Selective axis anchor screw posterior lumbar plating system

• US 20050216005A1
• Filed: 05/19/2005
• Published: 09/29/2005
• Est. Priority Date: 05/17/2001
• Status: Abandoned Application

• Current Assignee: Medical Device Advisory Development Group, LLC
• Original Assignee: Medical Device Advisory Development Group, LLC
• Inventors: Howland, Robert S.
• Application Number:
  US11/133,708
• Publication Number:
  US 20050216005A1
• Time in Patent Office: Days
• US Class Current: 606/281
• CPC Class Codes: A61B 17/7007 Parts of the longitudinal elements, e.g. their ends, being specially adapted to fit around the screw or hook heads
• CPC Class Codes: A61B 17/701 Longitudinal elements with a non-circular, e.g. rectangular, cross-section A61B17/7005, A61B17/7007 take precedence
• CPC Class Codes: A61B 17/7023 with a pivot joint
• CPC Class Codes: A61B 17/7035 Screws or hooks, wherein a rod-clamping part and a bone-anchoring part can pivot relative to each other
• CPC Class Codes: A61B 17/7038 to a different extent in different directions, e.g. within one plane only
• CPC Class Codes: A61B 17/7041 with single longitudinal rod offset laterally from single row of screws or hooks A61B17/7044 takes precedence
• CPC Class Codes: A61B 17/7058 Plates mounted on top of bone anchor heads or shoulders
• CPC Class Codes: A61B 17/8625 Shanks, i.e. parts contacting bone tissue
• CPC Class Codes: A61B 17/863 with thread interrupted or changing its form along shank, other than constant taper

Abstract

An anchor screw assembly includes a screw having a threaded portion and a head portion to which a swing bolt is pivotally coupled. A clamp assembly includes lower and upper clamp portions assembled into connecting beams that are securable on the swing bolt by a fastener. The clamp portions include first passages for receiving an intermediate region of the swing bolt therethrough to receivably retain the clamp assembly on the connecting beam and on the swing bolt. The head portion of the screw includes a shoulder, and the lower clamp portion has a seat that frictionally engages the shoulder when the clamp assembly is fully secured on the connecting beam and swing bolt, thereby securing the swing bolt relative to the screw. Multiple screw assemblies are screwed into adjacent vertebrae, and a connecting member is secured by the clamp assemblies between the anchor screw assemblies to stabilize the vertebrae. An optional cross-brace member interconnects two or more connecting members.

Claims

1. A spinal fixation system, comprising:

a first anchor screw assembly comprising a first screw having a threaded portion, a first swing bolt pivotally coupled to the screw and comprising an intermediate region extending along a longitudinal axis of the swing bolt, a first clamp assembly comprising a first passage for receiving the first swing bolt therethrough, the intermediate region and the first passage having similar cross-sections, and a first fastener for securing the first clamp assembly on the first swing bolt;

a second anchor screw assembly comprising a second screw having a threaded portion, a second swing bolt pivotally coupled to the second screw and comprising an intermediate region extending along a longitudinal axis of the second swing bolt, a second clamp assembly comprising a second passage for receiving the second swing bolt therethrough, the intermediate region and the second passage having similar cross-sections, and a second fastener for securing the second clamp assembly on the swing bolt; and

a connecting member having a plurality of slots extending therethrough, wherein each of the first and second clamp assemblies are adapted to slidably engage one of said slots, and wherein said connecting member comprises a first segment extending in a first plane, and a second segment extending in a second plane, said first plane and said second plane defining a first connecting angle therebetween.

2. The spinal fixation system of claim 1, wherein the first swing bolt comprises a threaded region opposite the first screw, and wherein the first fastener comprises a nut threadable onto the threaded region of the first swing bolt.

3. The spinal fixation system of claim 2, wherein the intermediate region of the first swing bolt comprises a smooth walled region for slidably receiving the first clamp assembly thereon, the smooth walled region being located between the threaded region and the first screw.

4. The spinal fixation system of claim 1, wherein the first clamp assembly comprises first and second clamp portions, each clamp portion having a first passage therethrough for receiving the first swing bolt therethrough, the first clamp assembly further comprising a narrowed waist portion for engaging a slot of said connecting member.

5. The spinal fixation system of claim 1, wherein the first clamp assembly comprises:

an upper clamp portion having a generally disc-shaped top portion and a smaller generally cylindrical bottom portion, and having a generally cylindrical central passage therethrough, the central passage having an upper section and a lower section wherein the upper section has a predetermined size for fitting an intermediate region of a swing bolt, and the lower section has an opening slightly larger than that of the upper section for mating with a lower clamp portion to provide a press fit therewith, and

a lower clamp portion having a generally disc-shaped bottom portion and a generally cylindrical shaped top portion, and a mating portion extending from an intermediate straight portion for forming a light press fit with the inside of the lower section of the central passage of the upper clamp portion, and adapted to form a sliding fit of the clamp assembly within an opening in a connecting beam, and the lower clamp portion includes a central passage therethrough having a size substantially identical to that of the upper section of the central passage of the upper clamp portion for receiving therethrough a swing bolt, and the lower clamp portion having a curved seat in the form of a recess formed in the bottom of the bottom portion of the lower clamp portion adapted to receive and engage a curved shoulder of an anchor screw in a manner to allow a swing bolt and the resulting clamp assembly to rotate and pivot relative to one another to facilitate selective axis spinal fixation.

6. A spinal fixation system as in claim 5 wherein the seat of the lower clamp portion is spherical.

7. A spinal fixation system as in claim 5 wherein the seat of the lower clamp portion is conical.

8. A spinal fixation system as in claim 5 wherein the seat of the lower clamp portion is cylindrical.

9. A spinal fixation system as in claim 5 wherein a lower surface of the generally disc-shaped top portion of the upper clamp portion and the generally disc-shaped bottom portion of the lower clamp portion are adapted to firmly clamp onto a connecting beam as a result of tightening a fastener onto an end of a swing bolt extending the central passages of the upper and lower clamp portions.

10. A spinal fixation system as in claim 5 including a plurality of upper clamp portions and lower clamp portions for receiving a like plurality of swing bolts and for forming a fit for each resulting clamp assembly with different openings in a connecting beam.

11. A spinal fixation system as in claim 5 wherein the mating portion extending from the intermediate straight portion of the lower clamp portion has an external diameter smaller than the internal diameter of the opening in the lower section of the upper clamp portion to provide a light press fit when the upper and lower clamp portions are captured in an opening in a connecting beam.

12. The spinal fixation system of claim 1, wherein the first screw comprises a shoulder adjacent the first swing bolt, and wherein the first clamp assembly substantially engages the shoulder when the first clamp assembly is secured on the first swing bolt in a manner that allows the first swing bolt to pivot with respect to the first screw.

13. The spinal fixation system of claim 1, wherein said connecting member comprises:

a first segment having a first slot formed therein, and

a second segment having a second slot formed therein.

14. The spinal fixation system of claim 13, further comprising:

a third segment extending in a third plane and having a third slot formed therein, said third segment located between and separating said first segment and said second segment, and

wherein said first segment and said third segment define a second connecting angle therebetween, and said second segment and said third segment define a third connecting angle therebetween.

15. A method for stabilizing vertebrae relative to one another using a plurality of swing bolt anchor screws, each swing bolt anchor screw comprising a swing bolt pivotally coupled to a threaded portion, the vertebrae being disposed adjacent one another along a central spinal axis, the method comprising:

screwing a threaded portion of a first swing bolt anchor screw into a first vertebra until a first pivot axis of the first swing bolt anchor screw has a predetermined orientation with respect to the spinal axis;

screwing a threaded portion of a second swing bolt anchor screw into a second vertebra adjacent the first vertebra until a second pivot axis of the second swing bolt anchor screw is substantially transverse to the first pivot axis;

placing a connecting member on the swing bolts of the first and second swing bolt anchor screws, the connecting member having at least one clamp member engaged in at least one slot through which at least one of the swing bolts extends, the connecting member extending at least between the first and second anchor screws and having at least a first segment in a first plane and a second segment in a second plane, with said first plane and said second plane defining a connecting angle therebetween; and

securing the at least one clamp member on at least one of the swing bolts of the first and second swing bolt anchor screws, thereby securing the connecting member to the at least one of the swing bolt anchor screws.

16. The method of claim 15, further comprising:

screwing a threaded portion of a third anchor screw into a third vertebra adjacent the first vertebra;

placing the connecting member on a swing bolt of the third anchor screw, the connecting member thereby also extending between the first swing bolt anchor screw and the third anchor screw; and

securing the connecting member on the third anchor screw.

17. The method of claim 16, wherein the third anchor screw comprises a third swing bolt anchor screw, wherein the threaded portion of the third swing bolt anchor screw is screwed into the third vertebra until a third pivot axis of the third swing bolt anchor screw is substantially transverse to the second pivot axis, and wherein a clamp member engaged in a slot on the connecting member is placed on a swing bolt of the third swing bolt anchor screw.

18. The method of claim 15, wherein the threaded portions of the first and second swing bolt anchor screws comprise head portions including shoulders, the swing bolts being pivotally coupled to the head portions, and wherein a lower portion of the clamp member frictionally engages at least one of the shoulders, thereby securing the at least one of the swing bolts with respect to the threaded portions.

19. The method of claim 15, wherein the swing bolts comprise threaded regions, and wherein the clamp members are secured on the swing bolts by threading a fastener onto the threaded regions.

20. The method of claim 15, wherein the predetermined orientation of the first pivot axis is generally parallel to the spinal axis.

21. A spinal fixation system, comprising:

a first pair of anchor screws, each of which is connected to a first connecting beam;

a second pair of anchor screws, each of which is connected to a second connecting beam;

a brace member interconnecting said first connecting beam and said second connecting beam.

22. The spinal fixation system of claim 21, wherein said first connecting beam comprises an attachment base to which the brace member is connected.

23. The spinal fixation system of claim 22, further comprising a stud formed on a surface of said attachment base, the stud adapted to engage a slot formed on said brace member.

24. The spinal fixation system of claim 22, further comprising a bolt extending through a first slot formed on said attachment base and through a second slot formed on said brace member.

25. The spinal fixation system of claim 21, wherein said first connecting beam comprises a first segment extending in a first plane, and a second segment extending in a second plane, said first plane and said second plane defining a first connecting angle therebetween.

26. The spinal fixation system of claim 21, wherein said first connecting beam comprises:

a first connecting member section having a first slot formed therein,

a second connecting member section having a second slot formed therein, and

a first hinge connecting said first and second connecting member sections.

27. The spinal fixation system of claim 26, wherein said first connecting beam further comprises:

a third connecting member section having a third slot formed therein, and

a second hinge connecting said second and third connecting member sections.