Abstract
In 1941, Mumford reported 4 cases which had persistent pain and disability on the acromioclavicular joint after its subluxation. In 1984, Rockwood also described some instances following a type II sprain which had persistent pain in the acromiaoclavicular joint, then he noted this type of injury as internal derangement of the acromioclavicular joint.
We have experienced three cases which had the same pathology described by Roc k wood. He explained the mechanism of its internal derangement as follows. Since fibers of the joint were initially disrupted, it is possible that shreds of the ligament or flakes of the articular cartilage are loose in the joint, causing symptoms. The meniscus may have been detached, and it will be noted, with motion, to pop and displace in and out of the joint like a torn meniscus in the knee.
We also fou n d abnormal movements of the affected a-c joints in our three cases of internal derangement. Case 1 had an abnormal movement to the longitudinal axis of the clavicle. Case 2 had an abnormal movement to the longitudinal axis of the clavicle and also had superior subluxation. Case 3 exhibited marked abnormal movement to the longitudinal axis of the clavicle and also showed posterior instability.
Taking these findings into consideration, w e think that the arthritic changes of the a-c joint caused by interposition of debris, torn meniscus and degenerated joint cartilage may be a cause of symptoms. We explain abnormal movement of the a-c joint to be an additional cause of symptoms.
