Bone screw

A self-drilling, self-tapping screw used in repairing broken bones by reattaching at least a first and a second bone section, said screw having an overall length and comprising:

• a) a tip region for penetrating the bone sections and initiating thread formation therein:
• said tip region having a point with an included angle of between about 45.degree. and about 50.degree. to provide a necessary strength and, yet, penetrate the bone, said tip region having a retention thread formed through substantially its entire length;
• b) a body region having a substantially uniform diameter and having a retention thread formed substantially throughout its entire length said retention thread of said tip region has a thread pitch which is slightly smaller than the thread pitch of said retention thread of said body region;
• c) a round head region including
• i) a head which has a maximum diameter and a drive recess and
• ii) a portion underlying said head which is without any thread, said drive recess being cruciform in shape said cruciform being formed by two orthogonal slots which each extend from between 70% and 95% of said maximum diameter to provide a required level of torque, said drive recess having retention means so said screw can be attached to a driver and inserted by a single hand of a user;
• d) a cutting flute extending over at least a portion of said overall length for cutting and removing bone fragments to permit penetration and thread formation by said screw in at least one of said bone sections which are being reattached by said screw;
• whereby a configuration of said head region including said drive recess provides said adequate level of torque required to permit said screw to be driven into said bone and adequate strength to resist deformation and twisting of said head off said body region of said screw during installation.

A head region for a self-drilling, self-tapping screw to be used in fractured bone reparation, said head region comprising

• i) a frusto-conical head which has a maximum diameter and a drive recess, and
• ii) a portion underlying said head which is without any thread, said frusto-conical head having an included angle of between about 90.degree. and about 120.degree.,said drive recess being cruciform in shape, said cruciform being formed by two orthogonal slots which each extend from between 70% and 95% of said maximum diameter to provide a required level of torque, said drive recess having retention means so said screw can be attached to a driver and inserted by a single hand of a user, each of said orthogonal slots being arcuate on its bottom to effect minimum removal of material from said head while providing maximum surface engagement with a driver received in said drive recess, a radius of an arc defining said arcuate bottom being proximate a maximum radius of said screw head, an upper face of said screw head having an arcuate configuration, a radius of arc defining said arcuate configuration of said upper face being in a range of between two and four times said maximum radius of said screw head;
• whereby a configuration of said head region including said drive recess provides said adequate level of torque required to permit the screw to be driven into said bone and adequate strength to resist both deformation of said drive recess and said head being twisted off a body region of the screw during installation.