Giant intraosseous lipoma of the ilium with acetabular involvement and pathologic fracture: a case report

Abstract Background Intraosseous lipoma is an uncommon benign lipogenic bone tumor, often underdiagnosed because many lesions are asymptomatic. Case presentation A 50-year-old man presented with left hip pain and limited mobility after a fall. Radiographs showed a large expansile osteolytic lesion of the left ilium with a pathologic fracture. CT demonstrated cortical thinning and focal disruption, with fracture extension to the superior and anterior acetabular margins. MRI showed predominantly fat-like signal intensity with internal heterogeneous areas and mild-to-moderate enhancement. Because focal sarcomatous change could not be completely excluded, an open biopsy was performed. Combined imaging and histopathological findings supported a benign lipomatous lesion. Preoperative assessment showed preserved acetabular roof and subchondral bone integrity. After thorough curettage and before bone grafting, intraoperative fluoroscopy confirmed adequate residual bone support without further fracture displacement, while passive hip motion revealed no obvious joint instability. The defect was reconstructed with allograft bone without prophylactic internal fixation, and final histopathology confirmed a benign intraosseous lipoma. Skin traction was maintained for the first postoperative month, followed by non-weight-bearing rehabilitation. Progressive weight bearing was initiated after satisfactory healing at 3 months. At 1 year, radiographs showed good fracture healing and graft incorporation. No tumor recurrence or radiographic evidence of hip arthritis was observed at the 2-, 5-, and 10-year follow-ups. Conclusions This case highlights diagnostic and surgical decision-making for large intraosseous lipomas involving the acetabular weight-bearing region, including preservation of the sclerotic wall, graft selection, and individualized consideration of prophylactic fixation.