US20130253596A1

US20130253596A1 - Triple lead bone screw

Info

Publication number: US20130253596A1
Application number: US13/776,479
Authority: US
Inventors: David Crook; Peter Harris; Chester Sharps
Original assignee: Amedica Corp
Current assignee: Sintx Technologies Inc
Priority date: 2009-06-19
Filing date: 2013-02-25
Publication date: 2013-09-26
Also published as: US20110152948A1; EP2442740A1; AU2010262817A1; US8382811B2; BRPI1012292A2; WO2010148299A1; TR201111950T1; KR20120084663A; MX2011012730A; AU2010262817B2

Abstract

Pedicle screw assemblies and related bone screws. In some embodiments, the bone screw may comprise a head portion and an axial shaft. The axial shaft may comprise a threaded portion comprising a triple lead thread disposed about the axial shaft. The axial shaft may further comprise a tapering portion and a non-tapering portion. The tapering portion may comprise multiple tapering portions tapering at differing rates, and may be positioned adjacent to a tip of the axial shaft. Each of the three leads may extend coextensively along at least a majority of the length of the axial shaft, the threaded portion, the tapering portion, and/or the non-tapering portion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No. 12/818,749, filed on Jun. 18, 2010, and titled “TRIPLE LEAD BONE SCREW,” which claims the benefit of U.S. Provisional Patent Application No. 61/218,574, filed on Jun. 19, 2009, and also titled “TRIPLE LEAD BONE SCREW.” Both of the aforementioned applications are incorporated by reference herein in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to a triple lead bone screw for use in surgical applications. More specifically, the present invention relates to a triple lead bone screw for use in spinal surgical applications, such as pedicle screw applications and the like.

BACKGROUND OF THE INVENTION

Triple lead screws are used in a variety of applications, including bone screw applications. These screws utilize three thread starts/leads between the distal end (i.e. tip) of the screw and the proximal end (i.e. head) of the screw. The three thread starts are typically spaced apart by about 120 degrees. The screws may be used to engage bone, or, more often, the triple lead portion is used to engage an anatomical plate or other implant structure. The advantage of triple lead screws relative to single or double lead screws is that triple lead screws are advanced farther with fewer turns, i.e. they are placed more quickly and with less effort. The disadvantage of triple lead screws relative to single or double lead screws is that triple lead screws typically have a lower pullout or backout strength, i.e. they may become dislodged more easily and with less effort.
What is still needed in the art is a triple lead pedicle screw or the like that overcomes the above mentioned disadvantage.

BRIEF SUMMARY OF THE INVENTION

In various exemplary embodiments, the present invention provides a triple lead pedicle screw or the like that is capable of being placed quickly with minimal effort and that resists pullout or backout at least as effectively as comparable single or double lead screws. This triple lead bone screw is ideally suited for the surgical correction of spinal deformities and other similar surgical procedures in which multiple screws must be placed. In such surgical procedures, a surgeon may be come fatigued and time is of the essence.
In one exemplary embodiment, the present invention provides a pedicle screw assembly, including: a bone screw having a head portion and a thread portion, wherein the thread portion includes an axial shaft and a triple lead thread disposed about the axial shaft; and a rod retention member selectively coupled to the head portion of the bone screw. Optionally, the triple lead thread of the thread portion of the bone screw includes leads that start with about 120 degrees of separation. Optionally, the triple lead thread of the thread portion of the bone screw includes leads that originate at different points along the axial shaft of the thread portion of the bone screw. Optionally, the triple lead thread of the thread portion of the bone screw includes leads that terminate at different points along the axial shaft of the thread portion of the bone screw. Optionally, the axial shaft of the thread portion of the bone screw includes a first tapering portion proximate a tip of the axial shaft of the thread portion of the bone screw. Optionally, the axial shaft of the thread portion of the bone screw includes a second tapering portion proximate the tip of the axial shaft of the thread portion of the bone screw. Preferably, the second tapering portion tapers more steeply than the first tapering portion. Optionally, the axial shaft of the thread portion of the bone screw includes a reduced diameter portion proximate the head portion of the bone screw. Optionally, the axial shaft of the thread portion of the bone screw includes one or more tapering portions proximate the head portion of the bone screw. Preferably, the rod retention member is selectively pivotably coupled to the head portion of the bone screw.
In another exemplary embodiment, the present invention provides a bone screw, including: a head portion; and a thread portion, wherein the thread portion includes an axial shaft and a triple lead thread disposed about the axial shaft. Optionally, the triple lead thread of the thread portion of the bone screw includes leads that start with about 120 degrees of separation. Optionally, the triple lead thread of the thread portion of the bone screw includes leads that originate at different points along the axial shaft of the thread portion of the bone screw. Optionally, the triple lead thread of the thread portion of the bone screw includes leads that terminate at different points along the axial shaft of the thread portion of the bone screw. Optionally, the axial shaft of the thread portion of the bone screw includes a first tapering portion proximate a tip of the axial shaft of the thread portion of the bone screw. Optionally, the axial shaft of the thread portion of the bone screw includes a second tapering portion proximate the tip of the axial shaft of the thread portion of the bone screw. Preferably, the second tapering portion tapers more steeply than the first tapering portion. Optionally, the axial shaft of the thread portion of the bone screw includes a reduced diameter portion proximate the head portion of the bone screw. Optionally, the axial shaft of the thread portion of the bone screw includes one or more tapering portions proximate the head portion of the bone screw.
In a further exemplary embodiment, the present invention provides a bone screw, including: a head portion; and a thread portion, wherein the thread portion includes an axial shaft and a triple lead thread disposed about the axial shaft, wherein the axial shaft of the thread portion of the bone screw includes a first tapering portion proximate a tip of the axial shaft of the thread portion of the bone screw, and wherein the axial shaft of the thread portion of the bone screw includes a second tapering portion proximate the tip of the axial shaft of the thread portion of the bone screw, wherein the second tapering portion tapers more steeply than the first tapering portion. Optionally, the triple lead thread of the thread portion of the bone screw includes leads that originate at different points along the axial shaft of the thread portion of the bone screw. Optionally, the triple lead thread of the thread portion of the bone screw includes leads that terminate at different points along the axial shaft of the thread portion of the bone screw. Optionally, the axial shaft of the thread portion of the bone screw includes a reduced diameter portion proximate the head portion of the bone screw. Optionally, the axial shaft of the thread portion of the bone screw includes one or more tapering portions proximate the head portion of the bone screw.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated and described herein with reference to the various drawings, in which like reference numbers are used to denote like screw components, as appropriate, and in which:

FIG. 1 is a planar side view of one exemplary embodiment of the triple lead pedicle screw assembly of the present invention, including the triple lead bone screw of the present invention and an associated rod retention member;

FIG. 2 is a perspective view of the triple lead pedicle screw assembly of FIG. 1;

FIG. 3 is a perspective view of one exemplary embodiment of the bone screw of the present invention;

FIG. 4 is a planar side view of the bone screw of FIG. 3;

FIG. 5 is another planar side view of the bone screw of FIG. 3;

FIG. 6 is a perspective view of another exemplary embodiment of the bone screw of the present invention;

FIG. 7 is a planar side view of the bone screw of FIG. 6; and

FIG. 8 is another planar side view of the bone screw of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

Again, in various exemplary embodiments, the present invention provides a triple lead pedicle screw or the like that is capable of being placed quickly with minimal effort and that resists pullout or backout at least as effectively as comparable single or double lead screws. This triple lead bone screw is ideally suited for the surgical correction of spinal deformities/anomalies/trauma and other similar surgical procedures in which multiple screws must be placed. In such surgical procedures, a surgeon may be come fatigued and operative time is of the essence.
Referring to FIGS. 1 and 2, in one exemplary embodiment, the triple lead pedicle screw assembly 10 of the present invention includes a triple lead bone screw 12 and a rod retention member 14.
The triple lead bone screw 12 includes a head portion 16 and a threaded portion 18. The head portion 16 of the triple lead bone screw 12 consists of an enlarged structure, such as a wholly or partially spherical structure, a wholly or partially cylindrical structure, or the like, having one or more tool receiving recesses 20 manufactured into the top surface thereof, by which the triple lead bone screw 12 is grasped and/or turned. Optionally, three such tool receiving recesses 20 are utilized and are spaced apart by about 120 degrees, although it will be readily apparent to those of ordinary skill in the art that other suitable configurations may be utilized. The threaded portion 18 of the triple lead bone screw 12 consists of three thread starts/leads between the distal end (i.e. tip) 22 of the screw 12 and the proximal end (i.e. head) 24 of the screw 12. Optionally, the three thread starts are spaced apart by about 120 degrees, although it will be readily apparent to those of ordinary skill in the art that other suitable configurations may be utilized. Optionally, the three thread starts/leads also originate and/or terminate at different positions along the length of the screw 12. In other words, the three thread starts/leads may or may not coincide along the length of the screw 12 and may be spaced apart by any desired constant or variable distance. Finally, one or more of the three thread starts/leads may be selectively broken or notched to create a biting surface, such as near the tip 22 of the screw 12 so that the screw will advance into bone from the first tum. Any suitable thickness, pitch, or other dimensions may be utilized, as well as any suitable materials (e.g. a biocompatible metal, ceramic, or plastic, bony material, etc.).
The rod retention member 14 consists of a U-shaped member 26 having a hole in the bottom. The threaded portion 18 of the bone screw 12 is disposed through this hole, with the head portion 16 of the bone screw being pivotably seated in the interior bottom of the U-shaped member, prior to the screw 12 being driven into bone. The rod retention member 14 includes a plurality of internally threaded, concentrically arranged, vertically extending arm members 28 between which a stabilizing rod or other similar stabilizing structure (not illustrated) is selectively disposed. This stabilizing rod is then “locked” into place via the engagement of an externally threaded cap (not illustrated) into the internal threads of the arm members 28, thereby “locking” the orientation of the rod retention member 14 with respect to the head portion 16 of the triple lead bone screw 12, as the stabilizing rod is in direct or indirect contact with the head portion 16 of the triple lead bone screw 12. It will be readily apparent to those of ordinary skill in the art that various other structures may also be disposed between the stabilizing rod and either or both of the externally threaded cap and the head portion 16 of the triple lead bone screw 12. In this manner, screws 12 may be placed in different anatomical structures, or different parts of the same anatomical structure, and securely joined by stabilizing structures in a predetermined configuration and alignment.
Referring to FIGS. 3-5, in one exemplary embodiment, the triple lead bone screw 12 of the present invention includes a head portion 16 and a threaded portion 18. The head portion 16 of the triple lead bone screw 12 consists of an enlarged structure, such as a wholly or partially spherical structure, a wholly or partially cylindrical structure, or the like, having one or more tool receiving recesses 20 manufactured into the top surface thereof, by which the triple lead bone screw 12 is grasped and/or turned. Optionally, three such tool receiving recesses 20 are utilized and are spaced apart by about 120 degrees, although it will be readily apparent to those of ordinary skill in the art that other suitable configurations may be utilized. The threaded portion 18 of the triple lead bone screw 12 consists of three thread starts/leads between the distal end (i.e. tip) 22 of the screw 12 and the proximal end (i.e. head) 24 of the screw 12. Optionally, the three thread starts are spaced apart by about 120 degrees, although it will be readily apparent to those of ordinary skill in the art that other suitable configurations may be utilized. Optionally, the three thread starts/leads also originate and/or terminate at different positions along the length of the screw 12. In other words, the three thread starts/leads may or may not coincide along the length of the screw 12 and may be spaced apart by any desired constant or variable distance. Finally, one or more of the three thread starts/leads may be selectively broken or notched to create a biting surface, such as near the tip 22 of the screw 12 so that the screw will advance into bone from the first tum. Any suitable thickness, pitch, or other dimensions may be utilized, as well as any suitable materials (e.g. a biocompatible metal, ceramic, or plastic, bony material, etc.).
Referring specifically to FIG. 5, the threaded portion 18 of the screw 12 includes an axial shaft 30 that may have a non-tapering portion 32, a first tapering portion 34, and a second tapering portion 36 disposed, in order, between the head portion 16 of the screw 12 and the rounded or pointed tip 38 of the screw 12. Preferably, the taper of the second tapering portion 36 is greater than the taper of the first tapering portion 34, with the second tapering portion sweeping a 45-degree arc, a 60-degree arc, etc. The threads are disposed about these various segments of the screw 12.
Referring to FIGS. 6-8, in another exemplary embodiment, the triple lead bone screw 12 of the present invention includes a head portion 16 and a threaded portion 18. The head portion 16 of the triple lead bone screw 12 consists of an enlarged structure, such as a wholly or partially spherical structure, a wholly or partially cylindrical structure, or the like, having one or more tool receiving recesses 20 manufactured into the top surface thereof, by which the triple lead bone screw 12 is grasped and/or turned. Optionally, three such tool receiving recesses 20 are utilized and are spaced apart by about 120 degrees, although it will be readily apparent to those of ordinary skill in the art that other suitable configurations may be utilized. The threaded portion 18 of the triple lead bone screw 12 consists of three thread starts/leads between the distal end (i.e. tip) 22 of the screw 12 and the proximal end (i.e. head) 24 of the screw 12. Optionally, the three thread starts are spaced apart by about 120 degrees, although it will be readily apparent to those of ordinary skill in the art that other suitable configurations may be utilized. Optionally, the three thread starts/leads also originate and/or terminate at different positions along the length of the screw 12. In other words, the three thread starts/leads may or may not coincide along the length of the screw 12 and may be spaced apart by any desired constant or variable distance. Finally, one or more of the three thread starts/leads may be selectively broken or notched to create a biting surface, such as near the tip 22 of the screw 12 so that the screw will advance into bone from the first tum. Any suitable thickness, pitch, or other dimensions may be utilized, as well as any suitable materials (e.g. a biocompatible metal, ceramic, or plastic, bony material, etc.).
Referring specifically to FIG. 8, the threaded portion 18 of the screw 12 includes an axial shaft 30 that may have a non-tapering portion 32, a first tapering portion 34, and a second tapering portion 36 disposed, in order, between the head portion 16 of the screw 12 and the rounded or pointed tip 38 of the screw 12. Preferably, the taper of the second tapering portion 36 is greater than the taper of the first tapering portion 34, with the second tapering portion sweeping a 45-degree arc, a 60-degree arc, etc. The threads are disposed about these various segments of the screw 12. In this exemplary embodiment, a reduced diameter portion 40 and one or more tapering portions 42 are also disposed along the axial shaft 30 between the head portion 16 and the threaded portion 18 of the screw 12.
Axial pullout testing of the triple lead bone screw 12 of the present invention demonstrated performance comparable to that of a conventional single lead bone screw.
Although the present invention has been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present invention, are contemplated thereby, and are intended to be covered by the following claims.

Claims

1. A pedicle screw assembly, comprising:

a bone screw comprising a head portion and a threaded portion, wherein the threaded portion comprises an axial shaft and a triple lead thread disposed about the axial shaft, wherein the axial shaft comprises a tapering portion and a non-tapering portion, wherein the tapering portion is positioned adjacent to a tip of the axial shaft, wherein the triple lead thread comprises three distinct thread leads, wherein each of the three leads terminates at a different point along a tapering portion of the axial shaft, and wherein each of the three leads extends coextensively along at least a majority of the length of the threaded portion; and

a rod retention member selectively coupled to the head portion of the bone screw.

2. The pedicle screw assembly of claim 1, wherein the rod retention member comprises a U-shaped member comprising a hole for receiving the head portion of the bone screw.

3. The pedicle screw assembly of claim 2, wherein the head portion is configured to be pivotably seated in the U-shaped member.

4. The pedicle screw assembly of claim 1, wherein each of the three leads extends coextensively along at least substantially the entire length of the threaded portion.

5. The pedicle screw assembly of claim 1, wherein the axial shaft further comprises a second tapering portion.

6. The pedicle screw assembly of claim 5, wherein the second tapering portion is positioned between the tapering portion and the non-tapering portion.

7. The pedicle screw assembly of claim 6, wherein the tapering portion tapers more steeply than the second tapering portion.

8. The pedicle screw assembly of claim 5, wherein at least one of the three leads terminates at a point along the second tapering section.

9. A bone screw, comprising:

a head portion; and

a threaded portion, wherein the threaded portion comprises an axial shaft and a triple lead thread disposed about the axial shaft, wherein the axial shaft comprises a tapering portion and a non-tapering portion, wherein the tapering portion is positioned adjacent to a tip of the axial shaft, wherein the triple lead thread comprises three distinct thread leads, wherein at least two of the three leads terminate at a different points along the tapering portion of the axial shaft, and wherein each of the three leads extends coextensively along at least a majority of the length of the axial shaft.

10. The bone screw of claim 9, wherein at least one of the three thread leads comprises a biting surface.

11. The bone screw of claim 10, wherein each of the three thread leads comprises a biting surface.

12. The bone screw of claim 10, wherein the biting surface comprises a notch formed within the at least one of the three thread leads.

13. The bone screw of claim 9, wherein the three thread leads start with about 120 degrees of separation.

14. The bone screw of claim 9, wherein at least one of the three thread leads originates at a different point along the threaded portion than the other two thread leads.

15. The bone screw of claim 9, wherein the axial shaft further comprises a reduced diameter portion, and wherein the reduced diameter portion is positioned adjacent to the head portion.

16. The bone screw of claim 9, wherein the axial shaft further comprises a second tapering portion.

17. The bone screw of claim 16, wherein the second tapering portion is positioned between the tapering portion and the non-tapering portion.

18. The bone screw of claim 16, wherein the tapering portion tapers more steeply than the second tapering portion.

19. The bone screw of claim 9, wherein each of the three leads terminates at a different point along the tapering portion of the axial shaft.

20. A bone screw, comprising:

a head portion;

an axial shaft; and

a tip, wherein the axial shaft comprises a tapering portion and a non-tapering portion, wherein the axial shaft further comprises a triple lead thread disposed about the axial shaft, wherein the triple lead thread comprises three distinct thread leads, wherein the tapering portion is positioned adjacent to the tip, and wherein each of the three leads extends coextensively along at least a majority of the length of the non-tapering portion.