Designed composite degradation for spinal implants

FIELD OF THE INVENTION

0001The present invention relates generally to composite materials to construct orthopedic devices for promoting bone fusion orthopedic devices.

0002The mammalian skeletal system, including long, short, flat, and irregular bones, is vulnerable to disease, injury, and congenital deficiencies, all of which can cause defects to the bone. Disease, injury, and deformity may have a disastrous impact on patient well being, ranging from acute pain to chronic debilitating pain.

0003Common treatments for defective bone tissue include joining or fusing fractured bone segments or portions together to stabilize the affected parts and can include removing and/or replacing portions of affected bone tissue, either in part or in whole. A bone plate or other prosthetic device can be inserted to eliminate disparate motion between the two bone portions to allow arthrodesis.

0004It is important, particularly for load-bearing bone, that the prosthetic device not stress shield the new bone growth and permit a weakened juncture or pseudoarthrodesis between the bone portions or adjacent vertebrae to be fused. It is known that for load bearing bone members, stronger, denser bone tissue results when new bone growth occurs under pressure. The problem arising is when and how to determine the amount of pressure or force desirable to develop a strong junction between the bone portions. The bone portions should be secured and supported during bone growth. However, the optimum support necessary for desired bone growth may vary over time as the bony juncture or bridge develops between the bone portions.

0005Similarly, stretched and/or torn ligaments can be treated by initially securing/immobilizing the ligaments. This can be accomplished using either, or both, internal and external prosthetic devices to augment or replace the stability lost as a result of the damage to the ligaments. Further, once-damaged ligaments can be susceptible to repeated injury. Consequently, it may be desirable to augment the treated ligament by implanting a prosthesis or device that allows limited movement of the affected spinal components while preventing the components from moving far enough to incur re-injury or cause new damage. Current treatment methods do not allow for an implanted device to initially secure or immobilize the ligaments and then allow limited movement of the same without a subsequent surgical revisitation.

0006In light of the above, there is a continuing need for materials for use in orthopedic devices, novel orthopedic devices, and treatments using these materials to stabilize and support damaged bone tissues, bony structures, and connecting tissue. There is also a need for materials, which provide variable loads to growing bone, as well as a measure of flexible support to injury or disease prone bones and connecting tissue. The present invention addresses these needs and provides other benefits and advantages in a novel and nonobvious manner.

BRIEF SUMMARY OF THE INVENTION

0007The present invention relates to composite materials with anisotropic properties used to construct orthopedic devices, and the manufacture of these devices. Various aspects of the invention are novel, nonobvious, and provide various advantages. While the actual nature of the invention covered herein can only be determined with reference to the claims appended hereto, certain forms and features, which are characteristic of the preferred embodiments disclosed herein, are described briefly as follows.

0008In one form, the present invention provides an anisotropic composite material used to construct orthopedic devices. The composite material comprises: a bio-stable flexible cord configured to be fixedly secured to two or more bone portions allowing translational, or rotational, or both translational and rotational movement of a first one of the bone portions relative to a second one of the bone portions. A more rigid and more biodegradable material engages with the cord such that the biodegradable material restricts the translational, rotational, or both the translational and rotational movement of the first of the bone portions relative to the second of the bone portions secured to the composite material.

0009The composite material can be used to construct orthopedic devices used to treat a variety of bone defects including, but not limited to, bone fractures, diseased bone tissues, spinal diseases, diseased/damaged vertebrae, torn or stretched ligaments, and the like.

0010In preferred embodiments, the devices comprising the composite material prevent, or at least reduce, stress shielding of new, developing bone tissue. In other embodiments, the orthopedic device of the present invention can be configured for articulating joints. In these embodiments, the composite material can allow a limited amount of movement, i.e. translation and/or rotation about the joint. The devices, with and without the biodegradable material, still provide a measure of support and/or restriction of the movement of bone portions attached to devices comprising the composite materials. In preferred embodiments, the devices of the present invention remain in place indefinitely.

0011Further objects, features, aspects, forms, advantages, and benefits shall become apparent from the description.

BRIEF DESCRIPTION OF THE DRAWINGS

0012<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a perspective view partly broken away of a composite material comprising an elongate cord including wound filaments and encased within a biodegradable matrix in accordance with the present invention.</li><li><figref idref="f0001">FIG. 2</figref> is a perspective view partly broken away of an alternative embodiment of an elongate composite material in accordance with the present invention</li><li><figref idref="f0002">FIG. 3</figref> is a perspective view of a plurality of non-biodegradable filaments supported by at least one biodegradable filament in accordance with the present invention.</li><li><figref idref="f0003">FIG. 4</figref> is a perspective view of a cord including a plurality of non-biodegradable filaments and at least one filament encased within a biodegradable matrix in accordance with the present invention.</li><li><figref idref="f0003">FIG. 4A</figref> is a cross-sectional view of one of the filaments encased in a biodegradable matrix of the cord illustrated in <figref idref="f0003">Fig. 4</figref>.</li><li><figref idref="f0004">FIG. 5</figref> is a perspective view of a bone having a bone defect which has been treated using an orthopedic device prepared using one of the cords illustrated in <figref idref="f0001">FIGS. 1, 2</figref>, or <figref idref="f0002">3</figref>.</li><li><figref idref="f0005">FIG. 6</figref> illustrates one embodiment of a composite material including a web material embedded within a biodegradable polymeric matrix.</li><li><figref idref="f0006">FIG. 7</figref> is a cross-sectional view of one embodiment of a composite material including a non-biodegradable cloth embedded between two biodegradable matrices in accordance with the present invention.</li><li><figref idref="f0006">FIG. 8</figref> is a cross-sectional view of an alternative embodiment of a fabric encased between two biodegradable matrices in accordance with the present invention.</li><li><figref idref="f0005">FIG. 9</figref> is a perspective view of a section of a spine, having a defect, which has been treated using a composite matrix in accordance with the present invention.</li></ul>

DESCRIPTION OF THE PREFERRED EMBODIMENTS

0013For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated herein, 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 alterations and further modifications in the described devices, systems, and treatment methods, and any further applications of the principles of the invention as described herein, are contemplated as would normally occur to one skilled in the art to which the invention relates.

0014In preferred embodiments, the present invention provides a composite material for use in the construction of an implantable orthopedic device or prosthesis used to facilitate support and repair of defective bone structures and/or connective tissue. The defective bone structures can be the result of damaged, traumatized, and/or diseased tissue. By use of the term "orthopedic device", it is intended to include within its meaning a device or implant that can be used to treat or repair defective, diseased, or damaged tissue of the muscular/skeletal system(s).

0015The biodegradable material of the present invention provides a composite material that includes a supporting matrix and a cord for an implantable orthopedic device. This supporting matrix can provide rigidity and support for both the implanted orthopedic fusion device and, consequently, the attached bone structures. In use, the biomechanical load supported by the composite material and/or orthopedic devices incorporating the composite can vary over time. This allows the orthopedic device to become dynamizable, or change its physical properties <i>in vivo.</i> This change in physical properties can be particularly important for developing strong, new bone tissue at the bone defection or fusion site. This prevents stress shielding of the new bone in-growth and minimizes the risk for the development of pseudoarthrodesis.

0016In one form, degradation of the matrix can occur naturally without the use of subsequent treatment. In other forms, degradation of the matrix can be initiated (or triggered), induced, and/or completed at a selected or predetermined time after implantation. The device and/or composite material can include a polymer susceptible to or sensitive to radiation energy, light (UV), solvents with different pH levels, thermal energy, or temperature, to initiate degradation. The treatment can include both invasive and non-invasive treatments. Preferably, the treatment can be accomplished using a UV radiation probe inserted in close proximity to the device (or composite material).

0017The following description specifically describes non-limiting, specific embodiments for use with the present invention.

0018<figref idref="f0001">FIG. 1</figref> is a perspective view of one embodiment of a composite material 10 including a cord 12 and a matrix 14. Cord 12 can be provided as a single elongate filament 16, or alternatively, as a plurality of filaments 18a, 18b, and 18c, ..., collectively referred to as filament 18. When cord 12 is a single filament, it can be provided as a large diameter rod or solid core encased within matrix 14. Implant 10 defines a longitudinal axis 20. In preferred embodiments, cord 16 and/or individual filaments 18a, 18b, 18c, extend substantially in the direction of longitudinal axis 20. Although it will be understood that one or more of individual elements 18a, 18b, 18c, ..., while extending generally in the direction of longitudinal axis 20, can either wind around that direction and extend substantially orthogonal or at an angle oblique to that direction at any given location within implant 10. In other embodiments, the plurality of filaments 18a; 18b, 18c, ... can be woven together to provide a flat mesh or a three-dimensional network of filaments.

0019Matrix 14 can substantially encase cord 12. Alternatively, at least a portion of cord 12 can extend through or beyond the surface of matrix 14. Matrix 14 can provide support to maintain a desired shape for an orthopedic device. Consequently, matrix 14 can be provided as a variety of biodegradable materials. Some of the materials can be readily formable in the operating room, for example, by heating the material and shaping the composite into a desired configuration to either conform to the bone defect and/or to induce the bone defect to be retained in a desired configuration. Alternatively, matrix 14 can be pre-formed or shaped by the supplier or manufacturer. Matrix 14 is illustrated as a substantially cylindrical elongate configuration. It should be understood that matrix 14 can be provided in any desirable configuration including as a substantially bent, planar, or flat configuration. Alternatively, matrix 14 can be provided in any desirable shape including a substantially spherical, square, rectangular, or amorphous configuration, which, as noted above, may or may not be moldable by hand either at elevated temperatures or under other conditions including light, moisture, or solvent activated.

0020In alternative embodiments, matrix 14 is bonded to cord 12. A biocompatible chemical adhesive can be used to bond the matrix and cord 12 together. The bond can also be derived from a mechanical interlock between the matrix 14 and the cord 12.

0021While composite 10 is illustrated as an elongate cylinder, it will be understood that other configuration are contemplated and are intended to be included within the scope of the present invention. For example composite 10 can be bent, planar, cuboid, spherical or of an amorphous shape as desired. Further composite 10 (and cord 12) can include various structures to permit it to be secured to bone tissues. Examples of various structures include without limitation: eyelets, loops, hooks, bone fasteners, pins, pegs, cements, glues, and combinations thereof

0022Cord 12 extends through at least a portion of matrix 14. Cord 12 can be formed or composed of a variety of individual filaments either separated from each other in matrix 14 or in direct contact with each other or loosely bundled together. Filaments 18a, 18b, 18c, ... can be braided or woven together and extend at least partially through matrix 14. Alternatively, filaments 18a, 18b, 18c, ... can extend parallel to each other through at least a portion of matrix 14. In still other embodiments, cord 12 and/or filament 18 can be substantially embedded within and completely surrounded by matrix 14, such that no portion of the cords or filaments are exposed or visible.

0023Each of filaments 18a, 18b, 18c, ... can be formed of the same material and/or of the same shape, diameter, and length. Alternatively, one or more of 18a, 18b, 18c, ... can be provided as a different material or formed in a different shape, diameter, length, or configuration as desired. Providing the individual filaments 18a, 18b, 18c, ... in different materials, shapes, and sizes can induce the implant to produce different desirable physical properties and, consequently, an orthopedic implant can be prepared tailored to treat the individual orthopedic defect or disease.

0024In one embodiment, cord 12 is elastic and/or flexible. Consequently, one or more of filaments 18a, 18b, 18c, ... can be an elastic or flexible material. Weaving the filaments 18a, 18b, 18c, ... together can modify the cord's elasticity or flexibility. For example, using either a loose weave or a tight weave, differing sizes of spaces 24 can exist between the individual filaments 18a, 18b, 18c, ... and can allow cord 12 to exhibit varying degrees of flexibility.

0025Cord 12 (and filaments, 18a, 18b, 18c ...) can exhibit a smooth exterior surface. Alternatively, cord 12 (and filaments, 18a, 18b, 18c ...) can exhibit an exterior surface that is roughened pitted, grooved, or knurled. The textured exterior surface of cord 12 can facilitate bonding the matrix material to the cord via a mechanical interlocking mechanism either solely or in conjunction with an adhesive. The three dimensional network of the filaments 18a, 18b, 18c ... making up cord 12 can include voids or spaces which can also facilitate bonding the matrix material 14 to the cord 12 via a mechanical interlocking mechanism. Additionally the surface of either matrix 14 or the cord 12 can be treated to facilitate good adherence. Such surface treatment can include corona discharge, plasma discharge, chemical etching, electron or ion beam radiation, and laser radiation, and the like as is known in the art.

0026Cord 12 can be provided as a non-biodegradable material. Examples of non-biodegradable materials are discussed more fully below. In addition, cord 12 can include one or more individual filaments, which may be composed of a biodegradable material. The biodegradable material for the filaments can compose a shape memory polymer, and/or other biocompatible polymeric material.

0027In one preferred embodiment, matrix 14 is composed of a biodegradable material 22. <i>In vivo,</i> matrix 14 erodes or biodegrades. As matrix 14 biodegrades, the rigidity of composite 10 decreases. In preferred embodiments, this decrease in rigidity is substantially linear over time. As discussed more fully below, the nature and composition of matrix 14 can be varied to allow matrix 14 to degrade over varying time periods including periods between a few days, a few weeks, a few months, and even over the course of one or more years. Matrix 14 can be formulated to have a desired half-life <i>in vivo</i>. By use of the term "half life", it is intended to mean that matrix 14 degrades to about one-half of its initial mass in the specified time period. In one preferred embodiment, matrix 14 has a half-life, <i>in vivo,</i> of less than about 6 months; more preferably, matrix 14 has a half-life of less than about 12 months; still more preferably, matrix 14 has a half-life of less than about 18 months. In other embodiments, matrix 14 can be formulated to have a half-life that is greater than or equal to one year; more preferably greater than or equal to 18 months.

0028<figref idref="f0001">FIG. 2</figref> is a perspective view of an alternative embodiment of an elongate composite material 30 in accordance with the present invention. Elongate composite 30 defines a central axis 35. Composite material 30 includes matrix 32 and a cord 34 engaged therein and extending generally along the axis 35. Cord 32 can comprise a single filament 36a or a plurality of filaments 36a, 36b, 36c, ..., collectively referred to as filament 36. In the illustrated embodiment, filaments 36a, 36b, 36c, ... are wound together to provide cord 34.

0029Generally, composite material 30 can be provided substantially as has been described above for composite material 10, including the description of the matrix 22 and and/or filaments 18a, 18b, 18c, ... The winding of filaments 36a, 36b, 36c,... can provide differing properties of that exhibited by the braiding of filaments 18a, 18b, and 18c including the ability to define a central cavity 38 therein. Central cavity 38 extends substantially parallel to axis 35. In one embodiment, central cavity 38 is substantially filled with the material of matrix 34. In other embodiments, yet another filament or cord can extend through central cavity 38. In effect, filaments 36a, 36b, 36c, ... can be wound around the central cord or filament. The central cord or filament can be the same or different from either cord 34 or filament 36. Additionally, the winding of filaments 36a, 36b, 36c, ... also generates additional spaces or voids 40 between individual filaments, for example, between filaments 36a and 36b. In still other embodiments cavity 38 can be filed with a therapeutic agent or osteogenic material.

0030<figref idref="f0002">FIG. 3</figref> is a perspective view of one embodiment of a composite material 49 that includes a tether or cord 50 in accordance with the present invention. Cord 50 comprises a plurality of filaments extending generally along a central axis 51. In preferred embodiments, cord 50 includes a first set of filaments 52 and at least a second set of filaments 54. Other sets or individual filaments can also be included within cord 50. In the illustrated embodiment, first set of filaments 52 can include a plurality of individual filaments 56a, 56b, 56c ... Filaments 56a, 56b, 56c ... can be the same filaments and can have the same length or configuration. Alternatively, a select one or more of filaments 56a, 56b, 56c ... can be different from the other filaments in either composition, physical properties, size, diameter, length, and the like. First set of filaments 52 can be provided substantially as has been described for filament 18 (and for cord 12). Additionally, it will be understood that the relative arrangements of filaments 56a, 56b, 56c ... can be either provided as a plurality of parallel filaments, wound filaments, braided filaments, and the like. One or more of filaments 56a, 56b, 56c ... can be provided as a substantially rigid filament formed of a non-biodegradable material, which is discussed in more detail below.

0031Cord 50 also includes a second set of filaments 54. Second set of filaments 54 can include a single filament 58 or a plurality of filaments arranged similarly to that discussed above for first set of filaments 52.

0032Filament 58 can be composed of a biodegradable material, discussed more fully below. Additionally, filament 58 can be a substantially rigid filament that provides support for cord 50 and/or lends further support to individual filaments of the first set of filaments 52. In the illustrated embodiment, filament 58 is provided to substantially interweave or woven into the plurality of filaments 56a, 56b, 56c ... In other embodiments, filament 58 can be provided to extend substantially parallel to one or more filaments of the first set of filaments 52, wrap around one or more filaments of the first set of filaments 52, and/or be spirally wound within the first set of filaments 52. Filament 58 can be provided to degrade <i>in vivo</i> at a desired degradation rate or within a desired time period. The degradation rate or the half-life of filament 58 can be tailored to suit the particular need, treatment, and/or application of cord 50. In one embodiment, the half-life of filament 58 is selected to be greater than about 6 months; more preferably, greater than or equal to about 1 year; still yet more preferably, greater than or equal to about 18 months. In other embodiments, filament 58 can be provided to have a half-life of less than about 1 year. Furthermore, filament 58 can be provided to have substantially the same configuration, length, diameter, mass, and/or tensile strength as that exhibited by either the individual filaments of the first set of filaments 52 and/or one ore more filaments 56a, 56b, 56c ...

0033In use, as the filaments of the second set 54 degrade <i>in vivo,</i> the rigidity of cord 50 and/or one or more of the individual filaments of the first set 52 can be decreased. This allows cord 50 and/or one or more filaments of the first set 52 to become more flexible. Consequently, if the bone portions to which cord 50 and/or the first set of filaments 52 are attached articulate, the flexibility or increasing flexibility over time allows increased movement of the articulating joint as new bone tissue grows and the defect is corrected. It will be understood that in preferred embodiments cord 50 remains secured to the bone portions albeit minus some or all of the filaments of the second set 54. Furthermore, it will be understood that in other aspects, cord 50 can be substantially as provided as described above for cords 12 and 34.

0034<figref idref="f0003">FIG. 4</figref> is a perspective view of an alternative embodiment of a composite material 70 for use in forming orthopedic devices in accordance with the present invention. Composite material 70 includes a cord 72 comprising a first set of filaments 74 and at least a second set of filaments 76. First set of filaments 74 can be provided substantially as has been described above for first set of filaments 52 for cord 50 and can include a plurality of individual filaments 75a, 75b, 75c, ... Second set of filaments 76 can comprise one, two, three, or more filaments, collectively referred to as filament 78. Referring additionally to <figref idref="f0003">Fig. 4A</figref>, filament 78 includes at least an outer coating or matrix 80 composed of a biodegradable material, discussed more fully below and an inner core material 77 that comprises one of: a large diameter rod, a solid core, a smaller wire, filament, braid, or plurality of filaments as desired. In one embodiment, the inner core material 77 can comprise a filament of cord similar to that defined by the first set of filaments 74. Alternatively, inner core material 77 can be the same or can be different from any one of filaments 75a, 75b, 75c, ... Additionally, core 77 can either be formed of a biodegradable material and/or a non-biodegradable material, both of which are discussed more fully below. Filament 78 including core material 77 and matrix 80 can be substantially rigid or provide rigidity to cord 72.

0035As matrix 80, comprising a biodegradable material, begins to erode, <i>in vivo,</i> the rigidity of filament 78 and/or core 77 begins to decrease. Consequently, the rigidity of cord 72 also begins to decrease. This allows the bone portions to which an implant is attached to articulate or carry an increasing amount of load to promote formation of hard cortical bone tissue and prevent pseudoarthrodesis. In other aspects, such as rigidity, size, configuration, diameter, half life, and the like, filament 78 can be provided substantially as has been described above for any one of the filaments 58 or cord 50. Additionally, cord 72 can be encased or substantially encased within a matrix such as matrix 14 or 32 of composite material 10 or 30, respectively.

0036One or more of filaments 75a, 75b, 75c and filament 78 can be bundled together to define an interior region 82 therein. Interior region can be a void, contain the matrix material, or a therapeutic agent, osteogenic material or another cord of plurality of filaments as discussed above for cavity 38. In other embodiments, the plurality of filaments 75a, 75b, 75c, ... can be woven together to provide a flat mesh or three-dimensional network of filaments.

0037<figref idref="f0004">FIG. 5</figref> is a perspective view of one embodiment of a bone 90 having a defect 92 therein. An orthopedic implant 94 comprised of an elongate composite material 95 is illustrated as attached to bone 90 and spanning defect 92. Orthopedic implant 94 can be comprised of a composite material as has been discussed above such as any one of composite materials 10, 30, 70 or cords 50 or 72 described above. In the illustrated embodiment, orthopedic implant 94 includes an outer matrix 96 substantially encasing a cord 98. Cord 98 comprises a first filament 100 and a second filament 102. The orthopedic implant 94 can be attached to the bone portions by any means commonly used and/or known in the art including, without limitation, bone screws 104a, 104b, 104c, and 104d, staples, wire, cable, and the like. It will be observed from the illustration that some of screws, such as 104a and 104d, can extend solely through cord 98 with or without going through matrix 96. Other screws, such as those listed as 104b and 104c, may extend through outer matrix 96 and may or may not contact cord 98. In use, outer matrix 96 slowly degrades, <i>in vivo.</i> After degrading, the residual portion of the implant, i.e., cord 98, can remain secured to the bone portions to provide additional support and/or restraint. However, as noted above and discussed more fully below, degradation of outer matrix 96 can allow increasingly greater stress on new bone growth within defect 92. This can provide optimal bone tissue growing conditions to ensure hard, dense cortical bone grows into the defect. In addition, an osteogenic material can be added to the bone defect, either supplied separately, combined with the outer matrix, and/or incorporated into the cord.

0038<figref idref="f0005">FIG. 6</figref> is perspective view of another embodiment of composite material 120 for use in the present invention. Composite material 120 comprises a woven or an array of cords to provide a mesh 122 and a matrix 124. Mesh 122 can be a flat (two-dimensional), fabric, or cloth-like material or three-dimensional network. Matrix 124 can be formed similarly as described above for matrices 96, 80, and 14. Consequently, matrix 124 can be a biodegradable or bioerodable material that can provide rigid support to the orthopedic implant formed from the composite material 120.

0039The mesh 122 can comprise a first set of filaments 126 and at least a second set of filaments 128. In the illustrated embodiment, first and second sets of filaments 126 and 128 are provided to lie substantially orthogonal to each other. It will be understood by those skilled in the art that the relative orientation of first set of filaments 126 and second set of filaments 128 can be provided as desired, including substantially parallel to each other, woven, braided, or oriented at an angle oblique to each other. Furthermore, first set of filaments 126 and second set of filaments 128 can comprise substantially the same material or comprise a different material from each other. Furthermore, first set of filaments 126 and second set of filaments 128 can have substantially the same properties including tensile strength, diameter, length, shape, and the like, or the two sets of filaments can have different tensile strength, diameter, length, shape and the like from each other. Additionally, first set of filaments 126 can be provided substantially as described above for first set of filaments 74 and/or first set of filaments 52. Similarly, second set of filaments 128 can be provided substantially as has been described above for first set of filaments 74 and 52, or second set of filaments 76 and/or 54.

0040First set of filaments 126 and second set of filaments 128 can be engaged with or secured to each other. The engagement can be in the form of bonding with or without glue, woven together, knotted together, overmolded on top of each other, or secured via a mechanical interlocking mechanism as desired.

0041In the illustrated embodiment, first and second sets of filaments 126 and 128, respectively, are substantially encased within matrix 124. It will be understood that one or more, or both, of first set of filaments 126 and second set of filaments 128 can be exposed or at least partially exposed extending out of matrix 124.

0042First set of filaments 126 can comprise a plurality of filaments 127a, 127b, 127c, ... and each filament can be composed of the same material and/or exhibit the same physical properties, size, and shape. Alternatively, each of filaments 127a, 127b, 127c, ... can be of a different material or of a different size, shape, or physical properties as desired.

0043Similarly, the individual filaments 129a, 129b, 129c, ... making up of the second set of filaments 128 can be of the same materials and/or same physical properties and sizes or they can be of different materials, sizes, and/or physical properties as desired.

0044In another embodiment, the first set of filaments 126 and second set of filaments 128 are composed of different materials and/or having different physical properties, sizes, and shapes. This can be used to prepare an orthopedic matrix having anisotropic properties, i.e., exhibiting different properties in different directions. For example, the second set of filaments 128 can comprise a biodegradable or non-biodegradable material. For example, the first and second set of filaments 126 and 128 can both be composed of biodegradable material either the same or different second material. The degradation rates or half-lives of the two materials may be different.

0045Alternatively, the first set of filaments 126 can be composed of a biodegradable material while the second set of materials are composed of a non-biodegradable material. Consequently, the second set of filaments 128 remains <i>in vivo</i> while the first set of filaments 126 erode away.

0046In yet another embodiment, the size and/or shape of the filaments in the first set of filaments 126 can be different from the filaments in the second set of filaments 128. One set of filaments can persist <i>in vivo</i> for a longer period of time.

0047This provides an orthopedic implant having various properties, which properties can be tailored to suit the particular application and treatment method used on the orthopedic defect.

0048Matrix 124 can be provided as a moldable or shapeable material that can be rigid <i>in vivo</i> and at ambient temperature and/or under pharmacological conditions. However, if desired, matrix 124 can be formulated to be hand or machine moldable either at an elevated temperature within a specified solvent or under specific conditions. For example, the matrix material 124 can comprise one or more cross-linkable polymeric materials such that upon initiation, the matrix material forms a cross-linked matrix having the desired or preformed configuration. Matrix material 124 can be bonded or secured to first set of filaments 126 and/or the second set of filaments 128 as desired with or without glue, overmolded, or secured via a mechanical interlocking mechanism.

0049<figref idref="f0006">FIG. 7</figref> is a cross-sectional view of one embodiment of a composite material 140 for use in the present invention. Composite material 140 can be provided substantially as has been described above for composite material 120. Alternatively, composite material 140 can be different from that described above. For example, composite material 140 can comprise a first matrix 142 and at least a second matrix 144. First and/or second matrix can be made of the same or different material. For example, first matrix 142 can be formed of a first biodegradable material, and second matrix 144 can be formed of a second biodegradable material. Additionally, a loose weave or cloth-like material 146 comprising a first set of filaments, 150 and a second set of filaments 152. The weave or cloth-like material 146 can be disposed in between first matrix 142 and at least a second matrix 144. Weave or material 146 can be provided substantially as has been described above for mesh 122. In selected embodiments, one or both of first matrix 142 and second matrix 144 can be bonded, over molded, or engaged to woven material 146, and more specifically, to fibers 148 composing the woven material 146. In other embodiments, first matrix and/or second matrix can be glued using a biocompatible adhesive to one or more of the woven material 146 and/or fibers 148.

0050Referring additionally, to <figref idref="f0006">FIG. 8</figref>, a composite material 160 is illustrated. Composite material 160 is similar to that illustrated above for composite material 140. Consequently, like reference numbers will be used to denote like components. Composite material 160 comprises a first matrix 142 and a second matrix 144 and a woven material 146 between. Additionally, a third set of filaments 162 is illustrated as a weaving or suturing to bind together first matrix 142, second matrix 144, and woven material 146. Third set of filaments 162 can be comprised substantially as has been described above for the first set of filaments 74, 52, 36, and 18. Alternatively, third set of filaments 162 can be provided as has been described above for second set of filaments 77 and 58. In yet another alternative, first matrix 142, second matrix 144, and woven material 146 can be fastened together by any means commonly used or known in the art including cords, strings, filaments, staples, clips, ties, bands, glues, cements, and combinations thereof.

0051<figref idref="f0005">FIG. 9</figref> is an illustration of a portion of a spinal column 170 with a defect and including a first vertebrae 172 and a second vertebrae 174. The bone defect can be treated using an orthopedic device 176. Orthopedic device 176 can comprise a material such as that described above for composite material 160, 140, and/or 120. In use, as the biodegradable component of orthopedic device 176 degrades, the residual component, i.e., either a woven matrix and/or a portion of a woven matrix, can remain secured to one or both of first and second vertebrae 172 and 174, respectively. This can allow the two vertebrate to articulate relative to each other, yet maintain the integrity and restrict movement or allow limited movement of the spinal column.

0052The biodegradable material included in one or more cords, filaments, and/or matrices described above can be formed or composed of a variety of materials including, without limitation, degradable or resorbable polymeric materials, composite materials, and ceramic materials.

0053In one embodiment, the biodegradable material can include polymeric materials formed from oligomers, homopolymers, copolymers, and polymer blends that include polymerized monomers derived from 1, d, or d/l lactide (lactic acid); glycolide (glycolic acid); ethers; amino acids; anhydrides; orthoesters; hydroxy esters; and mixtures of these monomeric repeating units.

0054Use of the term "copolymers" is intended to include within the scope of the invention polymers formed of two or more unique monomeric repeating units. Such copolymers can include random copolymers; graft copolymers; body copolymers; radial body, dibody, and tribody copolymers; alternating copolymers; and periodic copolymers. Use of the term "polymer blend" is intended to include polymer alloys, semi-interpenetrating polymer networks (SIPN), and interpenetrating polymer networks (IPN).

0055In a preferred embodiment, the biodegradable material comprises a biodegradable polymeric material including: poly(amino acids), polyanhydrides, polycaprolactones, poly(lactic-glycolic acid), polyhydroxybutyrates, polyorthoesters, and poly(d,l-lactide).

0056In other embodiments, the biodegradable material can comprise biodegradable ceramic materials and ceramic cements. Examples of biodegradable ceramic materials include: hydroxyapatite, hydroxyapatite carbonate, corraline, calcium phosphate, tricalcium phosphatem, and hydroxy-apatate particles. Examples of biodegradable ceramic cements include calcium phosphate cement. Such calcium phosphate cements are preferably synthetic calcium phosphate materials that include a poorly or low crystalline calcium phosphate, such as a low or poorly crystalline apatite, including hydroxyapatite, available from Etex Corporation and as described, for example, in <patcit id="pcit0001" dnum="US5783217A"><text>U.S. Patent Nos. 5,783,217</text></patcit>; <patcit id="pcit0002" dnum="US5676976A"><text>5,676,976</text></patcit>; <patcit id="pcit0003" dnum="US5683461A"><text>5,683,461</text></patcit>; and <patcit id="pcit0004" dnum="US5650176A"><text>5,650,176</text></patcit>, and <patcit id="pcit0005" dnum="WO9816268A"><text>PCT International Publication Nos. WO 98/16268</text></patcit>, <patcit id="pcit0006" dnum="WO9639202A"><text>WO 96/39202</text></patcit> and <patcit id="pcit0007" dnum="WO9816209A"><text>WO 98/16209, all to Lee et al</text></patcit>. Use of the term "poorly or low crystalline" is meant to include a material that is amorphous, having little or no long range order, and/or a material that is nanocrystalline, exhibiting crystalline domains on the order of nanometers or Angstroms.

0057In still other embodiments, the biodegradable material can be formed of composite materials. Examples of composite materials include as a base material or matrix, without limitation: ceramics, resorbable cements, and/or biodegradable polymers listed above. Each of the base materials can be impregnated or interspersed with fibers, platelets, and particulate reinforcing materials.

0058In one form, the biodegradable material comprises a resorbable, moldable material that can be molded at an elevated temperature and then allowed to set up into a hardened material at around body temperature, such as the material sold under the trade name BIOGLASS® discussed in <patcit id="pcit0008" dnum="WO9840133A"><text>WO 98/40133</text></patcit>.

0059The composite material of the present invention can be tailored to degrade at a predetermined or pre-selected rate by suitably selecting the size, thickness, and/or biodegradable material. In preferred embodiments, the biodegradable material degrades at a rate comparable to the new bone in-growth into the bone defect or bone fusion site. In particularly preferred embodiments, the rigid biodegradable component has an <i>in vivo</i> half life of greater than three months, more preferably the <i>in vivo</i> half life of the restricting component is greater than six months; still more preferably the <i>in vivo</i> half life is greater than one year. By use of the term "half life", it is understood that the degradation rate of the restricting component is such that the restricting component loses half of its initial mass <i>in vivo,</i> presumably due to resorption, degradation, and/or elimination.

0060Further, the biodegradable material can be formulated to degrade or can be induced to begin degradation by application of external stimuli. For example, the biodegradable material can degrade upon application of radiation such as UV radiation, thermal energy, and/or solvents --either neutral, basic, or acidic.

0061A nonbiodegradable or biostable material for use in the present invention can include resilient materials such as, without limitation, nitinol, titanium, titanium-vanadium-aluminum alloy, cobalt-chromium alloy, cobalt-chromium-molybdenum alloy, cobalt-nickel-chromium-molybdenum alloy, biocompatible stainless steel, tantalum, niobium, hafnium, tungsten, and alloys thereof; polymeric materials include polymerized monomers derived from: olefins, such as ethylene, propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, styrene, norbornene and the like; butadiene; polyfunctional monomers such as acrylate, methacrylate, methyl methacrylate; esters, for example, caprolactone and hydroxy esters; and mixtures of these monomeric repeating units. Preferred polymers for use in the present invention include carbon poly(ether, ether, ketone) (PEEK), poly(aryl ether, ketone) (PAEK), and the like.

0062In addition or in the alternative, it may be desirable to promote bone fusion between the adjacent vertebrae or between any bone portions on either side of a bone defect. In this embodiment, it may be desirable to include an osteogenic material or a bone growth material such as an osteoinductive or an osteoconductive material. For example, it may be desirable to introduce an osteogenic factor such as a bone morphogenic protein (BMP) or a gene encoding the same operationally associated with a promoter which drives expression of the gene in the animal recipient to produce an effective amount of the protein. The bone morphogenic protein (BMP) in accordance with this invention is any BMP able to stimulate differentiation and function of osteoblasts and osteoclasts. Examples of such BMPs are BMP-2, BMP-4, and BMP-7, more preferably rhBMP-2 or rhBMP-7, LIM mineralization protein (LMP) or a suitable vector incorporating a gene encoding the same operably associated with a promoter, as described in <patcit id="pcit0009" dnum="WO9906563A"><text>WO99/06563</text></patcit> (see also Genbank accession No. AF095585).

0063The composite materials and orthopedic devices of the present invention can be used by themselves or in conjunction with one or more known orthopedic devices as deemed medically prudent. Additionally or in the alternative, the present invention can be used with one or more devices disclosed in co-pending <patcit id="pcit0010" dnum="US20050085814A"><text>US patent Publication 2005-0085814 filed on October 21, 2003</text></patcit> entitled, "Dynamizable Orthopedic Implants and Their Use in Treating Bone Defects."

0064In preferred embodiment, the composite material of the present invention can provide initial support and/or fixation of selected bone structures. After a selected period of time or under certain conditions, the amount and nature of the support/fixation can vary to facilitate a desirable treatment. For example, use of a composite material according to the present invention allows that variable or dynamizable support develops new, strong bone tissue, thus minimizing the risk of pseudoarthrodesis.

0065The composite material of the present invention also finds advantageous use in the treatment of connecting tissue such as ligaments. For example, devices comprising the composite material can augment connecting tissue. After a predetermined period of time or condition, the composite material can allow limited translational, rotational, or translational and rotational movement of the connecting tissue and/or bone structures attached to the orthopedic device incorporating the composite. For example, if the natural connecting tissue is elastic, the composite material can serve to limit or restrict the overall length or amount that the connecting tissue stretches. This restriction can vary depending upon the length of time or pre-selected conditions used in forming the composite material used in constructing and using the device.

0066While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is considered to be illustrative and not restrictive in character, it is understood that only the preferred embodiments have been shown and described.

0067Any reference to a specific directions, for example, references to up, upper, down, lower, and the like, is to be understood for illustrative purposes only or to better identify or distinguish various components from one another. These references are not to be construed as limiting in any manner to the orthopedic device and/or methods for using the orthopedic device as described herein.

0068Unless specifically identified to the contrary, all terms used herein are used to include their normal and customary terminology. Further, while various embodiments of medical devices having specific components and structures are described and illustrated herein, it is to be understood that any selected embodiment can include one or more of the specific components and/or structures described for another embodiment where possible.

0069Further, any theory of operation, proof, or finding stated herein is meant to further enhance understanding of the present invention and is not intended to make the scope of the present invention dependent upon such theory, proof, or finding.