Developmental Patterns and Risk Factors of Scoliosis After Hemipelvectomy for the Pelvic Bone Tumor

Background: Postoperative scoliosis is often seen after hemipelvectomy for malignancies involving the pelvic area, but the details remain unclear. The objectives were to investigate the development patterns and risk factors of scoliosis after hemipelvectomy. Methods: We retrospectively reviewed 30 patients who underwent hemipelvectomy at our hospital between 1998 and 2020. The risk factors of scoliosis with a Cobb angle of >= 10 degrees were investigated. Results: The postoperative Cobb angle significantly increased in all patients compared with the preoperative one (p < 0.001), and the change ratio of the Cobb angle was significantly higher during the first postoperative year than thereafter. The external hemipelvectomy (EH) group demonstrated a larger Cobb angle and a higher change ratio than the internal hemipelvectomy group. Nine patients developed scoliosis with a final Cobb angle of >= 10 degrees, and the risk factors were EH (p = 0.017), P1+2+3+4 resection according to the Enneking classification (p = 0.005), iliac crest resection (p = 0.004), L5/S resection (p = 0.020), and no pelvic ring reconstruction after hemipelvectomy (p = 0.004). Conclusions: Approximately 30% of patients who underwent hemipelvectomy developed scoliosis with a Cobb angle of >= 10 degrees, and this angle increased rapidly during the first postoperative year. Hence, careful follow-up of scoliosis is required after hemipelvectomy.