ROTATOR CUFF TEAR ASSOCIATED WITH AN ACROMIOCLAVICULAR CYST IN RHEUMATOID-ARTHRITIS

We report two cases of a full-thickness rotator cuff tear followed by acromioclavicular cyst formation in patients with longstanding erosive polyarticular rheumatoid arthritis. One of the consequences of a rota tor cuff tear is articular instability with upward migration of the hu meral head. The ensuing chronic friction against the undersurface of t he acromioclavicular joint caused by arm movements can lead to a non-i nflammatory effusion of the acromioclavicular joint with cyst formatio n. Clinical and ultrasonographic features and a pathogenetic hypothesi s are discussed.