Scapulothoracic Dissociation

The scapula is a somewhat mobile structure which, although fixed to the thoracic cage both by muscular and skeletal attachments, can change position with regards to the underlying chest wall [1]. The Scapulothoracic position is maintained by both muscles (serratus, rhomboids etc) and the clavicle which itself attaches laterally to the scapula (acromioclavicular joint) and medially to the chest wall (sternoclavicular joint). Most injuries to the shoulder such as clavicle fractures or clavicular joint separations will not in and of themselves result in STD. True dissociation occurs when severe lateral displacement of the scapula disrupts both the muscular and skeletal connections between the scapula and the chest wall without tearing the overlying skin. However the more severe traumatic forces that cause separation between the scapula and the chest wall often yield associated injuries which disrupt the clavicle strut and the Scapulothoracic articulation causing the scapula to move laterally. Severe lateral traction can also cause brachial plexus injuries and vascular injuries. The most devastating injury is complete disruption of the brachial plexus which can result in a flail arm. If there is a complete brachial plexus avulsion, some authors recommend above elbow amputation of the limb [2,3].