The traction angle and cervical intervertebral separation

Seventeen normal young adults were evaluated for cervical intervertebral separation under different traction angles through motorized intermittent traction in the supine position. In all cases, the anterior and posterior intervertebral spaces were increased by traction at neutral position and in 30°flexion, but not in 15° extension. The effects of separation were 1) neutral position: anterior intervertebral separation C4-5 (12%) > C3-4 (8%), posterior intervertebral separation C6-7 (37%) > C3-4 (22%) > C4-5 (19%); and 2) 30° flexion: anterior intervertebral separation C2-3 (21%) > C 4-5 (16%) > C5-6 (15%) > C3-4 (10%), posterior intervertebral separation C6-7 (20%) > C5-6 (19%) > C4-5 (17%). There was a significant decrease in intervertebral separation posteriorly in extension traction, especially at C6-7 (-50%), C5-6 (-37%), C4-5 (-26%), and C3-4 (-14%). The separation of facet joint surfaces was found after traction at 15° extension, but not in the neutral or flexion positions.