Patent ID: 8636785

Claim:
A bone screw having a lead portion and a tail portion, and an intermediate transition portion, each of the lead portion and the tail portion comprising a root and a helical thread formed on the root, the thread on the lead portion having a diameter and the thread of the tail portion having a diameter wherein the diameter of the thread on the tail portion is greater than that of the thread on the lead portion, wherein the thread on the lead portion extends to a distal end of the screw, wherein the lead portion includes a first section in which the thread of the lead portion is of a constant diameter and a second section closer to the distal end of the screw in which the thread of the lead portion is of a reduced diameter relative to the thread of the lead portion that is of a constant diameter, wherein the intermediate transition portion is configured between the threads of the lead portion and the tail portion, wherein the tail portion is provided with a socket end, wherein the socket end of the tail portion is adapted to be flush with the surface of the bone or under the surface of the bone after the bone screw is fully inserted, wherein the thread on the lead portion of the screw is a double-start thread and the thread on the tail portion of the screw is a single-start thread, and in which the thread pitch of the thread on the tail portion is greater than the thread pitch of the thread on the lead portion, and wherein the single-start thread on the tail portion is a continuation of one of the threads of the double-start thread on the lead portion, wherein the thread aspect ratio of the thread on the tail portion is greater than the thread aspect ratio of the thread on the lead portion, wherein the lead portion and the tail portion are formed from a single block of metal, wherein a bore extends through the bone screw throughout its entire length.