Abstract:
An expandable interspinous process fixation system capable of restoring spinal stability and facilitating fusion. In one embodiment, the expandable interspinous process fixation system includes a central ramp, a first endplate, and a second endplate, the central ramp capable of being moved in a first direction to move the first and second endplates outwardly and into an expanded configuration. Each endplate supporting fixed and/or adjustable spinous process engaging plates.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. application Ser. No. 15/635,267, filed Jun. 28, 2017, which is a continuation-in-part of U.S. application Ser. No. 15/189,188, filed Jun. 22, 2016, which is a continuation-in-part of U.S. application Ser. No. 15/014,189, filed Feb. 3, 2016, which is a continuation-in-part of U.S. application Ser. No. 14/109,429, filed Dec. 17, 2013, now U.S. Pat. No. 9,370,434, which is a divisional of U.S. patent application Ser. No. 12/875,818, filed Sep. 3, 2010, now U.S. Pat. No. 8,632,595, the entire disclosures of which are incorporated herein by reference in their entireties for all purposes. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present disclosure is generally directed to surgical devices, systems, and methods. More particularly, the present disclosure is directed to expandable interspinous process fixation devices, systems, and methods. 
       BACKGROUND 
       [0003]    A spine comprises vertebrae which are a series of small bones, and also includes spinous processes. A spinous process is one of two bony protrusions arising from the posterior side of each vertebra in the human spine. Extending backwards and downwards from the main body of the vertebra, each spinous process is an extension of the lamina. The laminae are two bony plates that converge at the back of each vertebra to form the vertebral arch. The spinous processes curve outward from this junction. A variety of scenarios may exist where damage to the spine may occur including, but not limited to, injury or illness. Severe, even debilitating, pain can result from such damage. In some instances, artificial assistance may be necessary to address such damage. 
         [0004]    Surgical procedures exist that attempt to address such damage including using various vertebral fixation devices. Conventional devices exist to implant vertebrae fixation devices, but such devices often suffer from the problem of being purely manual and are usually complex. Such manual devices require the use of human muscle, which can fatigue, to perform the procedure. Moreover, the incision opening for insertion of these fixation devices may require substantial openings to achieve access to the spinous process. 
         [0005]    There are drawbacks associated with the known conventional fixation devices and methodologies. For example, present methods for installing a conventional fixation device often require that the adjacent vertebral bodies be distracted to restore a diseased disc space to its normal or healthy height prior to implantation of the fixation device. In order to maintain this height once the fixation device is inserted, the fixation device is usually dimensioned larger in height than the initial distraction height. This difference in height can make it difficult for a surgeon to install the fixation device in the distracted intervertebral space. 
         [0006]    As such, there exists a need for a fixation device capable of being installed inside an intervertebral disc space at a minimum to no distraction height and for a fixation device that can maintain a normal distance between adjacent vertebral bodies when implanted. 
       SUMMARY 
       [0007]    To meet this and other needs, devices, systems, and methods of fixation are provided. The fixation devices and systems may include expandable interspinous process fixation devices and system and associated method of implantation. 
         [0008]    In at least one embodiment, the present disclosure provides an expandable interspinous process fixation system which is a posterior, non-pedicle supplemental fixation device. In some embodiments, the interspinous process fixations system may be intended for use in the non-cervical spine. The interspinous process fixations system may attach firmly to adjacent spinous processes and immobilize a lumbar motion segment posteriorly. The device may be configured to withstand compressive, torsional, and shear loads seen in the lumbar spine. The device is intended to achieve supplemental fusion, treating various conditions, for example, degenerative disc disease; spondylolisthesis; trauma (i.e., fracture or dislocation); tumor; and/or other conditions. 
         [0009]    In at least one embodiment, a device according to the present disclosure allows for insertion of a spinous process fixation implant at a reduced height and then an increase of the height after insertion to achieve an accurate anatomical fit. Adjustability of the implant greatly reduces the complexity of inserting an interspinous device since one device covers a wide range of implant sizes, negating the need for several variations of implant lengths and widths. The implant may be preassembled, greatly reducing the number of steps required to insert the device, which simplifies the overall procedure and reduces operating room time. 
         [0010]    In at least one embodiment, the present disclosure provides a fixation device including first and second endplates for an intervertebral implant. The first endplate has a first lateral adjustment arm extending from a first edge thereof and the second endplate has a second lateral adjustment arm extending from a first edge thereof. A first fixed plate extends along a second edge of the first endplate opposite the first edge thereof. The first fixed plate extends substantially perpendicular to the first endplate and has an inner surface defining a first spinous process engaging surface. A second fixed plate extends along a second edge of the second endplate opposite the first edge thereof. The second fixed plate extends substantially perpendicular to the second endplate and has an inner surface defining a second spinous process engaging surface. A first sliding plate is adjustably mounted on the first lateral adjustment arm such that the first sliding plate extends substantially perpendicular to the first endplate and has an inner surface defining a third spinous process engaging surface. A second sliding plate is adjustably mounted on the second lateral adjustment arm such that the second sliding plate extends substantially perpendicular to the second endplate and has an inner surface defining a fourth spinous process engaging surface. An expansion assembly is positioned between the first and second endplates and is configured to selectively cause the first and second endplates to move apart. 
         [0011]    In at least one embodiment, the present disclosure provides a method including: inserting an expandable fixation device into an intervertebral disc space, wherein the expandable fixation device includes: a first endplate for an intervertebral implant, the first endplate having a first lateral adjustment arm extending from a first edge thereof; a second endplate for an intervertebral implant, the second endplate having a second lateral adjustment arm extending from a first edge thereof a first fixed plate extending along a second edge of the first endplate opposite the first edge thereof, the first fixed plate extending substantially perpendicular to the first endplate and having an inner surface defining a first spinous process engaging surface; a second fixed plate extending along a second edge of the second endplate opposite the first edge thereof, the second fixed plate extending substantially perpendicular to the second endplate and having an inner surface defining a second spinous process engaging surface; a first sliding plate adjustably mounted on the first lateral adjustment arm such that the first sliding plate extends substantially perpendicular to the first endplate and has an inner surface defining a third spinous process engaging surface; a second sliding plate adjustably mounted on the second lateral adjustment arm such that the second sliding plate extends substantially perpendicular to the second endplate and has an inner surface defining a fourth spinous process engaging surface; an expansion assembly positioned between the first and second endplates; the expansion assembly configured to selectively cause the first and second endplates to move apart; actuating the expansion assembly to cause movement of the first and the second endplates away from one another; adjusting the lateral position of the first sliding plate such that spinous processes are compressed between the first and third spinous process engaging surfaces and thereafter fixing the position of the first sliding plate; and adjusting the lateral position of the second sliding plate such that spinous processes are compressed between the second and fourth spinous process engaging surfaces and thereafter fixing the position of the second sliding plate. 
         [0012]    Additional features, advantages, and aspects of the present disclosure may be set forth or apparent from consideration of the following detailed description, drawings, and claims. Moreover, it is to be understood that both the foregoing summary of the present disclosure and the following detailed description are exemplary and intended to provide further explanation without limiting the scope of the present disclosure as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The accompanying drawings, which are included to provide a further understanding of the present disclosure, are incorporated in and constitute a part of this specification, illustrate aspects of the present disclosure and together with the detailed description serve to explain the principles of the present disclosure. No attempt is made to show structural details of the present disclosure in more detail than may be necessary for a fundamental understanding of the present disclosure and the various ways in which it may be practiced. In the drawings: 
           [0014]      FIG. 1  is a perspective view of the expandable fixation device in accordance with one embodiment of the present disclosure shown in an unexpanded position; 
           [0015]      FIG. 2  is a front elevation view of the expandable fixation device of  FIG. 1  in the unexpanded position; 
           [0016]      FIG. 3  is an exploded perspective view of the expandable fixation device of  FIG. 1 ; 
           [0017]      FIG. 4  is a left side view of the expandable fixation device of  FIG. 1  in the unexpanded position; 
           [0018]      FIG. 5  is a right side view of the expandable fixation device of  FIG. 1  in the unexpanded position; 
           [0019]      FIG. 6  is a perspective view of the expandable fixation device of  FIG. 1  shown in an expanded position; 
           [0020]      FIG. 7  is a front elevation view of the expandable fixation device of  FIG. 1  in the expanded position; 
           [0021]      FIG. 8  is a left side view of the expandable fixation device of  FIG. 1  in the expanded position; 
           [0022]      FIG. 9  is a right side view of the expandable fixation device of  FIG. 1  in the expanded position; 
           [0023]      FIG. 10  is a perspective view of the expandable fixation device in accordance with another embodiment of the present disclosure shown in an expanded position; 
           [0024]      FIG. 11  is an exploded perspective view of the expandable fixation device of  FIG. 10 ; 
           [0025]      FIG. 12  is a left side view of the expandable fixation device of  FIG. 10  in an unexpanded position; 
           [0026]      FIG. 13  is a right side view of the expandable fixation device of  FIG. 10  in the unexpanded position; 
           [0027]      FIG. 14  is a right side view of the expandable fixation device of  FIG. 10  in an intermediate position; 
           [0028]      FIG. 15  is a left side view of the expandable fixation device of  FIG. 10  in the expanded position; and 
           [0029]      FIG. 16  is a right side view of the expandable fixation device of  FIG. 10  in the expanded position. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    The aspects of the present disclosure and the various features and advantageous details thereof are explained more fully with reference to the non-limiting aspects and examples that are described and/or illustrated in the accompanying drawings and detailed in the following description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale, and features of one aspect may be employed with other aspects as the skilled artisan would recognize, even if not explicitly stated herein. Descriptions of well-known components and processing techniques may be omitted so as to not unnecessarily obscure the aspects of the present disclosure. The examples used herein are intended merely to facilitate an understanding of ways in which the present disclosure may be practiced and to further enable those of skill in the art to practice the aspects of the present disclosure. Accordingly, the examples and aspects herein should not be construed as limiting the scope of the present disclosure, which is defined solely by the appended claims and applicable law. Moreover, it is noted that like reference numerals represent similar parts throughout the several views of the drawings. 
         [0031]    Surgical intervention for back pain may occur for people with chronic back pain, perhaps for which other treatments have failed. Surgery may be required, for example, for people who have chronic lower back pain and sciatica (often diagnosed with a herniated disc), spinal stenosis, spondylolisthesis (vertebra of the lumbar spine slips out of place), vertebral fractures with nerve involvement, or other indications as assessed by a medical professional. Also, surgery may be necessary for people with discogenic lower back pain (e.g., degenerative disc disease) that may occur as part of the aging process. In these situations, among others, implants may be included in a course of treatment. Generally, the goal may be to achieve supplemental fusion or complete fusion of the spine. 
         [0032]    With reference to  FIGS. 1-9 , an embodiment of the fixation device  10  is shown. In the exemplary embodiment, the fixation device  10  includes a first endplate  20 , a second endplate  40 , first and second fixed plates  60 ,  70 , a pair of sliding plates  80 ,  90 , a central ramp  110 , and a driving ramp  130 . 
         [0033]    Each of the endplates  20 ,  40  includes a body  22 ,  42  extending between opposed ends  21 ,  23 ;  41 ,  43 . In the illustrated embodiment, each endplate body  22 ,  42  defines an outer surface  24 ,  44  connecting the first end  21 ,  41  and the second end  23 ,  43 , and an inner surface  26 ,  46  connecting the first end  21 ,  41  and the second end  23 ,  43 . In an embodiment, each endplate  20 ,  40  defines a through opening  25 ,  45 . The through openings  25 ,  45 , in an exemplary embodiment, are sized to receive bone graft or similar bone growth inducing material and further allow the bone graft or similar bone growth inducing material to be packed in a central area of the device  10 . 
         [0034]    The outer surface  24 ,  44  of each endplate  20 ,  40  may be flat and generally planar to allow the outer surface  24 ,  44  of the endplate  20 ,  40  to engage with an adjacent vertebral body. Alternatively, one or both of the outer surfaces  24 ,  44  can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral body. It is also contemplated that the outer surfaces  24 ,  44  can be generally planar but include a generally straight ramped surface or a curved ramped surface, angled, or otherwise configured. The presence of one or more ramped surfaces may allow for engagement with the adjacent vertebral body in a lordotic fashion. While not illustrated, in an exemplary embodiment, one or both outer surfaces  24 ,  44  may include texturing or other surface features to aid in gripping the adjacent vertebral bodies. Although not limited to the following, the texturing or other surface features can include teeth, ridges, friction increasing elements, keels, gripping or purchasing projections, or the like. 
         [0035]    Referring to  FIGS. 3, 5 and 9 , the inner surface  26  of the first endplate  20  defines a first pair of spaced apart extensions  30  at the first end  21  of the body  22  and a second pair of spaced apart extensions  34  at the second end  23  of the body. The extensions  30  at the first end  21  are positioned oppositely of the extensions  34  at the second end  23 , e.g., on the first end  21 , the extension  30  on the right side is at the edge while the extension on the left side is inward of the edge and on the second end  23 , the extension  34  on the right side is inward of the edge while the extension on the left side is at the edge. Similarly, the inner surface  46  of the second endplate  40  defines a first pair of spaced apart extensions  50  at the first end  41  of the body  42  and a second pair of spaced apart extensions  54  at the second end  43  of the body. With the second endplate  40 , the extensions  50 ,  54  are opposite of those on the first plate  20  i.e. on the first end  41 , the extension  50  on the right side is inward from the edge while the extension on the left side is at the edge and on the second end  43 , the extension  54  on the right side is at the edge while the extension on the left side is inward of the edge. With this configuration, the extensions  30  of the first endplate  20  overlap the extensions  50  of the second endplate  40  and the extensions  54  of the second endplate  40  overlap the extensions  34  of the first endplate  20 . 
         [0036]    Each of the extensions  30 ,  34 ,  50 ,  54  defines a respective ramped surface  31 ,  35 ,  51 ,  55 . The ramped surfaces  31 ,  35 ,  51 ,  55  are configured to be engaged by ramped surfaces on the central ramp  110  and the driving ramp  130 , as will be described hereinafter. Each of the extensions  30 ,  34 ,  50 ,  54  also defines a respective groove  33 ,  37 ,  53 ,  57 . The grooves  33 ,  37 ,  53 ,  57  are configured to be engaged by projections on the central ramp  110  and the driving ramp  130  to maintain the device  10  in an assembled condition and to guide movement of the endplates  20 ,  40 , as will be described hereinafter. 
         [0037]    Each endplate  20 ,  40  includes a fixed plate  60 ,  70  attached along one side edge of the body  22 ,  42 . Each fixed plate  60 ,  70  of the illustrated embodiment includes a body  62 ,  72  extending from a fixed end  61 ,  71  to a free end  63 ,  73 . The fixed plate bodies  62 ,  72  may have any desired shape to complement the intended engagement with respective spinous processes, and may be mirror images of one another or may be distinct from one another. The inner surface  64 ,  74  of each fixed plate  60 ,  70  includes a plurality of spikes  66 ,  76  or the like to grip the spinous processes when engaged therewith. The outer surface of each fixed plate may include a blind bore  67 ,  77 , through bore or the like. The bores  67 ,  77 , in an exemplary embodiment, are sized to receive bone graft or similar bone growth inducing material. 
         [0038]    A lateral adjustment bar  28 ,  48  extends outwardly from the opposite side edge of the body  22 ,  42  of each end plate  20 ,  40  to a free end  29 ,  49 . The adjustment bars  28 ,  48  support respective sliding plates  80 ,  90 . Each sliding plate  80 ,  90  of the illustrated embodiment includes a body  82 ,  92  extending from a connection end  81 ,  91  to a free end  83 ,  93 . The sliding plate bodies  82 ,  92  may have any desired shape to complement the intended engagement with respective spinous processes, and may be mirror images of one another or may be distinct from one another. The inner surface  84 ,  94  of each fixed plate  80 ,  90  includes a plurality of spikes  86 ,  96  or the like to grip the spinous processes when engaged therewith. The outer surface of each fixed plate may include a blind bore  87 ,  97 , through bore or the like. The bores  87 ,  97 , in an exemplary embodiment, are sized to receive bone graft or similar bone growth inducing material. 
         [0039]    The connection end  81 ,  91  of each sliding plate  80 ,  90  includes a connection assembly  88 ,  98  which allows the sliding plate  80 ,  90  to be mounted on a respective lateral adjustment bar  28 ,  48  such that the sliding plate  80 ,  90  is laterally adjustable but rotationally fixed. In the illustrated embodiment, each connection assembly  88 ,  98  defines a receiving bore  85 ,  95  extending laterally through the body  82 ,  92  and configured to receive the respective lateral adjustment bar  28 ,  48 . The receiving bores  85 ,  95  and the lateral adjustment bars  28 ,  48  have complementary shapes which allow lateral adjustment but prevent relative rotation. In the illustrated embodiment, the receiving bores  85 ,  95  and lateral adjustment bars  28 ,  48  have complementary rounded rectangle shapes, but other non-circular shapes are possible. 
         [0040]    To set the position of the sliding plate  80 ,  90  along the respective lateral adjustment bar  28 ,  48 , a set screw  100  extends into a through bore  89 ,  99  defined in the respective connection assembly  88 ,  98  and intersects with the receiving bore  85 ,  95 . Each set screw  100  includes a threaded portion  102  and a driving head  104  with an engagement end  103  extending toward the receiving bore  85 ,  95 . The threaded portion  102  is configured to engage threads within the through bore  89 ,  99 . A retaining ring  105  or the like may be positioned about each set screw  100  and engage a groove within the through bore  89 ,  99  to retain the set screw  100  with the through bore  89 ,  99  after assembly. Once the sliding plate  80 ,  90  is positioned at a desired lateral position along the respective lateral adjustment bar  28 ,  48 , the set screw  100  is threadably advanced such that the engagement end  103  engages the lateral adjustment bar  28 ,  48  and fixes the sliding plate  80 ,  90  relative to the respective endplate  20 ,  40 . 
         [0041]    The central ramp  110  includes a body  112  extending from a first end  111  to a second end  113 . A through bore  114  extends through the body  112  from the first end  111  to the second end  113  and is configured to receive a drive screw  120  therethrough. The drive screw  120  has a threaded portion  122  and drive head  124 . A flat washer  126  and a drag reducing washer  128  may be positioned within the through bore  114  between the drive head  124  and an internal shoulder defined within the through bore  114  (not show) to facilitate driving of the central ramp while minimizing drag. Notches  119  or the like may be defined along the central ramp body  112  configured for engagement with a delivery/positioning tool (not shown) or the like. 
         [0042]    The second end  113  of the central ramp  110  defines a first pair of ramps  116  and a second pair of ramps  117 . The first ramps  116  are aligned with and configured to slidably engage the ramps  31  on the first endplate  20 . The second ramps  117  are aligned with and configured to engage the ramps  51  on the second end plate  40 . Projections  118  adjacent the ramps  116  extend into the grooves  33  on the first endplate  20  while projection adjacent to the ramps  117  (not shown) extend into the grooves  53  on the second endplate  40 . Engagement between the projections  118  and grooves  33 ,  53  maintains the central ramp  110  assembled to the endplates  20 ,  40  and guides movement of the endplates  20 ,  40  as the central ramp  110  is advanced. 
         [0043]    The driving ramp  130  includes a ramp body  132  and a screw receiving portion  134 . A threaded blind bore  139  extends into the screw receiving portion  134  and is configured to receive the threaded portion  122  of the drive screw  120 . As such, rotation of the drive screw  120  in the advancement direction causes the central ramp  110  and the driving ramp  130  to move toward one another. 
         [0044]    The ramp body  132  of the driving ramp  130  defines a pair of first ramps  136  and a pair of second ramps  137  (see  FIG. 3 ). The first ramps  136  are aligned with and configured to slidably engage the ramps  55  on the second endplate  40 . The second ramps  137  are aligned with and configured to engage the ramps  35  on the first end plate  20 . Projections  138  adjacent the ramps  136  extend into the grooves  57  on the second endplate  40  while projections  138  adjacent to the ramps  137  extend into the grooves  37  on the first endplate  20 . Engagement between the projections  138  and grooves  37 ,  57  maintains the driving ramp  130  assembled to the endplates  20 ,  40  and guides movement of the endplates  20 ,  40  as the driving ramp  130  is advanced. 
         [0045]    Having generally described the components of the fixation device  10 , operation thereof will generally be described. The fixation device  10  may be inserted at its fully collapsed height as illustrated in  FIGS. 1, 2, 4 and 5  to allow for easy insertion into a collapsed interspinous space. During insertion, the spikes  66 ,  76  of the fixed plates  60 ,  70  may be compressed into the respective spinous processes. After insertion, the fixation device  10  may be expanded by rotating the drive screw  120  in an advancement direction. As the drive screw  120  is rotated, the central ramp  110  and driving ramp  130  are drawn toward one another, with the ramps  31  riding up the ramps  116 , the ramps  51  riding up the ramps  117 , the ramps  35  riding up the ramps  137 , the ramps  55  riding up the ramps  136 . Such movement causes the endplates  20 ,  40  to move away from one another, thereby increasing the height of the fixation device  10  to get the desired fit, or used to distract the interspinous space to relieve pressure on neurological elements. As the endplates  20 ,  40  move away from one another, the fixed plates  60 ,  70  and sliding plates  80 ,  90  move in conformity therewith. After expansion of the endplates  20 ,  40 , the sliding plates  80 ,  90  are moved along the lateral adjustment bars  28 ,  48  and compressed onto the spinous processes. Once positioned, the sliding plates  80 ,  90  are locked into position using the set screws  100 . 
         [0046]    Referring to  FIGS. 10-16 , another embodiment of the fixation device  10 ′ is shown. The fixation device  10 ′ of the present exemplary embodiment is similar to the fixation device  10  of the previous embodiment and includes a first endplate  20 ′, a second endplate  40 ′, first and second fixed plates  60 ,  70 , a pair of sliding plates  80 ,  90 , a central ramp  110 ′, and a driving ramp  130 ′. Only the differences between the embodiments will be described. Otherwise, the fixation devices  10 ,  10 ′ operate is substantially the same manner. 
         [0047]    In the present embodiment, the endplates  20 ′ and  40 ′ and the central ramp  110 ′ are configured to cause pivoting between the endplates  20 ′,  40 ′ prior to expansion thereof. As in the previous embodiment, each endplate  20 ′,  40 ′ includes a body  22 ′,  42 ′ extending from a first end  21 ′,  41 ′ to a second end  23 ′,  43 ′. Referring to  FIG. 14 , in the present embodiment, the first ends  21 ′,  31 ′ do not include extensions, but instead have a tapered end surface which defines the ramps  31 ′  51 ′. The second ends  23 ′,  43 ′ are similar to the previous embodiment and include extensions  34 ′,  54 ′ defining the ramps  35 ,  55 . The extensions  34 ′  54 ′ also define inward ramps  36 ,  56 . Inward of the extensions  34 ,  54 , each endplate body  22 ′,  44 ′ defines a retaining notch  29 ,  49 . The retaining notches  29 ,  49  are configured to be engaged by an inward end  113 ′ of the central ramp  110 ′ and prevent inward advancement of the central ramp  110 ′ until the endplates  20 ′  40 ′ have pivoted relative to one another. 
         [0048]    The central ramp  110 ′ includes a body  112 ′ extending from a first end  111 ′ to a second end  113 ′ with the body  112 ′ having a longer length compared to the central ramp body  112  of the previous embodiment. A through bore  114  extends through the body  112 ′ from the first end  111 ′ and is configured to receive the drive screw  120  therethrough. The first end  111 ′ of the central body  110 ′ defines ramps  116 ′ and  117 ′. The ramps  116 ′ and  117 ′ are configured to engage the ramps  31 ′ and  51 ′, respectively. 
         [0049]    The second end  113 ′ of the central ramp  110  defines a pair of extensions  123  on a first surface thereof and a pair of extensions  125  on the opposite surface. The extensions  123  are aligned with and configured to be received in the notches  29  defined by the first endplate  20 ′ and the extensions  125  are aligned with and configured to be received in the notches  49  defined by the second endplate  40 ′ (see  FIG. 13 ). The extensions  123  also define forward ramps  127  while the extensions  125  define forward ramps  129 . 
         [0050]    The driving ramp  130 ′ includes a ramp body  132 ′ and a screw receiving portion  134 ′. The screw receiving portion  134 ′ is shorter in length than in the previous embodiment. A threaded blind bore  139  extends into the screw receiving portion  134 ′ and is configured to receive the threaded portion  122  of the drive screw  120 . 
         [0051]    The ramp body  132 ′ of the driving ramp  130 ′ defines a pair of ramps  136 ′ aligned with and configured to slidably engage the ramps  55  on the second endplate  40 ′. The ramp body  132 ′ also defines a pair of ramps  137 ′ which are aligned with and configured to engage the ramps  35  on the first end plate  20 ′. Projections  138 ′ adjacent the ramps  136 ′,  137 ′ extend into the grooves  37 ,  57  on the endplates  20 ′,  40 ′. Engagement between the projections  138 ′ and grooves  37 ,  57  maintains the driving ramp  130 ′ assembled to the endplates  20 ′,  40 ′ and guides movement of the endplates  20 ′,  40 ′ as the driving ramp  130 ′ is advanced. 
         [0052]    Having generally described the components of the fixation device  10 ′, operation thereof will generally be described with reference to  FIGS. 12-16 . The fixation device  10 ′ may be inserted at its fully collapsed height as illustrated in  FIGS. 12 and 13  to allow for easy insertion into a collapsed interspinous space. As illustrated, in the collapsed position, the extensions  123  and  125  are positioned in the respective notches  29 ,  49 . During insertion, the spikes  66 ,  76  of the fixed plates  60 ,  70  may be compressed into the respective spinous processes. After insertion, the angular relation between the endplates  20 ′,  40 ′ is adjusted by rotating the drive screw  120  in an advancement direction. During initial advancement of the drive screw  120 , engagement of the extensions  123 ,  125  in the notches  29 ,  49  prevents the central ramp  110 ′ from advancing. Only the driving ramp  130 ′ is able to advance. As the driving ramp  130 ′ advances, the ramps  35  ride up the ramps  136 ′ and the ramps  55  ride up the ramps  137 ′. As illustrated in  FIG. 14 , such causes the endplates  20 ′,  40 ′ to pivot relative to one another with the ends  23 ′ and  43 ′ moving away from one another. Once the endplates  20 ′,  40 ′ have pivoted a maximum amount ( FIG. 14 ), the extensions  123 ,  125  are clear of the notches  29 ,  49 . As such, with continued rotational advancement of drive screw  120 , the central ramp  110 ′ is free to move toward the driving ramp  130 ′, with the central ramp  110 ′ and the driving ramp  130 ′ drawn to one another, with the ramps  31 ′ riding up the ramps  116 ′, the ramps  51 ′ riding up the ramps  117 ′, the ramps  35  riding up the ramps  136 ′, the ramps  55  riding up the ramps  137 ′, and the forward ramps  127 ,  129  riding along the inward ramps  36 ,  56 , as illustrated in  FIGS. 15 and 16 . Such movement causes the endplates  20 ′,  40 ′ to move away from one another, thereby increasing the height of the fixation device  10  to get the desired fit, or used to distract the interspinous space to relieve pressure on neurological elements. As the endplates  20 ′,  40 ′ pivot and then move away from one another, the fixed plates  60 ,  70  and sliding plates  80 ,  90  move in conformity therewith. After expansion of the endplates  20 ′,  40 ′, the sliding plates  80 ,  90  are moved along the lateral adjustment bars  28 ,  48  and compressed onto the spinous processes. Once positioned, the sliding plates  80 ,  90  are locked into position using the set screws  100 . 
         [0053]    The expandable fixation devices  10 ,  10 ′ may be manufactured from a number of suitable biocompatible materials including, but not limited to, titanium, stainless steel, titanium alloys, non-titanium metallic alloys, polymeric materials, plastics, plastic composites, PEEK, ceramic, elastic materials, or other suitable biocompatible materials. 
         [0054]    In an exemplary embodiment, bone graft or similar bone growth inducing material can be introduced around and/or within the fixation device  10 ,  10 ′ to further promote and facilitate the intervertebral fusion. The fixation device  10 ,  10 ′, in one embodiment, is preferably packed with bone graft or similar bone growth inducing material to promote the growth of bone through and around the fixation device. Such bone graft may be packed between the endplates of the adjacent vertebral bodies prior to, subsequent to, or during implantation of the fixation device. 
         [0055]    Some advantages of the devices described in this disclosure are the ability to insert a spinous process fusion implant at a reduced height and then increase the height after insertion to achieve an accurate anatomical fit. Since the size of the implant is adjustable, it also greatly reduces the complexity of inserting an interspinous device since one device covers a wide range of implant sizes, negating the need for several variations of implant lengths and widths. The implant may be preassembled, greatly reducing the number of steps required to insert the device, which simplifies the overall procedure and reduces operating room time. 
         [0056]    While the present disclosure has been described in terms of exemplary aspects, those skilled in the art will recognize that the present disclosure can be practiced with modifications in the spirit and scope of the appended claims. These examples given above are merely illustrative and are not meant to be an exhaustive list of all possible designs, aspects, applications or modifications of the present disclosure.