PURPOSE Valgus load opens the medial elbow compartment, causing elongation of the ulnar collateral ligament (UCL) that can eventually lead to attenuation and failure. Ideally, the muscles surrounding the medial aspect of elbow joint should coordinate medial elbow compression to prevent the medial elbow compartment from opening and loading the UCL. This study aimed to determine whether baseball pitchers have sufficient elbow varus strength to unload the UCL during pitching. METHODS Using an electromagnetic tracking device, we measured the peak elbow varus moment during pitches (fastball, slider, curveball, and changeup) by 14 professional and 8 collegiate pitchers. Elbow varus strength was measured with an isokinetic dynamometer system while the medial elbow joint space was monitored using ultrasonography. A paired t-test was used to compare the peak varus moment generated during pitching with the varus strength, and the relative intensity of muscular output required to unload the UCL was determined. RESULTS Except for curveballs, the muscular varus strength (57.5 ± 9.2 N·m) was not significantly larger (p = 0.165 ~ 0.853) than the peak varus moments during pitching (55.4 ± 13.0 N·m). Ten participants did not have sufficient muscular varus strength to completely unload the UCL from valgus loading when throwing fastballs and other pitch types. The relative intensity of muscular torque output required for stress shielding of the UCL ranged from 89.1%MVIVS ±21.7%MVIVS for curveballs to 103.1%MVIVS ±26.5%MVIVS for fastballs. CONCLUSIONS Our findings demonstrate that most of the valgus load on the elbow joint during pitching can be counteracted by the muscular varus moment, but valgus loading on the UCL is likely unavoidable in baseball pitching.

中文翻译：

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内侧肘肌肉组织的内翻强度，用于竞技棒球投手尺侧副韧带的压力屏蔽。


目的 外翻负荷打开肘内侧隔室，导致尺侧副韧带 （UCL） 伸长，最终导致衰减和衰竭。理想情况下，肘关节内侧周围的肌肉应协调肘内侧压迫，以防止肘内侧筋膜室打开并加载 UCL。本研究旨在确定棒球投手是否有足够的肘部内翻力量来在投球过程中卸载 UCL。方法 使用电磁跟踪设备，我们测量了 14 名专业投手和 8 名大学投手在投球（快球、滑球、曲线球和换球）期间的峰值肘内翻时刻。使用等速测力计系统测量肘内翻强度，同时使用超声检查监测肘关节内侧间隙。使用配对 t 检验将投球过程中产生的峰值内翻力矩与内翻强度进行比较，并确定卸载 UCL 所需的肌肉输出的相对强度。结果 除曲线球外，肌内翻强度 （57.5 ± 9.2 N·m） 无显著大于投球时峰值内翻时刻 （55.4 ± 13.0 N·m） （p = 0.165 ~ 0.853）。10 名参与者在投掷快球和其他投球类型时没有足够的肌肉内翻力量来完全减轻 UCL 的外翻负荷。UCL 应力屏蔽所需的肌肉扭矩输出的相对强度范围从曲线球的 89.1%MVIVS ±21.7%MVIVS 到快球的 103.1%MVIVS ±26.5%MVIVS。结论 我们的研究结果表明，投球过程中肘关节上的大部分外翻负荷可以被肌肉内翻力矩抵消，但在棒球投球中，UCL 上的外翻负荷可能是不可避免的。