Background

It remains unclear how the head and stem diameters for the radial head prosthesis could affect mechanical properties of the lateral collateral ligament measured by strain changes during elbow and forearm motions.

Methods

Eight cadaveric specimens were secured to the device, which allows elbow flexion-extension and forearm pro-supination. Using six different implant combinations comprising 2 sizes for the head (long- and short-axis of the native head) and 3 sizes for the stem (press-fit, −1 mm, and −2 mm downsizing), prostheses were attached via the posterior approach. A differential variable reluctance transducer placed on the central portion of the radial collateral ligament were used for strain measurement with elbow flexion at 0°, 30°, 60°, and 90°. At each position, the strain patterns with the forearm in the neutral and 45° pro-supination positions were also assessed.

Findings

Specimens implanted with long-axis head component showed greater increases in the ligament strain during elbow flexion than intact specimens or those implanted with short-axis head. Compared to press-fit stem, implants with downsizing to −1 mm approximated strain patterns during pro-supination with elbow extension to intact condition.

Interpretation

Morphologic variation of the head and stem components in radial head prostheses led to altered strain patterns in the lateral collateral ligament during elbow and forearm motions. A short-axis head component can be used to prevent excessive strain changes after the prosthesis application. Downsizing of the stem component might be an option for approximating the biomechanics at the radiocapitellar joint during forearm rotation to the intact elbow.

中文翻译：

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模块化radial骨头假体对肘外侧副韧带的缩小作用：尸体研究。

背景

尚不清楚the骨头假体的头部和茎部直径如何影响肘和前臂运动过程中的应变变化来测量侧副韧带的机械性能。

方法

将八个尸体标本固定到该设备上，以允许肘部屈伸和前臂前突。使用包括用于将所述头部（长期和天然头的短轴）2个大小六个不同的植入物的组合和3种尺寸的杆（压配合，-1毫米，和-2毫米小型化），假体附着经由所述后入路。放置在the侧副韧带中央部分的差分可变磁阻传感器用于应变测量，肘弯曲度分别为0°，30°，60°和90°。在每个位置，还评估了前臂处于中立位置和45°前旋位置的前臂应变模式。

发现

与完整标本或短轴头相比，植入长轴头组件的标本在肘部弯曲过程中韧带应变增加更大。与压入式茎杆相比，植入前缩窄到-1 mm时的应变模式近似，肘部伸展至完整状态。

解释

radial骨头假体中头部和茎组件的形态变化导致肘部和前臂运动过程中外侧副韧带的应变模式改变。短轴头部组件可用于防止假体应用后过度的应变变化。减小茎组件的尺寸可能是在将前臂旋转至完整肘部时，在放射小it关节处的生物力学近似的一种选择。