Abstract:
Multiple embodiments of the present invention provide methods and apparatuses for maintaining spacing between neighboring vertebrae, while minimizing the size of the surgical opening required. In one embodiment, an expandable spinal implant is made having movable parts that can arranged so as to have a small maximum cross-sectional width so that the cage can be inserted through a smaller surgical opening and then expanded to a full size assembly between the vertebrae.

Description:
CROSS-REFERENCED APPLICATIONS  
       [0001]     This application claims priority to co-pending, and commonly assigned U.S. provisional applications Ser. No. 60/637,312, entitled “MEDICAL IMPLANT, TOOLS, SYSTEM, METHOD, AND SURGICAL KIT,” filed Dec. 16, 2004; U.S. provisional application Ser. No. 60/660,422, entitled “MEDICAL IMPLANT SYSTEM AND METHOD OF USE,” filed Mar. 10, 2005, and to co-pending and commonly assigned U.S. provisional application Ser. No. 60/700,861, entitled “EXPANDABLE SPINAL INTERBODY CAGE,” filed Jul. 20, 2005, the disclosures of which are hereby incorporated 
     
    
     BACKGROUND  
       [0002]     1. Field of the Invention  
         [0003]     This disclosure relates to systems and methods for treating diseases of of human spines, and, more particularly, to interbody implant devices.  
         [0004]     2. Description  
         [0005]     The inter-vertebral spacing (between neighboring vertebrae) in a healthy spine is maintained by a compressible and somewhat elastic disc. The disc serves to allow the spine to move about the various axes of rotation and through the various arcs and movements required for normal mobility. The elasticity of the disc maintains spacing between the vertebrae, allowing room or clearance for compression of neighboring vertebrae, during flexion and lateral bending of the spine. In addition, the disc allows relative rotation about the vertical axis of neighboring vertebrae, allowing twisting of the shoulders relative to the hips and pelvis. Clearance between neighboring vertebrae maintained by a healthy disc is also important to allow nerves from the spinal chord to extend out of the spine, between neighboring vertebrae, without being squeezed or impinged by the vertebrae.  
         [0006]     In situations (based upon injury or otherwise) where a disc is not functioning properly, the inter-vertebral disc tends to compress, and in doing so pressure is exerted on nerves extending from the spinal cord by this reduced inter-vertebral spacing. Various other types of nerve problems may be experienced in the spine, such as exiting nerve root compression in neural foramen, passing nerve root compression. A few medical procedures have been devised to alleviate such nerve compression and the pain that results from nerve pressure. Many of these procedures revolve around attempts to prevent the vertebrae from moving too close to each other by surgically removing an improperly functioning disc and replacing it with a lumber interbody fusion (“LIF””) device. Although prior interbody devices, including LIF cage devices, may be effective at improving patient condition, the vertebrae of the spine, body organs, the spinal cord, other nerves, and other adjacent bodily structures make obtaining surgical access to the location between the vertebrae where the LIF cage is to be installed difficult.  
         [0007]     It would be desirable to reduce the size of the LIF cage to minimize the size for the required surgical opening for installation of the LIF cage, while maintaining high strength, durability and reliability of the LIF cage device.  
       SUMMARY  
       [0008]     Certain aspects of the present invention provide methods and apparatuses for maintaining spacing between neighboring vertebrae, while minimizing the size of the surgical opening required. In one aspect, an LIF cage is made having movable parts that can arranged so as to have a small maximum cross-sectional width so that the cage can be inserted through a smaller surgical opening and then expanded to a full size assembly between the vertebrae.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following Detailed Description taken in conjunction with the accompanying drawings, in which:  
         [0010]      FIG. 1A  is a perspective view of the first and second parts of one embodiment of an interconnecting multi-part LIF cage having a curved interconnecting side;  
         [0011]      FIG. 1B  is a plan view of the first and second parts of the interconnecting multi-part LIF cage  
         [0012]      FIG. 1C  is a side view of the back portion of the second part of the interconnecting multi-part LIF cage;  
         [0013]      FIG. 1D  is a perspective view of the second part of the interconnecting multi-part LIF cage;  
         [0014]      FIG. 1E  is a perspective view of the first part of the interconnecting multi-part LIF cage;  
         [0015]      FIG. 2A  is a perspective view of the first and second parts of an alternative embodiment of an interconnecting multi-part LIF cage having a linear interconnecting side;  
         [0016]      FIG. 2B  is a plan view of the first and second parts of the interconnecting multi-part LIF cage  
         [0017]      FIG. 2C  is a side view of the back portion of the second part of the interconnecting multi-part LIF cage;  
         [0018]      FIG. 2D  is a perspective view of the second part of the interconnecting multi-part LIF cage;  
         [0019]      FIGS. 2E  is a perspective view of the first part of the interconnecting multi-part LIF cage;  
         [0020]      FIG. 3  is a perspective view of the first and second parts, partially connected, of an interconnecting multi-part LIF cage having a linear interconnecting side;  
         [0021]      FIG. 4  is a perspective view of the first and second parts, partially connected, of an interconnecting multi-part LIF cage having a curved interconnecting side;  
         [0022]      FIG. 5  is a perspective view of one embodiment of an expandable cage, wherein the cage has multiple sliding parts;  
         [0023]      FIG. 6  is a perspective view of one sliding part of the expandable cage;  
         [0024]      FIG. 7  is a perspective view of a band which can restrain the expandable cage;  
         [0025]      FIG. 8A  is a perspective view of the expandable cage with a band placed around the circumference of the cage;  
         [0026]      FIG. 8B  is a plan view of the expandable cage;  
         [0027]      FIG. 9A  is a perspective view of an alternative embodiment of an expandable cage;  
         [0028]      FIG. 9B  is a plan view of the expandable cage;  
         [0029]      FIG. 9C  is a side view of the expandable cage;  
         [0030]      FIG. 10A  is a perspective view of an alternative embodiment of an expandable cage in an expanded state;  
         [0031]      FIG. 10B  is a plan view of the expandable cage in an expanded state;  
         [0032]      FIG. 10C  is a perspective view of the expandable cage in a contracted state;  
         [0033]      FIG. 10D  is a plan view of the expandable cage in a contracted state;  
         [0034]      FIG. 10E  is a side view of the expandable cage;  
         [0035]      FIG. 11A  is a perspective view of an alternative embodiment of an expandable cage in an expanded state;  
         [0036]      FIG. 11B  is a plan view of the expandable cage in an expanded state;  
         [0037]      FIG. 11C  is a perspective view of the expandable cage in a contracted state;  
         [0038]      FIG. 11D  is a plan view of the expandable cage in a contracted state;  
         [0039]      FIG. 11E  is a side view of the expandable cage;  
         [0040]      FIG. 12A  is a perspective view of one embodiment of an accordion-configuration expandable cage in its final configuration;  
         [0041]      FIG. 12B  is a plan view of the accordion-configuration expandable cage in its final configuration;  
         [0042]      FIG. 12C  is a side view of the accordion-configuration expandable cage in its final configuration;  
         [0043]      FIG. 12D  is a perspective view of the expandable cage, where the cage is partially folded towards its final configuration;  
         [0044]      FIG. 12E  is a plan view of the expandable cage, where multiple hinged parts are arranged longitudinally in a line;  
         [0045]      FIG. 13A  is a perspective view of an alternative embodiment of an accordion-configuration expandable cage in its final configuration;  
         [0046]      FIG. 13B  is a plan view of the accordion-configuration expandable cage in its final configuration;  
         [0047]      FIG. 13C  is a side view of the accordion-configuration expandable cage in its final configuration;  
         [0048]      FIG. 13D  is a perspective view of the expandable cage, where the cage is partially folded towards its final configuration;  
         [0049]      FIG. 13E  is a plan view of the expandable cage, where multiple hinged parts are arranged longitudinally in a line;  
         [0050]      FIG. 14A  is a perspective view of one embodiment of a spiral-configuration expandable cage in its final configuration;  
         [0051]      FIG. 14B  is a plan view of the spiral-configuration expandable cage in its final configuration; and  
         [0052]      FIG. 14C  is a perspective view of the expandable cage, where the cage is arranged longitudinally in a line. 
     
    
     DETAILED DESCRIPTION  
       [0053]     In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without such specific details.  
         [0054]      FIGS. 1A and 1B  depict a spinal implant  100 . In certain embodiments, the spinal implant  100  may be inserted between adjacent vertebra from a posterior approach. In some procedures, a Transforaminal lumbar interbody fusion (TLIF) surgery may be performed. In a TLIF approach, one entire facet joint may be removed. Removal of the facet joint, allows visualization into the disc space and access to the disc space. Because one entire facet is removed, typically such procedures are only performed on one side of the spine.  
         [0055]     In certain procedures, the surgeon may perform a posterior lumbar interbody fusion (PLIF). In such procedures, the spine is approached through an incision in the midline of the back and the left and right lower back muscles (erector spinae) are stripped off the lamina on both sides and at multiple levels.  
         [0056]     After the spine is approached, the lamina may be removed (laminectomy) which allows visualization of the nerve roots. The facet joints, which are directly over the nerve roots, may then be undercut (trimmed) to give the nerve roots more room. The nerve roots are then retracted to one side and the disc space is cleaned of the disc material. The spinal implant  100  may then be inserted into the disc space.  
         [0057]     As illustrated in  FIGS. 1A and 1B , there is a first part  10  and second part  20  of an interconnecting multi-part spinal implant  100 .  FIG. 1A  depicts an isometric view of the multi-part spinal implant  100 , and  FIG. 1B  depicts a top view of the multi-part spinal implant  100 . First part  10  has a back portion  12 , which can be, but need not be, convexly arcuate to better conform to the shape of the inter-vertebral space into which it is to be inserted. Second part  20  of the interconnecting multi-part spinal implant  100  has a back portion  22 , which can have, but need not have, a concave arcuate portion between two convex arcuate portions to better conform to the shape of the inter-vertebral space into which it is to be inserted. As shown in  FIG. 1B , the first part  10  and the second part  20  interconnect to form an arcuate connection.  
         [0058]     The upper end and lower end of first part  10 , and the upper end and lower end of second part  20 , can advantageously have a surface  30  having serrations  32  or another relief pattern disposed thereon, to facilitate retaining the first part  10  and second part  20  between the vertebrae (not shown) without unintended slippage. The first part  10  may have a male dove-tail retention  16  on an interconnecting side, and the second part  20  may have a female dove-tail retention slot  26 . The female dove-tail retention slot  26  may be sized sized to fit over the male dove-tail retention rail  16 , so that it is longitudinally slidably retained thereon.  
         [0059]     First part  10  and second part  20  may be generally hollow, having a cavity  15  in first part  10  and a cavity  25  in second part  20 , each of which cavities may be open at their upper and lower ends. If desired, cavities  15  and  25  can advantageously be filled with a material conducive to fusion in a manner adhering first part  10  and second part  20  to the adjacent vertebrae (not shown), such as bone slurry, bone morphogenetic protein (BMP) or the like. In certain embodiments, apertures  40  along the back portion  22  of the second part  20  may allow the healing material to flow into or out of the cavity  25 . Similar apertures (not shown) on the back portion  12  of the first part  10  may allow the healing material to flow into the cavity  15 . In certain embodiments, apertures  40  permit filler material injected into the spinal implant  100  to flow out of the cavities  15  and  25  and into contact with surrounding vertebrae and exterior surfaces of the cage  100 . Additional ports, such as port  42 , may also allow the healing material to flow into the cavity  15  after insertion.  
         [0060]      FIG. 1C  depicts a side view of the back portion  22  of the second part  20  of the multi-part spinal implant  100 . In certain embodiments, the serrations  32  may reside on the top and bottom sides of the multi-part spinal implant  100 . In some embodiments, the apertures  40  provide access into the cavity  25 .  
         [0061]      FIG. 1D  depicts an isometric view of the second part  20  of the multi-part spinal implant  100 .  FIG. 1E  depicts an isometric view of the first part  10  of the multi-part spinal implant  100 . As previously described, second part  20  has a female dove-tail retention slot  26 , that is sized to fit over male dove-tail retention rail  16  of the first part  10 , so that it is longitudinally retained thereon. In some embodiments, the retention rail  16  has at least one protrusion  48  on either end thereof and that mate with depressions  50  formed in either end of the retention slot  26 . The protrusions  48  fit into the depressions  50  when the first part  10  and the second part  20  are fully mated so that the two parts of the spinal implant  100  snap together and stay in the desired position. These bumps  48  are an example of a retention method. An alternative embodiment has straight mating surfaces and ratcheting teeth for retention. It should be noted that, although a flat-sided dove-tail shaped retention rail  16  is depicted, the retention rail  16  and the female retention slot  26  could also have curved sides provided that the rail  16  can still be longitudinally slidably retained in the slot  26 . Retention rail  16  and retention slot  26  may have any configuration of interlocking shapes that still permit longitudinal sliding. Note that there may be two or more such rails  16  and that the one or more rails and slot  26  may be segmented into two or more mating lengths shorter then the entire length of the parts. Second part  20  may have an aperture  44  and first part  10  may have an aperture  46  that interconnect the cavity  25  and the cavity  15 . When the spinal implant  100  is fully interconnected, apertures  44  and  46  match up to provide the interconnection between the two cavities  25  and  15 .  
         [0062]      FIGS. 2A-2E  depict another embodiment of a spinal implant or LIF cage  200 , having components substantially similar to those discussed in connection with and depicted in  FIGS. 1A-1E . Such substantially similar components are identified by the same reference numeral, accompanied by a prime (′) designation in  FIGS. 2A-2E .  FIGS. 2A and 2B  depict a first part  10 ′ and second part  20 ′ of an interconnecting multi-part LIF cage  200 .  FIG. 2A  depicts an isometric view of the multi-part LIF cage  200 , and  FIG. 2B  depicts a top view of the multi-part LIF cage  200 . In certain embodiments, the first part  10 ′ contains cavity  15 ′ and second part  20 ′ contains cavity  25 ′.  FIG. 2C  depicts a side view of the back portion  22 ′ of the second part  20 ′ of the multi-part LIF cage  200 .  FIG. 2D  depicts an isometric view of the second part  20 ′ of the multi-part LIF cage  200 . The second part  20 ′ comprises a female retention slot  26 ′.  FIG. 2E  depicts an isometric view of the first part  10 ′ of the multi-part LIF cage  200 . The first part  10 ′ comprises a male dove-tail retention rail  16 ′. As illustrated in  FIG. 2B , the first part  10 ′ and the second part  20 ′ interconnect to form a linear connection, in contrast to the arcuate connection illustrated in  FIG. 1 B .  
         [0063]      FIG. 3  depicts a first part  10 ′ and a second part  20 ′ interconnecting to form a multi-part LIF cage  200 .  FIG. 3  represents the LIF cage  200  of  FIGS. 2A-2E .  FIG. 4  depicts a first part  10  and a second part  20  interconnecting to form a multi-part spinal implant  100 .  FIG. 4  represents the spinal implant  100  of  FIGS. 1A-1E .  
         [0064]     With reference to  FIG. 4 , when it is desired to insert spinal implant  100  into a patient, first part  10  and second part  20  are partially interconnected by sliding retention rail  16  of first part  10  part-way into retention slot  26  of second part  20  at their respectively transversely smaller ends. As so connected, the combination of the first part  10  and second part  20  has a smaller maximum transverse thickness than would be the case with both parts fully interconnected. This facilitates surgical insertion of the spinal implant  100  because the smaller maximum transverse thickness requires a smaller surgical access incision.  
         [0065]     Once the partially interconnected first part  10  and second part  20  of spinal implant  100  are inserted between the desired vertebrae, the first part  10  and second part  20  must be fully interconnected to reach the fully assembled (snapped together, cojoined, etc.) final configuration, as shown in  FIG. 1A . To do so, second part  20  is pushed longitudinally forward while first part  1  is restrained from moving. This causes the slot  26  to longitudinally slide over rail  16  until the respective ends are generally flush, as depicted in  FIG. 1A . The position of the fully interconnected spinal implant  100  may then be manually adjusted to ensure that it is in the desired position between the two adjacent vertebrae.  
         [0066]     Once the spinal implant  100  is in the desired, final position, a filler material conducive to rapid healing in a manner adhering first part  10  and second part  20  to the adjacent vertebrae (not shown), such as bone slurry, bone morphogenetic protein (BMP) or the like, can be injected into the cavity  15  of first part  10  through port  42  ( FIG. 1A ). It should be noted that one or both of the first and second parts  10 ,  20  may be partially or completely filled;with the filler material prior to insertion and placement between the vertebra. Filler material may then be added to fill both parts and, if desired, to cause the filler material to spill out of apertures  40  ( FIG. 1A ) in the external side walls of the first and second parts  10 ,  20 , to cover all or part of the first and second parts  10 ,  20 , to further enhance stimulation of bone growth.  
         [0067]     There are many instruments that can be used to insert these LIF cages  100 ,  200  into the intervertebral space. Some of these instruments are described in a co-pending and commonly assigned U.S. patent application Ser. No. ______, entitled “INSTRUMENTS FOR INSERTING SPINAL DISC IMPLANTS,” filed ______, the disclosure of which is hereby incorporated herein by reference.  
         [0068]      FIG. 5  depicts a perspective view of an alternative embodiment of an expandable cage  300 . In this embodiment, the cage  300  has multiple sliding parts  302 A- 302 E. Each of sliding parts  302 A- 302 E is slidably interconnected to its adjacent part by an interconnected slot and rail (not shown). In certain embodiments, a ratchet locking means (not shown) may also be used to interconnect the sliding parts. In  FIG. 5 , the cage  300  is depicted as assembled to its full-size, final configuration, as it would be installed between the vertebrae. An aperture  320 , allows a filler material conducive to rapid healing, such as bone slurry, bone morphogenetic protein (BMP) or the like, to be injected into the cavity of the expandable cage  300 .  FIG. 6  depicts one sliding part  304  with a groove  306 .  FIG. 7  depicts a band  310  which may restrain the cage  300 . This band  310  is meant to hold the final shape of the embodiment  300 . The device would be inserted through the surgical port while collapsed and with the band  310  attached to the outside by some sort of mechanical or adhesive restraint. As the filler or expanding means is applied to attain expansion, the band  310  would act as a restraint to limit the expansion or help the device reach its final desired shape. A circle is shown as the final desired shape for simplicity, however the final or “set configuration” shape could be any closed shape, such as an ellipse. The groove  306  shown for the sliding part  304  may hold a band  310  or other restraining device. In certain embodiments, prior to insertion through a surgical incision, the cage  300  may be collapsed by applying force about the circumference, and then the cage  300  may be retained in the collapsed condition by means of a band  310  or other restraining device ( FIG. 7 ) placed around the circumference of the cage  300 .  FIG. 8A  depicts the band  310  placed around the circumference of the cage  300 . When the band or other retraining device is removed, the cage  300  will be allowed to expand to its final configuration, as shown in  FIG. 5 .  FIG. 8B  depicts a top view of the expandable cage  300 .  
         [0069]      FIG. 9A  depicts a perspective view of an alternative embodiment of the expandable cage  500 . In this embodiment, the cage  500  has multiple hinged parts  502 A- 502 D. In some embodiments, each of the hinged parts  502 A- 502 D is interconnected to its adjacent part  502  by a pin hinge. A pin hinge attachment is only one embodiment of the present invention. In other embodiments, molded-in hinge pins, double pin-ended links, snap-fit dome-in-socket, and the like can be used to interconnect the hinged parts. Accordingly, a pin  504  holds the hinged parts  502  together, so as to be pivotable with respect to each other. An aperture  506  allows a filler material, such as bone slurry, BMP or the like, to be injected into the cavity of the expandable cage  500 .  FIG. 9B  depicts a top view of the expandable cage  500 .  FIG. 9C  depicts a side view of the expandable cage  500 .  
         [0070]      FIG. 10A  depicts a perspective view of an alternative embodiment of the expandable cage  600 .  FIG. 10B  depicts a top view of the expandable cage  600 . FIGS.  10 A-B illustrate the expandable cage  600  in a set or expanded configuration.  FIG. 10C  depicts a perspective view of the expandable cage  600  in an insertion or a contracted state, and  FIG. 10D  depicts a top view of the expandable cage  600  in a contracted state. In the contracted state, the expandable cage  600  resembles an hourglass shape and has a greatly reduced cross-sectional width. In certain embodiments, by applying pressure to the cage  600 , the cage may be collapsed to the position depicted in FIGS.  10 C-D. In this embodiment, the cage  600  has multiple hinged parts  602 A-D. Each of the hinged parts  602  is interconnected to its adjacent part  602  by a pin hinge. A pin hinge attachment is only one embodiment of the present invention. In other embodiments, molded-in hinge pins, double pin-ended links, snap-fit dome-in-socket, and the like can be used to interconnect the hinged parts. Accordingly, a pin  604  holds the hinged parts  602  together, so as to be pivotable with respect to each other. An aperture  606  allows a filler material conducive to rapid healing, such as bone slurry, BMP or the like, to be injected into the :cavity of the expandable cage  600 .  FIG. 10E  depicts a side view of the expandable cage  600 .  
         [0071]      FIG. 11A  depicts a perspective view of an alternative embodiment of the expandable cage  700 .  FIG. 11B  depicts a top view of the expandable cage  700 . FIGS.  10 A-B illustrate the expandable cage  700  in an expanded state.  FIG. 11C  depicts a perspective view of the expandable cage  700  in a contracted state, and  FIG. 11D  depicts a top view of the expandable cage  700  in a contracted state. In the contracted state, the expandable cage  700  has a greatly reduce cross-sectional width. Thus by applying pressure to the cage  700 , the cage may be collapsed to the position depicted in FIGS.  11 C-D. In this embodiment, the cage  700  has multiple hinged parts  702 A- 702 F. In certain embodiments, each of the hinged parts  702 A- 702 F is interconnected to its adjacent part by a pin hinge. A pin hinge attachment is only one embodiment of the present invention. In other embodiments, molded-in hinge pins, double pin-ended links, snap-fit dome-in-socket, and the like can be used to interconnect the hinged parts. Accordingly, a pin  704  holds the hinged parts  702  together, so as to be pivotable with respect to each other.  FIG. 1I  E depicts a side view of the expandable cage  700 .  
         [0072]      FIG. 12A  depicts a perspective view of another embodiment of an accordion-configuration expandable cage  800 .  FIG. 12B  is a top view of the accordion-configuration expandable cage  800 .  FIG. 12C  is a side view of the accordion-configuration expandable cage  800 . In certain embodiments, the expandable cage  800  may have multiple hinged parts  802 ,  804 ,  806 ,  808 , and  810  which are shown in a foldable configuration. FIGS.  12 A-C illustrate the cage  800  in its set or expanded configuration, as it would be installed in the intertebral disc space. In certain embodiments, the hinged parts  802 ,  804 ,  806 ,  808 , and  810  may be interconnected by pin hinges. A pin hinge attachment is only one embodiment of the present invention. In other embodiments, molded-in hinge pins, double pin-ended links, snap-fit dome-in-socket, and the like can be used to interconnect the hinged parts. The cage  800  may advantageously have a surface  830  having serrations  832  or another relief pattern disposed thereon, to facilitate retaining the cage  800  between the vertebrae (not shown) without unintended slippage.  
         [0073]      FIG. 12D  depicts a perspective view of the expandable cage  800 , where the cage  800  is partially folded towards its full size or final configuration as it would be installed between the vertebrae.  FIG. 12E  depicts a plan view of the expandable cage  800 , where the multiple hinged parts  802 - 810  are arranged longitudinally in a line, which is one possible insertion configuration. Alternatively, the parts  802 - 810  may be arranged in a curve. Accordingly, the cage  800  is extended so as to have a small transverse width, for insertion through a surgical incision. As depicted in FIGS.  12 A-E, the hinged parts may each be hollow. As depicted in  FIGS. 12A and 12D , part  810  has a port  812  in a side thereof. Once the assembly is finally positioned, a material conducive to rapid healing in a manner adhering hinged parts  802 - 810  to the adjacent vertebrae (not shown), such as bone slurry, BMP or the like, may be injected through a lumen. This material may be injected prior to or after insertion. From there, cross-connect ports  816  between each of the parts  802 - 810  permit passage of the material from parts  810  to  808 , from  808  to  806 , from  806  to  804 , and from  804  to  802  until all the cavities of the cage  800  are filled.  
         [0074]      FIG. 13A  depicts a perspective view of another embodiment of an accordion-configuration expandable cage  900 .  FIG. 13B  is a top view of the accordion-configuration expandable cage  900 .  FIG. 13C  is a side view of the accordion-configuration expandable cage  900 . In certain embodiments, this expandable cage has multiple hinged parts  902 ,  904 ,  906 ,  908 , and  910  in a foldable configuration. FIGS.  13 A-C illustrate the cage  900  in its set or expanded final configuration, as it would be installed in the vertebrae. The hinged parts  902 ,  904 ,  906 ,  908 , and  910  are interconnected by multiple double pin-ended links  920 . Accordingly, one double pin-ended link  920  holds part  910  and  908  together. The cage  900  may advantageously have a surface  930  having serrations  932  or another relief pattern disposed thereon, to facilitate retaining the cage  900  between the vertebrae (not shown) without unintended slippage.  
         [0075]      FIG. 13D  depicts a perspective view of the expandable cage  900 , where the cage  900  is partially folded towards its full size or final configuration as it would be installed between the vertebrae.  FIG. 13E  depicts a plan view of the expandable cage  900 , where the multiple hinged parts  902 - 910  are arranged longitudinally in a line. Accordingly, the cage  900  is extended so as to have a small transverse width, for insertion through a surgical incision. The double pin-ended links  920  interconnect the hinged parts  902 - 910 . As depicted in FIGS.  13 A-E, the hinged parts may each be hollow. As depicted in  FIGS. 13A and 13D , part  910  has a port  912  in a side thereof. Once the assembly is finally positioned, a material conducive to rapid healing in a manner adhering hinged parts  902 - 910  to the adjacent vertebrae (not shown), such as bone slurry, BMP or the like, may be injected through a lumen. From there, cross-connect ports  916  between each of the parts  902 - 910  permit passage of the material from parts  910  to  908 , from  908  to  906 , from  906  to  904 , and from  904  to  902  until all the cavities of the cage  900  are filled.  
         [0076]      FIG. 14A  depicts a perspective view of an alternative embodiment of an expandable cage  1000 .  FIG. 14B  depicts a plan view of the expandable cage  1000 . FIGS.  14 A-B illustrate the cage  1000  in its fully expanded final configuration, as it would be installed in the vertebrae. In certain embodiments, the cage  1000  comprises at least one rectangular piece of material  1002  that may be flexible enough to bend into a set or spiral configuration upon an actuating event. For instance, the cage  1000  may be formed of using a memory metal, such as Nitinol .  FIG. 14C  depicts a perspective view of the expandable cage  1000 , where the cage is arranged longitudinally in a line. An additional half-circle shaped piece  1010  is connected to the rectangular piece  1002 . Accordingly, the cage  1000  is extended so as to have a small transverse width, for insertion through a surgical incision. As the cage enters the intervertebral space, the rectangular piece  1002  may bend and curl to form the spiral configuration in  FIG. 14A . As depicted in  FIGS. 14A and 14C , the rectangular piece has a port  1006 . Once the assembly is finally positioned, a material, such as bone slurry, BMP or the like, can be injected through a lumen. From there, cross-connect ports  1008  inside of the cage  1000  permit passage of the material from one cavity to the next cavity. Ultimately, all of the cavities of the cage  1000  may be filled.  
         [0077]     There are many instruments that can be used to insert these expandable cages  300 ,  500 ,  600 ,  700 ,  800 ,  900  and  1000  into the intervertebral space. Some of these instruments are described in a co-pending and commonly assigned U.S. patent application Ser. No. ______, entitled “INSTRUMENTS FOR INSERTING SPINAL DISC IMPLANTS,” filed ______, the disclosure of which is hereby incorporated herein by reference.  
         [0078]     It is important to note that any such advantages and benefits described in this application may not apply to all embodiments of the invention. When the word “means” is recited in a claim element, Applicant intends for the claim element to fall under 35 U.S.C. § 112, paragraph six. Often a label of one or more words precedes the word “means.” The word or words preceding the word “means” is a label intended to ease referencing of claim elements and is not intended to convey a structural limitation. Such means-plus-function claims are intended to cover not only the structures described herein for performing the function and their structural equivalents, but also equivalent structures. For example, although a nail and a screw have different structures, they are equivalent structures since they both perform the function of fastening. Claims that do not use the word means are not intended to fall under 35 U.S.C. § 112, paragraph 6.  
         [0079]     Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.