Anterior cervical discectomy and fusion. A comparison of techniques in an animal model.

An animal model for three-level anterior cervical discectomy and fusion was established in the goat. Twenty-one goats underwent surgery, with seven goats in each of three experimental groups. In Group I, all seven goats underwent three-level anterior cervical discectomy without fusion. In Group II, each of the seven goats had a three-level discectomy with autogenous bone performed according to the Smith-Robinson technique. In Group III, fresh-frozen allograft bone was used for each of the three-level discectomy and fusion. Each goat was then killed after 12 weeks. Analysis consisted of radiographic review, fluorochrome labeling, biomechanical rigidity and flexion and extension, axial compressive load, and torsion. Histologic analysis was also performed for evidence of fusion and vertebral body histomorphometric analysis. The analysis of results showed that radiographic union was judged to have occurred in 0 of 21 Group I disc spaces, 10 of 21 Group II disc spaces, and 8 of 21 Group III disc spaces. Histologic fusion was judged to have occurred in 0 of 21 Group I goats, 10 of 21 Group II goats, and 0 of 21 Group III goats. The histologic fusion rate was significantly higher in Group II than either Group I or Group III. Biomechanically, the spines that had autogenous bone grafting (Group II) were significantly stiffer in compressive axial load and in extension. Both Group II and Group III were stiffer in flexion than Group I. An evaluation of the peri-endplate vascularity showed that the vascularity measured 10.4% in Group I, 16.7% in Group II, and 8.5% in Group III.(ABSTRACT TRUNCATED AT 250 WORDS)