Patent Publication Number: US-9901460-B2

Title: Minimally invasive collapsible cage

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation patent application of U.S. patent application Ser. No. 13/254,965 filed Sep. 23, 2011, which was the National Phase of International Application PCT/US2010/027175 filed Mar. 12, 2010, which designated the U.S. That International Application was published in English under PCT Article 21(2) on Sep. 16, 2010 as International Publication Number WO 2010/105181A1. PCT/US2010/027175 claims the benefit of the U.S. Provisional Patent Application Ser. No. 61/160,051, filed Mar. 13, 2009. The disclosures of all of these applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     There is no admission that the background art disclosed in this section legally constitutes prior art. 
     The human spine includes thirty-three vertebrae. The vertebrae are vertically separated and cushioned from each other by fibro-cartilaginous structures commonly referred to as “discs.” The discs can become damaged or diseased thereby causing a deterioration of the discs. Deterioration of discs can lead to severe back problems. 
     One approach to dealing with damaged, diseased discs is to remove and replace the affected discs with artificial discs. Another approach to dealing with damaged diseased discs is to remove and replace the affected discs with fusion cages. Over time, the adjacent vertebrae fuse together over the fusion cages and provide support to the spinal column. 
     What is needed is a fusion cage that provides improved support to the adjacent vertebrae and which can be implanted through a single small incision. The invention provides an improved fusion cage. 
     SUMMARY OF THE INVENTION 
     In a first aspect, there is provided herein an articulating support cage that comprises a first support member having a first and second end and a second support member having a first and second end. A first end cap is pivotally connected to the first and second support members at the first ends. The first end cap supports a jackscrew for rotation. A second end cap is pivotally connected to the first and second support members at the second ends opposite the first ends. The second end cap has a threaded sleeve configured to engage a portion of the jackscrew. Rotation of the jackscrew into the threaded sleeve causes the first and second support members to extend outwardly from a collapsed condition to a deployed condition. 
     In another aspect, there is provided herein an articulating support cage for disc replacement within a spinal column that includes a first end cap having a jackscrew and a pair of hinge elements. The jackscrew is configured for rotational movement relative to the first end cap and is axially fixed within the first end cap. The jackscrew has a threaded section extending from the first end cap. A second end cap has a threaded sleeve and a pair of hinge elements. The threaded sleeve is configured to engage the threaded section of the jackscrew such that rotation of the jackscrew causes the first end cap to move toward the second end cap to a deployed condition. A pair of first leg segments has pivot ears at one end and are pivotally connected to the first end cap hinge element at the other end. A pair of second leg segments being pivotally connected to the first leg segment pivot ears and pivotally connected to the second end cap, the first leg segment pivot ears causing the first and second leg segments to be outwardly displaced relative to the first and second end cap hinge elements when the support cage is in a collapsed condition. 
     In another aspect, there is provided herein an articulating support cage where the first and second support members and the first and second end caps cooperate to define a profile having a parallel upper and lower surfaces. Alternatively, the profile may be configured as tapered upper and lower surfaces. The upper and lower surfaces may include an anchoring profile that is one of a plurality of teeth or a groove. 
     In another aspect, there is provided herein a method of implanting an articulating support cage including the steps of removing a disc from between adjacent vertebrae thereby creating a gap, providing an articulating support cage having first and second support members pivotally connected to first and second end caps. The first end cap supports a jackscrew for relative rotational movement and a fixed relative axial position. A threaded portion of the jackscrew engages a threaded sleeve extending from the second end cap. Rotation of the jackscrew causes the first and second end caps to move together and further causes the first and second support members to expand outwardly. The articulating support cage is moved to a collapsed position where the first and second end caps are positioned apart and the first and second support members are moved next to the threaded sleeve and jackscrew. A disc, or a portion of a disc, between two vertebrae is removed forming a gap. The collapsed support cage is inserted into the gap through a small incision. As the support cage is inserted, the jackscrew is rotated to begin expanding the support members to a deployed position. 
     Other systems, methods, features, and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawings may contain hidden features or elements shown in dotted lines and may include phantom views of various components or elements shown in dashed-dotted lines. 
         FIG. 1  is a plan elevational schematic view of an embodiment of an articulating fusible support cage, illustrated in a collapsed state. 
         FIG. 2A  is a plan elevational schematic view of an articulating fusible support cage, illustrated in a deployed state. 
         FIG. 2B  is a plan elevational schematic view of another embodiment of an articulating fusible support cage illustrated in a deployed state. 
         FIG. 3  is a side elevational schematic view of another embodiment of an articulating fusible support cage. 
         FIG. 4  is a side elevational schematic view of another embodiment of an articulating fusible support cage. 
         FIG. 5  is a plan elevational schematic view of another embodiment of an articulating fusible support cage, illustrated in a deployed state. 
         FIG. 6A  is an end view, in cross section, of a portion of the articulating fusible support cage of  FIG. 5 , shown partially in cross section. 
         FIG. 6B  is an end view, in cross section, of an other embodiment of a portion of an articulating fusible support cage, shown partially in cross section. 
         FIG. 6C  is an end view, in cross section, of an other embodiment of a portion of an articulating fusible support cage, shown partially in cross section. 
         FIG. 6D  is an end view, in cross section, of an other embodiment of a portion of an articulating fusible support cage, shown partially in cross section. 
         FIG. 7  is a plan elevational schematic view illustrating a method of inserting an articulating fusible support cage, first in an external position (in phantom) and then in an internal position. 
         FIG. 8  is a plan elevational schematic view of an embodiment of a method of deploying an inserted articulating fusible support cage, shown partially in cross section. 
         FIG. 9  is a side elevational schematic view of a portion of a human spinal column having a diseased disc, partially in cross section. 
         FIG. 10  is a side elevational schematic view of a portion of a human spinal column having a disc removed prior to insertion of an articulating fusible support cage, partially in cross section. 
         FIG. 11  is a side elevational schematic view of a portion of a human spinal column having an articulating fusible support cage inserted and deployed between two adjacent vertebrae, partially in cross section. 
         FIG. 12A  is a plan elevational schematic view of another embodiment of an articulating fusible support cage, shown in a collapsed state (in phantom) and in an expanded state. 
         FIG. 12B  is a plan elevational schematic view of another embodiment of an articulating fusible support cage, illustrated in a collapsed state. 
         FIG. 13  is an elevational schematic view of an embodiment of a portion of an articulating fusible support cage having an anchoring structure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Referring now to the drawings, there is illustrated in  FIG. 1  an embodiment of an articulating fusible support cage, shown generally at  10 , in a collapsed or unexpanded state, ready for deployment.  FIG. 2A  shows the support cage  10  expanded to a deployed state. The articulating fusible support cage  10  includes a plurality of articulating support members, shown as first and second support members  12  and  14 , and an actuator section, shown generally at  16 . The first and second support members  12  and  14  each include a first leg segment  18  that is pivotally connected to a second leg segment  20  by way of a hinge element  22 . The hinge element  22  may be any structure that permits one leg segment to pivot relative to the adjacent leg segment. As shown in  FIG. 3 , the hinge element  22  includes a pivot ear  24 , shown on one end of the first leg segment  18 , and a pivot tongue  26 , shown on a mating end of the second leg segment  20 . Referring again to  FIG. 1 , the pivot ear  24  is connected for rotation relative to the pivot tongue  26  by a hinge pin  28 . 
     Though shown as having two leg segments  18  and  20 , the first and second support members  12  and  14  may have more than two leg segments. Where more than two leg segments are employed, a resilient member (not shown) may be used to urge the leg segments away from the actuator section  16  during deployment. Alternatively, the hinge elements may include cooperating gear teeth (not shown) on adjacent pivot points that articulate the leg segments away from the actuator section  16 . 
     The actuator section  16  includes a first end cap  30  and a second end cap  44  that are connected by a jackscrew  36  and an internally threaded sleeve  42 . It is to be understood that, in certain embodiments, the second end cap  44  and the threaded sleeve  40  can be formed as an integral unit, as schematically illustrated herein. In other embodiments, the second end cap  44  and the threaded sleeve  42  can be distinct elements. 
     The first end cap  30  is pivotally connected to the first leg segments  18  of the first and second support members  12  and  14  by opposing hinge elements  21 . In the illustrated embodiment of  FIGS. 1 and 2A , the first end cap  30  includes a counterbored aperture  32  having a retaining lip  34 . The counterbored aperture  32  is configured to receive the jackscrew  36  which has a torque-transmitting head  36   a  and a threaded section  36   b . In the illustrated embodiment, the counterbored aperture  32  is sized to permit the jackscrew head  36   a  to be freely inserted and rotate therein. The retaining lip  34  retains the jackscrew head  36   a  in one direction within the aperture  32 . In certain embodiments, a retaining sleeve  38  having an access hole  40  may be press fit or otherwise secured within the aperture  32  to trap the jackscrew head  36   a . Thus, the jackscrew  36  is permitted to rotate relative to the first end cap  30  yet is restrained axially within the first end cap  30 . The access hole  40  is sized to permit a key (not shown), such as an allen wrench or a screw driver, to engage the jackscrew head  36   a  and rotate the jackscrew  36 . Alternatively, the jackscrew head  36   a  may be retained by a pin (not shown) that extends across a portion of the head  36   a . In another embodiment, the retaining lip  34  may be a flange that is roll-formed onto the jackscrew head  36   a.    
     The jackscrew threaded section  36   b  extends past the retaining lip  34  and engages the threaded sleeve  42  that extends from the second end cap  44 . The second end cap  44  is pivotally connected to the second leg segments  20  of the first and second support members  12  and  14  by opposing hinge elements  23 . The threaded sleeve  42  includes an internally threaded bore  46  configured to receive the jackscrew threaded section  36   b . The threaded sleeve  42  also may include a plurality of locking apertures  48  formed either on the surface or extending through the sleeve  42 . The locking apertures  48  of the threaded sleeve  42  may be infused with a filler material configured as a bone growth medium, such as bone chips, in order to cause the vertebrae to fuse to the cage  100 . Alternatively, other filler materials may be used in place of a bone growth medium. 
     Referring now to  FIG. 2A , the support cage  10  is shown in a deployed condition where the first and second support members  12  and  14  are extended outwardly from the actuator section  16 . As the jackscrew  36  is rotated, the first end cap  30  is drawn toward the threaded sleeve  42  by the head  36   a  pressing against the retaining lip  34 . In the illustrated embodiment shown in  FIG. 1 , when the support cage  10  is in a collapsed state, the pivot ears  24  of the first leg segment  18  are shaped to orient the first and second leg segments  18  and  20  at a slight outwardly extending angle, a, with respect to the actuator section  16 . The outwardly extending angle, α, orients the hinge elements  22  of the first and second leg segments  18  and  20  beyond a plane defined by the hinge elements  21  and  23  that connect the first and second end caps  30  and  44  to the first and second leg segments  18  and  20 . Thus, in operation as the jackscrew  36  is rotated, the leg segments  18  and  20  are forced away from the actuator section  16  and into the deployed condition. Thus, the opposing first and second support members  12  and  14  of the articulating fusible support cage  10  are configured to spread out across a disc space between adjacent vertebrae rather than being expanded against the vertebrae, as further explained herein. 
     As shown in  FIG. 1 , the articulating fusible support cage  10  has a collapsed length L 1  and a collapsed width W 1 . In one example, the collapsed length L 1  may be approximately 25 mm and the collapsed width W 1  may be approximately 10 mm. It should be understood that the length and width may be any suitable dimensions. As the first and second support members  12  and  14  are extended outwardly, as shown in  FIG. 2A , they may be moved out to a deployed length L 2  and a deployed width W 2 , or any distance between the collapsed and deployed dimensions. In one embodiment, the deployed length L 2  may be approximately 15 mm and the deployed width W 2  may be approximately 25 mm. 
     Referring now to  FIG. 2B , there is illustrated another embodiment of an articulating fusible support cage, shown generally at  100 . The support cage  100  includes a single sided support member  114  and an actuator section  116 . The support member  114  includes first and second leg segments  118  and  120 , respectively. As described above, the support member  114  may have more than the first and second leg segments  118  and  120  shown in  FIG. 2B . The first and second leg segments  118  and  120  are pivotally connected by a hinge element  122 . The first leg segment  118  is also pivotally connected to a first end cap  130  by opposing hinge element  121 . The second leg segment  120  is connected to a second end cap  144  by opposing hinge element  123 . The first end cap  130  includes a jackscrew  136  having a torque-transmitting head  136   a  and a jackscrew threaded section  136   b , and can be configured in a similar manner to the jackscrew  36 , described above. The second end cap  144  includes a threaded sleeve  142  that engages the jackscrew  136 . The threaded sleeve  142  can include locking apertures  148  that may be infused with a material configured as a bone growth medium such as bone chips, in order to cause the vertebrae to fuse to the cage  100 . As the jackscrew  136  is rotated, the first end cap  130  is drawn toward the second end cap  144  in a similar manner as described above. The first and second leg segments  118  and  120  pivot at the hinge elements  122  and extend outwardly. 
     Referring now to the embodiment shown in  FIG. 3 , the first and second leg segments  18  and  20  include locking apertures  50 , shown as being generally round in shape. The locking apertures  50  and the locking apertures  48  are provided as anchor points for subsequent bone growth to penetrate. When the articulating fusible support cage  10  is moved to the deployed condition, shown in  FIG. 2 , spaces that are formed between the first and second support members  12  and  14  and the actuator section  16  also provide locations for bone growth between adjacent vertebrae. Additionally, bone chips may be injected, infused or otherwise provided in the spaces to aid in bone fusion between the adjacent vertebrae. Alternatively, another medium, such as a polymer, epoxy or material simulating the mechanical properties of a spinal disc may be provided around the articulating fusible support cage  10  and through the locking apertures  48  and/or  50 . In certain embodiments, the locking apertures  50  may also provide passageways for anchoring screws (not shown) that anchor the cage  10  to the upper and lower vertebrae V1 and V2, as shown in  FIG. 11 . 
     Referring now to  FIGS. 3 and 4 , there are illustrated two embodiments of articulating fusible support cages  10  and  200  having different profile configurations. The articulating fusible support cage  10  includes upper and lower surfaces  52  and  54  that are generally parallel to each other. Thus, the articulating fusible support cage  10  has a generally constant thickness, T. In certain embodiments, at least the upper and lower surfaces  52  and  54  can have a plurality of teeth  56  disposed across the upper and lower surfaces  52  and  54  of the support cage  10 . The teeth  56  may be configured as any gripping surface that generally prevents or limits movement of the cage  10  relative to adjacent vertebra. 
     The articulating fusible support cage  200 , shown in  FIG. 4 , is substantially similar to the articulating fusible support cage  10 . The articulating fusible support cage  200  includes an actuator section  216 . The support cage  200  also includes a first leg segment  218  having pivot ears  224  that pivotally connect to a second leg segment  220 . The first leg segment  218  is also pivotally connected to a first end cap  230 . The second leg segment  220  includes a pivot tongue  226  that is pivotally connected to a second end cap  244 . The articulating fusible support cage  200  has a tapered profile from a first end having a thickness of T 1  to a second end having a thickness of T 2 , where T 1  is greater than T 2 . In the illustrated embodiment, the tapered profile extends over the length of the cage  200  from the first end cap  230  to the second end cap  244  and across an upper surface  252  and a lower surface  254 . It will be appreciated that the tapered profile may be oriented in other planes so that when the articulating fusible support cage  200  is in the deployed state, the tapered profile is similar to  FIG. 4 . For example, the profile may extend from the first leg segment  218  to the second leg segment  220  that is on the opposite side of the actuator section  216 . In the illustrated embodiments of the articulating fusible support cages  10  and  200 , the upper surfaces  52  and  252  and lower surfaces  54  and  254  are generally flat and smooth. 
     Referring now to  FIG. 5 , there is illustrated another embodiment of an articulating fusible support cage, shown generally at  300 . The articulating fusible support cage  300  includes first and second support members  312  and  314  that are pivotally connected to a first end cap  330  and a second end cap  344  by opposing hinge elements  321  and  323 , respectively. The first and second support members  312  and  314  each include at least two pivotally connected leg segments, illustrated as first and second leg segments  318  and  320  that are each connected by opposing hinge elements  322 . The first and second leg segments  318  and  320  include an anchoring profile, shown as a groove  356  in  FIGS. 5, 6A, and 6B , formed on a portion of at least an upper surface  352 . The groove  356  is illustrated as having a generally triangular cross section and a generally diamond plan view shape. However, the groove  356  may be any shape, either recessed into or extending from the upper surface  352 . As shown in  FIG. 6A , the groove  356  may be formed on both the upper surface  352  and a lower surface  354 , if desired. The groove  356 , when configured as an embedded groove, may include bone chips, adhesive, or other material to fix the support cage  300  to adjacent vertebrae. When configured as an extending diamond shaped anchoring profile, the groove  356  may be embedded into the adjacent vertebrae to prevent movement of the support cage  300  in order to promote bone growth and fusion of the cage to the vertebrae. 
     Referring now to  FIGS. 6C and 6D , there are illustrated two variations of another embodiment of a portion of an articulating fusible support cage  400 . An embodiment of a first leg segment  418 , shown in  FIG. 6C , includes an upper surface  452  having an anchoring profile comprising a plurality of extending projections  456 . The projections  456  may be teeth, formed in straight or staggered rows or a knurled surface that inhibits relative movement between the support cage  400  and adjacent vertebrae. The anchoring profile is also applicable to a second leg segment  420 , or any other surface of the cages described herein. The profiles of  FIGS. 6A-6D  provide an engagement interface to fix the position of the various embodiments of the support cage relative to adjacent vertebrae. The anchoring profiles become embedded in the surfaces of the adjacent vertebrae which prevents movement and promotes bone growth around the cage. 
     Referring now to  FIGS. 7-11 , there is illustrated one embodiment of a method of implanting the support cage  10 . Referring first to  FIG. 11 , the articulating fusible support cage  10  is shown as being inserted between adjacent vertebrae V1 and V2. As shown in  FIGS. 7 and 11 , the articulated fusible support cage  10  is inserted in a disc space S and over the surface of vertebra V1 in a collapsed condition as part of a minimally invasive surgical procedure to minimize incision size and speed patient recovery time. The support cage  10  may also be inserted between adjacent vertebrae from the posterior, lateral, or anterior side of the patient. 
     As shown in  FIGS. 9 and 10 , a diseased or damaged disc, D, or a portion of the disc, is removed from between the vertebrae. The configuration of a space, S, between adjacent vertebrae may suggest a choice of the constant thickness support cage  10  or the tapered profile support cage  200 . The support cage  10 , articulated to the collapsed condition, is inserted through an incision (not shown). During and/or after the hinge elements  22 , located between the first and second leg segments  18  and  20 , pass through the incision, the jackscrew  36  may be rotated to begin expanding the support cage  10 . The support cage  10  may be expanded completely or partially depending upon the area requiring support. As shown in  FIGS. 8 and 11 , with the disc completely removed, the support cage  10  is expanded outwardly to the fully deployed position. 
     The support cage  10  is configured to be expanded and contracted by rotation of the jackscrew  36  as explained previously. Additionally, the support cage  10  is prevented from expanding or contracting without rotation of the jackscrew  36 . This allows the final size of the support cage  10  to be fixed at any point between the fully collapsed and fully extended positions. Since the jackscrew  36  actively drives the first and second support members  12  and  14  outwardly, the movement of the support members  12  and  14  also tends to clear out surgical debris within the disc space S. Often, prior art support cages are inhibited from properly deploying because the surgical debris blocks a clear path of expansion. 
     Once the support cage  10  is deployed within the spinal column, the adjacent vertebrae V1 and V2 are brought into contact with the expanded first and second support members  12  and  14 . 
     It is to be understood that the first and second end caps  30 ,  44  and the threaded sleeve  42  also are load bearing structures and support the compressive, shear and tensile loads imparted by the spine. Thus, the upper and lower support surfaces  52  and  54  can extend across the entire support cage  10 . As shown in  FIG. 8 , the spaces defined by the expanded support cage  10  may be filled with bone chips  60  to aid in bone fusion between the adjacent vertebrae, using a suitable dispensing mechanism  61 . Bone chips  60  may be injected, infused or otherwise provided in the spaces of the expanded support cage  10 . Alternatively, another medium, such as a polymer, epoxy or material simulating the mechanical properties of a spinal disc may be provided around the articulating fusible support cage  10 . 
     Referring now to  FIG. 12A , there is illustrated another embodiment of an articulated fusion support cage, shown generally at  500 . The support cage  500  includes a plurality of arcuately-shaped, articulating support members, shown as first and second support members  512  and  514 , and an actuator section, shown generally at  516 . In the illustrated embodiment, the arcuately-shaped first and second support members  512  and  514  provide a generally circular circumference to the support cage  500  when fully expanded. 
     The first and second support members  512  and  514  each include an arcuate first leg segment  518  that is pivotally connected to an arcuate second leg segment  520  by way of a hinge element  522 . The hinge element  522  may be any structure that permits one leg segment to pivot relative to the adjacent component. In the illustrated embodiment, the hinge element  522  includes a pivot ear  524 , shown on one end of the first leg segment  518 , and a pivot tongue  526 , shown on a mating end of the second leg segment  520 , similar to the support cage  10  described above. The pivot ear  524  is connected for rotation relative to the pivot tongue  526  by a hinge pin  528 . 
     The actuator section  516  includes a first end cap  530  that is pivotally connected to each of the first leg segments  518  of the first and second support members  512  and  514  by opposing hinge elements  521 . The first end cap  530  supports a jackscrew  536 , similar to jackscrew  36  described above, having a head  536   a  and a threaded section  536   b . The jackscrew threaded section  536   b  engages a threaded sleeve  542  that extends from a second end cap  544  as part of the articulator section  516 . The second end cap  544  is pivotally connected to each of the second leg segments  520  of the first and second support members  512  and  514  by opposing hinge elements  523 . 
     When the arcuate first and second leg segments  518  and  520  are in the collapsed position, shown in phantom, the hinge elements  522  connecting the first leg segments  518  to the second leg segments  520  are offset outwardly from a plane of the hinge elements  522  of the first and second end caps  530  and  544 . The offset “A” permits the leg segments  518  and  520  to expand outwardly as the jackscrew  536  is rotated and the first and second end caps  530  and  544  are drawn together. 
     Referring now to  FIG. 12B , there is illustrated another embodiment of an articulating fusible support cage, shown generally at  600 . The support cage  600  is a single sided support cage, similar to the support cage  100 , shown in  FIG. 2B . The support cage  600  includes a single sided support member  614 . The support member  614  includes arcuately-shaped first and second leg segments  618  and  620 , respectively. As described above, the support member  614  may have more than the first and second leg segments  618  and  620  shown in  FIG. 12B . The first and second leg segments  618  and  620  are pivotally connected by a hinge element  622 . The first leg segment  618  is also pivotally connected to a first end cap  630  by hinge element  621 . The first end cap  630  includes a profile  650  that is generally arcuate in shape. The first end cap  630  having the profile  650  creates a larger surface area to support the vertebrae V1 and V2. Likewise, the second leg segment  620  is connected to a second end cap  644  by hinge element  623 . Similarly, the second end cap  644  includes a profile  652  that is generally arcuately shaped to create a larger support area for adjacent vertebrae. 
     The first end cap  630  includes a jackscrew  636 , configured in a similar manner to the jackscrew  136 , described above. The second end cap  644  includes a threaded sleeve  642  that engages the jackscrew  636 . The threaded sleeve  642  (and/or the first end cap  630 ) can include locking apertures  648  that may be infused with a material such as bone chips, in order to cause the vertebrae to fuse to the cage  600 . As the jackscrew  636  is rotated, the first end cap  630  is drawn toward the second end cap  644  in a similar manner as described above. The first and second leg segments  118  and  120  pivot about the hinge elements  621 ,  622 , and  623  and extend outwardly. The support cage  600  provides a generally rounded triangular shape when moved to the deployed position. 
     Referring now to  FIG. 13 , there is illustrated an embodiment of a first end cap  730  that includes a pivot ear  724  portion of a hinge element  722  and a counterbored aperture  732 . The counterbored aperture  732  holds a jackscrew  736 , configured similarly to jackscrew  36 . The jackscrew may be retained in the counterbored aperture  732  by a retaining sleeve  738  positioned against a jackscrew head  736   a . The end cap  730  includes a plurality of anchoring apertures  750 . In certain embodiments, the anchoring apertures  750  can be angled toward the adjacent vertebrae to accommodate anchoring screws (not shown). It should be understood that a second end cap (not shown) may be configured with similar anchoring apertures  750 , may also be provided as part of any of the above described cage embodiments. 
     While the invention has been described with reference to particular embodiments, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the essential scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed herein contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Furthermore, elements of any embodiment described herein may be applied to another of the disclosed embodiments and is considered to be within the scope of the invention. The publication and other material used herein to illuminate the invention or provide additional details respecting the practice of the invention, are incorporated by reference herein.