Abstract: An osteosynthesis device comprises a plate and screws which are screwed into bone through holes in the plate. The diameters of the holes at the top face of the plate are larger than at the bottom face of the plate. The screws have a spherical head which, when screwed in rests snugly against the wall of the screw hole with an annular contact surface. Both when the screw is located perpendicularly with respect to the plate and when located at an angle with respect to the plate, the contact surface is located above the center line of the hole depth.

Abstract: A plate is provided with clearance holes and fastening screws. Each screw is provided in the region of its head with a clamping part subdivided into tongues by means of slots and provided with an internal opening bounded by a conical surface. To each screw belongs an expander having a conical outer surface. The expander is axially displaceable in relation to the clamping part to force the tongues of the clamping part apart and lock the screw in relation to the plate. A rigid connection between the plate and the screws is thus provided, even if reabsorption of bone material takes place at the bearing surface of the plate.