Abstract: A shank portion of a bone screw is moved through an opening in a bottom of a recess in a plate into engagement with bone in a patient's body. End portions of resiliently deflectable sections of a head portion of a bone screw are slid along the bottom of the recess during rotation of the bone screw. Resiliently deflectable sections of the head portion are deflected by engagement with the bottom of the recess. As the deflectable sections of the head portion are deflected, outer end surfaces on the resiliently deflectable sections of the head portion move into engagement with a side surface of the recess. The bone screw is retained against loosening by engagement of the outer end surfaces on the resiliently deflectable sections of the head portion with the side surface of the recess. An outer side surface of the bone screw is aligned with an outer side surface of the plate.

Abstract: A drill for forming a hole in material has a shank with at least a base surface positioned at an angle to a longitudinal axis of the shank and a side surface. A cutting element having first and second ends is eccentrically connected to the base surface in such a manner that a longitudinal axis of the cutting element is situated at a predetermined distance from a longitudinal axis of the shank. An outer surface of the body of the cutting element is defined by at least a front surface and a rear surface intersecting each other along at least a cutting edge. The rear surface is tapered toward the longitudinal axis of the shank so that only the cutting edge and the drill point engage the material and a substantial open area exists between the outer surface of the cutting element and the hole during the entire process of drilling.