title: Analysis of the cervical spine sagittal alignment in young idiopathic scoliosis: a morphological classification of 120 cases.
abstract: OBJECTIVE
  To analyze the relationship between the cervical spine and global spinal-pelvic alignment in young patients with idiopathic scoliosis based on a morphological classification, and to postulate the hypothesis that cervical kyphosis is a part of cervico-thoracic kyphosis in them.
  
  
  METHODS
  120 young patients with idiopathic scoliosis were recruited retrospectively between 2006 and 2011. The following values were measured and calculated: cervical angles (CA), cervico-thoracic angles (CTA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), spinal sacral angle (SSA), hip to C7/hip to sacrum, thoracic kyphosis (TK), lumbar lordosis (LL), Roussouly sagittal classification, Lenke Type Curve and Lumbar Modifier. The cervical curves were classified as lordosis, straight, sigmoid and kyphosis. They were categorized into four groups as cervical non-kyphosis group (CNK Group), cervical kyphosis group (CK Group), cervical-middle-thoracic kyphosis group (CMTK Group), and cervical-lower-thoracic kyphosis group (CLTK Group) according to their morphological characters of sagittal alignments. All parameters were compared and analyzed among groups.
  
  
  RESULTS
  The incidence of cervical kyphosis was 40 % (48/120). The CA and the CTA were in significant correlation (r = 0.854, P = 0.00). The cervical spine alignments were revealed to be significantly different among groups (r = 85.04, P = 0.00). Significant differences among groups in CA, CTA and TK were also detected. A strong correlation between the group type and Lenke Lumbar Modifier was still seen (P < 0.05). Fisher's exact test revealed that the individual vertebral body kyphosis and wedging were directly related to the overall cervical kyphosis (P = 0.00, respectively).
  
  
  CONCLUSIONS
  The cervical kyphosis is correlated with global sagittal alignment, and is a part of cervico-thoracic sagittal deformity in young patients with idiopathic scoliosis. Despite the deformity in cervical alignment, the global spine could still be well-balanced with spontaneous adjustment. The correlation between our grouping based on the morphological characteristics of the sagittal alignments and Lenke Lumbar Modifier suggests that the coupled motion principle be appropriate to explain the modifications both in coronal and sagittal planes.
authors.affiliation: Orthopedic Department, Peking University Third Hospital, 49 North Garden Road, Haidian District, 100191, Beijing, China, miltonyu1977@gmail.com.
authors.forename: Miao
authors.initials: M
authors.lastname: Yu
authors.forename: Clement
authors.initials: C
authors.lastname: Silvestre
authors.forename: Tanguy
authors.initials: T
authors.lastname: Mouton
authors.forename: Rami
authors.initials: R
authors.lastname: Rachkidi
authors.forename: Lin
authors.initials: L
authors.lastname: Zeng
authors.forename: Pierre
authors.initials: P
authors.lastname: Roussouly
mesh_terms: D000293:Adolescent; D000328:Adult; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000145:classification / Q000000981:diagnostic imaging*; D008141:Lordosis / Q000145:classification / Q000000981:diagnostic imaging*; D008297:Male; D011859:Radiography; D012189:Retrospective Studies; D012600:Scoliosis / Q000145:classification / Q000000981:diagnostic imaging*; D013131:Spine / Q000000981:diagnostic imaging; D055815:Young Adult