Shoulder Pain in a Young Female: A Rare Case of Glenoid Aneurysmal Bone Cyst - A Case Report

Case Diagnosis: Aneurysmal bone cyst

Case Description or Program Description: A 24-year-old female presented with a one-year history of progressively worsening left shoulder pain, exacerbated by adduction, and impaired abduction past 90 degrees. Initially diagnosed with rotator cuff impingement/ strain, her condition worsened despite conservative treatment, leading to acute shoulder weakness and prompting further imaging.

Setting: Sports Medicine Clinic

Assessment/Results: X-ray of the left shoulder revealed a scapular lesion and MRI showed a multiloculated cystic lesion within the glenoid fossa. The patient was referred to orthopedic oncology, with a differential including an aneurysmal bone cyst (ABC) versus telangiectatic osteosarcoma. CT confirmed cortical thinning with incomplete fractures. Biopsy confirmed an ABC. The patient underwent fluoroscopy-guided injection with a calcitonin-albumin mixture, resulting in a 50 percent reduction in pain within a week. One month later, radiographs showed ossification, and she regained full range of motion, gradually increasing weight-bearing over several months.
At her one-year follow-up, persistent pain with resisted activities suggested incomplete healing. Repeat imaging confirmed cortical thinning, necessitating surgical intervention. She underwent left glenoid biopsy, tumor resection, saucerization, and injection with doxycycline and synthetic bone graft. At her two-week follow-up, she reported no adverse effects and was recovering well.

Discussion (relevance): Atraumatic shoulder pain and weakness in a young female typically stem from tendinopathy, neuropathy, labral injury, arthritis, autoimmune disorders, instability, or malignancy. Workup includes history, exam, imaging, and labs. Treatment typically involves rest, physical therapy, NSAIDs, and corticosteroids. However, it is crucial to consider a wide differential when acute weakness or worsening pain persists despite standard treatment, as in this case. The recommended approach for ABCs is aggressive intralesional curettage with bone grafts and possible adjuvant cryosurgery.

Conclusions: This case highlights the importance of maintaining a broad differential for atraumatic weakness and thoroughly working up patients. Recognizing rare conditions like ABCs is essential to prevent misdiagnosis and ensure proper management.