Abstract:
Surgical tools which are used to separate from one another a femoral cup and an acetabular ball in an implanted hip replacement prosthesis. At its distal end, elements of the surgical tool engage the femoral cup and the acetabular cup. When proximal handles of the tool are squeezed toward one another, the engagement elements move away from one another. Thus, a surgeon is able to separate the femoral cup and the acetabular ball from one another without pulling the acetabular cup away from the acetabulum or the femoral cup and/or femoral implant away from the femur, thereby accomplishing the separation without disrupting any bone ingrowth.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0001]    The present invention relates to surgical instruments used in connection with a hip prosthesis. More specifically, the invention has to do with surgical tools which are used to separate a femoral cup from an acetabular ball in an implanted hip replacement prosthesis. 
       The Related Art 
       [0002]    A reverse hip prosthesis is described in U.S. Pat. Nos. 8,313,531 B2 and 8,540,779 B2. The prosthesis and a revision surgery method also are described in U.S. Pat. No. 8,992,627 B2. The disclosures of these three patents are incorporated herein in their entireties by reference. 
       SUMMARY OF THE INVENTION 
       [0003]    As described in the patents referenced above, a femoral cup articulates on an acetabular ball when the prosthesis is implanted in a patient. The acetabular ball is affixed by means of a Morse taper to a stem which is affixed to and extends from the bottom of the concave surface of an acetabular cup. The surgical tools of the invention enable a surgeon to separate the femoral cup from the acetabular ball without pulling on the acetabular cup or the femoral implant and without disrupting any bone ingrowth. The surgical tool of the invention may be included as a component of a kit containing other surgical instruments and/or implant elements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a top elevation view of a first embodiment of a surgical tool of the invention. 
           [0005]      FIG. 1A  is a top elevation view of the femoral engagement component  5  of the first embodiment. 
           [0006]      FIG. 1B  is an end elevation view of  FIG. 1A . 
           [0007]      FIG. 2  is a side elevation view of the first embodiment of the surgical tool of the invention. 
           [0008]      FIG. 2A  is a bottom elevation view of an alternate embodiment of the second handle  3  of the first embodiment. 
           [0009]      FIG. 2B  is the same view as  FIG. 2A  following movement of the acetabular engagement component  6   a.    
           [0010]      FIG. 3  is a side elevation view of the tool of  FIG. 2  positioned on a prosthesis just prior to separation of the femoral cup from the acetabular ball. 
           [0011]      FIG. 4  is a section view of  FIG. 3  with a partial section of a femur as an added element. 
           [0012]      FIG. 5  is a side elevation view of a second embodiment of the tool of the invention wherein the handles have been squeezed toward one another. 
           [0013]      FIG. 5A  is a perspective view of portion A of  FIG. 5 . 
           [0014]      FIG. 6  is a perspective view of the second embodiment wherein the handles have not been squeezed toward one another. 
           [0015]      FIG. 7  is a top elevation view of  FIG. 6 . 
           [0016]      FIG. 8  is a side elevation view of the second embodiment engaged with a femoral implant/cup and an acetabular cup before the femoral cup and acetabular cup are separated from one another. 
           [0017]      FIG. 8A  is a section view of  FIG. 8 . 
           [0018]      FIG. 9  is a side elevation view of the second embodiment engaged with a femoral implant/cup and an acetabular cup after the femoral cup and acetabular cup have been separated from one another. 
           [0019]      FIG. 9A  is a section view of  FIG. 9 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Referring to the first embodiment, the surgical tool  1  of the invention, also referred to herein as a surgical instrument, is illustrated in a top elevation view in  FIG. 1  and a side elevation view in  FIG. 2 . The tool has a first handle  2  and a second handle  3 . Springs  4  tend to bias the handles apart from one another as illustrated in  FIG. 2 . The distal end of the first handle  2  has a femoral engagement component  5  attached thereto and the distal end of the second handle  3  has an acetabular engagement component  6  attached thereto. Fulcrum pin  7  hinges the first handle  2  to the second handle  3  so that when the handles are squeezed toward one another the femoral engagement component  5  and the acetabular engagement component  6  are moved away from one another. The pin  7  thus provides a fulcrum between the first and second handles. 
         [0021]    The femoral engagement component  5  illustrated in  FIG. 1A  is viewed from the direction of arrow A in  FIG. 2 . Femoral engagement component  5  may be rotatably connected to first handle  2  by means of axis pin  5   a.  Axis pin  5   a  allows a femoral engagement component  5  to rotate axially about the central axis of the first handle  2 . In  FIG. 1B , an end view of femoral engagement component  5  is illustrated as taken from the direction of arrow B in  FIG. 1A . Arrow C in  FIG. 1B  illustrates the directions in which femoral engagement component  5  can be rotated. 
         [0022]      FIGS. 2A and 2B  illustrate a bottom elevation view of an alternate embodiment of the second handle which is designated as  3   a.  A hinge  3   b  is provided on handle  3   a  to allow lateral pivoting of a portion of the handle located between pin  7  (see  FIG. 2 ) and acetabular engagement component  6   a.  Hinge  3   b  allows lateral movement in the directions of arrow D of  FIG. 2A .  FIG. 2B  provides an example of a hinged handle  3   a  having an acetabular engagement component  6   a  at the distal end thereof. 
         [0023]    In  FIGS. 3 and 4  the surgical tool  1  is positioned on a prosthesis just prior to separation of the femoral cup  20  from the acetabular ball  21 . The acetabular engagement component  6  is engaged with the circumferential edge  22  of acetabular cup  23  and the femoral engagement component  5  is engaged with the neck  24  of femoral cup  20 , or the outer hemispherical surface of femoral cup  20 , or both the neck  24  and the outer hemispherical surface of femoral cup  20 . And the femoral engagement component  5  may also engage the top (i.e., the proximal end) of femoral implant  25  which is implanted in femur  26 , shown in partial section. A liner  27  is illustrated in femoral cup  20 . The acetabular ball  21  is affixed to stem  28  of the acetabular cup. 
         [0024]    When handles  2  and  3  or  2  and  3   a  are squeezed toward one another, the femoral cup is separated from the acetabular ball. 
         [0025]    The second embodiment of the surgical tool of the invention is very similar to the first embodiment except for the acetabular engagement element. This embodiment is illustrated in  FIGS. 5-9A  and it is designated as tool  31 . A pivotable partial ring, referred to herein as acetabular engagement ring  36 , is employed to engage the acetabular cup in the second embodiment as distinguished from acetabular engagement component  6  in the first embodiment. The term “acetabular engagement element” may be used herein to refer to both the acetabular engagement component  6  and the acetabular engagement ring  36 . 
         [0026]      FIG. 5  is a side elevation view of tool  31 . The tool has a first handle  32  and a second handle  33 . Springs  34 , affixed to the handles with screws  41 , tend to bias the handles apart from one another. And in  FIG. 5 , the handles have been squeezed toward one another to an intermediate position between fully open as shown in  FIG. 6  and fully closed as shown in  FIG. 9 . The distal end of first handle  32  has a femoral engagement component  35  attached thereto. The distal end of second handle  33  has an acetabular engagement ring  36  pivotably attached thereto by means of ring pins  40 . (See also  FIG. 5A .) As can be seen from the drawings, ring  36  is pivotable about an axis which is perpendicular to the central axis of the distal portion of handle  33 . Fulcrum pin  37  hinges the first handle  32  to the second handle  33  so that when the handles are squeezed toward one another the femoral engagement component  35  and the acetabular engagement ring  36  are moved away from one another. The pin  37  thus provides a fulcrum between the first and second handles. 
         [0027]    As in the first embodiment, the femoral engagement component  35  of the second embodiment may be rotatably connected to first handle  32  by means of axis pin  35   a.  Axis pin  35   a  allows the femoral engagement component  35  to rotate axially about the central axis of the first handle  32  in the same manner as femoral engagement component  5  is allowed to rotate axially about the central axis of first handle  2  in the first embodiment. The alternate embodiment of second handle  3   a  which has a hinge  3   b  as described above (See  FIG. 2B ) can also be used with the second embodiment of the tool of the invention. 
         [0028]    Referring to  FIGS. 5A, 7, 8A and 9A , acetabular engagement ring  36  has a beveled edge  36   b  which engages beveled edge  22   a  of acetabular cup  23 . Ring  36  also has a tab  36   a  which is seated in indent  33   a  to prevent downward rotation of ring  36  below the horizontal central plane of the distal end of handle  33 . Thus, as can be seen in  FIGS. 6 and 7  wherein the handles are in the fully open position, tab  36   a  is seated in indent  33   a  and ring  36  is prevented from downward rotation in that position. 
         [0029]    In  FIGS. 8 and 8A  the surgical tool  31  is positioned on a prosthesis just prior to separation of the femoral cup  20  from the acetabular ball  21 . The beveled edge  36   b  of acetabular engagement ring  36  is engaged with the circumferential beveled edge  22   a  of acetabular cup  23  and the femoral engagement component  35  is engaged with the neck  24  of femoral cup  20  or the outer hemispherical surface of femoral cup  20 , or both the neck  24  and the outer hemispherical surface of femoral cup  20 . A femoral implant  25  is also illustrated and the femoral engagement component  35  may also engage the top (i.e., the proximal end) of implant  25 . A liner  27  is illustrated in femoral cup  20 . The acetabular ball  21  is affixed to stem  28  of the acetabular cup. 
         [0030]    When handles  32  and  33  are squeezed toward one another the femoral cup is separated from the acetabular ball as shown in  FIGS. 9 and 9   a.    
         [0031]    In the surgical method of the invention, femoral engagement component  5  or  35  is engaged with the neck of the femoral cup, or an outer hemispherical surface of the femoral cup or both the neck and the outer hemispherical surface of the femoral cup and/or the upper surface (i.e. the proximal end) of a femoral implant. Simultaneously, the acetabular engagement component  6  is engaged with the circumferential edge  22  of the acetabular cup  23 , or the circumferential beveled edge  36   b  of femoral engagement ring  36  is engaged with the circumferential beveled edge  22   a  of acetabular cup  23 , and then the first and second handles are squeezed toward one another thereby causing the femoral cup and the acetabular ball to be separated from one another.