"Milwaukee shoulder"--association of microspheroids containing hydroxyapatite crystals, active collagenase, ad neutral protease with rotator cuff defects. III. Morphologic and biochemical studies of an excised synovium showing chondromatosis.

Synovial tissue excised from the unstable right shoulder joint of a patient with an absent rotator cuff, severe glenohumeral joint degeneration, and hydroxyapatite-containing microspherules, collagen types I, II, and III, active collagenase, and neutral protease in the joint fluid showed extensive osteochondromatosis histologically. Electronmicroscopy revealed calcific foci in microvilli which could easily escape into the adjacent joint space through areas denuded of synovial cells. Fibrocytes demonstrated intensive pinocytotic activity of unknown significance. Energy dispersive analysis showed elemental ratios consistent with hydroxyapatite. A literature review suggested some relationships between the various pathologic lesions present in this joint. Whether similar synovial changes exist in the opposite shoulder joint of this patient and in 3 other subjects with nearly identical clinical, radiographic, and joint fluid findings is not known.