Cortical bone thickening in Type A posterior atlas arch defects: experimental report.

BACKGROUND CONTEXT: To date, no information about the cortical bone microstructural properties in atlas vertebrae with posterior arch defects has been reported.

PURPOSE: To test if there is an increased cortical bone thickening in atlases with Type A posterior atlas arch defects in an experimental model.

STUDY DESIGN: Micro-computed tomography (CT) study on cadaveric atlas vertebrae.

METHODS: We analyzed the cortical bone thickness, the cortical volume, and the medullary volume (SkyScan 1172 Bruker micro-CT NV, Kontich, Belgium) in cadaveric dry vertebrae with a Type A atlas arch defect and normal control vertebrae.

RESULTS: The micro-CT study revealed significant differences in cortical bone thickness (p=.005), cortical volume (p=.003), and medullary volume (p=.009) values between the normal and the Type A vertebrae.

CONCLUSIONS: Type A congenital atlas arch defects present a cortical bone thickening that may play a protective role against atlas fractures.