Aims This study reports on the medium- to long-term implant survivorship and patient-reported outcomes for the Avon patellofemoral joint (PFJ) arthroplasty. Patients and Methods A total of 558 Avon PFJ arthroplasties in 431 patients, with minimum two-year follow-up, were identified from a prospective database. Patient-reported outcomes and implant survivorship were analyzed, with follow-up of up to 18 years. Results Outcomes were recorded for 483 implants (368 patients), representing an 86% follow-up rate. The median postoperative Oxford Knee Score (0 to 48 scale) was 35 (interquartile range (IQR) 25.5 to 43) and the median Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC, 0 to 100 scale) was 35 (IQR 25 to 53) at two years. There were 105 revisions, 61 (58%) for progression of osteoarthritis. All documented revisions were to primary knee systems without augmentation. The implant survival rate was 77.3% (95% confidence interval (CI) 72.4 to 81.7, number at risk 204) at ten years and 67.4% (95% CI 72.4 to 81.7 number at risk 45) at 15 years. Regression analysis of explanatory data variable showed that cases performed in the last nine years had improved survival compared with the first nine years of the cohort, but the individual operating surgeon had the strongest effect on survivorship. Conclusion Satisfactory long-term results can be obtained with the Avon PFJ arthroplasty, with maintenance of patient-reported outcome measures (PROMs), satisfactory survival, and low rates of loosening and wear. Cite this article: Bone Joint J 2018;100-B:1162–7.

The aim of this study was to document the survivorship and patient reported outcome of the Avon patello-femoral replacement in a consecutive series with follow up of 10 years or more.All cases performed in Bristol from 1996 onwards were prospectively recorded. Follow up was at 1,2,5,7,10,12 and 15 years with the Bristol Patella Score, the Oxford and WOMAC scores and SF12. Implant survival was analysed using the Kaplan-Meier method.There were 323 PFJ replacements (280 individuals). Follow up was available for 286 cases in 250 patients (89% follow up). The 10 year survival rate was 77%, falling to 67% at 15 years. The most common reason for revision was tibio-femoral progression (45/74 revisions), with loosening or polyethylene wear recorded in 8 cases. The best results were seen in the youngest and the oldest patients. Good improvements were seen in PROMs, with the mean OKS improving from 19.5 to 34.1 at 2 years and 32.7 at the 15 years.The Avon patello-femoral knee replacement is a successful long-term tr...

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We present the ten- to 15-year follow-up of 31 patients (34 knees), who underwent an Elmslie-Trillat tibial tubercle osteotomy for chronic, severe patellar instability, unresponsive to non-operative treatment. The mean age of the patients at the time of surgery was 31 years (18 to 46) and they were reviewed post-operatively, at four years (2 to 8) and then at 12 years (10 to 15). All patients had pre-operative knee radiographs and Cox and Insall knee scores. Superolateral portal arthroscopy was performed per-operatively to document chondral damage and after the osteotomy to assess the stability of the patellofemoral joint. A total of 28 knees (82%) had a varying degree of damage to the articular surface. At final follow-up 25 patients (28 knees) were available for review and underwent clinical examination, radiographs of the knee, and Cox and Insall scoring. Six patients who had no arthroscopic chondral abnormality showed no or only early signs of osteoarthritis on final radiographs; while 12 patients with lower grade chondral damage (grade 1 to 2) showed early to moderate signs of osteoarthritis and six out of ten knees with higher grade chondral damage (grade 3 to 4) showed marked evidence of osteoarthritis; four of these had undergone a knee replacement. In the 22 patients (24 knees) with complete follow-up, 19 knees (79.2%) were reported to have a good or excellent outcome at four years, while 15 knees (62.5%) were reported to have the same at long-term follow-up. The functional and radiological results show that the extent of pre-operatively sustained chondral damage is directly related to the subsequent development of patellofemoral osteoarthritis.

Introduction The Bristol Knee Group has prospectively followed the results of over 500 isolated patellofemoral arthroplasties. Initial experience with the Lubinus prosthesis was disappointing. The main causes of failure were mal-tracking and instability leading to excessive polythene button wear and disease progression in the tibio femoral joint. This experience resulted in the design of a new prosthesis to correct the tracking problems and improve the wear. We have now performed over 425 Avon arthroplasties with a maximum follow-up of 9 years. Results Survivorship at 5 years and the functional outcome have been reported with 95.8% survivorship, and improved function with Oxford score from 18 to 39 points out of 48. There have been 14 cases with mal-tracking (3%). Several of these cases have required proximal or distal realignment with the Elmslie or Insall procedures. Two knees with patella alta required distalisation of the tibial tubercle. Symptomatic progression of the arthritic disease in the medial or lateral tibio-femoral compartments has occurred in 28 cases (7%) causing recurrent joint pain. Radiographic follow-up has shown a higher rate of disease progression emphasising the importance of careful assessment of patients prior to operation. We have investigated 8 cases of persistent unexplained pain. Analysis of these cases suggests 3 possible causes. An extended anterior cut leading to overstuffing, insufficient external rotation and over sizing of the femoral component leading to medial or lateral retinacular impingement. Six of these cases have been successfully treated by revision of the femoral component leading to dramatic resolution of the symptoms. Conclusion Minor misplacement of the femoral component can lead to retinacular impingement causing persistent pain. Attention to detail in the performance of the operation will prevent these problems. Disease progression remains a risk in any compartmental arthroplasty and may be inevitable, thus strict pre-operative criteria are essential.

Introduction In 1976 the senior author presented to the Associations the results of patellectomy with satisfactory results in less than 50% of cases. In 1989 with the increasing success of TKR we started a prospective study of the Lubinus prosthesis for patellofemoral arthritis. After 4 years results were not satisfactory. The main causes of failure were mal-tracking and instability leading to polythene button wear, and arthritic disease progression. A new prosthesis was designed in 1996 to correct these problems. Methods We have prospectively recorded the results of a consecutive cohort of 537 Avon arthroplasties. The outcomes have been assessed with survivorship, pain, Oxford and WOMAC scores. We have identified 24 patients from our own series and from tertiary referrals who have persistent pain, due to technical error rather than arthritic disease progression. Results Survivorship for revision at 5 Years was 96% and overall there were 63 revisions. Results over 10 years show excellent and consistent improvement in both pain and function as judged by the median WOMAC score and are similar to patients with a TKR. The pain score improved from 45% (16) to 87% (7.5), the function score improved from 50% (21) to 80% (12.5). The Oxford score improved from 39.5% (19) to 69% (33). Symptomatic arthritic disease progression occurred in 12% of cases causing recurrent pain. Persistent non-arthritic pain was due to three main causes: minor misplacement of the femoral or patella components or over sizing, leading to retinacular impingement and over stuffing of the patellofemoral joint. Conclusion This prosthesis has shown consistently good results with few problems over 14 years. New instruments will increase the accuracy of insertion and attention to detail in the performance of the operation will prevent problems. Disease progression remains the main cause of failure and strict pre-operative criteria are essential.

Although good long term results for fixed bearing uni-compartmental knee replacements (UKRs) have been reported mobile bearings predominate in some parts of the world. Three prospective studies have been undertaken comparing the short and medium term outcomes of fixed and mobile UKRs. A 5 year comparative cohort study of 47 Oxford mobile bearing and 57 St Georg Sled fixed bearing UKRs. A 2 year study of 50 fixed and 50 mobile bearing AMC Uniglide UKRs.(The implant system allows implantation of either a fixed or mobile tibial component with the same femoral component.) The 1 year results of a randomised controlled trial of 38 fixed and 33 mobile AMC Uniglide UKRs in patients under 70. In all groups the preoperative sex mix, average age and knee scores were extremely similar. All patients were assessed both pre and postoperatively by a research nurse and radiographs were taken; the results were entered on the Bristol Knee database. Results: Multiple problems were encountered, perhaps because of the introduction of MIS, but at 5 years 11 Oxford and 4 Sleds had failed. The major problem with the mobile bearing implant was instability though tibial fractures were also seen. Both groups had three cases of arthritic progression and loose cement was seen twice in the fixed bearing group. – Amongst the remaining patients the median scores for the Sled were better. Bristol Knee Score (Max 100) 95:90; Oxford (Max 48) 39:37; and reduced WOMAC (Best score 12) 18:24. 2 bearing exchanges and 3 revisions were needed in the mobile group with none in the fixed group. Again all scores were better for the fixed group. American Knee Score (AKS) (Max 200) 195:185; Oxford (Max48) 39:37; and reduced WOMAC (Max 12) 19:20. One fixed bearing implant had been revised but none in the mobile group, however 3 randomised to receive a mobile bearing had a fixed bearing inserted because the surgeon was unhappy about bearing stability; all three are doing well. All knee scores at one year show the fixed bearing implant to be performing better. AKS (Max 200) 194:173; Oxford (Max48) 39:33; and WOMAC(Max) 12 18:22. Conclusion. Although theoretically mobile bearings will give greater longevity there is frequently a short term price to pay particularly when the procedures are performed by inexperienced surgeons and trainees. Since the wear properties of polyethylene have improved in recent years these studies suggest that a fixed bearing option can be used more safely in many patients.

Purpose of Study: Fixed bearing unicompartmental knee replacement (UKR) has become popular since several series have now 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. Georg 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 survivorship and function. Results: Survivorship during the second decade was 87.5%. 58 patients (69 knees) had died with implant in situ and 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 in the opposite compartment, 4 for tibial loosening, 3 for polyethylene wear, 2 for femoral component fracture and 2 for infection. 99 knees were followed for 15 years, 21 knees for 20 years and four for 25 or more years. The average Bristol knee score of the surviving knees fell from 86 to 79 during the second decade, largely as a result of aging. A previous study of the St Georg. Fixed bearing UKR showed an 89% 10 year survivorship 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.

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.

Since 1996 over 400 isolated patellofemoral replacements using the Avon prosthesis have been undertaken in Bristol. As a result of the usually gratifying outcomes seen in patients over 55 years old, the indications for this surgery were soon extended to include the many younger patients who have severely disabling patellofemoral disease. We present results from a prospective cohort study of patients under 55 years of age at the time of surgery. 110 knees in 86 patients (median age 47 years, range 24–54) have been treated with Avon patellofemoral replacement (88 in females and 22 in males). Diagnoses included lateral facet OA (59 knees), patella dislocation (25 knees), trochlear dysplasia (41 knees) and post patellectomy instability (7 knees). 79 knees had undergone previous surgery. 17 knees required additional intra-operative procedures including 11 lateral releases and 2 patella realignments. All patients were assessed pre-operatively and at regular intervals using the Oxford, Bristol and WOMAC scores. All knees were scored preoperative and only one knee has been lost to follow-up due to the patient’s death, which was unrelated to surgery. Post-operative Oxford knee scores have been obtained for 106 knees with follow-up between 8 months and 8 years (mean follow-up 24 months). The mean Oxford score improved from 18 preoperatively to 31 at latest review. Bristol and WOMAC scores showed similar improvements. 16 knees required post-operative additional procedures including 6 lateral releases, 3 patella realignments and 11 revisions. Of the revisions 5 were for progression of tibiofemoral OA but none of these were knees with trochlear dysplasia. Equally good mean scores were seen when comparing patients with the 3 main underlying pathologies (trochlear dysplasia, patellar dislocation and lateral facet OA). At least 37% of the patients studied had pre-existing trochlear dysplasia and the majority of these patients report onset of symptoms, often patellar dislocation, in the first three decades of life. More than 90% of patients were overweight or obese according to their BMI at the time of surgery. Many of this type of patient, with disabling symptoms, wish to “live now”. The short-term improvements are frequently dramatic. As yet there is no suggestion of prosthetic failure. Revision presents little difficulty since minimal bone is resected in the primary proceedure. Radiological deterioration of the tibio femoral joint is seen in some cases of primary OA but not with trochlear dysplasia.

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.

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.

Functional outcome after patellofemoral joint replacement (PFA) for osteoarthritis remains inconsistent. It is believed that functional outcome for joint replacement is dependent upon postoperative joint kinematics. Minimal disruption of the native joint, as in PFA, should produce more normal kinematics and improved outcome. No previous studies have examined joint kinematics after isolated PFA. Aim: To investigate the sagittal plane kinematics of patellofemoral replacement and compare with the normal knee. Twelve patients who had undergone successful PFA at least two years previously were recruited. Patients performed flexion/extension against gravity, and a step up. Video fluoroscopy of these activities was used to obtain the Patellar Tendon Angle (PTA), the angle between the long axis of the tibia and the patella tendon, as a function of knee flexion. This is a previously validated method of assessing sagittal plane kinematics of a knee joint. The kinematic profile of the PFA joints was compared to the profiles for fourteen normal knees. Overall, the kinematic plot obtained for PFA reflected similar trends to that for normal knees; but the PTA was slightly but significantly increased throughout the entire range of flexion (two degrees). This is equivalent to an average displacement of the lower pole of the patella of 1.5mm. Sagittal plane knee kinematics after PFA are much more normal than after TKR and this should give improved functional outcome. The observed increase in PTA through range may result from increased patella thickness or a shallow trochlear groove and may influence patellofemoral contact forces.

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.

Progressive symptomatic tibiofemoral osteoarthritis (OA) following patellofemoral joint replacement (PFJR) may necessitate revision to total knee arthroplasty. This study was designed to quantify this problem in a prospective series of 103 consecutive patients who underwent PFJRs undertaken at our institution. At a mean follow-up of 7.1 years (66-102 months), 14 knees (14%) have been revised, 12 of those (12%) because of the development of symptomatic tibiofemoral OA, with a mean time to revision of 55 months (range 14 to 95 months). Available radiographs of the 89 unrevised knees were subject to blinded and randomised assessment by two observers. Postoperative AP knee radiographs were scored to assess for tibiofemoral OA progression, with definite progression seen in a median of 7% of medial compartments but 0% of lateral compartments, over a mean period of 51 months. Sulcus angles on preoperative 30 degrees skyline radiographs were measured to assess for trochlear dysplasia. Seventeen percent of the knees without preoperative trochlear dysplasia have been revised for progression of tibiofemoral OA, compared to none of the knees with preoperative trochlear dysplasia. Furthermore, in the unrevised knees, statistically significantly more radiographic progression of tibiofemoral OA was seen in those without preoperative trochlear dysplasia (p = 0.01). Our results suggest that progressive tibiofemoral OA following PFJR is an important cause of failure, but it is seen significantly less frequently when the patellofemoral arthritis is secondary to dysplasia of the femoral trochlea, suggesting that these patients are the ideal candidates for PFJR.

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.

Introduction: Isolated patello-femoral arthritis occurs in up to 10% of patients suffering osteoarthritis of the knee. Reports of patello-femoral replacements have given indifferent results. We report our experience of 350 cases of the Avon Arthroplasty. Method: In 1994 after experience with the Lubinus prosthesis which had a 50% failure rate at eight years, we defined the design criteria for a new prosthesis. Since September 1996, 350 knees have been treated with this design. Prospective review was undertaken and 150 knees have reached 2 years and 80 knees are at five years with 10 knees at eight years. The outcome was assessed using pain scores, Bartlett’s patella score and the Oxford knee score. Results: The patients recovered function rapidly and 20 cases (6%) suffered early complications which resolved. The median pain score improved from 15/40 points to 38 at five years. The movement increased from 114 to 120 at five years. The Bartlett patella score improved from 11/30 points to 25 at five years. The Oxford knee score improved from 19/48 points to 40 points at five years. The functional results are similar or better than those of a total knee replacement. Fourteen patients developed mal-alignment (4%) two of which required distal realignment. There have been no cases of deep infection, fracture, wear or loosening. Twenty seven knees (7%) developed evidence of disease progression, twenty two of which (6%) have required revision to a total knee replacement. Nineteen patients (5%) complained of some persistent anterior knee pain of uncertain cause. Conclusions: Results to date show a large improvement in pain and function and this improved design has reduced the problems of mal-alignment and polythene wear. There is a low complication rate and an excellent range of movement. Disease progression remains a problem which is not predictable. This type of prosthesis offers an alternative to total knee replacement in this small group of patients with isolated patello-femoral disease with a low morbidity.