COMPARATIVE STUDY OF ROTATIONAL STABILITY PARAMETERS OF TRANSPEDICULAR SPINAL FUSION IN EXPERIMENT

Objectives. To estimate macroscopically the strength, rigidity and limit of elasticity in the “spinal segments – transpedicular fixator” system. versus similar characteristics of the intact spine under dislocating rotational loads. Material and Methods. Еxperiments with anatomic specimens of Th12–L2 segments were performed. Unstable damages of L1 and transpedicular fixation with 4 screw transpedicular spinal system were imitated. All specimens were exposed to the testing rotational load in universal test machine Zwick 1464. Results. It is established that under rotational load general strength of the injured Th12–L1–L2 spinal segments fused with transpedicular fixator is 20 % lower than that in a corresponding intact spine segment. Rigidity parameters of fused segments are 17.5 % lower than those of intact segments. Destabilization of «spinal segments – transpedicular fixator» system under rotational loads is caused by the compression of a bone substance in Th12 and L2 bodies with screws and a turn of screws around longitudinal rods due to a rod slip in anchoring elements. Conclusion. The performed study may serve a basis for following data analysis from a viewpoint of metal resistance and for development of optimal rehabilitation loads to the injured spine during postoperative period.