Femoral Implant Design Significantly Decreases the Rate of Patellar Crepitus in Total Knee Arthroplasty

Abstract Background Patellar crepitus is a complication most commonly seen in patients implanted with a posterior stabilized total knee arthroplasty (TKA). Recently, design changes in the patellofemoral geometry and the intercondylar box ratio have been optimized in newer TKA designs. A comparative study was performed to analyze the incidence of patellar crepitus between a historical versus modern TKA design. Methods A retrospective review of all patients at our institution that underwent a primary TKA with either a PFC Sigma or Attune posterior stabilized TKA (Depuy, Inc.; Warsaw, IN) with a minimum of 1 year follow-up duration was performed. A total of 1165 subjects implanted with the PFC Sigma and 728 with the Attune design were analyzed. Patellar crepitus incidence, functional scores, and range of motion were recorded at each follow-up appointment. Statistical analyses were performed between the two groups to determine if there were differences in clinical outcomes. Results The incidence of crepitus in subjects implanted with the Attune was 0.55% versus 6.26% in the PFC Sigma cohort (p < 0.001) at one year and at two years was 0.83% vs. 9.4% respectively; (p < 0.001). There were small differences in extension, flexion, and Knee Society Scores between the two groups that weren't clinically meaningful. Conclusion The Attune posterior stabilized TKA demonstrated substantially less patellofemoral crepitus incidence than the historical control. We hypothesize these findings are related to femoral component changes including a thinner and narrower anterior flange and a reduced femoral intercondylar box ratio.