Abstract:
A screw cutting tool for cutting a screw comprising a first grip having a first cutting aperture, a second grip pivotally connected to the first grip, the second grip having a second cutting aperture, a measuring scale attached to a proximal end of the first or second grip, and a screw holder slidably attached to the measuring scale having a hole extending therethrough, wherein the hole aligns with the first and second cutting apertures in at least one position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/708,251 filed Oct. 1, 2012, the disclosure of which is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a method and device used for the cutting of screws, specifically, a method and tool for accurately cutting the lengths of orthopedic screws. 
         [0003]    Currently, a significant number of surgical implant systems that utilize screws are available. These systems typically include a number of different screw sizes, in both diameter and length, in order to accommodate the countless variables inherent in medical procedures. The inclusion of these varying screws, many of which end up unused, increases inventory and investment costs, as well as producing unnecessary waste. For instance, in the case of fracture fixation, systems include many differently sized bone plates and bone screws are provided, but only one plate and a few screws may be employed in a given procedure. 
         [0004]    Additionally, even with the plethora of screws provided in a given system, the screws may not be provided in the necessary increments. For instance, the screw lengths may be incremented in multiples of five millimeters, but a given procedure may require an in-between size (e.g., a length in the two and a half increment range). This is particularly prevalent in surgeries that require a high degree of accuracy, such as cranio-maxillofacial surgery. 
         [0005]    Thus, there exists a need for a method and apparatus for cutting screws to required lengths. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    One aspect of the present invention is a cutting tool with an attached measuring scale and screw holder allowing for a secure and accurate crop of a screw. Preferably, the cutting tool can be utilized in cutting screws having a variety of differing screw diameters. Additionally, the cutting tool catches the trimmed endpiece of the screw in order to facilitate easy and safe disposal of the endpiece. 
         [0007]    In accordance with one embodiment, the tool is designed to cut a screw and includes first and second grips pivotally connected to each other, each having a cutting aperture, a measuring scale attached to a proximal end of the first grip, and a screw holder slidably attached to the measuring scale, having a hole extending therethrough, wherein the hole aligns with the first and second cutting apertures in at least one position. 
         [0008]    In accordance with alternate embodiments, the tool may further include: a spring positioned against the first and second grips, wherein the spring biases the grips in an open position; multiple cutting sleeves within the first and second cutting apertures; a bracket capable of clamping the screw through manipulation of the grips about the pivotal connection, wherein the bracket rides along a pin engaged with slots on the bracket and both grips; a pivotal attachment between the measuring scale and the first or second grip; and additional cutting apertures on the first and second grips, with additional cutting sleeves therein. 
         [0009]    In accordance with another alternate embodiment, the tool may include: a first grip having a first cutting aperture; a second grip pivotally connected to the first grip, the second grip having a second cutting aperture; a measuring scale attached to a proximal end of the first or second grip; a screw holder slidably attached to the measuring scale having a hole extending therethrough and aligning with the first and second cutting apertures in at least one position; a spring positioned against the first and second grips capable of biasing the grips to an open position; a first cutting sleeve disposed within the first cutting aperture; a second cutting sleeve disposed within the second cutting aperture; an arcuate slot extending through the proximal end of the first grip; a bracket having a linear slot and a polymeric end portion capable of clamping the screw against its polymeric end portion through manipulation of the grips; and a pin fixedly attached to the first grip and extending through and engaged within the arcuate slot and the linear slot. 
         [0010]    Another aspect of the present invention is a method of cutting a screw utilizing a screw cutting tool. 
         [0011]    In accordance with one embodiment, the screw is inserted through a hole in the screw holder and its corresponding first and second cutting apertures, the screw holder is slid along the measuring scale to determine the desired length to be cut, and the grips are actuated to cut the screw. 
         [0012]    In accordance with alternate embodiments, the method may further include the steps of: clamping a trimmed endpiece of the screw for subsequent disposal, removing the holder from the measuring scale, and folding the measuring scale about a pivotal connection with the first or second grip. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of one embodiment of a screw cutting tool. 
           [0014]      FIG. 2  is a bottom view of the embodiment of the screw cutting tool shown in  FIG. 1 . 
           [0015]      FIG. 3  is a perspective view of the embodiment of the screw cutting tool shown in  FIG. 1 , with a screw engaged with the cutting tool. 
           [0016]      FIG. 4  is a cross-sectional side view of the embodiment of the screw cutting tool shown in  FIG. 1 , focused on the screw cutting portion of the tool. 
           [0017]      FIG. 5  is a cross-sectional front view of the embodiment of the screw cutting tool shown in  FIG. 1 , focused on the screw cutting portion of the tool. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  shows a side view of one embodiment of screw cutting tool  10 . Screw cutting tool  10  includes first grip  11   a  and second grip  11   b,  which are connected at a pivot  16 . Each grip  11   a,    11   b  features a spring  12  that is positioned between the grips  11   a,    11   b  to bias them in the open position. A measuring scale  13  features one or more scales drawn or etched thereon for precisely measuring screw length and is pivotally attached at the proximal end of the first grip  11   a,  with a screw holder  14  slidably attached to the measuring scale  13 . The pivotal connection of measuring scale  13  to the first grip  11   a  allows for the scale to be rotated into a folded configuration for easier storage of the tool. Likewise, the slidable connection of screw holder  14  with measuring scale  13  allows for the easy manipulation of that element, as well as for its removal to ease storage of the tool. It is to be understood that the measuring scale  13  could alternatively be attached to the proximal end of the second grip  11   b.    
         [0019]    Disposed on the first grip  11   a,  adjacent to pivot  16 , are three apertures  17   a,    17   b,    17   c  of varying diameters to receive different diameters of screws. Likewise, screw holder  14  includes varying diameter apertures  21   a,    21   b,    21   c  to align with, and correspond to, the diameters of the respective apertures  17   a,    17   b,    17   c  below. Thus, a screw can be matched to the closest diameter among one of the apertures  21   a,    21   b,    21   c  of screw holder  14  and placed therethrough and into a corresponding aperture  17   a,    17   b,    17   c.    
         [0020]    As shown in  FIG. 2 , cutting tool  10  also includes a bracket  15  having a rigid slotted portion  15   a  and a polymeric end portion  15   b  attached below the pivot  16  for the purpose of trapping a trimmed endpiece of a screw against the end portion  15   b  after a cut is made (the cutting of the screw is discussed more fully below). A pin  18  is fixedly engaged with the first grip  11   a  (see  FIG. 1 ) and is disposed within a linear slot  19  on the rigid slotted portion  15   a  of the bracket  15  and an arcuate slot  20  on the first grip  11   a  (see  FIG. 1 ). As the grips  11  are squeezed together about the pivot  16 , bracket  15  rides along the connection between the pin  18  and the linear slot  19  toward the resected screw, causing the polymeric end portion  15   b  to push against screw  2 . The end portion  15   b  may thus hold the trimmed endpiece in place and prevent the endpiece from being lost. 
         [0021]      FIG. 3  shows a perspective view of the cutting portion of the screw cutting tool  10 . Screw  2  is inserted through aperture  21   b  and corresponding aperture  17   b.  By aligning the screw holder  14  with the desired length as indicated through the use of the measuring scale  13 , screw  2  is held steady with the screw holder  14  in order to be cut to a desired length. Apertures  21   a,    21   b,    21   c  of holder  14  are sized so that a shank of screw  2  can pass therethrough, but its head cannot, such that screw  2  is essentially held in place by holder  14 . The connection between the measuring scale  13  and the screw holder  14  may contain a locking mechanism (not shown) to keep the screw holder  14  locked against the desired increment of the scale  13  to ensure an accurate resection. 
         [0022]      FIGS. 4 and 5  respectively show cross-sectional side and front views of the screw cutting tool  10 . First grip  11   a  features cutting sleeves  22   a,    22   b,    22   c,  while the second grip  11   b  features cutting sleeves  23   a,    23   b,    23   c.  The sleeves of both grips  11   a,    11   b  are positioned such that they both align with their respective aperture  17   a,    17   b,    17   c  and contact each other (i.e., aperture  17   a  is aligned with sleeves  22   a  and  23   a,  and so forth). Cutting sleeves  22   a,    22   b,    22   c  and  23   a,    23   b,    23   c  are provided in different diameters to accommodate screws  2  of varying diameters. Moreover, the sleeves may be formed of a material hard enough to facilitate the cutting of screws  2  and may not necessarily be formed of the same material used for the rest of the tool  10 . Suitable materials may be stainless steel, titanium or the like. Of course, the material may also be based upon the material of the given screws to be cut. 
         [0023]    In one embodiment method according to the present invention, as shown in the figures, screw  2  is inserted through aperture  21   b  of screw holder  14  until a head thereof engages the holder  14 . A portion of the shank of screw  2  necessarily extends into aperture  17   b  and thus the corresponding set of cutting sleeves  22   b  and  23   b.  Holder  14  may then be moved along scale  13  until the desired screw length is measured, whereupon the holder  14  may be held in place by a mechanism or other means to secure it against the measuring scale  13 . First and second grips  11   a,    11   b  may then be squeezed together, preferably under the power of a surgeon&#39;s hands. In this regard, first and second grips  11   a,    11   b  may be of an ergonomic design, and may be designed to equate greater force to the shearing of screw  2  than is applied by the surgeon. In this regard, it is contemplated to incorporate a gearing system or the like into the tool  10 . When first and second grips  11   a,    11   b  are actuated about pivot  16 , cutting sleeves  22   b  and  23   b  of their respective grips  11   a,    11   b  move in opposing directions, thereby producing a shear force sufficient to shear screw  2  into two pieces. It is noted that as this shearing occurs, the portion sheared from the remainder of screw  2  is held in place by bracket  15 . Thus, the operation of cutting tool  10  can be performed without worry of portions of screw  2  becoming dislodged therefrom and lost. 
         [0024]    Although the embodiment depicted in  FIGS. 1-5  is discussed in particular above, one skilled in the art would recognize that design variations are possible. For example, the number and shape of apertures  17   a,    17   b,    17   c  and corresponding cutting sleeves  22   a,    22   b,    22   c  and  23   a,    23   b,    23   c  provided could vary. Also, each of the cutting sleeves could be composed of a range of materials of sufficient hardness to cut screw  2  not limited by the range of materials used to make the rest of the tool  10  and the cutting sleeves may even be composed of different materials on a single tool  10 . Likewise, the bracket  15  could be provided in a number of different shapes, with differently-shaped slots, or be composed of different materials sufficient to grip screw  2 . Further still, spring  12  could be of any type that would bias the grips  11  apart. 
         [0025]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is to be understood unless otherwise indicated herein that the figures are not intended to be to scale. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended paragraphs.