The usefulness of planning using a preoperative lateral leg image to determine accurate posterior tibial slope in total knee arthroplasty

Abstract Objective Sagittal alignment of the tibia following total knee arthroplasty (TKA) can affect various factors, such as durability, range of motion, stability, and even kinematics. The aim of the present study was to investigate whether taking plain preoperative lateral leg X-ray images to plan the posterior tibial slope can give an insert placement with more accurate sagittal alignment. Methods A total of 100 patients who underwent total TKA with posterior-stabilized prostheses. were divided into a group of 50 cases in which the posterior tibial slope was determined intra-operatively with only the fibular axis as the landmark, and a group of 50 cases in which determination of the posterior tibial slope was planned preoperatively with reference to preoperative lateral leg images. For the posterior slope, tibial cutting was performed with the posterior slope built into the bone cutting guide of the insert as the target. The angle of the fibular axis and the posterior slope of the tibial insert were measured on the postoperative lateral leg X-ray image, and the difference from the target angle was examined in the two groups. Results In the group in which only the fibular axis was used for reference, the mean deviation from the target was 3.96°, while in the group in which planning was carried out preoperatively using lateral leg X-ray images, the mean deviation was 1.59° (P  Conclusion Drawing up a preoperative plan using lateral leg X-ray images gives a useful landmark at low cost for accurate determination of TKA posterior tibial slope.