[0001]    The present application is related to and claims the benefit under 35 USC 119(e) of U.S. Provisional Application Ser. No. 61/268,845 filed Jun. 17, 2009. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to devices and methods used to form holes or tunnels in bone. More particularly, the invention relates to broaches and punches used to make bone tunnels or holes intended to receive suture anchors and the like. 
         [0004]    2. Description of the Prior Art 
         [0005]    The partial or complete tear of ligaments, tendons and other soft tissue from the respective bone attachment sites is a common occurrence due to chronic or acute injury. Surgery may be required to reattach the torn soft tissue to bone. There are many devices on the market for soft tissue repair. Such devices may be threaded suture anchors, where the torn soft tissue is sutured to the anchor and the anchor is secured in the bone with threads, or push-in suture anchors which are placed into pre-formed holes. 
         [0006]    Various devices are used to form the holes and enable them to receive the selected suture anchor. (The terms “tunnel” and “hole” are used interchangeably herein). Simple drills have been used to drill holes through the hard cortical layer of bone and into the softer cancellous layer of bone. However, this procedure takes time and sometimes requires expensive equipment. Additionally, drilling removes bone tissue and has the potential for causing bone necrosis through overheating. Bone punches are sometimes used. These are simply pointed shafts having a conical tip which tends to create a hole through the cortex and into the cancellous bone. However, the conical tip tends to expand the cortex around the hole and create stress fractures which weaken the bone, thus comprising its strength. Additionally, when a hole is created with a traditional awl-type punch, the surgeon can have difficulty removing the punch due to the radial compressive forces holding the punch in the bone. The surgeon must either put extra pressure on the bone to pull against it, or wiggle the punch to create sufficient clearance to allow the punch to be removed thereby compromising the size of the hole. Both of these techniques can further fracture the cortical surface and compromise the size, integrity and margin of the hole. These events could result in patient injury or compromise the success of the repair. 
         [0007]    With some threaded anchors the surgeon may need to tap threads into a pre-drilled or pre-formed hole. This is helpful in some cases, but does increase the surgery time and increases risk to the patient. 
         [0008]    There is a need for a device and method suitable for quickly and easily forming a bone hole or tunnel without the disadvantages of the prior art. 
         [0009]    Accordingly it is an object of the present invention to provide a tunnel forming device which decreases damage to the native surrounding bone into which the anchor is inserted. 
         [0010]    It is a further object of this invention to provide a tunnel forming device to cut and displace bone tissue as it advances. 
       SUMMARY OF THE INVENTION 
       [0011]    These and other objects of this invention are achieved by the preferred embodiment disclosed herein. This invention is a broaching punch for forming a hole in bone. The punch comprises
       an elongated shaft having an axis, a proximal end and a distal end; a tapered tip situated at the distal end. The tapered tip has a distal-most point on the axis and has a generally spiral broaching surface extending proximally away from the point. The broaching surface comprises a spiral cutting edge formed on the tapered tip, the edge adapted to cut a predetermined size hole as it is pushed into the bone.       
 
         [0013]    In another aspect, this invention is a method of forming a hole in bone comprising providing a broaching punch constructed as described above, pushing the broaching punch a predetermined distance into the bone and turning the broaching punch about its axis to remove it from the bone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a front perspective view of the distal tip of a broaching punch constructed in accordance with the principles of this invention. 
           [0015]      FIG. 2  is a side elevational view of the distal tip of the instrument shown in  FIG. 1 . 
           [0016]      FIG. 3  is a side elevational view of an alternate embodiment of the instrument in  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    The working, distal end of a broaching punch  10  constructed in accordance with the principles of this invention is shown in  FIGS. 1 and 2 . Broaching punch  10  has an elongated body  11  with a distal end  12 , proximal end  14 , intermediate shaft  16  and conical, tapered tip  18 . Conical tip  18  terminates in a conical surface  19  having a penetrating distal point  20  which, in the preferred embodiment is sharp enough to be pushed into the cortical layer of bone. The punch may have a mallet impact surface (not shown) at its proximal end or simply a handle. 
         [0018]    Conical tip  18  extends proximally at an angle A relative to axis  22  and is provided with a helical broaching surface  30  having a spiral cutting edge  32 . Spiral cutting edge  32  faces distally and is a single continuous edge spiraling about axis  22  from a distal point  36  to a proximal point  38 . Distal point  36  is smoothly tapered into the body of broaching punch  10  at a spot proximal to the conical surface  19  and tip  20 , and proximal point  38  smoothly tapers into the surface of the body of broaching punch  10  at the distal end of conical tip  18 . Conical tip  18  abuts at its proximal end to a cylindrical surface  40 . Broaching surface  30  and spiral cutting edge  32  may be formed by a complementarily shaped cutting tool translating proximally along body  11  from a point proximal to conical surface  19  while simultaneously retracting radially from axis  22 . Broaching surface  30  is generally parallel to axis  22  although it may have other orientations. Cutting edge  32  may simply be a distally facing spiral surface  33  extending radially away from axis  22 . Other profiles may be used as well. For example, the radially outermost junction of cutting edge  32  with broaching surface  30  may be chamfered rather than being a right angle. In the preferred embodiment spiral surface  33  extends radially a distance of approximately on the order of 0.003 inches. Conical surface  19  may be formed with any desired tapered angle between point  20  and the transition to spiral cutting edge  32 , provided the surface is able to penetrate the bone as intended. 
         [0019]    Broaching punch  10  is used by placing tip  22  at a point on a bone where one desires to form a bone hole or tunnel. The axis  22  is aligned with the intended axis of the desired bone hole and broaching punch  10  is moved (e.g., pushed or tapped) into the bone. As the broaching punch  10  advances into the bone, cutting edge  32  cuts the bone which it contacts and pushes the bone debris along with it into the bone hole. This has the incidental and beneficial effect of compacting the bone debris somewhat, thereby enhancing the quality of the wall of the bone hole being formed. When broaching punch  10  has been advanced to the desired depth, that is until some or all of conical tip  18  is within the bone and the hole has the desired diameter, the punch may be withdrawn by simply rotating it counterclockwise about axis  22 . If desired, the punch could be advanced into the bone far enough to insert cylindrical surface  40  into the bone. 
         [0020]    An alternate embodiment of the invention is shown in  FIG. 3  as broaching punch  100 . The elements in  FIG. 3  are identical to like numbered elements in  FIGS. 1 and 2 .  FIG. 3  differs from  FIG. 1  in that the surface immediately proximal to conical tip  18  is surface  140  having a tapping thread  142 . Broaching punch  100  is used in the same manner as broaching punch  10  except that when the conical tip  18  is completely pushed into the bone, broaching punch  100  is then turned into the bone further in order to tap threads into the cortical (and cancellous) bone at the proximal end of the hole, which threads can then be used by a threaded suture anchor. Broaching punch  100  is removed from the bone by turning it counterclockwise just as with broaching punch  10 . 
         [0021]    It will be noted that all embodiments of the broaching punch disclosed herein cut the bone upon insertion of the punch into bone, thereby eliminating the stress cracks caused by prior art punches which simply compact cortical bone as the punch is inserted into bone. 
         [0022]    The principles of this invention may be used to produce an alternate embodiment of the broaching punch (not shown) in which the conical tip  18  is shorter and transitions into a cylindrical broaching section. That is, rather than using a spiral cutting edge  32  superimposed solely on a conical tip  18 , a spiral cutting edge could be superimposed on a cylindrical tip to form a cylindrical hole rather than a tapered hole. 
         [0023]    It will be understood by those skilled in the art that numerous improvements and modifications may be made to the preferred embodiment of the invention disclosed herein without departing from the spirit and scope thereof.
A device and method for forming bone tunnels. The device has a conical tip with a spiral cutting edge intended to be pushed into the bone. After penetrating the bone to the desired depth the device is able to be rotated back out of the tunnel without excessive strain on the wall of the bone tunnel.