Abstract:
A method of stabilizing a portion of a spine includes pivoting first and second members of an expandable spinal implant relative to one another to a closed configuration in which the spinal implant has a compact profile, inserting the spinal implant in the closed configuration into the spine between first and second vertebral bodies, and pivoting the first and second members crosswise to an expanded configuration while the spinal implant is within the spine. The first and second members are separate from and coupled to one another.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 11/697,322 filed on Apr. 6, 2007, which is a continuation of U.S. patent application Ser. No. 10/897,371 filed on Jul. 22, 2004, now issued U.S. Pat. No. 7,318,839, which claims the benefit of U.S. Provisional Application No. 60/489,731 filed on Jul. 23, 2003. The disclosures of the above applications are incorporated herein by reference. 
     
    
     INTRODUCTION 
       [0002]    The spinal column is a highly complex structure which houses and protects critical elements of the nervous system. In spite of these complexities, the spinal column is a highly flexible structure, capable of a high degree of curvature and twist through a wide range motion. Genetic or developmental irregularities, trauma, chronic stress, tumors, and disease, however, can result in spinal pathologies which either limit this range of motion, or threaten the critical elements of the nervous system housed within the spinal column. 
         [0003]    In various orthopedic surgical procedures, it is necessary to stabilize portions of a spinal column relative to one another. This need is typically a result of disease, damage or congenital deformation. In one method of treatment for intervertebral disk degeneration, the normal gap between adjacent vertebral bodies is surgically re-established and maintained with a rigid spacer inserted between the bodies. The rigid spacer is filled with bone graft material to facilitate bony fusion of the two vertebral bodies. A successful fusion stabilizes the spine, reduces pressure on the spinal cord and nerve roots, and reduces or eliminates back pain. 
         [0004]    While known devices for spinal fusion have proven to be effective in various applications, there remains a need for spinal implants that do not require large incisions for implantation, that can relieve localized stress on adjacent vertebral end plates, and that can prevent migration and retropulsion within the spinal column. 
       SUMMARY 
       [0005]    The present teachings provide an expandable spinal implant including a first member and a second member. The first member has first and second arms. The first and second arms of the first member both including an upper face partially defining an upper contact area of the implant and a lower face partially defining a lower contact surface of the implant. The second member has first and second arms that both include an upper face partially defining an upper contact area of the implant and a lower face partially defining a lower contact surface of the implant. The first and second members are pivotally coupled to each other for relative movement about a rotation axis between a closed position for inserting the implant into a spine and an expanded position for providing structural support to the spine. The rotation axis extends generally perpendicular to the upper and lower contact surfaces. 
         [0006]    The present teachings also provide an expandable spinal implant having first and second members both with a central portion and first and second arms extending from the central portion. The central portion of the second member is coupled to the central portion of the first member for rotation about a rotation axis between a closed orientation for insertion into a spine and an expanded orientation for providing structural support to the spine. The spinal implant further includes a locking mechanism for arresting relative movement between the first member and the second member. 
         [0007]    The present teachings provide a method of stabilizing a portion of a spine. The method includes providing a spinal implant having a first elongated member and a second elongated member. The first elongated member has a central portion rotatably coupled to a central portion of the second elongated member for rotation between a closed position and an expanded position. The method additionally includes orienting the first and second elongated members in the closed position and inserting the spinal implant into the spine between first and second vertebral bodies. The rotation axis is vertically oriented. The method further includes rotating the first and second elongated members to the expanded position while the spinal implant is within the spine. 
         [0008]    The present teachings further provide an expandable spinal implant that includes a first member having first and second arms and a central portion between the first and second arms, and a second member completely separate from the first member, the second member having first and second arms and a central portion between the first and second arms. The central portion of the first member is rotatably coupled to the central portion of the second member about a rotation axis substantially perpendicular to the central portions between a closed position for inserting the implant into a spine and an expanded position for providing structural support to the spine, the first and second members coupled to each other such that the first and second arms of the first member alternate with the first and second arms of the second member. 
         [0009]    The present teachings provide an expandable spinal implant that includes a first member having a central portion and first and second arms extending from the central portion of the first member, a second member having a central portion and first and second arms extending from the central portion of the second member, the central portion of the second member coupled to the central portion of the first member for rotation about a rotation axis between a closed orientation for insertion into a spine and an expanded orientation for providing structural support to the spine, and a locking mechanism for arresting relative movement between the first member and the second member, the locking mechanism including a locking member manually operable to engage the first member with the second member in the expanded orientation. 
         [0010]    The present teachings further provide an expandable spinal implant that includes a first member having a central portion and first and second arms extending from the central portion of the first member, a second member having a central portion and first and second arms extending from the central portion of the second member, and a pivot member engaging respective first and second openings of the central portions of the first and second members for rotation between a closed orientation for insertion of the spinal implant into a spine and an expanded orientation for providing structural support to the spine. 
         [0011]    The present teachings further provide a method of stabilizing a portion of a spine. The method includes pivoting first and second members of an expandable spinal implant relative to one another to a closed configuration in which the spinal implant has a compact profile, inserting the spinal implant in the closed configuration into the spine between first and second vertebral bodies, and pivoting the first and second members crosswise to an expanded configuration while the spinal implant is within the spine. The first and second members are separate from and coupled to one another. 
         [0012]    In another aspect, the method includes pivoting first and second members of an expandable spinal implant relative to one another to a closed configuration in which the spinal implant has a compact profile and inserting the spinal implant in the closed configuration into the spine between first and second vertebral bodies. The first and second members are separate from and coupled to one another. The method further includes pivoting the first and second members to an expanded configuration while the spinal implant is within the spine, and arresting a relative movement between the first and second members by operation of a leaf spring formed by corresponding first and second central portions of the first and second members. 
         [0013]    In a further aspect, the method includes inserting an expandable spinal implant in a closed configuration between first and second vertebral bodies of a spine, and pivoting first and second members of the expandable implant to an expanded configuration while the spinal implant is within the spine. The first and second members are separate from and coupled to one another. The method further includes rotating a threaded fastener received in a bore of an arm of one of the first or second members, and locking the first and second elongated members in the expanded configuration with the threaded fastener. 
         [0014]    Further areas of applicability of the present teachings will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present teachings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present teachings will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0016]      FIG. 1  is a side view of an expandable spinal implant constructed in accordance with the present teachings, the expandable spinal implant shown operatively positioned between vertebral bodies of a human spine; 
           [0017]      FIG. 2  is a cross-sectional view taken along the line  2 - 2  of  FIG. 1 , the expandable spinal implant shown in an expanded or open condition; 
           [0018]      FIG. 3  is a cross-sectional view similar to  FIG. 2 , the expandable spinal implant shown in a contracted or closed condition to facilitate insertion into the spine; 
           [0019]      FIG. 4  is a perspective view of an expandable spinal implant according to the present teachings, and shown removed from the spine for purposes of illustration; 
           [0020]      FIG. 5A  is a top perspective view of a first member of the expandable spinal implant of  FIG. 4 ; 
           [0021]      FIG. 5B  is a side view of the first member of the expandable spinal implant of  FIG. 4 ; 
           [0022]      FIG. 5C  is a bottom view of the first member of the expandable spinal implant of  FIG. 4 ; 
           [0023]      FIG. 6  is a top view of the expandable spinal implant of  FIG. 4 , shown in the closed position; 
           [0024]      FIG. 7  is a top view of the expandable spinal implant of  FIG. 4 , shown in the open position; 
           [0025]      FIG. 8  is a perspective view of an expandable spinal implant according to the present teachings, shown in the open position; 
           [0026]      FIG. 9  is a top view of the expandable spinal implant of  FIG. 8 , shown in the closed position; 
           [0027]      FIG. 10  is a top view of the expandable spinal implant of  FIG. 8 , shown in the open position; 
           [0028]      FIG. 11A  is a top view of a first member of the expandable spinal implant of  FIG. 8 ; 
           [0029]      FIG. 11B  is a side view of the first member of the expandable spinal implant of  FIG. 8 ; 
           [0030]      FIG. 11C  is an end view of the first member of the expandable spinal implant of  FIG. 8 ; 
           [0031]      FIG. 12A  is a top view of a second member of the expandable spinal implant of  FIG. 8 ; 
           [0032]      FIG. 12B  is a side view of the second member of the expandable spinal implant of  FIG. 8 ; 
           [0033]      FIG. 12C  is an end view of the second member of the expandable spinal implant of  FIG. 8 ; 
           [0034]      FIG. 13A  is a side view of a locking member of the expandable spinal implant of  FIG. 8 ; 
           [0035]      FIG. 13B  is an end view of the locking member of the expandable spinal implant of  FIG. 8 ; 
           [0036]      FIG. 14A  is a side view of a pivot member of the expandable spinal implant of  FIG. 8 ; and 
           [0037]      FIG. 14B  is an end view of the pivot member of the expandable spinal implant of  FIG. 8 . 
       
    
    
     DESCRIPTION 
       [0038]    The following description of various embodiments is merely exemplary in nature and is in no way intended to limit the present teachings, applications, or uses. 
         [0039]    With initial reference to  FIG. 1  and  FIG. 2 , an exemplary spinal implant constructed in accordance with the present teachings is illustrated and generally identified at reference number  10 . The spinal implant  10  is shown operatively associated with a human spinal column  12 . More specifically, the spinal implant  10  is shown positioned between a first vertebra  14   a  and a second vertebra  14   b  to stabilize the spine  12 . 
         [0040]    With continued reference to the environmental views of  FIGS. 1 and 2  and additional reference to  FIGS. 3 through 7 , the spinal implant  10  of the present teachings will be addressed in detail. The spinal implant  10  is illustrated to generally include a first member or first elongated member  16  and a second member or second elongated member  18 . As will become more apparent below, the first elongated member  16  and the second elongated member  18  are completely separate members and are coupled to one another for relative movement between a closed position or orientation (shown in  FIG. 3 ) and an expanded position or orientation (shown in  FIG. 2 ). As will be appreciated more fully below, the closed orientation facilitates insertion of the spinal implant  10  within the spine  12  through a small incision, while the expanded orientation disperses the load on the adjacent end plates. 
         [0041]    With particular reference to  FIG. 4 , the implant  10  is shown removed from the spine  12  for purposes of illustration and articulated to the open position. As shown in  FIG. 4 , the first elongated member  16  and the second elongated member  18  can be substantially identical to each other. For this reason, a description of the first elongated member  16  will serve to fully describe both the first elongated member  16  and the second elongated member  18  for the exemplary implant  10 . In view of this similarity, like reference numbers for implant  10  will be used throughout  FIGS. 1-7  to identify common elements of the first elongated member  16  and the second elongated member  18 . It will be appreciated, however, that the first and second elongated members need not be identical, as is illustrated in  FIGS. 8-14  for another exemplary implant  100  described below. 
         [0042]    Various different views of the first elongated member  16  are provided in  FIGS. 5A through 5C  in which the first elongated member  16  is separated from the second elongated member  18 . As seen in  FIGS. 5A-5C , the first elongated member  16  is illustrated to include a central or intermediate portion  20 . The central portion  20  is generally circular and upwardly extends from a lower surface of the implant. The central portion  20  has a height equal to approximately one-half the height of the implant  10 . As a result, an upper or inner surface  22  of the central portion  20  is disposed at approximately a horizontal mid-line of the implant  10 . The central portion  20  also includes a lower or outer surface  24 . 
         [0043]    Extending through the central portion  20 , between the upper surface  22  and the lower surface  24 , is a through slot  26 . The through slot  26  permits bone ingrowth through the implant  10  to more rigidly secure the implant  10  within the spine  12 . The through slot  26  also reduces the weight of the implant  10  while maintaining the strength of the implant  10 . Further, the through slot  26  allows the implant  10  to be easily held and positioned by a physician using suitable medical instrumentation. 
         [0044]    Extending from opposite sides of the central portion  20  are a first arm  28  and a second arm  30 . In the embodiment illustrated, the first arm  28  and the second arm  30  are identical and generally extend tangentially from the central portion  20 . The first arm  28  and the second arm  30  preferably extend from the central portion  20  parallel to each other, but are slightly offset from each other. As seen best in  FIG. 5B , the first arm  28  and the second arm  30  each include an upper wall  32 , a lower wall  34 , an outer wall  36 , and an inner wall  38 . The inner wall  38  extends from the lower surface  24  of the central portion  20  to a distance that is twice the distance between the upper surface  22  and the lower surface  24  to accommodate the central portion  20  of the second elongated member  18 , as described below. In this regard, a cavity is effectively defined to receive the central portion  20  of the second elongated portion  18 . 
         [0045]    As seen most clearly in  FIG. 5B , within both the first arm  28  and the second arm  30  is a center opening or window  40 . The window  40  is defined by the upper wall  32 , the lower wall  34 , the outer wall  36 , and the inner wall  38 . The window  40  reduces the weight of the implant  10  and permits bone ingrowth through the first arm  28  and the second arm  30  to better secure the implant  10  within the spine  12 . 
         [0046]    The upper wall  32  includes an upper face  42  that partially defines an upper contact surface  44 . The lower wall  34  includes a lower face  46  that partially defines a lower contact surface  48 . The upper contact surface  44  and the lower contact surface  48  are preferably convex in shape. Alternatively, the upper and lower contact surfaces  44  and  48  may be flat or conically shaped. 
         [0047]    Both the upper contact surface  44  and the lower contact surface  48  are preferably formed to include a plurality of teeth  50 . The teeth  50  extend towards the central portion  20 . When the implant  10  is in its expanded orientation (as shown in  FIG. 7 , for example), the teeth  50  of the various arms  28  and  30  of the implant  10  are concentrically arranged. Further, as seen most clearly in  FIG. 5A , the teeth  50  are ramped in the direction of expansion of the implant  10  from the closed position to the open position to ease the expansion of the implant  10  and to ease the insertion of the implant  10  within the spine  12 . The ramped teeth  50  function to prevent the implant  10  from migrating and prevent retropulsion from the spine. 
         [0048]    With particular reference to  FIG. 4 ,  FIG. 6 , and  FIG. 7 , the coupling of the first elongated member  16  with the second elongated member  18  will now be described. The first elongated member  16  and the second elongated member  18  are coupled such that the inner surface  22  of the first member  16  and the inner surface  22  of the second member  18  are in contact with each other. Further, the first arm  28  and the second arm  30  of the first elongated member  16  are each positioned between the first arm  28  and the second arm  30  of the second elongated member  18  such that the arms  28  and  30  of the first elongated member  16  alternate with the arms  28  and  30  of the second elongated member  18 . 
         [0049]    The first member  16  and the second member  18  are pivotally coupled to each other for relative movement about a rotation axis R (identified in  FIG. 4 ). The rotation axis R extends through the central portion  20 , generally perpendicular to the upper contact surface  44  and the lower contact surface  48 . This pivotal coupling permits relative rotation of the first member  16  and the second member  18  between the closed position and the open position. The first member  16  and the second member  18  are typically rotated between the closed position and the open position by a surgeon using appropriate operating room instrumentation. 
         [0050]    The elongated members  16  and  18  are illustrated coupled together in the closed position in  FIG. 6 . In the closed position, the first arm  28  of the first elongated member  16  is positioned parallel to and adjacent to the second arm  30  of the second elongated member  18 . Further, the second arm  30  of the first member  16  is positioned parallel to and adjacent to the first arm  28  of the second elongated member  18 . Positioning the arms  28  and  30  of the first elongated member  16  parallel to and adjacent to the arms  28  and  30  of the second elongated member  18  provides the implant  10  with a slim and compact profile that permits the implant  10  to be easily inserted within the spine  12  requiring only a minimal disruption of the vertebrae  14  and the dura (not shown). 
         [0051]    With particular reference to  FIG. 4  and  FIG. 7 , the first elongated member  16  and the second elongated member  18  are shown coupled together in the open position. In the open position the first arm  28  of the first elongated member  16  is positioned apart from and in a non-parallel relationship to the second arm  30  of the second elongated member  18 . Likewise, the second arm  30  of the first member  16  is positioned apart from and in a non-parallel relationship to the first arm  28  of the second elongated member  18 . Generally, in the open position the first member  16  and the second member  18  are rotated such that the arms  28  and  30  of the first member  16  and the arms  28  and  30  of the second member  18  have an overall configuration approximating that of an “X”. This “X” shaped configuration provides the implant  10  with a great deal of strength to support the vertebrae  14  of the spine  12 . 
         [0052]    The first elongated member  16  and the second elongated member  18  each further comprise a pair of protrusions  52  and a pair cooperating of recesses  54 . The protrusions  52  extend from the upper face  42  and the recesses  54  are located within the outer surface  24  of the central portion  20 . The recesses  54  have a sidewall  56  and a retention surface  58  (see  FIG. 5B ). As the first and second elongated members  16  and  18  are rotated from the closed position to the open position, the protrusions  52  rotate within the recesses  54  such that each protrusion  52  contacts both the sidewall  56  and the retention surface  58 . 
         [0053]    As seen most clearly in  FIG. 5A  and  FIG. 7 , cooperation between the protrusions  52  of the first elongated member  16  and the recesses  54  of the second elongated member  18 , as well as cooperation between the protrusions  52  of the second elongated member  18  and the recesses  54  of the first elongated member  16 , ensures that the first elongated member  16  stays coupled to the second elongated member  18  when the implant  10  is in the open position. Specifically, interaction between the protrusions  52  and the retention surface  58  prevents the first member  16  and the second member  18  from becoming vertically separated along the rotational axis R of the implant  10 . 
         [0054]    To secure the implant  10  in the open position, the implant  10  further includes a locking mechanism. The locking mechanism is preferably an active locking mechanism comprised of an arm or detail  60  that extends from the central portion  20  of both the first member  16  and the second member  18 . The detail  60  is flexible, preferably a leaf spring, and can be moved between a neutral position (as shown in  FIG. 5C ) and a collapsed position (as shown in  FIG. 6 ). 
         [0055]    As seen in  FIG. 6 , in the closed position the detail  60  of the second member  18  is resiliently collapsed against the inner wall  38  of the first member  16  (shown in  FIG. 5B ). Likewise, in the closed position the detail  60  of the first member  16  is resiliently collapsed against the inner wall  38  of the second member  18  (not particularly shown). As the first member  16  and the second member  18  are rotated from the closed position to the open position, the details  60  resiliently return from beyond the respective inner walls  38 . 
         [0056]    In the open position the details  60  automatically extend into their neutral positions as the details  60  are no longer restricted by the inner walls  38 . In its neutral position, the detail  60  of the first elongated member  16  abuts an outer surface  62  of the inner wall  38  of the second elongated member  16 . Similarly, the detail  60  of the second elongated member  18  abuts an outer surface  62  of the inner wall  38  of the first elongated member  14  to prevent the implant  10  from returning to its closed position. The implant  10  can only be returned to the closed position if pressure is applied to the details  60  to return them to their collapsed state where they no longer contact the corresponding outer surfaces  62  respectively and can each again recede beneath the inner wall  38  of the opposite elongated member  14  or  16 . 
         [0057]    An exemplary implantation of the implant  10  of the present teachings within the spine  12  will now be described. Before the implant  10  is inserted, the spine  12  must be prepared to receive the implant  10  by the operating surgeon. Preparation of the spine  12  involves making a small incision posteriorly within the dura. The adjacent vertebrae  14  are distracted to return normal spacing and the intervertebral disk is removed. Once the spine  12  has been prepared, the implant  10 , orientated in the closed position, is inserted between the first vertebra  14   a  and the second vertebra  14   b . To insert the implant  10  in the closed position requires only a small incision in the dura matter and only minimal distraction of the spine  12 , thus maintaining the integrity of the vertebrae  14  and permitting the surgeon to make the most efficient use of operating room time. When positioned in the open orientation ( FIG. 2 ), the spinal implant  10  stabilizes the spine  12  and facilitates the fusion of a pair of adjacent vertebrae  14 . 
         [0058]    After the implant  10  is properly installed within the spine  12 , the first member  16  and the second member  18  are rotated from the closed position to the open position so that the implant  10  may provide the required support between the adjacent vertebrae  14 . Rotation of the implant  10  from the closed position is effectuated by the attending surgeon using suitable operating room instrumentation. The implant  10  is maintained in the open position through interaction between the details  60  and the cooperating outer surfaces respectively. 
         [0059]    Rotation of the implant  10  into the open position is facilitated by the ramped teeth  50 , which are ramped in the direction of the expansion of the implant  10  from the closed position to the open position. The ramped teeth  50  also help maintain the implant  10  in the open position. Further, the ramped teeth  50  help maintain the implant  10  in its proper position between the vertebrae  14 . 
         [0060]    Adjacent vertebrae  14  may optionally be supported by multiple implants  10 . The process for inserting multiple implants  10  is substantially identical to the process described above for inserting a single implant  10 , with the exception being that at least one additional implant  10  is inserted between the vertebrae  14  during the insertion process. The use of multiple implants  10  is advantageous as multiple implants  10  provide additional support to the vertebrae  14  to further disperse stress loads. 
         [0061]    The implant  10  may be of various different sizes to properly fit patients having spines  12  and vertebrae  14  of different sizes. The size of the implant  10  may vary in numerous different ways. For example, the first elongated member  16  and the second elongated member  18  may be of various different lengths to support vertebrae  14  of different surface areas. Further, the first elongated member  16 , the second elongated member  18 , and the central portions  20  may be of different heights to support vertebrae  14  that are spaced at varying distances from each other. 
         [0062]    The implant  10 , may be manufactured from any biocompatible material that is suitably rigid to withstand the pressures exerted upon the implant  10  by the vertebrae  14 . Examples of materials that may be used to manufacture the implant  10  include, but are not limited to, titanium and allograft bone. As shown throughout the drawings, the first member  16 , and the second member  18 , each preferably comprise a single unitary structure. 
         [0063]    Referring to  FIGS. 8-14 , another exemplary spinal implant  100  according to the present teachings is illustrated. Elements of implant  100  that correspond in some fashion to elements of implant  10  are designated with the same reference numbers, but prefaced by the numeral  1 . Detailed repetitious description of elements or features that can be identical in implants  10  and  100  is omitted. 
         [0064]    Referring to  FIGS. 8-10 , the implant  100  includes first and second elongated members  116 ,  118  pivotably connected to each other by a pivot member  210  for relative rotation therebetween about a pivot axis R, such that the implant  100  can be expanded from a closed orientation illustrated in  FIG. 9  to an open (expanded) orientation illustrated in  FIG. 10 . In the closed orientation, the first and second members  116 ,  118  are substantially parallel, while in the open orientation the first and second members  116 ,  118  are at an angle defining substantially an “X” shape. The first elongated member  116  has first and second arms  128 ,  130  that interconnect with a central portion  120 . The second elongated member has first and second arms  128 ′,  130 ′ that interconnect with a central portion  120 ′. Recesses  172 ,  172 ′ are defined respectively in the central portions  120 ,  120 ′ of the first and second members  116 ,  118 , such that the recesses  172 ,  172 ′ are offset in the closed orientation, and aligned in open orientation. 
         [0065]    Referring to  FIGS. 11A-C  and  14 A-B, the first arm  128  of the first elongated member  116 , or, more generally, at least one of the arms,  128 ,  130 ,  128 ′,  130 ′, can be adapted to define an internally threaded bore  164  for accommodating a locking member  160  therein. The locking member  160  can be a fastener, such as an externally threaded screw, as illustrated in  FIGS. 13A and 13B , and can be threadably engaged with the internal threads of the bore  164 . 
         [0066]    The locking member  160  can include an end portion or boss  170  and a head  172  with an engagement formation or surface  174 . The locking member  160  can be deployed to secure the implant  100  in the open orientation by engaging the first arm  128  of the first member  116  with the central portion  120 ′ of the second member  118 , when the implant  100  is in the open orientation. In the open orientation, the recesses  172 ,  172 ′ in the central portions  120 ,  120 ′ of the first and second members  116 ,  118  become aligned and define a hole  168  that receives an end portion  170  of the locking member  160 . The locking member  160  can be deployed using a driver or similar tool that is inserted into the internal bore  164  of the first arm  128  and operated to engage the engagement formation  174  and to rotate the locking member  160 , thereby causing the locking member  160  to advance into the hole  128  and positively secure the implant  100  in the open orientation. 
         [0067]    Referring to  FIGS. 14A  and B, the pivot member  210  can be, for example, a fastener, such as screw or bolt, that engages openings  117 ,  119  in the respective central portions  120 ,  120 ′ of the first and second members  116 ,  118  for relative rotation therebetween. The pivot member  210  can include a head  212  and a stepped shank  214 , which is received into the central openings  117 ,  119  of the central portions  120 ,  120 ′ of the first and second members  116 ,  118 . The pivot member  210  can include a head formation  216  for receiving a tool for rotating the first and second members from the closed orientation to the open orientation after implantation. 
         [0068]    Referring to  FIGS. 11B and 12B , all except the first arm  128  of the first member  116  can include openings or windows  140  to promote ingrowth. The second arms  130 ,  130 ′ of the first and second members  116 ,  118  can be identical. The first arm  128 ′ of the first member  116  can be wider in cross-section than the first arm  128 ′ of the second member  118  for accommodating the internal bore  164  that receives the locking member  160 , although the implant  100  in the closed orientation can have substantially constant total W, as shown in  FIG. 9 . The threaded bore  164  of the first arm  128  can receive an instrument for inserting/deploying the implant  100 . The top and bottom surfaces of the arms  128 ,  130 ,  128 ′,  130 ′ can include a plurality of teeth  150  for engaging adjacent vertebrae as described above in connection with exemplary implant  10 . 
         [0069]    Similarly to implant  10 , implant  100  can be inserted in the spine  12  in the closed orientation through a small incision. After implantation, the first and second members  116 ,  117  are pivoted about the central axis R relative to each other to bring the implant  100  to the open orientation. The implant  100  is then positively locked in the open orientation by deploying the locking member  160  using a suitable driver or tool. 
         [0070]    It will be appreciated that implants  10  and  100  are merely exemplary illustrations, such that various features of exemplary implant  10  can be incorporated in exemplary implant  100 , and vice versa. 
         [0071]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the present teachings are intended to be within the scope of the present teachings. Such variations are not to be regarded as a departure from the spirit and scope of the present teachings.