Akagi胫骨前后轴在全膝关节置换术中的定位作用

Analysis of the tibial anteroposterior axis and its use in TKA

目的分析膝关节CT片上Akagi胫骨前后轴与髌腱中内1／3点、髌腱内侧缘等解剖标志的相互关系，确定全膝关节置换术中胫骨假体旋转定位的参照轴线。方法对40名青年健康志愿者行膝关节伸直中立位CT检查。Akagi胫骨前后轴定义为CT片上垂直于外科经上髁轴且经过后十字韧带中点的直线。于胫骨平台平面及预定截骨平面标记胫骨前后轴及其与髌腱相交点、后十字韧带中点与髌腱内侧缘及髌腱中内1／3点连线，分别测量胫骨前后轴与髌腱相交点内侧髌腱占髌腱总宽度的比例、后十字韧带中点与髌腱内侧缘及髌腱中内1／3点连线同胫骨前后轴之间的夹角。结果在胫骨平台平面，胫骨前后轴经过髌腱内侧缘外侧10．1％±8．3％处；在预定截骨平面，胫骨前后轴经过髌腱内侧缘外侧0．2％±10．0％处。在预定截骨平面，后十字韧带中点与髌腱内侧缘连线和胫骨前后轴的夹角为0．1°±2．7°，后十字韧带中点与髌腱中内1／3点连线和胫骨前后轴的夹角为10.3°±3．6°。结论全膝关节置换术中，当以胫骨结节中内1／3点为标准行胫骨假体旋转放置时，有导致胫骨假体相对于股骨假体过度外旋的可能。后十字韧带中点与髌腱内侧缘连线几乎与Akagi胫骨前后轴重叠，可以作为全膝关节置换术中胫骨假体旋转定位的参照轴线。

Objective To investigate the relationship between tibial anteroposterior axis and other anatomic landmarks in determining the rotation of tihial prosthesis in total knee arthroplasty using computed tomography. Methods Transverse CT scans of 40 volunteers＇ right knee in full extension were made. The anteroposterior axis of the tibia was defined as a line which was perpendicular to the transepicondylar axis and passing through the middle point of the posterior cruciate ligament. At the tibial plateau and optimum resection level, the mean medial percentage width of intersection point of the patellar tendon and the anteroposterior axis was measured. The mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament and the medial of the patellar tendon and the medial 1/3 of the patellar tendon were measured. Results At the tibial plateau level, the mean medial percentage width of intersection point of the patellar tendon was 10.1%±8.3%. At the optimum resection level, the mean medial percentage width of intersection point of the patellar tendon was 0.2%±10.0%. At the optimum resection level, the mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament and the medial of the patellar tendon was 0.1°±2.7°. The mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament and the medial 1/3 of the patellar tendon was 10.3°±3.6°. Conclusion There was a tendency to align the tibial component in external rotation relative to the femoral component when the medial 1/3 of the patellar tendon was used. The line connecting the middle of the posterior cruciate ligament and the medial of the patellar tendon can be used as a reliable axis for correct rotational orientation of the tibial component.