SPINOUS PROCESS FTXATTON TMPLANT

Cross Reference to related Co-Pending Applications This application claims the benefit of U.S. provisional application Serial No. 60/750,520 filed December 14th, 2005 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. IB 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 first plate component, a top pivoting plate and a bottom pivoting plate. The first plate component includes an elongated plate and front and back cross plates extending at right angle to the front and back of the elongated plate, respectively. Te top and bottom pivoting plates are configured to pivot around an axis perpendicular to the front and back cross plates, and the elongate

plate includes an inner surface facing an inner surface of the top pivoting plate and an inner surface of the bottom pivoting plate.

Implementations of this aspect of the invention may include one or more of the following features. The top and bottom pivoting plates are configured to be received within a gap formed between the front and back cross plates. The assembly further includes a post member configured to pass through concentrically aligned through- bore openings formed in the front cross plate, the top pivoting plate, the bottom pivoting plate and the back cross plate. The top and bottom pivoting plates arc configured to pivot around the post member and to set first and second pivot angles with the elongated plate thereby defining first and second spaces between the elongated plate and the top and bottom pivoting plates, respectively. The post member includes a locking element for securing and preventing pivoting of the top and bottom pivoting plates relative to the elongated plate. The post member may be an elongated bolt and the locking element may be threads formed at a portion of the bolt, dimensioned to engage inner threads in the back cross plate through-bore. The post member may be an elongated bolt and the locking element may be threads formed at a portion of the bolt, dimensioned to engage a nut after the bolt exits the back cross plate through-bore. The inner surfaces of the elongated plate, the top and bottom pivoting plates include protrusions configured to engage and frictionally lock the plates onto first and second spinous processes positioned in the first space between the elongated plate and the top pivoting plate and the second space between the elongated place and the top pivoting plate, respectively. The front and back cross plates are dimensioned to fit between the first and second spinous processes and comprise edges sculpted to conform to the shape of the spinous processes. The first and second pivot angles comprise values between zero and 180 degrees. The top and bottom pivoting plates are pivoted to first and second pivot angles of 90 degrees relative to the elongated plate for sidewise insertion of the assembly between the first and second spinous processes. The assembly may be assembled prior to or after being implanted between the first and second spinous processes. The assembly may further include an additional locking member for securing the top pivoting plate relative to the elongated plate. The additional locking member may be a set screw dimensioned to pass through and engage threads formed in the inner surface of a second through bore formed in the front cross plate and to frictionally engage the top pivoting plate.

The assembly may further include a top locking member configured to lock the elongated plate's top end and the top pivoting plate's top end. The top locking member may be a long bolt configured to be threaded through bolt holes formed through the top pivoting plate end, the first spinous process and the elongated plate 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's bottom end and the bottom pivoting plate's bottom end. The bottom locking member may be a long bolt configured to be threaded through bolt holes formed through the bottom pivoting plate bottom end, the second spinous process and the elongated plate bottom end. The bottom locking member may be staples, cables, sutures pins or screws. The protrusions may be teeth, spikes, serrations, rough coatings or ridges. The first plate component, the top and bottom pivoting plates may be made of stainless steel, titanium, gold, silver, alloys thereof or absorbable material. The first plate component, the top and bottom pivoting plates may have adjustable lengths. Each of the top and bottom pivoting plates may include a main body and an extending arm. The extending arm may be detachable from the main body and may be attached to the main body via a hinge.

In general, in another aspect, the invention features a method for stabilizing spinous processes of a spinal column, including providing a first plate component, a top pivoting plate and a bottom pivoting plate and. The first plate component includes an elongated plate and front and back cross plates extending at right angle to the front and back of the elongated plate, respectively, and engages an inner surface of said elongated plate with a first lateral surface of a first spinous process and a first lateral surface of a second spinous process. The top pivoting plate is pivoted toward the elongated plate to engage an inner surface of the top pivoting plate with a second lateral surface of the first spinous. The second lateral surface of the first spinous process is opposite to the first lateral surface of the first spinous process. The bottom pivoting plate is pivoted toward the elongated plate to engage an inner surface of the bottom pivoting plate with a second lateral surface of the second spinous process. The second lateral surface of the second spinous process is opposite to the first lateral surface of the second spinous process. The top and bottom pivoting plates are configured to pivot around an axis perpendicular to the front and back cross plates.

In general, in another aspect, the invention features an implantable assembly for stabilization of spinous processes including a first S-shaped plate having a first surface configured to engage a first lateral surface of a first spinous process and a second surface configured to engage a second lateral surface of a second spinous process and a second S-shaped plate having a first surface configured to engage a second lateral surface of the first spinous process and a second surface configured to engage a first lateral surface of the second spinous process. The first and second S- shapcd plates arc configured to pivot around an axis perpendicular to the center portions of the first and second S-shaped plates.

In general, in another 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.

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. IA is a side view of the human spinal column;

FIG. IB is an enlarged view of area A of FIG. IA;

FIG. 1 C 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;

FTG. 12 is a back side view of the elongated component of FTG. 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. 2OA is a right side view of the elongated plate component 210 of FIG. 15;

FIG. 2OB 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 ;

FTG. 22B depicts pivoting the front and back pivoting components of FTG. 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;

FTG. 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;

FTG. 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 90a and 90b, 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 FTG. 6) independent from each other, forming angles 162, 164 with plate 110, respectively. The pivoting motion of plates 120, 130 along directions 144a, 144b and 146a, 146b, 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 113a, a bottom end 113b, 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 90a, 90b, respectively and have edges 115 which are rounded and sculpted to correspond to the geometry of the spinous processes 90a, 90b 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 FTG. 10, FTG. 13 and FTG. 14, top pivoting plate 120 has a main body 122 with top and bottom ends 123a, 123b, respectively and inner 127 and outer surface 128, respectively. An arm 124 extends downward from the bottom end 123b 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 133a, 133b,respectively, and inner and outer surfaces 137, 138 respectively. An arm 134 extends upward form the top end 133a 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 30mm, 15mm, 15mm, respectively, and the assembly may have a width between 3mm to 10mm.

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 90a, 90b, 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 1 10 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 set screw 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 90a, 90b, 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 90a, 90b, as shown in FIG. 2. The cross plates 114, 116 are placed between the spinous processes 90a, 90b 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 90a, 90b. One spinous process 90a 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 90b 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 90a, 90b. On each of the inner surfaces 117, 127, 137 of the plates 1 10, 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 90a, 90b 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 1 10, is inserted sidewise between the top and bottom spinous processes 90a, 90b. 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 223a, 223b, 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 223b 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, 233b,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 233a 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. 2OC. ^' '

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 90a, 90b, 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- shapcd plate 310 pivots relative to a back S-shapcd plate 320 around pivot point 340 and the spinous process 90a of the top vertebra 92 is frictionally engaged between the upper arms of S-plates 310 and 320, while the spinous process 90b 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 9Oa ₅ 90b.

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 90a, 90b. 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 90a, 90b. 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 90a, 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 90b, 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 90a, 90b.

In another embodiment of the spinous process fixation assembly 400, shown in FlG. 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-shapcd 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 90a, 90b and having top and bottom edges configured to correspond to the geometry of the spinous processes 90a, 90b and lamina around which they will fit once implanted. Different sized blocks are used to accommodate different spacings between adjacent spinous processes 90a, 90b. 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 arc arranged so that their corresponding apertures 416, 426, 446, 436 arc 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 90a, 90b.

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 attached 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's back and paths A and B are opened along bony planes 95 and through Iigaments96 between the adjacent spinous processes 90a, 90b. 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 513a and 513b are attached to the spinous processes 90a, 90b, 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 513a, 523a, 513b, 523b surround and close around the spinous processes 90a, 90b. The ends 513a, 523a, and 513b, 523b are then attached to spinous processes 90a, 90b, respectively as shown in FlG. 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 faccctomy.

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 90a, 90b, as

shown in FTG. 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 90a, 90b and tightening of the plates 620, 630 and 610 around the spinous processes 90a, 90b. 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 Tl- T 12, 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 1 10 located on the right side of the FTG. 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 90a, 90b.

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. What is claimed is: