Abstract:
A distal tip wire relief section may be applied to any cannulated instrument or implant requiring the use of a guidewire with an enlarged head, such as a ball tip guidewire used in conjunction with an intramedullary nail. The implant incorporates an enlarged opening at the leading or distal portion of the cannula. The enlarged opening is selectively placed about the periphery of the distal portion to allow opening relief in areas where guidewire removal will be facilitated. Thus, a surgeon can reliably and repeatedly remove the guidewire after implantation of the implant by pulling the enlarged head of the guidewire proximally into and through the cannula.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to cannulated surgical instruments. More particularly, the present disclosure relates to surgical instruments or implants used in conjunction with guidewires having enlarged heads, and to methods for using the same. 
         [0003]    2. Brief Description of the Related Art 
         [0004]    Rods or nails are used in a variety of surgical procedures, such as to treat fractures of long bones in the body. For example, an intramedullary (or “IM”) rod or nail is a metal rod that can be inserted into the medullary cavity of a bone to bridge a fracture and aid in the healing process. 
         [0005]    In one surgical technique used for intramedullary nail implantation, a guidewire with a spherical or ball tip is surgically introduced to the medullary cavity of a bone to bridge a fracture. A guidewire tube is then passed over the inserted ball tip guide wire. With the guidewire tube now bridging the fracture gap, the ball tip guidewire is removed from the tube and medullary cavity. A smooth guidewire is then inserted into the hollow guidewire tube, and the tube is removed to leave only the smooth guidewire in the medullary cavity of the bone. The smooth guidewire can then be used to guide an intramedullary nail into the medullary cavity by passing the cannula of the nail over the smooth wire as the nail is inserted. Once the nail is properly placed and secured, the smooth guidewire is removed through the nail cannula. This technique may be referred to as a “wire exchange” technique because the ball tip guidewire is exchanged for the smooth guidewire before insertion of the IM nail. 
         [0006]    This wire exchange technique is typically performed because the size of the cannula in a traditional intramedullary nail is insufficient to allow passage of the enlarged head of a ball tip guidewire through the cannula. In a recent generation of intramedullary nails, however, improved designs and materials may allow for a larger nail cannulation which is sufficient to allow an enlarged head or ball tip of a guidewire to pass therethrough. Because the nail cannula is smaller than a typical guidewire tube, these recent designs may result in the ball tip becoming stuck or “hung up” when the shoulder between the ball tip and the wire shaft of the guidewire engages a lip or sharp edge of the distal terminus of the cannula. 
         [0007]    To prevent the possibility of the ball tip guidewire becoming stuck as it is pulled proximally into the cannula, a surgeon may choose to perform a “wire exchange,” thereby foregoing a savings in time that would result from using the ball tip guidewire as the guidewire for the intramedullary nail. Conversely, a surgeon attempting to save time in this manner may find that the ball tip of the guidewire becomes stuck at the distal end of the cannula. 
         [0008]    What is needed is an intramedullary nail design in which a ball tip guidewire can be reliably used during the implantation of a surgical instrument, throughout the implantation procedure and without the need for a wire exchange. 
       SUMMARY 
       [0009]    The present disclosure provides a distal tip wire relief section which may be applied to any cannulated instrument or implant requiring the use of a guidewire with an enlarged head, such as a ball tip guidewire used in conjunction with an intramedullary nail. The implant incorporates an enlarged opening at the leading or distal portion of the cannula. The enlarged opening is selectively placed about the periphery of the distal portion to allow opening relief in areas where guidewire removal will be facilitated. Thus, a surgeon can reliably and repeatedly remove the guidewire after implantation of the implant by pulling the enlarged head of the guidewire proximally into and through the cannula. 
         [0010]    In one embodiment, a surgical device is used with a guide wire having an enlarged tip. The device includes an elongated body with an internal wall, a proximal end and a distal end, the elongated body defining a longitudinal cannula spanning the proximal end and the distal end. The internal wall defines an enlarged distal opening providing a distal access to the cannula, the enlarged distal opening having a maximum radial extent that is larger than the maximum radial extent of a corresponding proximate portion of the cannula. The internal wall also defines a continuous transition between the enlarged distal opening and the cannula, so that the opening is adapted to slidingly receive the enlarged tip of the guide wire. 
         [0011]    In one aspect, the guide wire may have a ball tip with a maximum radial extent that is smaller than a maximum radial extent of the cannula. The guide wire may further include a wire shaft having a radial extent, so that a difference between the radial extents of the wire shaft and the ball tip is less than a difference between the radial extents of the ball tip and the cannula. 
         [0012]    In another aspect, the surgical device may be a surgical implant, such as an intramedullary nail, for example. Alternatively, the surgical device may be a reamer. 
         [0013]    In another aspect, the enlarged distal opening may be concave. The enlarged distal opening may also extend around less than the entirety of the periphery of the internal wall. 
         [0014]    In yet another aspect, the elongated body may include a lead-in portion at the distal end, the lead-in portion defining an oblique angle with respect to a centerline of the elongated body. 
         [0015]    In another embodiment, a method of placing a surgical instrument in a bone is provided and includes: guiding a guide wire with an enlarged distal tip along a path leading into a medullary cavity of a bone; providing a surgical instrument with a cannula and an enlarged relief portion at a distal end of the cannula, the distal relief portion having a radial extent that is larger than both of i) a maximum radial extent of the cannula proximate the distal relief portion and ii) a maximum radial extent of the enlarged tip of the guide wire; inserting the surgical instrument into the medullary cavity of the bone by guiding the cannula over the guide wire and moving the surgical instrument along the path of the guide wire; and, after the step of inserting the surgical instrument, removing the guide wire from the surgical instrument while the surgical instrument remains in the medullary cavity of the bone. 
         [0016]    In one aspect, the step of providing the surgical device with a cannula and a relief portion includes providing a surgical device with a cannula and a concave relief portion. 
         [0017]    In another aspect, a difference between the radial extents of the enlarged tip and the wire shaft of the guidewire is less than a difference between the radial extents of the enlarged tip and the cannula. 
         [0018]    In another aspect, the step of providing a surgical device may include providing a surgical implant, such an intramedullary nail, for example. Alternatively, the step of providing a surgical device may include providing a reamer. 
         [0019]    In yet another aspect, the enlarged distal opening extends around less than the entirety of the periphery of the internal wall of the surgical instrument at the distal end. 
         [0020]    In another embodiment, an intramedullary nail for implantation within a bone is provided and includes a nail having a distal end, a proximal end, and a longitudinal centerline extending between the distal and the proximal end. An internal wall of the nail bounds a bore extending through the nail along the centerline, with the bore having a maximum transverse extent. A lead-in portion is disposed at the distal end of the nail, with the lead-in portion defining a distal face at an oblique angle with respect to the centerline, the distal face having an enlarged opening therein leading to the bore. The enlarged opening has a maximum transverse extent that is greater than the maximum transverse extent of the bore, so that the distal face defines a ramped guide surface and the enlarged opening provides a continuous transition between the internal wall and the distal face. 
         [0021]    In one aspect, the opening in the distal face may be an ellipsoidal opening. The enlarged distal opening may also be concave. Further, the enlarged distal opening may extend around less than the entirety of the periphery of the internal wall. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following descriptions of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0023]      FIG. 1  is a partial section, elevation view of the distal tip of an intramedullary nail with a guidewire received therein, illustrating passage of a ball tip of a guidewire past a distal tip relief portion of the nail; 
           [0024]      FIG. 2A  is a perspective, partial section view of the distal tip relief portion of the intramedullary nail shown in  FIG. 1 , illustrating the ball tip extending past the distal tip of the nail; 
           [0025]      FIG. 2B  is a perspective, partial section view of the intramedullary nail and guidewire of  FIG. 2A , with the ball tip engaging the distal tip relief portion; 
           [0026]      FIG. 2C  is a perspective, partial section view of the intramedullary nail and guidewire of  FIG. 2A , with the ball tip received within the nail cannula; 
           [0027]      FIG. 3  is a perspective view of an intramedullary nail in accordance with the present disclosure, illustrating a ball tip guidewire extending therethrough; 
           [0028]      FIG. 4  is an elevation, section view of a tibia with a guidewire received within the tibial medullary canal; 
           [0029]      FIG. 5  is an elevation, section view of the tibia of  FIG. 4  with an intramedullary nail received within the medullary canal and over the guidewire; 
           [0030]      FIG. 5A  is a detail, partial section view of a distal portion of the tibia shown in  FIG. 5 , illustrating the guidewire and distal tip relief; and 
           [0031]      FIG. 6  is an elevation, section view of the tibia of  FIG. 4  with an intramedullary nail received within the medullary canal and the guidewire removed. 
       
    
    
       [0032]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate preferred embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION 
       [0033]    Referring to  FIG. 3 , intramedullary nail  10  (“IM nail  10 ”) has a cannula extending therethrough which receives guidewire  12  having ball tip  14  at a distal end thereof Distal portion  16  of IM nail  10  includes relief  18  adapted to facilitate guidance of ball tip  14  into the cannula of IM nail  10 , as described in detail below. Although an intramedullary nail is used in the figures and description herein to illustrate a distal portion with a relief in accordance with the present disclosure, it is also contemplated that such a relief portion may be applied to any instrument or implant adapted for use with a guidewire having an enlarged tip or end portion. For example, other devices which may incorporate a distal relief portion in accordance with the present disclosure may include surgical tools such as reamer heads. 
         [0034]    Referring generally to  FIGS. 1-2C , IM nail  10  ( FIG. 3 ) has elongated body  20  defining an axis or centerline and a bore or cannula  22  extending along the centerline. Cannula  22  extends along the entire length of IM nail  10  from proximal end  17  ( FIG. 3 ) to distal end  16 . As shown in  FIG. 3 , body  20  of IM nail  10  has curvature to conform with the natural curvature of a bone. Body  20  may further include a plurality of apertures  24  therethrough, such as for receiving screws or fasteners to affix IM nail  10  within the medullary canal of a bone. 
         [0035]    Guidewire  12  has enlarged ball tip  14  at its distal end. Referring to  FIG. 1 , a shoulder or corner  26  may be formed between ball tip  14  and the main wire shaft of guidewire  12 . Ball tip  14  has a diameter or maximum extent or dimension D B  which is at least slightly smaller than the minimum transverse extent or dimension D C  of cannula  22 , to establish a clearance therebetween. For example, the clearance between a ball tip with a diameter of 3.0 mm and cannula  22  may be at least 0.008-in. 
         [0036]    In the exemplary embodiment of  FIGS. 1-2C , ball tip  14  is a generally spherically shaped structure received within a generally cylindrical cannula. However, the enlarged tip portion of the guidewire may be any shape or configuration, and the cannula may likewise take a variety of shapes or configurations as long as the radial extent of the enlarged tip portion is less than the radial extent of the cannula in at least one rotational configuration, so that the enlarged tip portion may pass through the entirety of cannula  22  from distal end  16  to proximal end  17 . 
         [0037]    As best seen in  FIGS. 2A-2C , distal tip portion  16  of IM nail  10  includes distal tip relief  18  disposed at distal opening  28  and along inner wall  30 . Relief  18  has a maximum transverse extent that is larger than the maximum transverse extent of the corresponding or adjacent proximate portion of cannula  22 . A smooth transition is provided along relief  18  from distal surface  32  to the non-enlarged cannulated portion along inner surface  30 , such as the concave profile shown in the illustrated embodiment. This concave profile, forming the smooth transition of relief  18 , facilitates passage of ball tip  14  as it moves from outside of cannula  22  ( FIG. 2A ) to inside cannula  22  ( FIG. 2C ), as will be discussed in detail below. 
         [0038]    In an exemplary embodiment, as best seen in  FIGS. 2A-2C , relief  18  is created by sweeping a ball mill around a portion of inner surface  30  adjacent to distal surface  32 . Thus, because the ball mill has a spherical radius, relief  18  is also radiused and has a generally concave profile. The ball mill may have a diameter which is larger than the diameter of cannula  22 , so that relief  18  defines a concave surface with a radius of curvature larger than ball tip  14 . The ball mill may also be smaller than the diameter of cannula  22  to impart a concavity of relief  18  with a radius equal to or smaller than ball tip  14 . A smaller ball mill may also be moved along an arcuate path within distal opening  28 , thereby milling an area with a complex or large-radius concavity. In one exemplary embodiment, the ball mill has a 0.188-in cutting diameter, and can be moved through a complex arcuate path to create relief  18  with a diameter larger than 0.188-in, such as by programming the complex arcuate path into a computer numerical controlled (CNC) machine. 
         [0039]    Although relief  18  is shown extending only partially around the periphery of opening  28  in IM nail  10 , it is within the scope of the present disclosure that relief  18  can vary according to the needs of a particular embodiment or surrounding geometrical configuration. 
         [0040]    Referring again to  FIG. 1 , distal portion  16  of IM nail  10  defines a lead-in portion that is angled with respect to the centerline or axis of IM nail  10 . More particularly, distal surface  32  defines a ramped surface created by cutting distal portion  16  at an oblique angle θ. The angled or ramped distal surface  32  facilitates passage of IM nail  10  into the medullary cavity of a bone by creating a relatively sharp “point”  19  at distal portion  16  ( FIG. 1 ). Surface  32  also helps to guide ball tip  14  of guidewire  12  into relief  18  of IM nail  10 . In the illustrated embodiment, the bottom portion of opening  28  is shown as not having been subjected to material removal so that relief  18  does not extend entirely around the periphery of opening  28 . The angled profile of distal surface  32 , i.e. the lead-in, precludes the need for relief  18  at this bottom surface. Further, because IM nail  10  is curved downwardly ( FIG. 3 ), ball tip  14  of guidewire  12  is urged generally upwardly with respect to the perspective of  FIGS. 1-2C , thereby minimizing the potential for contact or “hanging up” of corner  26  against the non-enlarged portion of opening  28 . However, in other configurations, such as a straight IM nail or and IM nail with a non-angled distal surface  32 , relief  18  may extend entirely around the periphery of opening  28 . 
         [0041]    When guidewire  12  is disposed within cannula  22  and ball tip  14  is extended beyond opening  28  ( FIG. 2A ), guidewire  12  may be pulled proximally so that ball tip  14  moves towards opening  28 . As the wire moves proximally, ball tip  14  reaches opening  28  ( FIG. 2B ) and may contact relief  18 . Because relief  18  defines a maximum transverse extent which is larger than the maximum transverse extent of cannula  22 , corner  26  (formed between ball tip  14  and the main wire shaft of guidewire  12 , as discussed above) cannot become lodged or engaged or hung up at the junction between inner surface  30  and distal surface  32  ( FIG. 2C ). In an exemplary embodiment, and as shown in  FIG. 5A , the opening of relief  18  is sufficiently enlarged to ensure that the shaft of guidewire  12  will contact inner wall  30  before corner  26  can become stuck at edge  19  of relief  18 . That is to say, if relief  18  is sufficiently large, edge  19  of relief  18  will contact the surface of ball tip  14  rather than corner  26 , even when the shaft of guidewire  12  is moved transversely so as to contact inner wall  30 . Corner  26  is therefore precluded from engaging a sharp lip or corner of distal surface  32  ( FIG. 2C ) so that ball tip  14  will not become “hung up” on relief  18 . Therefore, ball tip  14  will reliably pass into relief  18 , and the smooth transition between distal surface  32  and inner surface  30  of cannula  22  will then ensure that ball tip  14  passes from relief  18  into cannula  22 . Once ball tip  14  has moved past relief  18 , as shown in  FIG. 2C , guidewire  12  may be pulled proximally through the remainder of cannula  22  and out of IM nail  10 . 
         [0042]    Referring now to  FIGS. 4-6 , an exemplary surgical procedure includes passing ball tip guidewire  12  into the medullary canal of a fractured femur F, such that guidewire  12  spans fracture B. With guidewire  12  fully inserted into the femur F (as shown in  FIG. 4 ), IM nail  10  may be inserted into the medullary canal using guidewire  12  as a guide. Once IM nail is fully inserted ( FIG. 5 ), guide wire  12  may be removed through cannula  22  of IM nail  10 . As discussed above and shown in  FIG. 5A , relief  18  ensures that ball tip  14  of guidewire  12  will not become stuck at edge  19  of distal end  16 . 
         [0043]    Advantageously, an intramedullary nail or other surgical instrument or implant may be used throughout a surgical procedure without the need for a “wire exchange.” A surgeon can pass a guidewire with an enlarged head, such as guidewire  12  with ball tip  14 , into a medullary canal to span a fracture gap. Rather than passing a temporary tube over the enlarged-head guidewire, removing the enlarged-head guidewire, and then inserting a smooth guidewire in its place, the enlarged-head guidewire may be left in place and the surgical implant installed directly over the guidewire without concern that the enlarged head of the guidewire will become stuck outside the distal end of the cannula. 
         [0044]    Also advantageously, a surgical instrument with an enlarged distal opening in accordance with the present embodiment may be used without a wire exchange, even where the instrument has a relatively small cannulation size. Using IM nail  10  as an example and referring to  FIG. 1 , relief  18  prevents ball tip  14  from becoming stuck at distal surface  32 , allowing the transverse extent D C  of cannula  22  to be only slightly larger than the size of the transverse extent D B  of ball tip  14 . Thus, only minimal clearance between ball tip  14  and cannula  22  is required, allowing instrument designers to maximize the thickness of body  20 . An instrument or implant made in accordance with the present disclosure therefore retains maximum implant or instrument strength while also eliminating the need to do a wire exchange during surgical implementation. For example, in one exemplary embodiment a cannulation size for an IM nail may be just over 3.0 mm in diameter (such as 3.008-in, as described above), while still allowing a guidewire with a 3.0 mm diameter ball tip to pass therethrough. 
         [0045]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.