Sternoclavicular Joint Injury 

A freely moveable synovial joint links the upper extremity to the torso, with the sternoclavicular joint (SCJ) participating in all movements of the upper extremity. The SCJ is a saddle-type joint that provides free movement of the clavicle in nearly all planes. The ability to thrust the arm and shoulder forward requires sound function of the SCJ. Because only about 50% of the medial end of the clavicle articulates with the manubrium, the SCJ has little inherent stability. Most of the SCJ's strength and stability originates from the joint capsule and supporting ligaments. The capsule surrounding the joint is weakest inferiorly, while it is reinforced on the superior, anterior, and posterior aspects by the various ligaments. These include the interclavicular, anterior and posterior sternoclavicular, and costoclavicular ligaments.

Usually only through the application of significant force do the ligaments supporting the SCJ become completely disrupted, enabling dislocation of the joint. Whether the SCJ subluxes or dislocates depends on the extent of the damage to the supporting ligaments and capsule. Sternoclavicular joint injuries (SJIs) are graded into 3 types.

• A first-degree injury, or simple sprain, constitutes an incomplete tear or stretching of the sternoclavicular and costoclavicular ligaments. Discomfort is mild, and no instability is present. This is the most common type of SJI.
• With a second-degree injury, the clavicle undergoes an anterior or posterior subluxation from its manubrial attachment, signifying a complete breach of the sternoclavicular ligament but at most, only a partial tear of the costoclavicular ligament.
• With a third-degree injury, complete rupture of the sternoclavicular and costoclavicular ligaments permits the clavicle to completely dislocate from the manubrium.

A significant direct or indirect force to the shoulder region can cause a traumatic dislocation of the SCJ.^[1] Anterior dislocations of the SCJ are much more common (by a 9:1 ratio), usually resulting from an indirect mechanism such as a blow to the anterior shoulder that rotates the shoulder backward and transmits the stress to the joint. Traumatic contact driving the shoulder forward can cause posterior dislocations of the SCJ, as can direct impact to the superior sternal or medial clavicular surfaces.

Frequency

United States

The ligaments and capsule of the SCJ contribute enough stability to make this one of the least dislocated joints in the body. Sternoclavicular dislocations are uncommon, accounting for only 3% of a series of 1603 shoulder girdle injuries. Posterior dislocations are considerably less common than anterior dislocations. Only 1 patient in the cited series of 1603 shoulder girdle injuries had a posterior dislocation.

Mortality/Morbidity

Mortality and significant morbidity occur infrequently with anterior dislocations of the SCJ. Problems are usually related to issues of physical appearance as well as pain and functional limitations for persons with an active lifestyle.

However, a posterior SCJ dislocation has an estimated 25% complication rate. Complications from posterior displacement of the clavicle have included pneumothorax, laceration of the superior vena cava, occlusion of the subclavian artery or vein, and disruption of the trachea. These and other complications can cause significant disability and even death.^[2]

Sex

Overall incidence of sternoclavicular joint injury is higher in males than in females, probably because of the activities (eg, motor vehicle crash, contact sports) associated with the injury. However, recurrent atraumatic anterior subluxation of the SCJ (usually associated with overall joint laxity) though rare, occurs more frequently in young girls.

Age

Incidence is increased in young adult males, since this population is engaged more often in activities associated with SJI, such as motor vehicle crashes and contact sports.