One adolescent patient with avascular necrosis of the femoral head and severe hip dysfunction secondary to osteomyelitis was treated with proximal femoral metaphyseal resection and total hip arthroplasty (THA) using a modular tumor prosthesis. The primary outcome of interest was restoration of hip function and ambulation. Secondary outcomes included pain, muscle recovery, strength, and return to activities. Outcomes were assessed at 8 weeks and 3 months postoperatively. Overall, the results of the report revealed that the patient regained the ability to walk by 8 weeks with rehabilitation and was pain-free at 3 months with partial recovery of muscle strength and function. These findings suggest that modular tumor prostheses may be an effective salvage option for restoring function in patients with severe hip destruction secondary to osteomyelitis.