Deltoid defect from a trans-deltoid synovial cyst in a patient undergoing reverse shoulder arthroplasty: a case report

Rheumatoid arthritis in the shoulder can lead to significant rotator cuff tears, glenohumeral arthritis, and eventually, a scenario consistent with cuff tear arthropathy. Several case reports have previously shown that massive rotator cuff tears and cuff tear arthropathy can lead to large cysts extending from the subacromial space through the acromioclavicular joint into a subcutaneous cyst, with a characteristic “geyser sign” on imaging.2,3,9,11,13,14 A single study has reported extension into the trapezius, but extension through the deltoid has not been reported.