title: Cervical Alignment Variations in Different Postures and Predictors of Normal Cervical Kyphosis: A New Understanding.
abstract: METHODS
  Comparative study of prospectively collected radiographic data.
  
  
  OBJECTIVE
  To predict physiological alignment of the cervical spine and study its morphology in different postures.
  
  
  BACKGROUND
  There is increasing evidence that normal cervical spinal alignment may vary from lordosis to neutral to kyphosis, or form S-shaped or reverse S-shaped curves.
  
  
  METHODS
  Standing, erect sitting, and natural sitting whole-spine radiographs were obtained from 26 consecutive patients without cervical spine pathology. Sagittal vertical axis (SVA), global cervical lordosis, lower cervical alignment C4-T1, C0-C2 angle, T1 slope, C0-C7 SVA and C2-7SVA, SVA, thoracic kyphosis, thoracolumbar junctional angle, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence were measured. Statistical analysis was performed to elucidate differences in cervical alignment for all postures. Predictive values of T1 slope and SVA for cervical kyphosis were evaluated.
  
  
  RESULTS
  Most patients (73.0%) do not have lordotic cervical alignment (C2-C7) upon standing (mean -0.6, standard deviation 11.1°). Lordosis increases significantly when transitioning from standing to erect sitting, as well as from erect to natural sitting (mean -17.2, standard deviation 12.1°). Transition from standing to natural sitting also produces concomitant increases in SVA (-8.8-65.2 mm) and T1-slope (17.4°-30.2°). T1 slope and SVA measured during standing significantly predicts angular cervical spine alignment in the same position. SVA < 10 mm significantly predicts C4-C7 kyphosis (P < 0.001), and to a lesser extent, C2-C7 kyphosis (P = 0.02). T1 slope <20° is both predictive of C2-C7 and C4-7 kyphosis (P = 0.001 and P = 0.023, respectively). For global cervical Cobb angle, T1 slope seems to be a more significant predictor of kyphosis than SVA (odds ratio 17.33, P = 0.001 vs odds ratio 11.67, P = 0.02, respectively).
  
  
  CONCLUSIONS
  The cervical spine has variable normal morphology. Key determinants of its alignment include SVA and T1 slope. Lordotic correction of the cervical spine is not always physiological and thus correction targets should be individualized.
  
  
  METHODS
  3.
authors.affiliation: University Orthopaedics, Hand and Reconstructive Microsurgery Cluster (UOHC), National University Health System, Singapore.
authors.forename: Hwee Weng Dennis
authors.initials: HWD
authors.lastname: Hey
authors.forename: Eugene Tze-Chun
authors.initials: ET
authors.lastname: Lau
authors.forename: Gordon Chengyuan
authors.initials: GC
authors.lastname: Wong
authors.forename: Kimberly-Anne
authors.initials: KA
authors.lastname: Tan
authors.forename: Gabriel Ka-Po
authors.initials: GK
authors.lastname: Liu
authors.forename: Hee-Kit
authors.initials: HK
authors.lastname: Wong
mesh_terms: D000328:Adult; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000502:physiology; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D000077708:Sitting Position; D000078783:Standing Position