Patent Publication Number: US-2009240256-A1

Title: Method And Apparatus For Implanting an Augment

Description:
FIELD 
     This disclosure relates generally to a method and apparatus for use in orthopedic surgery and, more particular, to a method and apparatus for selectively securing an augment to a tool. 
     BACKGROUND 
     A natural hip joint may undergo degenerative changes due to a variety of etiologies. When such degenerative changes become so far advanced and irreversible, it may ultimately become necessary to replace a natural hip joint with a prosthetic hip. If the acetabulum needs repair, all remnants of articular cartilage may be removed from the acetabulum and an acetabular prosthesis that will accommodate the head or ball of the hip prosthesis may be affixed to the acetabulum. 
     In some instances, it may also be necessary to remove a defect located adjacent to the acetabulum. It such cases, it may also be necessary to fill the space created by the removed defect with an augment. Sometimes it may be difficult to accurately locate the augment relative to the acetabulum and/or acetabular prosthesis. 
     SUMMARY 
     A tool for implanting an augment into a cavity in bone can include a proximal portion and a distal portion. The proximal portion can include a handle. The distal portion can include an adjustment member and an augment interface portion. A shaft can be interconnected between the proximal and distal portions. An engagement portion can be configured at the augment interface portion and coupled to the adjustment member. Movement of the adjustment member can urge the engagement portion in a direction outboard relative to the shaft. 
     According to additional features, the first wedge portion can define a first longitudinal axis. The second wedge portion can define a second longitudinal axis. Movement of the adjustment member can urge the first and second wedge portions between an unsecured position wherein the first and second longitudinal axes are collinear and a second position wherein the first and second longitudinal axes are offset. 
     According to still other features, the adjustment member can comprise a knob having a knurled outer surface. The distal portion can include a cannulated body extending generally between the adjustment member and the augment interface portion. A rod can be slidably disposed through the cannulated body and selectively coupled to the adjustment member and the wedge assembly. A set screw can extend through the cannulated body and engage a flat defined on the rod. The set screw can substantially inhibit rotation of the rod about its longitudinal axis. 
     A method for repairing a joint socket can include preparing a cavity of the joint socket. A defect can be removed from the joint socket. An augment can be provided having at least a first and a second opening. The augment can be secured to the tool by securing an augment interface portion of the tool at the first opening defined on the augment. The augment can be located at the defect site. A fastener can be passed through the second opening while the tool remains secured to the augment at the first opening. 
     According to additional features, the method can further include moving first and second wedge portions toward each other causing complementary angled slide surfaces defined on the respective first and second wedge portions to cooperatively engage such that at least one of the first and second wedge portions moves outboard. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and various examples, while indicating various embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a side perspective view of a tool for implanting an augment into a bone cavity according to the present teachings; 
         FIG. 2  is an exploded view of a distal engagement portion of the tool of  FIG. 1 ; 
         FIG. 3  is a sectional view of the distal engagement portion of the tool shown in an unengaged position and taken along line  3 - 3  of  FIG. 1 ; 
         FIG. 4  is a sectional view of the distal engagement portion of the tool shown in an engaged position; 
         FIG. 5  is a perspective view of an acetabulum shown with the tool secured to an augment and prior to implantation; 
         FIG. 6  is a perspective view the acetabulum of  FIG. 5  shown with the tool locating the augment at a removed defect site; 
         FIG. 7  is a perspective view of the acetabulum of  FIG. 6  shown with the tool removed from the augment and the augment being secured to the cup and acetabulum according to one example; 
         FIG. 8  is a sectional view of a distal engagement portion of a tool according to additional features and shown in an unengaged position (phantom line) and an engaged position (solid line); and 
         FIG. 9  is a sectional view of a distal engagement portion of a tool according to additional features and shown in an engaged position. 
     
    
    
     DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS 
     The following description of various embodiment(s) is merely exemplary in nature and is in no way intended to limit the application or uses. 
     With initial reference to  FIG. 1 , a tool for implanting an augment at a defect area of a joint socket is shown and generally identified at reference numeral  10 . While the following description is directed toward implanting an augment at an acetabular hip socket, it is appreciated that the tool  10  may be used to selectively secure other augments or implants for implantation at other areas of the body. 
     The tool  10  generally includes a proximal engagement portion  12 , a distal engagement portion  14  and a shaft  16  interconnected between the proximal and distal engagement portions  12  and  14 , respectively. The proximal engagement portion  12  can define a handle  20 . In one example, the shaft  16  can be generally curved between the proximal and distal engagement portions,  12  and  14 , respectively. 
     With continued reference to  FIG. 1  and additional reference to  FIG. 2 , the distal engagement portion  14  can define an adjustment member or knob  22  and an augment interface portion  24 . The knob  22  can define a generally cylindrical body  26  having a knurled outer surface  30 . A threaded bore  32  can be defined at least partially through the knob  22  from a first end. The knob  22  can define a boss  36  that is rotatably received in cylindrical pocket  38  defined in a body  40 . The body  40  generally extends between the adjustment member  22  and the augment interface portion  24 . The body  40  can generally define a longitudinal axis L 1 . The augment interface portion  24  can define a wedge assembly  42  having a first and a second wedge portion  44  and  46 , respectively. The first wedge portion  44  can define a first angled surface  50 . In one example, the first wedge portion  44  is integrally formed as part of the body  40 . The second wedge portion  46  can define a second angled surface  52 . In one example, the respective first and second angled surfaces  50  and  52  complement each other such that when engaged to each other, a terminal surface  54  of the second wedge portion  46  is substantially perpendicular to the longitudinal axis L 1  of the body  40 . 
     The first wedge portion  44  defines a first longitudinal axis L 2  and the second wedge portion  46  defines a second longitudinal axis L 3 . In one example, the longitudinal axis L 1  of the body  40  and the first longitudinal axis L 2  of the first wedge portion  44  are collinear. With additional reference now to  FIGS. 3 and 4 , a central bore  60  can be defined through the body  40 . A longitudinal axis L 4  of the central bore  60  can coincide with the longitudinal axis L 1  of the body  40 . An offset bore  62  can be defined longitudinally through the second wedge portion  46 . The offset bore  62  can define a longitudinal axis L 5 . A diameter of the offset bore  62  can be greater than a diameter of the threaded rod  66 . 
     The distal engagement portion  14  can additionally include a threaded rod  66  slidably disposed through the central bore  60  of the body  40  and the offset bore  62  of the second wedge portion  46 . The threaded rod  66  defines a proximal end  68 , an intermediate portion  70  and a distal end  72 . Threads  74  can be defined at the proximal end  68 . The threads  74  can threadably engage the threaded bore  32  formed in the knob  22 . A longitudinal flat  76  can be formed along a side of the threaded rod  66  on the intermediate portion  70 . A head  78  can be defined on the distal end  72  of the threaded rod  66 . In one example, the longitudinal flat  76  can be formed at a location stepped from the threads  74  and the head  78 . 
     A set screw  80  can threadably extend through a passage  81  defined in the body  40 . In one example, the set screw  80  can entirely nest within the body  40  in an operating position ( FIGS. 3 and 4 ). A terminal end  82  of the set screw  80  can slidably engage the longitudinal flat  76  of the threaded rod  66 . In one example, the set screw  80  can permit axial translation of the threaded rod  66  through the central bore  60  of the body  40  while precluding rotation of the threaded rod  66  about its axis. As will become appreciated from the following discussion, the threaded rod  66  must remain substantially rotationally fixed during rotation of the knob  22 . An O-ring  88  can be disposed between a first annular pocket  83  formed around the boss  36  of the knob  22  and a second annular pocket  84  formed around the cylindrical pocket  38  of the body  40 . 
     With specific reference now to  FIGS. 3 and 4 , use of the tool  10  to securably engage an augment  90  will be described. The augment  90  can define an engagement site  92 . The engagement site  92  can define a first and second stepped bore  94  and  96 , respectively. An annular ridge  98  can be defined between the first and second stepped bores  94  and  96 , respectively. It is appreciated that the augment  90  can define other engagement sites (such as, but not limited to, a uniform bore, a notch, an oblong depression, or other depressions having various geometries). 
     At the outset, the augment interface portion  24  of the tool  10  is positioned at the engagement site  92 . In this particular example, the augment interface portion  24  can be advanced into radial alignment with the second stepped bore  96 . Next, the knob  22  may be rotated. Rotation of the knob  22  can cause the thread  74  on the threaded rod  66  to withdraw into the threaded bore  32  of the knob  22 . Again, the set screw  80  can slidably communicate along the longitudinal flat  76  to ensure the threaded rod  66  is rotationally fixed about its axis. 
     Withdrawal of the threaded rod  66  into the knob  22  (e.g., axial movement in a direction upward, as viewed in  FIGS. 3 and 4 ) can cause the head  78  to draw upwardly and against the terminal surface  54  of the second wedge portion  46 . As a result, the complementary angled surfaces  50  and  52  of the first and second wedge portions  44  and  46 , respectively, can slidably engage. More specifically, the location of the offset bore  62  allows the second wedge portion  46  to be forced outboard and into engagement with the second stepped bore  96  of the augment  90 . Because the offset bore  62  has a larger diameter than the threaded rod  66 , the second wedge portion  46  can translate in a direction transverse to the longitudinal axis L 1 . Concurrently, the first wedge portion  44  can also be forced into engagement with the second stepped bore  96 , but at a diametrically opposed and offset location relative to the second wedge portion  46 . In one configuration, the body  40  of the tool  10  can be forced against the first stepped bore  94 . Those skilled in the art will appreciate that the interaction with the first stepped bore  94  is not necessarily required. Now the augment  90  is secured to the wedge assembly  42  at the augment interface portion  24  of the tool  10 . In one example, the surgeon can continue to keep the knob  22  in its rotated position until the augment  90  can be placed in its final destination (i.e., at the defect site). While not shown, a locking feature may be provided to fix the knob  22  at a predetermined rotational position to maintain an outward retention force onto the augment interface portion  24 . 
     With continued reference to  FIGS. 5-7 , an exemplary method for using the tool  10  will be described in greater detail. When surgery, such as revision surgery is performed, the primary acetabular cup (not shown) may be removed. An acetabulum  100  may then be reamed, such as with a reamer (not shown). The acetabulum  100  may be generally hemispherically reamed until concentric removal of all acetabular cartilage and/or bone cement is achieved. Once the acetabulum  100  has been appropriately reamed, acetabular trial gauges (not shown), which are well known in the art, may be used to determine and confirm the diameter of the acetabular cup to be used. At this point, a surgeon may access the defect to be reamed and identify an appropriate tool for achieving the proper reaming area. One such tool is disclosed in co-pending application U.S. Ser. No. 11/453,312, filed Jun. 14, 2006, entitled “Method and Apparatus for Reaming an Acetabulum,” also assigned to Biomet, Inc. of Warsaw, Ind., which is incorporated herein by reference. Once the acetabulum  100  has been reamed for receipt of an acetabular cup and the defect has been reamed for receipt of an augment, the acetabulum  100  can define an acetabular socket  102  and a reamed defect site  104 . 
     An acetabular cup  108  ( FIG. 7 ) and augment  90  may be implanted. Exemplary acetabular cups and augments may be found in co-pending application U.S. Ser. No. 11/357,868, filed Feb. 17, 2006, entitled “Method and Apparatus for use of Porous Implants,” also assigned to Biomet, Inc. of Warsaw, Ind., which is incorporated herein by reference. In one example, the acetabular cup  108  may be implanted at the acetabular socket  102  and the augment  90  may be implanted at the reamed defect site  104 . According to following description, the augment  90  can be implanted into the reamed defect site  104  prior to implanting the acetabular cup  108  into the acetabular socket  102 . It is appreciated, however, that the augment  90  may alternatively be implanted subsequent to implantation of the acetabular cup  108 . 
     Once the augment  90  has been located at the desired location in the reamed defect site  104  ( FIG. 6 ), the knob  22  may be rotated in a direction that advances the threaded rod  66  away from the knob  22 . Upon translation of the threaded rod  66  away from the knob  22 , the engagement force of the respective first and second wedge portions  44  and  46  onto the second stepped augment bore  96  is relieved. Explained differently, the respective first and second wedge portions  44  and  46  can move inboard ( FIG. 3 ). The augment interface portion  24  can then be withdrawn from the augment  90 . 
     According to one method of implanting the acetabular cup  108 , an impacting instrument (not shown) may be used to properly position the acetabular cup  108 . In one example, the impacting instrument may be threadably secured to an apical hole (not shown) of the acetabular cup  108 . Once the orientation of the acetabular cup  108  is acceptable, the impacting instrument may be solidly impacted to fully seat the acetabular cup  108  such that firm rim fixation is achieved. Once the acetabular cup  108  has been solidly impacted, the impacting instrument may be carefully removed from the acetabular cup  108 . 
     A plurality of bone screw holes (not specifically shown) may be bored through screw holes  112  in the acetabular cup  108 . Once fixation holes have been formed in the acetabulum  100 , a depth gauge (not shown), as is also known in the art, may be used to determine the length of the bone screws. With the length of the bone screws determined, a bone screw or multiple screws (not shown) may be inserted into screw holes  112 . Other bone screws, such as fixation screws  118 , may be similarly used though openings or bores  120  in the augment  90  to secure the augment  90 . A coupling screw  122  can also be optionally used to secure the augment  90  to the acetabular cup  108 . It is appreciated that other methods may be used to secure the acetabular cup  108  and/or the augment  90 . In one example, an adhesive (such as bone cement) may be additionally or alternatively used. 
     In one advantage of using the tool  10 , the augment  90  can be securely retained by utilizing only one of the bores  120 . As a result, a user can positively position the augment  90  into a desired position at the defect site  104  with the tool  10  while concurrently passing a fixation screw  118  through any of the other available bores  120 . Similarly, the coupling screw  122  can additionally or alternatively be passed through one of the bores  120  while the augment  90  is securely retained (by way of another bore  120 ) by the tool  10 . Furthermore, the slim profile of the distal engagement portion  14  provides a surgeon ample working space and a favorable viewing angle for accessing the remaining bores  120  and manipulating the augment  90  as a whole relative to the defect site  104  during implantation. 
     Turning now to  FIG. 8 , a tool  200  according to additional features will be described. The tool  200  can include a distal engagement portion  214 . The tool  200  can also define a proximal engagement portion  12  and a shaft  16 , such as described in relation to the tool  10  above. The distal engagement portion  214  can define a body  240  that has an augment interface portion  224 . The augment interface portion  224  can define an expanding member  226 . The distal engagement portion  214  can additionally include a threaded rod  266  that is slidably disposed through a central bore  260  of the body  240 . The threaded rod  266  can be advanced along its axis L 5  by way of a threaded knob, such as described above in relation to the tool  10 . The threaded rod  266  can define a head  278  at a distal end  272 . The expanding member  226  can be bound on opposite ends by the body  240  and the head  278 , respectively. In one example, the expandable member  226  can be formed of an elastomeric material. Advancement of the threaded rod  266  in a direction upward as viewed in  FIG. 8  along axis L 5  can cause the expandable member  226  to expand from a first position (phantom line) outwardly to a second position (solid line) into engagement with the bore  96  of the augment  90  to securably retain the augment  90  to the tool  200 . Once the augment  90  has been located and optionally secured at the desired location with fixation screws  118  and/or coupling screw  122  (see  FIG. 7 ) in the reamed defect site  104  (see  FIG. 6 ), the threaded rod  266  can be advanced in a direction downward (as viewed in  FIG. 8 ) along the axis L 5 . As the threaded rod  266  is advanced downward, the expandable member  226  becomes decompressed and therefore can return to its relaxed state (phantom line). In the relaxed state, the expandable member  226  does not securably engage the bore  96  and the tool  200  can thereafter be removed from the augment  90 . 
     Turning now to  FIG. 9 , a tool  300  according to additional features is shown. The tool  300  can include a distal engagement portion  314 . The tool  300  can also define a proximal engagement portion  12  and a shaft  16 , such as described in relation to the tool  10  above. The distal engagement portion  314  can define a body  340  that has an augment interface portion  324 . In one example, the augment interface portion  324  can be integrally formed with the body  340 . The augment interface portion  324  can generally define a raised radius portion of the body  340 . According to one example, the raised radius portion can have an outer dimension that is substantially equivalent to the bore  96  of the augment  90 . In this way, the augment interface portion  324  can define an interference fit with the bore  96  of the augment  90 . As can be appreciated in the example shown in  FIG. 9 , the tool  300  does not necessarily require any moving parts. While a shaft  366  is shown through a central bore  360  of the body  340 , it can alternatively be integrally formed with the body  340  or be removed entirely. In one example, a surgeon can attach the augment  90  to the tool  300  by inserting the distal engagement portion  314  into the bore  96 , thereby creating an interference fit between the augment interface portion  324  and the bore  96 . Once the augment  90  has been located at the desired location in the reamed defect site  104  (see  FIG. 6 ), the augment  90  can be held in place by a secondary tool, or by fixation screw  118  (see  FIG. 6 ) and/or by a coupling screw  122  (see  FIG. 7 ). The distal engagement portion  314  can then be withdrawn from the bore  96 . 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.