The prosthesis (1) has anchorage elements (2, 3) fixed in a superjacent lumbar vertebra (Va) and an underlying lumbar vertebra (Vb) using a pedicle screw (6) respectively. A connection unit is formed of a bore, a split ring and a spherical profile, and connects the element (3) to the screw. The connection unit permits each anchorage element to freely pivot with respect to the screw, while a guiding unit permits longitudinal connection elements (4) to freely displace in translation with respect to the element (3) when the vertebras are in movement with respect to each other.
