71.6 Dislocation of the acromio–clavicular joint

If only the ligaments between a patient’s clavicle and his acromion are torn, those joining his clavicle to his coracoid can prevent severe displacement. His clavicle is stable and you cannot move it backwards or forwards. If you want to see whether the gap between his acromion and his clavicle is greater than normal, compare it with an X–ray of the other side.

If all the ligaments joining his clavicle to his scapula are torn, the weight of his arm pulls his shoulder downwards, while his sternomastoid muscle pulls his clavicle upwards, as in A, Fig. 71-3. The joint is so wildly unstable that the lateral end of his clavicle rides free, high above his acromion, and you can easily move it backwards and forwards. X–ray him standing, and holding a 2 kg weight to distract his acromio–clavicular joint, because the dislocation may reduce itself spontaneously when he is lying down.

Treat a mild dislocation with a sling and active movements (71.2) until pain subsides. If a patient has a major dislocation, stick pads to his acromion and his elbow, and reduce his dislocation by binding them together with adhesive strapping; then put his arm in a sling, as in B, Fig. 71-3. Don’t refer these injuries for surgical repair.