Rotational Alignment of the Femoral Components in Total Knee Arthroplasty: A Modified Gap Technique Using Manual Distraction

ABSTRACT

PURPOSE: This study was undertaken to introduce a modified gap technique using manual distraction for achieving proper rotational alignment of the femoral components in total knee arthroplasty (TKA) and we compared the accuracy of the rotational alignment of the femoral components in TKAs when using a navigation system with that of another conventional technique. MATERIALS AND METHODS: We randomly used three different methods and implants (group 1 3degrees external rotation from the posterior condylar axis method, group 2 a modified gap technique using manual distraction and group 3 a navigation system, Orthopilot(R)) in 92 patients. We measured the posterior condylar angles (PCA the angle between the posterior condylar line and the transepicondylar axis) on computed tomography before and after surgery. RESULTS: The analysis showed no significant differences of the demographic data (age, height, weight, body mass index) and of the mean PCAs for the rotational alignment of the femoral components between the three groups (preoperative PCA 5.45degrees vs. 5.34degrees vs. 5.24degrees, respectively; postoperative PCA 1.91degrees vs. 1.17degrees vs. 1.37degrees, respectively, p>0.05). However, the conventional 3degrees external rotation method showed a higher frequency of outliers (p=0.028). CONCLUSION: The modified gap technique using manual distraction showed a higher accuracy of the femoral rotational alignment compared with that of the 3degrees external rotation method by reducing the outliers, and the modified gap technique using manual distraction showed similar results compared with those of the navigation method.