Bone Screw

• US 20090018589A1
• Filed: 07/13/2007
• Published: 01/15/2009
• Est. Priority Date: 07/13/2007
• Status: Active Grant

• Current Assignee: Southern Spine, LLC
• Original Assignee: Southern Spine, LLC
• Inventors: Bohleber, Brandi, Field, David C., Smisson, Hugh F. III, Gombar, Paul, Sanders, Walter R.
• Granted Patent: US 8,668,725 B2
• Time in Patent Office: Days
• US Class Current: 606/301
• CPC Class Codes: A61B 17/7059 Cortical plates A61B17/7007, A61B17/7058 take precedence
• CPC Class Codes: A61B 17/8057 the interlocking form comprising a thread
• CPC Class Codes: A61B 17/863 with thread interrupted or changing its form along shank, other than constant taper

Abstract

A bone screw is provided for securing a medical device to bone. The bone screw can engage with a bone screw hole in a medical device, such as an anterior cervical plate or sternal closure plate.

Claims

1. A bone screw, comprising:

a) a screw head;

b) a smooth cylindrical shaft region;

c) a first cylindrical shaft region comprising external threading, said threading having a first pitch and a first crest width;

d) a second cylindrical shaft region comprising external threading, said threading having a pitch that transitions from said first pitch to a second smaller pitch, and further having a crest width that transitions from said first width to a second smaller width;

e) a tapered shaft region comprising external threading, said threading having said second smaller pitch and said second smaller crest width, said tapered shaft further comprising at least one recessed flute; and

f) a sharp tip.

2. The bone screw of claim 1, wherein said tip comprises no threading or fluting.

3. The bone screw of claim 1, wherein said threading comprises a forward face and a backward face, and further wherein the angle between said forward face and the central axis of the screw is substantially constant throughout said threading.

4. The bone screw of claim 3, wherein said angle is about 50 degrees to about 70 degrees.

5. The bone screw of claim 1, wherein said threading comprises a forward face and a backward face, and further wherein the angle between said backward face and the central axis of the screw is substantially constant throughout said threading.

6. The bone screw of claim 5, wherein said angle is about 80 degrees to about 100 degrees.

7. The bone screw of claim 1, further comprising a ramping region between said smooth cylindrical shaft region and said first cylindrical threaded shaft region, wherein said ramping region comprises threading that progressively increases in depth, measured from the outer surface of said shaft to said thread crest, from a first thread depth to a second larger thread depth.

8. The bone screw of claim 7, wherein said ramping region comprises less than one full revolution of threading.

9. The bone screw of claim 1, wherein the diameter of said threading, measured from one crest of said threading to an opposite crest of said threading, is substantially constant along the majority of the threading on said screw.

10. The bone screw of claim 9, wherein said threading diameter is about 3.0 mm to about 5.0 mm.

11. The bone screw of claim 1, wherein said tapered shaft comprises three recessed flutes.

12. The bone screw of claim 11, wherein each said flute spans an angle of about 90 degrees.

13. The bone screw of claim 1, wherein said first pitch is about 5.0 mm to about 7.0 mm and said second smaller pitch is about 2.0 mm to about 4.0 mm.

14. The bone screw of claim 1, wherein said first crest width is about 0.3 mm to about 0.4 mm and said second smaller crest width is about 0.1 mm to about 0.2 mm.

15. The bone screw of claim 1, wherein the shaft diameters of said smooth cylindrical shaft region and said first and second threaded cylindrical shaft regions are substantially equal.

16. The bone screw of claim 1, wherein said screw head has a recessed portion for receiving a tool.

17. The bone screw of claim 1, wherein said screw is made of a titanium alloy.

18. The bone screw of claim 1, wherein at least a portion of said threading is sized and shaped to engage with a bone screw hole in an anterior cervical plate.

19. A bone screw for engaging with a bone screw hole in an anterior cervical plate, comprising:

a) a sharp tip;

b) a tapered shaft region comprising external threading, wherein the shaft diameter of said tapered region increases in the direction away from said tip, further wherein the diameter of at least a portion of said threading on said tapered region is smaller than the diameter of said screw hole;

c) a first cylindrical shaft region comprising external threading, wherein the shaft diameter of said first cylindrical region is smaller than the diameter of said screw hole, further wherein said at least a portion of said threading on said first shaft region is sized and shaped to engage with said screw hole;

d) a second cylindrical shaft region without external threading, wherein the shaft diameter of said second cylindrical region is smaller than the diameter of said screw hole; and

e) a screw head, wherein the diameter of said screw head is larger than the diameter of said screw hole.

20. The bone screw of claim 19, wherein said tip comprises no threading or fluting.

21. The bone screw of claim 19, wherein said threading comprises a forward face and a backward face, and further wherein the angle between said forward face and the central axis of the screw is substantially constant throughout said threading.

22. The bone screw of claim 21, wherein said angle is about 50 degrees to about 70 degrees.

23. The bone screw of claim 19, wherein said threading comprises a forward face and a backward face, and further wherein the angle between said backward face and the central axis of the screw is substantially constant throughout said threading.

24. The bone screw of claim 23, wherein said angle is about 80 degrees to about 100 degrees.

25. The bone screw of claim 19, further comprising a ramping region between said second cylindrical shaft region and said first cylindrical shaft region, wherein said ramping region comprises threading that progressively increases in depth, measured from the outer surface of said shaft to said thread crest, from a first thread depth to a second larger thread depth.

26. The bone screw of claim 25, wherein said ramping region comprises less than one full revolution of threading.

27. The bone screw of claim 19, wherein the diameter of said threading, measured from one crest of said threading to an opposite crest of said threading, is substantially constant along said first cylindrical shaft region.

28. The bone screw of claim 27, wherein said threading diameter is about 3.0 mm to about 5.0 mm.

29. The bone screw of claim 19, wherein said tapered shaft region comprises at least one recessed flute.

30. The bone screw of claim 29, wherein said tapered shaft region comprises three recessed flutes.

31. The bone screw of claim 30, wherein each said flute spans an angle of about 90 degrees.

32. The bone screw of claim 19, wherein the shaft diameter of said first cylindrical shaft region is substantially equal to the shaft diameter of said second cylindrical shaft region.

33. The bone screw of claim 19, wherein said screw head has a recessed portion for receiving a tool.

34. The bone screw of claim 19, wherein said screw is made of a titanium alloy.

35. An anterior cervical plating system, comprising:

a) an anterior cervical plate, comprising at least one hole for receiving a bone screw;

b) a bone screw, comprising a head;

a body, wherein a region of said body adjacent to said head is unthreaded and the rest of the body comprises external threading; and

a tip;

c) wherein the diameter of said head is larger than the diameter of said hole, further wherein the diameter of said body is smaller than the diameter of said hole, further wherein at least a portion of said external threading has a diameter larger than the diameter of said hole;

d) wherein said portion of external threading having a diameter larger than the diameter of said hole engages with said hole when said screw is rotated through said hole; and

e) wherein said unthreaded body region is positioned within said hole when said screw has been fully inserted in said hole.