Abstract:
An implantable spinous process fixation device includes a k-shaped component comprising an elongated plate and top and bottom deformable plates extending at first and second angles from a first surface of the elongated plate, respectively, thereby defining first and second spaces between the elongated plate and the top and bottom deformable plates and a compression element configured to compress and move the first and second deformable plates toward the elongated plate and to change the first and the second angles, respectively. The first and second spaces are configured to receive first and second spinous processes, respectively. Compressing and moving the first and second deformable plates toward the elongated plate results in engaging the first surface of the elongated plate and first surfaces of the top and bottom deformable plates with lateral surfaces of the first and second spinous processes, respectively.

Description:
CROSS REFERENCE TO RELATED CO-PENDING APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 60/750,520 filed Dec. 14, 2005 and entitled “SPINOUS PROCESS FIXATION IMPLANT”, the contents of which are expressly incorporated herein by reference. 
     This application is also a continuation of U.S. application Ser. No. 11/609,418 filed on Dec. 12, 2006 and entitled SPINOUS PROCESS FIXATION IMPLANT the contents of which are expressly incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a system and a method for spinal stabilization through an implant, and more particularly to spinal stabilization through attachment of the implant to the spinous processes along one or more vertebras. 
     BACKGROUND OF THE INVENTION 
     The human spine comprises individual vertebras  30  (segments) that are connected to each other to form a spinal column  29 , shown in  FIG. 1 . Referring to  FIGS. 1B and 1C , each vertebra  30  has a cylindrical bony body (vertebral body)  32 , three winglike projections (two transverse processes  33 ,  35  and one spinous process  34 ), left and right facet joints  46 , lamina  47 , left and right pedicles  48  and a bony arch (neural arch)  36 . The bodies of the vertebrae  32  are stacked one on top of the other and form the strong but flexible spinal column. The neural arches  36  are positioned so that the space they enclose forms a tube, i.e., the spinal canal  37 . The spinal canal  37  houses and protects the spinal cord and other neural elements. A fluid filled protective membrane, the dura  38 , covers the contents of the spinal canal. The spinal column is flexible enough to allow the body to twist and bend, but sturdy enough to support and protect the spinal cord and the other neural elements. The vertebras  30  are separated and cushioned by thin pads of tough, resilient fiber known as inter-vertebral discs  40 . Disorders of the spine occur when one or more of the individual vertebras  30  and/or the inter-vertebral discs  40  become abnormal either as a result of disease or injury. In these pathologic circumstances, fusion of adjacent vertebral segments may be tried to restore the function of the spine to normal, achieve stability, protect the neural structures, or to relief the patient of discomfort. 
     Several spinal fixation systems exist for stabilizing the spine so that bony fusion is achieved. The majority of these fixation systems utilize rods that attach to screws threaded into the vertebral bodies or the pedicles  48 , shown in  FIG. 3C . In some cases plate fixation systems are also used to fuse two adjacent vertebral segments. This construction usually consists of two longitudinal plates that are each placed laterally to connect two adjacent pedicles of the segments to be fused. This system can be extended along the sides of the spine by connecting two adjacent pedicles at a time similar to the concept of a bicycle chain. Current plate fixation systems are basically designed to function in place of rods with the advantage of allowing intersegmental fixation without the need to contour a long rod across multiple segments. Both the plating systems and the rod systems add bulk along the lateral aspect of the spine limits access to the pars and transverse processes for decortication and placement of bone graft. In order to avoid this limitation many surgeons decorticate before placing the rods, thereby increasing the amount of blood loss and making it more difficult to maintain a clear operative field. Placing rods or plates lateral to the spine leaves the center of the spinal canal that contains the dura, spinal cords and nerves completely exposed. In situations where problems develop at the junction above or below the fused segments necessitating additional fusion, the rod fixation system is difficult to extend to higher or lower levels that need to be fused. Although there are connectors and techniques to lengthen the fixation, they tend to be difficult to use and time consuming. 
     Accordingly, there is a need for a spinal stabilization device that does not add bulk to the lateral aspect of the spine and does not limit access to the pars and transverse processes for decortication and placement of bone graft. 
     SUMMARY OF THE INVENTION 
     In general, in one aspect, the invention features an implantable assembly for stabilization of spinous processes including a k-shaped component comprising an elongated plate and top and bottom deformable plates extending at first and second angles from a first surface of the elongated plate, respectively, thereby defining first and second spaces between the elongated plate and the top and bottom deformable plates and a compression element configured to compress and move the first and second deformable plates toward the elongated plate and to change the first and the second angles, respectively. The first and second spaces are configured to receive first and second spinous processes, respectively. Moving the first and second deformable plates toward the elongated plate results in engaging the first surface of the elongated plate and first surfaces of the top and bottom deformable plates with lateral surfaces of the first and second spinous processes, respectively. 
     Implementations of this aspect of the invention may include one or more of the following features. The compression element includes a plate placed on top of the top and bottom deformable plates and a bolt configured to pass through concentrically aligned through-bore openings formed in the center of the plate, the top and bottom deformable plates and the center of the elongated plate. The bolt comprises a head having a diameter larger that the diameter of the plate&#39;s through-bore and an elongated body having threads formed at a portion of the elongated body, the threads being dimensioned to engage inner threads in the elongated plate&#39;s through-bore. Tightening the bolt engages the bolt threads with the inner threads in the elongated plate&#39;s through-bore and compresses the head onto the plate and the plate onto the deformable top and bottom plates, causing them to move toward the elongated plate. The first surface of the elongated plate faces the first surfaces of the top and bottom deformable plates and all first surfaces comprise protrusions configured to engage and frictionally lock the elongated plate&#39;s first surface and the deformable top and bottom plates&#39; first surfaces onto the lateral surfaces of the first and second spinous processes. The may be teeth, spikes, serrations, rough coatings or ridges. The assembly may further include a top locking member configured to lock the elongated plate&#39;s top end and the top deformable plate&#39;s top end. The top locking member includes a long bolt configured to be threaded through bolt holes formed through the top deformable plate&#39;s end, the first spinous process and the elongated plate&#39;s top end. The top locking member may be staples, cables, sutures, pins or screws. The assembly may further include a bottom locking member configured to lock the elongated plate&#39;s bottom end and the bottom deformable plate&#39;s bottom end. The bottom locking member comprises a long bolt configured to be threaded through bolt holes formed through the bottom deformable plate&#39;s bottom end, the second spinous process and the elongated plate&#39;s bottom end. The bottom locking member may be staples, cables, sutures, pins or screws. The elongated plate, the top and bottom deformable plates and the compression element may be made of stainless steel, titanium, gold, silver, alloys thereof, absorbable material, non-metal materials including synthetic ligament material, polyethylene, extensible materials or combinations thereof. The elongated plate and the top and bottom deformable plates may have adjustable lengths. 
     In general, in another aspect, the invention features a method for stabilizing spinous processes, including providing a k-shaped component having an elongated plate and top and bottom deformable plates extending at first and second angles from a first surface of the elongated plate, respectively, thereby defining first and second spaces between the elongated plate and the top and bottom deformable plates and a compression element configured to compresses and move the first and second deformable plates toward the elongated plate and to change said first and said second angles, respectively. Next, placing first and second spinous processes within the first and second spaces, respectively, and then compressing and moving the first and second deformable plates toward the elongated plate via the compression element, thereby engaging lateral surfaces of the first and second spinous processes onto the elongated plate&#39;s first surface and the first and second deformable plates&#39; first surfaces, respectively. 
     Among the advantages of this invention may be one or more of the following. The assembly stabilizes vertebras by attaching plates to the spinous processes of the vertebras. This stabilization device does not add bulk to the lateral aspect of the spine and does not limit access to the pars and transverse processes for decortication and placement of bone graft. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and description below. Other features, objects and advantages of the invention will be apparent from the following description of the preferred embodiments, the drawings and from the claims 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the figures, wherein like numerals represent like parts throughout the several views: 
         FIG. 1A  is a side view of the human spinal column; 
         FIG. 1B  is an enlarged view of area A of  FIG. 1A ; 
         FIG. 1C  is an axial cross-sectional view of a lumbar vertebra; 
         FIG. 2  is a posterior view of a portion of the spine with a first embodiment of a spinous process fixation implant according to the present invention affixed thereto; 
         FIG. 3  is a top view of the spine with the spinous process fixation implant of  FIG. 2  affixed thereto; 
         FIG. 4  is a front side view of the spinous process fixation implant of  FIG. 2 ; 
         FIG. 5  is a back side view of the spinous process fixation implant of  FIG. 2 ; 
         FIG. 6  is a right side perspective view of the spinous process fixation implant of  FIG. 2 ; 
         FIG. 7  is partially exploded right side perspective view of the spinous process implant of  FIG. 2 ; 
         FIG. 8  is a left side perspective view of the spinous process fixation implant of  FIG. 2 ; 
         FIG. 9  is a top perspective view of the spinous process fixation implant of  FIG. 2 ; 
         FIG. 10  is an exploded right side perspective view of the spinous process fixation implant of  FIG. 2 ; 
         FIG. 11  is a front side view of the elongated component  110  of  FIG. 2 ; 
         FIG. 12  is a back side view of the elongated component of  FIG. 2 ; 
         FIG. 13  is a front side view of the top pivoting component of  FIG. 2 ; 
         FIG. 14  is a front side view of the bottom pivoting component of  FIG. 2 ; 
         FIG. 15  is a front side view of a second embodiment of a spinous process fixation implant according to the present invention, depicting the top and bottom pivoting components in the closed position; 
         FIG. 16  is a front side view of the spinous process fixation implant of  FIG. 15  with the top and bottom pivoting components in the open position; 
         FIG. 17  is a left side perspective view of the spinous process fixation implant of  FIG. 15 , depicting the top and bottom pivoting components in the closed position; 
         FIG. 18  is a left side perspective view of the spinous process fixation implant of  FIG. 15 , depicting the top and bottom pivoting components in the open position; 
         FIG. 19  is an exploded left side view of the spinous process fixation implant of  FIG. 15 ; 
         FIG. 20A  is a right side view of the elongated plate component  210  of  FIG. 15 ; 
         FIG. 20B  is a right side view of the top pivoting component  220  of  FIG. 15 ; 
         FIG. 20C  is a right side view of the bottom pivoting component  230  of  FIG. 15 ; 
         FIG. 21  is a front side view of a third embodiment of a spinous process fixation implant according to the present invention, depicting front and back pivoting components in the closed position around the spinous processes; 
         FIG. 22A  depicts insertion of the spinous process fixation implant of  FIG. 21  from the side with front and back pivoting components in the open position; 
         FIG. 22B  depicts pivoting the front and back pivoting components of  FIG. 21  to close them around the spinous processes; 
         FIG. 23  is a front side view of the embodiment of a spinous process fixation implant according of  FIG. 21 , depicting front and back pivoting components in the closed position and locked position around the spinous processes; 
         FIG. 24  is a front side view of a fourth embodiment of a spinous process fixation implant according to the present invention, depicting front top, front bottom and back pivoting components in the closed position around the spinous processes; 
         FIG. 25A  is a front side view of the front top pivoting component of the spinous process fixation implant of  FIG. 24 ; 
         FIG. 25B  is a front side view of the front bottom pivoting component of the spinous process fixation implant of  FIG. 24 ; 
         FIG. 25C  is a front side view of the back pivoting component of the spinous process fixation implant of  FIG. 24 ; 
         FIG. 26  is a front side view of the locking component of the spinous process fixation implant of  FIG. 24 ; 
         FIG. 27  is a front side view of a fifth embodiment of a spinous process fixation implant according to the present invention, depicting front and back pivoting components in the closed and locked position around the spinous processes; 
         FIG. 28  depicts cutting and opening paths A and B around superior and inferior adjacent spinous processes; 
         FIG. 29  depicts inserting back pivoting component of the spinous process fixation implant of  FIG. 27  along path A of  FIG. 28 ; 
         FIG. 30  depicts inserting front pivoting component of the spinous process fixation implant of  FIG. 27  along path B of  FIG. 28 ; and 
         FIG. 31  is a front side view of a sixth embodiment of a spinous process fixation implant according to the present invention, depicting a single K-component body. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to a system and a method for a spinous process fixation implant. 
     Referring to  FIG. 2 ,  FIG. 3 , and  FIG. 4 , a spinous process fixation assembly  100  stabilizes two adjacent vertebras  92 ,  94  of the human spine by engaging and locking their spinous processes  90   a  and  90   b , respectively. Spinous process fixation assembly  100  includes an elongate plate  110  and top and a bottom pivoting plates  120 ,  130 , located opposite to plate  110  and configured to form a K-shaped structure together with plate  110 . Top and bottom pivoting plates  120 ,  130  pivot around axis  140  (shown in  FIG. 6 ) independent from each other, forming angles  162 ,  164  with plate  110 , respectively. The pivoting motion of plates  120 ,  130  along directions  144   a ,  144   b  and  146   a ,  146   b , moves them close to or away from the elongated plate  110 , as shown in  FIG. 4 . Elongated plate  110  has a body  112  and front and back cross plates  114 ,  116 , extending at right angle to the front of the body  112  and back of the body  112 , respectively, as shown in  FIG. 10 ,  FIG. 11  and  FIG. 12 . Body  112  has a top end  113   a , a bottom end  113   b , an outer surface  118  and an inner surface  117 . Axis  140  passes through apertures  152  and  154  formed in the centers of the cross plates  114 ,  116 , respectively, as shown in  FIG. 11  and  FIG. 12 . Cross plates  114 ,  116  extend between the bottom surface and top surface of the adjacent spinous processes  90   a ,  90   b , respectively and have edges  115  which are rounded and sculpted to correspond to the geometry of the spinous processes  90   a ,  90   b  and lamina around which they will fit once implanted. Cross plates  114 ,  116  are substantially flat, parallel to each other and a gap is formed between them sized to hold portions of the top and bottom pivoting plates  120 ,  130 , as shown in  FIG. 7 . 
     Referring to  FIG. 10 ,  FIG. 13  and  FIG. 14 , top pivoting plate  120  has a main body  122  with top and bottom ends  123   a ,  123   b , respectively and inner  127  and outer surface  128 , respectively. An arm  124  extends downward from the bottom end  123   b  of the body  122  and a side plate  128  extends at right angle to the back of the body  122 . The arm  124  has an aperture  126  located at the bottom left corner and extends from the front side to the back side of the arm  124 . Similarly, bottom pivoting plate  130  has a main body  132  with top and bottom ends  133   a ,  133   b , respectively, and inner and outer surfaces  137 ,  138  respectively. An arm  134  extends upward form the top end  133   a  and has an aperture  136  at the top left corner, extending from the front side to the back side of the arm  134 , as shown in  FIG. 10 , and  FIG. 14 . A side plate  138  extends at right angle from to the back of the body  132 . All edges of plates  110 ,  120 ,  130  are rounded to prevent damage of the adjacent tissue during implantation or spinal movement. Plates  110 ,  120 ,  130  are made of stainless steel, titanium, gold, silver, alloys thereof, absorbable material, non-metal materials including synthetic ligament material, polyethylene, extensible materials or combinations thereof. Plates  110 ,  120 ,  130  may have adjustable lengths. In one example plates  110 ,  120 ,  130  have lengths of 30 mm, 15 mm, 15 mm, respectively, and the assembly may have a width between 3 mm to 10 mm. 
     Referring to  FIG. 7 , a long bolt  180  passes through apertures  152  and  154  of the cross plates  114 ,  116  of the elongated plate  110  and though apertures  126  and  136  formed in the top and bottom pivoting plates  120 ,  130 , respectively. Bolt  180  has a head  181 , a shaft  183  and threads  184  formed on the end portion of the shaft  183 . Threads  184  engage threads in the aperture  154  of the back cross plate  116 , in order to hold and secure the three components  110 ,  120 ,  130 , of the assembly  100  together. In other embodiments, a nut (not shown) is attached at the end of the bolt  180  to hold and secure the three components  110 ,  120 ,  130 , of the assembly  100  together. In other embodiments bolt  180  is threaded into the cartilage between the two vertebras to secure the three components  110 ,  120 ,  130  together and to attach the assembly  100  onto the spine. The inner surfaces  117 ,  127 ,  137  of plates  110 ,  120 ,  130 , respectively, have protrusions  111  that grab and frictionally engage the sides of the spinous processes  90   a ,  90   b , as shown in  FIG. 3 ,  FIG. 11 ,  FIG. 13  and  FIG. 14 . Protrusions  111  may be teeth, serrations, ridges, and other forms of rough surfaces or coatings that produce rough surfaces. The position of pivoting plates  120 ,  130  relative to each other and relative to plate  110  is locked with a set screw  182  passing trough the aperture  156  formed in the upper right corner of the front cross plate  114 . Tightening of the setscrew  182  locks the front and back cross plates  114 ,  116  to the pivoting plates  120  and  130 . Engaging and locking the spinous process fixation assembly  100  onto spinous processes  90   a ,  90   b , prevents the components  110 ,  120  and  130  from moving sidewise or up and down toward or away from each other during spinal movement. 
     The assembled spinous process fixation assembly  100  is implanted into the patient with the use of instrumentation (not shown) between the two adjacent spinous processes  90   a ,  90   b , as shown in  FIG. 2 . The cross plates  114 ,  116  are placed between the spinous processes  90   a ,  90   b  so that the body  112  of the elongated plate  110  and the top and bottom pivoting plates  120 ,  130  fall on the lateral sides of the spinous processes  90   a ,  90   b . One spinous process  90   a  lies between the top portion of the body  112  and the top pivoting plate  120 , as shown in  FIG. 3 , and the other spinous process  90   b  lies between the bottom portion of the body  112  and the bottom pivoting plate  130 , with their inner surfaces  117 ,  127 ,  137  facing the lateral surfaces of the spinous processes  90   a ,  90   b . On each of the inner surfaces  117 ,  127 ,  137  of the plates  110 ,  120 ,  130 , respectively, the protrusions  111  face toward the lateral surface of the adjacent spinous process. At this point, the top and bottom pivoting plates  120 ,  130  are pivoted as necessary to provide the desired fit of the plates to the spinous processes. The bolt  180  is tightened, clamping the protrusions  111  into the surfaces of the spinous processes and locking the three plates relative to each other by engaging the threads of the aperture  154 . The protrusions  111  and the threading of the bolt into aperture  154  of the back cross plate  116  frictionally secures the spinous process fixation assembly  100  onto the spinous processes  90   a ,  90   b  and helps prevent the device from shifting or slipping. 
     Referring to  FIG. 15 ,  FIG. 16 ,  FIG. 17 ,  FIG. 18 , in a second embodiment of the spinous process fixation assembly  200 , the top and bottom pivoting plates  220 ,  230  are designed to pivot past each other and to form any angle with the elongated plate  210  between 0 and 180 degrees. In particular, plates  220  and  230  pivot to a 90 degree angle relative to plate  210  and form a sidewise oriented T, shown in  FIG. 16  and  FIG. 180 . The assembly  200  of  FIG. 16 , with the pivoting plates  220 ,  230  at a 90 degree angle with the plate  110 , is inserted sidewise between the top and bottom spinous processes  90   a ,  90   b . Once the assembly is inserted, the plates  220  and  230  are pivoted upward and downward, respectively, and are placed at angles relative to the plate  210  necessary to provide the desired fit of the plates to the spinous processes. Sidewise implantation of the assembly  200  has the advantage of reduced trauma in the area between the spinous processes. 
     In this embodiment the top pivoting plate  220  has a main body  222  with top and bottom ends  223   a ,  223   b , respectively and inner  227  and outer surface  228 , respectively, shown in  FIG. 19 ,  FIG. 20 . Main body  222  has a width  229  dimensioned to allow plate  220  to pivot past plate  230  when placed in the gap  219  between the two cross plates  214 ,  216  of plate  210 . An arm  224  extends downward from the bottom end  223   b  of the body  222 . The arm  224  has an aperture  226  located at the center of the bottom end of the arm and extends from the front side to the back side of the arm  224 . A protruding annulus  225  surrounds aperture  226  and projects outward form the back side of the arm  224 . Annulus  225  is dimensioned to fit within aperture  254  of the back cross plate  216 . Aperture  226  includes inner threads (not shown) extending from the front to the back side of the arm  224 . Similarly, bottom pivoting plate  230  has a main body  232  with top and bottom ends  233   a ,  233   b , respectively, and inner and outer surfaces  237 ,  238  respectively. Main body  232  has a width  239  dimensioned to allow plate  230  to pivot past plate  220  when placed in the gap  219  between the two cross plates  214 ,  216  of plate  210 . An arm  234  extends upward form the top end  233   a  and has an aperture  236  located at the center of the top end of the arm and extends from the front side to the back side of the arm  234 , as shown in  FIG. 19  and  FIG. 20C . 
     Elongated plate  210 , top pivoting plate  220  and bottom pivoting plate  230  are assembled together, as shown in  FIG. 18 . Annulus  225  is inserted in the aperture  254  of the back cross plate  216  and the apertures  252 ,  236 ,  226  of the front cross plate  214 , bottom pivoting plate  230  and top pivoting plate  220 , respectively, are aligned. A long bolt  280  is inserted through the aligned apertures and threaded in the inner threads of the aperture  226 . The position of pivoting plates  220 ,  230  relative to each other and relative to plate  210  is locked with a set screw  282  passing trough the aperture  256  formed in the upper left corner of the front cross plate  214 . Tightening of the set screw  282  locks the front and back cross plates  214 ,  216  to the pivoting plates  220  and  230 . Once assembly  200  is implanted into the patient between the two adjacent spinous processes  90   a ,  90   b , the assembly is secured and locked in position, according to the process described above. 
     Referring to  FIG. 21 , in a third embodiment the spinous process fixation assembly  300  includes a front S-shaped plate  310  and a mirror image back S-shaped plate  320  connected at their centers via a bolt  380  forming an X-shaped structure. The front S-shaped plate  310  pivots relative to a back S-shaped plate  320  around pivot point  340  and the spinous process  90   a  of the top vertebra  92  is frictionally engaged between the upper arms of S-plates  310  and  320 , while the spinous process  90   b  of the bottom vertebra  42  is frictionally engaged between the lower arms of S-plates  310  and  320 . A bolt  380  is threaded through apertures formed in the centers of the front and back S-plates, as shown in  FIG. 21 . The inner surfaces of the upper and lower arms of the S-shaped plates are sculpted to fit the shape of the spinous processes and have protrusions that frictionally engage the sides of the spinous processes and together with the bolt  380  securely lock the assembly  300  between the spinous processes  90   a ,  90   b.    
     Assembly  300 , with the S-shaped plates  310 ,  320  assembled and oriented horizontally, as shown in  FIG. 22A , is inserted sidewise between the top and bottom spinous processes  90   a ,  90   b . Once the assembly is inserted, plates  310  and  320  are pivoted upward and downward, respectively, as shown in  FIG. 22B , and they assume a vertical orientation so that their corresponding inner surfaces surround spinous processes  90   a ,  90   b . Sidewise implantation of the assembly  300  has the advantage of reduced trauma in the area between the spinous processes. 
     Long bolts  370  may be added to this embodiment to further anchor the assembly  300  on the spinous processes. If they are added, appropriately sized holes must be drilled laterally through the spinous processes prior to placement of the device. Once the device is in place as described above, one long bolt  370  is threaded through a bolt hole on the top end of plate  310 , through the drilled hole in the spinous process  90   a , then out through a bolt hole on top end of plate  320 . A second long bolt  370  may also be threaded through a bolt hole on the bottom end of plate  310 , through the drilled hole in the spinous process  90   b , then out through a bolt hole on the bottom end of plate  320 . Tightening of bolts  380  and  370  securely locks the assembly  300  around spinous processes  90   a ,  90   b.    
     In another embodiment of the spinous process fixation assembly  400 , shown in  FIG. 24 , the front S-shaped plate include a top pivoting component  410 , shown in  FIG. 25A , and a bottom pivoting component  420 , shown in  FIG. 25B , forming the top and bottom portions of the S-curve, respectively. The back S-plate  430  is formed as one component S-shaped plate with a curved top portion  432 , a bottom curved portion  434  and a rounded center  438  having an aperture formed in its center  436 , shown in  FIG. 25C . The top pivoting component  410  includes an upward extending curved portion  412  and a lower rounded end  414  having an aperture  416  formed in its center. The bottom pivoting component includes a downward extending curved portion  422  and an upper rounded end  424  having an aperture  426  formed in its center. The front and back surfaces of the rounded end  424 , the back surface of the rounded end  414  and the front surface of the rounded center  438  have radial extending grooves  425 , shown in  FIG. 25B  and  FIG. 25C . Grooves  425  define one-degree arcs, thus allowing the plates  410 ,  420 ,  430  to rotate relative to each other by one degree steps. Assembly  400  further includes a block  440  dimensioned to fit between the adjacent spinous processes  90   a ,  90   b  and having top and bottom edges configured to correspond to the geometry of the spinous processes  90   a ,  90   b  and lamina around which they will fit once implanted. Different sized blocks are used to accommodate different spacings between adjacent spinous processes  90   a ,  90   b . The front and back surfaces of block  440  also include grooves  425  around an aperture  446  formed n the center of the block. The top pivoting plate  410 , bottom pivoting plate  420 , block  440  and the back plate  430  are arranged so that their corresponding apertures  416 ,  426 ,  446 ,  436  are aligned and a bolt  480  is threaded through these apertures. Once the assembly  400  is inserted, the plates  410  and  420  are pivoted upward and downward, respectively, and are placed so as to surround the spinous processes. The inner surfaces of the upper and lower arms of the S-shaped plates are sculpted to fit the shape of the spinous processes and have protrusions that frictionally engage the sides of the spinous processes and together with the bolt  480  securely lock the assembly  400  between the spinous processes  90   a ,  90   b.    
     Long bolts  370  may be also added to this embodiment to further anchor the assembly  400  on the spinous processes, as was described above. Alternatively, a staple  450  may be placed on the top and bottom open ends of the plates  410 ,  420  and  430 , as shown in  FIG. 27 . In other embodiments banding, cabling or suturing may be used to attach the ends of plates  410 ,  420  and  430  to the spinous processes. The outer surfaces of the plates  410 ,  420  and  430  may be rounded, as shown in  FIG. 24  or straight, a shown in the embodiment  500  of  FIG. 27 . 
     Referring to  FIG. 28 ,  FIG. 29  and  FIG. 30 , the process of implanting the spinous process fixation assembly between two adjacent vertebrae includes the following steps. First an incision is made in the patient&#39;s back and paths A and B are opened along bony planes  95  and through ligaments  96  between the adjacent spinous processes  90   a ,  90   b . Path B is mirror image of path A about the centered sagittal plane  98 . Next, the back component  510  of the assembly of  FIG. 27  is inserted along path A, as shown in  FIG. 29 , and the ends  513   a  and  513   b  are attached to the spinous processes  90   a ,  90   b , respectively. Next, the front component  520  is inserted along path B and a bolt  580  is threaded through the apertures  512 ,  522  formed in the centers of back and front components  510 ,  520 , respectively. The front and back components are pivoted around the axis passing through their central apertures  512 ,  522 , so that their ends  513   a ,  523   a ,  513   b ,  523   b  surround and close around the spinous processes  90   a ,  90   b . The ends  513   a ,  523   a , and  513   b ,  523   b  are then attached to spinous processes  90   a ,  90   b , respectively as shown in  FIG. 30 . The ends may be attached with any of the above mentioned methods including frictional engagement of protrusions, long bolts, staples, cabling, banding or suturing. Plates  510 ,  520  are dimensioned so when assembled, assembly  500  has a width  535  that covers and protects the spinal cord after laminectomy or facectomy. 
     In a sixth embodiment, shown in  FIG. 31 , spinous process fixation assembly  600  includes one K-shaped component having an elongated plate  610  and two deformable plates  620 ,  630  extending upward and downward, respectively, from the center  615  of the elongated plate. A top gap  612  is formed between the top portion of the elongated plate  610  and the upward extending plate  620 . A bottom gap  614  is formed between the bottom portion of the elongate plate  610  and the downward extending plate  630 . The K-shaped assembly is placed between the adjacent spinous processes  90   a ,  90   b , as shown in  FIG. 31 , and a plate  640  is placed in the center of the assembly  600  on top deformable plates  620 ,  630 . A bolt  680  is threaded through apertures formed in the center of plate  640  and the center  615  of the K-shaped component, as shown in  FIG. 31 . Tightening of the bolt  680  down applies pressure onto the plate  640 , which is transferred to the top and bottom deformable plates  620 ,  630 . Plates  620 ,  630  move closer to plate  610  and the widths of the top and bottom gaps  612 ,  614  is reduced, resulting in engaging protrusions  111  formed on the inner surfaces of plates  610 ,  620 ,  630  with the spinous processes  90   a ,  90   b  and tightening of the plates  620 ,  630  and  610  around the spinous processes  90   a ,  90   b . The ends of the plates  620 ,  630  may be further attached to the spinous processes with any of the above mentioned methods including long bolts, staples, cabling, banding or suturing. 
     Other embodiments are within the scope of the following claims. For example, vertebras  92  and  94  may be any two vertebras, including lumbar L1-L5, thoracic T1-T12, cervical C1-C7 or the sacrum. The fixation assembly  100  may extend along multiple vertebras. The K shaped structure may be also configured as a mirror image of the structure in  FIG. 2 , with the pivoting plates  120 ,  130  located on the left side and the elongated plate  110  located on the right side of the  FIG. 2 . The elongated plates  110 ,  220  and the top and bottom pivoting plates  120 ,  220 , and  130 ,  230  of the embodiments of  FIG. 4  and  FIG. 15 , respectively, may have adjustable lengths. Similarly, S-plates  310 ,  320  of the embodiment of  FIG. 21  and plates  410 ,  420 ,  430  of the embodiment of  FIG. 24  may have adjustable lengths. Similarly, elongated plate  610  and deformable plates  620 ,  630  of the embodiment of  FIG. 31  may have adjustable lengths. The main bodies  122 ,  132  of pivoting plates  120 ,  130  may be detached from the corresponding extending arms  124 ,  134 . Bodies  122 ,  132  may be attached to the extending arms  124 ,  134  via hinges (not shown) which allow them to swing open and close for better placement around the corresponding spinous processes  90   a ,  90   b.    
     Several embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.