A biomechanical evaluation of cervical spinal stabilization methods in a bovine model. Static and cyclical loading.

A bovine model was developed for biomechanical evaluation of surgical procedures stabilizing traumatic cervical injuries disrupting the anterior and posterior spinal column. Cervical spinal segments and C4-5 functional spinal units were tested statically, and C4-5 functional spinal units were tested cyclically in evaluation of 1) the intact cervical spine, 2) Rogers' wiring method, 3) Bohlman's triple-wire technique, 4) sublaminar wiring, 5) anterior cervical plate instrumentation, and 6) posterior hook plate stabilization. Anterior cervical plate instrumentation proved inadequate, and was the least rigid, with axial and flexural loading (P less than 0.05). There was no significant difference between each of the three posterior wiring methods, and all generally restored stability to equal that of the uninjured intact cervical spine. Posterior hook plating with an interspinous bone graft serving as an extension block was the most effective method in reducing flexural stress across the injured C4-5 segment (P less than 0.05). Cyclical in vitro testing was the most sensitive method in highlighting mechanical differences between instrumentation systems, particularly with "on-line" continuous measurement of anterior and posterior strains. Anterior cervical plate stabilization does not appear to confer enough stability in cervical facet injuries to obviate the need for posterior cervical stabilization procedures. The recently developed posterior hook plate technique offers biomechanical advantages that should be weighed against the greater technical precision needed for insertion and the increased potential for neurologic and vascular complications.