ABSTRACT
The various biomechanical responses such as stress distribution, facet contact force and nucleus pressure change in the lumbar spine under vertical static and dynamic loading conditions were. Investigated with a nonlinear three dimensional finite element model. Finite element model of one motion segment, consisted of two vertebral bodies(L3-4) with one disc, was developed from 1 mm thick transverse CT cross-sections. Geometrical nonlinearity was also considered for the large deformation on the disc. ABACUS package was used for calculation and its results were verified comparing with the existing in-vitro experimental data. Clinically useful results could be obtained with this analysis. Stress was concentrated on the endplate under static and dynamic loading condition, especially posterior and anterior aspect and central portion along midsagittal plane. The facet contact force showed some discontinuity when Δt/2=0.03 sec. This discontinuity was considered to de due to the vibration of upper vertebra. Relatively smooth contact force profile was detected when t/2=0.1342 sec. Intradiscal pressure and stress pattern changes on the vertebra were also analyzed.