Evaluation of cervical laminectomy and laminoplasty. A longitudinal study in the goat model.

STUDY DESIGN

An evaluation of the longitudinal radiologic changes up to 6 months induced by multilevel laminectomy and laminoplasty and the biomechanical responses in the goat model, complemented by biomechanical studies of intact specimens.

OBJECTIVES

To determine the long-term radiographic differences and biomechanical responses of laminectomy and laminoplasty in an in vivo animal model.

SUMMARY OF BACKGROUND DATA

Previous clinical and laboratory studies have indicated that multilevel laminectomy can cause increased flexibility in the cervical spinal column. Although the potential for laminoplasty to resolve these changes has been suggested, other evaluations have not supported this contention. Clarification of this controversy with long-term in vivo studies has not been performed.

METHODS

Ten adult goats were divided into two groups, one undergoing C3-C5 laminectomy and the other open-door laminoplasty. Lateral cervical spine radiographs were obtained at 4-week intervals for a 6-month period. After the goats were killed, biomechanical testing was performed using pure moment loading on the surgically treated specimens and on three intact (without surgery) cervical spinal columns.

RESULTS

In the laminectomy preparations, the cervical curvature index was noted to decrease by 59% at 16 weeks (P < 0.028) and by 70% at 24 weeks (P < 0.002), whereas the decrease in laminoplasty was not significantly different. Biomechanical testing indicated a significantly increased sagittal-plane slack motion in the laminectomy group (55 degrees) compared with that in intact specimens (39 degrees), but no significant difference between the laminoplasty and intact groups with respect to this motion. Laminectomy was found to be significantly stiffer (36%) in flexion than in extension, whereas the contrary was true for laminoplasty (37%).

CONCLUSIONS

Radiographic and biomechanical results in the goat model suggest that laminoplasty is superior to laminectomy in maintaining cervical alignment and preventing postoperative spinal deformities.