Influence of Pedicle Cortex Derforation on Stability of Pdeicle Screws Fixation

Abstract：Objective To explore the impact on long-term stability of the vertebral body fracture fixed with pedicle screw internal fixation with the pedicle cortex perforation. Methods 20 of fresh thoracic and lumbar vertebrae samples of adult sheep(T14 ~ L2 )were randomly divided into group A and group B. The compression fracture of the single rertebrae was made in L1 of the two groups. Then the samples of group B were removed a quarter of either side of lateral T14 thoracic pedicle,which is considered as the pedicle cortex perforation model. The model of two groups were inserted the screw and the inserting depth of the screw was the total length of the screw. After the samples of two group was fixed,the samples were performed fatigue test of 10,000 times by 1. 5 Hz load on the HY-3080 almighty material test machine. The range of motion(ROM)of the four direc-tions-anteflexion,retroflexion,left and right lateral curvature and the drawing force of the screw was measured and the differ-ence was compared. Results After the fatigue test,the ROM value of the four directions-anteflexion,retroflexion,left and right lateral curvature on group A were(1. 81 ± 0. 14)mm,(1. 68 ± 0. 37)mm,(4. 08 ± 0. 41)mm,(4. 18 ± 0. 12)mm;the ROM value of the four directions-anteflexion,retroflexion,left and right lateral curvature on group B iS(4. 49 ± 0. 40)mm,(3. 72 ± 0. 51)mm,(6. 67 ± 0. 64)mm,(6. 73 ± 0. 58)mm;group A range in all directions were less than group B,the difference was statistically significant(P < 0. 01). Conclusion The pedicle cortex perforation will seriously affect the long-term stability of the fractured vertebral body.