The surgical treatment of a secondary gonarthrosis caused by haemophilic arthropathy needs high quality in soft tissue balancing and accurate alignment in total knee arthroplasty (TKA), which are essential for good long-term results. Due to the early-onset severe arthropathy, haemophiliacs undergo prosthetic surgery at a younger age than general population; therefore to ensure a longer duration of implantation is a major objective to be reached in this setting. As several prospective randomised studies could show, Computer navigation in prosthetic surgery improve precision concerning geometry of axes, resection planes and implant alignment, by the determination of joint centres (actual axis), amount of bone resection, size of prostheses and check of ligament balance. At our department, since January 2006, we implanted four TKA in four patients (age range 45–52 years) affected by severe Haemophilia B; the same surgeon used a single system (Orthopilot system) in all cases.

The quality of implantation was studied on postoperative standardized long leg coronal and lateral x-rays. Our results showed that CAS had greater consistency and accuracy in implant placement. Complications influencing the clinical outcome did not occur. In our experience, drawbacks of the navigation systems are the additional costs and the additional operation time between 15 and 25 min. However, one of the most important advantages of using of this technique in patient affected by coagulation disease, according to the international literature, is the reduction of blood loss after operation. A long-term follow-up of these and of larger samples of patients is needed for testing cost/risk-benefit ratio of Orthopilot in prosthetic surgery of haemophiliacs. Therefore navigated total knee arthroplasty in haemophilic arthropathy is not yet a standard procedure, but this technique could become an important surgical choice in management of severe secondary osteoarthritis in the future.

The aim of this study was to identify what aspects of implant alignment and rotation affect functional outcome after total knee arthroplasty (TKA). 159 TKAs were performed at the Royal Perth Hospital between May 2003 and July 2004. All patients underwent an objective and independent clinical and radiological assessment before and after surgery. A CT scan was performed at six months. The alignment parameters that were measured included: sagital femoral, coronal femoral, rotational femoral, sagital tibial, coronal tibial and femoro-tibial mismatch. The cumulative error score, which represents the sum of the individual errors, was calculated. Functional outcome was measured using the Knee Society Score (KSS).

Good coronal femoral alignment was associated with better function at 1 year (p=0.013). Trends were identified for better function with good sagital and rotational femoral alignment and good sagital and coronal tibial alignment. Patients with a low cumulative error score had a better functional outcome (p=0.015). These patients rehabilitated more quickly and their length of stay in hospital was 2 days shorter.

Vertebral compression fractures can affect both sexes and constitute a major health care problem, due to negative impact on the patient’s function, quality of life and the costs to the health care system. Patients can be treated conservatively or by conventional fluoroscopic assisted vertebroplasty – injection of polymethylmethacrylate PMMA into the fractured vertebral body. Conventional vertebroplasty imposes technical challenges with possible complications including cement extravasations, nerve root compression, the possibility of breaching the walls of the pedicle by the osteoplasty needle and prolonged fluoroscopic radiation exposure of the surgeon and the medical team at large.

We present here a comparative study of 20 cases of thoraco-lumbar vertebral compression fracture, treated with robotic assisted vertebroplasty (research group) versus 30 cases of fractures treated by conventional fluoroscopic vertebroplasty (compared group). All patients were diagnosed as suffering from acute vertebral compression fractures (up to 3 weeks from the traumatic event) and were scored 7 and above in the VAS. The mean overall operation time of the fluoroscopic assisted vertebroplasty was 35 minutes compared to a mean operation time of 45 minutes at the robotic assisted vertebroplasty. There was a significant difference in the fluoroscopic time and subsequent exposure time to radiation between the groups: in the research group we used only an average of 3 seconds of fluoroscopic exposure (an average of 5 fluoroscopic images) compared to an average of 7 seconds of exposure (an average of 12 fluoroscopic images). No difference was found between the groups in regard with overall admission time or with the time between the operation and physiotherapy.

Conclusion: robotic assisted vertebroplasty is a new and safe approach aiming to shorten the duration of fluoroscopic exposure of the patient and surgeon thus reducing the exposure to radiogenic dose. This novel procedure, promotes better accuracy with regard to the cement injected thus reducing the potential complication of the operation.

Accuracy of implantation is an accepted prognostic factor for the long term survival of total knee replacement (TKR). The use of navigation demonstrated a significant higher accuracy of implant orientation in comparison to conventional methods. However, these systems are often thought to be technically demanding, to increase operating time and to involve a long learning curve. We performed a prospective, multicenter study to compare the accuracy of implantation of a TKR measured on post-operative X-rays in experienced and less experienced centers.

All centers used the same navigation system (Ortho-Pilot ®, Asculap, Tuttlingen, FRG): 4 had already a significant experience with it (group A – 182 cases), 9 centers were considered as beginners with less than 10 cases performed prior to the study (group B – 221 cases). Accuracy of implantation was measured on post-operative antero-posterior and lateral long leg X-rays with five items: mechanical femoro-tibial angle, coronal orientation of the femoral component, sagittal orientation of the femoral component, coronal orientation of the tibial component, sagittal orientation of the tibial component.

When the measured angle was in the expected range, one point was given. The accuracy note was defined as the sum of all points given for each patient, with a maximum of 5 points (all items fulfilled) and a minimum of 0 point (no item fulfilled). The mean accuracy note was compared in the two groups by a Student t-test at a 0.05 level of significance. Power of the study was 0.80.

There were no significant differences in pre-operative parameters between the two groups, except for the clinical KSS. The mean operative time was significantly longer in group B than in group A (110 minutes vs 90 minutes, p=0.01). However this difference occurred mainly during the first twenty cases in the beginner centres where we observed a clear tendency to achieve the same operative time as the experienced centres at the end of the study. The mean accuracy note was 4.3 ± 0.8 (range, 1 to 5) in the control group and 4.3 ± 0.9 (range, 1 to 5) in the study group (p > 0.05). The power of the study to detect a 0.25 point difference in the post-operative accuracy note was retrospectively calculated to be 0.80. There were no significant differences between the two groups for all individual radiographic items.

This study is, to our knowledge, the first one which investigates the learning curve of navigated TKR The used navigation system allowed a very accurate implantation of a TKR in both experienced and less experienced centers. There was no detectable learning curve with respect to accuracy of TKR implantation, clinical outcome and complication rate. The duration of the learning curve when considering the operating time was 30 cases.

Sixteen observers measured eight anatomic parameters on digitalised images of six acute distal radial fractures using the Patient Archiving Communication System (PACS) software and repeated the measurements two weeks later. Inter and intra observer variability for each parameter was calculated using intraclass correlation coefficients (ICC) and tolerance limits (TL). Highest inter-observer agreement was demonstrated in dorsal tilt (ICC 0.858; TL ± 14.2°) with poor agreement on the size of the gap and step. When compared with the results of a similar study published 10 years ago looking at observer variability in x-ray measurement of healed distal radial fractures, the reliability of computerized measurements is not significantly different to those achieved by manual techniques (dorsal tilt inter-observer TL on PACS ± 16° compared with TL ± 15° using ruler and protractor). These results suggest the current guidelines in the literature for acceptable radiological reduction limits based on < 10° change in palmar tilt, < 2mm radial shortening, < 5° change in radial angle and < 1–2mm articular step for acute distal radius fractures cannot be reliably measured

Unicompartmental knee replacement (UKR) is accepted as a valuable treatment for isolated medial knee osteoarthritis. Minimal invasive implantation might be associated with an earlier hospital discharge and a faster rehabilitation. However these techniques might decrease the accuracy of implantation, and it seems logical to combine minimal invasive techniques with navigation systems to address this issue.

The authors are using a non image based navigation system (ORTHOPILOT ^™, AESCULAP, FRG) on a routine basis for UKR. We prospectively studied 60 patients who underwent navigated minimally invasive UKR for primary medial osteoarthritis at our hospital between October 2005 and October 2006. We established a navigated control group of 60 patients who underwent conventional implantation of a UKA at our hospital between April 2004 and September 2005. There were 42 male and 78 female patients with a mean age of 65 years (range, 44–87 years). There were no differences in all preoperative parameters between the two groups.

The accuracy of implant positioning was determined using predischarge standard anteroposterior and lateral radiographs. The following angles were measured: femorotibial angle, coronal and sagittal orientation of the femoral component, coronal and sagittal orientation of the tibial component. When the measured angle was in the expected range, one point was given. The accuracy was defined as the sum of the points given for each angle, with a maximum of five points (all items fulfilled) and a minimum of 0 point (no item fulfilled). Our primary criterion was the radiographic accuracy index on the postoperative radiograph evaluation. All other items were studied as secondary criteria.

The mean accuracy index was similar in the two groups: 4.1 ± 0.8 in the study group and 4.2 ± 1.2 in the control group. 36 patients (60%) in the control group and 37 patients (62%) in the study group had the maximum accuracy index of five points. All measured angles were similar in the two groups. There were no differences between the percentages of patients in the two groups achieving the desired implant positions. Mean operating time was similar in the two groups. There were no intraoperative complications in either group. The groups had similar major postoperative complication rates during hospital stay (3% for both).

The used navigation system is based on an anatomic and kinematic analysis of the knee joint during the implantation. The modification of the existing software for minimal invasive approach has been successful. It enhances the quality of implantation of the prosthetic components and avoids the inconvenient of a smaller incision with potential less optimal visualization of the intra-articular reference points. However, all centers observed a significant learning curve of the procedure, with a significant additional operative time during the first implantations. The postoperative rehabilitation was actually easier and faster, despite the additional percutaneous fixation of the navigation device. This system has the potential to allow the combination of the high accuracy of a navigation system and the low invasiveness of a small skin incision and joint opening.

Authors have been using kinematic computer navigation for a total knee replacement surgery since 2003. A contribution and advantage of computer navigation is well recognized. Exact guidance of both tibial and femoral osteotomy along with precise soft tissue balance respecting individual anatomic constitution is achieved by exact collection and computer evaluation of data by a use of special sensors and probes. Use of kinematic navigation in experienced hands minimizes deviation from physiological mechanical Mikulicz axis. This is considered the most important step to achieve a good long term outcome after total knee arthroplasty.

We have been recently using Brain Lab kinematic navigation system in both primary and revision knee arthroplasties. 200 primary and 20 revision knee arthroplasties are included in the retrospective 3 year follow up study. A navigated revision surgery is recently performed only in cases where the axial deformity does not exceed 10 degrees and where no significant bone loss is presented (bone defects less that ½ cm). Standard cemented components are used in both primary and revision cases. A primary navigated knee arthroplasty had no exclusion criteria in the above study.

Technique: Medial patellar approach technique is used, navigation probes are placed in standard distal femoral and proximal tibial position. Data are collected using navigation probes and sensors. Loosen components and cement are removed next. Navigated proximal tibial osteotomy, distal femoral osteotomy and soft tissue balance are performed. Gentamycin cementing of standard components (tibia first) is performed at the end. A final verification of component balance and data storage terminates the procedure.

No need for conversion to a revision knee system using stem and wedges was noticed in the above series. Following the above inclusion criteria standard cemented implants were used only. We conclude that the use of navigation in cases of relatively uncomplicated knee revision arthroplasty guaranties good mid term outcome, good soft tissue balance, saves money on expensive knee revision systems and guaranties an alternative of second stage revision surgery with a use of extensive revision systems. Standard implant selection does not apply for those with deep bone defects and axial deformation higher than 10 degrees.

Revision TKR is a challenging procedure, especially because most of the standard bony and ligamentous landmarks are lost due to the primary implantation. However, as for primary TKR, restoration of the joint line, adequate limb axis correction and ligamentous stability are considered critical for the short- and long-term outcome of revision TKR. There is no available data about the range of tolerable leg alignment after revision TKR. However, it is logical to assume that the same range than after primary TKR might be accepted, that is ± 3° off the neutral alignment. One might also assume that the conventional instruments, which rely on visual or anatomical alignments or intra- or extramedullary rods, are associated with significant higher variation of the leg axis correction.

We used an image-free system (ORTHOPILOT TM, AESCULAP, FRG) for routine implantation of primary TKA. The standard software was used for revision TKA. Registration of anatomic and kinematic data was performed with the index implant left in place. The components were then removed. New bone cuts as necessary were performed under the control of the navigation system. The size of the implants and their thickness was chosen after simulation of the residual laxities, and ligament balance was adapted to the simulation results. The system did not allow navigation for centromedullary stem extension and any bone filling which may have been required. This technique was used for 54 patients. The accuracy of implantation was assessed by measuring the limb alignment and orientation of the implants on the post-operative radiographs.

Limb alignment was restored in 88%. The coronal orientation of the femoral component was acceptable in 92% of the cases. The coronal orientation of the tibial component was acceptable in 89% of the cases. The sagittal orientation of the tibial component was acceptable in 87% of the cases. Overall, 78% of the implants were oriented satisfactorily for the five criteria.

The navigation system enables reaching the implantation objectives for implant position and ligament balance in the large majority of cases, with a rate similar to that obtained for primary TKA. The navigation system is a useful aid for these often difficult operations, where the visual information is often misleading. The navigation system used enables facilitated revision TKA.

Anterior cruciate ligament (ACL) reconstruction allows overall good results, but there is still a significant rate of failure. It is well accepted that the main reason for ACL reconstruction failure is a misplacement of tibial or femoral tunnels. Conventional techniques rely mainly on surgical skill for intra-operative tunnel placement. It has been demonstrated that, even by experienced surgeons, there was a significant variation in the accuracy of tunnel placement with conventional techniques. Navigation systems might enhance the accuracy of ACL replacement.

10 cadaver knees with intact soft-tissue and without any intra-articular abnormalities were studied. We used a non image based navigation system (OrthoPilot ®, Aesculap, Tuttlingen, FRG). Localizers were fixed on bicortical screws on the distal femur and on the proximal tibia. Both kinematic and anatomic registration of the knee joint were performed by moving the knee joint in flexion-extension and palpating relevant intra- and extra-articular landmarks with a navigated stylus. The most anterior, posterior, medial and lateral point of both tibial and femoral attachment of the ACL were marked with metallic pins. The navigated stylus was positioned on these points, and the system recorded its position in comparison to the bone contours. Subsequently, we performed conventional plain AP and lateral X-rays and a CT-scan, and measured the position of the pins in comparison to the bone contours. Finally, all measurements were made again with a caliper after disarticulating the knee joint. We calculated the center of the footprint as the mid-point between the four pins of both tibial and femoral attachment for each measurement technique. All measurements were expressed as percentages of the bone size to compensate for the different sizes.

There were no significant difference in the paired measurements of the location of the ACL footprints on both femur and tibia between anatomic, radiographic, CT-scan and navigated measurements. There was a significant correlation between the paired measurements of the location of the ACL footprints on both femur and tibia with either measurement techniques.

Anatomic measurement is the gold standard experimental technique for the positioning of the ACL foot-print, and CT-scan measurement is currently the gold standard technique in clinical situation. According to this reference, the position of ACL attachments on the tibia and on the femur can be accurately defined by the navigation system. Intra-operative measurement of the location of the bone tunnels during ACL replacement with this navigation system should be accurate as well.

The use of two-dimensional plain X-rays for preoperative planning in total hip arthroplasty is unreliable. For example, in the presence of rotational hip contracture the lateral femoral off set can be significantly under-estimated. Pre-operative planning is of particular importance when using uncemented prostheses. The aim of this study was to determine the precision of a novel 3D CT-based preoperative planning methodology with the use of a cementless modular-neck femoral stem.

Pre-operative computerised 3D planning was performed using HIP-PLAN® software for 223 patients undergoing THA with a cement-less cup and cement-less modular-neck stem. Components were chosen that best restored leg length and lateral off set. Postoperative anatomy was assessed by CT-scan and compared to the pre-operative plan.

The implanted component was the same as the planned one in 86% of cases for the cup and 94% for the stem. There was no significant difference between the mean planned femoral anteversion (26.1° +/− 11.8) and the mean postoperative anteversion (26.9° +/− 14.1) (p=0.18), with good correlation between the two (coefficient 0.8). There was poor correlation, however, between the planned values and the actual post-operative values of acetabular cup anteversion (coefficient 0.17). The rotational centre of the hip was restored with a precision of 0.73mm +/3.5 horizontally and 1.2mm +/− 2 laterally. Limb length was restored with a precision of 0.3mm +/− 3.3 and femoral off set with a precision of 0.8mm +/− 3.1. There was no significant alteration in femoral off set (0.07mm, p=0.4) which was restored in 98% of cases. Almost all of the operative difficulties encountered were predicted pre-operatively.

The precision of the three-dimensional pre-operative planning methodology investigated in this study is higher than that reported in the literature using two-dimensional X-ray templating. Cup navigation may be a useful adjunct to increase the accuracy of cup positioning.

Computer navigation systems enable precise measurement and intra- operative knee range of movement analysis. We present a series of five knees that demonstrated unusual kinematics.

Five of 80 computer navigated knee replacements that were part of a prospective randomised trial were found to have unusual joint lines. Range of motion assessment was performed with computer assisted navigation after exposure and registration of bony landmarks and before bony resection was commenced. This revealed valgus alignment in extension that drifted into varus with knee flexion. We referred to these unusual patterns as ‘oblique joint lines’.

The data from the navigation log files of these five knees was analysed in detail. Average age of patients in this series was 68years and all were female. The average pre- operative angle between femoral axis and distal femoral articular surface was 101 degrees. All five knees had a tibial varus with average angle between the tibial axis and articular surface being 85 degrees. In two knees, more bone was resected from the medial posterior femoral condyle using 4 degrees external rotation. These two knees showed improved kinematics and horizontal joint line post- operatively.

Computer assisted navigation provides a precise understanding of the pre- operative knee kinematics. Bony cuts can be tailored to suit the pre- operative deformity. Increased external rotation of the femur with adequate medial soft tissue release is an alternate approach for difficult knees with ‘oblique joint lines’.

The ligament balancing technique involves precise measurement and equalisation of flexion and extension gaps. A force tension distractor that has separate arms for the medial and lateral joint compartments was used. We describe our experience of 40 total knee replacements (TKR) using this technique.

We undertook a prospective randomised trial using computer assisted navigation in TKRs applying two different soft tissue balancing techniques. The aim was to see how balancing techniques help us achieve a rectangular flexion extension gap. The 40 TKR that underwent the ligament balancing procedure were part of this trial. The distractor used was derived from the Freeman-Swanson knee instrumentation which measures the gap and tension in the medial and lateral compartments. The options to make the gap rectangular were: 1. adjustment of femoral cut by change in external rotation (for the flexion gap); 2. soft- tissue release or 3. a combination of both. Using computer assisted navigation it was possible to perform real time motion analysis during surgery.

We found that three degrees of external rotation for the femoral component was adhered to in only 16 out of 40 knees. The remaining 60% had external rotation of femoral component varying between two and eight degrees. No maltracking of the patella resulted in any of the TKR with increased rotation of the femoral component. The axis of movement was plotted on a graph at the end of the surgery by passive extension to flexion to which the operating surgeon was blinded.

Varying external rotation of femoral component might be an option in balancing difficult knees. Computer navigation enables precise tailoring of bony resection to suit different deformities.

The use of hard-on-hard hip prostheses has highlighted specific problems like the “stripe-wear” and the squeaking. Many authors have related these phenomena to a micro-separation between the cup and the head. The goal of the study was to model the hip kinematics under micro-separation regime in order to develop a computational simulator for total hip prosthesis including a joint laxity, and to use it to perform a sound analysis.

A three-dimensional model of the Leeds II hip simulator was developed on ADAMS® software. A spring was used to introduce a controlled micro-separation (less than 500 microns) during the swing phase of the walking cycle. The increase of the load during the stance phase induced a relocation of the head in the cup. Values of the medial-lateral separation predicted from the model were compared to experimental data measured using a LVDT of less than 5 microns precision. Theoretical wear path predicted from the model was compared to the literature data. The frequencies of the vibratory phenomena were determined, using the Fourier transformation.

There was an excellent correlation between the theoretical prediction and the experimental measurement of the medial-lateral separation during the walking cycle (0.92). Edge-loading contact occurred during 57% of the cycle according to the model and 47% according to the experimental data. Velocity and acceleration were increased during the relocation phase in a chaotic manner, leading to vibration. The contact force according to the model had also a chaotic variation during the micro-separation phase, suggesting a chattering movement. Fourier transformation showed many frequencies in the audible area.

A three-dimensional computational model of the kinematics of the hip after total replacement was developed and validated with an excellent precision under micro separation. It highlighted possible explanations for the squeaking that may occur during either relocation phase or edge loading.

There is a significant variation in registering anterior pelvic plane (APP) among experienced navigated hip surgeons reflecting negatively on the accuracy of determining the inclination and anteversion angles. Registering the APP in a lateral decubitus position is more challenging in obese patients as palpation of pubic tubercle or anterior superior iliac spines (ASIS) is inconsistent. We propose an alternative and easier novel method in which palpation of the posts (pegs) that stabilizes the pelvis will accurately determine the APP plane. The computer data obtained from peg’s palpation was compared to data obtained from post-operative CT scan of the pelvis in determining acetabular and cup version and inclination angles.

The APP was defined and registered in 40 navigated total hip arthroplasty (THA) patients using our novel method. The patient is securely stabilized in a lateral decubitus position as routine with multiple pegs. One peg is positioned against both ASIS with 2 EKG pads placed on the pegs (each represent an ASIS). The other peg supports the pubic symphysis with one EKG pad representing the pubic tubercle. All efforts are made to make sure that the distance between the EKG nipples and the corresponding ASIS or pubic tubercle is equal before scrubbing and draping of the hip. Registration is achieved afterwards, by touching the nipples of the EKG pads placed on the pegs through the drape while the patient is secured in lateral decubitus position. This way sterility is uncompromised. To test the validity of our method of identifying the APP plane, a post-operative CT scan measurements of cup inclination and version angles were independently observed and the data were compared to our navigation registration method using t-student test analysis.(p=0.05 is significant)

The mean CT-scan cup version was 19.4(S.D. ±6.3), and the mean of APP navigated cup version was 14.2(S. D.±3.1). There was no statistical significant difference (p=0.045). Similarly, there was no significant difference between mean CT scan cup inclination angle of 42.3(S. D.±3.7) and the mean navigated cup inclination of 40.9(S.D.± 4.6), (p= 0.69). Therefore, we conclude that the APP plane can be registered reliably and accurately by simply touching the EKG pads on the pegs and through the drapes. Not to mention, both the cup version and inclination angles were within safety zone of Lewinick.

It seems that the accuracy of measuring the inclination angle through our method, although not significant, is better than the accuracy of measuring the cup version. This emphasizes the point that identifying the pubic tubercle is difficult whichever method of registration is used. However, inaccessibility of ASIS or pubic tubercle during manual APP registration leads to great cup orientation inaccuracies. The readily palpable EKG nipples on the pegs, irrespective of patient’s weight or the thickness of surgical draping, makes this novel technique a reliable and an easier alternative registration method than the manual palpation of APP in navigated THA.

The purpose of mini-invasive hip arthroplasty is least damage to skin and muscles. Unlike Roettinger modification to Watson-Jones, our approach requires no special table or instruments. Besides, direction of skin incision is perpendicular to interval between glutei and tensor muscles, thus called a Crisscross Approach. Potentially, a cross shape exposure allows a larger view and therefore a lesser damage to skin and muscles during retraction. Skin incision, being in line with the femur (almost parallel), allows expansion of incision proximally and distally. No tendon or muscles are severed achieving a true inter-muscular minimally invasive approach.

After working with 3 cadavers to perfect the technique and with investigation and research board (IRB) approved consent, 40 prospective patients underwent mini-invasive crisscross technique from December 06–June 07 with 6 months follow up. A standard non-cemented hip was implanted. Previously disrupted hip muscles patients were excluded. Patients were positioned in a lateral decubitus with pelvis secured and flexed 20°–30°. Incision started 2 inches inferior and posterior to ipsilateral anterior superior iliac spine (ASIS) extending distally for 3 inches or more for obese or muscular patients. Acetabulum is exposed using curved Hohmann retractors one above and one below femoral neck after excising most of the anterior capsule with releasing the superior and inferior capsule. The femoral neck is osteotomised as routine extracting the femoral head. Then the same curved retractors are placed behind anterior and posterior rim of acetabulum with an optional third curved retractor may be placed at the inferior rim. The acetabulum is reamed with the usual straight reamers and the cup is then implanted as routine. Angled reamers are not necessary as our skin incision is in line with the reamer direction. Femoral neck exposure starts with the surgeon positioned anterior to pelvis. Paralysis of the muscles is confirmed with anesthesiologist and table is tilted 20°–30° posteriorly. Hip is then extended 20°–30°, externally rotated to 80°–90° and adducted with a retractor underneath femoral neck. Another curved retractor is placed gently on greater trochanter to protect glutei. Leg is allowed to drop in a bag. Canal finder and use of box osteotome is helpful to avoid breaching the femoral cortex or varus positioning of the stem. Broaching or reaming and final implant insertion is done as routine. Hip reduction is achieved as routine by reversing the table tilt and bringing the leg forward with traction and internal rotation.

36 out of 38 eligible patients were sent home after their rehab goals were met in 4 therapy sessions (2–3days). Full weight bearing was allowed in 4 weeks. One stem was undersized, two were in slight varus, and total blood loss was less than 5 gm/dl of Haemoglobin at post op day three. No dislocation or complications related to exposure. No neurovascular injury and no re-operation. Surgery time averaged 20 minutes longer mainly at femoral exposure. As experience is gained the time is lessened. Post-operative intravenous morphine pump administration was stopped in 24 hours in 82% of patients after surgery instead of the 48 hour routine.

Crisscross approach differs by transecting no tendon or muscles, requiring no special table or instruments with incision that gives more exposure, allows expansion and reduces skin damage resulting in true non-invasive approach. Exposure of the femur was difficult in the first few cases. Tilting the operating table posteriorly, releasing superior and inferior capsule as has been recommended by previous authors helped femoral exposure. Recovery from surgery in terms of rehab sessions and postoperative pain control were improved compared to our previous standard of care. Long term follow up is under current research investigation.

Most common complication of non-navigated classic total knee arthroplasty (TKA) relates to patella. Not resurfacing the patella makes exposure more difficult in a mini-approach which may add to its potential complications. Effect of navigated mini sub-vastus TKA on native patella is clinically and radiologically studied, observing also, whether severity of deformity or obesity adds to patellae complications in such approach.

92 of 100 subjects were eligible. Peri-operative radiological and navigation data with follow up visits to 24 months provided alignment, patella tilting or displacement data. Clinical outcome gauged by “KSS” documented pain from patella movements, or pain generated from stair climbing, or rising from a chair. Patella is considered subluxated if it displaced ≥ 5mm. No exclusion by obesity or severity of deformity. Results were evaluated with descriptive statistics.

Of the 92 patients, 3 had patella pain (3%). 72% had < 5° of patella tilting (of which 3 had patella pain) while 28% had a 5°–17° tilting. As for patellae displacement, 12% displaced laterally (≤3 mm) but with no pain. None had patellar displacement ≥ 4mm (which we define as subluxation), and none had a dislocation. Pre-operative knee deformity ranged from 19° varus to 13° of valgus. 70% of subjects had pre-operative varus/valgus deformity of < 10°. The other 30% had deformity of ≥ 10°. Post-operative mean mechanical axis alignment was 0° (± 1°) with a mean range of motion of −3.8° to 133.6°. No vascular injuries, skin necrosis, deep infection, or fractures.

The BMI ranged from 25–46 Kg/m². 16% had a BMI ≥ 40 with no patellar pain, tilting or displacement.

Incidence of native patella pain in a navigated mini sub-vastus TKA was low irrespective to body mass or pre-operative deformity. Perhaps navigation helped align the components ideally and thus reducing the complication rate of a mini-approach. However, 28% of native patella tilted > 5° but unlike tilting of a resurfaced patella, it did not correlate with patella pain. In this study, whether non-resurfacing caused the 3% of patella pain is undetermined. Nevertheless, the pain level was not severe to make the patients seek a revision of the patella. Finally, as we compare with other studies, we cannot conclude that mini sub-vastus approach is superior; however its low patella complication rate is comparable if not superior to classic approach.

Femoral component malrotation is a major cause of patello-femoral complications in total knee arthroplasty. In addition, it can affect varus/valgus stability during flexion which can lead to increased tibiofemoral wear.

Debate exists on where exactly to rotate the femoral component. The three principal methods utilise different anatomical landmarks: the posterior condylar axis, the transepicondylar axis and the antero-posterior axis (Whiteside’s line).

A prospective randomised controlled trial was undertaken. Sixty consecutive patients undergoing total knee arthroplasty by a single surgeon (LML) at the Royal Perth Hospital were randomised into 3 groups based on the intra-operative method for measuring femoral rotation using the PFC sigma prosthesis (Depuy) with computer navigation (Depuy/Brainlab). All patients received the usual post-operative treatment, rehabilitation and JRAC (Joint Replacement Assessment Clinic) follow up. All underwent a CT scan according to the Perth CT protocol designed specifically to accurately measure component alignment and rotation.

No significant difference in femoral rotation was found between the three groups using a one-way analysis of variance (p=0.67). However, Whiteside’s line had a significantly greater variability than the posterior condylar or transepicondylar axis using the F Test for variances (p=0.02, p=0.03). In conclusion, whilst there was no significant difference in femoral rotation, Whiteside’s line did show greater variability (−6° to 3°), and therefore we recommend the use of either the transepicondylar or posterior condylar axis in Total Knee Replacement.

The necessity of soft tissue release to achieve a stable, balanced knee in previous publications has a high rate and a wide range of 50–100% of total knee arthroplasties (TKA). This reflects disagreement regarding the determinants for soft tissue release which is partly due to lack of standardized quantitative measures. Recent advances in navigation may standardize and replace conventional methods regarding soft tissue balancing. We propose two navigation predictors that quantitatively determine the least amount of collateral ligament release necessary to achieve a stable neutral knee, thus reducing the frequency of release.

100 patients underwent navigated TKA. Data of 93 were eligible. Preoperative deformity ranged 18°varus −13° valgus. Ratio of Varus/Valgus= 66/27. Ages were 46–85 yrs. Mean BMI= 36Kg/m²

First navigation predictor determines collateral release when varus/valgus deformity is uncorrectable by stress deflection test before tibia resection. Second predictor determines release when delta mediolateral gap > 4mm before femoral resection using a Tensioner with two independent pads.

10 out of 93 cases (10.75 %), required collateral ligament release to achieve a postoperative mechanical axis of 0° (SE±0.11) with a mean mediolateral deflection in extension of 1.43°, and a mean range of motion of −3° to 127° of flexion. First predictor has 98% accuracy. Second predictor has 96% accuracy but their combination had 100% accuracy with no false negative predictions.

Balanced neutral TKA is achieved by soft tissue release, bone resection or as in this study, by adjusted navigated femoral resection (through rotation, size and level of resection) which balanced knees that otherwise should have soft tissue release. Navigation predictors are reliably accurate to quantitatively determine the necessity of soft tissue release to achieve a neutral stable knee with a significantly lower release rate in comparison to non navigated TKA series rate of 50–100%. (p< 0.001) (95% confidence interval).

Studies suggest that specialty hospitals and high surgical volume decrease adverse outcomes related to hip arthroplasty. Little is known, however, concerning the influence of imageless computer navigation systems on a surgeon’s experience and subsequent placement of implants in the setting of hip resurfacing arthroplasty.

A retrospective review of 71 consecutive hip resurfacing arthroplasties placed with computer assisted navigation during 2006 and 2007 was performed. Forty-seven operative days encompassing the surgeon’s entire experience with hip resurfacing were analysed. Within this single surgeon series, operative time, intraoperative cup inclination and femoral stem/shaft angles, as well as postoperative cup inclination and femoral stem/shaft angles were measured and compared over three discreet, sequential operative time intervals.

Intraoperative cup inclination angles were comparable to postoperative radiographic values as there was no significant difference (p=.059). Computer assisted navigation produced consistent values despite different levels of surgeon experience in the setting of intraoperative cup inclination (42.8°, 43.5°, and 40.1°) and postoperative cup (46.1°, 43.9°, and 42.9°) and femoral stem (147.9°, 146.5°, and 144.0°) radiographic alignment. A statistically significant difference existed between intraoperative femoral stem/shaft angles compared to postoperative radiographs measurements (p< .001), however, all means maintained a valgus orientation compared to the native neck angle. There was a correlation between evolving surgeon experience and intraoperative stem placement (143.5°, 142.1°, and 138.0°, respectively) despite the mean values remaining well clustered (p< .001). Operative times significantly decreased (p< .001) with surgeon experience, showing the largest decrease after the 1^st sequence interval (109.6, 97.8, and 94.8 min, respectively). No femoral notching (0/71) occurred throughout the series.

Computer assisted navigation provides a dependable method of accurate hip resurfacing arthroplasty component positioning as measured by cup inclination, in addition to a reliable technique for valgus stem placement and avoidance of notching. Furthermore, computer navigation allows for consistency and offers a protective effect on component alignment independent of surgeon procedural experience.

The navigation system recently introduced in an ACL reconstruction is reported that it would be helpful for determining the accurate tunnel position and better clinical results in. It also provides intra-operative information such as knee kinematics and anteroposterior translation and internal-external rotation of the tibia during the reconstruction. Our hypothesis was that a double bundle reconstruction would provide better anteroposterior and rotational stabilities than a single bundle reconstruction.

The aim of this study was to assess the changes of anteroposterior and rotational stabilities using a navigation system achieved by double bundle reconstruction (20 knees) and compare them with those by single bundle reconstruction (20 knees).

After registering the reference points, anteroposterior ad rotational stability test with 30° knee flexion using a navigation system was carried out and measured before and after reconstruction on both groups.

The anteroposterior stability showed significant improvement from 17.5 mm before the reconstruction to 5.1 mm after the reconstruction in the double bundle group and from 16.6 mm to 6.1 mm in the single bundle group, showing a significant inter-group differences (p< .05). The mean rotation stability of the double bundle group showed more significant improvement after reconstruction than those of the single bundle group (9.8° in single and 6.1° in double bundle group, p< .05).

The double bundle ACL reconstruction tends to be more stable in rotational stability than the single bundle reconstruction, but not so much in anteroposterior stability. Clinically the double bundle ACL reconstruction may provide better rotational stability reducing residual pivot shift phenomenon after reconstruction.

The aim of our study was to compare the precision and effectiveness of a CT-free computer navigation system against conventional technique (using a standard mechanical jig) in a cohort of unselected consecutive series of hip resurfacings.

One hundred and thirty nine consecutive Durom hip resurfacing procedures (51 navigated and 88 non-navigated) performed in 125 patients were analysed. All the procedures were done through a posterior approach by two surgeons and the study cohort include the hip resurfacings done during the transition phase of the surgeons’ adoption of navigation.

There were no significant differences in the gender, age, height, weight, BMI, native neck-shaft angles, component sizes and blood loss between the two groups. There was a significant difference in the operative time between the two groups (111 minutes for the navigated group versus 105 minutes for the non-navigated group; p=0.048). There were 4 cases of notching in the non-navigated group and none in the navigated group. There were no other intra-operative technical problems in either of the groups nor were there any femoral neck fractures.

No significant difference was found between the mean post-operative stem-shaft angles (138.5° for the navigated group versus 139.0° for the non navigated group, p=0.740). However there was a significant difference in the difference between the planned stem-shaft angle versus the post-operative stem-shaft angle (0.4° for the navigated group versus 2.1° for the non-navigated group; p=0.005). There was significantly more scatter in the difference between the post-operative stem-shaft angle and the planned stem-shaft angle in the non-navigated group (standard deviation = 3.6°) when compared with the navigated group (standard deviation = 0.9°; Levene’s test for equality of variances = p≤0.01). No case in the navigated group showed a post-operative stem-shaft angle of more than 5° deviation from the planned neck-shaft angle when compared to 33 cases (38%) in the non-navigated group (p≤0.001). While only 4 cases (8%) in the navigated group had a postoperative stem-shaft angle deviating more than 3° from the planned stem-shaft angle, this occurred in 50 cases (57%) in the non-navigated group (p≤0.001).

Hip resurfacing is a technically demanding procedure with a steep learning curve. Varus placement of the femoral component and notching have been recognised as important factors associated with early failures following hip resurfacing. While conventional instruments allowed reasonable alignment of the femoral component, our study has shown that use of computer navigation allows more accurate placement of the femoral component even when the surgeons had a significant experience with conventional technique.

Scarf osteotomy is widely used as a surgical treatment for hallux valgus. It is a versatile osteotomy, allowing shortening, depression or medial displacement of the capital fragment but it remains uncertain how stresses within the bone subsequently vary. The aim of this study was to design a computerised model to explore the effect on bone stress of changing the position of bony cuts for a scarf osteotomy.

A computerised image was constructed using finite element analysis. This utilises a mathematical technique to form element equations which represent the effect of applied force to the object appropriate to each finite element. Maximum bone stresses were then measured using different osteotomy variables. The osteotomy variables studied were the length of the longditudinal cut, apex of the distal cut to articular cartilage, resection level of the longditudinal cut and combinations of these variables. A saw bone model was used to test the findings of the study.

The results of this study show that lowering the longditudinal resection level and shortening via the distal cut beyond 6 mm will decrease bone stress. Additionally, raising the longditudinal resection level and shortening via the proximal cut caused an increase in bone stress. A saw bone model confirmed the findings of the study.

In conclusion, our experience is that finite element analysis is a very useful model in studying the bony stresses for a scarf osteotomy and assists in optimising the direction and angle of bony cuts used.

Correct alignment of the leg and positioning of the implant has shown to be an important factor in the successful long term outcome of total knee arthroplasty and navigation systems enable an accuracy of corrections and alignment within intervals of 1 mm or 1 degree. This study is to test if there is any discrepancy in accuracy which was sometimes observed in clinical trials between Orthopilot (Aesculap, Tuttlingen, German) and AxiEM (Medtronic Navigation, CoalCreek, Colo., USA).

A synthetic bone model (Sawbones, Pacific Laboratories, Vashon, Washington) including pelvis and leg with mobile joint made up of titanium which does not affect the electromagnetic field was constructed. Mechanical axis was checked by ORTHODOC system (Integrated Surgical System, CA, USA) that is a preplanning system for ROBODOC (ISS, CA, USA) assisted total knee arthroplasty (TKA) and total hip arthroplasty (THA). The CT images were scanned with 1.25 mm or less slice interval. The CT images were converted to 3-dimensional (3D) volume-rendered model in ORTHODOC. Two orthopaedic surgeons measured it ten times independently.

For the measurement of mechanical axis using navigation, 4 orthopaedic surgeons (two experts having more than 100 navigation experiences and two residents) registered anatomical landmarks and kinematic center of bone model ten times using Orthopilot as well as AxiEM. After that, one surgeon intentionally registered the wrong anatomical landmarks (10 mm medial and lateral to the center of distal femur, proximal tibial and ankle, and both malleoli) in both navigation system and observed the change of mechanical axis.

True mechanical axis was varus 1.25° using Orthodoc, Orthopilot displayed varus 1.10±0.64° and AxiEM did varus 1.78±0.79°. The difference of mechanical axis between two navigations was not observed (P=0.12) and there were no intra and inter-observer variation in statistical analysis (Correlation=0.934, P=0.00). In the case of erroneous identification of the anatomical landmarks, Orthipilot showed much less variation compared to AxiEM. AxiEM altered the mechanical axis more in palpating center of the distal femur and ankle center and Orthopilot did in palpating the center of ankle.

Both navigation systems provide high accuracy and reproducibility of mechanical axis of lower limb in experimental condition. But both were affected by the wrong identification of the anatomical landmarks. AxiEM had more variations. So surgeon should pay attention to register the precise anatomical landmarks.

Unexpected findings were sometimes observed such as hyper extension, oversize of femoral component, or anterior notching of anterior femoral cortex in total knee arthroplasty (TKA) using computer system. We conducted this study to evaluate these findings by a virtual simulation using ORTHODOC and then confirmed them on real patients with TKA.

Virtual simulations of distal femoral cut in 50 patients using ORTHODOC system were made by way of being perpendicular to mechanical axis (CAOS way) and to intramedullary guide (manual way) in the same knee and measured the difference of sagittal cutting planes. We compared the maximum AP dimensions of femoral condyle parallel to distal cut plane. We also compared sagittal alignment and size of the femoral component in 30 bilateral TKAs, one side using ROBODOC (CAOS way) and the other side using IM guide (manual way).

On virtual simulation, distal femoral cut was more extended (3.1±1.6°) in CAOS than in manual way and anteroposterior size of the femoral condyle in CAOS way was also larger than in manual way (p=0.001). Radiographic sagittal alignment of femoral component performed using CAOS way was slightly more extended than those using manual way, showing a significant difference (p=0.024). The larger femoral components were required in six patients on CAOS and in two patients on manual way, whereas twenty-two patients showed same size on both side.

CAOS can provide more accurate sagittal cut perpendicular to mechanical axis than manual system, which may lead to slightly extended position or larger femoral component.

In total knee arthroplasty, navigation systems that help achieve accurate alignment of the lower limbs have been applied widely, and these techniques are currently being used in minimally invasive unicondylar knee arthroplasty (MIS UKA) with good alignment results. To the best of our knowledge, there are no studies showing whether or not MIS UKA using a navigation system has a significant influence on the clinical results. This prospective study investigated the hypothesis that minimally invasive uni-compartmental knee arthroplasty using navigation system (NA-MIS UKA) will produce better short-term clinical results than MIS UKA without navigation system.

After a minimum two-year follow-up, the short-term functional results included the ranges of motion, Hospital for Special Surgery (HSS) scores, and WOMAC scores and the alignment accuracy of the components of 31 NA-MIS UKAs (NA-MIS group) compared with those of 33 MIS UKAs without a navigation system (MIS group). The surgery time was also recorded and compared.

The HSS and WOMAC scores showed significant improvement at the final follow-up in both groups, showing no significant inter-group difference (p=0.071, p=0.096, respectively). The ranges of motion also showed significant improvements in both groups, but there was no significant difference between two groups (p=.687). However, the surgery time was longer in MIS group than in NA-MIS group. NA-MIS UKA produces significant improvement in the desired mechanical axis with prosthetic alignment outliers compared with that without the navigation system.

However, at the final follow-up, there were no significant differences in any of the functional parameters between the two groups.

This prospective study was undertaken to compare the clinical and radiological results achieved using navigation assisted minimally invasive (NA-MIS) and conventional (CON) techniques in bilateral total knee arthroplasty (TKA).

Forty-two bilateral patients with a minimum 2-year follow-up who were available for study after NA-MIS TKA were included in this study. Clinical evaluations (ROM, HSS and WOMAC scores) were performed at 3 and 6 months and at 1 & 2 year postoperatively. Patient subjective preferences and radiological accuracies were compared at 1 year postoperatively.

Preoperative HSS scores were 68.5 in the NA-MIS group and 66.5 in the CON group, and these scores improved to 93.6 and 92.5 at 1 year postoperatively, respectively. Knees had a higher average HSS score in NA-MIS group than in the CON group till six months, but not after nine months postoperatively. In terms of WOMAC scores, pain scores in the NA-MIS group were better up to nine months postoperatively, but not at one & 2 year postoperatively, and total WOMAC scores were better up to six months, but not after nine months postoperatively. ROM was comparable in both groups at all times. However, more patients preferred NA-MIS sides than CON sides. Radiological results demonstrated no difference between the mean values of the two groups, although the NA-MIS group contained fewer outliers than the CON group.

NA-MIS TKA results in better functional scores than CON-TKA over the first or nine months postoperatively. However, no differences in any functional parameters were evident at one & two year postoperatively.

The aim of study was to provide normal value of anteroposterior and rotational stability of knee joints using navigation system.

From March 2007 to November 2007, 35 patients (23 men, 12 women) with a mean age of 36.1(16–57) years, who were treated with arthroscopy, without ligament injury of knee were included in our study. We measured amount of anteroposterior displacement and rotation of the knee in 0, 30, 60 and 90 degrees of flexion position using Orthopilot navigation system. All tests were performed by same single surgeon under manual maximal force.

The mean anterior displacement was 3.7±2.0, 6.6±2.2, 5.8±2.0 and 4.7±1.8 mm in 0, 30, 60 and 90 degrees of flexion respectively. The amount of anterior displacement at 30 degree of flexion was significantly larger than those of other degrees. The mean posterior displacement was 2.0±0.5, 2.2±0.4, 2.1±0.4 and 2.0±0.6 at each degree. There was no statistical difference in posterior displacement. The mean internal rotation was 10.3±2.7, 14.6±3.3, 16.2±2.9 and 15.0±4.3 degree at each degree. The amount of internal rotation at 0 degree of flexion was significantly smaller than those of other degrees. The mean external rotation was 8.4±3.4, 16.5±3.3, 13.3±3.8 and 15.0±4.3 degree at each degree. The amount of external rotation at 0 degree of flexion was significantly smallest and that of 30 degree was largest.

In the measurement of laxity using navigation, we could acquire previously mentioned results. The measurement of stability of knee will be useful in diagnosing ligament injury and evaluating degree of postoperative symptomatic improvement.

Bilateral sequential total knee replacement with a Zimmer NexGen prosthesis (Zimmer, Warsaw, Indiana) was carried out in 30 patients. One knee was replaced using a robotic-assisted implantation (ROBOT side) and the other conventionally manual implantation (CON side). There were 30 women with a mean age of 67.8 years (50 to 80).

Pre-operative and post-operative scores were obtained for all patients using the Knee Society (KSS) and The Hospital for Special Surgery (HSS) systems. Full-length standing anteroposterior radiographs, including the femoral head and ankle, and lateral and skyline patellar views were taken pre- and post-operatively and were assessed for the mechanical axis and the position of the components. The mean follow-up was 2.3 years (2 to 3).

The operating and tourniquet times were longer in the ROBOT side (p < 0.001). There were no significant pre- or post-operative differences between the knee scores of the two groups (p = 0.288 and p = 0.429, respectively). Mean mechanical axes were not significantly different in the two groups (p = 0.815). However, there were more outliers in the CON side (8) than in the ROBOT side (1) (p = 0.013). In the coronal alignment of the femoral component, the CON side (8) had more outliers than the ROBOT side (1) (p = 0.013) and the CON side (3) also had more outliers than the ROBOT side (0) in the sagittal alignment of the femoral component (p = 0.043). In terms of outliers for coronal and sagittal tibial alignment, the CON side (1 and 4) had more outliers than the ROBOT side (0 and 2).

In this series robotic-assisted total knee replacement resulted in more accurate orientation and alignment of the components than that achieved by conventional total knee replacement.

Navigation was used to achieve a balanced flexion-extension gap for total knee arthroplasty and it’s 3 years clinical results were reported.

From 112 osteoarthritic knees with varus deformity the flexion and extension gap were measured with distraction of 50 lb/inch using special torque wrench following completion of controlled medial release with guidance of navigation system & tibial bone cut. Distal & AP femoral bony cut were finished according to the data of measurement of flexion-extension gap. After confirmation of the balanced flexion-extension gap by navigation total knee arthroplasty was completed.

The differences between flexion and extension gap varied from case to case, and could be classified into 3 kinds; balanced, tight flexion gap and tight extension gap.

HSS score was 96.7, ROM was 128.5 degree. 39 patients (35%) can have comfortable kneeling 75 patients(67%) can sit with cross leg. Gap technique with navigation could provide excellent clinical results of total knee arthroplasty and 3 classifications of flexion and extension gap should be taken into considerations for balanced total knee arthroplasty

Computer based navigation system improved the accuracy of limb and component alignment and decreased the incidence of outliers. The majority of previous studies were based on the infrared navigation system. We evaluate the availability and accuracy of the electromagnectic(EM) navigation system in total knee arthroplasty

From July 2006 to January 2007, 40 patients (50 TKAs) with osteoarthritis were participated in this study. AxiEM(Medtronics) was used and Nexgen CR(26 cases), and Nexgen CR flex(24 cases) were used. We analyzed the failure mode of navigation (7 cases), operation time and radiologic results (limb and component alignment)

Total registration time was 4 minutes 45 seconds in average (Range : 3 minutes 45 seconds ~ 6 minutes 55 seconds). Failures in clinical applications resulted from non-recognition of EM tracker or paddle by metallic interference in 4 cases and from informational changes during surgery by fixation loss or loosening of the tracker in 3 cases. Radiologically, the mechanical axis changed from −11.2±7.21 (Range : −25.8~3.1) to 1.0±1.25(Range : −2.1~4.0) and 1 case of outlier occurred (valgus 4°). Component alignment is measured as followed: 89.3±1.6° of Theta angle, 89.9±1.5° of Beta angle, 1.8±2.5° of Gamma angle, 86.1±2.9 of Delta angle°. There were no complications related to the EM navigation.

The EM navigation system helped to achieve accurate alignment of component and lower leg axis without any complications. It had several advantages such as relatively less invasiveness in fitting small instruments, not disturbing operation field, no interrupted line of sight, portable use, and applicability to any implant. However, metallic interference may be still problematic.

The EM navigation had advantages; less invasiveness, no disturbing operation field, no interrupted line of sight, portable use and applicability to any implants. But metallic interference may be still problematic.

Computer assisted total knee arthroplasty (TKA) is still a relatively novel technique. Surgeons wishing to adopt any new practice undergo a learning curve. The learning curve experienced with navigated TKA, its duration and cost in terms of complications, has not been well defined in the literature. Therefore we set out to analyse the learning curve of a newly appointed consultant with no previous experience of navigated TKA by using a surgeon who has completed over 1000 TKAs in over 10 years of experience with this technique as a baseline.

The study used the inexperienced surgeon’s first ever fifty navigated TKAs and the experienced surgeon’s most recent fifty TKAs over the same period in the same theatre using the same CT free navigation system (Orthopilot^®) and prosthesis. Operative time, bone cuts and limb alignment before and after prosthesis implantation were recorded, along with the navigation specific difficulties and complications encountered by the inexperienced surgeon.

There was no statistical difference in the accuracy of postoperative limb alignment in either the coronal (p = 0.33) or sagital (p = 0.35) planes between the novice and experienced surgeon. There was also no difference in the executed bone cut angles (tibial p = 0.79, femoral p = 0.92). The operating time showed a difference between the two surgeons with the novice having a median of 80 mins (inter-quartile range of 20 mins) and the experienced surgeon had a median of 70 mins (inter-quartile range of 20 mins), p = 0.001. However there was a statistically significant reduction in operating time between the inexperienced surgeon’s first twenty and last twenty TKAs (p = 0.001). Comparison of the last 20 TKAs for each surgeon showed no difference in the operative time (medians of 70 mins and 75 mins respectively, p = 0.945). The navigation specific difficulties and complications recorded for the novice navigator were all related to the trackers: one loosening, one tibial tracker placed too proximally, one superficial infection in a tibial tracker wound and one incompletely engaged pin-tracker coupling which brought about the only conversion to manual TKA in this series.

We conclude that in terms of execution and outcome, a beginner using computer assisted TKA can match the results of an experienced navigator from the outset. The only parameter assessed that underwent a clear learning curve was the operative time, which took approximately 20 procedures to approach the same as the experienced surgeon.

Only limited data exists concerning outcomes after total knee arthroplasty (TKA) using a surgical robot. We conducted this study to evaluate the clinical and radiographical results in robotic-assisted implantation of TKAs with a minimum follow-up of two years.

A total of 50 primary TKAs using ROBODOC were included in this study. The mean duration of follow-up was 28.3 months. The radiographic measurement with regard to the change of mechanical axis, and the inclination of the femoral and tibial components were assessed. The value within ± 3° of optimum was classified to be “acceptable”, and the value exceeding more than ± 3° to be “outlier” results. Also we evaluated clinical results with the range of motion (ROM), Hospital for Special Surgery (HSS) scores, and Western Ontario and McMaster University (WOMAC) scores.

The mechanical axis was changed from 6.57 varus to 0.81 valgus. Mean coronal inclination of the femoral and tibial component were 88.61 and 89.76 at the last follow up. Also, mean sagittal inclination of the femoral and tibial component were 0.82 and 85.49. On the other hand, all prostheses had no radiolucent lines. On the clinical assessment, the range of motion improved from 124.9 to 128.4, and the improvement of HSS score and Womac score were 70.06 to 95.72 and 65.64 to 28.92 in each. No major adverse events related to the use of the robotic system have been observed. However, one case of the formation of seroma around the pin track and two cases of the partial abrasion of patellar tendon occurred in relation to procedures.

A surgical robot system in TKAs provides good clinical and radiographical results at least 2 years follow-up, however further study for the long term follow-up may be needed. A clear advantage of robot-assisted TKA seems to be ability to execute a highly precise preoperative planning and intraoperaive procedures. But current disadvantages such as increased operating times and inability of adjusting the preoperative planning during the procedure have to be resolved in the future.

Short leg radiographs remain the standard radiographs available in many UK hospitals. The aim of this study was to see if these radiographs are reliable when assessing the post-operative alignment of total knee arthroplasty in comparison to a Hip-Knee-Ankle (long leg) radiograph.

Twenty consecutive 6 week post-operative long leg radiographs, taken with a standardised protocol, and a short leg radiograph derived from the same digital image were each examined on two separate occasions by two observers. On the long leg radiograph the anatomical and mechanical axis were calculated and on the short leg radiograph the anatomical and surrogate mechanical axis were calculated. These data were used to investigate intra- and inter-observer error. A single observer also collected the same measurements on an additional 30 radiographs (total of 50) to further investigate any patterns of error.

On long leg radiographs, intra-observer agreement was good for both anatomical and mechanical axis for both observers (Intraclass Correlation Coefficients [ICC] of 0.95 to 0.98). The anatomical axis on short leg radiographs was also good (ICC = 0.92 and 0.76). Intra-observer agreement for the short leg radiograph derived mechanical axis was not as consistent (ICC = 0.73 and 0.56). Inter-observer variability was good for long leg radiographs for both anatomical (ICC = 0.89) and mechanical (ICC = 0.95) axis. On short leg radiographs, however, agreement was not as good, in particular for the mechanical axis (ICC = 0.51), but also the anatomical (ICC = 0.73). Taking the long leg radiograph values as the “gold standard” there was a difference in the magnitude of errors seen on short leg radiographs dependant on the knee alignment. Varus aligned knees (n=24) had an average error of 1.2° (0° to 3°) for the anatomical axis and 1.6° (0° to 4°) for the mechanical axis. Perfectly aligned knees (n=8) had an average error of 3.0° (1° to 6°) for the anatomical axis and 2.9° (1° to 5°) for the mechanical axis. Valgus aligned knees (n=18) had an average error of 3.4° (0° to 8°) for the anatomical axis and 5.8° (2° to11°) for the mechanical axis. Using a Mann-Whitney test the magnitude of error was greater for valgus knees for both anatomical (p< 0.0001) and mechanical (p< 0.00001) axes when compare to varus knees. Interestingly all except one knee measured on the long leg radiograph as valgus aligned appeared to be in varus on the short leg radiograph.

In conclusion, short leg radiographs are inadequate to make any comment on leg alignment in total knee arthroplasty. This is most pronounced in a valgus aligned knee.

Long term successful results of high tibial osteotomy (HTO) strongly depend on the degree of correction, and inadequate intraoperative measurements of the leg axis can lead to under or over correction, and surgeons have to solve these problems based on personal experience.

This study was undertaken to investigate and compare the clinical and radiological results of navigation assisted open wedge high tibial osteotomy (HTO) versus conventional HTO at 12 months after surgery, for unicompartmental gonarthrosis.

Forty navigated open HTOs with an anterior opening gap of approximately 70% of the posterior gap were included and compared with forty open HTOs performed using the conventional cable technique in terms of intraoperative leg axis assess.

Navigated HTOs corrected mechanical axes to 2.9° valgus (range 0.5–6.2) with few outliers (12.5%), and maintained posterior slopes (7.9±2.3° preoperatively and 8.3±2.8° postoperatively) (P> 0.05). However, in the conventional group, only 63% of cases were within the satisfactory range (valgus 2–5°), and tendencies toward undercorrection and an increase in posterior slope were observed. Clinically both groups showed satisfactory results.

Navigated HTO significantly improved the accuracy of postoperative mechanical axis and decreased correction variabilities with fewer outliers.

Total knee arthroplasty (TKA) is actually a satisfactory technique to reduce pain and enhance mobility in osteoartritic pathologies (OA) of the knee. However, life of the implant is strictly dependent on restoration of correct knee kinematics, as alteration of motion pattern could led to abnormal wear in prosthetic components and also damage soft tissues. The aim of our study was to evaluate new kinematic tests to be performed during surgery in order to improve the standard intra-operative evaluation of the outcome on the individual case. We used Kin-Nav navigation system to acquire anatomic and kinematic data, which were analysed by a dedicated elaboration software developed at our laboratory. Ten patients undergoing rotating platform cruciate substituting TKA were considered for this study. Immediately before the implant and immediately after component positioning, the surgeon performed 3 complete knee flexion imposing internal tibial rotation (IPROM) and 3 complete knee flexion imposing external tibial rotation (EPROM). Tibial rotation during IPROM and EPROM tests was plotted in function of flexion (in the range 10°–110°). Repeatability of IPROM and EPROM was tested by calculating ICC (Intra-class Correlation Coefficient) between 3 repeated curves. Distance between IPROM curve and EPROM curve was computed at various degree of flexion. Maximum distance obtained during all range of flexion before and after the implant were compared by Student’s t-test (significant level p=0.05).

ICC for repeated motions were 0.99 for IPROM and 0.98 for EPROM. Maximum distance between tibial rotation in IPROM and EPROM was 27.82±6.98 before implant and significantly increased (p=0.001) to 40.09±6.92 after TKA. In one case we observed that the value remained similar before and after implant (from 33.11 to 33.98) while in one case we observed very large increase of rotation (from 30.56 to 50.01).

The proposed kinematic tests were able to quantify the increase of tibial rotation after TKA implant. Future development of the study are encouraging and will include a larger sample and reflections on individual findings.

In orthopaedic trauma surgery, X-ray fluoroscopy is frequently employed to monitor fracture reduction and to guide surgical procedures where implants are inserted to fix the fractures. Fluoro-navigation is the application of real-time navigation on intraoperatively acquired fluoroscopic images to achieve the same goals. The theoretical advantages of fluoro-navigation are:

Minimising exposure to X-ray on surgeons, operating room personells and patients,

Fluoro-navigation is particular indicated in orthopaedic trauma as the fracture fragments are mobile and the orientations are not fixed before surgery. At this time, many procedures that require intraoperative fluoroscopic control can now be done with fluoro-navigation. These procedures include:

Fixation of femoral neck fractures with percutaneous cannulated screws,

Since 2001, we have been using fluoro-navigation orthopaedic trauma surgery. 535 different procedures of operative treatment of fractures were carried out. These operative procedures included. Operation, amount, success rate:

Femoral neck fractures, 65, 100%, Gamma nailing, 172, 100%, Femoral locked nails, 77, 98.5%, Tibial locked nails, 53, 100%, Sacro-iliac screws, 45, 95.1%, Pelvic acetabular fractures, 29, 96.1%, Ilizarov tension wires, 13, 100%, Percutaneous screws, 18, 100%, Distal locking without X-ray, 15, 100%, 3-D Navigation, 48 92.7%.

Our clinical experience has confirmed the advantages and the extended applications of this technique benefited many of our patients by enhancing minimally invasive technique in orthopaedic trauma surgery, better implant position and significantly decreasing the radiation of the fluoroscopy (p< 0.05). We have modified the operative procedures in order to adapt better with the fluoro-navigation procedures. We also worked with the industrial partners to design specific instruments as well as modified the existing surgical instruments to facilitate the fluoro-navigation procedures. Most of the failure were due to poor quality fluoro-images, unstable operating system and poorly adapted surgical instruments in the early phase of the applications.

Further improvement is expected in the system on the hardware and software for quicker image acquisition with improved quality, accurate and precise registration, increase interactivities and adaptation of surgical instruments as well as implants. There is a great need for the development of dedicated surgical instruments for orthopaedic trauma sugary in line with the further improvement of the navigation system. With the establishment of image libraries for implants and skeleton, further minimising the need for standard fluoroscopy will be possible. The combination of 3-D fluoroscopy and the navigation will improve percutaneous fixation of articular fractures. At the time, it is only possible to navigate the images obtained during the operation after fracture reduction or manipulation is completed. The possibility to navigate on each individual fracture fragment will extend the technique even more to real-time fracture reduction.

The fluoro-navigation system will also play an important role in surgical training as well as assessment in the virtual surgical environment. We also developed specific training models for fluoro-navigation for preoperative training and practice of standard procedures. This will help to promote further application of fluoro-navigation in orthopaedic trauma.

The recognition of its clinical significance will help to stimulate more research and thus encourages industries to devote more resources in the development of fluoro-navigation for orthopaedic trauma.

Flexion contracture is a common deformity encountered in patients requiring total knee arthroplasty (TKA). Both the soft tissue envelope and articular bones are involved in the knee extension lag. A few studies in the past have assessed the relationship between bone cuts and extension deficit by using goniometers and rulers. Using navigation for TKA enables the accurate measurement of knee flexion contracture and bone cuts. The aim of this study was to try to establish a relationship between extension lag correction and the size of bone cuts made.

One hundred and four continuous TKA were completed by a single consultant using the OrthoPilot® (BBraun, Aesculap) navigation system and Columbus implants. Seventy-four knees had preoperative flexion contracture (including neutral knees) while 30 were in hyperextension. Data was recorded prospectively using the navigation system. These included preoperative flexion and extension angles, actual bone cuts of tibia and femur (both medial and lateral), postoperative correction of flexion and extension angle, size of the prosthesis with thickness of polyethylene and soft tissue release. Of the 74 knees with fixed flexion, 57 had no release and 13 had a posterior release (four had an intermediate release and were excluded from the study).

For knees with fixed flexion (n = 70) there was a significant statistical difference between the pre and post implant extension angle (p < < 0.0001). There was no correlation between the thickness of bone cuts and postoperative extension lag either for the group with no release (p = 0.495) or posterior release (p = 0.516). There was also no correlation between bone cuts and preoperative angles for either type of release (p = 0.348 and p = 0.262). There was a significant difference between the preoperative extension deformity for the two soft tissue releases performed (p = 0.00019), the mean fixed flexion angles being −4.4° and −10.4° for no release and posterior release respectively.

Flexion contracture deformity in TKA can theoretically be solved in two ways: either by extensively releasing the soft tissue or by increasing the extension gap by cutting more bone (logically the distal femur). Appropriate soft tissue management and release in TKA is crucial in balancing the prosthesis in the coronal as well as the lateral plane. This study seems to confirm the supremacy of soft tissue management and release over bone cut resection. Cutting more or less bone could in fact lead to a poorer outcome as this will change the joint line level without having any additional beneficial effect in correcting the flexion contracture. Conversely adequate soft tissue release has corrected the flexion contracture when needed. In conclusion, there was no correlation between bone cut resection and extension lag correction and with large extension deficits, a posterior soft tissue release and osteophytes resection was more important than bone cuts.

Information on knee kinematics during surgery is currently lacking. The aim of this study is to describe intra-operative kinematics evaluations during uni-compartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) by mean of a navigation system. Anatomical and kinematic data were acquired by Kin-Nav navigation system and analysed by a dedicated elaboration software developed at our laboratory. The study was conducted on 20 patients: 10 patients undergoing mini-invasive UKA and 10 patients undergoing posterior-substituting-rotating-platform TKA. In both group of patients the surgeon performed passive knee flexion immediately before and immediately after the prosthetic implant. Pattern and amount of internal/external tibial rotation in function of flexion were computed and significant changes between before and after implant were evaluated adopting Student’s t-test (significant level p=0.05).

UKA implant did not significantly change the pattern of internal/external tibial rotation, nor the total magnitude of tibial rotation (15.75°±7.27°) during range of flexion (10°–110°), compared to pre-operative values (17.87°±7.34°, p=0.25). Magnitude of tibial rotation in TKA group before surgery (8.00°±3.67°) was significantly less compared to UKA patients and did not changed significantly after implant (5.96°±4.88°, p=0.09). Pattern of rotation before and after TKA implant were different between each other and between pattern in UKA patients both before and after implant.

Intra-operative evaluations on tibial rotation during knee flexion confirmed some assumptions on knee implants from post-operative methods and suggest a more extensive use of surgical navigation systems for kinematic studies.

Flexion contracture in total knee arthroplasty (TKA) remains a challenge. Soft tissue management and additional bone resection are traditional options for flexion contracture correction. Our hypothesis was that the post implant computer aided measurements would not be significantly different to the extension angles measured at six weeks post-operatively in the follow-up clinic.

One hundred continuous TKA were performed by a single consultant using the OrthoPilot^® (BBraun, Aesculap) navigation system and Columbus implants. Of the group, 45 were male and 55 were female. Average age was 68 (range 49–87), mean BMI was 32.86 (22.26–51.86) and mean Oxford score preoperatively was 42 (range 21–56) and post-operatively 28 (range15–50). Data recorded at the preoperative assessment clinic included clinical flexion contracture and Oxford scores. Intra-operatively data were recorded using the navigation system. These included pre-operative flexion and extension angles, actual bone cuts of tibia and femur (both medial and lateral), postoperative correction of flexion and extension angles and soft tissue releases. At six weeks post operation, patients were seen in the follow clinic and clinical flexion contracture and Oxford score reassessed by the Arthroplasty outcome service.

Measurements were grouped and comparisons were made using a Pearson Chi-square test. There was no relationship between post-implant extension angle measurements (by computer) and extension angles at six weeks (by goniometer) (p=0.682). Also, there was no relationship between pre-operative measurement angles collected at the pre-assessment (by goniometer) and the pre-implant angles measured on the table (by computer) (p=0.682). We found that BMI (up to 35) and postoperative Oxford scores were significantly related to the extension levels with values of (p=0.008) and (p=0.027) respectively. Pre-operative Oxford scores, pre-operative extension, amount of bony resection and soft-tissue releases did not show any significant relationship with the post-operative extension obtained at six weeks.

The conclusions that we draw from this study are that there might be other factors that are likely to influence extension lag between the operation and the follow-up at six weeks. One of the factors that we could identify was the BMI. Attention to extensor lag is important because it leads to a poorer knee function, as indicated by the Oxford scores. Despite most of the post-implant measurement angles showing no extensor lag, about 20% of our patients still had more than five degrees flexion contracture at six weeks.

Computer assisted total knee arthroplasty (TKA) enables the measurement of the dynamics of the knee both before and after the implant of the prosthesis. Much time has been spent looking at the outcomes of navigated TKA however less time has been invested on understanding how the data collected pre-operatively can inform the surgeon and help the surgical decision making process. The aim of this work was to use navigation as a tool to quantify and classify preoperatively valgus knees.

Between August 2006 and September 2007 a group of 51 patients who demonstrated intra-operative initial neutral or valgus aligned knees underwent navigated TKA using the Columbus knee prosthesis and the Orthopilot^® navigation system (BBraun, Tuttlingen, Germany). Demographic data were recorded, along with the preoperative radiograph appearance and clinical assessment of alignment. During the surgery the approach used and the knee mechanical femorotibial (MFT) angle though the range of flexion were recorded. The knees were then categorised as either “True” valgus or “False” valgus based on whether the MFT angle at 30°, 60° and 90° flexion was still valgus (True) or had gone into varus (False).

Five patients were excluded from the study group as they had incomplete data in knee flexion. Of the remaining 46 patients, 28 were True valgus and 18 were False valgus. For the two groups demographic data were compared. Male to female ratio was 9:19 for the True valgus and 4:14 for the False valgus. The mean age of the True group was 70 years (range 52–85 years) and the False was 69 years (range 53–84 years). For BMI the True group had mean of 31 (range 20–40) and False of 33 (range 26–42). Twenty-five of the 28 True valgus knees showed preoperative evidence of clinical genu valgum deformity and radiologic evidence of predominantly lateral compartment osteoarthritis. Five patients had ipsilateral hip replacements in the past and five had rheumatoid arthritis. Seventeen were operated by lateral parapatellar approach. Eighteen required ilio-tibial band release with additional lateral collateral ligament release in five knees. Six true valgus knees did not require any soft tissue release. Five patients required lateral retinacular release to achieve thumb free patellar tracking. The median operating time for the True valgus group was 80 mins. Ten of the 18 false valgus knees showed evidence of clinical varus deformity and radiological evidence of predominantly medial compartment osteoarthritis. Only one patient had an ipsilateral hip replacement in the past and one had rheumatoid arthritis. All 18 knees underwent TKA by medial parapatellar approach, requiring no additional soft tissue release in 17 knees and a moderate release in one knee. The median operating time for the False valgus group was 60 mins.

True valgus knees had more significant deformities clinically and radiologically, longer surgical time and more incidence of soft tissue release when compared to the False valgus knees. False valgus knees behaved like varus knees clinically, radiologically and intra-operatively and should therefore be treated as such when making surgical choices.

Although acetabular centre positioning has a profound effect on hip joint function, there are very few studies describing accurate methods of defining the acetabular centre position in 3D space. Clinical and plain radiographic methods are inaccurate and unreliable. We hypothesize that a 3D CT-based system would provide a gender-specific scaled frame of reference defining the hip centre coordinates in relation to easily identifiable pelvic anatomic landmarks.

CT scans of thirty-seven normal hips (19 female and 18 male) were analysed. The ratios of the hip centre coordinates to their corresponding pelvic dimensions represented its horizontal (x), vertical (y), and posterior (z) scaled offsets (HSO, VSO, and PSO).

The mean HSO for females was 0.08 ± 0.018, mean VSO was 0.35 ± 0.018, and mean PSO was 0.36 ± 0.017. For males HSO averaged 0.10 ± 0.014, VSO was 0.32 ± 0.015, and PSO was 0.38 ± 0.013. There was a statistically significant gender difference in all three scaled offsets (p=0.04, 0.002, and 0.03 for HSO, VSO, and PSO respectively). Inter-observer agreement tests showed a mean intra-class correlation coefficient of 0.95.

We conclude that this frame of reference is gender-specific giving a unique scale to the patient and allowing reliable derivation of the position of the hip centre from the pelvic dimensions alone. The gender differences should be borne in mind when positioning the centre of a reconstructed hip joint. Using this method, malpositioning, particularly in the antero-posterior (or z) axis, can be identified and addressed in a malfunctioning hip replacement. Pathological states, such as dysplasia and protrusio, can also be accurately described and surgery addressing them can be precisely planned.

The role of CAOS systems is now well established in several areas of orthopaedic surgery. The increasing use of these systems, particularly in knee arthroplasty, has been supported by clinical trials that demonstrate a more accurate final position of implanted devices compared with conventional instrumentation. CAOS technology is constantly evolving along with its expanding list of potential indications. This requires the adaptation of both software and hardware components. It is therefore essential that potential users have confidence in the accuracy of these systems. The aim of this project was to design and manufacture a standardised measurement object (phantom) to independently evaluate CAOS system performance.

The American Society for Testing and Materials (ASTM) International along with CAOS International recently drafted a standard for measuring technical accuracy of navigation systems. This proposed standard was obtained and its recommendations used to design a phantom model. This consisted of a 150×150×20mm base plate and two additional levels including a single 30° slope. This created a 3D surface on which points could be placed. Co-ordinates for 21 points were given to establish the x, y and z axes of a Cartesian system and then to have points at a variety of known locations in this 3D space. The final model was machined from a billet of marine grade aluminium alloy 6082-T6 (chosen for its dimensional stability) using a vertical computer numerical controlled (CNC) milling machine with the co-ordinate points drilled with a Ø0.8mm 60° BSO centre drill to a depth of 1.2mm. The drill holes, with chamfers of Ø1.0mm, were designed to accommodate a ball-nosed pointer tip of a known diameter. A Perspex base unit with three different sites of rigid tracker attachment was made to hold the phantom and provide its reference frame. This avoided the need to directly modify the phantom itself.

The final design has been used to measure the positional accuracy of a novel portable navigation system and demonstrate that it is not yet suitable for clinical evaluation due to errors of 1 – 6 mm in point location. It has also allowed independent technical validation of current pre-existing navigation systems.

Background: Leg length equality and femoral offset restoration are important parameters related to success of total hip arthroplasty (THA). However, it is not uncommon for errors to occur during surgery which can lead to less optimal functional result and potential source for litigation. Several techniques that are commonly used to assess leg length and femoral offset during THA include pre-operative templating, intra-operative measurements with a ruler using bony landmarks, assessing soft tissue tension and using measurement device with a reference pin in the iliac crest. We have previously reported on our precision to reconstruct the diseased hip with THA done without navigation. Post-operative radiographic analysis demonstrated that leg length was restored to within +/− 4mm of the contralateral side in only 60% of the patients with 4 patients needing a shoe lift. With regards to femoral offset reconstruction, it was increased by a mean of 5.1 mm and restored to within +/− 4mm of the normal contralateral side in only 25% of patients.

Computer navigation has proven to be a more precise tool to achieve optimal positioning of THA implants and precise biomechanical reconstruction of the hip joint. However, performing complete THA using navigation is complex including the requirement to change the position of the patient during registration. A recent stand-alone CT-free hip navigation software from Orthosoft Inc allows navigation to be used for limb length and offset measurements during THA. We report our results from a preliminary study using this technique in 14 hips undergoing THA.

In this technique, a tracker is placed over the iliac crest. There is no need to fix a tracker on the femur. Registration of the following are done: greater trochanter (using a screw), patella (using an ECG lead) and the plane of the operating table (using three points on the surface of the operating table in a triangular configuration). The centre of rotation of the hip is determined by either mapping the acetabulum or by using the appropriate sized calibrated reamer. With the definitive acetabular component in place, the new center of rotation is registered and the hip is reduced with trial femoral component. Re-registration of the new position of the greater trochanter and patella allows the computer to calculate the relative change in the limb length and offset compared to the pre-operative status. The differences in the pre-operative and post-operative limb length and offset were calculated using Imagika software and compared with the navigated values recorded by the computer.

The mean absolute error for the relative change in the limb length as measured by the computer when compared to the radiographic measurement was 1.25 mm with a standard deviation of 1.77 mm. The mean absolute error for the relative change in the offset as measured by the computer when compared with the radiographic measurement was 2.96 mm with a standard deviation of 2.56 mm. The process of navigation was quick and on average adds 10 minutes to the operative time.

Our preliminary study shows that the accuracy of the navigation software is very good in estimating the change in the limb length intra-operatively with a maximum error of 3 mm. The accuracy was also good in estimating the offset (3 mm or less except in one case where the error was 5 mm and this may be due to technical error in registration). This compares favorably with our own data on THA done without navigation. This easy to use navigation technique has the potential to decrease the magnitude of error in restoration of limb length and offset during THA.

We thank Francois Paradois and Michael Lanigan from Orthosoft Inc. for their technical advice.

The rotational alignment of the tibia is an as yet unresolved issue for arthroplasty surgeons. Functional variation may be due to minor malrotation of the tibial component. The aim was to find a reliable method for positioning the tibial component in arthroplasty.

CT scans of 21 knees were reconstructed in three dimensions and oriented vertically. A plane was taken 20 mm below the tibial spines. The centre of each tibial condyle was calculated from points taken round that condylar cortex. A tibial tubercle centre was also generated as the centre of the circle that best fit points on the surface of the tubercle in the plane of its most prominent point.

The derived points were identified by three observers with errors of 0.6 – 1mm. The medial and lateral tibial centres were constant features (radius 24mm ± 3mm, and 22mm ± 3mm respectively). An ‘anatomic’ axis was created perpendicular to a line joining these two points. The tubercle centre was found 20mm ± 7mm lateral to the medial tibial centre. Compared to this axis, an axis perpendicular to the posterior condylar axis was internally rotated by 6° ± 3°. An axis based on the tibial tubercle and the tibial spines was also internally rotated by 6° ± 10°.

We conclude that alignment of the knee when based on this ‘anatomic’ axis is more reliable than either of the posterior surfaces. It is also more reliable than any axis involving the tubercle, which is the least reliable feature in the region. The ‘anatomic’ axis can be used in navigated knee arthroplasty for referencing the rotational alignment of the tibial component.

Radiological measurements are an essential component of the assessment of outcome following knee arthroplasty. However, plain radiographic techniques can be associated with significant projectional errors because they are a two-dimensional (2D) representation of a three-dimensional (3D) structure. Angles that are considered within the target zone on one film may be outside that zone on other films. Moreover, these parameters can be subject to significant inter-observer differences when measured. The aim of our study therefore was to quantify the variability between observers evaluating plain radiographs following Unicompartmental knee arthroplasty.

Twenty-three observers, made up of Orthopaedic Consultants and trainees, were asked to measure the coronal and sagittal alignment of the tibial and femoral components from the post-operative long-leg plain radiograph of a Unicompartmental knee arthroplasty. A post-operative CT scan using the low dose Imperial knee protocol was obtained as well and analysed with 3D reconstruction software to measure the true values of these parameters. The accuracy and spread of the pain radiographic measurements were then compared with the values obtained on the CT.

On the femoral side, the mean angle in coronal alignment was 1.5° varus (Range 3.8, SD 1, min 0.1, max 3.9), whereas the mean angle in sagittal alignment was 8.6° of flexion (Range 7.5, SD 1.5, Min 3.7, Max 11.2). The true values measured with CT were 2.4° and 11.0° respectively. As for the tibial component, the mean coronal alignment angle was 89.7° (Range 11.6, SD 3.3, Min 83.8, Max 95.4), and the mean posterior slope was 2.4° (Range 8.7, SD 1.6, Min -2, Max 6.7). The CT values for these were 87.6° and 2.7° respectively.

We conclude that the plain radiographic measurements had a large scatter evidenced by the wide ranges in the values obtained by the different observers. If only the means are compared, the plain radiographic values were comparable with the true values obtained with CT (that is; accuracy was good) with differences ranging from 0.3° to 2.4°. The lack of precision can be avoided with the use of CT, particularly with the advent of low-dose scanning protocols.

To evaluate short term results of 126 computer assisted unicompartmental knee arthroplasty (UKA) with ligament balancing.

Between September 2003 and November 2007 we performed 126 computer asssited surgery UKA Preservation. We using kinematic navigation Ci system. This is cemented system with mobile or fixed bearing. Our groups included 72 women and 54 men. Average age at surgery was 71,2 years. The indication for UKA include primary or postraumatic osteoarthritis limited to one compartment, a functional anterior cruciate ligament, no inflamatory disease. In all cases was only medial femorotibial osteoarthritis. Arthroscopic partial medial menisectomy was performed in 25 cases. Approach: medial parapatellar arthrotomy. Clinical evaluation was performed by Hospital for Special Surgery knee scoring system (HSS). Imaging: AP,lateral and stress X-rays.

The average HSS score was 57 point (range, 40–79 points) preoperatively and 94 points (range 62–100 points) postoperatively. 90% patients were classified as excellent or good using the HSS. The average range of motion before surgery: S 0-0-120 gr., 6 days after surgery S 0-0-110 gr. and 3 months after surgery S 0-0-125 gr.

No significant difference in maximum flexion was seen between the preoperative and postoperative values. There were no infection, fracture of tibia plateau, poor pain, or sign of patellar impingement.

UKA together with modern design, reproductible instrumentation and kinematic navigation can eliminate the previous cause of early failures, contralateral tibiofemorial degeneration and tibial loosening. The patient’s selection must be strict regarding (the ideal patient more than sixty years old, low Body Mass Index, low demand of physical activity). Kinematic navigation reduces the possibility of surgeon’s mistake, alignement of the femoral and tibial component, resection level, soft tissue balancing. It increases the accuracy of the comoponent position, especially in the side of the tibia. A continued long term follow-up is necessary to evaluate polyethylene wear after 10 years.

To evaluate first short term results of the 82 Articular Surface Replacements (ASR) of the hip joint with kinematic navigation.

Between March 2006 and March 2007 we performed 82 resurfacings of the hip. In all cases we used Articular Surface Replacement of the Hip joint (ASR-DePuy) with kinematic navigation (Ci system). Our group included 47 women and 35 men. Patients’ mean age at surgery was 68.2 years. The indication for resurfacing was just primary osteoarthritis. Clinical evaluations were conducted using the Harris Hip Scoring system. Imaging studies: AP, axial X-rays.

Patients were followed for an average 12 months postoperative (7–20 months). The average postoperative Harris Hip Total Score was 97%, and 98% of the patients were in the good to excellent range of 80–100 points. No patients were lost to follow-up. We noted a greater range of movement, faster postoperative rehabilitation and shorter time of hospitalization compared with traditional total hip arthroplasty. There were no cases of neurological complication, deep infection, wound dehiscence or dislocation. All X-rays refer correct position of femoral component in both projections. Our experiences with Articular Surface Replacement of the Hip Joint (ASR-DePuy) powered by Ci navigation system are good, but long term followup will be continued.

Articular Surface Replacement of the Hip Joint with modern design, reproductible instrumentation and kinematic navigation can eliminate the previous cause of early resurface failures and loosening. The patient selection must be strict regarding. The kinematic navigation define precise position of the components of ASR. A continued long term follow-up is necessary after minimum 10 years.

There are many reports in the literature about the benefits of computer-aided surgery with regards to improved limb alignment, reduced blood loss and embolic events but surgeons remain sceptical about its routine use because of availability, cost and time implications. To maximise these benefits and overcome the distractions, a modified navigation technique has been developed after evaluation of the standard measurements.

The true varus/valgus angle of the distal femoral cut achieved with navigation is unknown but represents presumed accurate alignment with regards to the mechanical axis through the femoral head. With placement of the femoral tracker in the medial supracondylar region clear of the intramedullary canal, the navigated cut was correlated with the cut placement determined with the standard intramedullary jig in 10 patients undergoing knee replacement. In addition, jigged femoral rotation was checked with the tracker placement. Tibial slope, varus/valgus angle and rotation were determined using surgeon placement of an external alignment jig and confirmed with tracker placement.

The navigated distal femoral cut ranged from +3 degrees to −2 degrees when measured against the distal cutting block stabilised over an intramedullary rod. The femoral rotation was within 1 degree of the trans-epicondylar line as outlined by navigation when a 3 degree externally rotated jig was used. All of the tibial measurements were within 0.5 degrees of the navigated planned positions.

The femoral cuts are presumed to be accurately determined with navigation as judged from long-leg alignment x-rays but this study highlights the potential error if a fixed valgus cut angle with alignment jigs is used. Tibial preparation, however, was accurately predicted by the surgeon using a traditional external alignment jig. Bone preparation time was reduced to 4 minutes (modified technique) compared to 12 minutes (full navigation, p< 0.05).

With this information, computer-aided navigation is now routinely used to determine the distal femoral cut only and an external alignment jig is used for tibial preparation without navigation. The reduction in blood loss and embolic events and improved limb alignment is now achieved with a reduction in preparation time over full navigated techniques. Use of the pinless surface mounted femoral jig alone highlights these advantages further.

One of the most important factors on which Total Knee Replacements results depend is accuracy of restoration of normal mechanical axis. It is believed that computer navigated TKR give better implants position therefore should improve long term results. We decided to check if computer navigation actually improves restoration of mechanical axis and implants placement in a single surgeon, single implant type series. We prospectively assessed 58 patients (60 knees). Each group (navigated versus non navigated) consisted of 30 knees. Patients were assessed clinically and radiographically using weight bearing full-length AP and short lateral films (PACS and IMPAX software). Clinical Results at 2 years were comparable in both groups (89% vs. 88% good or excellent result). Radiological results proved to be better in navigated knees regarding mechanical axis. There were no statistically important differences in other radiological parameters.

This prospective study is designed to assess intra-operative trauma to soft tissue envelope around the knee joint especially quadriceps due to rigid body fixation on the femur and its influence on rehabilitation outcome obtained using a kinematic navigation system for TKR. We also evaluated the impact of the extra time needed to adopt this system on immediate post-operative rehabilitation.

One hundred and sixteen operations were performed with the aid of the kinematic navigation system. Results, including operation time, radiographic alignment of the prosthesis and complications, were compared with non-navigated group. Outcome measures included preoperative knee function, intra-operative factors, blood loss and postoperative rehabilitation.

The operation time (from skin to skin) in the navigation group was average 32 minutes longer compared historical controls. No major complications such as delayed wound healing, infection or pulmonary embolism occurred during this study. Mean blood loss in both the group showed no difference

A higher incidence and duration of early postoperative quadriceps dysfunction was not associated with computer-assisted TKA through the lateral Para patellar approach. No patient who received surgery had a lag of more than 20 degrees, at 48 hours postoperatively, regardless of the duration of intra-operative time used.

Although the total surgical time was longer, it does not translated into increased postoperative morbidity. Use of a kinematic navigation system has a short learning curve, and requires an additional operation time of less than 32 minutes. We found no impact of patients’ perioperative times on short-term outcomes obtained during our learning curve and next two years. The mechanical axis of the leg was within 3 degrees of neutral alignment along with accurate component alignment. The Computer-assisted TKA through a lateral parapatellar approach was not associated with delayed recovery of the patients during early postoperative rehabilitation.

The Authors performed a matched paired study between 2 groups UKR or CA-TKR implanted with a mini-incision (MICA group) in the treatment of isolated medial compartment knee arthritis. The Authors hypothesized that UKR offers a real less invasive surgery with lower economical costs despite a worse limb/implant alignment. Furthermore at a minimum 40 months follow-up they hypothesized that this small implant guarantees still both better clinical score and patient satisfaction than in the MICA group.

Thirty two patients with isolated medial compartment knee arthritis who underwent to a medial UKR from February 2001 to September 2002 were included in the study (UKR group). In all 32 knees the arthritic change was graded according to the classification of Älback ¹. Arthritic change did not exceed grade IV in the medial compartment and grade II in the patello-femoral compartment. All patients had an asymptomatic patello-femoral joint. All patients had a varus deformity lower than 8° and a body mass index lower than 30. No patient had any clinical evidence of ACL laxity or flexion deformity and all had a preoperative range of motion of a least 110°. At a minimum follow-up of 48 months, every single patients in group A was matched with a patient who had undergone a computer assisted TKR performed with a less invasive approach (shorter than 12 cm) for an isolated medial compartment knee arthritis between August 1999 and September 2002 (MICA group) in our hospital. At latest follow-up the clinical outcome was evaluated using both the Knee Society Score and a dedicated UKR score developed by the Italian Orthopaedic UKR Users Group (GIUM). The HKA angle and the Frontal Tibial Component angle (FTC) were measured at latest follow up on long leg standing anterior-posterior radiographs and the mean values between the 2 surgeons assessments were used as final values. Furthermore during the hospital staying we registered in both the groups when each patient was standing comfortably in full weight-bearing according to a self- answered questionnaire and the data were compared. Statistical analysis of the results was performed using parametric test (Student’s t-test). A statistical comparison of the percentage of results for the GIUM score was performed using the Chi-square test. A statistically significant result was given a p≤ 0.05.

Both hospital stay and operative time were statistically longer obviously in MICA group. In the UKR group the mean surgical time was 51.5 minutes (range: 36–75) (p< 0.001) while in the MICA group was 108.8 minutes (range: 80–132) (p< 0.001). In the UKR group the patients remained in the hospital for a mean of 5.1 days (range: 3–7) and in the MICA group 8.2 days (range: 4–16). At the latest follow-up the mean Knee Society Score was 80.5 (range: 70–100) and 78.4 (range: 70–87) for group A and B respectively. No statistically significant difference was seen for the Knee Society score between the 2 groups (p=0.08). The mean Functional score was 83.5 (range: 73–100) for group A and 78.8 (range: 59–90) for group B. A statistically significant difference was seen for the Functional score with superior results for group A (p=0.02). A statistically significant difference was seen for the GIUM score with better results for group A (p=0.01). The mean GIUM score was 76 (range: 67–90) and 73.02 (mean: 65–85) for group A and B respectively. At latest follow up the mean HKA angle was 176.8° for group A (range: 174°–182°) and 179.3° for group B (range 177–182) (p< 0.001). The mean FTC angle was 86.9° (range: 84°–90°) and 89.4° (range: 87°–92°) for group A and B respectively (p< 0.001). All TKR implants were positioned within 4 degrees of a HKA angle of 180° and FTC angle of 90°.

At the latest follow-up (minimum 48 months) no statistically significant difference was seen in the postoperative Knee Society score for either group. However, significant differences were seen between the 2 groups in the functional results and in the GIUM score with better results in the UKR group. All the patients achieved a range of motion greater than 120° and could walk for longer distances. During the hospital staying in this group the patients reported a statistically significant earlier full weight-bearing. This was despite a significant less accurate limb alignment. In addition to inferior results for the computer assisted mini-invasive TKR group the costs of the procedure were obviously greater because of the expensive implants and technology along with statistically significant longer surgical times and hospital stay

The aim of this work was to compare the oxygen saturations in patients in the early period following total knee joint replacement surgery performed using either computer navigation or conventional intramedullary mechanical jigs.

Between August and November 2007 twelve consecutive patients who had computer navigated total knee joint replacements were prospectively reviewed. A comparison group from the same period was made of twenty patients who had knee replacements performed with conventional jigs in this same period. Non-invasive oxygen saturations were measured and recorded as a percentage. Preoperative oxygen saturations measured at the assessment clinic were used a baseline. For the duration of the patients postoperative hospital stay oxygen saturations were measured five times a day as well as their oxygen requirements.

We found that the patients in the computer navigation group on average reached oxygen saturation levels on air equal to those measured in the assessment earlier than the intramedullary jig group (2.2 days versus 2.8 days). There was also a lower need for oxygen and shorter length of stay in the computer navigated group during this early post operative period (4.6 versus 6.0 days).

Previous studies using transcranial Doppler and transoesophageal echocardiograms have shown a reduction of systemic emboli with computer navigated total knee joint replacements. Using oxygen saturation monitoring we have shown there may be a considerable clinical advantage using computer navigated surgery over conventional intramedullary jigs in knee replacement surgery.

Navigated Total Knee Arthroplasty (TKA) is a new technique in our hospital. Any new procedure can be associated with both technical difficulties and difficulties due to patient and theatre staff expectations. The aim of this study was to demonstrate our learning curve and assess patient and staff acceptance. We highlight common technical problems unique to navigation and offer our solutions.

A prospective study of 231 consecutive Emotion TKA were implanted over a 30 month period with Orthopilot version 4.2 Navigation system using soft tissue management (BBraun Aesculap, Tutlingen). They were done by a single knee surgeon previously experienced only in non-navigated TKA. Patient height and weight were measured preoperatively and the BMI calculated. Tourniquet times were recorded digitally with fixed timing criteria. Informed consent was obtained.

Our results showed a significant decrease of tourniquet time with experience (p=< 0.0001) with other possible factors being preoperative deformity and BMI. There was full patient acceptance with the exception of the first patient. The surgical team had to modify patient positioning on the operating table, setup of the theatre and navigation equipment, placement of the scrub staff and delegation of tasks.

Navigated Emotion TKA with Orthopilot software provided a comfortable learning curve. It was readily acceptable to patients and staff and has been adopted as our standard practice. The discussion of problems and the introduction of solutions had a positive effect on building our team. Further investigation is needed to elucidate other variables that affect the tourniquet time.

Aim: To evaluate the accuracy of intra-operative point acquisition during navigated hip replacement using an ultrasound transducer probe relative to a percutaneous digitiser stylus (pointer)

To study intra- and inter-observer variability with the use of the ultra-sound transducer and percutaneous digitiser point probes

To assess the learning curve with the use of the ultrasound transducer probe

As part of a larger cadaver study evaluating navigated total hip replacement via the posterior approach, we assessed data relating to acquisition of bony landmarks of the Anterior Pelvic Plane (APP) by four surgeons with an ultrasound transducer and a percutaneous point probe. The surgeons had differing levels of experience with hip surgery in general, and also with surgical navigation per se, but none of them had previously used the ultrasound probe for the specific purpose of landmark acquisition.

Without fixing an absolute positional value for any of the bony landmarks, the points registered for individual landmarks by each surgeon were then studied, looking at the three-dimensional spread of these points relative to each other about the mean value. The data from all four surgeons were analysed, looking at the global dispersion of points acquired by the ultrasound and percutaneous point digitiser probes.

Our results show that with the exception of a few isolated outliers, the ultrasound probe generated values fell within a +/− 10 mm range. For all four surgeons, the global spread of ultrasound-registered points was noted to be less than that acquired by percutaneous point probe acquisition. Of interest was the finding that points registered by individual surgeons using the ultrasound probe tended to be grouped distinctly together but spatially separate from those of the other surgeons; it would appear that each operator was “homing” in on what he perceived to be the bony landmark in question on the projected ultrasound image.

With the percutaneous pointer probe, and with the anterior superior iliac spines as the target, there was closer grouping of points around the mean positional value for the two surgeons who were experienced with its use. However, at the symphysis pubis, the spread of points for these surgeons were not much different from the other two less experienced one, with these points showing a global spread as great as 25 mm.

Regardless of the experience of the surgeon, the use of the ultrasound transducer probe appears to be more accurate than percutaneous pointer probe for acquisition of the bony landmarks that constitute the anterior pelvic plane. The learning curve associated with its use is seemingly short and steep. Its accuracy is limited by the fact that the identification of the bony land marks on the on-screen display is open to interpretation by the individual. Methods to standardise the identification of these landmarks on ultrasound images may help improve its accuracy in the future.

Valgus knees present a surgically demanding challenge. Dissimilar bone and soft-tissue deformities compared to varus knees complicate restoration of proper alignment, positioning of components, and attainment of joint stability. Our study examined the relationship between tourniquet time and valgus deformity.

A prospective study of all valgus knees were implanted over a 30 month period with Emotion Ortho-pilot version 4.2 Navigation system (BBraun Aesculap, Tutlingen). They were done by a single knee surgeon. Tourniquet times (TT) were recorded digitally with fixed timing criteria. The software recorded all pre- and post-operative deformities. We performed the lateral parapatella approach for all valgus knees. No patella resurfacing was done but all tibiae were cemented.

There were a total of 56 valgus knees (1° to 22°, Mean 5.9°, SD 4.9). The TT varied from 42 min to 121 min (mean 72 min, SD 17.4). There was a statistically significant relationship between TT and Valgus deformity. Tourniquet Time = 59.6 + 2.1 * Pre-operative Valgus (p= < 0.0001, R² = 36.4%)

Thirty six percent of the observations were explained by this analysis. Other factors will need to be considered in future studies. This equation can be used as a guide in the allocation of theatre time. It applies to a specific surgical team and we would expect different teams to have different coefficients. This may be useful in comparisons of different teams.

To describe our experience with computer assisted combined anterior cruciate ligament (ACL) reconstruction and osteotomy. It may provide long-term symptom relief and improved function in patients with medial knee arthrosis and ACL-deficiency, while delaying or possibly eliminating the need for further surgical intervention such as arthroplasty.

Two patients who had medial unicompartmental arthrosis and chronic ACL-deficient knees underwent ACL reconstruction along with femoral osteotomy in one case and upper tibial osteotomy in the other. We used Orthopilot software to perform computer assisted combined anterior cruciate ligament (ACL) reconstruction and osteotomy.

Subjective evaluation at postoperatively indicated significant improvement compared to preoperative evaluation and better scores for patients who obtained normal knee range of motion. Objective evaluation by International Knee Documentation Committee showed improved score postoperatively. Both had minor complications occurred in the immediate postoperative period. The average correction angle of the osteotomy was 7 degrees (7–10).

Computer assisted ACL reconstruction and osteotomy may provide long-term symptomatic pain relief, increased activity and improved function. Only Anterior cruciate ligament reconstruction may not effectively provide pain relief to the ACL-deficient knee with degenerative medial arthrosis. The results of this study suggest that combined high tibial or femoral osteotomy and ACL reconstructions are effective in the surgical treatment of varus, ACL-deficient knees with symptomatic medial compartment arthritis. Computer aided surgery allows precise correction of the axial deformity and tunnel orientation intraoperatively.

Introduction: Revision hip surgery is likely to become more frequent with the continued use of cemented primary hip prostheses.

Primitive stem cells from bone marrow become osteocytes in the presence of hydroxyapatite ceramic (HAC). Consequently there is osseointegration of an HAC surface in bleeding cancellous bone/marrow.

However, damaged bone in the revision situation does not provide the necessary stem cells for osseointegration. Revision surgery using standard length (150mm) HA coated stems is not always satisfactory.

Using a 200 mm stem will extend the operating field into fresh, undamaged cancellous bone and marrow.

Method: Since 1988 more than 2600 HAC hips have been implanted for primary and revision hip cases. This includes 148 revisions. The continued use of primary HAC hips has reduced the necessity for revision hip surgery. There is a dwindling population of cemented, loosening hips requiring revision. Patients are assessed radiologically and using the Harris Hip Score (HHS) pre. and post-operatively on an annual basis.

Results: Since 1991 the longer 200mm stems have been used in 73 cases. The results have been rewarding.

The system works with improved HHS. Defects from debris disease fill in and stems are seen to bond to the host bone particularly at the tip. There have been no prosthetic fractures.

Only one case has needed re-revision when a stem remained un-bonded in the presence of a transverse femoral fracture. Two other stems are probably not bonded. This represents 4% failure.

Discussion: HA bonding is a successful system of fixation in primary hip arthroplasty. Using a 200mm stem in revision cases allows virgin bone marrow to provide the necessary stem cells for fixation. These longer HA coated stems should be used in revision surgery.

Introduction: There are few published reports outlining the outcome of those patients who have undergone revision hip arthroplasty surgery for recurrent infection.

From a consecutive series of 114 patients who had undergone a two-stage exchange without prolonged antibiotic therapy we report the outcome of those patients who continued to have persistent infection.

Methods: Fourteen patients were identified, all with microbiologically proven recurrent deep infection. Seven patients have undertaken further attempts at cure by a two-stage exchange and where again a prolonged course of antibiotic therapy was not routinely used. Infection was eradicated in six out of the seven patients (84%). The mean follow-up of this group is 90 months (range 25–150 months).

Results: From the initial series an overall cure rate of 93% was seen. The other patient has a pseudarthrosis.

Seven patients elected not to undergo a further two-stage revision. Five patients have retained their arthroplasty with lifelong suppressive antibiotic therapy. One has a pseudarthrosis and one disarticulation has taken place for inadequate tissue cover.

Discussion: This series would suggest that in patients willing to undertake further surgery in an attempt to eradicate infection they stand a good chance of a successful outcome.

Introduction: The purpose of this study was to review the results of revision total hip replacement, using cement, done by a single surgeon in a tertiary referral centre. 164 patients underwent revision hip surgery for aseptic loosening, infection or recurrent dislocation.

Methods: 95 patients had a one stage revision, 25 patients had two stage revisions and the remainder had either the stem or socket revised. 10 patients had application of a PLAD for recurrent dislocation. Structural and morselized bone grafting was carried out in patients with extensive bone loss. 46 patients had morselized impaction bone grafting to the acetabulum. The first hundred patients with revision of both components and minimum follow up of twelve months were reviewed. Patients were routinely followed up in the clinic and assessed using the Oxford Hip Score and Merle D’Abigne scores for pain, function and range of movements. Radiographs were assessed for any demarcation or loosening.

Results: The mean age at surgery was 69.99 years (36ys to 95yrs). The mean follow up was 25 months (12 to 60 months). There were 5 dislocations, 2 wound dehiscence, 3 DVT’s and 2 deep infections in the whole group. There were 2 dislocations, 2 DVT, 1 wound dehiscence and 1 infection in the study group. The preoperative scores were available for 83 patients and the average scores for pain, function and range of movements were 3.2, 2.8 and 1.6 respectively. The average scores at the latest follow up were 5.08, 4.2 and 4.0. The mean Oxford Hip scores were 26.65. X-rays showed no demarcation in the acetabulum in 88 patients and in the femur in 92 patients. The trochanter was united in 72 patients. In 13 patients the trochanter had migrated more than 1 cm.

Conclusion: Revision total hip replacement using cement has shown good results in the short term. Cemented revisions are safe, reliable and also cost effective.

Introduction: Extensive bone loss associated with revision hip surgery is a significant orthopaedic challenge. Acetabular reconstruction with the use of impaction bone grafting and a cemented polyethylene cup is a reliable and durable technique in revision situations with cavitatory acetabular bone defects. Slooff et al. (1996) reported the use of cancellous graft alone. Brewster et al. (1999) morselised the whole femoral head after removal of articular cartilage. This paper asks, is it really necessary to use pure cancellous graft?

Methods: 42 acetabular revisions using impacted morselised bone graft without removal of articular cartilage and a cemented cup were studied retrospectively. The mean follow up was 2.6 years (1–5yrs). Clinical and radiographic assessment was made using the Oxford Hip score, Hodgkinson’s criteria (1988) for socket loosening and Gie classification (1993) for evaluation of allograft consolidation and remodelling.

Results: 40(95%) sockets were considered radiologically stable (Type 0, 1, 2 demarcations). 2(5%) sockets were radiologically loose (Type 3 demarcation). There was no socket migration in our series. 27(64%) cases showed good trabecular remodelling (grade 3). 12(29%) cases showed trabecular incorporation (grade 2). Only 3(7%) cases showed poor allograft incorporation (grade 1). Average pre operative Oxford hip score was 41 and postoperative hip score was 27. There have been no socket re-revisions (100% survival) at an average of 2.6 years.

Conclusion: Early radiological and clinical survival results with retaining articular cartilage of femoral head allograft are similar and comparable to other major studies for acetabular impaction bone grafting in revisions. Minimal loss of allograft mass is 40% in obtaining pure cancellous graft. When there is a limited supply and demand of allograft, saving up to 40 % of the material is a valuable and cost effective use of scarce resources.

Introduction: The use of prolonged courses of parenteral or oral antibiotic therapy in combination with a two-stage exchange procedure in the management of the infected total hip arthroplasty is reported by many major series.

Methods: We present a series of 114 patients, all with microbiologically proven chronic deep infection, treated with a two-stage exchange with antibiotic loaded cement and where a prolonged course of antibiotic therapy has not been used. The mean follow-up for all patients is 74months (range 2–175months) with all surviving patients having a minimum 2 year follow-up.

Results: Infection was successfully eradicated in 100 patients (88%). The infection cure rate in our series is similar to that reported elsewhere where prolonged adjuvant antibiotic therapy was used.

Discussion: Using the technique described a prolonged course of systemic antibiotics does not appear to be necessary; the high costs of antibiotic administration, both to the patient and care facility are not incurred.

Introduction: There have been several recent studies outlining the role of femoroacetabular impingement (FAI) as a cause of early osteoarthritis in the non-dysplastic hip. The lesions can either be on the femoral side “cam” or acetabular “pincer”. The aim of surgical treatment of FAI is to improve the femoral head neck offset thereby improving joint clearance and preventing abutment of the femoral neck against the acetabulum. The classic treatment for FAI pioneered by Ganz involves dislocation of the femoral head through a trochanteric flip osteotomy. The procedure is extensive, technically difficult and not without complications.

Hip arthroscopic debridement of FAI lesions offers similar results to open procedures allowing for full inspection of the joint and the treatment of any chondral lesion but with a quicker recovery time. It nonetheless has a very long learning curve and even in the most experienced hands the treatment of impingement lesions is complicated and technically challenging.

The purpose of this cadaveric study was to assess the degree of exposure obtained using two different limited anterior approaches to the hip which would allow effective surgical treatment of cam and pincer FAI.

Methods: We investigated two mini anterior approaches to the hip joint based on the Heuter and direct anterior approach to compare the parts of the acetabulum and femoral head exposed for the treatment of FAI in a total of 20 hips in 10 (5 male, 5 female) cadaveric specimens. Neurovascular structures were recorded in relation to the two approaches. The area of femoral head and acetabular rim exposed via each approach was documented and quantified.

Results: We found that the two approaches were easy and reproducible. Both allowed exposure to the anterolateral aspect of the femoral head. The mean length of acetabular rim accessible via the Heuter approach was 1.9cm (1.1–2.4) and 2.2cm (1.2–3) using the direct anterior approach The area of acetabular rim accessible varied according to the approach (p< 0.001). We also found that the position of the anterior inferior iliac spine in relation to the acetabular rim also affected the area of acetabular rim exposed (p< 0.001). The most proximal nerve branch to sartorious was found 7.3cm (6.5–8.7cm) distal to the anterior inferior iliac spine. The most proximal nerve branch to rectus femoris was located 8.6cm (7–10) distal to the anterior inferior iliac spine and was consistently found to be distal to the nerve to sartorious.

Discussion: Treating impingement of the hip through a direct open approach is not a novel idea. A recent report of failed arthroscopic labral debridement, describes treatment of the underlying bony impingement in some cases by a combination of hip arthroscopy followed by anterior arthrotomy.

In summary cam and pincer impingement of the hip can be treated by either the direct anterior or Heuter approach. The choice of approach would be dictated after careful consideration as to which portion of the anterior acetabular rim required surgery, with more lateral acetabular lesions being favoured by the Heuter approach and more medial impingement sites by the anterior approach we have described.

Introduction: Immune responses in patients susceptible to aseptic loosening may differ to those without this susceptibility. We compared stimulated cytokine mRNA and protein expression in peripheral blood mononuclear cells (PBMC) in 34 subjects (M:F 16:18; mean age 75 years) with previous revision surgery for aseptic loosening versus 28 subjects (14:14; 75 years) with well-fixed implants after Charnley THA for osteoarthritis.

Methods: Extracted PBMCs were stimulated with endotoxin (LPS 200ng/mL), endotoxin-free titanium particles (Ti, endotoxin level =0 Eu/mL), or particles with adherent LPS (TiLPS, 140 Eu/mL). Cell lysate IL-1α, IL-1β, IL-1RA, IL-6, IL-10, IL-18, and TNF mRNA were assayed after 3 hours stimulation using standard rqRT-PCR techniques. Cell supernatant IL-1β, IL-1RA, IL-6 and TNF protein were assayed after 24 hours stimulation using a multiplex method.

Results: mRNA and protein levels in non-stimulated cells were lower in revision versus control subjects for all cytokines (p< 0.05 all analyses). mRNA expression relative to baseline was greater in revision subjects versus controls for all cytokines and all modes of stimulation (LPS, Ti, and TiLPS, p< 0.05 all analyses). LPS induced the greatest inflammatory cytokine response at both the mRNA and protein level in both groups, TiLPS particles induced a more attenuated response, and responses to Ti particles were weakest. In the control group endotoxin free particles showed a negative cytokine mRNA response for IL-1α, IL-1β, and IL-6 (p< 0.05), and reduced protein levels for IL-1β, IL-1RA, IL-6, and TNF versus non-stimulated cells (p< 0.05).

Discussion: Patients with a susceptibility to aseptic loosening have lower baseline but greater stimulated immune responses versus patients without loosening that may contribute to the pathogenesis of aseptic loosening.

Introduction: Antibiotic-associated Clostridium difficile diarrhoea may complicate surgery for proximal femoral fracture. We sought to determine whether a change in antibiotic policy in our unit influenced rates of infection with C. difficile following hip fracture surgery.

Methods: A 4 year case controlled study. A change in antibiotic prophylaxis was introduced during a 3 month period in 2005. Infection rates with C. difficile were compared for 2 years either side of this period. The initial regimen was one of three doses of cefuroxime (1.5 g). The new regimen is a single dose of cefuroxime (1.5 g) with gentamicin (240 mg) at induction. Infection was defined as diarrhoea with a positive isolate within 30 days of surgery.

Results: Prior to the change in prophylaxis, 912 patients underwent surgery for neck of femur fracture. Following the change, 899 patients underwent surgery over the period March 2005 to March 2007. 38 patients developed C. difficile infection (4.2%) in the initial group, compared with 14 patients (1.6%) in the group following the change in prophylaxis (P=0.009). Patients with C difficile infection also had a statistically significant increase in antibiotic exposure, inpatient stay, morbidity and inpatient mortality.

Discussion: The main challenges regarding antibiotic selection are failure of prophylaxis, often because of infection with MRSA, and C. difficile-associated diarrhoea as a consequence of antibiotic prophylaxis. Infection with C. difficile is reduced with the new regimen. We advocate the use of the new regimen as an effective alternative to multiple dose cephalosporins for the prevention of C. difficile infection in this group of high risk patients.

Introduction: The Scottish Arthroplasty Project (SAP) publishes an annual report including infection rates post-arthroplasty having obtained their results from the patients’ ICD-10 codes. The aim of this project was to validate the THR infection rate for one unit as published in the 2006 Scottish Arthroplasty Project (SAP) Report.

Method: The details of the SAP results were obtained. The BGH keeps its own record of post-operative THR infections; only those that met the dates and criteria of the SAP 2006 report were included and compared. The ICD-10 coding status was analysed in more detail.

Results: Published rate of infection in the 2006 SAP report after total hip replacement is three times lower than the unit recorded. 12 patients were eligible (1.49% infection rate), the SAP report recorded 4 cases of infection.

The SAP searches for infection only using three ICD-10 codes. Six ICD-10 codes had been used to classify these 12 patients.

Discussion: A recent cardiac surgery study comparing postoperative mortality rates from hospital statistics with the central cardiac database statistics found an over reporting by the national central database.* We have found the reverse with a threefold under calculation in the national report. However the unreported figures still do not place BGH as an outlier. The reasons for the discrepancy are multifactorial; but include poor coding practice, narrow range of code searching and difficulties in diagnosing infection. This audit shows that investigating the results of not only the outlying units but also randomly picking those who appear to have excellent results is worthwhile.

Introduction: The evolving pattern of bacterial resistance at septic revision surgery to the common antibiotics used during total hip arthroplasty is described.

Methods: A retrospective review of 72 case notes and microbiology data inclusive of bacterial sensitivity profiles was undertaken between January 2002 and April 2007. Data collected was combined with a previous study to demonstrate bacteriology trends over the last thirty years (327 cases). Antibiotic sensitivities to the two common infectious agents, Staphylococcus aureus and coagulase negative staphylococi were formulated into a hypothetical model combined with Gentamycin sensitivity, a constant factor (the sole antibiotic in bone cement), to assess the efficacy of the combination of antibiotics used in primary arthroplasty.

Results: When compared to previous microbiology data percentage isolates of each bacterium were found to be similar, confirming that the infectious agents at septic revision had remained the same, and were the common contaminants at primary surgery. The results also demonstrated an overall trend of increased resistance of the major organisms to the major classes of antibiotics used. Staphylococcus aureus and coagulase negative staphylococci were routinely tested against nine common antibiotics, inclusive of Gentamycin. Critical findings showed that the regimen used in routine primary surgery covers only 67% of staphylococcus infections (cefuroxine and Gentamycin); combinations that showed increased coverage included clindamycin and Gentamycin, and rifampicin plus Gentamycin, providing in excess of 100% coverage, and Erythromycin and Gentamycin, coverage in excess of 80%.

Discussion: Consequently we can recommend from prospective analysis of common infections at septic revision, that the antibiotic regimen at primary surgery is not sufficient to prevent infection (in isolation). Dynamic variations continuously develop in bacteria; genetic make up is regulated to optimise survival, continuously detrimentally affecting the efficacy of antibiotics against the power of super bugs, indicating a pattern in need of continuous monitoring and review.

The Exeter Universal Stem has limited published data with greater than 10 year results, this is from specialist orthopaedic centres using predominantly posterior approach. Our aim was to establish whether the published results could be reproduced in a District General Hospital (DGH) using a Hardinge approach.

We reviewed 131 consecutive primary THRs implanted into 127 patients between 1995 and 1997 (minimum10 year follow up). Surgery was performed through a Hardinge approach using the Exeter universal stem with the Ogee Elite acetabular component.

Outcome was assessed by patient review, completing an Oxford Hip Score (OHS) and reviewing the hospital records. Deceased patients’ hospital records were reviewed and their GP questioned.

5 of 131 hips required revision: 3 for infection at 4–7 years following implantation and 2 for aseptic loosening (one acetabulum only, one both components). There have been no cases of dislocation or sciatic nerve palsy. Kaplan-Meir survival analysis demonstrates ten year survival as follows: 95.3% survival with revision for any cause as the end point; 98.9% with revision for aseptic loosening of the stem as the endpoint, 98.1% with revision for aseptic loosening of the acetabular component as the endpoint, 97.2% with revision for infection as the endpoint.

The mean OHS was 22.7 (median =20, interquartile range 15–26).

This is the first series to report on the 10 year results with the Exeter Universal stem used exclusively in conjunction with the Ogee Elite acetabular component. It is also the first series to report the 10 year results using only the Hardinge approach. Our findings are the first to show that the Exeter universal stem in combination with the Ogee Elite acetabular component can be inserted through a Hardinge approach in a DGH setting with results comparable to surgery performed in a specialist unit and through a posterior approach.

Introduction. Presentation of results by survivorship analysis method offers uniformity of terminology and comparability of results, an essential aspect of scientific communication. The Swedish National Total Hip Arthroplasty Register (SNTHAR) has set the standards with revision as the failure endpoint.

We set out to examine the survivorship after primary Charnley low-frictional torque arthroplasty (LFA) with revision as the end point, but documenting all the operative findings.

Methods & Results. Between November 1962 and June 2005, 22,066 primary operations in 17409 patients had been carried out at the author’s hospital by over 330 surgeons. By June 2006, 1001 (4.5%) hips have been revised.

Survivorship with revision as the end point was: infection 95%, dislocation 98%, fractured stem 88.6%, loose stem 72.5%, loose cup 53,7%.

Infection and dislocation are early problems. With improved cementing techniques stem loosening does not become a problem until 11 years after the primary. Loosening and wear of the ultra high molecular weight polyethylene cup is a significant long-term problem.

Discussion. Since revision is an event interrupting a process, its timing will influence the survivorship analysis pattern and indications and detailed operative findings will become important issues. Since clinical results do not reflect the mechanical state of the arthroplasty to await symptoms would invariably mean that revisions are likely to be carried out late and as such the complexity of complications are likely to increase. Furthermore, if information gathered is of a single “indication for revision”, and not of the operative findings at revision, the information would be of limited value.

Our conclusion is that regular follow-up after hip replacement is essential. The frequency, judged from the revision patterns, would suggest that every two years would not be unreasonable. Recording of all operative findings at revision is essential.

Introduction: We describe our experience with the Exeter femoral component in a District General Hospital. We implanted 230 Exeter Universal stems in 215 patients between 1994 and 1996, which were reviewed at a mean of 11.2 years. Unlike previous studies we have used one acetabular implant, the Elite Ogee Cup in the majority of patients (218/230 patients).

Methods: 76 patients (79 hips) had died, and 121 patients were alive and well enough to attend for radiographic analysis at a minimum of 10 years. One patient was lost to follow up.

Results: No stems were revised for aseptic loosening. Three hips were revised for deep infection. Six acetabular components were revised: 4 for loosening, and 2 for recurrent dislocations. Taking the worst-case scenario including the one patient lost to follow up, the overall survival rate was 94.2%.

Discussion: Our results confirm excellent medium term results of the Exeter Universal femoral component, implanted outside of a specialist centre (either originating centre or teaching hospital). The excellent survival of the Exeter stem, in mix and match combination with the Ogee cup would indicate that this is a successful pairing.

Introduction: The open treatment of hip impingement is now a well-recognised technique with numerous publications about pathogenesis and surgical technique. There are very few publications of very small series discussing surgical results.

We present the results of 148 hips at a mean follow-up of 20 months (range 4 – 55).

Methods: This is a two surgeon series of sequential patients including the early learning curve. Patients were treated for impingement through a Ganz trochanteric osteotomy and open surgical hip dislocation. Patient data, operative findings and methods, complication and clinical follow up were recorded as a prospective audit and include Oxford and McCarthy Non Arthritic Hip scores.

Results: The patient demographics are as follows:

141 patients, 148 hips.

We have had the following complications: 4 trochanteric non unions requiring revision fixation, 2 deep vein thrombosis, 2 haematomas, 1 superficial infection, no deep Infections.

Life table survival curve with revision to arthroplasty defined as failure.

Discussion: The early to midterm results of this innovative procedure are encouraging even when including the decision making and surgical technique learning curves. We will present the hip scores and discuss the failures in detail to warn others embarking on this surgery which cases are more likely to lead to unsatisfactory outcomes.

Introduction: The triple tapered polished cemented C-stem has evolved from the study on long-term results of the Charnley design, when first fractures of the stem and then proximal strain shielding of the femur and stem loosening were identified as the continuation of the same process. The design utilises the common engineering principle of male (stem) and female (cement) tapers engaging under load, loading the proximal femur.

Methods and Results: The C-stem was tested extensively and introduced into clinical practice in December 1993. Up to the end of October 2007, 4558 have been implanted in primary operations.

None of the 4558 stems have been revised for aseptic loosening or fracture.

The patient’s mean age at surgery was 48 years (range 15–76), and 171 hips with a mean follow-up of 11 years (range 10–13.7) have now passed 10 years. There were 97 females and 64 males in this group with 10 patients having bilateral C-stems. The main underlying pathologies were Primary Osteoarthritis 30%, Developmental Dysplasia of the hip 27% and Avascular Necrosis of the hip 19%.

Clinical outcome graded according to d’aubigne and postel for pain, function and movement has improved from 3.1, 3.1 and 2.9 to 5.9, 5.7 and 5.6 respectively.

A good quality proximal femur had been maintained in 47.1% and improved in a further 29.9%.

Discussion: The results achieved with the C-Stem design and technique are encouraging and support the concept of loading the proximal femur, but place a demand on the understanding of the technique and its execution at surgery.

Method: This study reports upon 216 patients (97 Minimally invasive and 119 Standard) enrolled into a randomised control trial comparing a standard posterior approach to the hip with a single incision minimally invasive surgery (MIS) posterior approach at 6 weeks and 1 year post-operatively. Primary outcome measures included operative time, blood loss, length of stay and functional hip scores.

Results: The demographics and pre-operative hip scores for both cohorts were statistically similar. Intra-operative blood loss was significantly reduced in the MIS cohort (p=< 0.01). There was no difference in surgical time (p=0.37), time to discharge (p=0.24) or complication rate between the two groups.

Both groups had statistically improved post-operative hip scores, however, at the 1 year follow-up the MIS group were significantly better in terms of WOMAC, Harris Hip, Merle d’Aubigne and SF-12 scores when compared with a standard posterior approach.

Conclusion: This study demonstrates that MIS THA is a safe, reproducible technique in a DGH. We recommend the use of MIS techniques in primary THA and adhere to the principle that an incision need be no longer than necessary to perform the procedure safely.

Introduction: Between 1987 and 1997 we implanted 319 primary hybrid total hip arthroplasties in 289 patients using the ‘Plasmacup’ (B. Braun Ltd, Sheffield) with a conventional metal on polyethylene articulation. We have observed a high revision rate with this implant recently and therefore undertook a clinical review of this cohort.

Patients and Methods: The indications for surgery were osteoarthritis (223), secondary arthritis (83), inflammatory arthritis (10), and others (3). 17 patients have died and 20 have been lost to follow up. Survival analysis was calculated using implant failure defined as revision (including liner exchange), and includes the censored patients outlined above. Assessment of complications in surviving implants was made using AP radiographs of the hip.

Results: The cup survival rate (Kaplan-Meier method) was 91% at 10 years (95%CI ± 4%) and 67% at 13 years (95%CI +/−9%). The stem survival rate was 96% at 10 years (95%CI +/−3%) and 87% at 13 years (95%CI +/−7%). The median wear in cup revisions for osteolysis was 2.4mm (IQR 1.0–3.2mm), and the median wear in surviving cups was 1.3 mm (IQR 0.8 1.9mm), and was an independent predictor of failure (Cox: p=0.001). There have been 57 revisions (35 cup only, 18 cup and stem, 4 stem only). Indications for revision were osteolysis or loosening (34), wear (18), and infection (5). In surviving cups (214), 29 have expansile acetabular osteolysis and 8 have linear osteolysis. In surviving stems (244), 14 have expansile osteolysis and 23 have linear osteolysis.

Conclusions: There is a high late failure rate of the plasma cup using a conventional metal on polyethylene articulation. Patients with this implant/bearing combination should be closely monitored, particularly after 10 years.

Despite initial enthusiasm for minimally invasive total hip replacements (THR), there has been a marked paucity of level 1 evidence studies assessing it.

100 patients fulfilling the inclusion criteria were randomised in theatre to a standard posterior or muscle-sparing short incision (MIS) approach. A hybrid hip replacement was used routinely. Post-operative management was the same. Follow-up occurred at 2, 6 and 12 weeks. Patients, as well as functional and radiographic assessors were blinded.

50 patients were recruited to each group. There was no difference in demographics Mean incision length was 12.8cm and 19.1cm respectively. There was no statistically significant difference in operation time, post-op functional recovery (ILOA score) or length of stay. Pain (VAS) was similar post-operatively, and at 6 and 12 weeks. There was no significant difference in 10 metre walking speed or 6 minute walking distance at 2, 6 or 12 weeks; nor was there a difference in Oxford hip score, patient satisfaction with surgery (VAS), or SF-12 score at 6 or 12 weeks. Blood loss, fall in haematocrit, transfusion rate and CRP rise were similar. There was no significant difference in cementation of the stem (Barrack) or cup position (Dorr). There was one death from PE in the MIS group and one deep infection in the standard group. There was one dislocation in the standard group. The only statistical difference between the groups was less dependence on walking aids at 2 and 6 weeks in the MIS group; there was no difference at 12 weeks.

MIS surgery is safe, and may allow earlier independent mobility after THR. However, the claims of significantly reduced pain, less morbidity, better function and improved patient satisfaction appear to be unfounded.

Introduction: This minimally invasive (MI) anterior approach has been developed to improve patients’ rehabilitation and long-term function. It is aligned along the interneural plane of Smith-Peterson, with complete preservation of the musculotendinous structures. The femoral neck oeteotomy is performed without dislocation of the joint or resection of the joint capsule. As there is also no additional traction applied to the soft tissues it is one of the most tissue sparing techniques available for THA. The outcome was recorded prospectively and is compared with retrospective data of a conventional lateral approach. No other variables other than the surgical technique were changed for the protocol.

Methods: 55 patients underwent traditional THR (lateral approach) surgery in 2003 and 216 consecutive, non selected patients having an anterior minimal invasive procedure during 2004/05 were followed up for an independent review.

Results: The two groups of patients were comparable in terms of age and BMI. Blood loss dropped by 42%. Hospital stay was reduced by 2.1 days (+/−0.6.) Cup inclination was 45.56 (+/−3.4) in the traditional group and 44.8 (+/−3.7) in the MicroHip group. The dislocation rate was lower in the MicroHip group, being 1/216 compared with 3/55 in the traditional group. Harris Hip score for the MicroHip group was 91.35 at 3 months and 94.43 at 1 year. Average time for return to work was reduced from 8.2 to 2.7 weeks

Discussion: The results show that a truly minimal invasive approach improves the outcome of THR without additional risks. By the use of a treadmill incorporating a dynamic force plate there is even strong evidence that perception and therefore long term results can be improved.

Introduction: Hip Simulator studies show that use of highly cross-linked polyethylene in total hip replacement reduces polyethylene (PE) wear by a factor of 85–98%. Early clinical studies using RSA or computer-aided techniques of polyethylene wear measurement show a reduction of 50–80%. There is speculation about why this discrepancy in the clinical and laboratory data should exist. The results of a randomized, prospective double blinded (surgeon and patient) trial (RCT) of cross-linked versus conventional polyethylene, using a 100% reproducible method of PE wear measurement, are reported.

Materials And Methods: After Ethics Committee approval, the two authors enrolled 124 patients onto an RCT comparing Enduron (non cross-linked PE) and highly cross-linked Marathon PE (DePuy, Leeds, UK). Randomization was performed by the circulating nurse intra-operatively opening an envelope which determined whether the patient received an Enduron or Marathon liner appropriate to the size of the metal shell. Liners were implanted into identical metal shells (Duraloc 300) with one screw. They articulated with identical 28mm CoCr femoral heads and cemented Charnley Elite femoral stems. All patients were followed with anteroposterior and lateral radiographs at 3 days, 6 weeks, 3 months 6 months, 1, 2, 3 and 4 years. PE wear was measured with PWAuto, a validated computer-assisted technique with 100% reproducibility and accuracy of ±0.13mm.

Results: One hundred and thirteen patients had appropriate radiographs and follow-up interval. Mean follow-up was 2.6 years (range 2–4 years). Fifty-eight patients received Enduron liners and 55 patients received Marathon liners. At 6 months (E=0.32, M=0.31mm) and one year (E=0.37, M=0.31mm) the three-dimensional PE wear was identical in both groups. Thereafter, all PE wear measurements showed a significant difference in PE wear between the two groups. Wear of the conventional Enduron group continued (0.51mm at 2 years, 0.70 at 3 years, 0.97 at 4 years), while the crosslinked Marathon group showed virtually no further wear (0.32mm at 2 years, 0.32mm at 3 years, 0.33mm at 4 years).

Conclusions: This is the first study to confirm that Hip Simulator predictions of cross-linked PE wear can be reproduced in-vivo. Randomization, double-blinding, and the use of a 100% reproducible technique for wear measurement add further weight to this data.

Introduction: The long-term results of 70 Harris-Galante I uncemented acetabular components implanted in 53 patients who were under 50 years of age at the time of their hip arthroplasty are presented.

Methods: Follow up was both clinical, using Oxford and Harris Hip scores, and radiological. Kaplan-Meier survivorship analysis was performed to calculate the survivorship of the acetabular components. Failure was defined as either liner exchange or acetabular component revision due to aseptic loosening, osteolysis, infection or dislocation.

Results: The mean age of the patients at the time of surgery was 40 years (range 19–49 years), with follow up of between 12 and 16 (mean 13.6) years. All patients’ acetabular components were implanted primarily with cemented femoral components. The mean Oxford Hip Score at the end of the follow-up period was 20 out of 60 (range 12–46) and Harris Hip Score 81 (range 37–100).

At the end of the follow up period, 11 of the 70 acetabular components (polyethylene liner or the acetabular shell) had been revised. The cumulative survival was 94.0% (95% confidence interval 88.4–99.7) with revision of the metal shell as the end point, and 84.0% (95% confidence interval 74.5–93.5) with revision surgery of the acetabular shell or liner due to any reason as an end point. Radiologically, 4 patients require acetabular revision and 22 patients had femoral osteolysis in gruen zone 7, indicative of polyethylene failure. This gave a combined revision, impending revision and zone 7 osteolysis cumulative survival of 55.3% (95% confidence interval 40.6–70.0).

Discussion: In contrast to cemented acetabular components which undergo aseptic loosening and give groin pain, high density polyethylene lined metal shells do not give groin pain but cause silent acetabular and femoral osteolysis. The danger time for osteolysis is between 10–20 years, therefore follow up at that time is essential.

Introduction: Approximately 0.5 % of patients with metal on metal hip replacements develop post operative pain which is thought to be due to an immune reaction to metal wear particles, known as Aseptic Lymphocyte Dominated Vasculitis Associated Lesion (ALVAL). Treatment usually requires revision to a non metal on metal hip.. Is the development of ALVAL more likely in those patients with high wear rates?

Methods: Retrieved Metal on Metal (MOM) hip implants; periprosthetic tissue and blood samples were obtained from patients (n = 18) undergoing revision for unexplained pain at a mean of 2 years post operatively. The following variables were measured:

linear wear rate (depth of the femoral head and acetabular socket wear patch/time from operation);

All implants and tissue samples were analysed against control samples from patients undergoing revision of MOM hips for fractured femoral neck or impingement.

Results: Linear wear rates of retrieved implants, and blood levels of cobalt and chromium from patients with unexplained plain were greater than from control patients. Histolopathological analysis of tissue showed dense inflammatory infiltrates with healthy looking endothelial cells in all vessels from both patient groups.

Discussion and Conclusion: A painful MOM hip was associated with high wear rates and blood metal levels. The local inflammatory response was similar to “ALVAL”, ie lymphocyte dominated, but not exclusive to those patients with unexplained pain. We question whether ALVAL represents a vasculitis, or merely a classical lymphocyte driven inflammatory tissue response to metal debris particles.

Introduction: This study evaluates the effect on hospital length of stay (LOS) of patients receiving a total hip replacement (THR) as part of a patient centred approach. In order to meet the “18 week” target a pathway was developed by combining the latest research evidence with guidance from the NHS Institute for Innovation and Improvement.

Methods: We prospectively studied the first 134 THR patients who followed the new pathway. The pathway included an enhanced pre-assessment process. Admission dates were mutually agreed and a predicted discharge date of 4 days was provided. All patients attended a pre-operative education session. Patients were admitted on the day of surgery with staggered admission times and followed an intensive physiotherapy program. The surgeons, surgical techniques, and discharge criteria all remained unchanged.

Results: 100% of patients were admitted on the day of surgery and the average time between admission and start of surgery was 2hrs 41mins. All patients walked to theatre and 100% of patients received their first physiotherapy intervention within 18 hours post-operatively. The average length of stay was 3.85 days. 87% of patients went home on or before their predicted day of discharge. The patient feedback was excellent and satisfaction rates were very high. There were no alterations in surgical complication rates compared to before the pathway was introduced.

Discussion: This decrease in LOS was dramatic and highly clinically significant. The average LOS for THR patients prior to commencing this new pathway was 7.5 days. High patient satisfaction rates indicate that by adopting a patient centred approach, significant decreases to LOS can be achieved alongside improving the quality of care. Pressure to meet the “18 week” target provided an opportunity to improve working practice as well as increasing surgical capacity.

Introduction: We report on a group of 20 metal-on-metal resurfaced hips (17 patients) presenting with a soft tissue mass associated with various symptoms; these masses we termed pseudotumours. All patients underwent plane radiography; CT, MRI and ultrasound investigations were also performed for some patients. Where samples were available histology was performed.

Methods: All patients in this series were female. Presentation was variable; the most common symptom was pain or discomfort in the hip region. Other symptoms included spontaneous dislocation, nerve palsy, a noticeable mass or a rash. The common histological features were extensive necrosis and lymphocytic infiltration. Fourteen of the 20 cases (70%) have so far required revision to a conventional hip replacement and their symptoms have either settled completely or improved substantially since the revision surgery. Two of the three bilateral cases have asymptomatic pseudotumours on the opposite side.

Conclusions: We estimate that about 1% of patients develop a pseudotumour in the first five postoperative years after a hip resurfacing. The cause of these pseudotumours is unknown and is probably multi-factorial, further work is required to define this; they may be manifestations of a metal sensitivity response. We are concerned that with time the incidence of these pseudotumours will increase.

Introduction: Hip Resurfacing has increased in popularity, particularly in young, active patients. However, concerns remain regarding metal ion levels, hypersensitivity leading to aseptic lymphocytic-vasculitis-associated lesions(ALVAL) and AVN. The purpose of this study was to document our experience of revising resurfacing arthroplasty for ALVAL.

Methods: All patients undergoing conversion of hip resurfacing to total hip replacement at our institution were reviewed. The notes were reviewed for the reason for revision, the make of the implant, time interval between primary procedure and revision and final diagnosis. Radiographs were reviewed to assess for implant alignment, signs of loosening, neck thinning and AVN.

Results: Out of the 34 patients who had revision surgery 13 were revised for suspected ALVAL, with mean age of 58.8 years at a mean 42.9 months following primary surgery. Of the 13 resurfacings revisions 11 were Birmingham resurfacing and 1 each of Cormet and ASR resurfacing. Groin pain was the presenting complaint in all patients, 5 patients developed their symptoms immediately postoperatively whilst 8 developed symptoms at mean 28.25 months. Haematological investigations were non-diagnostic. Radiographs were normal in 4 patients, whilst 4 demonstrated a loose cup. Thinning of femoral neck and vertical cup alignment were present in 2 patients each while 1 patient had both vertical cup and thinning of femoral neck. All revisions were achieved with primary implants and all patients had immediate pain relief after surgery. Implants and tissue were sent for laboratory analysis. 3 patients had a confirmed histological diagnosis of ALVAL, the remaining cases had identical operative findings and are presumed ALVAL.

Discussion: ALVAL accounts for nearly 1/3 of all our revisions for failed resurfacing arthroplasty. Unexplained pain in patients with resurfacing arthroplasty should be considered for a diagnosis of ALVAL and investigated appropriately. Symptoms tend to resolve reliably following conversion to total hip arthroplasty.

Introduction: Patient selection has been critical to the excellent medium-term clinical results following hip resurfacing. Hypersensivity to metal ion debris has been described in previous generations of metal-on-metal bearings. This may also be a problem that affects modern designs. Characteristic histological changes have been identified (ALVAL). There are few studies that include large female numbers, and show separate outcome and implant survival.

Methods: Eighty-one female hips at a mean of 23 months (11–43) had an ASR hip resurfacing procedure at a single-surgeon independent centre. Mean age was 55 years (28–69). Harris Hip Scores (HHS) were recorded at one-year follow-up. Failures were analysed.

Results: HHS improved from 46.4 (11–77) to 90.2 (27–100). Overall, there was a 7.4 % revision rate. There were 3 femoral neck fractures. In the entire series of 98 female patients there were 3 cases of severe pain requiring revision (3.1%). All three patients had HHS < 50 at one year follow-up. Patients had groin pain, reduced flexion and a painful straight leg raise. Blood results were not suggestive of infection. Aspiration of the hip joint in each case revealed copious amounts of milky green grey aseptic fluid. All had similar macroscopic changes at revision. There were characteristic histological changes in keeping with ALVAL. All 3 patients were revised to THRs with ceramic bearings.

Discussion: The failure rate of 7.4% in the older female group is poor at this early stage following hip resurfacing. The incidence of metal hypersensitivity in our series suggests this complication may be more common than previously thought. Patients with persisting pain of unknown aetiology following resurfacing at other centres may have metal hypersensitivity.

Introduction: Resurfacing hip arthroplasty is a successful option for the treatment of the young and active patient with hip arthritis. However, it is complicated by femoral neck fracture and avascular necrosis, which may result from devascularisation during surgery. Devascularisation maybe caused by thermal necrosis. Thermal necrosis of bone has been shown to occur in temperatures of 47°C and above. We investigated the temperatures generated during femoral head preparation to see if the temperatures reached were great enough to induce osteonecrosis.

Method: Eight patients with osteoarthritis underwent standard resurfacing hip arthroplasty through the posterior approach. From the first over-drilling of the femoral heads until the prosthesis was cemented in place the temperatures generated at the bone surface were recorded using an infra-red thermal imaging camera. Images were captured every 4 seconds as the operation was performed with no interference to the surgeon

Results: The maximum temperatures generated occurred during sleeve reaming at 88.4°C. Seven patients had a temperature recorded greater than 47°C. Removing the femoral caput with an oscillating saw had the highest mean temperature 62.2°C, followed by sleeve reaming (mean 48.7°C). Female patients had the lowest temperature rises and patients receiving the larger femoral prosthesis the greatest temperatures at the bone surface.

Conclusions: Heat generated during femoral head preparation exceeded 47°C in all but one case. Osteonecrosis secondary to thermal insult is likely to occur during femoral head preparation. Strategies need to be devised to decrease the temperatures generated during femoral head preparation.

Thinning of the femoral neck occurs in 77% of patients undergoing hybrid Birmingham hip resurfacing using a posterior approach (Shimmin 2007). Villar recently reported lower neck thinning rates in uncemented Cormet resurfacings (11.7%) compared with hybrid Birmingham resurfacing (13.4%), both via a posterior approach.

We have evaluated implant position and femoral neck thinning in a cohort of 273 uncemented HA coated Cormet 2000 hip resurfacings using ‘B’-series (Titanium/HA coated) cups in 269 patients (mean age 54 years, 39% female) with a mean follow-up of 3 years (range 1–4 years).

Mean cup inclination was 45° (30°–63°), mean SSA 138° (120°–178°). No lucent or sclerotic zones have been identified around the stem of the component. Only one femoral neck fracture has occurred (incidence 0.36%)

We have identified only one case of femoral neck thinning in our series (0.36%).

Whilst Villar has demonstrated a slight reduction in neck thinning rates using the same implants compared to a hybrid fixation Birmingham resurfacing, his neck thinning rates are almost 40 times higher than in our series. Shimmins ‘severe neck thinning (> 10%) rates (27%) are approximately 120 times higher than our series. In addition, we have been unable to confirm the relationship between implant position and neck thinning described by Shimmin in our series using the combined Ganz/uncemented resurfacings compared with Birmingham resurfacings.

Implant design and surgical approach have an impact on ‘neck thinning after resurfacing; we should be wary of treating all resurfacing implants and techniques as a uniform cohort.

Introduction: The Birmingham Hip Resurfacing(BHR) has shown encouraging early to medium term results. It has tended to be used in patients wishing to achieve high functional activity. However there is little data available to support this notion. The purpose of the study was to report the functional levels of patients following BHR.

Methods: Since February 2000, 313 patients have undergone resurfacing by the senior author. Two hundred and sixty four patients with a minimum 12 month follow-up were assessed for functional activity using the modified UCLA activity score. Patients were asked to score their activity level during the pre-symptomatic period as well as pre-operatively and during follow-up.

Results: The mean age at surgery was 55.7 years. The mean follow-up period was 46.72 months. The revision rate for any reason was 3.8%. The mean pre-symptomatic, pre-operative, one year post-operative and final follow-up UCLA scores were 7.9, 3.7, 6.6 and 7.0 respectively. At one year 89% (235 patients) had improved by at least one activity grade from pre-operative levels and 35% (93 Patients) achieved functional scores the same as, or better than their pre-symptomatic levels. This increased to 45% at final follow-up. Of the 242 patients previously involved in moderate activity(UCLA> =5), 31% regained this activity level at one year, rising to 40% at last follow-up. Only 19% of the 180 patients participating in very active/impact sports(UCLA> =8) obtained these levels at one year, rising to 30% at last follow-up.

Conclusion: This is the first assessment of function after BHR comparing pre-symptomatic scores with those obtained during follow-up. Functional scores continue to improve beyond one year in all groups. Significant numbers of patients can achieve functional levels at least as good as before they developed symptoms from their hip, however, the proportion of patients achieving this goal reduces with increasing pre-symptomatic activity.

Introduction: The Birmingham Hip resurfacing was commercially introduced in 1997 and early originating centre series show good functional outcomes. Concerns have been raised over the longevity, functional outcomes and metal ion release from the implants. There are no series of medium term results from an independent district general hospital reported in the literature. We present a prospective series of 100 patients with mean 5 year follow up from a district general hospital. Each patient underwent yearly clinical, hip scoring, and regular radiographic evaluation.

Radiographic analysis was undertaken using Harris’, Hodgkinson’s and Amstutz’s criteria, evaluation of component position, neck narrowing and migration using diagnostic PACS workstations with standardised scaled images.

Results: Between June 2001 and Feb 2004 100 Birmingham Hip replacements were performed by two consultant surgeons (MP, AA). Mean follow up is 61.2 months (range 38–76 months). Harris hip scores (fig 1) improved from 46 pre-operatively to 90 post-operatively and no significant change over the next five years. There were no revisions in this period. Obese patients (BMI> 30) had a significantly (p< 0.03) lower post operative functional score as compared normal patients. No other factors were significant for outcome.

Component position was satisfactory in 93% of cases. Radiographic analysis showed no cups, or stems were definitely loose. Radiolucent lines were present in 8/100 acetabular and 3/100 femoral components, osteolytic lesions were seen in three acetabular components. Mean neck narrowing was 9mm. No patients show any radiographic evidence of avascular necrosis.

Conclusion This independent series shows the results of the Birmingham hip resurfacing are reproducible and comparable to those reported in the originating centre. The Birmingham hip resurfacing gives excellent clinical results, and there is no early evidence of radiographic failure. The high rate of neck narrowing gives us cause for concern and we would recommend regular radiographic follow up.

Introduction: Preliminary results of the Birmingham Hip Resurfacing Arthroplasty were promising. The first series with minimum 5 year follow up was published in 2005 and came from the designing centre. Survivorship and functional results were good. This is the first series with a minimum 5 year follow up not from the designing centre.

Methods: All patients who underwent BHR between the dates of October 1999 and May 2002 were included in the study.

Results: We report 114 of 117 (97% follow up) consecutive metal-on-metal hip resurfacings in 105 patients with a minimum of 5 years follow up. Revision of either the femoral or acetabular component during the study period is defined as failure. We had 4 failures giving a survivorship at 5 years of 96.5% (95% confidence interval (CI) 93–100). The mean follow up was 72 months and the mean age at implantation was 54.5 years old (Range 35–75). All patients were followed up clinically and radiographically.

The mean Harris hip score at follow up was 96.4. The mean Oxford Hip Score fell from 41.6 preoperatively (Range 16–57) to 15.3 postoperatively (Range 12–49) p< 0.0001. The UCLA Activity Scale rose from 3.93 preoperatively (Range 1–10) to 7.54 postoperatively (Range 4–10) p< 0.001.

Radiographic analysis revealed an average stem shaft angle of 130.6 degrees (Range 112–148) with average cup alignment of 36 degrees (Range 22–47). Neck thinning was present in 16 hips (14%) and we define a technique for measuring thinning.

Discussion: This study confirms that metal-on-metal resurfacing produces an excellent clinical and functional outcome in the younger patient who requires surgical intervention for hip disease. The results compare favourably with those from the originating centre and confirm that resurfacing is well suited for younger higher demand patients.

Introduction: Over 20,000 DePuy ASRTM hip resurfacing procedures have been performed since 2003, the implant design applying modern engineering and tribological principles to minimise metal-on-metal bearing wear. Enhanced fixation of both components, high-carbon cobalt-chromium alloy, reduced material thickness and small diametral clearance 100–150 microns are all supported by non-clinical testing. There are published reports of very low wear on hip joint simulators (Dowson D, et al. 2004 Dec;19(8 Suppl 3):124–30.), low wear on retrieval analysis (Morlock MM et al 1: Proc Inst Mech Eng [H]. 2006 Feb;220(2):333–44.) and excellent clinical results (Siebel T et al, Proc Inst Mech Eng [H]. 2006 Feb;220(2):345–53. We recently reported median whole blood chromium and cobalt ion levels of 1.56 ppb and 1.65 ppb at 24 months (Cobb AG et al, British Orthopaedic Association Congress 2007)

Methods: 1030 consecutive cases carried out by 3 of the surgeon-designers between July 2003 and May 2007 have been studied prospectively at annual intervals. 2 to 4 years follow-up data is available on 293 hips.

Results: There have been 11 revisions for fracture (1.06%), 6 in patients aged over 65 years(3.4%), 5 in patients aged up to 65 years (0.6%) (P< 0.001).

There have been 3 revisions for cup loosening (0.29%) and 3 for pain (0.29%). 5 patients have died (0.51%). There was one revision for infection and one for impingement.

Average Harris Hip Score rose from 57.0 to 97.1, and 60% of patients scored 100.

UCLA activity score was 6 or over in 91%, and the median score was 7.5.

All failures were evident by 12 months

The Cumulative Survival Rate at 3 years was 97.4%,, 99.5% for 55 years and under, 98.3% for under 65 years, and 94.2 % 65 years and over.

Discussion: The 2 to 4 year clinical follow-up of the latest generation of surface hip implants is satisfactory. Technical errors during implantation or patient selection accounted for most of the failures. The risk of failure between 12 months and 4 years is low.

Introduction: Total hip-joint arthroplasty is associated with a high rate of peri-operative blood transfusion, which has associated risk. Previous studies have identified individual factors than can predict those patients most at risk of post-operative allogenic blood transfusion. We undertook this study to attempt to identify further factors that may predict post-operative blood transfusion.

Methods: Data was collected pre-operatively for patient demographics including type of surgery, sex, age, BMI, ASA, pre-operative haemoglobin & pre-operative packed cell volume for all total hip arthroplasties performed by a single surgeon over twelve months (Total number 233; 166 primaries, 33 resurfacing & 20 revision arthroplasties: 14 excluded for insufficient data). Post-operative data collection included post-operative haemoglobin levels and allogenic transfusion requirements.

Results: Of 166 patients who underwent primary hip arthroplasty, 25 (15.1%) received allogenic blood transfusions, an average volume of 2.1 units per patient transfused. Analysis revealed significant predictive factors of gender (females > males, p=0.0019), advancing age (p=0.0045), lower height (p< 0.0000), lower pre-operative weight (p=0.0010), lower pre-operative haemoglobin (p< 0.0000), and lower pre-operative packed cell volume (p< 0.0000). Patients who underwent revision surgery were also more likely to have undergone transfusion compared to both primary (6.1% transfused, p=0.025) and resurfacing arthroplasty (35% transfused, p=0.009). BMI and ASA were found to not be significant risk factors. Pre-operative packed cell volume (PCV) showed the strongest correlation with post-operative blood transfusion. Cases with a PCV below the average of 39% had a rate of transfusion of 28%, 6.4 times greater than for those patients above the average at 4.4% (p< 0.0000).

Discussion: Pre-operative measurements of height, weight, haemoglobin and packed cell volume, together with factors including sex & type of surgery can identify those patients who are at greater risk of post-operative transfusion allowing selective transfusion prevention strategies.

Introduction: Effective utilisation of blood products is fundamental. The introduction of Maximum Surgical Blood Ordering Schedules (MSBOS) for operations provides guidance for effective cross-matching. A retrospective analysis of blood ordering practices was undertaken to establish an evidence-based MSBOS for revision THR and TKR. The impact of the use of intraoperative cell-salvage devices was also assessed.

Methods: The patient database was searched for cases of revision THR and TKR undertaken over 58months. These records were then cross-referenced with the transfusion database. The cross-match to transfusion ratios (CTR) and transfusion indexes (TI) were calculated using this data.

The gold standard for the CTR is 2:1 or less. Procedures with ratios greater than 3:1 should substitute for a ‘group and save’. The TI establishes the likelihood of blood being transfused for a certain procedure, i.e., the number of units transfused divided by the number of patients having the procedure. If the TI is less than 0.5, then cross-matching blood is considered unnecessary.

Results: For revisions of non-infected THR (n=269), the CTR=2.24 and TI=1.67. In infected cases (n=69), CTR=2.16 and TI=1.68.

In revisions of non-infected TKR (n=95), the CTR=4.33 and TI=0.48. In infected cases (n=54) the CTR=2.16 and TI=1.35.

There was considerable change in the practice of ordering cross-matched blood following the introduction of intraoperative cell-salvage devices (Revision THR: CTR=1.93, TI=0.84; Revision TKR: CTR=1.20, TI=0.16)

Discussion: The analysis confirmed that more blood was requested than was actually required. Overall the results suggest that cross-matching is still necessary for both the non-infected and infected revision THR but the number of units requested could be reduced to 2units. In revision TKR, transfusions were more likely in infected cases and, a ‘group & save’ may be sufficient for non-infected cases.

The introduction of this MSBOS in conjunction with intraoperative cell-salvage, could promote blood conservation and financial savings.

Since 2003 we have adopted an aggressive approach to the management of the SUFE deformity, an important cause of anterior femoro-acetabular impingement, associated with the development of early adult hip arthritis.

16 patients aged 16.7 years (range 11–20, 3 female, 13 male, 8 right, 8 left hips) underwent surgery to manage their SUFE deformity.

7 patients had secondary correction of deformity after previous in-situ pinning and 9 underwent primary surgical management using a Ganz approach (7) or primary in-situ pinning with femoral neck resection via a Smith-Peterson approach (2).

Of the 7 patients who had primary in-situ pinning 26 months (range 4–44 months) earlier, 2 had acetabular chondral flap tears with eburnated bone and 6 had significant labral degenerative changes associated with calcification or tears.

Only one of the nine patients who underwent primary aggressive management of their SUFE, had a labral tear.

4 patients underwent mobilisation of the femoral head on its vascular pedicle followed by anatomical realignment.

At an average follow-up of 22.3 months (range 1–41 months) 15 remained well with excellent function. Leg lengths remained equal in 12, with an average shortening of 2cm in the remaining 4 patients.

Segmental AVN occurred in the first patient after damage to the vascular pedicle during drilling of the neck; the technique has been modified to prevent further occurrences.

Removal of the trochanteric osteotomy screws has been performed in 4 cases.

Despite having performed over 400 surgical hip dislocation, the authors continue to find the management of this condition challenging; nevertheless, having seen the direct consequences of femoro-acetabular impingement at an early stage in these young patients, we believe that aggressive management to correct anatomical alignment is essential for the future well being of the hip.

We present the results of prospective evaluation of digital compared to plain radiographic pre-operative templating for primary total knee replacement. All consecutive patients undergoing primary knee replacement under the senior author (AS) were eligible. Patients with previous knee replacement or without calibrated digital or plain radiographs were excluded. Plain radiographs were templated against acetate templates supplied by the manufacturer. Digital images were templated with the help of commercial software TraumaCad. A 25mm spherical metal ball placed nearest to the affected knee joint acted as calibration object. AS performed all the templating. The ICC value for intra-rater reliability was 0.846 for tibial templating and 0.840 for femoral templating. PFC sigma cruciate substituting components were implanted in all patients. 28 consecutive patients between April 2006 and June 2007 were included. Accurate digital templating score was 80% for tibial implant and 40% for femur. Accuracy of analog templating was 55% for tibial implant and 50% for femur. There was no mismatch of over one size. The differences between templated and implanted sizes were plotted against their mean in Bland-Altman plot. The 95% confidence interval of the differences between digital and actual sizes were: 0.78 to − 0.75 sizes for tibial implant and 1.15 to −0.93 sizes for femoral implant. The 95% confidence interval of the differences between plain and actual sizes were: 0.38 to −0.99 size for tibial implant and 0.93 to −1.32 size for femoral implant. The two tailed P value for difference between digital and analog templating from a Wilcoxon matched pair signed rank test was 0.021 for tibia and 0.006 for femur. We found preoperative templating by the operating surgeon reliable and accurate but digital templating did not offer any additional advantage.

We aimed to determine the reliability, accuracy and consequently the clinical role of digital templating in the pre-operative work up for total knee arthroplasty patients.

With the increasing use of digital radiology images, analogue templating may soon be defunct. Digital templating is a more recent development and its role is yet to be determined.

Ten pre-operative digital radiographs were templated by four independent observers. Inter-observer and intra-observer reliability was assessed using the kappa measure of concordance. Subsequently, 40 consecutive total knee arthroplasty patients underwent pre-operative digital templating. This was a blinded process by a consultant surgeon not involved with the operation. Each patient underwent TKR using the PFC Sigma System sized intra-operatively, without the operating surgeon having knowledge of the pre-operative templating result. Comparison was made between the pre-operative digital templates and the blinded intra-operative sizing.

For both the femoral and tibial templating there was good to very good inter- and intra-observer agreement. For the femoral component the templating was correct in 47.5% (± 1 size difference 97.5%). The tibial templating was correct in 55% (± 1 size difference 100%).

The inter- and intra-observer reliability of digital templating process has been shown to be acceptable but the correlation between digital templating and the actual size implanted is poor. Our series shows a similar accuracy to the published data on analogue templating for the same implant. Like analogue templating, its clinical role remains uncertain and its poor correlation to the actual implant sizes limits its usefulness.

There is little good evidence about the relative merits of different knee replacement designs as no adequately powered randomised controlled trials have been undertaken. To address this, a pragmatic multi-centre randomised trial involving 116 surgeons in 34 UK centres was begun in 1999. Within a partial factorial design 1715 patients were randomly allocated to patella resurfacing or not, 539 to mobile bearing or not and 409 to metal backing of the tibial component or not. Primary outcome measures are the Oxford Knee Score (OKS), SF-12, EQ-5D and need for further surgery.

At two years there was no evidence of differences in complications, clinical outcome, functional status or quality of life measures between randomised groups.

95% of the patient are now 5 year post-operation and have been sent questionnaires. 93% of these have been returned. By January 2008, all will be past 5 years and will have been sent questionnaires. When the complete 5 year data set is available it will be analysed. The 5 year data relating to the randomised groups will be presented.

Purpose of Study: To assess the safety of our practice of Bilateral Simultaneous Total Knee Replacements.

Methods: We retrospectively reviewed 202 patients (404 knees) who underwent bilateral simultaneous total knee replacements using the DePuy PFC Sigma Cruciate Sacrificing Endoprosthesis between January 2000 and January 2006. There were 103 males and 99 females with an average age of 71.3 years (range 41–90 years) included. Indication for surgery was Osteoarthritis in 190 patients and Rheumatoid Arthritis in 12 patients. All patients were reviewed at 6 weeks, 1 year and then yearly post surgery.

Results: The average hospital stay was 12.4 days (range 5–38 days) with 6 patients needing HDUadmission post surgery. The average observed blood loss in the drains post surgery was 1200ml (700–2600ml) with an average drop in Haemoglobin of 4.1%, 71% of patients needed a blood transfusion post surgery. Two patients (0.99%) developed a deep vein thrombosis and 2 patients (0.99%) developed a pulmonary embolus.3 (1.48%) deaths were encountered in the immediate post operative period (within 30 days of surgery) and 6 (2.9%) patients suffered a myocardial infarct post surgery.14 (6.9%) patients developed a superficial wound infection of which 10(4.9%) needed a formal washout. 8(3.96%)knees needed a manipulation under anaesthesia for a poor range of movement, and 2(.99%) needed revision total knee replacement for infection.

Conclusion: Bilateral simultaneous total knee replacement is a safe procedure in our experience Complication rates observed comparable to published literature on the subject

Introduction: We report our experience with use of the SMILES prosthesis in primary knee arthroplasty.

Methods: The Stanmore Modular Individualised Lower Extremity System (SMILES prosthesis) has been shown to be effective in complex revision knee surgery. It incorporates a rotating hinge platform knee joint and can overcome the major problems of bone loss and ligamentous laxity.

38 patients (41 knees) who received a primary SMILES knee prosthesis by one of the senior authors between 1990 and 2006 were retrospectively studied. Knee function was assessed pre and post-operatively using the Oxford knee score (0–48 scoring system) and the Knee Society Score. Patients receiving surgery for tumours were excluded. The main indications for primary SMILES were bone loss and ligamentous laxity.

Results: The minimum follow-up was 18 months with a mean of 5 years (1–17). The mean age of the patients was 57.7 years (23–86); 15 of the patients were male. The indications for surgery were trauma (12), osteoarthritis with deficient medial collateral ligament (8), polio (7), rheumatoid arthritis (5), epiphyseal dysplasia (4), achondroplasia (2), avascular necrosis (1), osteogenesis imperfecta (1) and ankylosing spondylitis (1).

2 patients died and 5 were lost to follow-up. 2 patients required revision surgery (one for infection and one for re-bushing). Post-operative complications included peroneal nerve palsy (1) and DVT (1). The mean Oxford knee score improved from 9 pre-op to 44 post-op, and the mean knee society score improved from 24 pre-op to 71 post-op. The average range of motion was 57 degrees pre-op and 88 degrees post-op.

Conclusion: We conclude that the SMILES prosthesis offers significant improvement in clinician and patient assessed outcome scores in complex primary knee arthroplasty. The cost compares favourably with other designs and its use is well established.

Purpose: The aim of this study is to compare the long-term survival results of TKA in patients under the age of 60, using

revision surgery and

Method: From our knee database we identified a cohort of 60 total knee replacements that had been performed over 15 years previously. We identified those who had died, those who had been revised and established the Oxford Knee Score (OKS) for all those still surviving.

Results Using the following endpoint criteria the cumulative 15-year survival was (A) revision surgery alone = 78% (CI 12), (B) revision surgery or an OKS less than or equal to 24 (50% of total OKS) = 63% (CI 13), and (C) revision surgery or moderate pain = 48% (CI 14).

Conclusion The functional survival of TKA in patients under the age of 60 decreases in the second decade following implantation with a significant number of prostheses failing the patient due to knee pain

Introduction: The aim of this study was to investigate the function, limitations and disability of a large cohort of active golfers following total knee replacement (TKR).

Materials & Methods: The study group comprised the membership of the New Knee Golf Society (NKGS), UK. 211 members were reviewed with a questionnaire which asked the patient’s experience & difficulties of playing golf before and after TKR. The functional outcome was recorded using the Oxford knee score.

A total of 299 knees in 209 patients were included in the final analysis. The mean age was 69.6 years. Majority of the prostheses were cemented (95%) and had patellar resurfacing (89.6%). The mean post-operative period was 5.1 years.

Results: 196 patients (94%) returned to playing golf after a mean 4.6 months following the TKR. 184 (88%) continue to play at review. 92.8 % claimed significant improvement in their ability to play and enjoy golf following TKR citing reduction in pain and improved walking ability as the reasons. However, none claimed to have achieved a significant improvement in their handicap.

17 knees (5.7%) underwent revision surgery. 6 knees (2%) were revised for infection at mean 17.3 months & 11 (3.7%) for aseptic loosening or instability at mean 4.9 years. 7 left knees (lead knee) of 11 right-handed golfers required revision for aseptic loosening.

The main problems experienced after playing 18 holes were knee stiffness (47%) & swelling (18%).

Conclusion: Although the ability to play improved the handicap remained the same. The left TKR in a right-handed active golfer is more likely to require revision which may be due to the increased torque on the lead knee.

To establish the efficacy of a new arthroscopic technique, for the treatment of stiffness after TKR.

Introduction: The usual surgical procedure for stiffness after a total knee replacement is an open arthrolysis, though an arthroscopic procedure can be considered within six months of the index surgery. We have evolved a new procedure of capsulectomy and anterior release which can be used at any time after TKR in patients with a reduced range of movement (ROM).

Methods: 22 patients (10 women and 12 men) underwent arthroscopic capsulectomy and anterior release for the treatment of loss of movement after TKR. The mean age was 62 (range 47–71 yrs). Mean time between TKR and arthrolysis was 27 months (range 3–54). Indication for the arthroscopic procedure was decreased ROM following TKR. Arthroscopy was performed using anteromedial and anterolateral portals. The dense scar tissue was divided and completely excised arthroscopically. ROM was assessed pre-operatively, immediately post-operatively and at 2, 6, 12 weeks, 6 months and 1 year. The Oxford Knee Score (OKS) and American Knee Society Score (AKSS) were used pre-operatively and at 6 months and 1 year post-operatively.

Results: Pre-operatively mean flexion was 50 degrees (Range 20–90°). Post-operatively it was 94.5° (Range 55–125°). At 1 year this was maintained. The mean OKS pre-operatively was 18.4 (range 8–39). At 1 year it was 29.8 (range 9–39). The AKSS (knee and functional components) showed a similar improvement. The mean knee score increased from 47.3 pre-operatively to 71.6 at 1 year. The functional score rose from a mean of 51.3 pre-operatively to 76.9 at 1 year.

Conclusions: Our technique of arthroscopic capsulectomy and anterior release for the treatment of stiffness following TKR is both successful and safe. At 1 year post-operatively the patients have maintained an increased ROM and significantly improved Oxford and American Knee Society Scores.

The aim of this work was to compare the oxygen saturations in patients in the early period following total knee joint replacement surgery performed using either computer navigation or conventional intramedullary mechanical jigs.

Between August and November 2007 twelve consecutive patients who had computer navigated total knee joint replacements were prospectively reviewed. A comparison group from the same period was made of twenty patients who had knee replacements performed using conventional jigs. Non-invasive oxygen saturations were measured and recorded as a percentage. Preoperative oxygen saturations measured at the assessment clinic were used a baseline. For the duration of the patients postoperative hospital stay oxygen saturations were measured five times a day as well as their oxygen requirements.

We found that the patients in the computer navigation group on average reached oxygen saturation levels on air equal to those measured in the assessment earlier than the intramedullary jig group. There was also a lower need for oxygen in the computer navigated group during this early post operative period.

Previous studies using transcranial Doppler and transoesophageal echocardiograms have shown a reduction of systemic emboli with computer navigated total knee joint replacements. Using oxygen saturation monitoring we have shown there may be a considerable clinical advantage using computer navigated surgery over conventional intra-medullary rod jigs in knee replacement surgery.

Aim: The purpose of this study was to report our experience mid to long-term results of hybrid cement fixation in revision total knee arthroplasty.

Methods: Patients who underwent revision total knee arthroplasty using a hybrid cement technique (press-fit diaphyseal fixation and cemented metaphyseal fixation) with a titanium fluted revision knee implant were reviewed. There were 127 patients. Mean age at surgery was 71 years (range 41–94 years). There were 56 males and 71 females. Mean follow-up was 5 years (range, 2–12 years). A Kaplan-Meier survivorship analysis using an end-point of revision surgery or radiographic loosening was employed to determine probability of survival at 5 and 10 years.

Results: 127 patients (135 knees), 31 patients (36 knees) died and 2 patients (2 knees) were lost to follow-up. Six patients (six knees) were revised at a mean of 3.5 years (range 1–8 yrs). Of the 6 revisions, two were for re-infection, two were for (MCL) instability, and two were for aseptic loosening. Mean Knee Society clinical and functional scores were 86 and 55 points, respectively. The mean range of motion was 108 degrees. End of stem pain was not reported in this group of patients. Kaplan-Meier survivorship analysis revealed a probability of survival free of revision for aseptic loosening of 98% at 12 years.

Discussion: The results of this study suggest that the use of a hybrid cement technique in revision knee arthroplasty can provide good mid to long-term results. Radiographic analysis has shown continued satisfactory appearances regardless of constraint, stem size and augments. Our experience has shown that the survivorship of a hybrid fixation technique for revision knee arthroplasty is comparable to reported long-term survivorship of cemented revision knee arthroplasty.

Purpose: To examine the outcome of primary and revision knee arthroplasty in very elderly patients.

Methods and Results: Patients in their 90th year of life who underwent primary or revision knee arthroplasty between January 2000 and September 2007 were identified. Data was collected regarding demographics, ASA grade, co-morbid factors, complications, length of inpatient stay, the need for transfusion and discharge destination. Thirty day, 1 year and current mortality figures were calculated.

Twenty one procedures were performed on 18 patients with a mean follow up of 18.8 months (3–57.9). There were 14 primary total knee replacements and 7 revision procedures. The mean age at the time of surgery was 90 years and 10 months (89 years 1 month to 94 years 4 months). The majority of patients were female (15). All patients were ASA grade 2 or 3. The average orthopaedic inpatient stay was 17 days. Thirty percent of patients required a period of further inpatient rehabilitation or convalescence after discharge from our institution. Nine patients experienced a post-operative complication. Mortality at 30 days was 0%, at 1 year 6% (1/16), and is currently 17% (3/18).

Conclusion: Very elderly patients are able to tolerate primary and revision knee arthroplasty although there is a high rate of peri-operative complications. We propose that there should be a different tariff for arthroplasty procedures in extremely elderly patients to reflect the increased rate of complications and prolonged postoperative hospital stay.

The purpose of this study was to determine if a single physiotherapy intervention would enable patients to kneel following Unicompartmental knee arthroplasty (UKA).

Kneeling is an important functional activity that is frequently not performed after knee arthroplasty, thus affecting a patient’s ability to carry out basic tasks of everyday life. There is however no clinical reason why patients should not kneel and many with proposed knee surgery ask about the possibility of kneeling after their operation.

Sixty adults participated in a prospective randomised controlled trial with blinded assessments. At 6 weeks post-operatively UKA patients were randomised to either the Routine care group where no advice on kneeling was given or to the Kneeling intervention group where participants were taught and given advice on how to kneel and were encouraged to do so. They were re-assessed at 1 year. The primary outcome measure was Question 7 of the Oxford Knee Score which asks the question “Could you kneel down and get up again afterwards?”

Pre-operatively there was no difference in the kneeling ability of the two groups. At 1 year the difference in kneeling ability between the two groups was highly significant (p< 0.05). Spearman’s correlation coefficient showed no significant association between a change in score of Question 7 at 1 year and the following factors; scar position, numbness, range of flexion, arthritic involvement of other joints and pain. Linear regression analysis also confirmed that these factors were not successful in predicting a change in kneeling ability.

This study showed that the single factor predictive of kneeling ability was the physiotherapy intervention provided at 6 weeks post-operatively and it is suggested that kneeling should be incorporated into patient’s post-operative rehabilitation programmes.

Purpose: To evaluate the effects of underhanging/overhanging tibial components on clinical outcome following the Oxford unicompartmental knee arthroplasty (UKA), and to identify an acceptable sizing limit.

Method: One hundred and sixty-three knees which had undergone the Phase 3 medial Oxford UKA (Biomet, Swindon) were measured. Based on five-year post-operative radiographs, they were divided into groups with tibial component underhang (n=38), none or minimal overhang of less than three millimetres (n=121), and a group with overhang equal to or in excess of three millimetres (n=13). Clinical outcome was assessed by changes in the twelve-question Oxford Knee Score (ΔOKS) and pain score (ΔPS) component (questions 1,4,5,8,9) from pre-operative assessment to five years following surgery.

Results: At five years after surgery, ΔOKS was significantly worse in the overhang group compared to both the neutral and underhang groups (p=0.015, and p=0.028 respectively). ΔPS was also shown to be significantly worse between the overhang and the neutral group (p=0.026 respectively).

Conclusion: Appropriate sizing of the tibial component is essential to optimise load bearing in total knee arthroplasty. In UKA such sizing is critical due to halving of the bony support for the tibial component and the lack of room for a large stem. Excessive undersizing of the prosthesis may lead to subsidence and loosening, whilst excessive overhanging may cause local soft tissue irritation and pain.

This study demonstrates that medial overhang of less than three millimetres for the tibial component is acceptable in the Oxford UKA. Excessive overhang equal to this or more results in significantly worse ΔOKS and ΔPS. However, no difference in the five year ΔOKS and ΔPS was demonstrated between underhang and the other two groups in this study.

Following introduction of the second offer scheme in April 2004, Cardiff and Vale NHS Trust sent 227 patients (254 knees) to the independent sector treatment centre in Weston-Super-Mare for total knee arthroplasty. The Kinemax total knee system was used in all cases.

There was a perception that there were a large number of dissatisfied patients, and a previous British Orthopaedic Association report (of a 14 case sample) questioned the quality of the surgery performed.

All of the patients concerned were offered a review in order to assess the outcome. Of the 227 patients (254 knees), 77% have been reviewed (167 patients, 190 knees). 23% (59 patients, 64 Knees) have not been seen. Of these, 30 patients (34 knees) declined review on the basis that they were happy with the result of surgery. 14 Patients (15 knees) were unobtainable by post of by phone. A further 12 patients (12 knees) did not attend appointments. 3 Patients (3 Knees) had died.

The total number of re-operations was 27/254, giving a re-operation rate of 10.6%. There were 21 revisions, 17 for aseptic causes (oversized components, malalignment, aseptic loosening) and 4 for infection. There were 6 secondary patella resurfacings.

A life table survivorship analysis was calculated for the 254 knees. The cumulative survival rate at 3 years was 85.8%. These results are considerably worse than those reported in the current published literature. This has resulted in a significant economic impact on our service.

Aims & Objectives: To assess whether the incidence of infection in Primary Total knee Arthroplasty is increased as a result of previous steroid infiltration into the knee joint.

Introduction: Steroid injection into the arthritic joint is a well-known modality of treatment of the arthritic joints. Its efficacy is well documented. Increased incidence of Infection secondary to steroid injection as compared to uninjected joints is reported in recent literature.

Material & Methods: 440 patients underwent Total Knee replacement (PFC SIGMA-Depuy) by senior author during 1997–2005 at Wrightington hospital. 90 patients had intraarticular steroid injection prior to surgery of which 45 patients had injection with in 1 year prior to surgery. All patients had at least one year follow up. Infection rate was assessed by case note, x-rays and microbiology review till last follow up.180 patients of a matched cohort who had total knee replacement without steroid injection were compared for infection rate.

Results: 2 cases of superficial infection were noted in Injection group and 5 cases of superficial infection in Non Injection group. No cases of Deep infection noted in either group. Stastical analysis showed no significant difference in incidence of infection in either group.

Conclusion: Steroids are useful adjuncts in the management of patients with arthritic joints. This study shows no increased incidence of infection in patients given steroid injection prior to arthroplasty.

Removal of solidly fixed implants is a challenge in revision knee arthroplasty. It is fraught with the risk of intraoperative fractures and bone stock vital for the success of subsequent revision surgery. We describe the double extraction technique for extraction of solidly fixed implants. This technique was first tested in laboratory setting and then replicated in the operation theatre with successful results.

In this retrospective study we analysed all our patients in which we used the double extraction technique for the removal of solidly fixed implants. In this procedure, the surgeon and the assistant each place an osteotome on the cement metal interface at symmetric positions, directly opposite each other on the medial and lateral sides. They deliver synchronous blows with a mallet at positions around the interface until the cement fractures. The femoral component can then be easily removed. The technique was tested in a laboratory before it was used clinically. Polyurethane mouldings, representing a suitable substrate for cementing metal components were fixed on to a steel rod of similar weight and length as the lower leg. Stainless steel discs (40mm diameter × 4mm thickness) were cemented on to the polyurethane substrate to form a model of a cemented implant. The discs were instrumented to allow recording of the mechanical processes caused by the double extraction technique and to allow comparison with the single osteotome extraction technique. The methodology successfully demonstrated that the double osteotome technique increases the contact force of the second blow. When the synchronous blows are delivered, less energy is expended in the movement of tibia and more is contributed to the removal of the component.

In this study we looked at a total of 206 patients were the solidly fixed tibial and femoral components were removed using the double extraction technique. There were 86 men and 126 women. The mean age of the patients was 66.8 years (range 37–87 years). Only patients with solidly fixed implants were included in this study. Stability of implants was assessed with preopera-tive radiographs and then confirmed intraoperatively. Patients with loose implants intraoperatively were excluded from this study. We present our results with use of this technique in 206 patients with follow up of 1 to 5 years.

The St Leger total knee replacement is a bicondylar prosthesis developed as an cheaper alternative to other similar implants of its time. Between October 1993 and June 1999, 144 St Leger total knee replacements were implanted in 114 patients.

The aim of this study was to clinically and radiologically assess these patients after a mean follow up of 10.22 years.

Between February and July 2007 ninety-one patients recalled for clinical evaluation (using functional and objective American Knee Society Scores) and radiological assessment (using the American Knee Society Scoring System). 11 patients had died and 12 were lost to follow up or were medically unfit to attend evaluation. Of the ninety-one patients recalled, 18 had had their prostheses revised (19 knees). 63% of prostheses had survived 10 years or more.

Of the patients with St Leger knees in situ (99 knees) the American Knee Scores showed 78% poor, 10% fair, 6% good and 6% excellent results. Radiological assessment identified 12 arthroplasties that had failed (5 femoral components, 5 tibial components and 4 patellae,) 58 that needed close follow up (18 femoral components, 31 tibial components and 38 patellae) and 29 that were well fixed. A best-case Kaplan-Meier cumulative survivorship was 87% at 10 years. (Worst-case was 71% at 10 years)

These 10 year results showed that the St Leger total knee prosthesis did not perform as well as other bicondylar prostheses of the same generation and had a higher revision rate. Despite favourable published mid-term results, the long-term results for the St Leger total knee replacement have shown it to be unreliable and not worth the initial financial saving.

Introduction: Treatment options for the young active patient with isolated symptomatic medial compartment OA and pre-existing ACL deficiency are limited. Implant longevity and activity levels may preclude TKA, whilst HTO and unicompartmentasl knee arythroplasty (UKA) are unreliable due to ligamentous instability. UKAs tend to fail because of wear or tibial loosening resulting from eccentric loading. Combined UKA and ACL reconstruction may therefore be a solution.

Method: Fifteen patients with combined ACL reconstruction and Oxford UKA (ACLR group), were matched (age, gender and follow-up period) with 15 patients with Oxford UKA with intact ACL (ACLI group). Prospectively collected clinical and x-ray data from the last follow-up (minimum 3 years, range: 3 – 5) were compared. Ten patients from each group also underwent in-vivo kinematic assessment using a standardised protocol.

Results: At the last follow-up, the clinical outcome for the two groups were similar. One ACLR patient needed revision due to infection. Radiological assessment did not show any significant difference between relative component positions and none of the patients had pathological radiolucencies suggestive of component loosening. Kinematic assessment showed posterior placement of the femur on tibia in extension for the ACLR group, which corrected with further flexion.

Conclusions: The short-term clinical results of combined ACL reconstruction and UKA are excellent. Lack of pathological radiolucencies and near normal knee kinematics suggest that early tibial loosening due to eccentric loading is unlikely.

Purpose: Varus deformity after total knee replacement (TKR) is associated with poor outcome. This aim of this study was to determine whether the same is true for medial unicompartmental arthroplasty (UKA).

Methods: 158 patients implanted with the Oxford UKA, using a minimally invasive approach, were studied prospectively for five years. Leg alignment was measured with a long-arm goniometer referenced from Anterior Superior Iliac Spine, centre of patella and centre of ankle. Patients were grouped according to the American Knee Society Score (AKSS). Group A: > 0° varus (n=13, 8.2%); Group B: 0 to 4° valgus (n=39, 24.7%); Group C: 5–10° valgus (normal alignment, n=106, 67.12%). Comparisons were made between the three groups in terms of the absolute and the change in Oxford Knee Score (OKS) and AKSS over the five year period, and the presence of radiolucency.

Results: There was no significant difference in any outcome measure except for Objective-AKSS (p< 0.001). The means and standard deviations of the ΔOKS for the groups were:

24 ± 5,

The frequency of five year radiolucency for the groups A, B, and C were 42%, 35%, and 45% respectively.

Conclusion: The aim of the Oxford UKA is to restore knee kinematics and thus knee alignment to the pre-disease state. Therefore, as demonstrated by this study, about 30% of patients have varus alignment. This study also demonstrates that post-operative varus alignment does not compromise the outcome. The only score which did show worse outcome was the Objective-AKSS. This is because 10 or 20 points are deducted for varus alignment, which is not appropriate following UKA. Therefore, AKSS in its present form is not a reliable tool for assessment of UKA.

Introduction: The information in the literature about the relative merits of cemented and cementless unicompartmental knee replacement (UKR) is contradictory, with some favouring cementless fixation while others favouring cemented fixation. Cemented fixations give good survivorship but there is concern about the radiolucency which frequently develops around the tibial component. The exact cause of the occurrence of radiolucency is unknown but according to some, it may suggest suboptimal fixation.

Method: Sixty-two knees (31 in each group) were randomised to receive either cemented or cementless UKR components. The components were similar except that the cementless had a porous titanium and hydroxyappatite (HA) coating. Patients were prospectively assessed by an independent observer pre-operatively and annually thereafter. The clinical assessment included Oxford Knee Score, Knee Society Scores and Tegner activity score. Fluoroscopically aligned radiographs were assessed for thickness and extent of radiolucency under the tibial implant.

Results: At one year there were no differences in the clinical outcome between the groups and there were no loose components. No radiolucencies thicker than 1mm were seen. At one year none of the cementless tibias and 30% of the cemented tibias had complete radiolucencies. One out of 31 cementless (3%) and 12 out of 31 cemented (39%) had partial radiolucencies. This difference between these two groups was high significant (p< 0 0001).

Conclusions: This study clearly demonstrates that the incidence of radiolucency beneath the tibial component is influenced by component design and method of fixation. With identical designs of tibial component none of the cementless components developed complete radiolucences whereas 30% of the cemented components did. We conclude that HA achieves better bone integration than cement.

Introduction: The indications for patellectomy have been considerably narrowed in recent years, but there remains a cohort of patients with previous patellectomies that remain symptomatic. In addition, these patients can develop osteoarthrosis or instability, and their treatment is challenging. We report our experience of the use of a novel implant to substitute for the absent native patella.

Materials and Methods: Six patients were treated with the Augmentation Patella (Zimmer, Allendale, USA), which was sutured to the patellar tendon. All 6 patients had previously had a patellectomy for anterior knee pain syndrome or chondromalacia patellae, between 5 and 22 years previously. They all had an arthroscopy to document the extent of degenerative changes. Patients with trochlear changes only had the trochlea resurfaced (4 cases) and those with tibio-femoral changes as well had a total knee replacement (2 cases).

Results: One patient reported excellent relief of pain, with no evidence of radiological loosening. Two patients continued to complain of pain despite the implant being solidly fixed. One patient developed wound complications secondary to difficult closure due to the bulk of the implant. In two patients, the implant loosened within 15 months necessitating further surgery to retrieve the Augmentation Patella.

Discussion: The results of the Augmentation Patella in our series of patients with previous patellectomies have been disappointing. Previous studies, where this implant has been used with a remaining shell of patella, has yielded better results. This suggests that bony ingrowth is important for a successful outcome. We recommend that this device should only be implanted if bony contact is possible.

Introduction: The results of the mobile bearing Oxford unicompartmental knee replacement (UKR) in the lateral compartment have been disappointing with a five year survival of 82%. Therefore, it is recommended that mobile bearings should not be used for lateral UKR. This low survivorship is primarily due to high dislocation rate, all occurring in the first year. A detailed analysis of the causes of bearing dislocation confirmed the elevated lateral tibial joint line to be a contributory factor. A new surgical technique was therefore introduced in which care was taken neither to remove too much bone from the distal femur nor to over tighten the knee and therefore ensure that the tibial joint line was not elevated. Other modifications to the technique were also introduced including use of a domed tibial component.

Aim: The aim of this study is to compare the outcome of these iterations: the original series [series I], Series II with improved surgical technique and the domed tibial component [Series III].

Method: The primary assessment of outcome was bearing dislocation at one year. One year was chosen as all the dislocations in the first series occurred within a year. In series I, there were 53 knees, in series II 65 knees and in series III 60 knees, all with a minimum of one year follow up.

Results: In series I, there were 6 bearing dislocations (11%) and the average range of movement (ROM) was 110°. In the second series, there were 2 dislocations (3%) and the average ROM was 118°. In the third series, there were no primary dislocations and the average ROM was 125°.

Conclusions: The improved surgical technique and implant design has reduced the dislocation rate to an acceptable level so a mobile bearing can now be recommended for lateral UKR.

A number of measurements of patella height exist all of which use a position on the tibia as a reference. The Patellotrochlear Index has recently been proposed as a more accurate reflection of the functional height of the patella and described in normal knees.

Aim: A comparison of patellar height measurements in patients with patellofemoral dysplasia.

Method: A retrospective analysis of the MRI scans of 33 knees in 29 patients with patellofemoral dysplasia to assess the inter- and intraobserver reliability of four patellar height measurements: the Patellotrochlear Index (PTI), Insall-Salvati (IS), Blackburne-Peel (BP) and Caton-Deschamps (CD) ratios. We also assessed the correlation between the different measurements in predicting patella alta. Three blinded observers on two separate occasions performed the measurements.

Results: There were 21 females and 8 males with a mean age of 21.4 years (13–33).

Statistical analysis revealed good inter-observer reliability for all measurements (0.78 for PTI, 0.78 for IS, 0.73 for BP and 0.77 for CD). Intra-observer reliability was also good (0.80, 0.83, 0.75, 0.78 respectively). When comparing the different measurements for patella alta there was a weak correlation between the PTI and the others. There was a strong correlation between the CD and BP ratios (0.96) and a moderate correlation between IS and CD and IS and BP ratios (0.594 and 0.539 respectively).

Conclusion: All measurements are reproducible. The PTI however suggests patella alta exists in different patients to that suggested by the established measures. We propose the PTI as a more clinically relevant measure.

Purpose of Study: To develop a non-invasive technique to assess and analyse patella kinematics during the gait cycle.

Methodology and Results: Ten subjects with no history of patellofemoral syndrome or patella maltracking on clinical examination were individually assessed on eight dynamic walking trials each. Retroreflective markers were attached to the proximal, distal, medial and lateral poles of the patella and the position of the patella relative to the centre of the knee joint was tracked and recorded during their gait cycle using a nine camera (120Hz) ViconTM infra-red motion analysis system.

It was found that there was more medial-lateral motion (shift) of the patella than proximal-distal (tilt) motion during the gait cycle.

It was noted that the patella shift motion occurred in the swing phase or the early stance phase of the gait cycle of all subjects with the maximum patella shift occurring when the knee was flexed between 30–56 degrees in the majority of subjects.

Similarly the patellar tilt motion occurred in the swing phase or the early stance phase of the gait cycle with the maximum patella tilt occurring between 20–36 degrees of knee flexion in the majority of subjects.

Conclusion: The results of this study show that patella motion can be identified non-invasively using the ViconTM motion analysis system. These results indicate that normally the maximum amount of patella shift and tilt occurs in the swing and early stance phases of the gait cycle and that abnormal patella motion can be detected if excessive shift or tilt occurs outside of these phases.

Objective: The aim of the study was to test the hypothesis that insertion of a total knee replacement (TKR) may effect range of motion as a consequence of excessive stretching of the retinaculae.

Methods: 8 fresh frozen cadaver knees were placed on a customised testing rig. The femur was rigidly fixed allowing the tibia to move freely through an arc of flexion. The quadriceps were loaded to 175N in their physiologic lines of action using a cable, pulley and weight system. The iliotibial tract was loaded with 30N. Tibiofemoral flexion and extension was measured using an optical tracking system. Monofilament sutures were passed along the fibres of the medial patellofemoral ligament (MPFL) and the deep transverse band in the lateral retinaculum with the anterior ends attached to the patella. The posterior suture ends were attached to ‘Linear Variable Displacement Transducers’. Thus small changes in ligament length were recorded by the transducers. Ligament length changes were recorded every 10° from 90° to 0° during an extension cycle. A transpatellar approach was used when performing the TKR to preserve the medial and lateral retinaculae. Testing was conducted on an intact knee and following insertion of a cruciate retaining TKR (Genesis II). Statistical analysis was performed using a two way ANOVA test.

Results: The MPFL had a mean behaviour close to isometric, while the lateral retinaculum slackened by a mean of 6mm as the knee extended from 60 degrees (Fig 1). After knee replacement there was no statistically significant difference seen in ligament length change patterns in the MPFL, however the lateral retinaculum showed significant slackening from 10 to 0°.

Conclusion: The data does not support the hypothesis that insertion of a TKR causes abnormal stretching of the retinaculuae. This result relates specifically to the TKR design tested.

Objective: The aim of this study was to test the hypothesis that malrotation of the femoral component following total knee replacement (TKR) may lead to patellofemoral complications as a consequence of excessive stretching of the retinaculae.

Methods: 8 fresh frozen cadaver knees were placed on a customised testing rig. The femur was rigidly fixed allowing the tibia to move freely through an arc of flexion. The quadriceps and iliotibial tract were loaded to 205N in their physiologic lines of action using a cable, pulley and weight system. Tibiofemoral flexion and extension was measured using an optical tracking system. Monofilament sutures were passed along the fibres of the medial patellofemoral ligament (MPFL) and the deep transverse band in the lateral retinaculum with the anterior ends attached to the patella. The posterior suture ends were attached to ‘Linear Variable Displacement Transducers’. Thus small changes in ligament length were recorded by the transducers. Ligament length changes were recorded every 10° from 90° to 0° during an extension cycle. A transpatellar approach was used when performing the TKR to preserve the medial and lateral retinaculae. Testing was conducted following insertion of a cruciate retaining TKR (Genesis II). The femoral component was rotated using a custom built intramedullary device. Ligament length changes were measured at neutral rotation, 5° internal and 5° external rotation. Statistical analysis was performed using a two way ANOVA test.

Results: Internal rotation resulted in the MPFL slackening a mean of 1.7mm from 70-0° extension (p< 0.001). External rotation resulted in the MPFL tightening a mean of 1.5mm over the same range (p< 0.01). The lateral retinaculum showed less significant differences.

Conclusion: External rotation resulted in smaller length changes than internal rotation. Patellar tilting as a result of internal rotation may be caused by MPFL slackening and not lateral retinacular tension, contrary to popular understanding.

Objective: This study tested the hypothesis that complications resulting from overstuffing the patellofemoral joint after total knee replacement (TKR) may be a consequence of excessive stretching of the retinaculae.

Methods: 8 fresh frozen cadaver knees were placed on a customised testing rig. The femur was rigidly fixed and the tibia moved freely through an arc of flexion. The quadriceps and iliotibial tract were physiologically loaded to 205N using a cable, pulley and weight system. Tibiofemoral flexion/extension was measured using an optical tracking system. Monofilament sutures were passed along the fibres of the medial patellofemoral ligament (MPFL) and the deep transverse band in the lateral retinaculum with the anterior ends attached to the patella. The posterior suture ends were attached to ‘Linear Variable Displacement Transducers’. Thus, small changes in ligament length were recorded by the transducers. Length changes were recorded every 10° from 90°- 0° during an extension cycle. A transpatellar approach was used when performing the TKR to preserve the medial and lateral retinaculae. Testing was conducted following insertion of a cruciate retaining TKR (Genesis II). The patella was resurfaced and various patellar thicknesses were achieved by placing 2mm thick nylon washers behind the ‘onlay’ button. The thicknesses measured were 2mm understuff, pre-cut thickness, 2 and 4mm overstuff. Statistical analysis was performed using a two way ANOVA test.

Results: Patellar understuff resulted in the MPFL slackening an average of 1.6mm from 60 to 0° (p< 0.05). Overstuffing the patella 2mm resulted in no significant length changes whereas 4mm overstuff resulted in a mean increase in MPFL length of 2.3mm throughout extension (p< 0.001). No significant length changes seen in the lateral retinaculum

Conclusion: Overstuffing the PFJ stretches the MPFL, because it attaches directly between two bones. The lateral retinaculum attaches to the relatively mobile ITT, so overstuffing does not stretch it.

Purpose: To evaluate the patients who underwent acute surgical repair of medial patellofemoral ligament following first lateral dislocation of patella

Methods: Twenty four patients with mean age 19 yrs (12–41) who underwent acute repair of MPFL were reviewed. The mean follow-up was 14 months (2–35 months). All patients had MRI scan preoperatively and most of them were operated within two weeks of injury. Patients were evaluated clinically and Kujala and modified Lysholm were recorded. None of these patients had further dislocations and all had negative patellar apprehension tests. The mean Kujala and modified Lysholm scores were above 85.

Conclusion: Our results strongly support that in selected patients acute repair of MPFL prevents further dislocations and early return to sporting activities. The long term results are to be evaluated.

Idiopathic anterior knee pain (AKP) is common in adolescents and young adults. Most believe that the origin of the problem lies in the patello-femoral joint. Hamstring tightness has also been attributed as an important cause.

The aim of our study was to compare biometric parameters in patients with idiopathic AKP and controls. We also wanted to assess whether there was a difference in the relative electromyographic (EMG) onset times of the medial and lateral hamstrings.

We prospectively recruited patients with idiopathic anterior knee pain in the age group 11 to 25. Patients, but not the control population, had AP, lateral and skyline radiographs taken to rule out other pathology.

We had 34 patients (60 knees) with a minimum one year follow up. There was no difference in the symptoms of patients who attended physiotherapy as compared to those who did not. Patients with knee pain had significantly more hip external rotation (63 deg) as compared to the control (47 deg) group (p=0.001). Patients also had significantly more hamstring tightness (p=0.04).

Surface EMG was recorded (17 patients and controls each) from the medial and lateral hamstrings during 3 repetitions of a maximal voluntary isometric contraction exercise with the knee at 45° of flexion. The lateral hamstrings contracted 48.7 m.sec earlier than the medial hamstrings in patients as compared to controls.

AKP is a multifactorial and self-limiting disorder. Earlier contraction of the lateral hamstrings may cause tibial external rotation and contribute to the symptoms. Our data suggests that physiotherapy did not significantly alter the course of the condition. We believe that increased hip external rotation may contribute to the symptoms by increasing medial facet stress.

Introduction: Patellofemoral arthroplasty (PFA) is an established treatment of isolated patellofemoral osteoarthritis. We present our multi-surgeon, multi-implant series of patellofemoral joint arthroplasty performed over a ten year period.

Material & Results: his study was a retrospective review of all PFA performed in our unit over a ten year period from 1997 to 2006. The unit comprises seven specialist knee surgeons and numerous trainee surgeons. A total of 46 knees had the Lubinus implant (Waldemar Link), 30 knees had the FPV system (Wright Medical) and 25 knees had the Avon system (Stryker Howmedica).

101 arthroplasties in 91 patients were followed up for average period of 48.8 months (6–96 months). The average age was 57 years with female patients thrice as common as male patients. Concomitant procedures in the form of 23 lateral retinacular release or 6 osteochondral autograft transfer system (OATS) were performed. There were 6 complications with 2 infections and 4 stiff knees. Subsequent procedures included arthroscopic debridement (18), arthroscopic lateral retinacular release (8), tibial tuberosity transfer (3) and manipulation for stiffness (2). A total of 4 arthroplasties underwent revision to TKA, 2 for infection and 2 for progression of tibiofemoral osteoarthritis.

Conclusion: Thorough clinical history, physical examination and radiological investigation are essential before embarking on PFJ replacement. Other concomitant procedures like joint debridement, menisectomy or lateral retinacular release may be necessary to obtain optimum results. The necessity of revision surgeries in 31% of the cases of our study suggests that close follow-up of the patients is needed to address any concerns which can be easily resolved. PFJ replacement effectively addresses anterior knee pain, preserves the joint integrity, involves lesser surgical dissection and has good results of revision to TKA.

Introduction: The Bristol Knee group has performed over 600 patellofemoral arthroplasties in the last 18 years. Experience with the Lubinus prosthesis led to the development of the Avon Prosthesis. In the last 11 years we have prospectively recorded the results of over 470 consecutive Avon arthroplasties. The main cause of the 9.5% failure is arthritic disease progression in the tibiofemoral compartments.

Patients and Method: Over the last 11 years we have identified 21 patients from our own series and from tertiary referrals that have persistent pain, which was mainly due to technical error rather than arthritic disease progression. The causes can be classified into three main reasons: First, an incorrect anterior cut in the saggital plane which was cut in either too much flexion or extension. Second, the anterior cut had inadequate external rotation, which should be 3–6 degrees to lateralise the groove and facilitate correct tracking. Third, the prosthesis was oversized in several cases leading to retinacular impingement.

Results: The overall results followed up to 10 years showed excellent and consistent improvement in both pain and function as judged by the WOMAC 12 scale. Of those patients with persistent pain, seven had the femoral component revised to either resize the prosthesis or revise the alignment of the anterior resection and correctly inset the prosthesis, with good results. Ten cases were revised to a total knee replacement. In the remaining cases, two had an Insall realignment, one a patella distalisation, and in one no treatment was required. As a permanent solution new instruments were designed to reduce the incision size and increase the accuracy of the saggial alignment and to create an exact amount of external rotation.

Conclusion: The lessons from 11 years experience with the Avon arthroplasty has led to the development of improved instrumentation which should reduce the failures.

Statement of purpose: The aim of this study is to evaluate different designs of unicompartmental knee replacement (UKR) by comparing the peak von Mises and contact stresses in polyethylene (PE) bearings over a step-up activity.

Summary of Methods: A validated finite element (FE) model was used in this study. Three UKR designs were modelled: a spherical femoral component with a spherical PE bearing (fully-congruent), a poly-radial femoral component with a concave PE bearing (semi-congruent), and a spherical femoral component with a flat bearing (non-congruent).

Kinematic data from in-vivo fluoroscopy measurements during a step-up activity was used to determine the relative tibial-femoral position as a function of knee flexion angle for each model. Medial and lateral force distribution was adapted from loads measured in-vivo with an instrumented implant during a step-up activity. The affect that varying the bearing thickness has on the stresses in the bearing was investigated. In addition, varus-valgus mal-alignment was investigated by rotating the femoral component through 10 degrees.

Summary of Results: Only the fully congruent bearing experienced peak von Mises and contact stresses below the PE lower fatigue limit (17MPa) for the step-up activity (fully congruent PE peak contact stress, 5MPa). The highest PE contact stresses were observed for the semi-congruent and non-congruent designs, which experienced approximately 3 times the PE lower fatigue limit. Peak PE von Mises stresses for the semi-congruent and non-congruent designs were similar, peaking at approximately 25MPa. Peak PE von Mises stresses were ameliorated with increased bearing thickness. Varus-valgus mal-alignment had little effect on the peak stresses in the three UKR designs.

Statement of Conclusions: Fully congruent articulating surfaces significantly reduce the peak contact stresses and von Mises stresses in the bearing. The FE model demonstrates that fully congruent bearings as thin as 2.5mm can be used without increasing the contact stresses significantly. Fully congruent designs can use thinner bearings and enable greater bone preservation.

Statement of purpose: Finite element (FE) models of bone can be used to evaluate new and modified knee replacements. Validation of FE models is seldom used, and the quantification of modelling parameters has a considerable effect on the results obtained. The aim of this study is to develop a FE model of a cadaveric tibia and validate it against a comprehensive set of experiments.

Summary of Methods: Seventeen tri-axial rosettes were attached to a cleaned, fresh frozen cadaveric human tibia and the tibia was subjected to 13 loading conditions. Deflection and strain data were used for comparison with the FE model. A geometric model was created on the basis of computed tomography (CT) scans. The CT data was used to map 600 orthotropic material properties to the tibia. All experiments were simulated on the FE model. Measured principal strains were compared to their corresponding FE values using regression analysis. The validated tibia model was reduced in size (75mm to the proximal) and then re-modelled to represent only the proximal tibia. This re-modelled tibia was validated against the reduced size FE model. Virtual surgery was performed on the validated proximal model to implant a UKR.

Summary of Results: For the whole tibia model, the regression line for all axial loads combined had a slope of 0.999, an intercept of −6.24 micro-strain, and an R2 value of 0.962. The root mean square error as a percentage was 5%. For the proximal tibia model, correlation coefficients of 0.989 and 0.976 were obtained for the maximum and minimum principal strains respectively.

Statement of Conclusions: An FE model of an implanted proximal tibia has been validated against experimental data. This model is able to accurately predict the deflection and stresses in a replaced knee joint to obtain clinically relevant information. This will provide a virtual model of unicompartmental arthroplasty, where variables such as fixation method and bearing mechanics can be assessed.

Aim: To investigate the molecular features of progressive severities of cartilage damage, within the phenotype of Anteromedial Osteoarthritis of the Knee (AMOA).

Methods: Ten medial tibial plateau specimens were collected from patients undergoing unicompartmental knee replacements.

The cartilage within the area of macroscopic damage was divided into equal thirds: T1(most damaged), to T3 (least damaged). The area of macroscopically undamaged cartilage was taken as a 4th sample, N. The specimens were prepared for histological (Safranin-O and H& E staining) and immunohistochemical analysis (Type I and II Collagen, proliferation and apoptosis).

Immunoassays were undertaken for Collagens I and II and GAG content. Real time PCR compared gene expression between areas T and N.

Results: There was a decrease in OARSI grade across the four areas, with progressively less fibrillation between areas T1, T2 and T3. Area N had an OARSI grade of 0 (normal).

The GAG immunoassay showed decreased levels with increasing severity of cartilage damage (ANOVA P< 0.0001).

There was no significant difference in the Collagen II content or gene expression between areas.

The Collagen I immunohistochemistry showed increased staining within chondrocyte pericellular areas in the undamaged region (N) and immunoassays showed that the Collagen I content of this macroscopically and histologically normal cartilage, was significantly higher than the damaged areas (ANOVA P< 0.0001). Furthermore, real time PCR showed that there was a significant difference in Collagen I expression between the damaged and macroscopically normal areas (p=0.04).

Conclusion: In AMOA there are distinct areas, demonstrating progressive cartilage loss. We conclude that in this phenotype the Collagen I increase, in areas of macroscopically and histologically normal cartilage, may represent very early changes of the cartilage matrix within the osteoarthritic disease process. This may be able to be used as an assay of early disease and as a therapeutic target for disease modification or treatment.

Purpose: This study compared the efficacy and safety of Characterized Chondrocyte Implantation (CCI) to microfracture in the repair of symptomatic cartilage defects of the femoral condyle.

Methods: CCI (n=51) was compared to microfracture (n=61) in patients with grade III–IV symptomatic cartilage defects of the femoral condyles in a prospective, multicenter, randomized, controlled trial. Structural repair was assessed at 1 year by histopathologists blinded to the treatment using

computerized histomorphometry and

Results: CCI resulted in better structural repair than microfracture at 1 year post-treatment, as assessed by histomorphometry (p=0.003) and overall histology (p=0.012). Structural repair parameters relating to chondrocyte phenotype and tissue structure were also superior with CCI. Noninferiority of CCI was demonstrated for clinical outcome at 12–18 months, and both treatments were generally well tolerated.

Conclusion: At 1 year post-treatment, CCI resulted in superior tissue repair compared to microfracture. Short-term clinical outcome after 12–18 months was similar for both treatments, as was the safety profile. The superior structural repair achieved with CCI may lead to improved long-term clinical benefits.

Purpose: As a one-step surgical procedure, microfracture is frequently considered to be technically easier and associated with less postoperative morbidity than autologous chondrocyte implantation (ACI), which involves both arthrotomy and arthroscopy and therefore safety was assessed in patients with symptomatic cartilage lesions of the knee treated with characterized chondrocyte implantation (CCI) or microfracture.

Methods: CCI (n=57) was compared to microfracture (n=61) in patients with grade III–IV symptomatic cartilage defects of the femoral condyles in a Phase III, prospective, multi-center, randomized, controlled trial. Safety assessments included adverse events (AEs), physical examination, vital signs, hematology and clinical chemistry.

Results: At 18 months post-surgery, similar proportions of patients experienced AEs in the CCI (88%) and microfracture (82%) groups; 67% and 59%, respectively, experienced AEs considered treatment related. The AE profile was generally similar between groups, with no significant difference for hypertrophy, although significantly more CCI-treated patients had joint swelling (19% versus 4.9%; p=0.022) and treatment-related joint crepitation (12% versus 1.6%; p=0.028). Although the proportion of patients with severe AEs was similar for CCI (12%) and microfracture (13%), slightly more microfracture-treated patients experienced serious (life-threatening or requiring hospitalization) AEs (13% versus 8.8%). No patients discontinued due to AEs or died during the study.

Conclusion: Contrary to general opinion, the two-step CCI procedure, involving arthroscopy followed by arthrotomy, has a similar safety profile to that of microfracture, a one-step arthroscopic procedure, for treating cartilage lesions of the knee.

Aim: To assess the safety and clinical and radiological outcome of the TruFit CB porous, resorbable scaffold for symptomatic osteochondral and chondral articular defects in the knee.

Methods: 11 active sporting patients underwent cartilage repair using TruFit CB plugs (Smith & Nephew) for symptomatic defects on the medial or lateral femoral condyle. All had failed previous treatment (debridement/microfracture) and had persistent symptoms. Postoperatively patients were touch weight bearing for 2 weeks and partial until 4 weeks. Data was collected prospectively. The mean age was 34 (range 19 – 50) and 5 were male. Four lateral femoral condyle defects were treated, all associated with lateral meniscal tears. Four medial defects were associated with ACL injury (1), PCL injury (1) or isolated chondral injury (2). Single plugs were required in 5 (9mm in 3 and 7mm plugs in 2), 2 patients required 2 plugs (9mm and 7mm), and 2 required 3 (2×9mm + 1×7mm).

Results: All 11 patients were improved at a mean follow up of 14.5 months (3–21 months) with 4 currently back to full pre-injury level of sport. Subjective IKDC scores improved from 45 pre-op to 79 post-op (p< 0.05), Lysholm from 47 to 71 (p< 0.05), and latest Tegner activity score at 5. MRI evaluation including T2 mapping demonstrates reformation of the subchondral lamina and resorption of the graft. 2nd look arthroscopy was undertaken in 2 showing a well healed and well integrated surface.

Conclusion: These preliminary results indicate that TruFit CB plugs offer a potential solution for small focal chondral defects, offering an alternative to microfracture or osteochondral grafting with advantages of low morbidity and rapid recovery without the need for prolonged non-weight bearing.

Aims: To establish the best teaching method for medical students and ascertain the students’ preferred method of teaching.

Material and Methods: 30 medical students in were picked randomly and divided into two equal groups. Group 1 received Standard bedside teaching and Group 2 watched an interactive DVD. Each group then undertook a validated OSCE and the examiners were blinded as to which teaching method the students had received. The groups then received the other method of teaching followed by another OSCE. A questionnaire was given to all the students, to assess their satisfaction of the teaching session.

Results:

Conclusion: Interactive teaching method can be a useful technique for teaching medical students, however the students’ preferred method of teaching is standard bedside teaching. Efficiency of knowledge transfer can be improved if interactive teaching is followed by standard bed side teaching but not the other way around.

Aim: To review the short-term clinical results of a single-institution cohort undergoing opening wedge high tibial osteotomy (HTO).

Method: We undertook a prospective clinical and radiographic review of our cohort of patients who had undergone opening wedge HTO for varus malalignment. The Cincinnati scoring system was used for objective assessment. Pre- and post-operative radiographs were evaluated and Blackburne-Peel (BP) and Insall-Salvati (IS) ratios recorded, as well as integrity of the lateral hinge.

Results: we reviewed 55 knees (51 patients: 34 men and 17 women; mean age, 44.2 years; range 34–58 years) followed up for a minimum 12 months (range, 12–62 months). All patients had relief of pain, but six met our criteria of failed treatment where either revision fixation was required or proceeded to total knee arthroplasty for persisting symptoms. Cincinnati scores were 94.5% excellent (52/55) and 5.5% good (3/55) at 1 year, whilst at last follow-up they were 87.2% excellent (48/55), 9.1% good (5/55) and 3.6% fair (2/55). There was a significant improvement in mean American Knee Society score at 1 year and maintained at last follow-up (p< 0.05). Radiographically the lateral hinge was noted to be breached in 9.1% (5/55), but no incidence of non-union was identified. There was no significant change in IS index, however BP index diminished by a mean 15.3% (range, 7.4–28.2%).

Discussion: Medial opening wedge tibial osteotomy results in patellar infera, but successful clinical and functional outcomes have been demonstrated. The fact there is inconsistency between the two indices assessing patellar height ratio we believe reflects the inherent variability in the techniques employed. Distalisation of the tibial tubercle will mean the IS ratio remains unaffected, whilst the BP index more accurately demonstrates the lowering of patella relative to the joint line. However there may be other factors which are not immediately appreciated, such as changes in the tibial inclination or antero-posterior translation.

Introduction: Tourniquets are commonly employed in surgical procedures of the knee. The use of the same tourniquet on a repetitive basis without a standard protocol for cleaning has recently been questioned as a potential source of cross-infection. This study examines the contamination of the tourniquets in our institution and results of cleaning the tourniquets with a disinfectant and detergent wipe.

Material and methods: Tryptone soya agar plates were used to take samples from 20 tourniquets employed in knee replacement. Four specified sites on each tourniquet were cultured and incubated at 37° for 48 hrs.

Results: All sampled tourniquets were contaminated with colony counts varying from 9 to > 385.

Coagulase negative Staphylococcus was the most commonly grown organism from the tourniquets (96%).

Some tourniquets had growths of important pathogens including MRSA, Pseudomonas and Staphylococcus aureus (these organisms have not been previously cultured from tourniquets). On cleaning five tourniquets with clinell (detergent and disinfectant) wipes, there was a 99.2% reduction in contamination of the tourniquets five minutes after cleaning.

Conclusion: Contamination is more worrying in relation to pneumatic tourniquets, as they are commonly employed in knee surgery where implants are frequently used with the tourniquet lying within inches of the operative wound.

We have found a 99% reduction in contamination of tourniquets by employing disinfectant wipes. This is a simple, cost-effective and quick method to clean tourniquets and we recommend the use of wipes before every case in addition to the manufactures guidelines for general cleaning of tourniquets.

Aim: To assess the results and complications of the opening wedge form of distal femoral varus osteotomy (DFVO) in treating valgus arthritis and ligament instability of the knee.

Methods: Patients undergoing DFVO were assessed prospectively using validated scoring systems and pre/post operative alignment radiographs. All had failed non operative and arthroscopic procedures and were keen to avoid arthroplasty. The lateral based opening wedge osteotomy aimed to correct the weight bearing line to position 50% medial to lateral and was held with either the Puddu femoral plate (Arthrex UK) or the Tomofix plate (Synthes UK).

Results: 26 distal femoral osteotomies were performed in 23 patients with a mean age of 34 (16 –58). The mean duration of follow up is 32.5 months (1–72). 8 were undertaken for primary valgus malalignment, and 15 for secondary valgus with OA due to previous lateral menisectomy. Simultaneous additional procedures included microfracture (3), MACI (1), meniscal transplantation (1), and MCL advancement (1). Mean hospital stay was 4 days (2–6). Post op alignment was out by greater than 10% of intended in 2/3. 3 early major complications required re-operation: 2 for plate and screw cut out and 1 for infection. 2 developed delayed union requiring bone grafting. Failure with conversion to arthroplasty has occurred in 2 (1 lateral UKA, 1 TKA), and 2 patients are awaiting either multi-ligament reconstruction or collagen meniscal implantation. The overall mean Tegner score is 4 (2–6), and 20 of the 23 patients feel satisfied with the outcome having avoided arthroplasty.

Conclusion: Opening wedge DFVO is a technically difficult procedure with significant complications, but in the right indication offers long lasting pain relief and joint preservation prior to arthroplasty. New techniques including accurate closing wedge fixation systems and computer guided operative planning and surgery may offer improvements to this vital surgical option.

Objectives: This study aims to assess the psychological profile of patients prior to total knee replacement, medial unicompartmental knee replacement and patellofemoral joint replacement and determine its effect on outcome.

Methods: 113 patients were identified (41 TKR, 37 UKR and 35 PFJR). All patients had mental health assessed preoperatively using SF-12. From the 12 questions a mental and a physical summary score can be calculated (MCS and PCS). The reduced WOMAC score was used pre-operatively to assess knee function and symptoms and then recorded at 8 and 24 months post-operation to assess outcome.

Results: 54% of the patients had pre-operative psychological distress. There was no statistically significant difference demonstrated between them mean MCS scores between the three operation groups. Pre-operative MCS had a significant effect such that increasing psychological distress lead to a worse twenty-four month outcome (p = 0.016). The effect of MCS is most marked in postoperative pain levels (p = 0.008) compared to function (p = 0.016). The mean 24-month rWOMAC in the severely distressed group (MCS< 40) was 28.4 compared to 17.4 in the psychologically well group (MCS> 60).

Conclusions: Pre-operative mental function prior to knee arthroplasty may provide useful information to guide patients as to their expected outcome in the consent process. Those patients with a very high mental component may be counseled to that although their distress is likely to improve with surgery, their eventual outcome may be worse. The effect of MCS may however only be clinically relevant in those patients with severe mental symptoms.

Purpose: The objective of this study was to compare the safety and efficacy of 1 × 6 mL intra-articular administration of hylan G-F 20 with placebo.

Methods: In this prospective, multicenter, randomized, double-blind study, patients diagnosed with knee OA were randomized to one 6-mL injection of hylan G-F 20 or saline. The primary efficacy analysis (WOMAC A) was performed on the intent-to-treat population and was based on a repeated-measures model over the 26 weeks of the study.

Results: 253 patients were randomized to hylan G-F 20 (n=124) or placebo (n=129). Mean age was 63 years (42–84), BMI 29.4 (19.5–52.4 kg/m2), 71% were female, and all had primary knee OA of Kellgren Lawrence grade 2 (45%) or 3 (55%). Patients in the hylan G-F 20 group experienced a mean change from baseline in their WOMAC A Likert pain score (0–4 scale) over 26 weeks (primary efficacy criteria) of −0.84, which was statistically significantly different from the change reported in the placebo group (−0.69, p=0.047). Statistically significant differences favoring hylan G-F 20 were also reported for most of the secondary efficacy criteria: WOMAC A1 (estimate Odds Ratio over 26 weeks placebo/hylan G-F 20, 0.64, p=0.013), patient global assessment (0.69, p=0.029), and clinical observer global assessment (0.71, p=0.041); WOMAC B and C changes were not statistically significant between groups. The OMERACT-OARSI responder analysis indicated that 59% of the patients were responders in the hylan G-F 20 group versus 51% in placebo group (0.66, p=0.059). There was no statistically significant difference in the use of rescue medication (acetaminophen) between the 2 groups.

Discussion and Conclusion: This double-blind placebo-controlled study showed one injection of hylan G-F 20 provided symptomatic relief lasting up to 6 months in patients with knee OA; it avoids the need for multiple injections.

Aim To review 6 months of early discharge with a dedicated ‘Accelerated Discharge Team’ (A.T.T.) at our institution.

Patients and Methods The team consisted of four nurses and three physiotherapists. Patients undergoing hip or knee arthroplasty were assessed pre-operatively and post-operatively for admission to the care of the A.T.T. against fixed criteria. Patients were visited at home on the day of discharge and every day until released from the care of the team. 333 patients underwent lower limb arthroplasty during the study period of which 305 (91.6%) were admitted to the A.T.T.

Results The mean length of stay for primary knee replacements was 3.30 days. 73% (95% C.I. 64%–81%) of patients undergoing total knee arthroplasty went home by 3 days and 93% (95% C.I. 87%–97%) by 4 days. Results for hip arthroplasty were similar. Of the 305 patients, 12 (4%) were readmitted to hospital within 6 weeks of discharge. Almost 90% of patients responded to a satisfaction survey. 94.2 % of those responding indicated that they would use the A.T.T. scheme again.

Discussion In the year before implementing the A.T.T. the mean stay for primary hip and knee replacements was over 9 days. We reduced this to less than 3.5 days for over 90% of our patients during the study period. The total cost of the scheme was just under £100 000 for the 6 month period. We estimate that 2000 bed days were saved during the same period. This is cost effective on these terms alone. As well as transferring 12 elective orthopaedic beds to a different department we were able to perform an estimated 75 extra lower limb arthroplasty operations in the 6 month period.

Purpose: To review the existing coding for knee surgery and ascertain its appropriateness & accuracy for surgical procedures, associated co-morbidities and complications.

Methods: A retrospective review of 100 consecutive knee surgeries (50 arthroplasties and 50 arthroscopies) performed between July-August 2007 was undertaken. The coding data excel sheet and comprehensive hospital records were analysed.

Results: The accuracy of primary procedural codes was 100% & 88% respectively for arthroplasty & arthroscopy. However this respectively fell down to 56 & 60% when the accuracy for entire description of surgical procedure was taken into consideration. The procedural codes did not specifically reflect the surgery performed and lacked reproducibility esp. for arthroscopies. In arthroplasties, patients had similar codes irrespective of whether they had patellar resurfacing or not. Co-morbidities were coded appropriately in 24% of arthroplasty & 36% of arthroscopy patients. The common co-morbidities missed were drug allergies, hypercholesterolemia, heart conditions (IHD, MI, AF, valvular pathologies) and h/o malignancy & deep vein thrombosis. Post-op adverse events were coded in only 2/5 arthroplasties (40%) and 0/3 arthroscopies (0%) respectively.

Conclusion: Coding is a universal language of communication amongst healthcare professionals. Its accuracy is important not just for reimbursement but also for data quality and audit. Coding database also serves as a powerful research tool. The financial implications with respect to generation of appropriate reimbursement i.e. healthcare resource group (HRG) codes (which are dictated by official population and census survey procedural [OPCS4.4] & international classification of diseases [ICD–10] co-morbidity codes) are discussed. The limitations of the existing coding system are highlighted and discussed. Literature emphasizes on the qualification of coders, legible & comprehensive documentation of surgeries & co-morbidities by treating physicians and regular interaction between coders and clinicians. Reimbursement for arthroscopy is less in the NHS unlike in BUPA where it is on par with open surgeries.

It is established good practice that joint replacements should have regular follow-up and for the past seven years at the North Hampshire Hospital a local joint register has been used for this purpose and we compare this with results of the Swedish and UK national registries.

Since March 1999, all primary and revision knee arthroplasties performed at North Hampshire Hospital, Basingstoke have been prospectively recorded onto a database set up by one of the senior authors (JMB). Data from patients entered in the first six years of the register were analysed. All patients have at least one year clinical and radiological review then a minimum of yearly postal follow-up.

As of 31/12/2006, 2854 knee replacement procedures had been performed under the care of 13 consultants. OA was the most common diagnosis in over 75% of knees. 5.2% of patients had died and 4.6% were lost to follow-up. Our revision burden was 3.5% and we had a revision rate of 1.4% for primary total knee replacements. Audit of data for revisions and patello-femoral replacements has enabled us to change our practices. Mean length of stay was 7.2 days for primary total knee arthroplasty versus 4.0 days for unicompartmental knee arthroplasty and 5.4 days for patellofemoral replacement and mean flexion at discharge was 88.4, 93.7 and 88.7 degrees respectively. WOMAC and Oxford scores at 2 years had improved from a mean of 52 and 21 pre-operatively to 74 and 39 respectively for primary total knee arthroplasty. Our costs are estimated at approximately £35 per patient for their lifetime on the register.

Compared to other registries:

Our dataset is more complete and comprehensive

Aim: We studied the payments received by our hospital for 109 elective lower limb arthroplasty cases to see if this was fair and consistent under Payment by Results.

Methods: A cohort of patients who had Total Hip Replacement (THR), Total Knee Replacement (TKR), Resurfacing Hip Arthroplasty and Unicompartmental Knee Replacements were taken from the departmental database. Their diagnostic codes, operation details and comorbidities were established and compared with the payment the trust received using the Dr Foster database. This was confirmed with their hospital notes and the finance department.

Results: Twenty THRs and twenty TKRs were paid the standard tariff with one exception. Fifteen Hip Resurfacing arthroplasties showed variable payment from £4690 to £6673 per case. Most interesting were the Unicompartmental Knee Replacements. Despite having almost the same operative and diagnostic codes 46 out of 54 cases were significantly underpaid. During one financial year the trust lost more than £70,000 from this operation alone. This does not meet the Department of Health’s stated aim of being fair and consistent. Out of 109 cases reviewed 51 could have been coded differently and 47 of these were “underpaid”.

Conclusion: In an NHS increasingly driven by financial pressures it is vital that surgeons understand how Payment by Results works. There are significant financial gains to be made by those trusts who pay attention to the small print.

Purpose: Recent animal evidence has suggested that Bupivicaine may be harmful to articular cartilage. The purpose of this study was establish whether, following arthroscopy of the knee, infiltration of Bupivicaine around the portals is as effective as intra-articular infiltration for post-operative analgesia.

Method: Consecutive patients attending for knee arthroscopy were consented and randomised to one of two groups. Following arthroscopy, Group I received 20mls 0.5% Bupivicaine infiltrated into the joint; Group II received 20mls 0.5% Bupivicaine infiltrated around the portals. A Visual Analogue Score (VAS) was collected at one hour post-operatively and rescue analgesia recorded. A power calculation was performed. Ethical approval was granted.

Results: There were 68 patients in Group I (intra-articular) and 69 patients in Group II (portal). There was no significant difference in the age or sex distribution of patients in either group. The mean VAS score was 3.04 in Group I and 3.24 in Group II. There was no significant difference between the two groups (p=0.619). There was also no significant difference in the need for rescue analgesia (p=0.930). The study has demonstrated equivalence between the two groups, within one VAS point (Power = 80%).

Conclusion: We would recommend that following knee arthroscopy, Bupivicaine should be infiltrated around the portals, avoiding intra-articular infiltration.

Aim: To determine if extended scope physiotherapists perform to the same standards as their orthopaedic colleagues with regards to diagnosing knee pathology and making appropriate referrals for arthroscopy.

Method: Data was collected prospectively from Aug 2005. Patients were seen in a consultant led orthopaedic clinic by an Extended Scope Physiotherapist (ESP), a registrar or the consultant. All patients placed onto the waiting list for knee arthroscopy were considered for the study. The outpatient diagnosis and demographic data were recorded and compared against the arthroscopy findings. A single consultant surgeon performed the arthroscopies.

Results: 300 patients were included in the study (100 in each group). Each group was similar in terms of presenting complaint and demographics. There was no significant difference between the ESP’s and registrars in their ability to diagnose intraarticular pathology (CHI squared test: X 2.031, df 1, p=0.15). When only cruciate and meniscal pathology were considered there was also no significant difference between the ESP’s and the registrars (Fishers test p=0.12 and p=0.22 respectively, 2-tail test) The ESPs performed particularly well in their ability to diagnose cruciate injuries (sensitivity 100%, specificity 100% and PPV 100%). Both ESPs and registrars had high sensitivity but low specificity with regards to diagnosing meniscal pathology suggesting a low threshold for a positive diagnosis and a poor ability to correctly diagnose those patients who did not have a meniscal injury. Of the 300 patients only 9 unnecessary arthroscopies were requested. None were requested by the ESPs.

Conclusions: Extended scope physiotherapists perform a useful role in orthopaedic outpatients. They perform as well as orthopaedic registrars with regards to making the correct diagnosis and the selection of patients for arthroscopy.

The purpose of this study was to investigate the safety and outcome of bilateral simultaneous ACL reconstruction. In patients presenting with an ACL-deficient knee, 2 – 4% have bilateral ACL deficiency. A staged or simultaneous approach can be adopted when the patient requires reconstructive surgery for both knees. We report a case series of 8 patients (6 male, 2 female, average age 30.4 years) who underwent bilateral simultaneous ACL reconstruction.

Simultaneous or bilateral ACL reconstruction using ipsilateral patella tendon graft has been reported as a safe procedure with outcome and complication rate no different to unilateral procedures. Considerable cost savings of simultaneous over staged procedures have also been described. There are no case series in the published literature that describe the use of hamstring tendon autograft for bilateral simultaneous ACL reconstruction.

We used two camera stack systems and instrument sets to allow for simultaneous bilateral surgery by two surgical teams. Quadrupled hamstring tendon graft was used in 4 patients although in one patient patella tendon graft was used on the second side due to poor quality of hamstring tendons. Patella tendon graft was also used in a further 4 patients. At two weeks all patients were able to discard crutches and were independent in mobility. There was no difference in outcome at one year between those patients undergoing bilateral simultaneous ACL reconstruction in comparison to the outcomes of unilateral ACL reconstruction with respect to Lysholm, Tegner and IKDC scores. The mean follow up period was 2.3 years.

Our results demonstrate that bilateral simultaneous ACL reconstruction is safe and cost effective. A simultaneous approach also has the benefit of reducing the overall period of rehabilitation required by the patient. We report good short-term functional outcome but no long-term data is yet available.

This study evaluated the long term outcome of isolated posterior cruciate ligament (PCL) reconstruction. Thirty patients underwent surgery with hamstring tendon autograft after failing conservative management. At 10 years after surgery patients were assessed with radiographs, full IKDC examination and KT1000 instrumented testing. The mean IKDC subjective knee score was 87 out of a possible 100. Regular participation in moderate to strenuous activities improved from 26% preoperatively to 88% of patients. At 10 years endoscopic reconstruction of the PCL with hamstring tendon autograft is effective in reducing knee symptoms. Patients can expect to continue participating in moderate to strenuous activties over the long term. Osteoarthritis is observed in some patients with 18% showing some loss of joint space which compares favorably with non-operatively managed PCL injuries. This is a successful procedure for symptomatic patients with PCL laxity who have failed conservative management.

Purpose of study: The all inside fixation of meniscal tears with bio-degradable products is popular because of its fast application and reduction in risks of serious neurovascular complications. We reviewed the results of a consecutive series of all inside meniscal repairs performed by the senior author in a carefully selected patient population.

Materials & Results: The senior author performed 104 consecutive meniscal repairs (54 lateral & 50 medial meniscus) in 96 patients (66 male, 30 female), using all inside meniscal repair systems (18 Bionxx, 86 FasT Fix; Smith & Nephew). The average patient age at the time of repair was 31.6 years (range 17 – 46 years). On an average 2 arrows (range 1–4) were used in the Bionnx system and 2.5 sutures (range 1–7) for the Fas T fix system. The predominant tear pattern was a peripheral red on white type tear involving the body and posterior horn. Concomitant ACL reconstruction was undertaken in 50% cases. In 26.9 % cases the repaired meniscus was partially trimmed prior to repair and in 25 % cases a tear of the non repaired meniscus was stabilised by trimming alone. A further arthroscopic partial menisectomy was performed in 12 cases of failed repair (4 Bionxx, 8 Fas T fix) at an average of 16.16 months (range 1 month – 44 months). None of the other patients had symptoms or signs suggestive of meniscal pathology on follow up (minimum 12 months). The repair was successful in 90.69 % of Fas T fix repairs and 77.78 % of Bionxx repairs. The meniscal repair failure rate in the group which had an ACL reconstruction was 5.77 %. No major intra or post operative complications were noted.

Conclusion: Successful meniscal preservation is feasible by using an all-inside meniscal repair device. Patient selection and due consideration to the site and geometry of the meniscal tear is crucial.

Aims: To identify any changes in the demographics of ACL injured patients over the last decade.

Methods: Over a twelve month period, the demographic data from 117 consecutive new patients with ACL injuries attending one consultant’s clinic in 1994 was prospectively recorded. This was then compared with data from a similar cohort of 103 consecutive new ACL injured patients attending the same clinic some twelve years later.

Results:

Since 1994, the proportion of women seen with ACL injury doubled from 12% to 25%

Conclusion: The population of patients with new ACL injuries has changed significantly over the last twelve years. The average age, proportion of women and number of skiing related injuries have all increased significantly. We speculate that the most likely cause of these changes is the skiing population, which has enlarged and, due to retention of participants, has aged over the period of this study (1). Most skiing injuries are sustained abroad and the vast majority of skiers buy holiday insurance to cover themselves against injury. Yet it is the NHS that ends up footing the bill for any reconstructive surgery and rehabilitation. We propose that if the insurance companies maintained responsibility for their clients’ injuries until a full recovery had been made, the NHS would save millions of pounds.

Introduction: After adopting a new low suspensory bio-absorbable femoral fixation technique for single bundle, four strand, hamstring Anterior Crutiate Ligament (ACL) in conjunction with a rapid rehabilitation program, we observed at routine follow up that there was no evidence of femoral tunnel widening, as often observed with conventional high suspensory fixation systems.

Method: We conducted a retrospective observational cohort study to test the hypothesis that the Rigid-Fix (Mitek) system of femoral fixation, a low suspensory technique, is less prone to tunnel widening than traditional suspensory techniques.

14 subjects were recruited at routine follow up, and assessed by interview, clinical examination and plain digital raiodgraphs.

All radiographs were taken under clinical supervision, with a scale reference, hence allowing digital rescaling.

Results: All subjects had regained knee stability, and all but one had returned to their pre-injury level of sport. Clinically all knees were ligamentaly stable, exhibiting negative Luchman and pivot shift tests.

Examination of the radiographs demonstrated only a 1.1mm (+/− 0.9mm) mean femoral tunnel widening, which represents a 12% increase in diameter (21% increase in area), and compares very favourably to the observed tunnel widening in high suspensory techniques, as cited in the literature.

Conclusions: We conclude that the Rigid-Fix femoral ACL fixation system does not exhibit any evidence of clinically significant tunnel widening, even when used in conjunction with a rapid rehabilitation program.

Systems of low suspension benefit from the advantage of not relying on interference fit which risks posterior cortical ‘Blow Out’. A shorter graft working length within the tunnel lessens graft micro-movement, making early low biological fixation within the femoral tunnel more likely, and reduces the amount of tunnel widening. These micro-movement have been described as the ‘Windscreen Wiper’ and ‘Bungee Cord’ effects, and are well documented in traditional high suspensory fixation.

A recurrence of objectively measured knee laxity after anterior cruciate ligament (ACL) reconstruction has previously been reported in various papers; the purpose of this study was to accurately measure in vivo knee laxity after both bone-tendon-bone (BTB) and hamstring reconstruction using radiostereometric analysis (RSA), and to differentiate between graft fixation slippage and graft stretching and their relative contributions to any increase in laxity.

Twenty patients were studied prospectively after ACL reconstruction. Ten had been operated on using BTB grafts, and ten using hamstring (four-stranded semitendinosus/gracilis) grafts. Tantalum markers were inserted in the distal femur, proximal tibia and into the graft itself. (RSA) was used to measure sagittal laxity, graft stretching and fixation slippage early post-operatively, and then at intervals up to 1 year.

A steady increase in total anteroposterior laxity was found in both groups over the year. For the BTB group, total mean slippage of the bone plugs increased to 1.28 mm at 1 year. For the hamstring group, the tunnel attachments had slipped by a total of 6.82 mm. More stretching was found for the hamstrings grafts than for the BTB grafts and the amount of stretching increased significantly with time post-surgery. The hamstring grafts stretched by a mean of 4.18%, the BTB grafts by 1.18%.

This is believed to be the most detailed application of RSA in analysing the performance of the two commonly used grafts in ACL reconstruction. Details such as graft stretching and fixation slippage have not been available previously; the data obtained in this study may have implications for clinical practice.

Purpose of Study: To study the anatomy of the accessory bands of Gracilis and Semitendinosus in order to avoid inadequate graft harvesting during ACL reconstruction.

Methods and Results: Data was collected from 25 arthroscopically performed ACL reconstructions using the hamstring tendons. For each patient the exact number of accessory insertion bands of the Gracilis and Semitendinosus was recorded, as well as the distance of the proximal most band from the main insertion point on the tibial crest.

Of the 25 Gracilis tendons, the most common number of accessory bands was 2, varying from 0 to 3. The average distance of the proximal most band was 5.14cm. The most common number of accessory bands for the Semitendinosus tendon was 3, varying from 1 to 4. The average distance of the proximal most band was 8.14cm. Five of the Semitendinosus and none of the Gracilis tendons had a proximal band located > 10cm. Average length and diameter of the four strand graft was 7.7cm and 13.2cm.

Conclusion: Gracilis and Semitendinosus tendons are increasingly being used for soft tissue reconstructions. Awareness of accessory bands of these tendons is essential in preventing diversion of the tendon stripper leading to a short and inadequate graft. Previous studies have shown that the anatomy of these bands is highly varied. Such cadaveric studies have shown a high percentage of tendons with bands > 10cm proximal to their insertion [2]. Our study shows that 20% of Semitendinosus and none of the Gracilis tendons had bands more than 10cm proximal to their insertion. Gaining knowledge about accessory insertion bands of the hamstrings should assist reproducible and adequate graft harvest.

Purpose: To define the positions of the attachments of the anteromedial (AM) and posterolateral (PL) bundles of the ACL facilitating accurate tunnel placement during two-bundle reconstruction.

Methods: The positions of the femoral and tibial attachments of the AM and PL bundles was determined in 7 fresh-frozen, unpaired, cadaveric knees by 6 independent observers, using landmarks visible at arthroscopy. This included, on the tibia, the retro-eminence ridge (lying just anterior to the PCL), a bony landmark that could be reliably identified arthroscopically. Tantallum beads were then inserted so that the bundle attachments could be clearly identified on a plain lateral radiograph of the knee. The position of the centres of the AM and PL attachments were described relative to Amis and Jakob’s line on the tibia and Bernard’s grid on the femur.

Results: The AM femoral attachment lay high and deep in the notch with the most posterior fibres 1.8 mm anterior to the “over–the-top” position. The PL femoral attachment was low and shallow in the notch with the most anterior fibres 2.8 mm from the border of the articular cartilage. The centres of the bundles were 8.2 mm apart. The position of the bundles relative to Bernhard’s grid is shown in figure 1.

On the tibia, the centre of the AM attachment was located 18 mm anterior to the Retro-eminence ridge (RER). The centre of the PL bundle lay 8.4 mm posterior to the centre of the AM bundle. These positions were at 35% and 52% along Amis and Jacob’s line

Conclusions: This study details the morphology of the AM and PL bundle attachments and demonstrates reliable arthroscopic techniques to assist with accurate tunnel placement in reconstruction surgery. In addition, it provides reference data for radiographic evaluation of tunnel placement.

Introduction: The aims of this study were to determine whether patients were transfused appropriately, after a Unilateral Cemented Primary Total Knee Replacement (TKR), and whether it would be cost effective to use autologous transfusion drains compared with standard group & save and cross match protocols.

Method: Retrospective study of the pre- and postoperative day 1 haemoglobin values of all patients who underwent unilateral primary cemented TKR between November 2004 – November 2005 at the Kent & Sussex Hospital, Tunbridge Wells. Haemoglobin data and length of stay was obtained from computerised records & transfusion data from the blood transfusion department.

Results: 150 patients were assessed: 97 (65%) female and 53 (35%) male. 20 (14.6%) patients required blood transfusion. The mean preoperative haemoglobin for non-transfused and transfused patient’s was 13.7 and 12.5g/dl respectively (P = 0.0029). The mean postoperative haemoglobin for non-transfused and transfused patient’s was 11.1 and 9.27g/dl respectively (P< 0.001). The mean blood loss for non-transfused and transfused patient’s was 2.64 and 3.26g/dl respectively (P< 0.001). There was no significant correlation between length of stay and either preoperative haemoglobin or blood loss after surgery; Spearman’s correlation coefficient was 0.0222 and 0.0036 respectively. The cost of a standard group & save and cross match, plus the 56 required units of blood in this study was £15,443.60. The theoretical cost of using a CellTrans Autologous Transfusion System on these 150 patients would be £14,355.00, a saving of only £1,088.60. However, by only using the autologous drains on patients with a preoperative haemoglobin ≤ 12.5g/dl, this saving could be increased to £4,131.20 per annum.

Conclusion: Using autologous transfusion drains on patients with a preoperative haemoglobin ≤ 12.5g/dl would save over £4,000 per annum at Maidstone & Tunbridge Wells Hospital Trust. There is no correlation between length of stay in hospital and either preoperative haemoglobin or blood loss after surgery. Patients transfused had significantly lower pre- and postoperative haemoglobins.

Purposes of the study: Anterior cruciate ligament (ACL) deficiency is associated with degenerative osteoarthritis especially when it is present with meniscal injury; We assessed the impact of certain aetiological factors in chondral degeneration in the ACL deficient knee.

Methodology and Results: Fifty-eight patients who underwent consecutive primary arthroscopic anterior cruciate ligament reconstruction using the four strand hamstring graft between 10/06/2004 and 29/06/2006 were retrospectively analysed.

Patient’s charts and radiology findings were reviewed with special attention to operative notes and preoperative knee MR imaging. Patients with knee symptoms prior to presenting injury were excluded.

The mechanism of injury, the time elapsed from the original injury to anterior cruciate ligament reconstruction, associated meniscal injury, and quality of cartilage in the knee- at the time of MR imaging and ACL reconstruction were noted. Degenerative cartilage changes were graded upon reconstruction using the Outerbridge classification.

The average time from Injury to MR imaging and MR to ACL reconstruction was 4.85 and 12.65 months respectively.

We found a direct relationship between the time elapsed after the ACL injury and the severity of the chondral lesion (p< 0.05). Furthermore, a significant worsening in chondral degeneration of the involved knee was seen when the MR imaging and ACL reconstruction were more than 12 months apart (p< 0.01).

Conclusion: We conclude that chondral lesions and degeneration are more likely to be caused by an extended period of knee instability following ACL injury as opposed to age related degeneration or direct trauma to the weight bearing area of the knee.

Early reconstruction may protect the knee from chondral wear and subsequent degenerative arthritis.

Purpose of study: The aim of this study was to look at the clinical outcome of PLC interference screws in knee ligament reconstruction surgery.

Materials & Results: We prospectively followed up 60 patients who underwent primary anterior cruciate ligament (ACL) reconstructions using PLC (Calaxo; Smith & Nephew) screws to secure the graft in the tibial tunnel. [(35 male patients & 25 female). Average age 33.72 years]. In addition to the ACL, PLC screws were used to reconstruct the posterior cruciate ligament in one case and posterior cruciate ligament with the posterolateral corner in another three patients. Hamstring autografts were routinely preferred except in multiple ligament reconstructions, when allografts were also used.

25 (41.67%) patients presented with complications (synovitis in 10 patients, prominent tibial swelling in 21 patients and both in 7 patients). In comparison, no complications were noted in 60 other age and sex matched patients in whom PLLA (Bio RCI; Smith & Nephew) screws were used by the same surgeon.

The symptoms in the PLC screw group often settled conservatively and did not affect knee stability. 6 patients underwent exploration of the tibial tunnel site. A sterile white cheesy substance was noted which was removed, leaving an empty tibial tunnel. The ACL graft was found to be well attached to tibial tunnel in all cases. The PLC screw size did not have any correlation to the occurrence of complications. 2 patients required multiple washouts, one of whom developed a deep infection.

Conclusion: The degradation of PLC screws does not follow the gradual and controlled pattern demonstrated in the ovine model [Walsh WR et all, Arthroscopy. 2007 Jul;23(7):757–65. Comparison of PLLA and PLC interference screws in an ovine ACL reconstruction model.]. The unpredictable screw resorption, and the reaction to it can lead to serious clinical consequences.

The study aims to determine the effects of obesity on the patients’ symptoms and their knee function before knee arthroplasty, as well as their states of anxiety and depression.

Ethical approval was obtained before the start of the study. Weights and heights of all patients were measured and BMI calculated on admission. Anxiety and depression states were recorded using the Hospital Anxiety and Depression Scale (HADS). The severity of pain and loss of function of the knees undergoing arthroplasty was measured using the Oxford Knee Score and the American Knee Society Score. All scores were measured per-op and again at 6 weeks post-op.

To date, 28 patients were included. The mean body mass index was 28.9. Only six patients had a BMI of < 25. Patients with normal BMI (< 25) had mean anxiety and depression scores of 6.8 and 5.67 respectively. Overweight patients (BMI > 25) had scores of 5.59 and 4.9 respectively. Patients with BMI > 30 had scores of 6.71 (p= 0.22) and 7.0 (p= 0.04) respectively.

Patients with BMI > 30 had an improvement in anxiety scores of 1.33 points compared with 0.55 for patients with BMI < 30 (p= 0.3). Depression scores improved by 4 points in the BMI > 30 group compared with 0.67 in the BMI < 30 group (p= 0.03).

Improvements in the knee scores were comparable in both groups.

Obese patients with BMI of > 30 have higher rates of anxiety and depression pre-operatively. At 6 weeks follow up, there is an improvement in both measures of psychological distress but this is more pronounced for depressive symptoms.

Nerve blocks are a common form of peri-operative analgesia that is administered for patients undergoing joint Replacement surgeries. The long term sequel following these peripheral nerve blocks used in total knee replacement not reported in the literature. Nerve blocks given under the guidance of nerve stimulators are in practice in most of the hospitals and are considered safe.

We report a series of two cases with residual neurological deficit following these peripheral nerve blocks in total knee replacements. In both these cases the femoral, sciatic, obturator and lateral cutaneous nerve of thigh were blocked with 0.25% of Bupivacaine with the help of a nerve stimulator.

First patient post operatively had residual numbness in the right lower leg after 4 weeks of surgery. Nerve conduction studies confirmed absent response in right Saphenous and superficial peroneal nerves. Patient has no improvement in her neurological deficit even after 16 months post operatively. Further to this she developed complex regional pain syndrome on the affected side.

Second patient post operatively developed knee extensor weakness of grade II/V and loss of sensation in femoral nerve distribution. Nerve conduction studies confirmed severe femoral nerve damage around groin. She went through a turbulent phase, knee stiffness range of movements 0–20 degrees requiring Manipulation Under Anaesthesia, later Exploration and Release of adhesions which improved her range of movements to 0–95 degrees. At 12 months post operative the neurological status improved to grade 3/5 in knee extensors.

Conclusion: Long term Complications of Peripheral nerve blocks in total knee replacements are not reported in the literature. These complications though uncommon, unfortunately for patients affect the surgical outcomes. The purpose of this case series is not only to report complications but also to share our experience of managing these complications, their outcomes and relevant literature review.

Aims: Kinematics of the arthritic knee joint is to date not very well understood, yet this is a significant parameter affecting the results of knee arthroplasties; we studied the axial rotation of the tibia during knee flexion in osteoarthritic knees in order to understand better the kinematics of the arthritic joint.

Methods: Tibial rotation and the screw home mechanism were studied in 55 consecutive patients (31 females and 24 males) with diagnosed knee OA. The assessment was performed by consultant orthopaedic surgeons using the trackers and the software of a navigation system, prior to any soft tissue release. The Student t-test was used for the statistical analysis.

Results: We identified 3 different patterns of tibial rotation during knee flexion.

26 knees had normal tibial rotation pattern with the tibia rotating internally during knee flexion (mean rotation: 15.5°).

We also recorded that most of the tibial rotation occurs in the first 0–30° of flexion (70%) p< 0.001.

Conclusion: The screw home mechanism and the normal tibial rotation upon knee flexion were absent or distorted in the majority of osteoarthritic knees. We found three distinctive patterns of the tibial rotation (normal, erratic and reversed) during knee flexion.

Aim: Accurate soft tissue balance in total knee arthroplasty (TKA) is not only technically challenging but also difficult to teach to trainees; we believe that computer navigation provides a very useful tool for objective and reproducible soft tissue balance.

Methods: We studied 52 patients (31 females and 21 males) with knee osteoarthritis and recorded the change of the Medial (MCL) and Lateral Collateral Ligament (LCL) length at full extension and at 90o flexion. Pre- and post-operative results were compared. The assessment was performed by consultant orthopaedic surgeons using trackers and navigation knee replacement software. Data was analysed using the student t-test

Results: The navigation software programme was used to measure the change of the collateral ligament length. Ligament laxity is represented by a negative number and a positive number is used to represent stretching and apparent elongation of the ligament.

The medial collateral (MCL) length at full extension ranged from −9mm to 11mm and post-operatively was reduced to −16mm and 8mm, (p=0.042). At 90o flexion the length ranged from −3mm to 9mm and postoperatively was reduced to −8mm and 10mm (p=0.025).

The lateral collateral (LCL) length at full extension changed from −10mm to 9mm pre-operatively to −13mm and 6mm post-operatively (p=0.011). At 90o flexion the range from −8mm and 9mm pre-operatively changed to − 5mm and 11mm post-operatively (p=0.005).

All the above changes correspond to improvement in the post-operative axial alignment.

Conclusion: Our results demonstrate that computer navigation provides a useful adjunct to the accurate and reproducible soft tissue balance in knee arthroplasty which can be used to evaluate results and for training purposes.

To share our results following Medial Patellofemoral ligament (MPFL) reconstruction for patellar instability problems using ipsilateral semitendinosus graft anchored to the patella and the medial femoral condyle using biotenodesis screws.

Study design and methods: 35 patients were assessed with a mean follow up of 18 months. All patients had preoperative true lateral knee x-ray, MRI or CT scan to look at trochlear dysplasia and the sulcus tuberosity distance. They all under went MPFL reconstruction using ipsilateral semitendinosus tendon. Two patients had sulcus tuberosity distance greater than 20 mm and they under went a tibial tubercle transfer in addition. Two patients had trochlear dysplasia and hence a trochlearplasty was also done. In skeletally mature patients the hamstrings tendon were anchored to the medial side of the patella in a 5×15mm blind tunnel using biotenodesis screw. This significantly reduces the risk of having patella fracture. All patients were treated by the same surgeon and assessments were performed by a different surgeon based on kujala scores and tegner scores.

Results: Symptom relief was noted in all patients with in 3 months. No patient had patella dislocation or fracture after this procedure. They all had full range of movements and their kujala scores and tegner scores were good to excellent.

Conclusion: MPFL reconstruction using hamstrings tendon anchored to the medial side of the patella and femur using biotenodesis screw gave a good result clinically and is associated with fewer complications including patellar fractures.

Aim: The difficulty in accurately assessing coronal alignment of a total knee prosthesis (TKR) is widely accepted in the literature yet standard practice in the UK is to obtain AP and lateral knee views only; we compared standard AP knee films with long leg views of TKR in order to determine the most optimal way of assessment of the prosthetic knee alignment.

Methods: We included all patients who underwent TKR between January and September 2005 at Kings College Hospital under the care of one orthopaedic consultant. We excluded 11 patients with revision surgery, augmented prosthesis, high tibial osteotomies or severe tibiotalar joint arthritis.

We included 50 sets of radiographs from 48 patients (17 men and 31 women). The prostheses used were PFC (40) and Scorpio (10) and six of them were navigated and 44 were standard TKR.

We compared the difference between the angle of the tibial component with the mechanical axis of the tibia in the long leg image and the angle of the prosthesis with the midline of the visualised tibia in a standard antero-posterior knee view. Statistical analysis was carried out using the student t-test.

Results: The mean difference between the two views was 5.34o (range 1.9o – 12o) (p< 0.001). We did not find any difference between the Scorpio and PFC knees or between navigated and non navigated prostheses.

Conclusion:We concluded that the long leg views compared with the standard antero-posterior knee views provide more accurate information on the position and alignment of the tibial component of a TKR.

Purpose of study: The aim of this project was to ascertain whether tibio-femoral joint space width (JSW) measured both on Schuss and full extension radiographic views were predictive and accurate relative to the articular cartilage findings on arthroscopy.

Methods & Results: The study was a prospective trial. The criterion for recruitment was knee pain indicative of arthritis that required arthroscopic assessment with a view to possible surgical management. Joint space narrowing (JSN) was assessed in the affected knee, in both the standing full extension and Schuss views. Joint arthroscopy was performed and each compartment area of the knee was calibrated and graded corresponding to the arthritic changes identified. In the 60 patients recruited, 61.7% were found to have grade 4 arthritic changes on knee arthroscopy. JSN in those with associated grade 4 changes on arthroscopy on either full extension or Schuss views was 75.7% and 78.4% respectively. However in 24.3% of those with grade 4 changes on arthroscopy no JSN was demonstrated on either full extension or Schuss views. Arthroscopic assessment of severe arthritic changes of the knee was significantly superior compared to the radiographic method (p< 0.05).

Conclusions: The findings suggest that despite narrowed JSW measured on either radiographic view being indicative of severe articular cartilage loss, neither view accurately predicts articular cartilage loss in less advanced cases. In cases of grade 4 changes and no JSN the sites of articular cartilage loss corresponded to sites that are less likely to be accurately represented on either radiographic view. Our findings suggest that knee arthroscopy may be better suited to identifying smaller patches of cartilage loss whose surface area may not be sufficient to cause JSN but may still cause symptoms. We suggest knee arthroscopy is indicated in patients with knee pain suspicious of arthritis but who lack obvious JSN on either full extension or Schuss views. This enables micro-fracture techniques to be used with the aim of attenuating disease progression, and offers a thorough lavage that may also provide symptom relief.

Purpose: To evaluate the intra and inter-observer variation of the Schatzker and AO/OTA classifications in assessing tibial plateau fractures, using plain radiographs.

Summary: Fifty tibial plateau fractures were classified independently by 6 observers as per the Schatzker and AO/OTA classifications, using antero-posterior and lateral plain radiographs. Assessment was done on two occasions 8 weeks apart.

We found that both the Schatzker and AO/OTA classifications have a high intra-observer (kappa=0.57 and 0.53 respectively), and inter-observer (kappa=0.41 and 0.43 respectively) variation. Classification of tibial plateau fractures into unicondylar vs. bicondylar and pure splits vs. articular depression +/− split conferred improved inter and intra-observer variation.

Conclusions: The high inter-observer variation found for the Schatzker and AO/OTA classifications must be taken into consideration when these are used as a guidance of treatment and when used in evaluating patients’ outcome. Simply classifying tibial plateau fractures into unicondylar vs. bicondylar and pure splits vs. articular depression +/− split may be more reliable.

Purpose: To identify associative factors for radiolucency (RL) under the tibial component following the Oxford unicompartmental arthroplasty (UKA), and to evaluate its effect on clinical outcome scores.

Method: One hundred and sixty-one knees which had undergone primary Phase 3 medial Oxford UKA were included. Fluoroscopic radiography films were assessed at five years post-operatively for areas of tibial RL. The two groups of patients, with and without RL, were compared to

patients’ pre-operative demographics for age, weight, height, BMI,

Results: 101 (62%) knees were found to have tibial RL. All RL were categorised as physiological or they were < 1mm thick, with sclerotic margins and non-progressive. No statistical difference was found between knees with RL and those without, in terms of pre-operative demographics, intra- or post-operative factors, and clinical outcome scores (p> 0.1 in all variables).

Discussion: Radiolucency (RL) under the tibial component is a common finding following the Oxford UKA. Many theories have been proposed to explain the cause of RL, such as poor cementing, osteonecrosis, micromotion, and thermal necrosis. However, the true aetiology and clinical significance remain unclear. We attempted to address this.

We found no significant relationship between physiological RL, pre-operative demographics, intra-operative variables and clinical outcome scores in this study. Tibial RL remains a common finding following the Oxford UKA yet we do not know why it occurs but in the medium term, clinical outcome is not influenced by RL. In particular, it is not a sign of loosening. Physiological RL can therefore be ignored even if associated with adverse symptoms following the Oxford UKA.

Post traumatic myositisossificans is a benign condition of heterotropic ossification of unknown aetiology which typically is related to trauma from a single blow or repeated episodes of microtrauma. We describe an unusual case of myositis ossificans which developed as a complication at the donor site for hamstring autologous graft used in open anterior and posterior cruciate repair and posterolateral corner reconstruction in a 15 year old girl.

Case report: A 15 year old girl sustained a closed traumatic dislocation of her left knee when she fell from a trampoline. She underwent emergency manipulation under anaesthetic and closed reduction followed by MRI scan which showed a complete disruption of the lateral collateral ligament complex, posterolateral corner injury, complete tears of the anterior and posterior cruciate ligaments and a partial tear of the medial collateral ligament.

13 days later she had an open reconstruction of her anterior and posterior cruciate ligaments with allograft and a repair of popliteus and lateral structures with Larson reinforcement with controlateral hamstring autologous graft.

Eight months following open reconstruction the patient represented to her primary care practitioner with a painful lump in the postero-medial controlateral right thigh. MRI study showed that there was a lobulated hypervascular appearance with a thin enhancing rim of low signal on all sequences indicating calcification. An xray revealed a calcified mass consistent with the diagnosis of myositis ossificans.

Discussion and conclusion: To date we have found no reported cases of myositis ossificans occurring as a result of surgery to harvest hamstring autograft in the setting of ligament reconstruction about the knee. We believe that this is an unusual complication of the donor site which needs awareness amongst clinicians involved in primary and revision cruciate ligament reconstruction. We suggest that a management strategy of surveillance for this lesion is appropriate and excision biopsy should be reserved for specific indications such as malignant features on imaging or mass effect.

Purpose: The purpose of this study was to establish patient mortality following salvage treatment (debridement, retention of prosthesis and antibiotic therapy) for infection of primary joint replacement, performed at the unit.

Method: A series of 89 patients underwent salvage treatment for infected primary total joint replacement (47 hips and 42 knees) between 1998 and 2003. The average age of the patients was 70.3 years (range 31.8 to 89.1). A survival analysis was performed using death as the sole endpoint and there were no patients lost to follow-up.

Results: There were a total of 26 deaths with a mean time to death of 3.3 years (range 0.8 to 7.2). The 7-year cumulative patient survival of was 66% (CI 5, number at risk 21).

Conclusions: The morbidity associated with infected total arthroplasty has been well documented. This study highlights that patients undergoing salvage treatment for this condition have significant mortality, with up to a third of patients potentially dying by 7 years.

The purpose of this study was to assess the accuracy of a modified version of the pivot shift test in detecting ruptures of the anterior cruciate (ACL) ligament.

Methods: Two groups of patients aged 18 to 50 years were recruited from operating theatre lists examined at a check and consent clinic. One of the groups had ACL deficient knees and the control group had intact ACL, later proven at arthroscopy. A total of 48 independent examinations, 26 with ACL rupture and 22 without, were undertaken by a consultant or registrar proficient in the modified version of the pivot shift test. At the start of the consultation the examiner, who was blinded to the operation that the patient was listed for and to the patient’s history, performed the modified pivot shift test only. The result of the test was reported as positive or negative for ACL rupture to the study co-ordinator before the examiner continued with the consultation.

Results: Of the 26 examinations of ACL deficient knees, 22 were reported as positive and four negative for ACL rupture using the pivot shift test only. Of the 22 examinations of ACL intact knees one was reported as positive for ACL rupture and 21 as negative. This gives a specificity and sensitivity of the modified version of the pivot shift test as 95.5% (95% CI 75.1–99.8%) and 84.6% (95%CI 64.3–95.0%) respectively.

Conclusion: The modified pivot shift test is an accurate test for the detection of ACL rupture. Our modified pivot shift test compares favourably with data from previous accuracy studies of previously described versions of the pivot shift test. We now plan to assess the accuracy of the modified pivot shift test when carried out by medical students and junior doctors.