[Primary stability of AO-plate osteosynthesis of the lower cervical spinal column. II. Anterior spondylodesis with H-plate osteosynthesis].

For evaluation of stability changes H, HH, and HHH plate fixations were performed for artificially produced fractures-dislocations of the lower cervical spine on cadavers. Functional loading was simulated by mechanical device ensuring 10 000 flexion and extension-movements on the spine. Tensile moments determined by a screwdriver measuring the turning moments on the occasion of the primary fixation of the plate were compared with the release moment examined on screws following functional loading. Stability changes depending on the type of the injury have come to 6.11-23.17% of loss of the primary stability. Decrease in stability did not prove to be depending on the form of the graft applied. It has been established that following ASIF/AO/plate fixation of the lower cervical spine for fracture dislocations no external fixation is to be applied.