Implant Design and Effects on Patellofemoral Crepitus

Background Patellofemoral crepitus is a known complication of posterior stabilized (PS) total knee arthroplasty (TKA). This study compared the incidence of patellofemoral crepitus between two femoral components designs. Materials and Methods Between January 2005 and August 2010, 1,120 patients with complete 2-year follow-up had a PS TKA with two different prosthetic designs (group A, 553 patients; group B, 567 patients). Records were reviewed to identify the incidence of total, symptomatic, and operative patellofemoral crepitus. Results No statistical differences were observed in the incidence of total patellofemoral crepitus (group A 14.1%, group B 14.5%; p = 0.932) or symptomatic patellofemoral crepitus (group A 5.6%, group B 4.2%; p = 0.334). The incidence of operative crepitus was greater in group A (3.3%) than in group B (1.3%; p = 0.026). Analysis of mobile versus fixed bearing designs showed a higher incidence of total patellofemoral crepitus in mobile bearing TKA (16.04 vs. 4.93%; p = 0.006) within group B only. Conclusion Femoral component design with a smoother intercondylar box transition zone resulted in a lower incidence of operative patellofemoral crepitus. No statistical differences were noted regarding the incidence of total and symptomatic patellofemoral crepitus. Mobile bearing TKA exhibited greater total crepitus within group B. Level of Evidence Level III.