The present invention relates to orthopedic implants, and more particularly, to orthopedic implants made from metal mesh material.
In order to stabilize a bone or bony segment, such as the spinal column or a fractured bone, it is known to secure a rigid metal plate, rod, or other rigid support to the bone portions comprising the bone segment. Such rigid supports are useful, for example, in stabilizing and immobilizing a fracture of the bone since the support can be secured to the bone portions on each side of the fracture.
With respect to the spinal column, various techniques require access to an intervertebral disc space. Examples of such techniques include the repair of a herniated disc or the insertion of one or more interbody fusion devices, interbody spacers, or artificial discs. In order to access the disc space, one or more spinal ligaments and bony tissue may have to be severed or at least partially resected to allow insertion of surgical instruments and implants into the disc space. Posterior or anterior rigid metal supports can be used to stabilize the spinal column after these techniques are completed. Furthermore, devices inserted in the disc space can be made from rigid, inert metal material, bone material, or polymeric material.
It has been stated by some writers that the use of rigid metal plates to immobilize bones and bony portions can have certain drawbacks since such a plate will be in close contact with the vasculature and tissue along the bone. For example, it has been stated that the potential for screw back out and plate loosening creates a risk for erosion of the vasculature and the surrounding tissue. It has also been stated that rigid metal plates could bend in an undesired manner or break due to compressive loading and fatigue of the metal. A fracture or undesired bend in the plate could erode the tissue and vasculature surrounding the plate. Metal plates could also cause stress shielding.
In situations where spinal fusion is desired, it is known to place rigid metal supports in the disc space. Bone growth material can be placed in these supports. However, in the case of metal supports, openings must be formed through the walls of the support to accommodate fusion. In order to maintain the ability of the support to resist the in-vivo loads, these holes must be limited in number and in size so that the implant retains its structural integrity, providing relatively large regions on the implant which have no bone ingrowth.
Improved orthopedic implants that avoid at least some of the problems associated with rigid supports are therefore needed. The implants should be resistant to fatigue, stress shielding and the loads that are typically applied to the bone or bony segment. What is further needed are improved orthopedic implants to repair or replace resected ligaments or bony tissue, while the implant promotes bone ingrowth, fusion and/or healing. Also needed are improved orthopedic implants that have a profile that is as low as possible to avoid the potential complications associated with the vasculature and other tissue in this anatomic region. In addition, it is desirable to have orthopedic implants that avoid the complications with rigid supports. The present invention is directed toward meeting these needs, among others.
The present invention relates to orthopedic implants made at least partially from metal mesh material to form an orthopedic implant. In a preferred form, the metal mesh material includes metal wire of suitable tensile strength and which is not subject to substantial creep deformation or in vitro degradation. In a further preferred form, the mesh material can be treated in order to promote bone growth, to deliver pharmaceutical agents, such as antibiotics, anti-inflammatories or other beneficial treatments.
In one form, it is contemplated that the wire used to form the mesh can be made from stainless steel, cobalt-chrome alloy, titanium, titanium alloy, or nickel-titanium shape memory alloys, among others. It is further contemplated that the metallic wire can be interwoven with non-resorbable polymers such as nylon fibers, carbon fibers and polyethylene fibers, among others, to form a metal-polymer composite weave. Further examples of suitable non-resorbable materials include DACRON and GORE-TEX. In preferred embodiments, the mesh includes one or more reinforcing elements or members attached to the wires. Specific applications for the implants of the present invention include, for example, a prosthetic ligament, a tension band, an interbody fusion or spacer device, or an external fixation device that extends across one or more joints, bone defects or fractures of a bony segment or bone.
It is contemplated that the implants of the present invention can be constructed from one or more layers of mesh material. It is further contemplated that multiple layers of mesh material can be stacked one on top of another and attached by sewing, suturing, rivets, grommets, an adhesive, or other attachment system. It is also contemplated that the mesh layers can be seeded in vitro with bone forming cells, such as osteoblasts, and/or with growth factors. Multiple layers of osteoblast-seeded mesh may be stacked on top of one another and further allowed to or encouraged to proliferate. Due to the attachments formed between cells, a biologic metal-bone composite structure is created in-vitro. Bone growth material or bone material can also be placed between or within the mesh layers.
In one specific form of the present invention, layers of biologic metal-bone composite material can be stacked on top of each other to form a relatively rigid plate for immobilizing fractures or adjacent bone sections. In another form, the mesh material is used to form an annulus repair device. In a further form of the invention, one or more stiff rods may be attached to or placed between the layers of the woven material to act as reinforcing spars. The reinforced implant can be used in lieu of a fixation plate, for example, to wrap around a long bone to immobilize a fracture.
In another form of the present invention, the mesh material can be used to form a hollow implant having application as an interbody fusion device or interbody spacer. It is also contemplated that the mesh material can be seeded in vitro with osteoblasts, and/or formed with bone growth material or bone material between or within the layers. The hollow implant can act as a bag or container for holding material that allows the implant to resist compressive loads. Some examples of curable materials include those that are flowable above the body temperature, but solidify or otherwise cure in vivo to form a rigid core in the bag. Other examples of curing materials include polyarcylate, polymethacrylate, poly(methyl)methacrylate, calcium sulfate, various forms of calcium phosphate, and liquid silicone. Bone graft, hydrogel, or other non-curable material could be placed in the hollow interior. In a further form, the implant could be formed around a solid body made from bone or metal, for example.
In one embodiment, the hollow implant is in the form of a bag that has a hollow interior, an open end and an opposite closed end. The bag can have reinforcing fibers that extend through the hollow interior across at least the internal diameter of the bag. The bag can be flexible; for example, the bag can be collapsed much like a deflated balloon. The collapsed or smaller bag would facilitate surgical implantation at the targeted treatment site. The bag may be filled with a curing material under sufficient pressure in its liquid state to tension the reinforcing fibers and expand the bag to a desired volume either prior to or more preferably after implantation. Once the material cures, residual tensile stresses left in the reinforcing fibers apply compressive stress to the cured matrix material, thereby modulating the bulk mechanical properties of the structure.
In other embodiments, the mesh material forms a hollow implant that has an injection port through which bone growth material or other curing material can be injected. Once filled with material, the injection port can be closed by sutures, staples, adhesive, caps, and the like. Alternatively, the port can be self-sealing. In one specific application, the hollow implant is an interbody cage or spacer is insertable into an intervertebral disc space.
The mesh material of the present invention may be modified in a number of ways, including electrochemical surface modifications, coating applications and thermal treatments. For example, the mesh material can be anodized, can be thermally hardened, can have interwoven collagen material, can have collagen molecules immobilized to its surface, can be coated/impregnated with an elastomer, adhesive or a therapeutic agent, or can have alternating strands of metal wires and demineralized bone matrix or collagen. The alternate weave pattern may be used to adsorb or otherwise attach bone morphogenetic proteins, antibiotic agents or other therapeutic or beneficial molecules.
These and other aspects, forms, embodiments, features and advantages of the present invention will be apparent from the following description of the illustrated embodiments.
a), 1(b), 1(c), and 1(d) illustrate various weave patterns for mesh layers used to construct implants according to various embodiments of the present invention.
a), 2(b), and 2(c) illustrate various steps in forming mesh layers and base members used to construct implants according one embodiment of the present invention.
a) and 5(b) are an elevational view and a top plan view, respectively, of an annulus repair and ligament implant according to a further embodiment of the present invention.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the illustrated embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any such alterations and further modifications of the invention, and any such further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
The present invention relates to orthopedic implants made from metal material forming a mesh from which an implant can be fabricated. In a preferred form, the metal material includes metal wire or fiber of suitable tensile strength and which is not subject to substantial creep deformation or in vitro degradation. Preferably, the wire is of such size and/or material that the implant is flexible yet inelastic. It is contemplated that the metal mesh can be formed by weaving or knitting the wires into the desired pattern, or by attaching the wires to one another in the desired pattern by welding, thermal bonding, electrochemical adhesion, adhesive, or other attachment process.
As shown in
As shown in
a) through 2(c) illustrate various steps in the method of forming a base member 200 using mesh members 25, 25′, 25″ and 28. As shown in
It is contemplated that multiple layers of orthogonal mesh members 25, non-orthogonal mesh members 25′, or combinations of orthogonal/non-orthogonal mesh members 25, 25′, 25″ and 28 can be stacked one upon another. The properties of each layer and the properties between the various layers can be varied in order to modulate the properties of the implant in various directions and in various locations. The implant can be a laminated construct having differing plies or layers. This allows the properties of base member 100 to be varied in specific regions for any number of purposes, such as to provide extra reinforcement in highly loaded regions, allow for a specific stress-strain response pattern, or to provide predetermined failure locations on the implant.
The present invention contemplates that various materials may be used for the metal wire used in the mesh members 25, 25′, 25″ and 28. Examples of such materials include stainless steels, cobalt chrome alloys, titanium, titanium alloys, and nickel titanium. It is further contemplated that the metal wires forming mesh members 25, 25′, 25″ and 28 can be interwoven with non-metallic materials such as nylon fibers, carbon fibers, fibers made from collagen strands, or polyethylene fibers, for example. In a preferred embodiment the selected materials provide a radiopaquic implant.
The wire used to form mesh members 25, 25′, 25″ and 28 can be modified through a number of processes, such as electrochemical surface modifications, coating applications, thermal treatments and so forth. For example, mesh members 25, 25′, 25″ and 28 can be made from a titanium wire and subsequently anodized. Another surface modification that is contemplated is to provide collagen immobilized to the surface of mesh members 25, 25′, 25″ and 28. Other treatments contemplate that mesh members 25, 25′, 25″ and 28 can be thermally treated before and/or after weaving. Mesh members 25, 25′, 25″ and 28 can also be coated or impregnated with an elastomer such as silicone or polyurethane or a bone cement.
In addition to in vitro seeding of osteoblasts, other treatments for the mesh members 25, 25′, 25″ and 28 are contemplated that also provide an implant that allows for bone ingrowth and regeneration of bony tissue. For example, in one embodiment the mesh members 25, 25′, 25″ and 28 are provided with alternating strands of metal wire and demineralized bone matrix. In another embodiment, mesh members 25, 25′, 25″ and 28 are smeared or coated with an osteoinductive bone paste, such as OSTEOFIL. In another embodiment, mesh members 25, 25′, 25″ and 28 have alternating strands of metal wires and collagen, and the mesh members 25, 25′, 25″ and 28 are subsequently soaked in a pharmacological agent such as recombinant human bone morphogenic protein, antibiotic agents, or other similar material. Still other embodiments contemplate no treatment is provided on mesh members 25, 25′, 25″ and 28.
Several layers of mesh members 25, 25′, 25″ and 28 can be stacked on top of another to form base member 100, which is then cut or molded into the desired shape for use as a bone plate, ligament, annulus repair device, intervertebral cage or interbody spacer, or fracture immobilization device. The desired geometry of the implant can be cut from base member 100 using any number of cutting processes appropriate to the combination of materials and geometries used in the implant design.
Referring now to
Referring now to
Referring now to
Referring now to
In preferred embodiments, spars 38a, 38b are provided to exhibit greater resistance to deformation than that exhibited or observed for a fiber or a finite number of bundled fibers preferably a greater resistance to deformation than a bundle exceeding 10 fibers, still yet more preferably exceeding a bundle of 15 fibers. The individuals spars 38a, 38b can be formed of the same material as the fibers or a different material. If the spars 38a, 38b are formed of the same or similar material as the fibers, the spars 28a, 38b can be thicker and/or heated treated to increase the material strength. Alternatively, the spars can be formed of a different, harder material than the fibers. In one form, the spar exhibits greater tensile strength than the fibers. The spars can induce substantial inelasticity into the implant. The spars can be formed of a shape memory polymeric material, or metal or metal alloy similar to those forming the fibers or the spar can be formed of a shape memory metallic alloy such as NITINOL®.
The spar(s) can be connected or attached to the fibers by a wide variety of methods and materials. Typically the spar(s) will be attached to two or more fibers using the same or similar methods and materials that interconnect the fibers. Although it should be understood that in selected implants the methods/materials used to interconnect the plurality of fibers need not be the same methods/materials used to connect the spar(s) to the fibers.
As shown in
Referring now to
The mesh material of the present invention also has application with bags or other devices capable of holding various curing materials that are to be inserted internally to repair a fracture or to span a joint, such as between vertebrae. For example, in
The mechanical properties of the injected material can be altered to meet design parameters by varying the properties of the wire reinforcement. Examples of parameters that can be varied include the diameter of the wire, the number of wires, direction of the wires, and injection pressure for the curing material. The surface finish of the wire can also be treated to alter the surface interactive properties of the wire in relation to the injected material. For example, the wire can be provided with a coating or a thermal treatment in order to alter specific properties. The tissue growth/bone growth material used with implant 50 promotes bone growth and fusion and incorporation of implant 50. Also the external surface of the implant fibers treated with a bone cement to secure the implant to a selected bone or tissue structure.
Referring now to
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While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the illustrated embodiments have been shown and described, and that all changes and modifications that come within the spirit of the invention are desired to be protected.
This application is a continuation of U.S. patent application Ser. No. 10/082,579 filed Feb. 25, 2002 now U.S. Pat. No. 6,827,743, which claims the benefit of U.S. Provisional Application Ser. No. 60/272,264 filed Feb. 28, 2001, which is hereby incorporated by reference in its entirety.
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Number | Date | Country | |
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Child | 10900614 | US |