[Accuracy of rotational positioning of the femoral component using the tibial-cut-first technique]. / Bestimmung der Rotationsgenauigkeit der Femurkomponente bei Tibial-Cut-First-Technik.

ABSTRACT

AIM: Problems with the patellofemoral joint are still one of the most common difficulties after total knee arthroplasty. One of the main reasons for these problems seems to be the rotatory malposition of the femoral component. We examined the rotation of the femoral component and the symmetry of the flexion gap of knee prostheses implanted using the tibial-cut-first technique. METHOD: The radiographs of 58 consecutive patients who underwent primary LCS total knee arthroplasty in 2008 were examined retrospectively. The rotation of the femoral component was determined intraoperatively using the femoral positioner and depended on the amount of tibial resection and the tension of the collateral ligaments. The position was then checked by means of three anatomic landmarks the epicondylar axis, the posterior condyles and the Whiteside line. We used Kanekasu's technique for the radiographs. With this technique it was possible to ascertain the rotation of the femoral component after total knee arthroplasty easily and with a low level of radiation. It was also possible to determine the opening of the flexion gap. RESULTS: The radiographs showed a slight external rotation of the femoral component of 1.31°. The opening of the flexion gap was increased laterally, but only by 1.5°. CONCLUSION: In this study, determination of femoral rotation using the tibial-cut-first technique resulted in a slight external rotation of the femoral component. Furthermore, it is possible to create an almost symmetrical flexion gap with this method.