McFarland Daniel C, McCain Emily M, Poppo Michael N, Saul Katherine R
Department of Mechanical and AerospaceEngineering,North Carolina State University,911 Oval Drive,Raleigh, NC 27606e-mail:
J Biomech Eng. 2019 May 1;141(5). doi: 10.1115/1.4043035.
Degenerative wear to the glenoid from repetitive loading can reduce effective concavity depth and lead to future instability. Workspace design should consider glenohumeral stability to prevent initial wear. While glenohumeral stability has been previously explored for activities of daily living including push-pull tasks, whether stability is spatially dependent is unexplored. We simulated bimanual and unimanual push-pull tasks to four horizontal targets (planes of elevation: 0 deg, 45 deg, 90 deg, and 135 deg) at 90 deg thoracohumeral elevation and three elevation targets (thoracohumeral elevations: 20 deg, 90 deg, 170 deg) at 90 deg plane of elevation. The 45 deg horizontal target was most stable regardless of exertion type and would be the ideal target placement when considering stability. This target is likely more stable because the applied load acts perpendicular to the glenoid, limiting shear force production. The 135 deg horizontal target was particularly unstable for unimanual pushing (143% less stable than the 45 deg target), and the applied force for this task acts parallel to the glenoid, likely creating shear forces or limiting compressive forces. Pushing was less stable than pulling (all targets except sagittal 170 deg for both task types and horizontal 45 deg for bimanual) (p < 0.01), which is consistent with prior reports. For example, unimanual pushing at the 90 deg horizontal target was 197% less stable than unimanual pulling. There were limited stability benefits to task placement for pushing, and larger stability benefits may be seen from converting tasks from push to pull rather than optimizing task layout. There was no difference in stability between bimanual and unimanual tasks, suggesting no stability benefit to bimanual operation.
重复性负荷导致的关节盂退行性磨损会减小有效凹度深度，并引发未来的不稳定。工作空间设计应考虑盂肱稳定性以防止初期磨损。虽然此前已针对包括推拉任务在内的日常生活活动对盂肱稳定性进行了研究，但稳定性是否具有空间依赖性尚不清楚。我们在胸肱抬高90°时模拟了向四个水平目标（抬高平面：0°、45°、90°和135°）进行的双手和单手推拉任务，以及在抬高平面90°时向三个抬高目标（胸肱抬高：20°、90°、170°）进行的任务。无论用力类型如何，45°水平目标最为稳定，在考虑稳定性时它将是理想的目标位置。该目标可能更稳定，因为施加的负荷垂直于关节盂，限制了剪切力的产生。135°水平目标在单手推时特别不稳定（比45°目标稳定性低143%），此任务的作用力与关节盂平行，可能会产生剪切力或限制压缩力。推比拉不稳定（两种任务类型除矢状面170°和双手的水平45°外的所有目标）（p<0.01），这与先前的报告一致。例如，在90°水平目标处单手推比单手拉稳定性低197%。对于推任务，任务放置对稳定性的益处有限，将任务从推转换为拉可能比优化任务布局能带来更大的稳定性益处。双手和单手任务在稳定性上没有差异，表明双手操作对稳定性没有益处。
