ROTATIONAL MISMATCH OF SELF-ALIGN TIBIAL COMPONENT IN POSTERIOR-STABILIZED (PS) TOTAL KNEE ARTHROPLASTY

Abstract

Background: Rotational alignment of femoral and tibial prosthesis is one of the important factors for outcomes of total knee arthroplasty (TKA). Rotational malalignment may lead to patellar maltracking, anterior knee pain, femoro-tibial flexion instability and premature wear of the polyethylene inlay. Several studies have demonstrated higher revision rates and less favorable clinical results among patients with rotational malalignment. The transepicondylar axis is widely accepted as the best representation of the functional flexion-extension axis of the knee. On the other hand, no comparable agreement exists for tibial rotational alignment Objectives: The aim of this study was to determine the accurate rotational alignment of components by posterior cruciate lignment substituting TKA using the center-post self-align technique. Method: From January 2007 to May 2009, 54 patients (60 knees) underwent the cemented, posterior ligament substituting TKA using the center-post self-align technique of the tibial component and performed computer tomography postoperatively. The rotational angle between the femoral and tibial components and the rotational variance from the transepicondylar axis were measured. Results: The rotational alignment of femoral components were 90% in the neutral group: 48.3% external rotate (mean 1.15 , range 0.1 – 4.9), 48.3% internal rotate (mean 1.53 , range 0.2 -3.8) and 3.4% were in neutral alignment. The rotation alignment of tibial components were 71.7% in the neutral group: 41.2% external rotate (mean 2.03 , range 0.2 -6.7), 56.7% internal rotate (mean 2.59 , range 0.3 -6.7) and 1.67% had neutral alignment. We found no rotational mismatch between femoral and tibial components in this study. All 60 knees had good patellar tracking by no thumb test technique without lateral released procedure. Conclusion: Femoral component rotations were mostly in the safe zone. Using the center-post self-align technique in posterior cruciate ligament substiting TKA, tibial component rotation was much more varied than the femur. However, all tibial component rotations were in between medial most and medial 1/3 of the tibial tuberble