Grafinger R W, Datz L, Hitzl W, Dorn U
Universitätsklinik für Orthopädie, St. Johanns Spital Salzburg, Osterreich.
Z Orthop Unfall. 2008 Nov-Dec;146(6):782-7. doi: 10.1055/s-2008-1038998. Epub 2008 Dec 12.
Several studies have shown that the rotation of the femoral component is an essential factor in total knee replacement. Consequently, different intra-operative landmarks for femoral implantation were established but most of them are either hard to define or have a high variance, so reducing their utility value. The aim of this randomised, prospective study was to prove that a preoperative CT scan is a usable help for femoral orientation.
In 2006, 57 consecutive patients designated for implantation of a knee arthroplasty were split up in two groups (a and b) corresponding to a randomisation scheme. The implantation of the femoral component in group a) was done with a posterior condylar angle of three degrees of external rotation as invariable determined by the resection guide. In addition the surgeon could correct the rotation following any other landmarks (surgeon's own method). In group b) the posterior condylar angle was measured preoperatively with the help of a CT scan and transferred on a resection guide allowing variation of the posterior condylar angle in single degree steps. In this case variation of femoral rotation (surgeon's own method) was not possible. The rotation of all knee replacements (groups a and b) was measured postoperatively with a CT scan following the technique of Berger et al. The implantation with the femoral component lying parallel to the transepicondylar axis was regarded as correct. Differences were measured in degrees.
Regarding the degree of femoral malrotation without consideration of the direction (external/internal rotation) the difference between group a) and group b) was highly statistically significant (p < 0.000001). The highest range of malrotation in group b) was two degrees versus six degrees in group a). In group b) 19 of 30 (= 63.3 %) femoral components showed no malrotation at all, in group a) only 5 of 27 (= 18.5 %) components were implanted completely correctly.
Preoperative measurement of the posterior condylar angle was proven to be a simple, reproducible examination method which increases the rotational accuracy of total knee replacement.
多项研究表明，股骨组件的旋转是全膝关节置换术中的一个关键因素。因此，建立了不同的股骨植入术中标志点，但其中大多数要么难以界定，要么差异较大，从而降低了其实用价值。本随机前瞻性研究的目的是证明术前CT扫描有助于确定股骨方位。
2006年，57例拟行膝关节置换术的连续患者按照随机方案分为两组（a组和b组）。a组股骨组件的植入采用后髁角外旋3度，由截骨导向器固定。此外，外科医生可根据其他标志点（外科医生自己的方法）校正旋转角度。b组术前借助CT扫描测量后髁角，并将其转移至截骨导向器上，使后髁角能以单度步长变化。在这种情况下，无法采用外科医生自己的方法改变股骨旋转角度。按照伯杰等人的技术，术后用CT扫描测量所有膝关节置换术（a组和b组）的旋转情况。股骨组件与经髁间轴平行的植入被视为正确。测量差异度数。
不考虑方向（外旋/内旋），a组和b组股骨旋转不良程度的差异具有高度统计学意义（p < 0.000001）。b组最大旋转不良范围为2度，而a组为6度。b组30个股骨组件中有19个（= 63.3%）完全没有旋转不良，a组27个股骨组件中只有5个（= 18.5%）完全正确植入。
术前测量后髁角被证明是一种简单、可重复的检查方法，可提高全膝关节置换术的旋转精度。
