Biomechanicas Testing Of The L5_S1 Vertebral Axial Fixed Barbed Interlocking Device

Objective: The biomechanical testing of the interlocking internal lock with L5-S1 was carried out,and the stability was analyzed.To provide the theoretical basis for the clinical application of L5-S1 vertebral axial fixation with barbed internal locking.Methods:Six fresh adult spine specimens were selected,and the lumbar spine movement segment(L3-S5)was intersected,which was divided into the following seven groups to perform biomechanical test: normal control group(CG): complete structure;Experiment 1(EG1): bilateral isthmic division;Experimental group 2(EG2): bilateral isthmic division+ simple central screw fixation;Experimental group 3(EG3): bilateral isthmic division+simple central screw+bilateral pedicle screw fixation;Experimental group 4(EG4): bilateral isthmic fissure + internal interlocking screw + bilateral pedicle screw fixation;Experimental 5groups(EG5): bilateral isthmic division and internal locking screw with internal locking.The range of motion and axial compressive stiffness of the lumbar 5 sacral segment were measured respectively in flexion,left and right lateral flexion,and left and right rotation.Results:1)There was a significant decrease in the ROM of the interlocking screw group(EG2)in the group(CG),the isthmic division(EG1)and the simple axial screw group(EG5),with statistical differences.(EG2)the ROM of the internal locking screw group(EG2)was larger than the internal locking screw + pedicle screw group(EG3),axial screw and pedicle screw group(EG4).It is shown that the internal locking screw has similar biomechanical stability and can meet the normal physiological needs of the human body.2)Applying axial with force of 300 N in cases,groups of the whole range of motion of applying following force are reduced,and less of spondylolysis crack group(EG1)movement of ROM more than the normal group(CG),barbed screw group movement of ROM is the spondylolysis of cracked(EG1)and normal group decreased significantly,in the column under the condition of the damaged structure,axial line within the barbed lock screw can improve the stability of the lumbosacral vertebral;And barbed lock screw within the group(EG2)in applying compared with no axial following force,have no significant statistical difference,theoretically explain a thorn inside lock screw in physiological conditions and load cases with normal spinal similar biomechanical stability.3)In lateral bending test,barbed lock screw within the group(EG2)lateral movement of the ROM is the spondylolysis of cracked group(EG1)lateral movement of the ROM than normal group(CG)significantly reduced,and statistically significant;There was no statistical difference between the internal locking screw group(EG2)and the other three groups.It is indicated that after the destruction of the posterior column structure of the lumbosacral vertebra,the internal locking screw can enhance the stability of the lumbosacral vertebra and its effect is similar to that of the auxiliary posterior nail bar.4)In the process of spinning test,spondylolysis of crack groups(EG1)of the right and left rotation ROM than normal group(CG),pure axial screw group(EG5)right and left rotation ROM and normal group no significant statistical difference;Barbed lock screw within the group(EG2)group,barbed inside lock screw + pedicle screw(EG3)and axial screw + pedicle screw group(EG4)right and left rotation ROM than normal group,spondylolysis and decreased significantly,and has significant difference.Barbed lock screw within the group(EG2)line axis locked,on the right side of his left axial rotation and axial rotation ROM of statistical analysis,no significant statistical difference(P > 0.05),shows that the axial line lock screw axis locked within a thorn also provides about double side rotation resistance stability,and auxiliary vertebral arch screws for spinal column compared to fixed,its stability is weak,but with the axial screw + pedicle screw group(EG4)compared with no statistically significant difference,indicate that the lock screw line within a thorn axial locking and axial screw + pedicle screw locking three column with the same rotation resistance stability,but the technical operation and auxiliary posterior screw rod is simple.5)In axial compressive stiffness test,a thorn in the lock screw(EG2)set of axial compression stiffness is spondylolysis of cracked(EG1)set of axial compression stiffness is better than the normal group(CG),and statistically significant;Barbed lock screw within the group(EG2)of axial compression stiffness compared with the other three fixed way,its axial compression stiffness within less than a thorn lock screw + pedicle screw group(EG3)and axial screw + pedicle screw group(EG4),and stronger than the pure axial screw(EG5)set of axial compression stiffness,but statistical analysis to the other three groups,no statistical difference(P >0.05);Therefore,in the case of posterior column instability of the lumbosacral vertebra,the fixation of the internal locking screw in the auxiliary posterior pedicle screw fixation can significantly improve the stability of the axial compression load of the fixed segment.Conclusions:L5-S1 vertebral axial fixation with internal locking device has good biomechanical stability and can meet clinical needs.