Chapter 13 - Clinical Outcome, Postoperative Alignment, and Implant Survivorship After Kinematically Aligned Total Knee Arthroplasty

Abstract

This chapter reviews the clinical outcome, postoperative alignment, and implant survivorship after kinematically aligned (KA) total knee arthroplasty (TKA) based on results of international randomized controlled trials (RCTs), case-control studies, meta-analyses, and single-surgeon case series. The first section describes differences in patient-reported outcome scores and range of motion between patients treated with KA TKA and mechanical alignment (MA) TKA. Featured are a chronologic review of the findings of RCTs, a matched cohort of patients treated with calipered KA and MA performed with manual instruments and a medial pivot implant design published by the author of this chapter, and meta-analyses. Many studies used inclusion restrictions and postoperative correction restrictions in the KA cohort that biased the results against KA TKA and in favor of MA TKA. The second section discusses differences in KA and MA postoperative limb and joint line alignment and the accuracy of the calipered KA technique. The third section reports the mid- and long-term implant survival after KA TKA and discusses the differences in the rate of reoperations other than infection between the KA and MA TKA. The contrary and unexpected finding of negligible long-term risk of tibial component failure from a varus mechanism after KA TKA is highlighted. The explanation for the negligible risk is the lack of correlation between the degrees of varus alignment and component migration, low knee adduction moment during gait, and restoration of native tibial compartment forces after KA TKA, which MA TKA does not achieve. The educational objective is to provide compelling evidence that the KA target results in a better clinical outcome and that the calipered technique accurately restores the patient’s prearthritic joint lines. Surgeons that perform KA TKA can expect a low risk of mid- and long-term implant failure, and a negligible risk of varus failure of the tibial component that is lower than MA TKA.