Limb-Sparing Reconstruction for Pediatric Osteosarcoma: A Case Report of Shoulder Preservation With Proximal Humerus Anatomical Mega Prosthesis and Review of the Literature

Osteosarcoma of the proximal humerus presents significant challenges due to the proximity of critical neurovascular structures. This case report describes the management of an eight-year-old male diagnosed with high-grade intramedullary osteosarcoma of the proximal humerus with axillary lymph node involvement. Following neoadjuvant chemotherapy, the patient underwent wide resection, axillary lymph node dissection, and reconstruction using a proximal humerus anatomical mega prosthesis, followed by adjuvant chemotherapy. Radiotherapy was not required. Early postoperative range of motion was considerably good, with satisfactory shoulder and elbow function achieved. At the 1.5-year follow-up, there was no evidence of local recurrence or metastasis, and the prosthesis remained stable. This report demonstrates that limb-sparing surgery with prosthetic reconstruction offers favorable oncological and functional outcomes and may represent a preferable alternative to vascularized fibula grafting in pediatric patients with proximal humeral osteosarcoma.