The invention relates to an osteosynthesis device comprising a plate (10) and means for fixing a pin (20) that extends through the plate, in which the plate (10) includes a recess (12) for receiving the fixing means and the recess defines an inner edge (22), said fixing means comprising a ring (14) designed to receive the pin (20) and screwable locking means (32). According to the invention, the plate (10) has a threaded opening (26) on the edge of the recess (12), which opens into the inner edge (22), while the ring (14) is slit radially. The screwable locking means comprise 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).
