Are both the knees of the same size? Analysis of component asymmetry in 289 bilateral knee arthroplasties

BACKGROUND: Variations in the anatomy of knee are well described, however the true incidence of component asymmetry in bilateral total knee arthroplsties is rarely reported. Incidence of component asymmetry in bilateral total knee arthroplasties (TKA) was retrospectively analysed in 289 cruciate retaining total knee arthroplasties. MATERIALS AND METHODS: Medical records of these 289 patients were evaluated for the incidence of asymmetry of either femoral or tibial components. Clinical outcomes were compared between the cases of asymetrical components to that of symmetrical components. RESULTS: Incidence of femoral component asymmetry was found to be 9.2% and tibial component asymmetry to be 8.7%. Of 289 cases, TKA 178 were done in a single day (group A), while 111 were done at 2- to 3-day intervals (group B). Asymmetric and symmetric knees were equally distributed among both groups, male and female patients in both groups, and the incidence of component asymmetry was similar between all four different implants – Optetrak-CR (Exactech, Gainesville, FL, USA), Nexgen-CR (Zimmer, Warsaw, IN, USA), PFC-Sigma CR (DePuy, Warsaw, IN, USA), Genesis II CR (Smith and Nephew, Memphis, TN, USA) we used. The pre- and postoperative range of motion and pre- and postoperative knee society scores were compared between the symmetric and asymmetric cases in both the groups and the difference was found to be insignificant. CONCLUSION: We conclude that incidence of component asymmetry in bilateral total knee arthroplasty is around 9 % and independent sizing of both knees during bilateral arthoplasty is recommended rather than simply relying on the contralateral knee measurements.