Spinopelvic Reconstruction for a Giant Cell Tumor Involving the Sacroiliac Joint: A Case Report.

BACKGROUND/AIM: Giant cell tumors of the bone (GCTB) involving the sacroiliac joint are uncommon and pose significant surgical challenges due to their proximity to major neurovascular structures and the complexity of stabilizing the pelvic. We describe a case of sacroiliac joint GCTB successfully managed with preoperative denosumab, piecemeal tumor resection, and spinopelvic reconstruction. CASE REPORT: A 34-year-old woman presented with progressive gluteal pain and swelling. Imaging demonstrated an osteolytic lesion extending from the left sacrum to the ilium with extraosseous soft-tissue involvement. Histopathology confirmed the GCTB diagnosis. To facilitate resection and reduce intraoperative blood loss, denosumab (120 mg monthly) was administered for five months, resulting in marked peripheral ossification on computed tomography. The tumor was resected via a posterior approach with preservation of the S1-S3 nerve roots. Spinopelvic reconstruction was achieved using L4-S2 fixation, S2 alar-iliac screws, artificial bone graft, and unsintered hydroxyapatite/poly-L-lactide mesh. The postoperative course was uneventful, and no neurological deficits were observed. Follow-up computed tomography at three months and one year demonstrated stable instrumentation, preserved graft integrity, and no evidence of local recurrence. CONCLUSION: Preoperative denosumab followed by posterior tumor resection and spinopelvic reconstruction provided excellent short-term tumor control and functional recovery in this patient with sacroiliac joint GCTB. Given the high recurrence risk associated with pelvic lesions, continued long-term surveillance is essential.