Arthritis progression after patellofemoral joint replacement.

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.