Deterioration in knee joint proprioception has been postulated to occur following injury, resulting in further instability due to disruption of receptors and feedback mechanisms. Surgical reconstruction techniques may also influence post-operative proprioceptive ability (PA). We hypothesised that anterior cruciate ligament (ACL) reconstruction techniques which disrupt the knee capsule would result in a decrease in PA.

Following ethical approval, a total of 48 subjects (mean age: 28.1 ± 10.5, 34 male, 14 female) undergoing ACL reconstruction surgery were included in the study. Fifteen subjects underwent “open” capsule ACL surgery and patellar tendon graft, whereas 33 subjects had “closed” capsule surgery with a hamstring tendon graft. Knee proprioception was measured on a custom-designed test apparatus incorporating electromagnetic position sensors (Polhemus Fastrack) located on femoral and tibial landmarks to accurately track knee angle during flexion-extension (no load). Leg flexion-extension under partial weight-bearing (5kg) was also evaluated. Pre-operative PA was assessed bilaterally, and then again on operated joints at three, six and twelve months post-op. Proprioceptive ability was measured as the cumulative absolute error in knee angle (°) between five repeat measurements and a target angle.

We observed no significant difference in PA between injured and contralateral knees prior to ACL reconstruction. Post-operatively, no significant difference in PA was observed between “open” versus “closed” ACL techniques, irrespective of loading conditions. While trends indicated that PA during knee extension (no load) and leg flexion (partial weight-bearing) improved over the 12 months compared to pre-operative values in closed ACL surgery, these were not significantly different to open ACL results.

The proportion of subjects whose PA improved in at least two out of the three post-op evaluations was also similar (approx 50%) across all groups, irrespective of joint loading. The only difference was PA during leg flexion under partial weight bearing, where 27% of open ACL surgery patients showed improvement in two or more follow-up tests, as opposed to 58% of closed ACL surgery patients.

We present a method to determine pre- and postoperative PA during knee flexion/extension under no load as well as under partial weight-bearing. We saw no significant difference in PA of the knee under no-load versus load. We also saw no significant difference in postoperative PA following open capsule, patellar tendon graft versus closed capsule, hamstring tendon graft ACL reconstruction technique after 1 year follow-up.

There remains controversy as to whether computer-navigated TKA improves the overall alignment of the knee prosthesis. The aim of this study was to determine whether computer-assisted total knee arthroplasty provides superior prosthesis positioning when compared to a conventional jig-assisted total knee replacement.

A prospective controlled study comparing computer navigated and conventional jig-assisted total knee replacement in 23 patients who underwent bilateral TKA was undertaken to determine if there was any significant difference in component position. The 23 patients (46 knees) were randomised to receive one conventional jig-assisted total knee replacement, and a contra lateral computer-assisted total knee replacement. A single experienced knee surgeon performed all procedures.

A quantitative assessment of the spatial positioning of the implant in the 46 total knee replacements was determined using a low-dose dual-beam CT scanning technique. This resulted in six parameters of alignment that were compared. A blinded, independent observer recorded all radiological measurements.

Median external rotation of the femoral component relative to the trans-epicondylar axis was −2 degrees in the computer-assisted group and −3 degrees in the jig-assisted group. Median femoral component flexion was identical in both groups at 0 degrees. Median valgus angulation of the femoral and tibial components was +1 degree and 0 degree respectively for the computer-assisted group and 0 degree and −1 degree for the jig-assisted group. Median posterior tibial prosthesis slope was +5 degree in both the computer-assisted group and the jig-assisted group.

Computer-assisted implantation of total knee replacements does not offer a significant advantage in prosthesis alignment. Low dose dual-beam CT scanning provides a three dimensional model of the lower limb, allowing accurate measurement of prosthesis alignment.

Recent analysis of the Australian Joint Replacement Registry revealed the rate of revision of primary total hip arthroplasty was greater with cement-less fixation than with cemented fixation. The seven-year results of the New Zealand Joint Registry have also shown an increased revision rate with cement-less hip arthroplasty. The purpose of this study was to review the revision rate of cemented and cement-less total hip arthroplasty from those joint replacements registered with the New Zealand Joint Registry and to determine the cause for revision.

All 42 1000 primary total hip arthroplasties recorded in the New Zealand National Joint Registry since its establishment in 1999, until December 2006, were included in the study. The rate of revision of cemented and cement-less femoral and acetabular components was calculated for the study period, and for the first 90 days after the operation. The reasons for revision were evaluated and compared for different methods of fixation. Survival curves were constructed for each combination of femoral and acetabular component fixation.

Two hundred and eighty three cement-less (2.46%), 294 cemented (1.91%), and 321 cemented femoral with cement-less acetabular fixation (2.19%) primary total hip arthroplasties have been revised. The difference in revision rate between each group was statistically significant. There were only 573 primary total hip arthroplasties performed with cement-less femoral and cemented acetabular component, with 11 revised. The rate of revision was highest in the cement-less group (0.74% revised per year), and lowest in the cemented group (0.47%).

The predominant reason for revision in all three major groups was dislocation. Revision for loosening of the acetabulum was more common with cemented fixation. Revision for fractured femur was more common with cement-less fixation, and revision for deep infection was most common in the cemented group. These differences were all shown to be statistically significant. Revision for loosening of the femoral component and pain was more common in the cement-less group, but was not shown to be statistically significant.

In the first 90 days, there were a large number of revisions in the cement-less group (0.77%), compared to the cemented group (0.32%), and cemented femur with cement-less acetabulum group (0.57%). Dislocation was again the most common reason for revision. Revision for fractured femur was high in the cement-less group (0.19%) in the first 90 days. Excluding these early revisions, the number of revisions in the cemented and cement-less groups maintained a similar rate for the remainder of the study period.

This study confirmed that the revision rate for uncemented THA was higher than for cemented THA. The major difference was the early revision rate within 90 days. Addressing these problems would improve the overall early outcome.

Articular cartilage has a limited regenerative capacity. Tissue engineering strategies adopting seeding and differentiation of individual chondrocytes on porous 3D scaffolds of clinically relevant size remains a considerable challenge. A well documented method to produce small samples of differentiated cartilage tissue in vitro is via micro-mass (pellet) culture, whereby, high concentrations of chondrocytes coalesce to form. a spherical tissue pellet. However, pellet culture techniques are not applied clinically as it is only possible to produce small amounts of tissue (1–2mm). The aims of this study were to develop a method for mass-production of pellets, and investigate whether an alternative “pellet seeding” approach using smart 3D scaffold design would allow large numbers of spherical pellets to be fixed in place.

Chondrocytes were isolated from bovine articular cartilage via enzymatic digestion. Freshly isolated and expanded (passage 2) chondrocytes were placed in 96-well plates with round- or v-shaped wells at a range of densities from 0.1, 0.25 and 0.5 million cells per pellet, and centrifuged at 500g for 2 min. In order to assess pellet forming conditions, cells were treated with or without 300 mg/mL fibronectin (FN, Sigma) to improve cell-cell adhesion. Wells were also coated with or without silicone (Sigmacote) to prevent cell adhesion to wells. Pellets were cultured in vitro for up to 14 days and were assessed at various timepoints for size, shape, cell number (DNA assay) and cell differentiation capacity (histology). A robotic Bioplotter device was used to produce porous, biodegradable scaffolds by plotting −250μm polymer (PEGT/PBT) fibres in a layer-by-layer process. Scaffolds with specific 3D pore architecture were produced to allow spherical pellets to be press-fit in each pore thereby fixing them in place throughout the scaffold.

Primary and expanded chondrocytes plated at a density of 0.25 million cell/pellet in v-shaped 96-well plates without both FN and silicone treatment produced pellets with consistently better spherical shape and total cell number (as determined via DNA). Under these conditions, cell (re)differentiation and cartilage extracellular matrix formation was observed via positive staining for safranin-O. Mass production of pellets was achieved by culturing multiple 96-well plates in parallel. FN treatment promoted cell-cell adhesion, but also cell adhesion to well plates, irrespective of silicone treatment, resulting in irregular shaped pellets, as did the use of round-bottom shaped wells.

Smart scaffold design and layer-by-layer fabrication process allowed direct control over the fibre spacing and pore size (1.0–1.25mm). Multiple layers of spherical pellets (1.25–1.5mm) were press-fit in place, thereby limiting the need for direct cell adhesion to the scaffold. Continued culture of constructs containing pellets resulted in consistent tissue formation throughout the scaffold.

In this study, we describe an alternative approach to the design and seeding of scaffolds for cartilage tissue engineering. Current limitations involved with adherence and de-differentiation of single cell populations were avoided by taking advantage of smart 3D scaffold design and pellet-seeding and culture techniques. Further optimisation and automation of the process is necessary, however, such strategies could be beneficial for future scaffold-based cell therapies for repairing articular cartilage defects.

Squeaking is a rare complication of hard-on-hard hip bearings. Occasionally the noise is troublesome enough to warrant revision surgery. The purpose of this study is to contribute to the understanding of the mechanism(s) underlying squeaking.

We analyzed 10 alumina ceramic-on-ceramic bearings from squeaking hips collected at revision surgery. The reason for revision was given as squeaking (6 cases) or squeaking and pain (4 cases). Six of the 10 patients were male, average patient age was 48. Bearings were retrieved after an average of 23 months in service (11 to 61 months). There were 4 different designs of acetabular component from 2 different manufacturers. Nine have an elevated metal rim which is proud of the ceramic and one does not. Two bearings were 36mm in diameter, 6 were 32mm and 2 were 28mm.

All 10 bearings showed evidence of edge loading wear. Mean dimensions of the wear patch were 37mm by 12mm on the acetabular component and 32mm by 13mm on the femoral heads. Wear dimension was not related to bearing diameter. Seven of the 10 implants also had evidence of impingement of the femoral neck against the elevated metallic rim or the ceramic insert or both. There was no chipping or fracture of any of the ceramic components.

Squeaking is a recently recognized complication of hard on hard bearing surface. This retrieval study is the first of its kind, to our knowledge attempting to unravel the mechanism of this undesirable complication. Although impingement seems to be present in majority of cases, the latter does not seem to be necessary. Edge loading wear was the common factor in all cases and this may prove to be a critical mechanism.

Recent studies have assessed operative skill in surgical trainees “objectively” based on patient outcomes by attempting to statistically separate many contributory variables. Compression hip screw fixation (CHS) for neck of femur fracture (#NOF) is a standard operation commonly performed by orthopaedic trainees of varying experience. Our aim was to determine if trainees could be assessed objectively on their efficiency and aptitude in performance of this operation. A secondary aim was to evaluate the predictors of fixation failure for CHS described in the literature.

Records and radiographs for all CHS performed by trainees of all levels for acute adult #NOF were examined retrospectively for 2 calendar years. Preoperative patient and fracture variables were scored. Outcome measures included operative time, scores of accuracy of fracture reduction and fixation, blood loss and complications. Failure of fixation was compared to the scores given to radiographs. Multivariate analysis was used to apportion variance between multiple contributing factors.

Three hundred and eight two eligible operations were performed by 26 trainees. Operative time was effected by fracture complexity, trainee level and trainee operator (all p< 0.05). “Tip apex distance”, a measure of depth and centrality of screw placement in the femoral head, known to predict screw cut out was associated with trainee operator. Other outcome scores of fixation on radiographs were not correlated with fracture, patient or operator variables. Blood loss and complications were not associated with operator. The rate of failure of fixation was low and associated with scores of reduction quality only (p< 0.05).

Trainees of variable experience perform CHS with a low overall complication rate and the most noticeable performance difference seems to be in speed of surgery.

The purpose of this study was to evaluate the results of simultaneous bilateral total hip and total knee arthroplasty performed in New Zealand during the first five years of the New Zealand National Joint Register and to determine whether this was an acceptable practice.

All total knee and total hip arthroplasties collected on the National Joint Register between 1999 and 2003 were divided into three groups – unilateral joint arthroplasty, staged bilateral joint arthroplasty and simultaneous joint arthroplasty. The Oxford 12 questionnaire results at six months were assessed as well as the patients self reported complications. All deaths that occurred within 6 months of the surgery were also recorded.

Analysis between the three groups was then performed using ANOVA tables comparing age, the Oxford scores and complications.

There was generally a significant difference (p< .001) in age between unilateral hip and knee replacement and staged or simultaneous bilateral replacement, with patients undergoing bilateral simultaneous replacement being younger.

There was a significant difference (p< .001) in the Oxford 12 scores between unilateral hip and knee replacement and both staged and simultaneous bilateral hip and knee replacement, with the bilateral simultaneous replacements scoring the best.

The death rate within the first 6 months was low in all groups with only 1 patient dying within 3 months of the surgery from an unrelated cause. The complication rate was low in all groups, in particular the DVT and pulmonary embolus rate, as reported by the patients, was not increased in either the sequential staged group or the simultaneous bilateral group.

The New Zealand National Joint Register has proven to be a valuable tool in gaining early information regarding the outcome following bilateral and staged lower limb total joint arthroplasty. The results clearly show that in the appropriate clinical situation performing simultaneous bilateral total knee or total hip arthroplasty is a safe and effective procedure.

The purpose of this paper is to review the first six months experience of using the ‘Time Out’ procedure to avoid wrong site/side surgery and to evaluate the usefulness of this procedure in the routine preoperative check.

Over a period of 18 months all elective surgical hospitals in Christchurch (both private and public) have coordinated to develop a pre-operative ‘Time Out’ check list to ensure that the correct surgical procedure is performed on the correct site. This procedure involves a final check of patient details, including surgical procedure and site, immediately prior to surgical preparation of the operative site.

All forms during this six month period were prospectively collected and evaluated, specifically looking for system errors, which could proceed to wrong site surgery.

There were a total of 10,330 procedures performed during this period within the three hospitals of which 9,098 (87.2%) completed time out forms were returned.

There were no wrong side or wrong site surgeries performed during this six month period. However, there were three ‘near miss’ situations which were captured by the time out procedure.

Analysis of the time out forms also revealed numerous consent issues, incorrect documentation and systems errors which could potentially have lead to serious errors in management and which will be discussed in detail.

During this period there were 109 objections (1.2%) to the time out procedure.

The time out procedure has been shown to be a useful tool for avoiding wrong site/side surgery and has gained acceptance amongst both medical and nursing staff as being a valuable check prior to surgery. It has accentuated the collective team responsibility for determining the correct site and side of surgery and as such is recommended for use in all centres to eliminate system errors resulting in incorrect site/side surgery.

We have assessed the comparative function of young patients with hip or knee replacement using a high level function score.

A high level function score was developed for assessing running, walking, stair climbing and recreational activity. This was used on a series of patients after a total of 153 joint replacements including 99 THR and 54 TKR.

The groups were comparable with respect to age (average 57 years), gender and follow-up. Comparison between the groups showed that there was no significant difference in walking, stair-climbing and recreational activity. Patients with THR scored better on running ability and overall total score. Other differences noted included lower scores in bilateral joint replaced patients and posterior cruciate sacrificed knees.

Young patients undergoing hip or knee replacement have similar functional outcomes using a high activity function score. There were trends towards superior running ability and overall scores in the THR group.

Our aim was to assess the clinical and radiological medium-term outcome of a series of 153 consecutive total hip arthroplasties performed by two surgeons in Christchurch using the ABG hydroxyapatite-coated femoral stem and Duraloc 100-series uncemented acetabulum.

An independent clinical review using interviews and patient notes and radiological review of immediate postoperative and most recent x-rays was carried out.

At six to eleven years with approximately 95% follow-up, there were no stem failures, but two revisions following a fracture from significant trauma. Two cups were revised for loosening and one cup bone grafted for osteolysis. A dislocation occurred in 4.7% of cases requiring two liner exchanges and one cup revision. A low incidence of thigh pain and excellent radiographic results of the stem with high rates of bony ingrowth and no incidence of significant loosening was a feature of this series.

We report excellent results at medium-term follow up for an unceme4nted HA- coated femoral stem.

The purpose of the study was to assess the use of the Internet for medical information, both in the Orthopaedic Outpatient population, and in practicing Orthopaedic Surgeons in New Zealand.

To identify any potential sites that may be of use to the patient in gaining reliable information on their orthopaedic problem. 300 questionnaires were distributed to Orthopaedic Outpatient Clinics (Public Trauma, Public Elective, and Private) in Christchurch. Each clinic had 100 questionnaires. A second questionnaire was sent out to all Orthopaedic Surgeons currently practising in New Zealand. A literature search was also performed.

Overall 18% of patients use the Internet to look up medical problems. Internet use was highest amongst the younger population. 68% of patients had a computer at home. 52% of patients thought recommended Internet sites would be useful. 91 % of patients stated they used their Doctor as their most common source of healthcare information, with only 5% stating the Internet. 76% of Orthopaedic Surgeons used the Internet for work purposes. 54% thought that the Internet misinformed patients. Only 50% of surgeons had accessed the NZOA web site.

The Internet is becoming an increasingly common source of healthcare information for patients and doctors. The NZOA site has huge potential for both surgeons and the public with regard to useful links. At present this site is largely under-utilised.

The purpose of this study was to establish whether retransfusion of blood collected in drains following total joint replacement was a safe and effective procedure. All patients undergoing a total joint arthroplasty, with no history of infection, between March and October 2001, were entered into the study. A single surgeon operated on all patients and no patient was excluded from the study. Informed consent was obtained and all blood drained into a recollection system within 6 hours of surgery was retransfused .A prospective protocol was filled out in all cases documenting the pre and postoperative haemoglobin, amount transfused and any extra transfusion requirements. A special note was made of any complications encountered during retransfusion. The results were then compared to previously known transfusion rates within the same hospitals.

There were 141 Total Joint Arthroplasties performed within the study period -12 were bilateral and 12 were revisions procedures. The average drainage was 655ml (60–3280ml) and the average amount of retransfused blood from the drains was 225ml (100–1822ml). There were a total of 9 (6.3%) subsequent blood transfusions. Four (3.8%) in primary and 5 (20.8%) in bilateral or revision procedures.

Transfusing patients with salvaged blood from the drains in total joint arthroplasty is a safe, reliable and cost effective practice, which significantly reduces the requirement for a subsequent blood transfusion. As a result of this study the Christchurch Orthopaedic Group has adopted a routine practise of retransfusing drained blood in all total joint arthroplasties.

Despite a variety of reports to the contrary it was felt by the Christchurch Orthopaedic group that the “wait” on the orthopaedic waiting list has been escalating rapidly to the point that a routine operation is now in the order of approximately 3 years from the time of GP referral.

A review of the time taken for GP referrals to be assessed by an Orthopaedic Surgeon was undertaken. The waiting lists from October 98 to May 02 were analysed, in addition to the operation outputs from the Burwood Hospital elective theatre records over the same period. Time taken from referral to be seen, time taken from been placed on the waiting list to receive an operation and volume of elective procedures were evaluated. A breakdown was made of those removed from the list vs those operated on. A major reduction in the waiting list over the last three years was secondary to 1/3 of the people on the list (1177) been “culled”. This was initiated in January 1999 and completed by January 2001. Since January 1999, 2538 patients had received their operations. The waiting list had dropped from 3303 to a low of 1164. It has since climbed to 2036. That waiting longer than 12 months for surgery, initially 64%, had dropped to 29% and has climbed back up to 40%. The figures have climbed dramatically since the waiting list initiative for arthroplasty was discontinued. The culling of the list has been responsible for removal of 1/3 of people off the original list without having an operation and has given a false sense of success in reducing the waiting list to various political interests. The criteria set for culling people assessed as requiring an operation has been set arbitrarily There is twice the number of patients waiting to see an orthopaedic surgeon than 2 years ago of which a proportion are requiring reassessment to be deemed eligible for an operation that they have already been assessed as requiring.

The waiting list initiative was effective as an addition to the regular DHB lists in maintaining the lists at a manageable level. Even if all those culled represented a group that no longer required their operation the current list cannot be considered to have such a group as they have all been recently reviewed and are in genuine need. There is an apparent lack of concern and denial over the current escalation in the numbers on the waiting list, and no plan instituted to address it.

Hypotheses:

A subject’s response to commonly used knee assessment scores is variable, even in the presence of a normal knee.

Methods: A group of 150 New Zealand subjects with normal knees were given three commonly used knee assessment questionnaires. There were three age groups with 50 subjects in each group: 20 to 40, 40 to 60 and above 60 years of age. All were examined to determine that each knee was objectively normal. This group was then compared with a similar group of Canadian subjects and the results were analysed.

Results: The results showed significant differences in expectation between the age groups, with the older age group less happy to score maximum points for their ‘normal’ knee. The Hospital for Special Surgery Knee Score scored the lowest followed by the Knee Society Knee Score. In the over 60 years group there was a significant difference between the New Zealand and Canadian subjects with the Canadians tending to score higher in all scores.

Conclusions: These results have implications when trying to compare results of total knee arthroplasty between different countries and age groups. This study has been expanded to include other countries in an attempt to find a mathematical formula to make future comparisons more relevant.

Aim: To compare the function in two groups of high demand patients with a total knee arthroplasty (TKA) – one group using a posterior cruciate sacrificing (PCS) prosthesis and the other a posterior cruciate retaining (PCR) prosthesis of similar design.

Method: Patients were eligible for the study if they were greater than two years from surgery, less than 65 years of age and without other co-existing morbidity to significantly decrease their physical activities. Group A underwent surgery by one surgeon who routinely retained the posterior cruciate ligament whereas Group B underwent surgery by one surgeon who routinely sacrificed the PCL. A mobile bearing TKA of similar design was used in each group. All patients were selected and assessed by an independent assessor using a questionnaire developed specifically to assess higher levels of activity not usually assessed by other knee scores.

Results: Group A (28 TKA in 20 patients) were matched with Group B (25 TKA in 19 patients) for age, length of follow-up and range of motion. The gross activity score was 3.36 in Group A compared with 3.12 in Group B. The combined walking, running and stair climbing score was significantly better in Group A (7.68 compared to 6.64 in Group B). Group B perceived their TKA was closer to a normal knee (2.00 compared to 2.32) with decreased anterior knee pain.

Conclusions: Retaining the PCL in TKA results in better function without significant complications.

Aim: In 1990 the Christchurch Hospital Sarcoma Clinic established management guidelines for patients with suspected sarcomas, recommending referral prior to investigation, biopsy and excision. The aim of this study was to determine whether these guidelines are being followed.

Method: A review of the case notes of all sarcomas referred to the Sarcoma Clinic between 1990 and 1999 was performed.

Results: There were 53 referrals, 34 (22%) from orthopaedic surgeons, 56 (37%) from general surgeons, 16 (10%) from general practice and 47 (31%) from other specialties. Only 83 (54%) of the referrals had followed the guidelines. Twenty-five (74%) of the orthopaedic referrals, 19 (34%) of the general surgical, 10 (63%) of the general practice and 29 (62%) of the other specialties had followed the guidelines. Seventy (46%) of the referrals had failed to follow the guidelines. Thirty-four (49%) of these had undergone excision inadequate for sarcoma prior to referral, of which eight had been re-excised. Twenty-four patients had not been staged prior to excision despite having a positive fine needle aspiration (FNA) in four cases. Eighteen patients (26%) had FNA or biopsy prior to imaging or referral.

Conclusion: Forty-six percent of sarcoma patients had not been treated according to the recommended guidelines. Forty-nine percent of these had inadequate primary sarcoma excision and this may have compromised their outcome. Orthopaedic surgeons had the best record for following the guidelines at 74% of referrals but this could be further improved. Doctors and especially surgeons need to be more aware of the principle of early referral of patients with suspected sarcomas.

A patient’s response to knee assessment questionnaires is often subjective and linked to age and cultural expectations.

In New Zealand 150 people, split into three groups of ages 20 to 40 years, 40 to 60 years and over 60 years, were given three commonly used knee assessment questionnaires. All were examined objectively to determine that their knees were normal. Scores in these groups were compared to similar groups of Canadian subjects and the results analysed.

The results show significant differences in expectations between the age groups. Older people were reluctant to score maximum points for their normal knees. The Hospital for Special Surgery’s knee score gave the lowest results, followed by the Knee Society score. In the over-60-year group there was a significant difference between scores in New Zealand and Canada, with Canadians tending to score higher in all scores.

These findings have implications when it comes to comparing results of total knee arthroplasty in different countries and age groups. This study has been expanded to include other countries in an attempt to find a mathematical formula that will make future comparisons more relevant.

Since its introduction in Christchurch in 1989, the mobile bearing LCS prosthesis has been used in over 3 500 total knee arthroplasty (TKA) procedures. The prosthesis is unique in that it has a mobile articulation not only at the tibiofemoral joint but also at the patellofemoral joint. The tibiofemoral articulation may be posterior cruciate retaining (meniscal bearings - MB) or sacrificing (rotating platform - RP).

Clinical and radiological assessment of 569 patients over three to nine years shows no significant difference between MB and RP groups with respect to Knee Society and New Jersey knees or the WOMAC functional score. In 93% of patients results were good or excellent. There were more early complications among MB patients, with five MB dislocations. However, four of these dislocations occurred in the early years this prosthesis and may reflect surgical inexperience. Clinical evidence of posterior cruciate laxity was present in 15% of the MB group, but there was no significant difference between knee scores of this group, the rest of the MB group, or the RP group.

When resurfaced patellae were compared to knees that were not resurfaced, there was no significant difference. Patellae with more than 4 mm of lateral subluxation were identified, but their knee scores were not significantly different.

The early to medium-term results of our continuing study of the LCS mobile bearing prosthesis are at least comparable to those of studies of fixed bearing prostheses. We continue to use this implant with confidence, but await long-term results.

We compared function in two groups of high demand patients who had undergone total knee arthroplasty (TKA), one group using a posterior cruciate sacrificing (PCS) prosthesis and the other a posterior cruciate retaining (PCR) prosthesis of similar design.

Patients were eligible for the study if surgery had been performed more than two years ago and they were under 65 years of age and had no coexisting morbidity that markedly decreased their physical activities. One surgeon operated on 28 patients in group A (20 TKAs), routinely retaining the posterior cruciate ligament (PCL). A second surgery operated on 19 patients in group B (25 TKAs) and routinely sacrificed the PCL. A mobile bearing prosthesis of similar design was used in each group. Patients were independently selected and assessed using a questionnaire specifically developed to assess higher levels of activity not usually assessed by other knee scores. Patients in the two groups were matched in terms of age, range of motion and follow-up

The gross activity score was 3.36 in group A and 3.12 in group B. The combined walking, running and stair-climbing score was in group A (7.68) than in group B (6.64). Patients in group B had decreased anterior knee pain and perceived their TKA closer to a normal knee (2.00 compared to 2.32).

We conclude that retaining the PCL in TKA results in better patient function without obvious complications.