Does Resurfacing the Patella Increase the Risk of Extensor Mechanism Injury within the First 2 Years after Total Knee Arthroplasty?

Extensor mechanism injury (EMI) following total knee arthroplasty (TKA) is a potentially catastrophic complication and may lead to significant morbidity or need for revision reconstructive procedures. Patellar resurfacing (PR), while commonly performed during TKA, reduces overall patella bone stock and may increase the risk of EMI after TKA. The purpose of this study was to assess if PR in elderly patients raises the risk for subsequent EMI.The American Joint Replacement Registry (AJRR) was queried to identify Medicare patients ≥65 years old undergoing primary elective TKA for osteoarthritis between January 2012 and March 2020. Patient age, sex, and Charlson Comorbidity Index (CCI) were collected. Records were subsequently merged with Medicare claims records and evaluated for the occurrence of patella fracture, quadriceps tendon rupture, or patellar tendon rupture based on International Classification of Diseases 9 and 10 (ICD 9/10) diagnosis codes within 2 years of TKA. Patients were stratified based on whether PR occurred or not (NR). Logistic regression was used to determine the association between PR and EMI.A total of 453,828 TKA were eligible for inclusion and 428,644 (94.45%) underwent PR. The incidence of PR decreased from 96.06% in 2012 to 92.35% in 2022 ( < 0.001). Patients undergoing PR were more often female (60.93 vs. 58.50%,  < 0.001) and had a lower mean CCI (3.09 [1.10] vs. 3.16 [1.20],  < 0.001). Odds for EMI did not differ based on whether PR was performed (odds ratio [OR]: 0.85, 95% confidence interval [CI]: 0.65-1.11,  = 0.2246). Increasing age (OR: 1.06, 95% CI: 1.05-1.07,  < 0.0001]) and CCI (OR: 1.06, 95% CI: 0.95-1.19,  = 0.0009) were associated with EMI.PR is commonly performed during TKA in the United States and was not found to increase odds for EMI within 2 years of TKA in patients ≥65 years old. Increased age and medical comorbidity were associated with higher odds for subsequent EMI.