Introduction: There is an impression among Orthopaedic surgeons that mobile bearing knee replacement has a better functional outcome than fixed bearing knee replacement. Since kneeling demands a high level of function after knee replacement this study was undertaken to see if mobile bearings in either total or unicompartmental replacement conferred an advantage.

Methods: A prospective randomised study of 207 TKR patients receiving the same prosthesis (Rotaglid, Corin, UK) was performed. Patients were randomised into a mobile bearing group (102 patients with a mean age of 53 years) and a fixed bearing group (105 patients with a mean age of 55 years). Data was also prospectively collected on 215 UKR patients who received the same unicompartmental implant (AMC, Uniglide, Corin, UK). 136 patients (Mean age: 62 yrs) had a mobile insert and 79 (mean age: 65 yrs) a fixed insert.

All patients completed the Oxford Knee Questionnaire preoperatively as well as at 1 and 2 years postoperatively. Their stated kneeling ability and total scores were analysed with a perfect score for kneeling ability being 4, and 48 the maximum total score.

Results: In all groups both the kneeling ability and the total scores improved markedly from their preoperative state. At two years the total score for the fixed bearing devices was marginally better than for the mobile (Rotaglide 36;31 and Uniglide 37;33)

There was a more striking difference with respect to kneeling ability with the fixed bearing variants performing better, (Rotaglide 1.4; 0.9 and Uniglide 1.9; 1.4), However, the greatest difference was between the UKR and TKR groups (UKR 1.7; TKR 1.2). Pre-operatively less than 2% of TKR patients (7% of the UKR patients) could kneel. Post-operatively, the patients’ kneeling ability improved with 21% for the mobile bearing, 32% of fixed bearing UKR patients. The TKR patients kneeling ability was 13% of the mobile, 26% of fixed bearing patients were able to kneel with little or no difficulty. In all groups the stated kneeling ability was poor with less than 50% of any group being able to kneel with ease or only minor difficulty.

Conclusion: Those undergoing UKR appeared to perform better than those with a TKR. None of the forms of knee replacement used resulted in good kneeling ability, though this function was improved by arthroplasty in all groups. Mobile bearing inserts

Purpose: Revision patellofemoral arthroplasty (PFA) is a relatively uncommon procedure, with no published reviews identified in the literature. Revision PFAs performed at our institution were reviewed to determine the reasons for PFA failure, the technical ease of revision and to document patient-reported outcomes after revision.

Methods: A prospective review of a cohort of 411 Avon PFA patients identified 31 subsequent revision knee procedures in 27 patients. Data was collected from the institution’s prospective data base, operative reports, X-rays and medical records. Post-operative knee scores (Oxford Knee Score, WOMAC Osteoarthritis Index, Bristol Knee Score) were available on 26 knees.

Results: The commonest reason for revision was progression of osteoarthritis (18 cases) followed by undetermined pain (7 cases). Patients with undetermined pain were found to be revised sooner than patients with disease progression (33 months vs 63 months) and also reported poorer outcome scores at 2 years post revision than the disease progression group.

Only two trochlea components were loose at the time of revision and one patella had a large amount of macroscopic wear. All other components were found to be well fixed with minimal wear at the time of revision. There were no difficulties in removing either component. No cases required augments or stemmed femoral components due to bone loss.

Patients undergoing revision surgery did report improvement in their post revision outcome scores compared with their pre-operative scores. The average Oxford Knee Score improved from 17 to 23, Bristol Knee Pain Scores improved from 11 to 20 and Bristol Knee Functional Scores improved from 15 to 16. These results are poorer than those recorded by the overall cohort of primary PFA.

Conclusion: PFA is easy to revise to a primary total knee. Results of revision knees are improved from pre-operative scores but not as good as expected.

Introduction: There is an impression among Orthopaedic surgeons that mobile bearing knee replacement has a better functional outcome than fixed bearing knee replacement. Since kneeling demands a high level of function after knee replacement this study was undertaken to see if mobile bearings in either total or unicompartmental replacement conferred an advantage.

Methods: A prospective randomised study of 207 TKR patients receiving the same prosthesis (Rotaglid , Corin, UK) was performed. Patients were randomised into a mobile bearing group (102 patients with a mean age of 53 years) and a fixed bearing group (105 patients with a mean age of 55 years).

Data was also prospectively collected on 215 UKR patients who received the same Unicompartmental implant (AMC, Uniglide, Corin, UK). One hundred and thirty six patients (Mean age: 62 yrs) had a mobile insert and 79 (mean age: 65 yrs) a fixed insert.

All patients completed the Oxford Knee Questionnaire preoperatively as well as at 1 and 2 years postoperatively. Their stated kneeling ability and total scores were analysed with a perfect score for kneeling ability being 4 and 48 the maximum total score.

Results: In all groups both the kneeling ability and the total scores improved markedly from their preoperative state. At two years the total score for the fixed bearing devices was marginally better than for the mobile (Rotaglide 36;31 and Uniglide 37;33)

There was a more striking difference with respect to kneeling ability with the fixed- bearing variants performing better, (Rotaglide 1.4; 0.9 and Uniglide 1.9; 1.4), However, the greatest difference was between the UKR and TKR groups (UKR 1.7; TKR 1.2). Pre-operatively less than 2% of TKR patients (7% of the UKR patients) could kneel. Post-operatively, the patients’ kneeling ability improved with 21% for the mobile bearing, 32% of fixed bearing UKR patients.

The TKR patients kneeling ability was 13% of the mobile, 26% of fixed bearing patients were able to kneel with little or no difficulty. In all groups the stated kneeling ability was poor with less than 50% of any group being able to kneel with ease or only minor difficulty.

Conclusion: Those undergoing UKR appeared to perform better than those with a TKR. None of the forms of knee replacement used resulted in good kneeling ability, though this function was improved by arthroplasty in all groups. Mobile bearing inserts did not confer any advantage with respect to kneeling and in fact performed worse with regard to this particular knee function.

Objective: To review the results of the Avon patellofemoral arthroplasty at 5 to 8 years.

Methods: The Avon patellofemoral arthroplasty was introduced in clinical practice in September 1996. We present a prospective cohort review of all patients treated in the first three years. Patients were evaluated using the Bristol knee score (BSK), the Melbourne patella score (MPS) and the Oxford knee score (OKS).

Results: 109 patellofemoral arthroplasties were performed in 92 patients between September 1996 and November 1999. The median age was 68 years (range 46 to 86 years). Nine patients (12 knees) died and two patients (two knees) were unfit for follow-up. Ten knees in 9 patients were lost to follow-up giving a follow-up rate of 89%. The mean period of follow-up was 5.6 years.

The median pain score rose from 15/40 pre-operatively to 40 points at eight years. The median (MPS) rose from 10/30 points pre-operatively to 25 points at eight years. The median (OKS) rose from 18/48 pre-operatively to 38 at eight years. 87% of knees had mild or no pain at eight years. There were no cases of failure of the prosthesis itself. All 15 revisions resulted from progression of arthrititis in the tibio-femoral joint. The five-year survival rate for all causes with 86 cases at risk was 96%.

Conclusions: The results show that this type of arthroplasty can give predictable pain relief and excellent functional improvement in patients with isolated patello-femoral arthritis. Disease progression is the main reason for revision to total knee replacement and great care is required in assessing the indications for this procedure.

Introduction: Anterior Knee pain is a very common presentation in Orthopaedic out patient clinics. However, Trochlear Dysplasia as a condition is still not very well understood.

Materials and Methods: Operative findings in patients undergoing Trochleaplasty and in young patients undergoing Patella-femoral arthroplasty were studied. Patients having trochlear dysplasia were identified. All these patients were sent a questionnaire to explore the variety of symptoms they experienced. 87 patients were identified for the study. 71(82%) patients responded to the questionnaire.

Results: Two subgroups were identified, one with dislocation of patella and the other without dislocation of the patella. Patients in patella dislocation group were younger (12 years vs 24) than those who presented without dislocation of patella. Patella dislocation group had more patients with anterior knee pain (71% vs 52%) as teenagers as compared to the group without dislocations. Symptoms such as giving way, lack of trust and unable to participate in sports were more commonly seen in the group with patella dislocation whereas, limited walking distance and difficulty with climbing the stairs were more commonly seen in the group without dislocation. Symptoms such as pain, catching and locking were seen equally amongst the two groups.

Conclusion: We believe that the patients with trochlear dysplasia have a bimodal presentation. Patients with dislocation of patella present earlier than those without patella dislocation. These two groups also have different symptoms at presentation. It is important to identify these subgroups correctly for appropriate management.

Purpose of Study: Fixed bearing unicompartmental knee replacement (UKR) has become popular since several series have shown good 10 year survivorship and excellent function. However little is known about survival during the second decade.

Method: From the Bristol database of over 4000 knee replacements 203 St. George Sled UKR’s which had already survived 10 years were identified. The mean age at surgery was 67 years (48–85), with 64% being female. This cohort has been further reviewed at an average of 14.8 years (10–30) from surgery to determine survivor-ship and function.

Results: Survivorship during the second decade was 87.5%. 58 patients (69 knees) had deceased with implant in situ, only 2 after revision. A further 15 UKR’s have been revised at an average of 13 years post op; 7 for progression of disease, 4 for tibial loosening, 3 for polyethylene wear, 2 for femoral component fracture and 2 for infection.

99 knees were followed for 15 years and 21 knees for 20 years. The average Bristol knee score of the surviving knees fell from 86 to 79 during the second decade.

A previous study showed an 89% 10 year survivor-ship and this is now extended to 82% at 15 years and 76.5% at 20 years.

Conclusion: Satisfactory survival of fixed bearing UKR can be achieved in the second decade suggesting that the indications for mobile bearings require careful definition since there is a higher incidence of complications in many people’s hands.

The purpose of this study was to determine the incidence of revision total knee replacement (TKR) within 5 years of the index procedure at a large multi-surgeon unit using a single prosthesis and to determine the cause of failure of those implants.

This was a retrospective review of all primary Kine-max Plus TKR performed at the Avon Orthopaedic Center between 1.1.1990 and 1.1.2000. Cases were identified that required revision arthroplasty in any form within 5 years of the index procedure. Case notes and Xrays were reviewed to determine causes of failure.

There were 2826 primary Kinemax Plus TKR performed during the study period. Of these 20 were known to have required revision surgery within 5 years. 8 were revised for deep infection of the prosthesis and 12 for aseptic causes. The overall incidence of premature failure of the Kinemax Plus TKR at 5 years was 0.71%. The incidence of aseptic premature failure at 5 years was 0.42%. Detailed examination of the clinical records indicated that some form of technical error at the time of the index arthroplasty was responsible for the early failure of 6 prostheses. This equates to 0.21% of the procedures performed. Aseptic loosening of the remaining 6 cases could not be attributed to a specific cause.

Introduction: Following previously gratifying results in older patients the study aims to quantify the outcomes and identify any contraindications in patient selection for patello-femoral replacements using the Avon pros-thesis in patients under 55 years old.

Method: We present early outcome results for a prospective cohort study of patients under 55 years of age.110 knees in 86 patients (median age 47years, range 25–54) have been treated with Avon patello-femoral replacement (88 in females and 22 in males). Diagnoses included lateral facet OA (59 knees), patella dislocation (36 knees), trochlear dysplasia (39 knees) and post patellectomy instability (7 knees). 108 knees had undergone previous surgery. 14 knees required additional intra-operative procedures (including 11 lateral releases and 2 patella realignments). All patients were assessed pre-operatively using the Oxford, Bristol and WOMAC scores.

Results: No knees have been lost to follow-up. 82 knees have post operative scores available (mean follow-up 27 months). 8 have been revised (6 due to progression of OA). The mean Oxford, Bristol and WOMAC scores all improved: 18 to 32, 56 to 83 and 39 to 25 respectively. Asymptomatic deterioration of the tibio femoral joint is seen in some cases of primary OA but not with trochlear dysplasia. 21 knees required post-operative additional procedures including 6 lateral releases, 3 patella realignments and 5 revisions. Equally good results were seen when comparing patients with the 3 main diagnoses. Trochlear dysplasia is strongly predicted by young age at onset of symptoms and patellar dislocation.

Conclusion: Many of this type of patient, with disabling symptoms, wish to “live now”. The short-term improvements are frequently dramatic. Comparison of underlying pathologies has not identified groups that are performing less well to suggest restricting current indications. As yet there is no suggestion of prosthetic failure. Revision has presented little difficulty since minimal bone is resected primarily.

We identified 148 patients who had undergone a revision total knee replacement using a single implant system between 1990 and 2000. Of these 18 patients had died, six had developed a peri-prosthetic fracture and ten had incomplete records or radiographs. This left 114 with prospectively-collected radiographs and Bristol knee scores available for study. The height of the joint line before and after revision total knee replacement was measured and classified as either restored to within 5 mm of the pre-operative height or elevated if it was positioned more than 5 mm above the pre-operative height. The joint line was elevated in 41 knees (36%) and restored in 73 (64%).

Revision surgery significantly improved the mean Bristol knee score from 41.1 (sd 15.9) pre-operatively to 80.5 (sd 15) post-operatively (p < 0.001). At one year post-operatively both the total Bristol knee score and its functional component were significantly better in the restored group than in the elevated group (p < 0.01). Overall, revision from a unicondylar knee replacement required less use of bone graft, fewer component augments, restored the joint line more often and gave a significantly better total Bristol knee score (p < 0.02) and functional score (p < 0.01) than revision from total knee replacement.

Our findings show that restoration of the joint line at revision total knee replacement gives a significantly better result than leaving it unrestored by more than 5 mm. We recommend the greater use of distal femoral augments to help to achieve this goal.

We report the mid-term results of a new patellofemoral arthroplasty for established isolated patellofemoral arthritis. We have reviewed the experience of 109 consecutive patellofemoral resurfacing arthroplasties in 85 patients who were followed up for at least five years.

The five-year survival rate, with revision as the endpoint, was 95.8% (95% confidence interval 91.8% to 99.8%). There were no cases of loosening of the prosthesis. At five years the median Bristol pain score improved from 15 of 40 points (interquartile range 5 to 20) pre-operatively, to 35 (interquartile range 20 to 40), the median Melbourne score from 10 of 30 points (interquartile range 6 to 15) to 25 (interquartile range 20 to 29), and the median Oxford score from 18 of 48 points (interquartile range 13 to 24) to 39 (interquartile range 24 to 45). Successful results, judged on a Bristol pain score of at least 20 at five years, occurred in 80% (66) of knees. The main complication was radiological progression of arthritis, which occurred in 25 patients (28%) and emphasises the importance of the careful selection of patients. These results give increased confidence in the use of patellofemoral arthroplasty.

There have been several reports of good survivorship and excellent function at ten years with fixed-bearing unicompartmental knee replacement. However, little is known about survival beyond ten years.

From the Bristol database of over 4000 knee replacements, we identified 203 St Georg Sled unicompartmental knee replacements (174 patients) which had already survived ten years. The mean age of the patients at surgery was 67.1 years (35.7 to 85) with 67 (38.5%) being under 65 years at the time of surgery. They were reviewed at a mean of 14.8 years (10 to 29.4) from surgery to determine survivorship and function. There were 99 knees followed up for 15 years, 21 for 20 years and four for 25 years. The remainder failed, were withdrawn, or the patient had died.

In 58 patients (69 knees) the implant was in situ at the time of death. Revision was undertaken in 16 knees (7.9%) at a mean of 13 years (10.2 to 21.6) after operation. In seven knees (3.4%) this was for progression of arthritis, in three (1.5%) for wear of polyethylene, in four (2%) for tibial loosening, in two (1%) for fracture of the femoral component and in two (1%) for infection. Two knees (1%) were revised for more than one reason.

The mean Bristol knee score of the surviving knees fell from 86 (34 to 100) to 79 (42 to 100) during the second decade. Survivorship to 20 years was 85.9% (95% CI 82.9% to 88.9%) and at 25 years was 80% (95% CI 70.2% to 89.8%). Satisfactory survival of a fixed-bearing unicompartmental knee replacement can be achieved into the second decade and beyond.

Purpose of study: To examine the fate of the non operated on compartment of the knee, following unicompartmental knee replacement (UKR), by radiological assessment 10 years after operation.

Summary of methods and results: A total of 50 UKRs were performed on 45 carefully selected patients between 1989 and 1992. Fifteen patients died, two patients were lost to follow-up and two knees were revised. The radiographs of the remaining 30 knees were reviewed three times by blind and randomised assessment using Ahlback and Altman scoring systems to measure the progression of osteoarthritis within the joints. Standard long-leg weight-bearing anteroposterior views of the knee and skyline views of the patello-femoral joint were taken before, at eight months and ten years after operation. Two knees showed evidence of progression of osteoarthritis within the patello-femoral joint and three knees showed some progression of the opposite tibio-femoral compartment.

Statement of conclusion: Our study provides evidence that after ten years progressive OA within the retained compartments following UKR is rare and usually minor.

Aim: To assess the results of aseptic and aseptic cases using the PFC/TC3 system, and to correlate this with the restoration of joint line height.

Method: 148 patients underwent revision TKR using the PFC/TC3 system. No re-revision cases were included in this series. Data was prospectively collected (using the Bristol Knee Score) pre-operatively and at a mean of 4.2 years post-revision. 31 revisions were for infection and 53 revisions were for aseptic loosening. Revision for infection was done as a two-stage procedure and aseptic as a single operation. Measurements of the joint line height were made pre and post-operatively using Figgie’s method. The cases were divided into 3 groups on the basis of joint line restoration:

Lowered by more than 5 mm

Results: The mean pre-op total score for the infection group was 35/100 and 40/100 for the aseptic loosening group. The total score post-operatively was 67 for the infection group and 73 for the aseptic loosening group. The joint line was restored in 50% of infected cases and in 60% of aseptic loosening cases.

Conclusion: although the overall results were slightly less satisfactory for the infected revision group, there was no significant difference between the two groups either in total BKS scores or in reproduction of the joint line. The average outcome was much less good than for primary TKR.

Introduction: Correct prosthesis alignment and joint line reproduction in total knee replacement (TKR) is vital for a successful clinical outcome. It is acknowledged that the ideal coronal alignment of the knee following TKR should be between 4–10 degrees of valgus. A neutral or varus knee is associated with a higher failure rate. Previous studies have shown that ideal alignment is achieved in only around two-thirds of cases.

Joint line elevation > 8mm has been associated with inferior clinical outcome, and depression associated with retropatellar pain and increased risk of patella subluxation.

Recently, modifications have been made to the Kine-max-Plus Total Knee System instrumentation, theoretically providing better internal fixation to prevent a varus cut and a 12 mm measured resection from the “normal” tibial plateau. This study aims to examine whether these changes result in an improvement in alignment, and a more reliable restoration of joint line.

Materials and Methods: Two consecutive series, each of 75 patients who had undergone TKR using either the old (Group A) or the new (Group B) instrumentation were included in the study. Antero-posterior and lateral preoperative and postoperative knee radiographs were assessed using the American knee society radiographic analysis for prosthesis postionoing by 2 independent observers. The Tibial and Femoral Component Angles in the coronal plane (cTCA and cFCA) and in the sagittal plane (sTCA and sFCA) were measured, as was the change in joint line height.

Conclusion: Our results suggest that use of the new instrumentation is associated with better restoration of joint line, and is more effective in preventing implantation of the tibial component in varus. These figures relating to a modern instrumentation system provide a yardstick against which computer assisted and robotic surgery can be judged. Long-term follow-up will be required to assess the clinical significance of these results.

Purpose: To assess the outcome of customised hinged knee replacements when used to salvage catastrophically failed knee replacements in elderly patients.

Methods: Since 1993, 30 of the 280 (10.7%) revision knee replacements at the Avon Orthopaedic Centre, Bristol have used Endo customised hinged knee pros-theses (21 rotating, 9 fixed) for salvage of limb threatening situations in elderly patients. All were prospectively recorded and regularly reviewed. The average age was 75 years with a predominance of females. Surgical indications were 22 periprosthetic fractures (with or without aseptic loosening), 5 massive aseptic osteolyses, and 3 deep infections.

Results: The mean length of postoperative hospital stay was just 14.6 days and all patients were discharged walking with aids. At follow up (mean 3.0 years, range 0.5–9.3 years) 9 patients had died with their prostheses in situ and functioning. 2 had undergone amputation for recurrent sepsis and 2 had received further surgery for septic problems. 2 patients required further surgery for prosthetic disarticulation and one patient had successful on table vascular repair. 25 patients had mid or long term follow up. Their mean American Knee Scores (AKS) were 69.8 for knee and 35.6 for function (maximum 100), with a mean total knee flexion of 83 degrees. Mean Oxford knee scores (OKS) and WOMAC scores (both scored between 12 and 60 with low score indicating less difficulties) were 34.0 and 30.5 respectively.

Conclusions: Customised hinge revision knee replacements gave extremely rapid rehabilitation and hospital discharge which justified the high prosthetic cost. Complications were high but at mid and long-term review, no prostheses had failed from an aseptic cause and most of the knees of this challenging group were providing both stability and flex

Following total hip arthroplasty (THA) and total knee arthroplasty (TKR) only the ‘visible’ measured blood loss is usually known. This underestimates the ‘true’ total loss, as some loss is ‘hidden’. Correct management of blood loss should take hidden loss into account.

We studied 101 THAs and 101 TKAs (with re-infusion of drained blood). Following THA, the mean total loss was 1510 ml and the hidden loss 471 ml (26%). Following TKA, the mean total loss was 1498 ml. The hidden loss was 765 ml (49%). Obesity made no difference with either operation.

THA involves a small hidden loss, the total loss being 1.3 times that measured. However, following TKA, there may be substantial hidden blood loss due to bleeding into the tissues and residual blood in the joint. The true total loss can be determined by doubling the measured loss.

Purpose A new design of patello-femoral arthroplasty has been used to treat patients under 55 years suffering severe symptoms from chondral and early arthritic disease of the patello-femoral joint.

Materials and Methods and Results Fifty-two patello-femoral arthroplasties were performed in 45 patients under the age of fifty-five years when other treatments had failed. The average age was 48 years (range 36–54 years). Thirty-seven cases had undergone previous surgery for a variety of conditions, and the causes of the disorders were analysed. Results were assessed using pain scores and Bartlett’s and Oxford functional scores. 35 cases were reviewed at 8 months and 22 cases at two years. The median pain score improved from 10/40 points to 35 at two years. The Bartlett score increased from 10/30 points to 27 and the Oxford score from 19/48 points to 35 at two years. The range of movement increased from 114° to 121°. There have been no cases of deep infection, loosening, wear or instability. Disease progression, a potential risk has occurred in one case.

Conclusions This prosthesis offers a solution in younger patients with disabling symptoms of isolated early patello-femoral disease who have not responded to conservative surgical management.

The aim of this study was to examine causes of the failed knee arthroplasty.

Since 1980 the Bristol Knee Replacement Registry has prospectively recorded data on 3024 patients. Complete original and 5 year follow up data was available on 999 knees.

The surgery was judged a failure if there was no improvement in the American Knee Society score at 5 years or if there had been a revision within that time.

The prosthesis used was Kinematic in 471 knees, the Medial Unicompartmental Sled in 258 knees, the Kinemax Plus in 134 knees and a variety of other designs.

At 5 years, 79 (7. 9%) either showed no improvement in the American Knee Society score or had been revised. The failure rate was 7% for the Kinematic, 7% for the medial Sled and 5% for the Kinemax Plus. 20% of the less frequently used designs failed.

Five (0. 5%) knee replacements failed because of infection. 22 knees (2. 2%) had significant comorbidity that precluded a satisfactory functional outcome. For 7 knees (0. 7%), the patient exhibited patterns of abnormal illness behaviour that were thought to explain the poor outcome. A further 27 knees (2. 7%) failed because of technical errors either at the time of surgery (13 cases, 1. 3%), or in selecting a prosthesis which failed prematurely (14 cases 1. 4%). No cause for failure could be identified in 12 cases (1. 2%).

The high failure rate amongst infrequently used prosthesis emphasises the need to use established designs. No cause for failure could be identified in 12 cases and 5 were due to infection; such cases are hard to avoid. This study shows the importance of assessing both the overall physical and psychological state of the patient if disappointing results are to be avoided. The most frequent cause of an unsatisfactory outcome was a technical one, which should be avoidable.

Isolated patellofemoral arthritis occurs in up to 10% of patients suffering osteoarthritis of the knee. Previous reports of several different patellofemoral designs have given indifferent results. The Lubinus prosthesis has been shown to have a 50% failure rate at eight years in a study of 76 cases. The main reasons for failure were mal-alignment, wear, impingement and disease progression. As a result of these studies, a new prosthesis was designed to solve some of these problems.

The Avon patellofemoral arthroplasty was first implanted in September 1996. The cases have been entered into a prospective review with evaluations at eight months, two years and five years. The outcome was assessed using pain scores, Bartlett’s patella score and the Oxford knee score. To date, 186 knees have been treated; over 100 knees have been reviewed at two years and 20 knees at five years. The main pain score improved from a pre-operative level of 13.5 points out of 40 to 33.5 points at two years and 36 at five years. The mean pre-operative movement was 109° and this increased to 120° at five years. The Bartlett patella score improved from a pre-operative level of 10.5 points out of 30 pre-operatively to 23 points at two years and 25 at five years. The Oxford knee score was 20 points out of 48 pre-operatively and this improved to 35 points at two years and 40 points at five years. One patient developed subluxation, which required distal soft tissue realignment. No other patient has developed problems with alignment or wear. Ten knees have developed evidence of disease progression usually in the medial compartment of which six have required revision to a total knee replacement.

The results to date suggest that this improved design has all but eliminated the previous problems of malalignment and early wear. The functional results are as good or better than those of a total knee replacement. There is a low complication rate and an excellent range of movement. Disease progression remains a potential problem. This type of prosthesis offers a reasonable alternative to total knee replacement in this small group of patients with isolated, early patellofemoral disease.

The aim of this study was to report our experience of patellofemoral arthroplasty in isolated osteoarthrosis.

Material and Methods: The Lubinus Patellofemoral Arthroplasty was performed between 1989 and 1995 in 76 knees. The Avon Patella Femoral Arthroplasty was used from 1996 to 2001 in 187 knees. The average age of the patients was 65.5 years (range 36–87) with a male to female ratio of 1: 5. All the patients have been prospectively reviewed with standard radiographs, the Bristol Knee Score, and more recently Bartlett and Oxford scores.

Results: Patients with the Lubinus prosthesis were followed for an average of 7.4 years (range 5–10 years). Eleven patients (14 knees) have died and the remaining 62 knees have a 100% follow-up. The cumulative revision rate was 28% (21 out of 76). Survivorship at 8 years was 65% (Cl 49 to 77) for revision and 48% (Cl 36 to 59) for revision plus moderate pain. The two main complications were Maltracking 32% and progressive tibio-femoral arthritis in 9%.

The Avon Arthroplasty with improved design features for better tracking and congruity was introduced in 1996 and 187 have now been inserted in 147 patients. One hundred and nine knees have been followed for 8 months and 82 have completed the 2 year follow-up. Two patients have undergone revision to a TKR 97.5% (survivorship 2 out of 82). Three patients have had a unicompartmental arthroplasty added for disease progression. There have been no cases of patella maltracking or subliaxation.

Four year survivorship for moderate pain and revision is 96% (79 out of 82). Functional scores compared favourably with parallel series of total knee replacements.

Conclusion: The medium-term results of the Lubinus Patello Femoral Arthroplasty are unsatisfactory. We suggest the use of this prosthesis should be discontinued. The Avon Arthroplasty has improved results in the short-term.