Effect of halo-vest components on stabilizing the injured cervical spine.
METHODS
An in vitro biomechanical study.


OBJECTIVE
The objectives were to develop a new biofidelic skull-neck-thorax model capable of quantifying motion patterns of the cervical spine in the presence of a halo-vest; to investigate the effects of vest loosening, superstructure loosening, and removal of the posterior uprights; and to evaluate the ability of the halo-vest to stabilize the neck within physiological motion limits.


BACKGROUND
Previous clinical and biomechanical studies have investigated neck motion with the halo-vest only in the sagittal plane or only at the injured spinal level. No previous studies have quantified three-dimensional intervertebral motion patterns throughout the injured cervical spine stabilized with the halo-vest or studied the effect of halo-vest components on these motions.


METHODS
The halo-vest was applied to the skull-neck-thorax model. Six osteoligamentous whole cervical spine specimens (occiput through T1 vertebra) were used that had sustained multiplanar ligamentous injuries at C3/4 through C7-T1 during a previous protocol. Flexibility tests were performed with normal halo-vest application, loose vest, loose superstructure, and following removal of the posterior uprights. Average total range of motion for each experimental condition was statistically compared (P < 0.05) with the physiologic rotation limit for each spinal level.


RESULTS
Cervical spine snaking was observed in both the sagittal and frontal planes. The halo-vest, applied normally, generally limited average spinal motions to within average physiological limits. No significant increases in average spinal motions above physiologic were observed due to loose vest, loose superstructure, or removal of the posterior uprights. However, a trend toward increased motion at C6/7 in lateral bending was observed due to loose superstructure.


CONCLUSIONS
The halo-vest, applied normally, effectively immobilized the cervical spine. Sagittal or frontal plane snaking of the cervical spine due to the halo-vest may reduce its immobilization capability at the upper cervical spine and cervicothoracic junction.
Ivancic
Paul C
PC
Department of Orthopaedics and Rehabilitation, Biomechanics Research Laboratory, Yale University School of Medicine, New Haven, CT 06520-8071, USA. paul.ivancic@yale.edu
Beauchman
Naseem N
NN
Tweardy
Lisa
L
D001696:Biomechanical Phenomena / Q000502:physiology; D002574:Cervical Vertebrae / Q000033:anatomy & histology / Q000293:injuries* / Q000502:physiology; D016267:External Fixators / Q000592:standards / Q000706:statistics & numerical data*; D019416:Head Movements / Q000502:physiology; D006801:Humans; D008022:Ligaments / Q000033:anatomy & histology / Q000502:physiology; D008953:Models, Anatomic; D016059:Range of Motion, Articular / Q000502:physiology; D012149:Restraint, Physical / Q000295:instrumentation* / Q000379:methods*; D013124:Spinal Injuries / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome; D021801:Zygapophyseal Joint / Q000033:anatomy & histology / Q000502:physiology