Jonathan Eldridge

The Avon patellofemoral arthroplasty: FIVE-YEAR SURVIVORSHIP AND FUNCTIONAL RESULTS

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.

The Posterior Condylar Offset Ratio.

INTRODUCTION Posterior Condylar Offset is an area of interest in knee arthroplasty research and clinical outcome. The aim of the study is to define a quantifiable Posterior Condylar Offset Ratio, a normal value for this ratio and to confirm its reproducibility on pre-operative radiographs. METHOD We propose a new Posterior Condylar Offset Ratio which is defined as the maximal thickness of the posterior condyle projecting posteriorly to a straight line drawn as the extension of the posterior femoral shaft cortex, divided by the maximal thickness of the posterior condyle projecting posterior to a straight line drawn as the extension of the anterior femoral shaft cortex on a true lateral radiograph of the distal quarter of the femur. We have measured this on 100 true lateral radiographs (50 females, 50 males, and mean age 65 years). RESULTS The mean ratio was 0.44 (SD 0.02) and was shown to have good reproducibility (intra-observer error 0.899 and inter-observer error 0.882. The ratio was also very consistent between male and female patients (0.44 (SD 0.02) for the males and 0.45 (SD 0.02) for the females). Adjusting the ratio for reported posterior condyle articular cartilage thickness increased the ratio to 0.47 (SD 0.02). CONCLUSION We suggest our Posterior Condylar Offset Ratio is a useful tool to aid further research in this area of knee arthroplasty and propose a normal value of 0.44 on radiographs and 0.47 on post-operative knee arthroplasty radiographs.

Adolescent knee pain and patellar dislocations are associated with patellofemoral osteoarthritis in adulthood: A case control study

BACKGROUND There is a lack of information about the association between patellofemoral osteoarthritis (PFOA) and both adolescent anterior knee pain (AKP) and previous patellar dislocations. METHODS This case-control study involved 222 participants from our knee arthroplasty database answering a questionnaire. One hundred and eleven patients suffering from PFOA were 1:1 matched by gender with a unicompartmental tibiofemoral arthritis control group. Multivariate correlation and binary logistic regression analysis were performed, with odds ratios (ORs) and 95% confidence intervals (CIs) calculated. RESULTS An individual is 7.5 times more likely to develop PFOA if they have suffered from adolescent AKP (OR 7.5, 95% CIs 1.51 to 36.94). Additionally, experiencing a patellar dislocation increases the likelihood of development of PFOA, with an adjusted odds ratio of 3.2 (95% CIs 1.25 to 8.18). A 44-year difference in median age of first dislocation was also observed between the groups. CONCLUSION This should bring into question the traditional belief that adolescent anterior knee pain is a benign pathology. Patellar dislocation is also a significant risk factor. These patients merit investigation, we encourage clinical acknowledgement of the potential consequences when encountering patients suffering from anterior knee pain or patellar dislocation.

Trochleoplasty with a flexible osteochondral flap

Aims The Bereiter trochleoplasty has been used in our unit for 12 years to manage recurrent patellar instability in patients with severe trochlea dysplasia. The aim of this study was to document the outcome of a large consecutive cohort of patients who have undergone this operation. Patients and Methods Between June 2002 and August 2013, 214 consecutive trochleoplasties were carried out in 185 patients. There were 133 women and 52 men with a mean age of 21.3 years (14 to 38). All patients were offered yearly clinical and radiological follow‐up. They completed the following patient reported outcome scores (PROMs): International Knee Documentation Committee subjective scale, the Kujala score, the Western Ontario and McMaster Universities Arthritis Index score and the short‐form (SF)‐12. Results Outcomes were available for 199 trochleoplasties in 173 patients giving a 93% follow‐up rate at a mean of 4.43 years (1 to 12). There were no infections or deep vein thromboses. In total, 16 patients reported further patella dislocation, giving an 8.3% rate of recurrence. There were 27 re‐operations, giving a rate of re‐operation of 14%. Overall, 88% were satisfied with the operation and 90% felt that their symptoms had been improved. Conclusion All PROMs improved significantly post‐operatively except for the mental component score of the SF‐12. Trochleoplasty performed using a flexible osteochondral flap is an effective treatment for recurrent patellar instability in patients with severe trochlea dysplasia and gives good results in the medium term.

Revision of isolated patellofemoral arthroplasty to total knee replacement

Background Patellofemoral arthroplasty is becoming an established treatment for isolated patellofemoral arthritis. Revision to total knee replacement occasionally is required. Lessons learned from patients requiring revision surgery and their subsequent post-revision outcomes are described. Method This study reviewed 49 patellofemoral arthroplasties in 43 patients who had revision to a total knee replacement. These cases were obtained from a cohort of 487 patellofemoral arthroplasties prospectively reviewed between 1989 and 2006. Results The most common reason for revision was progression of arthritis in the tibiofemoral joint (30 knees in 26 patients). Persistent pain from technical error was found in 11 knees (10 patients), and 4 knees in 4 patients had unexplained persistent pain. The revision procedure was straightforward with no technical difficulties. All patients had a primary cemented total knee replacement without requiring bone grafting or prosthetic augmentation. The patients reported significant improvements in the Oxford Knee Score (26/48 points) P = 0.003 and the Bristol Pain Score (25/40 points) P = 0.0001 compared with the scores before patellofemoral arthroplasty. The outcomes were less favorable than expected and were worse than those seen after a successful primary patellofemoral arthroplasty. Conclusion Reasons for patellofemoral arthroplasty failure were identified. Patellofemoral arthroplasty was easy to revise to a primary knee arthroplasty; however, good clinical results could not be guaranteed. These results emphasize the need for careful patient selection and precise surgical technique during the primary operation.