2017 年 36 巻 1 号 p. 15-19
Introduction: Several methods have been proposed to determine proper femoral component rotation alignment in total knee arthroplasty (TKA). Usually the epicondylar axis, the posterior condylar axis and Whiteside’s line are used for landmarks. However, sometimes recognition of these landmarks is difficult intraoperatively. We decide on the rotation angle of the femoral component using the epicondylar view via a preoperative radiograph. The angle consists of the clinical epicondylar axis (CEA) and the posterior condyle line minus two degrees. We think the influence of the residual cartilage of the posterior lateral femoral condyle is about two degrees in varus osteoarthritis (OA).
Objective: The objective of this study was to evaluate the rotation alignment of the femoral component after TKA, and the usefulness of our method for the decision of femoral component rotation alignment.
Methods: There were 43 patients (7 males, 36 females) with varus OA who underwent primary TKA. The average age was 78.1 years (range, 64-87 years). The rotation angle of the femoral component was decided by the above-mentioned method. We evaluated the angle between the posterior border of the femoral component and the CEA, and the surgical epicondular axis (SEA) using postoperative computed tomography. These angles were expressed as∠CEA and∠SEA. External rotation was expressed as plus.
Results: The mean∠CEA was−1.1 (−5-1)°. The mean∠SEA was 0.48 (−3-3)°. The mean angle of∠SEA−∠CEA was 1.5 (0-3)°. The femoral component was placed in internal rotation to CEA and parallel to SEA.
Conclusion: Internal placement of the femoral component was considered to be caused abnormal patella tracking and dislocation and low value of Knee Society Knee scoring. We think that it can be difficult to recognize some landmarks intraoperatively. We decide on the rotation angle of the femoral component using the epicondylar view of preoperative radiographs. From the results of this study, the femoral component was placed in internal rotation to CEA and parallel to SEA. We conclude that our method for the decision of the femoral component rotation alignment is useful for TKA of varus OA of the knee.
