Abstract:
An orthopedic instrument for installing a new reverse hip prosthesis, particularly the acetabular cup thereof, wherein the cup can be affixed to the pelvis with or without screws. The acetabular cup is releasably attached to the instrument and the instrument is used to position the cup in the pelvis. Optional screw guides are provided in the instrument in case the surgeon wishes to use screws to affix the cup to the pelvis.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention has to do with an orthopedic instrument and its use in hip replacement surgery for implanting an acetabular cup in the pelvis of a patient. More specifically, the invention relates to a new orthopedic instrument designed for implanting the reverse hip acetabular cup described in Published PCT Application No. WO 2011-112353-A1, dated Sep. 15, 2011, and entitled “Interlocking Reverse Hip and Revision Prosthesis” and its parent, Published U.S. Patent Application No. 2011-0218637-A1, dated Sep. 8, 2011, the disclosures of which are incorporated herein by reference. 
         [0003]    2. The Related Art 
         [0004]    The prior art discloses apparatus for implanting various portions of a prosthesis, such as an acetabular cup, into an anatomy. For example, U.S. Pat. No. 7,727,282 discloses an apparatus that rigidly engages a prosthesis member to allow for positioning it relative to the anatomy. 
       SUMMARY OF THE INVENTION 
       [0005]    The orthopedic instrument of the invention was developed to implant a revolutionary new reverse hip prosthesis in a patient. In particular, the instrument is used to position and securely affix the acetabular cup component of the prosthesis in the pelvis of a patient. 
         [0006]    Two methods of using the instrument are available to the surgeon. In one method, the acetabular cup is affixed to the pelvis without using screws and in the other method at least one screw is used. Drill guides can be incorporated in the instrument in case the surgeon wishes to use screws. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The mechanical elements of the invention are illustrated in the drawings summarized as follows: 
           [0008]      FIG. 1  is a semi-transparent elevational view of the orthopedic instrument. 
           [0009]      FIG. 2  is a top section view of the acetabular impactor taken along section line  2 - 2  of  FIG. 1 . 
           [0010]      FIG. 3  illustrates a section view of the acetabular impactor with the acetabular cup releasably engaged thereto. 
           [0011]      FIG. 4  is a perspective view of the acetabular cup. 
           [0012]      FIG. 5  illustrates in perspective a sleeve used to guide the drill bit when a screw hole is drilled in the pelvic bone. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    Referring to the drawings, the main components of the orthopedic instrument  22  are a handle  20  and an acetabular impactor  21 . The handle  20  is comprised of a shaft  9 , an impactor head  10  at the proximal end of the shaft  9  and a threaded portion at the distal end. The threaded portion of the handle is comprised of an axially disposed, internally threaded annular portion. The acetabular impactor  21  is comprised of threads  8  at the proximal end for removably affixing the acetabular impactor  21  to the handle  20  by screwing the acetabular impactor  21  and handle  20  together. The threads  8  are comprised of an axially disposed externally threaded portion. In a variation of the invention which is not illustrated in the drawings, the threads on the handle can be external and the threads on the acetabular impactor can be internal. 
         [0014]    Other elements of the acetabular impactor  21  include recess  1 , hemispherical head  2 , proximal conical extension  11 , retaining tongues  5 , release levers  6 , hemi-circular retaining ring  7  and recesses  17 . The retaining ring  7  acts as a spring to allow the retaining tongues  5  to move laterally to removably engage the acetabular cup  14 . Optional elements of the acetabular impactor include conical protective/supportive sheet  12  and channels  3  and  4  as drill guides and for screw insertion. 
         [0015]    The acetabular cup  14  has a stem  15  which is accommodated by recess  1  in acetabular impactor  21 . A circumferential groove  16  is located in the concave surface of the acetabular cup in proximity to the circumferential edge of the cup. As illustrated in  FIG. 3 , the retaining tongues  5  engage the circumferential groove  16  when the acetabular cup is releasably engaged with the orthopedic instrument  22 . In a variant of the invention, reference number  16  can designate diametrically opposed recesses for the retaining tongues  5 . Surface  18  of the acetabular cup is adapted for secure attachment to the acetabular socket of a pelvis. In a preferred embodiment the surface  18  is convex but other shapes suitable for secure attachment to a pelvic bone can be used as will be apparent to those skilled in the art. Referring to  FIG. 4 , the screw holes  25  are optionally threaded and preferably are threaded in a portion of the holes having a Morse taper, the taper having a larger diameter on the concave surface  19  of the acetabular cup  14  and a smaller diameter on the opposite side  18 , said opposite side preferably having a convex shape. 
         [0016]    An orthopedic system is provided according to the invention when the acetabular cup  14  is removably engaged with the orthopedic instrument  22  or when the acetabular cup  14  is removably engaged with the acetabular impactor  21 . 
         [0017]    There are two methods according to the invention. The first method is employed when the surgeon does not use screws to affix the acetabular cup  14  in the pelvis. The second method is employed when the surgeon uses at least one screw to affix the acetabular cup  14  to the pelvis. 
         [0018]    In the first method, the acetabular cup  14  is releasably engaged with the distal end of the orthopedic instrument  22  by snap fitting the cup over the retaining tongues  5  to engage the circumferential groove  16 . Then the acetabular cup  14  is positioned in the acetabular socket of the pelvis and the impactor head  10  is impacted, such as with a hammer, to affix the acetabular cup  14  in the acetabular socket. The orthopedic instrument  22  then is released from the acetabular cup by pressing release levers  6  inwardly. 
         [0019]    In the second method, the acetabular cup  14  is releasably engaged with the distal end of the orthopedic instrument  22  in the same manner as described above. Then the acetabular cup  14  is positioned in the acetabular socket of the pelvis and the impactor head  10  is impacted to set the acetabular cup  14  in place. Then the handle  20  is unscrewed from the acetabular impactor  21  and a sleeve  23  of  FIG. 5  is inserted into one or both of channels  3  or  4 . Sleeve  23  is also optionally provided with threads  24 , preferably on a Morse taper, to mate with the threads in screw holes  25 . When a sleeve  23  is threaded into a screw hole  25 , the sleeve will not spin during drilling and the engagement of the acetabular cup  14  with the acetabular impactor  21  is enhanced. The sleeve  23  is sized with suitable outer and inner diameters to prevent or minimize wobbling of the drill bit during drilling of the pelvic bone. The length of the sleeve  23  is sized to insure that the drill bit penetrates the bone to the appropriate depth without going too deep. After the hole is drilled, the sleeve  23  is removed, the screws are installed and the acetabular impactor  21  is released from the acetabular cup  14  as described above.