Abstract:
Methods for treating spinal pathologies, and more specifically methods for treating articulating surfaces of facet joints of cervical vertebrae. 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. 10/762,008, filed Jan. 21, 2004 now abandoned, 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 cervical facet joints. 
     BACKGROUND OF THE INVENTION 
     Back and neck pain are common ailments. 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 capable of causing neurological compressions inside either the foramenae or spinal canal. These facts induce 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 returns 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 spinal 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 cervical vertebrae facet joint articular facets. The method comprises creating a space between a superior articular facet of a selected cervical vertebra and an inferior articular facet of a cervical vertebra immediately above the selected vertebra; using an inferior facet rasp to prepare an articulating surface of the inferior articular facet for an inferior implant having an articulating surface and a fixation surface; using a superior facet rasp to prepare an articulating surface of the superior articular facet for a superior implant having an articulating surface and a fixation surface; fixing the inferior implant on the inferior articular facet such that the fixation surface of the inferior implant interacts with the articulating surface of the inferior articular facet; and fixing the superior implant on the superior articular facet such that the fixation surface of the superior implant interacts with the articulating surface of the superior articular facet. In addition, the articulating surface of the superior implant and the articulating surface of the inferior implant are positioned to articulate with one another following the fixation of the superior implant to the superior articular facet and fixation of the inferior implant to the inferior articular facet. 
     Also disclosed is another method for providing articulating surfaces for cervical vertebrae facet joint articular facets. The method comprises creating a space of from about 4 mm to about 15 mm between a superior articular facet of a selected cervical vertebra and an inferior articular facet of a cervical vertebra immediately above the selected vertebra; placing a generally disk-shaped inferior implant having an articulating surface and a fixation surface in the created space; fixing the inferior implant on the inferior articular facet such that the fixation surface of the inferior implant interacts with an articulating surface of the inferior articular facet; placing a generally disk-shaped superior implant having an articulating surface and a fixation surface in the created space; and fixing the superior implant on the superior articular facet such that the fixation surface of the superior implant interacts with an articulating surface of the superior articular facet. In addition, the articulating surface of the superior implant and the articulating surface of the inferior implant are positioned to articulate with one another following the fixation of the superior implant to the superior articular facet and fixation of the inferior implant to the inferior articular facet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a lateral elevation view of a normal human spinal column; 
         FIG. 2A  is an anterior view of a normal human cervical vertebra; 
         FIG. 2B  is a posterosuperior view of a normal human cervical vertebra; 
         FIG. 3  is a posterior perspective view of a cervical vertebral facet joint; 
         FIG. 4  is a lateral elevation view of a cervical vertebral facet joint; 
         FIG. 5  illustrates a cervical facet implant; 
         FIGS. 6A-C  illustrate a facet implant in conjunction with cervical vertebrae; 
         FIG. 7  illustrates an alternate embodiment of a cervical facet inferior implant in conjunction with a trans-lateral mass screw; 
         FIG. 8  is a flow chart generally illustrating a method for providing articulating surfaces for cervical facet joint articular facets; 
         FIG. 9  is an illustration of a rasp being used to prepare an articulating surface; 
         FIG. 10  is an illustration of a rasp; and 
         FIG. 11  is an illustration of an aiming device for use in positioning a trans lateral mass 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 cervical vertebrae  12  are illustrated. It will be understood by those skilled in the art that while the cervical 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 transverse process  24  that 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 . Connecting the transverse process  24  on each side of the body  14  is a lateral mass  26 . Two inferior articular processes  28  extend downward from the junction of the laminae  20  and the transverse processes  24 . The inferior articular processes  28  each have a natural bony structure known as an inferior articular facet  32 , which faces downward. On the superior articular facet  30  is a superior articulating surface  38 . Similarly, a superior articular facet  30  faces upward from the junction of the lateral mass  26  and the pedicle  16 . On the inferior articular facet  32  is an inferior articulating surface  40 . 
     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 C3-C4 facet joint, the superior portion of the joint is formed by bony structure on the C4 vertebra (e.g., a superior articular surface and supporting bone on the C4 vertebra), and the inferior portion of the joint is formed by bony structure on the C3 vertebra (e.g., an inferior articular surface and supporting bone on the C3 vertebra). 
     Turning now to  FIG. 5 , an exemplary cervical facet resurfacing implant according to the present invention is illustrated. The exemplary facet implant  100  generally has a superior implant  102  and an inferior implant  104 . The superior implant  102  generally has a disk-shaped portion  106  and a tab  108  extending from the disk-shaped portion  106 . The disk-shaped portion  106  includes an articulating surface  110  and a fixation surface  112 . 
     The inferior implant  104  also generally has a disk-shaped portion  114  and a tab  116  extending from the disk-shaped portion  114 . The disk-shaped portion  114  includes an articulating surface  118  and a fixation surface  120 . 
     It should be noted that the term “disk-shaped” is not restricted to circular or ovular shapes. A generally disk-shaped implant may have multiple sides, such as a square-shaped, hexagonal-shaped, or octagonal-shaped implant. While each of these shapes appear similar from a lateral perspective and are capable of performing a similar function according to the present invention, a circular or ovular disk-shape is preferred. 
     Turning now to  FIGS. 6A-C , an exemplary cervical facet resurfacing implant according to the present invention is illustrated in conjunction with a facet joint. 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  106  includes a disk-shaped portion  106 , which has an articulating surface  110  and a fixation surface  112  and is configured for placement on a specifically prepared superior articulating surface  38 . 
     The disk-shaped portion  106  of the superior implant  102  may range from about 1 mm thick to about 6 mm thick. In an exemplary embodiment, the thickness of the superior implant  102  ranges from about 2 mm to about 4 mm. In another exemplary embodiment, the thickness of the superior implant  102  ranges from about 1.5 mm to about 2.5 mm. The disk-shaped portion  106  of the superior implant  102  may also range from about 3 mm in diameter to about 14 mm in diameter. In an exemplary embodiment, the diameter of the superior implant  102  ranges from about 6 mm to about 12 mm. In another exemplary embodiment, the diameter of the superior implant  102  ranges from about 8 mm to about 10 mm. 
     The fixation surface  112  may be generally flat or generally curved and is configured to interact with the superior articulating surface  38 . The articulating surface  110  may be generally curved and may be configured to interact with an articulating surface  118  of the inferior implant  104 . 
     Extending from the disk-shaped portion  106  of the superior implant is a tab  108  configured to interact with or for attachment to the lateral mass  26  of the vertebra  12 . The tab  108  may be generally curved so that it matches the natural curvature of the vertebra  12 . For example, the tab  108  and the disk-shaped portion  106  of the superior implant  102  may form an angle ranging from about 110 degrees to about 160 degrees. In one exemplary embodiment, the tab  108  and the disk-shaped portion  106  of the superior implant  102  form an angle ranging from about 120 degrees to about 150 degrees. In another exemplary embodiment, the tab  108  and the disk-shaped portion  106  of the superior implant  102  may form an angle ranging from about 130 degrees to about 145 degrees. 
     The tab  108  may include a hole or a slot or the like configured to receive a fixation device, such as a screw or the like. In other words, the fixation device passes through the hole or slot of the tab  108  and into the lateral mass  26  of the vertebra  12 . 
     The superior implant  102  may have a surface fixation mechanism for fixing the superior implant  102 , such as by fixing the fixation surface  112 , to the superior articulating surface  38 . The surface fixation mechanism may be any fixation mechanism known in the art, such as at least one of: one or more pegs, one or more pips, ridges, one or more grooves, one or more fins, and one or more screws. In an exemplary embodiment, the surface fixation mechanism includes at least one fin  122 . The fin  122  helps prevent the superior implant  102  from migrating along the superior articulating surface. In another exemplary embodiment, the surface fixation mechanism may include 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  112  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 superior articulating surface  38 . 
     The fixation surface  112  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; a material facilitating bone ingrowth; and combinations thereof. For example, the fixation surface  112  may have a porous surface that is beaded, threaded, textured, etc. Further, the fixation surface  112  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  112  and the superior articular facet  30 . 
     In one exemplary embodiment, the fixation surface  112  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  or the facet joint  36 . The fixation surface  112  of the superior implant  102  may be generally flat or generally curved for improved interaction with the superior articulating surface  38 . 
     The articulating surface  110  in one exemplary embodiment is generally configured to articulate or interact with the articulating surface  118  of the inferior implant  104 . Accordingly, the articulating surface  110  of the superior implant  102  may be generally flat or generally curved. The superior implant  102  articulating surface  110  may be configured such that it acts as a “female” surface wherein it is concave or configured to accept a “male” articulating surface  118  of an inferior implant  104 . Conversely, the superior implant  102  articulating surface  110  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  118  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 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 a disk-shaped portion  114 , which has an articulating surface  118  and a fixation surface  120  and is configured for placement on a specifically prepared inferior articulating surface  40 . 
     The disk-shaped portion  116  of the inferior implant  104  may range from about 1 mm thick to about 6 mm thick. In an exemplary embodiment, the thickness of the inferior implant  104  ranges from about 2 mm to about 4 mm. In another exemplary embodiment, the thickness of the inferior implant  104  ranges from about 1.5 mm to about 2.5 mm. The disk-shaped portion  114  of the inferior implant  104  may also range from about 3 mm in diameter to about 14 mm in diameter. In an exemplary embodiment, the diameter of the inferior implant  104  ranges from about 6 mm to about 12 mm. In another exemplary embodiment, the diameter of the inferior implant  104  ranges from about 8 mm to about 10 mm. 
     The fixation surface  120  may be generally flat or generally curved and is configured to interact with the inferior articulating surface  40 . The articulating surface  118  may be generally curved and may be configured to interact with an articulating surface  110  of the superior implant  104 . 
     Extending from the disk-shaped portion  114  of the inferior implant is a tab  116  configured to interact with or for attachment to the inferior articular process  28  of the vertebra  12 . The tab  116  may be generally curved so that it matches the natural curvature of the vertebra  12 . For example, the tab  116  and the disk-shaped portion  114  of the inferior implant  104  may form an angle ranging from about 10 degrees to about 70 degrees. In one exemplary embodiment, the tab  116  and the disk-shaped portion  114  of the inferior implant  104  form an angle ranging from about 20 degrees to about 60 degrees. In another exemplary embodiment, the tab  116  and the disk-shaped portion  114  of the inferior implant  104  may form an angle ranging from about 30 degrees to about 50 degrees. 
     The tab  116  may include a hole or a slot or the like configured to receive a fixation device, such as a screw or the like. In other words, the fixation device passes through the hole or slot of the tab  116  and into the inferior articular process  28  of the vertebra  12 . 
     The inferior implant  104  may have a surface fixation mechanism for fixing the inferior implant  104 , such as by fixing the fixation surface  120 , to the inferior articulating surface  40 . The surface fixation mechanism may be any fixation mechanism known in the art, such as at least one of: one or more pegs, one or more pips, ridges, one or more grooves, one or more fins, and one or more screws. In an exemplary embodiment, the surface fixation mechanism includes at least one fin, such as the fin shown as  122  on the superior implant  102 . The fin helps prevent the inferior implant  104  from migrating along the superior articulating surface. In another exemplary embodiment, the surface fixation mechanism may include 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  120  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  120  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  120  may have a porous surface that is beaded, threaded, textured, etc. Further, the fixation surface  120  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  120  and the inferior articular facet  32 . 
     In one exemplary embodiment, the fixation surface  120  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  120  of the inferior implant  104  may be generally flat or generally curved for improved interaction with the inferior articulating surface  40 . 
     The articulating surface  118  in one exemplary embodiment is generally configured to articulate or interact with the articulating surface  110  of the superior implant  102 . Accordingly, the articulating surface  118  of the inferior implant  104  may be generally flat or generally curved. The inferior implant  104  articulating surface  118  may be configured such that it acts as a “female” surface wherein it is concave or configured to accept a “male” articulating surface  110  of a superior implant  102 . Conversely, the inferior implant  104  articulating surface  118  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  110  of an 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. 
     Turning next to  FIG. 7 , there is provided an alternate embodiment  200  of a cervical facet inferior implant in conjunction with a trans-lateral mass screw. In another exemplary embodiment, the inferior implant  204  is configured to interact with or attach to a trans-lateral mass fixation mechanism  202 . As shown, the trans-lateral mass fixation mechanism  202  is a screw, but may be any like fixation mechanism. For example, the inferior implant  204  may include a threaded hole  212  either extending from or bored into the fixation surface  210  of the inferior implant  204 . The manner in which the inferior implant  204  and the trans-lateral mass fixation mechanism  202  interact may vary with different anatomies. For example, it may be preferable to offset the trans-lateral mass screw  202  from the inferior implant  204  such that when the trans-lateral mass screw  202  and inferior implant  204  interact, the trans-lateral mass screw  202  is not perpendicular to the inferior implant  204 . The trans-lateral mass screw  202  may range from about 0 degrees offset from perpendicular to about 60 degrees offset from perpendicular. 
     The articulating surface  208  of the inferior implant  204  is generally configured to articulate or interact with the articulating surface  110  of the superior implant  102  shown in  FIG. 5 . Accordingly, the articulating surface  208  of the inferior implant  204  may be generally flat or generally curved. The inferior implant  204  articulating surface  208  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  110  of a superior implant  102 . Conversely, the inferior implant  204  articulating surface  208  may also be configured such that it acts as a “female” surface wherein it is configured to accept a “male” articulating surface  110  of a superior implant  102 . 
     A trans-lateral mass fixation mechanism  202  is configured to interact with the inferior implant  204 . The trans-lateral mass fixation mechanism  202  secures the inferior implant  204  to the inferior articular facet  32 . The trans-lateral mass fixation mechanism  202  may be any fixation mechanism known in the art, such as a translaminar screw. The trans-lateral mass fixation mechanism  202  may be made from any material known in the art for medical fixation devices. For example, the trans-lateral mass fixation mechanism  202  may be made from titanium, titanium/aluminum/vanadium (Ti/Al/V) alloys, Tantalum, CrCo, ceramic, carbon or carbon composite materials. 
     Turning next to  FIG. 8 , 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  802  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 15 mm. In one exemplary embodiment, the space ranges from about 4 mm to about 8 mm. It should be understood that a rasp can be any tool used to scrape, grate, or file the facets. 
     Flow progresses to process block  804  wherein the articulating surface  40  of the inferior articular facet  32  is prepared for an inferior implant  104 . Such preparation may be made by a rasp, such as a rasp specifically designed for preparing a surface for the cervical facet implant. Progression then continues to process block  806  wherein the articulating surface  38  of the superior articular facet  30  is prepared for a superior implant  102 . Again, such preparation may be made by a rasp, such as a rasp specifically designed for preparing a surface for the cervical facet implant. 
     Each of the rasps of process blocks  804  and  806  may be either a single shaft rasp or a double action rasp, such as those illustrated in  FIGS. 10-12  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  802 . 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  804  and  806  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. 9 , 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  802 . 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 8 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. 
     In one embodiment, the steps of process blocks  802 ,  804  and  806  are repeated on the contralateral side of facet joint  36  prior to performing the steps of process block  808 . 
     Progression then flows to process block  808  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 the disk-shaped portion  114  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 alternative embodiment, a trans-lateral mass screw  202  is used to secure an inferior implant  204  to the inferior articular facet  32 . In this embodiment, the above method would also include using the trans-lateral mass screw  202  to secure the inferior implant  204  to the inferior articular facet  32 . 
     To facilitate placement of the trans-lateral mass screw  106 , an aiming device such as the device illustrated in  FIG. 11  may be used. The aiming device  1100  can be used to position a drill for creating a trans-lateral mass hole for the trans-lateral mass screw  202 . 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 trans-lateral mass screw  202 . Once the hole is drilled, the trans-lateral mass screw  202  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  808 , including any steps associated with the drilling or placement of the trans-lateral mass screw  202 , are repeated on the contralateral side of facet joint  36  prior to performing the steps of process block  810 . 
     Progression then continues to process block  810  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 the disk-shaped portion  106  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  802 ,  804 ,  806 ,  808  and  810  are then repeated on the contralateral side. 
     Turning now to  FIG. 10 , a single handed rasp is illustrated. The rasp  1000  includes a handle  1002  and a shaft  1004  connecting the handle  1002  to the working end of the rasp  1000 . Attached to the shaft  1004  at the working end of the rasp  1000  is a head  1006 . 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 (e.g. when the rasp is moved from the anterior to the posterior direction of the facet joint) but not when the cutting surface  1008  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). 
     The rasp  1000  is configured to prepare the articulating surfaces of a facet joint. In an exemplary embodiment, the rasp  1000  is 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  1006  may be generally curved to properly prepare the surface for the implant. 
     In addition, the rasp  1000  may be made from any appropriate material commonly used for medical tools. In one exemplary embodiment, at least part of the rasp  1000  is made from titanium, although the rasp 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.