Self-compressing screws for generating and applying compression within a body

Patent metadata

Field	Value
Publication number	US-10898249-B2
Application number	US-201615009521-A
Country	US
Kind code	B2
Filing date	Jan 28, 2016
Priority date	Jan 28, 2015
Publication date	Jan 26, 2021
Grant date	Jan 26, 2021

Abstract

A compression screw comprising: a shaft capable of being stretched, the shaft having a proximal end and a distal end, the proximal end of the shaft comprising a bone-engaging feature and the distal end of the shaft comprising a distal screw thread, and the proximal end of the shaft comprising a drive feature for turning the shaft; wherein inserting the compression screw into bone across a fracture line generates a force, and wherein the force generates a stress in the shaft that causes the shaft to stretch to less than its elastic limit; and wherein, after the shaft is inserted into a bone, the shaft attempts to foreshorten to its original un-stretched condition, thereby generating and maintaining compression across the fracture line.

First claim

What is claimed is:

1. A compression screw comprising:
a shaft having a longitudinal axis capable of being stretched, said shaft having a proximal end and a distal end, said proximal end of said shaft comprising an external proximal screw thread and said distal end of said shaft comprising a distal screw thread, a pitch of said proximal screw thread is finer than a pitch of said distal screw thread, and said proximal end of said shaft comprises a drive feature for turning said shaft, wherein said compression screw is a single component, wherein said shaft is a single unitary piece of metal that is slotless,
wherein inserting said compression screw into bone across a fracture line is configured to generate a force, and wherein said force is configured to generate a stress in said shaft that causes said shaft to stretch to less than its elastic limit, wherein the shaft is configured to reversibly axially stretch along the longitudinal axis from an original un-stretched condition to a stretched condition, wherein the stretched condition is longer than the original un-stretched condition, and
wherein, after said shaft is inserted into the bone, said shaft is configured to attempt to axially contract along the longitudinal axis to the original un-stretched condition, thereby generating and maintaining compression across the fracture line.

2. The compression screw according to claim 1 wherein said shaft comprises a low modulus alloy.

3. The compression screw according to claim 2 wherein said low modulus alloy is a shape memory or superelastic alloy.

4. The compression screw according to claim 3 wherein said shape memory or superelastic alloy comprises Nitinol.

5. The compression screw according to claim 1 wherein said drive feature comprises at least one selected from the group consisting of a slot, a cruciform recess, a hex recess and a hexalobe recess.

6. The compression screw according to claim 1 wherein said distal end of said shaft comprises a self-cutting feature.

7. The compression screw according to claim 1 wherein said external proximal screw thread and said distal screw thread are mirrored so as to increase the compression-holding capabilities of the compression screw.

8. The compression screw according to claim 1 wherein, when said shaft attempts to foreshorten to the original un-stretched condition, it does so at a load which is engineered to be low enough so as not to strip said distal screw thread through the bone.

9. The compression screw according to claim 1 wherein said shaft has a cross-sectional area that is engineered to control the recovery load so as not to cause said distal screw thread to pull through the bone.

10. The compression screw according to claim 1 wherein said distal screw thread and said external proximal screw thread are spaced apart and separated by a portion of said shaft that is threadless.

11. The compression screw according to claim 1 wherein said shaft includes a cannulation that extends from said proximal end of said shaft to said distal end of said shaft.

12. The compression screw according to claim 1 wherein said external proximal screw thread and said distal thread have a cross sectional shape defined by an inclined portion and a flat portion, wherein the flat portion is substantially perpendicular to the longitudinal axis.

13. The compression screw according to claim 1 wherein the proximal end of said shaft that comprises the external proximal screw thread is the most proximal end of the compression screw.

14. A compression screw comprising:
a shaft having a longitudinal axis capable of being stretched, said shaft having a proximal end and a distal end, said proximal end of said shaft comprising an external proximal screw thread and said distal end of said shaft comprising a distal screw thread, said external proximal screw thread having a finer pitch than said distal screw thread, and said proximal end of said shaft comprises a drive feature for turning said shaft, wherein said compression screw is a single component, and said shaft is a single unitary piece of metal that is slotless,
wherein inserting said compression screw into bone across a fracture line is configured to generate a stretching force along the longitudinal axis of said compression screw due to a pitch differential between said distal screw thread and said external proximal screw thread, and wherein said stretching force is configured to generate a stress in said shaft that causes said shaft to stretch to less than its elastic limit, wherein the shaft is configured to reversibly axially stretch along the longitudinal axis from an original un-stretched condition to a stretched condition, wherein the stretched condition is longer than the original un-stretched condition, and
wherein, after said shaft is inserted into the bone, said shaft is configured to attempt to axially contract along the longitudinal axis to the original un-stretched condition, thereby generating and maintaining compression across the fracture line.

15. The compression screw according to claim 14 wherein, when said shaft attempts to foreshorten to the original un-stretched condition, it does so at a load which is engineered to be low enough so as not to strip either said external proximal screw thread or said distal screw thread through the bone.

16. The compression screw according to claim 14 wherein said distal screw thread and said external proximal screw thread are spaced apart and separated by a portion of said shaft that is threadless.

17. The compression screw according to claim 14 wherein said shaft includes a cannulation that extends from said proximal end of the shaft to said distal end of said shaft.

18. The compression screw according to claim 14 wherein said external proximal screw thread and said distal thread have a cross sectional shape defined by an inclined portion and a flat portion, wherein the flat portion is substantially perpendicular to the longitudinal axis.

19. The compression screw according to claim 14 wherein the proximal end of said shaft that comprises the external proximal screw thread is the most proximal end of the compression screw.

20. A compression screw comprising:
a shaft having a longitudinal axis capable of being stretched, said shaft having a proximal end and a distal end, said proximal end of said shaft comprising an external proximal screw thread and said distal end of said shaft comprising a distal screw thread, wherein a pitch of said external proximal screw thread is finer than a pitch of said distal screw thread, said distal screw thread and said external proximal screw thread are spaced apart and separated by a portion of said shaft that is threadless, and said proximal end of said shaft comprises a drive feature for turning said shaft, wherein said compression screw is a single component, wherein said shaft is a single unitary piece of metal that is slotless,
wherein inserting said compression screw into bone across a fracture line is configured to generate a force, and wherein said force is configured to generate a stress in said shaft that causes said shaft to stretch to less than its elastic limit, wherein the shaft is configured to reversibly axially stretch along the longitudinal axis from an original un-stretched condition to a stretched condition, wherein the stretched condition is longer than the original un-stretched condition, and
wherein, after said shaft is inserted into the bone, said shaft is configured to attempt to axially contract along the longitudinal axis to the or

Assignees

• Mx Orthopedics Corp
• Arthrex Inc

Inventors

• Palmer Matthew
• Nealon Kaitlyn
• Devaney Robert
• Fonte Matthew

Classifications

• A61B17/7037

  wherein pivoting is blocked when the rod is clamped · CPC title

• A61B17/866

  Material or manufacture · CPC title

• A61B17/864

  hollow, e.g. with socket or cannulated · CPC title

• A61B17/863 Primary

  with thread interrupted or changing its form along shank, other than constant taper · CPC title