A quantitative sutdy of vertebral displacement and angulation in the normal cervical spine under axial load.

Cervical traction of one-third the person's weight was applied for 3 minutes to normal subjects. The mean and standard deviation of displacement and rotation between adjacent cervical vertebra was calculated in the sagittal plane. The average separation between adjacent vertebra was 0.7 mm with a standard deviation of 0.5 mm. The average angular motion between adjacent vertebra was 0.9 degrees with a standard deviation of 2.4 degrees.