# Patent

## Title
Systems and methods for the fixation or fusion of bone at or near a sacroiliac joint

## Abstract

At least one bone fixation device comprising a stem having a maximum outer diameter is inserted into the sacroiliac joint through a minimally invasive incision path sized approximately at or about the maximum outer diameter of the stem in soft tissue, into the iliac bone, across the sacroiliac joint and into the sacrum. The stem is inserted through the incision path to a position within the sacroiliac joint between the iliac bone and the sacrum, to fuse the sacroiliac joint, without invasive joint preparation, removal of cartilage, or scraping at or near the sacroiliac joint. Desirably, at least a portion of the stem includes a surface permitting bony in-growth.

## Background
RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent application Ser. No. 11/653,504, filed Jan. 16, 2007, entitled “Systems and Methods for the Fixation or Fusion of Bone,” now U.S. Patent Application Publication No. 2007-0156241-A1 (now abandoned), which is a continuation-in-part of U.S. patent application Ser. No. 11/136,141, filed May 24, 2005, entitled “Systems and Methods for the Fixation or Fusion of Bone,” now U.S. Pat. No. 7,922,765, which is a continuation-in-part of U.S. patent application Ser. No. 10/914,629, filed Aug. 9, 2004, entitled “Systems and Methods for the Fixation or Fusion of Bone” (now abandoned). This application is also related to U.S. Provisional Patent Application Ser. No. 61/000,166, filed Oct. 24, 2007 and entitled “Systems and Methods for the Fixation or Fusion of Bone At or Near a Sacroiliac Joint.”


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.
According to one aspect of the invention, at least one bone fixation device comprising a stem having a maximum outer diameter is inserted into the sacroiliac joint through a minimally invasive incision path sized approximately at or about the maximum outer diameter of the stem in soft tissue, into the iliac bone, across the sacroiliac joint and into the sacrum. The stem is inserted through the incision path to a position within the sacroiliac joint between the iliac bone and the sacrum, to fuse the sacroiliac joint, without invasive joint preparation, removal of cartilage, or scraping at or near the sacroiliac joint. Desirably, at least a portion of the stem includes a surface permitting bony in-growth.



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. 1 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 in FIG. 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 to FIG. 9 and illustrating a drill bit being introduced over the guidewire.
FIG. 11 is a schematic similar to FIG. 10 and illustrating a bore formed in the bone remaining after withdrawal of the drill bit.
FIG. 12 is a schematic similar to FIG. 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.
FIG. 17 is a lateral anterior anatomic view of bones in the hip region of the body, showing the iliac bones, the sacrum, and the sacroiliac joint therebetween.
FIG. 18 is a posterior anatomic view of the hip region shown in FIG. 17, showing the incision paths for inserting one or more bone fixation devices into the sacroiliac joint through soft tissue, into the iliac bone, across the sacroiliac joint and into the sacrum.
FIG. 19 is a posterior anatomic view as shown in FIG. 18, after insertion of the one or more bone fixation devices into the sacroiliac joint, to fuse the sacroiliac joint.



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 a device 10 sized and configured for the fixation of bone fractures or for the fixation of bones which are to be fused (arthrodesed). The device 10 comprises an elongated, stem-like structure. The device 10 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, the device 10 may be formed from a suitable durable biologic material or a combination of metal and biologic material, such as a biocompatible bone-filling material. The device 10 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.
The device 10 can take various shapes and have various cross-sectional geometries. The device 10 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, the device 10 can be conical or wedge shaped.
The structure 10 includes surface texturing 12 along at least a portion of its length to promote bony in-growth on its surface. The surface texturing 12 can comprise, e.g., through holes, and/or various surface patterns, and/or various surface textures, and/or pores, or combinations thereof. The device 10 can be coated or wrapped or surfaced treated to provide the surface texturing 12, 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. The device 10 may further be covered with various other coatings such as antimicrobial, antithrombotic, and osteoinductive agents, or a combination thereof. The surface texturing 12 may be impregnated with such agents, if desired.
The configuration of the surface texturing 12 can, of course, vary. By way of examples, FIG. 1 shows the surface 12 as an open mesh configuration; FIG. 2 shows the surface 12 as beaded configuration; and FIG. 3 shows the surface 12 as a trabecular configuration. Any configuration conducive to bony in-growth will suffice.
In use (see FIGS. 4 and 5), the device 10 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. In FIG. 4, the device 10 is shown being tapped into bone through bone segments 14 (i.e., across a fracture line or between adjacent bones to be fused) with a tap 16. The bone may be drilled first to facilitate insertion of the device 10. The bony in-growth surface 12 along the surface of the device 10 accelerates bony in-growth into the device 10. Boney in-growth into the device 10 helps speed up the fusion process or fracture healing time.
The bony in-growth surface 12 may cover the entire outer surface of the device 10, as shown in FIG. 4, or the bony in-growth surface 12 may cover just a specified distance on either side of the joint surface or fracture line, as shown in FIG. 5.
The size and configuration of the device 10 can be varied to accommodate the type and location of the bone to be treated as well as individual anatomy.
As FIG. 6 shows, the device 10 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 the device 10 is tapped into the bone or the fracture segments 14. The device 10 may also include a beveled distal tip 18 to further add in insertion of the device 10 into bone, as shown in FIG. 7. As shown in FIGS. 8A and 8B, the conical shape also helps drive the joint surfaces or fracture fragments together, reducing the gap (G) between the bone segments 14.
In FIGS. 9 to 12, the device 10 is cannulated, having a central lumen or throughbore 20 extending through it, to assist in the placement of the device 10 within bone.
In use, the physician can insert a conventional guide pin 22 through the bone segments 14 by conventional methods, as FIG. 9 shows. A cannulated drill bit 24 can then be introduced over the guide pin 22, as seen in FIG. 10. A single or multiple drill bits 24 can be employed to drill through bone fragments or bone surfaces to create a bore 26 of the desired size and configuration. In the illustrated embodiment, the drill bit 24 is sized and configured to create a conical bore 26 similar in size and configuration to the device 10. The bore 26 is desirably sized and configured to permit tight engagement of the device 10 within the bore 26 and thereby restrict movement of the device 10 within the bore 26. The pre-formed bore 26 may be slightly smaller than the device 10, while still allowing the device 10 to be secured into position within the bore 26 by tapping. As seen in FIG. 11, the drill bit 24 is then withdrawn. The device 10 is then inserted into the bore 26 over the guide pin 22, as FIG. 12 shows. The guide pin 22 is then withdrawn.
Alternatively, the device 10 itself can include screw-like threads along the body for screwing the device into place. In the arrangement, the device 10 be self-tapping. Also in this arrangement, the device 10 can be cannulated for use with a guide pin 22, or it need not be cannulated.
Multiple devices 10 may be employed to provide additional stabilization. While the use of multiple devices 10 will now be described illustrating the use of multiple devices 10 of the same size and configuration, it is contemplated that the devices 10 may also be of different size and/or configuration, e.g., one device 10 is of a cylindrical configuration and a second device 10 is of a conical configuration.
In many cases, it may be desirable to couple a series of devices 10 together, e.g., to provide stabilization over a larger surface area. A series of devices 10 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 of devices 10 are coupled by threaded engagement. As illustrated in FIG. 13, a first device 10A includes a recess 28 at one end providing a series of internal threads 30. In the illustrated embodiment, the first device 10 is of a cylindrical configuration, but may be of any desired configuration. The internal threads 30 couple with a series of complementary external threads 32 on a second device 10B of a similar or of a different configuration to couple the first and second devices 10A and 10B together.
The devices 10A and 10B are desirably coupled together prior to being inserted into the pre-formed bore 26. The series of internal and external threads 30 and 32 provide an interlocking mechanism that permits a series of devices 10 to be stacked and connected to cover a larger area or multiple bone segments 14 (e.g., a bone having multiple fractures) and thereby provides additional stabilization, as seen in FIG. 14.
FIG. 15 illustrates another embodiment in which a device 10′ includes an opening or fenestration 34 to allow another device 10 to pass through, thereby providing additional stabilization. The fenestration 34 can be sized and configured to permit another device 10 to be passed through the device 10′ at virtually any angle. The fenestration 34 can also be sized and configured to limit movement of the second device 10 relative to the second device 10′.
In use, and as shown in FIG. 16, the physician taps a first device 10′ having a fenestration 34 through the bone segments. A second device 10 is then inserted (e.g., by tapping) through the fenestration 34 of the first device 10′ into place.
It is further contemplated that device 10′ may also be adapted for coupling with another device 10A (e.g., by a series of external and internal threads), permitting the devices 10′ and 10A to be additionally stacked and connected, as also shown in FIG. 16.
Arthrodesis of the Sacroiliac Joint
As shown in FIG. 17, the human hip girdle is made up of three large bones joined by three relatively immobile joints. One of the bones is called the sacrum and it lies at the bottom of the lumbar spine, where it connects with the L5 vertebra. The other two bones are commonly called “hip bones” and are technically referred to as the right ilium and the left ilium. The sacrum connects with both hip bones at the sacroiliac (SI) joint.
The sacroiliac joint functions in the transmission of forces from the spine to the lower extremities, and vice-versa. Sacroiliac joint fusion is typically indicated as a surgical treatment for degenerative sacroiliitis, inflammatory sacroiliitis, iatrogenic instability of the sacroiliac joint, osteitis condensans ilii, or traumatic fracture dislocation of the pelvis.
Currently, screw and screw with plates are used for sacro-iliac fusion. At the same time the cartilage has to be removed from the “synovial joint” portion of the SI joint. This requires a large incision to approach the damaged, subluxed, dislocated, fractured, or degenerative joint.
FIGS. 18 and 19 show one or more devices 100, as previously described and shown, e.g., in FIG. 1, each of which is sized and configured for the fusion (arthrodesis) of the sacro-iliac joint. As previously described, each device 100 comprises an elongated, stem-like structure. Each device 100 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, each device 100 may be formed from a suitable durable biologic material or a combination of metal and biologic material, such as a biocompatible bone-filling material. The device 100 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.
A given device 100 can take various shapes and have various cross-sectional geometries. A given device 100 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. A given device 100 can be conical or wedge shaped. The devices 100 used for a given arthrodesis can be of different sizes and shapes, depending upon the anatomic conditions encountered.
One or more of the devices 100 (see FIG. 18) desirably includes surface texturing 120 along at least a portion of its length to promote bony in-growth on its surface, as previously described. The surface texturing 120 can comprise, e.g., through holes, and/or various surface patterns, and/or various surface textures, and/or pores, or combinations thereof. The device 100 can be coated or wrapped or surfaced treated to provide the surface texturing 120, 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. The device 100 may further be covered with various other coatings such as antimicrobial, antithrombotic, and osteoinductive agents, or a combination thereof. The surface texturing 120 may be impregnated with such agents, if desired.
One or more of the devices 100 are individually inserted in a minimally invasive fashion through an insertion path 140 in the soft tissue, into the respective iliac bone, across the respective sacroiliac joint and into the sacrum, as FIGS. 18 and 19 show. Conventional tissue access tools, obturators, cannulas, and/or drills can be used for this purpose. No joint preparation, removal of cartilage, or scraping are required before formation of the insertion path or insertion of the device 100, so an minimally invasive insertion path sized approximately at or about the maximum outer diameter of the device 100 need be formed.
In a representative procedure, one to six, or perhaps eight, devices 100 might be needed, depending on the size of the patient and the size of the devices 100.
The described method comprises providing at least one device 100 comprising a stem having a maximum outer diameter. The method creates a minimally invasive incision path sized approximately at or about the maximum outside diameter through soft tissue, into the iliac bone, across the sacroiliac joint and into the sacrum. The method includes, without further joint preparation, removal of cartilage, or scraping at or near the sacroiliac joint, inserting the stem through the incision path to a position within the sacroiliac joint between the iliac bone and the sacrum, to fuse the sacroiliac joint. Preferably, at least a portion of the stem includes a surface permitting bony in-growth.
After installation, the patient would be advised to prevent loading of the sacroiliac joint while fusion occurs. This could be a six to twelve week period or more, depending on the health of the patient and his or her adherence to post-op protocol.
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

1. A joint fusion device, the joint fusion device comprising:
an elongated, stem-like device having a triangular cross section free of external screw threads and lateral fenestrations, the device being sized and configured for placement to fuse a sacroiliac joint, which lies between an iliac bone and a sacrum, in response to an axially applied, non-rotational force, the elongated, stem-like device having an exterior surface treated to provide bony in-growth and/or on-growth upon placement, wherein the elongated, stem-like device is formed from one or more materials selected from a group consisting of titanium, titanium alloys, tantalum, chrome cobalt, and surgical steel, wherein the triangular cross section of the elongated, stem-like device is configured to inhibit movement of the sacroiliac joint without the use of an additional component transversely intersecting the device through a lateral fenestration, wherein the elongated, stem-like device has a minimum length greater than a thickness of the iliac bone at the sacroiliac joint.

2. A joint fusion device according to claim 1 further comprising a porous surface conducive to bony in-growth.

3. A joint fusion device according to claim 2 wherein the porous surface is formed by a coating.

4. A joint fusion device according to claim 1 further comprising hydroxyapatite.

5. A joint fusion device according to claim 1, wherein the elongated, stem-like device comprises a lumen to accommodate close fitting passage over a guide pin during placement.

6. A joint fusion device according to claim 1, wherein the elongated, stem-like device has a maximum length less than a distance between a lateral surface of the iliac bone and a midline of sacral vertebral bodies.

7. A joint fusion device, the joint fusion device comprising:
an elongated, stem-like device having a triangular cross section free of external screw threads and lateral fenestrations, the device being sized and configured for placement to fuse a sacroiliac joint, which lies between an iliac bone and a sacrum, in response to an axially applied, non-rotational force, the elongated, stem-like device having an exterior surface treated to provide bony in-growth and/or on-growth upon placement, wherein the elongated, stem-like device is formed from one or more materials selected from a group consisting of titanium, titanium alloys, tantalum, chrome cobalt, and surgical steel, wherein the triangular cross section of the elongated, stem-like device is configured to inhibit movement of the sacroiliac joint without the use of an additional component transversely intersecting the device through a lateral fenestration, wherein the elongated, stem-like device has a maximum length less than a distance between a lateral surface of the iliac bone and a midline of sacral vertebral bodies.

8. A joint fusion device, the joint fusion device comprising:
an elongated, stem-like device having a triangular cross section free of external screw threads and lateral fenestrations, the device being sized and configured for placement to fuse a sacroiliac joint, which lies between an iliac bone and a sacrum, in response to an axially applied, non-rotational force, the elongated, stem-like device having an exterior surface treated to provide bony in-growth upon placement, wherein the elongated, stem-like device is formed from one or more materials selected from a group consisting of titanium, titanium alloys, tantalum, chrome cobalt, and surgical steel, wherein the triangular cross section of the elongated, stem-like device is configured to inhibit movement of the sacroiliac joint without the use of an additional component transversely intersecting the device through a lateral fenestration, wherein the elongated, stem-like device has a length that is approximately equal to a distance between a lateral surface of the iliac bone and a dorsal sacral foramina of the sacrum.