Abstract:
Embodiments of the invention include devices and methods for manipulating bone. Instruments of some of the embodiments are insertable into a vertebral body or between vertebral bodies to apply forces to the vertebral bodies to strengthen bone or prepare bone to be strengthened.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to an apparatus and method for strengthening, reshaping and/or manipulating bone.  
         [0003]     2. Description of the Related Art  
         [0004]     Adjacent spinal vertebrae are separated by an intervertebral disc. Both the vertebrae and the disc can become damaged, requiring repair. Many techniques have been developed for repairing spinal structures including vertebroplasty, kyphoplasty, primary disc arthroplasty, revision disc arthroplasty, a window osteotomy accompanied bone grafting or mechanical insert fusion, pedicle screw fixation, and spinal fusion. These techniques may involve either the bonding of a material to a vertebra or vertebrae (spinal fusion, vertebroplasty, kyphoplasty, a window osteotomy accompanied by bone grafting or mechanical insert fusion) and/or the positioning of a mechanical element through or between vertebrae (pedicle screw fixation, primary disc arthroplasty, revision disc arthroplasty). The success of bonding may depend, in part, on the strength of the vertebral bone to which the added material becomes bonded. The success of mechanical-element insertion may depend, in part, on the strength of the vertebral body, because both the insertion process and the normal activity of the patient after surgery generate vertebral stress that is more easily withstood if the vertebrae are strengthened.  
       SUMMARY OF THE INVENTION  
       [0005]     An embodiment of the present invention relates to an instrument for strengthening two spaced apart portions of bone. The instrument comprises first and second fixed shape, bone displacing and compressing elements that are sized and configured to be positionable within a space between the two spaced apart portions of bone. The first and second elements are movable to displace and compress the two spaced apart portions of bone, respectively. The instrument also comprises an actuator connected to the first and second elements and configured to actuate the first and second elements to displace and compress the two spaced apart portions of bone with sufficient force and for a sufficient amount of time to substantially strengthen the two spaced apart portions of bone.  
         [0006]     Another embodiment of the present invention relates to a method of strengthening two spaced apart portions of bone. The method comprises inserting an instrument having two fixed shaped elements into a space between the two spaced apart portions of the bone, and applying a displacing and compressing force with each of the two fixed shape elements to one of the two spaced apart portions of bone with sufficient force and for a sufficient amount of time to substantially strengthen the two spaced apart portions of bone.  
         [0007]     Still another embodiment of the present invention relates to an instrument for manipulating two spaced apart portions of bone. The instrument comprises first and second fixed shape means, positionable within a space between the two spaced apart portions of bone, for displacing and compressing the two spaced apart portions of bone, respectively, after being inserted into the space. The instrument also comprises means for actuating the first and second fixed shape means to displace and compress the two spaced apart portions of bone, respectively, after being inserted into the space, with sufficient force and for a sufficient amount of time to substantially manipulate the two spaced apart portions of bone.  
         [0008]     Other features of the present invention will become more apparent upon consideration of the following detailed description of preferred embodiments taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION ON THE DRAWINGS  
       [0009]      FIG. 1  is a schematic block diagram of an embodiment of the apparatus.  
         [0010]      FIG. 2 ( a ) is a schematic front view of a vertebra to which the intravertebral apparatus is applied and FIGS.  2 ( b ),  2 ( c ),  2 ( d ),  2 ( e ),  2 ( f )( 1 ), and  2 ( f )( 2 ) are schematic side views showing an intravertebral embodiment of the apparatus and a vertebra to which it is applied.  
         [0011]      FIG. 3  shows a flow chart of an intravertebral method.  
         [0012]     FIGS.  4 ( a ) through  4 ( g ) are schematic diagrams showing an intervertebral embodiment of the apparatus and vertebrae to which it is applied.  
         [0013]      FIG. 5  shows a flow chart of an intervertebral method.  
         [0014]      FIG. 6  shows a flow chart of an alternative embodiment of the intervertebral method.  
         [0015]      FIG. 7  shows a schematic diagram of one embodiment of a mechanical actuator.  
         [0016]      FIG. 8 ( a ) shows a schematic diagram of the embodiment of the mechanical actuator shown in  FIG. 7  whose displacing and compressing section is positioned between two spaced apart portions of bone.  
         [0017]     FIGS.  8 ( b ) and  8 ( c ) show schematic diagrams of additional embodiments of a mechanical actuator and an electromechanical actuator, respectively, whose displacing and compressing sections are positioned between two spaced apart portions of bone. 
     
    
     DETAILED DESCRIPTION  
       [0018]      FIG. 1  shows an instrument  10  for contacting, displacing, compressing, and/or aligning two spaced apart portions of bone. The bone may be cancellous bone, cortical bone, or other types of bone. The degree of compression is selected to be sufficient to substantially strengthen the bone to substantially improve any subsequent repair thereto. The degree of displacement and the shape of the portion of the instrument contacting the bone are selected to create a specific and final desirable bone geometry. In the event that a medical fusion device, an artificial disc, a non-fusible spacer, or other medical device is to be subsequently positioned between the two spaced apart portions of bone, the instrument  10  reshapes and/or manipulates the bone to create a specific and desirable bone geometry that matches or accommodates the subsequently inserted device. In the event that autograft bone, allograft bone, synthetic bone, a bone graft substitute, and/or a biocompatible material is to be added to the compressed bone, the instrument  10  reshapes and/or manipulates the bone to accommodate the subsequently added material.  
         [0019]     In one embodiment, the instrument  10  is an intravertebral tool, sized and configured to be inserted into a cavity formed within a single vertebra, to shape and enlarge the cavity, and to manipulate opposing portions of bone within the cavity. In another embodiment, instrument  10  is an intervertebral tool, sized and configured to be inserted between two adjacent vertebrae, to manipulate the bone of each vertebra, and to create a recess within each vertebra bounded by the bone. But it should be understood that the instrument  10  is also usable on structures other than spinal vertebrae. Additionally, although the instrument  10  is illustrated and described in the context of the treatment of a human spine, it should be understood that the instrument  10  may be used to treat other animals.  
         [0020]     The instrument  10  comprises an actuator  12  and a bone displacing and compressing section  14 . In an intravertebral embodiment, the bone displacing and compressing section  14  is sized and configured to be inserted through an opening in a cavity formed in a vertebral body. The bone displacing and compressing section  14  may act as a mechanical tamp, enlarging and shaping the cavity into which it is inserted by displacing bone that it encounters. In an intervertebral embodiment, the displacing and compressing section  14  is sized and configured to be inserted between two adjacent vertebrae. In both embodiments, the actuator  12  actuates the bone displacing and compressing section  14  so that the section  14  may move within a space in which the section  14  is inserted (within or between bones), so that the section  14  may contact and displace bone encountered by the section  14 , and so that the section  14  may compress and strengthen the bone it contacts after insertion. Embodiments may differ in the length of time the section  14  is actuated by the actuator  12  to displace and/or compress or manipulate the bone, the amount of force the section  14  applies to the bone, and the speed with which the section  14  is actuated to move within a vertebral body or between vertebrae. In the intravertebral embodiment, the actuator  12  actuates the section  14  to apply less force to the bone, for less time, and to move at a slower speed than in the intervertebral embodiment.  
         [0021]     In one embodiment, the instrument  10  is inserted into the space between the two spaced apart portions of bone, the actuator  12  actuates the section  14  to perform one displacing and compression operation on the two spaced apart portions of bone, the instrument  10  is removed, and the bone is repaired, further strengthened, and/or reshaped, by for example, adding allograft bone, autograft bone, synthetic bone, bone graft substitute, or biocompatible material to the compressed bone, as shown in  FIGS. 3 and 5  and as will be discussed in more detail below. In another embodiment, after the bone-compressing and material-adding steps, the instrument  10  is again inserted into the space between the two spaced apart portions of bone, and the actuator  12  actuates the section  14  to perform another displacing and compressing operation. This time, though, the bone is compressed through contact between the section  14  and the added material. Then, the instrument  10  is removed. This alternative embodiment is shown in  FIG. 6 , which will be discussed in more detail below. Moreover, this process of compressing and adding material to the bone can be repeated until the bone is rebuilt to possess a desired geometry.  
         [0022]     The actuator  12  can comprise any type of device known to those skilled in the art for actuating the section  14  to move, and to displace and compress bone, such as a mechanical actuator, a pneumatic actuator, an electrical actuator, an electromechanical actuator, or a hydraulic actuator. Two examples of a mechanical actuator are shown in FIGS.  7 ,  8 ( a ), and  8 ( b ) , which will be discussed below.  
         [0023]     The bone displacing and compressing section  14  may comprise two fixed shape elements  16  and  18  that are actuated to move by the actuator  12  in opposite directions along a single axis to produce a continuous compressing force applied to vertebral bone. But it is within the scope of the present invention for the actuator  12  to actuate the elements  16  and  18  to perform controlled directional displacement in directions other than opposite directions with respect to each other. For example, it is within the scope of the present invention for the elements  16  and  18  to move in directions at a 45 degree or a 90 degree angle with respect to each other, or at any other angle between 0 and 180 degrees. It is also within the scope of the present invention for the section  14  to comprise a single, fixed shape, bone displacing and compressing element or more than two fixed shape, bone displacing and compressing elements.  
         [0024]     The shape of the elements  16  and  18  is selected so as to produce a substantially stable vertebra as a result of reshaping, manipulating, compressing, and/or strengthening the vertebra with the elements  16  and  18 , and a) subsequently bonding allograft bone, autograft bone, synthetic material, such as synthetic bone or bone graft substitute, or biocompatible material to the vertebra, or b) subsequently bonding or attaching an attachment mechanism to the vertebra. More specifically, the fixed shape elements  16  and  18  may be hemispherically shaped, or spoon shaped, or have a flat outer peripheral surface. In addition, the shape of the elements  16  and  18  can be selected to accommodate or match the shape of the subsequent graft or a subsequently inserted artificial disc or medical device. It is also within the scope of the present invention for these elements to be in the shape of: a convex polyhedron, such as a cube, a dodecahedron, a icosahedron, an octahedron, and a tetrahedron; an Archimedean solid; a Catalan solid; a uniform polyhedron; an irregular solid; a sphere; an ellipsoid; an ovoid; a rectangular solid; a cylinder; or a cone. It is further within the scope of the present invention for the elements  16  and  18  to be in the shape of: a part of a convex polyhedron, such as a cube, a dodecahedron, a icosahedron, an octahedron, and a tetrahedron; a part of an Archimedean solid; a part of a Catalan solid; a part of a uniform polyhedron; a part of an irregular solid; a part of a sphere; a part of an ellipsoid; a part of an ovoid; a part of a rectangular solid; a part of a cylinder; or a part of a cone.  
         [0025]     The elements  16  and  18  may have the same shape or may be shaped differently from each other. In addition, the elements  16  and  18  may be detachable from the section  14  so that differently shaped elements  16  and  18  may be attached to the section  14 . This detachable embodiment is useful when performing repeated compression and filling operations that require the elements  16  and  18  to have a different shape during different compression operations. When the shape of the element  16  and/or the element  18  is to be changed after the first compression operation, the element  16  and/or the element  18  may be simply detached from the section  14  and replaced with an element or elements of a different shape. Alternatively, different instruments  10  having differently shaped elements  16  and  18  may be used during different compression operations.  
         [0026]     The fixed shape elements  16  and  18  are movable by the actuator  12  from an inserting position to a compressing position. In the inserting position, the elements  16  and  18  are closer together than in the compressing position. In one embodiment, in the inserting position, the elements  16  and  18  are adjacent or make contact with each other, and in another embodiment, they are merely closer to each other than in the compressing position. In the compressing position, the fixed shape elements  16  and  18  are spaced apart by the distance needed to contact the bone within a single vertebra or between vertebrae to compress the bone with a sufficient force for a sufficient amount of time to strengthen the bone for one of the repair protocols noted below.  
         [0027]     In one embodiment, the elements  16  and  18  are moved only once substantially along a single axis in opposite directions from the inserting position to the compressing position to compress and strengthen the vertebral bone in a single continuous compressing operation. In another embodiment, the two elements  16  and  18  are moved multiple times substantially along the single axis in opposite directions from the inserting position to the compressing position to compress and strengthen the vertebral bone in multiple continuous compressing operations with the addition of bone-repair materials between the compressing operations. The two elements  16  and  18  may substantially simultaneously displace and compress the vertebral bone or the elements  16  and  18  may displace and compress the vertebral bone at completely different times, or at overlapping times, i.e., before one of elements  16  and  18  is finished displacing and compressing bone, the other of elements  16  and  18  starts displacing and compressing bone.  
         [0000]     Intravertebral Tool and Method  
         [0028]     In the intravertebral embodiment, the size and configuration of the elements  16  and  18  are selected so that the elements  16  and  18 : 1) can be inserted in the inserting position through an opening in the cavity of a single vertebral body; and 2) can be moved apart by the actuator  12  from the inserting position to the compressing position to compress the bone by the amount needed to strengthen the bone for one of the repair protocols noted below. Movement of the elements  16  and  18  from the inserting to the compressing position may also enlarge the cavity and/or reshape the cavity into a desired shape to accommodate any material or device subsequently inserted into the cavity, for example, for repair and/or strengthening purposes.  
         [0029]     This procedure, sometimes called a window osteotomy with compaction, is shown in FIGS.  2 ( a ),  2 ( b ),  2 ( c ),  2 ( d ),  2 ( e ),  2 ( f )( 1 ), and  2 ( f )( 2 ).  FIG. 3  illustrates the method steps accompanying the physical manipulation of the intravertebral tool  10  and a portion of a vertebra  20  shown in FIGS.  2 ( a ) through  2 ( f )( 2 ). FIGS.  2 ( a ) through  2 ( f )( 2 ) do not show the other tissue or bones surrounding the vertebra  20 , and it is assumed that prior to the step shown in  FIG. 2 ( a ), the surgeon has created a clear path between the instrument  10  and the vertebra  20  via any surgical procedure known to those skilled in the art if such a clear path does not exist prior to surgery.  
         [0030]      FIG. 2 ( a ) and  FIG. 2 ( b ) show front and side views of a portion of the vertebra  20  that has suffered some damage or in which pathology exists, such as a compression fracture (not shown), or needs to be strengthened. In step S 1 , a surgeon cuts out or drills out a portion  22  of the vertebral cortical bone, for example with a box chisel, to produce a window  24  into the interior of the vertebra  20 , as shown in FIGS.  2 ( a ) and  2 ( b ), and to create a cavity  26  in the vertebra, as shown in  FIG. 2 ( b ). The window  24  can be cut at such a position in the vertebra  20  so as to permit anterior, posterior, lateral, or anteriolateral access into the interior thereof. The interior of the vertebra  20  contains cortical bone  27  and cancellous bone  28 . The instrument  10  may be used to compress or reposition one or both of the cortical bone  27  and the cancellous bone  28 . In step S 2 , the surgeon positions the elements  16  and  18  to the inserting position if they are not already in that position and inserts the elements  16  and  18  through the window  24  into the cavity  26 , as shown in  FIG. 2 ( c ). This step may entail activating the actuator  12  to move the elements  16  and  18  to the inserting position, or in one embodiment, the surgeon may also move the elements  16  and  18  manually to the inserting position.  
         [0031]     In step S 3 , the surgeon activates the actuator  12  to actuate the elements  16  and  18  to move from the inserting position to the compressing position, as shown in  FIG. 2 ( d ). In this step, the actuator  12  accelerates the elements  16  and  18  in opposite directions to contact, displace, and compress the bone at the top and the bottom of the cavity  26 . In addition, or alternatively, the actuator  12  accelerates the elements  16  and  18  to realign bone fragments of the vertebra  20  in the anterior-posterior direction, the medial-lateral direction, or the superior-inferior direction. As a result of this single continuous compression operation along a single vertical axis, the cavity  26  is enlarged and the resulting bony structure is made more dense as it is compressed and is thereby strengthened. In step S 4 , the surgeon activates the actuator  12  to actuate the elements  16  and  18  to move from the compressing position to the inserting position and then removes the instrument  10  from the cavity  26  through the window  24 , as shown in  FIG. 2 ( e ). In step S 5 , the surgeon fills the cavity  26  with allograft bone, autograft bone, biocompatible material, bone graft substitute, or synthetic material, such as PMMA (polymethylmethacrylate), collectively denoted by reference characters  29   a , as shown in  FIG. 2 ( f )( 1 ), or inserts an implant or medical device  29   b  into the cavity to further strengthen the vertebra, as shown in  FIG. 2 ( f )( 2 ). When an implant is used as the element  29   b , the implant can be composed of any suitable material to repair the bone, as known to those skilled in the art, such as titanium, stainless steel, or a polymer, such as PEEK (polyetheretherketone). Alternatively, a medical device  29   b  that does not fuse to the bone of the vertebra  20  can be inserted into the cavity  26  to repair the vertebra  20 . Thus, the instrument  10  strengthens the bone prior to repair, rebuilding, and/or remodeling.  
         [0032]     It is within the scope of the present invention to perform steps S 2  through S 5  on a vertebra previously filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material, such as PMMA, or into which an implant or a medical device was previously inserted. In this case, the material, the implant, or the medical device that was inserted into the cavity  26  is removed before steps S 2  through S 5  are performed. It is also within the scope of the present invention to perform steps S 2  through S 5  again, after the bone has been compressed once and the cavity  26  has been newly filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material, or after the insertion of an implant or a medical device into the cavity. In this case, the elements  16  and  18  contact and displace the autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, the synthetic material, the implant, or the medical device, and compress the vertebral bone through the autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, the synthetic material, the implant, or the medical device. Additional autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material may then be inserted into the cavity  26 . This repeated cavity-filling and tamping step may be performed multiple times.  
         [0033]     It is also within the scope of the present invention to position the first and second elements  16  and  18  so that the distance between the outer periphery of these two elements is smaller than or precisely matches the width of the window  24  prior to insertion. As a result, as the elements  16  and  18  are inserted into the cavity  26 , they slide on and contact the top and bottom portions of bone. After insertion, in this embodiment, the actuator  12  actuates the elements  16  and  18  to compress the bone from this position of contact.  
         [0034]     In the event that the cavity  26  is to be filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material, the actuator  12  actuates the first and second elements  16  and  18  to compress the two spaced apart portions of vertebral bone with sufficient force and for a sufficient amount of time to substantially strengthen the vertebral bone prior to subsequently filling the cavity  26  with the autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, or the synthetic material. In addition, the actuator  12  actuates the first and second elements  16  and  18  to compress the two spaced apart portions of vertebral bone with sufficient force and for a sufficient amount of time to strengthen the vertebral bone subsequently filled with the autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, or the synthetic material substantially above the strength the vertebra  20  would possess if the vertebra  20  were filled with autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, or the synthetic material without being previously compressed by the elements  16  and  18 .  
         [0035]     In the event that the cavity  26  is to be filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material and a pedicle screw is to be fixed to the vertebra  20 , the actuator  12  actuates the first and second elements to compress the two spaced apart portions of vertebral bone with sufficient force and for a sufficient amount of time to substantially augment subsequent pedicle screw fixation on the vertebra  20 .  
         [0036]     In the event that an implant is to be inserted into the cavity  26  to subsequently fuse to the two spaced apart portions of bone, the actuator  12  actuates the first and second elements  16  and  18  to compress the two spaced apart portions of vertebral bone with sufficient force and for a sufficient amount of time to increase the strength of the vertebra  20  subsequently fused to the implant substantially above the strength the vertebra  20  would possess if the implant-fused vertebra  20  was not previously compressed by the first and second elements  16  and  18 .  
         [0037]     In the event that the vertebra  20  has a compression fracture and the cavity  26  is to be filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material, the actuator  12  actuates the first and second elements  16  and  18  to compress the two spaced apart portions of vertebral bone with sufficient force and for a sufficient amount of time to substantially strengthen the vertebral bone prior to filling the cavity with the autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, or the synthetic material. In addition, in this case, the actuator  12  actuates the first and second elements  16  and  18  to compress the two spaced apart portions of vertebral bone with sufficient force and for a sufficient amount of time to substantially restore the anatomical structure of the vertebra  20  after the cavity is filled with the autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, or the synthetic material. Further in this case, the actuator  12  actuates the first and second elements  16  and  18  to compress the two spaced apart portions of vertebral bone with sufficient force and for a sufficient amount of time to increase the strength of the vertebra  20  after fusing to the autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, or the synthetic material substantially above the strength the vertebra  20  would possess if the vertebra  20  was subsequently filled with the autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, or the synthetic material without being previously compressed with the first and second elements  16  and  18 .  
       Intervertebral Embodiment  
       [0038]     In the intervertebral embodiment, the size and configuration of the elements  16  and  18  are selected so that the elements  16  and  18  can be inserted into the space between two adjacent vertebrae  30  when the elements  16  and  18  are in the inserting position. In addition, the moving of the elements  16  and  18  from the inserting to the compressing position by the actuator  12  can compress portions of each vertebra and create a recess in each vertebra bordered by the compressed bone of that vertebra. Further, the actuator  12  may actuate the elements  16  and  18  to compress the vertebral bone sufficiently 1) to strengthen the vertebral bone, 2) to substantially improve the functioning of any structure comprising the strengthened vertebrae and an intervertebral disc (not shown) or element positioned therebetween, such as a fusion device, a non-fusible device, or a disc-arthroplasty device, 3) to substantially improve the results of a revision repair, such as a disc-cage repair, a bone-nucleus repair, or a revision disc arthroplasty, which repairs a previously-repaired vertebral structure requiring further repair, and/or 4) to strengthen a structure comprising the compressed bone and a material or an element subsequently fused thereto substantially above the strength of such a structure formed without compression by elements  16  and  18 .  
         [0039]     This procedure is called endplate access with impaction grafting because access to the vertebrae is gained through the area where the endplates of an intervertebral disc attach to the vertebrae, as shown in FIGS.  4 ( a ),  4 ( b ),  4 ( c ),  4 ( d ),  4 ( e ),  4 ( f ), and  4 ( g ).  FIG. 5  shows the method steps accompanying the physical manipulation of the intervertebral tool and the vertebrae  30  shown in FIGS.  4 ( a ) through  4 ( g ). FIGS.  4 ( a ) through  4 ( g ) do not show the other tissue or bones surrounding the vertebrae  30 . Moreover, prior to the steps shown in FIGS.  4 ( a ) through  4 ( g ), the surgeon can create access to the vertebrae  30  by removing the intervertebral disc and/or portions of their endplates (not shown). This operation permits access to the vertebrae  30  through the areas in which the endplates were attached, so that a clear path exists between the instrument  10  and the vertebrae  30 .  
         [0040]     Alternatively, the surgeon can remove the intervertebral disc while leaving the endplates attached to the vertebrae  30 . In this alternative embodiment, the elements  16  and  18  directly contact the endplates and compress the bone of the vertebrae  30  through their contact with the endplates. Moreover, since the endplates may also contain cancellous bone, the compressing operation of the elements  16  and  18  also compresses and strengthens any cancellous bone existing in and below the endplates. In addition, since the endplates may contain osteoporotic, diseased, or damaged cortical bone, the elements  16  and  18  may also compress such bone when moving from the inserting to the compressing position. While this end-plate compression and strengthening is not shown in FIGS.  4 ( a ) through  4 ( g ) or  FIG. 5 , it is within the scope of the present invention to practice each of the steps shown in FIGS.  4 ( a ) through  4 ( g ) and  FIG. 5  on two endplates attached to the vertebrae  30  to compress and strengthen the bone of the endplates and of the vertebrae  30  in a single, continuous compression operation.  
         [0041]      FIG. 4 ( a ) shows a schematic side view of two spaced apart vertebrae  30 , that have suffered damage, such as a compression fracture, or need to be strengthened. In  FIG. 4 ( a ), the instrument  10  is positioned a distance away from a space  32  between the vertebrae  30 , either outside the body, or inside the body, but not yet inserted into the space  32  between the vertebrae  30 . In step S 10 , the surgeon positions the elements  16  and  18  to the inserting position if they are not already in that position and inserts the elements  16  and  18  into the space  32  between the vertebrae  30 , as shown in  FIG. 4 ( b ). This step may entail activating the actuator  12  to move the elements  16  and  18  to the inserting position, or in one embodiment, the surgeon may also move the elements  16  and  18  manually to the inserting position. The vertebrae  30  contains cancellous bone  34  and cortical bone  35 . The instrument  10  may be used to compress one or both of the cancellous bone  34  and the cortical bone  35 . In step S 11 , the surgeon activates the actuator  12  to actuate the elements  16  and  18  to move from the inserting position to the compressing position, as shown in  FIG. 4 ( c ). In this step, the actuator  12  accelerates the elements  16  and  18  in opposite directions to contact, displace, and compress the bone of the two vertebrae  30  at the top and the bottom of the space  32 . As a result of this single continuous compression operation along a single vertical axis, a recess  36  is formed within each vertebra  30  bounded by the compressed bone, and the bone is compressed and strengthened.  
         [0042]     In step S 12 , the surgeon activates the actuator  12  to actuate the elements  16  and  18  to move from the compressing position to the inserting position and removes the instrument  10  from the space  32 , as shown in  FIG. 4 ( d ). In step S 13 , the surgeon fills the recesses  36  of each vertebra  30  with allograft bone, autograft bone, bone graft substitute, biocompatible material, or synthetic material, collectively denoted by reference numeral  38 , as shown in  FIG. 4 ( e ). This step S 13  is optional. In the event that step S 13  is not performed, in the embodiment in which an implant is subsequently inserted between the two vertebrae  30 , the implant fuses directly to the compressed and strengthened bone of the two vertebrae  30 . Returning to the embodiment shown in FIGS.  4 ( a ) through  4 ( g ), if a spinal fusion procedure is to be performed, the surgeon performs step S 14  to insert an implant  40  into the space  32  to contact the allograft, autograft, bone graft substitute, biocompatible material, or synthetic material applied to the recesses  36 , as shown in  FIG. 4 ( f ). If a primary disc arthroplasty procedure is to be performed, the surgeon performs step S 15  to insert an artificial disc  42 , as shown in  FIG. 4 ( g ).  
         [0043]     It is also within the scope of the present invention to perform steps S 10  through S 12  as part of a revision disc arthroplasty, in which the vertebrae  30  were previously filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material and an artificial disc was previously implanted between the vertebrae  30 . In this case, the artificial disc and the allograft, autograft, bone graft substitute, biocompatible material, or synthetic material that were inserted into the recesses  36  are removed before steps S 10  through S 12  are performed.  
         [0044]     In addition, it is within the scope of the present invention to perform steps S 10  through S 12  again, after the bone of the vertebrae  30  has been compressed once by the instrument  10  and the recesses  36  have been newly filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material. As a result, the elements  16  and  18  compress the bone of the vertebrae  30  through contact with the autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, or the synthetic material. It is also within the scope of the present invention to perform these repeated tamping and filling operations multiple times. Such an embodiment is shown in  FIG. 6  and will now be further discussed.  
         [0045]     Steps S 20  through S 23  are the same as steps S 10  through S 13  and are, therefore, not further discussed. After step S 23 , the surgeon again inserts the instrument  10  between the vertebrae  30 , manipulates and compresses the bone of each vertebra  30  with the elements  16  and  18  to create another recess or reform the previously formed recess in each vertebra  30 , removes the instrument  10 , and again fills the recesses with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material, in step S 24 . This repetition of steps S 20  through step S 23  can be performed one or more times to create a desired bone geometry. In addition, this repetition of steps S 20  through S 23  can be performed one or more times to create a desired bone geometry to accommodate a subsequently inserted mechanical fusion device, artificial disc, non-fusible spacer, or other non-fusible medical device. After step S 24 , the surgeon inserts into the intervertebral space a mechanical fusion device in step S 25  or an artificial disc, a non-fusible spacer, or other non-fusible medical device in step S 26 .  
         [0046]     It is within the scope of the present invention to position the first and second elements  16  and  18  so that the distance between the outer periphery of these two elements is smaller than or precisely matches the width of the space  32  between adjacent vertebrae  30  prior to insertion. As a result, as the elements  16  and  18  are inserted into the space  32 , they slide on and contact the top and bottom portions of the bone of the two vertebrae  30 . After insertion, in this embodiment, the actuator  12  actuates the elements  16  and  18  to compress the bone from this position of contact.  
         [0047]     In the event that the recess  36  of each vertebra  30  is to be filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material, the actuator  12  actuates the first and second elements  16  and  18  to compress the vertebral bone of the two spaced apart vertebrae  30  with sufficient force and for a sufficient amount of time to create the recesses  36  and to substantially increase the strength of the vertebrae prior to filling the recesses  36  with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material. In addition, in this case, the actuator  12  actuates the first and second elements  16  and  18  to compress the vertebral bone of the two spaced apart vertebrae  30  with sufficient force and for a sufficient amount of time to strengthen the vertebrae  30  subsequently filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material substantially above the strength the two vertebrae  30  would possess if the two vertebrae  30  were subsequently filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material without being previously compressed by the fixed shape elements  16  and  18 .  
         [0048]     In the event that the recess  36  of each vertebra  30  is to be filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material and a fusible implant  38  is to be placed into the space  32  to join the two adjacent vertebrae  30  by subsequently fusing to vertebral bone and/or the autograft bone, the allograft bone, the bone graft substitute, the biocompatible material, or the synthetic material in each recess  36 , the actuator  12  actuates the first and second elements  16  and  18  to compress the vertebral bone of the two spaced apart vertebrae  30  with sufficient force and for a sufficient amount of time to substantially increase the strength of the vertebrae both before and after fusion to the fusible implant  40 . This increased strength of the vertebrae  30  after fusion to the implant  40  is substantially greater than the strength the vertebrae  30  would possess if the vertebrae  30  were fused to the fusible implant  40  without being previously compressed by the elements  16  and  18 .  
         [0049]     In the event that a primary disc arthroplasty is to be performed so as to replace the intervertebral disc between the two adjacent vertebrae  30  with an artificial intervertebral disc  42 , and in the event that the recess  36  of each vertebra  30  is to be filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material, the actuator  12  actuates the first and second elements  16  and  18  to compress the vertebral bone of the two spaced apart vertebrae  30  with sufficient force and for a sufficient amount of time to substantially reinforce the subsequent primary disc arthroplasty substantially above the level of reinforcement that would exist if the two vertebrae  30  were not previously compressed by the first and second elements  16  and  18 .  
         [0050]     In the event that a revision disc arthroplasty is to be performed on a spinal structure defined by the two adjacent vertebrae  30  and an artificial intervertebral disc  42  positioned between the two adjacent vertebrae  30 , and in the event that the recess  36  of each vertebra  30  is to be filled with autograft bone, allograft bone, bone graft substitute, biocompatible material, or synthetic material, the actuator  12  actuates the first and second elements  16  and  18  to compress the vertebral bone of the two spaced apart vertebrae  30  with sufficient force and for a sufficient amount of time to substantially reinforce the subsequent revision disc arthroplasty substantially above the level of reinforcement that would exist if the two vertebrae  30  were not previously compressed by the first and second elements  16  and  18 .  
       Actuator Embodiments  
       [0051]      FIG. 7  illustrates one mechanical embodiment of the actuator  12 . The mechanical actuator  50  shown in  FIG. 7  comprises a scissor-like device comprising first and second movable members  52  and  54  and a pivot element  56  around which members  52  and  54  rotate. The movable member  52  has a handle  58  at one end and the movable member  54  has a handle  60  at one end. The other end of the movable member  52  has attached thereto the fixed shape element  16 , while the other end of the movable member  54  has attached thereto the fixed shape element  18 .  FIG. 7  shows the mechanical actuator  50  in the compressing position in which the fixed shape elements  16  and  18  and the handles  58  and  60  are spaced away from each other. When the surgeon grasps the handles  58  and  60  and moves them toward each other into an inserting position to minimize the distance therebetween, the fixed shape elements  16  and  18  also move toward each other to an inserting position. Conversely, when the surgeon moves the handles  58  and  60  in opposite directions away from each other into the compressing position, the fixed shape elements  16  and  18  move away from each other to the compressing position.  
         [0052]     Although the elements  16  and  18  generally move in an arcuate path in response to movement of the handles  58  and  60 , their movement from the inserting to the compressing position and from the compressing to the inserting position is substantially linear when moved over the distances required to act on two spaced apart portions of bone, as shown in  FIG. 8 ( a ). Alternatively, a different kind of mechanical actuator  12  can be provided that permits completely linear movement of the elements  16  and  18  over their entire range of motion. One example of such a device is the jack illustrated in  FIG. 8 ( b ). In this figure, the actuator  12  is in the form of a screw, one end of which is attached to a rotatable handle to be rotated by the surgeon, and the other end of which translates this rotary motion of the screw into rectilinear motion to move the elements of the displacing and compressing section  14  linearly. In both of these embodiments, the displacing and compressing section  14  is moved by the application of direct external power by hand. In the embodiment shown in  FIG. 8 ( c ), indirect external power is applied to the section  14  by a controller comprising the actuator  12 . The controller controls the displacement of the section  14  by the use of an electromechanical mechanism, a hydraulic mechanism, or a pneumatic mechanism to move the section  14  and the elements  16  and  18  (not shown) linearly between the compressing and inserting positions. In addition, unlike the previous embodiments, the embodiments shown in FIGS.  8 ( b ) and  8 ( c ) each internally deploy a jack, which is part of the actuator for actuating movement of the elements  16  and  18 , inside the space between the two spaced apart portions of vertebral bone.  
         [0053]     Although several specific mechanical embodiments of the mechanical actuator  12  have been illustrated in FIGS.  7 ,  8 ( a ), and  8 ( b ), it should be understood that the use of other types and configurations of mechanical actuators are also contemplated, as would occur to one of ordinary skill in the art. More specifically, any type of mechanical actuator may be used that is capable of imparting relative displacement between the fixed shape elements  16  and  18  between the inserting and compressing positions.  
         [0054]     In both the intervertebral and intravertebral embodiments, the amount of force used to manipulate or compress the bone and the amount of time during which this compression force is applied can be further determined by conducting various clinical tests, as are known to those skilled in the art.  
         [0055]     While the present invention has been described with reference to the specific structures and embodiments disclosed herein, it is to be understood that it not limited to the details thereof, but is intended to cover such modifications or changes as may come within the scope of the following claims.