Intraoperative Neurophysiological Monitoring Alerts During Three-Column Osteotomy: Incidence and Risk Factors.

PRUPOSE:To analyze the incidence and risk factors of intraoperative neurophysiological monitoring (IONM) alerts in patients undergoing three-column osteotomy. METHODS:A total of 551 patients (340 males and 211 females) with an average age of 31.9 years undergoing posterior 3-column osteotomy were retrospectively reviewed. The coronal Cobb angle of main curve and sagittal global kyphosis were measured on preoperative standing whole spinal x-rays. The Frankel scores at preoperation, postoperation, and the last follow-up were recorded and applied for assessment of neurologic status. Surgical procedures and other factors associated with IONM alerts were analyzed. RESULTS:A total of 98 (17.8%) IONM alerts were reported during surgery, including 82 somatosensory evoked potential alerts and 91 motor evoked potential alerts. Positive wake-up test was revealed in 57 patients (10.3%) even after prompt managements, and new neurologic deficits were observed in 50 patients (9.1%) at immediate postoperation. Of the 50 patients with new neurologic deficits at postoperation, the Frankel scores were A in 5 patients, B in 4, C in 9, and D in 32. The χ 2 test showed that patients with congenital deformities, global kyphosis >90°, vertebral column resection procedure, cervicothoracic/thoracic osteotomy, blood loss >3,000 mL, and preoperative neurologic deficit were at a higher risk of IONM alerts. CONCLUSIONS:The incidence of IONM alerts in patients undergoing 3-column osteotomy was 17.8%. Congenital deformities, global kyphosis >90°, vertebral column resection, cervicothoracic/thoracic osteotomy, blood loss >3,000 mL, and preoperative neurologic deficit indicated high risk of IONM alerts.