Conforming patellar button design improves outcome of total knee arthroplasty.

Abstract

Patellar resurfacing is commonly performed during total knee arthroplasty (TKA), and the patellar button design can vary within a TKA implant. Implant design is known to affect patella kinematics, contact mechanics, and ultimately the outcome of TKA. The aim of this study was to compare the patient-reported outcomes of TKA with either a conforming (CP) or medialized dome (MD) patellar component. The study was a prospective cohort study of 100 TKAs performed between December 2015 and August 2017. We compared a consecutive series of 50 TKA subjects with a CP, with the previous 50 TKA subjects with an MD patella. The primary outcome measure was difference in Knee Injury and Osteoarthritis Score (KOOS) at 12 months. Other patient-reported outcome measures included EQ5D as a general health measure, and patient satisfaction. There was no significant difference in baseline characteristics, KOOS, or EQ5D between the two groups. At 12 months, the CP Group had a higher mean KOOS function score (87 vs. 80, P = 0.04), and greater patient satisfaction (98% vs. 82% satisfied, P = 0.009) compared with the MD group. The CP Group had significantly lower frequency of pain with level walking, less difficulty with stairs, and lower mean EQ5D mobility at 12 months compared with the MD group. TKA performed using a conforming patella has superior results over a medialized dome patellar component for KOOS function, patient satisfaction, walking pain, stair performance, and mobility at 12 months postoperatively. The differences observed with the change in patellar design may be unique to this prosthesis.