Background

The brachialis muscle lies in close anatomic relation to the anterior capsule of the elbow joint. The contribution of the brachialis muscle to elbow stability has not yet been fully investigated. Therefore, the aim of this biomechanical in-vitro study was to analyze its influence on joint stability.

Methods

Nine fresh frozen cadaveric elbows were evaluated for stability against valgus and varus/posterolateral rotatory forces. Brachialis loading was measured indirectly using strain gauges. Three distinct scenarios were analyzed: A) with intact lateral ulnar and ulnar collateral ligaments B) with a ruptured lateral ulnar collateral ligament C) with ruptured lateral ulnar and ulnar collateral ligaments.

Findings

In all scenarios, an increased strain was observed under posterolateral rotatory/varus forces. The maximum measured strain occurred with elbow flexion of 30° and pronation of the forearm. The strain was significantly higher with dual-ligament rupture (mean - 210.5 μm/m; min. 97.8 μm/m; max. -310 μm/m; SD 107.8 μm/m; p = .034) compared to intact ligaments (mean − 106.9 μm/m; min. -32.51 μm/m, max. -287 μm/m; SD 100.2 μm/m) and single-ligament rupture (mean – 109.5 μm/m; min. - 96.7 μm/m; max - 130.4 μm/m; SD 18.2).

Interpretation

A strain of the brachialis muscle was observed under varus/posterolateral rotatory forces with a pronated forearm and the strain increased significantly in the event of a dual-ligament rupture. This suggests that the brachialis muscle may influence varus/posterolateral rotatory stability of the elbow. Hence, a concomitant tear of the brachialis muscle might result in pronounced instability following simple elbow dislocation.

Level of evidence

Basic Science Study, Biomechanics.

中文翻译：

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肱肌在副韧带损伤肘部稳定性中的作用：生物力学研究

背景

肱肌与肘关节前囊的解剖关系密切。肱肌对肘部稳定性的贡献尚未得到充分研究。因此，这项生物力学体外研究的目的是分析其对关节稳定性的影响。

方法

评估了九个新鲜冷冻的尸体肘部对抗外翻和内翻/后外侧旋转力的稳定性。使用应变仪间接测量肱肌负荷。分析了三种不同的情况：A) 具有完整的外侧尺侧和尺侧副韧带 B) 具有破裂的外侧尺侧副韧带 C) 具有破裂的外侧尺侧和尺侧副韧带。

发现

在所有情况下，在后外侧旋转/内翻力下观察到应变增加。最大测量应变发生在肘部弯曲 30° 和前臂旋前。与完整韧带 （平均− 106.9 μm/m；最小 -32.51 μm/m，最大 -287 μm/m；SD 100.2 μm/m）和单韧带断裂（平均 – 109.5 μm/m；最小 - 96.7 μm/m；最大- 130.4 微米/米；标准差 18.2)。

解释

在前臂内翻/后外侧旋转力作用下观察到肱肌拉伤，并且在双韧带断裂的情况下拉伤显着增加。这表明肱肌可能会影响肘部的内翻/后外侧旋转稳定性。因此，伴随的肱肌撕裂可能导致简单的肘关节脱位后明显的不稳定。

证据级别

基础科学研究，生物力学。