Abstract:
An acetabular prosthesis for implantation in an acetabulum and surrounding pelvis is described. The acetabular prosthesis includes an acetabular cup having a substantially concave inner surface and a substantially convex outer surface, wherein an area defining a groove is located on the outer surface of the acetabular cup. An optional spacer member, having a raised ridge formed on a surface thereof, slidably engages the groove. The spacer provides augmentation and load bearing support in cases where bone tissue loss has occurred in and around the acetabulum. A fastener, such as a surgical screw, is used to secure the acetabular cup, and the optional spacer, to the acetabulum. At least one attachment member is integrally formed with the acetabular cup for fastening to a surface of the pelvis, such as the ilium and/or the ischium. Another optional spacer member is provided for the attachment member to provide augmentation around the attachment points on the pelvis. A fastener, such as a surgical screw, is used to secure the attachment member, and the other optional spacer, to the pelvis. The described acetabular prosthesis is especially useful in revision hip implant procedures where significant bone tissue loss has occurred either in or around the acetabulum and/or the pelvis.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to a method and apparatus for use in orthopedic surgery and, more particularly, to a method and apparatus for providing a modular acetabular prosthesis having various modular attachment components for use during an orthopedic surgical procedure. 
     BACKGROUND OF THE INVENTION 
     A natural hip joint may undergo degenerative changes due to a variety of etiologies. When these degenerative changes become so far advanced and irreversible, it may ultimately become necessary to replace a natural hip joint with a prosthetic hip. When implantation of such a hip joint prosthesis becomes necessary, the head of the natural femur is first resected and a cavity is created within the intramedullary canal of the host femur for accepting the hip prosthesis. The hip prosthesis may be inserted and supported within the host femur by cementing the hip prosthesis within the host femur. Alternatively, the hip prosthesis may be impacted into the host femur so that it is snugly fit and supported by the host femur. If the acetabulum also needs repair, all remnants of articular cartilage are generally removed from the acetabulum and an acetabular prosthesis which will accommodate the head or ball of the hip prosthesis is affixed to the acetabulum. The acetabular prosthesis is affixed to the acetabulum by means of cement, screws or other appropriate fixation means. 
     Due to any number of reasons, however, a small portion of patients that undergo such orthopedic surgical procedures may require subsequent revision surgery to replace the prosthetic device with a new prosthetic device generally referred to as a revision prosthesis. One example of such a device is generally known as a protrusio cage. 
     In this regard, a revision acetabular prosthesis will generally include additional mounting points, such as integral extension members or hooks that provide additional stability for the revision acetabular prosthesis. These additional mounting points are generally required due to additional bone loss or defects exhibited at the acetabulum, such as collar/rim defects or pelvic discontinuity defects. 
     Various types of revision acetabular prostheses are currently available and different surgeons prefer different types of revision acetabular prostheses. Some surgeons prefer to use what is known as an ilium flange that is formed integral with the acetabular prosthesis and enables further securement of the acetabular prosthesis in the ilium region of the pelvis. Other surgeons prefer to use what is known as an obturator hook that is able to provide inferior fixation of the acetabular prosthesis by engaging the obturator foramen which is a large aperture adjacent the acetabulum. Because of this, a hospital must maintain a large inventory of different revision acetabular cups to meet the various surgeons&#39; preferences. Moreover, the surgeon will generally have to have several revision acetabular cups available during surgery to account for any type of condition that may arise during the surgical procedure. This increased inventory of prosthetic devices increases the overall hospital costs and inventory control. Furthermore, by requiring the multiple revision acetabular cups to be available during the surgical procedure, multiple prosthetic devices must be sterilized prior to the surgical procedure, thereby increasing the surgical time, cost and complexity. 
     As previously noted, during hip revision procedures, surgeons often encounter significant defects due to osteolysis at the acetabular implant site or due to the removal of bone tissue that has become attached to the removed acetabular implant. These defects are usually filled with bulk bone allograft, bone cement, or morselized bone graft. Each material type raises it&#39;s own set of concerns. 
     With respect to bulk bone allograft, many doubts exist as to whether significant portions of a bulk allograft actually become viable over time. Dead allograft may not provide long term structural support. Additionally, higher infection rates are sometimes connected to the use of bulk allograft. Finally, bulk allograft is also expensive and sometimes unavailable or difficult to obtain. 
     With respect to bone cement, when defects are filled with bone cement, subsequent revision procedures may be made more difficult because there is even less bone tissue to work with. 
     With respect to morselized bone graft, this has become the material of choice; however, it may not provide significant structural support. Motion of the acetabular implant is of real concern. For example, motion can prevent bone tissue from infiltrating the porous surface of the acetabular implant and thus can place too much load on a thin walled acetabular implant and screws, potentially causing them to fail. Additionally, morselized bone graft is very expensive and is sometimes unavailable or difficult to obtain. 
     What is needed then is a method and apparatus for providing a modular acetabular prosthesis having various modular attachment components for use during an orthopedic surgical procedure. This will, in turn, provide more surgical flexibility during implantation of the acetabular prosthesis, provide the surgeon with a variety of surgical options at the time of the surgical procedure, provide a universal acetabular cup that can be configured for use in many circumstances, reduce hospital inventory and inventory tracking requirements, and reduce the overall surgical time, cost and complexity. 
     SUMMARY OF THE INVENTION 
     In accordance with a first embodiment of the present invention, an acetabular prosthesis for implantation in an acetabulum and surrounding pelvis is provided, the acetabular prosthesis comprising: (1) an acetabular cup having a substantially concave inner surface and a substantially convex outer surface, the outer surface operable to be received in the acetabulum; (2) an area defining a receptacle located in the outer surface of the acetabular cup; (3) a spacer member having an appendage formed on a surface thereof for mating engagement with the receptacle, wherein the spacer member is disposed between the outer surface of the acetabular cup and the acetabulum; and (4) an attachment member integral with the acetabular cup for fastening to a surface of the pelvis. 
     In accordance with a second embodiment of the present invention, an acetabular prosthesis for implantation in an acetabulum and surrounding pelvis is provided, the acetabular prosthesis comprising: (1) an acetabular cup having a substantially concave inner surface and a substantially convex outer surface, the outer surface operable to be received in the acetabulum; (2) an attachment member integral with the acetabular cup for fastening to a surface of the pelvis; and (3) a spacer member adjacent to the attachment member, wherein the spacer member is disposed between the attachment member and the surface of the pelvis. 
     In accordance with a third embodiment of the present invention, a method for implanting an acetabular prosthesis in an acetabulum and surrounding pelvis is provided, comprising: (1) providing an acetabular cup having a substantially concave inner surface and a substantially convex outer surface, the outer surface operable to be received in the acetabulum, the outer surface of the acetabulum cup having an area defining a receptacle located therein, the acetabular cup having an attachment member integral therewith for fastening to a surface of the pelvis; (2) providing a spacer member having an appendage formed on a surface thereof for mating engagement with the receptacle; (3) securing the spacer member to the outer surface of the acetabular cup; (4) engaging the outer surface of acetabular cup with the acetabulum such that the spacer member is disposed between the outer surface of the acetabular cup and the acetabulum; (5) securing the acetabular cup to the acetabulum; and (6) securing the attachment member to the surface of the pelvis. 
     In accordance with a fourth embodiment of the present invention, a method for implanting an acetabular prosthesis in an acetabulum and surrounding pelvis is provided, comprising: (1) providing an acetabular cup having a substantially concave inner surface and a substantially convex outer surface, the outer surface operable to be received in the acetabulum, the acetabular cup having an attachment member integral with the acetabular cup for fastening to a surface of the pelvis; (2) providing a spacer member adjacent to the attachment member; (3) securing the spacer member to the attachment member; (4) engaging the outer surface of acetabular cup with the acetabulum such that the spacer member is disposed between the attachment member and the surface of the pelvis; (5) securing the acetabular cup to the acetabulum; and (6) securing the spacer member and the attachment member to the surface of the pelvis. 
     A more complete appreciation of the present invention and its scope can be obtained from the following detailed description of the invention, the drawings and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a rear perspective view of an acetabular prosthesis, in accordance with one embodiment of the present invention; 
     FIG. 2 is another rear perspective view of an acetabular prosthesis, in accordance with one embodiment of the present invention; 
     FIG. 3 is a rear elevational view of an acetabular prosthesis, in accordance with one embodiment of the present invention; 
     FIG. 4 is a rear plan view of an acetabular prosthesis, in accordance with one embodiment of the present invention; 
     FIG. 5 is a front plan view of an acetabular prosthesis, in accordance with one embodiment of the present invention; 
     FIG. 6 is a side perspective view of several acetabular spacer members for an acetabular prosthesis, in accordance with one embodiment of the present invention; 
     FIG. 7 is a bottom plan view of several acetabular spacer members for an acetabular prosthesis, in accordance with one embodiment of the present invention; 
     FIG. 8 is a top perspective view of several acetabular spacer members for an acetabular prosthesis, in accordance with one embodiment of the present invention; 
     FIG. 9 is a bottom perspective view of several acetabular spacer members for an acetabular prosthesis, in accordance with one embodiment of the present invention; 
     FIG. 10 is a front perspective view of two attachment spacer members for an acetabular prosthesis, in accordance with one embodiment of the present invention; 
     FIG. 11 is a top plan view of two attachment spacer members for an acetabular prosthesis, in accordance with one embodiment of the present invention; and 
     FIG. 12 is a side perspective view of two attachment spacer members for an acetabular prosthesis, in accordance with one embodiment of the present invention. 
    
    
     The same reference numerals refer to the same parts throughout the various Figures. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description of the preferred embodiments concerning a method and apparatus for providing a modular acetabular prosthesis for use in orthopedic surgical procedures are merely exemplary in nature and are not intended to limit the invention or its application or uses. Moreover, while the present invention is described in detail below with reference to performing a revision type implantation procedure, it will be appreciated by those skilled in the art that the present invention is clearly not limited to only revision type orthopedic surgical procedures and may be used with various other orthopedic surgical procedures as well. 
     Referring to FIGS. 1-5, an acetabular prosthesis  10 , according to the general teachings of the present invention, is shown. The acetabular prosthesis  10  includes a modified hemispherical acetabular cup  12 . The acetabular cup  12  is said to be “hemispherical” in that it is not a perfect hemisphere; but rather, it includes an arcuate portion  14  extending along the periphery thereof without extending beyond the hemisphere of the acetabular cup  12 . 
     The acetabular cup  12  is preferably constructed from any suitable biocompatible material, such as titanium, stainless steel, titanium alloy, cobalt-chrome-molybdenum alloy, and the like. 
     It should be noted that the acetabular cup  12  would normally also be associated with other components, such as a congruent shell or bearing liner (not shown) retained within the acetabular cup  12 , via bone cement or a ring lock (not shown), which are not depicted for purposes of clarity. 
     The acetabular cup  12  preferably includes a substantially concave inner surface  16  and a substantially convex outer surface  18 , wherein the outer surface  18  is operable to be received in the acetabulum. The inner surface  16  is preferably smooth, whereas the outer surface  18  may be smooth or roughened with a porous surface layer (not shown) to facilitate bone tissue in-growth. 
     An area defining an optional receptacle or groove  20  is located in at least a portion of the outer surface  18  of the acetabular cup  12 . The groove  20  preferably includes tapered end portions  22 ,  24 . The groove  20  is preferably located in proximity to a peripheral surface of the acetabular cup  12 , and generally in the superior region of the acetabular cup  12 . The exact purpose of the groove  20  will be explained later in detail. 
     The acetabular cup  12  preferably includes at least one, and more preferably, a plurality of throughbores  26  located therein. It should be noted that the groove  20  is bisected by at least one of the throughbores  26 . The throughbores  26  provide a number of functions, such as enabling fastening members (not shown) to pass through the acetabular cup  12 . Additionally, the throughbores  26  provide for the infiltration of bone cement to improve adhesion, as well as providing for new bone tissue in-growth. At least one of the throughbores  28  includes a threaded surface  30  thereon for receiving an insertion instrument (not shown) for properly aligning the acetabular prosthesis  10  within the acetabulum. Throughbore  28  also includes a recessed area  28 A which permits the insertion instrument (not shown) to securely engage the acetabular cup  12  and permits controlled rotation of same. It will be noted that any graft material and/or bone cement should preferably be placed into the acetabulum before securing the acetabular cup  12  thereto. 
     A more specific description of the typical installation of an acetabular prosthesis can be found in U.S. Pat. Nos. 5,314,490; 5,326,367; 5,326,368; 5,702,477; 5,871,548; 5,931,870; and 6,162,257, the entire specifications of which are incorporated herein by reference. 
     The acetabular cup  12  preferably includes at least one, and more preferably, three substantially rigid attachment or extension members  32 ,  34 , and  36  integrally formed with the acetabular cup  12  for fastening the acetabular prosthesis  10  to at least a portion of one or more surfaces of the pelvis (not shown), such as the ilium and/or the ischium. Preferably, attachment member  32  is used for attachment to the ischium, whereas attachment members  34  and  36  are used for attachment to various surfaces of the ilium (e.g., anterior and posterior). 
     Attachment member  32  is shown as being substantially triangularly shaped; however, it is envisioned that the shape may be altered to other configurations. It will be noted that attachment member  32  has two distinct portions, i.e., a first substantially curved portion  32 A originating from, and contiguous with, the inner surface  16  of the acetabular cup  12 , and a second substantially planar portion  32 B extending out from, and angling away from, the first portion  32 A. The curvature profile may be modified to meet any anatomical requirements. 
     Attachment member  32  preferably includes at least one, and more preferably, a plurality of throughbores located therein. In this view, a throughbore  38  is provided in the curved portion  32 A and another throughbore  40  is provided in the planar portion  32 B. The throughbores  38 ,  40  provide a number of functions, such as enabling fastening members such as a surgical screw (not shown) to pass therethrough in order to allow the fastening member  32  to be secured to the ischium. 
     Attachment member  34  is shown as being substantially rectangularly shaped; however, it is envisioned that the shape may be altered to other configurations. It will be noted that attachment member  34  has two distinct portions, i.e., a first substantially curved portion  34 A originating from, and contiguous with, the inner surface  16  of the acetabular cup  12 , and a second substantially planar portion  34 B extending out from, and angling away from, the first portion  34 A. The curvature profile may be modified to meet any anatomical requirements. 
     Attachment member  34  preferably includes at least one, and more preferably, a plurality of throughbores  42  located therein. In this view, additional throughbores  42 A and  42 B are provided in the curved portion  34 A. The throughbores  42 ,  42 A, and  42 B provide a number of functions, such as enabling fastening members such as a surgical screw (not shown) to pass therethrough in order to allow the fastening member  34  to be secured to at least a portion of a surface of the ilium. 
     Attachment member  36  is also shown as being substantially rectangularly shaped; however, it is envisioned that the shape may be altered to other configurations. It will be noted that attachment member  36  also has two distinct portions, i.e., a first substantially curved portion  36 A originating from, and contiguous with, the inner surface  16  of the acetabular cup  12 , and a second substantially planar portion  36 B extending out from, and angling away from, the first portion  36 A. Again, the curvature profile may be modified to meet any anatomical requirements. 
     Attachment member  36  preferably includes at least one, and more preferably, a plurality of throughbores  44  located therein. In this view, an additional throughbore  44 A is provided in the curved portion  36 A. The throughbores  44  and  44 A provide a number of functions, such as enabling fastening members such as a surgical screw (not shown) to pass therethrough in order to allow the fastening member  36  to be secured to at least another portion of a surface of the ilium spaced away from attachment member  34 . 
     The installation of the acetabular prosthesis  10  would be accomplished in any number of ways, as are currently known in the art. The surgeon would surgically prepare the acetabulum and surrounding pelvic area to receive the acetabular prosthesis  10 . This preparation would typically include removing any debris (e.g., bone fragments, bone cement) from the acetabulum. The surgeon would then install an allograft, if necessary, and install bone cement, if necessary, into the acetabulum. The acetabular cup  12  would then be received into, and anatomically aligned with, the acetabulum. At least one fastening member, such as a surgical screw, would then be placed through one of the throughbores  26  and into the interior of acetabulum, thus securing the acetabular cup  12  to the acetabulum. The attachment members  32 ,  34 , and  36  would then be secured to the ischium and ilium, respectively, with fastening members, such as surgical screws. 
     However, if the acetabulum and/or the surrounding pelvic structures have any significant defects present, the loading will be borne primarily by the allograft and/or bone cement material, as previously described. Therefore, it is desirable to have the surfaces of the acetabular prosthesis  10  actually abut against the respective surfaces of the acetabulum and/or the surrounding pelvic structures, as opposed to using allografts and bone cement to fill the gap therebetween. Because the acetabular prosthesis  10  is constructed of metallic material, it is much stronger than allografts and bone cement, and therefore is much more able to withstand the loads and forces associated with standing, walking, and running activities. 
     Therefore, the present invention preferably employs at least one augment or spacer member to compensate for the fact that the acetabulum and/or the surrounding pelvic structures may have defects therein which prevent the outer surface  18  of the acetabular cup  12  from contacting the surface of the acetabulum, and/or the outer surfaces  32 C,  34 C, and  36 C, respectively, from contacting the respective surfaces of the pelvis, i.e., the ischium and the ilium. 
     The spacer members are preferably constructed from any suitable biocompatible material, such as titanium, stainless steel, titanium alloy, cobalt-chrome-molybdenum alloy, etc. and is preferably made of the titanium alloy Ti-6AI-4V. 
     Referring to FIGS. 6-9, several different types of acetabular spacer members  60 ,  62 , and  64  for use with the outer surface  18  of the acetabular cup  12 , according to the general teachings of the present invention, are shown. It should be noted that only one spacer member would generally be used at a time in practice; however, multiple spacer members may be used in some instances. For example, if there is a relatively small defect in the superior region of the acetabulum, acetabular spacer member  60  can be employed. If there is a larger defect, either acetabular spacer member  62  or  64  may be used. It is envisioned that either smaller and/or larger acetabular spacer members may also be employed with the present invention. 
     The acetabular spacer members  60 ,  62 , and  64  are preferably substantially curved so that the lower surfaces  60 A,  60 B, and  60 C, substantially conform to the curvature of the outer surface  18  of the acetabular cup  12 . Additionally, the acetabular spacer members  60 ,  62 , and  64  preferably include an area defining a substantially curved and raised appendage or ridge  66 ,  68 , and  70  formed on the lower surface  60 A,  60 B, and  60 C, respectively, thereof for mating, and more preferably, sliding engagement with the groove  20 . Finally, each acetabular spacer member  60 ,  62 , and  64  preferably has at least one throughbore  72 . The throughbores  72  preferably include a threaded surface  74  thereon. It should be noted that the raised ridges  66 ,  68 , and  70  are bisected by the respective throughbore  72 . 
     The purpose of the raised ridges  66 ,  68 , and  70 , respectively, is to allow the respective acetabular spacer member  60 ,  62 , or  64  to slidingly mate with the groove  20  on the outer surface  18  of the acetabular cup  12 . This allows the surgeon the option of positioning the respective acetabular spacer member  60 ,  62 , or  64  practically anywhere along the length of the groove  20  to best deal with the particular acetabular defect in the superior-posterior region. For example, the acetabular spacer member  60 ,  62 , or  64  can slide in a superior-posterior direction with respect to the acetabulum. It is also envisioned that the acetabular spacer member  60 ,  62 , or  64  can slide in a medial direction, as well. Once the final position of the acetabular spacer member is determined, the surgeon can then secure the respective acetabular spacer member to the acetabular cup  12  by inserting a fastening member, such as a surgical screw, through one or more available throughbores  72  which preferably aligns with one or more of the throughbores  26  which bisect the groove  20 . The screw would preferably extend upwardly through the acetabular cup  12  and into the respective acetabular spacer member, with the screw tip not extending past the upper surface of the respective acetabular spacer member. The modified acetabular prosthesis  10  can then be installed in the acetabulum, as previously described, such that the acetabular spacer member  60 ,  62 , or  64  is disposed between the outer surface  18  of the acetabular cup  12  and the acetabulum. 
     Unfortunately, the use of acetabular spacer members  60 ,  62 , or  64  alone is sometimes not enough to address each and every particular clinical situation. The use of the acetabular spacer members  60 ,  62 , or  64  may address the defect in the acetabulum, but it may not address a defect in the surrounding pelvic structures, or alternatively, the use of the acetabular spacer members  60 ,  62 , or  64  may alter the attachment point of the attachment members  32 ,  34  or  36  such that an undesirable gap is created between the respective outer surfaces  32 C,  34 C, and  36 C and the pelvis. 
     Therefore, the present invention employs at least one other augment or spacer member to compensate for the fact that the surrounding pelvic structures may have defects therein which prevent the outer surfaces  32 C,  34 C, and  36 C of rigid attachment members  32 ,  34 , and  36 , respectively, from contacting the respective surfaces of the pelvis, i.e., the ischium and the ilium. 
     Referring to FIGS. 10-12, two different types of attachment spacer members  100  and  102  for use with the attachment members  32 ,  34 , and  36 , respectively, according to the general teachings of the present invention, are shown. It should be noted that more than one attachment spacer member can be used at one time in practice. For example, if there is a relatively small defect in the surface of the ischium, or attachment member  32  can not abut it, an attachment spacer member  100  or  102  can be employed. If there is a defect in the surface of the ilium (either anterior and/or posterior), or attachment member  34  or  36  can not abut it, an attachment spacer member  100  or  102  can be employed. It is envisioned that either smaller and/or larger attachment spacer members may also be employed with the present invention. 
     The attachment spacer members  100  and  102  preferably have at least one flat surface  100 A and  102 A, respectively, for mating adjacently against the planar portions  32 B,  34 B, and  36 B of attachment members  32 ,  34 , and  36 , respectively. The other surface of the attachment spacer members  100  and  102  may be either flat and parallel  100 B or flat and non-parallel (i.e., inclined)  102 B. 
     Each attachment spacer member  100  and  102  preferably has at least one throughbore  104 . At least one of the throughbores  104  preferably include a threaded surface  106  thereon. The surgeon can then secure the respective attachment spacer member  100  or  102  to the outer surface  32 C,  34 C, or  36 C, respectively, by inserting a fastening member, such as a surgical screw, through one or more available throughbores  104  which preferably aligns with one or more of the throughbores  40 ,  42 ,  44 , respectively, in planar portions  32 B,  34 B, or  36 B, respectively. The further modified acetabular prosthesis  10  then can be installed in the acetabulum, as previously described, such that the attachment spacer members  100  and/or  102  are disposed between the outer surface  32 C,  34 C, or  36 C, respectively, of the planar portions  32 B,  34 B, or  36 B, respectively, of the attachment members  32 ,  34 , or  36 , respectively, and the pelvis, i.e., the ischium and/or the ilium. Preferably, two diagonally opposed and spaced throughbores  104  are used to attach the attachment spacer member  100  and  102  to the outer surface  32 C,  34 C, or  36 C, respectively, of the planar portions  32 B,  34 B, or  36 B, respectively, of the attachment members  32 ,  34 , or  36 , respectively, and the pelvis, i.e., the ischium and/or the ilium. Bone screws (not shown) can then be inserted through the two diagonally opposed throughbores  104 , and the aligned one or more of the throughbores  40 ,  42 ,  44 , respectively, to secure the attachment members  32 ,  34 , or  36 , respectively, to the pelvis. 
     It should be noted that sometimes it is only necessary to use the attachment spacer members  100  and/or  102  alone, instead of using them in conjunction with an acetabular spacer member  60 ,  62 , or  64 . In that scenario, it is beneficial that the groove  20  is employed in the outer surface  18  of the acetabular cup  12 , as opposed to a raised appendage or ridge which may interfere with the proper alignment of the acetabular cup  12 , or might irritate the acetabulum. 
     The foregoing description is considered illustrative only of the principles of the invention. Furthermore, because numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and process shown as described above. Accordingly, all suitable modifications and equivalents that may be resorted to that fall within the scope of the invention as defined by the claims that follow.