Expandable vertebral implant and methods of use
An implant for insertion between vertebral body endplates includes first and second end members, each with a respective endplate contact surface. The implant further includes a collapsible intermediate section disposed between the first and second end members and an inflatable member contained within the intermediate section. The intermediate section may be expandable upon the introduction of a substance into the inflatable member between a first size to space the first and second end members a first distance apart and a second enlarged size to space the first and second end members a second greater distance apart. The inflatable member may increase in size from a compressed size in which the inflatable member will pass through an opening in the intermediate section and an expanded size in which the inflatable member will not pass through the opening and is thereby captively retained within the intermediate section.
Spinal implants are often used in the surgical treatment of spinal disorders such as degenerative disc disease, disc herniations, scoliosis or other curvature abnormalities, and fractures. Many different types of treatments are used, including the removal of one or more vertebral bodies and/or intervertebral disc tissue. In some cases, spinal fusion is indicated to inhibit relative motion between vertebral bodies. In other cases, dynamic implants are used to preserve motion between vertebral bodies. In yet other cases, relatively static implants that exhibit some degree of flexibility may be inserted between vertebral bodies.
Regardless of the type of treatment and the type of implant used, surgical implantation tends to be a difficult for several reasons. For instance, access to the affected area may be limited by other anatomy. Further, a surgeon must be mindful of the spinal cord and neighboring nerve system. The size of the implant may present an additional obstacle. In some cases, a surgeon may discover that an implanted device has an inappropriate size for a particular application, which may require removal of the implant and insertion of a different implant. This trial and error approach may increase the opportunity for injury and is certainly time-consuming. Expandable implants are becoming more prevalent as a response to some of these concerns. However, the expansion mechanism in these devices tends to be complex and large. Consequently, existing devices do not appear to address each of these issues in a manner that improves the ease with which the device may be surgically implanted.
SUMMARYIllustrative embodiments disclosed herein are directed to an implant for insertion between vertebral body endplates. The implant may include first and second end members, each with a respective endplate contact surface. The implant may further include a collapsible intermediate section disposed between the first and second end members and an inflatable member contained within the intermediate section. The collapsible intermediate section may be flexible and may be implemented using, for example, a continuous threaded tether, multiple tethers, or a mesh member. The collapsible intermediate section may be compliant or semi-rigid and naturally assume a compressed, but expandable insertion height. The intermediate section may be expandable upon the introduction of a substance into the inflatable member between a first size to space the first and second end members a first distance apart and a second enlarged size to space the first and second end members a second greater distance apart. The inflatable member may increase in size from a compressed size in which the inflatable member will pass through an opening in the intermediate section and an expanded size in which the inflatable member will not pass through the opening and is thereby captively retained within the intermediate section.
The various embodiments disclosed herein are directed to vertebral implants that are characterized by at least one expandable portion. The expandable portion may be assume a compressed first state during installation of the implant and may be expanded once the implant is positioned within the body. An exemplary implant 10 for supporting vertebral bodies is illustrated in
The end members 22, 24 are adapted to engage the endplates of upper and lower vertebral bodies V1, V2. The expandable portion 26 is engaged between the end members 22, 24 to maintain an intervertebral axial space S between the upper and lower vertebral bodies V1, V2 following the removal of one or more vertebral levels (shown in phantom in
The expandable portion 26 is expandable in a direction that is substantially transverse to the bone contact surfaces 32, 34 of the end members 22, 24. The bone contact surfaces 32, 34 of the end members 22, 24 may be planar or define surface features and/or a number of anchor elements 80 adapted for engagement with the vertebral endplates to inhibit movement of the end members 22, 24 relative to the vertebral bodies V1, V2. For example, in one embodiment, the bone contact surfaces 32, 34 may be roughened, such as, for example, by knurling and/or etching (e.g., photochemical etching). In other embodiments, various types of projections or protrusions may extend from the bone contact surfaces 32, 34, such as, for example, a number of spikes, ridges, teeth, axial grooves, checkerboard-type grooves, or any other type of anchoring element 80 that would occur to one of skill in the art. Although the bone contact surfaces 32, 34 of the end members 22, 24 are illustrated in
In one or more embodiments, the implant 10 may be expanded through the introduction of an injectable substance that fills an inflatable balloon-like member 36, thereby causing the end members 22, 24 to move opposite one another. The number 90 in
The end members 22, 24 include similar shapes, which permits the end members 22, 24 to fit the vertebral bodies V1, V2 in a similar manner. The end members 22, 24 generally include respective bone contact surfaces 32, 34 and an opposing surface 54 facing opposite the bone-contact surfaces 32, 34, and a peripheral wall 52 extending therebetween. In the illustrated embodiment, the end members 22, 24 include a kidney shape, though other shapes may be used. In further embodiments, the end members 22, 24 may take on other types of configurations, such as, for example, a circular shape, semi-oval shape, bean-shape, D-shape, elliptical-shape, egg-shape, or any other shape that would occur to one of skill in the art. In other embodiments, the end members 22, 24 could also be described as being annular, U-shaped, C-shaped, V-shaped, horseshoe-shaped, semi-circular shaped, semi-oval shaped, or other similar terms defining an implant including at least a partially open or hollow construction. Thus, end members 22, 24 may be constructed for use in a variety of procedures, including but not limited to those requiring an anterior approach, a lateral approach, a posterior approach, or a trans-foraminal approach.
It should further be appreciated that the size and/or configuration of the end members 22, 24 may be specifically designed to accommodate any particular region of the spinal column and/or any particular vertebral level. For example, in embodiments associated with the upper thoracic or cervical region of the spine, the end members 22, 24 may be designed to have a D-shaped configuration, whereas embodiments associated with the lumbar region of the spine may be configured to have a horseshoe-shape, a U-shape, or other types of open-sided configurations.
In one embodiment, the end members 22, 24 have an outer profile that is substantially complementary to the size and shape of the peripheral portion or outlying region of the vertebral bodies V1, V2, such as the cortical rim or the apophyseal ring of the vertebral endplates. For example, as illustrated in
Additionally, each of the bone contact surfaces 32, 34 may include one or more apertures or recesses 50 formed by an inner surface 82. The recess 50 is open at the bone contact surfaces 32, 34 and provided to enhance bony fusion between the end members 22, 24 and vertebral bodies V1, V2. The recesses 50 may be blind holes in that they do not extend through the end members 22, 24. The recesses 50 may be through-holes in that they do extend through the end members 22, 24. In one or more implementations, the implant 10 may be inserted in conjunction with bone growth materials that may include, for example, bone graft, bone morphogenetic protein (BMP), allograft, autograft, and various types of cement, growth factors and mineralization proteins. In a further embodiment, the bone growth promoting materials may be provided in a carrier (not shown), such as, for example, a sponge, a block, a cage, folded sheets, or paste. The bone growth materials may be loaded into the apertures 50 or generally applied to the bone-contact surfaces 32, 34.
The tethers 42 may be constructed of a complaint biocompatible material, such as a resin or polymer that may include materials such as nylon, polyethylene, polyurethane, silicone, polyethylene, polypropylene, polyimide, polyamide, and polyehteretherketone (PEEK). Further, the tethers 42 may be constructed of a wide variety of woven or nonwoven fibers, fabrics, metal mesh such as woven or braided wires, polymeric fibers, ceramic fibers, and carbon fibers. Biocompatible fabrics or sheet material such as ePTFE and Dacron®, Spectra®, and Kevlar® may also be used. The tethers 42 may be cable-like, with a circular cross section or tape-like with a flattened cross section. Other cross sections may be possible or desirable, including for example, triangular, rectangular, polygonal, elliptical, or other cross sections. Furthermore, the tethers 42 may be secured to one or both of the end members 22, 24 using a variety of methods, including for example, tying, adhering, welding, or other methods that would occur to one skilled in the art.
The tethers 42 may be compliant in that they assume a shape that is determined by the spacing between the end members 22, 24. That is, the tethers 42 may be similar to a rope or thread and assume a random shape when the end members 22, 24 are brought in proximity to one another. In one embodiment, the tethers 42 are semi-rigid in that they assume a particular bent, curved, or splined shape to maintain a compressed height between the end members 22, 24. However, as the end members 22, 24 are pushed apart, such as by inflating the balloon-like structure 36, the tethers 42 will straighten to allow the end members 22, 24 to separate. Those skilled in the art will comprehend that a semi-rigid characteristic may be obtained through the use of flexible resin or composite materials or through the use of a thin metal filament, rod, or spring (not explicitly shown).
The balloon-like structure 36 may be constructed of a complaint biocompatible material, such as a resin or polymer that may include materials such as nylon, polyethylene, polyurethane, silicone, polyethylene, polypropylene, polyimide, polyamide, and polyehteretherketone (PEEK). The balloon-like structure 36 may be formed from materials that are used in other conventionally known biomedical applications, such as balloon angioplasty. Further, the balloon-like structure 36 may be reinforced with concentric layers of similar or dissimilar materials and/or fabrics (not specifically shown). For instance, a reinforcing structure may be constructed of a wide variety of woven or nonwoven fibers, fabrics, metal mesh such as woven or braided wires, polymeric fibers, ceramic fibers, and carbon fibers. Biocompatible fabrics or sheet material such as ePTFE and Dacron®, Spectra®, and Kevlar® may also be used. Furthermore, the balloon-like structure 36 may be a separate member or may be secured to one or both of the end members 22, 24.
In one embodiment, the balloon-like structure 36 includes permeable end surfaces 39. That is, the end surfaces 39 include a perforated, grated, or mesh-like structure that allows the injectable substance 90 to pass from within the balloon-like structure 36 and through the apertures 50 to contact the corresponding vertebral bodies V1, V2 (see e.g.,
Various techniques may be used to introduce an injectable substance 90 into the balloon-like structure 36. In the embodiment shown, a fill port 52 is provided on the balloon-like structure 36. Notably, while only one fill port 52 is depicted, additional ports 52 may be used. Further, the port 52 may be located in different locations depending on a particular implementation and angle of approach. The fill port 52 may be attached to a syringe or other pumping mechanism (see
A variety of injectable substances may be inserted into the balloon-like structure 36 to cause the end members 22, 24 to separate. In one embodiment, the injectable substance is a fluid, such as a gas or a liquid. In one embodiment, the injectable substance is a solid, such as a powder. In one embodiment, the injectable substance is a curable liquid that solidifies after a predetermined amount of time or under the influence of an external catalyst. For instance, an injectable liquid may cure under the influence of heat or light, including ultraviolet light. Some examples of in situ curable liquids include epoxy, PMMA, polyurethane, and silicone. A curable substance may cure to a substantially rigid state or to a flexible, but relatively incompressible state.
The implant 10 may be inserted into a patient according to the process steps illustrated in
In one embodiment, a single tool 100 is used to position and fill the balloon-like structure. In one embodiment, the balloon-like structure is positioned between the end members 22, 24 using a different tool (not shown) than the inflation tool 100. In one embodiment, the balloon-like member 36 is pre-positioned between the end members 22, 24 and inserted into the intervertebral space along with the end members 22, 24.
The inflation tool 100 may be implemented as a syringe-like structure including a reservoir portion 102 and a delivery portion 104. The delivery portion 104 is configured to engage the fill port 52 to transfer the injectable substance from the reservoir portion 102 into the balloon-like structure 36. Other delivery mechanisms are certainly appropriate. For instance, pneumatic or hydraulic fittings may be appropriate. The delivery portion 104 may be implemented as a needle, as tubing, or other cannulated devices. In any event, as the injectable substance is introduced into the implant 10, the end members 22, 24 are forced apart due to the expansion of the contained balloon-like structure 36. Ultimately, the implant 10 is expanded to an expanded second state including a second height H2 as shown in
In embodiments described above, the expandable portion 26 included a collapsible portion 41 comprised of a series of cords or tethers 42. In the embodiment shown in
In certain implementations, where the injectable substance remains fluid or takes an extended period of time to cure, the end members 22D, 24D are provided with position locks 156, 158. In one embodiment, attachment member 172 includes protruding features 156 and attachment member 170 includes recessed features 158 disposed at various heights about the interior thereof. Thus, when the attachment members 170, 172 are joined to one another, the protruding features 156 engage the recessed features 158 to provide a locked height that prevents compression of the implant 10D. That is, as the balloon-like structure 36 is filled with an injectable substance, the end members 22D, 24D will separate and expand to a position where a protrusion 156 engages a recess 158. At this point, introducing additional injectable substance will force the protrusion 156 to disengage from the recess 158 and ultimately engage a next higher recess 158. The protrusions 156 and/or the recesses 158 may be angled, tapered, or oriented to permit expansion of the implant 10D but not compression in the reverse direction. Those skilled in the art will comprehend a variety of ways to implement this type of unidirectional locking. The protruding features 156 may be implemented using a variety of features, including but not limited to ball plungers, expanding pegs, protruding stops, and shape-memory alloys. In the latter case, the protruding features 156 may be positioned in a first retracted position and then, upon the application of elevated temperatures (which may be provided by body temperatures), the protruding feature 156 will expand to engage a recess 158 corresponding to a desired implant height.
Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper”, and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc and are also not intended to be limiting. Like terms refer to like elements throughout the description.
As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.
The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. For instance, the embodiments disclosed herein have contemplated a single implant positioned between vertebral bodies V1, V2. In other embodiments, two or more smaller implants may be inserted between the vertebral bodies V1, V2. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
Claims
1. An implant for insertion between vertebral body endplates in a patient, the implant comprising:
- a first end member including a first endplate contact surface;
- a second end member including a second endplate contact surface;
- a collapsible intermediate section disposed between the first and second end members; and
- an inflatable member contained within the intermediate section,
- the intermediate section being expandable upon the introduction of a substance into the inflatable member, the intermediate section being expandable between a first size to space the first and second end members a first distance apart and a second enlarged size to space the first and second end members a second greater distance apart.
2. The implant of claim 1 wherein the collapsible intermediate section is flexible.
3. The implant of claim 1 wherein the collapsible intermediate section comprises a plurality of tethers secured about a perimeter of the first and second end members.
4. The implant of claim 1 wherein the collapsible intermediate section comprises a single tether coupled between a perimeter of the first and second end members.
5. The implant of claim 4 wherein the single tether is coupled to the first and second end members with the tether disposed beneath the first and second endplate contact surfaces.
6. The implant of claim 1 wherein the collapsible intermediate section comprises a mesh member secured about a perimeter of the first and second end members.
7. The implant of claim 1 wherein the collapsible intermediate section maintains the first size to space the first and second end members the first distance apart when the inflatable member is not expanded through the introduction of the substance.
8. The implant of claim 1 wherein the collapsible intermediate section comprises attachment members slidably engaged to permit movement of the end members in an expansion direction, the attachment members including position locks at predetermined heights to stabilize the implant.
9. An implant for insertion between vertebral body endplates in a patient, the implant comprising:
- a first end member including a first endplate contact surface;
- a second end member including a second endplate contact surface;
- a collapsible intermediate section disposed between the first and second end members, the intermediate section including an opening; and
- an interior member positionable within the intermediate section, the interior member inflatable between a compressed size in which the interior member will pass through the opening and an expanded size in which the interior member will not pass through the opening.
10. The implant of claim 9 wherein the collapsible intermediate section is flexible.
11. The implant of claim 9 wherein the collapsible intermediate section comprises a plurality of tethers secured about a perimeter of the first and second end members, the distance between adjacent tethers forming the opening.
12. The implant of claim 9 wherein the collapsible intermediate section comprises a single tether coupled between a perimeter of the first and second end members in a plurality of runs, the distance between adjacent runs forming the opening.
13. The implant of claim 12 wherein the single tether is coupled to the first and second end members with the tether disposed beneath the first and second endplate contact surfaces.
14. The implant of claim 9 wherein the collapsible intermediate section comprises a mesh member secured about a perimeter of the first and second end members.
15. The implant of claim 9 wherein when the interior member is at the compressed size, the first and second end members are a first distance apart and when the interior member is at the expanded size, the first and second end members are a second greater distance apart.
16. The implant of claim 15 wherein the collapsible intermediate section maintains the first and second end members the first distance apart when the interior member is at the compressed size.
17. The implant of claim 9 wherein the collapsible intermediate section comprises attachment members slidably engaged to permit movement of the end members in an expansion direction, the attachment members including position locks at predetermined heights to stabilize the implant.
18. A method of supporting vertebral bodies, the method comprising the steps of:
- positioning an implant between endplates of the vertebral members while the implant is in a first orientation having a first height;
- inserting an inflatable member through an opening in the implant;
- introducing a substance into the inflatable member;
- inflating the inflatable member to an expanded size in which the inflatable member is captively retained within the implant; and
- separating first and second end members and increasing a height of the implant.
19. The method of claim 18 wherein the substance includes a bone growth promoting substance.
20. The method of claim 18 wherein the step of separating first and second end members and increasing a height of the implant comprises forcing a bone-contact surface of the first and second end members into contact with the endplates of the vertebral members.
21. The method of claim 18 wherein the step of separating first and second end members and increasing a height of the implant comprises extending a collapsible intermediate section that is coupled between the end members.
22. The method of claim 18 wherein the step of separating first and second end members and increasing a height of the implant comprises extending a tether that is coupled between the end members.
23. A method of supporting vertebral members, the method comprising the steps of:
- coupling first and second end members with a collapsible intermediate section;
- positioning an inflatable member within the collapsible intermediate section;
- inserting an amount of a substance into the inflatable member;
- filling the inflatable member with the substance and causing the inflatable member to contact faces of the first and second end members;
- exerting an expansion force at the faces and expanding the collapsible intermediate section and separating the first and second end members to an increased height; and
- further expanding the first and second members into contact with the vertebral members.
24. The method of claim 23 wherein the substance includes a bone growth promoting substance.
25. The method of claim 23 wherein prior to filling the inflatable member with the substance and causing the inflatable member to contact faces of the first and second end members, the inflatable member is sized to pass through an opening in the collapsible intermediate section.
26. The method of claim 23 wherein the step of exerting an expansion force at the faces and expanding the collapsible intermediate section comprises extending a tether that is coupled between the first and second end members.
Type: Application
Filed: Jul 21, 2006
Publication Date: Jan 24, 2008
Inventor: Jason A. Edie (Memphis, TN)
Application Number: 11/491,450