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%).