Adult Hip and Knee Replacement Service, Hospital for Special Surgery, New York, NY.
J Arthroplasty. 2019 Feb;34(2):281-285. doi: 10.1016/j.arth.2018.09.080. Epub 2018 Sep 28.
Prior studies have found that greater proximal tibial varus was associated with increased external femoral rotation at time of total knee arthroplasty. These works suggest that measuring the tibial plateau-tibial shaft (TPTS) angle on preoperative weight-bearing long leg radiographs could predict significant variations in the posterior condylar angle.
A minimum of 68 patients were needed to reach 80% power. Patients were included if they had primary medial compartment osteoarthritis and excluded if they had a valgus mechanical axis. The clinical posterior condylar angle (cPCA) was defined as the angle between the anatomic transepicondylar axis and posterior condylar line. Correlation analyses were performed to test for any relationship between the TPTS and cPCA. Two patient groups were created based on TPTS angle: TPTS ≤4° (mild varus) and TPTS >4° (moderate varus). Mechanical axis and rotational measurements were compared between the groups using independent t-tests.
The mean mechanical axis and TPTS angle were 6.9° and 4.8° of varus, respectively. The mean cPCA was 5.0° (standard deviation [SD], 1.4°; range, 2.4°-7.9°). No correlation was found between the TPTS angle and cPCA (P = .15). The mean cPCA in the mild varus group (n = 28 patients) was 5.2° (SD, 1.5°; range, 2.7°-7.9°), and the mean cPCA in the moderate varus group (n = 45 patients) was 4.4° (SD, 1.7°; range, 0.6°-7.5°). These groups were not statistically significantly different from each other (P = .62).
The present study does not support the conclusions of previous works and suggests that the amount of distal femoral rotation cannot be predicted by tibial varus alignment measured on preoperative long leg radiographs. Consequently, we believe that proximal tibial varus should not be used to preoperatively predict external rotation of the femoral component in patients with isolated medial compartment osteoarthritis.
先前的研究发现，全膝关节置换术中胫骨近端内翻越大，股骨外旋越大。这些研究表明，在术前负重全长下肢 X 线片上测量胫骨平台-胫骨骨干（TPTS）角可以预测后髁角的显著变化。
需要至少 68 例患者才能达到 80%的效力。如果患者患有原发性内侧间室骨关节炎，则将其纳入研究范围；如果患者存在外翻机械轴，则将其排除在外。临床后髁角（cPCA）定义为解剖髁间轴与后髁线之间的角度。进行相关分析以测试 TPTS 与 cPCA 之间的任何关系。根据 TPTS 角度将患者分为两组：TPTS≤4°（轻度内翻）和 TPTS＞4°（中度内翻）。使用独立 t 检验比较两组之间的机械轴和旋转测量值。
平均机械轴和 TPTS 角度分别为 6.9°和 4.8°的内翻。平均 cPCA 为 5.0°（标准差[SD]，1.4°；范围，2.4°-7.9°）。未发现 TPTS 角度与 cPCA 之间存在相关性（P=0.15）。轻度内翻组（n=28 例患者）的平均 cPCA 为 5.2°（SD，1.5°；范围，2.7°-7.9°），中度内翻组（n=45 例患者）的平均 cPCA 为 4.4°（SD，1.7°；范围，0.6°-7.5°）。这两组之间没有统计学上的显著差异（P=0.62）。
本研究不支持先前研究的结论，表明不能通过术前全长下肢 X 线片上测量的胫骨内翻来预测股骨远端的旋转量。因此，我们认为在单纯内侧间室骨关节炎患者中，不应使用胫骨近端内翻来预测股骨组件的外旋。
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