The sternoclavicular (SC) joint is the pivot on which the shoulder girdle moves on the trunk. Dislocation of this joint most often results from a fall onto the shoulder.
This joint is a diarthrodial joint, permitting rotary movement of the clavicle. Internal rotation of the arm is associated with the maximum degree of rotation of the clavicle so that the bone protrudes anteriorly.
A sharp, forward thrust of the shoulder girdle, as in the motion of throwing, depends on the integrity of this joint. Elevation of the arm above 110 degrees is associated with clavicular rotation.
In an anterior dislocation, severe pain and tenderness are present over the SC joint. Any movement of the shoulder causes increased pain. Pain is increased when the patient is supine, and the individual prefers to be in the sitting position, supporting the arm on the injured side.
The anteriorly displaced medial end of the clavicle is generally quite visible. The inner end of the clavicle is most commonly dislocated anteriorly and lies in front of the manubrium. The capsule may be torn and interposed to prevent reduction.
Reduction, if possible, is effected by abducting the arm and pulling the shoulder girdle backward, at the same time manipulating the clavicle backward into the sternal facet. The patient is kept flat on his back with a sandbag placed over the clavicle. His or her arms are held at the side, and only minimal movement of the hands is permitted. It is extremely difficult to maintain this position for the 3 weeks necessary for capsule healing. Instability of the joint and redislocation are frequent occurrences.
Surprisingly, many persistent dislocations permit rotation of the clavicle and excellent function. Occasionally, the displaced bone becomes firmly bound down with adhesions. Movement of the shoulder is painful and restricted, particularly internal rotation and abduction above 110 degrees.
Surgery is indicated for pain, restricted motion at the shoulder, deformity, and as an emergency in posterior dislocations with compression of the great vessels.
One may reduce the dislocation and provide stability by a sling between the clavicle and the first rib or by tenodesis, using the subclavius tendon. If the dislocation is old and degeneration of the joint is probable, resection of the inner end of the clavicle should be done. This is compatible with excellent function.
Posterior dislocation of the SC joint is rare. It is caused by both direct and indirect trauma, and the backward displacement of the inner end of the clavicle is extremely hazardous to the mediastinal structures, causing pressure against the trachea and great vessels.
Most acute dislocations are of the anterior type and can be reduced by manipulation. When this is unsuccessful, a torn, posteriorly displaced meniscus or interposed capsule blocks reduction. An anteriorly displaced medial end of the clavicle may become a permanently fixed prominence; or may be completely unstable, spontaneously reducing with the arm at the side or when the patient lies down and redisplacing as the arm is raised overhead and externally or internally rotated.
In any event, whether the displacement is fixed or recurring, little disability is noted for everyday activity, and no other treatment is necessary.
For persons engaged in strenuous activities or sports, the demands of the activity cause such complaints as aching, swelling, and rapid fatigue. In addition, osteoarthritic changes may cause persistent aching and stiffness and restrict the full range of movement of the shoulder. These constitute the rare indications for surgical intervention.
Reduction and stabilization of the SC joint for an acute anterior dislocation should never be advised when closed reduction is unsuccessful, since the vast majority of such patients often become relatively asymptomatic. Cosmetic surgery to remove the bony prominence is not permissible.