Biomechanical Analysis Of Three-vertebral Fixation For Thoracolumbar Fracture Of Spine

Objective To compare the biomechanical properties between the two-level fixation by implantation of pedicle-screws into the adjacent upper and lower vertebrae of the fractured vertebra and the three-level fixation by implantation of pedicle screws into the fractured vertebra and its adjacent upper and lower vertebrae in the treatment of thoracolumbar fracture. Methods The thoracolumber spine specimens of eight cavaders were used in this study. The soft tissue and paraspinal muscles were removed without violating the ligaments or facet joint capsules. On the day of testing the specimens were throwed and the L1 fracture model was created with boring of the aimed vertebra combine with Panjabi method and embedding T11 and L3 in polyester resin. Each specimen was tested in four groups:control models(no fracture and no fixation), L1 fracture models(no fixation), two-level fixation models, and three-level fixation models. During the experiment, the flexion , extension , bilateral bending and axial rotation loading were applied to the specimens and the rang of motion was measured with the ND-500 test machine of rotation and the electronic test machine of computer control. Obtained data was analysis used statistical method , and to compare difference in the middle of each groups. Results there were significant differences in ROMs and stiffness between the two-level fixation and three-level fixation models (p<0.01) .All of the two kind ways for transpedical of fixation (fixed with 4 , 6 pedical screws ) can restore the stability of injured thoracolumbar vertebra in axial compression , bending , rotation . there were no significant statistical difference in stability between 4 pedicle screws fixation with control groups(no fracture and no fixation)(p>0.05); There were significant statistical difference of spine stability capacity of 6 pedicle screws fixation compare with 4 pedicle screws fixation (p<0.01) .Conclusion biomechanical test prove that the three-level vertebra fixation can obviously enhance the stability of spine in the fractured vertebra pedicle of thoracolumbar fracture . The procedure of three-vertebrae 6 pedicle-screws implantation is practical , effective .