Haruta Yohei, Kawahara Shinya, Tsuchimochi Kanenobu, Hamasaki Akihiko, Hara Toshihiko
Department of Orthopedic Surgery, Aso-Iizuka Hospital, 3-83 Yoshio-machi, Iizuka-city, Fukuoka 820-8505, Japan.
Department of Orthopedic Surgery, Aso-Iizuka Hospital, 3-83 Yoshio-machi, Iizuka-city, Fukuoka 820-8505, Japan.
Knee. 2018 Aug;25(4):644-649. doi: 10.1016/j.knee.2018.04.011. Epub 2018 May 16.
An intramedullary (IM) rod is used to resect the distal femur vertically to the femoral mechanical axis in the coronal plane in many cases of total knee arthroplasties (TKA). The valgus angle between the mechanical axis and the anatomical axis of the distal femur is estimated preoperatively. It is known the deviation of the IM rod in the femoral canal could influence the femoral component alignment. However, there is no published data regarding how many degrees of deviation to make with the IM rod. The purpose of this study is to measure each deviation of the IM rod using three-dimensional (3D) computer simulations.
Preoperative CT scans on 30 knees undergoing TKA were studied. The line connecting central points at 10 and 20 cm proximal from the intercondylar notch was defined as the anatomical axis and the point at which the anatomical axis intersects the surface of the distal femur was considered as the entry point of the IM rod. The medio-lateral (ML) and antero-posterior (AP) deviations between the anatomical axis and the IM rod were measured.
The ML and AP deviations were 0.8 and 1.1° on average. The IM rod was deviated medio-laterally more than 1.0° in three knees (10%).
Surgeons should note the ML difference of the resection thickness of the distal femur for coronal alignment. If the ML difference varies greatly from the preoperative planning, they need to adjust at most 1.0° of valgus angle to achieve the appropriate coronal alignment. Level of evidence III, Therapeutic.
在许多全膝关节置换术（TKA）病例中，髓内（IM）杆用于在冠状面内垂直于股骨机械轴切除股骨远端。术前估计股骨远端机械轴与解剖轴之间的外翻角度。已知IM杆在股骨髓腔内的偏差会影响股骨组件的对线。然而，关于IM杆应偏差多少度尚无公开数据。本研究的目的是使用三维（3D）计算机模拟测量IM杆的每个偏差。
研究了30例行TKA的膝关节的术前CT扫描。连接髁间切迹近端10 cm和20 cm处中心点的线定义为解剖轴，解剖轴与股骨远端表面相交的点被视为IM杆的入点。测量解剖轴与IM杆之间的内外侧（ML）和前后侧（AP）偏差。
ML和AP偏差平均分别为0.8°和1.1°。在三个膝关节（10%）中，IM杆在内外侧的偏差超过1.0°。
外科医生应注意股骨远端切除厚度在ML方向上的差异，以实现冠状面对线。如果ML差异与术前规划有很大不同，他们最多需要调整1.0°的外翻角度以实现合适的冠状面对线。证据等级III，治疗性。
