The invention relates to an osteosynthesis device having a plate (10) which includes a recess (12) which defines an inner edge (22) and receives a ring (14) designed to receive the pin (20). According to the invention, the plate (10) has a threaded opening (26) on the edge of the recess (12), which 25 opens into the inner edge (22), while the ring (14) is slit radially. The device includes a screw (32) that can be screwed through the threaded opening (26) so as to bear against the ring (14) and cause the ring (14) to bear with force against a portion of the inner edge (22) and tighten the ring (14) on the pin (20).
