DEVELOPMENT AND VALIDATION OF A VISCOELASTIC FINITE-ELEMENT MODEL OF AN L2 L3 MOTION SEGMENT/

The prediction of the time dependent response of the spine to dynamic loading conditions is essential in understanding the injury mechanisms leading to occupationally related low back disorders (OLBD). Many pre vious finite element (FE) models of the lumbar spine have over-simplif ied the geometry and the material properties of their elements, yieldi ng results limited generalizability. This study reports on the develop ment and validation of a nonlinear viscoelastic FE model that can quan tify the mechanical responses of the L2/L3 motion segment to time vary ing external loads. This model was developed by consideration of the i ntrinsic material properties of its individual constituents. A piecewi se parameter identification method was adopted due to the inherent com plexity in determining the role and contribution of each element to th e overall behavior of the motion segment. The results of simulation of four loading conditions (quasistatic, constant loading rate, creep an d cyclic relaxation) showed a satisfactory agreement with experimental observations in the literature. The detailed estimates of the state o f stress/strain of this validated FE model can be used to test the rol e of epidemiological risk factors such as prolonged awkward posture, s peed of lift (strain rate effect) and complex repetitive loading in OL BD. (C) 1997 Elsevier Science Ltd.