Abstract:
In an exemplary embodiment, the present invention discloses interspinous process spacers that can be placed between adjacent spinous processes for minimally invasive surgical treatment of a spinal disease or defect. In particular, the present invention, in one embodiment, discloses an interspinous process spacer having a distraction end, a central support portion, and a trailing end. Also disclosed in the present invention are systems and kits including such implants, methods of inserting such implants, and methods of alleviating pain or discomfort associated with a spinal column disease or defect.

Description:
FIELD OF THE INVENTION 
     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 
     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. 
     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 
     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. 
     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 
       The invention will be more readily understood with reference to the embodiments thereof illustrated in the attached figures, in which: 
         FIG. 1  is a perspective view of one embodiment of an implant according to the invention for creating, increasing, or maintaining distraction between adjacent spinous processes; 
         FIG. 2  is a side view of the implant of  FIG. 1 ; 
         FIG. 3  is an end view of the implant of  FIG. 1 ; 
         FIGS. 4-7  are side views demonstrating various steps according to one embodiment of a method of installation of the implant of  FIG. 1 ; 
         FIGS. 8-9  are front and rear perspective views of another embodiment of an implant according to the invention; 
         FIG. 10  is a perspective view of one embodiment of a ring attachable to the implant of  FIGS. 8-9 ; 
         FIG. 11  is a front perspective view of another embodiment of an implant according to the invention; 
         FIG. 12  is a partial front perspective view of another embodiment of an implant according to the invention; 
         FIG. 13  is a partial front perspective view of another embodiment of an implant according to the invention; 
         FIG. 14  is a partial front perspective view of another embodiment of an implant according to the invention; 
         FIG. 15A  is a partial cross-sectional side view of another embodiment of an implant according to the invention; 
         FIG. 15B  is a perspective view of the embodiment of  FIG. 15A ; 
         FIGS. 16-23  are perspective views demonstrating various steps according to one embodiment of a method of installation of the implant of  FIG. 1 ; 
         FIGS. 24-25  depict a perspective view of the implant of  FIG. 1  shown in an implanted position; and 
         FIG. 26  is a perspective view of one embodiment of a removal tool according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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 
     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. 
     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 “spacers.” 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. 2 ), 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. 
     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 sagittal 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. 
     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. No. 11/366,388, 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. 
     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 (see e.g., protrusions  46  and/or knurling  47  in  FIG. 2 ) 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. 
     Referring now to  FIGS. 1-3 , 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. 24-25 , 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. 1-3 , 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. According to one embodiment, implant  10  may comprise a unitary body with a general barbell-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 . As best seen in  FIG. 2 , 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 circular profile or perimeter when viewed perpendicular to axis  12 . In alternate embodiments, however, implant  10  need not have a circular cross-sectional profile and the cross-sectional profile may vary along its length (e). For example, in one exemplary embodiment, distraction portion  20  may have a circular cross-sectional profile, and central support portion  24  may have a polyganol cross-sectional profile, and trailing end portion  22  may have a rectangular cross-sectional profile. 
     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 minor diameter  26  adjacent the first end  14  to a major diameter  28  adjacent central support portion  24 . In one exemplary embodiment, the distraction portion  20  is tapered along a cone angle  30  and cone angle  30  may be between about 1 and 65 degrees. In alternate embodiments, cone angle  30  may be between about 65 and 80 degrees. In one variation, distraction portion  20  may additionally include a ramped, toothed, fluted, threaded or grooved section  32 . According to one embodiment, grooved section  32  generally comprises helical or spiral ramp peaks  36  extending from first end toward support portion  24 . Ramp peaks  36  of section  32  may have a separation sufficiently narrow to prevent the adjacent spinous process from riding within the grooves  34  defined between the peaks  36 . In this regard, the peaks  36  may be configured and dimensioned to engage or contact a portion of the spinous process bone and cause the implant  10  to advance or travel along axis  12  when implant  10  is rotated. In one variation, distraction portion  20  is configured and dimensioned such that when implant  10  is rotated about axis  12 , the adjacent spinous processes ride upon ramp peaks  36  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 rotation 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. 
     Trailing end portion  22  adjacent second end  16  may comprise a generally frustoconical, wedged, or tapered shape narrowing along axis  12  from a major diameter  38  adjacent central support portion  24  to a minor diameter  40  adjacent the second end  16 . Those skilled in the art will appreciate that such 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  is generally symmetrical to distraction portion  20  with generally similar lateral length, cone angle  31  and major and minor diameters, and in some embodiments may also include a spiral ramped section or any other toothed, fluted, threaded or grooved sections, similar to distraction portion  20 . 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 . For example, in at least one alternate embodiment, angle  31  could be less or greater than cone angle  30  for distraction portion  20 . 
     Referring to  FIG. 3 , in one embodiment, a hexagonal shaped socket or indentation  42  may be provided to receive an installation or driving tool such as a hexagonal shaped driver tool. One exemplary driving tool  43  constructed according to the invention is shown in  FIGS. 5-7 . In alternate embodiments, any other known rotational driving tools and engagement means may also be used, including but not limited to, a flat driver, a star shaped driver, or a threaded driver, among others. As best seen in  FIG. 3 , 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  45  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 the 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. 
     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 diameters  28 ,  38  of portions  20 ,  22 . In this regard, when viewed from the side, as seen in  FIG. 2 , 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 1 mm. In another embodiment, distance  23  is about 2 mm and distance  25  is about 3 mm. 
     As best seen in  FIG. 2 , 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 or generally vertical 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. In alternate embodiments, the shoulder or transition from the central support portion  24  to the lateral end portions  20 ,  22  may be gradual, curved, or ramped and may server to center the adjacent spinous process within the support portion  24 . 
     In one embodiment, textures, such as knurling  47 , 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 teeth or protrusions  46  may extend laterally inward from wall sections  44 . Protrusions  46  may have a saw-tooth shape, have an angled undercut, or may have other sharpened end portions to grip and/or engage bone. In an alternate embodiment, protrusions  46  may comprise cylindrical spikes with sharp points. According to one variation, six protrusions  46  may be radially spaced about the perimeter of each wall section  44 , however, in alternate embodiments more or less protrusions may be provided as desired. In some embodiments, the geometry and spacing of the protrusions may be varied between each wall or along an individual wall section  44 . For example, a combination of saw-tooth shaped protrusions may be used in combination with spike shaped protrusions. In general, protrusions  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. 
     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 a biocompatible polyurethane, 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, elastomer or the like, and the end portions may be made from a rigid material, such as titanium or the like. 
     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. 1-3 , the first end  14  of implant  10  may be initially inserted or advanced laterally between compressed adjacent spinous processes as shown in  FIGS. 4-7 , for example. The supraspinous ligament may or may not be removed. In an initial pre-implantation condition, shown in  FIG. 4 , 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 rotated, the ramp peaks  36  draw the implant  10  further between the spinous processes and, the wedged or tapered shape of the distraction portion may distract the spinous processes further apart from one another, until the implant is rotated and advanced laterally into an implanted position ( FIGS. 11-12 ) 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 rotated to act or perform in a cam-like manner to translate the rotational force to separate the spinous processes in the longitudinal or cranial-caudal direction as the implant is rotated. The maximum distraction of spinous processes by the implant  10  is distance (c) depicted in  FIG. 6 . 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 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. 
     Referring to  FIGS. 8-10 , another embodiment of an interspinous process implant  60  is shown. Implant  60  is similar to implant  10  described above, however, in this embodiment, the distraction portion  20  comprises a plurality of spiral grooves or flutes  62  disposed about axis  12  and extending from a narrow first end  14  toward central support portion  24 . In this embodiment, generally sharp peaks or ridges  64  may be formed along the edge of the flutes  62  and generally positioned at an angle with a plane perpendicular to axis  12  to form an inclined ramp. The ridges  64  are configured and dimensioned to engage or contact a portion of the spinous process bone and when implant  60  is rotated about axis  12 , ridges  64  generally cause the implant to advance or travel along axis  12 . In this embodiment, flutes  62  extend in a spiral direction to facilitate insertion of implant  60  in a “quarter rotation technique” such that a surgeon may insert implant  60  by rotating the device one fourth of a revolution or ninety degrees. In this regard, in one embodiment, each ridge  64  extends one fourth of the way around the periphery of distraction portion  20 . In alternate embodiments, each ridge  64  may extend one half, three fourths, or any other fractional distance around the periphery as desired to facilitate a corresponding fractional rotation insertion technique. According to one embodiment, six flutes are provided, however, in alternate embodiments, more or less spiral flutes may be used. 
     Referring to  FIG. 8 , according to one embodiment of the invention, implant  60  may have a trailing end portion  22  with an external hexagonal shaped portion  65  instead of an internal hexagonal socket or indentation  42  as described above. Like indentation  42 , hexagonal portion  65  may be provided to engage an installation tool such as a hexagonal socket shaped driver tool. As described above with respect to implant  10 , in alternate embodiments any other known rotational driving tools and engagement means may also be used. Also similar to indentation  42  described above, in one embodiment, a threaded section  45  may be provided to accommodate a threaded connection of an installation or removal tool ( FIG. 26 ) with implant  60 . In this regard, the threaded connection between the 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 the 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  60  from the body of a patient should a surgeon so desire. 
     Referring to  FIGS. 8-10 , according to another aspect, embodiments of implants according to the invention may comprise a separate protrusion ring  66  that may be snap fitted around central support portion  24 . As best seen in  FIG. 10 , protrusion ring  66  may comprise a thin C-shaped body  67  with a plurality of protrusions  68  extending laterally from one side. Protrusions  68  may be similar to protrusions  46  described above and are generally radially spaced around the perimeter of body  67 . In one variation, body  67  of ring  66  has an opening  69  to facilitate insertion over implant  60  adjacent the lateral sides of central support portion  24  with the protrusions facing laterally inward as depicted in  FIGS. 8-9 . Protrusions  68  may be configured and dimensioned to limit or reduce rotational, twisting, and/or lateral movement of implant  60  with respect to spinous processes when installed. In this embodiment, ring  66  and implant  60  may be made from different materials. For example, according to one embodiment, implant  60  may be made from a radiolucent material, such as PEEK, and the ring(s)  66  may be made from a radio-opaque material, such as titanium, tantalum or any other suitable material known to those skilled in the art. In this regard, the ring(s)  66  may serve a dual purpose as a marker device recognizable under fluoroscopy as well as serving the function of limiting or reduce rotational movement when installed. In alternate embodiments, rings  66  may be provided that are entirely free of protrusions or that may sit within grooves of central support portion  24  and could function solely as marker devices without limiting movement of implant  60  relative to spinous processes when installed. For example, in one alternative embodiment, a pair of rings  66  may be provided on either lateral side of support portion  24  to provide visual markers under fluoroscopy indicating the width of support portion  24  to facilitate alignment of implant  60  with the spinous process(es) when installed. Similarly, a surgeon may visualize the central openings and/or perimeter of rings  66  under lateral fluoroscopy to gauge the lateral alignment with the spinous process(es) when installed. 
     Referring to  FIG. 11 , another embodiment of an interspinous process implant  70  is shown. Implant  70  is similar to implants  10 ,  60  described above, however, in this embodiment the distraction portion  20  comprises a plurality of laterally spaced rows of outwardly protruding teeth  72  disposed about axis  12  and spaced from a narrow first end  14  to a central support portion  24 . In this embodiment, the individual teeth  72  are radially spaced apart by a laterally extending groove or flute  74 . As can be seen in  FIG. 11 , the teeth  72  nearer first end  14  are generally narrower than teeth  72  adjacent central support portion  24 . In one variation, teeth  72  extend at an angle with a plane perpendicular to axis  12  to form an inclined ramp segment. The teeth  72  are configured and dimensioned to engage or contact a portion of the spinous process bone and when implant  70  is rotated about axis  12 , teeth  72  cause the implant to advance or travel along axis  12 . 
     Referring to  FIG. 12 , another embodiment of an interspinous process implant  80  is shown. Implant  80  is similar to implants  10 ,  60  described above, however, in this embodiment, the distraction portion  20  comprises a plurality of flat facetted surfaces  82  radially disposed about axis  12  and extending angularly from a narrow first end  14  to a maximum diameter adjacent central support portion  24 . In this embodiment, sharp edges or ridges  84  may be formed along the edge of the facet surfaces  82  at an angle with a plane perpendicular to axis  12  to form an inclined ramp. In this embodiment, surfaces  82  generally extend the entire length of distraction portion  20  and ridges  84  generally form a linear path from the first end toward the central support portion. The ridges  84  are configured and dimensioned to engage or contact a portion of the spinous process bone and when implant  80  is rotated about axis  12 , ridges  84  cause the implant to advance or travel along axis  12 . 
     Referring to  FIG. 13 , another embodiment of an interspinous process implant  90  is shown. Implant  90  is similar to implant  80  described above, however, in this embodiment the flat facetted surfaces  82  radially disposed about axis  12  are staggered, twisted or stepped angularly from a narrow first end  14  to a maximum diameter adjacent central support portion  24 . A plurality of flat surface segments  82  extend the length of distraction portion  20  and ridges  84  generally form a series of linear segments along a path from the first end toward the central support portion. Similar to implant  80  described above, the ridges  84  are configured and dimensioned to engage or contact a portion of the spinous process bone and when implant  80  is rotated about axis  12 , ridges  84  cause the implant to advance or travel along axis  12 . In this variation, a surgeon implanting the device during surgery may experience enhanced tactile feedback due to the segmented ridges. For example, during insertion a surgeon may be able to count the clicks or segment rotations to monitor the progress of the insertion. 
     Referring to  FIG. 14 , another embodiment of an interspinous process implant  100  is shown. Implant  100  is similar to implant  10  described above, however in this embodiment the spiral ramp grooves  34  and peaks  36  are segmented or less smooth along their path. Similar to implant  10  described above, the peaks  36  are configured and dimensioned to engage or contact a portion of the spinous process bone and when implant  100  is rotated about axis  12 , peaks  36  cause the implant to advance or travel along axis  12 . In this variation, like implant  90  described above, a surgeon implanting the device during surgery may experience enhanced tactile feedback due to the segmented peaks  36 . For example, during insertion a surgeon may be able to count the clicks or segmental advancement to monitor the progress of the implant insertion. 
     Referring to  FIGS. 15A-B , another embodiment of an interspinous process implant  110  is shown. Implant  110  is similar to implant  10 , described above, however, in this embodiment the distraction portion  20  comprises a plurality of wing members  112  disposed about axis  12 . Wing members  112  are moveable from a first position to a second position, shown in  FIGS. 15A-B . During installation, wing members  112  are configured to remain in a first position below the profile of peaks  36  such that when implant  110  is implanted, the spinous processes are distracted in a similar manner as described above with respect to implant  10 . When implant  110  is installed in an implanted position, wing members  112  may be selectively moved into a second position, as shown in  FIGS. 15A-B , wherein the wing members  112  generally protrude or extend radially beyond peaks  36 . In this regard, according to one embodiment, wing members  112  may have a tapered first side  114  and a generally flat second side  116 . Wings  112  may be attached to implant  110  such that when in a second position, second side  116  is generally perpendicular to support portion  24  to create a larger lateral barrier, wall, or blocking portion adjacent central support portion  24 . According to one variation, wing members  112  may be biased toward the second position by a biasing member, such as an O-ring  118 . As best seen in  FIG. 15  A, in this variation, each wing member  112  may comprise a cantilevered body or pivot arm  120  pivotable about a pivot point  122  and the O-ring  118  may apply a radially inward biasing force to a tail portion  124  of one side of the wing body  120  to cause an opposite tip portion  126  of each wing member  112  to pivot about point  122  toward the second position. When implant  110  is advanced over a guidewire, the guidewire extends within the central cannula and contacts the tail portion  124  of each wing member and the tail portion  124  is forced radially outward, forcing the tip portion  126  to pivot inward toward the first position. One skilled in the art may appreciate that utilizing such a configuration, the wing members  112  may remain in a first position to facilitate implantation over a guidewire and then once the guidewire is removed, the wing members may spring or bias outwards to the second position to form a larger lateral barrier, wall, or blocking portion adjacent central support portion to limit or reduce the possibility of lateral migration of implant  110  in the body. In alternate embodiments, alternative mechanisms may be utilized to achieve the aforementioned result. For example, in one alternative a torsion spring may be positioned adjacent pivot point  122  to bias the wing members  112  toward the second position. Also, in alternative embodiments, the shapes and dimensions of wing members may be altered as desired. 
     Kits having at least one implant such as those depicted in  FIGS. 11-15 , 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 60 mm. For example, in one variation implants having overall lengths (e) of 25 mm and 50 mm may be provided. 
     Material 
     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. 
     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, and polyurethane (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. 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 
     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. 
     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. 
     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. 
     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. 
     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. 
     Referring to  FIGS. 16-25 , 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. 16 , 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. 17-18 , by inserting a series of sequentially larger diameter tubes  206 ,  208 ,  210 ,  212 ,  214  to dilate the tissue surrounding guidewire  202 . Referring to  FIG. 19 , 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. 20 , 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. 20 , may be utilized to size the space between adjacent processes  5 . Referring to  FIG. 21 , 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. 
     Referring to  FIGS. 22-23 , one exemplary embodiment of a method of installing implant  10  is shown. Implant  10  is advanced 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 rotated 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 rotated and advanced laterally into an implanted position ( FIGS. 22-25 ) 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 . Referring to  FIGS. 24-25 , once implant  10  is installed, the guidewire may be removed through the cannulation leaving the implant  10  in the interspinous space. 
     Referring to  FIG. 26 , one embodiment of an implant removal tool  260  is shown. Removal tool  260  generally comprises an elongate cannulated body  262  with an externally threaded distal tip  264  rotatably connected to thumb barrel member  266 . Distal tip  264  is generally configured and dimensioned to engage threaded section  45 , described above, of an implant to accommodate a threaded connection of removal tool  260  and an implant. In this regard, a surgeon may rotate distal tip  264  by rotating thumb barrel  266  to establish a threaded connection between the tool and the implant. As described above, such a threaded connection facilitates a laterally fixed relative connection between the implant and tool so that the implant does not dislodge from the trailing end and a surgeon may remove or back out the implant from the body if desired. 
     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.