Finite element analysis of effects of movable artificial lumbar vertebra implantation on stress of adjacent intervertebral discs / 中华创伤杂志

ABSTRACT

Objective To compare the effects of movable artificial lumbar vertebra implantation and traditional vertebral excision and fusion on the stress of adjacent intervertebral discs,so as to provide reference for the biomechanical safety of new prosthesis implantation.Methods The total lumbar vertebra CT scan data of a healthy adult were imported into the compute r-aided software Mimics 16.0 for three dimensional reconstruction.The reconstructed three dimensional model was smoothed using computer-aided software Geomagic Studio 12.0.Subsequently,meshing,parameter setting and ligaments reconstructing were completed using computer-aided software Hypermesh 13.0 and Solidworks 2013,successfully constructing the finite element model of lumbar vertebral physiology group.On the basis of the finite element model of physiological group,three vertebral bodies and two intervertebral spaces were fused and fixed,and a simplified finite element model of fusion group was constructed.The partitioned prosthesis model was inserted into the established finite element model of physiological group,replacing the L 3 vertebral body and the adjacent two intervertebral discs in the model,constructing the finite element model of non fusion group.Three finite element models were imported into computer-aided software Abaqus/Explict and loaded under six motion modes including anteflexion,dorsiflexion,left and right rotation,and left and right bending.The stress changes of adjacent intervertebral discs were calculated.Results The maximum Mises stress of the adjacent intervertebral disc in the direction of forward flexure,dorsal extension,left and right rotation and left and right lateral bending of the three finite element models was located at the site of loading and increased with the increase of loading.Under the maximum loading,the Mises stress of adjacent intervertebral discs in the above directions in the fusion group (L1-2 respectively were 0.79,0.96,1.26,1.92,1.34,1.57 MPa while L4-5 respectively were 0.52,1.13,1.50,1.74,0.94,0.87 MPa) was significantly higher than that in the physiological group (L1-2 respectively were 0.42,0.53,0.57,0.66,0.64,0.72 MPa while L4-5 respectively were 0.23,0.29,0.68,0.63,0.37,0.34 MPa).The Mises stress of adjacent intervertebral disc in the non-fusion group (L1-2 respectively were 0.38,0.57,0.75,1.02,0.87,0.90 MPa while L4-5 respectively were 0.18,0.26,0.81,0.98,0.30,0.27 MPa) was similar to that in the physiological group,although there was some difference.Conclusion Movable artificial lumbar disc prosthesis implantation can better avoid the stress increase of adjacent intervertebral discs,and its long-term implantation in the human body is expected to reduce the incidence of degeneration of adjacent intervertebral discs.