[Clinico-radiological study of the centers of instantaneous rotation of the lumbar spine].

The author, after a description of CIR's modality of calculus and its mathematical principles, underlines application of such method in diagnosis of lumbar-sacral pathology. A new spine's conception springs from this study: the "motor segment" with its functional and anatomical aspects. This interpretation gives us a new study's method of the lumbar-sacral dynamic and its pathology.