Data from: Glenohumeral joint kinematics following clavicular fracture and repairs

Background. The purpose of this biomechanical study was to determine the effect of shortened clavicle malunion on the center of rotation of the glenohumeral (GH) joint, and the capacity of repair to restore baseline kinematics. Methods. Six shoulders underwent automated abduction (ABD) and abbreviated throwing motion (ATM) using a 7-DoF automated upper extremity testing system in combination with an infrared motion capture system to measure the center of rotation of the GH joint. ATM was defined as pure lateral abduction and late cocking phase to the end of acceleration. Torsos with intact clavicle underwent testing to establish baseline kinematics. Then, the clavicles were subjected to midshaft fracture followed by kinematics testing. The fractured clavicles underwent repairs first by clavicle length restoration with plate fixation, and then by wiring of fragments with a 2-cm overlap to simulate shortened malunion. Kinematic testing was conducted after each repair technique. Center of rotation of the GH joint was plotted across all axes to outline 3D motion trajectory and area under the curve. Results. Throughout ABD, malunion resulted in increased posterior and superior translation compared to baseline. Plate fixation restored posterior and superior translations at lower abduction angles but resulted in excess anterior and inferior translation at overhead angles. Throughout ATM, all conditions were significantly anterior and superior to baseline. Translation with malunion was situated anterior to the fractured and ORIF conditions at lower angles of external rotation. Plate fixation did not restore baseline anteroposterior or superoinferior translation at any angle measured. Conclusions. This study illustrates the complex interplay of the clavicle and the GH joint. While abnormal clavicle alignment alters shoulder motion, restoration of clavicle length does not necessarily restore GH kinematics to baseline. Rehabilitation of the injured shoulder must address the osseous injury and the dynamic forces of the shoulder girdle.背景：本项生物力学研究旨在探讨锁骨畸形愈合伴短缩对盂肱（glenohumeral, GH）关节旋转中心的影响，以及修复手术对恢复基线运动学状态的能力。 方法：本研究采用7自由度（7-DoF）自动化上肢测试系统结合红外运动捕捉系统，对6个肩关节标本实施自动化外展（abduction, ABD）及简化投掷动作（abbreviated throwing motion, ATM）测试，以测量盂肱关节的旋转中心。其中，简化投掷动作被定义为纯侧向外展及从晚期扣机阶段至加速末期的运动流程。首先对锁骨完整的标本进行运动学测试以建立基线运动学数据；随后人为造成锁骨中段骨折，并再次开展运动学测试。对骨折后的锁骨标本依次采用两种修复方式：一是通过钢板固定恢复锁骨长度，二是通过骨折块2cm重叠钢丝固定以模拟短缩型畸形愈合。每一种修复操作完成后均开展运动学测试。最后，对盂肱关节旋转中心在各轴向上的运动数据进行绘图，以勾勒出三维运动轨迹及曲线下面积。 结果：在全程外展运动中，与基线状态相比，畸形愈合组的后移及上移幅度均有所增加。钢板固定可在较低外展角度下恢复后移及上移，但在肩关节过顶角度时会导致过度的前移及下移。在全程简化投掷动作中，所有实验组的前移及上移幅度均显著高于基线状态。在外旋角度较低时，畸形愈合组的位移相较于骨折组及切开复位内固定（open reduction internal fixation, ORIF）组更偏前方。钢板固定无法在任意测试角度下恢复基线状态下的前后向或上下向位移。 结论：本研究阐明了锁骨与盂肱关节之间复杂的相互作用机制。尽管锁骨排列异常会改变肩关节运动，但仅恢复锁骨长度并不一定能使盂肱关节运动学恢复至基线状态。肩部损伤的康复治疗需同时兼顾骨损伤与肩带的动态受力情况。