Thebiomenchanical Effect Of Double Transverse Connectors Position On The Stability Of The Long-Segmental Spinal Pedicle Screw Fixation During The Pedicle Cortex Perforation

The experimental study of the effect of double transverse position on long segmental spinal fixation with pedicle cleavage: Using 50 fresh adult sheep thoracolumbar specimens(T13-L5 segment),through vertebral body partial perforation and pulling machine to compress the vertebral body,a L2 vertebral compression fracture model was established.And then the model of vertebral fracture was made by random digital table,which was divided into A,B,C,D,E 5 groups.Using the posterior vertebral pedicle screw fixation,and the long segmental(T14-L4 vertebral body)fixation was used,Then the cortical bone of the lateral 1/4 of the pedicle was removed,and the screw thread was revealed to be accompanied by a right cleavage of T14 with a compression fracture model,and then the double cross connection is fixed to the different position of the specimen,the model is made.Group A and B did not place transverse connection.Group C placed transverse connection in T14~L1 and L1~L3.D group placed transverse connection between T14~L1 and L3~L4.E group placed transverse connection between L1~L3 and L3~L4 respectively.After the specimen model was completed,10000 fatigue tests were carried out by the tensile force and the rotating biomechanics machine.After the fatigue test,the axial compression stiffness the screws maximum pullout strength of the T14 right vertebral body,flexion,lateral bending and rotation of the 6 direction range(Range of the Motion,ROM)as the experimental index,and each index was measured and recorded,then the SPSS17.0 software forstatistic analysis.The analysis of the experimental data shows that: After the fatigue test,the axial compression stiffness of the A group and the maximum pulling force of the split pedicle screw were significantly higher than those in the B group,the difference was statistically significant(P<0.05),indicating that the axial compression stiffness of the spinal internal fixation system decreased significantly after the pedicle cleavage.The B group was compared with the three groups of C,D and E(P values were 0.370,0.183,0.910),indicating that increased transverse connection could not improve the axial compression stiffness of internal fixation,and the maximum pull-out force of D,C,E and B five groups increased in sequence,the difference was statistically significant(P<0.05).indicating that the maximum pulling force of the screw can be greatly improved when the double transverse connection is located on both sides of the internal fixation in the long segment.In terms of three dimensional range of motion of specimen,the range of flexion and extension of group A increased significantly compared with group B after fatigue test,and the difference was statistically significant(P<0.05),indicating that pedicle rupture would lead to increased activity of internal fixation system.The range of lateral and axial rotation of D,C、E and B increased sequentially,and the difference was statistically significant(P<0.05),indicating that the double lateral joints placed on both sides of the internal fixation system in the long segment can reduce the activity of the internal fixation system.The results of the experiment suggest that:In the long segmental pedicle screw fixation system,when pedicle splitting occurs,placing two transverse connections near the distal position can reduce the lateral and axial rotation of the internal fixation,and at the same time,it can compensate for the loosening of screws caused by insufficient pedicle strength.