OBJECTIVES: The authors analyzed patients who underwent posterior vertebral column resection (PVCR). All patients had spinal cord monitoring (SCM) attempted but some did not have predictable and usable tracings. SUMMARY OF BACKGROUND DATA: Posterior vertebral column resection is a powerful technique to correct severe spinal deformities but it has the potential for major neurologic complications. Spinal cord monitoring is extremely helpful in managing these difficult patients. METHODS: Spinal cord monitoring data, operative reports, charts, and radiographs of 112 consecutive adult and pediatric patients (mean age, 23.5 years; range, 5.8-74.0 years) who underwent PVCR were reviewed. All surgical procedures were performed between 2002 and 2010 by 1 surgeon at a single institution. RESULTS: Twenty patients (11 male, 9 female; mean age, 15.9 years) of 112 (17.9%) did not have detectable SCM tracings during surgery. Average preoperative and postoperative scoliosis for these 20 patients was 79.2 degrees and 41.3 degrees , respectively. Average preoperative and postoperative kyphosis was 106.6 degrees and 59.8 degrees , respectively. Thirteen of the 20 were revisions. Preoperative neurologic status included acute progressive myelopathy (n = 9), no lower extremity function (n = 6), chronic weak lower extremities (n = 2), chronic quadriparesis (n = 1), and normal (n = 2). Four of 9 patients with acute progressive myelopathy developed transient paraplegia postoperatively. They had angular kyphosis (mean, 116.3 degrees ) and 3 were revisions. Compared with the 92 patients who had obtainable intraoperative SCM and no spinal cord deficits, the risk of developing postoperative paraplegia in patients who had no SCM tracings was statistically higher (p = .0008). All 4 with spinal cord deficits after surgery regained varying degrees of lower extremity function and resumed ambulatory status at most recent follow-up. CONCLUSIONS: The prevalence of unobtainable intraoperative SCM during PVCR was 17.9% (20 of 112). Postoperative transient paraplegia occurred exclusively in patients with no monitorable data as a result of angular kyphosis with acute progressive myelopathy. The rate of transient spinal cord deficits was significantly higher when there was no obtainable SCM (4 of 20 vs. 0 of 92 with SCM; p = .0008).