Aims The aim of this study was to evaluate the kinematics of the elbow following increasing length of the radius with implantation of radial head arthroplasties (RHAs) using dynamic radiostereometry (dRSA). Methods Eight human donor arms were examined by dRSA during motor-controlled flexion and extension of the elbow with the forearm in an unloaded neutral position, and in pronation and supination with and without a 10 N valgus or varus load, respectively. The elbows were examined before and after RHA with stem lengths of anatomical size, + 2 mm, and + 4 mm. The ligaments were maintained intact by using a step-cut lateral humeral epicondylar osteotomy, allowing the RHAs to be repeatedly exchanged. Bone models were obtained from CT scans, and specialized software was used to match these models with the dRSA recordings. The flexion kinematics of the elbow were described using anatomical coordinate systems to define translations and rotations with six degrees of freedom. Results The greatest kinematic changes in the elbows were seen with the longest, + 4 mm, implant, which imposed a mean joint distraction of 2.8 mm in the radiohumeral joint and of 1.1 mm in the ulnohumeral joint, an increased mean varus angle of up to 2.4° for both the radius and the ulna, a mean shift of the radius of 2.0 mm in the ulnar direction, and a mean shift of the ulna of 1.0 mm posteriorly. Conclusion The kinematics of the elbow deviated increasingly from those of the native joint with a 2 mm to a 4 mm lengthening of the radius. This confirms the importance of restoring the natural length of the radius when undertaking RHA.

中文翻译：

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用动态放射立体测量分析评估桡骨头关节置换术延长的肘部运动学。


目的 本研究的目的是使用动态放射立体测量法 （dRSA） 评估植入桡骨头关节置换术 （RHA） 后桡骨长度增加后肘部的运动学。方法 在前臂处于无负荷的中立位置时，在肘部运动控制屈曲和伸展期间，以及分别有和没有 10 N 外翻或内翻负荷的旋前和旋后，通过 dRSA 检查了 8 个人类供体手臂。在 RHA 前后检查了解剖尺寸 + 2 mm 和 + 4 mm 的柄长的肘部。通过使用阶梯式切割肱骨外上髁截骨术保持韧带完整，允许 RHA 反复交换。骨骼模型从 CT 扫描中获得，并使用专门的软件将这些模型与 dRSA 记录进行匹配。使用解剖坐标系描述肘部的屈曲运动学，以定义具有六个自由度的平移和旋转。结果肘部的运动学变化最大，出现在最长的 + 4 mm 植入物上，它在桡肱关节中施加了 2.8 mm 的平均关节牵引，在尺肱关节中施加了 1.1 mm，桡骨和尺骨的平均内翻角增加了高达 2.4°，尺骨方向半径平均偏移了 2.0 mm， 尺骨向后平均移位 1.0 mm。结论 肘关节的运动学与自然关节的运动学偏差越来越大，桡骨延长了 2 mm 至 4 mm。这证实了在进行 RHA 时恢复桡骨自然长度的重要性。