SHEAR LOAD SHARING IN THE HUMAN LUMBAR SPINE

There is growing concern that low back pain is related to shear load [Norman, 1998]. However, in contrast to axial compressive properties, little is known about the shear mechanical properties of spine. At shear failure in human spine, the disc supports 77% of the shear load [Cripton. 1995]. Evaluation of shear load sharing using porcine spine showed that in the initial overload phase the neural arch was not involved [Yingling, 1999]. We hypothesised that shear load sharing mechanisms in the human and porcine spine are different and that there is early involvement of the neural arch in the human spine.