title: Asymmetry in atlas bone specimens: a pilot study using radiographic analysis.
abstract: OBJECTIVE
  Vertebral asymmetries can present a challenge to analysis of the anatomical and biomechanical misalignment component of chiropractic vertebral subluxation. The objective of this study was to determine the extent of asymmetry among 10 natural bone atlas specimens using radiographic analysis.
  
  
  METHODS
  Ten natural atlas bone specimens' images were recorded using a digital radiographic system, and evaluations were made by 2 independent examiners using the system's software. Mean differences, standard deviations, and agreements were evaluated in regard to bilateral differences.
  
  
  RESULTS
  The mean bilateral difference for both examiners was 0.96 mm, with a standard deviation of +/-0.67 mm. There were no statistically significant differences between the mean values for left and right measurements.
  
  
  CONCLUSIONS
  The mean of 0.96 +/- 0.67 mm indicates that measurements up to 1.63 mm (1 SD) or 2.30 mm (2 SDs) are clearly within a reference range of variation for this sample. This information could be used to assist the clinician measuring lateral misalignment of the atlas in determining the amount of expected normal asymmetry for the individual patient before concluding that lateral misalignment of the atlas is present.
  
  
  CONCLUSIONS
  These 10 specimens showed an average difference of 0.95 mm +/- 1 SD (0.67 mm) or 2 SDs (1.34 mm) between the left and right sides of the atlas vertebrae. Differences found on radiographs may be due to asymmetry and not actual misalignment. On the average, for these 10 vertebra specimens, a lateral disposition of 1.62 mm on either side should be allowed when arriving at a conclusion for lateral displacement of the atlas.
authors: Assistant Director of Research, Sherman College of Straight Chiropractic, PO Box 1452, Spartanburg, SC 29304.
authors: John
authors: J
authors: Hart
authors: Matt
authors: M
authors: Christopher
authors: Ralph
authors: R
authors: Boone