Screw

The central portion of the screw according to the invention has a series of segments varying in diameter, typically having a segment located near the screw head with a large diameter, a segment located near the front portion with a small diameter, and intermediate segments tapering in the direction of the segment with the small diameter. A continuous thread extends along the central portion from the screw head to the screw tip where the thread has a substantially uniform outside diameter along the entire length of the central portion. The screw, which is particularly well-suited as a pedicle screw, has improved resistance to tearing, cutting and bending, and, largely independent of bone quality, good hold in bone.