A Biomechanical Study Of Thoracolumbar Vertebral Burst Fracture Pedicle Fixation And Vertebral Bone Grafting In Different Methods

Objective:Thoracolumbar burst fractures posterior transpedicular pedicle screw fixation and bone grafting through the pedicle or the spinal canal, study the biomechanical stability and bone defect void residual rate of the injured vertebral body by different processing methods, provide a reliable operation method of thoracolumbar vertebrae burst fractures for clinical treatment.Methods:18fresh lumbar spine specimens of calves, aged form4to6month were collected. The L3vertebra was performed to simulate a burst fracture injury. Posterior pedicle screws fixation alone (A group,n=6), posterior pedicle screws fixation with body augmenters by bone grafting via vertebral pedicles (B group,n=6), posterior pedicle screws fixation with body augmenters by bone grafting via spinal canal (C group,n=6), and record the bone implant quantity of B、C. All specimens was observed the defect of the injury vertebral by X-ray and CT; After CT scanning,calculating the defect void survival rate of the injury vertebral;Measure the biomechanical stiffness stability of all specimens by ElectreForce-3510high precision biological material testing machine. Analysis the image and the biomechanical stability between different groups.Results:(1)The average quantity of bone grafting of group B(4.58±0.66)g, group C(5.72±0.78)g, the difference between B and C was statistically significant(P<0.05).(2)From the X-ray and CT scanning of group A, we can see that there is a large bone defect of the injury vertebral; In group B, after the operation we can see that the" eggshell" voids of the injury vertebral had bone implanted in the gap, but bone filled with uncertain, there is large bone defect void also; In group C, there is a large quantity of bone filling and well-distributed, after the bone grafting operation, there is small bone defect interstice in the injury vertebral.(3)The defect void survival rate of the injury vertebral, group A (0.520±0.055)、group B (0.397±0.025) and group C(0.195±0.025), compared with group A and B, the defect void survival rate of group C was fewer, the difference was significant (P<0.05); And the difference between group A and B was also significant(P<0.05).(4)The flexion-stiffness of group A (49.82±8.72) N/mm, group B (51.59±11.68) N/mm, group C (75.83±16.05) N/mm, groups A and B were lower than group C, the difference was significant (P<0.05); While between group A and B, there was no significant difference. Extension-stiffness of group A (77.45±18.38)N/mm,which ware lower than the group C(128.15±41.83)N/mm, the difference was significant(P<0.05).Conclusion:Thoracolumbar burst fracture pedicle screw fixation with bone grafting via spinal canal can implant more quantity of bone, the graft-bone have been well-distributed, bone defect void surviving rate is smaller after the operation, and afford the better stability.