Patella component diameters of 38 mm and up might be associated with higher revision rates after patella resurfacing.

Abstract

Purpose Patellar resurfacing in Total knee arthroplasty is considered standard in the United States. Complications of patella resurfacing include aseptic loosening or patella fractures possibly resulting in loss of the extensor mechanism. The goal of this study was to evaluate the Genesis II patella button and to report its outcome and complications. Material & Methods Between 01/2010 and 08/2016 the Genesis II patella button was implanted in 1,056 patients (267 men and 550 women) by the senior author at the authors’ institution as part of a posterior stabilized total knee arthroplasty. Results Of 1,056 cases 35 cases (14 women, 15 men, 5 bilateral, 3.3%) showed early loosening of the Genesis patella button at a mean 52.5 months postoperatively. Buttons of 38mm and larger patella components showed a significantly higher loosening rate than the 29, 32, 35mm buttons (p<0.01). Mean BMI of patients identified with aseptic loosening was 31.7kg/m2, mean age at time of revision surgery was 63.3 years. All of the patients with loosening of the patella button required revision surgery; in 33 cases an exchange of the button was performed, in two cases a removal of the button and patellar bone grafting was indicated. No complications occurred after revision surgery. Conclusion The current study reports a 3.3% patella loosening rate in the short follow up for the Genesis II patella button. Button 35mm and larger showed a significantly higher revision rate than smaller buttons and the authors advise caution when using large diameter patella components.

The Double-Patella Sign

“…Meding et al also identified and quantified the increased risk of patellar component loosening and fracture after TKA in patients with BMI > 30 kg/m 2 at 6 times and 1.7 times increased risk, respectively, when compared with BMI < 30 kg/m 2 . More recently, investigations have depicted that larger diameter (≥ 38 mm) and thicker (> 7.5 mm) patellar components result in significantly increased risk of patellar component loosening 9 . Thicker patellar components may cause overstuffing of the patellofemoral joint, resulting in increased force during flexion, which may increase the sheer force across the patella and subsequent loosening 10 .…”

“…Meding et al also identified and quantified the increased risk of patellar component loosening and fracture after TKA in patients with BMI > 30 kg/m 2 at 6 times and 1.7 times increased risk, respectively, when compared with BMI < 30 kg/m 2 . More recently, investigations have depicted that larger diameter ( ‡ 38 mm) and thicker (> 7.5 mm) patellar components result in significantly increased risk of patellar component loosening 9 .…”