Bone screw

• US 5,019,078 A
• Filed: 11/17/1989
• Issued: 05/28/1991
• Est. Priority Date: 11/17/1988
• Status: Expired due to Term

• Current Assignee: Synthes USA LLC (Johnson & Johnson), Queen's University At Kingston
• Original Assignee: Synthes USA LLC (Johnson & Johnson)
• Inventors: Perren, Stephen M., Frigg, Robert, Mathys, Robert Jr., Gisin, Paul
• Primary Examiner(s): Hafer, Robert A.
• Assistant Examiner(s): ROONEY, KEVIN
• Application Number:
  US07/437,581
• Time in Patent Office: 557 Days
• Field of Search: 606/60, 606/61, 606/72, 606/73
• US Class Current: 606/313
• CPC Class Codes: A61B 17/8625 Shanks, i.e. parts contacting bone tissue

Abstract

A bone screw has a smooth shaft segment, a threaded segment and a tapered transition segment between the shaft and the threaded segment.

Claims

1. A bone screw having a head, a smooth shaft segment having a diameter D₁ adjacent said head, a threaded segment and a transition segment between the smooth shaft segment and the threaded segment, said transition segment tapering from a diameter D₁ adjacent said smooth shaft segment to a lesser diameter D₂ adjacent said threaded segment, the ratio ##EQU3## being between 0.001 and 0.040.

2. The bone screw claimed in claim 1, wherein the ratio is between 0.010 and 0.030.

3. The bone screw claimed in claim 1, wherein the transition segment has a self-cutting thread.

4. The bone screw claimed in claim 1, wherein the transition segment narrows continuously from D₁ to D₂.

5. The bone screw claimed in claim 1, wherein the transition segment has a shallow thread.

6. The bone screw claimed in claim 1 and comprising a milling segment between the threaded segment and the transition segment.

7. The bone screw claimed in claim 1, wherein the threaded segment has a minor diameter d₁ and a major diameter d₂, the ratio d₁ /d₂ being between about 0.80 and 0.89.

8. The bone screw claimed in claim 7, wherein the ratio is between about 0.83 and 0.86.

9. The bone screw claimed in claim 1, wherein the threaded segment has an automatically expanding screw tip at its end remote from the transition segment.

10. The bone screw claimed in claim 9, wherein the tip is a Trocar tip.

11. The bone screw claimed in claim 1, wherein the transition segment is from about 11 to about 15 mm from the remote end of the threaded segment.

12. The bone screw claimed in claim 11, wherein the transition segment is from about 12 to about 14 mm from the remote end of the threaded segment.

13. The bone screw claimed in claim 1, wherein the tip of the threaded segment has a corkscrew shape.