The Journal of Bone and Joint Surgery, Vol 74, Issue 1 22-27, Copyright © 1992 by Journal of Bone and Joint Surgery, Inc
Cervical stability after foraminotomy. A biomechanical in vitro analysis
TA Zdeblick, D Zou, KE Warden, R McCabe, D Kunz and R Vanderby
Division of Orthopedic Surgery, University of Wisconsin, Madison.
Laminectomy or facetectomy of the cervical spine, or both, may be needed
for decompression of the spinal cord or of the nerve-roots. Acute stability
of the cervical spine was tested after laminectomy and progressive staged
foraminotomies in an in vitro model. Twelve cervical spines from human
cadavera were used in the experiment. Biomechanical testing included the
application of an axial load, the application of a flexion and extension
moment, and the application of a torsional moment. Each specimen was tested
intact, after laminectomy of the fifth cervical vertebra, and after
progressive foraminotomy of the sixth cervical root. Foraminotomy was
performed by resection of 25, 50, 75, and 100 per cent of the facet joint
and capsule. Torsional stiffness decreased dramatically when more than 50
per cent of the facet had been resected. Statistically equivalent subsets
were the intact specimen, laminectomy, 25 per cent facetectomy, and 50 per
cent facetectomy in one subset, and 75 and 100 per cent facetectomy in the
least-stiff subset. Flexion-moment testing showed that the posterior strain
did not differ among three groups: the intact specimens, those that had
been treated with laminectomy, and those that had been treated with a 25
per cent facetectomy. The 50 per cent facetectomy resulted in a 2.5 per
cent increase in posterior strain, and the 75 or 100 per cent facetectomy,
in a 25 per cent increase in posterior strain compared with the intact
specimen. Segmental hypermobility of the cervical spine results if a
foraminotomy involves resection of more than 50 per cent of the
facet.(ABSTRACT TRUNCATED AT 250 WORDS)