title: Intervertebral motion between flexion and extension in asymptomatic individuals.
abstract: METHODS
  Measure and analyze variation in intervertebral motion in asymptomatic subjects.
  
  
  OBJECTIVE
  Gain further insight into intervertebral motion during flexion and extension in asymptomatic individuals, identify factors that contribute to variation in motion, and establish a quantitative database using a clinically practical imaging tool.
  
  
  BACKGROUND
  Several authors have reported on normal values for intervertebral motion during flexion and extension of the cervical spine. However, the sources of the wide variations in intervertebral motion are poorly understood.
  
  
  METHODS
  Fluoroscopic images of the cervical spine in maximum flexion and extension were analyzed for 140 asymptomatic volunteers using a validated and clinically applicable image analysis system. Several independent variables were analyzed for their contribution to variation in motion. The dependent variables studied included sagittal plane rotation and translation, and displacements between vertebrae measured at the anterior and posterior aspects of each motion segment.
  
  
  RESULTS
  There was considerable variation in measured intervertebral motion. Intervertebral level and total gross rotation between C2 and C6 significantly affected all measures of intervertebral motion. The intervertebral motion measures were all interrelated. After adjusting for differences in gross motion between C2 and C6, intervertebral levels and the three displacement measures could be used to explain almost 90% of the variation in sagittal plane intervertebral rotations. In addition, the data suggest that currently accepted clinical guidelines for shear should be raised at all levels except C6-C7.
  
  
  CONCLUSIONS
  A database describing intervertebral motion in asymptomatic subjects representing both sexes and a wide age range was established that should aid in interpreting intervertebral motion in patients. Evaluating various aspects of intervertebral motion may improve the clinical efficacy of radiographic flexion-extension studies of the cervical spine.
authors.affiliation: Department of Orthopedic Surgery, Baylor College of Medicine, Houston, TX, USA. creitman@bcm.tmc.edu
authors.forename: Charles A
authors.initials: CA
authors.lastname: Reitman
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Mauro
authors.forename: Lyndon
authors.initials: L
authors.lastname: Nguyen
authors.forename: James M
authors.initials: JM
authors.lastname: Ziegler
authors.forename: John A
authors.initials: JA
authors.lastname: Hipp
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016208:Databases, Factual; D005260:Female; D005471:Fluoroscopy; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009333:Neck; D016059:Range of Motion, Articular / Q000502:physiology*; D012016:Reference Values; D012399:Rotation; D013131:Spine / Q000000981:diagnostic imaging / Q000502:physiology*; D021801:Zygapophyseal Joint / Q000033:anatomy & histology / Q000502:physiology*