title: Modeling of the sagittal cervical spine as a method to discriminate hypolordosis: results of elliptical and circular modeling in 72 asymptomatic subjects, 52 acute neck pain subjects, and 70 chronic neck pain subjects.
abstract: METHODS
  Computer analysis of digitized vertebral body corners on lateral cervical radiographs.
  
  
  OBJECTIVE
  Using elliptical and circular modeling, the geometric shape of the path of the posterior bodies of C2-C7 was sought in normal, acute pain, and chronic pain subjects. To determine the least squares error per point for paths of geometric shapes, minor axis to major axis elliptical ratios (b/a), Cobb angles, sagittal balance of C2 above C7, and posterior tangent segmental and global angles.
  
  
  BACKGROUND
  When restricted to cervical lordotic configurations, normal, acute pain, and chronic pain subjects have not been compared for similarities or differences of these parameters. Conventional Cobb angles provide only a comparison of the endplates of the distal vertebrae, while geometric modeling provides the shape of the entire sagittal curves, the orientation of the spine, and segmental angles.
  
  
  METHODS
  Radiographs of 72 normal subjects, 52 acute neck pain subjects, and 70 chronic neck pain subjects were digitized. For normal subjects, the inclusion criteria were no kyphotic cervical segments, no cranial-cervical symptoms, and less than +/- 10 mm horizontal displacement of C2 above C7. In pain subjects, inclusion criteria were no kyphotic cervical segments and less than 25 mm of horizontal displacement of C2 above C7. Measurements included segmental angles, global angles of lordosis (C1-C7 and C2-C7), height-to-length ratios, anterior weight bearing, and from modeling, circular center, and radius of curvature.
  
  
  RESULTS
  In the normal group, a family of ellipses was found to closely approximate the posterior body margins of C2-C7 with a least squares error of less than 1 mm per vertebral body point. The only ellipse/circle found to include T1, with a least squares error of less than 1 mm, was a circle. Compared with the normal group, the pain group's mean radiographic angles were reduced and the radius of curvature was larger. For normal, acute, and chronic pain groups, the mean angles between posterior tangents on C2-C7 were 34.5 degrees, 28.6 degrees, and 22.0 degrees, C2-C7 Cobb angles were 26.8 degrees, 16.5 degrees, and 12.7 degrees, and radius of curvature were r = 132.8 mm, r = 179 mm, and r = 245.4 mm, respectively.
  
  
  CONCLUSIONS
  The mean cervical lordosis for all groups could be closely modeled with a circle. Pain groups had hypolordosis and larger radiuses of curvature compared with the normal group. Circular modeling may be a valuable tool in the discrimination between normal lordosis and hypolordosis in normal and pain subjects.
authors.affiliation: Biomechanics Laboratory, Department of Sciences of Physical Activity, Universite du Quebec a Trois Rivieres, Quebec, Canada.
authors.forename: Donald D
authors.initials: DD
authors.lastname: Harrison
authors.forename: Deed E
authors.initials: DE
authors.lastname: Harrison
authors.forename: Tadeusz J
authors.initials: TJ
authors.lastname: Janik
authors.forename: Rene
authors.initials: R
authors.lastname: Cailliet
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Ferrantelli
authors.forename: Jason W
authors.initials: JW
authors.lastname: Haas
authors.forename: Burt
authors.initials: B
authors.lastname: Holland
mesh_terms: D000208:Acute Disease; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging*; D002908:Chronic Disease; D016002:Discriminant Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007738:Kyphosis / Q000000981:diagnostic imaging; D016018:Least-Squares Analysis; D008141:Lordosis / Q000000981:diagnostic imaging*; D008953:Models, Anatomic; D019547:Neck Pain / Q000000981:diagnostic imaging*; D011859:Radiography