Sternoclavicular dislocations are uncommon, accounting for less than 3% of shoulder girdle injuries.1 The medial clavicle may be displaced anteriorly, posteriorly, or rarely superiorly (Figure 101-1).2 Bipolar clavicular dislocations (i.e., simultaneous dislocation of both clavicular articulations) also occur rarely.3 Anterior dislocations are considerably more common than posterior dislocations. However, posterior dislocations deserve more attention due to the far higher incidence of associated complications.1 Also, since the medial clavicular physis closes relatively late in life, what appears to be a posterior sternoclavicular dislocation in young patients may actually be a medial epiphyseal disruption with posterior displacement.4
Superior view of the position of the medial end of the clavicle in a sternoclavicular joint dislocation. (Used with permission from eOrthopod.org.)
Sternoclavicular dislocations result from direct trauma to the sternoclavicular joint or to the glenohumeral joint with the force directed toward the sternoclavicular joint. Tremendous force is usually required to disrupt the sternoclavicular joint. Common mechanisms of injury include motor vehicle collisions and contact sports.3 Falls, minor trauma, or various medical conditions without trauma result in sternoclavicular dislocations less commonly.5-7
Anterior dislocations are often due to indirect forces transmitted through the anteromedial shoulder. As the shoulder is externally compressed and rolled backward, the lateral clavicle is pulled back and down beyond its limit of motion. The first rib acts as a fulcrum to spring the sternal end of the clavicle anteriorly from its articulation (Figure 101-2).1,8,9
Clinical photo of an anterior sternoclavicular joint dislocation. (Used with permission from Knoop KJ, Stack LB, Storrow AB, Thurman RJ (eds): The Atlas of Emergency Medicine, 4th ed. New York: McGraw-Hill; 2016. Photo contributor: R. Jason Thurman, MD.)
Posterior dislocations may be due to direct or indirect forces.1,10-13 With indirect trauma, the shoulder is externally compressed and rolled forward from a force applied posterolaterally to the shoulder. The costoclavicular ligament acts as a fulcrum that produces displacement of the sternal end of the clavicle posteriorly from its articulation (Figure 101-3).11 Less commonly, a posterior dislocation may be due to a direct blow to the anteromedial clavicle.12
CT scan of a posterior sternoclavicular joint dislocation. (Used with permission from Tintinalli JE, et al: Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8th ed. New York: McGraw-Hill; 2016.)
Spontaneous and atraumatic sternoclavicular subluxations and dislocations do occur, often in those with laxity in other joints or in association with inflammatory conditions.7,8,14-16 Both anterior and posterior subluxations have been described, ...