Pseudodislocation of the acromioclavicular joint.

Two patients are reported, one adolescent and one young adult, each of whom sustained a fracture separation of the lateral part of the clavicle which gave the clinical and radiological appearance of a complete acromioclavicular dislocation. At operation a longitudinal rupture was found in the periosteal envelope, and the lateral part ofthe clavicle was displaced through it; thejoint itself and the coracoclavicular ligaments were intact. The extent of this injury can only be diagnosed at operation. Failure to operate may lead to permanent deformity.