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明确锁骨短缩畸形愈合对盂肱关节（glenohumeral joint，GH）旋转中心的影响，以及修复手术恢复运动学基线的能力。方法：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个肩部标本开展自动化外展（ABD）及简化投掷动作（ATM）测试，以测量盂肱关节的旋转中心。简化投掷动作（ATM）被定义为纯侧向外展，以及从后期抬肩相至加速末期的动作序列。先对锁骨完整的肩部标本开展测试，以确立运动学基线。随后对锁骨造成中段骨折，再次进行运动学测试。对骨折的锁骨先采用钢板固定以恢复锁骨长度完成修复，随后采用2cm重叠的骨碎片钢丝固定术，以模拟短缩畸形愈合状态。每一种修复方式完成后均进行运动学测试。对盂肱关节旋转中心沿所有轴进行绘图，以勾勒出三维运动轨迹及曲线下面积。结果：在整个自动化外展过程中，与基线状态相比，畸形愈合会导致后方及上方位移增大。钢板固定可在较低外展角度下恢复后方及上方位移，但在肩过头位角度时会造成过度的前方及下方位移。在整个简化投掷动作过程中，所有测试工况的位移均显著偏向于前方及上方，与基线状态存在显著差异。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。在所测量的所有角度下，钢板固定均未能使前后向及上下向位移恢复至基线水平。结论：本研究阐明了锁骨与盂肱关节之间复杂的相互作用关系。尽管锁骨排列异常会改变肩部运动，但恢复锁骨长度并不一定能使盂肱关节运动学恢复至基线水平。肩部损伤的康复治疗必须兼顾骨性损伤与肩带的动态受力情况。