Bone compression and fixation devices
A bone screw, for drawing first and second bone fragments together, includes a shaft having a distal section and a proximal section. The distal section has a first external male screw thread and a minor diameter. The proximal section has a second external male screw thread. A major diameter of the distal section is larger than a major diameter of the proximal section. The bone screw includes a sleeve that has an internal female screw thread configured to mate with the second male screw thread. A distal portion of the sleeve has an outer diameter. The outer diameter is equal to or smaller than the minor diameter of the distal section of the shaft.
1. A bone screw for drawing first and second bone fragments together, comprising:
a shaft having a distal section and a proximal section, the distal section having a first external male screw thread and a minor diameter, the proximal section having a second external male screw thread, a major diameter of the distal section being larger than a major diameter of the proximal section; and
a sleeve having an open proximal end and an open distal end and an internal female screw thread configured to mate with the second external male screw thread, a distal portion of the sleeve being tapered and having an outer diameter that tapers from a first outer diameter that is larger than the major diameter of the distal section of the shaft to a second outer diameter that is smaller than the major diameter of the distal section of the shaft,
wherein an outer surface of the tapered distal portion of the sleeve from the first outer diameter to the second outer diameter is void of threads, the tapered distal portion of the sleeve comprising two or more axially extending slots extending through the outer surface of the tapered distal portion and proximally from the distal end of the sleeve between two or more flexible phalanges which include the internal female screw thread,
wherein the sleeve is configured to slide over the second external male screw thread along a first portion of the proximal section of the shaft in a distal direction without rotating the sleeve relative to the shaft, and engage with and screw over the second external male screw thread for at least a complete revolution along a second portion of the proximal section of the shaft in the distal direction by rotating the sleeve relative to the shaft.
2. The bone screw of claim 1 , wherein a pitch of the first external male screw thread is larger than a pitch of the second external male screw thread.
3. The bone screw of claim 1 , wherein the proximal section of the shaft is a wire.
4. The bone screw of claim 1 , wherein the sleeve includes two or more radially extending projections.
5. The bone screw of claim 1 , wherein the major diameter of the distal section of the shaft is approximately 1.3 mm.
6. The bone screw of claim 1 , wherein the proximal section of the shaft includes a smooth, non-threaded section proximate the distal section of the shaft.
7. The bone screw of claim 6 , wherein a portion of the proximal section of the shaft extends proximally from the sleeve in a compressed position.
8. The bone screw of claim 1 , wherein the distal portion of the sleeve is frustoconical in shape.
9. The bone screw of claim 1 , wherein the outer surface of the tapered distal portion of the sleeve is smooth and configured to contact a surface of the first bone fragment when the shaft is engaged with the second bone fragment and can subsequently be drawn into a hole created by the shaft.
10. The bone screw of claim 1 , wherein a proximal portion of the sleeve does not contain threads.