Developmental cervical spinal canal size: population reference range.

Background: The developmental size of the cervical spinal canal varies considerably. Neural compression and injury are more likely with a developmentally small spinal canal. This study was designed to develop a population reference range for developmental cervical spinal canal size for the Hong Kong population. Methods: Prospective study of 522 ambulatory patients (256 males, 266 females, mean age 55±18 years; range, 20-89 years) who underwent computed tomography (CT) neck examinations. Using a manually operated segmentation program, spinal canal, and vertebral body cross-sectional area (CSA), anteroposterior (AP) sagittal diameter, and width were measured at each level from C3-C7. Patient height and weight were measured. Results: Considerable variation in spinal canal size existed with, for example, a 164-168% variation exists for males and females between the largest and smallest spinal canal CSA at C5. All spinal canal measurements increased slightly with height (r=0.25-0.36, P<0.001), while vertebral body AP sagittal diameter increased with age (r=0.48-0.51, P<0.001). All spinal canal measurements were larger (<0.0001) in males. Although spinal canal CSA was larger in males (at C5, males 276.0±41.5 mm Conclusions: There is a large variation in developmental cervical spinal canal size within the Hong Kong population. A reference range of developmental spinal canal size was developed which will enable an objective assessment of an individual's cervical spinal canal size relative to the wider population.