Offset helix surgical fixation screws and methods of use

• US 6,503,251 B1
• Filed: 10/23/2000
• Issued: 01/07/2003
• Est. Priority Date: 10/23/2000
• Status: Expired due to Fees

• Current Assignee: John H. Shadduck
• Original Assignee: John H. Shadduck
• Inventors: Shadduck, John H.
• Primary Examiner(s): Philogene, Pedro
• Application Number:
  US09/694,417
• Time in Patent Office: 806 Days
• Field of Search: 606/72, 606/73, 606/232, 606/60, 606/62, 606/64, 606/65, 606/67, 411/187, 411/389, 411/397, 411/395, 411/413, 411/411, 411/415, 411/385
• US Class Current: 606/311
• CPC Class Codes: A61B 17/0401 Suture anchors, buttons or pledgets, i.e. means for attaching sutures to bone, cartilage or soft tissue; Instruments for applying or removing suture anchors A61B17/0642 takes precedence; fixation devices for tendons or ligaments A61F2/0811
• CPC Class Codes: A61B 17/8685 comprising multiple separate parts
• CPC Class Codes: A61B 2017/00004 (bio)absorbable, (bio)resorbable, resorptive for implantable prostheses A61F2210/0004
• CPC Class Codes: A61B 2017/0409 Instruments for applying suture anchors for applying suture clamps, clips or locks A61B2017/0488
• CPC Class Codes: A61B 2017/044 with a threaded shaft, e.g. screws
• CPC Class Codes: A61B 2017/0445 cannulated, e.g. with a longitudinal through-hole for passage of an instrument
• CPC Class Codes: A61B 2017/0458 Longitudinal through hole, e.g. suture blocked by a distal suture knot
• CPC Class Codes: A61F 2/0805 Implements for inserting tendons or ligaments
• CPC Class Codes: A61F 2/0811 Fixation devices for tendons or ligaments
• CPC Class Codes: A61F 2002/0858 Fixation of tendon or ligament between anchor and bone, e.g. interference screws, wedges
• CPC Class Codes: A61F 2002/087 Anchor integrated into tendons, e.g. bone blocks, integrated rings

Abstract

A surgical fixation screw that can be driven with significantly reduced torque thus allowing for theaded fixation bodies to be made substantially of bioabsorbable materials. The novel fixation body, also called an offset helix fixation body, extends along a first (central) axis. The fixation body comprises first and second helically-mating members that mate along a constant-lead helical interface that extends about a second (non-central) axis. The second axis is angularly offset from the first axis of the fixation body from about 1° to 20°. Alternatively, the second axis is parallel to, but laterally offset from, the first axis. Thus, the first and second members of the fixation body can travel helically relative to one another about the helical mating interface between a first insertion configuration and a second anchor configuration. In the insertion configuration, the screw'"'"'s outer periphery has a first (lesser) transverse sectional dimension to allow reduced torque in helically driving the screw into a space in a bone. After being driven into a space or bore, the first and second members then can be moved helically relative to one another about the helical mating interface to an anchor configuration in which the screws outer periphery is expanded radially outward to provide a second (greater) transverse sectional dimension for securing the fixation body in the space or bore.

Claims

1. A fixation device comprising:

an elongate body extending about a first axis of said body;

the body comprising a first member and a second member that mate along a helical interface that extends about a second axis;

wherein said helical interface provides for helical movement of said first member relative to said second member about said second axis between a first position and a second position;

wherein said first axis is offset from said second axis; and

wherein said offset axes thereby cause at least a portion of an outer periphery of said body assembly to be altered from a lesser cross-sectional dimension to a greater cross-sectional dimension when said first and second members are moved from said first position to said second position.

2. The fixation device of claim 1 wherein said body in said first position defines an outer periphery having a particular cross-section and in said second position defines an outer periphery having a greater cross-section in the distal end of the body.

3. The fixation device of claim 1 wherein said body in said first position defines an outer periphery having a particular cross-section and in said second position defines an outer periphery having a greater cross-section extending substantially along the length of the body.

4. The fixation device of claim 1 wherein said body in said first position defines a substantially cylindrical outer periphery for insertion into a bore and in said second position defines a conical outer periphery for anchoring said body assembly in the bore.

5. The fixation device of claim 1 further comprising a helical thread carried about the exterior of said body.

6. The fixation device of claim 1 wherein said second axis is angularly offset from said first axis.

7. The fixation device of claim 1 wherein said second axis is laterally offset relative to said first axis.

8. The fixation device of claim 1 wherein said first and second members are of a biocompatible metal.

9. The fixation device of claim 1 wherein at least one of said first and second members is of bioabsorbable material.

10. The fixation device of claim 1 further comprising a driver-engaging structure within the proximal end of said body.

11. The fixation device of claim 1 wherein said first and second members have cooperating faces along a helical mating interface, further comprising serrations in said faces for engaging one another.

12. The fixation device of claim 1 further comprising a longitudinal passageway extending between proximal and distal ends thereof.

13. The fixation device of claim 1 further comprising a suture or a loop attached to said fixation device.

14. The fixation device of claim 1 further comprising a gripping tooth surface in an exterior of the either the first or second member.

15. The fixation device of claim 5 wherein the radially-outward exposure of said helical interface between the first and second members is along the lands of said helical thread.

16. A bone fixation device, comprising:

a fixation body assembly extending about a longitudinal axis;

the fixation body comprising paired first and second members that slidably mate along a helical interface in said body;

at least one helical thread formed in an exterior of the body assembly; and

wherein in a particular relative helical position of the paired first and second members, a sharp distal portion of the helical thread of the first member is exposed for cutting into a bone.

17. The bone fixation device of claim 16, wherein the sharp distal portion of said first member is of a substantially strong material selected from the class consisting of metals, ceramics, plastics, or a combination thereof, and the second member is of a bioabsorbable material.

18. The bone fixation device of claim 16, wherein the second member is de-matable from the paired member in situ.

19. The bone fixation device of claim 16, wherein the second member is of resilient material.

20. A method for securing a fixation body in bone with a body assembly comprising first and second members that moveably mate about a helical interface of the fixation body to provide first and second relative helical positions of the first and second members, the central axis of the fixation body and the axis of the helical interface being offset, comprising the steps of:

providing a bore in the bone;

introducing the fixation body into the bore with the first and second members in the first position;

moving the first member of the fixation body relative to the second member about the helical interface toward the second position;

wherein the first position provides the fixation body with a lesser cross-sectional dimension to allow introduction into the bore with reduced force and the second position provides the fixation body with at least a portion having a greater cross-sectional dimension for anchoring the fixation body in the bore.

21. The method of claim 20 wherein the fixation body has at least one helical thread and the introducing step comprises helically driving the body into the bore.

22. The method of claim 20 wherein the moving step comprises applying a proximal tensioning force on either the first or second member to move the fixation body toward the second position.

23. The method of claim 20 wherein the moving step comprises applying torque to either the first or second member to cause relative helical movement between the members.

24. A method for securing an implantable body in a bone with a fixation body comprising first and second members that slidably mate along a helical interface in said body, said body having at least one helical thread formed in an exterior of the body, comprising the steps of:

helically driving the implantable body into the bone with the first and second members in a particular relative helical position that exposes a substantially sharp distal thread portion of the first member to thereby cut a path in the bone;

helically removing the first member of the body from the bone thereby leaving the second member in the bone; and

wherein the free space provided by removal of the first member provides for more rapid ingrowth around the second member to secure the implantable body in the bone.

25. The method of claim 24 wherein the second member is of a bioabsorbable material.