A Biomechanical Study On The Treatment Of Thoracolumbar Fractures With Internal Fixation Of The Pedicle Of The Injured Vertebrae

Objective:The paper is to research and evaluation Biomechanical of pedicle screw fixation for thoracolumbar fractures.Methods:8cases of L5(T12)specimens of calf thoracic spine were studied.They were used to make fracture specimens,and third lumbar vertebrae and their upper and lower lumbar intervertebral discs were removed by the Curr method.Specific production of four models:first,the normal model,not fixed screws.Second,the manufacture of L3 fracture,in L2,L4 bilateral pedicle screw fixation(4 nails).Third,the manufacture of L3 fracture,in L2,L3 and L4 bilateral pedicle screw fixation(6 nails).Fourth,the manufacture of L3 fracture,in L1,L2,L3,L4 bilateral pedicle screw fixation(8 nails).The specimens were subjected to axial compression test,forward / backward flexion extension test,torsion test and pullout test.In particular,the axial compression test was performed on a universal electronic testing machine(DSFW-50)controlled by a micro machine.In the axial compression test,the loading speed is constant at 5 mm/min and the load pressure is between 0N-500 N.In the flexion and extension test,fixed extension instrument on the spinous process of L2/L3,and the computer is responsible for collecting data,recording the different fixed method of displacement.At the end of the test,4 screws,6 screws and 8 nails were randomly taken to improve the test precision and reduce the error.The torsion test machine(NJ-50B)was used to carry out the torsion test,and the maximum torsional force was not more than 10 N.m.After the end of the basic test,the 3 test to ensure the accuracy of the test,the use of hydraulic universal testing machine(WE-10A)pullout tests were carried out,along the upper and lower vertebral disc separation into 5 parts,each part of the nail into the screw in the short and long nail in(6.5mm×35mm)(6.5mm×55mm)of each one,fixed specimens.Loading along the longitudinal axis of the screw to maintain the loading rate is constant:2mm/min,testing the maximum axial pullout force of short nails and long nails.Results:1、Axial compression test results showed that: under the load of 100 N,200 N,300 N,400 N,500 N,there was no significant difference between the 4 nail model and the normal group,the difference does not have analytical significance(P>0.05).6 screw displacement model and 8 model are less than 4 nail nail model,the difference has analytical significance(P<0.05);6 screw displacement model and 8 nail model had no significant difference,no statistical difference meaning(P>0.05).2、Reach test results suggest that in 20 N,40 N,60 N,80 N,100 N under load,4 nail model displacement and normal displacement of no significant difference,the difference does not have analytical significance(P>0.05);4 nail model,normal group and 6 nail model,8 nail model displacement differences were statistically significant.Meaning(P<0.05).There was no significant difference between the 6 nail model and the model group of the 8nails,the difference does not have analytical significance(P>0.05).3、After the tensile test results suggest that in 20 N,40 N,60 N,80 N,100 N under load,4 nail model displacement is greater than the normal group,the difference was analytical significant(P<0.05);6,8 nail nail model model of displacement is less than the normal group,4 nail model,the difference has analytical significance(P<0.05);6 nail nail displacement model and 8 model had no significant difference,no statistical significance(P>0.05).4、Torsion test results suggest that in 5 N.m,10 N.m load,4 models,6 models,nail nail nail 8 model of torsional degree less than the normal group,the difference has analytical significance(P<0.05);6,8 nail nail model model is less than 4 degree twist nail model,the difference has analytical significance(P< 0.05);8 nail the model is less than 6 degree twist nail model,the difference has analytical significance(P<0.05).5、Long nails,short nails pull-out test results show that: the maximum axial pullout strength of short nails is less than long nails,the difference has statistical significance(P<0.05).The maximum pullout force of short nails was 56.35%.Conclusion:The biomechanical study of thoracolumbar vertebral fracture with vertebral pedicle internal fixation showed that vertebral fixation internal fixation can effectively reduce the stress concentration caused by dislocation or fracture may also reduce the displacement distance,with improved biomechanical stability,can enhance the stability of spinal column,so it has very important value in clinical practice in.