• Satoshi Oki, Noboru Matsumura, Wataru Iwamoto, Hiroyasu Ikegami, Yoshimori Kiriyama, Toshiyasu Nakamura, Yoshiaki Toyama, and Takeo Nagura.
• Department of Orthopedic Surgery, School of Medicine, Keio University, Tokyo, Japan. satoshiohki@gmail.com
• Am J Sports Med. 2012 Nov 1;40(11):2617-26.

BackgroundScapulothoracic dyskinesis is an important consequence of acromioclavicular joint dislocations. However, no reports have described changes in 3-dimensional motions of the scapula and clavicle with respect to the thorax caused by acromioclavicular joint dislocation.HypothesisSectioning of the acromioclavicular (AC) and coracoclavicular (CC) ligaments affects scapular and clavicular motion in a whole-cadaver model.Study DesignControlled laboratory study.MethodsWe evaluated shoulder girdle motion (scapula, clavicle, and humerus) relative to the thorax of 14 shoulders from 8 whole cadavers after sequential sectioning of the AC and CC ligaments (trapezoid and conoid ligaments). An electromagnetic tracking device measured 3-dimensional kinematics of the scapula and clavicle during humerothoracic elevation in the coronal and sagittal planes and adduction in the horizontal plane.ResultsSectioning of the AC ligament increased clavicular retraction during sagittal plane elevation and horizontal plane adduction. Sectioning of the trapezoid ligament decreased scapular external rotation during sagittal plane elevation and horizontal plane adduction. Sectioning of the conoid ligament decreased scapular posterior tilting during sagittal plane elevation and horizontal plane adduction. Acromioclavicular and CC ligament sectioning also delayed clavicular posterior rotation and increased clavicular upward rotation during coronal plane elevation.ConclusionOur study revealed that AC and CC ligament disruption affected in vitro shoulder girdle kinematics in the whole-cadaver model.Clinical RelevanceThe results of this cadaveric study revealed that AC and CC ligament disruption could cause dyskinesis of the scapula and clavicle. The kinematic changes could be a potential source of pain and dysfunction in the shoulder with AC joint dislocation, and therefore surgical reconstruction may be indicated in certain patients.

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