[Femoropatellar osteoarthritis treated by prosthesis. Retrospective study of 50 implants]

51 prosthesis were performed in 47 patients and were studied in order to assess long term results. One patient was lost for follow up. The diagnosis was: primitive arthritis in 48 knees and post traumatic arthritis in 3 knees. 25 knees had patellofemoral subluxation, 16 patients had been previously operated on patellofemoral joint. The average age at the time of surgery was 60.5 years and follow up time averaged 3 years. 22 prosthesis had more than 4 years follow-up. The operations were performed using a lateral approach with tibial tubercle osteotomy and lateral patellar retinaculum release. The trochlear component was asymetric and made of chrome cobalt alloy; the patellar component was shaped in polyethylene. Both components were cemented.

Using the Guepar scoring system, 41 (82 per cent) PFA were rated excellent or good and 9 poor. Post operative roentgenograms demonstrated patellofemoral alignment in all knees, even in cases of preoperative patellar subluxation, without tilting of the patella. Follow up roentgenograms demonstrated progressive but moderate deterioration of the tibio femoral joint in 9 cases. In 3 cases, more severe tibio femoral arthritis were treated by T.K.R one to three years after P.F.A. In one of these knees, we discovered an asymptomatic loosening of trochlear component. The last 6 poor results were always due to persistent pain.

The purpose of this study was to assess the results of P.F.A. and to clarify the indications. It appears that the 82 per cent success rate of this study may be compared with the results of literature. All the authors have found P.F.A. to be a viable solution, preferable to patellectomy (even in older patients) or isolated patellofemoral realignment. The clinical and radiological results did not deteriorate with time. Persistent patellofemoral malalignment was not observed in this study thanks to the use of a lateral approach. The presence of tibio femoral arthritis adversely affected the outcome, but accelerated changes on the tibio femoral joint after P.F.A. were not observed.