First case of medullary osteogenic sarcoma of the pelvis: 12-year follow-up of reconstruction with hemipelvis allograft after resection.

A 45-year-old male patient with low-grade central osteosarcoma (LGCO) in the periacetabular region underwent wide resection, fresh frozen hemipelvis allograft reconstruction, and total hip prosthesis. To the best of our knowledge, this case is the first example of low-grade osteogenic sarcoma in flat bones. Aseptic loosening of the acetabular cup was observed 44 months after the operation, and it was revised with a constrained acetabular cup. Recurrent subluxation due to constraint ring failure and cup malposition was observed at 89 months after the revision surgery. Revision operation was performed with cage + non-constrained cup. Twelve years after the first operation, he is in exceptionally functional and disease-free condition. He can walk unlimited distances without pain. Radiographs show complete union at the junction of the allograft and disease-free bone.