Abstract:
Methods for treating spinal pathologies, and more specifically methods for treating articulating surfaces of facet joints. The methods involve providing artificial articulating surfaces for facet joint articular facets. In addition, various types of rasps may be used to prepare the articulating surfaces prior to placement of the artificial articulating surfaces.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. application Ser. No. 10/651,871, filed Aug. 29, 2003, which is incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to prostheses for treating spinal pathologies, and more specifically to a system and method for treating articulating surfaces of facet joints. 
     BACKGROUND OF THE INVENTION 
     Back pain, such as in the “small of the back”, or lumbosacral (L4-S1) region, is a common ailment. In many cases, the pain severely limits a person&#39;s functional ability and quality of life. A variety of spinal pathologies can lead to back pain. 
     Through disease or injury, the laminae, spinous process, articular processes, or facets of one or more vertebral bodies can become damaged, such that the vertebrae no longer articulate or properly align with each other. This can result in an undesired anatomy, loss of mobility, and pain or discomfort. With respect to vertebral articular surface degeneration, facet joints may show a reduced thickness of cartilage and may advance to entire disappearance thereof. Furthermore, surrounding the degenerated articular surfaces, there is bony formation able to give neurological compressions inside either the foramenae or spinal canal. These facts induce lower back and nerve roots pain which affect a large part of the population. 
     The vertebral facet joints, for example, can be damaged by either traumatic injury or by various disease processes, such as osteoarthritis, ankylosing spondylolysis, and degenerative spondylolisthesis. The damage to the facet joints often results in pressure on nerves, also called a “pinched” nerve, or nerve impingement. The result is pain, misaligned anatomy, and a corresponding loss of mobility. Pressure on nerves can also occur without facet joint pathology, e.g., a herniated disc. 
     Degenerative spinal diseases can involve articular surfaces only, but may also have a more invasive pathology including traumatic, infectious, tumorous or dysmorphic (spondylolisthesis, for example) effecting the destruction of all or part of the articular process. The locking of vertebral motions by spinal arthrodesis or ligamentoplasty induces, beyond a spinal stiffness, an increased force on the joint facets of the adjacent vertebrae above and below the fusion, usually sustained by the considered intervertebral space and therefore an increase of degeneration of these joint facets. 
     One type of conventional treatment of facet joint pathology is spinal stabilization, also known as intervertebral stabilization. By applying intervertebral stabilization, one can prevent relative motion between the vertebrae. By preventing this movement, pain can be reduced. Stabilization can be accomplished by various methods. One method of stabilization is spinal fusion. Another method of stabilization is fixation of any number of vertebrae to stabilize and prevent movement of the vertebrae. Yet another type of conventional treatment is decompressive laminectomy. This procedure involves excision of the laminae to relieve compression of nerves. With regard to discal prostheses, they provide a “space” between two vertebral bodies while preserving some motion. They solve the aging intervertebral disc problem but do not function to reduce the force on posterior joint facets. 
     These traditional treatments are subject to a variety of limitations and varying success rates. Furthermore, none of the described treatments puts the spine in proper alignment or return the spine to a desired anatomy. In addition, stabilization techniques, by holding the vertebrae in a fixed position, permanently limit a person&#39;s mobility. Some procedures involving motion devices have a high incidence of spontaneous fusion. There is thus a need in the art for a system and procedure capable of increasing the percentage of good results in disc replacement surgery. In addition, there is a need in the art for better results than are commonly achieved through trans-articular fusions. Further, there is a need in the art for a system and procedure that permits greater mobility in cases of spinal problems involving only the facet joints, and for obviating the need for spinal fusion associated with degenerative and congenital problems of the spine. 
     BRIEF SUMMARY OF THE INVENTION 
     Disclosed is a method for providing articulating surfaces for facet joint articular facets. The method comprises creating a space between an inferior articular facet and a superior articular facet; using an inferior facet rasp to prepare the articulating surface of the inferior articular facet for placement of an inferior implant; using a superior facet rasp to prepare the articulating surface of the superior articular facet for placement of a superior implant; placing the inferior implant on the inferior articular facet such that an articulating surface of the inferior implant is positioned on the articulating surface of the inferior articular facet; and placing the superior implant on the superior articular facet such that an articulating surface of the superior implant is positioned on the articulating surface of the superior articular facet. 
     Also disclosed is a method for providing articulating surfaces for facet joint articular facets using a translaminar fixation mechanism. The method comprises placing an inferior implant on an articulating surface of an inferior articular facet; securing the inferior implant to the inferior articular facet with a fixation mechanism that passes through a lamina on a vertabra that comprises the inferior articular facet; and placing an superior implant on an articulating surface of a superior articular facet such that an articulating surface of the superior implant is capable of articulating with an articulating surface of the inferior implant. 
     Further disclosed is method for providing articulating surfaces for facet joint articular facets using a translaminar fixation mechanism and rasps to create a space between the articular facets. The method comprises creating a space between an inferior articular facet and a superior articular facet; using an inferior facet rasp to prepare the articulating surface of the inferior articular facet for placement of an inferior implant; using a superior facet rasp to prepare the articulating surface of the superior articular facet for placement of a superior implant; placing the inferior implant on the inferior articular facet such that an articulating surface of the inferior implant is positioned on the articulating surface of the inferior articular facet; securing the fixation surface of the inferior implant to the inferior articular facet with a fixation mechanism that passes through a lamina on a vertabra that comprises the inferior articular facet; and placing the superior implant on the superior articular facet such that an articulating surface of the superior implant is positioned on the articulating surface of the superior articular facet; wherein the articulating surface of the inferior implant and the articulating surface of the superior implant are configured to articulate with one another. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a lateral elevation view of a normal human spinal column; 
         FIG. 2  is a superior view of a normal human lumbar vertebra; 
         FIG. 3  is a posterior perspective view of a vertebral lumbar facet joint; 
         FIG. 4  is a lateral elevation view of a vertebral lumbar facet joint; 
         FIGS. 5A-5C  illustrate a facet implant alone and in conjunction with a facet joint in a posterior perspective view; 
         FIG. 6  is a flow chart generally illustrating a method for providing articulating surfaces for facet joint articular facets; 
         FIG. 7  is an illustration of a rasp being used to prepare an articulating surface; 
         FIGS. 8-10  are illustrations of different types of rasps; and 
         FIG. 11  is an illustration of an aiming device for use in positioning a translaminar screw. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to  FIG. 1 , the human spinal column  10  is illustrated. The spinal column  10  is comprised of a series of thirty-three stacked vertebrae divided into five regions. The cervical region includes seven vertebrae, known as C1-C7. The thoracic region includes twelve vertebrae, known as T1-T12. The lumbar region contains five vertebrae, known as L1-L5. The sacral region is comprised of five vertebrae, known as S1-S5. The coccygeal region contains four vertebrae  12 , known as Co1-Co4. 
     Turning now to  FIGS. 2 and 3 , normal human lumbar vertebrae  12  are illustrated. It will be understood by those skilled in the art that while the lumbar vertebrae  12  vary somewhat according to location, they share many features common to most vertebrae  12 . Each vertebra  12  includes a vertebral body  14 . Two short bones, the pedicles  16 , extend backward from each side of the vertebral body  14  to form a vertebral arch  18 . At the posterior end of each pedicle  16 , the vertebral arch  18  flares out into broad plates of bone known as the laminae  20 . The laminae  20  fuse with each other to form a spinous process  22 . The spinuous process  22  provides muscle and ligament attachment. 
     The transition from the pedicles  16  to the laminae  20  is interrupted by a series of processes. Two transverse processes  24  thrust out laterally on each side from the junction of the pedicle  16  and the lamina  20 . The transverse processes  24  serve as guides for the attachment of muscles to the vertebrae  12 . Four articular processes, two superior  26  and two inferior  28 , also rise from the junctions of the pedicles  16  and the laminae  20 . The superior articular processes  26  are oval plates of bone rising upward on each side from the union of the pedicle  16  with the lamina  20 . The inferior processes  28  are oval plates of bone jutting downward on each side. The superior and inferior articular processes  26  and  28 , respectively, each have a natural bony structure known as a facet. The superior articular facet  30  faces upward, while the inferior articular facet  32  faces downward. The superior articular facet  30  and the inferior articular facet  32  have articulating surfaces  38  and  40 , respectively. 
     As shown in  FIGS. 3 and 4 , when adjacent vertebrae  12  are aligned, the superior articular facet  30  and inferior articular facet  32  interlock. Capped with a smooth articular cartilage, the interlocked vertebrae form a facet joint  36 , also known as a zygapophysial joint. An intervertebral disc  34  between each pair of vertebrae  12  permits gliding movement between vertebrae  12 . Thus, the structure and alignment of the vertebrae  12  permit a range of movement of the vertebrae  12  relative to each other. 
     The facet joint  36  is composed of a superior half and an inferior half. The superior half is formed by the vertebral level below the intervertebral disc  34 , and the inferior half is formed by the vertebral level above the intervertebral disc  34 . For example, in the L4-L5 facet joint, the superior portion of the joint is formed by bony structure on the L-5 vertebra (e.g., a superior articular surface and supporting bone on the L-5 vertebra), and the inferior portion of the joint is formed by bony structure on the L-4 vertebra (e.g., an inferior articular surface and supporting bone on the L-4 vertebra). 
     Turning now to  FIGS. 5A and 5B , an exemplary facet implant according to the present invention is illustrated alone and in conjunction with a facet joint. The exemplary facet implant  100  generally has a superior implant  102  and an inferior implant  104 . The superior implant  102  generally has an articulating surface  108  and a fixation surface  110 . The inferior implant  104  generally has an articulating surface  112  and a fixation surface  114 . 
     The superior implant  102  is configured for placement on superior articular facet  30 . The superior implant  102  may be fixed to the superior articulating surface  38  using cemented and/or cementless fixation techniques. In an exemplary embodiment, the superior implant  102  has an articulating surface  108  and a fixation surface  110  and is configured for placement on a specifically prepared superior articulating surface  38 . The articulating surface  108  may be generally curved and may be configured to interact with an articulating surface  112  of the inferior implant  104 . 
     The superior implant  102  may have a surface fixation mechanism for fixing the superior implant  102 , such as by fixing the fixation surface  110 , to the superior articulating surface  38 . The surface fixation mechanism may be any fixation mechanism known in the art, such as: one or more pegs, one or more pips, ridges or grooves, one or more screws. In an exemplary embodiment, the surface fixation mechanism includes a plurality of ridges, grouped in regions such that the ridges in different regions are oriented in different directions. For example, the surface fixation mechanism may include four regions on the fixation surface  110  where each of the four regions has ridges oriented in a different direction. The various orientations of the ridges prevent the superior implant  102  from moving in different directions with respect to the superior articulating surface  38 . 
     The fixation surface  110  of the superior implant  102  may also have a porous coating; a porous onlay material; a biologic coating; a surface treatment, such as to facilitate bone ingrowth or cement fixation; and combinations thereof. For example, the fixation surface  110  may have a porous surface that is beaded, threaded, textured, etc. Further, the fixation surface  110  may have a hydroxyapatite coating or may be plasma-sprayed. In addition to the examples listed, any known method of improving fixation of biologic implants may be used to improve the interaction of the fixation surface  110  and the superior articular facet  30 . 
     In one exemplary embodiment, the fixation surface  110  of the superior implant  102  is configured to interact only with the superior articulating surface  38  and does not interact directly with any other aspect of the superior articular facet  30 , the superior articular process  26 , or even the facet joint  36 . The fixation surface  110  of the superior implant  102  may be generally curved for improved interaction with the superior articulating surface  38 . 
     The articulating surface  108  in one exemplary embodiment is generally configured to articulate or interact with the articulating surface  112  of the inferior implant  104 . Accordingly, the articulating surface  108  of the superior implant  102  may be generally curved. The superior implant  102  articulating surface  108  may be configured such that it acts as a “female” surface wherein it is concave or configured to accept a “male” articulating surface  112  of an inferior implant  104 . Conversely, the superior implant  102  articulating surface  108  may also be configured such that it acts as a “male” surface wherein it is convex or configured to be accepted by “female” articulating surface  112  of an inferior implant  104 . 
     The superior implant  102  may be composed of any material commonly used in the art for articulating medical implants. Such materials include, but are not limited to, cobalt-chromium alloys, ceramics (alumina ceramic, zirconia ceramic, yttria zirconia ceramic, etc.), titanium, ultra high molecular weight polyethylene (UHMWPE), pyrolytic carbon, titanium/aluminum/vanadium (Ti/Al/V) alloys, Tantalum, Carbon composite materials and combinations thereof. For example, the superior implant  102  may be generally composed of titanium, but have a UHMWPE articulating surface. Some materials are more appropriate for articulating surfaces and some more appropriate for fixation surfaces, but any materials known in the art for use with articulating and fixation surfaces can be used in the present invention. Such materials are commonly used in joint arthroplasty and the like. 
     The superior implant  102  may be from about 2 mm thick to about 15 mm thick. In an exemplary embodiment, the thickness (T s ) of the superior implant  102  ranges from about 6 mm to about 10 mm. In another exemplary embodiment, the thickness (T s ) of the superior implant  102  ranges from about 3 mm to about 5 mm. 
     The inferior implant  104  is configured for placement on inferior articular facet  32 . The inferior implant  104  may be fixed to the inferior articulating surface  40  using cemented and/or cementless fixation techniques. In an exemplary embodiment, the inferior implant  104  has an articulating surface  112  and a fixation surface  114  and is configured for placement on a specifically prepared inferior articulating surface  40 . The articulating surface  112  may be generally convex and may be configured to interact with an articulating surface  108  of the superior implant  102 . 
     The inferior implant  104  may have a surface fixation mechanism for fixing the inferior implant  104 , such as by fixing the fixation surface  110 , to the inferior articulating surface  40 . The surface fixation mechanism may be any fixation mechanism known in the art, such as: one or more pegs, ridges or grooves, one or more screws. In an exemplary embodiment, the surface fixation mechanism includes a plurality of ridges, grouped in regions such that the ridges in different regions are oriented in different directions. For example, the surface fixation mechanism may include four regions on the fixation surface  114  where each of the four regions has ridges oriented in a different direction. The various orientations of the ridges prevent the inferior implant  104  from moving in different directions with respect to the inferior articulating surface  40 . 
     The fixation surface  114  of the inferior implant  104  may also have a porous coating; a porous onlay material; a biologic coating; a surface treatment, such as to facilitate bone ingrowth or cement fixation; and combinations thereof. For example, the fixation surface  114  may have a porous surface that is beaded, threaded, textured, etc. Further, the fixation surface  114  may have a hydroxyapatite coating or may be plasma-sprayed. In addition to the examples listed, any known method of improving fixation of biologic implants may be used to improve the interaction of the fixation surface  110  and the superior articular facet  30 . 
     In one exemplary embodiment, the fixation surface  114  of the inferior implant  104  is configured to interact only with the inferior articulating surface  40  and does not interact directly with any other aspect of the inferior articular facet  32 , the inferior articular process  28 , or even the facet joint  36 . The fixation surface  114  of the inferior implant  104  may be generally flat or generally curved for improved interaction with the inferior articulating surface  40 . 
     In another exemplary embodiment, the inferior implant  104  is configured to interact with or attach to a translaminar fixation mechanism  106 . For example, the inferior implant  104  may include a threaded hole either extending from or bored into the fixation surface  114  of the inferior implant  110 . The manner in which the inferior implant  104  and the translaminar fixation mechanism  106  interact may vary with different anatomies. For example, it may be preferable to offset the translaminar screw  106  from the inferior implant  104  such that when the translaminar screw  106  and inferior implant  104  interact, the translaminar screw  106  is not perpendicular to the inferior implant  104 . The translaminar screw  106  may range from about 0 degrees offset from perpendicular to about 20 degrees offset from perpendicular. In one exemplary embodiment, the translaminar screw  106  ranges from about 5 degrees offset from perpendicular to about 15 degrees offset from perpendicular. In another exemplary embodiment, the translaminar screw  106  is about 10 degrees offset from perpendicular. 
     The articulating surface  112  of the inferior implant  104  in one exemplary embodiment is generally configured to articulate or interact with the articulating surface  108  of the superior implant  102 . Accordingly, the articulating surface  112  of the inferior implant  104  may be generally convex. The inferior implant  104  articulating surface  112  may be configured such that it acts as a “male” surface wherein it is convex or configured to be accepted by a “female” articulating surface  108  of a superior implant  102 . Conversely, the inferior implant  104  articulating surface  112  may also be configured such that it acts as a “female” surface wherein it is configured to accept a “male” articulating surface  108  of a superior implant  102 . 
     The inferior implant  104  may be composed of any material commonly used in the art for articulating medical implants. Such materials include, but are not limited to, cobalt-chromium alloys, ceramics (alumina ceramic, zirconia ceramic, yttria zirconia ceramic, etc.), titanium, ultra high molecular weight polyethylene (UHMWPE), pyrolytic carbon, titanium/aluminum/vanadium (Ti/Al/V) alloys, and combinations thereof. For example, the inferior implant  104  may be generally composed of a ceramic material or a cobalt-chromium alloy. Some materials are more appropriate for articulating surfaces and some more appropriate for fixation surfaces, but any materials known in the art for use with articulating and fixation surfaces can be used in the present invention. Such materials are commonly used in joint arthroplasty and the like. 
     The inferior implant  104  may be from about 2 mm thick to about 15 mm thick. In an exemplary embodiment, the thickness (T i ) of the inferior implant  104  ranges from about 6 mm to about 12 mm. In another exemplary embodiment, the thickness (T i ) of the inferior implant  104  ranges from about 3 mm to about 5 mm. 
     One exemplary embodiment of the present invention includes a translaminar fixation mechanism  106  configured to interact with the inferior implant  104 . The translaminar fixation mechanism  106  secures the inferior implant  104  to the inferior articular facet  32 . The translaminar fixation mechanism may be any fixation mechanism known in the art, such as a translaminar screw. The translaminar fixation mechanism may be made from any material known in art for medical fixation devices. For example, the translaminar fixation mechanism may be made from titanium, titanium/aluminum/vanadium (Ti/Al/V) alloys, Tantalum, CrCo, ceramic, carbon or carbon composite materials. 
     Turning next to  FIG. 6 , there is provided a flow diagram generally illustrating a method for providing articulating surfaces for facet joint articular facets. The overall flow begins at process block  602  wherein a space is created between the superior articular facet  30  and the inferior articular facet  32 . It will be understood by those skilled in the art that prior to creating the space, it may be preferable or even necessary to expose the facet joint  36  at an effected level and remove the capsule. The effected level may be exposed through use of any appropriate procedure, such as a modified “Wiltse” approach. The creation of the space at process block  602  may be accomplished by using a curette or similar device and by removing the cartilaginous surfaces of the facet joint  36 . In one exemplary embodiment, the created space is sufficient for using a rasp on an articulating surface of an articular facet. The space created between the superior articular facet  30  and the inferior articular facet  32  may range, for example, from about 2 mm to about 5 mm. In one exemplary embodiment, the space ranges from about 3 mm to about 4 mm. 
     Flow progresses to process block  604  wherein a rasp is used to prepare the articulating surface  40  of the inferior articular facet  32  for an inferior implant  104 . Progression then continues to process block  606  wherein a rasp is used to prepare the articulating surface  38  of the superior articular facet  30  for a superior implant  102 . 
     Each of the rasps of process blocks  604  and  606  may be either a single shaft rasp or a double action rasp, such as those illustrated in  FIGS. 8-10  and described in detail herein. The process of preparing the articulating surfaces  38  and  40  of the articular facets  28  and  30  may involve using multiple rasps of increasing thickness while widening the space created in process block  602 . For example, a 2 mm rasp may initially be used, then a 4 mm rasp, then a 6 mm rasp, then an 8 mm rasp, etc., until a desired result is achieved. In addition, the rasps of process blocks  604  and  606  may be the same rasp. Further, a single rasp can be used to prepare the articulating surfaces  38  and  40  concurrently. The articulating surfaces  38  and  40  may be prepared such that a bleeding bone bed is created to facilitate bone ingrowth for the superior implant  102  and inferior implant  104 . 
     As shown in  FIG. 7 , when the single handed rasp is used to prepare articulating surface  38  and/or articulating surface  40 , the working end of the tool may be positioned inside the space created in process block  602 . The rasp may then be moved from an anterior to a posterior position inside the facet joint  36  in order to effect a clean and uniform resection of the created space in the shape and dimension of both implants. In other words, the articulating surface  38  is prepared such that its shape and dimension resembles the superior implant  102  and the articulating surface  40  is prepared such that its shape and dimension resembles the inferior implant  104 . The anterior/posterior movement of the rasp may be continued until the rasp is too small for the space created. The rasp may be too small when the space created is so wide that the rasp cannot prepare both the articulating surfaces  38  and  40  concurrently. A larger (thicker) rasp may then be used. Increasingly larger rasps may be used until the created space is increased such that it ranges from about 4 mm to about 15 mm. In one exemplary embodiment, the rasps are designed to cut only when moving in a posterior direction to help prevent injury during the resurfacing process. 
     When a double action rasp is used, the working end of the rasp is positioned inside the created space and then the fixation appendages are secured to the lamina or to a cephalad position of the superior facet  26 . The rasp is then moved in a cephalad/caudad direction by alternately squeezing and releasing the handles. Like the single handed rasp, double action rasp creates a clean and uniform resection of the created space in the shape and dimension of both implants. The alternately squeezing and releasing of the handles may be continued until the rasp is too small for the space created. The rasp may be too small when the space created is so wide that the rasp cannot prepare both the articulating surfaces  38  and  40  concurrently. A larger (thicker) rasp may then be used. Increasingly larger rasps may be used until the created space is increased such that it ranges from about 4 mm to about 15 mm. In one exemplary embodiment, the rasps are designed to cut only when moving in a caudad direction to help prevent injury during the resurfacing process. 
     In one embodiment, the steps of process blocks  602 ,  604  and  606  are repeated on the contralateral side of facet joint  36  prior to performing the steps of process block  608 . 
     Progression then flows to process block  608  wherein the inferior implant  104  is placed on the prepared/resurfaced articulating surface  40  of the inferior articular facet  32 . In one exemplary embodiment, the inferior implant  104  is placed such that it interacts with the articulating surface  40  of the inferior articular facet  32 , but not with other aspects of the inferior articular facet  32 . 
     In one exemplary embodiment, a translaminar screw  106  is used to secure the inferior implant  104  to the inferior articular facet  32 . In this embodiment, the above method would also include using the translaminar screw  106  to secure the inferior implant  104  to the inferior articular facet  32 . This exemplary embodiment preferably includes placing the translaminar screw  106  prior to placing the inferior implant  104  described in process block  608 . 
     To facilitate placement of the translaminar screw  106 , an aiming device such as the one illustrated in  FIG. 11  may be used. The aiming device can be used to position a drill for creating a translaminar hole for the translaminar screw  106 . A drill can then be used to create the hole, which may have a diameter of about 2 mm, depending on the diameter of the translaminar screw  106 . Once the hole is drilled, the translaminar screw  106  can be introduced into the hole and then used to secure the inferior implant  104  to the inferior articular facet  32 . 
     In one embodiment, the steps of process blocks  608 , including any steps associated with the drilling or placement of the translaminar screw  106 , are repeated on the contralateral side of facet joint  36  prior to performing the steps of process block  610 . 
     Progression then continues to process block  610  wherein the superior implant  102  is placed on the prepared/resurfaced articulating surface  38  of the superior articular facet  30 . In one exemplary embodiment, the superior implant  102  is placed such that it interacts with the articulating surface  38  of the superior articular facet  30 , but not with other aspects of the superior articular facet  30 . 
     In one embodiment, the steps of process blocks  602 ,  604 ,  606 ,  608  and  610  are then repeated on the contralateral side. 
     Turning now to  FIG. 8 , a single handed rasp is illustrated. The rasp  800  includes a handle  802  and a shaft  804  connecting the handle  802  to the working end of the rasp  800 . Attached to the shaft  804  at the working end of the rasp  800  is a head  806 . The head  806  has at least one cutting surface  808 . In one exemplary embodiment, the cutting surface  808  is configured to cut when the cutting surface  808  is moved in a first direction (e.g. when the rasp is moved from the anterior to the posterior direction of the facet joint) but not when the cutting surface  808  is moved in a direction opposite to the first direction (e.g. when the rasp is moved from the posterior to the anterior direction of the facet joint). 
     Turning now to  FIG. 9 , a double action rasp is illustrated. The rasp  900  includes two handles  902  and a shaft  904  connecting the handles  902  to the working end of the rasp  900 . Attached to the shaft  904  at the working end of the rasp  900  are a head  906  and at least one fixation appendage  910 . The head  906  has at least one cutting surface  908 . In one exemplary embodiment, the cutting surface  908  is configured to cut when the cutting surface  908  is moved in a first direction (e.g. when the rasp is moved in a cephalad direction of the facet joint) but not when the cutting surface  908  is moved in a direction opposite to the first direction (e.g. when the rasp is moved in a caudad direction of the facet joint). In addition, the fixation appendages  910  may be configured for interaction with the lamina  20  or with a cephalad position of the superior facet  26 . In one exemplary embodiment of a double action rasp  900 , squeezing the handles  902  of the rasp  900  causes the head  906  to move in a cephalad position and releasing the handles  902  causes the head  906  to move in a caudad direction. 
     Turning now to  FIG. 10 , another double action rasp is illustrated. Attached to the shaft  1004  at the working end of the rasp  1000  are a head  1006  and a fixation appendage  1010 . The fixation appendage  1010  may be rigid or capable of pivoting to accommodate various working angles. The head  1006  has at least one cutting surface  1008 . In one exemplary embodiment, the cutting surface  1008  is configured to cut when the cutting surface  1008  is moved in a first direction but not when the cutting surface  1008  is moved in a direction opposite to the first direction. In one exemplary embodiment, the rasp is a double action rasp like the rasp  900  where squeezing the handles of the rasp causes the head  1006  to move in a first direction and releasing the handles causes the head  1006  to move in a second direction. 
     The rasps  800 ,  900  and  1000  of  FIGS. 8-10  are configured to prepare the articulating surfaces of a facet joint. In an exemplary embodiment, the rasps  800 ,  900  and  1000  are configured to prepare articulating surfaces  38  and  40  of the articular facets  28  and  30  such that the shape and dimension of the prepared articulating surfaces resembles the shape and dimension of the superior implant  102  and inferior implant  104 . For example, if the superior implant  102  and/or inferior implant  104  are curved, the head  806 ,  906  and  1006  may be generally curved to properly prepare the surface for the implant. 
     In addition, the rasps  800 ,  900  and  1000  may be made from any appropriate material commonly used for medical tools. In one exemplary embodiment, at least part of the rasps  800 ,  900  and  1000  are made from titanium, although the rasps could also be made from any material known in the art. 
     While the present invention has been described in association with several exemplary embodiments, the described embodiments are to be considered in all respects as illustrative and not restrictive. Such other features, aspects, variations, modifications, and substitution of equivalents may be made without departing from the spirit and scope of this invention which is intended to be limited solely by the scope of the following claims. Also, it will be appreciated that features and parts illustrated in one embodiment may be used, or may be applicable, in the same or in a similar way in other embodiments.