The rotator cuff is theorized to contribute to force couples required to produce glenohumeral kinematics. Impairment in these force couples would theoretically result in impaired ball-and-socket kinematics. Although less frequently used than traditional kinematic descriptors (e.g., Euler angles, joint translations), helical axes are capable of identifying alterations in ball-and-socket kinematics by quantifying the variability (i.e., dispersion) in axis orientation and position during motion. Consequently, assessing glenohumeral helical dispersion may provide indirect evidence of rotator cuff function. The purpose of this exploratory study was to determine the extent to which rotator cuff pathology is associated with alterations in ball-and-socket kinematics. Fifty-one participants were classified into one of five groups based on an assessment of the supraspinatus using diagnostic imaging: asymptomatic healthy, asymptomatic tendinosis, asymptomatic partial-thickness tear, asymptomatic full-thickness tear, symptomatic full-thickness tear. Glenohumeral kinematics were quantified during coronal plane abduction using a biplane x-ray system and described using instantaneous helical axes. The degree to which glenohumeral motion coincided with ball-and-socket kinematics was described using the angular and positional dispersion about the optimal helical axis and pivot, respectively. No statistically significant difference was observed between groups in angular dispersion. However, symptomatic individuals with a full-thickness supraspinatus tear had significantly more positional dispersion than asymptomatic individuals with a healthy supraspinatus or tendinosis. These findings suggest that symptomatic individuals with a full-thickness supraspinatus tear exhibit impaired ball-and-socket kinematics, which is believed to be associated with a disruption of the glenohumeral force couples.

理论上，肩袖有助于产生盂肱运动学所需的力偶。理论上，这些力偶的损伤会导致球窝运动学受损。虽然螺旋轴比传统的运动学描述符（例如，欧拉角、关节平移）使用频率较低，但它能够通过量化运动过程中轴方向和位置的变化（即分散）来识别球窝运动学的变化。因此，评估盂肱螺旋分散度可以提供肩袖功能的间接证据。这项探索性研究的目的是确定肩袖病理学与球窝运动学改变的相关程度。根据使用诊断成像对冈上肌的评估，将 51 名参与者分为五组之一：无症状健康、无症状肌腱变性、无症状部分撕裂、无症状全层撕裂、有症状全层撕裂。使用双平面 X 射线系统对冠状面外展期间的盂肱运动学进行量化，并使用瞬时螺旋轴进行描述。分别使用围绕最佳螺旋轴和枢轴的角度和位置分散来描述盂肱运动与球窝运动学一致的程度。组间角色散没有观察到统计学上的显着差异。然而，患有全层冈上肌撕裂的有症状个体比具有健康冈上肌或肌腱变性的无症状个体具有显着更多的位置离散。这些发现表明，有症状的冈上肌全层撕裂患者表现出球窝运动学受损，这被认为与盂肱力偶破坏有关。