Medium term results of Avon patellofemoral joint replacement

Abstract

Background: Ten to fifteen percent of knee arthritis is reported to be isolated patellofemoral arthritis. Total knee arthroplasty is not recommended for isolated patella femoral arthritis particularly in young patients. We present the retrospective review of 45 consecutive patellofemoral replacements performed in 41 such patients, between June 2002 and January 2007.

Materials and methods: All patients were operated by single surgeon (SM) or under his supervision. All forty five patients had minimum three year followup and had the data collected prospectively. No patient was lost to followup. This data was later collated by review of notes, radiographs, and a clinical followup. The patients were assessed using knee function score and Melbourne patellofemoral score.

Results: The average followup was 4.5 years. The preoperative average Melbourne (Bartlett) score was 10 (range 5-21). Preoperative knee functional score averaged 57 (range 23-95). The average range of movement was 116° (range 100°-140°). Postoperatively, the average Melbourne knee score improved to 25 (range 11-30), while the knee function score was 85 (range 28 - 100). The difference was statistically significant (P<0.05). Eighty-five percent rated the result as good or excellent, while 12% rated it as fair. Five percent thought the result was poor. The most common complaint was clicking at 40° of flexion (n=7). Six patients underwent arthroscopic lateral release, which improved the symptoms in four patients. Two knees were revised one due to progression of tibiofemoral arthritis and the other due to persistent clicking, yielding a survival rate of 95.6% at an average five year followup.

Conclusion: The Avon patellofemoral joint replacement provides predictably good results and excellent survivorship in the medium term, for isolated patellofemoral arthritis. However, progression of tibiofemoral arthritis remains unpredictable and therefore patient selection is crucial to ensure success. Clicking remains a potential problem and can compromise the postoperative results in upto 15% of the cases.

Keywords: Anterior knee pain; arthritis; arthroplasty; patellofemoral maltracking; replacement.

Figure 1

Preoperative anteroposterior (a) and lateral (b) skyline (c) Merchant's view of right knee showing lateral tilting and severe patellofemoral arthritis

Figure 2

Intraoperative picture (a) of the same patient showing an eburnated patella and trochlea. Intraoperative photograph (b) following patellofemoral joint replacement

Figure 3

Postoperative anteroposterior radiograph (a) lateral radiograph (b) and postoperative skyline view (c) of the same patient shows well placed prosthesis