Abstract:
In one embodiment, a device for measuring a length of a bone tunnel is provided. The device includes: a gauge comprising an annular shaft coupled to a handle, the handle including a constrained channel configured for receiving a passing pin from the annular shaft and displaying the passing pin in relation to a scale. In another embodiment, a method for measuring length of the bone tunnel is provided. A method and another device are provided.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The invention disclosed herein relates to a device for use in ligament reconstruction surgery, and more specifically, a device and method for performing measurements. 
         [0003]    2. Description of the Related Art 
         [0004]    Common techniques for reconstruction of ligaments require the drilling of a tunnel through bone. For example, reconstruction of a torn anterior cruciate ligament (ACL) requires drilling through the femur of a patient. Once a femoral tunnel has been drilled. a surgeon needs to perform measurements to determine the depth of the tunnel to aide in selection of the appropriate repair technique. 
         [0005]    While a variety of devices are available to measure the length of the femoral tunnel, many of these devices are complicated to use and may lead to confusion during surgical procedures. For example, some devices make use of a guide wire that is passed into the femoral tunnel and received by a measuring device as it exits the femoral tunnel. Unfortunately, the various receiving devices presently available often do not securely retain the guide wire. Accordingly, this may lead to erroneous measurements, and worse yet to glove damage or laceration of the surgeon. 
         [0006]    Thus, what are needed are methods and apparatus to provide for accurate and safe measurement of the femoral tunnel. Preferably, the methods and apparatus are simple and easy to understand during a surgical procedure as well as cost-effective. 
       SUMMARY 
       [0007]    In one embodiment, a device for measuring a length of a bone tunnel is provided. The device includes: a gauge comprising an annular shaft coupled to a handle, the handle including a constrained channel configured for receiving a passing pin from the annular shaft and displaying the passing pin in relation to a scale. 
         [0008]    In another embodiment, a method for measuring length of the bone tunnel is provided. The method includes: placing a gauge over a passing pin, the tunnel gauge including an annular shaft coupled to a handle, the handle also having a constrained channel configured for receiving the passing pin from the annular shaft and displaying the passing pin in relation to a scale; and, comparing a reference mark on the passing pin to the gauge to determine the length. 
         [0009]    In a further embodiment, a device for measuring a length of a bone tunnel is provided. The device includes: a passing pin having a region configured to be maintained within a constrained channel of a measurement device; and, a gauge including an annular shaft coupled to a handle, the handle also having a constrained channel configured for receiving the passing pin from the annular shaft and displaying the passing pin in relation to a scale. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The features and advantages of the invention are apparent from the following description taken in conjunction with the accompanying drawings in which: 
           [0011]      FIG. 1  is an isometric view of a tunnel gauge according to an embodiment of the invention; 
           [0012]      FIG. 2  is an isometric view of a handle of the tunnel gauge of  FIG. 1 , from a different angle; 
           [0013]      FIGS. 3A ,  3 B and  3 C, collectively referred to herein as  FIG. 3 , provide another isometric view of the handle of the tunnel gauge of  FIG. 1 .  FIG. 3A  provides the isometric view of a complete embodiment of the handle, while  FIG. 3B  provides a cutaway of the isometric view of  FIG. 3A .  FIG. 3C  provides a close-up view of the cutaway shown in  FIG. 3B , additionally with a cross-section of the passing pin; 
           [0014]      FIG. 4  provides an isometric view of a passing pin suited for use with the tunnel gauge of  FIG. 1 ; 
           [0015]      FIG. 5  is a blown up isometric view of a portion of the handle of the tunnel gauge with the passing pin loaded therein; and, 
           [0016]      FIG. 6  is an isometric cutaway view of the tunnel gauge in use with the passing pin. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Disclosed herein are methods and apparatus for performing measurements of a bone tunnel. As discussed herein, the bone tunnel is a femoral tunnel (i.e., a hole that has been drilled through a portion of a femur of a patient). However, this is merely exemplary and it is not limiting of the teachings herein. 
         [0018]    Generally, the apparatus disclosed herein is a two-part apparatus. In order to measure the femoral tunnel, a first part, a passing pin, is inserted into the femoral tunnel. Insertion of the passing pin is stopped when a reference mark on the passing pin aligns with an outer surface of the femoral condyle. A second part of the device, a tunnel gauge, is then disposed over a portion of the passing pin that has emerged from an opposing side of the femur. By placing the tunnel gauge against the opposing side of the femoral condyle and by referencing a scale on the tunnel gauge, a surgeon is able to determine a depth of the femoral tunnel. 
         [0019]    Referring now to  FIG. 1 , there is shown an exemplary tunnel gauge  10  according to the teachings herein. In this example, the tunnel gauge  10  includes a shaft  1  and a handle  2 . Generally, the shaft  1  is mounted to the handle  2  at a base  3 . 
         [0020]    Note that merely for convenience of referencing and an explanation of the teachings herein, the terms “distal” and “proximal” as well as other such relational or descriptive terms are used. This terminology should not be construed to imply any orientation for implementation of the methods and apparatus disclosed herein. Generally, the term “distal” and “proximal” are with respect to an individual using the device (e.g., a physician). For example, when inserting a passing pin, an end of the passing pin that is being inserted may be referred to as a “distal” end of the passing pin. Similarly, when placing the tunnel gauge  10  against the femur, it may be considered that the shaft  1  is a distal portion of the tunnel gauge  10 , while the handle  2  is a proximal portion of the tunnel gauge  10 . 
         [0021]    In the exemplary embodiment, the tunnel gauge  10  is disposed about a longitudinal axis, A. Again, the longitudinal axis, A, and any other techniques for referencing are merely for purposes of explanation and are not limiting of the teachings herein. 
         [0022]    In the embodiment shown, the shaft  1  is an annular cylinder. The shaft  1  includes a receiver  4 , a tapered section  5 , and an elongated section  6 . The shaft  1  may be mounted to the handle  2  at the body  3  by any one (or more) of a variety of suitable techniques. For example, the shaft  1  may be threaded into a receiving section within the body  3 . The shaft  1  may be glued, hot melted, fastened or otherwise mated or joined with the body  3 . 
         [0023]    Generally, the shaft  1  has an inner diameter designed to accommodate a passing pin (as shown in  FIG. 4 , and as discussed further herein). For example, the shaft  1  may have an inner diameter that is slightly larger than 2.4 mm or 2.7 mm, such that it may securely accommodate passage of the 2.4 mm or 2.7 mm passing pin, respectively. 
         [0024]    In this embodiment, the handle  2  may be characterized as having a relatively flat body of a given thickness, T, and of a given width, W. Generally, the handle  2  is presented in the form that considers ergonomic convenience for a user. For example, in this embodiment, the handle  2  includes bilateral depressions  11 . The bilateral depressions  11  are provided such that a surgeon may easily grip the handle  2  between the thumb and forefinger. 
         [0025]    The handle  2  includes a central channel  9 . The channel  9  is configured to receive the passing pin as it emerges from the elongated section  6  of the shaft  1 . In order to view the central channel  9  (and therefore the passing pin), a window  7  is provided within the body of the handle  2 . In this example, the window  7  presents as a cutaway along a length of the handle  2 . 
         [0026]    Disposed within the window  7  is at least one gauge  8 . The gauge  8  is disposed along a length of the channel  9  within the window  7 . Accordingly, as the passing pin is received within the channel  9 , and extends into the handle  2 , a depth of the femoral tunnel may be ascertained. That is, the gauge  8  includes at least one scale for measuring depth of the femoral tunnel (i.e., a length of the femoral tunnel). This will be explained in greater detail further herein. 
         [0027]    In this example, the gauge  8  is provided in centimeters, with subdivisions of millimeters. However, any linear scale deemed appropriate may be used in the gauge  8  (i.e., system international (SI), English, metric or other standards may be used). 
         [0028]    Referring now to  FIG. 2  some of the foregoing aspects are shown from another angle. In addition, it may be seen that the handle  2  may include an exit-way  12  from the channel  9 . Generally, the exit-way  12  may be provided to facilitate cleaning of the handle  2  after use. For example, it may be desirable to flush a sterilizing cleaning fluid through at least one of the receiver  4  and the exit-way  12  to ensure removal of all debris as well as sterilization of the tunnel gauge  10 . 
         [0029]    Referring to  FIGS. 3A and 3B , additional isometric views of the handle  2  are shown.  FIG. 3A  is provided merely for understanding the depiction in  FIG. 3B , which depicts a cutaway portion of the handle  2 . As shown in  FIG. 3B , the channel  9  may be configured with a “C” shaped cross-section. That is, the channel  9  may be configured to securely retain the passing pin while providing for display thereof. An example of this is better shown in  FIG. 3C . 
         [0030]    Referring now to  FIG. 3C  there is shown an exploded view of the cutaway portion of the channel  9  of  FIG. 3B . Further, in this illustration, a portion of a passing pin  21  is shown. As may be seen in  FIG. 3C , the channel  9  may include at least one section of retaining material  31 . More specifically, retaining material  31  may be included to retain the passing pin  21  within the channel  9 . In this example, retaining material  31  is disposed symmetrically about the channel  9 . However, in some embodiments, retaining material  31  is provided on merely one side of the channel  9 . In use, the retaining material  31  provides for observation of the passing pin  21  while narrowing an open portion of the channel  9  substantially enough that the passing pin  21  could not be diverted out of the channel  9  (i.e., the open portion of the channel  9  has a width that is less than a diameter or width of the passing pin  21 ). 
         [0031]    In this embodiment, the retaining material  31  provides for a “constrained channel”  9 . It may be considered that the term “constrained channel” generally refers to any type of channel that may be characterized as having a particular geometry (e.g., a cross-section) that provides for retention of the passing pin  21  or any other similar component (e.g., a guide wire, a drill, a drill shank, and the like). 
         [0032]    More specifically, in this example, the passing pin  21  exhibits a cross-section of a dimension, denoted as “CS.” The constrained channel  9  has a relatively narrow opening. That is, a dimension for the opening provided for display of the passing pin  21  is less than that of the cross-section of the passing pin  21 . Accordingly, it should be understood that the constrained channel  9  may have a narrow opening the generally limits the capability of the passing pin to migrate from the channel  9 . 
         [0033]    Also shown in  FIG. 3C , is a measuring mark  33 . In this example, the measuring mark  33  is characterized as a single line disposed about a circumference (or perimeter, as the case may be) of the passing pin  21 . In some embodiments, the measuring mark  33  is disposed about the passing pin  21  by use of laser etching. However, any technique for providing a measuring mark  33  that is deemed appropriate may be used. 
         [0034]    In some embodiments (not shown), the measuring mark  33  includes a plurality of marks. For example, the measuring mark  33  may include another scale. The another scale may be compared to markings in the gauge  8 . 
         [0035]    Referring now to  FIG. 4 , an embodiment of the passing pin  21  is shown. In this example the passing pin  21  is a unitary device. The passing pin may be flexible, rigid or exhibit any appropriate combination of properties. The passing pin  21  may include a reference mark  23  which serves as a stop point during insertion of the passing pin  21  into the femoral tunnel. In addition, the passing pin  21  may include at least one marking indicator  24  to enhance visibility of the reference mark  23 . In this example, the marking indicator  24  is an elongated stripe that extends along a portion of the length of the passing pin  21 . 
         [0036]    In some embodiments, the passing pin  21  includes a fluted end. The fluted end may be provided so that the passing pin  21  may also provide for drilling of the femoral tunnel. In this example, the passing pin  21  includes a pointed end which facilitates its insertion into the femoral tunnel, once the femoral tunnel has been drilled and the drill removed. The pointed end of the passing pin  21  allows it to penetrate any drilling debris remaining in the tunnel. In use, the passing pin  21  is inserted into the femoral tunnel until the reference mark  23  is aligned with a distal cortex of the femur. 
         [0037]    Referring back to  FIG. 1 , once the passing pin  21  has been inserted, the tunnel gauge  10  is disposed over the portion of the passing pin  21  which extends from the femur, and in some instances from a skin of the patient. Once the shaft  1  of the tunnel gauge  10  has been disposed over the passing pin  21 , the shaft  1  is then pushed through the surrounding tissue. Accordingly, the tapered section  5  of the shaft  1  facilitates insertion of the shaft  1  by displacing the tissue. Once the receiver  4  has been abutted against a proximal cortex of the femur, it is possible to accurately measure a depth of the femoral tunnel. 
         [0038]    Referring now to  FIG. 5 , an embodiment of the tunnel gauge  10  with the passing pin  21  loaded therein is shown. It may be seen that, in this example, the femoral tunnel is about 41 mm deep. 
         [0039]    According to  FIG. 6  a cutaway view of the tunnel gauge  10  and passing pin  21  is shown in use. All surrounding tissue has been removed from this illustration to better depict cooperation of the passing pin  21  with the tunnel gauge  10 . 
         [0040]    Having thus introduced embodiments of the tunnel gauge  10 , some additional aspects are now provided. 
         [0041]    In some embodiments, the handle  2  and the shaft  1  are a unitary structure. For example, the handle  2  and the shaft  1  may be fabricated from a biocompatible plastic. This may be performed by injection molding or other suitable techniques. In some additional embodiments, one of the handle  2  and the shaft  1  is fabricated from a plastic or polymeric material while the other component is fabricated from metal or a metallic material. One exemplary polymeric material is polyphenylsulfone (PPSU). PPSU may be characterized as a material having a high heat resistance and excellent hydrolytic stability. Other materials that may withstand repeated cycling through sterilization environment (i.e., cleaning with steam, alcohol or other suitable materials) and that provide desired structural integrity may be used. 
         [0042]    The passing pin  21  may be provided in a variety of configurations. For example, the passing pin  21  may be generally cylindrical (such as in the form of a wire), may be annular (such as in the form of a straw), or of another cross-sectional geometry (such as a square, a rectangle, a triangle, or an n-gon) as deemed appropriate and suited for use with the constrained channel  9 . The passing pin  21  may include at least one loop or eyelet, such as for carrying suture. Although discussed herein as the passing pin  21 , any device suited for insertion through the femoral tunnel (or any other bone tunnel) may be used with the tunnel gauge  10 . For example, the tunnel gauge  10  may be configured to receive a drill. 
         [0043]    In some embodiments, the handle  2  may be separated from the shaft  1  to facilitate cleaning and sterilization of the tunnel gauge  10 . 
         [0044]    Although presented herein with regards to reconstruction of ligaments and drilling of a femoral tunnel, the tunnel gauge  10  may be used to ascertain a depth or length of any type of bone tunnel, as deemed appropriate. 
         [0045]    While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.