Movement associated reduction of spatial capacity of the equine cervical vertebral canal.

Laterolateral radiographs of equine necks are reported to be inaccurate in determining the site of spinal cord lesions even when a myelogram is carried out. The goal of this study was to assess constrictions present in the cervical vertebral canal at any time point throughout the extremes of movement. Sixteen equine cervical vertebral columns without history of cervical disease were used. After removal of the spinal cord, the dura mater was filled with polyurethane foam and during its plastic phase the cervical vertebral column was passively moved in flexion-extension, lateral bending and 30° rotated flexion and extension. Resulting moulded foam structures were scanned with a 3D laser scanner. Functional narrowing of the vertebral canal was located in the dorsolateral or ventrolateral regions, explaining its under-representation on laterolateral radiographs.