Co-occurring Acromioclavicular Joint Cyst and Hemarthrosis of the Shoulder Associated With Rotator Cuff Tear Arthropathy.

Both acromioclavicular joint (ACJ) cysts and hemarthrosis of the shoulder are rare conditions of massive rotator cuff tear that eventually lead to cuff tear arthropathy. We herein report the first case of a patient with co-occurring ACJ cyst and hemarthrosis of the shoulder. An 80-year-old right-hand-dominant man presented to our outpatient department with a six-month history of repeatable right shoulder pain and swelling. Clinical examination revealed a 5 x 5 x 5 cm elastic hard or hard shoulder lump overlying the ACJ on skin with subcutaneous bleeding and swelling of the shoulder. Shoulder pain at rest and a fully reduced active range of motion (ROM), particularly in flexion and abduction, were also noted. Radiographs demonstrated moderate degeneration of the glenohumeral joint including a bone cyst of the humeral head. Magnetic resonance imaging (MRI) revealed a massive rotator cuff tear with atrophy of the supraspinatus, infraspinatus, and subscapularis muscles. The T2-weighted MRI images showed that the cyst was in direct contact with the markedly degenerated glenohumeral joint. Based on these findings, the patient was diagnosed with massive rotator cuff tear with ACJ cyst and hemarthrosis of the shoulder. The patient underwent distal clavicle resection and reverse total shoulder arthroplasty (RSA). At 12-month follow-up, the patient showed no pain symptoms, no recurrence of the cyst, and excellent ROM. We experienced a very rare case of ACJ cyst and hemarthrosis of the shoulder occurring simultaneously with rotator cuff tear arthropathy. This report is very valuable in that it suggests that RSA is useful for both ACJ cysts and hemarthrosis of the shoulders associated with rotator cuff tear arthropathy.