Abstract:
Interspinous process implants are disclosed. Also disclosed are systems and kits including such implants, methods of inserting such implants, and methods of alleviating pain or discomfort associated with the spinal column.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation application of U.S. patent application Ser. No. 12/107,222 filed on Apr. 22, 2008, which is incorporated by its entirety herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is generally directed to intervertebral or interspinous process implants, systems and kits including such implants, methods of inserting such implants, and methods of treating spinal stenosis or for alleviating pain or discomfort associated with the spinal column. 
       BACKGROUND OF THE INVENTION 
       [0003]    Occurrences of spinal stenosis are increasing as society ages. Spinal stenosis is the narrowing of the spinal canal, lateral recess or neural foramen, characterized by a reduction in the available space for the passage of blood vessels and nerves. Clinical symptoms of spinal stenosis include extremity pain, radiculopathy, sensory or motor deficit, bladder or bowel dysfunction, and neurogenic claudication. Pain associated with such stenosis can be relieved by surgical or non-surgical treatments, such as medication, physical therapy, back braces and the like. While spinal stenosis is generally more prevalent of the elderly, it can occur in individuals of all ages and sizes. 
         [0004]    There is a need for implants that may be placed between spinal processes for minimally invasive surgical treatment of spinal stenosis. 
       SUMMARY OF THE INVENTION 
       [0005]    Certain embodiments of the present invention are generally directed to minimally invasive implants, in particular, interspinous process implants or spacers. Other embodiments of the invention are further directed to systems and kits including such implants, methods of inserting such implants, and methods of alleviating pain or discomfort associated with the spinal column. 
         [0006]    Some embodiments of the present invention provide spacers or implants and methods for relieving pain and other symptoms associated with spinal stenosis, by relieving pressure and restrictions on the blood vessels and nerves. Such alleviation of pressure may be accomplished in the present invention through the use of an implant placed between the spinous process of adjacent vertebra. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The invention will be more readily understood with reference to the embodiments thereof illustrated in the attached figures, in which: 
           [0008]      FIG. 1  is a front perspective view of one embodiment of an implant according to the invention for creating, increasing, or maintaining distraction between adjacent spinous processes; 
           [0009]      FIG. 2  is a rear perspective view of the implant of  FIG. 1 ; 
           [0010]      FIG. 3  is top view of the implant of  FIG. 1 ; 
           [0011]      FIG. 4  is side view of the implant of  FIG. 1 ; 
           [0012]      FIGS. 5-9  are views demonstrating various steps according to one embodiment of a method of installation of the implant of  FIG. 1 ; 
           [0013]      FIGS. 10-11  are side and perspective views of one embodiment a first end portion of another implant according to the invention; 
           [0014]      FIGS. 12-13  are front and rear perspective views of one embodiment a second end portion of the implant of  FIGS. 10-11 ; 
           [0015]      FIGS. 14-15  are side and perspective views of another embodiment a first end portion of another implant according to the invention; 
           [0016]      FIG. 16  is a front perspective view of another embodiment a second end portion of the implant of the implant of  FIGS. 14-15 ; 
           [0017]      FIGS. 17-18  are side and perspective views of another embodiment a first end portion of another implant according to the invention; 
           [0018]      FIG. 19  is a front perspective view of another embodiment a second end portion of the implant of the implant of  FIGS. 17-18 ; 
           [0019]      FIGS. 20-23  are side and perspective views of another embodiment of an implant according to the invention for creating, increasing, or maintaining distraction between adjacent spinous processes; 
           [0020]      FIGS. 24-32  are perspective views demonstrating various steps according to one embodiment of a method of installation of the implant of  FIG. 1 ; 
           [0021]      FIGS. 33-34  depict perspective views of the implant of  FIG. 1  shown in an implanted position; and 
           [0022]      FIGS. 35-38  are perspective views demonstrating various steps according to one embodiment of a method of installation of the implant of  FIGS. 20-23 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Embodiments of the invention will now be described. The following detailed description of the invention is not intended to be illustrative of all embodiments. In describing embodiments of the present invention, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected. It is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. 
       Implants 
       [0024]    Some embodiments of the present invention are directed to minimally invasive implants, in particular, interspinous process spacers. Implants in accordance with the invention may come in many shapes and sizes. The illustrative embodiments provided herein-below provide guidance as to the many types of implants that may be advantageously used in accordance with the present invention. In particular, the implants are adapted such that their insertion technique (including methods of the present invention) is minimally invasive, and generally simpler, and/or safer than those installed in open or more invasive techniques. According to one aspect, implants according to the present invention may be advantageously inserted into a patient as an out-patient procedure. 
         [0025]    Embodiments of the present invention include implants adapted to be placed between first and second adjacent spinous processes. The implants may be adapted such that after insertion of an implant into a patient, a portion of the implant maintains a desired amount of distraction or spacing between two adjacent spinous processes. The implants or portions thereof that substantially maintain a desired spacing between spinous processes are also referred to herein as “7spacers.” In various embodiments described herein, the implants may include spinous process support surfaces, indented portions or saddle portions spaced apart by a distance (a) ( FIG. 4 ), which generally corresponds to a desired distance for distraction or spacing of two adjacent spinous processes. Other embodiments similarly provide a desired distance for distraction or spacing of two adjacent spinous processes. Depending on the material and/or design of the implant, the desired distraction or spacing distance may vary somewhat after insertion, for example if a patient moves its spine into a position that causes further distraction. For example, in certain embodiments the implant may be resiliently compressible or expandable in the cranial-caudal direction such that the implant may support and or adjust to dynamic movement of the spine. Although not depicted in the figures discussed below, it is contemplated that embodiments of the present invention may be extended to provide distraction or spacing of more than two adjacent spinous processes. 
         [0026]    Implants according to the present invention may be adapted to be inserted between a first and second spinous process at any region in the spine. Although typically implants according to the present invention may be inserted in the lumbar region, it is contemplated that it is possible to configure inserts according to the present invention for insertion into other regions such as for example, the thoracic or cervical region. In general, implants according to the invention may have varying profiles when viewed in a saggittal or axial plane. In this regard, the implants can have varied cross-sectional shapes to conform to the varied anatomical shapes of the interspinous spaces of the spine. 
         [0027]    Certain embodiments of implants of the invention may secure themselves in place without a supplemental attachment mechanism or fastening device attached directly to a spinous process or other portion of the spine. Alternatively, implants in accordance with the invention may be attached to one or more spinous processes or other portion of the spine, or may attach to itself in such a manner as to secure the implant between two adjacent spinal processes. By way of example, implants in accordance with the present invention may be attached to one or both spinous processes or other portion of the spine by one or more pins, screws, wires, cables, straps, surgical rope, sutures, elastic bands, or other fastening devices. Other exemplary implants, attachment mechanisms, and methods are disclosed in U.S. patent application Ser. Nos. 1/366,388 and 11/691,357, the entire contents of which are incorporated herein by reference. “Securing” implants between spinous processes, does not require that the implant not move at all, but rather means that the implant does not move so far away from between the spinous processes that it does not perform the function of maintaining a desired distraction distance or space between the adjacent spinous processes. 
         [0028]    Implants in accordance with the present invention may be secured between spinous processes by methods other than using a fastening device. For example, according to certain embodiments, implants in accordance with the present invention may be secured in place with respect to spinous processes by mechanical forces resulting from the design of the implant, including the shape itself. Exemplary implants may also be secured to spinous processes, by surface modifications to portions of the implant, such as to create frictional forces or other bonds between the implant and spinous processes. Such surface modifications may include mechanical modifications to the surface and/or one or more coatings. Exemplary coatings which may be utilized include, but are not limited to, titanium plasma sprays and chrome sprays or the like. Such mechanical forces and/or surface modifications may be utilized in addition to, or in place of various other attachment methods described herein. 
         [0029]    Referring now to  FIGS. 1-4 , one exemplary embodiment of an implant  10  according to the invention is shown for creating, increasing, or maintaining distraction between adjacent spinous processes. In general, implant  10  is adapted and configured to be placed between adjacent spinous processes. For example, referring to  FIGS. 33-34 , a posterior and side view, respectively, of implant  10  is shown in implanted positions between to two adjacent spinous processes  5 . As best seen in  FIGS. 1-4 , implant  10  generally comprises an elongate member extending laterally along axis  12  from a first lateral end  14  to a second lateral end  16 . In one embodiment, implant  10  may be cannulated with a central cannula or opening  18  extending along axis  12 . One skilled in the art may appreciate that, in operation, cannulation  18  may facilitate advancement, travel, or delivery to an implant location over a guidewire. In another variation, implant  10  may be solid and without a cannulation and in this regard may be advanced or inserted by a practitioner without the use of a guidewire. According to one embodiment, implant  10  may comprise a unitary body with a general barbell-like or spade-like shape, and generally includes a first end portion or distraction portion  20  adjacent first end  14 , a second end portion or trailing end portion  22  adjacent second end  16  and a central support portion or saddle portion  24  disposed between the distraction and trailing end portions  20 ,  22 . In one embodiment, a radio-opaque marker  29  may extend through a portion of implant  10 . As best seen in  FIG. 4 , support portion  24  may have a height (a) and width (d), and the implant may have an overall length (e). As best seen in  FIG. 3 , in one embodiment, implant  10  has a generally arrow or spade shaped profile or perimeter when viewed perpendicular to axis  12  and distraction portion  20  is generally flatter or narrower when viewed from the side, as shown in  FIG. 4 . 
         [0030]    Distraction portion  20  is generally configured and dimensioned to facilitate lateral insertion between adjacent spinous processes. In one embodiment, distraction portion  20  generally comprises a frustoconical, wedged, or tapered shape widening along axis  12  from a tip  26  adjacent the first end  14  to a shoulder  28  adjacent central support portion  24 . In one exemplary embodiment, the distraction portion  20  resembles a generally flattened spear head that tapers greater in a lateral direction than in vertical direction. In this regard, as best seen in  FIG. 3 , portion  20  is generally tapered along a cone angle  30  in a lateral direction and cone angle  30  may be between about 10 and 65 degrees. Also, as best seen in  FIG. 4 , portion  20  is generally ramped or tapered along a cone angle  31  in a vertical direction and cone angle  31  may be between about 1 and 65 degrees. In alternate embodiments, cone angle  30  may be between about 30 and 80 degrees, and cone angle  31  may be between about 5 and 30 degrees. 
         [0031]    In one variation, distraction portion  20  may additionally include a ramped, wedged, fluted, grooved, a cam or cam-like profile section  32  intermediate the tip  26  and shoulder  28 . In this regard, the ramped section  32  and more gradual taper in the vertical direction facilitates lateral insertion with the generally flatter dimension positioned between the adjacent spinous processes. In one variation, distraction portion  20  is configured and dimensioned such that when implant  10  is advanced between adjacent spinous processes laterally along axis  12 , the adjacent spinous processes engage or ride upon ramp section  32  and are distracted or separated apart as implant  10  is advanced laterally along axis  12  during implantation. The rate at which the distraction occurs may be readily controlled by a surgeon by controlling the rate of lateral advancement of implant  10 , so that the surgeon may advance implant  10  along axis  12  as slow or as fast as desired. In this regard, implant  10  may be characterized as self-distracting, as the implant itself distracts or separates the spinous processes as it is being implanted, i.e. without requiring an additional distraction step or device. 
         [0032]    Trailing end portion  22  adjacent second end  16  may comprise a flange and/or generally frustoconical, wedged, or tapered shape narrowing along axis  12  from a major dimension  38  adjacent central support portion  24  to a minor dimension  40  adjacent the second end  16 . Those skilled in the art will appreciate that a tapered feature may be desirable to minimize wear and trauma with adjacent soft tissue and/or bone when implant  10  is installed in a patient. In one embodiment, trailing end portion  22  may comprise a flange portion  39  that extends circumferentially about central support portion  24 . In one variation, flange portion  39  may extend around a majority of the circumference of support portion  24 , and in one embodiment, best seen in  FIG. 4 , flange  39  may be generally flatter along the bottom section. In another embodiment trailing end portion  22  may comprise a tapered portion  41  that may be generally symmetrical to distraction portion  20  with generally similar lateral length and cone angle  31 . In alternate embodiments, however, the trailing end portion  22  need not be symmetrical whatsoever and may have any shape irrespective of the dimension of distraction portion  20 . 
         [0033]    In one embodiment, a socket or indentation  42  may be provided to receive an installation or driving tool with a correspondingly shaped driver tool. Any known driving tools and engagement means may be used, including but not limited to, a flat driver, a star shaped driver, a threaded driver, or a custom shaped driver, among others. In one variation a driver  43  may be provided with an external shape configured to fit within socket  42 . In another variation, driver  43  may comprise a flexible shaft such that the implant  10  may travel along a curved or arcuate path. For example, those skilled in the art may appreciate that such a flexible driver configuration may facilitate insertion of an implant in the L5-S1 region of the spine where direct lateral insertion may be more difficult. As best seen in  FIG. 2 , indent  42  may be concentric with cannula  18  to facilitate insertion with a cannulated driver tool over a guidewire extending through cannula  18  and indentation  42 . In one variation, a threaded section may be provided internal to indentation  42  to accommodate a threaded connection of an installation or removal tool ( FIG. 26 ) with implant  10 . In this regard, the threaded connection between a tool and the implant facilitates a laterally fixed relative connection between the implant and tool so that the implant does not dislodge from the trailing end and may efficiently transfer both lateral translational and rotational forces applied on the tool to the implant during installation. One skilled in the art may appreciate that the threaded connection may also facilitate the removal of implant  10  from the body of a patient should a surgeon so desire. 
         [0034]    Central support portion  24  is provided between the distraction and trailing end portions  20 ,  22 . In one embodiment, support portion  24  may have a diameter or height (a) less than the major dimensions  28 ,  38  of portions  20 ,  22 . In this regard, when viewed from the top, as seen in  FIG. 3 , implant  10  may appear to have a general H-like shape or a barbell-like shape, with the lateral sides  20 ,  22 , being longitudinally spaced a distance  23 ,  25 , respectively beyond central support portion  24 . In one variation, distances  23 ,  25  do not need to be equal. According to one embodiment, lateral sides  20 ,  22  may be spaced a distance  23 ,  25  between about 1 mm and about 6 mm from the support portion  24 . In one particular embodiment, distances  23 ,  25  is about 4-5 mm. 
         [0035]    Referring to  FIG. 4 , when viewed from the side, the transition from the distraction portion  20  to the central support portion  24  is less abrupt to facilitate lateral insertion into the interspinous space with implant  10  in a first or lower profile position. In one variation, as shown in  FIGS. 1-4 , a small transition bump  27  or height differential may be provided at the transition from the distraction portion  20  to the central support portion  24 . According to one embodiment bump  27  may have a height of about 1 mm. In other embodiments a smooth transition may be provided without a bump or height differential. For example, in one exemplary embodiment, a flexible bumper member or sleeve may be positioned about support portion so as to be flush with distraction portion  20  when viewed from the side. Implant  10  is configured and dimensioned to facilitate rotation of about 90 degrees into a second or higher profile position upon implantation and once distraction portion  20  has passed laterally beyond the spinous processes. As best seen in  FIG. 3  when viewed from the top, in one embodiment, the transition from the distraction portion  20  to the central support portion  24  and the transition from the central support portion  24  to trailing end portion  22  may be abrupt. In this regard, a shoulder wall section  44  may be formed at either end of central support portion  24 , and when implant  10  is implanted, wall sections  44  may serve to limit or block movement of the implant along axis  12  and/or dislodgement from the interspinous space. 
         [0036]    In one embodiment, textures, such as knurling, serrations, abrasions, or other similar features may be provided along the surface of central support portion  24  to facilitate gripping or frictional contact with bone, such as the spinous process, to limit or reduce movement and/or dislodgement from the interspinous space once installed. In one variation, one or more barbs  46  may extend from wall sections  44 . Barbs  46  may have a saw-tooth shape, have an angled undercut, or may have other sharpened end portions to grip and/or engage tissue or bone to resist counter rotation of implant  10 . According to one variation, two barbs  46  may be radially spaced about the perimeter of a wall section  44 , however, in alternate embodiments more or less barbs may be provided as desired. In some embodiments, the geometry and spacing of the barbs may be varied between each wall or along an individual wall section  44 . In general, barbs  46  may be configured and dimensioned to limit or reduce rotational, twisting, and/or lateral movement of implant  10  with respect to spinous processes when installed. In yet another embodiment, the wall sections  44  may have a star grind surface feature to limit rotational movement when installed. In other embodiments, one or more protrusions or spikes may be provided along central portion  24  and may extend radially outward to engage the spinous process. 
         [0037]    In some embodiments, all or a portion of implant  10  may be resiliently compressible or expandable in the cranial-caudal direction such that the implant may support and or adjust to dynamic movement of the spine. For example, according to one embodiment, central support portion  24  may include a flexible bumper member to at least partially cushion the compression of adjacent spinous processes. In one variation, the bumper member may comprise a cylindrical sleeve provided to extend around the periphery of central support portion  24 . In some embodiments, the bumper member may be integrated into the support portion and in alternate embodiments the bumper member may be fit over the support portion. In one variation, the bumper member may be made from biocompatible polyurethane, polycarbonate-urethane, elastomer, or other similar material. In still other embodiments, implant  10  may be made from varying materials along its length, such that for example the central support portion may be made from a resilient material, such as polyurethane, polycarbonate-urethane, elastomer or the like, and the end portions may be made from a rigid material, such as titanium or the like. 
         [0038]    The implant itself may serve to dilate or distract the spinous processes as it is being inserted and/or after insertion. For example, in embodiments in which the implant is similar to that depicted in  FIGS. 1-4 , the first end  14  of implant  10  may be initially inserted or advanced laterally between compressed adjacent spinous processes as shown in  FIGS. 5-9 , for example. In one variation, the supraspinous ligament is not removed. In an initial pre-implantation condition, shown in  FIG. 5 , the adjacent spinous processes  5  may be compressed or narrowly spaced such that the initial space or longitudinal distance  50  between the processes may be about equal to or slightly larger or smaller than distance (b) of implant  10 . During lateral insertion of the implant, one or more ramp surfaces or portions of the implant may contact one or both of the spinous processes  5  and may initially distract the processes a distance (b). As the implant is advanced laterally, the ramp  32  and/or the wedged or tapered shape of the distraction portion may distract the spinous processes further apart from one another, until the implant is advanced laterally into an implanted position ( FIGS. 8-9 ) and the spinous processes are fitted into the central support portion  24  of the implant  10 . In operation, the ramp surfaces engage the adjacent spinous processes as the implant is laterally advanced to act or perform in a cam-like manner to translate the lateral force to separate the spinous processes in the longitudinal or cranial-caudal direction as the implant is advanced. The maximum distraction of spinous processes by the implant  10  is distance (c) depicted in  FIG. 7 . According to one embodiment, distance (c) is greater than distance (a) such that the spinous processes  5  may be slightly “over distracted” during installation. In this regard, one skilled in that art may appreciate that such an over distraction may facilitate enhanced tactile feedback to a surgeon during installation as the spinous processes drop into the central support portion to signify a desired lateral placement in the patient with the spinous processes positioned within the central support portion. Once the implant is laterally advanced to the position shown in  FIG. 8 , the flange  39  of trailing end portion  22  may contact and/or abut the lateral side of the spinous processes to prevent further lateral translation and implant  10  may be subsequently rotated about one quarter turn or about 90 degrees into the final implantation position as shown in  FIG. 9 . In this regard, in the final implantation position, the shoulder wall sections  44  may contact the lateral sides of the spinous processes to limit or block movement of the implant along axis  12  and/or dislodgement from the interspinous space. Also, once the implant is implanted and after the spinous processes are fitted into the central support portion  24 , the implant may maintain the spinous processes in a distracted or spaced condition, for example where the distance (a) of the implant is greater than a pre-implantation distance between the spinous processes. 
         [0039]    Referring now to  FIGS. 10-19 , various alternative embodiments of two-piece implant assemblies are shown with the trailing end  22  detachably connectable to the central support portion  24 . In this regard, the implant assemblies may readily accommodate a flexible bumper member as described above. For example, in a variation wherein the bumper comprises a cylindrical sleeve, the sleeve may be assembled over the central support portion prior to attaching the trailing end portion  22  to the central support portion  24 . Referring to  FIGS. 10-13 , one embodiment of an interspinous process implant assembly  60  is shown disassembled. Implant  60  is similar to implant  10  described above, however, in this embodiment implant  60  is an assembly of two pieces with the trailing end portion  22  threadably attachable to central support portion  24 . In this embodiment, external threading  62  may be provided on the proximal end of support portion  24  which may engage internal threading  64  provided on trailing end portion  22 . A pin, set screw or other fixation element  66  may extend at least partially through the trailing end portion  22  and through opening  68  in support portion  24  to fixedly secure the central support portion  24  to the trailing end portion  22 . In this regard, fixation element  66  prevents undesirable disassembly of assembly  60 . Referring to  FIGS. 14-16 , an alternative two-piece implant  70  is shown with a bayonet type connection between the trailing end  22  and central support portion  24 . In this embodiment, bayonet type fingers  72  may be provided on the proximal end of support portion  24  which may engage internal bayonet feature  74  provided on trailing end portion  22  to connect the trailing end to the central support portion  24 . Referring to  FIGS. 17-19 , an alternative two-piece implant  80  is shown with a snappable connection between the trailing end  22  and central support portion  24 . In this embodiment, prongs  82  may be provided on the proximal end of support portion  24  which may engage internal indentations provided on trailing end portion  22  to connect the trailing end to the central support portion  24 . 
         [0040]    Referring now to  FIGS. 20-23 , another embodiment of a two-piece implant assembly  90  is shown with a first portion  92  slidably disposed about a second portion  94 . According to this embodiment, first portion  92  and second portion  94  are slidable with respect to each other along axis  12  or along the length of the implant. According to one aspect of this embodiment, the first and second portions  92 ,  94  are interlockingly connected such as with a dovetail (or other inter locking shape) to allow one half of the implant to slide onto the other. Referring to  FIG. 20 , in an initial position first portion  92  may be disposed proximally along axis  12  and second portion  94  may be disposed distally. As shown in  FIG. 21 , second portion  21  may be slidingly advanced along axis  12  such as for example during implantation in the interspinous space. For example, the first portion  92  may be initially advanced into the interspinous space until the distraction portion  20  reaches the contralateral side of the spinous processes and the second portion  94  may subsequently be advanced into the interspinous space. In this regard, those skilled in the art may appreciate that implant  90  may cause less distraction of the interspinous space than an integral implant. A deflectable arm  96  may be provided on the first portion to snappably engage the second portion once the first portion has been slidingly advanced in the distal direction, as shown in  FIGS. 22-23 . In this regard, the two pieces  92 ,  94  of the implant interlock to form a solid implant when placed in the interspinous space. Also, as best seen in  FIGS. 22-23 , when portions  92 ,  94  are interlocked, implant  90  has a generally similar profile to implant  10  described above. 
         [0041]    Kits having at least one implant such as those depicted in  FIGS. 1-24 , may include various sizes of implants having varying heights (a), widths (d), and overall lengths (e), for example having variations with incremental distances. In one embodiment, a system or kit may be provided that has implants having heights (a) between about 6 mm to about 22 mm. For example, in one variation implants having heights (a) of 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, and 20 mm may be provided. In another variation, a system or kit may be provided that has implants having widths (d) between about 6 mm to about 18 mm. For example, in one variation implants having widths (d) of 8 mm, 12 mm, and 16 mm may be provided. In yet another variation, a system or kit may be provided that has implants having overall lengths (e) between about 20 mm and about 65 mm. For example, in one variation implants having overall lengths (e) of 25 mm and 60 mm may be provided. 
       Material 
       [0042]    Implants in accordance with the present invention may be made of one or more materials suitable for implantation into the spine of a mammalian patient. Materials in accordance with the present invention may be biocompatible with a mammalian patient and/or may have one or more surface coatings or treatments that allow the spacers to be biocompatible. Materials in accordance with the present invention may include one or more materials having sufficient load capability and/or strength to maintain the desired spacing or distraction between spinous processes. Depending on the design employed, certain embodiments may have components or portions made of a material having certain flexibility, as desired for the particular application. Additionally, the materials of the present invention may be made of one or more materials that maintain their composition and shape for as long a time as possible without degrading or decomposing or changing shape, such that replacement of the implant is avoided. 
         [0043]    Suitable materials for use in accordance with the present invention would be known to those skilled in the art. Non-limiting examples include one or more materials selected from medical grade metals, such as titanium or stainless steel, biocompatible polymers, such as polyetheretherketone (PEEK), ceramics, deformable materials, bone, allograft, demineralized or partially demineralized bone, allograft ligament, polyurethane, and polycarbonate-urethane (for example, for portions of the insert where cushioning is desired). Similarly, any fastening devices may be made of materials having one or more of the properties set forth with respect to the implant itself. For example, screws or pins may include titanium and straps may include polyethylene. In some embodiments, primarily radiolucent material may be used. In this regard, radio-opaque material or markers may be used in combination with the radiolucent material to facilitate implantation. Exemplary radio-opaque material includes but is not limited to titanium alloys, tantalum or other known radio-opaque marker material. As indicated above, implants in accordance with the present invention may have one or more portions that may have modified surfaces, surface coatings, and/or attachments to the surface, which may assist in maintaining the spacer in a desired position, for example by friction. Other embodiments of implants according to the invention may include hydrophilic and/or hydrophobic coatings or combinations thereof. For example, all or part of an implant, such as all or part of distraction portion  20 , may have a hydrophilic coating to reduce friction and facilitate lateral insertion between bony parts. Similarly all or part of an implant, such as all or part of central support portion  24 , may have a hydrophobic coating to increase friction to deter dislodgement from between bony parts. Suitable surface modifications, coatings, and attachment materials would be known to those skilled in the art, taking into consideration the purpose for such modification, coating, and/or attachment. 
       Methods for Treating Stenosis and Methods of Inserting an Implant 
       [0044]    Methods are provided for treating spinal stenosis. Methods are also provided for inserting an implant. These methods may include implanting a device to create, increase, or maintain a desired amount of distraction, space, or distance between adjacent first and second spinous processes. The adjacent first and second spinal processes may be accessed by various methods known by practitioners skilled in the art, for example, by accessing the spinous processes from at least one lateral side/unilateral, bilateral, or midline posterior approach. 
         [0045]    Certain methods of the present invention include creating an incision in a patient to be treated, dilating any interspinous ligaments in a position in which the implant is to be placed in the patient, sizing the space between adjacent spinous processes (for example using trials), and inserting an implant of the appropriate size between the adjacent spinous processes. Methods of the present invention may include securing the implant to one or more of the spinous processes, to one or more other portions of the patient&#39;s spine, and/or to itself such that the implant maintains its position between the spinous processes. 
         [0046]    Methods of the present invention may include dilating or distracting the spinous processes apart from one another before sizing and/or before inserting the implant. Methods may vary depending on which implant is being inserted into a patient. For example, certain implants may require distracting the spinous processes apart before inserting the implant, while other implants may themselves dilate or distract the spinous processes while inserting the implant. In embodiments where the implants themselves dilate or distract the spinous process, the implant may have, for example, a predetermined shape to dilate, distract, or otherwise move or separate apart adjacent spinous processes such as a cam or cam-like profile, it may have a distraction device that is deployed, and/or it may have a tapered expander to distract an opening between the adjacent spinous processes or other features to facilitate distraction of the adjacent spinous processes. 
         [0047]    According to certain embodiments, spacers may be placed between the spinous processes anterior to the supraspinous ligament, avoiding the nerves in the spinal canal. The procedure may be performed under local anesthesia. For surgical procedures, in which an implant is being inserted into the lumbar region, the patient may be placed in the right lateral decubitus position with the lumbar spine flexed or in another flexed position. According to one method, a surgeon may desire to use fluoroscopy to align in parallel the adjacent vertebral bodies corresponding to the adjacent spinous processes to gauge the desired distraction distance. 
         [0048]    According to certain embodiments, one or more probes may be used to locate the space between the spinous processes. Depending on the design of the spacer to be inserted, the space may be widened, for example with a dilator before inserting the implant. 
         [0049]    Referring to  FIGS. 24-32 , one embodiment of a surgical method according to the invention for implanting an implant  10  in the spine is disclosed. According to this embodiment, the adjacent first and second spinal processes  5  may be accessed from one lateral side through a minimally invasive procedure. In this regard, according to certain methods of the invention, a unilateral approach may be used to install implant  10  without removal of the supraspinous ligament. In this method, as shown in  FIG. 24 , a guide wire  202 , such as a K wire, is inserted laterally through the skin and into the interspinous space  204 . According to one method, a working portal may be created concentric to the guidewire  202 , as shown in  FIGS. 25-26 , by inserting a series of sequentially larger diameter tubes  206 ,  208 ,  210 ,  212 ,  214  to dilate the tissue surrounding guidewire  202 . Referring to  FIG. 27 , once a dilating tube having a sufficiently large inner diameter to accommodate implant  10  is positioned about guidewire  202 , the smaller diameter tubes  206 ,  208 ,  210 ,  212  may be withdrawn, leaving the guidewire  202  and the outer tube  214 . Referring to  FIG. 28 , one or more trials  215  may then be inserted to appropriately size the interspinous space  204  and the trials  215  may also be utilized to dilate interspinous ligaments. In one exemplary embodiment, a generally cannulated cylindrical trial  215 , shown in  FIG. 28 , may be utilized to size the space between adjacent processes  5 . Referring to  FIG. 29 , an alternate embodiment of a trial  216  that may be used is shown which may comprise a ramped tip portion  217  adjacent its distal end and multiple longitudinal indentations or markings  218  on at least a portion of central portion  219  and may provide visual indication when viewed under fluoroscopy of the width of the spinous processes and facilitate the surgeon&#39;s selection of an appropriately sized implant. Similarly, the appropriate diameter of central portion  219  of trial  216  may be selected to gauge the amount of distraction desired. In this regard, the spacing of the spinous processes may be viewed under fluoroscopy to facilitate the surgeon&#39;s selection of an appropriately sized implant. Finally, an implant of the appropriate size may be inserted between the adjacent spinous processes. 
         [0050]    Referring to  FIGS. 30-32 , one exemplary embodiment of a method of installing implant  10  is shown. Implant  10  is advanced laterally over guidewire  202  through cannulation  18  to the interspinous space  204 . During lateral insertion of the implant between the spinous processes, one or more ramp surfaces or portions of the implant may contact one or both of the spinous processes  5  and may initially distract the processes. Implant  10  may be laterally advanced along the guidewire to further advance implant  10  between the spinous processes and, the wedged or tapered shape of the distraction portion  20  may distract the spinous processes further apart from one another, until the implant is in an implanted position ( FIGS. 31-34 ) with the distraction portion  20  positioned on the contralateral side of the spinous processes and the spinous processes are fitted into the central support portion  24  of the implant  10 . Once the implant is laterally advanced to the position shown in  FIG. 31 , the flange  39  of trailing end portion  22  may contact and/or abut the lateral side of the spinous processes to prevent further lateral translation and implant  10  may be subsequently rotated about one quarter turn or about 90 degrees into the final implantation position as shown in  FIG. 32 . In this regard, in the final implantation position, the shoulder wall sections  44  may contact the lateral sides of the spinous processes to limit or block movement of the implant along axis  12  and/or dislodgement from the interspinous space. Referring to  FIGS. 33-34 , once implant  10  is installed, the guidewire may be removed through the cannulation leaving the implant  10  in the interspinous space. 
         [0051]    Referring to  FIGS. 36-41 , one exemplary embodiment of a method of installing implant  90  is shown. Implant  90  is advanced laterally over guidewire  202  through cannulation  18  to the interspinous space  204 . Referring to  FIGS. 36-37  the first portion  92  may be initially advanced into the interspinous space until the distraction portion  20  reaches the contralateral side of the spinous processes. As shown in  FIGS. 38-40 , the second portion  94  may subsequently be advanced into the interspinous space. Once the implant is laterally advanced to the position shown in  FIG. 40 , implant  90  may be subsequently rotated about one quarter turn or about 90 degrees into the final implantation position as shown in  FIG. 41 . Referring to  FIG. 41 , once implant  90  is installed, the guidewire may be removed through the cannulation leaving the implant  10  in the interspinous space. 
         [0052]    While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations can be made thereto by those skilled in the art without departing from the scope of the invention.