 12 years with a broken polar inferior screw. The patient underwent an easy surgical revision because of a fair bone stock. There was no wear of the polyethylene.

According to the NEROT classification, nineteen inferior scapular notches were observed with a mean occurrence time of 4.6 years. The seven type-1 notches appeared at a mean of 2 years and the five type-2 notches at a mean of 4.3 years. We observed four type-3 notches which reached the inferior screw at 5,6,7 and 8 years, and three type-4 notches which extended beyond the inferior screw at 6,7 and 8 year follow-up, respectively. There seem to be two distinct patters of notches: mechanical, stable proximal humeral bone loss because of an impingement between the humeral component and the inferior scapular pillar and biological, progressive in size, evolving over time with proximal humeral bone loss because of polyethylene disease; the longer the follow-up, the more severe the notch. Fourteen inferior spurs, stable after emergence, were reported with a mean occurrence time of 2.5 years range 1 to 6 years. One joint ossification occurred at 6 months and was stable at 6 year follow-up. The humeral results consisted in five medial (5,6,710, and 11 years) proximal bone looses and three bone-cement interface medial borders on the two thirds of the height of the stem at a mean follow-up of 5 years. In these eight cases, there was a notch associated. We reported one case of septic humeral loosening at 2 year follow-up.

For acute proximal humeral complex fractures in elderly population, when re-fixation of the tubercles on the classical orthopaedics devices is impossible, the use of a DELTA III prosthesis shows, with a mean follow-up of 6.3 years, worrying images in 70% of the cases.

These images are on the glenoid in 70% of the cases, appeared before seven years in 86% and are progressive in 50% of the cases. But, we have only one re-intervention for an aseptic loosening of the base plate at a twelve year evolution. New developments in design and bearing surfaces and a more long term results will probably provide more durable utilization of the reverse concept in this indication.

C.J. Wang J.M. Chen S.L. Hsu T. Wong W.Y. Chou

This study compared the functional outcomes of total hip arthroplasty (THA) in one hip and extracorporeal shockwave (ESWT) in the other hip in patients with bilateral hip necrosis.

Seventeen patients with bilateral hip necrosis were treated with THA for late stage ONFH in one hip and ESWT for early lesion in the other hip. In THA, only one type of prosthesis was used and all components were cementless. In EWST, each hip received 6000 shocks at 28 Kv (equivalent to 0.62 mJ/mm2 energy flux density) in a single session. The evaluations included pain score, Harris hip score, radiographs and MR images at 6 and 12 months and then yearly.

Significant improvements in pain score and Harris hip score were noted after treatment in both hips. However, the magnitudes of improvement showed significant differences between the two sides favoring the ESWT side. On subjective assessment, 13 patients rated ESWT better than THA; 4 patients reported comparable results of THA and ESWT, and none graded THA better than ESWT. In THA side, abnormal radiographs were noted in 47% (8 of 17) including component mal-position, nonprogressive radiolucency, and suspected component loosening. In ESWT side, significant reduction of bone marrow edema and a trend of decrease in the size of the lesion were observed after treatment.

ESWT and THA are effective for early and late stages of ONFH respectively.

However, better functional outcomes were observed in ESWT-treated hips than hips treated with THA in patients with bilateral hip disease in short-term.

T. Lovell W. Hozack S. Kreuzer P. Merritt M. Nogler L. Puri T. Wuestemann A. Bastian

The current decade has seen a marked rise in popularity of minimally invasive hip replacement, done through a variety of surgical approaches. A specific downside to the direct anterior approach includes the significant difficulty getting a “straight shot” down the femoral canal for either straight, nonflexible reaming or broaching as with standard approaches. Improper alignment in the femoral canal can lead to sub-optimal load transfer and thus compromised fixation. The femoral broach and stem insertion path for this approach is best described as a curved one, rather than the typical straight path. Some femoral components appear to be more suitable to this technique due to their geometries. The purpose of the study was to describe the effects that the single geometric parameter, stem length, has on its insertion path into the femoral canal. Due to the potential introduction of human error associated with repetitively performing a specific motion, both a physical study and a computer generated analysis were conducted.

For the physical portion of the study, a femoral implant body of generic fit and fill geometry was designed and manufactured. The length of the stem was varied from 40 mm to 100 mm in 10 mm increments. A medium sized synthetic femur (Sawbones, Pacific Labs, Seattle, WA) was machined to match the volume of the full length stem. The insertion path constraints were defined such that the stem had to maintain the greatest allowable insertion angle while still making contact on both the medial and lateral side of the canal during translation in the X direction. To reduce the variability in applying the constraints, a single author conducted the insertion procedure for each length stem while the path was videotaped from a fixed position directly in front of the setup. The most proximal lateral point of the stem was tracked through the insertion path and the X, Y coordinates were recorded at a frequency of 2 FPS. The area under this curve, referred to as the minimum insertion area (MIA), was calculated.

For the computer generated portion of the study, a CAD model of the standard length Omnifit® (Stryker Orthopaedics) was utilized. The stem was modified to create 5 additional models where the length was progressively shortened to 65%, 55%, 45%, 35%, and 25% of original length or 91mm, 77mm, 63mm, 49mm, and 35mm respectively. The femur was created from a solidified mesh of a computed tomography (CT) scan with the canal virtually broached for a full length stem. The models were each virtually assembled within the femoral canal with the similar constraints as the physical study. Again, the most proximal lateral point of the stem was tracked through the insertion path with the coordinates recorded and the MIA was calculated.

There was a non-linear relationship between stem length and the MIA with the rate of change decreasing as the stem length decreased. That is, the greatest decrease in MIA was between the standard length and next longest length in the computer simulation. It was noted that marked change in MIA began to subside between the 77mm and 63mm stems and continued this trend of having less influence onward through to the shorter lengths. Although the results of the physical study showed a higher variability than the computer generated portion, it does confirm the results of the computer generated study.

Minimizing the trauma associated with THR has led most of the above authors to the direct anterior approach. However, the femoral broach and stem insertion path is best described as a curved one, rather than the typical straight path used in other approaches. This curved insertion path also has benefits for other approaches since the broaches and stem can be kept away from the abductors, minimizing the potential injury to them. Shorter stem length makes this curved insertion path easier to perform. This is the first study to describe the effect that stem length has on its insertion path into the femoral canal. As expected, the physical portion of the study showed more variability than the computer generated portion. However, the physical and computer studies correlated well, with shorter stem lengths clearly allowing a more curved insertion path. The improvement tapered off in stem lengths below 63mm. This length correlates well with the other attempts at a shorter stem. This study provides quantitative data to help with shorter stem design and possible computer navigated insertion paths.

S. Kamada M. Naito Y. Nakamura T. Teratani A. Takeyama H. Karashima K. Kinoshita N. Kashima Y. Tanaka K. Ida D. Kuroda

The Mayo-Stem is short and tapered in the anteroposterior and mediolateral directions, designed to enhance early fixation through multiple point contact in the proximal medullary cavity. The purpose of this study was to investigate the clinical and radiographic results of total hip arthroplasty (THA) using this short stem in younger patients.

A total of 97 cementless THAs using this short stem were investigated. The length of the stem used ranged from 90mm to 110 mm. The average age of the patients at the time of surgery was 50.9 years (33–64 years). The average follow-up period was 64 months (38–108 months).

The Harris hip score was used for clinical evaluation. The valgus angles of the stems and the changes in radiographic findings around the stems after surgery were investigated on the AP radiographs of hip.

The average Harris hip score was 52.0 points pre-operatively and 93.9 points at the latest follow-up. An intraoperative femoral fissure fracture of the proximal femur occurred in 15 hips (15.4%), which were treated by circlage wires. The average valgus angle of the stem was 3.5° (range: −6°–18°). The development of bone trabeculae was seen around the curve of the stem (Gruen zones 3 and 5) in 79.4 % of hips one year after surgery. A radiolucent line was found on the lateral side of the stem (Gruen zones 1, 2, and 3) in 13.4 % of hips, which occurred in connection with the development of bone trabeculae. Subsidence of the stems (> 2mm) was seen in three hips in which intraoperative femoral fissure fracture had not occurred. These hips did not get the development of bone trabeculae. In two hips of the three hips, the valgus angles of the stems were 15° and 17° respectively. In the case of the third hip, the stem was small to the proximal femur.

Overall the clinical result of THA using a short-stem was basically gratifying.

The development of bone trabeculae, the stem size to the proximal femur and the stem position were important factors for the fixation of stem. Intraoperative fissure fracture treated by circlage wires and radiolucent lines with the development of bone trabeculae did not affect the fixation of stem.

C.J. Wang F.S. Wang J.Y Ko S.Y. Huang J.M. Chen

The effect of shockwave in osteonecrosis of the femoral head (ONFH) is poorly understood. The purpose of this study was to investigate the regeneration effects of shockwave in ONFH.

This study consisted of 14 femoral heads from 14 patients undergoing total hip arthroplasty for ONFH. Seven patients with seven hips who received shockwave prior to surgery were designated as the study group, whereas, seven patients with seven hips who did not receive shockwave were assigned to the control group. Both groups showed similar demographic characteristics. The femoral heads were investigated with histopathological examination and immunohistochemical analysis with von Willebrand factor (vWF), VEGF, platelet endothelial cell adhesion molecule-1 (PECAM-1) also referred to as (CD 31) and vascular cell adhesion molecule (VCAM) for angiogenesis, and with proliferation cell nuclear antigen (PCNA), Dickkopf-1 (DKK1) and Winless 3a (Wnt 3) for bone remodelling and regeneration.

In histopathological examination, the study group showed significantly more viable bone and less necrotic bone, higher cell concentration and more cell activities including phagocytosis than the control group. In immunohistochemical analysis, the study group showed significant increases in vWF (P< 0.01), VEGF (P¼0.0012) and CD 31 (P¼0.0023), Wnt3 (P¼0.008) and PCNA (P¼0.0011), and decreases in VCAM (P¼0.0013) and DKK1 (P¼0.0007) than the control group.

Shockwave treatment significantly promotes angiogenesis and bone remodelling than the control. It appears that application of shockwave results in regeneration effects in hips with ONFH.

Shunji Nakano Hirofumi Kosaka Masaru Nakamura Takashi Chikawa Yugi Taoka Tateaki Shimakawa Akira Minato Takaaki Ikata Megumi Sogame

Objective: The number of hip prostheses replacement surgeries particularly in elder people with osteoporosis, has been increasing every year; given this scenario, treatment of postoperative periprosthetic femoral fracture has become a critical problem. Osteosynthesis is generally selected as the procedure of choice for the surgical treatment of fractures, provided the stem prostheses do not show loosening. Stable fixation of periprosthetic femoral fracture is difficult in the elderly because they have osteoporotic bone and most of the intramedullary space is occupied by the metal stem implanted in the proximal femoral shaft. With a view to solving this problem, we developed a new surgical treatment for postoperative periprosthetic femoral fracture; this procedure use a trimming intramedullary nail, which we have termed “docking nail.” [Materials] The subjects were 3 patients (81, 75 and 76 years old) who had suffered a femoral shaft fracture around the femoral prosthesis after total hip replacement; in all 3 patients, there was no apparent sign of loosening of the stem prosthesis. The implanted stem was cemented in one patient and uncemented in the other two.

Method: Using information on the size and shape of the stem prosthesis as well as information from the pre-operative radiographs, we cut the docking nail till the proper length was achieved and trimmed it to suit the cutting site in order to ensure that it was compatible with tip of the stem. We then performed osteosynthesis using instruments of an ordinary supracondylar type intramedullary nail. In cases where it was difficult to reposition or where it was necessary to remove excessive cement and bone from around the tip of stem and graft a free bone in the bony defect, we exposed the fracture site as minimally as possible. The major difference between our procedure and the conventional procedure is that in our procedure, the docking nail is connected to the tip of the implanted stem to ensure proper alignment. Postoperative immobilization was not used in any of the patients except for the 81-year-old patient, for whom partial weight-bearing was allowed at 4 weeks, and full weight bearing at 12 weeks. The mean follow up period was 22 months (range, 6–48 months).

Result: Within 3 months, bony union with good alignment was achieved in all 3 patients without malunion or infection. The clinical and radiographic examinations conducted during the follow-up period showed good results.

Conclusion: The advantages of this method are that it is less invasive and simple compared to the conventional methods. Its only disadvantage is that it requires considerable, preoperative planning and minor trimming of the nail. Although this series is small, we think that this new treatment can be recommended and will be beneficial for treating periprosthetic femoral fractures without a loose stem. However, these preliminary findings need to be confirmed by further investigations.

Dr. Ashok Rajgopal

We undertook a study of 52 knees in 34 patients who underwent a cruciate retaining total knee arthroplasty (TKA) for severely deformed knees. At an average follow up of 12 years the knees were evaluated clinically and radiologically by means of stress radiographs and Magnetic Resonance Imaging (MRI) to assess the functional status of the posterior cruciate ligament (PCL). The knee scores showed a consistent and sustained improvement over the pre-operative levels. Stress radiographs did not show any posterior translation of the tibia. In 43 knees an intact PCL was visualized on MRI scans.

These observations suggest that the PCL is present at long term review even in knees that underwent arthroplasty for severe deformities.

A. Croce M. Ometti P. Dworschak

The use of neck modular adapter is a relative new solution for hip revision arthroplasty. This device assure a lot of advantages for the orthopaedic surgeon because Bioball can be use in different situations in order to solve different complications: hip prosthesis dislocation, correction of length (up to +21mm), save an old stem not mobilized, reduction of operation length.

The hip prosthesis dislocation, in spite of the continuous progress of implants’ materials and design, is still an actual event in the orthopaedic clinical practice, both after total hip replacement or a endoprosthesis. Furthermore, dislocation has an important social-economic impact because of a protracted hospitalization and rehabilitation and elevated costs of an eventual revision. Although using heads with a diameter larger than 28 mm we obtain virtually a greater range of motion, with a contemporary increase of degree necessary to cause the head-neck impingement, the risck of dislocation hasn’t a significant increase using head with a diameter of 22 mm.

Neck modular adapters (Bioball) allow to correct easily the biomechanics parameters of the dislocated prosthesic joint, avoiding the revision of the stem. Other indications for the use of the neck modular adapter are total hip replacement and intraoperatory correction of the limb length. Vantages are the possibilty to obtain a great range of motion through a small thickness of the 12/14 adapter, the possibility to extend the limb length up to 21 mm and to use ceramic heads during revisions, because the combination head/neck has a tribological unweared surface. In fact, in normal conditions, if the stem is not mobilizated, the use of ceramic head is rash; the Bioball adapter, instead, can be used with a old stem, so we can set a ceramic head. Every stem with a Biolox cone can be combined with a metal or ceramic head up to the 5XL size (+21 mm) through a Bioball adapter; in this way the cup is not removed.

We have two kinds of neck modular adapters: 12/14 allow both to extend the neck and to correct the offset, and 14/16 that allow to extend only the neck, because of the largest diameter of the prosthesic neck and the small thickness of the adapter. For these neck modular adapters exist different sizes, from M to 5XL (+21mm). Recently to these two types of Bioball were introduced also solutions for special stems (like for Exeter, ABG I, ABGII, PCA and others) We have also proving heads and necks. The proving and definitive heads have to be of the Bioball system because these are inserted on a modular neck with a no-standard diameter.

In the common practice the use of these adaptors has not to be considered as a routinary procedure, but have to be taken in consideration as a valid aid for orthopaedic surgeon to quickly and less invasively, solve technically demanding procedures with a real benefit for high-surgical risk patients.

Wang Huijuan Sheng Lin Weng Xisheng

Resection of the distal femur to properly fit the prosthetic component is a crucial step for prosthesis alignment during TKA. In this study, we development a new integrative(Five-In-One, FIO) femur resection method, which performs distal femoral resection in one procedure instead of the standard five cutting steps. The accuracy and operating time are comparable to the conventional cutting methods using foam bone model experimentation and in 9 patients.

In vitro comparison: Uniformly-sized foam bone femur models were used in this study. New five-in-one cutting devices and conventional cutting devices of the same prosthetic size of #44 were installed and resection of the distal femur by five experienced orthopaedic surgeons. Each surgeon performed five cases with each device. Then a femoral prosthesis (#44) was installed on each cut femur mode and anterior-posterior and lateral X-ray radiographs were taken. The angles facet length and distance between anterior and posterior oblique facets were then measured with goniometer and vernier calliper. The corresponding angles from a standard femoral prosthesis (#44) were also measured. The angular difference between the resection femur and prosthesis was calculated and named Angular Deviation. The valgus angle and anteversion angle were measured on anteriorposterior and lateral X-ray radiographs respectively. The mean value from the five measurements obtained from each surgeon using the same cutting method was used for the comparison of the modified and standard resection model. The operating time of each cutting procedure was recorded. students’t-tests were used for the statistical analysis.

In vivo following up: 9 patients with use of the five-in-one cutting instrument and the Deluxe prosthesis have been evaluated during operating, and followed up for at least one year. Operating time were recorded and HSS clinical and functional scoring systems before the surgery, three months and one year after surgery.

The angular deviation of the new FIO Cutting Device was significantly less than the conventional device in all four anatomic measurements (p < 0.05). The distance deviation in the FIO group was also significantly less in the FIO group compared to the conventional procedure (p < 0.05). The average valgus angle and anteversion angle of the five-in-one cutting device which were measured on anterior-posterior and lateral X-ray radiographs respectively were 6.86° and 3.02° respectively. They were not significantly different when compared with the data of the conventional cutting device, which were 6.56o and 3.06o respectively. The mean of the cutting time of the five-in-one device was 9.70 minutes, which was significantly less than the conventional cutting device which was 21.84 minutes averaged (p < 0.05).

Our data demonstrated that the angular accuracy of the distal femoral resection with the newly Five-in-one technique was greatly improved compared to the conventional cutting method. With the use of the new technique, operative time was also shortened over two folds compared to the conventional method. We conclude that the new five-in-one cutting device is more accurate and shorten operating time compared with the conventional device in the vitro study.

The mean HSS score before surgery was 48.69, 84.7 three months after surgery, and 85.6 at one year after surgery. The survivorship was 100% of patients.

D. K. Bae K. H. Yoon S. J. Song M.C. Shin J.H. Noh M.J. Park H.J. Cho I.H. Choi

In conventional high tibial osteotomy it is difficult to obtain the ideal correction angle consistently and there is high variability of postoperative alignment. We assessed the reliability, accuracy and variability of closed wedge high tibial osteotomy using computer-assisted surgery compared to the conventional technique. Fifty closed wedge HTO procedures were performed and analysed between July 2005 and July 2006, using the CT-free navigation system(Vector Vision® version 1.1, Brain-LAB, Heimstetten, Germany) for medial compartment osteoarthritis of the knee and fifty knee operations using conventional closed-wedge HTO, performed between 1994 and 2006, were retrospectively reviewed as a control group. The mean age was 59.4 years for the navigation group and 60.7 years for the conventional group. In the navigation group, the mean mechanical axis (MA) before osteotomy was varus 8.2°, and the mean MA after the fixation was valgus 3.6°. On the radiographs, the mean preoperative MA was varus 7.3°, and the mean postoperative MA was valgus 2.1°. In the conventional group, the mean MA was varus 10.6° preoperatively and valgus 0.1° postoperatively via the radiograph. The mean preoperative posterior slope angle (PSA) was 11.0°, which decreased to 9.0° in the navigation group. The mean preoperative PSA was 10.4°, which decreased to 6.4° in the conventional group(p = 0.000). There was a positive correlation between measured data taken under navigation and by radiographs(r > 0.3, P < 0.05). The mean correction angle was significantly more accurate in the navigation group(p < 0.002). The variability of the correction was significantly lower in the navigation group (2.3° versus 3.7°, p = 0.012), and the distribution of MA was also narrower in the navigated group.

We concluded that navigation provides reliable real-time intraoperative information and may increase accuracy, and improve the precision of closed-wedge HTO.

M. A. Rosa A. Pisani G. Maccauro G. Arrabito

Aims: The innovative surgical procedure of humeral resurfacing emiarthroplasty is currently used for the treatment of younger patients, in need of a bone-preserving implant, affected by primary gleno-humeral osteoarthritis and rheumatoid arthritis, secondary degenerative joint disease, post-traumatic arthritis or mal-unions of the humeral head, loss of articular cartilage, joint incongruity and stiffness, avascular osteonecrosis of the humeral head, combined loss of the gleno-humeral joint surface and rotator cuff loss of function and pain unresponsive to nonoperative measures. Published reports have indicated a large variation in the benefits of this procedure. The aim of this study is to analyse the clinical results obtained by the authors in a preliminary report of a two-years experience in the surgical actuation of this procedure, that represents one of the most innovative options in the field of the shoulder arthroplasty.

Materials and Methods: The authors report the outcomes of their experience in humeral head surface replacement emiarthroplasty. In the last two years 25 selected patients have been treated according to the surgical implantation of the “bone sparing” Global Cap conservative anatomic prosthesis (DePuy). The mean age of the patients was 52 years (range, 34 to 76 years). They have been followed for a mean of 8 months, (range, 4 to 16 months).

Preoperative diagnoses were: osteoarthritis, rheumatoid arthritis, psoriasic arthritis, osteonecrosis and post traumatic arthritis. 8 patients underwent contextual cuff tear repair.

Results: Constant score for the whole group improved from a mean preoperative score of 22 to 60 at the last follow-up. Periprosthetic osteolisys was seen in 3 cases. One case of stiffness required narcosis mobilization at 5 months after surgery. Our results are comparable to those obtained with others modern R.R.H. and are similar to Copeland’s own series.

Conclusions: The preliminary results of our study show how some pre-operative factors appear to influence the functional improvement and the personal satisfaction rate of the patients after humeral resurfacing emiarthroplasty. The most important are represented by: the presence of erosions in the glenoid cartilage, possible previous shoulder surgery and associated cuff tears. The gender of the patients doesn’t appear a discriminating factor. The age appears to influence only boundedly the clinical post-operative outcomes. In our opinion, the initial diagnoses is determinant: patients affected by systemic pathology, like rheumatoid arthritis, or by cuff tear obtain the least functional improvement and satisfaction; on the contrary, patients affected by primary and secondary degenerative joint diseases, post-traumatic cartilage lesions and avascular osteonecrosis of the humeral head obtain better results.

PJ Tong SX Zhang HT Jin L Chen WF Ji J Li

The purpose of this study was to analyze the long-term effect of arterial perfusion of drugs and bone marrow stromal cells (bMSCs) on osteonecrosis of femoral head (ONFH). From Jan 1997 to Mar 2004, one hundred and seventeen patients with ONFH were consecutively enrolled to receive a digital subtraction angiography (DSA) in arteriae circumflexa femoris medialis and arteriae circumflexa femoris lateralis. In DSA, a dosage of drugs (urokinase, salvia injection, and tetramethylpyrazine) and autologous bMSCs or only the drugs were perfused into the arteries. The morphological changes of the arteries in DSA after perfusion were recorded. Symptoms radiographs, and the Harris hip-rating score were determined preoperatively and at each follow-up examination at one month, six months, one year, 2 years and 5 years after the treatment. 83 patients were followed up for more than five years. The median follow-up period was 7.9 years.

After the drugs had been perfuse, the arteries became thicker, and more than 2 branches appeared in DSA. Five years after the operation, the Harris hip score of 32 patients (38 hips) treated by arterial perfusion of simplex drugs (group A) increased from 59.24±5.28 to 71.80±6.37 (p< 0.01), and the excellent and good rate of centesimal evaluation was 57.9%. The Harris hip score of 51 patients (59 hips) treated by arterial perfusion of drugs and autologous bMSCs (group B) increased from 59.52±4.85 to 78.29±6.05 (p< 0.01), and the excellent and good rate was 78.0% which was significantly higher than that of group A (p=0.035). Since two years after operation, the Harris hip score of group A was significantly higher than that of group B (p< 0.01).

Among the patients in group B, the rate of excellent and good in early stages (˜,˜ a and ˜ b according to Ficat classifying, 50 hips) was 84.0%, which was better than the rate in the terminal stage (Ficat III, 9 hips, the excellent and good rate was 44.4%)(p = 0.028), and the rate of excellent and good in low age group (< 40 years, 33 hips) was also better than that in high age group (≥ 40 years, 26 hips)(p=0.038).

We conclude that arterial perfusion of drugs and autologous bMSCs treating osteonecrosis of femoral head is safe and effective. The long-term therapeutic effect is more satisfactory than that of simplex arterial perfusion of drugs.

J. Fuchs W. Shields W. Schmidt I. Liepins J. Racanelli

Introduction: Uncemented proximally filling porous-coated femoral components must be designed with an optimal level of press-fit. Excessive press-fit yields higher femoral stress which can result in periprosthetic femoral fracture (PPFx), whereas insufficient femoral stress can lead to a lack of initial mechanical stability, which “is necessary to achieve bone ingrowth into the porous surface” (Manley P.A. et. al., J Arthroplasty10:63–73, 1995) of the implant. An optimal press-fit design should also provide an accurate and repeatable femoral stem seating height in all patients.

A battery of cadaveric tests, physical “bench-top” tests, and finite element analyses (FEA) should be used in order to both quantitatively and qualitatively optimize a femoral press-fit design. In this study, a method is proposed to quantitatively rank candidate press-fit stem designs relative to successful predicates based on stem seating height and PPFx risk by recreating impact loading applied during surgery through a controlled “bench-top” model.

Methods: Three press fit candidate designs A, B & C and two clinically successful predicate proximal fit and fill stems (Secur-Fit™ Max (Fit & Fill 1) and Meridian® TMZF® (Fit & Fill 2), Stryker, Mahwah NJ) were evaluated. Five foam cortical shell Sawbones® femur samples (Item# 1130, Pacific Research Laboratories, Inc., Vashon, WA) were prepared for each press-fit design. A stem impactor was attached to the stem and then the stem was hand inserted in the femur. Then the construct was mounted in the drop tower using a vice and initial drop height was set to generate approximately 5500 N of impaction force when fully seated. Each stem was serially impacted until stable then step loaded until PPFx occurred. The height above/below the medial resection plane was measured after each impaction.

Results: All press-fit designs had an initial stable seating height within the desired range without causing PPFx, using an average impaction load of 5341 N. All of the press-fit designs required, on average, roughly a 200% increase in impact load (10925 N) to cause PPFx. The press-fit deign which ranked first based on seating height accuracy, defined as the design closest to zero at stable, was Design C at −0.02 mm countersunk. Design A with a standard deviation of 0.09 mm ranked first for repeatability, defined as the design with the smallest standard deviation at stable. Finally the press-fit design which ranked first for lowest PPFx risk, defined as the design that is most countersunk prior to PPFx, was Fit & Fill 1 at 6.30 mm countersunk.

Discussion: This controlled “bench-top” impact loading model successfully showed that it can quantitatively evaluate stem seating height and PPFx risk for several different femoral press-fit designs. In order to determine the optimal design, each press-fit design was ranked with equal weight given to seating height and fracture risk. Using this test method one design alternative, press-fit Design C, ranked first as the optimal combination of seating height accuracy and consistency with a low risk of PPFx. A limitation of this impaction model is that it does not directly predict PPFx rate, it only quantifies risk of fracture. Another limitation is that this model does not simulate all of the variably that is inherent to actual patient bone types. This test is one step in a battery of tests, including cadaveric evaluation and FEA, which should be used in order to optimize a femoral press-fit design.

K. Gokaraju B.G.I. Spiegelberg M.T.R. Parratt J. Miles S.R. Cannon T.W.R. Briggs

There is limited literature available on the use of metal prosthetic replacements for the treatment of non-traumatic lesions of the proximal radius. This study discusses the implant survivorship and the functional outcome of the elbow following insertion of metal proximal radius endoprostheses performed at the Royal National Orthopaedic Hospital.

We present a series of six patients treated with endoprosthetic reconstruction of the proximal radius following resection of non-traumatic pathologies. The patients included four females and two males, with a mean age of 39 years at the time of surgery. Their diagnoses included Ewing’s sarcoma, chondroblastoma, benign fibrous histiocytoma, radio-ulna synostosis and renal carcinoma metastases in two patients. Follow-up extended to 192 months with a mean of 76 months. During this time there were no complications with the prostheses, the most recent radiographs demonstrated secure fixation of the implants and none required revision. One patient developed posterior interosseuous nerve neuropraxia following surgery, which partially recovered, and another patient passed away as a result of disseminated metastatic renal cell carcinoma which was present preoperatively.

The patient with radio-ulna synostosis had a 25° fixed flexion deformity of the elbow post-operatively but good flexion, supination and pronation. All other patients had full ranges of movement at the elbow.

Functional scores were assessed using the Mayo Elbow Performance Score with patients achieving a mean score of 86 out of 100.

The results of the use of proximal radial endoprostheses for treatment of non-traumatic lesions are encouraging with regards to survivorship of the implant and functional outcome of the elbow.

M. Kawasaki Y. Tamai T. Fujibayashi T. Takemoto

Total Hip Arthroplaty (THA) using posterior approach(PA) that resect muscle have done from September, 2005 to August, 2006, but, for the purpose of a lower invasive surgery, we changed to THA using direct anterior approach(DAA) that preserve muscle from September, 2006. The purpose of this study was to compare the inflammation degree and clinical results of MIS-THA using PA with that of MIS-THA using DAA.

From September 2005 to May 2008,73 hips in 69 patients were treated with consecutive primary cement-less MIS THA. The breakdown of the patients was DAA, 51 hips, and PA, 22. The average age at operation was 66 years and 58 years. The average followup after primary THA was 1.5 years and 2.8 years. The sex ratio (M/F) was DAA 2/44, and PL 6/15. For the inflammation degree, CRP at the seventh day and 14 day after surgery of DAA was significantly lower than those of PA (p< 0.01). WBC of the seventh day of DAA was significantly lower than that of PA.CPK on DAA at the first was significantly lower than that of PL (p< 0.01), and CPK of PL took time for a long time to decrease to the level before the operation compared with DAA. For clinical results, there were no significant difference operative time, blood loss volume and complication in DAA and PA. No significant differences in the HHS at the final follow up were observed between DAA and PA. In the radiographic assessment, there was no significant difference in neutral position of stem of DAA(46hips) and PA (18hips), and there was no significant difference in abduction angle of socket in DAA(average 45°) and PA (47°). The day of SLR possibility was significantly earlier DAA (average 4 day) than PA (7). No significant differences in hospital stay were observed between DAA (average 21 days) and PA (26).

In the current study, there was thought that DAA was lower inflammation degree than PA, because normalization of CRP after surgery in DAA was significantly early in comparison with PA, and CPK of the first day after surgery was significantly lower in DAA than in PA. In the clinical assessment, the day of SLR possibility only was significantly earlier in DAA than in PA. This may imply muscle recovery of DAA is more rapid than that of PA. In the future, DAA will help to the further early rehabilitation and the early hospital discharge.

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Joseph F. Fetto P. Walker

Recent trends in surgical techniques for THR, i.e. MIS and anterior approaches, have spawned an interest in and possible need for shorter femoral prostheses. Although, previously published clinical investigations with custom short stems have reported very encouraging results (Walker, et al, 1,2), the transition to off-the-shelf (OTS) versions of shorter length prostheses has not met with the same degree of success. Early reports with OTS devices have documented unacceptably high and significant incidences of implant instability, migration, mechanical/aseptic failure, and technical difficulty in achieving reproducible implantation outcomes. They have highlighted the absolute need for a better understanding of the consequences of changes in implant design as well as for improvements in instrumentation and surgeon training.

Several basic questions must be addressed. First, what is the purpose of a stem? Second, can stem length be reduced and if so by how much can this be safely done. Third, what are the effects of stem shortening and are there other design criteria which must take on greater importance in the absence of a stem to protect against implant failure.

To examine these questions a testing rig was constructed which attempts to simulate the in vivo loading situation of a hip, fig.1(Walker, et, al.). Fresh cadaveric femora were tested with the femora intact and then with femoral components of varying stem length implanted to examine the distribution of stresses within the femur under increasing loads as a function of stem length. This was correlated with observations of prospective DEXA measurement of proximal femoral bone mass and implant migration following THR(Leali, 3).

Our studies indicated that a stem is not an absolute requirement in order to achieve a well functioning, stable implant. However in order to reduce the possibility of mechanical failure a reduced stem or stemless implant absolutely must have, inherent to its design, a provision for sufficient contact with both the medial and lateral proximal metaphyseal femur. As well it must also have a flat posterior surface parallel to, and in contact with, the posterior surface of the proximal femoral metaphysis. These conditions will provide support against distal migration as well as bending moments in the A/P plane. As a consequence of this latter condition, appropriate anteversion must be achieved in the neck region of the prosthesis and not by rotation of the implant within the proximal metaphyseal cavity of the femur.

In conclusion, this study demonstrates that simply reducing the length of an existing implant to accommodate changes in surgical techniques may not be a reasonable or safe design change. Such shortened versions of existing stem designs should undergo rigorously in vitro testing before being released for implantation.

N. Kitamura K. Arakaki K. Susuda E Kondo K. Yasuda

Introduction: While plain radiographs are the clinical standard for routine follow-up after total knee arthroplasty (TKA), periprosthetic osteolysis can be difficult to identify on radiographs because it is often obscured by the metallic prosthesis. This study sought to evaluate the pattern and size of periprosthtic osteolytic lesions after TKA in patients with rheumatoid arthritis using multi-detector computed tomography (MDCT).

Methods: We evaluated 25 primary cemented alumina-ceramic TKAs (LFA-I, Kyocera) using minimum 10-year CT scans. All TKAs had an alumina-ceramic femoral component, a titanium tibial baseplate with a poly-ethylene insert, and a polyethylene patella component, which had been fixed with cement. The average age at the time of surgery was 54.1 years. The average time interval between surgery and the computed tomography scan was 12.6 years. None of the patients in this study documented periprosthetic infection or had undergone bone grafting.

Results: The MDCT detected 31 lesions in 12 knees: 23 femoral and 8 tibial lesions.

All lesions occurred around the prosthetic rim, and the mean size of osteolysis per knee was 2.1 +/−1.5 cc (range, 0.4–4.7 cc). Only seven lesions in 6 knees were diagnosed as osteolysis on plain radiographs: 2 lesions at anterior femoral condyle and 5 lesions at tibial condyles. None of the lesions around the posterior condylar flanges detected on CT was identified on plain radiographs. None of the implants showed radiographic loosening or required reoperation.

Discussion: As the alumina-ceramic TKA allowed the CT scans to obtain clear images with little metal artifact, we could easily detect lesions and joint space communication. This study demonstrated that plain radiographs underestimated osteolysis, and that lesions around posterior femoral condyles were the most difficult to identify on radiographs. Although most of the lesions were small and may be of little clinical importance, this study confirmed that MDCT can accurately detect osteolysis and measure lesion volumes in alumina-ceramic TKA.

C.C. Lee W.P. Lin L.C. Horng C.C. Jiang

We conducted a prospective, randomized study comparing the outcomes of total knee arthroplasty (TKA) respectively through a quadriceps-sparing (QS) approach and a MIS medial parapatellar (MP) approach at 2-year follow-up. Sixty patients (80 knees) with primary osteoarthritis were enrolled in this study. Patients were blinded to be treated with and randomized to be grouped by either MP group (40 knees) or QS group (40 knees). Thirty-seven MIS MP TKAs and thirty-eight QS TKAs completed the 2-year follow-up.

According to the isokinetic study, the recovery of muscle strength (peak muscle torque) and normalization of muscle balance (H/Q peak-torque ratio) were comparable in both groups at either 2-month or 2-year follow-up. Tourniquet and surgical time in the QS group was significantly longer (approximately 20 minutes) than that in the MP group. The hip-knee-ankle axis measured after surgery was significantly more varus in the QS group than that in the MP group. The axis in both groups did not significantly progress at 2-year follow-up. There were no infections and no revisions at 2-year follow-up in both groups. More outlier cases (4 knees) were noted in the QS group when compared with the MP group (no outlier).

However, no differences regarding the clinic outcomes (including VAS, HSS knee score, ROM and satisfaction) were observed between these two groups after either two months or two years upon operation. In both groups, there was a significant improvement of these parameters at 2-year follow-up in contrast with 2-month follow-up and pre-operative status.

In this study, we conclude that MIS medial parapatellar TKAs could achieve comparable recovery of muscle strength, normalization of hamstring-quadriceps muscle balance and clinical outcomes when compared with QS TKAs; moreover it provides more reliable alignment and fewer complications than quadriceps-sparing TKAs.

RC Wasielewski KC Sheridan RS Palutsis

Great disparity appears in the literature regarding the occurrence of minor and major complications after two-incision total hip arthroplasty (THA). Advocates of twoincision THA contend that this minimally invasive surgical (MIS) technique provides faster rehabilitation with fewer restrictions and financial advantages stemming from shorter hospital stays and quicker returns to work. These advantages, however, cannot be fully realized unless the procedure can be performed within acceptable risk levels.

The operative, perioperative, and postoperative complications of a consecutive series of 200 two-incision THAs from a single surgeon were analyzed. Of the 8 femur fractures which occurred in this series, four occurred intraoperatively. All four were nondisplaced and treated with a cerclage cable through the anterior incision. The prosthesis was retained in each case. Of the four postoperative fractures, two were nondisplaced, permitting retention of the prosthesis. These were treated with a trochanteric plate with wiring above and below the lesser trochanter. The other two postoperative fractures were displaced, necessitating revision to a longer, uncemented stem and cerclage wiring.

Other complications in this series included two nondisplaced greater trochanter fractures > 2cm, 14 asymptomatic greater trochanter fractures ≤2 cm, one malpositioned cup requiring revision, one loose stem, seven cases of heterotopic ossification ≥Grade 2, four dislocations, one superficial infection, 80 lateral femoral cutaneous nerve neuropraxias (78 of which resolved within six weeks), and four femoral nerve neuropraxias (three of which resolved in 6 to 12 weeks).

In this series, two-incision THA was performed with a low incidence of major complications but a high incidence of minor complications. Despite the minor complications, most patients experienced an accelerated recovery and rehabilitation owing to reduced tissue trauma.

To help surgeons avoid complications, we recommend periodic retraining sessions where concerns and pitfalls can be addressed and recent enhancements, taught.

Superficial nerve complications, such as those encountered in high numbers in this series, can be avoided by moving the anterior incision slightly lateral and splitting the fibers of the tensor fascia lata. The risk of minor trochanteric fractures can be reduced by first lateralizing broach-only stems with a long straight 9mm reamer and/ or by using direct visualization.

D. Janssen D. Waanders K.A. Mann N. Verdonschot

The stability of cemented hip implants relies on the fixation of the cement mantle within the bone cavity. This fixation has been investigated in experiments with cement-bone interface specimens, which have shown that the cement-bone interface is much more compliant than is commonly assumed. Other studies demonstrated that the mechanical response of the interface is dependent on penetration of the cement into the bone. It is, however, unclear how cement penetration exactly affects the stiffness and strength of the cement-bone interface. We therefore used finite element (FE) models of cement-bone specimens to study the effect of cement penetration depth on the micromechanical behavior of the interface.

The FE models were created based on micro computed tomography (micro CT) data of two small cement-bone interface specimens (8x8x4 mm). The specimens had distinct differences with respect to interface morphology. In these models we varied the penetration depth, with six different penetration levels for each model. We then incrementally deformed each model in tension and in shear, until failure of the models. Failure was simulated to occur in the bone and cement when the local ultimate tensile stress was exceeded, by locally reducing the material stiffness to near zero. From the resulting force-displacement curves we established the apparent tensile stiffness and strength for each of the models.

Our results indicated that the strength and stiffness of the cement-bone interface increased with increasing cement penetration depth, both in tension and in shear. However, after reaching a certain penetration depth, both strength and stiffness did not further increase. This depth was dependent on the specific interface morphology. We furthermore found that the strength of the models was higher in shear than in tension. After failure of the models, damage was mainly found in the cement, rather than in the bone.

The FE-based techniques developed for the current study are suitable for exploration of a variety of aspects that may affect the cement-bone interface micromechanics, such as biological changes to the bone and variations of cement material properties.

Qing Liu YiXin Zhou HaiJun Xu Jing Tang ShenJie Guo QiHeng Tang

Prosthetic reconstruction of high-riding hips is technically demanding. Insufficient bony coverage and osteopenic bone stock frequently necessitate transacetabular screw fixation to augment primary stability of the metal shell. We sought to determine the validity of the previously reported quadrant system, and if needed, to define a specialized safe zone for augmentation of screw fixation to avoid vascular injuries in acetabular cup reconstruction for high-riding hips.

Volumetric data from computed tomography enhancement scanning and CT angiography of eighteen hips (twelve patients) were obtained and input into a three-dimensional image-processing software. Bony and vascular structures were reconstructed three-dimensionally; we virtually reconstructed a cup in the original acetabulum and dynamically simulated transacetabular screw fixation. We mapped the hemispheric cup into several areas and, for each, measured the distance between the virtual screw and the blood vessel.

We found that the rotating centers of the cups shifted more anterior-inferiorly in high-riding hips than those in ordinary cases, and thus the safe zone shifted as well. Screw fixation guided by the quadrant system frequently injured the obturator blood vessels in high-riding hips. We then defined a specialized safe zone for transacetabular screw fixation for high-riding hips.

We conclude that the quadrant system can be misleading and of less value in guiding screw insertion to augment metal shells for high-riding hips. A new safe zone specific to high-riding hips should be used to guide transacetabular screw fixation in these cases.

H. Ozturk A.M.H. Jones S.L. Evans P.B. Nair M. Browne

Excessive implant migration and micromotion have been related to eventual implant loosening. The aim of this project is to develop a computational tool that will be able to predict the mechanical performance of a cementless implant in the presence of uncertainty, for example through variations in implant alignment or bone quality. To achieve this aim, a computational model has to be developed and implemented. However, to gain confidence in the model, it should be verified experimentally. To this end, the present work investigated the behavior of a cementless implant experimentally, and compared the results with a computational model of the same test setup.

A synthetic bone (item 3406, Sawbones Europe AB, Sweden) was surgically implanted with a Furlong cementless stem (JRI, Sheffield, UK) in a neutral position and subjected to a compression fatigue test of −200 N to −1.6 kN at a frequency of 0.5 Hz for 50000 cycles. Measurements of the micromotion and migration were carried out using two linear variable differential transducers and the strain on the cortex of the femur was measured by a digital image correlation system (Limess Messtechnik & Software Gmbh).

A three-dimensional model was generated from computed tomography scans of the implanted Sawbone and converted to a finite element (FE) model using Simple-ware software (Simpleware Ltd, Exeter, UK). Face-to-face elements were used to generate a contact pair between the Sawbone and the implant. A contact stiffness of 6000 N/m and a friction coefficient of 0.3 were assigned. The analysis simulated a load of −1.6 kN applied to the head of the implant shortly post implantation. The motions and strains recorded in the experiment were compared with the predictions from the computational model. The micromotion (the vertical movement of the implant during a single load cycle), was measured at the proximal shoulder, at the distal tip of the implant and at the bone-implant interface. The maximum value calculated proximally using FE was 61.3 μm compared to the experimental value of 59.6 μm. At the distal end, the maximum micromotion from FE was 168.9 μm compared to 170 μm experimentally. As a point of reference, some authors have suggested that in vivo, fibrous tissue formation may take place at the bone-implant interface when the micromotion is above 150 μm. The maximum micromotion found computationally at this interface was 99 μm which is below the threshold value defined. The longitudinal strain over the surface of the bone was variable and reached values of up to 0.15% computationally and 0.4% experimentally; this may be related to the coordinate systems used. However, it was noted that digital image correlation identified qualitatively similar strain patterns, and has great potential for measuring low level surface strains on bone.

In conclusion, the good correlation between the computational modelling and experimental tests provides confidence in the model for further investigations using probabilistic analyses where more complex configurations (for example change in implant alignment) can be analyzed.

Raman Thakur

Failure of internal fixation of intertrochanteric fractures is associated with delayed union or malunion resulting in persistent pain and diminished function. We evaluated 15 elderly patients treated with a tapered, fluted, modular, distally fixing cementless stem.

At an average follow up of 2.86 years, mean Harris hip score improved from 35.90 preoperatively to 83.01 (P < 0.01). Fourteen stems had stable bony ingrowth and one stem was loose. Distal fixation with a tapered fluted modular cementless stem allows stable fixation with good functional outcome in a reproducible fashion in this challenging cohort of patients.

V. Antoci M.J. Phillips V. Antoci K.A.

Background: In the present study, the characteristics and mid-term to long-term outcomes of total knee arthroplasty (TKA) associated infections treated with different types of approaches were evaluated.

Methods: A retrospective study of the results of 71 infected TKA treated between August 1993 and August 2005. The data included medical records, gender, periprosthetic infection (PPI) classification, patients’ comorbidities, PPI diagnostic criteria, microbiology and histopathology results, surgical and antimicrobial therapy, treatment modality, complications, follow up, and treatment results.

Results: Median age was 70 years (range 43–88). Median follow-up 5.8 years (range 2–12). Thirty-three patients had multiple risk-factors for PPI. The main pathogens isolated were Coagulase-negative staphylococci 26 (37%), Staphylococcus aureus 16 (22.4%).

The treatment methods of TKA infection was two-stage exchange in 59 (83%), debridement and retention −5 (7.2%), arthrodesis −5 (7.2%), excision arthroplasty 2 (2.8%). At final followup, 17 knees (24%) had required reoperation: 10 knees (14%) -component removal for reinfection. Two knees were reinfected 3 times, three knees – two times. The median time to first reoperation for reinfection was 1.2 years (range, 0.04–2.5 years). By Kaplan-Meier survival analysis the estimated survivals free of reoperation for infection were 90.5% (confidence intervals, 85.3–96.1%) at 5 years and 82% (confidence intervals, 70.3–94.5%) at 10 years. The Knee Society scores: Pain scores, Functional scores, ROM improved.

Conclusions: TKA infections treatment is a difficult task leading to a high rate of unsatisfactory mid-term and long-term results. About one forth of patient require reoperation, 14% become reinfected in first 2.5 years. Half of reinfected patients get reinfected repeatedly. In most cases patients are reinfected with the same micro-organism but more virulent. TKA infection treatment option should be chosen according to the type of infection (acute or chronic), the duration of infection, the stability of the implant, the type of microorganism causing infection, bone quality and integrity, and the quality of the soft-tissue.

H. Warashina M. Matsushita M Hiroishi R Yoneda J Otsuka S Koh T Aoki H Inoue E Horii Y Osawa

Acetabular component malposition during total hip Arthroplasty (THA) increases the risk of dislocation, reduces the range of motion, and can be the cause of early wear and loosening. Variability in implant alignment also affects the result of THA. The purpose of this study was to compare acetabular cup positioning of three different approaches in THA.

Three different approaches for cementless THA were studied in 108 operations.

The direct anterior approach was used in 56, the anterolateral approach in 32 and the posterolateral approach in 50. The same cementless cup was used in all cases. The same surgeon performed all procedures with mini-incision surgery, using different approaches. To determine the accuracy of the cups, the inclination and anteversion angles were measured with a CT-investigation of the pelvis.

There were no statistical differences between the three groups regarding means of the inclination and anteversion angles. But a significant range of variance, the lowest variations being in the group of the direct anterior approach, the highest in the group of the anterolateral approach.

W.Y. Shon S. Biswal N.B. Giripunje

Transtrochanteric rotational osteotomy (TRO) is a controversial procedure with reported inconsistent results. We reviewed 50 patients (60 hips) who underwent this procedure for extensive osteonecrosis of the femoral head, focusing on varization to determine its effectiveness as a head-preserving procedure in young adults. The mean age of the patients was 28 years (range, 18–46 years). Using the Ficat-Arlet classification, 40 hips had Stage II and 20 hips had Stage III involvement. According to the classification system of Shimizu et al., the extent of the lesions were Grade C in 54 hips and Grade B in six hips; the location of the lesions were Grade c in 56 hips and Grade b in four hips. Minimum follow-up was 18 months (mean, 84 months; range, 18–156 months). The mean preoperative Harris hip score was 44.7 points (range, 32–62 points) which improved to an average postoperative score of 80.1 points (range, 44–100 points) at the latest follow-up. Forty-four hips showed no radiographic evidence of progression of collapse. Ten hips showed progressive collapse, seven hips showed progressive varus deformity, three hips had stress fractures of the femoral neck, and one hip had infection. We believe TRO with varization is worth attempting for extensive osteonecrosis of the femoral head in young adults, although failures and complications are not uncommon.

R. Valentini B Martinelli

We refer about our experience in treating of 30 Pts with periprosthetic fractures (15 involved the hip prosthesis and 15 involved knee prosthesis) from jan 2002 to june 2008 with three different kinds of locked plates. The first system used has been the L.I.S.S. based on titanium plates and screws with the screws inserted in the plate by thread holes, the second was the so-called O’Nil system with the steel plates and the titanium screws screwed in a titanium conical insert, the third hardware system was represented by steel screws and plates with the screws screwed on the thread plate hole.

The results have been good and excellent in the most part of the patients, with only one complication regarding a non-union and plate mobilisation settle using a bicortical screws series.

Moreover we present our biomechanical study based on the collaboration with the Mechanical Engineering Department of our University regarding the relationship “screw-plate” using the Finite Elements Method (FEM), outlining the specific features of the three individual system of locked plates.

K. I. Eleftheriou N. Ali R. Thakrar H. V. Parmar

A significant number of patients are affected by localised articular damage that is neither appropriate for traditional arthroplasty, nor for biological repair. A focal resurfacing system utilizing a matched contoured articular prosthetic (HemiCAP®) has been introduced for the treatment of such cases. Independent results on these implants are limited.

We retrospectively evaluated the use of this resurfacing system in 14 patients (13 male, one female), mean age 40.3 years (range 28–49) with focal femoral condyle defects. All procedures were performed by the same consultant orthopaedic surgeon. Clinical evaluation consisted of the Knee injury and Osteoarthritis Outcome Score (KOOS) assessment. Radiographic evaluation was conducted independently to look for signs of any migration of the prosthesis or any radiolucency around it.

10 patients were treated on the medial femoral condyle, two on the lateral, and two received bicondylar implants. Average follow-up was 20 months (range 6–42). All but two patients (no improvement) described a good to excellent response of their symptoms. The KOOS score at follow-up was 79.6, compared to 61.2 prior to treatment (p=0.03). No signs of device migration or radiolucency around the device were observed. None of the patients required re-operation, and there were no cases of superficial/deep infection, thromboembolic events or other significant complication.

Our short-term results demonstrate that the use of the joint preserving HemiCAP® system provides good pain relief and functional improvement in such patients.

P.K. Puthumanapully M. Browne A. New

Uncemented porous-coated total hip prostheses rely on osseointegration or bone ingrowth into the pores for a stable interface and long term fixation. One of the criteria for achieving this is good initial stability, with failure often being associated with migration and excessive micromotion. This has particularly been noted for long stem prostheses. To minimize micromotion and increase primary stability, a short stemmed implant ‘PROXIMA’(DePuy; Leeds, UK) with a prominent lateral flare was developed with the aim of providing a closer anatomical fit, more physiological loading and limiting bone resorption due to stress shielding. This study aims to simulate bone ingrowth and tissue differentiation around a well fixed porouscoated short stemmed implant using a mechanoregulatory algorithm and finite element analysis (FEA). Specific emphasis is made on the design of the implant and its effect on osseointegration.

An FE model of the proximal femur was generated using computer tomography (CT) scans. The PROXIMA was then implanted into the bone maintaining a high neck cut and adequate cancellous bone on the lateral side to accommodate the lateral flare and for osseointegration. A granulation tissue layer of 0.75mm was created around the implant corresponding to the thickness of the porous coating used. The mechanoregulatory hypothesis of Carter et al (J. Orthop, 1988) originally developed to explain fracture healing was used with selected modifications, most notably the addition of a quantitative module to the otherwise qualitative algorithm. The tendency of ossification in the original hypothesis was modified to simulate tissue differentiation to bone, cartilage or fibrous tissue. Normal walking and stair climbing loads were used for a specified number of cycles reflecting typical patient activity post surgery.

The majority of the tissue type predicted to be formed, simulating a month in vivo, is fibrous and indicates a weak interface proximally after this period. The stronger tissues, bone and cartilage occupy the mid-lower regions, indicating a strong interface distally. This can be explained by the unique lateral flare that provides extra stability to the distal regions of the implant, especially on the lateral side. The percentage of bone ingrown around the implant at different stages is also important and there was a significant rise from 15% after 10 cycles to about 30% after 30 cycles, simulating a month in vivo. It was also noted that initial bone formation was very high, even after a few cycles, which leads to a stronger interface early on. Fibrous tissue occupied around 45% at almost all stages and did not vary considerably.

Cartilage however, was replaced by bone as tissue differentiation occurred, reducing from about 30% after 10 cycles to 20% after 30 cycles. This further indicates the trend of tissue ossification through the regions of stronger tissues, gradually proceeding in the direction of the weaker tissues.

The unique lateral flare design and the seating of the implant entirely in the cancellous bed without any diaphyseal fixation provides contrasting results in terms of bone ingrowth around the implant. The lateral flare minimises micromotion and provides better stress distribution at the interface under the region. This accounts for a large percentage of the mid to distal regions under the flare being covered with either bone or cartilage. From the predictions of the algorithm, the significant lateral flare of the PROXIMA helps in stabilizing the implant and provides better osseointegration in the distal regions around the implant.

R.C. Takemoto S. Arno N. Kinariwala K. Chan D. Hennessy N.Q. Nguyen P.S. Walker J. Fetto

Over the last two decades, design modifications in cementless total hip arthoplasty have led to longer lasting implants and an increased success rate. However, there remains limitations to the cementless femoral stem implant. Traditional cementless femoral components require large amounts of bone to be broached prior to stem insertion (1). This leads to a decrease in host bone stock, which can become problematic in a young patient who may eventually require a revision operation during his or her lifetime. Osteopenia, only second to distal stress shielding can lead to aseptic loosening of the implant and stem subsidence, which also accelerates the need for a revision operation (24). Recent literature suggests that thigh pain due to distal canal fixation, micro-motion, uneven stress patterns or cortex impingement by the femoral stem is directly correlated to increased stem sizes and often very disabling to a patient (58). In this study, we sought to determine whether reducing stem length in the femoral implant would produce more physiologic loading characteristics in the proximal femur and thus eliminate any remaining stress shielding that is present in the current design. We analyzed the surface strains in 13 femurs implanted with

no implants,


ultra short and

short stem proximal fill implants in a test rig designed to assimilate muscle forces across the hip joints, including the ilio-tibial band and the hip abductors.

Analysis of the resulting surface strains was performed using the photoelastic method. For each femur, intact and with the different stem length components in place, the fringe patterns were compared at the same applied loads. The highest fringe orders observed for all tests were located on the lateral proximal femur and medial proximal femur. The fringes decreased as they approached the neutral axis of bending (posterior and anterior). Distal fringe patterns were more prominent as the stem length increased. The results demonstrate that the stemless design most closely replicated normal strain patterns seen in a native femur during simulated gait. The presence of a stemless, ultra short and short stem reduced proximal strain and increased distal strain linearly, thereby increasing the potential for stress shielding. The stemless design most closely replicated normal strain patterns observed in a native femur and for this reason has the potential to address the shortcomings of the traditional cementless femoral implant.

R.H Hallock B.M. Fell

Long term clinical data and patient satisfaction is reported on 152 patients implanted with the UniSpacer interpositional spacer during the first four years of clinical use with a minimum 5-year, maximum 9-year follow-up. 156 UniSpacer™ Knee System implants were implanted in 152 patients (4 bilateral), for treatment of isolated medial compartment osteoarthritis over a 4-year period. The minimum follow-up for this group of patients is 5 years with a range of 60 to 108 months. Revisions to a TKR within one year of the implantation date during the first and second year of UniSpacer implantations were 6% and 5% respectively. By years three and four, the TKR revision rate within the first year had dropped to 0% (zero). The data reflects the improvement in surgical technique and the development of proper patient selection criteria. The long term data provides validation that the UniSpacerÔ can provide a successful, long term, bone preserving, treatment alternative to the current HTO, UKR or TKR procedures.

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T M Coon M D Driscoll S Horowitz M A Conditt

Successful clinical outcomes following unicompartmental knee arthroplasty (UKA) depend on accurate component alignment, which can be difficult to achieve using manual instrumentation. A new technology has been developed using haptic robotics that replaces traditional UKA instrumentation. This study compares the accuracy of UKA component placement with traditional jig-based instrumentation versus robotic guidance.

85 UKAs performed using standard manual instrumentation were compared to 67 performed with a robotically guided implantation system without instrumentation. Each was performed using a minimally invasive surgical approach. The two groups were identical in terms of age, gender and BMI. The coronal and sagittal alignment of the tibial components were measured on pre-and post-operative AP and lateral radiographs. Postoperative tibial component alignment was compared to the pre-operative plan.

The RMS error of the tibial slope was 3.7° manually compared to 1.2° robotically. In addition, the variance using manual instruments was 9.8 times greater than the robotically guided implantations (p< 0.0001). In the coronal plane, the average error was 3.0 ± 2.2° more varus using manual instruments compared to 0.3 ± 1.9° when implanted robotically (p< 0.0001), while the varus/valgus RMS error was 3.7° manually compared to 1.8° robotically. The average depth of medial tibial plateau resection was significantly less with inlay tibial components (3.9 ± 0.9mm) relative to onlay tibial components (6.8 ± 0.9mm, p< 0.0001). In addition, a significantly higher percentage of robotic inlay patients went home the day of surgery (12% vs. 1%, p< 0.0001).

Tibial component alignment in UKA is significantly more accurate and less variable using robotic guidance compared to manual, jig-based instrumentation. By enhancing component alignment, this novel technique provides a potential method for improving outcomes in UKA patients.

K.F. Mohammad

The treatment of comminuted fractures of the radial remains controversial. When preservation of the radial head mechanics is required, the choice between open reduction and internal fixation and radial head replacement remains a difficult choice. Current literature does not provide guidelines but suggest that fracture complexity and technique are critical for success. We compared the outcomes of 30 patients who were treated with either open reduction and internal fixation or radial head replacements between 2005 and 2008.

Twenty six Mason type III and 4 Mason type IV fractures of the radial head were enrolled in the study. Twenty underwent open reduction and internal fixation (group I) and 10 underwent radial head replacements (group II). The mean age at operation was 37 and 49 years respectively and the duration of follow up 32 and 31 weeks respectively.

The indications for radial head replacement were severe comminution, primary fracture dislocations and fracture dislocations with radial head excised. All patients were evaluated for pain, motion, strength, stability and function using the Broberg and Morley functional rating index.

Elbow range of motion averaged 9 degrees (extension loss) to 97 degrees (flexion in group I and 10 to 98 degrees in group II. Average pronation and supination were 71.5 and 72 (group I) and 69 and 74.5 (group II). The loss in strength in flexion, supination and pronation between the groups were not comparable (P> 0.05). The Broberg and Morley functional rating score average was 81.9 (group I) and 82.2 (group II).

These results show that patients who were treated with open reduction and internal fixation did not have a significant advantage over patients who received radial head replacements in terms of range of motion, loss in strength and their functional rating score.

M. Takagi S. Kobayashi K. Sasaki Y. Takakubo H. Kawaji Y. Tamaki Masaji Ishii

Aim: To ameliorate surgical strategy of disabled rheumatoid hip joints, perioperative status and clinical features of the patients undergoing total hip arthroplasty (THA) were retrospectively evaluated.

Materials and Methods: 150 joints of 106 patients were studied (male/female rate; 1:6, mean age; 60 years and duration of the disease; 15 years). All patients received cemented THA (mean follow-up period; 8 years). Mode of bone defect with acetabular reconstruction type, femoral bone quality, survivorship, steroid use and complications were surveyed.

Results: In preoperative status, proturusio acetabuli was found in 37% with type I; 54%, II; 34% and III; 12% by Sotelo-Garza classification. Superior bone defect was recognized in 56%, collapse and/or defect of femoral head in 19%, and geode formation in 0.2%. Femoral medullar canal was classified as type A; 1%, type B; 53% and type C; 46% by Dorr classification. The presence of fracture before surgery was 5%. Anatomical reconstruction was achieved in all cases including application of 42% bone grafting (autogenous alone; 51%, application of artificial substitute; 39% and of cross-plating system; 10%). Acetabular revision rate due to aseptic loosening (%/years) was improved by graft methods (whole series; 5/8, any grafting; 6/8, autogenous alone; 8/8, artificial substitute; 4/8 and cross-plate system; 0/4). Revision rate for any reasons was 9% (aseptic acetabulum 5%, aseptic femur 5%, dislocation 2% and infection 1%). Dislocation (11%), infection (3%) and severe thrombotic events (1%) were experienced. Steroid use was found in 73%, associated with increased risk of protrusio acetabuli, superior bone defect with protrusio acetabuli and fractures.

Discussion and Conclusion: The study indicated that steroidal medication significantly related to the perioperative status of bone defects and perioperative fractures of rheumatoid patients undergoing THA. Improved ace-tabular procedures could promise better survivorship of the implant.

N. Dunbar A.D. Pearle D. Kendoff M.A. Conditt S.A. Banks

Unicompartmental knee arthroplasty (UKA) is an increasingly attractive and clinically successful treatment for individuals with isolated medial compartment disease who demand high levels of function. A major challenge with UKA is to place the components accurately so they are mechanically harmonious with the retained joint surfaces, ligaments and capsule. Misalignment of UKA components compromises clinical outcomes and implant longevity. Cobb et al. (JBJS-Br 2006) showed that robot-assisted placement of UKA components was more accurate than traditional techniques, and subsequently that the clinical outcomes were improved. Cobb’s method, however, employed rigid intraoperative stabilization of the bones in a stereotactic frame, which is impractical for routine clinical use. Robotic systems have now advanced to include dynamic bone tracking technologies so that rigid fixation is no longer required. The question is -Do these robotic systems with dynamic bone tracking provide the same accuracy advantages demonstrated with robotic systems with rigidly fixed bones? We compared robot-assisted and traditionally instrumented UKA in six bilateral pairs of cadaver specimens. In all knees, a CT-based preoperative plan was performed to determine the ideal positions and orientations for the implant components. Traditional manual instruments were utilized with a tissue-sparing approach to implant one knee of each pair. A haptic robotic system acting as a virtual cutting guide was used to perform the robot-assisted UKA, again with a tissue-sparing approach. Postoperative CT scans were obtained from all knees, and the 3D placement errors were quantified using 3D-to-3D registration of implant and bone models to the reconstructed CT volumes.

The magnitudes of femoral implant orientation error were significantly smaller for the robot-assisted implants compared to traditionally implanted components (4° vs 11°, p< 0.001), but the magnitudes of femoral placement error did not reach significance (3mm vs. 5mm, p=0.056). The magnitudes of tibial implant placement error were not significantly different (4mm vs. 5mm and 7° vs. 7°, p> 0.05).

Well-placed UKA implants can provide durable and excellent functional results, which is an increasingly attractive option for young and active patients with severe compartmental osteoarthritis who wish not to have or to delay a total knee replacement.

Previous studies have demonstrated significant improvement in implant placement accuracy and clinical results with robot-assisted surgery using rigid bone fixation. This study demonstrates it is possible to achieve significant accuracy improvements with robot-assisted techniques allowing free bone movement. Additional larger trials will be required to determine if these differences are realized in clinical populations.

A.M. Omari A.J. Barnett B.J. Burston N. Atwal G. Gillespie B. Squires R. Ramakrishnan

The aim of this study was to investigate the use of large diameter head THR to treat fractured neck of femur, and to demonstrate if this conferred greater stability.

Forty-six (46) independent, mentally alert patients with displaced intracapsular fractures underwent THR. Mean age was 72.1 years. Outcome measures were dislocation, reoperation/ revision rate, Oxford hip score (OHS), Euroqol (EQ-5D) and residential status. Data was collected prospectively, with review being carried out at 3 months and 1 year.

At mean follow-up (12.5 months) there were no dislocations. Reoperation, revision and infection rate were all 0%. Two patients died (4.3%). Mean pre-injury and postoperative OHS were 12.1 and 17.9 respectively. Mean pre-injury and postoperative EQ-5D index scores were 0.97 and 0.83 respectively. Mean postoperative walking distance was 2.5 miles. There were no changes in residential status.

This is the first published series utilizing 36-mm diameter metal-on-metal THR for the treatment of fractured neck of femur. We have demonstrated that it affords patients excellent stability with no recorded dislocations.

M.J. Kuhn M.R. Mahfouz M.R. Anderle R.D. Komistek D.A. Dennis D. Nachtrab

Many nonoperative techniques exist to alleviate pain in unicompartmental osteoarthritic knees including physical therapy, heel wedges and off-loading knee braces [1]. Arthritic knee braces are particularly effective since they can be used on a regular basis at home, work, etc. Previous knee brace studies focused on their ability to stabilize anterior cruciate ligament (ACL) deficient knees. A standard technique for analyzing brace effectiveness is the use of an athrometer to look at the range-of-motion. Although this is helpful, it is more useful to use X-ray or fluoroscopy techniques to analyze the in vivo 3-D conditions of the femur and tibia. One method for doing this is Roentgen Steroephotogrammetric Analysis, which uses a calibration object and two static X-rays to perform 3-D registration of the femur and tibia. This technique is limited to static and typically non-weight bearing analysis.

We have analyzed five patients with moderate to severe osteoarthritis in both step up and step down activities with two different knee braces and also without a knee brace. Fluoroscopy of the five patients performing these activities was obtained as well as a CT scan of the knee joint for each patient. 3-D models of the femur and tibia were obtained from manual segmentation and overlaid to the fluoroscopy images using a novel 3-D to 2-D registration method [2]. This allowed analysis of 3-D in vivo weight bearing conditions. This work builds off of an analysis where 15 patients were analyzed in vivo during gait with and without knee braces [3].

All five patients experienced substantially less pain when performing the step up and step down activities with a knee brace versus without a knee brace. It should be noted that none of the five patients were obese, which can limit brace effectiveness. Preliminary results show that medial condyle separation was increased by 1.4–1.6 mm when using a knee brace versus not using a knee brace during the heel-strike and 33% phases of step up and step down activities. Also, the condylar separation angle was reduced by an average of 1.5–2.5°. Finally, consistently less condylar separation was seen during step down versus step up activities (0.5–1 mm), which can be attributed to a greater initial impact force on the knee joint during step down versus step up activities.

J Velyvis S Horowitz M A Conditt

Unicompartmental knee arthroplasty is realizing a resurgence due to factors such as improved alignment and sizing of components during surgery. This study compares the early results of two implantation techniques – robotic-assisted and standard manual alignment guides – to evaluate how a new technology developed to improve accuracy affects early patient outcomes.

For this study, we chose a prospective consecutive series of 20 patients in each group to receive a medial unicompartmental knee arthroplasty. The patients were evaluated clinically using standard outcomes measures (Knee Society, WOMAC and Oxford scores) as well as for modes of failure. Average follow-up for the manual onlay technique was 12 months and for the robotic-assisted inlay technique was and 10 months. Patients were not statistically different in terms of BMI, age, or diagnosis (p> 0.05).

Knee society score (p=0.65), total WOMAC score (p=0.75) and Oxford knee score (p=0.88) were not statistically different between the three groups. Five patients in the robotic-assisted inlay group complained of persistent tibial pain that resolved in four patients. There were no revisions for the manual onlay implant group and there was one revision for persistent tibial pain in the robotic-assisted inlay group, consisting of a conversion to a standard manual onlay UKA tibial component.

Patient outcomes were similar with inlay robotic-assisted unicompartmental knee arthroplasty compared with conventional manual onlay implant techniques. Roboticassisted inlay components resulted in slightly increased complaints of tibial pain and had one revision for tibial pain, however the revision was to a standard onlay UKA tibial component.

K. Knahr A. Pokorny A. Frank

Background: Recently, the new phenomenon of “squeaking” noises emitted from THAs with ceramic-onceramic bearings has spared international interest. It shows a frequency of 0,7–19,5% in literature, but infrequently requires revision surgery. However, an even higher incidence of various other noises from those THAs audible to the human ear have become popular in the process: this noise can resemble clicking, grinding or creaking and can be caused by distinct movements, during longer periods of walking, or can be constant with movement. The incidence of those noises can reach up to 30% of THAs. However, memory has faded that other bearings like metal-on-metal and PE/ceramic have been associated with noises in the past.

Therefore we aimed to investigate the occurence of acoustic emissions in patients, who had all received the same implant but with alternate bearings, to investigate the nature of noise, duration and clinical consequence for all 3 bearings (polyethylene/ceramic, metalon-metal, ceramic-on-ceramic).

Method: Between 1999–2001, 360 patients were matched in a prospective randomised trial. All of them received a cementless Zimmer© Alloclassic Variall™ implant at the Orthopaedic Hospital Vienna – Speising, Austria with either a ceramic-on-ceramic bearing, a metal-on-metal bearing or a polyethylene/ceramic bearing. A questionnaire was sent via mail, including questions on first occurence of hip noise, information on the kind and duration of the phenomenon and possible adverse evaluation on behalf of the patient. In case of a positive report, the patient was invited to a clinical examination and radiographic analysis. In addition, a specialised audiography was conducted in patients with audible sensations. Finally, the SF-36 and WOMAC were analysed. A number of patients received further examination with methods of gait analysis in order to detect the distinct point of occurence of the noise during the gait cycle.

Results: 33 patients reported an audible phenomenon from their THA, 14 received a ceramic-onceramic bearing (Cerasul), 13 a polyethylene/ceramic bearing (Durasul) and 6 a metal-onmetal bearing (Metasul). The most common noise was a distinct clicking, followed by a creaking noise. Only 1 patient reported a squeaking sensation, he received a polyethylene/ceramic bearing.

Conclusion: The emission of specific noises from THAs of all bearings has been well documented in recent trials and could be verified in this survey of cementless THAs. No trend towards an increased incidence of noise from THAs with ceramic-on-ceramic bearings could be detected. Interestingly, the single case of „squeaking” was reported from a patient with polyethylene/ceramic bearing. Microseparation and subluxation of the femoral head with resulting edge loading and formation of stripe wear has recently been suspected as the main cause for “noisy hips.” So far 2 ceramic-on-ceramic hips of this study group population have been revised. Both articulations showed areas of stripe wear due to subluxation of the joint.

S M. Zingde F. Leszko R D. Komistek J P. Garino W J. Hozack D A. Dennis M R. Mahfouz

Previous clinical studies have documented the incidence of squeaking in subjects having a ceramic-onceramic (COC) THA. An in vivo sound sensor was recently developed used to capture sound at the THA interface. In this first study, it was determined that subjects having all bearing surface types demonstrated variable sounds. Therefore, in this follow-up study, the overall objective was to simultaneously capture in vivo sound and motion of the femoral head within the acetabular cup during weight-bearing activities for subjects implanted with one of four different ceramic-on-ceramic (COC) THA.

Twenty subjects, each implanted with one of four types of Ceramic-on-Ceramic THA (9 Smith and Nephew, 8 Stryker, 2 Wright Medical Technologies and 1 Encore) were analyzed under in vivo, weightbearing conditions using video fluoroscopy and a sound sensor while performing gait on a treadmill. Patients were pre-screened and two groups were defined: a group diagnosed as audible squeakers (9 THAs) and a control group of THA patients not experiencing audible sounds (11 THAs). Two tri-axial piezoelectric accelerometers were attached to the pelvis and the femoral bone prominences respectively. The sensors detect frequencies propagating through the hip joint interaction. Also, 3D kinematics of the hip joint was determined, with the help of a previously published 2D-to-3D registration technique. In vivo sound was then correlated to 3D in vivo kinematics to determine if positioning of the femoral head within the acetabular cup is an influencing factor.

For the audible group, two had a Smith and Nephew (S& N) THA, six a Stryker THA and one a Wright Medical (WMT) THA. Both of the S& N subjects, 5/6 Stryker and the Wright Medical subjects experienced femoral head separation. The maximum separation for those subjects was 4.6, 5.0 and 2.1 mm for the S& N, Stryker and WMT subjects, respectively. The average separation was 4.3, 2.0 and 2.1 mm for the S& N, Stryker and WMT subjects, respectively. For the eleven subjects in the control group, seven subjects had a S& N THA, two a Stryker and one each having a WMT and Encore THA. All 11 of these subjects demonstrated hip separation with the maximum values being 3.8, 3.4, 1.9 and 2.4 mm for the S& N, Stryker, WMT and Encore THA, respectively. The average separation values were 1.8, 2.3, 1.9 and 2.4 mm for the S& N, Stryker, WMT and Encore THA subjects, respectively.

Four distinct sounds were produced by subjects in this study, which were squeaking, knocking, clicking and grating. Only 3/20 subjects produced a “squeaking” sound that was detected using our sound sensor. One of these subjects had a Stryker THA and two had a WMT THA. Further analysis of the nine subjects who were categorized as audible squeakers revealed that only 0/2, 1/6 and 1/1 subjects having a S& N, Stryker and WMT THA, respectively, demonstrated a squeaking sound that was detected using our sound sensor. Both (2/2) S& N subjects demonstrated a knocking and clicking sound, but neither produced a grating sound, while 5/6 Stryker subjects produced a knocking sound, but only 1/6 demonstrated a clicking or grating sound. Besides the squeaking sound, the only other sound produced by the WMT audible squeaker was a knocking sound. Only 1/11 control group subjects demonstrated a squeaking sound, which was a subject having a WMT THA. With respect to the control group subjects having a S& N THA, 5/7, 1/7 and 3/7 subjects produced a knocking, clicking or grating sound, respectively. Only 1/2 subjects having a Stryker THA produced a knocking or grating sound.

This is the first study to compare multiple COC THAs in analyzing correlation of femoral head separation (sliding) and sound. It was seen that all the THA groups had occurrences of separation and each case of separation correlated with the sound data. These results lead the authors to believe that the influence of squeaking is multi-factorial, and not necessarily attributed only to the bearing surface material.

Dan. J. Berry

Metal-on-metal bearings have become popular in the last ten years because of a low wear rate combined with the ability to use large head sizes for conventional total hip arthroplasty (THA) and to facilitate resurfacing hip arthroplasty. Further advantages of metal-metal bearings include the fact that they are not at risk for fracture, and they can be made as modular or non-modular acetabular implants.

It was recognized early that metal-on-metal implants had the potential to increase serum ion levels, and this was demonstrated in a number of studies. The significance of elevated ion levels, however, for most patients has been primarily a theoretical concern of toxicity, carcinogenesis or mutagenicity, and to date very few, if any, systemic problems related to systemic metal ions have been documented with certainty. Nevertheless, most surgeons have avoided use of the implants in patients who are likely to become pregnant, patients with renal disease, or patients with major systemic illnesses which have a high likelihood of leading to renal disease. Furthermore, most have avoided using them in patients with known dermal metal allergies, even though the connection between dermal metal allergies and metal bearings has not been established.

Unexpectedly, an extremely important concern has emerged with metal bearings: the finding of local inflammatory reactions related to metal bearings. These inflammatory reactions can take several forms including pain with a milky effusion, local tissue necrosis, or large fluid collections or pseudotumors. The histology of these different reactions appears to be predominantly lymphocytic in nature and a term for at least some of these reactions has been coined “AVALS”. Whether these local reactions are primarily immunologic in nature or primarily related to dose of local metal ions or debris remains uncertain. While there is much still to be learned, it appears that certain patient populations may be at increased risk for metal reactions, possibly related to implant size (women and smaller patients). It also seems verticallyoriented implants, which create edge loading, increase wear and increase risk of local metal reactions.

Perhaps the most important question is the incidence of local metal reactions, which remains to be defined. To date the problems in most series have been infrequent, less than 1 or 2 percent. However, in a few selected series the incidence has been higher, and when screening has been done for asymptomatic patients with fluid or masses around the joint, the rate has been higher in at least one reported series.

Surgeons may interpret the importance of local metal reactions differently, but certainly ultimately incidence of this problem will have a very major effect on the future of these bearings.

C.S. Ranawat

The recent introduction of modern ceramic-on-ceramic total hip arthroplasties have demonstrated excellent clinical and radiographic results without catastrophic failure such as implant fracture associated with earlier designs. In laboratory wear testing, ceramicon-ceramic provides the least volumetric wear among all bearing surfaces. In recent years, with modern ceramic-on-ceramic bearing surfaces, clinical results with 5-to 7-year follow up have been good to excellent in 95–97% of cases. In spite of excellent results, certain limitations still exist including occasional fracture, stripe wear, squeaking, and neck-socket impingement producing metallic third body. Future improvement in ceramics (and other hard-bearing surfaces) and its coupling with other hard bearing surfaces appears to have significant advantages in reducing dislocation, impingement, stripe wear and squeaking.

M. Tada K. Inui H. Yoshida S. Takei S. Fukuoka Y. Matsui K. Yoshida

Good mid-term results of Oxford UKA (OxUNI) for anteromedial osteoarthritis (OA) were reported. The designers of prosthesis reported a 98% 10-year survival rate for a combined series of phase I and II, and these findings were supported by published results from other series, with 10-year survival ranging from 91% to 98%. In order to obtain good results, the designers of this prosthesis mentioned the importance of adhering to strict indication for OxUNI, especially only for OA cases with intact anterior cruciate ligament (ACL). OxUNI combined with ACL reconstruction (ACLR) is a viable treatment option for only young active patients, in whom the ACL has been primarily ruptured. On the other hand, it was not clear whether the result of OxUNI combined with ACLR for OA with secondary ruptured ACL was good. In this study we compare the short-term results of OxUNI combined with ACLR for OA with secondary ruptured ACL with that for usual OA with intact ACL.

382 OxUNI were performed at two hospitals by one surgeon between January 2002 and August 2005. Among those, 367 cases, followed over two years postoperatively (272 patients, women: 283, men: 84) were assessed. Follow up ratio was 96.1%. The mean patient age at the time of surgery was 72.0 (47~93) years. The mean follow-up period was 39.3 (24~67) months. Thirty three knees of OA were treated with OxUNI combined with ACLR, by using synthetic graft. Clinical results were assessed by the Oxford Knee Score (OKS) and active range of motion (ROM). Patients are asked a series of 12 questions, and their response scores range from 0 (worse) to 4 (best) for each, yielding an overall score range of 0–48. All living patients were contacted, and the status of the implant was established at the time of last follow from hospital records. We evaluate the survival rate for OxUNI with or without ACLR, using the endpoint of revision for any reason.

The pre-and postoperative clinical scores were compared using the paired Student’s t-test. Survivor-ship curves were constructed using the Kaplan-Meier method, and survivorship between groups was compared using logrank and Wilcoxon methods. All analyses were performed using 95% confidence intervals and a P value of < 0.05 was considered significant.

The mean OKS at final follow-up was 42.1 (preoperative; 21.7), and the mean active ROM was 125.2° (preoperative; 113.4°). OKS and active ROM were significantly improved. There were no significant differences in OKS and active ROM between OxUNI with ACLR and OxUNI with intact ACL. Fourteen knees among 367 knees were revised; nine for loosening of tibial component, four for dislocation of bearing and one for progression of lateral OA. Overall 5-year survival rate was 95.6%. When survival rate was assessed separately with or without ACLR, that of OxUNI with intact ACL was 96.7% and that of OxUNI with ACLR was 83.8%. There was significant worse survival rate between the two groups (P=0.0071).

The 5-year survival rate for OxUNI with intact ACL was 96.7%, which was equivalent to those of original series from Oxford. However, 5-year survival rate for Oxford UKA with ACLR was 83.8% in our series. Four knees in nine of loosening of tibial component were replaced by OxUNI combined with ACLR. Therefore, even if ACL was reconstructed, the results of OxUNI for OA with secondary ruptured ACL was proved to be pessimistic.

There was significantly worse survival rate for OxUNI with ACLR, compared with OxUNI with intact ACL. So we conclude that combined ACL reconstruction and OxUNI for anteromedial OA with secondary ruptured ACL is not recommended, which must be treated with TKA.

J.N. Argenson S. Parratte X. Flecher JM. Aubaniac

Unicompartmental knee arthroplasty (UKA) is a logic procedure when osteoarthritis or avascular necrosis is limitad to one femorotibial compartment. The indications for the procedure includes osteoarthrosis or osteonecrosis with full-thickness loss of articular cartilage limited to one of the tibiofemoral knee compartments. Physical examination should ensure full range of knee motion. Frontal and sagittal knee stability has to be tested. A particular attention should be given to the state of the anterior cruciate ligament. The status of the patellofemoral joint should be analysed by physical examination and patellofemoral view at 30, 60 and 90° of flexion. Preoperative anteroposterior varus and valgus stress radiographs should be done to confirm the complete loss of articular cartilage in the involved compartment, the full thickness cartilage in the opposite compartment and the possibility of full correction of the deformity to neutral.

The so-called minimally invasive surgery (MIS) procedure using a specific instrumentation is able to provide quicker recovery since the extensor mechanism disruption is eliminated. More importantly the radiological evaluation has shown that precise implantation of the components is possible with an MIS approach which is important for the long term results of the arthroplasty. The clinical results at ten years of follow-up of cemented metal-backed UKA performed through a conventional approach have shown results comparable to those obtained with total knee arthroplasty. The in vivo kinematic evaluation of patients implanted with UKA has shown that kinematics similar to the normal knee can be obtained, enhancing the importance of a functional anterior cruciate ligament.

Recent design improvements have increased the femorotibial area of contact to accommodate high flexion angles. Additionally our experience has demonstrated that modern UKA is a valid alternative for young and active patients with unicompartmental tibiofemoral noninflammatory disease, including both osteoarthritis and avascular necrosis. Compared to medial UKA lateral UKA represents in our experience only 5% of all UKA implantations.

However the long term results of lateral UKA compares at least equally with those reported for medial UKA.

W. L. Walter

Ceramic on ceramic articulations had been used since 1970s but with high failure rate.

More recent third generation alumina ceramic had improved results due to better material properties to resist wear and fracture and better methods of fixation with metal back acetabular components. A new clinical problem of squeaking has emerged in the last decade and is now a relatively common occurrence in ceramic on ceramic total hip arthroplasty, with a reported incidence from less than 1% to 20% depending on the definition of the noise. We report experience with over 3000 ceramic-on-ceramic hips including the 10 year minimum follow-up of the first 301 cases.

Methods: Between June 1997 and Feb 1999, 301 consecutive primary cementless hip arthroplasties were performed on 283 patients under the care of the two senior authors. The mean age of the patients was 58.

All patients are asked on follow-up as part of a questionnaire: Has your hip ever made a squeaking noise? To date of the more than 3000 ceramic on ceramic hips that we follow, 74 hips (71 patients) responded yes to this question. Patient demographic and outcome data were analysed in all squeaking hips and compared with all primary ceramic on ceramic hips operated on at our unit.

Results: Of the first 301 cases there have been 9 revision surgeries in 8 hips as follows.

Two acetabular components revised for psoas tendonitis, one of these subsequently had both components revised for acetabular osteolysis with femoral revision to improve anteversion.

There were six other femoral component revisions: four for periprosthetic femoral fractures, one for aseptic loosening and one for transient sciatic nerve palsy. There has been one squeaking hip in this group not requiring revision due to the mild and intermittent nature of the noise. All complications occurred within the first 3 years, no further complication has arisen since.

When comparing the 74 squeaking hips to the entire cohort of primary hips we found that taller, heavier and younger patients are significantly more likely to have hips that squeak.

Squeaking hips have a significantly higher range of post-operative movement than silent hips.

Squeaking hips have a significantly higher Harris hip score. There was no difference in the satisfaction scores between squeaking and silent hips.

Conclusion: In summary, we have reported the large series of third generation alumina ceramic on ceramic articulation with 10 year results, and have demonstrated that it can produce excellent survivorship with good clinical and radiographic outcome. We believe that this result had provided very encouraging evidence to support the use of third generation ceramics as articulation for primary hip arthroplasty, especially in young and active patients.

K. Kobayashi M. Sakamoto Y. Tanabe T. Sato A. Ariumi G. Omori Y. Koga

Progression of osteoarthritis (OA) of the knee is related to alignment of the lower extremity. Postoperative lower extremity alignment is commonly regarded as an important factor in determining favourable kinematics to achieve success in total knee arthroplasty (TKA) and high tibial osteotomy (HTO). An automated image-matching technique is presented to assess three-dimensional (3D) alignment of the entire lower extremity for natural and implanted knees and the positioning of implants with respect to bone.

Sawbone femur and tibia and femoral and tibial components of a TKA system were used. Three spherical markers were attached to each sawbone and each component to define the local coordinate system. Outlines of the 3D bone models and the component computer-aided design models were projected onto extracted contours of the femur, tibia, and implants in frontal and oblique X-ray images. Threedimensional position of each model was recovered by minimizing the difference between the projected outline and the contour. The relative positions were recovered within −0.3 ± 0.5 mm and −0.5 ± 1.1° for the femur with respect to the tibia, −0.9 ± 0.4 mm and 0.4 ± 0.4° for the femoral component with respect to the tibial component, −0.8 ± 0.2 mm and 0.8 ±0.3° for the femoral component with respect to the femur, and −0.3 ± 0.2 mm and −0.5 ± 0.4° for the tibial component with respect to the tibia.

Clinical applications were performed on 12 knees in 10 OA patients (mean age, 72.5 years; range, 62–87 years) to check change in the 3D mechanical axis alignment before and after TKA and to measure position of the implant with regard to bone. The femorotibial angle significantly decreased from 187.8° (SD 10.5) to 175.6° (SD 3.0) (p=0.01). The 3D weight-bearing axis was drawn from the centre of the femoral head to the centre of the ankle joint. It intersected significantly medial (p=0.01) and posterior (p=0.023) point at the proximal tibia before TKA. The femoral component rotation was 3.8° (SD 3.3) internally and the tibial component rotation was 14.1° (SD 9.9) internally. Compared with a CT-based navigation system using pre-and post-operative CT for planning and assessment, the benefit to patients of our method is that the post-operative CT scan can be eliminated.

Dr Bharat S. Mody

The performance of high flexion postures such as cross legged sitting, are not part of the assessment criteria to assess either function of a natural knee joint or after Total Knee Replacement (TKR) surgery, in assessment systems used by the orthopaedic fraternity today. This is probably because TKR was initially developed and widely employed in the western countries. However, increasing numbers of this surgery are being performed in the eastern parts of the world, comprising more than half of the global population, where postures such as cross legged sitting are a basic necessity of activities of daily living.

It has been a general perception that achieving flexion beyond 120 degrees after Total Knee Replacement surgery is not a routine result. The implant manufacturing industry has recognized this need and put implant designs on the market with accompanying literature which would suggest that the implant design itself contributes towards a higher range of movement post surgery.

We have performed a prospective study involving a hundred Total Knee Replacements using standard implants (PFC Sigma, Cruciate Sacrificing design, Depuy, J& J, NJ, USA). This implant is not supposed to be specifically designed to deliver a high range of flexion. We found that incorporating certain specific surgical steps as a standard part of the operative procedure delivers a high range of flexion greater than 135 degrees in seventy five percent of patients which allowed them to adopt the cross legged sitting posture after surgery.

This paper conveys the message that achieving a high range of flexion after surgery does not need any special implant design. It discusses the surgical steps which seem to contribute towards this result. The implications in terms of cost saving for health care system are immense.

T.R. Yoon K.S. Park K. Thevarajan Y.J. Cho H.K. Yang

We performed this study to evaluate the clinical and radiological results of metal on metal articulation change for the treatment of ceramic liner or head fractures in total hip arthroplasty (THA).

We retrospectively reviewed 8 patients with revision THA using liner cementation (metal on metal) due to ceramic fracture (liner fracture; 5 cases, head fracture; 3 cases).

They were followed up for an average of 30 months (range 12 to 68 months). At the surgery, we removed ceramic liner and head, the joint cavity was irrigated with saline to remove remnants of ceramic particles. After that, the inner surface of the metal shell was roughened with a high-speed diamond burr to improve the fixation strength of the liner.

Metal inlay polyethylene (Metasul®, Centerpulse Orthopedics, Austin, TX) liner was used and the back surface of the liner was routinely down sized and roughened like spider web with an electrical burr to ensure stable fixation with bone cement.

We evaluated clinical result using Harris Hip Score (HSS) and the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC) score and radiological evaluation was done using the mothod of DeLee and Charnley for the acetabular osteolysis and method of Gruen et al. for the femoral osteolysis.

The mean Harris hip scores improved from 65.3 pre-operatively to 93.8 at the final follow-up. There were no changes in cup position, no progression of osteolytic lesion around the femoral and acetabular components and no measurable wear of metal on metal bearing articulation at the last follow-up radiographs. There was one case of recurrent dislocation after surgery and the patient treated with greater trochanter distal advancement.

This study showed that for the treatment of ceramic liner or head fractures, after thorough removal of ceramic particles, cementation into a metal shell and changing the articulation to metal-on-metal provided good clinical and radiological results.

R. Nizard A. Cogan D. Hannouche A. Raould L. Sedel

Hard-on-hard bearing surface have been accepted as a valuable alternative for young and active patients needing a hip replacement because these combinations are resistant to wear. Initial development of alumina-on-alumina bearings faced complications such as fractures, and socket loosening. But, with the increasing number of prostheses implanted, noise occurrence appeared as a new complication. The primary aim of the present survey was to quantify the prevalence of having noise in a population receiving alumina-on-alumina hip arthroplasty.

Two hundred and eighty-four ceramic-on-ceramic hips were performed in 238 patients (126 males and 112 females) from January 2003 to December 2004. The average age at the index operation was 52.4 ± 13.4 years (range, 13 to 74 years). We used the same type of prosthesis for all patients manufactured in all cases by Ceraver-Osteal®. Clearance between femoral and insert was between 20 and 50 microns in order to achieve minimal wear. The survey was conducted by an independent surgeon who did not participated in patients care during the last 6 months of 2007. He interviewed the patients by phone with a standardized questionnaire (appendix) that aimed to assess if noise was present and the characteristics of this noise if present. No suggestion was done on how they could describe the noise and they felt free to use the word that they considered to be the most adapted. Satisfaction was evaluated asking if the patient was very satisfied, satisfied or dissatisfied with its prosthesis.

When the noise was present, the X-ray was independently evaluated to assess if sign of component fracture was present.

Four patients (six hips) died of unrelated cause during the follow-up. Three patients (three hips) lived outside France and could not be followed (1.3%). Nine patients (ten hips) could not be traced and are considered lost to follow-up (3.8%). Two hundred and twenty-two patients with 265 hips were therefore surveyed. Among these 265 hips, 28 experienced noise generation (10.6%). It was defined as a snap for 6 patients, as a cracking sound by 6, as rustling by 6 patients, as a squeaking by 7 patients (2.6%), a tinkling by 2 patients, one patient was unable to define the sound she felt. No factor related to the patient influenced the occurrence of noise. Twelve patients were dissatisfied with the result of the hip prosthesis, 5 of them experienced noise (41.7%); 210 were satisfied or very satisfied 23 of them experienced noise (11%); this difference was significant (p=0.002). No patients required revision for noise.

The origins of noise occurrence are unknown but several hypotheses can be suggested.

Squeaking may be due to absence of sufficient lubrication. Other types of noise can be due to microseparation, occult dislocation, impingement between the femoral neck and the acetabular rim but demonstration remain an issue.

PJC Heesterbeek NLW Keijsers N Verdonschot AB Wymenga

Balancing the PCL in a PCL-retaining total knee replacement (TKR) is important, but sometimes difficult to execute in an optimal manner. Due to the orientation of the PCL it is conceivable that flexion gap distraction will lead to anterior movement of the tibia relative to the femur. This tibio-femoral repositioning influences the tibio-femoral contact point, which on its turn affects the kinematics of the TKR. So far, the amount of tibiofemoral repositioning during flexion gap distraction is unknown which leads to uncertain kinematic effects after surgery. The goal of this study was to quantitatively describe the parameters of the flexion gap (gap height, anterior tibial translation and femoral rotation) and their relationship while the knee is distracted during implantation of a PCL-retaining TKR with the use of computer navigation. Furthermore, the effect of PCL elevation angle on the flexion gap parameters was determined.

In 50 knees, during a ligament-guided TKR procedure, the flexion gap was distracted with a double-spring tensor with 100 and 200 N after the tibia had been cut. The flexion gap height, anterior tibial translation and femoral rotation were measured intra-operatively using a CT-free navigation system. PCL elevation was calculated based on the femoral and tibial insertion sites as indicated by the surgeon with the pointer of the navigation system.

To identify a relationship between flexion gap height increase and anterior tibial translation, the ratio between anterior translation and gap height increase was determined for each patient between 100 and 200 N.

The mean gap height increased 2.2 mm (SD 0.96) and mean increase in anterior tibial translation was 4.2 mm (SD 1.6). Hence, on average, for each mm increase in gap height, the tibia moved 1.9 mm (SD 0.96) in anterior direction. Knees with a steep PCL showed significantly more AP translation for each mm gap height increase (gap/AP-ratio was 1 : 2.31 (SD 0.63)) compared to knees with a flat PCL (gap/AP-ratio was 1 : 1.73 (SD 0.50)).

The increase in femur (exo)rotation was on average 0.60° (SD 1.4).

With a tensioned PCL the tibia will move anteriorly on average 1.9 mm for every extra mm that the flexion gap is increased. The flexion gap dynamics can be explained in part by the orientation of the PCL: the greater the elevation angle, the more anterior tibial displacement during distraction of the flexion gap. The surgeon must be aware that distraction of the flexion gap influences the tibiofemoral contact point. The tibio-femoral contact point will move posteriorly and stresses in the PCL will rise and produce limited flexion and pain. In case of a conforming insert AP-movement will be limited but high PE stresses may be introduced that can lead to wear. This information may be helpful in selecting the optimal soft tissue balancing procedure and the optimal PE insert thickness in PCL retaining TKR.

H. Enomoto T. Nakamura S. Yanagimoto H. Kaneko Y. Fujita A. Funayama Y. Suda Y. Toyama

In the light of the increasing popularity of femoral resurfacing implants, there has been growing concern regarding femoral neck fracture. This paper presents a detailed investigation of femoral neck anatomy, the knowledge of which is essential to optimise the surgical outcome of hip resurfacing as well as short hip stem implantation.

Three-dimensional lower limb models were reconstructed from the CT-scan data by using the Mimics (Materialise NV, Leuven, Belgium). We included the CT data for 22 females and nine males with average age of 60.7 years [standard deviation: 16.4]. A local coordinate system based on anatomical landmarks was defined and the measurements were made on the unaffected side of the models.

First, the centre of the femoral head was identified by fitting an optimal sphere to the femoral head surface. Then, two reference points, one each on the superior and the inferior surface of the base of femoral neck were marked to define the neck resection line, to which an initial temporary neck axis was set perpendicular. Cross-sectional contours of the cancellous/cortical border were defined along the initial neck axis. For each cross-sectional contour, a least-square fitted ellipse was determined. The line that connects the centre of the ellipse at the base of the femoral neck and the centre of the femoral head was defined as the new neck axis. The above process was repeated to reduce variances in the estimation of the initial neck axis. The neck isthmus was identified according to the axial distributions of the cross-sectional ellipse parameters.

The short axis of the ellipse decreased monotonically since it was calculated from the center of the femoral head to the neck resection level (base of neck), whereas the long axis changed with the local minima. The cross section at which the long axis of the fitted ellipse had the local minima was determined as the neck isthmus.

The following measurements were made on the proximal part of the femur. The neck axis length measured from the center of the femoral head to the lateral endosteal border of the proximal femur was 67.3 mm [6.4]. The length between the center of the femoral head and the neck isthmus was 22.5 mm [2.7]. The diameter of the ellipse long axis at the neck isthmus was 27.6 mm [3.5] and was 23.6 mm [3.3] for the short axis.

The center of the neck isthmus did not align with the neck axis. The deviation of the isthmus from the neck axis which we defined as the isthmus offset was 0.7 mm [0.4].

If an alternative neck axis was defined between the center of the femoral head and the center of the neck isthmus, there would be a certain degree of angular shift with respect to the original neck axis. An angular shift of 1.8 degrees between the two axes can be expected for a 0.7-mm isthmus offset. In the worst case, an angular shift of 4.59 degrees was estimated for a subject with the largest isthmus offset of 1.93 mm.

Further investigations would be necessary to determine the axis configuration that represents the clinically relevant centre of the femoral neck. In order to reduce the deviations in the three-dimensional determination of the femoral neck axis, the reference anatomical landmarks and methods of evaluation should be carefully selected.

Y. Takahashi G. Pezzotti A. Kakimoto J. Hashimoto N. Sugano

Multiaxial rotation of femoral component is generated in a wide range against UHMWPE tibial insert during ambulation or deep bending activities. Simultaneously, microscopic oscillation and twisting might accompany with such a wide-range motion.

Such a combined in-vivo kinetics is expected to bring more severe wear to the sliding surface of knee joint prostheses than that in a case of single macro-kinetics (i.e., that commonly reproduced by conventional wear simulators). In order to reproduce clinical surface degradation correctly and quantitatively in simulator tests, we have to consider microscopic motions at the joint bearing surfaces. The purpose of this study is to analyze the influence of the composite knee motion on wear using a non-destructive spectroscopic approach.

The crystalline phase in UHMWPE is pre-oriented in the tibial insert from the manufacturing process, but the orientation of crystalline lamellae is sensitive to mechanical loading. Therefore, the orientation of the crystalline lamellae on the surface of retrieved UHMWPE tibial inserts could reflect the local motions in vivo generated in the joint during ambulation. The visualization of (orthorhombic) crystalline lamellae might ultimately lead to the possibility of tracking back the wear history of the joint. In this study, polarized Raman spectroscopy was employed in order to non-destructively visualize the lamellar orientation in UHMWPE tibial inserts, which were retrieved after exposures in human body elapsing several years.

According to this Raman analysis and in comparison with an unused insert, the orientation of surface lamellae was found to have been clearly changed due to wear in accordance to the local motion of the femoral component. Additionally, we could obtain information about the origin of delamination from the in-depth profile for lamellae orientation angle. This study not only shows the possibility of optimizing the UHMWPE structure to minimize wear but also gives a hint for the development of knee simulators of the next generation.

J. Victor D. Van Doninck L. Labey

The understanding of rotational alignment of the distal femur is essential in total knee replacement to ensure that there is correct placement of the femoral component. Many reference axes have been described, but there is still disagreement about their value and mutual angular relationship. Our aim was to validate a geometrically-defined reference axis against which the surface-derived axes could be compared in the axial plane. A total of 12 cadaver specimens underwent CT after rigid fixation of optical tracking devices to the femur and the tibia. Three-dimensional reconstructions were made to determine the anatomical surface points and geometrical references. The spatial relationships between the femur and tibia in full extension and in 90° of flexion were examined by an optical infrared tracking system.

After co-ordinate transformation of the described anatomical points and geometrical references, the projection of the relevant axes in the axial plane of the femur were mathematically achieved. Inter-and intra-observer variability in the three-dimensional CT reconstructions revealed angular errors ranging from 0.16° to 1.15° for all axes except for the trochlear axis which had an interobserver error of 2°. With the knees in full extension, the femoral transverse axis, connecting the centres of the best matching spheres of the femoral condyles, almost coincided with the tibial transverse axis (mean difference −0.8°, SD 2.05). At 90° of flexion, this femoral transverse axis was orthogonal to the tibial mechanical axis (mean difference −0.77°, SD 4.08). Of all the surfacederived axes, the surgical transepicondylar axis had the closest relationship to the femoral transverse axis after projection on to the axial plane of the femur (mean difference 0.21°, SD 1.77). The posterior condylar line was the most consistent axis (range −2.96° to − 0.28°, SD 0.77) and the trochlear anteroposterior axis the least consistent axis (range − 10.62° to +11.67°, SD 6.12). The orientation of both the posterior condylar line and the trochlear anteroposterior axis (p = 0.001) showed a trend towards internal rotation with valgus coronal alignment.

J.H. Currier D.W. Van Citters B.H. Currier A.S. Perry J.P. Collier

Squeaking of ceramic-on-ceramic (CoC) hips is a clinical phenomenon that is concerning with regard to the long term performance of these joint devices. Investigations into the cause of the squeaking have focused on patient factors and demographics, surgical placement, and other non-ceramic components in the devices. The current study tests latest-generation CoC devices to measure the vibration modes and frequencies of the components individually as well as assembled in the complete surgical construct.

Audio data from clinical cases of squeaking hips were analysed to determine the frequencies present. Retrieved CoC hips (n = 7) and never-implanted CoC bearing couples (n = 3) were tested in the laboratory for squeaking under loaded articulation.

Bovine serum was introduced into the CoC articulation and dried to promote stick-slip motion at the articulation. Squeaking sounds from the in vitro tests were recorded for audio analysis. Low mass, high frequency-response ceramic shear piezoelectric accelerometers (PCB Piezotronics) were adhered to the hip components along multiple axes to measure vibrations during testing.

Clinical audio shows that squeaking occurs at fundamental frequencies in the range of 1 to 3 kHz, with harmonics above the fundamental frequency. Retrieved CoC bearing couples squeaked at fundamental frequencies from 1.5 kHz to 3.8 kHz. Fourier Transform analysis of the audio closely matched the concurrent output from the accelerometers mounted directly on the ceramic components. This held true even in the absence of metal components in the system. With metal components included in the test construct (acetabular shell, acetabular cup, femoral stem), those components also vibrated at the same frequencies as the ceramic bearing couples, indicating that the CoC articulation is the source of the vibrations, with metal components conducting and emanating the sound.

The never-implanted bearing couples were made to squeak and vibrated at fundamental frequencies ranging from 1 kHz to 8 kHz.

Squeaking from CoC hips can be reproduced in the lab using components from clinical retrievals. Instrumentation of the explanted hips confirms that the vibration frequencies of the ceramic components themselves match the audible squeaking. The squeaking of ceramic components mounted with soft polymers and with no metal contact at any point indicates that the ceramic components themselves are the source of the clinical squeaking. The measured vibration of ceramic components in the audible range is an observation not predicted by modeling studies reported in the literature to date.

R. Strachan F. Iranpour P. Konala B. Devadesan S. Chia A. Merican A. Amis

Controversy still exists in the literature regarding efficacy and usefulness of CASN in knee arthroplasty. However, obsession with basic alignments and proper correction of mechanical axes fails to recognise the full future potential of CASN which seems to lie in enhanced dynamic assessment. Basic dynamics usually at least includes intraoperative assessment of limb alignments, flexion-extension gap balancing and simple testing through ranges of motion. However our upgraded CASN system (Brainlab) is also capable of enhanced assessment not only including the provision of data on initial to final alignments but also contact point observations. The system can also perform an enhanced ‘Range Of Motion’ (ROM) analysis including observation of epicondylar axis motion, valgus and varus, antero-posterior shifts as well as flexion and extension gaps. Tracking values for both tibiofemoral and patellofemoral motion have also been obtained after performing registration of the prosthetic trochlea.

Observations were then made using a set of standardised dynamic tests. Firstly, the lower leg was placed in neutral alignment and the knee put through a flexionextension cycle. Secondly the test was repeated but with the lower leg being placed into varus and internal rotation. The third test was performed with the lower leg in valgus and external rotation.

We have been able to carry out these observations in a limited case series of 15 total knee arthroplasties and have found it possible to observe and quantify marked intra-operative variation in the stability characteristics of the implanted joints before corrections have been made and final assessments performed. Indeed contact point observation has found several cases of edge loading before corrections have been made. Also ROM analysis has demonstrated the ability of the system in other cases to observe and then make necessary adjustments of implant positions and ligament balance which alter the amounts of antero-posterior and lateral translations. In this way paradoxical antero-posterior and larger rotational movements have been minimised. Cases where conversion to posterior stabilisation has been necessary have been encountered. Also patellar tracking has been observed during such dynamic tests and appropriate adjustments made to components and soft tissue balancing.

Although numbers in this case series are small, it has been possible to begin to observe, classify and quantify patterns of instability intra-operatively using simple stress tests. Such enhanced intra-operative information may in future make it possible to create algorithms for logical adjustments to ligament balance, component sizes, types and positions. In this way CASN becomes a more useful tool.

A. Borgwardt S. Ribel-Madsen L. Borgwardt B. Zerahn L. Borgwardt

A major concern in metal on metal bearings has been the elevated serum concentrations of cobalt and chromium. Recent papers have suggested that metal hypersensivity in a few cases could cause periprostetic lymphocyte accumulation leading prosthetic loosening.

To measure the lymphocyte activation and proliferation in vitro by re-exposure of the cells to cobalt, chromium, nickel and titanium. To correlate the lymphocyte assay data to the serum concentration of metals and plasma cytokines.

A prospective clinical study with the ASR (DePuy) and ReCap (Biomet) resurfacing hip implants. Blood samples were collected one and two years postoperatively, lymphocytes were isolated by density gradient centrifugation, cultured in a medium containing the patient’s serum and exposed to metal salts.

Cells were analyzed by flow cytometry, evaluating number, viability, size and CD69 activation.

A negative control and a positive control (phytohaemagglutinine) were included in the assay, and the responses to the metals were calculated in proportion to controls. 11 patients were assessed at one and two years follow up, 16 patients were assessed only at two years.

Serum chromium and cobalt were measured preoperatively, six months, one year and two years postoperatively by graphite furnace absorptiometry. Plasma cytokines were measured by multiplexed immunoassay.

In the assay the negative and positive controls gave the expected responses.

When exposed to metals no response was found in the lymphocytes in any patients.

There were no difference in response between one and two years.

The results seems to indicate that the metal hypersensitivity is a rare condition in metal on metal arthroplasty. The results indicate that the method can be used to monitor hypersensitivity to implant metals.

J.H. Currier I.M. Tomek B.H. Currier J.C. Huot M.B. Mayor D.W. Van Citters

A common feature of retrieved ceramic-on-ceramic (CoC) hips is the presence of metal transfer on the femoral head. This metal transfer represents an important change in the articulating surface and can have consequences in terms of lubrication, friction, wear, and squeaking. Given the potential impact of metal transfer on the performance of CoC bearing couples, a good understanding of the factors surrounding its occurrence is warranted. This study documents the metal transfer onto a ceramic femoral head with two subluxations onto the rim of the cup which occurred during surgery. This metal transfer is compared to that on other ceramic heads retrieved for various reported reasons, including squeaking, pain and loosening.

The first ten retrieved alumina heads of current ceramic technology (Ceramtec, Plochingen, Germany) submitted to our retrieval laboratory were assessed to document the phenomenon of metal transfer. Nine devices underwent in vivo service (mean duration 32 mo., range 13 to 84) and the tenth device was removed intra-operatively and serves as an instructive control case. It was impacted onto a trunnion and during final testing for stability subluxed anteriorly over the titanium lip of the cup. The metal transfer was immediately noted by the surgeon and the head was removed.

All ceramic heads were examined under light microscopy (Nikon Dissecting Microscope, Tokyo, Japan) and white light optical profilometry (NewView 7300, Zygo, Middlefield, CT).

The control ceramic head showed two distinct metal transfer streaks from two discrete subluxation events that were documented by the surgeon (IMT). Those streaks are aligned in a direction approximately 24o to the right (clockwise) of a line through the polar apex of the head and parallel to the axis of the femoral neck. Microscopy and profilometry indicate that they were laid down in a direction from equator-toward-pole.

Seven of the retrieved ceramic heads showed streaks of metal transfer that are very similar to those on the control ceramic head in terms of: alignment (equator-toward-pole, 20 to 45o off-axis) width (tapered point growing to approximately 1.0 to 1.5 mm), depth of metal deposition (0.25 to 0.40 μm), and depositional texture.

It is notable that the metal transfer streaks commonly observed on retrievals bear a close resemblance to that caused by a single intra-operative event wherein a hip abduction force pulled the head into contact with the titanium cup/liner rim. An important implication is that this demonstrates that metal transfer can occur with a single instance of rim contact, wherein the femoral head is forced against the metal cup rim. If metal transfer onto the head were to occur during final reduction of the hip, its presence may well be undetected and any deleterious in vivo impact of the metal transfer would be in effect from the day of surgery.

J.D. Johnston S.E. Kulshreshtha D.J. Hunter D.A. Wilson B.A. Masri

Objective: Unicompartmental knee arthropasty (UKA) has recently attracted increased popularity and usage, though issues exist regarding tibial component failure. UKA instability may be due to insufficient bony support at the proximal tibia. Pre-operative knowledge of ‘safe’ resurfacing depths offering subchondral bony support could help minimize UKA instability. We recently developed a novel CT imaging tool (CTTOMASD) which assesses subchondral bone mineral density (BMD) in relation to depth from the subchondral surface. The objective of this work was to determine the in-vivo precision of CT-TOMASD safe resurfacing depths in human tibial compartments.

Seven knees from seven donors (2M:5F; age:46+/−11) were scanned three times via QCT (GE Lightspeed; BMD Phantom; 0.625x0.625x0.625mm resolution). CTTOMASD regional analyses were performed for medial and lateral compartments; outputting density versus depth plots fit with polynomial regression equations. As density decreases with increased depth from the subchondral surface, a density threshold of 300mg/ cm3 was arbitrarily set to correspond with the safe resurfacing depth. The 300mg/cm3 density threshold corresponds to the average density of subchondral trabecular bone, and is ~2x the density of weak epiphyseal trabecular bone located beneath stiffer subchondral trabecular bone. Precision was defined using coefficients of variation (CV%).

In-vivo precision errors associated with CT-TOMASD safe resurfacing depths were less than 2.7%. CV% was 2.7% for the medial compartment depth and 2.6% for the lateral compartment depth.

CT-TOMASD demonstrates repeatable measures of safe resurfacing depths invivo.

Safe resurfacing depths are measured in relation to defined density thresholds which can be adjusted according to UKA design and patient specifics (e.g., size, sex). CT induces a low radiation dosage due to the low presence of radiosensitive tissues at the knee (~1/10th of a long-leg standing radiograph). CT-TOMASD has potential to be used as a pre-operative imaging technique for improved UKA stability and longevity.

S.D. Steppacher T.M. Ecker M. Tannast S.B. Murphy

Patients who are less than 50 years old at the time of total hip arthroplasty (THA) have been known to have higher failure rates than patients who are older. Wearinduced osteolysis and associated component loosening is the most common mode of failure reported. The current investigation prospectively assessed the survivorship and clinical results of alumina ceramic-ceramic THA in patients younger than 50 years.

238 consecutive hips in 201 patients treated by alumina ceramic-ceramic THA were studied. The mean age at operation was 41.4 ± 7.5 years (range, 18 – 50 years).

The preoperative Merle d’Aubigné score was 11.1 ± 1.6 (6 – 15). The preoperative diagnosis included primary osteoarthritis or impingement (105 hips, 44%), developmental dysplasia of the hip (90 hips, 38%), osteonecrosis of the femoral head (17 hips, 7%), post-traumatic osteoarthrosis (16 hips, 7%), and rheumatoid arthritis (6 hip, 3%). 144 hips (61%) were replaced with the use of surgical navigation for acetabular component positioning. The mean cup diameter was 51.8 ± 3.7 (range, 46 – 60 mm). 73 (31%) bearings were 28 mm and 165 (69%) bearings were 32 mm.

At mean follow-up of 5.6 ± 2.3 years (2 – 11 years), the mean Merle d’Aubigné score was 17.4 ± 0.9 (14 – 18). There were no radiographic signs of osteolysis. There were two revisions (0.8%): one for acute cup displacement and one for a ceramic liner fracture. In addition, one hip was treated by I& D for acute infection and another with I& D but without evidence of infection. Other complications included one greater trochanter fracture and one calcar fracture, both repaired at surgery, and one transient peroneal nerve palsy. The 10-year Kaplan Meier survivorship of the implants (revision of any component for any reason) was 98.7% (95% confidence interval 96.3–100%). There were no hip dislocations.

Results of THA in patients less than 50 years using alumina ceramic-ceramic bearings at two to eleven years follow-up are promising with no case of osteolysis or dislocation.

T. Fujii M. Kondo K. Tomari H. Kitagawa Y. Kadoya

Several anatomical landmarks are preferable in order to achieve the precise decision of femoral component rotation in order to achieve a satisfying result in total knee arthroplasty (TKA). The posterior condylar axis (PCA) is apparent and allows minimization of interobserver error compared with the transepicondylar axis or anterior-posterior axis. The rotation angle based on PCA observed during surgery differs from the angle measured on pre-and postoperative epicondylar view, because X-rays do not reflect the posterior condylar cartilage. We investigated the influence of the posterior condylar cartilage on setting the rotation angle of the femoral component in 184 knees in 112 patients with varus osteoarthritis undergoing TKA.

Medial and lateral thickness of the resected posterior femoral condyle was measured before and after removing the cartilage to determine its thickness. The amount of rotation angle influenced by the cartilage is expressed as an inverse trigonometric function (arctangent) of the distance between the posterior condylar surfaces and the difference in thickness between the medial and lateral cartilage.

Average thickness of the lateral and medial cartilage turned out to be 2.1±0.7mm and 0.7±0.7mm, respectively. The average rotation angle influenced by this difference was calculated to be 1.7±1.3°. These findings suggest that using PCA as a guide to determine the rotation angle of the femoral component results in approximately 1.5–2.0° of excess external rotation in varus osteoarthritis. Because of significant individual variability in condylar twist angle, formed by the intersection of the clinical epicondylar axis with the PCA, preoperative CT or epicondylar view is recommended in order to calculate this angle in each subject. Thickness of the posterior condylar cartilage should be taken into consideration when finalizing the rotation angle of the femoral component by PCA in addition to transepicondylar and anterior-posterior axis.

L.D. Angibaud B. Stulberg J. Mabrey D. Covall J. Steffens A. Hayes J Weisenburger H. Haider

A tibial insert with choices in posterior slope, size, and thickness is proposed to improve ligament balancing in total knee arthroplasty. However, increasing slope, or the angle between the distal and proximal insert surfaces, will redistribute ultra-high molecular weight poly-ethylene (UHMWPE) thickness in the sagittal plane, potentially affecting wear. This study used in-vitro testing to compare UHMWPE wear for a standard cruciate-retaining (CR) tibial insert (STD) and a corresponding 6° sloped insert (SLP). Our hypothe sis was that slope variation would have little effect on wear.

Two of each style inserts were tested on an Instron-Stanmore knee simulator with a force-control regime. The gait cycle and other settings followed ISO 14243-1 & 2, except for the reference position, which was posteriorly shifted 6 mm to simulate the worst-case scenario. The STD insert was tilted 6° more than the SLP to level the articular surfaces. Wear was gravimetrically measured at intervals according to strict protocol.

No statistical difference (p=0.36) was found between wear for the STD (9.5 ±1.8 mg/Mc) and SLP (11.4 ±0.5 mg/Mc) inserts.

The overall wear rate measured was higher than previously published rates using implants similar to the STD inserts. This may relate to the shift in the reference position and the 6° slope, leading to increased shear loads. This is the first time the effect of tibial insert slope on wear has been evaluated in-vitro. When limited to 6°, wear testing suggests that al tering the tibial insert slope will have a minor effect on UHMWPE wear.

Y. Kajino T. Kabata T. Maeda T. Murao H. Yoshida K. Tanaka K. Tomita

The position of the acetabular component affects the result of total hip arthroplasty(THA) in terms of postoperative dislocation, impingement, wear etc.

However, as it is much difficult to place the component in the appropriate position for the cases of severe acetabular deformity, we used a Computed tomography(CT)-based navigation for THA in such cases. Therefore, the purpose of this study was to estimate the accuracy of a CT-based navigation in terms of acetabular component positioning in THA for severe acetabular deformities.

13 patients (1 man, 12 women), 14 hips underwent THA using a posterolateral approach with a CT-based navigation. The diagnoses were severe developmental dysplasia (Crowe group III, IV) in 6, ankylosis in 3, destructive arthritis after infection in 2, Charcot joint, and arthrodesed hip. And, we evaluated the differences of component position from the center of the anterior pelvic plane(APP), anteversion angle, and inclination angle relative to APP between the intraoperative data from the navigation system and the data from postoperative CT. Considering the intra-observer error, the measurement was done three times respectively and the mean value was accepted. We also estimated the difference between the component size planned and that implanted.

The mean difference between intraoperative records and actual postoperative results of the component position shows 3.3 mm(range: 0–7.0, SD: 2.2) for the horizontal position, 3.2 mm(range: 0–9.7, SD: 4.5) for the vertical position, 4.4 mm(range: 2.0–7.7, SD: 1.6) for the antero-posterior position from the center of the APP, 1.3 degrees(range: 0–3.0, SD: 0.9) for the inclination and 2.9 degrees(range: 0.3–8.3, SD: 2.2) for the anteversion respectively. All components were placed in the safe zone by Lewinnek. The component size was predicted in 10/14(71.4%) hips. There were no complications related to the use of the navigation.

This study showed the accuracy of cup positioning using a CT-based navigation in THA for the cases of severe acetabular deformity. We concluded that this system was a useful tool for surgeon to identify orientation, implant acetabular component at the precise position and angle, and to reduce the incidence of some complications especially for patients with these severe acetabular deformities.

Robin Goytia Benjamin McArthur Philip Noble Sabir Ismaily David Irwin Molly Usrey Michael Conditt Kenneth Mathis

Several studies have suggested that, in TKR, gender specific-prostheses are needed to accommodate anatomic differences between males and females. This study was performed to examine whether gender is a factor contributing to the variability of the size, shape and orientation of the patellofemoral sulcus.

3D computer models of the femur were reconstructed from CT scans of 20 male and 20 female femora. The patellofemoral groove was quantified by measuring landmarks at 10 degree increments around the epicondylar axis. The orientation of the groove was defined by the tracking path generated by a sphere moving from the top of the groove to the intercondylar notch. To assess the influence of gender on the shape of the distal femur, all morphologic parameters were normalized for differences in bone size.

Overall, the distal femur was 15% larger in males compared to females. The male condyles were 4% wider than the female for constant AP depth (p=0.13). When normalized for bone size, there was no gender difference in most patello-femoral dimensions, including the length, width, angle or tilt of the sulcus. Female femora had a less prominent medial anterior ridge (p=0.07), and a larger normalized radius of curvature of the tracking path (p=0.03). In addition, the orientation of the sulcus differed by 1–2 degrees in both the coronal and axial planes. Overall, gender explained 4.7% of the anatomic variation of the parameters examined, varying from 0 to 15.9%.

The size, shape and orientation of the patello-femoral groove are highly variable.

While the patello-femoral morphology of male and female femora are very similar, some of the anatomic variability is related to gender, particularly the prominence of the medial ridge and the sulcus radius of curvature. The biomechanical and clinical significance of these differences after TKA have yet to be determined.

Sung-Do Cho Yoon-Seok Youm Chang-Yun Jung Ki-Bong Park

The purpose of this prospective study was to investigate the necessity of gender-specific design in total knee arthroplasty (TKA) for Korean women.

One hundred and seventeen women (151 knees) who underwent primary TKA by one surgeon with Nexgen® LPS (Zimmer, Warsaw, IN) were evaluated. The mean age was 70 (range 52–80) years. The size of the implant was determined by considering anteroposterior (AP) dimension and the amount of posterior condylar resection. Size C was used in 72 knees, size D in 57 and size E in 22. We measured the mediolateral (ML) widths of distal femur at four points (anterior, distal anterior, distal posterior, posterior) intraoperatively after bone cutting, and compared them with the ML widths of the corresponding femoral implants. The ML/AP ratio was calculated in each size group.

The mean ML widths of the distal femur checked at all four points were larger than those of the implants. The ML/AP ratio of the distal femur decreased as the size increased from C to E, especially that of the anterior point. Overhanging occurred in 7 cases (4.6%, size C -2 cases, size D -2 cases, E -3 cases) : Nexgen® LPS implant was used in 5 cases because there was only minimal antero-lateral overhanging, resulting in no postoperative problem such as pain or limited motion. Gender-specific design was used in only 2 cases (1.3%, size D -1 case, size E -1 case) with trochlear dysplasia due to general overhanging.

In conclusion, gender-specific design of Nexgen® TKA was rarely necessary in 117 Korean women(151 knees); overhanging occurred in 7 knees (6 women) and gender-specific design was used in only two knees (1.3%) with trochlear dysplasia. Further research is obviously mandatory to assess the necessity of gender-specific design.

Yves Catonné F Khiami H Sari Ali JY Lazennec

Introduction: In patients with gonarthrosis secondary to a femoral or a tibial mal union, the technical problems are different according to the localization and the importance of the deformity, the presence of boneless, the cutaneous and ligamenteous status and the degree of preoperative motion.

Material and Methods: Between 1995 and 2003, 34 TKR have been performed in patients with mal unions either post trauma (26 cases) either secondary to surgery (osteotomy with hypercorrection). There were 21 males and 13 females. The average age was 63 years (38 to 77) The mal union was localized to the femur (9 cases) or the tibia (23 cases) or to the both femur and tibia (2 cases). The deformity was variable : varus, valgus, flessum, recurvatum or rotationnal mal union. IKS scoring, HKA, MFA and MTA angles were evaluated pre and post operatively. 11 cases of intra articular mal unions, secondary to epiphyseal fractures were operated : a TKR posterostabilized (9 cases) or constrained (2 cases) was performed.

In the extra articular mal unions (23) the technique depended on the degre of intraosseous deformity : medial or lateral release or osteotomy performed when the intra osseous deformity was more than 10°. TKR was associated with an osteotomy in one time surgery in 5 femoral mal unions and 12 tibial deformities.

Results: The average follow up was 8 years (4 to 13 years). Complications consisted in 5 phlebitis, 2 superficial skin necrosis, 4 stiff knees (flexion less than 80°). There was no infection in this short serie. The average IKS score was 65 before and 163 after operation. The average flexion was 83° preoperatively and 98° after surgery. Average HKA angle was 167° pre and 182° post operatively in the varus deformities. In the valgus deformity it was 191° pre and 181° post surgery.

Discussion: Average IKS scoring is less good in post traumatic mal unions than in the habitual TKR specially because of the motion : the knee is often stiff preoperatively and remain often stiff postoperatively. A quadriceps release is sometimes indicated either during the TKR either in a second time. Constrained implants (constrained condylar knee or rotating hinge) are necessary in some cases of medial or lateral insuffisency of the collateral ligament.

J. B. Grimes

A higher than expected failure rate of the Zimmer Durom acetabular component has been reported. A study by Zimmer did not reveal a design defect. This study investigated impaction deformation of two cup designs.

Eleven Durom cups and modular heads (Zimmer, Warsaw, IN) were retrieved at an average of 13.9 months. The Birmingham Hip Resurfacing (Smith & Nephew, Memphis, TN) served as a control. Cups were impacted into a two-point acetabular loading model made of 30 grade urethane foam (Sawbones, Vashon, WA). A coordinate measuring machine with 2 micron (um) accuracy was used to map the inside diameters of the cups before, during and after impaction. Machinist’s dye was used to check head-cup contact.

The Durom porous coating was essentially devoid of tissue ingrowth. Two heads used with size 62/56 Duroms had equatorial wear stripes. The outside diameter of the Durom was 2.93±0.03mm larger than the nominal diameter. Dome wall thickness was 3.23±0.07mm for the Durom and 6.08±0.65mm for the BHR (n=11). Inside diameters of all cups had less than 10um deviation from roundness before impaction and after removal from the model. The mean diametral deformation of the Durom was 89.8±14.8um, significantly greater than the BHR, 57.2±25.0um (p< 0.002). Non-impacted cups exhibited polar contact—circular areas of dye at the dome with no contact near the rim. Duroms with greater deformation exhibited linear contact—a 2cm band of dye extending from rim to rim with no contact on either side of the band.

The Durom is a relatively thin-walled acetabular component with low clearance and an aggressive rim flare. Impaction of this cup into an acetabular model resulted in deformation which approached the diametral clearance. Maximal deformation with larger cups and warping of the articular surface correlated with observed wear stripes. The absence of residual cup deformation indicated deformation is a dynamic phenomenon which can be detected only under conditions simulating in vivo use. It is likely that impaction deformation, with consequent friction and wear, contributed to the early failure of the Durom acetabular component.

S. Matsuda H. Mizu-uchi H. Miura Y. Iwamoto

Total knee arthroplasty (TKA) has become one of the most successful procedures in orthopedics, and its survival rates are reportedly greater than 90% after 15 years.

Malpositioning of the component, however, can lead to various failures, such as aseptic loosening, instability, polyethylene wear, and patellar dislocation. Navigation systems for TKA have been developed to improve postoperative alignment. Many clinical and experimental studies of these navigation systems have shown that the accuracy of implanted components has improved.

We have compared the alignment of 150 total knee replacements implanted using a computed tomography-based navigation system and using the conventional alignment guide system when performed by a single surgeon. The knees were evaluated using full-length weight-bearing anteroposterior radiographs and computed tomography scans. For the navigated group, the average hip-knee-ankle angle, the femoral component angle to the femoral mechanical axis, and the tibial component angle to the mechanical tibial axis were 179.5, 89.4 and 89.7 degrees. The rotational femoral and tibial component angles to the planning axis were 0.6 and 0.3 degrees. The ideal angles of all alignments in the navigated group were obtained at significantly higher rates than in the conventional group. Our results demonstrated significant improvements in component positioning with CT-based navigation system, especially with respect to rotational alignment.

Recently, we established a new method for 3D reconstruction from postoperative CT images in order to accurately measure the alignment of the component relative to any designed plane. The results showed that the discrepancy between the two-dimensional and three-dimensional evaluations was 0.3 ± 1.8 (−2.7–3.4) degrees.

The coronal femoral angle for 36 knees (97.3%) and the coronal tibial angle for all the 37 knees (100%) were obtained within 3 degrees from the optimal angle. It is possible to measure the postoperative alignment for TKA more accurately on the basis of the defining plane. Three-dimensional analysis is necessary to evaluate the accuracy of the navigation system.

We conclude that navigation system is a very useful tool for achieving proper postoperative alignment. Controversy still exists regarding accuracy in rotational alignment with image-free navigation, but our results showed that CT-based system significantly improved accuracy of rotational alignment. We should keep using and improving the systems to establish more simplified and accurate systems.

H. Wook Kang Jun Bae Kim Suk Joo Lyu

Purpose: The purpose of the study is to measure the resected surface of femur of the Korean patients during total knee arthroplasty surgery and to compare these measurements with the dimensions of femoral implants in current use.

Materials and Methods: Morphometric data (7 parameters) were obtained in 500 cases of resected femur of the Korean patients who underwent total knee arthroplasties, and these data were compared with four current implants designs.

Results: The range of medial-lateral width at the given implant varies widely. The anterior width of the resected femur at the condyle is smaller than the widths of the most implants, creating an overhang. The medial-lateral width of the condyle at the level of transepicondylar line is wider than most of the present implants. However the widths of the resected posterior condyles were narrower at anterior-posterior alignment, causing overhang at the posterior condyles. We felt this will cause anterior tensioning at flexion and reduce the ability to flex further.

Conclusion: The shape of the femur in Korean knee is different from that of current TKR implants in use, which are based on the anthropometric data of Caucasians. Therefore new design, better suited to the morphometric measurements of Korean knee, is necessary. Though historically this mismatch of the implant was well tolerated, new design to better fit the measurement of Korean knee should be considered for functional enhancement such as range of motion, durability and function.

Fred Cushner

Introduction: Wound Hemearthrosis remains a major concern following TKA. This prospective study evaluates the use of a knotless interlocking suture system and its relationship to wound appearance and OR efficiency.

Methods: Two groups of patients undergoing TKA in our institution were evaluated using two different wound closure techniques. Group I consisted of twenty five patients who underwent standard closure using interrupted vicryl for the arthrotomy, deep fascia, superficial fascia, followed by staples. Group II consisted of twenty five patients who underwent closure using three separate running barbed sutures (Quill, Angiotech Inc)– first for the arthrotomy, followed by deep fascia, subcuticular and staples. We compared closure times, drain output and postoperative day to achieve zero wound drainage on the dressings.

Results: Closure times for Group II averaged 10 minutes faster than Group I. Drain output was decreased in the barbed suture cohort. Wounds achieved zero drainage, on average, one day sooner in Group II and no patients were returned to the OR for hematoma evacuation or arthrotomy disruption.

Conclusions: Use of this new technique for closure of TKA incisions can lead to faster operative times, lower drainage outputs and less immediate postoperative wound drainage. It appears that hemostasis is obtained quicker with the use of this barbed suture system while at the same time while maximizing OR efficiency.