title: Deformity Angular Ratio Describes the Severity of Spinal Deformity and Predicts the Risk of Neurologic Deficit in Posterior Vertebral Column Resection Surgery.
abstract: METHODS
  Retrospective review of prospectively collected data.
  
  
  OBJECTIVE
  To 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).
  
  
  BACKGROUND
  Although 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.
  
  
  METHODS
  A 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.
  
  
  RESULTS
  The incidence of spinal cord monitoring (SCM) events was 20.5%. Eight patients (4.0%) had new neurologic deficits. Patients with a high total DAR (≥25) were significantly younger (20.3 vs. 29.0 yr, 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 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).
  
  
  CONCLUSIONS
  For patients undergoing a PVCR, the DAR can be used to quantify the angularity of the spinal deformity, which is strongly correlated to the risk of neurologic deficits. Patients with a total DAR greater than or equal to 25 or sagittal DAR greater than or equal to 15 are at much higher risk for intraoperative SCM events and new neurologic deficits.
  
  
  METHODS
  3.
authors.affiliation: Department of Spine Surgery, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.
authors.forename: Xiao-Bin
authors.initials: XB
authors.lastname: Wang
authors.affiliation: Department of Orthopedic Surgery, The Spine Hospital, Columbia University Medical Center, New York, NY.
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Lenke
authors.affiliation: Intraoperative Monitoring Service, New York Presbyterian Hospitals/Columbia University Medical Center, New York, NY.
authors.forename: Earl
authors.initials: E
authors.lastname: Thuet
authors.affiliation: Department of Orthopedic Surgery, The Spine Hospital, Columbia University Medical Center, New York, NY.
authors.forename: Kathy
authors.initials: K
authors.lastname: Blanke
authors.affiliation: Department of Neurological Surgery, Washington University School of Medicine, St. Louis, MO.
authors.forename: Linda A
authors.initials: LA
authors.lastname: Koester
authors.affiliation: Intraoperative Monitoring Service, Washington University School of Medicine, St. Louis, MO Department of Orthopedic Surgery, Washington University School of Medicine in St. Louis, MO.
authors.forename: Michael
authors.initials: M
authors.lastname: Roth
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D064926:Neurophysiological Monitoring / Q000379:methods*; D019635:Neurosurgical Procedures / Q000009:adverse effects / Q000379:methods*; D010027:Osteotomy / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000601:surgery; D012720:Severity of Illness Index; D013131:Spine / Q000000981:diagnostic imaging* / Q000601:surgery; D055815:Young Adult