Sternoclavicular Joint Injury

Sternoclavicular (SC) joint injuries are uncommon. The sternoclavicular joint is a diarthrodial joint composed of the sternum and clavicle. It is stabilized by the posterior capsular ligament which provides the most anterior-posterior stability and the anterior sternoclavicular ligament which restricts superior displacement. The costoclavicular ligament helps provide medial clavicle and anterior first rib stability. The interclavicular ligament passes over the sternum to provide medial traction of both clavicles. The inter-articular disc ligament attaches to the first rib and also provides stability of the sternoclavicular joint. In between the two articular surfaces and within the joint space is a fibrocartilaginous articular disc which functions as an important shock absorber. It is the only synovial articulation between the upper limb and axial skeleton. The subclavius muscle also supports the integrity of the joint. There are vital anatomic structures behind the clavicle which include the innominate artery and vein, vagus nerve, phrenic nerve, internal jugular vein, trachea, and esophagus. The medial clavicle physis appears in late adolescence and does not ossify until the age of 25. Movement of the joint occurs from transmission of movement from the scapula and the rest of the shoulder girdle. In abduction, the sternoclavicular joint has 35 degrees of range. Anterior-posteriorly it can move 70 degrees. There is also a rotational component. Injuries to the sternoclavicular joint can be traumatic or atraumatic. In traumatic injuries, the mechanism is usually a high energy injury such as a motor vehicle accident or injury during contact or collision sports. A sprain of the joint can occur when no laxity or instability occurs. Anterior dislocation is more common than posterior, which are associated with greater morbidity due to adjacent mediastinal and vascular structures. Atraumatic subluxations occur in younger patients with overhead elevation of the arm. This most commonly affects adolescent females with multidirectional instability. The subluxation is often painless and does not affect activities of daily living. It can be associated with trapezius palsy or spinal accessory nerve palsy.