Abstract:
A spinal implant configured to facilitate focused treatment of spinal tumors includes a plurality of irradiated implant seeds configured to concentrate the dosage and duration of radiation treatment of tumors.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/118,235 filed Nov. 26, 2008, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein. 
     
    
     BACKGROUND 
       [0002]    The treatment of spinal tumors typically involves removal of healthy tissue that surrounds the tumor in order to avoid violating the tumor outer capsule, which can allow malignant cells to escape and metastasize. In some instances, removal of the tumor involves violation of the tumor outer capsule. For example, where the tumor surrounds the spinal cord, the tumorous tissue is cut in order to allow the tumor to slide past the spinal cord during removal. Regardless of whether the outer capsule of the tumor is violated during removal of the tumor, it is usually desirable to apply radiation therapy to the tumor location in order to reduce the risk of metastasis. Radiation therapy is also applied in instances where the tumor is not removed, either because the tumor is inoperable or because the surgical procedure would be impractical. 
         [0003]    Radiation therapy is conventionally delivered to the spinal region using an extracorporeal radiation source, such as a proton beam, that is directed generally at the tumor or incision site, or can alternatively be delivered more systemically using intravenous delivery. Unfortunately, conventional spinal radiation therapy exposes a large quantity of healthy tissue to radiation. 
         [0004]    Brachytherapy has been used to treat prostate cancer interstitially by implanting seeds having concentrated doses of radiation within the prostate tissue. Low dose radiation (LDR) seeds are implanted surgically into the prostate, and remain in the prostate permanently. High dose radiation (HRD) seeds are implanted in the prostate on a more temporary basis. 
         [0005]    Conventional LDR seeds include casings sized as desired and formed from an implant grade material, such as titanium, and filled with a radioactive material. The seeds can be provided as stranded seeds whose casings are attached to one or more other pellets, or free seeds whose pellets are not attached to any other casings. The casings can be filled with any suitable isotope, depending on the desired level of radiation emission and half life. Typical isotopes include iodine-125 and palladium-103. Both materials continuously emit low-energy x-rays that travel only a short distance, which keeps the radiation away from surrounding organs. 
         [0006]    HDR brachytherapy seeds involve the temporary insertion of wire made from iridium-195, which emits a higher-energy x-ray than palladium or iodine. Typically, thin plastic catheters are inserted into the prostate through a template. The iridium wire is inserted into these catheters one at a time then left in place for a short period of time, for instance a few seconds. 
         [0007]    It is therefore desirable to provide a focused irradiated implant for the treatment of spinal tumors. 
       SUMMARY 
       [0008]    In accordance with one aspect, a brachytherapy spinal implant is provided, including a spinal implant and a plurality of irradiated seeds. The spinal implant includes a body extending along a longitudinal axis, a superior endplate disposed at one longitudinal end of the body, and an inferior endplate disposed at an opposing longitudinal end of the body, each end plate defining a vertebral-engaging surface configured to engage a complementary vertebral endplate. The irradiated seeds are attached to the implant body so as to direct radiation toward the spine in a desired direction when the brachytherapy implant is disposed in an intervertebral space. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The foregoing summary, as well as the following detailed description of a preferred embodiment of the application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the irradiated spinal implant for brachytherapy treatment of the present application, there is shown in the drawings a preferred embodiment. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
           [0010]      FIG. 1  is a top perspective view of a brachytherapy spinal implant constructed in accordance with one embodiment including a brachytherapy seeds attached to a spinal implant body; 
           [0011]      FIG. 2A  is a side elevation view of one of the brachytherapy seeds illustrated in  FIG. 1 ; 
           [0012]      FIG. 2B  is a sectional perspective view of one of the brachytherapy seeds illustrated in  FIG. 1 ; 
           [0013]      FIG. 3A  is a top plan view of the brachytherapy spinal implant illustrated in  FIG. 1  showing an endplate thereof; 
           [0014]      FIG. 3B  is an enlarged top plan view of the endplate illustrated in  FIG. 3A , showing seed-receiving apertures; 
           [0015]      FIG. 3C  is a top plan view similar to  FIG. 3B , showing the brachytherapy seeds installed in the seed-receiving apertures; 
           [0016]      FIG. 3D  is a sectional side elevation view of a portion of the endplate illustrated in  FIG. 3C  constructed in accordance with one embodiment; 
           [0017]      FIG. 3E  is a perspective view of a portion of the endplate illustrated in  FIG. 3A  as indicated at line  3 E- 3 E of  FIG. 1 , showing one of the seeds being inserted into the endplate; 
           [0018]      FIG. 4A  is a perspective view of one of the brachytherapy seeds illustrated in  FIG. 1  constructed in accordance with one embodiment; 
           [0019]      FIG. 4B  is a perspective view of one of the brachytherapy seeds illustrated in  FIG. 1  attached to the implant in accordance with another embodiment; 
           [0020]      FIG. 4C  is an exploded perspective view of one of the brachytherapy seeds illustrated in  FIG. 1  attached to the implant in accordance with another embodiment; 
           [0021]      FIG. 4D  is a schematic exploded top plan view of a portion of the implant illustrated in  FIG. 1 , showing one of the seeds attached to the implant in accordance with another embodiment; 
           [0022]      FIG. 4E  is a schematic exploded to plan view of a portion of the implant illustrated in  FIG. 1 , showing one of the seeds attached to the implant in accordance with another embodiment; 
           [0023]      FIG. 4F  is an exploded perspective view of a portion of the implant illustrated in  FIG. 1 , showing one of the seeds attached to the implant in accordance with another embodiment; 
           [0024]      FIG. 5A  is a perspective view of a brachytherapy bone fastener constructed as a bone screw in accordance with one embodiment; 
           [0025]      FIG. 5B  is a sectional side elevation view of the bone screw illustrated in  FIG. 5A , illustrating an embedded brachytherapy seed; 
           [0026]      FIG. 5C  is a sectional side elevation view of the bone screw illustrated in  FIG. 5A , illustrating a pair of embedded brachytherapy seeds; 
           [0027]      FIG. 5D  is a sectional side elevation view of the bone screw illustrated in  FIG. 5A , illustrating a plurality of embedded brachytherapy seeds; 
           [0028]      FIG. 5E  is a sectional side elevation view of a brachytherapy bone fastener containing a radionuclide in accordance with another embodiment; 
           [0029]      FIG. 5F  is a sectional side elevation view of a brachytherapy bone fastener constructed from a radionuclide in accordance with another embodiment; 
           [0030]      FIG. 5G  is a sectional side elevation view of a brachytherapy bone fastener illustrated as a bone nail; 
           [0031]      FIG. 6A  is a perspective view of a portion of a human spine having a malignant vertebral body; 
           [0032]      FIG. 6B  is a perspective view similar to  FIG. 6A , showing a plurality of brachytherapy seeds implanted in and around the spine; 
           [0033]      FIG. 6C  is a perspective view of the portion of the spine illustrated in  FIG. 6A  with the malignant vertebral body removed, and brachytherapy seeds implanted in and around the spine; and 
           [0034]      FIG. 6D  is a perspective view of similar to  FIG. 6C , but showing an intervertebral implant disposed between adjacent vertebrae occupying an intervertebral space where the malignant vertebral body was removed. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “lower” and “upper” designate directions in the drawings to which reference is made, it being appreciated that the actual orientation may differ during use. The directional terms “inner” and “outer” refer to directions toward and away from, respectively, the geometric center of the brachytherapy implant  20  and related parts thereof, unless otherwise indicated. The words, “distal,” “proximal,” “anterior”, “posterior”, “superior,” “inferior,” “medial,” and “lateral” and related words and/or phrases designate preferred positions and orientations in the human body to which reference is made and are not meant to be limiting. The terminology includes the above-listed words, derivatives thereof and words of similar import. 
         [0036]    Referring to  FIG. 1 , a brachytherapy spinal implant  20  is configured as a spinal implant  21 , which is illustrated in accordance with one embodiment as an expandable intervertebral implant  22 , that retains or otherwise carries or supports one or more radiation sources illustrated irradiated seeds  24  at one or more seed attachment locations  77  of the implant  22 . The irradiated seeds  24  are configured to emit predetermined doses of radiation. The implant  22  is illustrated as an expandable corpectomy spacer configured to replace at least a portion of a diseased or damaged vertebral body. The implant  22  includes superior and inferior endplates  28  and  30 , respectively, sized and configured to contact corresponding neighboring engagement surfaces of neighboring vertebrae  50  and can be provided in a range of surface geometries to accommodate a range of lordotic or kyphotic angles defined by the neighboring vertebrae  50 . In one embodiment, the engagement surfaces of the neighboring vertebrae  50  define vertebral endplates. Alternatively, for instance when a hemicorpectomy is performed, the engagement surfaces of one or both of the neighboring vertebrae  50  can be defined by a sectioned vertebra. The superior and inferior endplates  28  and  30  thus present respective vertebral-engaging surfaces  35  and  37  that carry outwardly projecting anti-expulsion features such as teeth, spikes, ridges, or other texturing  27 . The endplates  28  and  30  are disposed at opposing ends of an implant body  26  that extends along a central longitudinal axis  23 . 
         [0037]    The implant body  26  includes a first or inner body member  32  having a generally tubular configuration, a second or outer body member  34  having a generally tubular configuration, and an expansion ring  36 , all of which are hollow so as to provide an axial bore interior to and along a longitudinal axis  23  of the adjustable intervertebral implant  22 . The body members  32  and  34  and the expansion ring  36  each presents a respective radially outer surface  54 ,  56 , and  58 . In use, the first or inner member  32  is preferably sized and configured to be slightly smaller than the second or outer member  34  so that the first member  32  is moveably disposed within the second member  34 . However it should be noted that other arrangements of moveably associating the first member  32  and the second member  34  are contemplated. 
         [0038]    The endplates  28  and  30  may be connected to the inner and outer members  32  and  34 , respectively, by any connection mechanism known in the art, including, but not limited to, interference-fit, threading, screwing, bonding, and the like. As illustrated, the implant  22  can include an endplate cap  42  that is inserted into a central opening  46  extending longitudinally through the respective superior endplate  28 , and can be threadedly coupled to the inner member  32 . Alternatively, the endplate cap  42  can be integral with the inner member  32 . The endplate cap  42  defines a side wall  44  coupled at its lower end to a base  45  that cooperatively define an interior void  48 . A surgeon is thus able to insert osteobiological or other biocompatible material such as PMMA or bone cement into the void  48  to promote vertebral bone fusion at the complementary end plate of the superior vertebral body  50 . 
         [0039]    In this manner, the intervertebral implant  22  can be provided in a kit with a plurality of different endplates  28  and  30 , thus enabling the user to select the desired endplates that best conform with the contours of the patient&#39;s vertebral endplates. By way of example, various endplates  28  and  30  may be provided that include varying shapes including, but not limited to, circular, square, rectangular, oval, kidney-shaped, etc. and/or one or more of the following characteristics: a generally wedge-shaped surface, curved surface, flat surface, etc. Alternatively, the upper and lower endplates  28  and  30  may be integrally formed with the inner and outer members  32  and  34 . 
         [0040]    The radially inner surface of the expansion ring  36  includes threading that is configured to mate with the threading  39  formed on the outer radial surface of the inner member  32 , such that rotation of the expansion ring  36  causes the inner member  32  to translate or move generally linearly with respect to the outer member  34  along the longitudinal axis  23  of the adjustable intervertebral implant  22 . That is, in use, the inner and outer members  32  and  34  are preferably coaxially disposed along a common longitudinal axis  23  and are preferably slidably disposed (e.g., telescopic) with respect to one another so that the axial position of the inner member  32  is adjustable with respect to the outer member  34 . Rotation of the expansion ring  36  thereby causes the inner and outer members  32  and  34  to expand or contract depending on the relative direction of the rotation. 
         [0041]    One or more set screws  40  can be inserted into a screw opening  41  of the expansion ring  36  to selectively lock the height of the adjustable intervertebral implant  22 . Alternatively, the expansion ring  36  can be self-locking. In one embodiment, the set screw  40  can be positioned at a depth sufficient to enable the expansion ring  36  to be freely rotated and provide a desired height while still ensuring the secure coupling of the set screw  40  within the corresponding opening  41  due to the interference therebetween. The advancement of the set screw  40  via an appropriate instrument causes the distal end of the advanced set screw  40  to bear against the outer surface of the inner member  32  and prevent the expansion ring  36  from further rotation, thereby locking the height of the adjustable intervertebral implant  22 . 
         [0042]    The intervertebral implant  22  may be constructed from any biocompatible material or combination of any biocompatible material known in the art including, but not limited to, stainless steel, titanium, titanium alloys, ceramics, polymers including, but not limited to polytetrafluoroethylene (“PTFE”), and the like. In one embodiment, the inner and outer tubular members  32  and  34  are formed from a radiolucent material, such as, for example, a polymer or polyetheretherketone (“PEEK”), while the expansion ring  36  is preferably formed from a metal, such as, for example, titanium or stainless steel. 
         [0043]    The implant  22  one or more relatively large bone packing apertures  52  formed in the outer surface  58  of the outer member  34 . The aperture  52  defines a shelf  60  that extends radially or horizontally through the outer member  34 . The implant  22  can also include an array of smaller apertures  64  that are illustrated as extend radially into or through the outer surface  58  of the outer member  34 , though it should be appreciated that the apertures  64  can also extend into the inner member  32  or ring member  36  as shown in  FIG. 1 . The one or more bone packing apertures  52  and smaller apertures  64  provide access to an internal bore  62  extending longitudinally inside the implant body  26 . It should be appreciated that the implant  22  can be fabricated with apertures  52  and  64 , or that one or more apertures  52  and  64  can be created (e.g., drilled) into the implant in situ, for instance prior to or during the surgical procedure. The bore  62  can extend through one or both endplates  28  and  30 . 
         [0044]    A surgeon is thus able to insert an osteobiological or other biocompatible material such as PMMA or bone cement through one or both of the apertures  52  and  64  into the bore  62  to promote vertebral bone fusion at end plate of the inferior vertebral body  50 . Gravitational forces will assist in applying the graft material direction to the end plate of the vertebral body  50 . The intervertebral implant  22  is not limited to inclusion of the bone packing aperture  52  or the smaller apertures  64 , and may not include apertures therein or may include additional variably shaped or located apertures, depending upon the specific application or configuration of the implant  22 . The apertures  52  and  64  can further provide seed attachment locations  77 , as described in more detail below. 
         [0045]    Reference now to  FIGS. 1-2 , the brachytherapy implant  20  includes one or more brachytherapy seeds  24  that can be mounted or otherwise attached to the intervertebral implant  22 . Each brachytherapy seed  24  can include a bio-compatible protective shell  66  that defines an internal core  68  containing a radionuclide  70 . The radionuclide can be selected from any suitable isotope as desired, such as an isotope of iodine, palladium, iridium, or any alternative isotope that emits a desired dose of radiation. Specific examples of isotopes include iodine-125 and palladium-103, which emit low doses of radiation, and palladium-103, which emits high doses of radiation. Thus, the radiation seeds  24  may emit radiation for a limited amount of time, e.g., a few months, but may be configured to emit radiation indefinitely or for a relatively short amount of time, depending upon treatment preferences. 
         [0046]    The shell  66  can be constructed from any suitable implant-grade material, such as polyetheretherketone (PEEK), titanium, and the like. The shell  66  is illustrated as an elongate ovoid or tubular structure, though it can alternatively define any suitable shape as desired, such as a sphere, a curved structure, or any desired polygonal structure. As illustrated, the shell  66  defines an elongate cylindrical body  67  extending along a central axis A. The cylindrical body  57  defines a pair of opposing rounded ends  69  that define opposing outer end surfaces  73 . The cylindrical body  67  defines an outer side surface  71  extending between the opposing ends  69 . 
         [0047]    In certain embodiments, it is desirable to direct radiation toward the tumor while directing the radiation away from the spinal cord. Hence, the seeds  24  can be variably positioned and oriented on the implant  22  so as to irradiate the treatment site at close range without adversely affecting other parts of the body and generally serve to prevent the growth or re-growth of malignant spinal tumors in and around the implant location. The seeds  24  can each include a radio-opaque marker  63  disposed on the shell  66  or inside the shell  66  so as to be viewable within the treatment site with the aid of fluoroscopy. 
         [0048]    While the brachytherapy seeds  24  are illustrated and described in accordance with one embodiment, it should be appreciated that the seeds  24  could be constructed in accordance with any suitable alternative embodiment. For instance, the brachytherapy seeds  24  can define a unitary solid member constructed from a radionuclide. Furthermore, it should be appreciated that the seeds  24  can provide one or more components of the implant  22 . For instance, the anti-expulsion features  27  can be formed from brachytherapy seeds  24  geometrically configured to provide teeth, spikes, ridges, texturing, or the like that projects longitudinally out from the endplates  28  and  30  as illustrated in  FIG. 1 . 
         [0049]    The seeds  24  can be constructed and/or positioned as desired. The implant  22  is illustrated as including various embodiments of seeds  24  illustrated as being constructed and/or positioned as indicated by a one or more first seeds  24 A, one or more second seeds  24 B, one or more third seeds  24 C, one or more fourth seeds  24 D, one or more fifth seeds  24 E, and one or more sixth seeds  24 F, though it should be appreciated that the implant  22  can include any alternative type of seed connected and positioned on the implant  22  as desired. 
         [0050]    Referring also to  FIGS. 3A-E , the first seeds  24 A are disposed in one or both of the endplates  28  and  30  and extend longitudinally out from the endplates toward the adjacent vertebrae  50 . In particular, the implant  22  can include one or more seed attachment locations  77  illustrated as seed-receiving apertures  72  extending longitudinally into one or both of the endplates  28  and  30 . It should be appreciated that the implant  22  can be fabricated with apertures  72 , or that one or more apertures can be created (e.g., drilled) into the implant  22  in situ, for instance prior to or during the surgical procedure. 
         [0051]    The apertures  72  can be provided in combination with the teeth  27  as illustrated, or can be provided as an alternative to the teeth  27 . One of the outer ends  69  of the first seeds  24 A can be inserted into the apertures  72  in any desired manner along the direction of arrow A. For instance, the apertures  72  can define a diameter or cross-sectional dimension substantially equal to the outer diameter or alternative cross-sectional dimension of the first seeds  24 A (for instance the shells  66 ), such that the first seeds  24 A can be press-fit into the apertures  72 . Alternatively or additionally, one or more of the apertures  72  can define a cross-sectional dimension greater than that of the first seeds  24 A. An osteobiological or other biocompatible material such as PMMA or bone cement can be inserted into the apertures  72  to bond the shells  66  to one or both of the endplates  28  and  30 . Alternatively, the shells  66  can be ultrasonically welded to the implant  22 . 
         [0052]    The apertures  72  can extend into one or both of the endplates  28  and  30  at a depth D that can be less than the longitudinal length of the seeds  24 A, such that the seeds  24 A are configured and positioned similar to the anti-repulsion teeth or spikes  27  common in the art for both preventing dislodgement of the brachytherapy spinal implant  20 . Thus, the first seeds  24 A present a vertebral-engaging surface  25  that can assist the teeth  27  of the endplates  28  and  30  in securing the implant  20  to the vertebrae  50  or may replace the teeth  27  and provide the securement of the implant  20  to the vertebrae  50 . The vertebral-engaging surface  25  can be round as illustrated, or can be spiked and shaped as a pyramid or cone, as desired. Expansion of implant  20  or an alternatively constructed expandable interbody spacer can further assist in urging the surfaces  25  of the first seeds  24 A to penetrate the adjacent vertebral endplates. The first seeds  24 A can include additional cladding that can be coupled to the shell  66  to provide a desired geometry at the vertebral-engaging surfaces  25  configured to penetrate the adjacent vertebral endplates. The depth D of certain ones of the apertures  72  can be different than certain others of the apertures  72 , such that the seeds  24 A protrude at variable lengths L from one or both of the endplates  28  and  30 , as desired. Alternatively, the depth D can be constant, such that the length L of protrusion is constant. 
         [0053]    The first seeds  24 A protrude superiorly from the superior endplate  28 , and inferiorly from the inferior endplate  30 , when the apertures  72  extend parallel to the longitudinal axis L. Alternatively, the apertures  72  can extend along a direction that intersects the longitudinal axis L, such that the axis A of the inserted seeds  24 A extends in a direction having a superior or inferior directional component, and extends at an angle with respect to the longitudinal axis L. 
         [0054]    Alternatively or additionally, one or more, up to all, of the apertures  27  can extend into one or both of the endplates  28  and  30  a depth greater than or equal to the longitudinal length of the seeds  24 A, such that the seeds  24 A do not protrude longitudinally out from the corresponding endplate, and are impacted in the endplate. Accordingly, some of the seeds  24 A can be recessed in the endplate  28  so as to not protrude from one or both of the endplates  28  and  30 , while others of the seeds  24 A protrude from one or both of the endplate  28  and  30 , as shown in  FIG. 3D . Alternatively still, the entirety of one or both endplates  28  and  30  can be provided as a seed whose outer shell defines the outer vertebral-engaging surface of the endplates  28  and  30 , and whose radionuclide is disposed inside the outer shell in the manner described above. In each of the embodiments described herein, radiation is directed outward from one or both endplates  28  and  30  in superior and inferior directions, respectively, into the adjoining vertebral bodies  50 , which may be a common site for the recurrence of tumors. 
         [0055]    Alternatively still, the seeds  24 A could extend radially outward from the second body member  34 , so as to provide the second seeds  24 B as illustrated in  FIG. 1 . In particular, one of the outer ends  69  of the seeds  24 B is inserted into a complementary aperture  64 , which can define a diameter or cross-sectional dimension slightly greater than or substantially equal to that of the seed  24 B such that the seed  24 B can be press fit into the aperture  64 . Alternatively, the aperture  64  can be sized greater than the seed  24 C such that an osteobiological or other biocompatible material  65  such as PMMA or bone cement can be inserted into the apertures  64  to bond the shells  66  to the implant  22  inside the apertures  64 . Alternatively, the shells  66  can be ultrasonically welded to the implant  22 . 
         [0056]    The aperture  64  can have a depth that causes the seed  24 B to protrude out from the implant  22 , or can allow the seed  24 B to be recessed, or inwardly displaced, with respect to the outer wall of the implant  22 . When the implant  22  is disposed between the adjacent vertebrae  50 , the apertures  64  can face anteriorly, posteriorly, medially, laterally, or anywhere therebetween. Furthermore, the apertures  64  can be angled upward in a superior direction, or downward in an inferior direction. Accordingly, seeds  24 B can be installed in the apertures  64  so as to direct radiation anteriorly, posteriorly, medially, laterally, or anywhere therebetween. Thus, the radiation can be directed toward tumor sites and away from healthy tissue. In one embodiment, it may be desirable to attach the radiation seeds  24  such that they do not extend in a direction toward the spinal cord. 
         [0057]    Referring now to FIGS.  1  and  4 A-B, the one or more third seeds  24 C include an coupling element  74  extending out from the shell  66 . In one embodiment, the coupling element  74  includes cladding  76  that facilitates attachment of the seeds  24 C to the implant  22 . The cladding can be provided as a polymer, such as poly-ether-ether-ketone (PEEK) or titanium or any alternative implant-grade material, and can thus be made from the same material as part or all of the implant  22 . The seeds  24 C can be provided with the coupling element  74  attached to the shell  66 , or the coupling element can be provided separately and attached to the shell in situ. In one embodiment the coupling element  74  is ultrasonically welded to the shell  66 . 
         [0058]    The coupling element  74  has a diameter or cross-sectional dimension substantially equal to or slightly less than that of the aperture  64 , such that the coupling element is press-fit into the apertures  64  as illustrated in  FIG. 4A . Alternatively, the coupling element  74  can define a diameter or cross-sectional dimension substantially less than that of the aperture  64 , such that the shell  66  is loosely received in the aperture  64  and adhesively attached therein. The coupling element  74  can be attached to the implant  22  using a bone cement or alternative adhesive that bonds the coupling element  74  to the implant  22  in the corresponding aperture  64 . Alternatively, the coupling element can be ultrasonically welded to the implant  22 . Alternatively still, the coupling element  74  can have a threaded outer surface  75  configured to mate with a correspondingly threaded inner surface  78  of the apertures  64  as illustrated in  FIG. 4B . The coupling element  74  can be coupled to one of the outer ends  69  of the shell  66 , and extends along a portion of the length of the shell  66  less than an entire length of the shell  66  such that the body portion  67  of the shell  66  protrudes out from the coupling element  74 . 
         [0059]    As illustrated, the shell  66  is positioned in the coupling element  74  so as to be aligned with the aperture  64  when the coupling element is inserted into the aperture  64 , such that the shell  66  projects radially out from the implant  22 . Alternatively, the shell  66  can be positioned in the coupling element  74  such that the shell  66  extends in a direction that is angularly offset with respect to the aperture  64  when the coupling element  74  is installed in the aperture  64 . 
         [0060]    The coupling element  74  can be made from titanium, gold, or any desired material, and can provide a radiation shield that prevents or significantly limits radiation from passing therethrough. Accordingly, the seed  24 C can emit radiation from locations that are not covered by the coupling element  74 . Accordingly, use of the coupling element  74  to couple or assist in coupling the second seeds  24 C to the implant  22  enables a surgeon to tailor the emission of radiation from the brachytherapy spinal implant  20  by permitting selection of the location of the second seeds  24 C and the number of second seeds  140   b  that are coupled to the implant  100 . Alternatively, the second seeds  140   b  can be preassembled to the brachytherapy spinal implant  100 . 
         [0061]    Referring now to  FIGS. 4C-E , one or more fourth seeds  24 D can be attached edgewise to any surface of the implant  22 , such that the side surface  71  is attached to the implant  22  at seed attachment locations  77  at any surface of the inner body member  32 , outer body member  34 , or expansion ring  36 . As illustrated, the outer surface  58  of the of the outer body member  34  defines the seed attachment location  77 . 
         [0062]    As illustrated in  FIG. 4C , for instance, the fourth seeds  24 D can be attached directly to the outer surface  58  of the outer body member  34 . In particular, an osteobiological or other biocompatible material such as PMMA or bone cement, can be applied to the seeds  24 D and/or the outer surface  58 , and the side surface  71  can then be applied to the outer body member  34  at a seed attachment location  77 . Alternatively, the seed  24 D can be ultrasonically welded to the implant  22 . 
         [0063]    The seed  24 D can be oriented such that the central axis A extends substantially parallel to the longitudinal axis so that an adequate length of the seed  24 D can be bonded to the outer surface  58 . Alternatively or additionally, as illustrated in  FIG. 4D , one of the side surfaces  71  can be rounded to conform to the curvature of the outer surface  58  such that the seeds  24 D can be attached to the outer surface  58  at any orientation relative to the longitudinal axis L. Thus, it should be appreciated that a kit can be provided including one or more spinal implants  21  and seeds  24  not attached to the implants  21 , and provided as having different shapes and/or sizes configured to attach to various attachment locations  77  of the implants  21  as described above. The spinal implants  21  can alternatively or additionally be provided having seeds pre-attached. 
         [0064]    Referring now again to  FIG. 1 , the one or more fifth seeds  24 E can be attached to an internal surface of the implant  22 . For instance, the seeds  24 E can be attached to attachment locations  77  on the shelf  60  of the bone packing aperture  52 . The seeds  24 E can be attached with an osteobiological or other biocompatible material such as PMMA or bone cement, in addition or alternative to a groove formed in the shelf  60  in the manner described above. Alternatively or additionally, the seeds  24 E can be ultrasonically welded to the implant  22 . It should thus be appreciated that the axis A of the seeds  24 E can be oriented in any direction perpendicular to the longitudinal axis L of the implant  22 . Thus, when the implant  22  is installed in an intervertebral space, the axis A can be oriented in a horizontal plane perpendicular to the longitudinal axis L, and in or angled with respect to the medial, lateral, posterior, or anterior direction. 
         [0065]    Referring now to  FIGS. 1 and 4F , the implant  22  can define one or more see attachment locations  77  in the endplate cap  42 . As illustrated, the sixth seeds  24 F are attached to the base  45  of the endplate cap  42 . The seeds  24 F can be attached using an osteobiological or other biocompatible material such as PMMA or bone cement, in addition or alternative to a groove formed in the base  45  in the manner described above. Alternatively, the seeds  24 F can be ultrasonically welded to the implant  22 . Thus, the axis A of the sixth seeds  24 F can be oriented in any direction perpendicular to the longitudinal axis L of the implant  22 . Thus, when the implant  22  is installed in an intervertebral space, the axis A can be oriented in a horizontal plane perpendicular to the longitudinal axis L, and in or angled with respect to the medial, lateral, posterior, or anterior direction. 
         [0066]    While the brachytherapy implant  20  has been described in connection with the expandable implant  22 , it should be appreciated that the implant  20  could assume any construction suitable for implantation in a human spine. Furthermore, while the brachytherapy implant  20  has been described as including the six types of brachytherapy seeds  24 A-F at the locations illustrated and described, it should be appreciated that the implant  20  can include one or more of the types of seeds  24 A-F. Furthermore, one or more, up to all, of the seeds  24 A-F can be attached at any of the attachment locations  77 , or at any alternative location on the implant  22  as desired. 
         [0067]    While the spinal implant  21  of the brachytherapy spinal implant  20  has been illustrated and described with respect to is configured as a spinal implant  21 , which is illustrated in accordance with one embodiment as an expandable intervertebral implant  22 , the spinal implant  21  can assume any alternative configuration as desired, and can be expandable or rigid. Furthermore, it should be appreciated that the implant  21  can be constructed such that the endplates  28  and  30  are pivotable with respect to each other in order to restore movement between the adjacent vertebrae. For instance, as illustrated in  FIGS. 5A-D , the spinal implant  21  can be provided as a brachytherapy bone fastener such as a screw  90  that includes one or more seeds  24  mounted in or to the bone screw  210 . Alternatively, the bone screw  90  can integrally contain a radionuclide. The bone screw  90  can be provided as a pedicle screw, a screw for coupling a plate to a bone, such as an anterior plate or an anterior cervical plate, or other orthopedic bone anchor. 
         [0068]    The screw  90  can contain a longitudinally extending threaded shaft  92 , and a head  94  disposed at a proximal end of the shaft  92 . The screw  90  can be made from any suitable implant-grade material such as titanium. The head  94  can be threaded so as to mate with corresponding threads of a bone plate, such that the screw  90  can be a self-locking screw. The distal end of the shaft  92  can present cutting flutes such that the screw  90  is a self-tapping screw. The screw  90  can contain a cannulation  96  extending longitudinally from the head  94  into the shaft  92  that terminates proximal of the distal end of the shaft  92 . The cannulation  96  can contain any number of seeds  24  as desired, for instance one, two, or three as illustrated in  FIGS. 5A-D , respectively. The seeds  24  can be press-fit in the cannulation  96 . Additionally or alternatively, an osteobiological or other biocompatible material such as PMMA or bone cement can be inserted into the apertures. Alternatively, the shells  66  can be ultrasonically welded to the implant  22 . The one or more seeds  24  are preferably preassembled to and/or within the bone screw  90 . Alternatively, the one or more seeds  24  are coupled to the bone screw  90  in situ, that is prior to surgery or intraoperatively. The bone screw  90  may be implanted into bone and the one or more seeds  24  may be subsequently coupled to the bone screw  90 . 
         [0069]    Alternatively, referring to  FIG. 5E , the cannulation  96  can directly contain a radionuclide  70  of the type described above, as opposed to the cannulation  96  containing seeds  24  that contain the radionuclide  70 . In this regard, it should be appreciated that the shaft  92  provides an outer shell that surrounds the radionuclide  70 , such that the fastener  90  is generally constructed as described above with respect to the brachytherapy seeds  24 , but is configured as a bone fastener. 
         [0070]    Alternatively still, referring to  FIG. 5F , the fastener or screw  90  can be constructed from a desired radioactive isotope of the type described above. Thus, at least one or both of the head  94  and the shaft  92  can be constructed from the isotope. A coating  95  can be applied to the outer surface of the head  94  and/or shaft  92  that is formed from the radioactive isotope, so as to provide a shell  66  of the type described above with respect to the shell  66  of the brachytherapy seeds  24 . 
         [0071]    Referring now to  FIG. 5G , it should be further appreciated that the fastener  90  constructed in accordance with any of the embodiments described above could alternatively include a shaft  92  that is unthreaded, and can thus be smoothed or ribbed or otherwise textured to provide a nail or pin  98  as shown in  FIG. 5G , that can be implanted directly into spinal bone or soft tissue as desired. 
         [0072]    While examples of spinal implants  21  have been described, it should be appreciated that the brachytherapy implant  20  can include brachytherapy seeds  24  attached to or provided with any spinal implant as desired, including any desired intervertebral implant, cage, spinal rod, or the like, or other implants such as bone plates. It should be appreciated that a kit can be provided including one or more spinal implants and one or more seeds  24  that can be shaped and sized according to the method and/or location of implantation either in the spinal implant or directly into spinal bone or other tissue. Moreover, the brachytherapy seeds  24  can be constructed as an entire spinal implant, such as the screw  90 , the nail  98 , or a corpectomy device, an interbody spacer, a spinal rod, an implant configured for insertion interior to a vertebral body, and the like. 
         [0073]    Referring now to  FIG. 6A , a spine  100  includes a plurality of adjacent vertebrae, including an inferior vertebral body  50 A, a superior vertebral body  50 B, and a malignant vertebral body  50 C disposed between and adjacent the vertebral bodies  50 A and  50 B. Disc material  102  separates the vertebral bodies. A tumor or metastasis  104  is shown at an outer surface of the vertebral body  50 C, though it should be appreciated that the tumor  104  could be disposed inside the vertebral body  50 C. 
         [0074]    In accordance with one method, one or more brachytherapy seeds  24  can be implanted into the spine  100 , either directly or carried by a spinal implant of the type described above or any alternatively constructed implant. Referring to  FIG. 6B , a method for treating the spinal tumor  104  can include implanting the brachytherapy seeds  24  directly or percutaneously into or on the malignant vertebral body  50 C, in addition to or as an alternative to implanting the brachytherapy seeds  24  to the adjacent vertebral bodies  50 A-B or any alternative location on the spine  100 . For instance, one of the outer end surface  73  of one or more brachytherapy seeds  24  can be spike-shaped in the manner described above, and driven directly into the various locations of the spine  100 . The seeds  24  can be disposed entirely in the spine  100 , or can protrude out from the spine  100 . 
         [0075]    Alternatively or additionally, one or more apertures  106  can be formed in the various locations of the spine  100 , and a seed  24  can be implanted into each aperture  106 . The seeds  24  can be press-fit in the apertures  106  without adhesive, or can be bonded to the aperture using a bone cement or alternative adhesive  108 . The seeds  24  can be implanted prior to or subsequent to cement injection. Alternatively, the coupling element can be ultrasonically welded to the spine  100 . Alternatively or additionally, the side surface  71  of one or more seeds  24  can be bonded directly to the spine  100 , using an adhesive or ultrasonic welding. 
         [0076]    Alternatively, the brachytherapy seeds  24  can be implanted indirectly into the spine  100 , for instance via another spinal implant. In one embodiment, the spinal implant can include a screw  90  or nail  98  that carries one or more brachytherapy seeds  24  in the manner described above. The screw  90  and nail  98  can thus be driven into the spine  100  at locations as desired. The head  94  can be flush with the spine  100 , or protrude out form the spine  100  as desired. 
         [0077]    Referring now to  FIG. 6C , the method of treating the tumor  104  can include removing the tumor  104  from the spine  100 . In one embodiment, a corpectomy is performed whereby a portion or all of the vertebral body  50 C that carries the tumor  104  is removed to define an intervertebral space  110  disposed between the adjacent vertebrae  100 A and  100 B. Alternatively or additionally, a hemicorpectomy is performed whereby a portion of a vertebral body is removed. In the illustrated embodiment, the surrounding disc material  102  has also been removed. It is appreciated that though the tumor  104  has been removed, it is common for malignant cells to remain in the spine  100 , particularly if the tumor capsule is violated, which can allow malignant cells to escape and metastasize at various other locations in the spine  100 . Thus, the seeds  24  can be implanted directly or indirectly to the vertebral endplates  51  of the adjacent vertebrae  50 A and  50 B in addition to the above-described spinal locations. 
         [0078]    Referring to  FIG. 6D , another method for indirectly implanting brachytherapy seeds in the spine  100  includes implanting the brachytherapy implant  20 , or any alternative brachytherapy intervertebral implant, in the intervertebral space  110 . The implant  22  can be provided having seeds  24  installed thereon or therein, or alternatively the seeds  24  can be installed in or on the implant  20  after the implant has been affixed in the intervertebral space  110 . The seeds  24  can be disposed at any location on or in the implant  22  in orientations as described above suitable to direct radiation toward the likely locations that may contain one or more malignant cells. The expansion ring  36  can be manipulated as desired to bring the end plates  28  and  30  into engagement with the end plates of the vertebrae  50 A and  50 B. 
         [0079]    It will be appreciated by those skilled in the art that changes could be made to the embodiment described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiment disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the present description.