BACKGROUND:Identifying the time course of rotational knee alignment is crucial for elucidating the etiology in knee osteoarthritis. OBJECTIVE:The aim of this study was to propose new rotational indices for calculating the change in relative rotational angles between the femur and tibia in standinganteroposterior (AP) radiographs. METHODS:Forty healthy elderly volunteers (20 women and 20 men; mean age, 70 ± 6 years) were assessed. The evaluation parameters were as follows: (1) femoral rotational index: the distance between the sphere center of the medial posterior femoral condyle and the lateral edge of the patella, and (2) tibial rotational index: the distance between the medial eminence of the tibia and the lateral edge of the fibula head. The indices were standardized by the diameter of the sphere of the medial posterior femoral condyle. This study (1) identified the relationship between changes in rotational indices and the simulated rotational knee angles in the standing position, (2) proposed a regression equation for the change in relative rotational angles between the femur and tibia in standing AP radiographs, and (3) verified the accuracy of the regression equation. RESULTS:The rotational indices increased in direct proportion to simulated rotational knee angles (femoral index: r > 0.9,p < 0.0001; tibial index: r > 0.9, p < 0.0001). Based on the results, the regression equation with the accuracy of 0.45 ± 0.26° was determined. CONCLUSIONS:The proposed regression equations can potentially predict the change in relative rotational angles between the femur and tibia in a pair of standing AP radiographs taken at different dates in longitudinal studies.

中文翻译：

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站立前后膝关节X线片中膝关节旋转角度的新评估指标

背景：确定膝关节旋转对线的时间过程对于阐明膝关节骨关节炎的病因至关重要。目的：本研究的目的是提出新的旋转指数，用于计算站立前后 (AP) 射线照片中股骨和胫骨之间的相对旋转角度的变化。方法：评估了 40 名健康老年志愿者（20 名女性和 20 名男性；平均年龄，70 ± 6 岁）。评价参数如下：（1）股骨旋转指数：股骨后髁的球心与髌骨外侧缘的距离；（2）胫骨旋转指数：股骨后髁内侧隆起的距离。胫骨和腓骨头的外侧边缘。这些指数通过内侧后股骨髁球的直径进行标准化。本研究 (1) 确定了站立位旋转指数变化与模拟膝关节旋转角度之间的关系，(2) 提出了站立 AP 射线照片中股骨和胫骨之间相对旋转角度变化的回归方程，以及 ( 3) 验证了回归方程的准确性。结果：旋转指数与模拟膝关节旋转角度成正比增加（股骨指数：r > 0.9，p < 0.0001；胫骨指数：r > 0.9，p < 0.0001）。根据结果​​确定了精度为0.45±0.26°的回归方程。结论：所提出的回归方程可以潜在地预测在纵向研究中在不同日期拍摄的一对站立 AP 射线照片中股骨和胫骨之间相对旋转角度的变化。