Patent Publication Number: US-2007118134-A1

Title: Surgical Tools and method to facilitate spinal surgery

Description:
FIELD OF THE INVENTION  
      The present invention relates to surgical tools and methods and, more particularly, surgical tools and methods to facilitate spinal surgeries.  
     BACKGROUND OF THE INVENTION  
      Intervertebral discs can have many problems that require a surgeon to access the intervertebral disc or disc space. For example, in some instances, a surgeon may need to implant a graft to facilitate fusing adjacent vertebral bodies, such as, for example, during a TLIF procedure. To implant the graft, the surgeon needs access to the vertebral disc to remove all or part of the disc nucleus and, in some cases, the disc annulus (generically referred to as “disc material”). After removal of the disc material, the surgeon implants a graft to facilitate fusion between the superior and inferior disc. Alternatively, a surgeon may implant an artificial disc instead of fusing the vertebral bodies. Frequently, to provide adequate access, the surgeon removes a portion of the bone associated with the vertebral column, such as, for example, a portion of the lamina, facet, or the like.  
      As can be appreciated, the surgical site is relatively small for the procedure. Furthermore, the spinal cord and other nerves are located relatively close to the surgical area. To safely perform the surgery, a surgeon, for example, may take a significant portion of the surgical time locating the various nerves and orienting themselves in the surgical area.  
      Thus, it would be desirous to develop a surgical tool and method that facilitates the spinal surgical procedures.  
     SUMMARY OF THE INVENTION  
      To attain the advantages and in accordance with the present invention, a method to facilitate surgical access to a vertebral disc is provided. The method begins by locating an inferior pedicle and guiding a bone cutting device to the inferior pedicle. The bone cutting device is used to remove a portion of the vertebral body to provide access to the disc space. Typically the bone cutting device is removed and a speculum is inserted along the bone cutter guide until the speculum contacts and/or pierces a disc annulus between the inferior vertebral body and a superior vertebral body. The speculum is moved to ensure the nerves are out of the surgical area. The speculum also provides a shield to inhibit inadvertent damage to the nerve why the surgeon is operating.  
      The present invention also provides a system to facilitate spinal surgery. The system comprises a bone cutter and a guide coupled to the bone cutter. The guide facilitates placement of the bone cutter on a portion of the inferior vertebral body to be removed to provide surgical access. The system further includes a speculum that is coupled to the guide. The speculum has a surface proximate an annulus of the intervertebral disc. The surface being movable to distract the nerve from the surgical access, such that the system facilitates removal of bone and isolation of nerves to provide surgical access and reduce time in surgery.  
      Moreover, the present invention provides a tool to facilitate the removal of bone. The bone removal tool facilitates the surgical procedures. The bone removal tool comprises a bone cutter and a bone cutter guide. The bone cutter guide couples to or is integrated with the bone cutter. A track coupled to the bone cutter such that the bone cutter is movable on extenders such that the bone cutter can be moved to contact a vertebral body.  
      The foregoing and other features, utilities and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
      The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention, and together with the description, serve to explain the principles thereof. Like items in the drawings are referred to using the same numerical reference.  
       FIG. 1  is a anterior, lateral perspective view of a spinal segment;  
       FIG. 2  is a posterior, lateral perspective view of a vertebrae;  
       FIG. 3  is a flowchart illustrative of the surgical methodology consistent with an embodiment of the present invention;  
       FIG. 4  is a view of conventional pedicle screw extensions;  
       FIG. 5  is a perspective view of a part consistent with an embodiment of the present invention; and  
       FIG. 6  is a perspective view of a speculum consistent with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
      The present invention will now be described with reference to FIGS.  1  to  6 . The drawings are provided for illustration and should not be considered limiting or to scale. Moreover, although the present invention is explained with specific reference to a TLIF procedure, one of ordinary skill in the art will recognize on reading the disclosure that the present invention may be used in other surgical procedures, such as, for example, a PLIF procedure, other fusion procedures, or the like.  
       FIG. 1  shows an anterior, lateral perspective view of a spinal segment  100 . Segment  100  includes a superior vertebrae  102 , an inferior vertebrae  104 , and an intervertebral disc  106 . A spinal cord  108  has a number of nerves  110  extending from the cord  108 . As can be seen, the nerves  110  generally extend from the neural foramen  112  close to the pedicle of superior vertebrae  102 .  
      In a TLIF procedure, for example, often the surgeon removes a portion of the inferior vertebrae  104 , such as, for example, the facet  114 , to allow surgical access to disc  106 .  FIG. 2  shows another view of segment  100  with a view of lamina  202  and facet  114 . A rod may be implanted to facilitate fusion. In this case, a pedicle screw may be threaded into the vertebral body, such as pedicle screw  118  shown threaded into superior pedicle  102  in  FIG. 1 . Typically, two (2) screws  118  are used on each vertebral body although only one is shown for convenience. To facilitate fusion, rods are connected to screws  118  in a conventional manner, not shown or further described as it is generally well known in the art.  
      As can be appreciated, the surgeon performing the surgical procedure needs to take great care to avoid injury to spinal cord  108  and/or nerves  110 . The present invention, however, provides orientation and safety features for the surgeon removing or reducing the time the surgeon needs to enter the disc space  106  and minimizing the potential injury to cord  108  and/or nerves  110 . Moreover, the present invention provides a platform to allow the surgeon the ability to remove bone associated with the vertebral body and access the disc space in a reproducible and standardized fashion. Thus, the present invention reduces the overall surgical time and provides the ability for surgeons with less developed surgical skills to avoid damage to the patient and minimizes the learning curve thus leading to increased acceptance of, for example, minimally invasive fusion technology.  
      The present invention will be described with reference to  FIG. 3 , and flowchart  300  illustrating a use of the present invention. For convenience, flowchart  300  relates only to use of the present invention and does not address conventional surgical procedures, such as for a TLIF procedure. First, the surgeon would use conventional methods to cannulate the inferior pedicle, step  302 . For example, the surgeon may use conventional guide wires and conventional surgical navigation technology to locate the inferior pedicle  116 . Once the surgeon locates inferior pedicle  116 , a dilator placed over the guide wire provides access to the pedicle, step  304 . A pedicle screw  118  and extender  402  (see  FIG. 4 ) as are generally known in the art may be threaded into pedicle  116 . If a pedicle screw  118  and extender  402  are not used, an alternative structure may be placed that locates the pedicle and provides a track or stable platform.  
      After pedicle screw  118  and extender  402  or some other similar structure is provided, the surgeon would insert a bone cutter guide  500   a  and bone cutter  500   b  (collectively part  500 ), as shown bone cutter  500   b  is attached to bone cutter guide  500   a  as unitary member. Part  500  has a track or groove  502  that can clamp on, for example, extender  402 . Part  500  movably couples to extender  402  or some similar structure. The movable connection could be slidable, geared, rotational, or the like. Part  500  would be moved along extender  402  using the track or groove  502  until cutter  500   b  abuts a portion of the vertebral body, step  306 . In some instances, it is likely the tool will need to be rotated or angled (medially and laterally) about the long axis LA ( FIG. 4 ) of the extender to properly align the bone cutter  500   b . As shown, bone cutter  500   b  is a simple box shape. Other shapes are possible, such as, for example, a wedge shape, a circular shape, a conical shape, other random shapes, or the like.  
      Once placed next to the vertebral body, bone cutter  500   b  may need to be angularly oriented. Optionally, part  500  may have an angular orientation device  504  to align cutter  500   b  with the portion of the vertebral body to be removed. Angular orientation device  504  may be a simple cam or the like. If angular orientation is necessary, the device is oriented as necessary, step  308 . Once oriented, the surgeon use the bone cutter  500   b  to remove portions of the vertebral body consistent with conventional surgical procedures, step  310 , such as, for example, the surgeon may remove a portion of the facet joint. Bone cutter  500   b  may be shaped in a box shape as is conventional or other shapes, such as, circular, rectangular, triangular, other geometric or random shapes. Bone cutter  500   b  is used to remove a portion of the vertebral body only as necessary. If bone cutter  500   b  is hollow or has a through hole, bone cutter  500   b  may remain in place, but is preferably removed, step  312 . A speculum  600  having a substantially flat portion  602  and handle  604  is inserted to the disc annulus, step  312 . Flat portion  602  may terminate in a lip  606 . Once placed speculum  600  is moved towards the superior pedicle. Flat portion  602  (and lip  606  is used) push on nerve  608  (shown in phantom, which corresponds to nerve  110 ) and holds nerve  608  against the superior pedicle  102 . Underside  610  of speculum  600  provides a shield as the surgeon accesses disc  106 . Once speculum  600  is placed such that nerve  608  is removed from the surgical area, the surgeon can complete the operation,  314 . Optionally, speculum  600  may have a distractor  612 , which may take many shapes by is generally flat and long similar to flat portion  602 . Distractor  612  may extend beyond flat portion  602  and terminate in a leading edge  614 . Leading edge may pierce the disc annulus to provide a platform or base for the surgical sight. Speculum  600  may be placed to maintain separation of vertebral bodies to facilitate access to disc  106 . Distraction or separation of distractor  612  and flat portion  602  may be obtained by, for example, turning a cam  616 , a scissor operation, or the like.  
      An embodiment of the present invention has been described with a degree of particularity. It should be understood that this description has been made by way of example, and that the invention is defined by the scope of the following