Abstract:
The present invention generally relates to orthopedic devices and methods for treating bone defects. The orthopedic devices can provide sufficient support to the bone defect while allowing bone ingrowth and minimizing the risk to stress shield and/or pseudo-arthrodesis. The bone fixation devices include a biodegradable material or component that further resists relative motion of attached bones and allows the device to gradually transfer at least some load from the device to the growing bone structure in vivo and permitting an increase in the relative motion of bones attached to the device.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to orthopedic devices for promoting bone fusion and methods for treating orthopedic defects using the orthopedic devices.  
       BACKGROUND OF THE INVENTION  
       [0002]     The spine is composed of both rigid and flexible elements which form a complex structure that can readily accommodate a wide range of motions and adjust to a wide range of loads. Unfortunately, like any complex physiological structure, the spine is also vulnerable to disease, injury, and congenital deficiencies, all of which can cause defects to the spine and, in particular, to the vertebral body and intervertebral discs. Spinal disease, injury, and deformity may have a disastrous impact on patient well being, ranging from acute pain to chronic debilitating pain and, in the most severe cases, partial or complete paralysis.  
         [0003]     Some of the most common pathologies of spinal defects include fractured, diseased, or decayed vertebral bodies; torn or stretched ligaments; and damaged or diseased intervertebral discs.  
         [0004]     Common treatments for damaged, diseased, or defective vertebrae include joining or fusing fractured bone segments or portions together to stabilize the affected parts and removing the affected vertebrae, either in part or in whole. Classically, the damaged disc is excised, the adjacent vertebrae are mechanically joined together, and oftentimes bone is grafted into the region, particularly in the disc space between the two vertebrae, to promote fusion of the adjacent vertebrae. The vertebrae can be mechanically joined using a prosthetic device such as a bone plate that is attached to the adjacent vertebrae with bone screws. The bone plate eliminates disparate motion between the two bone portions to allow arthrodesis.  
         [0005]     It is known that for load bearing bone members, stronger, denser bone tissue results when new bone growth occurs under pressure and that the risk of a weakened juncture or pseudoarthrodesis increases when a prosthetic device stress shields new bone growth. The problem arises of when and how much pressure or force to apply to develop a strong junction between the bone portions. The bone portions should be secured and supported during initial 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.  
         [0006]     Similarly, torn and/or structural ligaments can be treated by initially securing/immobilizing the ligaments. This can be accomplished using internal and/or external prosthetic devices to augment or replace the stability lost as a result of the damaged ligaments. Further, the treated 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 ligaments, i.e., stretching and rotation of the ligaments. Current treatment methods do not allow for an implanted device to initially secure/immobilize the ligaments and then allow limited movement of the same without a subsequent surgical revisitation.  
         [0007]     In light of the above, there is a continuing need for devices and treatments that stabilize and support damaged bone tissue, bony structures, and connecting tissue and 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 this need and provides other benefits and advantages in a novel and nonobvious manner.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The present invention relates to orthopedic devices and the manufacture and use thereof. 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.  
         [0009]     In one form, the present invention provides an orthopedic device for securing two or more bone portions. The orthopedic device comprises: an elongate member including a receptacle therein and 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; and a restricting component comprising a biodegradable material and disposed in the receptacle to inhibit the translational, the rotational, or both the translational and rotational movement of the first of the bone portions relative to the second of the bone portions.  
         [0010]     The orthopedic device can be used to treat a variety of bone defects including but not limited to: bone fractures, diseased bone tissue, spinal diseases, diseased/damaged vertebrae, torn or stretched ligaments, and the like.  
         [0011]     In preferred embodiments, the device prevents 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 device can allow a limited amount of movement, i.e. translation and/or rotation about the joint. The devices, with and without the biodegradable component, still provide a measure of support and/or restriction of the movement of bone portions attached to the device. In preferred embodiments, the devices of the present invention remain in place indefinitely.  
         [0012]     In another form, the present invention provides a device for securing bone portions. The device can comprise: a body member comprising a first arm and an opposite second arm defining a receptacle therebetween; an elongate rod disposed within the receptacle; a restricting component comprising a biodegradable material and disposed within the receptacle; and a cap configured to engage the first and second arms and secure the rod and the bioabsorbable restricting component in the receptacle.  
         [0013]     In still other forms, the present invention provides a method for treating a bone defect. The method comprises: providing an orthopedic device that includes an elongate member having at least one receptacle therein and a restricting component disposed within the at least one receptacle. The restricting component is composed of a biodegradable material. The method further includes securing the elongate member to a first bone portion with a first fastener and to a second bone portion with a second fastener to restrict translational or rotational movement or both the translational and rotational movement of the first bone portion relative to the second bone portion. The secured device can support and effectively immobilize the two bone portions relative to each other. In vivo, the biodegradable material can degrade and, consequently, allow translational or rotational movement or both translational and rotational movement of the first bone portion relative to the second bone portion. Preferably the elongate member remains secured to the first and second bone portions. The degradation of the biodegradable material can occur over time. This effectively transfers at least a portion of the support and/or biomechanical load from the elongate device to the new bone growth at the treatment site.  
         [0014]     Further objects, features, aspects, forms, advantages, and benefits shall become apparent from the description and drawings contained herein.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1   a  is a perspective view of one embodiment of a bone fixation device comprising an elongate member in the form of a bone plate in accordance with the present invention.  
         [0016]      FIG. 1   b  is a partial, perspective view of another embodiment of a bone fixation device similar to the device of  FIG. 1   a , illustrating the restricting component symmetrically disposed in the receptacle in accordance with the present invention.  
         [0017]      FIG. 1   c  is a partial, perspective view of still another embodiment of a bone fixation device similar to the device of  FIG. 1   a , illustrating the restricting component asymmetrically disposed in the receptacle in accordance with the present invention.  
         [0018]      FIG. 2   a  is a perspective view of one embodiment of an orthopedic device having a two-part telescoping elongate member in accordance with the present invention.  
         [0019]      FIG. 2   b  is a perspective view of another embodiment of an orthopedic device having a two-part telescoping elongate member in accordance with the present invention.  
         [0020]      FIG. 2   c  is a perspective view of still another embodiment of an orthopedic device having a two-part telescoping elongate member in accordance with the present invention.  
         [0021]      FIG. 3   a  is a perspective view of one embodiment of an orthopedic device having telescoping elongate members joined by a loop of material in accordance with the present invention.  
         [0022]      FIG. 3   b  is a perspective view of another embodiment of an orthopedic device having telescoping elongate members joined by a loop of material in accordance with the present invention.  
         [0023]      FIG. 3   c  is a perspective view of still another embodiment of an orthopedic device having telescoping elongate members joined by a loop of material in accordance with the present invention.  
         [0024]      FIG. 4   a  is a perspective view of an embodiment of an orthopedic interconnection device comprising an anchoring body and an attached elongate member in accordance with the present invention.  
         [0025]      FIG. 4   b  is a perspective view of another embodiment of an orthopedic interconnection device comprising an anchoring body and an attached elongate member in accordance with the present invention.  
         [0026]      FIG. 4   c  is a perspective view of still another embodiment of an orthopedic device comprising an anchoring body and an attached elongate member in accordance with the present invention.  
         [0027]      FIG. 5  is a perspective view of an embodiment of an orthopedic interconnection device comprising a pedicle screw, an attached elongate member, and a restricting component in accordance with the present invention.  
         [0028]      FIG. 6  is a plan view illustrating one embodiment of a method of treating the spine by attaching a bone plate having bioabsorbable restricting components in accordance with the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     For 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.  
         [0030]     In preferred embodiments, the present invention provides an implantable orthopedic device or prosthesis 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 that can be used to treat or repair defective, diseased, and/or damaged tissue of the muscular/skeletal system(s).  
         [0031]     The devices 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 device according to the present invention that allows the variable or dynamizable support develops new, strong bone tissue, thus minimizing the risk of pseudoarthrodesis.  
         [0032]     The biodegradable component of the present invention provides a restricting component for the inventive device. This restricting component can provide rigidity and support for both the implanted orthopedic fusion device and, consequently, the attached bone structures. In use, the load supported by the bone fixation device and supported by the restricting component can vary. embodiment, member  16  has limited freedom to move while secured to two or more bone portions.  
         [0033]     When a first end  17  of member  16  is secured to a first bone portion, and a second end  19  is secured to a second bone portion, the two bone portions are free to move relative to each other and/or member  16 .  
         [0034]     In one form, receptacles  24 ,  22   a ,  22   b ,  22   c  . . . are provided as over-sized openings relative to the threads and/or shank of a bone fastener. In other forms, receptacles  24 ,  22   a ,  22   b ,  22   c  . . . are provided as oblong openings. When provided as oblong openings, they can be oriented with the long dimension of the oval, either parallel with each other or at one or more angles with each other.  
         [0035]     Restricting component(s)  32 ,  32   a ,  32   b ,  32   c  . . . can be disposed in one or more of receptacles  24 ,  22   a ,  22   b ,  22   c  . . . It will be understood that in alternative embodiments, each one of receptacles  24 ,  22   a ,  22   b ,  22   c  . . . need not include restricting component  32 ,  32   a ,  32   b ,  32   c  . . . respectively. Restricting component  32  is operatively positioned to further inhibit or restrict the motion of bone portions (not shown) attached to device  10 . In one embodiment, receptacle  24  has a rim or edge  23 . Restricting component  32  can be deposited in receptacle  24  between edge  23  and fastener  42 . In other embodiments, restricting component  32  completely surrounds fastener  42 . In this embodiment, restricting component  32  can initially fill up or cover over receptacle  24 . Fastener  42  can then be inserted through restricting component  32  and receptacle  24 . In other embodiments, restricting component  32  can be deposited in receptacle  24  and define an opening therethrough for receiving fastener  42 . In one preferred embodiment, restricting component  32  is operatively positioned within receptacle  24  such that restricting component  32  contacts only a portion of the edge  23  of receptacles  22   a ,  22   b ,  22   c . This allows the fixation device to become dynamizable, or change its support characteristics in vivo. This change in support characteristics 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 ingrowth and minimizes the risk for the development of pseudoarthrodesis.  
         [0036]     The devices of the present invention also find advantageous use in the treatment of connecting tissue such as ligaments. The devices can augment the connecting tissue. After a predetermined period of time or condition, the device can allow limited movement, either translational or rotational or both translational and rotational, of the connecting tissue and/or attached bone structures as desired. For example, if the natural connecting tissue is elastic, the device 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 preselected conditions in forming and using the device. The following description specifically describes non-limiting, specific embodiments for use with the present invention.  
         [0037]     It should be understood that other configurations can be used which impart the ability of the elongate member to change resistance to translational and/or rotational movement as the biodegradable component of the device biodegrades.  
         [0038]      FIG. 1   a  is a perspective view of one embodiment of an orthopedic device  10  comprising an elongate member  16  defining an elongate axis  52 . In the illustrated embodiment, member  16  comprises a bone plate  18 . Device  10  can include one receptacle  24  or a plurality of receptacles  22   a ,  22   b ,  22   c  . . . Bone fastener  42  can be inserted through receptacle  24  to secure elongate member  16  to one, two, or more bone portions.  
         [0039]     In a preferred embodiment, one or more of receptacles  22   a ,  22   b ,  22   c  . . . are sized to have a larger opening than the outer diameter of the threads and/or shank of fastener  42 . In this  
         [0040]     Restricting component  32  is operatively positioned within receptacle  24  such that it further restricts the translational and/or rotational motion of attached bone portions. Receptacles  24 ,  22   a ,  22   b ,  22   c  . . . can be configured to allow or restrict movement of secured bone portions in only one direction, or two or more directions, as desired. Similarly, receptacles  24 ,  22   a ,  22   b ,  22   c  . . . can be configured to allow either rotation or translation or both, as desired.  
         [0041]     Restricting component  32  comprises a biodegradable material, discussed more fully below. In vivo, the biodegrading material degrades. In a preferred embodiment, after restricting component  32  has been eliminated, fastener  42  continues to secure elongate member  16  to attached bone portions. Elongate member  16  continues to provide at least some support to attached bone and to restrict at least some of the translational and/or rotational motion of attached bone portions.  
         [0042]     One example of a similar bone plate is disclosed in U.S. Pat. No. 6,152,927, which is incorporated herein by reference in its entirety.  
         [0043]      FIG. 1   b  is a partial, perspective view of another embodiment of an orthopedic device  12 . Device  12  is formed similarly to device  10  and, consequently, the same reference numbers are used to denote like components. Device  12  comprises at least one receptacle  24 . A restricting component  34  is symmetrically disposed in receptacle  24 . In a preferred embodiment, restricting component  34  is placed in contact with the entire rim or edge  23  shown in dashed lines of receptacle  24 . Fastener  42  extends through restricting component  34  and can be used to secure elongate member  16  to a portion of bone. When present, restricting component  34  is operatively positioned within device  12  so as to further restrict the motion of bone portions attached to device  12 .  
         [0044]      FIG. 1   c  is a partial, perspective view of another preferred embodiment of an orthopedic device  14 . Device  14  is formed similarly to device  10  and, consequently, the same reference numbers are used to denote like components. Device  14  comprises at least one receptacle  24 . In the illustrated embodiment, restricting component  36  is asymmetrically disposed in receptacle  24 .  
         [0045]     In embodiments such as those illustrated in  FIGS. 1   a ,  1   b , and  1   c , elongate member  16  includes more than one feature, for example multiple receptacles  22  fitted with biodegradable restricting component  32 ,  34 , and  36 . Elongate member  16  can be secured to at least one portion of bone by a variety of fasteners including bone nails, staples, bone adhesives, bone screws, bone hooks, and the like.  
         [0046]     A variety of biodegradable restricting components, both biodegradable and bio-stable, can be used within the same orthopedic device to optimize the change in translational and/or rotational motion of bone portions attached to the devices as the restricting components biodegrade.  
         [0047]      FIG. 2   a  is a perspective view of one embodiment of an orthopedic device  62  in accordance with the present invention. Device  62  includes an elongate member  81  that comprises an assembly of two or more telescoping rod members. In the illustrated embodiment, elongate member  81  comprises a first rod  72  and a second rod  82 . Second rod  82  is slidably received within a lumen  73  of first rod  72 . First rod  72  also includes a receptacle  75  formed therein. Receptacle  75  can be sized to accommodate a first restricting component  86 .  
         [0048]     In the illustrated embodiment, receptacle  75  is illustrated as a slot  76  extending substantially parallel to the elongate axis  77  of first rod  72 . In alternative embodiments, receptacle  75  can be provided as a cylindrical opening.  
         [0049]     Second rod  82  is slidably received within lumen  73  of first rod  72 . In this embodiment, second rod  82 , in the absence of a restricting component, can freely move either translational and/or rotational within lumen  73 . Additionally, second rod  82  can include one or more openings positioned along its length to be in registry with receptacle  75 . One or more restricting components, either  86  or  87 , can be inserted through receptacle  75  and into the openings formed in second rod  82 , similar to the insertion of a peg in a hole or an opening.  
         [0050]     First restricting component  86  is positioned in receptacle  75  to inhibit movement of rod  82  in relationship to rod  72 . In preferred embodiments, a second restricting component  87  can be disposed in the same slot  76 . It will be understood to those skilled in the art that a plurality of restricting components can be inserted through slot  76  and is intended to be included within the scope of the present invention.  
         [0051]     When receptacle  75  is provided as slot  76 , the first and second restricting components  86  and  87  can be positioned within slot  76  to initially allow no rotational or translational movement of second rod  82  in relation to first rod  72  (and corresponding to the attached first and second bone portions). In other embodiments, first and second restricting components  86  and  87  can be positioned in slot  76  to allow either limited translational movement of second rod  82  within lumen  73  and/or limited rotational movement of second rod  82  within lumen  73 .  
         [0052]     First rod  72  and second rod  82  are configured to be secured to a bone defect. For example, first rod  72  can include an opening  90  extending therethrough to receive a fastener  92 . In the illustrated embodiment, fastener  92  is illustrated as a bone screw. Similarly, second rod  82  can be provided with opening  91  extending therethrough to receive a fastener  92 . In the illustrated embodiment, both first rod  72  and second rod  82  are illustrated as cylindrical, elongate rods. In other embodiments, it will be understood that alternative configurations of first rod  72  and second rod  82  are intended to be included within the scope of the present invention. For example, first and second rods  72  and  82  respectively can be provided to have a square or rectangular cross section. In still other embodiments, first rod  72  can be provided in the form of a “U-shaped” rod defining a channel into which second rod  82  can be received.  
         [0053]     One or more of restricting components  86  and  87  can be formed of a biodegradable material as described more fully below. In alternative embodiments, only first restricting component  86  need be composed of the biodegradable material. The second restricting component  87  can be composed of any biocompatible material including biocompatible polymeric materials, metallic materials, and ceramic materials, discussed more fully below.  
         [0054]      FIG. 2   b  is a perspective view of another embodiment of an orthopedic device  64 . Orthopedic device  64  is formed similarly to device  62  and, consequently, the same reference numbers will be used to denote like components. Device  64  includes an elongate member  95  comprising an assembly of rods  72  and  84 . First rod  72  can be provided as has been described for  FIG. 2   a . Second rod  84  is slidably disposed within lumen  73  of rod  72 . Second rod  84  includes a plurality of openings  100 ,  102 ,  104 , . . . Each of openings  100 ,  102 ,  104  . . . can be sized and positioned about rod  84  to receive a restricting component similar to a peg or plug in an opening. In the illustrated embodiment, the openings  100 ,  102 ,  104  . . . are illustrated as being linearly aligned with the elongate axis  83 . In other embodiments, openings  100 ,  102 ,  104  . . . can be axially displaced and/or radially displaced from each other in second rod  84 . Consequently, in still yet alternative embodiments, second rod  84  can be provided as an imperforate rod including a plurality of openings extending therethrough. In this fashion, a surgeon can selectively pick a particular opening or set of openings in which to insert a restricting component. Consequently, the length of device  64  can be varied by selectively using one or more of openings placed around or in second rod  84 .  
         [0055]     First rod  72  includes receptacle  75 , which is illustrated as slot  76 . It will also be understood that slot  76  need not extend in the axial direction along first rod  72 . In alternative embodiments, slot  76  can be formed as an arc either horizontally or spirally about first rod  72 . In still other embodiments, receptacle  75  can be provided as a round, oblong, rectangular, square, or polygonal opening in first rod  72 .  
         [0056]      FIG. 2   c  is perspective view illustrating the orthopedic device  64  in position to be secured to bone portion  91  and a second bone portion  93 . As can be seen from the figure, a first restricting component  86  has been inserted into a first opening  100  and a second restricting component  88  has been inserted into a second opening  106 . In this embodiment, the orthopedic device  64  inhibits rotation of first rod  72  in relation to second rod  84 . Similarly, device  64  inhibits rotation of first bone portion  91  in relationship to second bone portion  93 . Additionally, it can be observed from the gap  96  in slot  76  above restricting component  86  and a corresponding gap  97  below restricting component  88  that second rod  84  can still travel to a limited degree within the lumen  72  of first rod  72 . This permits limited movement of first bone portion  91  in conjunction to second bone portion  93  when the two bone portions are attached to first rod and second rod  72  and  84 , respectively.  
         [0057]     As has been described above, it will be understood that in alternative embodiments gaps  96  and  97  can be eliminated by the selective sizing of slot  76  and/or selective placement of one or more restricting components  86  and/or  88 . In this embodiment, first rod  72  and second rod  84  are not free to move either translationally or rotationally with respect to each other. Similarly, first bone portion  91  and second bone portion  93  are not free to move relative to each other.  
         [0058]     In use, after implantation, the restricting components  86  and/or  88  begin to erode or degrade. When restricting components  86  and/or  88  have been either partially degraded and/or fully degraded, second rod  84  is permitted to either rotate and/or traverse within lumen  73  of first rod  72 . This in turn allows translation and/or rotation of first bone portion  91  relative to second bone portion  93 . Preferably, first rod  72  and second rod  84  remain secured to bone portions  91  and  93 , respectively. Since second rod  84  remains within lumen  73  of first rod  72 , bone portions  91  and  93  cannot completely separate from each other, thus preventing re-injury to the previous bone defect. Consequently, the orthopedic device  64  continues to restrict either rotational and/or translation movement of the first bone portion  91  relative to the second bone portion  93 .  
         [0059]      FIG. 3   a  is a perspective view of orthopedic device  100  in accordance with the present invention. Device  100  includes an elongate member  101  comprising a telescoping assembly of a first rod  110  and a second rod  120 . Rods  110  and  120  can be provided substantially as described for rods  72  and  82  except as further discussed below. First rod  110  includes a lumen  111  extending at least partly therethrough in the longitudinal direction. Second rod  120  is slidably disposed within lumen  111  of first rod  110 . As illustrated, rod  120  includes an opening  114  through which a bone fastener can be inserted. Similarly, second rod  120  includes an opening  115  through which a bone fastener can be inserted. It will be understood that the term “bone fastener” can be any orthopedic fastener known in the art, including glues, staples, bone screws, hooks, and the like.  
         [0060]     The first rod  110  and the second rod  120  are operatively linked together by a restricting component  130 . Restricting component  130  is provided in the form of a loop  131  that is fixedly attached to second rod  120  and first rod  110 . Restricting component  130  initially inhibits translational and/or rotational motion of first rod  110  relative to second rod  120 . Restricting component  130  may be comprised of a biodegradable material as described more fully below. In vivo, restricting component  130  biodegrades. As the restricting component degrades, the range of motion of first rod  110  relative to second rod  120  increases. Similarly, the rotational and/or translational motion of bone portions attached to first rod  110  and second rod  120  also increases.  
         [0061]      FIG. 3   b  is a perspective view of an alternative embodiment of an orthopedic device  102  according to the present invention. Device  102  includes an elongate member or assembly  103  that comprises a first rod  116 , a second rod  126 , and at least one restricting component  130 . At least a portion of a second rod  126  is slidably disposed within first rod  116 . Initially, first rod  116  and second rod  126  are connected by restricting component  130 , illustrated as loop  131 . Loop  131  can comprise either a biodegradable material described below or a non-biocompatible material. Further, loop  131  can be either flexible or non-flexible. In the illustrated embodiment, a first end  132  of loop  131  is attached to first rod  116 . This attachment can be accomplished by welding, gluing, over molding, and the like to secure end  132  to the side of rod  116 . In the alternative, first end  132  can be received within a receptacle formed in the side of rod  116 . A second end  133  of loop  131  can be similarly secured or attached to second rod  126 . The distal ends of both rods  126  and  116  include openings  119  and  120 , respectively, for attaching device  102  to bone portions using any bone fasteners known in the art.  
         [0062]     First rod  116  also includes receptacle  80  formed therein. Receptacle  80  is illustrated as a slot  81  extending substantially parallel to the longitudinal axis of rod  116 . In alternative embodiments, receptacle  80  can be formed as described above for slot  76 . In still other embodiments, receptacle  80  can be provided as a round, oblong, rectangular, square, or polygonal opening in first rod  116 .  
         [0063]     Receptacle  80  can be sized as desired and/or selected depending upon the intended application, method of treatment, and type of tissue defect and the like. In the illustrated embodiment, receptacle  80  is sized to allow a gap  85   a  above pin  87  and a gap  85   b  below pin  87 . This permits initial limited translational movement of second rod  126  to travel within lumen  113 . The limited “travel” of rod  126  within lumen  113  can be further restricted or eliminated depending upon the length and placement of loop  131 .  
         [0064]     Second rod  126  can be provided substantially as described above for second rod  120  of device  100 .  
         [0065]     A second restricting component  86  is positioned in receptacle  80 . Second restricting component  86  can be provided as a plug or pin  87 . Second restricting component  86 , similar to first restricting component  130 , can be composed of either a biodegradable or a biostable material.  
         [0066]     In one embodiment both pin  87  and loop  131  may be made of the same material, and may be sized so as to fully biodegrade at the same time. In another embodiment pin  87  and loop  131  may be formed of different materials, made in different thickness, or treated differently so that loop  131  and pin  87  have differing biostabilities and therefore contribute to the stability of device  102  within different time frames. In still another embodiment, pin  87  is formed of a biostable material, while loop  131  is comprised of a biodegradable material. As pin  87  biodegrades, the restriction imposed on the rotational, or translational, or both rotational and translational movement of first rod  116  and the second rod  126  relative to one another is reduced and eventually eliminated. However, loop  131  continues to further restrict the movements of first rod  116  and second rod  126  relative to one another, and, consequently, the bone portions to which they are attached.  
         [0067]     It should be understood that any combination of restricting components such as loop  131  and pin  87  or a plurality of pins and loops having differing biostabilities are intended to be within the scope of the invention.  
         [0068]      FIG. 3   c  illustrates an alternative embodiment of an orthopedic rod device  104  according to the present invention. Device  104  is formed similarly to device  102  and, consequently, the same reference numbers are used to denote like components. In this embodiment, first rod  117  is provided with an inner surface  82  in lumen  94  that restricts the degree of slidable travel of second rod  126 . Surface  82  is illustrated as the bottom of lumen  89 . The translational, or rotational or both the translational and rotational movement of rods  117  and  126  relative to one another may be further restricted by any of the means already discussed, for example, a bioabsorbable loop  131  or pin  87  disposed within receptacle  80  in the side of rod  117  and any combination of similar restricting components thereof, where at least one of the restricting components is biodegradable. It should also be understood that any element, for example a lip, edge, pin, screw or the like, operatively positioned on the lumen  94  of first rod  117  in the slidable path of second rod  126  may be used to restrict the slidable travel of second elongate member  126  within first elongate member  117 .  
         [0069]     Additionally, the lumen  94  of first rod  117  can have differing internal diameters or a gradually tapering internal diameter that restricts movement of second rod  126 . In still yet other embodiments, second rod  126  can be formed to include a lip, edge, pin, screw, or the like to inhibit its movement relative to the first rod  117 .  
         [0070]      FIG. 4   a  is a perspective view of orthopedic device  200  according to the present invention. Orthopedic device  200  can be provided as an interconnection element for use with a spinal rod system. Orthopedic device  200  includes a body  170  having a pair of arms  175   a  and  175   b  extending therefrom in a substantially parallel arrangement. Arms  175   a  and  175   b  define a receptacle  176  therebetween. In the illustrated embodiment, receptacle  176  can be viewed as a channel or trough formed in body  170 . Consequently, receptacle  176  includes a bottom or cradle region  173  and an opposite, open end  177 . An elongate rod  180  is disposed within receptacle  176 . Additionally, a restricting component  172  is disposed in receptacle  176 . In the illustrated embodiment, restricting component  172  is positioned adjacent cradle region  173 . Consequently, restricting component  172  is positioned between rod  180  and body  170 .  
         [0071]     A cap  190  is provided to engage arms  175   a  and  175   b  to secure elongate rod  180  and restricting component  173  within receptacle  176 . Cap  190  can include internal threads (not shown) that can engage with the external threads on first arm  175   a  and second arm  175   b . Cap  190  can include a tool-engaging aperture, such as hex imprint  192 . Other means for engaging a tool to cap  190  are also contemplated for the present invention. Consequently, cap  190  can be used to clamp body  170 , rod  180 , and restricting component  172  together.  
         [0072]     Restricting component  172  can be formed of a biodegradable material discussed more fully below. Positioning restricting component  172  between elongate rod  180  and body  170  initially inhibits the translational or rotational or both the translational and rotational movement of elongate rod  180  relative to body  170 . As discussed in previous embodiments, restricting component  172  can degrade in vivo. As the biodegradable material degrades, the force and/or frictional engagement between restricting component  172  and rod  180  decreases. Consequently, rod  180  is allowed translational and/or rotational movement relative to body  170 . The further the biodegradable material erodes, the less the frictional engagement between restricting component  172  and rod  180 . After the biodegradable material has completely eroded, elongate rod  180  is still retained within the receptacle  176 . Consequently, rod  180  cannot be disengaged in vivo. After the biodegradable material has completely eroded, orthopedic device  200 , which can be secured to two or more bone portions, still provides limited support and restricts movement of the two or more bone portions.  
         [0073]      FIG. 4   b  is a perspective view of an alternative embodiment of an orthopedic device  202 . Orthopedic device  202  is structurally similar to orthopedic device  200 . Consequently, same reference numbers will be used to denote like components. Orthopedic device  202  includes body  170  having first and second arms  175   a  and  175   b  defining a receptacle  176  therebetween. Elongate rod  180  and a restricting component  192  are also disposed within receptacle  176 . In this embodiment, restricting component  192  is provided as a block  194  and positioned proximal to upper end  177  of receptacle  176 . Consequently, engaging cap  190  to first and second arms  175   a  and  175   b  forces restricting component  192  to engage rod  180 . This induces a frictional engagement that restricts the relative movement of elongate rod  180  relative to body  170 . Restricting component  192  can be formed of a biodegradable component, discussed more fully below. As noted in the earlier embodiments, as the biodegradable material erodes in vivo, the frictional engagement between restricting component  192  and elongate rod  180  decreases. This initially allows rod  180  to move either translationally and/or rotationally relative to body  170 .  
         [0074]      FIG. 4   c  is a perspective view of yet another embodiment of an orthopedic device  204  in accordance with the present invention. Orthopedic device  204  is provided substantially as has been described for orthopedic devices  200  and  202 . Consequently, the same reference numbers will be used to denote like components. In this embodiment, orthopedic device  204  includes a first restricting component  172  and a second restricting component  192 . Both first and second restricting component  172  and  192  are disposed within receptacle  176 . In the illustrated embodiment, restricting component  172  is disposed in the cradle region  173  and second restricting component  192  is disposed proximal to upper end  177  between elongate member  180  and cap  190 . Engaging cap  190  to first and second arms  175   a  and  175   b  forces the first and second restricting components  172  and  192  to engage with rod  180  and body  170 . This induces a frictional engagement that inhibits or restricts movement of rod  180  within receptacle  176 . As noted before, restricting component  172  and/or restricting component  192  or both can be formed of a biodegradable material. It will be understood that restricting component  172  can comprise a first biodegradable material. Restricting component  192  can comprise a second biodegradable material that is the same or different from the first biodegradable material. Consequently, the degradation rate of first restricting component  172  can be the same or different from that of the degradation rate of the second restricting component  192 . Furthermore, restricting component  172  and restricting component  192  can be sized to have different thicknesses or treated differently so that they have differing biostability or erode at different rates or within different time frames. Additionally, one of either restricting component  172  and restricting component  192  can be formed of a biostable material that does not appreciably erode or disintegrate in vivo.  
         [0075]      FIG. 5  is a perspective view of another embodiment of an orthopedic device  210  in accordance with the present invention. Device  210  is illustrated as a pedicle screw  174 . Pedicle screw  174  include an interconnection body  194  having a receptacle  276  formed therein. Additionally, an elongate rod  220  and a restricting component  186  are disposed within receptacle  276 . In the illustrated embodiment, restricting component  186  is provided as a sleeve  187  that partially or completely surrounds a portion of rod  220 . Restricting component  186  comprises a biodegradable material discussed more fully below. Cap  190  can be provided to engage onto first and second arms  275   a  and  275   b  to secure body  194 , rod  220 , and restricting component  186  together. This effectively inhibits relative translational and/or rotational movement of rod  220  relative to body  194 . Since restricting component  186  is formed of a biodegradable material, which is discussed more fully below, in vivo the biodegradable material erodes or degrades. The degradation of the biodegradable material allows the captured rod  220  limited translational and/or rotational movement. As with other embodiments, since rod  220  can be secured to a first and second bone portion, this also allows a relative translational or rotational movement of the respective bone portions.  
         [0076]     In use, any of the orthopedic devices  10 ,  12 ,  14 ,  62 ,  64 ,  100 ,  102 ,  104 ,  200 ,  202 ,  204 , and  210  can be used to secure and treat bone defects. For example, as illustrated in  FIG. 6 , orthopedic device  10  can be used to treat a spinal defect. In this specific illustration, the spinal defect occurs either on the inferior end plate  300  of vertebra  302  and/or the superior end plate  304  of vertebra  306 , or both. The surgeon can perform either a full or partial discectomy if desired and if the defect occurs in the nucleus pulposa and/or spinal disc structure. The discectomy can include either replacing the disc with a disc prosthesis and/or inserting a spinal spacer between the affected vertebrae, which spinal spacer can include an osteogenic material to induce bone fusion or not, as desired.  
         [0077]     Referring to  FIG. 6 , bone orthopedic device  10  is affixed to the spine using two or more bone fasteners  42 . In this embodiment, bone fasteners  42  are embedded in the restricting component  32 . Initially device  10  maintains the desired disc space height  308  and maintains vertebrae  302  and  306  in a rigid confirmation relative to one another. As biodegradable restricting component  32  degrades, the range of motion available to vertebra  302  and  304  relative to one another increases. This in effect allows the two vertebrae to exert increasing amounts of force on new bone tissue growing between the vertebrae.  
         [0078]     The biodegradable component included in one or more of the restricting components describe herein can be formed or composed of a variety of rigid materials including, without limitation, resorbable polymeric materials, resorbable composite materials, and resorbable ceramic materials.  
         [0079]     In preferred embodiments, the material selected to provide the structural features of the elongate member, the bone plates, the elongate rods, and interconnection elements include resilient materials such as, without limitation, nitonal, 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; reinforced polymeric materials, carbon poly(ether, ether, ketone) (PEEK), poly(aryl ether, ketone) (PAEK), and the like. Consequently, if desired, bridge portion  25  exhibits an elastic property and preferably performs analogous to a series of leaf springs stacked on top of each other.  
         [0080]     In one embodiment, the biodegradable material  14  can include polymeric materials formed from oligomers, homopolymers, copolymers, and polymer blends that include polymerized monomers derived from l, d, or d/l lactide (lactic acid); glycolide (glycolic acid); ethers; acids; anhydrides; 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. Specific examples of biodegradable polymeric materials for use in the present invention include poly(l,d-lactide) (PLDLA).  
         [0081]     Use 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).  
         [0082]     In a preferred embodiment, the biodegradable material  14  comprises a biodegradable polymeric material including: poly(amino acids), polyanhydrides, polycaprolactones, poly(lactic-glyclolic acid), polyhydroxybutyrates, polyorthoesters, and poly(d,l-lactide).  
         [0083]     In other embodiments, the biodegradable material can comprise biodegradable ceramic materials and ceramic cements. Examples of biodegradable ceramic materials include: hydroxy apatite, 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 U.S. Pat. Nos. 5,783,217; 5,676,976; 5,683,461; and 5,650,176, and PCT International Publication Nos. WO 98/16268, WO 96/39202 and WO 98/16209, all to Lee et al. 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.  
         [0084]     In 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.  
         [0085]     In 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 WO 98/40133, which is incorporated by reference herein.  
         [0086]     The restricting components of the present invention can be tailored to degrade at a predetermined or pre-selected rate by suitably selecting the size, thickness, and/or restricting component. 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 restricting component has an in vivo half life of greater than three months, more preferably the in vivo half life of the restricting component is greater than six months; still more preferably the in vivo 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 in vivo, presumably due to resorption, degradation, and/or elimination.  
         [0087]     In 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 a osteogenic factor such as a bone morphogenic protein (BMP). Examples of bone growth materials include an osteoinductive factor, such as an osteoinductive protein or a nucleotide or a nucleotide sequence encoding an osteoinductive protein operably associated with a promoter (e.g., provided in a vector such as a viral vector), for example a bone morphogenetic protein 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, most preferably, rhBMP-2. Purified recombinant BMPs are preferred for use in the inventive compositions for their provision of high osteoinductive potentials. BMP gene sequences and methods for producing recombinant and naturally-derived BMPs are known in the art, and for additional information on this subject reference may be made, for instance, to U.S. Pat. Nos. 5,108,753; 5,187,076; 5,366,875; 4,877,864; 5,108,922; 5,116,738; 5,013,649; 5,106,748; and 4,294,753; and International Publication Nos. WO93/00432; WO94/26893; and WO94/26892. The osteoinductive factor may also be LIM mineralization protein (LMP) or a suitable vector incorporating a gene encoding the same operably associated with a promoter, as described in WO99/06563 (see also genbank accession No. AF095585). When such vectors are employed as osteogenic factors in accordance with the invention, they are preferably delivered in conjunction with cells, for example autologous cells from the recipient of the implant. Most preferably the vector is delivered in conjunction with autologous white blood cells derived from bone marrow or peripheral blood of the recipient.  
         [0088]     The osteogenic factor will be incorporated in an amount which is effective to stimulate the formation of bone within the animal recipient. In more preferred compositions incorporating protein osteogenic factors, the osteogenic factor will be incorporated in a weight ratio of about 1:100 to about 1:1000 relative to the overall composition, more preferably about 1:100 to about 1:500. As will be understood, when the osteogenic factor comprises a nucleotide sequence, sufficient amounts of the delivery vehicle (vector) will be incorporated to cause significant transduction of cells, so as to cause the generation of sufficient protein at the site to induce bone formation.  
         [0089]     Additionally, or in the alternative, the present invention can be used with one or more of the devices disclosed in co-pending U.S. patent application Ser. No. ______ filed on Oct. 21, 2003 and entitled “Dynamizable Orthopedic Implants and Their Use in Treating Bone Defects”, Attorney Docket No. 4002-3274, which is hereby incorporated by reference in its entirety.  
         [0090]     While 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 and that all changes and modifications that come within the spirit of the invention are desired to be protected. Any 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.  
         [0091]     Further, all publications, patents, and patent applications cited in this specification are herein incorporated by reference as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference and set forth in its entirety herein.  
         [0092]     Unless 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.  
         [0093]     Further, 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.