Effect of Acromioclavicular Joint Injuries on the Acromioclavicular Joint Complex and Scapulohumeral Rhythm: A Functional and Mechanical Perspective

This overview approaches the acromioclavicular joint (ACJ) and ACJ injuries from a mechanical perspective that places the ACJ complex-the scapula, clavicle, ACJ, AC and coracoclavicular ligaments, and periscapular muscles-into the context of its ability to facilitate scapulohumeral rhythm (SHR) functions of scapula placement and humeral mobility. Mechanical concepts underlying this perspective include linkage of the scapula and clavicle into a single segment, the "claviscapula," the role of the AC and coracoclavicular ligaments in torque transduction and horizontal and vertical stability, and the deleterious effects of decoupling the claviscapular segment. The clinical examination and surgical treatment should address anatomic restoration of individual structures and the effect on the functional integrity of the entire ACJ complex within SHR. This context, which unifies anatomic injury with functional consequences, can be used to create a more comprehensive understanding of the clinical presentation and effect on ACJ function and SHR.