[Method for studying internal tensions at the intervertebral junction in extreme postures. Description of...

The authors describe a device for measuring the resultant tensions existing at the intervertebral junction (or its constitutive elements) in all spine attitudes. The reported method has been applied to the L4-L5 junction of a spine taken from the corpse of a 50 years old man. Although incomplete, the results suggest the following points: --the L4-L5 intervertebral junction seems to be very deformable, particularly in the sagittal plane; --the intervertebral disk is probably an elastic support which sustains shear stresses during flexion, extension and bending movements in the frontal plane; --during flexion, articular processes seem to be movement leaders as well as supports; --ligaments seem to play a small mechanical role, but their proprioceptive function seems essential.