Pataky Joshua, Seelam Vijitha, Engle Lyndsay, Khandare Sujata, Armstrong April D, Vidt Meghan E
Biomedical Engineering, Pennsylvania State University, University Park, PA, USA.
Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, PA, USA.
Clin Biomech (Bristol). 2021 Dec;90:105494. doi: 10.1016/j.clinbiomech.2021.105494. Epub 2021 Oct 5.
Rotator cuff tear is a common musculoskeletal injury, negatively affecting shoulder function. Rotator cuff tear severity ranges from small to massive tears, but it is unclear how tear severity affects glenohumeral joint loading and how changes contribute to secondary injury. This study's objective was to determine how glenohumeral joint contact force changes with tear severity during functional task performance using computational models.
Eight models of increasing tear severity were developed, ranging from no rotator cuff tear to massive three-tendon tears. Simulations were performed using models representing increasing tear severity and kinematics for five functional tasks (n = 720 simulations). For each task, magnitude and orientation of peak resultant joint contact force for each tear severity was identified, then compared to the no rotator cuff tear model.
For all tasks, compared to the no rotator cuff tear model, joint contact force magnitude decreased 9.5% on average with infraspinatus involvement, then plateaued at 20.8% average decrease with subscapularis involvement. Projected orientation of peak joint contact force vector was located more superior in the glenoid with increased tear severity, with significant changes (p < 0.0003) for all tasks with infraspinatus involvement.
Decreased magnitude and superior orientation of joint contact force suggest fewer intact muscles contribute to force distribution across the joint, although more work is needed characterizing associated compensation strategies. All force vectors remained oriented within the glenoid rim for all tasks and models, suggesting the system prioritizes joint stability. This work identifies how joint contact force changes with rotator cuff tear severity.
肩袖撕裂是一种常见的肌肉骨骼损伤，对肩部功能有负面影响。肩袖撕裂的严重程度从小型撕裂到大型撕裂不等，但尚不清楚撕裂严重程度如何影响盂肱关节负荷以及这些变化如何导致继发性损伤。本研究的目的是使用计算模型确定在功能任务执行过程中盂肱关节接触力如何随撕裂严重程度而变化。
建立了八个撕裂严重程度逐渐增加的模型，范围从无肩袖撕裂到大型三肌腱撕裂。使用代表撕裂严重程度增加和运动学的模型对五项功能任务进行模拟（n = 720次模拟）。对于每项任务，确定每种撕裂严重程度下峰值合成关节接触力的大小和方向，然后与无肩袖撕裂模型进行比较。
对于所有任务，与无肩袖撕裂模型相比，冈下肌受累时关节接触力大小平均降低9.5%，然后在肩胛下肌受累时平均降低20.8%时趋于平稳。随着撕裂严重程度增加，峰值关节接触力矢量的投影方向在关节盂中更靠上，冈下肌受累的所有任务均有显著变化（p < 0.0003）。
关节接触力大小的降低和方向的上移表明，较少的完整肌肉参与了整个关节的力分布，尽管需要更多工作来表征相关的补偿策略。对于所有任务和模型，所有力矢量仍保持在关节盂边缘内，表明该系统优先考虑关节稳定性。这项工作确定了关节接触力如何随肩袖撕裂严重程度而变化。
