Accuracy of matching tibial slope in manual kinematically aligned total knee arthroplasty.

Abstract

Reproduction of the posterior tibial slope (PTS) during total knee arthroplasty (TKA) improves patient outcomes and minimizes complications including subsidence, polyethylene wear, and instability. The use of imaging has been previously studied as a way of measuring PTS angle and its association with surgical outcomes. There is a lack of literature on the accuracy of matching PTS during manual kinematically aligned (KA) TKA. This is a retrospective study including 299 primary manual KA TKAs between October 2021 and August 2024 by a single surgeon. The primary outcome was comparison of pre-operative and post-operative PTS angles. Measurements were performed on lateral radiographs as the angle between the tangent line of the tibial plateau and a line perpendicular to the tibial shaft axis. The average pre-operative tibial slope was 10.3<b>°</b> (std dev, 4.8) compared to an average post-operative measurement of 5.3<b>°</b> (std dev, 3.2) (p < 0.00001). Range of motion improved post-operatively, with average extension increasing from 4.4<b>°</b> to 0.9<b>°</b> and flexion maintained from 118.5<b>°</b> to 117.2<b>°</b>. Complications were infrequent, with one superficial infection, two prosthetic joint infections requiring revision, two additional reoperations for polyethylene exchanges, and five manipulations under anesthesia with subsequent improvement in range of motion. In this study, we found a significant difference in pre-operative and post-operative tibial slope angle on radiographic measurements following manual KA TKA.