Determining femoral rotational alignment in total knee arthroplasty: reliability of techniques

Several anatomic axes routinely are used for determining femoral rotational alignment in total knee arthroplasty. The purpose of this study was to determine the reliability of these techniques. The transepicondylar axis, anteroposterior axis, and balanced flexion gap tension line were identified relative to the posterior condylar axis in 8 fresh frozen cadaver knees by 3 independent observers. The flexion-extension axis was defined in each knee for comparison. The anteroposterior and balanced tension axes defined most reliably the flexion-extension axis and best balanced the flexion gap with no significant interobserver differences. The transepicondylar axis was less predictable and significantly more externally rotated than the anteroposterior axis (P < .005) and the balanced tension line (P < .00001). Flexion gap tensioning may offer superior reliability because of its independence of obscured or distorted bone landmarks.