For evaluation of stability changes-concerning primary stability of the lower cervical spine either posterior ASIF plate fixation according to Roy-Camille or combined fixation (anterior H plate and posterior plate fixation according to Roy-Camille) were performed for arteficially produced fracture-dislocations of the lower cervical spine on cadavers. Functional loading was simulated by a mechanical device ensuring 10 000 flexion and extension movements on the corpses. Tensile moments determined by a screwdriver measuring the turning moment were compared with the release moment examined on screws following functional loading, unloaded free screws were used as reference. Decreasing of stability depending on the type of the injury has come posteriorly to 2,52-18,65%, anteriorly to 0,57-20% of the primary rate. It has been established that external fixation is not warranted in the postoperative treatment of patients with fracture dislocations of the lower cervical spine following either ASIF plate fixation according to Roy-Camille or combined plate fixation. General rules of the operative fracture management are valid for treatment of the cervical spine built of segmental elements.