Finite element analysis of the influence of new anterior cervical spine memory compression fixator on adjacent segments / 中华骨科杂志

ABSTRACT

Objective:To compare the effect of the new anterior cervical spine memory compression fixation device (GYZ memory alloy plate) and traditional titanium plate on the range of motion (ROM) and stress of the adjacent segment after anterior cervical discectomy and fusion.Methods:An adult male volunteer was recruited for a fee. After excluding cervical malformations, fractures, infections and other diseases, C 3-C 7 thin-layer CT scans were performed. Import the scanned data into the finite element modeling software to establish the finite element model of the physiological group and verify itseffectiveness. After C 5,6 discectomy, the intervertebral fusion device was inserted, and the anterior fixation was assisted by a conventional titanium plate or a new type of fixator. Thus, the finite element model of the traditional titanium plate group and the new fixer group was established. The three models were imported into the finite element analysis software ANSYS 16.0, and a vertical downward axial load of 73.6 N was loaded to simulate the head weight and the torque of 1.0 N·m to simulate the cervical spine flexion, extension, left lateral bending, right lateral bending, left rotation and right rotation.Compare the changes of intervertebral disc ROM and stress in adjacent segments of physiological group, traditional titanium plate group and new type fixator group. Results:The intervertebral disc ROM under six conditions was basically similar to the results of previous studies, and the model was effective. In the adjacent segment C 4,5, the three groups of activities in the flexion, extension, left lateral bending, right lateral bending, left rotation and right rotation conditions were: physiological group 3.9°, 4.2°, 3.7°, 3.7°, 2.2° and 2.2°, traditional titanium plate group 4.6°, 4.7°, 4.3°, 4.4°, 3.3° and 3.1°, and new fixture group 4.4°, 4.3°, 4.0°, 4.2°, 2.8° and 2.7°. The maximum stresses of the intervertebral discs under three different working conditions were: physiological group 1.81, 1.60, 3.99, 2.06, 3.63 and 3.41 MPa, traditional titanium plate group 1.86, 1.67, 4.21, 2.16, 3.82 and 3.63 MPa, and new fixture group 1.84, 1.64, 4.17, 2.14, 3.78 and 3.58 MPa. In the adjacent segment C 6,7, the activities of the three groups in six working conditions were: physiological group 3.1°, 3.2°, 2.5°, 2.5°, 1.2° and 1.3°, traditional titanium plate group 4.2°, 3.7°, 3.4°, 3.0°, 2.1° and 2.2°, and new fixture group 3.5°, 3.3°, 2.5°, 2.7°, 1.8° and 1.9°.The maximum stress of the intervertebral disc under three different working conditions was: physiological group 0.45, 0.66, 1.12, 0.85, 0.84 and 0.82 MPa, traditional titanium plate group 0.62, 0.93, 1.55, 1.24, 1.44 and 1.27 MPa, and new fixture group 0.61, 0.92, 1.54, 1.22, 1.07 and 1.24 MPa. The ROM and disc pressure of adjacent segments in the conventional titanium plate group were higher than those of the new fixator group. Conclusion:Compared with the traditional titanium plate, the new type of anterior cervical memory compression fixator has less effect on the ROM and stress of adjacent segments, which may slow down the process of adjacent segments degeneration to a certain extent.