A system for gripping spinous processes, includes a first plate (1) and a second plate (20), which are installed face to face, and a shaft (3), which is installed approximately perpendicularly with respect to the two plates and passes at least partially through one of them, the plates including an inner face and an outer face, a surface of the inner face of the plates is provided with raised roughening features (6), the first plate is movable relative to the second plate, the first plate is fixed in translation with respect to the shaft, and the shaft and the second plate form a non-return pawl mechanism including a series of notches that cooperate with the non-return pawl mechanism such that the movement of the plates toward each other is irreversible without external aid, whereby spinous processes can be effectively gripped between the two plates.
