Patent Publication Number: US-2005124993-A1

Title: Facet fusion system

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application is a continuation-in-part of co-pending U.S. utility patent application entitled, “Facet Fusion System,” having Ser. No. 10/725,832, filed on Dec. 2, 2003, which is entirely incorporated herein by reference. Co-pending U.S. utility patent application entitled “Facet Fusion System,” having Ser. No. 10/725,832 claims priority to co-pending U.S. provisional application entitled, “Facet Fusion Apparatus and Method of Use,” having Ser. No. 60/430,311, filed on Dec. 2, 2002, which is entirely incorporated herein by reference. 
    
    
     TECHNICAL FIELD  
      The present disclosure generally relates to surgical instruments, and in particular, relates to a facet fusion system.  
     BACKGROUND  
      Skeletal structures are formed of bones and adjoining structures which include cartilage, for instance. For various reasons, these skeletal structures may require artificial support or stabilization. For example, the human spine is composed of a column of thirty-three bones, called vertebrae, and their adjoining structures. The twenty-four vertebrae nearest the head are separate bones capable of individual movement and generally are connected by anterior and posterior longitudinal ligaments and by discs of fibrocartilage, called intervertbral discs, positioned between opposing faces of adjacent vertebrae. Each of these vertebrae includes a vertebral body and a dorsal arch that enclose an opening, called the vertebral foramen, through which the spinal cord and spinal nerves pass. The remaining nine vertebrae are naturally fused to form the sacrum and the coccyx and are incapable of individual movement.  
      Each vertebra capable of individual movement is joined to the adjoining vertebra at facet joints. Facet joints allow for movement of the spine in all directions. Arthritis, degenerative disc disease, and other various degenerative conditions can result in the need to surgically fuse the facet joints together.  
      Facet joint fusion can reduce or eliminate pain and/or complications experienced by patients with degenerating facet joints. Currently, facet joints are fused by decorticating the joint in an open procedure followed by inserting a bone implant. In this process, often times the facet joint is not completely decorticated resulting in a low fusion success rate.  
      Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.  
     SUMMARY  
      Preferred embodiments of the present disclosure provide a facet fusion system for fusing a facet joint. Briefly described in architecture, one embodiment of the system can be implemented as follows. A facet fusion system comprises a trochar and a retractor, both being arranged and configured for use during percutaneous retraction. A facet bur is adapted for decorticating the facet joint. The trochar, retractor, and facet bur are implemented to prepare the facet joint for fusion.  
      Other systems, methods, features and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      The embodiments of present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
       FIG. 1  is a diagram illustrating two vertebrae within the human spine.  
       FIG. 2  is a functional block diagram of one embodiment of a trochar used in facet fusion surgery on the facet joint of  FIG. 1 .  
       FIG. 3  is a perspective view diagram of a retractor used in facet fusion surgery on the facet joint of  FIG. 1 .  
       FIG. 4  is a perspective view diagram of a facet bur used in facet fusion surgery on the facet joint of  FIG. 1 .  
       FIG. 5  is a perspective view diagram of a sizing insert used in facet fusion surgery on the facet joint of  FIG. 1 .  
       FIG. 6 a  perspective view diagram of a trapezoidal implant used in facet fusion surgery on the facet joint of  FIG. 1 .  
       FIG. 7  is a perspective view diagram of a T-shaped implant used in facet fusion surgery on the facet joint of  FIG. 1 .  
       FIG. 8  is a perspective view diagram of the trapezoidal implant of  FIG. 6 , further including a cage construction.  
       FIG. 9  is a perspective view diagram of the T-shaped implant of  FIG. 7 , further including a cage construction.  
       FIG. 10  is a functional block diagram of a facet joint with the trapezoidal cage implant of  FIG. 8  and stapling device.  
       FIG. 11  is a functional block diagram of a facet joint with the T-shaped cage implant of  FIG. 9  and stapling device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Having summarized various aspects of the present disclosure, reference will now be made in detail to the description as illustrated in the drawings. While the disclosure will be described in connection with these drawings, there is no intent to limit it to the embodiment or embodiments disclosed therein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of the invention as defined by the appended claims. It should be emphasized that many variations and modifications may be made to the above-described embodiments. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.  
       FIG. 1  is a diagram illustrating two vertebrae within the human spine. As shown in  FIG. 1 , spinal column  10  includes two vertebrae  16   a  and  16   b . Intervertebral disk  12  is located between vertebrae  16   a  and vertebrae  16   b . Invetertebral disk  12  serves to cushion the vertebrae from impact due to bodily movement.  
      As stated above, each of the vertebrae includes a vertebral body and a dorsal arch that enclose an opening, called the vertebral foramen  15 , through which the spinal cord and spinal nerves pass. The vertebral foramen is the opening between every two vertebrae where the nerve roots exit the spine. The nerve roots travel through the foramen to reach the rest of the body. Without the foramen, nerve signals could not travel to and from the brain to the rest of the body.  
      Also included in  FIG. 1  are facets  8   a  and  8   b  and facet joint  14 . Facets  8   a  and  8   b  are the “bony knobs” that meet between each vertebra to form the facet joints  14  that join your vertebrae together. There are two facet joints between each pair of vertebra, one on each side. They extend and overlap each other to form a joint between the neighboring vertebra facet joints.  
      The facet joints  14  are what are known as synovial joints. A synovial joint, such as the knee or elbow, is a structure that allows movement between two bones. In a synovial joint, the ends of the bones are covered with a material called articular cartilage. This material is a slick spongy material that allows the bones to glide against one another without much friction.  
      Surrounding facet joint  14  is a watertight sack made of soft tissue and ligaments. This sack creates what is called the “joint capsule.” The ligaments are soft tissue structures that hold the two sides of the facet joint together. The ligaments around the facet joint combine with the synovium to form the joint capsule that is filled with fluid (synovial fluid). This fluid lubricates the joint to decrease the friction, just like oil lubricates the moving parts of a machine.  
      As stated above, fusion of a facet joint  14  may be required when a patient suffers from arthritis, or other degenerative disease which makes movement painful in the spinal region.  
       FIG. 2  is a perspective view diagram of one embodiment of a trochar  18  used in facet fusion surgery on the facet joint  14  of  FIG. 1 . As shown in  FIG. 2 , the trochar  18  comprises a hollow body portion  17  having at least one tapered end  19 . The trochar  18  preferably includes a substantially sharpened, pointed tip  20  toward the tapered end  19 . This device may be used for decorticating the facet joint  14  in order to prepare for the facet fusion surgery.  
       FIG. 3  is a perspective view diagram of a retractor  20  used in facet fusion surgery on the facet joint  14  of  FIG. 1 . As shown in  FIG. 3 , the retractor  20  comprises a main body portion  32  having a handle  34  extending therefrom. The main body portion  32  is preferably hollow. The trochar  18  and the retractor  20  are used to perform percutaneous retraction and dissection of the facet joint  14  in a manner known to those skilled in the art. More specifically, the trochar  18  is placed into a position such as to dilate surrounding muscle. The retractor  30  is then placed over the facet joint  14 . The retraction and dissection partially prepares the facet joint  14  for fusion.  
       FIG. 4  is a perspective view diagram of a facet bur  50  used in facet fusion surgery on the facet joint  14  of  FIG. 1 . As shown in  FIG. 4 , the facet bur  50  comprises a head  51  having a substantially T-shaped cross-section. The head  51  comprises an extension  56  and a planar surface  54 . The facet bur  50  includes a shaft  52  extending from the head  51 . The shaft  52  is adapted to releasably engage a power source for rotation, such as a surgical drill, or the like. The head  51  is arranged and configured to decorticate the facet joint  14  upon being engaged therewith while rotating at a desired speed, thereby tapering the facet joint  14  into a substantially wedge shaped configuration. While tapering the facet joint  14  with the extension  56 , the planar surface  54  disposed substantially adjacent the extension  56  engages a posterior surface of the facets  8   a  or  8   b  in order to plane the surface thereof. The extent to which the top of each facet  8   a  or  8   b  is planed is determined by the configuration of the implant to be used. Depending on the size and shape of the implant used, a greater or lesser degree of planing is required.  
       FIG. 5  is a perspective view diagram of a sizing insert  60  used in facet fusion surgery on the facet joint  14  of  FIG. 1 . As shown in  FIG. 5 , the sizing insert  60  comprises a body portion  64  and a handle  62 . After the facet to be fused has been located, decorticated, and planed as desired and described herein, the sizing insert  60  is inserted into the area of the facet joint  14  where an implant will be positioned for fusion. As is obvious to one of ordinary skill in the art, the system of the present disclosure preferably comprises a plurality of sizing inserts  60 , each having at least a slight dimension variation. If a particular sizing insert  60  does not fit, a sizing insert  60  of a different size will be placed into the facet joint  14  until the proper size is determined. The handle  62  allows for easy insertion and removal of the sizing insert  60 .  
      It should be understood that although the body portion  64  is illustrated as being substantially wedge-shaped, it may comprise any suitable configuration. Sizing inserts  60  of various dimensions can be placed in the facet one after the other until the user can ascertain the necessary implant size to be placed in the facet cavity for fusion.  
       FIG. 6 a  perspective view diagram of a trapezoidal implant  70  used in facet fusion surgery on facet the joint  14  of  FIG. 1 . As shown in  FIG. 6 , the trapezoidal implant  70  is positioned in the facet joint cavity  14  for fusion. The trapezoidal implant  70  should preferably correspond in size and shape to the dimension to the selected sizing insert  60 , as stated above. The burring of the facets  8   a  and  8   b  and wedging of the trapezoidal implant  70  into position results in a sufficient amount of friction to hold trapezoidal implant  70  in the desired position. The trapezoidal implant  70  may comprise bone, coral, or any suitable material lending itself to fusion in such an environment.  
       FIG. 7  is a perspective view diagram of a T-shaped implant  80  used in facet fusion surgery on the facet joint  14  of  FIG. 1 . As shown in  FIG. 7 , the embodiment of the T-shaped implant  80  is synthetic. The synthetic T-shaped implant  80  comprises a fusion portion  81  and a cap  83 . The fusion portion  81  is adapted to engage an internal portion of the facet joint  14 . The cap  83  is adapted to engage a posterior portion of the facet joint  14  in order to secure the T-shaped implant  80  in the desired position. The fusion portion  81  is illustrated as having a tapered cross-section, however, it should be understood that the fusion portion  81  may comprise any suitable configuration. The synthetic T-shaped implant  80  may comprise polished stainless steel, high-density polyethylene, or any suitable material. Similar to the trapezoidal implant  70 , the T-shaped implant  80  is selected in a size and configuration substantially corresponding to that indicated as appropriate by the sizing insert  60 . The burring of the facet and wedging of an appropriately sized and configured implant into position results in a sufficient amount of friction to hold the implant  80  in the desired position.  
       FIG. 8  is a perspective view diagram of the trapezoidal implant  70  of  FIG. 6 , having a cage construction. As shown in  FIG. 8 , the implant  90  is configured with fusion apertures  93  on various portions of the implant  90  to form a cage-like member  92 . The fusion apertures  93  allow the bone access to an inner cavity  94  defining a volumetric area into which graft material can be placed. As is evident, the fusion apertures  93  may be any size shape or number, and may be located anywhere on implant  90 , depending on the particular situation.  
      In addition, a lid  96  can also be included and can be removed from the end of the implant  90 , thereby opening the cavity  94  to provide access thereto. Fusion material such as bone morphogenic protein (BMP) or polyether ether keyton (PEEK) may be inserted into the cavity  94  of the implant  90 . A collagen-based sponge, or other similar material, may be used as a carrier material for the BMP solution. The BMP infused sponge may be inserted into trapezoidal implant  90 . As the trapezoidal implant  90  is subjected to pressure once it is positioned in facet joint  14 , the fusion material fuses with the facet joint  14  to solidify the fusion. The fusion apertures  93  allow for fusion of the surrounding bone to fusion material disposed within the implant  90 .  
       FIG. 9  is a perspective view diagram of the T-shaped implant  80  of  FIG. 7 , further including a cage construction. As shown in  FIG. 9 , a synthetic T-shaped implant  100  can also be implemented with fusion apertures  103  to form a cage-like member. As in  FIG. 8 , the fusion apertures  103  may be any size, shape and number, and may be located on any portion of synthetic T-shaped implant  100 .  
      The lid  106  may be removed from the end of T-shaped implant  100 . Fusion material such as bone morphogenic protein (BMP) or polyether ether keyton (PEEK) may be inserted into the cavity  104  of the implant  90 . A collagen-based sponge, or other similar material, may be used as a carrier material for the BMP solution. The BMP infused sponge may be inserted into the T-shaped implant  100 . As the T-shaped implant  100  is subjected to pressure once it is positioned in the facet joint  14 , the fusion material fuses with facet joint to solidify the fusion.  
       FIG. 10  is a functional block diagram of the facet joint  14  with the trapezoidal cage implant  90  of  FIG. 8  and a stapling device  1   10 . As shown in  FIG. 10 , the optional stapling device  110  may be implemented after the appropriate size trapezoidal cage implant  90  is selected and positioned in the facet joint cavity  14 . This allows the optional stapling device  110  to engage the facet joint  14  and the trapezoidal cage implant  90 , which included fusion aperture  93 . The optional stapling device  110  secures the trapezoidal cage implant  90  in position in the facet joint  100 . The optional stapling device  110  comprises any suitable material that can be heated to allow for some compression, such as Nitinol, or the like. As is evident from  FIG. 10 , the fusion aperture  93  allows an avenue for the bone to access the fusion material located within implant  90 . This avenue facilitates bone growth, which allows for a successful facet fusion surgery.  
       FIG. 11  is a functional block diagram of the facet joint  14  with the T-shaped cage implant  100  of  FIG. 9  and a stapling device. As shown in  FIG. 11 , the optional stapling device  110  may be implemented after the appropriate size T-shaped cage implant  100  is selected and positioned in the facet joint cavity  14 . This configuration allows the optional stapling device  110  to engage the facet joint  14  and the T-shaped cage implant  100 . The optional stapling device  110  secures T-shaped cage implant  100  in position in the facet joint  100 . The optional stapling device  110  comprises any suitable material that can be heated to allow for some compression, such as Nitinol, or the like. As is evident from  FIG. 11 , the fusion aperture  103  allows an avenue for the bone to access the fusion material located within implant  100 . This avenue facilitates bone growth, which allows for a successful facet fusion surgery.  
      It should be emphasized that the above-described embodiments of the present disclosure, particularly, a “preferred” embodiment, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the disclosure. Many variations and modification may be made to the above-described embodiment(s) of the disclosure without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present disclosure and protected by the following claims.