Reverse shoulder arthroplasty for corticosteroid-induced deltoid myopathy in a patient with systemic lupus erythematosus: a case report.

A 50-year-old woman who had been previously diagnosed with systemic lupus erythematosus consulted our clinic for pain and weakness in her right shoulder. On examination, she had an atrophied deltoid muscle, a painful right shoulder on movement, and a tender mass in the deltoid area. The patient was diagnosed with corticosteroid-induced deltoid myopathy, shoulder pain, and loss of range of motion that did not resolve with conservative treatment. We decided to perform reverse shoulder arthroplasty. No complications were observed at the last follow-up visit at 3 years postoperative. Unlike deltoid insufficiency that results from axillary nerve injury, deltoid myopathy due to corticosteroid use contains intact fibers,. Therefore, we increased the effectivity of the remaining deltoid fibers by extending the moment arm of the anterior fibers using reverse shoulder arthroplasty and achieved reliable improvements in clinical symptoms and function without increasing the risk of dislocation.