title: Cervical Spine Compensation in Adolescent Idiopathic Scoliosis.
abstract: METHODS
  Cross-sectional.
  
  
  OBJECTIVE
  To determine associations between cervical spine alignment and Lenke type for adolescent idiopathic scoliosis (AIS).
  
  
  BACKGROUND
  Although the lumbosacral spine and pelvis are standard considerations for evaluation of AIS, few studies have examined cervical spine alignment. These studies did not consider Lenke types upon which treatment decisions are based.
  
  
  METHODS
  Stratified random sampling from 3,654 full-length preoperative lateral films of patients in a multicenter database of surgically treated AIS was done to obtain a representative sample from all Lenke types and thoracic curve modifiers. The C2-C7 sagittal Cobb and C2-C7 sagittal vertical axis (SVA) distances were measured by reviewers unaware of the patient's Lenke classification. C2-C7 sagittal Cobb and C2-C7 SVA among curve types and thoracic modifiers was compared using analysis of variance.
  
  
  RESULTS
  There were 387 females and 84 males among patients in 471 randomly selected films; mean age at surgery was 14.8 ± 2.0 years. Significantly less cervical kyphosis was seen in Lenke 3 or 4 curves and greater cervical kyphosis in Lenke 1, 2, 5, and 6 curves. No significant differences in C2-C7 SVA were seen.
  
  
  CONCLUSIONS
  Patients with AIS appear to compensate for abnormal thoracic sagittal alignment with changes in cervical sagittal alignment. This seems intuitive for Lenke 1 and 2 curves in which surgical restoration of thoracic kyphosis is a recognized goal and has been shown to improve cervical alignment. Cervical kyphosis was also noted in Lenke 5 and 6 curves, which suggests a need to consider compensatory thoracic and cervical sagittal alignment during surgical planning. Patients with Lenke 3 and 4 curves had more normal cervical alignment, which suggests that with the major portion of the curve located in the middle of the spine, there is more ability above and below to maintain a more normal sagittal alignment.
authors.affiliation: Kaiser Permanente Downey Medical Center, Orthopaedic Spine Department, 9333 Imperial Highway, Downey, CA 90242, USA.
authors.forename: Elizabeth P
authors.initials: EP
authors.lastname: Norheim
authors.affiliation: Norton Leatherman Spine Center, 210 East Gray Street, Suite 900, Louisville, KY 40202, USA. Electronic address: leah.caareon@nortonhealthcare.org.
authors.forename: Leah Y
authors.initials: LY
authors.lastname: Carreon
authors.affiliation: Department of Orthopaedics, Texas Scottish Rite Hospital for Children, 2222 Wellborn Street, Dallas, TX 75210, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Sucato
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine, 660 S Euclid Avenue, Campus Box 8233, St. Louis, MO 63110, USA.
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Lenke
authors.affiliation: Norton Leatherman Spine Center, 210 East Gray Street, Suite 900, Louisville, KY 40202, USA.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Glassman
keywords: Adolescent idiopathic scoliosis; Lenke type; radiograph; sagittal measures