Shoulder and Humerus Injuries

The sternoclavicular joint is the most frequently moved, nonaxial joint of the body. It also has the least amount of bony stability of any major joint because less than half of the medial end of the clavicle articulates with the upper sternum. Therefore, joint stability depends on the integrity of the surrounding ligaments, which give the sternoclavicular joint surprising strength. As a result, the majority of injuries to this area are simple sprains, and dislocations and fractures are uncommon.

Forcing the shoulder forward suddenly, or applying a medially directed force to the shoulder, may result in a sprain to the sternoclavicular joint. Pain and swelling are localized to the joint, and treatment is symptomatic with ice, sling, and analgesics. Differential diagnosis in the nontrauma patient should include consideration of septic arthritis, especially in injection drug users.

Dislocations are unusual and typically result from motor vehicle crashes or sports injuries. If the shoulder is rolled forward at the time of impact, a posterior dislocation may result from a direct blow or from an indirect force to the shoulder. An anterior sternoclavicular joint dislocation may result from the same indirect force if the shoulder is rolled backward at the moment of impact. Posterior sternoclavicular joint dislocations are much less common than anterior dislocations.

Patients with a sternoclavicular joint dislocation have severe pain that is exacerbated by arm motion and lying supine. The shoulder appears shortened and rolled forward. On examination, anterior dislocations have a prominent medial clavicle end that is visible and palpable anterior to the sternum, although swelling and tenderness may impede diagnosis. In posterior dislocations, the medial clavicle end is less visible and often not palpable (Figure 268-1), and the patient may have signs and symptoms of impingement of the superior mediastinal contents.

Routine radiographs may not be diagnostic. Special views and comparison with the other clavicle may be helpful. CT is the imaging procedure of choice (Figures 268-2 and 268-3), and IV contrast may be administered to further delineate injury to adjacent mediastinal structures (Figure 268-4).