Finite element analysis on lumbar interbody fusion

The aim of this paper is to evaluate the effect ofinterbody fusion on lumbar spine via finite element (FE) method. Based on CTscanning images and CAD three-dimensional reconstruction technique, detailedand anatomically accurate normal and fused human lumbar spine FE models forthe L2-L4 motion segment with or without L3-L4 fusion are built. The lumberspine models include vertebrae, intervertebral disc and various ligaments. Apreviously developed hyperelastic fiber reinforced constitutive model isused to characterize the nonlinear anisotropic material property ofintervertebral disc annulus fibrosus. The proposed FE model is validated bycomparing numerical results of axial compressive load-displacement withexperimental data available in literature. Commercial FE analysis softwarepackage ABAQUS/Standard is used to simulate the normal and fused lumberspine segment under flexion, extension and axial rotation. The lumbar spinemotion range and stress distribution of two models under different loadingconditions are obtained and compared. Numerical simulation results show thatunder the same loading condition, the fused model has a much smaller bodymotion range compared the normal one. Interbody fusion brings out obviouslydifferent stress distribution in adjacent vertebral bodies, but has minorimpact on adjacent intervertebral disc. The results also suggest that facetjoints play an important role in maintaining normal physiological functionof spine. The analysis results can provide references and guidelines forhuman lumbar fusion neurosurgical operation in clinic.