[Optical methods in the study of superficial displacements of the lumbar vertebrae under a vertical load. Initial results and methodological aspects].

In order to assess superficial displacements under load in human lumbar vertebrae, the authors used three different optical methods: photogrammetry under non coherent light; double-exposure holographic interferometry; speckle granularity under laser exposure. Without any structural interposition, the displacements are measured within 10 mu for linear variations and 0.1 degrees for angular variations. Photogrammetry seems to be more adequate for the study of large range of displacements while holographic and speckle techniques are useful to assess, in the displacements, the part of the disc and the osseous structure deformation respectively.