Stress analysis of the disc adjacent to interbody fusion in lumbar spine

After anterior interbody fusion in the lumbar spine, the accelerated degene ration of the disc adjacent to the fusion levels was clinically observed. T o understand the stress distribution of the adjacent disc, this study creat ed a finite element model of the lumbar spine from L1-L5 vertebral body. Th e fusion model modified from the intact model was used to simulate the ante rior interbody fusion. Various loading conditions, which included flexion, extension, lateral bending, and torsion, were applied to the finite element model to study the corresponding stress distribution. From the finite elem ent model calculation, at a lower fusion site or more fusion levels, the st ress of the disc adjacent to interbody fusion increased more than upper fus ion site or single fusion level under flexion, torsion and lateral bending. Larger stress increase was estimated at the upper disc adjacent to interbo dy fusion than the lower disc adjacent to interbody fusion. In stress distr ibution, the upper disc adjacent to interbody fusion had a little alteratio n under torsion. (C) 2001 IPEM. Published by Elsevier Science Ltd. All righ ts reserved.