Kim Su Cheol, Kang Seung Gyoon, McGarry Michelle H, Lee Thay Q, Yoo Jae Chul
Department of Orthopaedic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA.
Clin Orthop Surg. 2025 Aug;17(4):649-656. doi: 10.4055/cios24233. Epub 2025 Jan 10.
This study aimed to evaluate the differences in long head of biceps (LHB) motion between the normal and subscapularis intrasubstance partial tear conditions and identify the arm positions that exhibit the most significant LHB motion differences using a cadaveric biomechanical study.
The LHB tendons of 6 fresh-frozen cadaveric shoulders (2 men and 4 women; mean age, 68.4 ± 2.3 years; range, 65-71 years) were marked with metal beads and mounted in a custom-made shoulder testing system. Data for arm positions at 20° or 60° of forward flexion or abduction, with neutral rotation and maximum internal and external rotation with a torque of 1.5 N·m, were collected. Considering the scapulohumeral rhythm, 20° or 60° forward flexion or abduction in a cadaveric shoulder corresponds to 30° or 90° shoulder elevation . Mediolateral (subluxation) and inferosuperior (excursion) LHB motions were measured using a 3-dimensional digitizer, and the differences between normal and subscapularis partial tear conditions were analyzed.
While the LHB mediolateral motion difference was the highest during 60° forward flexion with neutral rotation (1.2 ± 0.4, = 0.042), 20° forward flexion with neutral rotation (0.9 ± 0.3, = 0.024) and 60° abduction with maximum external rotation (0.9 ± 0.3, = 0.036) also demonstrated high mediolateral LHB motion difference between the normal and subscapularis partial tear conditions. In contrast, the LHB inferosuperior motion difference was the highest during 20° forward flexion with neutral rotation (0.7 ± 0.3, = 0.045) between the normal and subscapularis partial tear conditions.
Upon comparing normal and subscapularis partial tear conditions in this cadaveric study, high pathological movements of the LHB were observed during arm forward flexion with neutral rotation and abduction with external rotation. Repetitive activity in these arm positions could aggravate the condition in a partial subscapularis tear.
本研究旨在通过尸体生物力学研究，评估正常情况和肩胛下肌实质内部分撕裂情况下肱二头肌长头（LHB）运动的差异，并确定表现出最显著LHB运动差异的手臂位置。
对6具新鲜冷冻尸体肩部（2名男性和4名女性；平均年龄68.4±2.3岁；范围65 - 71岁）的LHB肌腱用金属珠标记，并安装在定制的肩部测试系统中。收集在向前屈曲或外展20°或60°、中立旋转以及最大内旋和外旋且扭矩为1.5 N·m时的手臂位置数据。考虑到肩肱节律，尸体肩部的20°或60°向前屈曲或外展对应于30°或90°的肩部抬高。使用三维数字化仪测量LHB的内外侧（半脱位）和上下（偏移）运动，并分析正常情况和肩胛下肌部分撕裂情况之间的差异。
虽然在中立旋转60°向前屈曲时LHB的内外侧运动差异最大（1.2±0.4，P = 0.042），但中立旋转20°向前屈曲（0.9±0.3，P = 0.024）和最大外旋60°外展（0.9±0.3，P = 0.036）时，正常情况和肩胛下肌部分撕裂情况之间的LHB内外侧运动差异也很大。相比之下，在中立旋转20°向前屈曲时，正常情况和肩胛下肌部分撕裂情况之间的LHB上下运动差异最大（0.7±0.3，P = 0.045）。
在本尸体研究中比较正常情况和肩胛下肌部分撕裂情况时，发现在手臂中立旋转向前屈曲和外旋外展期间，LHB出现了明显的病理性运动。在这些手臂位置的重复性活动可能会加重肩胛下肌部分撕裂的病情。
