Abstract:
A method and apparatus for an osteotomy fixation or arthrodesis cage allows the adjustment of the relative position of two bone segments while supporting the joining of those bone segments into one structure through the implant and methods described herein. The implant&#39;s embodiments fixate to the adjacent bones while inter-positioning its body between the bone segments. This inter-positioning allows anatomical adjustments in the distance between and angle of the bone segments. The adjustment is further enhanced by the use of shape memory materials that when activated through the application of heat energy, transition from a second shape to a first shape while changing the distance between the bones or their relative angle. This method and apparatus can be used on any adjacent bone or bone segments including but not limited to the vertebrae of the spine or long bone such as the tibia or metatarsal.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to bone fixation devices for the stabilization, orientation and fusion of diseased joints (arthrodesis) or surgical cuts in bone (osteotomies). 
     2. Description of the Related Art 
     Repair of bone fractures, osteotomies, or the joining of two bone across a joint are long practiced medical techniques. Often these repairs can be facilitated by immobilization with a splint or cast but often require surgical exposure of the bone and fixation with biocompatible implants designed to reduce (bring together) and hold two or more bony structures. 
     Wire fixation wires, pins, screws, staples, plates and rods have a long history of use. In spite of these technologies healing sometimes does not occur and the anatomy of the healed bone is often abnormal. The prior art is replete with examples of devices that hold the bones together, but is more limited in references to those devices that present a goal of achieving anatomical adjustments. 
     In the prior art, U.S. Pat. No. 6,127,597 to Beyar describes systems for the percutaneous bone and spinal stabilization, fixation and repair through using devices that are placed in the medullary cavity of bone and expanded to engage and hold the bone segments. Described are self expanding implants, implants expandable by external power, and solid phase formation devices that expand. Though some of the embodiments utilize shape memory metals such as nitinol as the mechanism for expansion all suffer from a limited ability to provide fixation to the bone segments or anatomical correction. 
     U.S. Pat. No. 6,773,437 B2 describes a shape memory metal fixation staple and method for correcting deformities of the growing adolescent but does not correct the patient&#39;s anatomy through the use of the implant, but restricts the growth of a portion of the spine so that the deformity is corrected over years as the child grows. Once the correction is achieved, the implants are removed. This fixation implant that has an anatomical goal suffers from the delay in the correction and the removal of the implant. The implant alone does not achieve the anatomical correction, the growth of the skeleton does. 
     Implants that provide fixation and anatomical correction of the spine are described in U.S. Pat. No. 6,264,656 B1, U.S. Pat. No. 6,923,830 B2 and U.S. Pat. No. 7,003,394 B2 by Michelson; U.S. Pat. No. 6,743,255 B2 by Ferree and U.S. Pat. No. 6,656,178 B1 by Veldhuizen, and there are several that expand U.S. Pat. No. 6,488,710 by Besselink, U.S. Pat. No. 6,835,206 B2 by Jackson, and U.S. Pat. No. 7,018,415 B1 by McKay, but are all limited in use by the static nature of their anatomical correction, fixation elements that are separate components or fixation elements that are limited in their fixation ability, such as grooves, slots, ridges or external threads. Though these devices have fixation features and an anatomical form factor they have a history of failure due to the poor fixation ability of external threads, slots and rough surfaces and are limited by their form so as to fit the anatomy versus effect the anatomy. 
     The subject invention overcomes the history or poor fixation with these types of devices and allows the surgeon to effect the anatomy and relative position of the bone segments by actively changing the implant shape in the spinal disk space or space between bone created with an osteotomy or resection of a joint. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, bone fixation devices for the stabilization, orientation and fusion of diseased joints (arthrodesis) or surgical cuts in bone (osteotomies) are placed into a bony site to stabilize two adjacent bone segments. These segments could have normal anatomical features such as vertebra of the spine or separated through surgical cuts that subsequently require rejoining. 
     It is therefore an object of the present invention to join bone segments while allowing the surgeon to control the distance between the segments and the relative orientation of those segments while providing a method of fixation of those segments to one another. 
     It is a further object of the present invention to allow the surgeon, through the setting of the shape changing temperature of the material used to make the implant and control of the heat applied to the implant, to adjust the orientation, separation and fixation forces applied to the bone segments by the implant. 
     Still other objects, features, and advantages of the present invention will become evident to those of ordinary skill in the art in light of the following. Also, it should be understood that the scope of this invention is intended to be broad, and any combination of any subset of the features, elements, or steps described herein is part of the intended scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  provides a perspective view of an inter-vertebral cage according to a first embodiment. 
         FIG. 1B  provides a front view of the inter-vertebral cage in a first shape according to the first embodiment. 
         FIG. 1C  provides a front view of the inter-vertebral cage in the first shape according to the first embodiment. 
         FIG. 2A  provides a perspective view of the inter-vertebral cage in a second shape according to the first embodiment. 
         FIG. 2B  provides a front view of the inter-vertebral cage in the second shape according to the first embodiment. 
         FIG. 3  provides a flowchart illustrating the method steps for utilizing the inter-vertebral cage according to the first embodiment. 
         FIG. 4A  provides a partial section view of the inter-vertebral cage in the second shape according to the first embodiment. 
         FIG. 4B  provides a partial section view of the inter-vertebral cage in the first shape in an installed position according to the first embodiment. 
         FIG. 5  provides a flowchart illustrating the method steps for utilizing the inter-vertebral cage according to an extension of the first embodiment. 
         FIG. 6A  provides a perspective view of an inter-vertebral cage according to an extension of the first embodiment. 
         FIG. 6B  provides a front view of the inter-vertebral cage in a first shape according to the extension of the first embodiment. 
         FIG. 6C  provides a front view of the inter-vertebral cage in the first shape according to an extension of the first embodiment. 
         FIG. 7A  provides a perspective view of the inter-vertebral cage in a second shape according to an extension of the first embodiment. 
         FIG. 7B  provides a front view of the inter-vertebral cage in the second shape according to an extension of the first embodiment. 
         FIG. 8A  provides a perspective view of an inter-vertebral cage in a first shape according to a second embodiment. 
         FIG. 8B  provides a front view of the inter-vertebral cage in the first shape according to the second embodiment. 
         FIG. 8C  provides a front view of the inter-vertebral cage in the first shape according to the second embodiment. 
         FIG. 9A  provides a perspective view of the inter-vertebral cage in a second shape according to the second embodiment. 
         FIG. 9B  provides a front view of the inter-vertebral cage in the second shape according to the second embodiment. 
         FIG. 10  provides a flowchart illustrating the method steps for utilizing the inter-vertebral cage according to the second embodiment. 
         FIG. 11A  provides a partial section view of the inter-vertebral cage in a second shape according to the second embodiment. 
         FIG. 11B  provides a partial section view of the inter-vertebral cage in a first shape in an installed position according to the second embodiment. 
         FIG. 12A  provides a perspective view of an inter-vertebral cage in a first shape according to an extension of the second embodiment. 
         FIG. 12B  provides a front view of the inter-vertebral cage in the first shape according to the extension of the second embodiment. 
         FIG. 12C  provides a front view of the inter-vertebral cage in the first shape according to the extension of the second embodiment. 
         FIG. 13A  provides perspective view of the inter-vertebral cage in a second shape according to the extension of the second embodiment. 
         FIG. 13B  provides a front view of the inter-vertebral cage in the second shape according to the extension of the second embodiment. 
         FIG. 14  provides a method flowchart illustrating the method steps for utilizing the inter-vertebral cage according to the extension of the second embodiment. 
         FIG. 15A  provides a partial section view of the inter-vertebral cage in a second shape before contraction according to the second embodiment. 
         FIG. 15B  provides a partial section view of the inter-vertebral cage in a first shape after contraction according to the second embodiment. 
         FIG. 16A  provides perspective view of the inter-vertebral cage according to a third embodiment. 
         FIG. 16B  provides a front view of the inter-vertebral cage in a first shape according to the third embodiment. 
         FIG. 17A  provides a front view of the inter-vertebral cage in it&#39;s second shape in a representation of an improperly curved spine according to the third embodiment. 
         FIG. 17B  provides a front view of the inter-vertebral cage in it&#39;s first shape where it assumes an expanded position to provide proper curved spine alignment according to the third embodiment. 
         FIG. 18  provides a method flowchart illustrating the method steps for utilizing the inter-vetebral cage to angularly adjust vertebrae according to the third embodiment. 
         FIG. 19A  provides a front view of an inter-vertebral cage in a second shape including a separate closeout according to an extension of the third embodiment. 
         FIG. 19B  provides a front view of an inter-vertebral cage in a first shape in an installed position before installation of the separate closeout in a second shape according to the extension of the third embodiment. 
         FIG. 19C  provides a front view of the inter-vertebral cage in a first shape with the installed separate closeout in a first shape according to the extension of the third embodiment. 
         FIG. 20  provides a flowchart illustrating the method steps for utilizing the inter-vertebral cage according to the extension of the third embodiment. 
         FIG. 21A  provides a section view of a cage in a second shape utilized in a tibia end portion adjustment operation according to a fourth embodiment. 
         FIG. 21B  provides a section view of a cage in a first shape utilized in a tibia end portion adjustment operation according to the fourth embodiment. 
         FIG. 22  provides a flowchart illustrating the method steps for utilizing the cage according to the fourth embodiment. 
         FIG. 23A  provides a front view of a cage having a spacing member and a closeout disposed on an inner faces of the engagement plates according to a fifth embodiment. 
         FIG. 23B  provides a perspective view of the cage having a spacing member and a closeout disposed on an inner faces of the engagement plates according to the fifth embodiment. 
         FIG. 23C  provides a front view of a spacing member having “Z” shaped expansion members according to the fifth embodiment. 
         FIG. 23D  provides a front view of a spacing member having interlaced expansion members according to the fifth embodiment. 
         FIG. 23E  provides a front view of a spacing member having “C” shaped expansion members according to the fifth embodiment. 
         FIG. 23F  provides a front view of a spacing member having “O” shaped expansion members according to the fifth embodiment. 
         FIG. 23G  provides a front view of a spacing member having interlaced expansion members according to the fifth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. It is further to be understood that the figures are not necessarily to scale, and some features may be exaggerated to show details of particular components or steps. 
     As illustrated in  FIGS. 1A-2B , an inter-vertebral cage  100  may be constructed from virtually any alloy exhibiting a shape-memory effect. Examples of shape-memory effect materials include, but are not limited to nitinol, AuCd, FePt 3 , beta Brass, and InTl. Shape memory effect materials allow an object to be: formed in an original shape; deformed while cooled to a martensitic state; then heated to a point where the deformed object phase changes from the martensitic state to an austenitic state, thereby returning the deformed object to its original shape; and when it cools it retains this original shape or first shape. Accordingly, the inter-vertebral cage  100  is formed in an original or first shape  127  ( FIGS. 1A-1C ), and annealed to set its original shape. The inter-vertebral cage  100 , while cold and in its martensitic phase, is then deformed to a second shape  128  ( FIGS. 2A-2B ). Next, the inter-vertebral cage  100  is heated until it phase changes to an austenitic phase, thereby returning from the deformed or second shape  128  to the original or first shape  127 . Finally, the inter-vertebral cage  100  cools whereby the inter-vertebral cage  100  retains the original first shape  127 . 
     While this embodiment has been shown with the inter-vertebral cage  100  moving from the second shape  128  to the first shape  127 , it should be apparent that the inter-vertebral cage  100  is usable at virtually any point along the transition between the second shape  128  and the first shape  127 . Accordingly, an end-use shape may designate any shape between the second shape  128  and up to and including the first shape  127 . The amount of heat energy applied to the deformed shape determines the amount of transition from the second shape  128  to the first shape  127 . 
     The inter-vertebral cage  100  is utilized as a structural component for fixating two vertebrae together in cases where a disc is removed from between the two vertebrae. As shown in  FIG. 1A , the inter-vertebral cage  100  includes a body  104  having a first engagement plate  102 , a second engagement plate  103 , and a spacing member  101  disposed between the first and second engagement plates  102  and  103 . The spacing member  101  includes a planar section  109  disposed between a bend  137  and a bend  138 . The first engagement plate  102  includes a first end  118  in communication with a first end  125  of the spacing member  101 , and a second end  119  in communication with a first stop  115 . The second engagement plate  103  includes a first end  121  that is in communication with a second end  126  of the spacing member  101 , and a second end  122  that is in communication with a second stop  116 . The first and second stops  115  and  116  are substantially planar in shape with curvature as appropriate to match the bone anatomy, and extends as a continuous or interrupted section across the entire length of the second ends  119  and  122  of the first and second engagement plates  102  and  103 . The inter-vertebral cage  100  further includes a first leg  106  extending from a central point of the first stop  115 , and a second leg  107  extending from a central point of the second stop  116 . While this embodiment has been shown with planar stops  115  an  116 , one of ordinary skill in the art will recognize that the size and shape of the stops  115  and  116  may be altered to adapt to anatomy or varying attachment conditions, and that virtually any amount of protrusion from the engagement plates may be considered a stop. 
     For the purpose of clarity and to provide reference points, a horizontal axis  190  and a vertical axis  191  have been provided in  FIG. 1B . One of ordinary skill in the art will recognize that references to horizontal and vertical directions are complementary to the cited axes  190  and  191 . It should further be understood that a vertical plane is defined as a plane passing through the vertical axis  191  and the horizontal axis  190 , and a horizontal plane passes through the horizontal axis  190  and is perpendicular to the vertical plane. Additionally, the term “elevation” is utilized in reference to vertical displacement, wherein a lower elevation is recognized below the horizontal axis  190  and a higher elevation is recognized above the horizontal axis  190 . As such, an object may move from a given elevation to a higher or lower elevation. 
     The inter-vertebral cage  100  further includes a bend  135  disposed between the first leg  106  and the first stop  115 , and a bend  136  disposed between the first stop  115  and the first engagement plate  102 . The inter-vertebral cage  100  still further includes a bend  139  disposed between the second engagement plate  103  and the second stop  116 , and a bend  140  disposed between the second stop  116  and the second leg  107 . One of ordinary skill in the art will recognize that the sizes of the bends  135 - 136  and  139 - 140 , and the ranges of the bends  135 - 136  and  139 - 140  may be adjusted to increase or decrease the span of the inter-vertebral cage  100 . 
     The first engagement plate  102  is substantially planar, and includes a first aperture  110 . The second engagement plate  103  is substantially planar, and includes a second aperture  111 . The first and second apertures  110  and  111  can be round or rectangular in shape, one or multiple, and consuming slightly less than the area of an engagement plate  102  or  103 , such that the apertures  110  and  111  are substantially centrally located within the first and second engagement plates  102  and  103 . In this example, the first and second engagement plates  102  and  103  are disposed symmetrically about the spacing member  101 . While this embodiment has been shown with a spacing member  101  in contact with symmetrical engagement plates  102 - 103 , one of ordinary skill in the art will recognize that the shape, length, and width of the spacing member  101  and the engagement plates  102 - 103  may be changed to provide increased height, load capability, an increased aperture size, different location on the engagement plates  102 - 103 , or a different geometry. Illustratively, the spacing member  101  may be located differently with respect to the engagement plates  102 - 103 , and does not have to span the entire length of the plates  102 - 103 . Further, the spacing member  101  may be broken up into multiple spacing members  101 . 
     The inter-vertebral cage  100  further includes engagement areas  143  and  144 , as shown in  FIG. 1B . Engagement area  143  includes a first engagement surface  145 , a second engagement surface  146 , and a third engagement surface  147 . The first engagement surface  145  is disposed on an outer surface of the first engagement plate  102 , the second engagement surface  146  is disposed on a side of the first stop  115  nearest the spacing member  101 , and the third engagement surface  147  is disposed on a face of the first leg  106  that is nearest the first engagement surface  145 , such that an object between the first engagement surface  145  and the third engagement surface  147  is compressed when moving from the second shape to the first shape, and contacts the second engagement surface  146 . Similarly, the second engagement area  144  includes a first engagement surface  148 , a second engagement surface  149 , and a third engagement surface  150 . The first engagement surface  148  is disposed on an outer surface of the second engagement plate  103 , the second engagement surface  149  is disposed on a face of the second stop  116  that lies nearest the spacing member  101 , and the third engagement surface  150  is disposed on an inner face of the second leg  107 , such that the third engagement surface  150  is disposed opposite from the first engagement surface  148 , and material between the first and third engagement surfaces  148  and  150  is compressed while in contact or close proximity with the second engagement surface  149 . While the first and second engagement areas  143 - 144  have been shown with three engagement surfaces, one of ordinary skill in the art will recognize that the number and locations of the engagement surfaces may vary, depending on the specific configuration, number of legs, and in vivo conditions. 
     The inter-vertebral cage  100  further includes a closeout  105  that extends from an inner surface of the first engagement plate  102 . In this embodiment, the closeout  105  spans the entire length of the first engagement plate  102 , and extends toward the second engagement plate  103 , such that a cavity  108  is created between the spacing member  101 , the first engagement plate  102 , the second engagement plate  103 , and the closeout  105 . While the closeout  105  has been shown as protruding from the first engagement plate  102 , one of ordinary skill in the art will recognize that the closeout may extend from other surfaces, and that the closeout  105  may be broken into multiple segments. 
     The inter-vertebral cage  100  may further include at least one barb  113  disposed on the first engagement surface  145  and the first engagement surface  148 . The barbs  113  are oriented such that they restrict the movement of the inter-vertebral cage  100  out of an installed position. One of ordinary skill in the art will recognize that additional barbs  113  may be added to the engagement surface or leg, and utilized to provide increased resistance, and that the sizes of the barbs  113  may be adjusted as necessary to ensure adequate resistance. 
     In the first shape  127 , as shown in  FIGS. 1A-1C , the first engagement plate  102  and the spacing member  101  are disposed at an angle  162 , and the second engagement plate  103  is disposed at an angle  163  relative to the spacing member  101 . In this example, the first engagement plate  102  and the second engagement plate  103  are disposed substantially perpendicular to the spacing member  101  and in proximity to each other, such that the first engagement plate  102  and the second engagement plate  103  are substantially symmetrical about the spacing member  101 , and a cavity  108  is created between the first engagement plate  102  and the second engagement plate  103 . While the first and second engagement plates  102  and  103  have been shown as being substantially perpendicular to the spacing member  101 , one of ordinary skill in the art will recognize that the angles  162  and  163  may be adjusted to adapt to location specific features, or varying angles of correction. 
     The first stop  115  is disposed at an angle  161  relative to the first engagement plate  102 . In this example of the first shape  127 , the first stop  115  is disposed substantially perpendicular relative to the first engagement plate  102 , and extends away from the second engagement plate  103 . Similarly, the second stop  116  is disposed at an angle  164  relative to the second engagement plate  103 . In this first shape  127 , the second stop  116  is disposed substantially perpendicular to the second engagement plate  103 , and extends away from the first engagement plate  102 . The first leg  106  is disposed at an angle  160  relative to the first stop  115 , and extends downward towards the spacing member  101 . In this first shape  127 , the angle  160  is approximately sixty degrees. However, one of ordinary skill in the art will recognize that the specific angles of this embodiment may be adjusted to overcome irregular implant site conditions. Similarly, the second leg  107  is disposed at an angle  165  relative to the second stop  116 , and also extends towards the spacing member  101 . In this first shape  127 , the angle  165  is substantially identical to the angle  160 , such that the legs  106  and  107  are symmetrical, and apply an evenly distributed load. Additionally, the closeout  105  is substantially planar and is disposed at an angle  166  relative to the first engagement plate  102 . In this first shape  127 , the angle  166  is substantially ninety degrees, such that the closeout  105  contacts the second engagement plate  103 , thereby transferring loads from the first engagement plate  102  to the second engagement plate  103 , and from the second engagement plate  103  to the first engagement plate  102 . While this embodiment has been shown with a substantially planar closeout  105  disposed at an angle of approximately ninety degrees, one of ordinary skill in the art will recognize that the closeout  105  may be of virtually any shape that provides a closing out function. It should further be understood that the closeout may be disposed at virtually any angle that maintains a stand off from the attaching engagement plate. 
     In the second shape  128 , the inter-vertebral cage  100  is deformed as shown in  FIGS. 2A-2B , such that the bends  137  and  138  of the first shape  127  are extended to obtuse angles  172  and  173 . Accordingly, in the second shape  128 , the first engagement plate  102  is disposed at an angle of one hundred and ten degrees relative to the spacing member  101 , and the second engagement plate  103  is likewise disposed at an angle of one hundred and ten degrees relative to the spacing member  101 . The bends  136  and  139  are similarly contracted from their positions in the first shape  127  to angles  171  and  174 , thereby slightly rotating the first and second stops  115  and  116  towards the spacing member  101 . Similarly, the bends  135  and  140  are extended to angles  170  and  175 , such that the first and second legs  106  and  107  are disposed at an angle of approximately one hundred and ten degrees relative to their respective stops  115  or  116 . Additionally, the closeout  105  is deformed towards the spacing member  101 , thereby contracting angle  166  to an angle  176 . In this second shape  128 , the closeout  105  is disposed at an angle of approximately seventy-five degrees relative to the first engagement plate  102 . In this position, the first leg  106  and the second leg  107  are disposed substantially parallel to each other, such that the legs  106  and  107  may be inserted into bones simultaneously. While the engagement plates  102 - 103  and legs  106 - 107  have been shown at particular angles relative to the spacing member  101 , one of ordinary skill in the art will recognize that other angles are possible, and should be viewed as part of this invention. It should further be recognized that the use of the parallel legs  106  and  107  is conducive to the impaction of the legs  106  and  107  into vertebra or the insertion of the legs  106  and  107  into pre-drilled holes; however, other angles may be utilized to address alternative situations, including the insertion of one leg at a time. 
     Upon the application of energy, the inter-vertebral cage  100  in the deformed or second shape  128  (deformed martensitic phase), commences to change from the martensitic state to the austenitic state. Upon completion of the austenitic phase change, the inter-vertebral cage  100  has returned to the original or first shape  127 . Upon cooling, the inter-vertebral cage  100  retains the original or first shape  127 . One of ordinary skill in the art will recognize that upon the transformation of a shape memory alloy to the original shape  127 , a force is created, and accordingly, the inter-vertebral cage  100  may be utilized in applications where retaining and residual forces are required. 
     In this first embodiment, the phase change from the deformed or second shape  128  to the original or first shape  127  creates forces as shown in  FIG. 1C . The bend  135  moves from the angle  170  (obtuse angle associated with second shape  128 ) to a more acute angle  160  (acute angle associated with the first shape  127 ), thereby rotating the first leg  106  toward the first engagement plate  102 . In a similar fashion, the bend  140  moves from the angle  175  (obtuse angle associated with second shape  128 ) to a more acute angle  165  (acute angle associated with the first shape  127 ), thereby rotating the second leg  107  towards the second engagement plate  103 . The bend  136  moves from the angle  171  (obtuse angle associated with second shape  128 ) to a smaller angle  161  (associated with the first shape  127 ). Similarly, the bend  139  moves from the angle  174  (obtuse angle associated with second shape  128 ) to a smaller angle  164  (associated with the first shape  127 ). Additionally, the bend  137  moves from angle  172  (obtuse angle associated with second shape  128 ) to angle  162  (smaller angle associated with first shape  127 ). Similarly, the bend  138  moves from the angle  173  (obtuse angle associated with second shape  128 ) to angle  163  (smaller angle associated with first shape  127 ). Further, the closeout  105  moves from angle  176  (acute angle associated with second shape  128 ) to the angle  166  (larger angle associated with first shape  127 ). 
     In this first embodiment, compressive forces are created between the first engagement surface  145  and the third engagement surface  147 . Additionally, compressive forces may be created between the second engagement surface  146  and the third engagement surface  147  as the first leg  106  closes down on material disposed between the first leg  106  and the first engagement plate  102 . Compressive forces are also created between the third engagement surface  150  and the first engagement surface  148 , and between the third engagement surface  150  and the second engagement surface  149  as the second leg  107  moves towards the second engagement plate  103 . Compressive forces are further created between the first engagement plate  102  and the second engagement plate  103  as the bends  137 - 138  contract to angles  162  and  163 , respectively. When the first and second legs  106  and  107  are secured, a thrust force component is created as the inter-vertebral cage  100  moves from the first shape  127  to the second shape  128 . The thrust force, shown in  FIG. 1C , lies perpendicular to the plane of the spacing member  101  and away from a third engagement area  151 . The thrust force is created when the legs  106  and  107  are pinned, and the first and second engagement plates  102  and  103  move towards each other during the shape change. 
       FIG. 3  provides a flowchart illustrating the method steps associated with utilizing the inter-vertebral cage  100  to fuse two vertebrae together. The process commences with step  10 , wherein a surgeon fixates a first vertebra  180  and a second vertebra  181  at a desired working position. The surgeon continues with step  12 , wherein a first location is identified in the first vertebra  180 , and a second location is identified in the second vertebra  181  at a spacing complementary to a spacing between the legs  106  and  107  of the inter-vertebral cage  100 . The process continues with step  14 , wherein the surgeon inserts the legs  106 - 107  into the first and second locations, such that the first and second engagement plates  102  and  103  are disposed between the first and second vertebrae  180  and  181 . In step  16 , the surgeon applies energy to the first and second legs  106  and  107  of the inter-vertebral cage  100 , thereby securing the inter-vertebral cage  100  to the first and second vertebrae  180  and  181 . The process continues with step  18 , wherein the surgeon applies energy to the body  104  of the inter-vertebral cage  100  to move the first and second vertebrae  180  and  181  into a desired corrective position. Once the first and second vertebrae  180  and  181  are in the desired corrective position, the surgeon inserts bone graft material into the cavity  108 , such that the bone graft material unites with the first and second vertebrae  180  and  181  through the first and second apertures  110  and  111 . Upon bone fusion, the graft material and the first and second vertebrae  180  and  181  become a single unit. 
       FIG. 4A  provides a side view of the inter-vertebral cage  100  in the second shape  128 , wherein the first leg  106  and the second leg  107  are substantially parallel to each other, and the closeout  105  is angled slightly downward. Upon insertion of the first leg  106  into the first location on the first vertebra  180 , and the insertion of the second leg  107  into the second location on the second vertebra  181 , the body  104  moves between the vertebrae  180  and  181 , until the second engagement surface  146  and the second engagement surface  149  contact the respective vertebra  180  or  181 . The barbs  113  engage the vertebrae  180  and  181 , thereby securing the inter-vertebral cage  100  to the vertebrae  180  and  181 . Upon full insertion, the spacing member  101  and the engagement plates  102  and  103  are disposed between the vertebrae  180  and  181 . In this position, the closeout  105  does not contact the second engagement plate  103 . Upon the application of energy to the legs  106  and  107 , the legs  106  and  107  move from the second shape  128  to the first shape  127 , thereby drawing the legs  106  and  107  toward the inter-vertebral cage  100 , and further securing the inter-vertebral cage  100  to the vertebrae  180  and  181 , as shown in  FIG. 4B . Upon the application of energy to the body  104 , the closeout  105  moves from the second shape  128  to the first shape  127 , thereby extending towards the second engagement plate  103 , and the bends  137  and  138  contract to the first shape  127 , thereby drawing the second engagement plate  103  towards the first engagement plate  102 , until the second engagement plate  103  contacts the newly extended closeout  105 . At this point, the cavity  108  is substantially closed out, as shown in  FIG. 4B . While this embodiment has been shown with bone graft material being inserted after the application of energy to the body  104  of the inter-vertebral cage  100 , one of ordinary skill in the art will recognize that bone graft material may be inserted into the cavity  108  at alternate times, or not at all. 
       FIG. 5  provides a flowchart illustrating the method steps of the process disclosed in  FIG. 3  in an alternate order. In this extension of this first embodiment, bone graft material may be inserted into the cavity  108  before the application of energy to the body  104 . The process commences with step  22 , wherein a surgeon fixates a first vertebra  180  and a second vertebra  181  at a desired working position. The surgeon continues with step  24 , wherein a first location is identified in the first vertebra  180 , and a second location is identified in the second vertebra  181  at a spacing complementary to a spacing between the legs  106  and  107  of the inter-vertebral cage  100 . The process continues with step  26 , wherein the surgeon inserts the inter-vertebral cage  100  into the first and second locations, such that the body  104  is disposed between the first and second vertebrae  180  and  181 . The surgeon then inserts bone graft material into the cavity  108  to promote fusion of the vertebrae  181  and  180 , step  28 . In step  30 , the surgeon applies energy to the first and second legs  106  and  107  of the inter-vertebral cage  100 , thereby securing the inter-vertebral cage  100  to the first and second vertebrae  180  and  181 . The process continues with step  32 , wherein the surgeon applies energy to the body  104  of the inter-vertebral cage  100  to move the first and second vertebrae  180  and  181  into a desired corrective position. While this extension of the first embodiment has been shown with the insertion of bone graft material before the application of energy to the inter-vertebral cage  100 , one of ordinary skill in the art will recognize that a surgeon will add bone graft material after moving the first and second vertebrae  180  and  181  into the desired corrective position if an improper amount of bone graft material remains in the cavity  108 . Accordingly, this extension of the first embodiment may include an additional step of adding additional bone graft material after step  32 . The bone graft material unites with the first and second vertebrae  180  and  181  through the first and second apertures  110  and  111 . Upon bone fusion, the graft material and the first and second vertebrae  180  and  181  become a single unit. One of ordinary skill in the art will further recognize that either process may be employed to achieve similar results. While the method of implanting inter-vertebral cage  100  has been presented, one of ordinary skill in the art will further recognize that the sequence of steps may be changed to meet a specific clinical need. 
     In an extension of the first embodiment, an inter-vertebral cage  192  is substantially identical to the inter-vertebral cage  100 , however the inter-vertebral cage  192  includes additional legs. Accordingly, like parts have been referenced with like numerals. As shown in  FIGS. 6A-6C , the inter-vertebral cage  192  includes a spacing member  101  attached to first and second engagement plates  102  and  103 , and first and second stops  115  and  116  disposed at the ends of the first and second engagement plates  102  and  103 . The inter-vertebral cage  192  further includes a first leg  106 , a second leg  107 , a third leg  193 , and a fourth leg  194 . The first leg  106  and the third leg  193  extend from the first stop  115  in a similar fashion to the inter-vertebral cage  100 , however, the first and third legs  106  and  193  are disposed at extreme ends of the first stop  115 . Similarly, the second and fourth legs  107  and  194  are disposed at extreme ends of the second stop  116 . One of ordinary skill in the art will recognize that other embodiments that include fewer or a greater number of legs are within the scope of this invention. Additionally, it should further be understood that while these legs are shown as being symmetrical, and balanced, it is possible to provide an odd number of legs, as dictated by body conditions. 
     The inter-vertebral cage  192  is also formed from a shape memory alloy, and accordingly, also moves from a second shape  128  to a first shape  127 , or any point therebetween, in similar fashion to the inter-vertebral cage  100 .  FIGS. 6A and 6B  provide illustrations of the inter-vertebral cage  192  in the first shape  127 , and  FIGS. 7A-7B  provide an illustration of the inter-vertebral cage  192  in a deformed or second shape  128 . Upon the transformation of the inter-vertebral cage  192  from the second shape  128  to the first shape  127 , forces are created as shown in  FIG. 6C . Operation of the inter-vertebral cage  192  is substantially identical to the inter-vertebral cage  100 , however in the case of the inter-vertebral cage  192 , four legs are disposed within a first and second vertebrae, and energy must also be applied to the additional legs  193  and  194 . The surgeon must further identify a third location in the first vertebra  180 , and a fourth location in the second vertebra  181 , at a spacing complementary to the four legs  106 ,  107 ,  193 , and  194  of the inter-vertebral cage  192 . All other aspects of the inter-vertebral cage  192  are obvious to one of ordinary skill in the art when compared to the inter-vertebral cage  100 , and therefore, will not be further described. 
     In a second embodiment, an inter-vertebral cage  200  is similar in function to the inter-vertebral cage  192 , however the inter-vertebral cage  200  includes a vertebrae distraction function. The inter-vertebral cage  200  is similarly constructed from a shape memory alloy, and therefore, may be returned to any point up to an original shape with the application of energy. As shown in  FIGS. 8A-8B  and  9 A- 9 B, the inter-vertebral cage  200  includes a body  204  having a spacing member  201 , a first engagement plate  202 , and a second engagement plate  203 . The spacing member  201  includes an extension section  212 , a bend  237 , and a bend  238 . The extension section  212 , in a first shape  227 , includes a width  211 , and, in a second shape  228 , a width  213 . 
     The first engagement plate  202  includes a first end  217  in communication with a first end  231  of the spacing member  201 , and a second end  218  in communication with a first stop  215 . The second engagement plate  203  includes a first end  223  that is in communication with a second end  232  of the spacing member  201 , and a second end  224  that is in communication with a second stop  216 . The first and second stops  215  and  216  are substantially planar in shape, and extend the entire length of the second ends  218  and  224  of the first and second engagement plates  202  and  203 . The first engagement plate  202  includes a first aperture  221  substantially identical to that of the first embodiment, and the second engagement plate  203  includes a second aperture  222  substantially identical to that of the first embodiment. 
     This second embodiment includes a plurality of legs extending from the stops  215  and  216 . Illustratively, in this particular example, a first leg  206 , a second leg  207 , a third leg  208 , and a fourth leg  209  are utilized for securing the inter-vertebral cage  200  to bones. In this second embodiment, the first leg  206  and the third leg  208  are disposed on extreme ends of the first stop  215 , and the second and fourth legs  207  and  209  are disposed on extreme ends of the second stop  216 , in similar fashion to the inter-vertebral cage  192 . While this second embodiment has been shown with the inter-vertebral cage  200  having four legs, one of ordinary skill in the art will recognize that fewer or more legs may be utilized as necessary to adapt to in vivo conditions. 
     The inter-vertebral cage  200  includes a bend  235 , a bend  236 , a bend  239 , and a bend  240 , as shown in the first embodiment. The bends  235  through  240  move through a range of angles bordered by an original or first shape  227 , and a deformed or second shape  228 , in similar fashion to the first embodiment. 
     The inter-vertebral cage  200  further includes a closeout  205  attached to the first engagement plate  202 . In this embodiment, the closeout  205  is extended downward slightly in the second shape  228 , and extends towards the second engagement plate  203  upon the application of energy. Upon full extension of the closeout  205 , and the contraction of the bends  237 - 238 , the closeout  205  is in contact with the second engagement plate  203 , thereby providing load bearing support between the first engagement plate  202  and the second engagement plate  203 . 
     The extension section  212  provides the capability to increase the width  213  associated with the second shape  228  to the width  211  associated with the first shape  227 . In this second embodiment, the extension section  212  is a curvature formed into the shape memory material. The curvature flattens out upon the application of energy to the body  204 . As such, the bend  237  and the bend  238  move away from each other. The extension section  212  may be flattened out to any point along the transformation from the deformed position to the original position, as previously disclosed. While this embodiment has been shown with a single extension section  212 , one of ordinary skill in the art will recognize that multiple extension sections may be utilized to create increased displacements. Additionally, the amount of displacement for a given extension section may be altered by varying the radius, and or thickness of the extension section, as well as its form. 
     In a second embodiment of the spacing member  201 , the spacing member  201  includes a third engagement surface  210  with “S” or “Z” shaped extension members that run from bend  237  to  238 . This member is deformed so that it is a straight member in its first shape and “S” or “Z” shaped in its second shape. When placed into the bone and heated the extension member changes back to a straight member, and causes the extension section  212  to increase in length from  213  to  211 . 
     The feature of lengthening the spacing member  201  and adjusting the closeout  205  allows the implant to be used to change the relative angles and positions of the bones. Through partial heat activation of the extension section  212  the bone angle can be set. 
       FIG. 10  provides a method flowchart illustrating the steps associated with utilizing the inter-vertebral cage  200  to move a first and a second vertebra  280  and  281  to a corrective position. The method shown in  FIG. 10  is similar to the method of  FIG. 3 . However, the method of  FIG. 10  provides the ability to separate and lift the first vertebra  280  from the second vertebra  281 . As shown in step  50  of the method flowchart, a surgeon fixates a first vertebra  280  and a second vertebra  281  at a desired working position. The process continues with step  52 , wherein the surgeon must identify securing locations in the first and second vertebrae  280 - 281 , at a spacing complementary to leg spacings  206 - 209  of the inter-vertebral cage  200 . Step  54  provides for inserting the legs  206 - 209  of the inter-vertebral cage  200  into the securing locations, such that the engagement plates  202  and  203  and the spacing member  201  of the inter-vertebral cage  200  are disposed between the vertebrae  280  and  281 . Upon insertion, the surgeon moves to step  56 , wherein energy is applied to the legs  206 - 209  of the inter-vertebral cage  200 , thereby securing the inter-vertebral cage  200  to the first and second vertebrae  280  and  281 . The process continues with step  58 , wherein energy is applied to the body  204  of the inter-vertebral cage  200 , thereby moving the first and second vertebrae  280  and  281  into a desired corrective position, locking the closeout  205 , and further distracting the first vertebra  280  and the second vertebra  281  by moving the extension feature  212  from the width  213  to width  211 . The surgeon may then insert bone graft material into the cavity  219 , thereby promoting the fusion of the first vertebra  280  and the second vertebra  281 , step  60 . 
     As shown in  FIG. 11A , the legs  206 - 209  of a inter-vertebral cage  200 , in a deformed position, are inserted into the first vertebra  280  and the second vertebra  281 , such that the engagement surfaces  145  through  150 , as described in the first embodiment, contact the first and second vertebra  280  and  281 . Upon full insertion, energy is applied to the legs  206 - 209 , such that the legs  206 - 209  move toward the engagement plates  202 - 203 , thereby securing the inter-vertebral cage  200  to the each respective vertebra  280  or  281 . Upon the application of energy to the body  204 , the closeout  205  extends toward the second engagement plate  203 , and the bends  237  and  238  contract, thereby moving the engagement plates  202  and  203  closer together. When the second engagement plate  203  contacts the closeout  205 , the vertebrae  280  and  281  are aligned in the desired corrective position, and the closeout  205  provides support in the vertical direction. Upon further application of energy, the extendable feature  212  of the spacing member  201  flattens out to provide separation between the first and second vertebra  280  and  281  and set the curvature of the spinal vertebral bodies, as shown in  FIG. 11B . 
     Once the first and second vertebrae  280  and  281  are in the desired corrective position, the surgeon inserts bone graft material into the cavity  219 , such that the bone graft material unites with the first and second vertebrae  280  and  281  through the first and second apertures  221 - 222 . Upon bone fusion, the graft material and the first and second vertebrae  280  and  281  become a single unit. 
     In an extension of the second embodiment, an inter-vertebral cage  250  is similar in design to the inter-vertebral cage  200 , however the inter-vertebral cage  250  includes a spacing member  251  providing a contraction function instead of an extension function, as shown in  FIGS. 12A-12C . Accordingly, like parts have been annotated with like numerals. The inter-vertebral cage  250  is similarly constructed from a shape memory alloy, and therefore, may be returned to any point up to an original shape with the application of energy. The inter-vertebral cage  250  includes a body  204  having a spacing member  251 , a first engagement plate  202 , and a second engagement plate  203 . The spacing member  251  includes a contraction section  252 , a bend  237 , and a bend  238 . The contraction section  252 , in a first shape  227 , includes a width  253 , an, in a second shape  228 , as shown in  FIGS. 13A-13B , a width  254 . All other aspects and components of the inter-vertebral cage  250  are identical to those presented in the second embodiment, and therefore, will not be further described. 
     The contraction section  252  provides the capability to decrease the width  254  associated with the second shape  227  to the width  253  associated with the first shape  227 . In this extension of the second embodiment, the contraction section  252  is a curvature formed in the shape memory material. The curved portion constricts upon the application of energy to the body  204 . As such the bends  237  and  238  move toward each other. The contraction section  252  may be constricted to any point along the transformation from the deformed position to the original position, as previously disclosed. While this embodiment has been shown with a single contraction section, one of ordinary skill in the art will recognize that multiple contraction sections may be utilized to create increased contractions. One of ordinary skill in the art will further recognize that the inclusion of both a contraction section  252  and an extension section  212  of the second embodiment in a spacing member is within the scope of this invention. 
       FIG. 14  provides a method flowchart illustrating the steps associated with utilizing the inter-vertebral cage  250  to move a first and a second vertebra  280  and  281  to a corrective position. The method shown in  FIG. 14  is similar to the method of  FIG. 10 . However, the method of  FIG. 14  provides the ability to contract the first vertebra  280  and the second vertebra  281 . As shown in step  62  of the method flowchart, a surgeon fixates a first vertebra  280  and a second vertebra  281  at a desired working position. The process continues with step  64 , wherein the surgeon must identify securing locations in the first and second vertebrae  280 - 281 , at a spacing complementary to leg spacings  206 - 209  of the inter-vertebral cage  250 . Step  66  provides for inserting the legs  206 - 209  of the inter-vertebral cage  250  into the securing locations, such that the engagement plates  202  and  203  and the spacing member  251  of the inter-vertebral cage  250  are disposed between the vertebrae  280  and  281 . Upon insertion, the surgeon moves to step  68 , wherein energy is applied to the legs  206 - 209  of the inter-vertebral cage  250 , thereby securing the inter-vertebral cage  250  to the first and second vertebrae  280  and  281 . The process continues with step  70 , wherein energy is applied to the body  204  of the inter-vertebral cage  250 , thereby moving the first and second vertebrae  280  and  281  into a desired corrective position, and further contracting the first vertebra  280  and the second vertebra  281  by constricting the contraction section  252  from the width  254  to width  253 . The surgeon may then insert bone graft material into the cavity  219 , thereby promoting the fusion of the first vertebra  280  and the second vertebra  281 , step  72 . While the method of implanting inter-vertebral cage  250  has been presented, one of ordinary skill in the art will recognize that the sequence of steps may be changed to meet a specific clinical need. 
     Upon the application of energy to the body  204  and legs  206 - 209  of the inter-vertebral cage  250 , forces are generated as shown in  FIG. 12C . As the legs  206 - 209  move closer to the first and second engagement plates  202 - 203 , compressive forces are created between the legs  206 - 209  and the engagement plates  202 - 203 . Compressive forces are created between the first and second engagement plates  202 - 203  when the engagement plates move together. Additionally, compressive forces are created between the first and second engagement plates  202  and  203  when the contraction section  252  constricts. 
     As shown in  FIG. 15A , the legs  206 - 209  of a inter-vertebral cage  250 , in a deformed position, are inserted into the first vertebra  280  and the second vertebra  281 , such that the engagement surfaces  145  through  150 , as described in the first embodiment, contact the first and second vertebra  280  and  281 . Upon full insertion, energy is applied to the legs  206 - 209 , such that the legs  206 - 209  move toward the engagement plates  202 - 203 , thereby securing the inter-vertebral cage  250  to the each respective vertebra  280  or  281 , as shown in  FIG. 15B . Upon the application of energy to the body  204 , the closeout  205  extends toward the second engagement plate  203 , and the bends  237  and  238  contract, thereby moving the engagement plates  202  and  203  closer together. When the second engagement plate  203  contacts the closeout  205 , the vertebrae  280  and  281  are aligned in the desired corrective position, and the closeout  205  provides support in the vertical direction. Upon further application of energy, the contraction section  252  of the spacing member  251  constricts to bring the first and second vertebra  280  and  281  closer together, as shown in  FIG. 15B . 
     Once the first and second vertebrae  280  and  281  are in the desired corrective position, the surgeon inserts bone graft material into the cavity  219 , such that the bone graft material unites with the first and second vertebrae  280  and  281  through the first and second apertures  221 - 222 . Upon bone fusion, the graft material and the first and second vertebrae  280  and  281  become a single unit. 
     In a third embodiment, an inter-vertebral cage  300 , as shown in  FIGS. 16A-16B , is similarly constructed from shape memory material, and, in similar fashion to the first and second embodiments, may move from a second shape  328  to a first shape  327 . It should be apparent that the inter-vertebral cage  300  is usable at virtually any point along the transition between the second shape  328  and the first shape  327 , as shown in  FIGS. 17A-17B . Accordingly, an end-use shape may designate any shape between the second shape  328  and up to and including the first shape  327 . The amount of heat energy applied to the deformed shape determines the amount of transition from the second shape  328  to the first shape  327 . 
     As shown in  FIGS. 16A-16B , the inter-vertebral cage  300  includes a spacing member  301  disposed between a first engagement plate  302  and a second engagement plate  303 . The spacing member  301  includes a planar section  312  disposed between a bend  337  and a bend  338 . The inter-vertebral cage  300  further includes a closeout  305  extending from the first engagement plate  302 , and legs  306  through  309  disposed on the engagement plates  302  and  303  in similar fashion to the inter-vertebral cage  192 . The engagement plates  302  and  303  further include a first end  318  and a second end  319 , wherein stops  320  and  321  are disposed on the second ends  319  of the engagement plates  302  and  303 . The engagement plates  302  and  303  further include apertures  310  and  311  to aid in bone grafting operations. The inter-vertebral cage  300  further includes bends  335 - 336  and  339 - 340 , and first through third engagement surfaces  345 - 350 , in similar fashion to the previous embodiments. 
     In the first shape  327 , the second ends of the engagement plates  302  and  303  are disposed at a maximum angle relative to each other, thereby creating a width  315  between the second ends  319  of the engagement plates  302  and  303 , as shown in  FIG. 17B . In this specific example, the engagement plates  302  is disposed at an angle  362  relative to the planar section  312  of the spacing member  301 , and engagement plate  303  is disposed at an angle  363  relative to the planar section  312 . In this specific example, each engagement plate  302 - 303  is disposed at an angle of approximately one hundred and ten degrees relative to the planar section  312  of the inter-vertebral cage  300 . While one hundred and ten degrees has been shown, one of ordinary skill in the art will recognize that virtually any angle may be utilized. In similar fashion to the previously disclosed embodiments, the legs  306  through  309  contract towards their respective engagement plates  302  or  303 . In this first shape  327 , the legs  306 - 309  are disposed at angle  360  and  365  relative to the stops  320  and  321 , and the stops  320  and  321  are disposed at angle  361  and  364  relative to the engagement plates  302  and  303 . In this specific example of the first shape  327 , the legs  306  through  309  are disposed at an angle of approximately eighty degrees relative to the planar section  312  of the spacing member  301 . One of ordinary skill in the art will recognize that this invention is not limited the legs being disposed at approximately eighty degrees relative to the planar section  312 . 
     Additionally, the closeout  305  extends toward the second engagement plate  303  until it contacts the second engagement plate  303 . In this example of the first shape  327 , the closeout  305  is disposed at an angle  366 . Specifically, the closeout  305  is disposed substantially parallel to the planar section  312  of the spacing member  301 . While the closeout has been shown as being substantially parallel to the planar section  312  of the spacing member  301 , one of ordinary skill in the art will recognize that other angles are possible, and should be construed as part of this invention. 
     In the second shape  328 , the inter-vertebral cage  300  is deformed as shown in  FIG. 17A , such that bends  337  and  338  of the first shape  327  are contracted to angles  372  and  373 , respectively. In this specific example of the second shape  328 , the engagement plates  302  and  303  are disposed at an angle of ninety degrees relative to the planar section  312  of the spacing member  301 . However, one of ordinary skill in the art will recognize that any angle from the second shape  328  up to an including the first shape  327  may be utilized as an end use shape. The bends  335 - 336  and  339 - 340  are similarly extended from their positions associated with the first shape  327 . In this second shape, the legs  306 - 309  are disposed at an angle  370  and  375  relative to the stops  320  and  321 . The stops  320  and  321  are disposed at angle  371  and  374 , such that the legs  306 - 309  are disposed substantially perpendicular to the planar section  312  of the spacing member  301 , and substantially parallel to each other. In this specific example, the legs are disposed at an angle of substantially ninety degrees relative to the stops  320  and  321 , and the stops  320  and  321  are disposed at an angle of substantially ninety degrees relative to the engagement plates  302  and  303 . While substantially perpendicular angles have been shown to describe the relationships between the components of the inter-vertebral cage  300 , one ordinary skill in the art will recognize that other angles are possible, and should be viewed as part of this invention. One of ordinary skill in the art will further recognize that the use of parallel legs  306 - 309  is conducive to the impaction of the legs  306 - 309  into vertebrae or the insertion of the legs into pre-drilled holes; however, other angles may be utilized to address alternative situations, including the insertion of one leg at a time. 
     Upon the application of energy, the inter-vertebral cage  300  in a deformed or second shape  328  commences to change from the martensitic state to the austenitic state. Upon completion of the austenitic phase change, the inter-vertebral cage  300  has returned to the original or first shape  327 . Upon cooling, the inter-vertebral cage  300  retains the original or first shape  327 . One of ordinary skill in the art will recognize that upon the transformation of a shape memory alloy to the original shape  327 , a force is created, and accordingly, the inter-vertebral cage  300  may be utilized in applications where retaining and residual forces are required. 
     In this third embodiment, the phase change from the deformed or second shape  328  to the original or first shape  327  creates forces as shown in  FIG. 17B . The bend  335  moves from the angle  370  (angle associated with second shape  328 ) to a more acute angle  360  (acute angle associated with the first shape  327 ), thereby rotating the first leg  306  and the third leg  308  toward the first engagement plate  302 . In a similar fashion, the bend  340  moves from the angle  375  (angle associated with second shape  328 ) to a more acute angle  365  (acute angle associated with the first shape  327 ), thereby rotating the second leg  307  and the fourth leg  309  towards the second engagement plate  303 . The bend  336  moves from the angle  371  (angle associated with second shape  328 ) to a smaller angle  361  (associated with the first shape  327 ). Similarly, the bend  339  moves from the angle  374  (angle associated with second shape  328 ) to a smaller angle  364  (associated with the first shape  327 ). Additionally, the bend  337  moves from angle  372  (substantially perpendicular angle associated with second shape  328 ) to angle  362  (obtuse angle associated with first shape  327 ). Similarly, the bend  338  moves from the angle  373  (substantially perpendicular angle associated with second shape  328 ) to angle  363  (obtuse angle associated with first shape  327 ). Further, the closeout  305  moves from angle  376  (acute angle associated with second shape  328 ) to the angle  366  (larger angle associated with first shape  327 ). 
     In this third embodiment, compressive forces are created between the first engagement surface  345  and the third engagement surface  347 . Additionally, compressive forces may be created between the second engagement surface  346  and the third engagement surface  347  as the first leg  306  closes down on material disposed between the first leg  306  and the first engagement plate  302 . Compressive forces are also created between the third engagement surface  350  and the first engagement surface  348 , and between the second engagement surface  349  and the third engagement surface  350  as the second leg  307  moves towards the second engagement plate  303 . Expansive forces are further created by the first engagement plate  302  and the second engagement plate  303  as the bends  337 - 338  expand to angles  362  and  363 , respectively. When the first through fourth legs  306 - 309  are secured, a thrust component is created as the inter-vertebral cage  300  moves from the first shape  327  to the second shape  328 . The thrust force, shown in  FIG. 17B , lies perpendicular to the plane of the spacing member  101  and towards the closeout  305 . The thrust force is created when the legs  306 - 309  are pinned, and the first and second engagement plates  302  and  303  move away from each other during the shape change. 
       FIG. 18  provides a flowchart illustrating the method steps associated with utilizing the inter-vertebral cage  300  to angularly adjust and fuse two vertebrae together. The process commences with step  80 , wherein a surgeon fixates a first vertebra  380  and a second vertebra  381  at a desired working position. The surgeon continues with step  82 , wherein a first securing location is identified in the first vertebra  380 , and a second securing location is identified in the second vertebra  381  at a spacing complementary to a spacing between the legs  306 - 309  of the inter-vertebral cage  300 . The process continues with step  84 , wherein the surgeon inserts the legs  306 - 309  into the securing locations, such that the first and second engagement plates  302  and  303  are disposed between the first and second vertebrae  380  and  381 . In step  86 , the surgeon applies energy to the legs  306 - 309  of the inter-vertebral cage  300 , thereby securing the inter-vertebral cage  300  to the first and second vertebrae  380  and  381 . The process continues with step  88 , wherein the surgeon applies energy to the body  304  of the inter-vertebral cage  300  to angularly adjust the first vertebra  380  relative to the second vertebra  381 , and into a desired corrective position. Once the first and second vertebrae  380  and  381  are in the desired corrective position, the surgeon moves to step  90 , wherein bone graft material is inserted into the cavity  314 , such that the bone graft material unites with the first and second vertebrae  380  and  381  through the first and second apertures  310  and  311 . Upon bone fusion, the graft material and the first and second vertebrae  380  and  381  become a single unit. 
       FIG. 17   a  provides a side view of the inter-vertebral cage  300  in the second shape  328 , wherein the legs  306 - 309  are substantially parallel to each other, and the closeout  305  is angled slightly downward. Upon insertion of the legs  306  and  308  into the first location on the first vertebra  380 , and the insertion of the legs  307  and  309  into the second location on the second vertebra  381 , the body  304  moves between the vertebrae  380  and  381 , until the second engagement surfaces  346  and  349  contact the respective vertebra  380  or  381 . Upon full insertion, the spacing member  301  and the engagement plates  302  and  303  are disposed between the vertebrae  380  and  381 . In this position, the closeout  305  does not contact the second engagement plate  303 . Upon the application of energy to the legs  306 - 309 , the legs  306 - 309  move from the second shape  328  to the first shape  327 , thereby drawing the legs  306 - 309  toward the inter-vertebral cage  300 , and further securing the inter-vertebral cage  300  to the vertebrae  380  and  381 . Upon the application of energy to the body  304 , the bends  337  and  338  extend to the first shape  327 , thereby drawing the second engagement plate  303  away from the first engagement plate  302 . 
     The closeout  305  similarly moves from the second shape  328  to the first shape  327 , thereby extending towards the second engagement plate  303  until the closeout  305  contacts the extended engagement plate  303 . At this point, the cavity  314  is substantially closed out, as shown in  FIG. 17B . While this embodiment has been shown with bone graft material being inserted after the application of energy to the body  304  of the inter-vertebral cage  300 , one of ordinary skill in the art will recognize that bone graft material may be inserted into the cavity  314  at alternate times, or not at all. 
     In an extension of the third embodiment, an inter-vertebral cage  390  is similar in form and function to the inter-vertebral cage  300 ; however, the inter-vertebral cage  390  does not include an integral closeout, as shown in  FIGS. 19A-19C . Accordingly, like parts have been labeled with like numerals. As shown in  FIG. 19A , the inter-vertebral cage  390  additionally includes an inner surface  392  disposed on a side of the first engagement plate  302  closest to the cavity  314 , an inner surface  393  disposed on a side of the second engagement plates  302  closest to the cavity  314 , a first retention feature  391  and a second retention feature  394  disposed on the inner surfaces  392 - 393 . In this specific example, the retention features  391  and  394  are raised features that are disposed on each surface. The second retention feature  394  is disposed at a predetermined distance from the first retention feature  391 . The retention features  391  and  394  are disposed in alignment with the opposing pair, and are located in proximity to the location of the integral closeout of the previous embodiments. In this fashion, an object may be retained between the retention features  391  and  394 . While this embodiment has been shown with two retention features  391  and  394 , one of ordinary skill in the art will recognize that a multitude of retention features or retention feature designs, included but not limited to tabs, slots, threads, and grooves, at a predetermined spacing may be utilized. 
     As shown in  FIG. 19B , the closeout  395  is a separate component and is similarly constructed from shape memory material. Though one skilled in the art would recognize that non-shape memory materials could be used for the closeout to maintain the separation of the engagement plates  302  and  303 . Accordingly, the closeout  395  includes a first shape  396  and a second shape  397 . In this specific example, in the first shape  396  the closeout  395  is planar in shape, and is of a length  398  that is complementary to a distance between the retention features  391  and  394  disposed on the first engagement plate  302  and the second engagement plate  303 . In the second shape  397 , the closeout  395  deformed to a curved shape, and a length  399 . In this example, the length  399  is shorter than the length  398 , and therefore may fit between the highest parts of the retention features  391  and  394 . 
     Use of the inter-vertebral cage  390  is substantially identical to the inter-vertebral cage  300 , however, two additional steps are required. As shown in the method flowchart of  FIG. 20 , the process commences with step  80 , wherein a first vertebra  380  and a second vertebra  381  are fixated at a desired working position. In step  82 , a first securing location is identified in the first vertebra  380 , and a second securing location is identified in the second vertebra  381 . The inter-vertebral cage  390  is inserted into the first and second securing locations of the first and second vertebrae  380  and  381  utilizing any of the methods previously disclosed, step  84 . Once inserted, energy is applied to the legs  306 - 309  to secure the inter-vertebral cage  390  to the first and second vertebrae  380  and  381 , step  86 . Energy is then applied to the body  304  of the inter-vertebral cage  390  to reorient the first and second vertebrae  380  and  381 , step  88 . Next, step  90 , bone graft is inserted into the cavity  314 . The process then requires the insertion of the closeout  395  in the second shape  397  between the first and second retention features  391  and  394 , step  92 . Energy is then applied to the closeout  395  to force the closeout  395  to move from the second shape  397  to the first shape  396 , thereby extending the length  399  of the closeout  395  to length  398 , step  94 . Upon the application of energy to the closeout  395 , the closeout  395  must be guided between the first and second retention features  391  and  394 . Once extended, the closeout is permanently installed between the retention features  391  and  394 , and the first and second engagement plates  302  and  303 , thereby closing out the cavity  314 , providing load bearing capability between the engagement plates  302  and  303 , and aiding in the retention of bone graft material in the cavity  314 . While the method of implanting inter-vertebral cage  390  has been presented, one of ordinary skill in the art will recognize that the sequence of steps may be changed to meet a specific clinical need. 
     While the non-integral closeout  395  has been shown as an extension of the third embodiment, one of ordinary skill in the art will recognize that the use of a non-integral closeout  395  is possible with all embodiments of this invention. 
     In a fourth embodiment a cage  490  is utilized in an opening wedge osteotomy to change the angulation of an end portion of a tibia  420 . The cage  490  is similar in form and function to the inter-vertebral cage  390  according to the extension of the third embodiment that does not include an integral closeout. Accordingly, like parts have been referenced with like numerals. As shown in  FIG. 21A , the cage  490  includes the inner surface  392  disposed on a side of the first engagement plate  302  closest to the cavity  314 , the inner surface  393  disposed on a side of the second engagement plate  303  closest to the cavity  314 , the first retention feature  391  and the second retention feature  394  disposed on the inner surfaces  392 - 393 . In this specific example, the retention features  391  and  394  are raised features that are disposed on each surface. The second retention feature  394  is disposed at a predetermined distance from the first retention feature  391 . The retention features  391  and  394  are disposed in alignment with the opposing pair, and are located in proximity to the location of the integral closeout of the previous embodiments. In this fashion, an object may be retained between the retention features  391  and  394 . While this embodiment has been shown with two retention features  391  and  394 , one of ordinary skill in the art will recognize that a multitude of retention features or retention feature designs, included but not limited to tabs, slots, threads, and grooves, at a predetermined spacing may be utilized. Further, one of ordinary skill in the art will recognize that if the strength of the shape memory metal or the bone graft placed between the vertebrae, for all embodiments of the spinal cage, or for this fourth embodiment, for use in an osteotomy is high, a closeout or retention features will not be needed to resist the functional loading of the bone. The need for a closeout would also be eliminated if the length of the engagement plates  302  and  303  were short, or other implants outside the scope of this invention were intended for use in the procedure so as to share the functional load of the bone. 
     As shown in  FIG. 21B , the closeout  395  is a separate component and is similarly constructed from shape memory material. Accordingly, the closeout  395  includes a first shape  396  and a second shape  397 . In this specific example, in the first shape  396 , the closeout  395  is planar in shape, and is of a length  398  that is complementary to a distance between the retention features  391  and  394  disposed on the first engagement plate  302  and the second engagement plate  303 . In the second shape  397 , the closeout  395  is deformed to a curved shape, and a length  399 . In this example, the length  399  is shorter than the length  398 , and therefore may fit between the highest parts of the retention features  391  and  394 . 
     As shown if  FIG. 21A , the tibia  420  includes a tubular portion  422  connected to a knuckle portion  421 . The knuckle portion  421  is severed at an adjustment plane  424 , up to the point where only a small segment remains connected on the opposite end of the knuckle portion  421 , thereby creating a first bone  426  and a second bone  427 . The first bone  426  includes a bone working face  431  and the second bone  427  includes an end portion adjusting face  432  disposed on the partially connected second bone  427 . The partially connected second bone  427  hinges about a connection point  429 , and is rotated away from the adjustment plane  424 , such that the cage  490  may be impacted or inserted into a position between the first bone  426  and the second bone  427 . Installation and operation of the cage  490  is substantially identical to the installation and operation of the cage  390 , however, additional steps may be required in the current application. Illustratively, in this embodiment, the legs  306 - 307  of the cage  490  are impacted into the partially connected second bone  427  and the knuckle portion  421  of the first bone  426 , such that the body  304  is disposed between the end portion adjusting face  432  and the bone working face  431 . Upon the application of activation energy, the legs  306 - 307  of the cage  490  move toward their respective engagement plates  302  or  303  to secure the cage  490  to the first and second bones  426 - 427 . Upon the application of activation energy to the body  304 , the engagement plates  302 - 303  move toward each other to align the end portion adjusting face  432  with a desired corrective plane  428 . After the desired position has been reached, the closeout  395  is inserted between the retention features  391  and  394 , and energized, such that the closeout  395  supports the cage  490  in the vertical direction. 
     Use of the cage  490  is substantially identical to the inter-vertebral cage  390 , however additional steps are required in the tibial end portion adjustment operation. As shown in the method flowchart of  FIG. 22 , the process commences with step  470 , wherein a surgeon fixates the first bone  426  at a desired working position. The process continues with the severing of the first bone  426  at an adjustment plane  424 , such that only a small portion remains connected to the first bone  426 , thereby forming a partially connected second bone  427 , step  471 . In step  472 , the surgeon fixates the partially connected second bone  427  and the first bone  426  at a desired working position. In step  473 , the surgeon identifies a first location in the first bone  426  and a second location in the partially connected second bone  427 , at a spacing complementary to a leg spacing of the cage  490 . The cage  490  is inserted into the first and second securing locations of the first bone  426  and the second bone  427  utilizing any of the methods previously disclosed, step  474 . Once inserted, energy is applied to the legs  306 - 309  to secure the cage  490  to the first bone  426  and the partially connected second bone  427 , step  475 . Energy is then applied to the body  304  of the cage  490  to reorient the partially connected second bone  427  relative to the first bone  426 , step  476 . Next, in step  477 , bone graft material  430  is inserted into the cavity  314  of the cage  490  and between the bone working face  431  and the end portion adjusting face  432  to promote bone fusion. 
     The process then requires the insertion of the closeout  395  in the second shape  397  between the first and second retention features  391  and  394 , step  478 . Energy is then applied to the closeout  395  to force the closeout  395  to move from the second shape  397  to the first shape  396 , thereby extending the length  399  of the closeout  395  to the length  398 , step  479 . Upon the application of energy to the closeout  395 , the closeout  395  must be guided between the first and second retention features  391  and  394 . Once extended, the closeout  395  is permanently installed between the retention features  391  and  394 , and the first and second engagement plates  302  and  303 , thereby closing out the cavity  314 , providing load bearing capability between the engagement plates  302  and  303 , and aiding in the retention of bone graft material in the cavity  314 . 
     While this embodiment has been shown with a partial cut through the knuckle portion  421  of a tibia  420 , one of ordinary skill in the art will recognize that the methods described in this fourth embodiment may be applicable to fully severed bones, partially severed bones, or the like. One of ordinary skill in the art will further recognize that cage  490  and its methods may be applicable to bones other than tibia bones, and that the sizes, lengths, displacements, and angles of the cage or cage components may be adjusted for use in specific applications, as described in the embodiments of this disclosure. 
     One of ordinary skill in the art will further recognize the preferred embodiment and each alternate embodiment could accomplish the same function and have the same design features through apertures  110  and  111  that are holes, slots, grooves, an irregular opening or an open mesh structure. 
     Additionally, one of ordinary skill in the art will further recognize that the spacing member  101  planar section  109  of the preferred embodiment and all similar design features of each alternate embodiment could be located not on the first ends  118  and  121  but between the engagement plates  102  and  103  at a number of different locations along its inner face  500  or periphery  502 , as shown in  FIG. 23A-G . At this location the spacing member  501 , allows a number of designs for the shape changing members that distract, contract or change the angle of the first and second bones. Finally, this skill in the art would understand that the expansion or contraction nature of the planar section  109  in each of the embodiments could be achieved not by having a curved section that straightened but by having a planar section that was cut into several members spanning the engagement plates  102  to  103  where these members were “S”  503 , “Z”  504  or interlaced  505  or  506  so that in the first shape they were straight and in the second shape they returned to their contracted “S”, “Z” or interlaced shape so as to contract spacing member  501  or alternatively they are straight in the first shape and “S”, “Z” or interlaced in their second shape so as to straighten to cause expansion of the cage and separation of bone. The expansion and contraction members can be selected from the family of shapes that include but are not limited to “S”, “Z”, “C”, “O”  508  or “C”  507  shaped. 
     Although the present invention has been described in terms of the foregoing preferred embodiment, such description has been for exemplary purposes only and, as will be apparent to those of ordinary skill in the art in light of the multiple alternate embodiments that many alternatives, equivalents, and variations of varying degrees will fall within the scope of the present invention. That scope, accordingly, is not to be limited in any respect by the foregoing detailed description; rather, it is defined only by the claims that follow.