Bone screw
AssigneeSynthes USA, LLC
InventorsFridolin J. Schlapfer, Martin Hess
Life of this patent
Estimating the term…
Abstract
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.
Claims34
A bone screw having a central axis and including a head, a front portion having a thread and tapering toward a tip, and a central portion, wherein at least a section of the central portion comprises:
- a contiguous thread with a substantially constant throughout said at least a section of the central portion outside diameter;
- and
- M segments having a body widening toward the head and N segments having a circular-cylindrical cross-section, wherein M≧1 and N≧2, with M and N integral numbers larger than 0 and differing at most by a magnitude of 1, and the M and N segments mutually alternate.
A bone screw comprising:
- a screw head;
- a front portion tapering towards a tip;
- and
- a central portion disposed between the head and the front portion, at least a section of the central portion including a substantially contiguous thread defining a thread inner diameter and a thread outer diameter;
- wherein the thread outer diameter is substantially constant, and the thread inner diameter varies along the at least a section the central portion.
A bone screw comprising:
- a screw head having a substantially frusto-spherical shape;
- a front portion tapering toward a tip;
- and
- a central portion disposed between the head and the front portion, wherein at least a section of the central portion includes a substantially contiguous thread defining a thread inner diameter and a thread outer diameter, and the thread inner diameter varies along the at least a section, and wherein the thread outer diameter is substantially constant along the at least a section of the central portion.
Dependencies are inferred from the claim text.