“Milwaukee shoulder” syndrome: Microspherules containing hydroxyapatite, active collagenase and neutral protease in patients with rotator cuff defects and glenohumeral osteoarthritis

A new syndrome involving the shoulder joints is described, associating HA crystals in microspheroids, active collagenase, neutral protease with destruction of the fibrous rotator cuff and glenohumeral osteoarthritis. This pathogenetic mechanism postulated for this destructive arthropathy may have applicability for the devolutionary joint changes associated with other microcrystals found in joints and almost certainly applies to other joints besides the shoulder

“Milwaukee shoulder”—association of microspheroids containing hydroxyapatite crystals, active collagenase, and 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