Failure of halo vest to prevent in vivo motion in patients with injured cervical spines.

Forty-two patients with cervical spine injuries immobilized in halo vests were studied prospectively to determine in vivo vertebral segmental motion. Lateral radiographs taken in the supine and upright positions within 5 days of injury demonstrated intervertebral motion. At noninjured levels, the positional change accounted for an average 3.9 degrees of angulation with the greatest motion occurring between the occiput and C1 (8.0 degrees). At the injured levels, sagittal plane angulation averaged 7.0 degrees and translation averaged 1.7 mm between the two positions. Fracture site motion did not correlate with either the fracture type or the injury level. Fracture site motion greater than 3 degrees of angulation or 1 mm of translation was observed at 35 (77%) of 45 injured levels. When treating patients who have unstable cervical injuries with halo vests, supine and upright radiographs should be obtained. If excessive motion is present, alternative methods of treatment should be considered.