Self-holding screw head

Patent metadata

Field	Value
Publication number	US-10426535-B2
Application number	US-201715399233-A
Country	US
Kind code	B2
Filing date	Jan 5, 2017
Priority date	Jan 5, 2017
Publication date	Oct 1, 2019
Grant date	Oct 1, 2019

Abstract

A screw insertion system has a screw having a threaded shaft and a head. The head has a conically tapered outer surface, the taper increasing in distance from a central longitudinal axis of the screw from a free end of the head towards a larger diameter adjacent the connection between the head and the threaded shaft. The conically tapered head outer surface has preferably two helically extending partially rounded threads. The head has a drive element for engaging a driver. A tubular screw holder has an outer surface and internal bore extending between a leading end and a trailing end for receiving the screw. The leading end having a conically tapered inner threaded portion for engaging the conically tapered outer thread of the screw head. The tubular screw holder outer surface having a diameter less than or equal to the maximum diameter of the conically tapered head.

First claim

The invention claimed is:

1. A screw insertion system comprising:
a screw having a threaded shaft at a leading end and a head at a trailing end, the head having a threaded external surface extending from a first end to a second end thereof, the head having a first diameter at the first end and a second diameter at the second end connected to the threaded shaft, each of the first diameter and the second diameter being measured at a root of a helical thread of the threaded external surface, the first diameter of the head being less than the second diameter of the head and the head having a drive element located within the first diameter open to the first end of the head;
a screw holder having a through bore with a trailing end and a leading end, an interior surface at the leading end having a threaded portion, the threaded portion having a first diameter located towards the trailing end of the screw holder and a second diameter at the leading end of the screw holder, the second diameter of the screw holder greater than the first diameter of the screw holder, the second diameter of the screw holder generally equal to the second diameter of the head; and
a driver extending through the screw holder engagable with the drive element on the head.

2. The screw insertion system of claim 1 , wherein the head has a conical outer shape between the first and second diameter of the head, and the threaded portion of the interior surface of the screw holder threaded portion has a matching conical shape.

3. The screw insertion system of claim 2 , wherein the conical outer shape has an opening angle of about 20°.

4. The screw insertion system of claim 1 , wherein the head has a part-spherical outer shape between the first and second diameters of the head.

5. The screw insertion system of claim 1 , wherein the threaded external surface of the head includes external threads that are at least partially rounded threads and the threaded portion of the screw holder includes interior threads that are at least partially rounded threads.

6. The screw insertion system of claim 5 , wherein the at least partially rounded threads have rounded roots and flattened crests.

7. The screw insertion system of claim 5 , wherein the external threads on the head and the interior threads on the screw holder are left-handed threads.

8. The screw insertion system of claim 1 , wherein the driver has an outer diameter being slidably received within the bore of the screw holder.

9. The screw insertion system of claim 1 , wherein an outer diameter of the screw holder does not exceed the second diameter of the head.

10. The screw insertion system of claim 1 , wherein the drive element of the head is an internal hex drive.

11. A screw insertion system comprising:
a screw having a threaded shaft and a head connected to the threaded shaft, the head having a conically tapered outer surface increasing in distance from a central longitudinal axis of the screw from a free end of the head towards a larger diameter adjacent the connection between the head and the threaded shaft, the conically tapered outer surface having at least one helically extending partially rounded threads, the head having a recessed drive element open to the free end of the head; and
a tubular screw holder having an outer surface and internal bore extending between a leading end and a trailing end for receiving the screw, the leading end having a conically tapered inner threaded portion for engaging the conically tapered outer thread of the head, the tubular screw holder outer surface having a diameter less than or equal to a maximum diameter of the conically tapered head.

12. The screw insertion system of claim 11 , further comprising a driver extending through a base in the tubular screw holder for engaging the recessed drive element in the head.

13. The screw insertion system of claim 11 , wherein the at least one partially rounded thread on the head and a thread of the conically tapered inner threaded portion on the screw holder are left-handed threads.

14. The screw insertion system of claim 11 , wherein the recessed drive element of the head is an internal hex drive.

15. The screw insertion system of claim 11 , wherein the at least one helically extending partially rounded thread has a rounded root and a flattened crests.

16. The screw insertion system of claim 11 , wherein the conically tapered outer surface has an opening angle of about 20°.

17. The bone fastener of claim 16 , wherein the at least one helically extending partially rounded thread on the head has curved flanks, a curved root intermediate the curved flanks, and a flat crest on the conically tapered outer surface of the head extending between adjacent curved flanks forming the at least one helically extending partially rounded thread.

18. A bone fastener comprising:
a threaded shaft at a leading end and a head connected to the shaft at a trailing end, the head having a threaded outer surface extending from a free end to an end connected to the shaft;
the head having a first diameter at the free end and a second diameter at the end connected to the shaft, each of the first diameter and the second diameter being measured at a root of a thread of the threaded outer surface, a crest adjacent to the second diameter being a maximum diameter of the bone fastener; and
the first diameter being less than the second diameter.

19. The bone fastener as claimed in claim 18 , wherein the threaded shaft has a threaded portion at the leading end.

20. The bone fastener as claimed in claim 18 , wherein the threaded outer surface on the head has a conical shape.

21. The bone fastener as claimed in claim 20 , wherein the conical shape has an opening angle of 18° to 22°.

22. The bone fastener as claimed in claim 18 , wherein the threaded outer surface of the head includes left-hand threads and the threaded shaft includes right-hand threads.

23. The bone fastener as claimed in claim 22 , wherein the threaded outer surface of the head includes double or triple lead threads.

Assignees

• Stryker European Holdings I Llc

Inventors

• Zander Nils
• Wieland Manfred

Classifications

• A61B17/8891

  at its periphery · CPC title

• A61B17/921

  for intramedullary devices · CPC title

• A61B17/862 Primary

  at the periphery of the screw head · CPC title

• A61B17/8615

  at the central region of the screw head · CPC title

• A61B17/7233 Primary

  with special means of locking the nail to the bone · CPC title