• Xiao-Bin Wang, Lawrence G Lenke, Earl Thuet, Kathy Blanke, Linda A Koester, and Michael Roth.
• *Department of Spine Surgery, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011; P. R. China †Department of Orthopedic Surgery, The Spine Hospital, Columbia University Medical Center, 5141 Broadway, New York, NY, 10034; USA ‡Intraoperative Monitoring Service, New York Presbyterian Hospitals/Columbia University Medical Center, 5141 Broadway, New York, NY, 10034; USA §Department of Neurological Surgery, Washington University School of Medicine, 660 S Euclid Ave., St. Louis, MO 63110; USA ¶Intraoperative Monitoring Service, Washington University School of Medicine, 660 S Euclid Ave., Campus Box 8233, St. Louis, MO 63110; USA.
• Spine. 2016 Mar 4.

Study DesignRetrospective review of prospectively collected data.ObjectiveTo assess the value of the Deformity Angular Ratio (DAR, maximum Cobb measurement divided by number of vertebrae involved) in evaluating the severity of spinal deformity, and predicting the risk of neurologic deficit in posterior vertebral column resection (PVCR).Summary Of Background DataAlthough the literature has demonstrated that PVCR in spinal deformity patients has achieved excellent outcomes, it is still high risk neurologically. This study, to our knowledge, is the largest series of PVCR patients from a single center, evaluating deformity severity and potential neurologic deficit risk.MethodsA total of 202 consecutive pediatric and adult patients undergoing PVCRs from November 2002 to September 2014 were reviewed. The DAR (coronal DAR, sagittal DAR and total DAR) was used to evaluate the complexity of the deformity.ResultsThe incidence of SCM events was 20.5%. Eight patients (4.0%) had new neurologic deficits. Patients with a high total DAR (≥25) were significantly younger (20.3yrs vs. 29.0yrs, P = 0.001), had more severe coronal and sagittal deformities, were more myelopathic (33.3% vs. 11.7%, P = 0.000), needed larger vertebral resections (1.8 vs. 1.3, P = 0.000), and had a significantly higher rate of spinal cord monitoring (SCM) events than seen in the low total DAR (<25) patients (41.1% vs. 10.8%; P = 0.000). Patients with a high sagittal DAR (≥15) also had a significantly higher rate of SCM events (34.0% vs. 15.1%, P = 0.005) and a greater chance of neurologic deficits postoperatively. (12.5% vs. 0, P = 0.000).ConclusionFor patients undergoing a PVCR, the DAR can be used to quantify the angularity of spinal deformity, which is strongly correlated to the risk of neurologic deficits. Patients with a total DAR ≥25 or sagittal DAR ≥15 are at much higher risk for intraoperative SCM events and new neurologic deficits.Level Of Evidence3.

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