Abstract:
An implantable spacer for placement between adjacent spinous processes is provided. The spacer includes a body and a wing rotatably connected to the body. The wing includes two U-shaped configurations that together define a substantially H-shaped configuration for retaining the spacer between adjacent spinous processes. An actuator assembly is connected to the body and to the wing with the proximal end of the spacer being connectable to a removable driver that is configured to engage the actuator assembly. While connected to the spacer, the driver is rotatable in one direction to deploy the wing from an undeployed to a deployed configuration and in an opposite direction to undeploy the wing. In the deployed configuration, the spacer acts as a space holder opening up the area of the spinal canal, maintaining foraminal height, reducing stress on the facet joints and relieving pain for the patient.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of and is a continuation-in-part of U.S. Provisional Patent Application Ser. No. 60/967,805 entitled “Interspinous spacer” filed on Sep. 7, 2007 which is incorporated herein by reference in its entirety. This application also claims priority to and is a continuation-in-part of U.S. patent application Ser. No. 12/220,427 entitled “Interspinous spacer” filed on Jul. 24, 2008 which is a non-provisional of U.S. Provisional Patent Application Ser. No. 60/961,741 entitled “Insterspinous spacer” and filed on Jul. 24, 2007 and is a continuation-in-part of U.S. patent application Ser. No. 12/217,662 entitled “Interspinous spacer”, filed on Jul. 8, 2008 which is a non-provisional of U.S. Provisional Patent Application No. 60/958,876 entitled “Interspinous spacer” filed on Jul. 9, 2007 and a continuation-in-part of U.S. patent application Ser. No. 12/148,104 entitled “Interspinous spacer” filed on Apr. 16, 2008 which is a non-provisional of U.S. Provisional Patent Application Ser. No. 60/923,971 entitled “Interspinous spacer” filed on Apr. 17, 2007 and U.S. Provisional Patent Application Ser. No. 60/923,841 entitled “Spacer insertion instrument” filed on Apr. 16, 2007, all of which are hereby incorporated by reference in their entireties. This application is also a continuation-in-part of U.S. patent application Ser. No. 11/593,995 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Nov. 7, 2006 which is a continuation-in-part of U.S. patent application Ser. No. 11/582,874 entitled “Minimally invasive tooling for delivery of interspinous spacer” filed on Oct. 18, 2006 which is a continuation-in-part of U.S. patent application Ser. No. 11/314,712 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Dec. 20, 2005 which is a continuation-in-part of U.S. patent application Ser. No. 11/190,496 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Jul. 26, 2005 which is a continuation-in-part of U.S. patent application Ser. No. 11/079,006 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Mar. 10, 2005 which is a continuation-in-part of U.S. patent application Ser. No. 11/052,002 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Feb. 4, 2005 which is a continuation-in-part of U.S. patent application Ser. No. 11/006,502 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Dec. 6, 2004 which is a continuation-in-part of U.S. patent application Ser. No. 10/970,843 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Oct. 20, 2004, all of which are hereby incorporated by reference in their entireties. 
     
    
     FIELD 
       [0002]    The present invention generally relates to medical devices, in particular, implants for placement between adjacent spinous processes of a patient&#39;s spine. 
       BACKGROUND 
       [0003]    With spinal stenosis, the spinal canal narrows and pinches the spinal cord and nerves, causing pain in the back and legs. Typically, with age, a person&#39;s ligaments may thicken, intervertebral discs may deteriorate and facet joints may break down—all contributing to the condition of the spine characterized by a narrowing of the spinal canal. Injury, heredity, arthritis, changes in blood flow and other causes may also contribute to spinal stenosis. 
         [0004]    Doctors have been at the forefront with various treatments of the spine including medications, surgical techniques and implantable devices that alleviate and substantially reduce debilitating pain associated with the back. In one surgical technique, a spacer is implanted between adjacent spinous processes of a patient&#39;s spine. The implanted spacer opens the neural foramen, maintains the desired distance between vertebral body segments, and as a result, reduces impingement of nerves and relieves pain. For suitable candidates, an implantable interspinous spacer may provide significant benefits in terms of pain relief. 
         [0005]    Any surgery is an ordeal. However, the type of device and how it is implanted has an impact. For example, one consideration when performing surgery to implant an interspinous spacer is the size of the incision that is required to allow introduction of the device. Small incisions and minimally invasive techniques are generally preferred as they affect less tissue and result in speedier recovery times. As such, there is a need for interspinous spacers that work well with surgical techniques that are minimally invasive and provide quick, easy and effective solutions for doctors and their patients. The present invention sets forth such a spacer. 
       SUMMARY 
       [0006]    According to one aspect of the invention, an implantable spacer for placement between adjacent spinous processes is provided. The adjacent spinous processes includes a superior spinous process and an inferior spinous process. Each of the superior and inferior spinous processes has two lateral surfaces. The implantable spacer includes a body having a longitudinal axis. A wing is connected to the body and capable of movement with respect to the body. The wing has at least a first pair of extension members having longitudinal axes. The wing has at least one caming surface. The spacer further includes an actuator assembly connected to the body. The actuator assembly includes an actuator and a shaft connected to the actuator. The actuator assembly is configured such that the actuator is disposed inside the body such that the shaft is accessible at the proximal end of the spacer. The actuator is configured to move relative to the spacer body to contact the caming surface of the wing to move the wing from a first position to a second position. 
         [0007]    According to another aspect of the invention, an implantable spacer for placement into an interspinous process space between adjacent spinous processes is provided. The adjacent spinous processes include a superior spinous process and an inferior spinous process. The implantable spacer includes a body having longitudinal axis, a first end and a second end. The first end is configured to be positioned inside the interspinous process space proximally to the spinal canal relative to the second end. The spacer further includes at least one movable element and a mechanism for moving the at least one movable element from a first position to a second position. The at least one movable element is configured to laterally stabilize the spacer relative to at least one of the superior or inferior spinous process when in said second position. The mechanism is configured such that movement of the at least one movable element from the first position to the second position is effected by moving the mechanism relative to the spacer body in a direction away from spinal canal. 
         [0008]    According to another aspect of the invention, an implantable spacer for placement into an interspinous process space between adjacent spinous processes is provided. The adjacent spinous processes include a superior spinous process and an inferior spinous process. The implantable spacer includes a body having longitudinal axis, a first end and a second end. The first end is configured to be positioned inside the interspinous process space proximally to the spinal canal relative to the second end. The spacer further includes at least one movable element. The spacer also includes an actuator assembly connected to the body. The actuator assembly includes an actuator mechanism for moving the at least one element from a first position to a second position. The at least one movable element is configured to laterally stabilize the spacer relative to at least one of the superior or inferior spinous processes when in said second position. The spacer includes a locking mechanism for locking the at least one movable element in said second position. The locking mechanism includes a body link having at least one outer surface angled with respect to the longitudinal axis and configured such that effecting movement of the at least one element from a first position to a second position moves the body link relative to the body to create a force to lock the at least one movable element in place. 
         [0009]    According to another aspect of the invention, an implantable spacer for placement into an interspinous process space between adjacent spinous processes is provided. The adjacent spinous processes include a superior spinous process and an inferior spinous process. The implantable spacer includes a spacer body and movable wing combination. The movable wing has a first position and a second position and at least one extension member for laterally stabilizing the spacer body with respect to the at least one spinous process when in said second position. The at least one extension member shares the length of the spacer body when in said first position. 
         [0010]    According to another aspect of the invention, an implantable spacer for placement into an interspinous process space between adjacent spinous processes is provided. The adjacent spinous processes include a superior spinous process and an inferior spinous process. The implantable spacer includes a body having longitudinal axis, a first end and a second end. The body has a superior spinous process engaging surface and an inferior spinous process engaging surface. The spacer includes at least one movable element and an actuator assembly. The actuator assembly is connected to the body and configured for moving the at least one movable element from a first position to a second position. The at least one movable element is configured to laterally stabilize the spacer relative to at least one of the superior or inferior spinous processes when in said second position. When in the second position, the spacer is positionable within the interspinous process space such that the superior spinous process engaging surface faces the superior spinous process and the inferior spinous process engaging surface faces the inferior spinous process. The spacer is configured to abut at least one of the superior spinous process and inferior spinous process on a corresponding superior spinous process engaging surface and inferior spinous process engaging surface at a location along the body that is outside the location of the movable element when in the second position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The invention is best understood from the following detailed description when mad in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to-scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. 
           [0012]      FIG. 1   a  illustrates a perspective view of a spacer in an undeployed configuration according to the present invention. 
           [0013]      FIG. 1   b  illustrates a perspective view of a spacer in a deployed configuration according to the present invention. 
           [0014]      FIG. 2  illustrates an exploded perspective view of a spacer according to the present invention. 
           [0015]      FIG. 3   a  illustrates a perspective view of a body of a spacer according to the present invention. 
           [0016]      FIG. 3   b  illustrates a side view of a body of a spacer according to the present invention. 
           [0017]      FIG. 3   c  illustrates a top view of a body of a spacer according to the present invention. 
           [0018]      FIG. 3   d  illustrates a cross-sectional view taken along line F-F in  FIG. 3   c  of a body of a spacer according to the present invention. 
           [0019]      FIG. 4   a  illustrates a perspective view of a wing according to the present invention. 
           [0020]      FIG. 4   b  illustrates a top view of a wing according to the present invention. 
           [0021]      FIG. 4   c  illustrates a side view of a wing according to the present invention. 
           [0022]      FIG. 4   d  illustrates a cross-sectional view taken along line J-J in  FIG. 4   b  of a body of a spacer according to the present invention. 
           [0023]      FIG. 4   e  illustrates a cross-sectional view taken along line H-H in  FIG. 4   b  of a body of a spacer according to the present invention. 
           [0024]      FIG. 5   a  illustrates a perspective view of an actuator of a spacer according to the present invention. 
           [0025]      FIG. 5   b  illustrates a side view of an actuator of a spacer according to the present invention. 
           [0026]      FIG. 6   a  illustrates a perspective view of a shaft of a spacer according to the present invention. 
           [0027]      FIG. 6   b  illustrates a side view of a shaft of a spacer according to the present invention. 
           [0028]      FIG. 7   a  illustrates a perspective view of a body link of a spacer according to the present invention. 
           [0029]      FIG. 7   b  illustrates a cross-sectional view of a body link of a spacer according to the present invention. 
           [0030]      FIG. 8  illustrates a cross-sectional view of a spacer in an undeployed configuration according to the present invention. 
           [0031]      FIG. 9  illustrates a cross-sectional view of a spacer in a deployed configuration according to the present invention. 
           [0032]      FIG. 10  illustrates a spacer according to the present invention deployed in an interspinous process space between two adjacent vertebral bodies and a supraspinous ligament. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    Before the subject devices, systems and methods are described, it is to be understood that this invention is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims. 
         [0034]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. 
         [0035]    It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a spinal segment” may include a plurality of such spinal segments and reference to “the screw” includes reference to one or more screws and equivalents thereof known to those skilled in the art, and so forth. 
         [0036]    All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed. 
         [0037]    The present invention is described in the accompanying figures and text as understood by a person having ordinary skill in the field of spinal implants and implant delivery instrumentation. 
         [0038]    With reference to  FIGS. 1   a  and  1   b , a spacer  10  according to the present invention is shown.  FIG. 1   a  illustrates the spacer  10  in a first position or undeployed configuration and  FIG. 1   b  illustrates the spacer  10  in a second position or deployed configuration. The spacer  10  includes a body  12 , an extension member, wing or arm  14 , and an actuator assembly  18 . The wing  14  and the actuator assembly  18  are connected to the body  12 . When in the undeployed configuration shown in  FIG. 1   a , the longitudinal axis of the wing  14  is substantially parallel to the longitudinal axis of the body  12  whereas when in the deployed configuration shown in  FIG. 1   b , the wing  14  is substantially perpendicular to the longitudinal axis of the body  12 . As seen in  FIG. 1   a , a portion of the wing  14  overlaps or shares a length of the body  12 , thereby, advantageously reducing the length of the overall spacer  10 . 
         [0039]    Turning to  FIG. 2 , an exploded perspective view of the spacer  10  is shown illustrating the body  12 , wing  14  and components of the actuator assembly  18 . 
         [0040]    Turning to  FIGS. 3   a ,  3   b ,  3   c  and  3   d , there is shown a perspective view, side view, top view and sectional view, respectively, of the body  12  according to the present invention. The body  12  has a size and shape that allows for implantation between adjacent spinous processes and facilitates delivery into a patient through a narrow port or cannula. The body  12  has a proximal end  20  and a distal end  22  and two oppositely located sidewalls  24  integrally joined at the distal end  22 . When implanted in an interspinous process space, one of the sidewalls  24  serves as a superior spinous process engaging surface and the other serves as an inferior spinous process engaging surface. In one variation, the sidewalls  24  are substantially flat surfaces and substantially parallel to each other. The body  12  forms a generally U-shaped channel between the sidewalls  24  with the open end of the U-shaped channel located at the proximal end  20 . Inside the body  12 , the body  12  defines an actuator assembly receiving portion  26  and a wing receiving portion  28  between the sidewalls  24 . The wing receiving portion  28  is located near the distal end  22  of the body  12  and is connected to the actuator assembly receiving portion  26  which together form the U-shaped passageway  30  inside the body  12 . The wing receiving portion  28  is arcuate in shape which provides the wing  14  with a smooth bearing surface for rotation. The actuator assembly receiving portion  26  includes a body link receiving portion  32 . 
         [0041]    The outside of the body  12  includes ridges  34  along at least a portion of the sidewalls  24 . In one variation, the body  12  does not include ridges  34 . The ridges  34  and sidewalls  24  on which they are formed function to provide a traction surface for contact with the ends of the spinous processes of the superior and inferior vertebrae or other tissue of the interspinous process space between which the spacer  10  is implanted. When implanted, one of the sidewalls  24  faces the superior spinous process and the other sidewall  24  facet the inferior spinous process. The distance between sidewalls is sufficient to occupy the interspinous process space according to surgeon preference. In one variation, the ridges  34  are angled towards the proximal end  20  to ease insertion and help prevent the spacer from backing out as the ridges grip the spinous processes and adjacent tissue to help keep the spacer  10  in place. In one variation, as shown in  FIG. 3   c , a slight saddle-shaped channel or scallop  36  is formed on the outer surface of the sidewalls  24  extending longitudinally between the proximal end  20  and the distal end  22  to help seat, conform and center the body  12  between spinous processes. The channel  36  is shown in conjunction with ridges  34  in  FIGS. 3   a  and  3   c . The distal tip  22  of the spacer body  12  is rounded to ease passage of the spacer  10  through tissue and ligament. The distal tip  22  serves as the leading end of the spacer  10  being positionable closer to the spinal canal relative to the proximal end  20 . 
         [0042]    With reference now to  FIGS. 4   a - 4   e , there is shown a perspective, top, side, a first cross-sectional and a second cross-section view, respectively, of the wing  14  according to the present invention. The wing  14  includes at least two extending members  38   a ,  38   b  interconnected by a cross-member  40  that together form a single U-shaped channel. In the variation shown in  FIGS. 4   a - 4   e , four extending members  38   a ,  38   b ,  38   c  and  38   d  are part of the spacer  10 . The four extending members  38   a ,  38   b ,  38   c  and  38   d  are interconnected by at least one cross-member  40  and form two adjacent generally U-shaped channels such that together, the U-shaped channels form a generally H-shaped wing  14  as seen in  FIG. 4   b . One substantially U-shaped channel is defined between extending members  38   a  and  38   b  configured and sized for receiving a superior spinous process and laterally retaining the spacer with respect to the superior spinous process and a second substantially U-shaped channel is defined between extending members  38   c  and  38   d  configured and sized for receiving an inferior spinous process and laterally retaining the spacer with respect to the inferior spinous process. The inner surfaces of the extending members may contact or engage or conform to and generally face the lateral sides of the spinous processes when the spacer is implanted. In this regard, the extending members are configured and dimensioned to generally prevent or limit lateral movement of the spacer when the spacer is implanted. In the variation shown, extending members  38   a  and  38   c  form one side of the wing  14  and have longitudinal axes that are coincident. Also, extending members  38   b  and  38   d  form a second side of the wing  14  and have longitudinal axes that are coincident. Each extending member  38   a ,  38   b ,  38   c ,  38   d  is substantially rectangular in shape. In another variation, the extending is any suitable shape for preventing or limiting lateral movement of the spacer with respect to at least one of the spinous processes. Each extending member  38   a - 38   d  includes a substantially flat inner surface and a slightly curved outer surface. The curved outer surface contributes to the bullet-like profile of the spacer  10  when in the undeployed configuration and conforms more closely to the shape of the body  12  to ease installation as the spacer is moved through tissue to the interspinous process space. The flat inner surface and the curved outer surface of each extending member  38  meet to form edges  42   a ,  42   b ,  42   c ,  42   d . In one variation, the edges  42   a ,  42   b ,  42   c ,  42   d  are relatively sharp and therefore, advantageous for passing or cutting through tissue as the wing  14  is moved from an undeployed configuration to a deployed configuration. 
         [0043]    With particular reference to  FIG. 4   e , the cross-member  40  includes a first caming surface  44  and a second caming surface  46 . The first and second caming surfaces  44 ,  46  are angled with respect to each other to form a wedge-shape such that one end forms a pointed lock engaging end  48  for engaging with the actuator and the other end forms a curved seating end  50  for seating in the wing receiving portion  28  of the body  12 . The cross-member  40  includes end portions  40   a  configured as curved seating surfaces for seating in the wing receiving portion  28  of the body  12 . The curved seating surfaces extend around at least half of the circumference of the cross-member  40 . The cross-member  40  is fixed with respect to the extending members  38   a ,  38   b ,  38   c ,  38   d  such that movement of the cross-member  40  translates to movement of the extending members  38   a ,  38   b ,  38   c ,  38   d.    
         [0044]    With brief reference back to  FIG. 2 , the actuator assembly  18  will now be described. The actuator assembly  18  includes an actuator  54 , a shaft  56  and an optional body link  58 . The body link  58  and actuator  54  are connected to the shaft  56 . 
         [0045]    Turning now to  FIGS. 5   a  and  5   b , the actuator  54  will now be described. The actuator  54  includes a proximal end  60  and a distal end  62 , a first surface  64 , a second surface  66 , a receiving portion  68  for the pointed lock engaging end  48  of the cross member  40  and a shaft receiving portion  70  configured to receive the shaft  56 . The first surface  64  is configured to conform and correspond to the first caming surface  44  and curved seating end  50  of the cross member  40  when the spacer  10  is in the undeployed configuration such that the first caming surface  44  and curved seating end  50  of the cross member  40  are in juxtaposition with the first surface  64  of the actuator  54 . The second surface  66  is configured to conform and correspond to the second caming surface  46  of the cross member  40  when the spacer is in the deployed configuration. The first surface  64  and the second surface  66  define a wedge-shaped space for receiving the cross-member  40 . The receiving portion  68  is configured to receive and retain the pointed lock engaging end  48  of the cross member  40 . First and second surfaces  64  and  66  are configured to be substantially at the same angle with respect to the longitudinal axis permitting rotation of the cross-member by approximately 90 degrees. The first and second surfaces  64  and  66  in conjunction with the receiving portion  68  serve as bearing surfaces for the first and second caming surfaces  44 ,  46  to effect rotation of the wing  14  to and from an undeployed configuration and a deployed configuration. In one variation, the first surface  64  bears at least part of the force from the first caming surface  44  for moving the wing  14  from a first position to a second position and the second surface  66  bears at least part of the force from the second caming surface  46  when the wing is in the second position preventing the wing from over-rotation. The distal end  62  of the actuator  54  is bulbous and configured to retain the cross member  40  within the actuator  54  when the spacer  10  is assembled. 
         [0046]    Turning now to  FIGS. 6   a  and  6   b , the shaft  56  of the actuator assembly  18  will now be described. The shaft  56  is substantially cylindrical in shape and, in one variation, includes a threaded outer surface for engagement with the threaded inner surface of the body link  58 . In a variation without a body link  58 , the threaded outer surface of the shaft  56  engages with a threaded inner surface of the body  12 . The proximal end of the shaft  56  includes a socket  72  such as a hex socket for receiving a hexagonally-shaped driving tool. When the spacer  10  is assembled, the proximal end of the shaft  56  is accessible at the proximal end of the spacer  10  for connection with a driving tool. The distal end of the shaft  56  includes an actuator engagement portion  74  configured to connect to the actuator  54 . The actuator engagement portion  74  is a projection that connects to the shaft receiving portion  70  on the actuator  54 . 
         [0047]    Turning now to  FIGS. 7   a  and  7   b , the body link  58  will now be described. The body link  58  is sized and configured to be disposed inside the link receiving portion  32  of the body  12  and configured to link the shaft  56  to the body  12 . The body link  58  includes a threaded bore  82  configured to receive the threaded shaft  56 . In the variation of  FIGS. 7   a  and  7   b , the body link  58  further functions as a body expander such that the body link  58  includes at least one diverging outer surface  76 . The at least one angled surface is configured such that it diverges from proximal end  78  toward the distal end  80  of the body link  58 . As a result, the body link  58  is larger at the distal end  80  relative to the proximal end  78 . In the variation shown in  FIGS. 7   a  and  7   b , the angled outer surface  76  comprises four angled sides which in combination diverge outwardly from the proximal end  78  toward the distal end  80  to form a wedge-like shape. However, the invention is not so limited so long as the body link  58  has a diverging surface. Another example of a diverging body link  58  is a body link  58  having a cone-shaped outer surface. Whether the variation of the spacer includes a diverging or non-diverging body link  50 , the shape of the link receiving portion  32  corresponds to the shape of the body link  50  and the link receiving portion  32  is sufficiently large enough to permit the body link  50  to travel inside it as the shaft  56  is moved to deploy the wing  14 . 
         [0048]    Assembly of the actuator assembly  18  will now be described in reference to  FIGS. 2 ,  5   a ,  5   b ,  6   a ,  6   b ,  7   a  and  7   b . The shaft  56  of the actuator assembly  18  is connected to the actuator  54  by inserting the actuator engagement portion  74  of the shaft  56  into the shaft receiving portion  70  of actuator  54 . The shaft receiving portion  70  is a slot with a constricted neck portion into which the actuator engagement portion  74  of the shaft  56  slides laterally into and cannot be removed along the longitudinal axis. The shaft  56  is connected to the body link  58  by inserting the threaded portion of the shaft  56  into the threaded bore  82  of the body link  58  to complete the assembly of the actuator assembly  18 . 
         [0049]    Assembly of the remainder of the spacer  10  will now be described. The wing  14  is connected to the actuator assembly  18 . The wing  14  is connected to the actuator  54  such that the pointed lock engaging end  48  of the cross member  40  of the wing  14  is inserted into the receiving portion  68  of the actuator  54 . The wing  14  and actuator assembly  18  are inserted through the opening at the proximal end  20  of the body  12  until the wing  14  is seated in the wing receiving portion  28 , the actuator assembly  18  is disposed inside the actuator assembly receiving portion  26  and the body link  58  is located in the body link receiving portion  32 . The end portions  40   a  of the cross-member  40  rest against corresponding curved surfaces of the wing receiving portion  28  of the body  12  advantageously providing a large contact surface area suitable for bearing large loads, in particular, shear forces on the wing. The body link  58  is inserted and snapped through the opening at the proximal end  20  of the body  12  into the complementarily-shaped body link receiving portion  32  and retained therein via an interference fit engagement with the body  12 . With the body link  58  in place, the wing  14  and the actuator assembly  18  are secured inside the body  12 . The wing  14  is seated in wing receiving portion  28  such that wing  14  is capable of rotational movement with respect to the body  12 . 
         [0050]    Once assembled, the spacer  10  is ready for delivery into the patient. To deliver the spacer  10  within the patient, the spacer  10  is releasably attached to a delivery instrument (not shown). For example, a delivery instrument may connect to the proximal end  20  of the spacer  10  via notches (not shown) formed in the body  12  or connect to outer holes (not shown) formed in the cross member  40  of the wing  14 . The spacer  10  is provided or otherwise placed in its undeployed state or closed configuration as illustrated in  FIG. 1   a  wherein at least a part of the length of the wing  14  shares/overlaps a part of the length of the body  12  when in an undeployed configuration and, in particular, at least half of the length of the wing  14  is shared/overlapped by the length of the body  12 . A small midline or lateral-to-midline posterior incision is made in the patient for minimally-invasive percutaneous delivery. In one variation, the supraspinous ligament is avoided. In another variation, the supraspinous ligament is split longitudinally along the direction of the tissue fibers to create an opening for the instrument. Dilators may be further employed to create the opening. In the undeployed state and attached to a delivery instrument, the spacer  10  is inserted through a port or cannula, if one is employed, which has been operatively positioned to an interspinous process space within a patient&#39;s back with the proximal end extending outside the patient. In some circumstances, it may not be necessary to use a cannula where the device is inserted with the delivery instrument alone or through a larger opening in the tissue. The spacer is then advanced to within the targeted interspinous process space between two adjacent spinous processes. If a cannula is employed, the spacer  10  is advanced beyond the end of the cannula or, alternatively, the cannula is pulled proximately to uncover the spacer  10  within. The surgeon may examine the positioning of the spacer  10  via fluoroscopy and reposition it if necessary. 
         [0051]    With particular reference now to  FIGS. 8 and 9 , deployment of the spacer  10  from an undeployed configuration illustrated in  FIG. 8  to a deployed configuration illustrated in  FIG. 9  while positioned within the interspinous process space will now be described. With particular reference first to  FIG. 8 , a driver (not shown) such as a hex-shaped tool is inserted into the hex socket  72  of the shaft  56  and turned to move or pull the shaft  56  towards the proximal end  20  of the body  12  in a direction indicated by the arrow “A”. Since the actuator  54  is connected to the shaft  56 , the actuator  54  also moves (is pulled) towards the proximal end  20  rotating the wing  14  in a direction indicated by the arrow “B”. The entire wing  14  rotates through an angle of approximately 90 degrees from the undeployed configuration through intermediate configurations into the second or deployed configuration shown in  FIG. 9  in which the wing  14  is perpendicular to the longitudinal length of the body  12 . The proximal direction of motion of the shaft  56  and connected actuator  54  relative to the body  12  (pull deployment) advantageously avoids pushing the spacer  10  deeper into the interspinous space and towards the spinal canal during the process of deployment. Instead, the proximal direction of motion or pulling of the actuator assembly  18  provides for a safer implant and a secure positioning casing installation for the surgeon. The surgeon may examine the positioning of the spacer  10  via fluoroscopy with the spacer  10  in an intermediate configuration and choose to reposition it by moving the spacer  10  along a general posterior-anterior direction with the wings  14  partially deployed. Alternatively, the surgeon may choose to reposition the spacer  10  by returning the spacer  10  to first or closed configuration by rotating the driver in an opposite direction and then moving the spacer  10  into position and continuing with deployment of the wings  14 . 
         [0052]    With particular reference to  FIG. 9 , in the deployed configuration the second surface  66  of the actuator  54  abuts the second caming surface  46  of the cross member  40 . Further rotation of the wing  14  is prevented by the bulbous distal end  62  being lodged or wedged between the cross member  40  and distal end  22  of the body  12 . If the shaft  56  is further proximally advanced pulling the actuator  54  proximally along with it, the wing  14  will not rotate any further; however, in a variation of the spacer  10  that includes a body link  58  that functions as an expander as described above, the body link  58  will advance distally in a direction indicated by arrow “C” in  FIG. 9 . The diverging outer surface  76  of the body link  58  will wedge toward the distal end  22  spreading the proximal end  20  of the sidewalls  24  outwardly in a direction indicated by arrows “D” relative to the distal end of the sidewalls  24 . The spring force of the outwardly biased sidewalls  24  will exert a force from both directions back onto the shaft  56  tightening it in place, thereby, advantageously providing a self locking feature that prevents the threaded shaft or screw  56  from backing out and the wing collapsing. Also, the expanded proximal end  20  of the sidewalls  24  provides additional customized distraction of the spinous processes. The surgeon can drive the shaft  56  to further spread the sidewalls  24  thereby providing greater distraction of the spinous processes according to surgeon preference giving the surgeon additional flexibility in selecting the degree of distraction for a particular patient. Furthermore, the outwardly expanded proximal end  20  of the sidewalls  24  creates a wedge-shaped seat for the spinous process. With the sidewalls  24  in an expanded configuration, the spacer  10  assumes an overall wedge-like shape advantageous for retainment in the interspinous process space. With the sidewalls  24  in an expanded configuration the wedge-shaped seat forms an angle between the sidewall  24  and the wing  14  that is slightly less than 90 degrees on each side of the body  12 . This feature advantageously secures the spacer  10  within the patient and helps keep it in place between spinous processes. 
         [0053]    The spacer  10  may be undeployed for removal from the interspinous space by rotating the shaft  56  in the opposite direction to fold the wing  14  into the closed or undeployed configuration or any intermediate configuration. In the undeployed configuration, the spacer  10  can be removed from the patient or re-adjusted and re-positioned and then re-deployed as needed. This process can be repeated as necessary until the clinician has achieved the desired positioning of the spacer in the patient. Following final positioning, the driver and delivery instrument is detached from the spacer  10  and removed from the operative site leaving the spacer  10  implanted in the interspinous process space as shown in  FIG. 10 . In  FIG. 10 , the spacer  10  is shown with the wing  14  receiving the superior spinous process  138  of a first vertebral body  142  and the inferior spinous process  140  of an adjacent second vertebral body  144  providing sufficient distraction/spacing to open the neural foramen  146  to relieve pain. In one variation of the spacer  10  of the present invention, the spacer  10  is configured such that the body  12  seats the superior and inferior spinous processes  138 ,  140  at a location along the length of the body  12  that is outside location of the wing  14  when in the deployed configuration. Hence, the wing  14  serves as a lateral stabilizer, locator for the spacer  10  instead of a seating location for the spinous processes  138 ,  140 . Therefore, the spacer  10  provides for a longer seating location for the superior and inferior spinous processes making it easier for the surgeon to install the spacer  10 . In one variation, the shape of the arm  14  is such that it conforms to the spinous processes  138 ,  140 . The supraspinous ligament  152  is also shown in  FIG. 10 . The spacer  10  maintains the spinous processes in a distracted or spaced condition, for example where the distance of the implant is greater than a pre-implantation distance between the spinous processes. 
         [0054]    The wing  14  is movably or rotatably connected to the body  12  to provide rotational movement from an undeployed configuration to a deployed configuration that arcs through about a 90 degree range or more. The wing  14  is rotationally movable between at least an undeployed, collapsed or folded state (as shown in FIG.  8 ) and a fully deployed state (as shown in  FIG. 9 ). In the undeployed state, the wing  14  is aligned generally or substantially axially (i.e., axially with the longitudinal axis defined by the body  12  or to the translation path into the interspinous process space of the patient) to provide a minimal lateral or radial profile. In the deployed state, the wing  14  is positioned generally or substantially transverse to the collapsed position (i.e., transverse to the longitudinal axis defined by the body  12  or to the translation path into the interspinous space of the patient). In another variation, the wing  14  may also be linearly moveable or translatable from the deployed state to and from an additionally extended state. More specifically, the wing  14  can be extended in the general vertical or horizontal direction along an axis substantially parallel or perpendicular to the spine. The wing  14  is connected to the body  12  in a manner that enables it to be moved simultaneously or independently of each other, as well as in a manner that provides passive deployment and/or vertical extension or, alternatively, active or actuated deployment and/or vertical extension. 
         [0055]    The spacer  10  is as easily and quickly removed from the body of the patient as it is installed. To remove the spacer  10 , the delivery instrument is inserted into an incision and reconnected to the spacer  10 . The shaft  56  is rotated in the opposite direction via a driver to fold the wing  14  into a closed or undeployed configuration such that the wing  10  is clear or disengaged from the superior and inferior spinous processes. In the undeployed configuration, the spacer  10  can be removed from the patient along with the instrument or, of course, re-adjusted and re-positioned and then re-deployed as needed with the benefit of minimal invasiveness to the patient. 
         [0056]    Any of the spacers disclosed herein are configured for implantation employing minimally invasive techniques including through a small percutaneous incision and through the superspinous ligament. Implantation through the superspinous ligament involves selective dissection of the superspinous ligament in which the fibers of the ligament are separated or spread apart from each other in a manner to maintain as much of the ligament intact as possible. This approach avoids crosswise dissection or cutting of the ligament and thereby reduces the healing time and minimizes the amount of instability to the affected spinal segment. While this approach is ideally suited to be performed through a posterior or midline incision, the approach may also be performed through one or more incisions made laterally of the spine with or without affect to the superspinous ligament. Of course, the spacer may also be implanted in a lateral approach that circumvents the superspinous ligament altogether. 
         [0057]    Other variations and features of the various mechanical spacers are covered by the present invention. For example, a spacer may include only a single U-shaped arm which is configured to receive either the superior spinous process or the inferior spinous process. The surface of the spacer body opposite the side of the single arm may be contoured or otherwise configured to engage the opposing spinous process wherein the spacer is sized to be securely positioned in the interspinous space and provide the desired distraction of the spinous processes defining such space. 
         [0058]    Furthermore, depending on the variation of the spacer employed, distraction of the interspinous space is provided by the body of the spacer such that the superior and inferior spinous processes rest on either side of the body and the H-shaped wing keeps the spacer in position with each U of the H-shaped wing encompassing at least a portion of the spinous process. Alternatively, distraction of the interspinous process space is provided by the wing such that each U of the H-shaped wing supports the superior and inferior spinous processes within the U-shaped saddle. The U-shaped saddle can be made shallower or deeper to provide a desired amount of distraction for the spinous processes. 
         [0059]    The extension arms of the subject device may be configured to be selectively movable subsequent to implantation, either to a fixed position prior to closure of the access site or otherwise enabled or allowed to move in response to normal spinal motion exerted on the device after deployment. The deployment angles of the extension arms may range from less than 90 degrees (relative to the longitudinal axis defined by the device body) or may extend beyond 90 degrees. Each extension member may be rotationally movable within a range that is different from that of the other extension members. Additionally, the individual superior and/or inferior extensions may be movable in any direction relative to the strut or bridge extending between an arm pair or relative to the device body in order to provide shock absorption and/or function as a motion limiter, or serve as a lateral adjustment particularly during lateral bending and axial rotation of the spine. The manner of attachment or affixation of the extensions to the arms may be selected so as to provide movement of the extensions that is passive or active or both. In one variation, the saddle or distance between extensions can be made wider to assist in seating the spinous process and then narrowed to secure the spinous process positioned between extensions. 
         [0060]    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, polymers, resins, ceramics, biologically absorbable materials and the like. Polymers including PEEK, PEK, PAEK, PEKEKK or any polyetherketone or polyetherketone metal composite can be employed. In the variation in which the body link  58  is configured as an expander, a slightly flexible construction of the body  12  is desirable to effect the desired self-locking features described above in which case suitable materials such as polymeric materials are appropriately selected for the entire spacer or for selected components of the spacer. Any component 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, a surface of any of the implants 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 ingrowth or establish a mineralized connection between the bone and the implant, and reduce the likelihood of implant loosening. Lastly, any assembly or its components can also be entirely or partially made of a shape memory material or other deformable material. 
         [0061]    The preceding merely illustrates the principles of the invention. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. The scope of the present invention, therefore, is not intended to be limited to the exemplary embodiments shown and described herein. Rather, the scope and spirit of present invention is embodied by the appended claims.