Abstract:
A method, kit, and system to separate muscle fiber prior to threading pedicle screws. By separating the muscle fiber prior to threading the pedicle screws, the muscle fiber does not need to be cut to place rods, which facilitates minimally invasive surgical methods.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a device useful in saving muscle during surgery and, more particularly, to a device useful in minimally invasive spinal surgery to avoid or reduce cutting muscle fiber along the spine.  
       BACKGROUND OF THE INVENTION  
       [0002]     Minimally invasive surgery is preferable to non-minimally invasive surgery. Conventionally, many spinal surgeries include the placement of implants through minimally invasive techniques.  
         [0003]     However, conventional methods and devices still require cutting muscle tissue about the spine decreasing the effectiveness of minimally invasive procedure. For example, and much abbreviated from the actual procedure, when placing a rod and two pedicle screws, a surgeon may use a navigation system to locate where the surgeon want to place the screw. The surgeon inserts a guide wire and dilator to the located point and threads the pedicle screw into the pedicle. The surgeon repeats the process for the second pedicle screw. Once the screws are placed, a surgical incision is made to provide access such that a spinal rod can be inserted between the screws. Except by happenstance, the surgeon needs to cut through muscle fiber to insert the spinal rod. Cutting the muscle reduces the effectiveness of the minimally invasive surgery.  
         [0004]     It would be advantageous to develop a device and method that would drastically reduce the need to cut muscle fiber during minimally invasive surgical procedures.  
       SUMMARY OF THE INVENTION  
       [0005]     To attain the advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method for saving muscle during surgery is provided. The method comprising the steps of locating a first place on a first pedicle to thread a first pedicle screw and inserting a first guide wire at the first place. Placing a first dilator over the first guide wire to separate muscle fiber and expanding and inserting at least one additional dilator over the first dilator to separate the muscle fiber from the first pedicle to a second pedicle. The at least one additional dilator or a subsequent final extending from the first pedicle to the second pedicle exposing a surgical area. The second guide wire can than be placed to thread the second pedicle screw such that the first place and the second place reside in the surgical area in the muscle fiber.  
         [0006]     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  
       [0007]     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.  
         [0008]      FIG. 1  is a top elevation view of muscle fiber over a superior pedicle and an inferior pedicle;  
         [0009]      FIG. 2  is a side elevation view of  FIG. 1 ;  
         [0010]      FIG. 3  is a top elevation view of muscle fiber with a guide wire and dilator placed separating muscle fiber consistent with an embodiment of the present invention;  
         [0011]      FIG. 4  is a top elevation view of  FIG. 3  with a subsequent dilator separating a portion of muscle fiber extending between superior pedicle and inferior pedicle;  
         [0012]      FIG. 5  is a top elevation view of  FIG. 3  with a subsequent dilator separating a portion of muscle fiber extending between superior pedicle and inferior pedicle;  
         [0013]      FIG. 6  is a top elevation view of  FIG. 3  where the muscle fiber is separated exposing the surgical site without needlessly cutting muscle fiber; and  
         [0014]      FIG. 7  is a flowchart outlining possible procedural steps useful in using the muscle saving device consistent with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0015]     The present invention will now be described with reference to FIGS.  1  to  7 . Referring first to  FIGS. 1 and 2 , a posterior view and a lateral view of a spinal segment  100  is shown. The Figures are not drawn to scale and only show those potions of the anatomy necessary to understand the present invention. Segment  100  has a layer of muscle  102  comprising substantially parallel muscle fibers  104 . Muscle  102  resides posterior to a superior pedicle  106  and an inferior pedicle  108 .  
         [0016]     To implant a rod between superior pedicle  106  and  108 , as mentioned above and with reference to  FIG. 3 , a surgeon would locate and place a guide wire  302  using conventional navigation technologies on superior pedicle  106 , for example, although the surgeon could start with inferior pedicle  108 . Next, a dilator  304  is inserted over the guide wire to provide surgical access through the skin. Dilator  304  expands muscle fibers  104  making an exposure area  306  exposing pedicle  106 . Conventionally, at this point, a pedicle screw would be threaded over guide wire  302  and dilator  304  would be removed.  
         [0017]     Instead of threading a screw and removing dilator  304 , the present invention comprises at least one additional dilator, and typically a series of dilators inserted over initial dilator  304 . Referring now to  FIG. 4 , a second dilator  402  is shown inserted over first dilator  304 . Second dilator  402  expands exposure area  306  towards the next pedicle, which in this case is inferior pedicle  108 . While second dilator  402  is shown having a leading edge  404  giving it a knife, tear drop, or wedge shape, the successive dilators could be any shape including conventional circular shapes. However, it is believed a wedge shape will assist in spreading the muscle fibers. Also, instead of successive dilators, a means of expanding a first dilator is possible. Such, for example, use of a gas to pressurize the dilator and designing the dilator so it can expand in only the desire direction. Alternatively, the dilator may be made out of an expandable material, such as, a shaped memory alloy that can be caused to expand on activation. To be expandable in the desired direction, dilator  402 , for example, may comprise at least one substantially rigid portion  402   r  and at least one substantially elastic portion  402   e . The at least one substantially rigid portion  402   r  would reside at least at the portion of dilator  402  that was not to expand. Leading edge  404  may also be relatively rigid if desired to facilitate muscle fiber separation. While the example above is described with a second dilator, first dilator  304  could be expandable making dilator  402  unnecessary and optional.  
         [0018]     The dilators according to the present invention could be place over the guide wire and/or screw as described above. Additionally, extenders may or may not be used to assist the surgeon in placement of the dilators as desired.  
         [0019]     Referring now to  FIG. 5 , a segment  100  is shown with a series of dilators  402  installed over first dilator  304 . A sufficient number of dilators  402  have been installed such that inferior pedicle  108  is exposed in a second exposure area  502 . While all dilators  402  are shown as successively inserted, internal dilators  402  can be removed as desired.  
         [0020]     Referring now to  FIG. 6 , once the appropriate portion of pedicle  108  is exposed, a final dilator  602  is inserted and the dilators  402  are removed providing a surgical access  604  between superior pedicle  106  and inferior  108  along a particular muscle fiber. Guide wires  302  and  606  are located, and pedicles screws can be threaded over guide wires  302  and  606  in a conventional manner. Muscle fiber  104  moves relatively freely in a lateral direction A. Thus, location of guide wires and eventually the pedicle screws can be aligned properly.  
         [0021]     Because fibers  104  were spread from superior pedicle  106  to inferior pedicle  108 , a rod can be inserted without cutting across muscle fibers  104 . The rod would be installed using any conventional method.  
         [0022]     For completeness,  FIG. 7  is a representative flowchart  700  of using the present invention. First, a surgeon locates a pedicle screw placement on a first pedicle and inserts a guide wire, step  702 . Next, the surgeon places a dilator over the guide wire, step  704 . A series of dilators are inserted to spread the muscle fiber without cutting the fiber from a first pedicle to a second pedicle, step  706 . Successive dilators are external and larger than preceding dilators. Step  706  is repeated until the surgical area between pedicles is exposed. Once the surgical area is exposed, a final dilator is placed extending between first pedicle and second pedicle and exposing a surgical area, step  708 . To the extent expandable dilators are used, step  706  would be replaced with a step of expanding the dilator to spread the muscle fiber until the surgical area between pedicles is exposed. Moreover, the final dilator can be the expandable dilator and/or the final dilator that actually spreads muscle. The preceding dilators are removed, step  710 . A second pedicle screw placement is located, step  712 . Finally, the muscle fibers are laterally aligned such that the surgical area encompasses the first and second pedicle screw placement areas, step  714 . Notice, location of the second pedicle screw can be done before or after dilation of the muscle fiber. Moreover, and optionally, preceding internal dilators can be removed subsequent to placement of an external dilator, step  707 .  
         [0023]     Notice, once the surgical area is exposed, if the final dilator has an access  606   a  for the second guide wire, such as a hole or punch sport, the guide wire can be inserted using surgical navigation techniques through the dilator access  606   a . The second pedicle screw, with or without extenders, could be threaded, before or after the incision. Notice, because the muscle fiber is spread prior to the incision, less or no muscle fiber needs to be cut. Cutting less muscle fiber increases the effectiveness of minimally invasive procedures.  
         [0024]     An embodiment of the present invention and many of its improvements have 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 claims.