[The contributions of facet joint to the stiffness of the lumbar spine].

In this paper, the changes in the stiffness of eight lumbar spinal segments, as affected by left unilateral partial or total facetectomy, were investigated by means of an electro-mechanical technique. The results showed that with unilateral facetectomy, the stiffness of lumbar spinal segment was 39% less in axial rotation, 14% less in extension, 13% less in lateral bending and 9% less in flexion. This observation suggests that in general clinical practice, close attention must be paid to the patients with facet injury, because in this situation the ability of lumbar spine in resisting torque may be decreased significantly.