[Femoro-patellar prosthesis. A retrospective study of 45 consecutive cases with a follow-up of 3-12 years]

Forty-five consecutive patients operated between 1986 and 1995 were evaluated to assess the long term results of patellofemoral arthroplasty. Revision had to be performed in 8 cases for the following reasons: loosening (3), lateral impingement (3), malposition (1) and persistent patella instability (1). Two groups of patients were identified based upon the preoperative assessment: 21 had primary osteoarthritis without anatomic malalignment (group C) and 24 had a history of patellofemoral instability and trochlear dysplasia demonstrated by clinical and radiological evaluation (group D). Only 43% of good results were found in group C whereas in group D, the percentage of good results was close to 83%. The most common cause of poor results in group C was the degenerative involvement of the femorotibial compartments (5 patients had to undergo total knee arthroplasty subsequently). For group D patients, femorotibial osteoarthritis was not a determinant factor as regards the outcome of patellofemoral arthroplasty. To the authors, it appears that the best indication for patellofemoral arthroplasty is femoropatellar osteoarthritis with malalignment in patients having a normal femorotibial axis even in the presence of femorotibial osteoarthritis as long as the latter does not exceed grade II.