Abstract:
A medical procedure includes providing a prosthesis which includes (i) a body portion having a rear surface and a bearing surface, and (ii) an anchor peg including a shaft extending from the rear surface of the body portion, wherein the anchor peg includes a plurality of outwardly extending fins secured to the shaft, and further wherein the plurality of outwardly extending fins each possesses a first diameter. The medical procedure further includes creating an anchor hole in a natural bone, the anchor hole possessing a second diameter which is less than the first diameter. In addition, the method procedure includes positioning the anchor peg within the anchor hole so that each of the plurality of outwardly extending fins deforms so as to possess (i) a concave side which faces an open end of the anchor hole, and (ii) a convex side that faces a closed end of the anchor hole.

Description:
[0001]     This application is a continuation of co-pending application Ser. No. 09/802,150, filed on Mar. 8, 2001, which in turn claims priority to U.S. Provisional Application Ser. No. 60/190,391, entitled “Apparatus and Method for Securing a Cementless Glenoid Component to a Glenoid Surface of a Scapula”, filed on Mar. 17, 2000. The disclosure of each of the above-identified provisional and utility patent applications are hereby totally incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to a glenoid component, and more particularly to an apparatus and method for securing a cementless glenoid component to a glenoid surface of a scapula.  
       BACKGROUND OF THE INVENTION  
       [0003]     During the lifetime of a patient, it may be necessary to perform a total shoulder replacement procedure on the patient as a result of, for example, disease or trauma. In a total shoulder replacement procedure, a humeral component having a head portion is utilized to replace the natural head portion of the arm bone or humerus. The humeral component typically has an elongated intramedullary stem which is utilized to secure the humeral component to the patient&#39;s humerus. In such a total shoulder replacement procedure, the natural glenoid surface of the scapula is resurfaced or otherwise replaced with a glenoid component which provides a bearing surface for the head portion of the humeral component.  
         [0004]     Glenoid components have heretofore been designed which include a number of plastic inserts coupled to metal backings. The metal backings are provided to secure the plastic inserts to the glenoid surface of the scapula. However, use of such two-piece glenoid components has a number of drawbacks associated therewith. For example, it is possible over the useful life of the glenoid component for the plastic inserts to separate from the metal backing thereby necessitating replacement of the glenoid component. In addition, over time wear of the plastic insert inherently occurs at the interface between plastic insert and the metal backing. It is possible for the plastic insert to wear to a degree which necessitates replacement of the glenoid component. It should be appreciated that in either case, such replacement of the glenoid component requires the patient to again be subjected to a surgical procedure and the subsequent recovery period associated therewith.  
         [0005]     In response to the shortcomings associated with two-piece glenoid component designs, a number of one-piece glenoid components have heretofore been designed. In regard to such one-piece designs, a body portion, having a bearing surface defined therein for receiving the head of the humeral component, has a number of attachment pegs integrally formed therewith. The attachment pegs are advanced and thereafter secured into a corresponding number of holes which are drilled in the glenoid surface of the scapula by use of bone cement. An example of such a one-piece glenoid component that is designed to be secured to the scapula by use of bone cement is disclosed in U.S. Pat. No. 5,032,132 issued to Matsen, III et al.  
         [0006]     As with the two-piece designs, certain one-piece glenoid components which have heretofore been designed have a number of drawbacks associated therewith. For example, recent studies have speculated that it may be desirable to secure artificial components to natural bone structures without the use of bone cement. Glenoid components which have been designed to be secured to the scapula by the use of bone cement generally cannot be secured to the scapula without use of the same.  
         [0007]     What is needed therefore is a glenoid component which overcomes one or more of the above-mentioned drawbacks. What is particularly needed is a glenoid component which may be secured to the glenoid surface of the scapula without the use of bone cement.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with one embodiment of the present invention, there is provided a glenoid component for securement to a glenoid surface of a scapula so as to provide a bearing surface for a head portion of a humerus. The glenoid component includes a body portion having a first surface configured to contact the glenoid surface of the scapula and a second surface configured to receive the head portion of the humerus. The glenoid component also includes an anchor peg extending from the first surface of the body portion for penetrating the glenoid surface of the scapula so as to secure the body portion to the glenoid surface of the scapula. The anchor peg has a first end portion and a second end portion, with the first end portion of the anchor peg being secured to the first surface of the body portion, and the second end portion of the anchor peg having a number of fins secured thereto. The glenoid component also includes a first stabilizing peg extending from the first surface of the body portion for penetrating the glenoid surface of the scapula so as to prevent movement of the body portion relative to the glenoid surface of the scapula.  
         [0009]     In accordance with another embodiment of the present invention, there is provided a method of securing a glenoid component to a glenoid surface of a scapula so as to provide a bearing surface for a head portion of a humerus. The glenoid component has (i) a body portion which has a first surface configured to contact the glenoid surface of the scapula and a second surface configured to receive the head portion of the humerus, (ii) an anchor peg extending from the first surface of the body portion, the anchor peg having a number of fins secured thereto, and (iii) a first stabilizing peg extending from the first surface of the body portion. The method includes the step of drilling an anchor hole and a first stabilizing hole in the glenoid surface of the scapula. The method also includes the step of advancing the anchor peg into the anchor hole so as to position the number of fins in the anchor hole. The method further includes the step of advancing the first stabilizing peg into the first stabilizing hole. The anchor peg advancing step and the first stabilizing peg advancing step are performed contemporaneously such that the first surface of the body portion is advanced into contact with the glenoid surface of the scapula.  
         [0010]     In accordance with a further embodiment of the present invention, there is provided a glenoid component for securement to a glenoid surface of a scapula so as to provide a bearing surface for a head portion of a humerus. The glenoid component includes a body portion having a first surface configured to contact the glenoid surface of the scapula and a second surface configured to receive the head portion of the humerus. The glenoid component also includes an anchor peg having a shaft portion which extends outwardly from the first surface of the body portion for penetrating the glenoid surface of the scapula so as to secure the body portion to the glenoid surface of the scapula. The shaft portion of the anchor peg has a number of fins defined therein. The glenoid component further has a first stabilizing peg extending outwardly from the first surface of the body portion for penetrating the glenoid surface of the scapula so as to prevent movement of the body portion relative to the glenoid surface of the scapula. Each of the body portion, the anchor peg, the number of fins, and the stabilizing peg are integrally molded with one another.  
         [0011]     In accordance with yet another embodiment of the present invention, there is provided a glenoid component for securement to a glenoid surface of a scapula so as to provide a bearing surface for a head portion of a humerus. The glenoid component includes a body portion having a first surface configured to contact the glenoid surface of the scapula, and a second surface configured to receive the head portion of the humerus. The glenoid component also includes an anchor peg extending from the first surface of the body portion for insertion into an anchor hole formed in the glenoid surface of the scapula so as to secure the body portion to the glenoid surface of the scapula. The anchor peg has an outwardly extending fin secured thereto. The fin is configured to deform upon insertion of the anchor peg into the anchor hole such that a removal force required to remove the anchor peg from the anchor hole is greater in magnitude than an insertion force required to insert the anchor peg into the anchor hole. The glenoid component also includes a first stabilizing peg extending from the first surface of the body portion for insertion into a stabilizing hole formed in the glenoid surface of the scapula so as to prevent movement of the body portion relative to the glenoid surface of the scapula.  
         [0012]     In accordance with another embodiment of the present invention, there is provided a bearing component for securement to a natural bearing surface of a first bone so as to provide a bearing surface for a contact portion of a second bone. The bearing component includes a body portion having a first surface configured to contact the natural bearing surface of the first bone and a second surface configured to receive the contact portion of the second bone. The bearing component also includes an anchor peg extending from the first surface of the body portion for penetrating the natural bearing surface of the first bone so as to secure the body portion to the natural surface of the first bone. The anchor peg has a first end portion and a second end portion with the first end portion of the anchor peg being secured to the first surface of the body portion and the second end portion of the anchor peg having an outwardly extending fin secured thereto. The bearing component also includes a first stabilizing peg extending from the first surface of the body portion for penetrating the natural bearing surface of the first bone so as to prevent movement of the body portion relative to the natural bearing surface of the first bone.  
         [0013]     It is therefore an object of the present invention to provide a new and useful glenoid component.  
         [0014]     It is moreover an object of the present invention to provide an improved glenoid component.  
         [0015]     It is a further object of the present invention to provide a new and useful method of securing a glenoid component to a glenoid surface of a scapula.  
         [0016]     It is also an object of the present invention to provide an improved method of securing a glenoid component to a glenoid surface of a scapula.  
         [0017]     It is yet another object of the present invention to provide a method of securing a glenoid component to a glenoid surface of a scapula which does not require the use of bone cement.  
         [0018]     The above and other objects, features, and advantages of the present invention will become apparent from the following description and the attached drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is an exploded perspective view which shows a glenoid component which incorporates the features of the present invention therein positioned between a glenoid surface of a scapula and a humeral component;  
         [0020]      FIG. 2  is a perspective view of the glenoid component of  FIG. 1 ;  
         [0021]      FIGS. 3-5  are elevational views of the glenoid component of  FIG. 2 ;  
         [0022]      FIG. 6  is an enlarged view of a portion of  FIG. 5  which is encircled and indicated as  FIG. 6 ;  
         [0023]      FIG. 7  is a plan view of the glenoid component of  FIG. 2 ;  
         [0024]      FIG. 8  is a cross sectional view taken along the line  8 - 8  of  FIG. 7 , as viewed in the direction of the arrows; and  
         [0025]      FIG. 9  is a cross sectional view taken along the line  9 - 9  of  FIG. 1  as viewed in the direction of the arrows, note that the fins of the glenoid component are not shown in cross section for clarity of description. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
         [0027]     Referring now to  FIG. 1 , there is shown a glenoid component  10  located between a glenoid surface  12  of a scapula  14  and a humeral component  16 . The humeral component  16  has been implanted or otherwise secured to a humerus  18 . As shall be discussed below in greater detail, the glenoid component  10  is configured to be secured to the glenoid surface  12  of the scapula  14  without the use of bone cement in order to replace the natural glenoid surface  12  during a total shoulder replacement procedure. In such a manner, the glenoid component  10  functions as a bearing surface for receiving a head portion of the humerus  18  (i.e. a head portion  20  of the humeral component  16  implanted in the humerus  18 ).  
         [0028]     As shown in  FIGS. 1-8 , the glenoid component  10  includes a body portion  22  having a first generally convex surface  24  and a second generally concave surface  26 . The convex surface  24  is configured to abut or otherwise contact the glenoid surface  12  of the scapula  14  when the glenoid component  10  is secured thereto. The concave surface  26  of the body portion  22  provides a bearing surface for the head portion  20  of the humeral component  16  implanted into the humerus  18 .  
         [0029]     The glenoid component also includes an anchor peg  28  and a number of stabilizing pegs  30 ,  32 ,  34 . The anchor peg  28  and the stabilizing pegs  30 ,  32 ,  34  are secured to the convex surface  24  of the body portion  22  and extend outwardly therefrom. As shown in  FIG. 1 , the anchor peg  28  is received into an anchor hole  38  which is drilled or otherwise formed in the glenoid surface  12  of the scapula  14 , whereas the stabilizing pegs  30 ,  32 ,  34  are received into a number of respective stabilizing holes  40 ,  42 ,  44  which are also drilled or otherwise formed in the glenoid surface  12  of the scapula  14 .  
         [0030]     Although it is contemplated that the anchor peg  28  and/or any one or all of the stabilizing pegs  30 ,  32 ,  34  may be embodied as separate components which are secured to the body portion  22 , the anchor peg  28  and the stabilizing pegs  30 ,  32 ,  34  are preferably integrally formed with one another and the body portion  22 . In one exemplary embodiment, the body portion  22 , the anchor peg  28 , and the stabilizing pegs  30 ,  32 ,  34  are integrally molded using a polymeric material such as polyethylene or ultra-high molecular weight polypropylene (UHMWPE).  
         [0031]     As shown best in  FIGS. 5 and 6 , the anchor peg  28  includes a beveled shaft portion  46  which is secured at its proximal end to the convex surface  24 . The distal end portion of the shaft portion  46  has a conical tip  48  defined therein which is provided as a “lead in” to facilitate insertion of the anchor peg  28  into the anchor hole  38  drilled in the glenoid surface  12  of the scapula  14 .  
         [0032]     In addition to the conical tip  48 , the distal end portion of the shaft portion  46  also has a number of fins  50  secured thereto. The fins  50  extend radially outwardly from the shaft portion  46  of the anchor peg  28  in a substantially perpendicular direction relative to the shaft portion  46  such that the outer diameter of each of the fins  50  is greater than the outer diameter of the shaft portion  46 . Each of the fins  50  preferably extends continuously around the entire outer periphery of the shaft portion  46 , although the fins  50  may alternatively be embodied as a series of individual flange sections which line substantially all of the outer periphery of the shaft portion  46 .  
         [0033]     Although the anchor peg  28  is herein shown in the figures to include four fins  50 , it should be appreciated that the anchor peg  28  may be embodied to include any number of fins. For example, the anchor peg  28  may be embodied to include only a single (i.e. one) fin  50 . In addition, although each of the fins  50  is herein shown in the figures to possess the same sized outer diameter, it should be appreciated that other fin configurations are also contemplated for use with the glenoid component  10  of the present invention. For example, the fins  50  may be provided in a tapered configuration in which the respective outer diameters of the fins  50  gradually increases from the distal end of the shaft portion  46  to the proximal end portion of the shaft portion (i.e. the fin positioned on the distal end of the shaft portion  46  has a smaller diameter relative to the fin positioned on the proximal end of the shaft portion  46 ). In such a configuration, the anchor hole  38  drilled in the scapula  14  would be drilled in a similarly tapered manner so as to provide a corresponding sidewall configuration for engagement by the fins  50 .  
         [0034]     Although it is contemplated that the fins  50  may be embodied as separate components which are secured to the shaft portion  46  of the anchor peg  28 , the fins  50  are preferably integrally formed with the shaft portion  46  of the anchor peg  28 . Consistent with as described above, in one exemplary embodiment, the fins  50  are integrally molded with the shaft portion  46  of the anchor peg  28  (and hence also integrally molded with the body portion  22  and the stabilizing pegs  30 ,  32 ,  34  of the glenoid component  10 ) using a polymeric material such as polyethylene or ultra-high molecular weight polypropylene (UHMWPE).  
         [0035]     As shown in  FIG. 9 , the fins  50  are configured to curl, bend, or otherwise deform when the anchor peg  28  is inserted into the anchor hole  38 . This is caused when the fins  50  are advanced into the anchor hole  38  since it is drilled so as to have a diameter which is slightly larger than the diameter of the shaft portion  46  of the anchor peg  28 , yet smaller than the outer diameter of the fins  50  thereby causing deformation of the fins  50  upon contact with the sidewalls of the anchor hole  38  as the fins  50  are “forced” into the anchor hole  38 . Such deformation of the fins  50  allows the fins  50  to function as upwardly turned “barbs” which secure the glenoid component  10  to the scapula  14  by providing resistance to removal or “pull out” of the anchor peg  28  from the anchor hole  38  much in the same way that the threads of a screw provide resistance to pull out of the screw from the material into which it is driven. In addition, over a period of time subsequent to securement of the glenoid component  10  to the scapula  14 , bone tissue or other types of tissue will grow into the spaces between the fins  50  thereby providing further resistance to pull out of the anchor peg  28  from the anchor hole  38 .  
         [0036]     Moreover, the fins  50  of the present invention are configured in a manner which provides numerous advantages over heretofore designed anchoring structures. For example, the fins  50  are configured to be relatively thin in design and possess a relatively large outer diameter thereby providing for a relatively large amount of deformation or “curling” which in turn creates a large amount of anchoring force when the anchor peg  28  is inserted into the anchor hole  38 . In one exemplary embodiment, each of the fins  50  has a nominal thickness of 0.023 inch with a distance of 0.052 inch between adjacent fins. Moreover, in such an exemplary embodiment, the fins  50  have an outer diameter of 0.346 inch and extend outwardly from a shaft portion  46  which has a diameter of 0.188 inch.  
         [0037]     Such a configuration of the fins  50  as described above eliminates the need for the use of bone cement to secure the anchor peg  28  to the glenoid surface  12  of the scapula  14  thereby reducing the complexity of a typical total shoulder replacement procedure along with eliminating any potential shortcomings associated with the use of bone cement. In particular, the above-described configuration of the fins  50  provides a glenoid component  10  which “locks” into place upon insertion into the anchor hole  38  drilled in the scapula  14 . More specifically, preliminary laboratory tests have indicated that when inserted into a test material such as white pine wood, the removal force required to remove the glenoid component  10  is over twice as large in magnitude as the insertion force required to press fit the glenoid component  10  into the test material. The creation of such a relatively large removal force facilitates the use of the glenoid component  10  without the use of bone cement.  
         [0038]     The stabilizing pegs  30 ,  32 ,  34  are provided to prevent rotation or other types of movement of the body portion  22  of the glenoid component  10  relative to the scapula  14  once the glenoid component  10  has been secured to the glenoid surface  12 . Each of the stabilizing pegs  30 ,  32 ,  34  includes a cylindrical shaft portion  56  which is secured at its proximal end to the convex surface  24  of the body portion  22 . The distal end of each of the shaft portions  56  has a conical tip  58  defined therein which, similarly to as described above in regard to the anchor peg  28 , functions as a “lead in” to facilitate insertion of the stabilizing pegs  30 ,  32 ,  34  into their respective stabilizing holes  40 ,  42 ,  44  drilled in the glenoid surface  12  of the scapula  14 .  
         [0039]     The stabilizing pegs  30 ,  32 ,  34  may be arranged in any orientation on the convex side  24  of the body portion  22  which fits the needs of a given glenoid component  10 . For example, as shown best in  FIG. 7 , the stabilizing peg  30  may be spaced apart from the anchor peg  28  in a direction which is substantially opposite from the direction in which the stabilizing pegs  32 ,  34  are spaced apart from the anchor peg  28 . Moreover, one arrangement of the stabilizing pegs  30 ,  32 ,  34  which has been found to be particularly useful for preventing rotation or other types of movement of the glenoid component  10  relative to the scapula  14  is an arrangement shown in  FIG. 7  in which a first pair of pegs (i.e. the anchor peg  28  and the stabilizing peg  30 ) are positioned in a normal relationship with a second pair of pegs (i.e. the stabilizing pegs  32 ,  34 ). In particular, as shown in  FIG. 7 , the anchor peg  28  and the stabilizing peg  30  are aligned with respect to one another along a first imaginary line  60 , whereas the stabilizing peg  32  and the stabilizing peg  34  are aligned with respect to one another along a second imaginary line  62 . The imaginary line  60  is normal or otherwise substantially perpendicular to the imaginary line  62 .  
         [0040]     In addition, it should be appreciated that any number of stabilizing pegs may be utilized to fit the needs of a given glenoid component  10 . In particular, although the glenoid component  10  is described herein as having three stabilizing pegs, and has significant advantages thereby in the present invention, it should be appreciated that the glenoid component  10  may be alternatively embodied to include any number of stabilizing pegs. For example, the glenoid component  10  may be embodied to include only a single (i.e. one) stabilizing peg.  
         [0041]     Moreover, as shown in  FIGS. 3-5  and  8 , the stabilizing pegs  30 ,  32 ,  34  may alternatively be configured to have a number of serrations  64  defined therein. The serrations  64  may be utilized in a similar manner as the fins  50  of the anchor peg  28  in that over a period of time subsequent to securement of the glenoid component  10  to the scapula  14 , bone tissue or other types of tissue will grow into the serrations  64  thereby providing resistance to pull out of the glenoid component  10  from its secured position on the glenoid surface  12  of the scapula  14 . Moreover, if a particular surgeon or procedure requires (or simply desires) the use bone cement in the stabilizing holes  40 ,  42 ,  44  due to, for example, governmental regulation or the like, the serrations  64  may be utilized to receive a portion of the bone cement in order to increase the area of contact between the bone cement and the stabilizing pegs  30 ,  32 ,  34  thereby increasing the bond between the stabilizing pegs  30 ,  32 ,  34  and the walls of the stabilizing holes  40 ,  42 ,  44 .  
         [0042]     Hence, the glenoid component  10  may be secured to the glenoid surface  12  of the scapula  14  in a number of different manners. In a first or “cementless” manner, each of the anchor peg  28  and the stabilizing pegs  30 ,  32 ,  34  is press fit or otherwise interference fit into their respective holes  38 ,  40 ,  42 ,  44  without the use of bone cement. In a second or “cemented” manner, the anchor peg  28  is press fit or otherwise interference fit into the anchor hole  38  in the same manner as described above; however, the stabilizing pegs  30 ,  32 ,  34  are clearance fit into their respective stabilizing holes  40 ,  42 ,  44  with the use of bone cement. Such multiple uses of the glenoid component  10  of the present invention provides flexibility in regard to its use thereby fulfilling the needs of a given surgeon or shoulder replacement procedure.  
       OPERATION OF THE PRESENT INVENTION  
       [0043]     In operation, the glenoid component  10  of the present invention is utilized in the performance of a total shoulder replacement procedure in order to provide an artificial bearing surface for the head portion of the humerus without the use of bone cement. In particular, the anchor hole  38  and the stabilizing holes  40 ,  42 ,  44  are first drilled or otherwise formed in the glenoid surface  12  of the scapula  14  by use of a suitable drilling tool (not shown). It should be appreciated that a drill guide or pattern (not shown) may be utilized to properly position and align the holes  38 ,  40 ,  42 ,  44  on the glenoid surface  12  of the scapula  14 .  
         [0044]     Once the holes  38 ,  40 ,  42 ,  44  have been drilled in the glenoid surface  12  of the scapula  14 , the glenoid component  10  is secured to the scapula  14 . In particular, the glenoid component  10  is oriented such that the anchor peg  28  and the stabilizing pegs  30 ,  32 ,  34  are pointed in the general direction of the glenoid surface  12  of the scapula  14 . Thereafter, the glenoid component  10  is advanced toward the glenoid surface  12  such that the anchor peg  28  and each of the stabilizing pegs  30 ,  32 ,  34 , are contemporaneously advanced into the anchor hole  38  and the stabilizing holes  40 ,  42 ,  44 , respectively.  
         [0045]     As described above, the fins  50  are configured to curl, bend, or otherwise deform when the anchor peg  28  is inserted into the anchor hole  38  so as to allow the fins  50  to function as “barbs” which secure the glenoid component  10  to the scapula  14  by providing resistance to pull out of the anchor peg  28  from the anchor hole  38  much in the same way that the threads of a screw provide resistance to pull out of the screw from the material into which it is driven. In addition, as described above, over time a period of time subsequent to securement of the glenoid component  10  to the scapula  14 , bone tissue or other types of tissue will grow into the spaces between the fins  50  thereby providing further resistance to pull out of the anchor peg  28  from the anchor hole  38 .  
         [0046]     Hence, insertion of the anchor peg  28  into the anchor hole  38  anchors or otherwise retains the body portion  22  of the glenoid component  10  into contact with the glenoid surface  12  of the scapula  14 . Moreover, insertion of the stabilizing pegs  30 ,  32 ,  34  into the stabilizing holes  40 ,  42 ,  44  in the manner described above prevents rotation or other types of movement of the body portion  22  of the glenoid component  10  relative to the glenoid surface  12  of the scapula  14 .  
         [0047]     Once the glenoid component  10  has been secured to the glenoid surface  12  of the scapula  14  in the manner described, the concave surface  26  of the body portion  22  of the glenoid component  10  provides a bearing surface for receiving the head portion  20  of the humeral component  16  implanted in the humerus  18 . In such a manner, the concave surface  26  of the body portion  22  functions as a suitable artificial replacement for the natural glenoid surface  12  of the scapula  14 .  
         [0048]     Hence, as described herein, the glenoid component  10  of the present invention provides numerous advantages over heretofore designed glenoid components. For example, the glenoid component  10  is configured to be secured to the glenoid surface  12  of the scapula  14  without the use of bone cement. Moreover, the glenoid component  10  of the present invention is preferably provided as a one-piece, integrally molded component thereby overcoming many of the drawbacks associated with heretofore designed multiple-piece designs.  
         [0049]     While the invention has been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.  
         [0050]     There are a plurality of advantages of the present invention arising from the various features of the glenoid component described herein. It will be noted that alternative embodiments of the glenoid component of the present invention may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of a glenoid component that incorporate one or more of the features of the present invention and fall within the spirit and scope of the present invention as defined by the appended claims.  
         [0051]     For example, the embodiment of one bearing component in accordance with the concepts of the present invention has herein been described in regard to the glenoid component  10 . However, it should be appreciated that the concepts of the present invention may also be incorporated into an acetabular, patellar, femoral, humeral, tibial, ulnar, radial, wrist, and/or ankle component for a prosthetic joint assembly.