US20060036251A1 - Systems and methods for the fixation or fusion of bone - Google Patents

Abstract

A stem-like bone fixation device allows for bony in-growth on its surface and across fracture fragments or between bones that are to be fused.

Description

FIELD OF THE INVENTION
• This application relates generally to the fixation of bone.
BACKGROUND OF THE INVENTION
• Many types of hardware are available both for fracture fixation and for the fixation of bones that are to fused (arthrodesed).
• Metal and absorbable screws are routinely used to fixate bone fractures and osteotomies. It is important to the successful outcome of the procedure that the screw is able to generate the compressive forces helpful in promoting bone healing.
SUMMARY OF THE INVENTION
• The invention provides bone fixation devices and related methods for stabilizing bone segments. The systems and methods include a stem-like structure adapted for passage between adjacent bone segments. At least a portion of the stem-like structure includes a surface that enhances bony in-growth. Boney in-growth into the stem-like structure helps speed up the fusion process or fracture healing time.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of a bone fixation stem having a boney in-growth surface of a mesh configuration.
• FIG. 2 is a perspective view of an alternative embodiment of a bone fixation stem having a boney in-growth surface of a beaded configuration.
• FIG. 3 is a perspective view of an alternative embodiment of a bone fixation stem having a boney in-growth surface of a trabecular configuration.
• FIG. 4 is a schematic view of a bone fixation stem of the type shown in Fig. being inserted into bone across a fracture line or bone joint.
• FIG. 5 is a schematic view of a bone fixation stem positioned within bone and illustrating a boney in-growth surface of the stem extending across a fracture line or bone joint.
• FIG. 6 is a front plan view of an alternative embodiment of a bone fixation stem having a boney in-growth surface in which the stem has a conical configuration.
• FIG. 7 is front plan view of an alternative embodiment of a bone fixation stem having a boney in-growth surface in which the stem has a beveled distal tip.
• FIGS. 8A and 8B are schematics illustrating the insertion of a conical bone fixation stem of the type shown inFIG. 6 to reduce the gap between bone segments.
• FIG. 9 is a schematic illustrating a guidewire being introduced into bone across bone segments.
• FIG. 10 is a schematic similar toFIG. 9 and illustrating a drill bit being introduced over the guidewire.
• FIG. 11 is a schematic similar toFIG. 10 and illustrating a bore formed in the bone remaining after withdrawal of the drill bit.
• FIG. 12 is a schematic similar toFIG. 11 and illustrating insertion of a bone fixation stem into the pre-formed bore.
• FIG. 13 is an exploded front plan view illustrating the coupling of a pair of bone fixation stems by threaded engagement.
• FIG. 14 is a schematic illustrating a pair of bone fixation stems coupled together and inserted into bone across multiple bone segments.
• FIG. 15 is a front plan view illustrating passage of a bone fixation stem through a fenestration in another bone fixation stem.
• FIG. 16 is a schematic illustrating the placement of a series of bone fixation stems in bone.
DESCRIPTION OF THE PREFERRED EMBODIMENT
• Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention that may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
• FIG. 1 shows adevice10 sized and configured for the fixation of bone fractures or for the fixation of bones which are to be fused (arthrodesed). Thedevice10 comprises an elongated, stem-like structure. Thedevice10 can be formed—e.g., by machining, molding, or extrusion—from a material usable in the prosthetic arts, including, but not limited to, titanium, titanium alloys, tantalum, chrome cobalt, surgical steel, or any other total joint replacement metal and/or ceramic, sintered glass, artificial bone, any uncemented metal or ceramic surface, or a combination thereof. Alternatively, thedevice10 may be formed from a suitable durable biologic material or a combination of metal and biologic material, such as a biocompatible bone-filling material. Thedevice10 may be molded from a flowable biologic material, e.g., acrylic bone cement, that is cured, e.g., by UV light, to a non-flowable or solid material.
• Thedevice10 can take various shapes and have various cross-sectional geometries. Thedevice10 can have, e.g., a generally curvilinear (i.e., round or oval) cross-section, or a generally rectilinear cross section (i.e., square or rectangular), or combinations thereof. As will be described in greater detail later, thedevice10 can be conical or wedge shaped.
• Thestructure10 includes surface texturing12 along at least a portion of its length to promote bony in-growth on its surface. Thesurface texturing12 can comprise, e.g., through holes, and/or various surface patterns, and/or various surface textures, and/or pores, or combinations thereof. Thedevice10 can be coated or wrapped or surfaced treated to provide the surface texturing12, or it can be formed from a material that itself inherently possesses a surface conducing to bony in-growth, such as a porous mesh, hydroxyapetite, or other porous surface. Thedevice10 may further be covered with various other coatings such as antimicrobial, antithrombotic, and osteoinductive agents, or a combination thereof. Thesurface texturing12 may be impregnated with such agents, if desired.
• The configuration of thesurface texturing12 can, of course, vary. By way of examples,FIG. 1 shows thesurface12 as an open mesh configuration;FIG. 2 shows thesurface12 as beaded configuration; andFIG. 3 shows thesurface12 as a trabecular configuration. Any configuration conducive to bony in-growth will suffice.
• In use (seeFIGS. 4 and 5), thedevice10 is inserted into a space between two adjacent bone surfaces, e.g., into a fracture site or between two bones (e.g., adjacent vertebral bodies) which are to be fused together. InFIG. 4, thedevice10 is shown being tapped into bone through bone segments14 (i.e., across a fracture line or between adjacent bones to be fused) with atap16. The bone may be drilled first to facilitate insertion of thedevice10. The bony in-growth surface12 along the surface of thedevice10 accelerates bony in-growth into thedevice10. Boney in-growth into thedevice10 helps speed up the fusion process or fracture healing time.
• The bony in-growth surface12 may cover the entire outer surface of thedevice10, as shown inFIG. 4, or the bony in-growth surface12 may cover just a specified distance on either side of the joint surface or fracture line, as shown inFIG. 5.
• The size and configuration of thedevice10 can be varied to accommodate the type and location of the bone to be treated as well as individual anatomy.
• AsFIG. 6 shows, thedevice10 can be angled or tapered in a conical configuration. The degree of angle can be varied to accommodate specific needs or individual anatomy. A lesser degree of angle (i.e., a more acute angle) decreases the risk of splitting the bone as thedevice10 is tapped into the bone or thefracture segments14. Thedevice10 may also include a beveleddistal tip18 to further add in insertion of thedevice10 into bone, as shown inFIG. 7. As shown inFIGS. 8A and BB, the conical shape also helps drive the joint surfaces or fracture fragments together, reducing the gap (G) between thebone segments14.
• In FIGS.9 to12, thedevice10 is cannulated, having a central lumen or throughbore20 extending through it, to assist in the placement of thedevice10 within bone.
• In use, the physician can insert aconventional guide pin22 through thebone segments14 by conventional methods, asFIG. 9 shows. Acannulated drill bit24 can then be introduced over theguide pin22, as seen inFIG. 10. A single ormultiple drill bits24 can be employed to drill through bone fragments or bone surfaces to create abore26 of the desired size and configuration. In the illustrated embodiment, thedrill bit24 is sized and configured to create aconical bore26 similar in size and configuration to thedevice10. Thebore26 is desirably sized and configured to permit tight engagement of thedevice10 within thebore26 and thereby restrict movement of thedevice10 within thebore26. Thepre-formed bore26 may be slightly smaller than thedevice10, while still allowing thedevice10 to be secured into position within thebore26 by tapping. As seen inFIG. 11, thedrill bit24 is then withdrawn. Thedevice10 is then inserted into thebore26 over theguide pin22, asFIG. 12 shows. Theguide pin22 is then withdrawn.
• Alternatively, thedevice10 itself can include screw-like threads along the body for screwing the device into place. In the arrangement, thedevice10 be self-tapping. Also in this arrangement, thedevice10 can be cannulated for use with aguide pin22, or it need not be cannulated.
• Multiple devices10 may be employed to provide additional stabilization. While the use ofmultiple devices10 will now be described illustrating the use ofmultiple devices10 of the same size and configuration, it is contemplated that thedevices10 may also be of different size and/or configuration, e.g., onedevice10 is of a cylindrical configuration and asecond device10 is of a conical configuration.
• In many cases, it may be desirable to couple a series ofdevices10 together, e.g., to provide stabilization over a larger surface area. A series ofdevices10 may be coupled together be any suitable means, e.g., by a snap fit engagement or a groove and tab key arrangement. In one embodiment, a series ofdevices10 are coupled by threaded engagement. As illustrated inFIG. 13, afirst device10A includes arecess28 at one end providing a series ofinternal threads30. In the illustrated embodiment, thefirst device10 is of a cylindrical configuration, but may be of any desired configuration. Theinternal threads30 couple with a series of complementaryexternal threads32 on asecond device10B of a similar or of a different configuration to couple the first andsecond devices10A and10B together.
• Thedevices10A and10B are desirably coupled together prior to being inserted into thepre-formed bore26. The series of internal andexternal threads30 and32 provide an interlocking mechanism that permits a series ofdevices10 to be stacked and connected to cover a larger area or multiple bone segments14 (e.g., a bone having multiple fractures) and thereby provides additional stabilization, as seen inFIG. 14.
• FIG. 15 illustrates another embodiment in which adevice10′ includes an opening orfenestration34 to allow anotherdevice10 to pass through, thereby providing additional stabilization. Thefenestration34 can be sized and configured to permit anotherdevice10 to be passed through thedevice10′ at virtually any angle. Thefenestration34 can also be sized and configured to limit movement of thesecond device10 relative to thesecond device10′.
• In use, and as shown inFIG. 16, the physician taps afirst device10′ having afenestration34 through the bone segments. Asecond device10 is then inserted (e.g., by tapping) through thefenestration34 of thefirst device10′ into place.
• It is further contemplated thatdevice10′ may also be adapted for coupling with anotherdevice10A (e.g., by a series of external and internal threads), permitting thedevices10′ and10A to be additionally stacked and connected, as also shown inFIG. 16.
• The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.

Claims (13)

1. A bone fixation device for stabilizing bone segments

comprising a stem adapted for passage between bone segments, at least a portion of the stem including a surface permitting bony in-growth.

2. A bone fixation device as inclaim 1

wherein the stem structure is of a cylindrical configuration.

3. A bone fixation device as inclaim 1

wherein the stem is of a conical configuration.

4. A bone fixation device as inclaim 1

wherein the stem is cannulated.

5. A bone fixation device as inclaim 1

wherein the stem includes a threaded end portion for coupling with another stem.

6. A bone fixation device as inclaim 1

wherein the stem comprises a prosthetic material.

7. A bone fixation device as inclaim 1

wherein the stem comprises a biologic material.

8. A bone fixation device as inclaim 1

wherein the stem includes a fenestration permitting passage of another stem.

9. A bone fixation device as inclaim 1

wherein the stem is cannulated.

10. A bone fixation device as inclaim 1

wherein the stem is threaded.

11. A bone fixation device according toclaim 1

further comprising a coupling to couple the stem with another stem:

12. A method for bone fracture fixation using the bone fixation device as defined inclaim 1.

13. A method for bone fixation using the bone fixation device as defined inclaim 1.

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