US 20070162132 A1
Implants and methods for augmentation, preferably by minimally invasive procedures and means, of body tissue, including in some embodiments repositioning of body tissue, for example, bone and, preferably vertebrae are described. The implant may comprise one or more chain linked bodies inserted into the interior of body tissue. As linked bodies are inserted into body tissue, they may fill a central portion thereof and for example in bone can push against the inner sides of the cortical exterior surface layer, for example the end plates of a vertebral body, thereby providing structural support and tending to restore the body tissue to its original or desired treatment height. A bone cement or other filler can be added to further augment and stabilize the body tissue. The preferred implant comprises a single flexible monolithic chain formed of allograft cortical bone having a plurality of substantially non-flexible bodies connected by substantially flexible links.
1. An apparatus for augmentation of body tissue comprising:
a flexible elongated member having a longitudinal length substantially larger than its height or its width, wherein the member comprises:
a plurality of substantially non-flexible bodies; and
a plurality of substantially flexible links interconnecting the bodies, the bodies and links connected end-to-end to form the elongated member,
wherein the elongated member is formed of a biocompatible material.
2. The apparatus of
3. The apparatus of
4. The apparatus of
5. The apparatus of
6. The apparatus of
7. The apparatus of
8. The apparatus of
9. The apparatus of
10. The apparatus of
11. The implant of
12. The implant of
13. An apparatus for augmenting a body tissue comprising an elongated member having a longitudinal length greater than either its height or width, the elongated member formed of allograft bone and comprising:
a plurality of bodies and
a plurality of links interconnecting the bodies wherein the links are more flexible and have a greater degree of demineralization than the bodies.
14. The apparatus of
15. The apparatus of
16. The apparatus of
17. A method of treating osteoporotic bone comprising:
providing a monolithic, flexible, elongated member having a longitudinal length greater than either its height or its width, the elongated member formed of allograft bone comprising a plurality of bodies connected together by a plurality of links wherein the links are located between the bodies and the links have a greater degree of demineralization and flexibility than the bodies,
inserting the elongated member into the interior of the bone.
18. The method of
19. The method of
20. The method of
21. The method of
22. The method of
23. The method of
creating an opening in the cortical exterior surface of a bone; and
creating a cavity within the interior of the bone.
24. The method of
25. The method of
26. The method of
creating an opening in the exterior surface of the bone;
creating a passageway from the opening to the interior of the bone; and
filling at least one of the opening and the passageway with a plug of bone cement to prevent the escape of the elongated member from the interior of the bone.
27. The method of
28. The method of
29. The method of
30. A method of treating the spine comprising:
providing a flexible elongated member having a longitudinal length greater than its height or width, the elongated member formed of allograft bone comprising a plurality of bodies connected together by a plurality of links wherein the links are located between the bodies and the links have a greater degrees of demineralization and flexibility than the bodies; and
inserting the elongated member between two adjacent vertebrae.
31. The method of
32. The method of
33. The method of
34. A method of manufacturing an allograft bone implant comprising:
machining from bone an elongated member having a longitudinal length greater than either its height or width, the elongated member having a plurality of bodies connected together by a plurality of links wherein the links are located between the bodies and the bodies are connected along a line in end-to-end fashion.
35. The method according to
36. The method of
37. The method of
38. The method of
covering the plurality of bodies to prevent the bodies from being subject to demineralizing solution, and
exposing the links and covered bodies to demineralizing solution.
This application claims priority to U.S. Provisional Patent Application No. 60/753,782, filed Dec. 23, 2005 and U.S. Provisional Application No. 60/810,453, filed Jun. 2, 2006, the entirety of each of which is incorporated by reference herein.
The invention relates to implants, and more particularly to flexible chain implants for augmenting or supporting bones or other structures, such as, for example vertebral discs.
Vertebral compression fractures, as illustrated in
More recently, minimally invasive surgical procedures for treating vertebral compression fractures have been developed. These procedures generally involve the use of a cannula or other access tool inserted into the posterior of the effected vertebral body, usually through the pedicles. The most basic of these procedures is vertebroplasty, which literally means fixing the vertebral body, and may be done without first repositioning the bone.
Briefly, a cannula or special bone needle is passed slowly through the soft tissues of the back. Image guided x-ray, along with a small amount of x-ray dye, allows the position of the needle to be seen at all times. A small amount of polymethylmethacrylate (PMMA) or other orthopedic cement is pushed through the needle into the vertebral body. PMMA is a medical grade substance that has been used for many years in a variety of orthopedic procedures. Generally, the cement is mixed with an antibiotic to reduce the risk of infection, and a powder containing barium or tantalum, which allows it to be seen on the X-ray.
Vertebroplasty can be effective in the reduction or elimination of fracture pain, prevention of further collapse, and a return to mobility in patients. However, this procedure may not reposition the fractured bone and therefore may not address the problem of spinal deformity due to the fracture. It generally is not performed except in situations where the kyphosis between adjacent vertebral bodies in the effected area is less than 10 percent. Moreover, this procedure requires high-pressure cement injection using low-viscosity cement, and may lead to cement leaks in 30-80% of procedures, according to recent studies. In most cases, the cement leakage does no harm. In rare cases, however, polymethymethacrylate or other cement leaks into the spinal canal or the perivertebral venous system and causes pulmonary embolism, resulting in death of the patient.
More advanced treatments for vertebral compression fractures generally involve two phases: (1) reposition, or restoration of the original height of the vertebral body and consequent lordotic correction of the spinal curvature; and (2) augmentation, or addition of material to support or strengthen the fractured or collapsed bone.
One such treatment, balloon kyphoplasty (Kyphon, Inc.), is disclosed in U.S. Pat. Nos. 6,423,083, 6,248,110, and 6,235,043 to Riley et al., each of which is incorporated by reference herein in its entirety. A catheter having an expandable balloon tip is inserted through a cannula, sheath or other introducer into a central portion of a fractured vertebral body comprising relatively soft cancellous bone surrounded by fractured cortical bone. Kyphoplasty then achieves the reconstruction of the lordosis, or normal curvature, by inflating the balloon, which expands within the vertebral body restoring it to its original height. The balloon is removed, leaving a void within the vertebral body, and PMMA or other filler material is then injected through the cannula into the void as described above with respect to vertebroplasty. The cannula is removed and the cement cures to augment, fill or fix the bone.
Disadvantages of this procedure include the high cost, the repositioning of the endplates of the vertebral body may be lost after the removal of the balloon catheter, and the possible perforation of the vertebral endplates during the procedure. As with vertebroplasty, perhaps the most feared, albeit remote, complications concerning kyphoplasty are related to leakage of bone cement. For example, a neurologic deficit may occur through leakage of bone cement into the spinal canal. Such a cement leak may occur through the low resistance veins of the vertebral body or through a crack in the bone which was not appreciated previously. Other complications include additional adjacent level vertebral fractures, infection and cement embolization. Cement embolization occurs by a similar mechanism to a cement leak. The cement may be forced into the low resistance venous system and travel to the lungs or brain resulting in a pulmonary embolism or stroke.
Another approach for treating vertebral compression fractures is the Optimesh system (Spineology, Inc., Stillwater, Minn.), which provides minimally invasive delivery of a cement or allograft or autograft bone using an expandable mesh graft balloon, or containment device, within the involved vertebral body. The balloon graft remains inside the vertebral body after its inflation, which prevents an intraoperative loss of reposition, such as can occur during a kyphoplasty procedure when the balloon is withdrawn. One drawback of this system, however, is that the mesh implant is not well integrated in the vertebral body. This can lead to relative motion between the implant and vertebral body, and consequently to a postoperative loss of reposition. Additional details regarding this procedure may be found, for example, in published U.S. Patent Publication Number 20040073308, which is incorporated by reference herein in its entirety.
Still another procedure used in the treatment of vertebral compression fractures is an inflatable polymer augmentation mass known as a SKy Bone Expander. This device can be expanded up to a pre-designed size and (Cubic or Trapezoid) configuration in a controlled manner. Like the Kyphon balloon, once optimal vertebra height and void are achieved, the SKy Bone Expander is removed and PMMA cement or other filler is injected into the void. This procedure therefore entails many of the same drawbacks and deficiencies described above with respect to kyphoplasty.
In some cases of fractured or otherwise damaged bones, bone grafts are used to repair or otherwise treat the damaged area. In the United States alone, approximately half a million bone grafting procedures are performed annually, directed to a diverse array of medical interventions for complications such as fractures involving bone loss, injuries or other conditions necessitating immobilization by fusion (such as for the spine or joints), and other bone defects that may be present due to trauma, infection, or disease. Bone grafting involves the surgical transplantation of pieces of bone within the body, and generally is effectuated through the use of graft material acquired from a human source. This is primarily due to the limited applicability of xenografts, transplants from another species.
Orthopedic autografts or autogenous grafts involve source bone acquired from the same individual that will receive the transplantation. Thus, this type of transplant moves bony material from one location in a body to another location in the same body, and has the advantage of producing minimal immunological complications. It is not always possible or even desirable to use an autograft. The acquisition of bone material from the body of a patient typically requires a separate operation from the implantation procedure. Furthermore, the removal of material, oftentimes involving the use of healthy material from the pelvic area or ribs, has the tendency to result in additional patient discomfort during rehabilitation, particularly at the location of the material removal. Grafts formed from synthetic material have also been developed, but the difficulty in mimicking the properties of bone limits the efficacy of these implants.
As a result of the challenges posed by autografts and synthetic grafts, many orthopedic procedures alternatively involve the use of allografts, which are bone grafts from other human sources (normally cadavers). The bone grafts, for example, are placed in a host bone and serve as the substructure for supporting new bone tissue growth from the host bone. The grafts are sculpted to assume a shape that is appropriate for insertion at the fracture or defect area, and often require fixation to that area for example by screws, pins, cement, cages, membranes, etc. Due to the availability of allograft source material, and the widespread acceptance of this material in the medical community, the use of allograft tissues is likely to expand in the field of musculoskeletal surgery.
Notably, the various bones of the body such as the femur (thigh), tibia and fibula (leg), humerus (upper arm), radius and ulna (lower arm) have geometries that vary considerably. In addition, the lengths of these bones vary; for example, in an adult the lengths may vary from 47 centimeters (femur) to 26 centimeters (radius). Furthermore, the shape of the cross section of each type of bone varies considerably, as does the shape of any given bone over its length. While a femur has a generally rounded outer shape, a tibia has a generally triangular outer shape. Also, the wall thickness varies in different areas of the cross-section of each bone. Thus, the use of any given bone to produce an implant component may be a function of the bone's dimensions and geometry. Machining of bones, however, may permit the production of implant components with standardized or custom dimensions.
As a collagen-rich and mineralized tissue, bone is composed of about forty percent organic material (mainly collagen), with the remainder being inorganic material (mainly a near-hydroxyapatite composition resembling 3Ca3(PO4)2Ca(OH)2). Structurally, the collagen assumes a fibril formation, with hydroxyapatite crystals disposed along the length of the fibril, and the individual fibrils are disposed parallel to each other forming fibers. Depending on the type of bone, the fibrils are either interwoven, or arranged in lamellae that are disposed perpendicular to each other.
Bone tissues have a complex design, and there are substantial variations in the properties of bone tissues depending upon the type of bone (i.e., leg, arm, vertebra) as well as the overall structure. For example, when tested in the longitudinal direction, leg and arm bones have a modulus of elasticity of about 17 to 19 GPa, while vertebra tissue has a modulus of elasticity of less than 1 GPa. The tensile strength of leg and arm bones varies between about 120 MPa and about 150 MPa, while vertebra have a tensile strength of less than 4 MPa. Notably, the compressive strength of bone varies, with the femur and humerus each having a maximum compressive strength of about 167 MPa and 132 MPa respectively. Again, the vertebra have a far lower compressive strength usually of no more than about 10 MPa.
With respect to the overall structure of a given bone, the mechanical properties vary throughout the bone. For example, a long bone (leg bone) such as the femur has both compact bone and spongy bone. Cortical bone, the compact and dense bone that surrounds the marrow cavity, is generally solid and thus carries the majority of the load in major bones. Cancellous bone, the spongy inner bone, is generally porous and ductile, and when compared to cortical bone is only about one-third to one-quarter as dense, one-tenth to one-twentieth as stiff, but five times as ductile. While cancellous bone has a tensile strength of about 10-20 MPa and a density of about 0.7 g/cm3, cortical bone has a tensile strength of about 100-200 MPa and a density of about 2 g/cm3. Additionally, the strain to failure of cancellous bone is about 5-7%, while cortical bone can only withstand 1-3% strain before failure. It should also be noted that these mechanical characteristics may degrade as a result of numerous factors such as any chemical treatment applied to the bone material, and the manner of storage after removal but prior to implantation (i.e. drying of the bone).
Notably, implants of cancellous bone incorporate more readily with the surrounding host bone, due to the superior osteoconductive nature of cancellous bone as compared to cortical bone. Furthermore, cancellous bone from different regions of the body is known to have a range of porosities. For example, cancellous bone in the iliac crest has a different porosity than cancellous bone in a femoral head. Thus, the design of an implant using cancellous bone may be tailored to specifically incorporate material of a desired porosity.
There remains a need in the art to provide safe and effective devices and methods for augmentation of fractured or otherwise damaged vertebrae and other bones, preferably devices that may be implanted utilizing minimally invasive methods of implantation.
A flexible chain according to one embodiment comprises a series or other plurality of preferably solid, substantially non-flexible body portions (also referred to as bodies or beads) and a series of flexible link portions (also referred to as links or struts). The preferably solid, substantially non-flexible body portions preferably are capable of withstanding loads that are applied in any direction, and the flexible link portions of the implant preferably are disposed between the substantially non-flexible body portions and preferably are flexible in any direction, although they may be flexible in only selected or desired directions. The bodies may be substantially solid, semi-solid or hollow and preferable of sufficient strength to support the loads typical for the body location in which they are implanted. The link portions may be solid, semi-solid, or hollow and preferably of sufficient flexibility to allow the adjacent bodies to touch one another upon bending of the elongate member or chain. The material of both portions, the flexible link and non-flexible body portions, preferably is the same and form one single, flexible monolithic chain (FMC).
In one aspect of the invention, an apparatus for augmentation of body tissue, for example bone, comprises a flexible elongated member, or chain, having a longitudinal length substantially larger than its height or its width. The flexible elongated member comprises a plurality of substantially non-flexible bodies and a plurality of substantially flexible links interconnecting the bodies. The bodies and links are connected end-to-end to form the elongated member, wherein the elongated member is formed of a biocompatible material.
The bodies may be different sizes and shapes than the links or they may be the same shape, same size, or both. In addition, each body and link may be a different size and shape than other bodies or links. In one embodiment, the beads can be shaped so that they can fit together to minimize interstial spaces. For example, the beads may be shaped as cubes or other polyhedrals that can be stacked together in such a way that there is little space between beads, or a predetermined percentage range of interstial space.
The elongated member may be formed as an integral monolithic chain, which may be formed of bone, such as, for example, allograft bone. The flexible links may be formed of bone that has been demineralized to a greater extent than the bodies. Optionally, a coating may be applied to at least a portion of the elongated member, e.g. a coating comprising a therapeutic agent, a bone cement, an antibiotic, a bone growth stimulating substance, bone morphogenic protein (BMP) or any combination thereof. Therapeutic agents, or drug agents (e.g., antibodies), or biologics (e.g., one or more BMPs) can be coated, or attached via peptides, adsorbed, sorbed or in some other way perfused onto or into the elongated member; either the bodies, the links or both. In some embodiments, the coating may comprise a bone cement that may be activated upon insertion into the bone. In other embodiments, at least a portion of the bodies comprise an outer surface configured to promote bone in-growth.
In another aspect, a flexible chain implant may be impacted or inserted into a cavity, void or hollow space, e.g., through a small narrow opening. Such cavities may be, for example, voids in long bones, intervertebral disc spaces or vertebral bodies. Such voids may have occurred due to infections, disease, trauma fractures, degenerative disc disease process, tumors or osteotomies. In other embodiments, a void may be created by using a tool to compact or remove cancellous or cortical bone or other tissue prior to implantation. The chain may thereafter be implanted to fill the created void. Depending on the insertion or impaction force and depending on the amount or the length of chain devices inserted, the device will fill and/or support the tissue structure, preferably bone structure to a restored size and/or height. In an alternative embodiment, no void or cavity may be present, and even if a void or cavity is present the chain implant or elongated member may be inserted and/or implanted in a manner to compact the material and bone cells within the bone and to further fill the bone in a manner that it can better support a load and preferably fill the bone in a manner to restore its original and/or treated size and height.
In another aspect, one or more flexible monolithic chains may be implanted into diseased, damaged or otherwise abnormal bones to treat, for example, long bone infections, comminuted complex fractures, tumor resections and osteotomies. An FMC device may also be used to treat disease or abnormal pathology conditions in spinal applications, including, for example, degenerative disc disease, collapsed intervertebral discs, vertebral body tumor or fractures, and vertebral body resections. The elongated member or chain device can be used as a preventive measure to augment a bone, spinal disc or an implant, e.g., and intervertebral body implant to promote fusion. The elongated member may be used within a vertebra or between two vertebra. The elongated member or chain also may be used for example in an intervertebral body fusion procedure, for example, as an implant inserted into the disc space between two vertebra, as an implant inserted into and retained by the disc annulus, or in combination with an additional implant inserted in the disc space between two vertebra.
In another embodiment, a kit comprises various combinations of assemblies and components according to the present invention. A kit may include, for example, a package or container comprising an elongated member, for example an FMC device, and a cannula or other introducer or device for implanting the elongated member. In other embodiments, a kit may comprise instruments to create a cavity (e.g., balloon catheter), an FMC device and a cement or other filler material and/or a syringe or other apparatus for injecting a FMC device and/or such filler material into a vertebral body.
The present invention can be better understood by reference to the following drawings, wherein like references numerals represent like elements. The drawings are merely exemplary to illustrate certain features that may be used singularly or in combination with other features and the present invention should not be limited to the embodiments shown.
FIGS. 3A-D is an illustration depicting a method of fabricating a flexible monolithic chain.
FIGS. 4A-C are perspective views of other embodiments of a flexible monolithic chain having flexible portions and non-flexible portions with substantially uniform dimensions.
FIGS. 9A-D are top views depicting a minimally invasive method for implanting a flexible monolithic chain within a vertebral body.
Bodies 210 of chain 200 are preferably formed of bone, e.g., cortical bone, cancellous bone or both, but preferably cortical bone. In other embodiments, chain 200 may be comprised of any biocompatible material having desired characteristics, for example a biocompatible polymer, metal, ceramic, composite or any combination thereof. Bodies 210 may be absorbable or resorbable by the body. For some applications, the bodies 210 preferably have osteoinductive properties or are made at least partly from osteoinductive materials. The outer circumferential shape of the body may be the same as adjacent links. Alternatively or in addition, the outer circumferential shape of the body may be the same size as adjacent links. Bodies 210 may be of uniform or non-uniform size, shape and/or materials, and may be linked in series, for example by one or more flexible or semi-flexible linking portions 220, which can form struts of any desired length between bodies 210. Linking portions are preferably, although not necessarily, formed of the same material as bodies 210.
A chain 200 may have any desired number of linked bodies 210, and may have a first end 202 and a second end 204. In other embodiments, chain 200 may be formed in a loop, ring, or other configuration having no ends, or may be configured to have multiple extensions and/or multiple ends, for example like branches of a tree.
The one or more linking portions 220 may be comprised of any biocompatible material having desired characteristics of flexibility, strength, and the like. In preferred embodiments, linking portions 220 may be formed, at least in part, of substantially the same material as bodies 210. In some embodiments, chain 200, including bodies 210 and/or linking portions 220, may be resorbable. The bodies 210 may be of uniform or non-uniform size, and may be spaced by linking portions 220 at uniform or non-uniform increments.
All dimensional aspects of the chain 200 can be made to fit any particular anatomy or delivery device. For example, for applications of vertebral body augmentation, the diameter 230 of bodies 210, e.g., as shown in
In some embodiments, each of the bodies 210 and struts 220 of a chain may be of the same configuration and/or dimensions as other bodies 210 and struts within the chain 200. In other embodiments, bodies 210 and/or struts 220 within a chain may have different configurations or dimensions. In still other embodiments, the non-flexible bodies 210 and flexible portions 220 may be of the same shape and size to form a relatively uniform structure, for example as shown in
A chain 200 may be made as long as practical for a particular application. For example, an exemplary chain 200 for implantation into a bone may be about 100 mm in length. In other embodiments, chain 200 may be of other lengths, for example less than about 1 mm, between about 1 mm and about 100 mm, or greater than 100 mm. In some embodiments, two or more chains 200 and/or other implants may be used in combination with each other. Chain 200 may be connected end to end to form larger chains.
While the present invention is preferably directed to the creation of implants from allograft material, the present invention may also be applied to implants that utilize other materials, including but not limited to the following: xenograft, autograft, metals, alloys, ceramics, polymers, composites, and encapsulated fluids or gels. Furthermore, the implants described herein may be formed of materials with varying levels of porosity, such as by combined bone sections from different bones or different types of tissues and/or materials having varying levels of porosity.
Also, the implants described herein may be formed of bone materials with varying mineral content. For example, cancellous or cortical bone may be provided in natural, partially demineralized, or demineralized states. Demineralization is typically achieved with a variety of chemical processing techniques, including the use of an acid such as hydrochloric acid, chelating agents, electrolysis or other treatments. The demineralization treatment removes the minerals contained in the natural bone, leaving collagen fibers with bone growth factors including bone morphogenic protein (BMP). Variation in the mechanical properties of bone sections is obtainable through various amounts of demineralization. Advantageously, use of a demineralizing agent on bone, e.g., cortical or cancellous bone, transforms the properties of the bone from a stiff structure to a relatively pliable structure. Optionally, the flexibility or pliability of demineralized bone may be enhanced when the bone is hydrated. Any desired portions of bone components, e.g., link portions 220 or any other desired portion, may be demineralized or partially demineralized in order to achieve a desired amount of malleability, elasticity, pliability or flexibility, generally referred to herein as “flexibility”. The amount of flexibility can be varied by varying in part the amount of demineralization.
In some embodiments, flexibility of demineralized or partially demineralized regions may be further enhanced by varying the moisture content of the implant or portions thereof. Bone components initially may be provided with moisture content as follows: (a) bone in the natural state fresh out of the donor without freezing, (b) bone in the frozen state, typically at −40° C., with moisture content intact, (c) bone with moisture removed such as freeze-dried bone, and (d) bone in the hydrated state, such as when submersed in water. Using the expansion and contraction properties that can be obtained during heating and cooling of the bone material, and the concomitant resorption of moisture along with swelling for some bone material, permits alternate approaches to achieving a desired flexibility of an implant within a bone or other region.
The implants may be formed entirely from cortical bone, entirely from cancellous bone, or from a combination of cortical and cancellous bone. While the implants may be created entirely from all bone material, it is also anticipated that one or more components or materials may be formed of non-bone material, including synthetics or other materials. Thus, while the implants disclosed herein are typically described as being formed primarily from bone, the implants alternatively may be formed in whole or in part from other materials such as stainless steel, titanium or other metal, an alloy, hydroxyapatite, resorbable material, polymer, or ceramic, and may additionally incorporate bone chips, bone particulate, bone fibers, bone growth materials, and bone cement. Also, while solid structures are described herein, the structure optionally may include perforations or through bores extending from one outer surface to another outer surface, or recesses formed in outer surfaces that do not extend through inner surfaces (surface porosity), or recesses formed internally. Surface texture such as depressions and/or dimples may be formed on the outer surface. The depressions and/or dimples may be circular, diamond, rectangular, irregular or have other shapes.
The flexible monolithic chain devices described herein may be used to treat disease and pathological conditions in general orthopedic applications such as long bone infections, comminuted complex fractures, tumor resections and osteotomies. Additionally the device can be used to treat disease and pathological conditions in spinal applications, such as, for example, degenerative disc disease, collapsed intervertebral discs, vertebral body tumor or fractures, vertebral body resections or generally unstable vertebral bodies. In other embodiments, a flexible monolithic chain device may be used in maxillofacial applications or in non-fusion nucleus replacement procedures.
As shown in
After machining the general desired shape in step A of
In step C of the exemplary method of
In step D, the shaped chain 200, if formed of bone, may be demineralized, e.g., in container 320 containing a demineralizing solution 322 (e.g., hydrochloric acid) or using another method. Demineralization may be allowed to occur for a specified amount of time, for example to allow the smaller, lower volume portions 220 of the device 200 to become more flexible or elastic, while the larger bodies 210 of the device remain structurally intact and substantially rigid. The amount of time and/or the concentration or composition of the demineralizing solution may be varied to provide the desired amount of flexibility or elasticity.
In some embodiments, this secondary process of demineralization can be applied to specific portions of the device 200, e.g., by masking or shielding the portions that do not or should not be treated. For example, by masking the non flexible portions 210, the flexible portions 220 can be partially or entirely demineralized, and the non-flexible portions 210 may retain their original mineralized state prior to the masking. Alternatively, an allograft device may be submerged entirely into demineralization acid without masking any portions of the device. Due to the relatively smaller shape and size of the flexible portions 220, including the surface area exposed to the demineralized agent, and depending for example upon the amount of exposure to the demineralization acid, the flexible portions 220 may demineralize entirely, or at least substantially more than the larger portions 210, which may undergo only surface demineralization. Therefore, the smaller portions 220 may become flexible and elastic while the larger portions 210 may remain relatively stiff and substantially non-flexible. For example,
The following Table 1 provides examples of demineralization times of four monolithic chains having different strut configurations. Each of the chains were formed of cortical allograft bone and had body portions 210 that were approximately 5 mm in diameter. Configurations and dimensions of the struts 220 differed between the samples. In all four samples, the struts were fully demineralized between about 3½ and 4 hours, while the beads were demineralized to an extent, but were not fully demineralized across their entire thickness. Strut dimensions correspond to distance 238 in
Table 2 below provides an example of approximate incremental changes in flexibility of strut portions 220 of a sample, e.g., Sample 1 of Table 1, as a function of duration of exposure to the hydrochloric acid bath.
Of course, other samples will attain different flexibility in different exposure times depending upon a host of factors, including concentration of acid bath, chain dimensions, temperature, original bone sample mineralization and condition, etc.
Various other configurations and methods for manufacturing monolithic or other chain implants may be used. The choice of methods may depend, at least in part, on the material or materials to be used in the particular chain device 200. If the device is made of a biocompatible polymeric material, the device can be manufactured by using conventional manufacturing methods such as but not limited to milling and turning. Alternatively, if the chain device 200 is made out of a biocompatible polymeric material, the entire device can also be injection molded.
If the chain 200 is made of a metallic material, it can be manufactured by using conventional manufacturing methods such as but not limited to milling and turning. However, the flexible components may undergo secondary processes such as annealing. The secondary process can be limited to the flexible portions of the device only, for example by masking or shielding the non-flexible portions.
In some embodiments, a chain implant 200 can be formed of any type of biocompatible material that will allow for sufficient flexibility in areas of reduced material sections (e.g., relatively narrow and flexible portions 220), while having larger sections (e.g., bodies 210) that are substantially rigid and allow for load bearing characteristics. The reduced material portions 220 may be flexible, pliable, or have elastic properties in all directions preferably without fracturing or breaking. Alternatively, the reduced material portions 210 may allow for fracture during device 200 insertion, or at another stage in a method, to allow for proper void filling. Materials may be metallic and include but are not limited to titanium and steels. Polymeric and alternatively allograft tissue materials can be used. Instead of or in addition to bone device 200 may comprise one or more other materials, e.g., a metal (titanium, a steel, or other metal), an alloy, or a polymer. In some embodiments, the material of the device 200 may have osteoconductive, osteoinductive, and/or osteogenic properties. In other embodiments, the implant device 200 may be made out of non-monolithic materials.
Referring to FIGS. 4A-C, a chain 200 may have any desired geometric configuration. For example, rigid portions 210 and flexible portions 220 may have the same or different shapes, such as cubes, cylinders, any polyhedral shapes, balls, banana or kidney shaped, or any combination thereof. Portions 210 and/or 220 may have any desired cross-sectional shape, such as for example rectangular, circular, elliptical, pentagonal, hexagonal, etc. The flexible 220 and non-flexible 210 portions may be of the same shape to form relatively uniform shaped structures as shown in FIGS. 4A-C.
As shown in
As shown in
Prior to insertion of the cannula, a passageway may be formed into the interior of the vertebral body, for example using a drill or other instrument. The chain 200 may then be inserted through the passageway, and may compact or compress the bone material inside the vertebral body. Alternatively, after the passageway is formed in the vertebral body, instruments such as, for example, currettes or balloon catheter may be used to compress and compact the bone inside the vertebral body to create a cavity. The instruments may then be removed. Alternatively, the balloon portion of the catheter may remain within the vertebral body or may form a container for the implant. The cavity in the vertebral body also may be formed by removing bone material as opposed to compacting the bone. For example, a reamer or other apparatus could be used to remove bone material from the inside of the vertebral body.
Whether a cavity is first formed in the bone structure or the chain(s) are inserted without first creating a cavity, as more linked bodies 210 of chain 200 are inserted into vertebral body 12, they may fill central portion 612 and provide structural support to stabilize a vertebral body. In a vertebra that has collapsed, as the chain implant 200 fills central portion 612 the implant, and particularly the linked bodies 210, can push against the interior or inner sides of endplates 614 and 616, thereby tending to restore vertebral body 12 from a collapsed height h1 to its original or desired treated height h2 and provide structural support to stabilize vertebral body 12. Instead of using the insertion of the chain implant to restore the height of the vertebra, an instrument can be inserted through the passageway to restore the height of the vertebra and plates. For example, a balloon catheter can be inserted to restore vertebra end plates, or an elongated instrument that contacts the inside of the end plates and pushes on them may be utilized. Additionally, the flexibility of one or more portions 220 between bodies 210 may allow bending of chain within space 612, e.g., in a uniform pattern or in a non-uniform or tortuous configuration, to aid in ensuring a thorough integration of the implant 200 within the bone 12. The configuration of bodies 210 attached by flexible portions also may permit bending to substantially fill the cavity and/or vertebral bone so no large pockets or voids are created or remain which may result in weak spots or a weakened bone structure. The flexible links may also allow the chain to collapse and possibly become entangled so that it becomes larger than its insertion hole so that it cannon be easily ejected.
In other embodiments, chain 200 may be inserted into a bone such as a vertebral body 12, e.g., through the lumen 604 of a cannula 602 or other sheath, and such sheath may be removed after implantation within the bone 12. In such embodiments, chain 200, or a portion thereof, may remain in vertebral body 12, for example, to continue augmenting the vertebra and maintain proper lordosis. In other embodiments, PMMA or another bone cement or filler (for example bone chips) may be inserted sequentially or simultaneously into vertebral body 12, e.g., through shaft and/or a cannula 602, along with bodies 210 to further enhance fixation or repair of the damaged region. Alternatively, only a plug of bone cement may be inserted into the hole that was initially formed to insert chains 200 (e.g., plug 812 of
In some embodiments, flexible chain 200 may be coated with an adhesive, such that chain 200 may be inserted into vertebral body 12 in a flexible state and may become tangled and/or convoluted during or after insertion. After insertion, bodies 210 may become attached together by the adhesive so that the flexible chain becomes a mass that may be locked into the vertebral body, or otherwise secured such that chain 200 may not be easily removed through the insertion opening.
In other embodiments, linked bodies 210 may be coated with an adhesive and chain may be inserted, with or without becoming tangled or convoluted, into a vertebral body. During or after insertion of some or all linking bodies 210 of a chain 200, a portion of chain 200 may be exposed to an energy source (e.g., an ultraviolet light, ultrasonic radiation, radio waves, heat, electric filed, magnetic field), for example to activate the adhesive, such that the exposed portion of chain 200 becomes joined to form a mass, or becomes rigid, or both, thereby further augmenting the vertebral body 12 and/or preventing removal or ejection of chain 200 through the insertion opening.
In some embodiments, chains 200 may be implanted completely within vertebral body 12 as shown in
FIGS. 9A-D show another example of a flexible monolithic chain device being implanted into vertebral body. In
Other suitable procedures and materials for inserting a cannula through which an FMC may be introduced are described, for example, in U.S. Provisional Patent Application No. 60/722,064, filed Sep. 28, 2005 entitled “Apparatus and Methods for Vertebral Augmentation using Linked Bodies”, which is incorporated by reference herein in its entirety. A chain or other implant 200 may compact the cancellous and/or osteoporotic bone inside a collapsed vertebral body during insertion into the vertebral body. Alternatively, a tool such as, for example, currettes or balloon catheter may be used to compress and compact the bone inside the vertebral body to create a cavity. The cavity in the vertebral body also may be formed by removing bone material as opposed to compacting the bone. For example, a reamer or other apparatus could be used to remove bone material from the inside of the vertebral body.
In other embodiments, PMMA or another bone cement or filler (for example bone chips or material collected from reaming the bone) may be inserted into vertebral body 12, e.g., through the introducer 910 or another cannula, sheath, syringe or other introducer, simultaneously with implant 200 to further enhance fixation or repair of a damaged region. Alternatively, the PMMA, bone cement or filler may be inserted into the interior of the bone after the chains (or portions thereof) have been inserted into the interior of the bone. Alternatively a bone growth promoting filler may be inserted into the vertebral body, and a plug of bone cement may be utilized to hold the implant 200 and filler material in the vertebrae 12. In this manner, the plug of cement is not inserted into the interior of the bone, but covers the opening created in the bone to insert the implant.
A minimally invasive system for fusion or non-fusion implants and insertion instruments is shown in FIGS. 10A-C. As described above, a flexible monolithic chain device 1000 device may be inserted into a vertebral body 12, e.g., through a cannula 1030 or other introducer inserted through a pedicle 14 as shown in
As shown in
In some embodiments, one or more of the bodies 1010 may have one or more openings or cavities 1012 or 1014. Such openings or cavities 1012, 1014 may be empty or may be filled, for example with a cement, bone filler, adhesive, graft material, therapeutic agent, or any other desired materials. In other embodiments, an implant device 1000 may be coated with different substances that will support and promote bone healing, reduce infections and/or deliver therapeutic agents to the treated site. Additionally, the non-flexible or flexible portions may also have porous surfaces 1016, for example to facilitate in growth of bone or other tissues.
The flexible monolithic chain devices and/or methods described herein may be used in conjunction with or instead of other methods or devices for augmenting vertebral bodies or other bones, such as, for example are described in U.S. Provisional Patent Application No. 60/722,064, filed Sep. 28, 2005 entitled “Apparatus and Methods for Vertebral Augmentation using Linked Bodies”, which is incorporated by reference herein in its entirety.
Although the apparatus and methods described herein thus far have been described in the context of repositioning and augmenting vertebrae for example in the context of vertebral compression fractures and deformations in spinal curvature, various other uses and methods are envisioned. For example, in some embodiments, an implantable monolithic chain 200 may be used to augment vertebrae where a compression or a compression fracture has not yet occurred and thus can be preventative in nature. Also, in some embodiments the chain can be used in-between two vertebra. For example, the chain implant can be inserted in the annulus of a spinal disc, or the disc can be removed and the chain implant inserted in-between adjacent vertebra to promote fusion of adjacent vertebrae. The chain implant in some embodiments may be insertable in an additional implant, such as a cage implanted in-between adjacent vertebrae. The chain implant may also be used to reposition and/or augment other damaged bone regions such as a fractured or weakened proximal femur 1400 as shown in
In some embodiments, the implants and methods described herein may be used in conjunction with other apparatus and methods to restore lordosis and augment the vertebral body. For example, one or more chains 200 may be used in conjunction with known procedures, e.g., a balloon kyphoplasty, that may be used to begin repositioning of a vertebral body and/or create a space within the body for chain 200. In other embodiments, one or more chains 200 may be used in conjunction with other tools or external fixation apparatus for helping to manipulate or fix the vertebrae or other bones in a desired position.
In another embodiment, a kit comprises various combinations of assemblies and components. A kit may include, for example, a cannula or other introducer and one or more flexible monolithic chains 200. The one or more chains 200 may be provided in different sizes, e.g., different lengths and/or diameters. In other embodiments, a kit may include an introducer, one or more chains, and a syringe or other apparatus for injecting a cement or other filler into a vertebral body or other space. In other embodiments, a kit may comprise one or more balloon catheters, curettes, and other instruments and may additionally include anchoring elements, tensioning members, fixation members, or any combination thereof, for example as described in U.S. Provisional Patent Application No. 60/722,064, entitled “Apparatus and Method for Vertebral Augmentation using Linked Bodies”, filed Sep. 28, 2005, which is incorporated by reference herein in its entirety. One skilled in the art will appreciate that various other combinations of devices, components and assemblies can be made and are intended to fall within the scope of the present invention.
In other embodiments, various minimally invasive implants and methods for alleviating discomfort associated with the spinal column may employ anchors and other implants described herein. For example, a monolithic chain implant within an expandable container (not shown), may be implanted between spinous processes of adjacent vertebrae to distract the processes and alleviate pain and other problems caused for example by spinal stenosis, facet arthropathy, and the like. For example, augmentation systems described herein may be used instead of or in addition to expandable interspinous process apparatus and methods described in U.S. Patent Publication number 2004/018128 and U.S. Pat. No. 6,419,676 to Zucherman et al. For example, a cannula may be inserted laterally between adjacent spinous processes to insert a container that may be filled with the flexible chains and expand the container and thus keep the adjacent spinous processes at the desired distance. Alternatively, a balloon container, with a deflatable balloon portion can be inserted laterally through adjacent spinous processes and filled with the flexible chains to expand the balloon to a desired size to hold adjacent spinous processes at a desired distances. The balloon can thereafter be sealed and detached from the catheter. Other materials may be inserted within the balloon volume to supplement flexible bodies.
While the foregoing description and drawings represent the preferred embodiments of the present invention, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope of the present invention as defined in the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other specific forms, structures, arrangements, proportions, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description.