Patent Publication Number: US-2012029523-A1

Title: Guide pin positioner

Description:
FIELD OF THE INVENTION 
     This invention relates to surgical instruments used in arthroscopic surgical procedures to guide instruments into the proper position of a surgical worksite. More particularly, the invention relates to guides for positioning drills or guide pins through portals in arthroscopic ligament reconstruction surgical procedures. 
     BACKGROUND OF THE INVENTION 
     Surgical procedures for arthroscopic repair of torn tendons, ligaments or other soft tissue are well known. One such common repair involves the replacement of one of the cruciate ligaments of the knee. There are some such procedures where a surgeon must select the proper location at which to drill bone tunnels adapted to receive graft ligaments such as bone-tendon-bone or soft tissue ligament constructs. 
     The subject invention is useful in positioning such bone tunnels on the femur at locations which approximate the anatomic location of the ACL or PCL. Other guides are known which position such bone tunnels. The issue that they present is an inability to obtain a visual observation of the site where the pin will be drilled as the hub of the guide obstructs this view when placed at the femoral attachment point of the ruptured ligament against the medial aspect of the lateral femoral condyle. 
       FIG. 1  shows an existing guide made by Arthrex Inc. of Naples, Fla. that features a hollow shaft  10  having a through passage  12  for positioning the hub  14  located at the distal end. The surgeon places the head against the superior inner wall of the medial femoral condyle by manipulating the proximal end  16 . Passage  12  continues through hub  14  to the bone contact surface  18 . The surface  18  is in a plane that intersects the axis of the passage  12  at an oblique angle with the intent that the angled orientation will put surface  18  flush with the bone when advanced from the incision and properly rotated on its axis for flush engagement. A spike  20  is located off center from the passage  12  as shown in  FIG. 2 . The spike  20  holds the shaft steady as a pin  22  is drilled into the bone  24  as shown in  FIG. 4 . The problem with the design is that the hub  14  is a solid mass and prevents the surgeon from seeing the precise location where the pin  22  will engage the proximal cortical surface of the knee and to readily see where the edges of the tunnel that will be drilled as a drill or reamer is advanced over the guide pin and into the bone. The use of this tool as a guide in double bundle PCL reconstruction makes the angle of surface  18  with respect to a plane perpendicular to the axis of passage  12  smaller or less oblique whereas a more oblique angle for a single tunnel ACL procedure allows a better approximation of the femoral ACL footprint so that an elliptical shape is created at the tunnel where the ratio of the long to the short dimension is about 1.5 to 2. 
     Also generally related to the present invention are U.S. Pat. Nos. 5,211,647; 5,425,733; 5,350,383; 6,629,977; 6,716,234 and 6,875,216. 
     The present invention addresses the issue of visual access to the site where the guide pin will enter the bone and the location and angle of the reamer as it makes the tunnel. This is accomplished with an open structure of a base ring supported with spaced struts that can be disposed in a perpendicular plane to the axis of the passage through the tool body or askew. The base ring can be circular or elliptical and when elliptical can be skewed with the axis of the tool body so as to give visual indication of the bone structure at the entrance of the tunnel to be made by the reamer. Alternatively the base ring and support structure of struts with gaps or a solid taper can also provide visual access by being clear plastic, for example. Those and other features of the present invention will be more readily apparent to those skilled in the art from a review of the detailed description and the associated drawings while recognizing that the full scope of the invention is to be found in the appended claims. 
     SUMMARY OF THE INVENTION 
     A guide for a pin for proper placement for guiding a reamer to make a bone tunnel for femoral ACL/PCL reconstruction features a base ring with spaced struts to allow visual access to the native ligament stump. Alternatively the base ring can be supported by a see-through structure. The ring can be circular where it contacts the bone or elliptical depending on the relation of the plane in which the distal surface of the ring is disposed and the axis of the cannulated tool body. The dimensional differences between the inner and outer surface of the base ring allows visualization of two different dimensions for a proposed tunnel location and allows for providing predictable tunnel aperture geometry. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a prior art guide showing the solid distal hub that blocks visualization of the native ligament stump; 
         FIG. 2  is an end view of  FIG. 1 ; 
         FIG. 3  is a perspective view of the instrument of  FIG. 1  adjacent the bone; 
         FIG. 4  is an extreme close up view of the instrument of  FIG. 3  adjacent the bone; 
         FIG. 5  is a side view of the preferred embodiment of the present invention that enables visualization of the native ligament stump for setting of a guide pin thereon; 
         FIG. 6  is an end view of  FIG. 5 ; 
         FIG. 7  is a perspective view of the instrument of the present invention juxtaposed next to a bone and showing also a close up view; 
         FIG. 8  is an alternative view of the instrument of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 5  shows the instrument  26  that has a handle  28  at its proximal end with an elongated hollow shaft  30  that extends from the proximal end  32  to a distal end  34 . Axial passage  36  extends from the distal end  34  back through the handle  28  and is designed to slidably receive pin  52 . A plurality of struts  38  form fenestrations  39  and hold a base ring  40  away from the distal end  34 . Struts  38  and fenestrations  39  form a see-through structure  41  which is annular and tapered to connect the smaller diameter of shaft end  34  to the layer size of ring  40 . Ring  40  has an inner surface  42  and an outer surface  44  and a slanted contact surface  46  that engages the bone  48 . Surface  46  is disposed in a plane oriented at a predetermined angle to the axis of the shaft  30 . In the preferred embodiment the angle is about 30 to 45 degrees. When viewed in the direction of arrow  50  the shape defined by the inner surface  42  is elliptical with preferably the ratio of the long dimension to the short dimension being greater than about 1.1 or more depending on the angle of surface  46  as discussed above. 
     Significantly, with the base ring  40  being supported in an open structure of spaced apart struts  38  that can be plastic or metal there is not only an ability to see where the pin  52  will actually locate but the ring  40  using inside surface  42  or outside surface  44  allows a view of the perimeter of the tunnel that will be formed with a reamer (not shown) that will be guided over the pin  52 . Alternatively to the struts  38  and fenestrations  39 , the supporting structure can be a solid frustoconical shape that is clear such as plastic so that the surgeon can have visual access of the center of the tunnel as determined by the pin  52  anchor location as well as the tunnel orientation when made by the reamer. 
     Looking at the bottom view or end view of  FIG. 6  it is possible to see passage  36  of the shaft  30 . The support structure  38  that can be spaced struts or a continuous transparent structure, allows the base ring  40  to stand off from the shaft  30  so that the ring  40  can be placed squarely over the native ligament stump  58 . The angled orientation of the surface  46  allows it to sit squarely or flush against the bone structure. Additionally, surface  46  can be roughened to hold it steady against the bone structure as the pin is advanced. 
     In some procedures there is no need to skew the plane of surface  46  with respect to a plane perpendicular to the axis of the passage  36  and in those cases the ring  40  is circular rather than elliptical. In either case the surface  46  is spaced apart from the distal end  34  of the passage  36  so that the intervening structure allows a line of sight to the ring  40  and the ligament stump  58  so that the pin  52  will be drilled at the appropriate starting location on an axis that is suitable for the reamer to create the tunnel for the ligament graft. 
     The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.