There is increasing pressure to develop virtual reality surgical simulation that can be used in surgical training. However, little is known of the attitudes of the surgical community towards such simulation, and which aspects of simulation are most important.

A postal survey on attitudes to surgical simulation was sent to all New Zealand orthopaedic surgeons and advanced trainees. This comprised 44 questions in ten sections, using either a visual analogue scale (0 to 10) or free text box replies. Results were analysed for two sub-groups; surgeons qualified before 1990 and those qualified in or after 1990 or still in training.

Of 208 possible responses, 142 were received, a response rate of 68%. Only 4 respondents had tried a surgical based simulator. Earlier qualified surgeons were more likely to agree that simulation was an effective way to practice surgical procedures, median score 7.7 versus 5.6 (p=0.03). Both groups thought the most important task for simulation was practicing angulation/spatial orientation (median score 8.4/10), while a realistic view of the operation was the most important requirement (median score 9/10). Both groups were unconvinced that simulation would impact on their practice in the next five years, with this statement being scored lower by later qualified surgeons, median score 2.4 versus 4.1 (p=0.04).

Orthopaedic surgeons in New Zealand are supportive of surgical simulation but do not expect simulation to have an impact in the near future. Intriguingly, later qualified surgeons and trainees are more sceptical than their earlier qualified colleagues.

Introduction: This study examined the cohort of patients selectively screened over a 5 year period with ultrasonography according to our risk factors (positive Ortolani or Barlow manoeuvre, breech presentation, first degree affected relative and talipes equinovarus) for developmental hip dysplasia (DDH). The aims were to evaluate the success of those managed in a Pavlik harness and identify predictive factors for those that failed treatment.

Methods: 728 patients were selectively screened between 1999 and 2004. Of those, 128 patients (189 hips) were identified as having hip instability. Failure was defined as inability to achieve or maintain hip reduction in a Pavlik harness. A proforma was designed to document patients’ risk factors and ultrasound findings at time of initial dynamic ultrasound scan where the senior radiographer and treating consultant were present. Each hip was classified according to Graf type. Acetabular indices were recorded prior to discharge.

Results: All 128 patients with hip instability were managed in a Pavlik harness. This was abandoned for surgical treatment in 9 patients (10 hips) giving a failure rate of 5.3 %. All those successfully managed had an acetabular index of less than 30 degrees at follow up (6 – 48 months). 7 hips in the series were classified as Graf type IV, of these, 6 went on to fail management in a Pavlik harness. 67% of those that failed were also breech presentation compared to 22% of those managed successfully. There were no complications associated with management in a Pavlik harness.

Discussion: Our overall rate of selective screening is 14 per 1,000 with a subsequent treatment rate of 2.3 per 1,000, which is comparable with other centres. Our rate of failure for DDH in a Pavlik harness (5.3 %) is extremely encouraging. Graf type IV hips and breech presentation correlated with a high likelihood of treatment failure.

Aim: Assessing Polyethylene wear is very important in following up patients after Total hip replacement (THR) and Livermore method (using callipers) is routinely used by clinicians in calculating this wear. Our aim was to assess if ‘Imagika’, a new computer software programme can accurately assess polyethylene wear(PE-wear). We also compared the computer software with the Livermore method in calculating wear.

Method: We used 15 different THR X rays of patients who had an ABG total hip replacement done. X rays that were included for the calculations were taken at different time intervals following the operation. Wear was calculated on each X ray by 3 clinicians using both the methods, on 3 separate occasions. We compared the Livermore method and the computer software for consistency of measurements and also calculated the inter and intra observer variability for both.

Results: There was a statistically significant difference (at the 5% level) between the measurements taken by the Imagika software and the Livermore method. F(1,88) = 5.38, p< 0.05. There was a statistically significant difference in the inter-observer measurements using the Livermore method. F(2,42) = 4.18, p< 0.05, but there was no significant inter-observer variation using the Imagika computer software. There was no statistically significant difference (at the 5%level) in the intra-observer variability of both groups.

Conclusion: The Imagika computer software proved to be better than the Livermore method in calculating wear with regards to inter-observer bias. There was also a significant difference between measurements taken using both methods. We conclude that the computer software may be a more accurate tool in the assessment of PE-wear in the future.

Introduction: Patello-femoral complications are a major problem after total knee arthroplasty (TKA). Purpose of the present study was to analyze patello-femoral complications and function after two different posterior-stabilized TKA designs (Optetrak 913 vs IB-II).

Materials and Methods: This study was performed in two consecutive phases. In the first phase 1410 TKA’s performed by the senior author between 1994 and 1998 were considered for chart review. Within this period, the last 300 IB-II and the first 300 913 performed were analyzed for patello-femoral complication rate. In the second phase, of the 600 charts analyzed, two matched groups (50 patients each of IB-II and 913), were selected for a clinical (Knee Society score), functional (HSS Patellar score) and radiological assessment (AP, Lateral, Merchant, modified-wb Merchant views).

Results: A lateral retinacular release was performed in 30% for the IB-II and 16% for the 913 (p=0.02). The following patello-femoral complications were encountered (phase-1):

IB-II 913

Patellar clunk 3.5% 0.3%

Dislocation 0% 0.3%

Fracture 0% 0.3%

Loosening 0% 0%

Clinical results at follow-up (phase-2) did not show any significant difference between the two matched groups in terms of Knee and Function scores (p=0.7). Patellar score showed a higher rate of excellent and good results in the 913 group (88% vs 81%: p=.043). Anterior knee pain was only mild and activity related in 26% of the IB-II and 14% of the 913 (p=.025). In a multivariate regression analysis, radiographic patellar tilt, subluxation, and height, did not correlate with clinical outcomes, whilst bone-implant contact showed a trend towards a higher incidence of pain, particularly when associated with asymmetric patellar resection.

Discussion: At an intermediate follow-up, the Optetrak 913 prostheses showed fewer complications and an improved patello-femoral function compared to the IB-II prosthesis.

Introduction: Patello-femoral evaluation after total knee arthroplasty (TKA) is not addressed by most knee scoring systems. Patellar radiographic assessment after TKA is obtained with static, unloaded views that may not reproduce the in-vivo patello-femoral kinematics. The purpose of this study was to develop and validate new reliable and reproducible clinical and radiographic assessment tools for analysis of the patello-femoral joint in TKA.

Materials and Methods: The existing axial Merchant view was modified by positioning the standing patient in the semi-squatted position with the knees at 45°. Relationship between X-ray source, the angle of incidence on the joint, and the cassette position, were kept unchanged from the original view. The standing position and consequent muscle involvement were the only differences. The quality of the view was confirmed on a cadaveric knee model with multiple markers. Safety, reproducibility and clinical reliability were obtained in 100 posterior-stabilized TKA’s. These patients were assessed by a new Patella Scoring System (0–100 points). This system considers anterior knee pain, crepitus, stair performance and quadriceps strength. Radiographic abnormalities are calculated as deductions. Intra- and inter-observer variability were obtained comparing the results of two different investigators.

Results: The modified Merchant view showed significant patello-femoral tracking changes in 68% of patients. Twenty-one cases of bone-implant contact were observed when load was applied. Correlation between excellent-good clinical outcome and excellent patello-femoral performance was significantly higher for the Patellar Score compared to Knee Society Clinic or Function scores (p=.022, p=.014). Multivariate regression analysis of radiographic tilt, subluxation, and height, did not correlate with clinical outcomes, whilst bone-implant contact showed higher incidence of pain, particularly when associated with asymmetric patellar resection.

Conclusion: These new patello-femoral clinical and radiological assessment methods employed in the study represent additional valuable tools for the comprehensive evaluation of results in TKA.

Aim To assess whether prosthetic femoral stem centralisers have a detrimental effect on the maroporosity of the cement mantle, and if so, whether this is independent of their design and the rate of implantation.

Methods 30 identical moulded prosthetic femora were divided into 3 groups. Group 1; no centraliser (control), Group 2; centraliser A, Group 3 centraliser B. Using third generation cementation techniques and pressure monitoring, Charnley C-stems +/− the appropriate centraliser were implanted to a constant depth. Half in each group were implanted as rapidly as possible and the other half over 90 seconds. The stems were removed and the cement mantle then underwent a preliminary arthroscopic examination prior to being sectioned transversely at 3 constant levels. Each level was then photographed and digitally enlarged to a known scale to allow examination and determination of any cement voids (macropores) surface area.

Results There were no significant pressure fluctuations between the groups. Preliminary arthroscopic examination revealed that cement voids appeared more common when a centraliser was used. This difference was statistically confirmed (p=0.002) following sectioning of the specimens with cement voids found in 85% of femora when a centraliser was used and only 20% in the control group. Centraliser B performed worst with cement voids of a larger volume and more frequent occurrence (p=0.002). The macroporosity of the cement mantle was independent of the rate of implantation (p=0.39).

Conclusion The use of femoral stem centralisers is helpful in preventing malposition of the implant but results in increased macroporosity of the cement mantle. This may have implications regarding the longevity of an implant in terms of early loosening and therefore their design and use must always be carefully considered.

Introduction and Aims: CT is one of the most versatile and useful medical imaging modalities for computer assisted surgery (CAS) and monitoring bone remodelling. However, the high radiation dosage hinders its widespread use. We describe a method for generating smooth and accurate Finite Element (FE) meshes using CT data with reduced radiation exposure.

Method: We have performed serial CT assisted osteodensitometry measurement on seven patients who had a total hip replacement. FE models were generated automatically with cubic Hermite basis functions for both geometry and density. The meshes were fitted to the geometric and density data sets using least square’s fitting. Density was displayed over the surface of the elements using a colour spectrum. The effect of reducing radiation dosage was studied by generating five different types of FE meshes from each patient with different numbers of CT slices. The different mesh types were generated by varying the gap between slices.

Results: The mesh with the smallest number of CT slices used seven CT scans, with the gap between slices of 3cm on average while the mesh with the largest number of slices used 22 scans with the gap of 0.8cm. For the mesh with the largest number of CT slices, the average error after the geometric fitting was less than 0.5mm. The average error for the density fitting was 70.2 mg/ml. When expressed as the percentage to the overall density data range (0 ~ 1500 mg/ml), the average error was 4.7%. Meshes generated with a smaller number of CT slices had larger errors, and this increased as the number of slices used decreased. The error in geometry dropped dramatically (more than 50%) when more than 10 slices were used, whereas the error in density decreased approximately linearly as the number of slices increased. Overall, it was possible to generate realistic and smooth meshes with a geometrical error of less than 1.5mm and a density error less than 7% using 10 CT slices.

Conclusion: One strength of the current study is that we have used cubic Hermite elements, which requires much less information in generating FE meshes without sacrificing too much accuracy. Our study has shown that we can generate realistic and smooth meshes with about 10 CT slices of the proximal femur. This is important to enhance the power of CT in clinical applications.

Aim: To identify the local and systemic morbidity of simultaneous sequential bilateral total knee arthroplasty in a large patient population and to undertake a comparative statistical analysis with a group of matched patients who underwent staged bilateral total knee replacement during the same period.

Methods: Theatre records at two regional district general hospitals were scrutinised to identify all patients who had undergone simultaneous sequential and staged bilateral total knee arthroplasty over a three year period. Patient case notes and hospital charts were retrospectively reviewed to obtain several outcome measures to allow subsequent risk factor assessment.

Results: 134 patients with 268 primary knee arthroplasties undergoing a simultaneous procedure were identified. The average age was 70 with a minimum follow up of 12 months. The study results revealed 1.5% mortality, 5.2% local complication and 14.9% systemic complication rates and this increased with age. During the same period 34 patients (68 knees) who had undergone staged procedures at least 3 months apart were also identified. Statistically significant findings between both groups included the reduced length of hospital stay, a 3-fold increase in the requirement for banked blood (particularly when either suction drainage or low molecular weight heparin thromboprophylaxis was used) and a higher degree of intra operative instability in those undergoing simultaneous bilateral total knee replacement.

Conclusions: Patients can continue to enjoy the benefits of simultaneous bilateral knee arthroplasty, however, extreme caution must be taken in selection of patients over 75 years, high dependency facilities must be available and an acceptable alternative to banked blood transfusion needs to be used.

Bone autograft contains living cells that participate in the healing process. Fragmentation and heat production during cutting will kill cells. We have investigated how excessive graft fragmentation and heating can be avoided.

Two prototype cutters were fabricated. Each had a single cutting edge at the front end of a 12 mm diameter collection barrel. The principal difference between the cutters was the rake angle (at the cutting edge): 23° on cutter #1 and 45° on cutter #2.

Thrust load, feed-rate, and torque were measured using an instrumented drill press. A total of 58 tests on specimens of fresh bovine cancellous bone (distal femur, ex-abattoir) and medium density polyurethane foam (Sawbones, WA. USA) (density 252 kg/m³) were conducted: twenty-four at 100 rpm and thirty-four at 200 rpm.

Small flake-like fragmented bone chips were encountered at low thrust loads. As thrust load was increased the chips became thicker. The average cutting energy for bone was 43.7 Nm (s.d. 48.2 Nm) for cutter 1 and 37 Nm (s.d. 27 Nm) for cutter 2. The average cutting energy for the foam was 13.9 Nm (s.d. 6.0 Nm) for cutter 1 and 8.1 Nm (s.d. 3.0 Nm) for cutter 2. Polyurethane results showed a similar trend.

A higher rake angle on a bone graft tool is associated with a lower cutting energy. In turn, a lower cutting energy will generate a lower temperature in the graft, a result that is beneficial for cell survival. Graft tool design can also influence bone chip size. These experimental results are being used for the development of cell-friendly tooling.

Periprosthetic bone density (BD) changes can be tracked using computed-tomography (CT) assisted osteodensitometry. Patient-specific computer-generated models allow for good visualisation of density changes in bone. We describe techniques for generating smooth and realistic finite element (FE) models that contain both BD and geometry from quantitative CT data using cubic Hermite elements.

FE models were created for three patients who had a total hip replacement. CT-scans were performed at 10 days, one year, and 3 years after the operation and calibrated using a synthetic hydroxyapatite phantom. FE models of the proximal femur were automatically generated from the CT data. Each model had on average 300 tri-cubic Hermite elements. Models were least squares fitted to the entire dataset. BD data was also sampled and fitted using the same cubic interpolation functions. Density was displayed using a colour spectrum.

Realistic patient-specific FE models were obtained. Density and changes in BD were easy to identify. The error in the geometric fitting (RMS distance between data points and the model surface) was generally less then 0.5 mm. The average error for the density fitting (RMS difference between each density data point and the interpolation function value at the same point) was 61.64 mg/ml or 3.08%.

CT osteodensitometry’s potential use as a clinical tool for monitoring changes to BD can be significantly enhanced when used in conjunction with realistic patient-specific finite element (FE) models. Realistic models can be generated with an economic use of scan data, thus keeping radiation dosage down.

Introduction: Previous in vivo kinematic studies have assessed total knee arthroplasty (TKA) motion under weight-bearing conditions. This in vivo study analyzed and compared posterior cruciate retaining (PCR) and posterior stabilized (PS) kinematics under passive and weight-bearing conditions in subjects implanted with both a PCR and PS TKA.

Methods: Eighteen subjects were implanted with a PCR and a PS TKA, by a single surgeon using a similar surgical technique. Both implant designs had similar condylar geometry. Femorotibial contact positions for all 18 subjects (PCR and PS), implanted by a single surgeon, were analyzed using video fluoroscopy. Each subject,while under fluoroscopic surveillance, performed a weight-bearing deep knee bend and a passive, nonweight-bearing flexion. Video images were downloaded to a workstation computer and analyzed at varying degrees of knee flexion. Femorotibial contact paths for the medial and lateral condyles, axial rotation and femoral condylar lift-off were then determined using a computer automated model-fitting technique. Femorotibial contact anterior to the tibial midline in the sagittal plane was denoted as positive and contact posterior was denoted as negative.

Results: Under passive and weight-bearing conditions, the PCR TKA experienced more paradoxical anterior translation than the PS TKA. Under passive, non weight-bearing conditions, the PS TKA, on average, experienced 3.5 mm of posterior femoral rollback, compared to only 0.6 mm for the PCR TKA. Under weight-bearing conditions, the PS TKA experienced only 0.6 mm of posterior femoral rollback, compared to 0.9 mm for the PCR TKA. The maximum anterior slide was 10.0 mm for the PCR TKA and only 2.7 mm for the PS TKA. There was greater variability in both the PCR and PS anteroposterior data. Subjects having a PCR TKA experienced more normal axial rotation patterns. Sixteen of 18 PCR TKA experienced a normal axial rotation pattern under weight-bearing conditions, while only 9/18 PS TKA experienced a normal pattern. Nonweight-bearing, passive axial rotation patterns were more abnormal for both groups than the weight-bearing patterns. The greatest difference between passive and weight-bearing conditions occurred in the condylar lift-off data. Under passive conditions, both TKA groups experienced significantly greater magnitude and incidence of condylar lift-off. The maximum amount of condylar lift-off under passive conditions was 5.0 mm for the PCR TKA and 6.4 mm for the PS TKA.

Discussion: This is the first in vivo kinematic study to assess a comparison between PCR and PS TKA implanted by the same surgeon in the same patient. Subjects in this study experienced more abnormal kinematic patterns, especially condylar lift-off, when tested under passive, nonweight-bearing conditions. Subjects having a PS TKA experienced less variability in their kinematic data, but PCR TKA, on average, experienced more normal axial rotation and less condylar lift-off.

Introduction Comminuted intra-articular fractures of the distal radius are severe injuries where the outcome depends on accurate anatomical reduction and reconstitution of the articular surface, and early mobilisation. This prospective outcome study aims to assess the anatomical and functional outcome of internal fixation of these complex fractures using a fragment specific fixation system.

Methods Fifty consecutive comminuted intra-articular distal radius fractures presenting at our hospital were treated by the one surgeon (MP). Inclusion criteria were age under 80 and AO classification C-3. Various combinations of wires, buttress pins/clips and plates were utilized according to each fracture configuration. No post-op splintage was used. All patients commenced hand therapy from day one post-op. Patients were reviewed at two weekly intervals till fracture union and monthly thereafter. All patients were independently assessed by a hand therapist for range of motion and grip strength. Patient function was assessed using the DASH (Disabilities of the Arm, Shoulder and Hand) and the PRWE scores. Thirteen males and 37 female with an average age of 53.8 (29 to 72) were treated with the TriMed between February 2002 and February 2003. Average follow-up was seven months (3 to 14).

Results All fractures had healed at the six week review, with mean palmar tilt of 12°, radial tilt of 19° and radioulnar variance of 5 mm, with articular step less than 1 mm. The mean DASH score was 19 (SD 9) and mean PRWE score was 19 (SD 11). Average range-of-motion was 65 (SD 17) dorsi-flexion, 55 (SD 19) palmar-flexion, 73 pronation and 67 supination. Grip strength recovered to 85% on average when compared to the opposite hand. There were no deep or superficial wound infections. Three patients had difficulty regaining early hand function, with difficulty complying with physiotherapy. One had borderline mental retardation. Two displayed symptoms of RDS, one responding to medication, and one requiring guanethidine arm block.

Conclusions Intra-articular distal radius fractures can be reliably and anatomically reduced and stabilized using fragment-specific fixation. Fixation of markedly comminuted fractures is secure enough to allow immediate motion. Clinical and radiographic results are excellent, and patient satisfaction is high. Patient compliance with hand therapy is critical for a good functional result.

Introduction: Previous in vivo kinematic analyses of the hip joint have determined that femoral head separation from the medial aspect of the acetabular component occurs in metal-on-polyethylene THA. The present study analyzes subjects having either an alumina-on-alumina (AOA),alumina-on-polyethylene (AOP),metal-on-metal (MOM) or metal-on-polyethylene (MOP) THA during gait to determine if the incidence of hip joint separation varies based on articular surface material.

Methods: Forty subjects were analyzed in vivo using video fluoroscopy. Ten subjects had a AOA THA, ten an AOP THA, ten a MOM THA, and ten having a MOP THA. All THA subjects were implanted by two surgeons and were judged clinically successful (Harris hip scores > 90.0). Each subject performed normal gait on a treadmill and an abduction/adduction leg lift maneuver while under fluoroscopic surveillance. The two-dimensional (2D) fluoroscopic videos were converted into 3D using a computer automated model-fitting technique. Each implant was analyzed at varying flexion angles to assess the incidence of hip joint separation.

Results: During gait and the abduction/adduction leg lift, no separation was observed in subjects having an AOA THA or in subjects having a MOM THA. Similar to our previous studies pertaining to subjects having a THA with a polyethylene acetabular insert, all ten subjects having a MOP THA and 6/10 subjects having an AOP THA experienced hip joint separation. The maximum amount of separation was 7.4 mm for a subject having an AOP THA and 3.1 mm for a subject having a MOP THA.

Discussion: This study shows femoral head separation from the medial aspect of the acetabular component can occur in the presence of a polyethylene liner. The femoral head often remains in contact with the liner, hinging superolaterally. Potential detrimental effects resulting from hip joint separation include premature polyethylene wear, component loosening (secondary to impulse loading conditions) and hip instability. Wear may be enhanced due to creation of multidirectional wear vectors or excessive loads due to eccentric femoral head pivoting. The absence of separation observed in AOA and MOM THA designs may be related to increased wettability of these materials and tighter radial tolerances resulting in a cohesive lubrication film. This data may be of value in hip simulation studies to better duplicate wear patterns observed in retrieval analyses and assist in the understanding of the lubrication regime and wear rates in AOA and MOM designs, allowing for the synthesis of prosthetic components that minimize wear and optimize kinematics.

Introduction: Patient specific cementless femoral components for THR were developed as a means of addressing the anatomic variations of the proximal femur and hip joint in an effort to achieve long term implant survival and optimum patient function. Design rules were developed with goals of achieving rigid initial stability, maximal endosteal contact for bone integration, and the precise restoration of hip kinematics.

Methods: Beginning in 1989, this series of cementless titanium implants included proximal circumferential HA coating over a macrotextured surface for biologic fixation. All patients who were candidates for cementless arthroplasty (age < 65, active, or overweight) received a custom femoral component. Forty-nine consecutive primary THR in 39 patients were performed during the study period. No patients died and one patient was lost prior to 10 years; all had well fixed stems at latest follow up. The remaining 38 patients (48 hips), 16 females and 22 males, with average age 54 (28-70) and weight 181 (98-270) at surgery, were evaluated at minimum 10 years (range 10-11).

Results: Average modified Harris Hip Scores were 49 (27-87) pre- and 89 (24-100) postoperatively, with pain scores of 17 (0-40) and 42 (10-44) respectively. All femoral components remain well-fixed (Engh Class 1) at final follow-up. No areas of osteolysis were seen distal to the proximal HA-bone interface. Small, focal areas of probable osteolysis were seen at the implant shoulder (4 cases), at the calcar corner (2 cases), and at both sites (1 case). Complications included four proximal margin femoral fissures recognised at surgery, two patients with dislocation, and one non-fatal PE. Reoperations included six head and liner exchanges; two for recurrent dislocation, and four for excessive wear with associated osteolysis (3 pelvic, 1 femoral); and one for fixation and grafting of a trochanteric nonunion.

Discussion: The use of cementless femoral implants based on individual patient characteristics and a set of strict design rules has resulted in excellent clinical and radiographic results at 10-year follow-up. Recent data with some OTS systems have shown comparable excellent results and have diminished the need for the routine use of custom implants in uncomplicated primary situations. However, this series validates the design concepts of this system, supports its use in more complex situations, and suggests applicability on a routine basis where other available implants may be less than optimal.

Introduction: Conventional approaches to cementless revision THR include cemented and cementless stems, which are graft dependent for initial stability (Type 3 reconstructions), distally fixed extensively porous coated implants and modular implants. CT and radiographic visualization, preoperative planning, and patient specific implant fabrication enable the surgeon to achieve the following objectives simultaneously and without compromise: bypass or fill specific bony defects, implement precisely the surgeon’s individual implant design goals, optimise proximal, distal, or regional fit objectives, achieve supplemental fixation via collars, fluted stems, and targeted ingrowth zones/ treatments, and establish head center, neck length, lateral offset, anteversion angle, and leg length.

Methods: This series of cementless titanium implants achieved initial press-fit fixation on host bone with bony attachment via proximally HA coated macrotextured surface. The extramedullary portion of the implant is designed to restore leg length and normal joint mechanics. The initial 44 consecutive revision hips using this rationale were reviewed for inclusion. At surgery, all femoral reconstructions were completed without resorting to Type 3 structural grafts. Six patients died prior to 10 years f/u, and three (4 hips) were lost. Two stems were removed prior to minimum follow up: one at five weeks post-op for deep sepsis, and one for aseptic loosening presumed secondary to metabolic derangements from poorly controlled end-stage renal disease. The remaining 31 patients (34 hips), 18 females and 13 males with a mean age of 61 (range 31-75) and average weight of 168 (85-240) pounds, were evaluated at minimum 10 years (range 10 to 11 years).

Results: All 34 components remain well-fixed (Engh Class 1) at last follow up (97% implant survival). Stress shielding was uncommon outside the calcar region. Average modified Harris Hip Scores were 49 (10-88) pre-operative and 81 (48-100) at final follow-up, with pain scores of 18 (0-44) and 41 (30-44) respectively. Complications included fracture (intraop: 4 fissures, 2 stable type II, 1 unstable type III, and 1 late periprosthetic fractures distally), and three dislocations.

Discussion: The concept of a metaphysical loading, proximally ingrown, collared patient specific revision implant gave results comparable to Engh’s series of extensively coated revision stems, while avoiding the high failure rate associated with structural allograft, the worrisome proximal bone loss associated with fully porous coated stems, the high cost of modular implants.

Introduction: Previously, in vivo kinematic studies have determined the in vivo kinematics of the femur relative to the metal base-plate. These kinematic studies have reported posterior femoral rollback in posterior stabilized (PS) TKA designs, but the actual time of cam/post engagement was not determined. The objective of this present study was to determine, under in vivo conditions, the time of cam/post engagement and the kinematics of the femur relative to the polyethylene insert.

Methods: Femorotibial contact positions for twenty subjects having a PS TKA, implanted by two single surgeons, were analyzed using video fluoroscopy. Ten subjects were implanted with a PS TKA that is designed for early cam/post engagement (PSE) and ten subjects with a PS TKA designed for later cam/post engagement (PSL). Each subject, while under fluoroscopic surveillance, performed a weight-bearing deep knee bend to maximum flexion. Video images were downloaded to a workstation computer and analyzed at ten-degree increments of knee flexion. Femorotibial contact paths for the medial and lateral condyles, axial rotation and condylar lift-off were then determined using a computer automated model-fitting technique.

Results: Subjects implanted with the PSE TKA experienced, on average, the cam engaging the post at 48° (10 to 80°). Subjects having the PSL TKA experienced more consistent results and did experience engagement in deep flexion (Average 75°). Subjects having the PSE TKA experienced, on average, −5.5 mm (1.5 to −9.3) of posterior femoral rollback (PFR), while subjects having the PSL TKA experienced only −2.6 mm (8.5 to −9.0) of PFR. Subjects having the PSE TKA experienced more normal axial rotation patterns. Nine subjects having the PSE TKA experienced condylar lift-off (maximum = 1.9 mm), while only 4/10 having the PSL TKA experienced condylar lift-off (maximum = 2.7 mm).

Discussion: This is the first study to determine the in vivo contact position of the cam/post mechanism. Subjects having a PSE TKA experienced earlier cam/post engagement than subjects having the PSL TKA. Some subjects did not experience any cam/post engagement throughout knee flexion. Subjects having the PSE TKA experienced more PFR and better axial rotation patterns, but subjects having a PSL TKA experienced lesser incidence of condylar lift-off. Results from this study suggest that there may be an advantage to early cam/post engagement, which leads to more normal axial rotation patterns caused by the medial condyle moving in the anterior direction as the lateral condyle rolls in the posterior direction.

Introduction: Understanding the in vivo motions of human joints has become increasingly important. Researchers have used in vitro (cadavers), non-invasive (gait labs), and in vivo (RSA, fluoroscopy) approaches to assess human knee motion. The objective of this study was to use fluoroscopy and computer tomography (CT) to accurately determine the 3D, in vivo, weight-bearing kinematics of normal knees.

Methods: Five normal knees clinically assessed as having no pain or ligamentous laxity were analyzed. Using CT scanning, slices were obtained six inches proximal to the joint line on the femur and six inches of the proximal tibia. Three-dimensional CAD models of each subject’s femur, tibia and patella were recreated from the 3D bone density data. Each subject was then asked to perform five weight-bearing activities while under fluoroscopic surveillance: (1) deep knee bend, (2) normal gait, (3) chair rise, (4) chair sit, and (5) stair descent. The computer-generated 3D models of each subject’s femur and tibiaon (> 1

Aim: To report the early results of the Elite Hylamer hip with Zirconium femoral heads in patients younger than 60 years. Methods: 29 hips were implanted in 26 patients by a single surgeon with a specialist interest in hip arthroplasty. Third generation cementing techniques were used for all implants. All patients have been followed up. There has been one death. Results have been analysed using the life table method using the Peto method for 95% confidence intervals. Results: Mean age 49.2 years (range 31–57). 12 Females and 17 Males.15 of 29 hips (53.3%) have been revised or are currently on the waiting list for revision surgery. These failures have occurred in 7 Females and 8 Males. Mean time to failure 35.4 months (range 18 to 68 months). All failures have been as a result of aseptic loosening. Survivorship analysis reveals a 32.42% survival at 5 to 6 years (6.9% standard error). Conclusions: At the time of its introduction, Hylamer was thought to represent a significant step forward in the reduction of the problem of osteolysis. This however has not been our experience. In the light of the catastrophic failure rate in this series of patients, all postoperative X-rays were critically reviewed. We were unable to observe any dramatic technical errors by way of implant malpositioning and cement mantle deficiencies to account for the observed failures. We have also seen that statistically there is no difference in the hip scores for the patients whose hips have failed and those who have not yet met the criteria for failure. In view of this it is imperative that patients with this implant should be reviewed both clinically and radiologically. We feel that these results should be published earlier rather than later to ensure that others remain vigilant in the follow up of their patients

Aims: The aim of this study was to þnd out if undisplaced displaced distal radial fractures require plaster immobilisation. Methods: In this prospective study, undisplaced distal radial fractures were divided into two groups; plaster immobilisation was used for one group while removable volar splint was used for the other group. Follow up was at six weeks, three months and six months. Patients were assessed by clinical examination, grip strength, radiological assessment, EQ-5D and a Short Form 12 questionnaire. Results: At 3 months, no difference was found between the two groups in clinical evaluation, radiological assessment, the functional outcome, grip strength, and visual analogue score for pain. Conclusions: We conclude that undisplaced distal radius fractures can probably be treated with out a plaster cast and put straight into wrist orthosis.

Pelvic osteolysis secondary to polyethylene wear is a major complication following THR. Identification of implant specific characteristics associated with osteolysis is essential. The purpose of this study is to compare incidence of CT scan identifiable osteolysis in 2 groups of young, active patients following THR; one with multi-holed acetabular shells with screws, one with cups without screw holes.

Between 1990–1993, 77 patients (85 hips) underwent THR with a cementless titanium, multi-holed shell with screws, modular, compression molded polyethylene and an uncemented titanium femoral stem. Average follow-up: 9 years, average age at surgery: 51 years. Between 1984–1987, 163 patients (183 hips) underwent THR with a cementless cobalt-chrome, solid shell, modular, heat-pressed polyeth-ylene liner and uncemented cobalt-chrome femoral stem. Average follow-up: 16 years, average age at operation: 52 years. All polyethylene was irradiated in air. At most recent follow-up, CT scans with metal suppression software was obtained to evaluate incidence of pelvic osteolysis. Patients classified: Group 1-no osteolysis, Group 2-cavitary osteolysis, Group 3-segmental osteolysis.

Patients with titanium, multi-holed shells had: Group 1-50.0%, Group 2-38.7%, and Group 3-11.3%. Patients with cobalt-chrome, solid shells had: Group 1-59.3%, Group 2-33.3% and Group 3-7.4%.

Although the patients with solid cups had much longer follow-up, less secure capture mechanism, less congruency between polyethylene and shell, and heat-pressed polyethylene, the incidence and extent of pelvic osteolysis was less than in the patients with multi-holed shell with screws. The presence of 6.5 mm cancellous screws is a serious independent risk factor for pelvic osteolysis following THR.

The objective of this present study was to determine the in vivo kinematic patterns for subjects implanted with a patellofemoral arthroplasty (PFA).

Twenty subjects, all having a PFA, were studied (< 2 years post-op) under fluoroscopic surveillance to determine patellofemoral contact positions, sagittal plane, and medial/lateral translation using a skyline view.

The patellofemoral contact patterns for each subject having a PFA was highly variable, 11.9 mm of translation. The average amount of patella rotation during the full flexion cycle was 26.3 degrees, while one subject experienced 48.6 degrees. The average amount of medial/lateral translation was 3.8 mm (5 > 5 mm). Five subjects experienced grater than 5 mm of motion.

This was the first study to ever determine the in vivo kinematics for subjects having a PFA and the in vivo medial/lateral translation patterns of the patellofemoral joint. Subjects in this study experienced high variability and some abnormal rotational patterns. Most of the subjects who underwent PFA in this study had a previous history of subluxed or dislocated patella which affects the normal patella tracking, especially regarding tilting and translation. This tracking may also be directly affected by patellofemoral conformity, a consequence of femoral implant design. Finally, after PFA the patello-tibial tilt angle is influenced by the anteroposterior positioning of the femoral component.

The results of this very first in vivo kinematic study may play an important role, not only for design consideration of patellofemoral replacement but also for surgical technique in order to obtain optimal implant positioning.

The objective of the present study was to analyse kinematics of subjects having a UKA during stance phase of gait, where the ACL was intact at the time of the operative procedure.

Femorotibial contact positions for nineteen subjects (15 medial UKA (MUA); 14 lateral UKA (LUA); HSS > 90, post-op > 3 yrs) were analysed using video fluoroscopy.

During stance-phase of gait, on average, subjects having a medial UKA experienced 0.8 mm of anterior motion (7.7 to – 2.3 mm), while subjects having a lateral UKA experienced −0.4 mm (0.9 to – 2.1 mm) of posterior femoral rollback (PFR). Eight of 15 subjects having a medial UKA and two out of four lateral UKA experienced PFR. Eight of 15 subjects having a medial UKA experienced normal axial rotation (average = 0.9 degrees) and one out of four subjects having a lateral UKA experienced normal axial rotation (average = −6.0 degrees).

High variability in the kinematic data for subjects experiencing an anterior slide and opposite axial rotation suggests that these subjects had an ACL that was not functioning properly and was unable to provide an anterior constraint force with the necessary magnitude to thrust the femur in the anterior direction at full extension. Progressive laxity of the ACL may occur over time, and at least in part, lead to premature polyethylene wear occasionally seen in UKA. Our results support the findings of other studies that the ACL plays a significant role in maintaining satisfactory knee kinematics, which may also, in part, contribute to UKA longevity.

The objective of this present study is to conduct a comparative analysis of the kinematic data derived for all subjects having a TKA who were analysed over the past eight years at our laboratory.

Femorotibial contact positions for 705 subjects having either a fixed bearing PCR or PS TKA or mobile bearing TKA were analysed in three-dimensions using video fluoroscopy.

During a deep knee bend, all PS TKA types subjects experienced a medial pivot motion, averaging −3.8 of lateral condyle posterior femoral rollback (PFR), respectively. Subjects having a fixed bearing PCR TKA experienced only −0.7 mm of lateral condyle PFR and an anterior slide of 1.6 mm for the medial condyle. Twenty-nine percent of the PCR TKA analysed had a lateral pivot and 71% experienced a medial pivot. Subjects having a mobile bearing TKA experienced −2.8 mm of lateral condyle PFR and 0.4 mm of medial condyle anterior slide. Fifty-one percent of the moble bearing implants experienced a medial pivot and 43% experienced a lateral pivot. During gait, PS and PCR fixed bearing TKA types experienced similar kinematic patterns. Subjects having a mobile bearing TKA experienced minimal motion, probably due to the mobile bearing TKA having greater sagittal conformity and had the lowest standard deviation.

There was great variability in the data comparing various TKA designs. Subjects in this multicentre analysis predominantly experienced a medial pivot motion, although certain TKA designs did demonstrate a lateral pivot motion.

A procedure is presented which allows the efficient production of a patient specific computer model of the femur, for surgical planning. Similar models require long processing times and/or high performance computing.

The method uses 24 key landmark points to customise a generic femur to patient data, using a desktop computer. By using non-linear elements a smooth, curved surface is obtained. A finite element mesh of a generic femur consisting of 384 elements was created using the analysis software CMISS (Bioengineering Institute, University of Auckland). A rectangular shaped host mesh was defined to enclose the generic femur. Datasets of 5 human femurs were obtained using a hand-held laser scanner on dry bones and the visible human dataset. Key landmark data points were selected on the generic femur along with corresponding target points on each data set. The host mesh was then deformed using a least squares algorithm, causing customisation of the generic femur to the patient specific model. Each customised model was compared with its entire dataset. The fitting process took less than 100 seconds on a 180 MHz 02 computer (SGI, CA, USA). The algorithm yielded an average root mean square (RMS) of 3.09mm with a standard deviation of 0.15mm. Operator time for positioning the projection points was less than 5 minutes.

This paper presents a novel means for customisation of human femoral geometry with generation of patient specific models on a PC from scan data in under 10 minutes. Current work is focusing on stress analysis, surgical simulation and planning.

A 5 year review into the workload and subsequent financial implications of pelvic and acetabular reconstruction at a regional tertiary referral centre.

To ascertain the level and means of financial recompense for performing pelvic/acetabular reconstruction on patients from other healthcare trusts at a tertiary referral centre.

The records of all 120 patients who underwent either pelvic or acetabular reconstruction between 1995–2000 were examined. Epidemiological data and information on all possible costs of their stay was accumulated (itemised finance department figures were used).

The individual patient billing system of ECRs (Extra Contractual Referrals) was changed in 1998 and replaced by the OATs system (Out of Area Treatments) whereby an annual lump sum was received based on historic referral patterns. We investigated the financial effects that occurred.

60 out of 120 patients treated, were from other health-care trusts. From 1995–1998, 25 ECR patients were treated at an estimated cost of £480, 000. The trust received £280, 000, a net loss of £200, 000. From 1998–2000, 34 OATS patients were treated at an estimated cost of £650, 000, amounting to a net gain of £1. 15 million pounds.

‘Out of area’ referrals for pelvic and acetabular reconstruction have increased by 50 % in the last 2 years. However the new payment system i. e. OATS has resulted in the tertiary referral centre being generously rewarded, unlike prior to 1998 and the old ECR system. It is therefore recommended that annual review must be carried out to ensure that funding will meet the demand for specialist services in the future and prevent subsidisation of some centres by other trusts.

Aim: To measure contact pressures in vivo in patients with unicompartmental arthritis fitted with osteoarthrosis (OA) braces to see if the arthritic side of the joint is unloaded.

Method: A thin flexible sensor (TekScan) was manoeuvered arthroscopically into the medial compartment of the knee joint under local anaesthesia in patients with unicompartmental OA of the knee undergoing either therapeutic or diagnostic arthroscopy. All 15 patients had been fitted with a brace before the arthroscopy. Measurements were made within the compartment of double leg stance and single leg stance. Ground reaction force using a load cell was measured for 14 patients and the knee sensor data were normalised relative to this. Recordings were then repeated with the patients with different commercially available braces.

Results: The first two groups of patients showed significant reductions in pressures. Normalised knee sensor forces were reduced to 68%(Sd 22%) and 61%(Sd31%). In the last group of patients, reductions in pressure recordings were less between no-brace and brace. Three patients produced low signals suggesting incorrect sensor replacement.

Conclusions:

Significant unloading of the osteoarthritic compartment could be observed by applying manually a valgus force to the knee.

Aim: To evaluate the technique of percutaneously harvested bone graft mixed with morphogenic bone protein and endoscopically delivered to ununited long bone fractures.

Methods: Thirty-eight patients with established delayed union of long bone fractures were bone-grafted endoscopically. Morphogenic bone protein (OP1) was used in 12 cases and the graft was supplemented with calcium sulphate pellets (Osteoset). The minimum follow-up was eight months. The study group included eight femoral shaft fractures, two humeral shaft fractures and the remainder were tibial shaft fractures.

Results: Four fractures failed to unite with this technique. Two femoral shaft non-unions required repeat surgery, one humeral shaft non-union and one tibial shaft non-union required supplementary grafting and fixation. The technique requires radiological imaging to supplement endoscopic preparation and graft delivery. For tibial fractures this can be used as a day-stay technique but most patients required one night in hospital.

Conclusions: Endoscopic bone grafting can be supplemented with graft substitute (Osteoset) and morphogenic protein (OP1). It is as effective as standard open ‘onlay’ grafting but good fixation of the fracture is necessary before graft and supplements are effective.

The work of Sloof, Ling and Gie has established allografting as a modern technique in revision total hip arthroplasty. The use of allograft enhances the local bone stock and provides a secure fixation for cemented components. Its association with the problem of heterotopic ossification has not been previously considered.

The records and x-rays of 114 patients after revision hip surgery were reviewed. All had been operated upon by three Consultant Orthopaedic Surgeons using standard techniques.

35 patients had undergone revision with impaction allografting of both the femur and acetabulum, 29 had allografting of the femur only, 18 of the acetabulum alone and the final 32 patients (acting as controls) had cemented revision arthroplasty without impaction allografting. Fresh frozen allograft was used in all cases and prepared using a bone mill.

No patient was given radiation or Indomethacin after their revision surgery, even if they had pre-existing heterotopic ossification.

The immediate pre-operative x-rays and x-rays at least a year post-revision were assessed independently by a musculoskeletal radiologist. He was blinded to the type of revision procedure and graded the heterotopic ossification according to the Brooker Classification.

Our results report the incidence of heterotopic ossification after revision hip arthroplasty with fresh frozen allograft when compared with cemented revision arthroplasty from our unit and other studies.

Shoulder movements from neutral into flexion, extension, abduction, adduction and external rotation are easily measured with a goniometer. In the neutral position, the glenohumeral ligaments, which act as the reins of the joint, limit movement and are symmetrically relaxed. The torso obstructs internal rotation with the arm adducted at the side and the full range of movement cannot be attained.

The torso is cleared when the shoulder is abducted, usually to 90°. However, this degree of abduction places the shoulder within the painful arc of impingement and may influence the degree of internal rotation. Further, owing to shoulder joint stiffness, some patients may not be able to abduct the shoulder to 90°. Because of these problems, it has become internationally accepted to measure internal rotation in the near-neutral position by determining the vertebral level behind the back to which the thumb can reach.

We assessed 200 symptomatic and asymptomatic shoulders to determine the correlation between the ‘hand behind back’ and angular measurements of internal rotation at 90° or 30° of abduction.