US 20060095136 A1
A bone fusion device provides stability to bones during a bone fusion period. The bones include, for example, the vertebrae of a spinal column. The bone fusion device comprises one or more extendable tabs attached to the bone fusion device by associated rotating means. The bone fusion device is preferably inserted by using an arthroscopic surgical procedure. During arthroscopic insertion of the device, the tabs are pre-configured for compactness. In this compact configuration, the tabs are preferably deposed along and/or within an exterior surface of the bone fusion device. After the bone fusion device has been positioned between the bones, one or more tab(s) are extended. In some embodiments, the position of each tab relative to the bone fusion device is adjustable. Typically, the tabs advantageously position and brace the bone fusion device in the confined space between the bones until the bones have fused.
1. A bone fusion device for insertion between bones comprising:
first and second ends;
an interior cavity deposed between the first and second ends;
an exterior surface;
a conduit providing a pathway from the interior cavity to the exterior surface; and
one or more tabs for bracing the bone fusion device in a space between the bones, wherein the one or more tabs comprise an adjustable element.
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17. A bone fusion device for insertion between adjacent bones, comprising:
a. a hollow body having one or more holes along a length of the body; and
b. one or more extendable tabs each attached to the hollow body by a screw,
wherein the one or more extendable tabs are aligned along a surface of the hollow body in a compact position during insertion into a patient.
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29. A method of implanting a bone fusion device between bones, the method comprising:
inserting the bone fusion device between the bones, wherein the bone fusion device comprises an internal cavity, an exterior surface, and an extendable tab, wherein the extendable tab comprises an associated rotating element;
pre-configuring the extendable tab to lie within the exterior surface by using the rotating element such that the bone fusion device has a minimized form factor;
driving a lead screw into the cavity; and
extending the tab to a desired position by using the rotating element.
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This patent application claims priority under 35 U.S.C. § 119(e) of the co-pending U.S. Provisional Patent Application, Ser. No. 60/624,836, filed Nov. 03, 2004, and entitled “BONE FUSION DEVICE,” which is hereby incorporated by reference in its entirety.
This invention relates generally to bone fusion devices. More specifically, the present invention relates to devices for fusing vertebrae of the spine that can be inserted arthroscopically.
The spinal column is made up of vertebrae stacked on top of one another. Between the vertebrae are discs which are gel-like cushions that act as shock-absorbers and keep the spine flexible. Injury, disease, or excessive pressure on the discs can cause degenerative disc disease or other disorders where the disc becomes thinner and allows the vertebrae to move closer together or become misaligned. As a result, nerves may become pinched, causing pain that radiates into other parts of the body, or instability of the vertebrae may ensue.
One method for correcting disc-related disorders is to insert a fusion cage between the vertebrae to act as a structural replacement for the deteriorated disc. The fusion cage is typically a hollow metal device usually made of titanium. Once inserted, the fusion cage maintains the proper separation between the vertebrae to prevent nerves from being pinched and provides structural stability to the spine. Also, the inside of the cage is filled with bone graft material which eventually fuses permanently with the adjacent vertebrae into a single unit.
The use of fusion cages for fusion and stabilization of vertebrae in the spine is known in the prior art. U.S. Pat. No. 4,961,740 to Ray, et al. entitled, “V-Thread Fusion Cage and Method of Fusing a Bone Joint,” discloses a fusion cage with a threaded outer surface, where the crown of the thread is sharp and cuts into the bone. Perforations are provided in valleys between adjacent turns of the thread. The cage can be screwed into a threaded bore provided in the bone structure at the surgical site and then packed with bone chips which promote fusion.
U.S. Pat. No. 5,015,247 to Michelson entitled, “Threaded Spinal Implant,” discloses a fusion implant comprising a cylindrical member having a series of threads on the exterior of the cylindrical member for engaging the vertebrae to maintain the implant in place and a plurality of openings in the cylindrical surface.
U.S. Pat. No. 6,342,074 to Simpson entitled, “Anterior Lumbar Underbody Fusion Implant and Method For Fusing Adjacent Vertebrae,” discloses a one-piece spinal fusion implant comprising a hollow body having an access passage for insertion of bone graft material into the intervertebral space after the implant has been affixed to adjacent vertebrae. The implant provides a pair of screw-receiving passages that are oppositely inclined relative to a central plane. In one embodiment, the screw-receiving passages enable the head of an orthopaedic screw to be retained entirely within the access passage.
U.S. Pat. No. 5,885,287 to Bagby entitled, “Self-tapping Interbody Bone Implant,” discloses a bone joining implant with a rigid, implantable base body having an outer surface with at least one bone bed engaging portion configured for engaging between a pair of bone bodies to be joined, wherein at least one spline is provided by the bone bed engaging portion, the spline being constructed and arranged to extend outwardly of the body and having an undercut portion.
U.S. Pat. No. 6,582,467 to Teitelbaum et al. entitled,“Expandable Fusion Cage,” discloses an expandable fusion cage where the surfaces of the cage have multiple portions cut out of the metal to form sharp barbs. As the cage is expanded, the sharp barbs protrude into the subcortical bone of the vertebrae to secure the cage in place. The cage is filled with bone or bone matrix material.
U.S. Pat. No. 5,800,550 to Sertich entitled, “Interbody Fusion Cage,” discloses a prosthetic device which includes an inert generally rectangularly shaped support body adapted to be seated on hard end plates of vertebrae. The support body has top and bottom faces. A first peg is movably mounted in a first aperture located in the support body, and the first aperture terminates at one of the top and bottom faces of the support body. Further, the first peg projects away from the one of the top and bottom faces and into an adjacent vertebra to secure the support body in place relative to the vertebra.
U.S. Pat. No. 6,436,140 to Liu et al. entitled, “Expandable Interbody Fusion Cage and Method for Insertion,” discloses an expandable hollow interbody fusion device, wherein the body is divided into a number of branches connected to one another at a fixed end and separated at an expandable end. The expandable cage may be inserted in its substantially cylindrical form and may be expanded by movement of an expansion member to establish lordosis of the spine. An expansion member interacts with the interior surfaces of the device to maintain the cage in the expanded condition and provide a large internal chamber for receiving bone in-growth material.
These patents all disclose fusion cage devices that can be inserted between vertebrae of the spine in an invasive surgical procedure. Such an invasive surgical procedure requires a long recovery period.
The present invention is a bone fusion device for insertion between bones that are to be fused together, such as, for example, the vertebrae of a spinal column. The bone fusion device comprises one or more extendable tabs. The bone fusion device is in its most compact state when the tabs are aligned with the body of the device such that the tabs lie within the exterior of the device. In this compact form, the bone fusion device is preferably inserted between the vertebrae by using an arthroscopic procedure. The bone fusion device of some embodiments is filled with bone graft material. In these embodiments, the bone graft material is typically relocated from the interior to the exterior of the bone fusion device by using a lead screw. After the device has been positioned between the vertebrae, and the lead screw is inserted to optionally deliver the bone graft material, selected tabs are extended. Each tab typically has an associated rotating means. The position of each tab relative to the bone fusion device is adjustable depending upon the configuration of the associated rotating means. In this way, the tabs are advantageously positioned in the confined space between the vertebrae to help brace the device until the bone has fused. Further, the tabs of the bone fusion device provide a larger surface area to which the bones attach and fuse during a healing period.
According to an embodiment of the present invention, the body of the bone fusion device is a round cylinder with end faces. The bone fusion device has conduits or holes that allow the bone graft material within the device to flow to the exterior of the device where the material contacts and grafts to the vertebrae. The extendable tabs are arranged in various configurations on the exterior of the bone fusion device, including the end faces. Preferably, the tabs are attached to the body of the device on more than one side to optimally brace the device from multiple directions between the adjacent vertebrae. Alternatively, the bone fusion device has a rectangular shape with end faces and extendable tabs attached to multiple exterior surfaces.
Optionally, the bone fusion device of some embodiments includes protrusions, threading, and/or sharp features on the exterior surface and/or the extendable tabs. These features are configured to engage the adjacent vertebrae to provide a tighter interface between the device and the vertebrae.
FIGS. 3A-B illustrate a section of a vertebral column showing the bone fusion device inserted between two adjacent vertebrae in place of an intervertebral disc.
FIGS. 4A-B illustrate a detailed view of the worm screw drive and the extendable tabs of some embodiments.
FIGS. 5A-B illustrate the small form factor of some embodiments.
FIGS. 6A-B illustrate a cross section view of the small form factor of some embodiments.
FIGS. 7A-B are perspective drawings illustrating the tabs and tab bays of some embodiments.
In the following description, numerous details and alternatives are set forth for purpose of explanation. However, one of ordinary skill in the art will realize that the invention can be practiced without the use of these specific details. For instance, the figures and description below often refer to the vertebral bones of a spinal column. However, one of ordinary skill in the art will recognize that some embodiments of the invention are practiced for the fusion of other bones, including broken bones and/or joints. In other instances, well-known structures and devices are shown in block diagram form in order not to obscure the description of the invention with unnecessary detail.
Also shown in
As further illustrated in
After insertion of the device 100 into the space between the patient's vertebrae, the surgeon selectively extends particular tabs 131-136 by rotating each selected tab's respective rotating means 111-116. The more each rotating means 111-116 is rotated, the farther its respective tab 131-136 elevates and extends outward from its initial position 121-126 along the body of the device 100. Each tab's 131-136 position is individually adjustable so as to optimally brace the device 100 between the vertebrae. Due to the compressive forces commonly associated with spinal column vertebrae, some embodiments include a range of motion for each tab that is slightly greater than 90 degrees. It was particularly discovered during the reduction to practice of the present invention, that the tabs of these embodiments are preferably rotated to an angle that is slightly more than about 90 degrees with respect to the surface of the bone fusion device. The tabs extended in this configuration were found to be capable of withstanding the greatest amount of compressive force.
Preferably, the tabs 131-136, when extended, abut tightly against the surfaces of the vertebrae that are immediately adjacent to the bone fusion device 100. In some embodiments, the tabs 131-136 have sharp protrusions along the length of the tab for engaging the adjacent vertebrae, while the tabs 131-136 of some embodiments have screw-type threads for screwing into and engaging the vertebrae. Optionally, the tabs of some embodiments have surface texturing to encourage and enhance the growth of new bone on the tabs 131-136. This surface texturing is often similar to the surface texturing used on the main body of the device 100. Regardless of their texturing and/or particular physical characteristics, the tabs 131-136 advantageously wedge the bone fusion device 100 in a fixed position between the vertebrae and provide a larger surface area with which the adjacent vertebrae fuses during the healing period. Moreover, bone growth material, such as protein, is typically applied to the tabs 131-136 to stimulate the regeneration of bone cells needed for bone fusion. The application of bone growth material is described further in relation to
In an alternative embodiment of the invention, the tabs of the device 100 have sharp ridges or threads which bite into the adjacent vertebrae, further helping to brace the device between the vertebrae. It will be readily apparent to one skilled in the art that there are a number of variations for the body and the tabs 131-136 of the bone fusion device 100. For instance, the bone fusion device 100 employs different numbers and/or configurations of tabs in different embodiments. Hence, the tabs 131-136 depicted in
Preferably, the end face 245 has an opening 240, which provides access to a cavity within the interior of the bone fusion device 200. In some embodiments, bone graft materials, such as the bone chips and/or the synthetic bone matrix that were mentioned above, are pre-loaded into the cavity within the bone fusion device 200 through the opening 240. Several conduits or holes 250 in the bone fusion device 200 permit the bone graft material to flow from the interior cavity to the exterior surfaces of the device 200 that are in contact with the vertebral bone. Typically, the bone graft material is relocated from the interior cavity to the exterior of the bone fusion device 200, after the device 200 has been positioned between the vertebrae. However, in some embodiments the bone graft material is delivered to the site of the bone fusion device 200 by arthroscopic means that originate external to the device 200. Regardless of the delivery means, the bone graft material and the surface texturing of the bone fusion device 200 encourage bone growth and fusion with the adjacent vertebrae that are in contact with the device 200. As bone fusion and healing progresses, the bone fusion device 200 preferably becomes embedded within the two fused vertebrae of the spine.
Preferably, during the insertion and placement of the bone fusion device 300, the tabs 321-324 are deposed in a position aligned along the body of the bone fusion device 300, such that the tabs 321-324 lie substantially within the exterior surfaces of the device 300. In some embodiments, the tabs 321-324 are flush with the exterior surface. In these embodiments, the form factor of the bone fusion device 300 is configured to be as compact as possible. For instance, the form factor of some embodiments has a diameter of approximately 0.28 inches and a length of approximately 1.0 inch. In contrast, the form factor of these same embodiments has a diameter of approximately 0.48 inches when the tabs 321-324 are fully extended.
By minimizing the space occupied, the bone fusion device 300 is advantageously inserted arthroscopically into the patient's body. If instead, the device 300 were inserted in its fully extended form, a larger surgical incision would be required, and a greater displacement of the muscles and nerves would be needed. However, its compact form factor allows the bone fusion device 300 to be inserted by advantageously utilizing minimally invasive arthroscopic techniques. Then, the tabs 321-324 of the bone fusion device 300 are extended after arthroscopic insertion to optimally increase the form factor and brace the device 300 between the vertebrae 330 and 335. In some embodiments, selected tabs 321-324 are extended.
While the particular embodiment described above has a rectangular shape, it will be readily apparent to one skilled in the art that the cross-section of the bone fusion device 300 has different shapes in various embodiments. For instance, a more circular bone fusion device such as the device 100 illustrated in
The tab bays 421-424 allow the tabs 431 to lie flush and/or within the exterior surface 420 of the bone fusion device 400 when not extended. Also when not extended, the tab 431 and tab bay 421 provides a conduit 450 from the interior cavity 405 to the exterior surface 420 of the bone fusion device 400, such that the bone graft and/or growth material within the interior cavity 405 has a directed path to the exterior surface 420. Typically, the insertion of the lead screw 415 forces the material within the interior cavity 405 to relocate to the exterior surface 420.
The tab 431 includes a rotating means 411 and gear teeth 455. When the tab 431 is not extended, the gear teeth 455 provide a series of passive grooves by which the lead screw 415 traverses the interior cavity 405. Typically, the tab 431 remains fixed as the lead screw 415 is screwed into the interior cavity 405. In these embodiments, the threading of the lead screw 415 does not address or affect the gear teeth 455 during the insertion of the lead screw 415.
However, the gear teeth 455 do employ the threading of the lead screw 415 when the lead screw 415 has been fully inserted into the cavity 405, in some embodiments. For instance, in a particular implementation of the invention, the lead screw 415 is driven into the cavity 405, until it reaches an endcap 406. The endcap 406 allows the lead screw 415 to continue rotating in place, but does not allow the lead screw 415 to continue its forward progress through the cavity 405. When the lead screw 415 of these embodiments rotates without making forward progress, the rotating lead screw's threading contacts and engages the gear teeth 455 of each tab 431. Accordingly, the motion and angle of the spiraling threads, when applied against the gear teeth 455, causes the tabs 431 to elevate and extend. The combination of the gear teeth 455 on the tabs 431 and the inserted lead screw 415, is referred to, in some embodiments, as a worm screw drive mechanism.
In an alternative embodiment of the worm screw drive mechanism, the rotating means 411 is turned to raise the tab 431. In these embodiments, the rotating means 411 for the tab 431 typically comprises a turn screw type mechanism such that when the rotating means 411 is turned, the gear teeth 455 drive or rotate against the stationary threads of the inserted lead screw 415. Similarly, due to the angle of the stationary lead screw's spiral threads, the gear teeth 455 cause the tab 431 to elevate and extend above the exterior surface 420 of the bone fusion device 400.
As mentioned above, the tabs 431 of some embodiments have a range of motion that exceeds 90 degrees with respect to the exterior surface 420 of the bone fusion device 400. Accordingly,
At the step 815, the bone fusion device is positioned in the region where bone fusion is to occur, also typically by using one or more arthroscopic tool(s). Once the bone fusion device is positioned in the region between the two vertebrae, the process 800 transitions to the step 820, where the lead screw is inserted and driven into the bone fusion device. The lead screw is typically driven into a cavity in the center of the bone fusion device. Preferably, the cavity contains a bone growth material comprising collagen and/or a matrix for the promotion of bone growth. Accordingly, insertion of the lead screw into the cavity causes the bone growth material to be relocated from the interior cavity to the exterior surface of the bone growth device. The bone fusion device of some embodiments has a particular pattern of conduits or pores that extend from the interior cavity to the exterior surface for facilitating the relocation of bone growth material to particular locations at the exterior of the device. For instance, some embodiments have pores that facilitate the relocation of bone growth material to particular tabs.
At the step 825 of the
As mentioned above, the small incision and minimally invasive (arthroscopic) surgical procedure advantageously promote health and rapid recovery by the patient. Preferably, bone growth occurs around the bone fusion device and particularly at the locations of the extended tabs, such that the bone fusion device is further secured by the bone growth, which further promotes a superior, robust bone fusion result.
The present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of principles of construction and operation of the invention. Such reference herein to specific embodiments and details thereof is not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modification may be made in the embodiments chosen for illustration without departing from the spirit and scope of the invention.