Abstract:
A system, apparatus, and method for locating, measuring and evaluating the enlargement of a foramen are provided. An instrument has a handle, an angled region, and a tip to be inserted into the foramen. An instrument can be pressed onto the foramen to determine its location and whether the empty space within the foramen is large enough for the maximum width of the tip to be inserted. If the tip cannot insert, the foramen can be cut to enlarge it enough for the tip to insert. A kit of several instruments or a single instrument with tips of different maximum widths are provided for determining the amount of empty space within the foramen through the course of the enlargement.

Description:
FIELD OF INVENTION  
         [0001]    The present invention is directed to surgical instruments and methods, and more particularly to a system, method and apparatus for locating, measuring and/or evaluating the enlargement of a foramen.  
         BACKGROUND OF THE INVENTION  
         [0002]    Spinal surgeons frequently must work with openings within the body known as “foramina.” It may be difficult to visualize or to evaluate the size or diameter of these foramina, such as, for example, during surgery or if the foramen is very small. In this situation, locating, measuring, or evaluating the enlargement of the foramen can be very difficult. For example, the openings where nerves exit the side of the spine, called “neural foramina,” are frequently very narrow. The neural foramen can be particularly narrow in patients with a common condition known as “spinal stenosis,” where the spinal nerves are compressed by enlarged, arthritic facet joints. Inability to relieve this narrowing frequently will cause “failure” in back surgery, particularly when the surgery involves “decompression” or opening of the spinal canal and foramina to relieve the pressure on the spinal cord.  
           [0003]    In some patients, the neural foramen is so small that the surgeon must search to find it before attempting to enlarge it. When found, the surgeon resects pieces of the bone surrounding the foramen with surgical instruments, such as, for example, “Kerrison” ronguers, until he or she believes that the foramen has been adequately enlarged around the exiting nerve. This uncertainty about when the foramen is adequately enlarged frequently results in the surgeon overestimating the size of the foramen and discontinuing the enlargement prematurely. The greatest number of failures in spinal stenosis decompression surgeries occur because the surgeon has not adequately enlarged the foramen to provide adequate space for the exiting nerve.  
           [0004]    Accordingly, a need exists for a system and method of finding and accurately evaluating the enlargement of foramina in patients undergoing surgery.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention is directed to a system, method and apparatus for locating, measuring and/or evaluating the enlargement of a foramen.  
           [0006]    One embodiment of the invention includes a foraminal instrument including a handle, an angular region, and a tip. For purposes of this disclosure, the term “handle” refers to a graspable region of the instrument. In such an embodiment, the tip can be shaped in any manner that allows its maximum width to be inserted into the open space in a foramen, for instance, between an exiting nerve and the edge of a neural foramen. In one preferred embodiment, the tip is substantially rounded or substantially spherical. In such an embodiment, the maximum width of the tip of the foraminal instrument can be any size between a size just smaller than the open space in an unenlarged foramen to a size approximately equal to the desired amount of open space in an enlarged foramen. For example, in a neural foramen, this preferable range would be approximately 0.5 mm to 8 mm.  
           [0007]    In another embodiment, the angled region extends at an angle, preferably about 60 to 80 degrees, more preferably about 70 to 78 degrees, and most preferably about 76 degrees from the handle. In such an embodiment, the angled region may be substantially curved or substantially linear.  
           [0008]    The invention is also directed to a foramen opening system including multiple instruments as described above, each having a tip with a different maximum width. In an alternative embodiment, the kit includes a single instrument with multiple tips with different maximum widths. By inserting tips with different maximum widths into the foramen through the course of the surgery, a surgeon is able to identify the current size or location of the open space in the foramen and how much additional enlargement is necessary.  
           [0009]    The invention is also directed to a method of evaluating the enlargement of a foramen including locating a foramen in an unenlarged state, pressing an instrument with a tip of a certain maximum width into the foramen, determining whether the tip inserted into the foramen, and cutting away the edge of the foramen if the tip did not insert into the foramen. This procedure can be repeated until the tip of the instrument inserts into the foramen in an enlarged state.  
           [0010]    Another embodiment also includes repeating this method with a second instrument with a larger maximum width than the first instrument. This allows the foramen to be enlarged in stages, to give the surgeon an idea of how large the open space in the foramen is throughout the course of the surgery, and how much more enlargement is necessary. Finally, in another embodiment, an instrument with a tip having a smaller maximum width is pressed near the foramen until it inserts into the foramen. This allows the foramen to be located before it is enlarged. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings where:  
         [0012]    [0012]FIG. 1 shows a side perspective view of an exemplary foraminal instrument, according to one embodiment of the invention;  
         [0013]    [0013]FIG. 2 shows a enlarged plan view of the tip shown in the embodiment of FIG. 1 as it is inserted into the neural foramen;  
         [0014]    [0014]FIG. 3 shows a side view of another embodiment of a system according to one embodiment of the invention; and  
         [0015]    [0015]FIG. 4 is a flow chart of another embodiment of a method according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    This invention relates to an apparatus, system, and method for locating, measuring and evaluating the enlargement of a foramen to ensure an optimal surgical outcome. For purposes of this application, the term “foramen” refers to an opening or orifice in the body, more particularly in the spine, and the term “tip” is the end region of a projecting object. The term “unenlarged state” for a foramen refers to the size of the foramen opening before any enlargement occurs, and “enlarged state” for a foramen refers to the size of the foramen opening after it has been at least somewhat enlarged.  
         [0017]    As shown in FIG. 1, one embodiment of the invention includes a foraminal instrument including a handle  10 , an angled region  12 , and a tip  14 . The handle  10  is preferably around 7.5-8 cm long, but one skilled in the art will recognize that any length that can be comfortably grasped in one hand and extending toward the area near the foramen (not shown) would be sufficient. The handle  10  can also be textured or balanced to provide a better grasp on the instrument, and can include indentations  16  on which labels (not shown) and the like may be attached.  
         [0018]    The angled region  12  protrudes from the handle  10  at an angle  18 . In this embodiment, the angled region  12  is curved. It is also within the scope of the invention for the angled region  12  to protrude linearly at a given angle from the handle. The angled region  12  is preferably at an angle  18  of between about 60 to 80 degrees, more preferably between about 70-78 degrees, and most preferably at about 76 degrees from the handle  10 . The thickness of the angled region  12  near the tip  14  in the embodiment shown in FIG. 1 is narrower than the maximum width  20  of the tip  14 , to allow at least part of the angled region  12  to insert into the foramen (not shown) with the tip  14 . However, in other embodiments, the angled region  12  does not partially insert into the foramen (not shown) and can be of any thickness as long as the maximum width  20  of the tip  14  is narrow enough to insert into the desired open space in the foramen.  
         [0019]    Although the tip  14  in the embodiment of the invention shown in FIG. 1 is substantially spherical, it is within the scope of the invention for the tip to be shaped in any way that would allow it to be inserted into the open space of a foramen, such as the space in a neural foramen not taken up by the exiting nerve. For example, the tip may also be rounded, which allows the same approximate size of the empty space in the foramen to be determined regardless of slight changes in the orientation of the tip. However, it is also within the scope of the invention for the tip to be in any other shape the surgeon desires.  
         [0020]    [0020]FIG. 2 shows the angled region  12  of the instrument and the tip  14  from the embodiment shown in FIG. 1 in more detail. The tip  14  is shown inserted into a neural foramen  100  in the space  106  between an exiting nerve  102  and the edge of the foramen  100 . Maximum widths  104  of the tip in some preferred embodiments include: a width equal to the desired enlarged space [enlarging width](preferably around 5 to 8 mm, and more preferably around 6 mm for a neural foramen); a width small enough to insert in the space  106  before any enlargement is made [inserting width] (preferably 0.5 mm to 2 mm, and more preferably around 1.2 mm for a neural foramen); and any intermediate width in between the enlargement and insertion widths to determine an intermediate size of the open space  106  and the extent of additional enlargement necessary.  
         [0021]    The invention is also directed to a foramen opening system, shown in FIG. 3. In such a system, four instruments  300 ,  302 ,  304 ,  306  with tips  310 ,  312 ,  314 ,  316  having different maximum widths  320 ,  322 ,  324 ,  326  are included in a surgical kit. The first instrument  300  has a maximum width  320  small enough to be inserted into a narrowed neural foramen (not shown) before it is enlarged by the surgeon. The maximum width  320  of this tip  310  is preferably around 0.5 mm to 2 mm, and more preferably around 1.2 mm for a neural foraminal instrument. The second instrument&#39;s tip  312  and the third instrument&#39;s tip  314  have intermediate maximum widths  322 ,  324  to provide a measure of the extent of foraminal opening. For neural foraminal instruments, the preferred maximum widths  322 ,  324  would be around 2 mm to 4 mm (more preferably 3 mm), and 4 mm to 5 mm (more preferably around 4.5 mm), respectively. The fourth instrument&#39;s tip  316  has a maximum width  326  equal to the desired space between the exiting nerve and the edge of the foramen (shown in FIG. 2), preferably around 5 mm to 8 mm, more preferably 6 mm for a neural foraminal instrument. Although four instruments  300 ,  302 ,  304 ,  306  are shown in FIG. 3, a higher or lower number of instruments can be included in the kit to locate and measure the foramen (shown in FIG. 2), depending on the needs of the surgeon.  
         [0022]    Another embodiment (not shown) of a foramen opening system includes a single handle and an angled region, such as are shown in the embodiment of FIG. 1. However, the embodiment also includes several interchangeable tips (not shown). Each tip can be removably coupled to the angled region and has one of a selection of maximum widths, as described according to the embodiment shown in FIG. 4. The tips can be coupled to the angled region by any means capable of holding the tip in a fixed position, such as, for example, an angled region with outer threads and a tip with inner threads, etc.  
         [0023]    Yet another embodiment (not shown) includes two angled regions fixedly coupled to each end of a handle. Each angled region is fixedly coupled to a tip having a different maximum width. This embodiment would allow a surgeon to determine the location and/or size of the foramen at two different stages of the enlargement with the same instrument.  
         [0024]    The invention further includes a method of evaluating the enlargement of the neural foramen. Referring to FIG. 4, the method includes locating the foramen  400 , pressing an instrument against the foramen  402 , determining if the instrument inserts into the foramen  404 , and cutting the edge of the foramen  414  if the instrument does not insert  412 . The pressing  402 , determining  404 , and cutting  414  steps can then be repeated until the instrument inserts into the foramen  406 .  
         [0025]    In one embodiment, the instrument that is inserted into the foramen has a tip with a maximum width equal to the desired space between the exiting nerve and the edge of the foramen. Thus, the surgeon can be assured that the foramen is sufficiently enlarged when it is possible to insert this maximum width into the space and can therefore end the surgery  408 .  
         [0026]    In another embodiment, the surgeon repeats  410  this process with multiple instruments with tips of increasing maximum width in order to determine the current size of the open space in the foramen during the course of enlargement. This method can also be used with one instrument and multiple fixed or replaceable tips as discussed above.  
         [0027]    In another embodiment (not shown), the step of locating  400  the foramen includes dragging the tip of a foramen locating instrument toward the spine in the area near the foramen. The tip of the instrument preferably has a maximum width of around 0.5 mm to 2 mm, more preferably around 1.2 mm to ensure insertion into the foramen. When the tip inserts into the foramen, the surgeon is able to determine its location. The surgeon can then begin enlarging the foramen by cutting  414  the foramen&#39;s edges.  
         [0028]    Although specific embodiments are disclosed herein, it is expected that persons skilled in the art can and will design alternate instruments and methods that are within the scope of the following claims either literally or under the Doctrine of Equivalents.