Abstract:
A drill guide comprising: a body comprising a hole extending therethrough for guiding a drill; and an alignment tool, the alignment tool being operable to connect the body to an intramedullary rod, such that the orientation of the body is fixable with respect to the intramedullary rod in an anteroposterior plane and in a transverse plane.

Description:
[0001]    The present invention relates to a drill guide particularly, but not exclusively, a femoral drill guide for use during a partial knee replacement. 
       BACKGROUND  
       [0002]    During knee arthroplasty, particularly a partial knee replacement, the joint is prepared by first resecting the tibial plateau. Following resection of the tibial plateau, one or more holes are then drilled into the femoral condyle to receive a cutting guide for resecting the condyle. Conventionally, a hole is made in the intramedullary canal of the femur, into which an intramedullary rod is inserted. The intramedullary rod acts as a reference for the drilling of the hole or holes which locate the cutting guide. These holes may also serve to locate the femoral component of the prosthetic following resection of the femoral condyle. 
         [0003]    The femoral component may comprise a single fixation peg or two fixation pegs which are received in holes in the femur. In addition or as an alternative, the femoral component may comprise one or more webs. The webs may be thin layers of material, which may extend between the pegs. 
         [0004]    A two peg component provides greater coverage (i.e. a larger degree of rotation) and may be selected where the patient&#39;s lifestyle is such that they are squatting regularly. 
         [0005]    As described previously, the intramedullary rod is used as a reference for locating the hole(s) for receiving the cutting guide. A drill guide may be used to reference from the intramedullary rod in order to properly locate the cutting guide. Existing drill guides require the surgeon to align the drill guide with the intramedullary rod in various planes so that the guide hole is placed in the correct position on the femur. 
         [0006]    In a known technique, a tibial template is placed on the resected tibial plateau and the drill guide inserted into the operative wound. A feeler gauge is then inserted in between the tibial template and the drill guide. Due to this layering of components there is a stack up in the tolerances of each component. 
         [0007]    It is desirable to provide a drill guide which has a simplified alignment process. 
       STATEMENTS OF INVENTION  
       [0008]    According to a first aspect of the invention, there is provided a drill guide comprising: a body comprising a hole extending therethrough for guiding a drill; and an alignment tool, the alignment tool being operable to connect the body to an intramedullary rod, such that the orientation of the body is fixable with respect to the intramedullary rod in an anteroposterior plane and in a transverse plane. 
         [0009]    According to a second aspect of the invention, there is provided a drill guide comprising: a body comprising a hole extending therethrough for guiding a drill; wherein the body comprises a fixed foot and a movable foot which are receivable within a joint; wherein the movable foot is releasably attached to the body and, when in a released state, the movable foot is translatable with respect to the fixed foot, such that the fixed foot contacts a first bone of the joint and the movable foot contacts a second bone of the joint. 
         [0010]    According to a third aspect of the invention, there is provided a drill guide comprising: a body and a tubular element, the tubular element having a hole extending therethrough for guiding a drill; wherein the tubular element is pivotably mounted with respect to the body such that the angle of the tubular element with respect to the body is adjustable. 
         [0011]    Any of the above aspects of the invention may be combined with one or more of the other aspects of the invention and/or one or more of the optional features set out below. 
         [0012]    The alignment tool may comprise a first arm and a second arm, the first arm being operable to connect the alignment tool to the body and the second arm being operable to connect the alignment tool to the intramedullary rod. 
         [0013]    The first and second arms may be pivotably connected to one another such that the distance between the first and second arms can be altered. 
         [0014]    The intramedullary rod may be cannulated and the second arm is received within the intramedullary rod. 
         [0015]    The body may have a mounting hole for receiving the alignment tool. 
         [0016]    The mounting hole may be angled to the left or right lateral side of the body. 
         [0017]    The mounting hole may be angled to the left or right lateral side of the body by 7°. 
         [0018]    The mounting hole may be angled in the vertical plane relative to the body. 
         [0019]    The mounting hole may be angled down by 5°. 
         [0020]    The alignment tool may comprise a handle. 
         [0021]    The movable foot may be releasably attached to the body by a screw which passes through a slot in the body and into the movable foot. 
         [0022]    The movable foot may be locked in position by tightening the screw such that a section of the body disposed between a head of the screw and the movable foot is held therebetween. 
         [0023]    The drill guide may further comprise an incremental locking means for locking the movable foot in predefined positions. 
         [0024]    A leading edge of the movable foot may be curved in the plane of the movable foot. 
         [0025]    An underside of the movable foot may be curved along its length. 
         [0026]    The hole may comprise first and second holes, which extend through the body at different angles. 
         [0027]    The first and second holes may be angled at 0° and 10° respectively or 5° and 15° respectively. 
         [0028]    The body may further comprise a protrusion on a left lateral side of the body and a protrusion on a right lateral side of the body. 
         [0029]    The distance between the protrusions may be equal to a width of a femoral component. 
         [0030]    The drill guide may further comprise a locking mechanism for locking the angle of the tubular element with respect to the body. 
         [0031]    The drill guide may further comprise an indexing mechanism for positioning the tubular element in predefined angles with respect to the body. 
         [0032]    The tubular element may be translatable with respect to the body. 
         [0033]    The tubular element may be translatable toward the top or bottom of the body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0034]    For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: 
           [0035]      FIG. 1  is a side view of a drill guide in accordance with the invention, wherein the drill guide is in use; 
           [0036]      FIG. 2  is a top view of the drill guide; 
           [0037]      FIG. 3  is a front view of the drill guide; and 
           [0038]      FIG. 4  is a second side view of the drill guide in  FIG. 1  during drilling. 
       
    
    
     DETAILED DESCRIPTION  
       [0039]      FIG. 1  shows a drill guide  2  in accordance with a first embodiment of the invention, wherein the drill guide is located in a knee joint between the tibia and the femur. The drill guide  2  comprises a body  4 . The body  4  has a first drilling hole  6  and a second drilling hole  8  which each extend longitudinally through the body  4  (as shown in  FIG. 3 ). The first and second drilling holes  6 ,  8  are aligned at different angles which correspond to the required location of holes for the single peg femoral component or the two peg femoral component. In the Figures, the first and second drilling holes  6 ,  8  are shown angled at 0° and 10° respectively, however the angles may be chosen as 5° and 15° or other suitable angles for the femoral components which may be used. 
         [0040]    The body  4  of the drilling guide  2  is provided with protrusions  10 ,  12  on both the left lateral and right lateral side of the body  4 . The distance from the end of one protrusion to the other is equal to the width of the femoral component and thus provides a means of aligning the drill guide  2  in the centre of the femoral condyle. 
         [0041]    The drill guide  2  may be supplied in different sizes which correspond to the size of the femoral component e.g. the width of the component and/or the radius of curvature of the component. Alternatively, the protrusions  10 ,  12  may be replaced with different sized protrusions to indicate the correct width of the component. 
         [0042]    The body  4  is provided with a fixed foot  14  and a movable foot  16 . The movable foot  16  is releasably attached to the body  4  by a screw  18  or other such means which passes through a slot  19  in the body  4  and into the movable foot  16 . The movable foot  16  is locked in position by tightening the screw  18  such that the section of the body  4  disposed between the head of the screw  18  and the movable foot  16  is held therebetween. The movable foot  16  is released by undoing the screw  18  sufficiently so that the body  4  is no longer held between the head of the screw  18  and the movable foot  16 . The movable foot  16  is then free to translate toward or away from the fixed foot  14 . 
         [0043]    The body  4  and movable foot  16  may be provided with an incremental locking means  20 . The incremental locking means  20  allows the movable foot  16  to be translated and locked in predefined positions. The incremental locking means  20  may be provided with a scale for determining the position of the movable foot  16 . 
         [0044]    The fixed foot  14  is narrow to allow reference off the posterior femoral condyle without interference from femoral osteophytes. 
         [0045]    The movable foot  16  has a leading edge which is curved in the plane of the movable foot  16 . This allows the movable foot  16  and therefore the drill guide  2  to be angled relative to the vertical cut on the tibial plateau. The underside of the movable foot  16  is also curved along its length. This curvature allows the drill guide  2  to be rotated about the tibial plateau in the anteroposterior plane. 
         [0046]    The drill guide  2  further comprises an alignment tool  22  for aligning the body  4 . The alignment tool  22  has a handle  23  and a bifurcated end, the bifurcated end having a first arm  25  and a second arm  26 . The first arm  25  is received within a mounting hole  28  provided on the top of the body  4  of the drill guide  2 . The drill guide  2  is provided with two mounting holes  28  for use of the drill guide  2  on a left or right knee. An intramedullary rod  24  is passed into the intramedullary canal of the patient, which provides a reference for the drill guide  2 . At least an end portion of the intramedullary rod  24  is cannulated and the second arm  26  is received within the intramedullary rod  24 . Alternatively, the second arm  26  may be cannulated so that the intramedullary rod  24  is received within the second arm  26 . 
         [0047]    The first and second arms  25 ,  26  are pivotably mounted on the handle  23  of the alignment tool  22  such that the distance between the first and second arms  25 ,  26  may be altered. 
         [0048]    The mounting holes  28  are angled relative to the body  4 , either to the left or right lateral side of the body  4  as shown in  FIG. 2 , to provide the correct alignment, preferably 7°, for the drill guide  2  relative to the intramedullary rod  24 . Also the mounting holes  28  may be angled in the vertical plane relative to the body  4 ; preferably they are angled down by 5°, as shown in  FIG. 2 . 
         [0049]    In use, following resection of the tibial plateau, the drill guide  2  is inserted into the operative wound of the patient, with the movable foot  16  aligned with the fixed foot  14 . The movable foot  16  is then translated vertically such that the fixed foot  14  contacts the posterior femoral condyle and the movable foot  16  contacts the tibial plateau. 
         [0050]    The position of the movable foot  16  is determined by the amount of bone resected from the tibial plateau. The scale on the incremental locking means  20  may correspond to a setting on a previously used resection guide. This allows the surgeon to easily adjust the movable foot  16  to the correct position for the amount of bone resected from the tibial plateau so that the drill holes are correctly aligned on the distal femoral condyle. 
         [0051]    The alignment tool  22  is connected to both the body  4  and the intramedullary rod  24  by inserting the first arm  25  into the correct mounting hole  28  and by inserting the second arm  26  into the cannulated end of the intramedullary rod  24 . 
         [0052]    The protrusions  10 ,  12  on the body  4  are then used to align the drill guide  2  in the centre of the femoral condyle. The pivotably mounted first and second arms  25 ,  26  allow the distance between the first and second arms  25 ,  26  to be altered. This allows the drill guide  2  to be moved laterally whilst maintaining the correct alignment with the intramedullary rod  24  in both the anteroposterior and transverse planes. 
         [0053]    As mentioned previously, the curvature of the underside of the movable foot  16  allows the drill guide to be rotated about the tibial plateau in the anteroposterior plane. This therefore enables the drill guide  2  to correctly align the drilling holes  6 ,  8  without the knee being in perfect 90° flexion. 
         [0054]    As shown in  FIG. 4 , once the drill guide  2  is correctly aligned a drill  30  is passed through one of the first and second drilling holes  6 ,  8  and drilled into the distal femoral condyle. The drill  30  is drilled into the distal femoral condyle until a stop  32  on the drill  30  abuts the body  4  and prevents the drill  30  from drilling any deeper. The length of the first and second drilling holes  6 ,  8  and the length of the drill  30  therefore controls the depth of the hole. 
         [0055]    Following drilling, the hole may be used to mount a cutting guide and/or milling spigot for resection of the femoral condyle to the desired shape for the femoral component. 
         [0056]    In an alternative embodiment of the invention, the fixed foot may contact the tibial plateau and the movable foot may contact the posterior femoral condyle. 
         [0057]    In another embodiment of the invention, the first and second drilling holes  6 ,  8  may be replaced by a single drilling hole which is pivotably mounted in the body  4 . By virtue of this pivotable mounting, the angle of the single drilling hole may be adjusted to correspond to the femoral component and locked in position by a locking mechanism. The locking mechanism and single drilling hole may be provided with an indexing mechanism which provides discrete angles for the single drilling hole. 
         [0058]    The present invention has been described in reference to a knee replacement; however the invention may be adapted to be used in other joints. 
         [0059]    The present invention provides a drill guide which does not require the use of feeler gauges and which has a direct connection to the intramedullary rod so as to simplify alignment of the drill guide.