Mobile-bearing, congruent patellofemoral prosthesis: short-term results.

PURPOSE To report the short-term outcome of the low contact stress (LCS) patellofemoral prosthesis in 51 knees. METHODS 12 men and 37 women aged 23 to 79 (mean, 53.4) years underwent 51 consecutive LCS patellofemoral replacements. All patients had symptomatic isolated arthritis in the patellofemoral joint with well-preserved tibiofemoral compartments. All knees were evaluated pre- and post-operatively. The new Oxford scoring system was used. Anteroposterior, lateral, and skyline weight-bearing radiographs were reviewed. RESULTS The mean follow-up period was 4.2 years; no patient was lost to follow-up. The mean new Oxford Knee score was 13.9 preoperatively and improved by 13.7 at 3 months (p<0.001) and by further 7.1 at 12 months (p<0.001). Any change after 12 months was not significant (p=0.73). 18 of the knees developed patellar maltracking and resulted in subluxation and lateral tilt of the patella with severe polyethylene wear. 10 (20%) of the knees were revised; 8 with patellar maltracking were revised to total knee arthroplasty (n=3) or patellofemoral arthroplasty with a different implant (n=5), whereas 2 with disease progression were revised to total knee arthroplasty. The estimated survival rate of the prosthesis was 73% at 4.5 years and 48% at 5.5 years. CONCLUSION The revision rate for the LCS patellofemoral prosthesis was high (20%).