The halo vest: an evaluation of motion and forces across the neck.

Flexion-extension motion and compression-distraction forces across the cervical spine were evaluated in 6 patients in halo vests and in 1 patient in a halo cast. Motion in the vest was evaluated in supine and upright positions and averaged 31% of normal motion at the levels tested. Compression-distraction forces showed great individual variation and frequent compression. The average distraction force varied in different positions by nearly 20 pounds in the vest and over 30 pounds in the cast. Methods of improving cervical spine stability in halo orthoses are discussed.