Bone Anatomy and Rotational Alignment in Total Knee Arthroplasty

TLDR

The study investigates how bone anatomy determines rotational alignment in total knee arthroplasty using CT. Axial CT images of 109 knees from 83 varus osteoarthritis patients were analyzed by drawing anteroposterior axes on the distal femur and proximal tibia based on the epicondylar axis and the medial one‑third of the tibial tuberosity, and measuring the angle between these lines as rotational mismatch. Nearly half of knees (49.5%) exhibited a rotational mismatch of ≥5°, with 11.9% exceeding 10°, showing a tendency for tibial components to be externally rotated relative to femoral components, indicating that bone landmarks cause mismatch and surgeons should check and realign tibial components to match femoral rotation to avoid complications.

Abstract

The purpose of the current study was to investigate the bone anatomy in determining the rotational alignment in total knee arthroplasty using computed tomography. Axial images of 109 knees in 83 patients with varus osteoarthritis who had total knee arthroplasty were analyzed. On the images of the distal femur and the proximal tibia, a baseline for the anteroposterior axis of each component was drawn based on the epicondylar axis for the femur and the medial (1/3) of the tibial tuberosity for the tibia. The angle between these two lines was analyzed as the rotational mismatch between the components when they were aligned to the anatomic landmarks of each bone. Fifty-four knees (49.5%) had an angle of 5 degrees or greater and 13 knees (11.9%) had an angle of 10 degrees or greater. There was a tendency to align the tibial component in external rotation relative to the femoral component. The results indicated that the landmarks of each bone were the intrinsic cause of the rotational mismatch in knees with varus osteoarthritis. Surgeons doing total knee arthroplasties should be aware of this and check the rotational mismatch between the components. When it is present, the tibial component should be realigned to match the femoral component rotation to minimize problems caused by the mismatch.