The authors report the results of their biomechanical experimental study on the fixation of various lesions of the spine, using Roy Camille metal plates, and the results of Fischer -- Gonon (using Harrington rods) and Kempf -- Jaeger (using Kempf rods). They conclude to: the efficiency of the posterior techniques of fixation, the necessity, in the thoraco-lumbar and lumbar segments to associate an anterior graft (fibula), in order to reinforce the late stability, the best functional results achieved by a "short" fixation in association with an anterior graft (double approach technique). According to their experience, the authors advocate for the use of Roy Camille metal plates screwed in the pedicles, the Harrington or Kempf rods helping in the per operative course to gain further reduction, namely in cases of disymetrical displacements.