Abstract:
Multiple implants and methods for the minimally invasive treatment of spinal stenosis are disclosed. A spinal implant device includes a spacer region and an attachment region. The spacer region is adapted to be positioned between first and second spinous processes of first and second vertebral bodies to limit movement of the first spinous process and the second spinous process toward one another. The attachment region attaches to the first spinous process via a fastener that extends substantially along a long axis of the spinous process.

Description:
REFERENCE TO PRIORITY DOCUMENTS 
       [0001]    This application is a continuation of and claims priority to co-pending U.S. patent application Ser. No. 11/881,584 issuing as U.S. Pat. No. 8,303,630 on Nov. 6, 2012, which is incorporated herein by reference in its entirety, and which claims priority of the following co-pending U.S. Provisional Patent Applications: (1) U.S. Provisional Patent Application Ser. No. 60/834,209, filed Jul. 27, 2006; (2) U.S. Provisional Patent Application Ser. No. 60/834,003, filed Jul. 28, 2006; (3) U.S. Provisional Patent Application Ser. No. 60/860,942, filed Nov. 24, 2006. Priority of the aforementioned filing dates is hereby claimed. The disclosures of the Non-provisional and Provisional Patent Applications are hereby incorporated by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    The present disclosure is related to orthopedic devices implanted between skeletal segments. The implanted devices are used to adjust and maintain the spatial relationship(s) of adjacent bones. Depending on the implant design, the motion between the skeletal segments may be returned to normal, increased, modified, limited or completely immobilized. 
         [0003]    Progressive constriction of the central canal within the spinal column is a predictable consequence of aging. As the spinal canal narrows, the nerve elements that reside within it become progressively more crowded. Eventually, the canal dimensions become sufficiently small so as to significantly compress the nerve elements and produce pain, weakness, sensory changes, clumsiness and other manifestation of nervous system dysfunction. 
         [0004]    Constriction of the canal within the lumbar spine is termed lumbar stenosis. This condition is very common in the elderly and causes a significant proportion of the low back pain, lower extremity pain, lower extremity weakness, limitation of mobility and the high disability rates that afflict this age group. 
         [0005]    The traditional treatment for this condition has been laminectomy, which is the surgical removal of the lamina portion of bone and the adjacent ligamentous structures that constrict the spinal canal. Despite advances in surgical technique, spinal decompression surgery can be an extensive operation with risks of complication from the actual surgical procedure and the general anesthetic that is required to perform it. Since many of these elderly patients are in frail health, the risk of developing significant peri-operative medical problems remains high. In addition, the surgical resection of spinal structures may relieve the neural compression but lead to spinal instability in a substantial minority of patients. That is, removal of the spinal elements that compress the nerves may weaken the vertebral column and lead to spinal instability and vertebral mal-alignment. With instability, the vertebrae will move in an abnormal fashion relative to one another and produce pain, nerve re-impingement, weakness and disability. Further, re-stabilization of the spinal column requires additional and even more extensive surgery. Because of these issues, elderly patients with lumbar stenosis must often choose between living the remaining years in significant pain or enduring the potential life-threatening complications of open spinal decompression surgery. 
         [0006]    Recently, lumbar stenosis has been treated by the distraction—instead of resection—of those tissues that compress the spinal canal. In this approach, an implantable device is placed between the spinous processes of the vertebral bodies at the stenotic level in order to limit the extent of bone contact during spinal extension. Since encroachment upon the nerve elements occurs most commonly and severely in extension, this treatment strategy produces an effective increase in the size of the spinal canal by limiting the amount of spinal extension. In effect, the distraction of the spinous processes changes the local bony anatomy and decompress the nerves at the distracted level by placing the spinal segment into slight flexion. 
         [0007]    Unfortunately, the placement of a conventional inter-spinous implant requires surgical exposure of the posterior and lateral aspects of the spinous processes as well as the posterior aspect of the spinal column. Since these operations still carry a significant risk of peri-operative complications in the elderly, there remains a need in the field for devices and methods that reduce the scope of the surgical procedure and its inherent risks. 
       SUMMARY 
       [0008]    This application discloses a series of novel devices and methods for the minimally invasive treatment of spinal stenosis. In an embodiment, distraction members are percutaneously placed into the space between two adjacent spinous processes. The distraction members are attached to a distraction platform and the platform is configured to adjustably distract and set the distance between the distraction members. With actuation of the distraction platform, the outer surfaces of the distraction members forcibly abut the spinous processes and distract the adjacent spinous processes away from one another. The inner surface of at least one distraction members forms a guide channel that is adapted to guide and position an orthopedic implant into the distracted interspinous space. The implant is adapted to maintain the increased distance between the spinous processes after removal of the distraction members and distraction platform. 
         [0009]    In an alternative embodiment, distraction members are percutaneously placed into the tissues adjacent to the spinous processes and used to introduce an implant delivery device. The implant is attached to and contained within the delivery device. With actuation, the implant is rotated into the inter-spinous space and used to forcibly separate the spinous processes. 
         [0010]    In another embodiment, a pin or similar anchor is placed at least partially through a first spinous process and positioned so that the distal end abuts a surface of an adjacent spinous process. The pin is used to separate the two adjacent spinous processes and maintain the increased distance between them. In another embodiment, a pin is placed into the base of the superior facet of the lower vertebra and used to limit vertebral extension by preventing the downward travel of the inferior facet of the superior vertebra. Preferably, the pin has a hollow central cavity that accommodates a bone graft or a bone graft substitute and is adapted to fuse with the surrounding bone at the insertion site of the inferior vertebra. Additional embodiments are disclosed that modify the facet joint anatomy and provide direct nerve decompression and/or a limit of vertebral extension. 
         [0011]    In another embodiment, an implant is attached onto at least one vertebral bone and adapted to limit the motion of the attached bone relative to an adjacent vertebra. The motion pathway permitted by the implanted is substantially curvilinear and has at least one center of rotation near the natural Instantaneous Axis of Rotation between adjacent vertebrae. Further, the implant permits greater relative motion between the adjacent vertebrae in flexion than it does in extension. 
         [0012]    In one aspect, there is disclosed an orthopedic device, comprising a first member adapted to be attached onto at least one vertebra arid adapted to limit the motion of the attached vertebra relative to an adjacent vertebra, wherein the first member defines a motion pathway of the attached vertebra, wherein the motion pathway is substantially curvilinear and has at least one center of rotation near a natural instantaneous axis of rotation between the attached vertebra and the adjacent vertebrae and, wherein the first member provides limited relative motion between two vertebrae such that the relative motion is greater in flexion than it is in extension. 
         [0013]    In another aspect, there is disclosed a method for the treatment of spinal stenosis in which an orthopedic implant is introduced into a space between the spinous processes of two adjacent vertebras using a minimally invasive surgical technique, comprising: placing two extension members into the space between two adjacent spinous processes of adjacent vertebrae, wherein the extension members are coupled to a distraction platform device capable of adjusting a distance between the extension members; using the distraction platform to separate the extension members, wherein the outer surface of each extension member is adapted to abut a spinous process of each adjacent vertebra so that separation of the extension members by the platform produces an increase in the distance between the adjacent spinous processes, wherein an inner surface of at least one extension members forms a guide channel that is adapted to guide and position an orthopedic implant into the distracted inter-spinous space; placing an orthopedic implant into the space between the two adjacent spinous processes, wherein the implant is adapted to maintain the increase in distance between the adjacent spinous processes after removal of the extension members; and removing the extension members and the distraction platform. 
         [0014]    In another aspect, there is disclosed a method for the treatment of spinal stenosis in which an orthopedic implant is introduced into the space between the spinous processes of two adjacent vertebrae using a minimally invasive surgical technique, comprising: positioning two extension members adjacent to, but not into, an inter-spinous space between two adjacent spinous processes, wherein the extension members are coupled to a distraction platform device capable of setting a distance between the extension members; using the distraction platform to separate the extension members, wherein the outer surface of each extension member is adapted to separate tissue adjacent to the inter-spinous space, wherein an inner surface of at least one of the extension members forms a guide channel that is adapted to guide and position an implant delivery device into the tissue adjacent to the inter-spinous space, wherein the implant is adapted to be attached onto the delivery device and be at least partially contained therein, wherein the implant delivery device is adapted to rotate the attached implant about a center point that is substantially contained within the delivery device and through an angle range of 45 to 135 degrees; deploying the implant delivery device onto the extension members, wherein the implant delivery device has an attached orthopedic implant; placing the attached orthopedic implant into the space between the two adjacent spinous processes, wherein the implant is adapted to maintain a distance between the spinous processes after removal of the extension members; and removing the delivery device, extension members and the distraction platform. 
         [0015]    In another aspect, there is disclosed a method for the treatment of spinal stenosis, comprising: placing a body of a pin at least partially through a first spinous process such that one end of the pin is positioned to abut a surface of a second, adjacent spinous process that faces the first spinous process; and using the pin to set and maintain a distracted space between the spinous processes. 
         [0016]    In yet another aspect, an orthopedic device is disclosed. In one embodiment, the device comprises a first member configured to attach onto at least one first vertebra and limit motion of the first vertebra relative to a second, adjacent vertebra. The first member defines a substantially curvilinear motion pathway of the first vertebra having at least one center of rotation near a natural instantaneous axis of rotation between the first vertebra and the second vertebra. The first member is configured to provide limited relative motion between the first vertebra and the second vertebra such that the relative motion is greater in flexion than it is in extension. 
         [0017]    In another aspect, an assembly for placement or an orthopedic implant within a target inter-spinous space of a spinal column is disclosed. In one embodiment, the assembly comprises: (i) an implant placement device comprising: at least a first extension member and a second extension member each of the first and second extension members comprising an elongated segment configured to extend from a proximal aspect to a distal aspect and each of the first and second extension members configured to be positioned within the target inter-spinous space at the distal aspect thereof, and a distraction mechanism configured to connect to the proximal aspect of each of the first and the second extension members, and to forcibly move the first extension member relative to the second extension member the movement configured to produce at least some expansion of the target inter-spinous space, (ii) a guide channel formed at least in part by a bore configured to extend from a proximal opening to distal opening in between the first and second extension members, and (ii) an orthopedic implant configured to be advanced at least partially through the guide channel and be positioned within the target inter-spinous space. The first and second extension members are removed from the target inter-spinous space, yet the orthopedic implant remains positioned within the inter-spinous space to maintain first and second vertebral bones of the spinal column separated by a desired distance. 
         [0018]    In another embodiment, the assembly comprises: (i) an implant placement device comprising: at least a first extension member and a second extension member each of the first and second extension members comprising an elongated segment configured to extend from a proximal aspect to a distal aspect and each of the first and second extension members configured to be positioned within the target inter-spinous space at the distal aspect thereof, and a distraction mechanism configured to connect to the proximal aspect of each of the first and the second extension members, and to forcibly move the first extension member relative to the second extension member the movement configured to produce at least some expansion of the target inter-spinous space, the first and second extension members thereby creating a guide channel therebetween, (ii) an elongated member configured to be slidably positioned within the guide channel during advancement of the first and second extension members towards the target inter-spinous space, the elongated member being shaped to separate tissues ahead of the advancing first and second extension members, and (iii) an orthopedic implant configured to be advanced at least partially through the guide channel and be positioned within the target inter-spinous space. The elongated member is removed prior to advancement of the orthopedic implant through the guide channel. The first and second extension members are removed from the target inter-spinous space after the advancement of the orthopedic implant. 
         [0019]    The implants and methods described permit treatment of spinal stenosis through a minimally invasive surgical procedure. Other features and advantages will be apparent from the following description of various embodiments, which illustrate, by way of example, the principles of the disclosed devices and methods. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  shows a perspective view of an installer device that is adapted to position an implant in the inter-spinous space between two vertebras. 
           [0021]      FIG. 2  shows the installer device in a distracted state. 
           [0022]      FIG. 3  shows the installer device with an implant at the distal region of the installer arms. 
           [0023]      FIG. 4  illustrates an exemplary implant placed within the inter-spinous space. 
           [0024]      FIGS. 5A and 5B  show perspective and cross-sectional views of an implant, respectively. 
           [0025]      FIGS. 6A and 6B  show another embodiment of an installer device without and with an exemplary imp/ant, respectively. 
           [0026]      FIGS. 7  A and  7 B show prospective and cross-sectional views of an exemplary implant in the un-deployed state. 
           [0027]      FIGS. 8A and 8B  show prospective and cross-sectional views of an exemplary implant in the deployed state. 
           [0028]      FIG. 9A  shows another embodiment of an installer device and an implant delivery instrument. 
           [0029]      FIG. 9B  shows perspective views of an implant delivery instrument. 
           [0030]      FIG. 10  shows the delivery instrument after actuation such that an implant has rotated to a deployment position. 
           [0031]      FIG. 11  shows the linkage mechanism of the implant delivery instrument. 
           [0032]      FIG. 12  shows the delivery instrument coupled to the installer device prior to deployment of the implant. 
           [0033]      FIG. 13  shows the implant in the inter-spinous space after deployment with the delivery instrument removed. 
           [0034]      FIG. 14A  shows another embodiment of an implant. 
           [0035]      FIG. 14B  shows an alternative application of the implant. 
           [0036]      FIG. 15  shows an implant positioned in a inter-spinous space with a fixation screw anchoring the implant in place. 
           [0037]      FIGS. 16 and 17  show perspective views of a device that is configured for placement between the spinous processes of two adjacent vertebras. 
           [0038]      FIGS. 18 and 19  show exploded views of the device. 
           [0039]      FIG. 20  shows a side, cross-sectional view of the device mounted to a pair of vertebrae. 
           [0040]      FIG. 21  shows a side, cross-sectional view of the device mounted to a pair of vertebrae. 
           [0041]      FIG. 22  shows perspective views of another embodiment in the disassembled state. 
           [0042]      FIG. 23  shows additional views of the assembled implant of  FIG. 22 . 
           [0043]      FIG. 24  shows the implant of  FIG. 22  mounted on the sacrum. 
           [0044]      FIG. 25  illustrates an oblique view of the mounted implant of  FIG. 24 . 
           [0045]      FIG. 26  shows an additional embodiment. 
           [0046]      FIGS. 27A  and B show the implant of  FIG. 26  placed into the spinal column. 
           [0047]      FIG. 28A  shows an additional embodiment of an orthopedic implant. 
           [0048]      FIG. 28B  shows an additional embodiment of an orthopedic implant. 
           [0049]      FIG. 29A  shows a lateral view of the vertebral bodies while  FIG. 29B  shows the implant in place. 
           [0050]      FIGS. 30A and 30B  show an additional embodiment of an implant. 
           [0051]      FIG. 31  shows perspective views of the implant. 
           [0052]      FIG. 32  shows the implant of  FIG. 31  placed into the spinal column. 
       
    
    
     DETAILED DESCRIPTION 
       [0053]      FIG. 1  shows a perspective view of an installer device  1605  that is adapted to position an orthopedic implant in the inter-spinous space between the spinous processes of two adjacent vertebras. For clarity of illustration, the vertebral bodies are represented schematically and those skilled in the art will appreciate that actual vertebral bodies include anatomical details not shown in  FIG. 1 . The device  1605  includes a platform  1610  having an actuator  1615  that can be used to separate a pair of distraction arms  1620   a  and  1620   b.  The platform member  1610  may include a scale for measuring the distraction distance or the distraction force. The scale can display the measured distance in a recognized physical unit or as an arbitrary designation (such as, for example, A, B, C, etc.) that is used for implant selection. 
         [0054]    Each distraction arm  1620  has a semi-circular inner surface so that, in the non-distracted state, the arms  1620  collectively form an interior circular conduit. A curvilinear trocar with sharpened distal end  1625   b  and discoid proximal member  1625   a  is positioned through the circular conduit formed by arms  1620 . Discoid proximal member  1625   a  has locking tabs on its inferior surface that interact with complimentary tabs  1622  of arms  1620  and lock the trocar to the distraction arms. The sharpened end  1625   b  emerges from the distal end of arms  1620  and, at the time of device insertion, end  1625   b  divides the skin and soft tissue ahead of advancing arms  1620 . Preferably, the distraction arms  1620  are positioned into the inter-spinous space at the stenotic spinal level under x-ray guidance. The trocar is removed and actuator  1615  is rotated to separate the distraction arms and apply a distraction force upon the spinous processes of the two adjacent vertebras. 
         [0055]      FIG. 2  shows the device  1605  in a distracted state. With rotation of actuator  1615 , each distraction arm  1620  is forcibly driven into the spinous process of the adjacent vertebral bone producing distraction of the inter-spinous space. In an embodiment, arms  1620  are curved, although the arms can be also straight or partially curved. A pathway is formed between the separated arms  1620  through which an implant can be driven into the inter-spinous space. The size of the needed implant is given by reading the scale along platform member  1610 .  FIG. 3  shows the device  1605  with an exemplary implant  1805  positioned at the distal region of the arms  1620 . The implant  1805  is inserted into the proximal aspect of the pathway and advanced distally until it rests within the inter-spinous space. The implant is held in place by a placement handle (not shown) and the distraction arms and platform are then removed. Finally, the implant is distracted by actuating the placement handle. The implant is shown in  FIG. 4  resting within the inter-spinous space. 
         [0056]      FIGS. 5A and 5B  illustrate perspective and cross-sectional views, respectively, of the implant  1805 . The implant  1805  includes a first piece  1905  and a second piece  1910  that are movably attached to one another. A pair of wedge-shaped bearing members  1915  form a bearing surface between the two pieces  1905  and  1910 . In addition, the pieces  1905  have respective shoulders  1925  that abut one another to guide and limit relative movement there between. The bearing members  1915  and the shoulders  1925  guide movement between the two pieces  1905  and  1910  such that the pieces can move and increase the dimensions of the implant  1805 . The implant can be initially delivered into the inter-spinous space in a state of reduces size and then transitioned to the state of enlarged size after it is positioned within the inter-spinous space. 
         [0057]      FIGS. 6A and 6B  show another embodiment of an installer device  2105 . The device  2105  includes a platform  2110  having an actuator  2115  that can be used to separate a pair of distractor arms  2120 . In this embodiment, the distractor arms are straight. As discussed below, the arms  2110  can be used as a guide for positioning an implant  2205  into the inter-spinous space ( FIG. 6B )  FIGS. 7A and 78  show perspective and cross-sectional views of an exemplary implant  2205  in the un-deployed state. Implant  2205  contains at least longitudinal tract  2207  that interacts with the inner aspect of arms  2210 . The implant  2205  includes first and second members  2210  and  2215  that are movably attached. When the members  2210  and  2215  are moved toward one another, one or more pivotably mounted arias  2220  are moved to a position that extends outwardly from the implant  2205 . The arms can be moved to the extended position after implantation in the inter-spinous space. 
         [0058]      FIGS. 8A and 8B  show perspective and cross-sectional views of an exemplary implant  2205  in the deployed state. Note that the distal arms  2220  have a bearing articulation with the deploying portion of member  2210  while the proximal arms  2220  have a deformable base that is integrally attached to member  2210 . Either mechanism may be employed on any of mounted arms  2220 . 
         [0059]      FIG. 9A  illustrates an additional embodiment. A distraction platform with straight distraction arms is percutaneously positioned under x-ray guidance. The arms are placed lateral to the inter-spinous space. A delivery instrument  2303  is attached to the implant and used to place the implant into the inter-spinous space.  FIG. 9B  shows perspective views of the delivery instrument  2302 . In the illustrated embodiment, the instrument  2302  includes a two-piece handle having a first arm  2310  and a second arm  2320  that is movably mounted relative to the first arm  231   b  in a pivot or trigger fashion. The first and second arms are ergonomically arranged such that an operator can grasp the arms using a single hand. For example, the first arm  2310  is sized and shaped to support an operator&#39;s palm and thumb such as on a thumb grip  2322 . Likewise, the second arm  320  can be grasped by the operator&#39;s fingers to pull the second arm  2320  toward the first au u  2310  and actuate the instrument  2302 . A biasing member  2325  is interposed between the first and second arms. It should be appreciated that the instrument can be actuated with other mechanisms and need not use a two-piece handle configuration. 
         [0060]    With reference still to  FIG. 9B , a housing  2311  extends outward from the handle. The housing  2311  is sized and shaped to contain the implant  2205 . In the illustrated embodiment, the housing  2311  has an elongated, tube-like shape and is partially hollow so as to contain the implant  2205  as well as an internal actuation mechanism that expels the implant from the housing. A slot  2330  is located at or near a distal end of the housing  2311 . The slot communicates with an internal cavity in the housing  2311  in which the implant  2205  resides. The slot is sufficiently long and wide such that the implant  2205  can pass through the slot during deployment of the implant.  FIG. 10  illustrates the internal mechanism of the placement device.  FIG. 11  shows the instrument  2302  after actuation such that the implant  2205  has rotated (as represented by the arrow R) to a deployment position. 
         [0061]      FIG. 12  shows the delivery instrument  2302  coupled to the installer device  2105  prior to deployment of the implant  2205 . The elongated housing  2311  is placed in between the distractor arms  2120  such that a distal end of the housing  2311  is lateral to the inter-spinous space between the vertebrae. The delivery instrument is then actuated to rotate the implant  2205  into the inter-spinous space.  FIG. 13  shows the implant  2205  in the inter-spinous space after removal of delivery instrument  2302 . 
         [0062]      FIG. 14A  shows another embodiment of an implant. In this embodiment, the implant comprises a curved pin or screw  2805  that is sized and shaped to be passed through the spinous process of a vertebrae. The screw  2805  has a curved contour that permits a portion of the screw to extend through the spinous process with a distal region of the screw extending through the inter-spinous space. A proximal end of the screw  2805  is positioned at the exterior of the spinous process. The distal end of the screw  2805  abuts a surface of the spinous process of the adjacent vertebra. The pin may be at least partially comprised of a bone graft or bone graft substitute so as to fuse with the spinous process in which it is embedded. The pin maybe embedded in a first spinous process and abut a second spinous process, as shown in  FIG. 14A , or it may be alternatively embedded in the second spinous process and abut the first spinous process, as shown in  FIG. 14B . 
         [0063]      FIG. 15  shows an implant positioned in an inter-spinous space and affixed to the spine with a fixation screw  3010 . The implant  3005  is positioned within the disc space such that outer surface of the implant abuts adjacent vertebrae. A fixation screw  3010  extends through the spinous process and into the implant  3005 . The screw may be at least partially comprised of a bone graft or bone graft substitute so as to fuse with the spinous process in which it is embedded. If the interior aspect of implant  3005  is also at least partially comprised of a bone graft or bone graft substitute, then screw  3010  can fuse with both the spinous process and implant  3005 . This provides a bone bridge between the implant  3005  and the spinous process without direct fusion of the implant onto the spinous process. 
         [0064]      FIGS. 16 and 17  show perspective views of a device  105  that is configured for placement between the spinous processes of two adjacent vertebral bodies. The device  105  includes a spacer region or central region  110  that is sized and shaped to fit between the spinous processes of the two adjacent vertebral bodies. The device  105  further includes a pair of attachment members  115  that are adapted to attach and anchor onto the spinous process of at least one of the vertebral bodies. The central region  110  can have a variety of shapes and sizes for placement between the spinous processes. The attachment members  115  can also have various sizes and shapes for attachment to the spinous processes. 
         [0065]      FIGS. 18 and 19  show exploded views of the device  105 . The device  105  includes attachment members  115  that are adapted to attach and anchor onto the spinous process of at least one of the vertebral bodies. Each attachment member  115  has a pair of downwardly-extending aims  305  that are sized to receive a spinous process therebetween. An upper portion of the attachment member  115  is sized and shaped to sit over the spinous process. The upper portion has a borehole that is sized to receive a threaded screw  410  during implantation: A locking mechanism  415  can be within the attachment, member  115  to serves to prevent unwanted movement and/or back out of the screw  410 . While illustrated as a locking cam, the locking mechanism  415  may include any locking mechanism known in the art. 
         [0066]    A first bearing member  425  has a rounded articulating surface that is adapted to interact with a complimentary articulating surface on a second bearing member  430 . The member  425  is sized and shaped to be received in a cavity inside the member  430  so as to permit at least some rotational movement therebetween. A third bearing member  440  is at least partially dome-shaped and is adapted to couple to the members  425  and  430 . In particular, the member  440  mates with the member  430  such as through a threaded engagement. 
         [0067]    With reference still to  FIGS. 18 and 19 , member  430  includes a protrusion  445  that is sized and shaped to mate with an indentation  450  in the member  425 . In the assembled device, the interaction of protrusion  445  and indentation  450  serves to limit the amount of rotation and lateral flexion between the members  425  and  430 . 
         [0068]      FIG. 20  shows a side, cross-sectional views of the device mounted to a pair of vertebrae. The members  115  can be coupled to one another by mating the member  425  beneath the member  430  such that articulating surfaces abut one another and permit rotational movement therebetween. The member  440  is positioned below the member  430  and secured thereto such as in a threaded relationship. This retains the device in the assembled state. 
         [0069]      FIG. 21  shows an enlarged, cross-sectional view of the device in the assembled state and mounted between vertebrae. The member  425  has a rounded surface  605 . The surface  605  interacts with a complimentary rounded surface  610  on the member  430 . A space  630  is formed when the member  440  is secured onto the member  430 . The member  425  resides within the space  630  in the assembled device. The space  630  permits a certain amount of “play” between the articulation of members  430  and  425 . In an embodiment, the space  630  contains a malleable member that keeps members  425  and  430  in a preferred, neutral position and acts to return these members to the neutral position when they move away from it. 
         [0070]    In addition, the curvilinear surfaces  605  and  610  define a spherical path of motion that is centered at Point A (shown in  FIG. 20 ). That is, the surfaces  605  and  610  can move relative to one another along a pathway that is curvilinear or spherical. Alternative motion paths that are non-spherical may be alternatively made. In specific, a configuration that is similar, but not identical, to a hyperbolic paraboloid may be incorporated within the articulating surface. Moreover, the interaction of the protrusion  445  and indentation  450  allows a variable degree of rotational movements of one vertebral body relative to the other. The extent of rotation and lateral flexion permitted is dependant on the degree of flexion of the vertebral bodies. That is, with the vertebral bodies in flexion, the extent of rotation and lateral flexion permitted by the device is greater that amount of 14 rotation and lateral flexion that is permitted when the vertebral bodies are in extension. This feature reproduces the natural motion characteristics between the vertebral bodies. 
         [0071]      FIG. 22  illustrates perspective views of device  3305  in the disassembled state.  FIG. 23  shows sectional views of the assembled device  3305 . Threaded wall  3320  surrounds central cavity  3315  and contains multiple full thickness bore holes  3325 . The distal aspect of wall  3320  contains interior threads  3340  that couple with complimentary threads  3520  of distal member  3510 . The central cavity  3315  is adapted to house a bone graft or bone graft substitute and permit fusion between the bone graft within cavity  3315  and the vertebral bone surrounding the outer aspect of device  3305 . After placement of bone graft material within cavity  3315 , distal member  3510  is screwed onto device  3305 . The fusion forms across bore holes  3325 . 
         [0072]    The proximal aspect of device  3305  contains hexagonal cut out  3360 . Cut out  3360  is adapted to accept a hex screw driver and the latter is used to drive device  3305  into bone. The proximal aspect of device  3305  contains at least one flap  3605  that is movably attached to device  3305 . When a force is applied to the proximal aspect of device  3305 , flap  3605  transiently and reversibly moves towards the center line of the device. In this way, flap  3605  functions as a malleable member and imparts a spring-like quality to the proximal aspect of device  3305 . 
         [0073]    In use, the central cavity  3315  is filed with a bone graft and distal member  3510  is threaded onto device  3305 . Once assembled, distal member  3510  is rigidly attached to  3305 . Under x-ray guidance, the device is percutaneously driven into the base of the superior articulating surface of the lower vertebral body and abuts the inferior surface of the inferior articulating surface of the superior vertebra. Preferably, a single device is used on each side of the vertebral midline, so that two devices  3305  are used at each stenotic level. The devices are shown attached to bone in  FIGS. 24 and 25 . As illustrated, each device  3305  limits the downward travel of the inferior articulating surface of the superior vertebra and limits the degree of extension at that spinal level. With time the bone contained within cavity  3315  will fuse with the adjacent bone and rigidly anchor the device to the vertebra. Because of the fusion the device does not to be anchored into the pedicle portion of the vertebra and it can be short in length. 
         [0074]      FIG. 26  illustrates device  3705 . The device is intended to reside within the facet joint and be anchored onto one, but not both, of the adjacent vertebras. The device may be affixed onto the vertebral bone using pins and a bone screw or the device may be at least partially comprised of a bone graft or bone graft substitute so as to fuse onto the adjacent bone. The device may be coated/made with osteo-conductive (such as deminerized bone matrix, hydroxyapatite, and the like) and/or osteo-inductive (such as Transforming Growth Factor “TGF-B,” Platelet-Derived Growth Factor “PDGF,” BoneMorphogenic Protein “BMP,” and the like) bio-active materials that promote bone formation. Further, one or more surfaces may be made with a porous ingrowth surface (such as titanium wire mesh, plasma-sprayed titanium, tantalum, Porous CoCr, and the like), provided with a bioactive coating, made using tantalum, and/or helical rosette carbon nanotubes (or other carbon nanotube-based coating) in order to promote bone in-growth or establish a mineralized connection between the bone and the implant. 
         [0075]    The device is shown anchored to bone in  FIGS. 27A and 27B . It is intended to at least partially replace the function of a natural facet joint that been at least partially removed at surgery. It may alternatively be used within an intact but degenerated facet joint to reestablish a functional articulation.  FIG. 28A  shows an additional embodiment of an orthopedic implant  705  positioned on two vertebral bodies of the lumbar spine. The implant  705  is attached onto the superior articulating surface and lamina of the lower vertebra and functions to stop the downward movement of the inferior articulating surface of the upper vertebral body. In this way, the device stops the extension of the two vertebral bodies and keeps them in relative flexion. The device can include contains one or more bore holes through which one or more screws are passed and anchored onto the underlying bone. As shown, the inferior aspect of the lamia of the upper vertebra is preferably removed (laminotomy) to decompress the nerve elements prior to device placement. 
         [0076]      FIG. 28B  shows an additional embodiment of an orthopedic implant  805  positioned on two vertebral bodies of the lumbar spine. The implant  805  is attached onto the superior articulating surface and lamina of the lower vertebra and transverses the facet joint between the two vertebral bodies. The superior surface of the device abuts the inferior aspect of the pedicle of the upper vertebral body. The implant functions to stop the extension of the two vertebral bodies and keeps them in relative flexion. The implant  805  can contain one or more bore holes through which screws are passed and anchored onto the underlying bone.  FIG. 29A  shows a lateral view of the vertebral bodies and  FIG. 29B  shows the implant  805  in place. Note that implant placement will necessarily place the lower articulating surface of the upper vertebral body more posteriorly and at least partially realign an anterior spondylolisthesis. 
         [0077]      FIGS. 30A and 30B  show an additional embodiment of an implant  1305 . In an embodiment, the implant  1305  is a “c” shaped implant.  FIG. 31  shows perspective views of the implant  1305 . The implant  1305  functions to separate the top of the superior articular surface of the inferior body from the inferior aspect of the pedicle of the upper vertebral body. The implant  1305  has a size and shape such that the opening of the “C” can be positioned over at least a portion of the vertebral body. In an embodiment, a separate attachment device is not used to attach the implant  1305  to bone. In another embodiment, the implant  1305  contain one or more bore holes through which screws are passed and anchored onto the underlying bone.  FIG. 32  shows the implant  1305  positioned on the bone. 
         [0078]    The disclosed devices or any of their components can be made of any biologically adaptable or compatible materials. Materials considered acceptable for biological implantation are well known and include, but are not limited to, stainless steel, titanium, tantalum, combination metallic alloys, various plastics, resins, ceramics, biologically absorbable materials and the like. Any components may be also coated/made with osteo-conductive (such as deminerized bone matrix, hydroxyapatite, and the like) and/or osteo-inductive (such as Transforming Growth Factor “TGF-B,” Platelet-Derived Growth Factor “PDGF,” Bone-Morphogenic Protein “BMP,” and the like) bio-active materials that promote bone formation. Further, any surface may be made with a porous ingrowth surface (such as titanium wire mesh, plasma-sprayed titanium, tantalum, porous CoCr, and the like), provided with a bioactive coating, made using tantalum, and/or helical rosette carbon nanotubes (or other carbon nanotube-based coating) in order to promote bone in-growth or establish a mineralized connection between the bone and the implant, and reduce the likelihood of implant loosening. Lastly, the system or any of its components can also be entirely or partially made of a shape memory material or other deformable material. 
         [0079]    Although embodiments of various methods and devices are described herein in detail with reference to certain versions, it should be appreciated that other versions, embodiments, methods of use, and combinations thereof are also possible. Therefore the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.