The invention relates to an osteosynthesis assembly formed by a plate and at least one screw provided with a head, designed to maintain said plate by crossing through an orifice of said plate to fasten it to a bone, said plate having as many orifices (2) as there are screws, characterized in that:at least one of said orifices of said plate has, over at least a portion of its periphery, a metal, ceramic or polymer collar, at which the nominal diameter of the orifice is reduced to a value below said nominal diametersaid screw designed to cross through said orifice has a conical or curved under-head threadingthe collar and the thread bottom of the under-head threading have a tightening of at least 0.01 mm if the collar is made from metal or ceramic and at least 0.05 mm if the collar is made from polymer, so as to create a hard spot toward the end of the placement of the screw, said hard spot remaining after the screw has been placed.
