Osteosynthesis device with plate provided with a threaded hole for receiving a locked fastening screw

In an osteosynthesis device with a plate and a screw for fixing the plate on a bone, the head of the screw includes a thread for its locking with the internal thread in its receiving hole. The internal surface of the plate hole includes a first frustoconical section that extends at an angle 30-60° with respect to the hole central axis, and a second frustoconical section that extends between the first frustoconical section and the plate lower face, at an angle 8-12° with respect to the hole central axis. The internal surface of the hole also includes at least three upper undercuts, and at least three lower undercuts, which upper and lower undercuts allow a degree of freedom in angulation of the screw, and also preserve a portion of hole internal thread on all the generatrices of the hole internal surface located in planes parallel to the central axis.