9.04 Acromio-clavicular joint separation

agk’s Library of Common Simple Emergencies

Presentation

The patient fell on the point of the shoulder. He may come in right away because it hurts even without movement (first or second degree tear), or he may come in days later without pain, having noted that the injured shoulder hangs lower or the clavicle (collar bone) rides higher (third degree).

What to do:

• Examine the shoulder. The diagnosis is supported by tenderness at the lateral end of the clavicle where it joins the acromion process coming up from the scapula and by pain on pulling the humerus down towards the feet, distracting the acromio-clavicular joint. Strength may be decreased because of pain, but other bones, joints, range of motion, sensation and circulation should be documented as intact.
• X ray the shoulder to be sure there is no associated fracture of the lateral clavicle or fracture or dislocation of the humerus.
• Support the injured joint with a sling.
• Provide additional analgesia. Ibuprofen or naproxen usually suffices.
• Arrange for re-evaluation by an orthopedic surgeon and physical therapy to begin shoulder range of motion excercises within a week.

What not to do:

• Do not bother with weight-bearing x ray views to differentiate first, second and third-degree separations based on the widening of the distance between the clavicle and scapula. These are painful and do not change the initial treatment.
• Do not allow the patient to wear a sling and immobilize the shoulder for more than a week without at least beginning pendulum exercises. The shoulder capsule will contract and restrict the range of motion.

Discussion

A partial tear of the ligaments between acromion and clavicle produces pain but no widening of the joint (first degree tear). A second-degree A-C separation shows up on x ray a widened joint, but is otherwise the same on examination and treatment. In a third-degree or complete separation, the ligament from the coracoid process to the clavicle is probably also torn, allowing the collarbone to be pulled superior by the sternocleidomastoid muscle, but often releiving the pain of the stretched A-C joint. Long-term shoulder joint stability and strength remain almost normal, but patients may desire sugical repair to regain the appearance of the normal shoulder or the last few percent of function for athletics.

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