Patent Publication Number: US-2011054628-A1

Title: Reflex fixation geometry revision and reconstruction system reverse articulation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND 
     1. The Field of the Invention. 
     The present disclosure relates generally to the field of artificial joints and joint implants, and more particularly, but not necessarily entirely, to acetabular reconstruction using an artificial hip prosthesis having an articulation that is reversed with respect to the normal hip prosthesis. 
     2. Description of Related Art 
     It is common practice in the orthopedic industry to use artificial implants to replace diseased, damaged or otherwise compromised joints, such as in the hip, knee, shoulder, or spine. For example, the human hip joint is formed by the acetabulum of the pelvis on one side and the proximal femur on the other. The hip joint acts mechanically as a ball and socket joint, wherein the ball-shaped head of the proximal femur is positioned within the socket-shaped acetabulum of the pelvis. In a total hip arthroplasty or joint replacement, both the femoral head and the surface of the acetabulum are replaced with prosthetic devices. A total hip replacement is typically used when both the natural femoral head and acetabulum are diseased or damaged. 
     A traditional artificial hip implant includes an acetabular component and a femoral component. An acetabular shell or cup component, which is traditionally hemispherical in shape and attachable to the acetabulum, may be attached to the acetabulum in a cemented application or in a cementless application, i.e., a press-fit with osseous growth fixing the shell to the bone. A bearing or liner may be secured within a cavity of the acetabular shell using several different mechanical locks to secure the bearing or liner to the shell component. 
     On the femoral side, a traditional femoral implant may be located in the medullary canal of the femur and commonly has a spherical head and an elongated stem. The spherical head may be seated in and articulate with the acetabular bearing or liner. 
     When the artificial hip implant itself becomes damaged or the bone surrounding or contacting the hip implant becomes further diseased or damaged, it is sometimes necessary for a surgeon to repair the prosthetic hip joint using a reconstruction or revision hip implant. Currently in a reconstruction hip surgery, surgeons may place a reconstructive cage or shell into a deficient acetabulum on the pelvis side of the hip joint along with a bone graft (either allograft or a substitute) into which the cemented cup for receiving a prosthetic femoral head is placed in the best position possible to obtain a more stable joint. Cementing the cup into the cage, independent of the position of the cage, allows for optimum angulation of the cup for increased stability. 
     Bone loss at or around the acetabulum often results in the cage being attached to the acetabulum in a position that is more vertical than desired. In other words, a base of the cage may be rotated vertically with respect to a vertical midline of the patient. The result of the vertical placement of the cage leads to an undesirable placement of the cup. 
     There are some known designs that are indicated for use as a cementless device and allow a certain, but often inadequate, flexibility in terms of orientation of the inner liner to provide the best stability. Many of these devices are somewhat ‘eccentric’ or off axis and do not have adequate initial fixation or provision for secondary biological or bone fixation. 
     The goal of an artificial implant is to restore the natural biomechanics of the natural joint. However, restoring the biomechanics of the joint continues to be a difficult problem. It is noteworthy that none of the devices known to applicant provides a hip implant that satisfactorily restores the mechanics of the hip joint. There is a long felt, but currently unmet, need for a hip implant that satisfactorily restores the natural joint mechanics of the hip joint, as illustrated by the number of hip implants in the marketplace attempting to restore the natural joint mechanics. 
     Despite the advantages of many of the known devices, improvements are still being sought. However, these known devices are also characterized by several disadvantages that may be addressed by the present disclosure. The present disclosure minimizes, and in some aspects eliminates, the failures, and other problems, of these devices by utilizing the methods and structural features described herein. 
     The features and advantages of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the disclosure without undue experimentation. The features and advantages of the disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of the disclosure will become apparent from a consideration of the subsequent detailed description presented in connection with the accompanying drawings in which: 
         FIG. 1  is a schematic view of an orthopedic device, specifically an embodiment in the form of a hip implant, including a first component and a second component made in accordance with the principles of the present disclosure; 
         FIG. 1A  is a side view of a part of the first component of  FIG. 1  and illustrating a convex articulation surface; 
         FIG. 2  is an exploded side, perspective view of an embodiment of a first component of the orthopedic device made in accordance with the principles of the present disclosure; 
         FIG. 3  is a side, perspective view of an another embodiment of the first component of the orthopedic device made in accordance with the principles of the present disclosure; 
         FIG. 4  is a bottom perspective view of the embodiment of the first component of the orthopedic device of  FIG. 3 ; 
         FIG. 5  is a bottom view of the embodiment of the first component of the orthopedic device of  FIG. 3 ; 
         FIG. 6  is a schematic side view of an embodiment of the second component of the orthopedic device made in accordance with the principles of the present disclosure; 
         FIG. 7  is a schematic side view of another embodiment of the second component of the orthopedic device made in accordance with the principles of the present disclosure; 
         FIG. 8  is a schematic side view of another embodiment of the second component of the orthopedic device made in accordance with the principles of the present disclosure; 
         FIG. 9  is a schematic side view of another embodiment of the second component of the orthopedic device made in accordance with the principles of the present disclosure; 
         FIG. 10  is a schematic side view of another embodiment of the second component of the orthopedic device made in accordance with the principles of the present disclosure; 
         FIG. 10A  is a schematic top view of a stem component of the second component of the orthopedic device of  FIG. 10  and made in accordance with the principles of the present disclosure; 
         FIG. 10B  is a schematic bottom view of a proximal body portion of the second component of the orthopedic device of  FIG. 10  and made in accordance with the principles of the present disclosure; 
         FIG. 10C  is a schematic bottom view of a concave articulation surface portion of the orthopedic device of  FIG. 10  and made in accordance with the principles of the present disclosure; 
         FIG. 10D  is a schematic top view of the concave articulation surface portion of the orthopedic device of  FIG. 10  and made in accordance with the principles of the present disclosure; 
         FIG. 11  is a schematic side, cross-sectional view of an embodiment of the orthopedic device made in accordance with the principles of the present disclosure; 
         FIG. 12  is a schematic side, cross-sectional view of an embodiment of the orthopedic device utilized in a revision surgery and made in accordance with the principles of the present disclosure; and 
         FIG. 13  is a schematic side, cross-sectional view of another embodiment of the orthopedic device utilized in a revision surgery and made in accordance with the principles of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles in accordance with the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications of the inventive features illustrated herein, and any additional applications of the principles of the disclosure as illustrated herein, which would normally occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the disclosure claimed. 
     Before the present orthopedic device and method of restoring joint mechanics in a joint, such as a hip joint, are disclosed and described, it is to be understood that this disclosure is not limited to the particular configurations, process steps, and materials disclosed herein as such configurations, process steps, and materials may vary somewhat. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present disclosure will be limited only by the appended claims and equivalents thereof. 
     It must be noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. 
     In describing and claiming the present disclosure, the following terminology will be used in accordance with the definitions set out below. 
     As used herein, the terms “comprising,” “including,” “containing,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps. 
     As used herein, the phrase “consisting of” and grammatical equivalents thereof exclude any element, step, or material not specified in the claim. 
     As used herein, the term “proximal” shall refer broadly to the concept of portion nearest to the center of a patient&#39;s body, or from the point of origin. For example, a natural femoral bone includes a proximal end having a femoral head that forms part of a hip joint proximally and a distal end having femoral condyles that form part of the knee joint distally. Thus, the proximal femur is so named because it is the proximal-most portion of the femur and is nearest to the center of the patient&#39;s body. As another example, a patient&#39;s knee is proximal with respect to the patient&#39;s toes. 
     On the other hand, as used herein, the term “distal” shall generally refer to the opposite of proximal, and thus to the concept of a portion farthest from a midline or trunk of a patient&#39;s body, depending upon the context. Thus, the distal femur, for example, is so named because it is the distal-most portion of the femur and is farthest from the patient&#39;s midline or trunk. As another example, a patient&#39;s fingers are distal with respect to the patient&#39;s shoulder. 
     As used herein, the phrase “in an at least a partially proximal-to-distal direction” shall refer generally to a two-dimensional concept of direction in which the “proximal-to-distal” direction defines one direction or dimension. An item that extends in a non-parallel direction with respect to the “proximal-to-distal” direction, that is, at a non-straight angle thereto, thereby involves two components of direction, one of which is in the “proximal-to-distal” direction and the other having some other component of direction, for example a direction orthogonal to the “proximal-to-distal” direction. As a specific example, a patient&#39;s natural femur extends in a substantially proximal-to-distal direction. 
     Referring now to the figures, it will be appreciated that the present disclosure relates to an orthopedic device for replacing a joint in a patient&#39;s body. The device  10  of the present disclosure may function to restore the natural joint mechanics, or in other words targets restoration of the natural joint mechanics. With proper joint stability and proper restoration of the joint mechanics, the stress and strains placed on the artificial joint, i.e., the bearing or articulating surfaces at the joint interface, will be reduced, thereby reducing wear debris. 
     By way of example,  FIG. 1  illustrates an embodiment of the orthopedic device  10  of the present disclosure, which may comprise a first component  100  that may be attachable to an acetabulum of a patient and a second component  200  that may be attachable to a proximal femur of the patient. 
     It will be understood that the first component  100  may comprise a shell  110  that may be directly attached or may be attachable to the acetabulum of the patient. The first component  100  may further comprise an insert  140  that may be attachable to the shell  110 . 
     It will be appreciated that the shell  110  may be attached to the acetabulum in any method known, or that may become known in the future, in the art. For example, the shell  110  may be attached to the acetabulum using bone cement or the shell may be attached to the acetabulum via a press-fit between the shell  110  and the bone of the acetabulum itself. As illustrated in  FIGS. 1-5 , the shell  110  of the first component  100  may include a first body  112  having an outer surface  114  and a cavity  116 , which may be defined at least in part by a wall  118 . It will be appreciated that the wall  118  may be tapered to form a mating tapered engagement with a portion of the insert  140 , which engagement is described more fully below in connection with the insert  140 . 
     The shell  110  may be substantially semi-spherical in shape, but it will be appreciated that other shapes may be utilized without departing from the spirit or scope of the present disclosure. As used herein, the phrase “substantially semi-spherical” means a partial, part or portion of an object that resembles or has some of the characteristics of a sphere, but it should be noted that the above phrase is broad enough to include and does in fact encompass an object having a curved outer surface or an object having a convex surface, whether or not such an object can be characterized as a sphere or portion of a sphere. 
     As illustrated best in  FIGS. 1 , and  3 - 5 , at least one flange  120  may extend from the first body  112 . It will be appreciated that the type of flange  120  utilized may vary somewhat and may include flanged augments, hooked augments, finned augments and even plain augments, all of which are known in the art. Without regard to the specific flange  120  utilized, the at least one flange  120  may include a first through hole  122  such that a fastener  130 , such as a cancellous screw or other fastener, may be extendable into the first through hole  122  and into the surrounding bone. It will be appreciated that each flange  120  may include a first through hole  122  for allowing passage of the fastener  130  therethrough, which may aid in securing the shell  110  to the bone. 
     Similarly, it will be appreciated that at least one through hole  124 , i.e., a second through hole, may be present in the shell  110  itself and the through hole  124  may extend through the wall or tapered wall  118  of the cavity  116  on the inner portion of the shell  110  and may open to the outside of the shell  110  at the outer surface  114  of the first body  112 . Thus, a fastener  130  may be extendable into the through hole  124  and into the surrounding bone. 
     As illustrated in  FIGS. 1-5 , the insert  140  may have a body  142 , a neck  144  and a head  146 . It will be appreciated that the body  142  of the insert  140  may be attachable to the cavity  116  of the shell  110 . To accomplish the connection, the body  142  of the insert  140  may include a tapered outer surface  150  (illustrated best in  FIG. 2 ), which may structurally correspond with the wall  118  of the shell  110 . Thus, the tapered outer surface  150  of the body  142  of the insert  140  may function to matingly engage the wall  118 , which may also be tapered, of the shell  110  in a self-locking friction fit. The tapered outer surface  150  of the body  142  of the insert  140  and the tapered wall  118  of the cavity  116  of the shell  110  may each comprise an angle that is within a range of self-locking taper angles. 
     It will be appreciated that the insert  140  may comprise at least one modular connection with respect to the body  142 , the neck  144  and the head  146 . In other words, the body  142  may be modular with respect to the neck  144  and the neck  144  may further be modular with respect to the head  146 . Thus, the neck  144  may be modular with respect to both the body  142  and the head  146 . The at least one modular connection may be a self-locking taper interlock between corresponding components as illustrated, for example, in  FIG. 2 . It will be appreciated that the insert  140  may be a monoblock piece and does not necessarily have to comprise at least one modular piece. However, it will be appreciated that many advantages may be gained by using a modular design, such as a reduction in inventory, and one of skill in the art can determine when a modular design may be better suited than a monoblock design and vice-versa without departing from the spirit or scope of the present disclosure. 
     The body  142  may include a top portion  142   a  and a bottom portion  142   b , also referred to herein as a first base portion. Further, a recess  152  may be formed in the bottom or first base portion  142   b  of the body  142  and may be defined by a tapered sidewall  153 . The recess  152  may further be defined by an undulating surface  154  that may be tapered and may open to an exterior portion of the body  142 . It will be appreciated that the recess  152  may be present when the body  142  is a modular piece with respect to the neck  144  and may not be present when the body  142  is a unitary, monoblock piece with respect to the neck  144 . 
     The neck  144  of the insert  140  may be affixed or attached to both the head  146  and the body  142 . Accordingly, the body  142  and the head may be affixed or attached to the neck  144  in either a modular embodiment or a monoblock embodiment. As illustrated, the neck  144  may extend with respect to the body  142 . 
     As discussed above, if there is a modular connection between the neck  144  and the body  142 , then the neck  144  may comprise an outer tapered portion  156  that may engage the corresponding tapered sidewall  153  of the recess  152  of the body  142  in a tapered friction fit. Further, the outer tapered portion  156  of the neck  144  may comprise a plurality of first teeth  158  that may substantially surround a perimeter of the outer tapered portion  156 . The undulating surface  154  of the recess  152  in the body  142  may include a plurality of second teeth  154   a  for engaging the first teeth  158 , such that the neck  144  may be indexable in a plurality of differing orientations with respect to the body  142 . 
     A neck  144  that is indexable neck  144  may permit the adjustment of the version angle and the neck shaft angle to provide maximum joint stability. In other words, referring to  FIG. 2 , it can be seen that the neck  144  may be adjusted to accommodate various varus or valgus angles depending upon the position of the neck  144 . For example, by moving and indexing the neck  144  at a six o&#39;clock, nine o&#39;clock or twelve o&#39;clock position, the varus or valgus angle can easily be changed to correspond to a particular patient&#39;s anatomy and needs. Further, the neck-shaft angle can be between a range of angles, for example between about a 120° to about a 150° angle, and more specifically between about 125° to about 147° angle. It will be appreciated that the average neck shaft angle may be about a 135° angle. 
     One embodiment of the insert  140  (illustrated in  FIG. 2 ) may include an imaginary central body axis represented by the line A-A and an imaginary central neck axis represented by the line B-B, wherein the central neck axis B-B is offset at an angle α with respect to the central body axis A-A. It will be appreciated that the angle α between axes may be within a range of angles of about ten degrees to about sixty degrees, and more specifically within a range of about twenty degrees to about fifty degrees, and very specifically about thirty-five degrees. An offset central neck axis B-B may be used in situations where bone loss is severe and the position of the shell  110  is too vertically oriented in the acetabulum, such that a neck having an angle may be required to restore the natural joint mechanics. Further, an offset neck  144  that is also indexable may allow for correction of the version angle, thereby promoting stability and increased range of motion. 
     The neck  144 , as opposed to the body  142 , may include a second base portion  159  with the tapered outer portion  156  extending from the second base portion  159  (illustrated best in  FIG. 2 ) for engaging the tapered sidewall  153  of the recess  152  in a friction fit. The neck  144  may further have a support  160  located at the second base portion  159  creating an angular offset of the neck  144  with respect to the first base portion  142   a  of the body  142  when the neck  144  is attached to the body  142 . The angular offset of the neck  144  may thus create differing version angles as the neck  144  may be oriented in each of the plurality of differing orientations that are available from which to choose or select. 
     It will be appreciated that the support  160  may be shaped as a wedge, to thereby create the angular offset referred to above. In other words, the support  160  may have a triangular cross-section. The angular offset represented by θ and created by the support  160  may be within a range of angles of about three degrees to about twenty degrees, and more specifically within a range of angles of about six degrees to about fifteen degrees. 
     Likewise, in the modular embodiment with respect to the head  146 , the neck  144  may comprise an outer tapered portion  162  and may include a plurality of teeth, similar to the plurality of teeth  158  at the opposite side of the neck  144 , for indexing purposes, if desired. Further, in the modular connection between the neck  144  and the head  146 , the head  146  may include a recess  164  defined by a tapered sidewall  164   a  for receiving and matingly engaging the outer tapered portion  162  of the neck  144 . 
     The head  146  of the first component  100  may be shaped and sized in various dimensions. However, it may be advantageous to use an oversized or large head  146  that may marry or matingly engage a corresponding surface, i.e., a concave articulation surface  214  described more fully below, in the second component  200 . When an oversized or large head  146  is used, the result may be increased joint stability. Recent trends in the orthopedic industry tend to favor oversized or large heads due to the stability that may be provided thereby. 
     Whether in a modular embodiment or a monoblock embodiment, the head  146  of the insert  140  may include a convex articulation surface  147 . It will be appreciated that with the convex articulation surface  147  being formed as part of the first component  100 , the convex articulation surface is thereby located on the acetabular side of the device  10 . Thus, the traditional hip implant system, in which the convex articulation surface is located on the femoral side of the hip implant, is altered by the present disclosure. 
     The first component  100  of the present disclosure may be a monoblock component or it may include at least one modular junction, or a plurality of modular junctions. For example, as illustrated in  FIG. 2 , any combination of the components could be modular and could create a modular junction. Specifically, the shell  110 , the insert  140 , the neck  144  and the head  146  of the first component  100  may all be modular pieces to create a quad-body component  100 . Additionally, other combinations of the above components may be modular to form a bi-body or tri-body embodiment. 
     Further, the first component and its various modular parts may be manufactured from various biocompatible materials without departing from the spirit of scope of the present disclosure. For example, the shell  110 , neck  144  and head  146  may be manufactured from relatively hard biocompatible materials, including chrome-cobalt, titanium, titanium alloys and other metallic materials, and also ceramic materials or diamond materials. Further, the insert  140  may be manufactured from various biocompatible materials including both soft and hard materials, including polymeric materials, chrome-cobalt, titanium, titanium alloys and other metallic materials, and also ceramic materials or diamond materials. However, it will be appreciated that the type of materials may vary somewhat, such that the insert  140  may be manufactured from a harder biocompatible material and the shell  110 , neck  144  and head  146  may be manufactured from a softer biocompatible material without departing from the scope of the present disclosure. 
     Referring now to  FIGS. 6-10B , the second component  200  is illustrated and may comprise a concave articulation surface portion  210  and a femoral stem component  230 . It will be appreciated that the concave articulation surface portion  210  may be part of a monoblock stem embodiment (illustrated best in  FIG. 6 ) or it may be part of a modular stem embodiment (illustrated best in  FIGS. 7-10 ) and may comprise a plurality of modular attachment pieces  212  each having a different shape or size. 
     In either embodiment whether monoblock or modular, the concave articulation surface portion  210  may further comprise a concave articulation surface  214 . The concave articulation surface portion  210 , including the concave surface  214  itself, may function along with the head  146  of the insert  140  and its convex articulation surface  147  to form an artificial joint. It will be appreciated that the concave articulation surface  214  may be part of the second component  200 , which is a femoral component, and the convex articulation surface  147  may be part of the first component  100 , which is an acetabular component, and the two surfaces  214  and  147  may engage each other in the formation of the artificial joint. 
     The concave articulation surface  214  may be a modular attachment piece that may be securable to the concave articulation surface portion  210 . In the modular embodiment of the concave articulation surface  214 , there may be a plurality of modular attachment pieces that function as concave articulation surfaces  214 , and each may have a different thickness than the others. Each of the plurality of modular attachment pieces that function as a concave articulation surface  214  may provide a surgeon with an ability to adjust the joint mechanics of the hip or other joint by utilizing a particular thickness for the concave articulation surface  214 . Each of the modular attachment pieces that function as a concave articulation surface  214  may be lockable to the concave articulation surface portion  210  in any modular interlocking mechanism that is known or that may become known in the future in the art. For example, a self-locking tapered fit, i.e., a morse taper may be utilized. However, a morse taper is simply one of a myriad of mechanisms that may be utilized to interlock the modular concave articulation surface  214  to the concave articulation surface portion  210 . 
     Referring now to  FIGS. 12 and 13 , two different embodiments of a modular attachment piece  270 , which may be utilized in a revision surgery, are illustrated. It will be appreciated that the modular attachment pieces  270  illustrated in  FIGS. 12 and 13  may be utilized in connection with the various embodiments disclosed herein for the first component  100 , which itself may be attachable to the acetabulum of the patient. Accordingly, the first component  100  may include the shell  110 , which may be directly attached to the acetabulum, and the insert  140  that may be attachable to the shell  110  as disclosed herein. 
     The embodiments of modular attachment pieces  270  of  FIGS. 12 and 13  may be configured and dimensioned to attach to the femoral stem component  230  of an artificial hip implant  10 . For example, in a revision surgery where the acetabular component  100  of the implant has failed and must be replaced, but where the femoral component  230  is well placed and has good stability in the femur and is not damaged or otherwise compromised, the modular attachment piece  270  of the present disclosure may be utilized to transform a traditional hip implant into a reverse articulation hip implant as disclosed herein. 
     The modular attachment pieces  270  of  FIGS. 12 and 13  may each comprise a concave articulation surface  214 , which may engage with the convex articulation surface  147  of the first component  100  to form an artificial joint. Referring specifically to  FIG. 12 , the modular attachment piece  270  may comprise a cup  271  with a cavity  272  formed therein. The cavity  272  may be substantially semi-spherical and may be defined by the concave articulation surface  214 . The modular attachment piece  270  may also comprise a support  274  that may extend downwardly from a base  271   a  of the cup  271 . A recess  276  may be formed within the support  274  and may be defined by a tapered sidewall  278  for matingly engaging a tapered end portion  300  of a neck portion  302  of the femoral component  230  in a friction fit. It will be appreciated that the cup  271  of the modular attachment piece  270  may be configured and dimensioned to either semi-constrain or constrain the convex articulation surface  147 . Thus, the modular attachment piece  270  may be directly attachable to the femoral stem component  230  during a revision surgery, which may be existing and implanted within the femur of the patient. 
     Referring specifically now to  FIG. 13 , the second component  200  may comprise an adapter  280  that may be attachable to the modular attachment piece  270 . It will be appreciated that the modular attachment piece  270  may be attached in any number of ways to the adapter  280 , including tapered connections, key and hole connections, bayonet connections, or any other modular connection. It will be appreciated that any modular connection is intended to fall within the scope of the present disclosure. A recess  286  may be formed within the adapter  280  and may be defined by a tapered sidewall  288 . The tapered sidewall  288  may matingly engage the tapered end portion  300  of the neck portion  302  of the femoral component  230  in a friction fit. It will be appreciated that there may be a plurality of modular attachment pieces  270  that may be utilized and attached to the adapter  280 . Further, as illustrated, the concave articulation surface  214  of the modular attachment piece  270  in  FIG. 13  may not substantially constrain the convex articulation surface  147 . 
     It will be appreciated that the concave articulation surface  214 , whether modular or monoblock, and perhaps the concave articulation surface portion  210  may be manufactured from any hard biocompatible material. For example, the concave articulation surface  214  and the concave articulation surface portion  210  may both be manufactured from a ceramic, metal, metallic alloys, or even diamond or diamond-based material. However, it will be appreciated that while the concave articulation surface  214 , whether modular or monoblock, may be manufactured from any biocompatible, hard material, the concave articulation surface portion  210  may be manufactured from a relatively soft, biocompatible material. For example, the concave articulation surface portion  210  may be manufactured from a polymeric material, which is relatively soft in comparison to ceramic, metal or diamond. 
     The femoral stem component  230  of the second component  200  may further comprise a proximal body portion  240  and a distal stem portion  250 . The femoral stem component  230  may be part of a monoblock stem embodiment (illustrated best in  FIG. 6 ) or it may be part of a modular stem embodiment (illustrated best in  FIGS. 7-10 ). 
     It will be appreciated that the second component  200  may be monoblock stem (illustrated in  FIG. 6 ), a bi-body stem having two modular pieces (illustrated in  FIGS. 7 and 8 ), or a tri-body stem (illustrated in  FIGS. 9 and 10 ). 
     It will be appreciated that in a monoblock stem embodiment of  FIG. 6  the concave articulation surface portion  210  and the femoral stem component  230  may be one, unitary piece. The monoblock stem embodiment may be used with particular type of a patient having predetermined indications that suggest using a monoblock stem. 
     The modular stem embodiments of  FIGS. 7-10  may comprise at least one modular junction, and possibly a plurality of modular junctions, between the modular pieces of the second component  200 , for example the concave articulation surface portion  210 , the proximal body portion  240  and the distal stem portion  250 . 
     The modularity and potential indexability of the proximal body portion  240 , and other modular pieces disclosed herein, may permit a surgeon to index the proximal body portion  240 , or other modular piece or pieces, to obtain maximum bone contact. The modularity and indexability of the first and second components  100  and  200  of the present disclosure particularly aid in maximizing bony contact on the medial calcar portion of the femur. In other words, by indexing or moving the proximal body portion  240 , or other modular piece, a surgeon can selectably locate the modular piece of the implant within the femur to optimize bony contact and hence implant stability at the bone-implant interface. 
     Specifically, the bi-body stem embodiment of  FIGS. 7 and 8  may comprise one modular junction, which may be formed between the concave articulation surface portion  210 , the concave articulation surface  214  itself, the proximal body portion  240  and the distal stem portion  250 . More specifically, the modular junction may be formed between: (i) the concave articulation surface  214  and the concave articulation surface portion  210 ; (ii) the concave articulation surface portion  210  and the proximal body portion  240 ; or (iii) between the proximal body portion  240  and the distal stem portion  250 . 
     The tri-body stem embodiment of  FIGS. 9 and 10 , on the other hand, may comprise a plurality of modular junctions between the concave articulation surface portion  210 , the concave articulation surface  214  itself, the proximal body portion  240  and the distal stem portion  250 , which may be modular pieces with respect to each other. In other words, there may be a modular junction formed between: (i) the concave articulation surface  214  and the concave articulation surface portion  210 ; (ii) the concave articulation surface portion  210  and the proximal body portion  240 ; or (iii) the proximal body portion  240  and the distal stem portion  250 . It will further be appreciated that any combination of the above modular junctions may be utilized together to form a tri-body stem and without departing from the spirit or scope of the present disclosure. 
     It will be appreciated that any of the modular junctions described herein, in which at least two modular components or pieces are joined together, may be formed by a first tapered portion  220  or  260  being located on, or formed as part of, one of the modular components or pieces, such as items  210 ,  214 ,  240  or  250 . The first tapered portion  220  or  260  may engage a tapered sidewall, such as  224  or  244  defining a recess  222  or  242  in another one of the modular components or pieces in a tapered, friction fit, i.e. a morse taper. 
     While a self-locking friction fit, i.e. a morse tapered friction fit is illustrated and disclosed herein, it should be noted that each of the modular junctions, whether part of the first component  100  or the second component  200 , may utilize other modular interlocking mechanisms without departing from the scope of the present disclosure. 
     It will be appreciated that the modular connection between the first tapered portion  220  or  260  and the tapered sidewall  224  or  244  of the recess  222  or  242  at any modular junction described herein may be as illustrated in  FIGS. 7-10 . In other words, the modular connection may comprise the tapered, friction fit only as described above, or the modular connection may include additional characteristics such as an indexable feature described below. 
     More specifically, a modular connection between two modular components or pieces, such as items  210 ,  214 ,  240  and  250  may comprise the structure for the tapered, friction fit and may further comprise structure for indexing one modular component with respect to another modular component. 
     For example, in the embodiment illustrated in  FIG. 7  (as well as one of the modular connections in  FIGS. 10 ,  10 A and  10 B), the modular connection may be between the proximal body portion  240  and the distal stem portion  250 . As illustrated in  FIGS. 7 ,  10 A and  10 B, a plurality of first teeth  221  may be located near the first tapered portion  220 , which may be formed on a proximal end  250   a  of the distal stem portion  250 . The plurality of first teeth  221  may surround the entire first tapered portion  220 , or alternatively may surround a part or even a majority of the first tapered portion  220  at a base  220   a  of said first tapered portion  220 . 
     Additionally, a plurality of second teeth  226  corresponding with the plurality of first teeth  221  may be formed as part of the sidewall  224  defining the recess  222  near an opening  223  of said recess  222 . In this example, the recess  222  may be formed in a distal end  240   b  of the proximal body portion  240 . Since the plurality of second teeth  226  correspond with the plurality of first teeth  221 , the number, shape, size and location of the second teeth  226  may be directly proportional to the first teeth  221 . Further, the first teeth  221  may engage the second teeth  226  in a mating engagement and function to allow one modular piece to be indexed with respect to another modular piece. It will be appreciated that as the number of teeth increases the number of predetermined indexable orientations also increases and vice-versa. 
     In another embodiment illustrated in  FIG. 8 , the modular connection may be between the concave articulation surface portion  210  and the proximal body portion  240 . In this embodiment, only a tapered, friction fit is illustrated, such that the first tapered portion  260  and the recess  242  do not include teeth  221  or  226  for indexing purposes. Further, the first tapered portion  260  may be formed at a distal end  210   b  of the concave articulation surface portion  210 . Further, the recess  242  may be formed in a proximal end  240   a  of the proximal body portion  240 . It will be appreciated that an indexable feature as disclosed herein, such as first and second teeth  221  and  226  that matingly engage each other in an indexable manner, may be utilized in this embodiment to permit the concave articulation surface portion  210  to be indexed with respect to the entire stem component  230 . 
     Referring now to the embodiment in  FIG. 9 , a tri-body stem is illustrated having two modular connections, which may be as described and disclosed in connection with  FIGS. 7 and 8 . Even though the indexable feature of the present disclosure is not illustrated in  FIG. 9 , it will be appreciated that an indexable feature as disclosed herein may be utilized by the present embodiment at one or more of the modular connections without departing from the spirit or scope of the present disclosure. 
     Referring specifically to  FIGS. 10-10D , another tri-body stem embodiment is disclosed in which both modular connections may be tapered, friction fits and may also be indexable. Specifically, the modular connection between the concave articulation surface portion  210  and the proximal body portion  240  may include a plurality of first teeth  261  that may be located near the first tapered portion  260 , which may be formed on the distal end  210   b  of the concave articulation surface portion  210  (see  FIG. 10C ). The plurality of first teeth  261  may surround the entire first tapered portion  260 , or alternatively may surround a part or even majority of the first tapered portion  260  at a base  260   a  of said first tapered portion  260 . 
     Additionally, a plurality of second teeth  246  corresponding with the plurality of first teeth  261  may be formed in the sidewall  244  of the recess  242  near an opening  243  of said recess  242  (see  FIG. 10D ). In this example, the recess  242  may be formed in a proximal end  240   a  of the proximal body portion  240 . Since the plurality of second teeth  246  correspond with the plurality of first teeth  261 , the number, shape, size and location of the second teeth  246  may be directly proportional to the first teeth  261 . Further, the first teeth  261  may engage the second teeth  246  in a mating engagement and function to allow one modular piece to be indexed with respect to another modular piece. It will be appreciated that as the number of teeth increases the number of predetermined indexable orientations also increases and vice-versa. It will be appreciated that the modular connection between the proximal body portion  240  and the distal stem portion  250  as illustrated in  FIGS. 10 ,  10 A and  10 B may be as described with respect to the modular connection in  FIG. 7 . 
     Further, the indexable features of the present disclosure, i.e., the plurality of first teeth  221  or  261  and the plurality of second teeth  226  and  246 , may or may not be tapered. If the first teeth  221  and  261  and the second teeth  226  and  246  are tapered, then the result is a double tapered, friction fit. In such an embodiment, a primary taper occurs at the tapered, friction fit between the first tapered portion  220  and  260  and the sidewall  224  and  244  of the recess  222  and  242 , while a secondary or back-up taper occurs between the tapered connection of the first teeth  221  and  261  and the second teeth  226  and  246 . 
     Further, it is to be understood that in the various embodiments of a modular connection the first tapered portion  220  may extend from the distal end  250   a  of the stem component  250 , while the first tapered portion  260  may extend from the proximal end  210   a  of the concave articulation surface portion  210 . Further, it will be appreciated that the location of the first tapered portion and the recess may be reversed without departing from the spirit or scope of the present disclosure. 
     Additionally, each of the various modular connections described and shown herein may be used in various combinations depending upon the surgical or biomechanical need of the patient. Thus, the above modular connections may be mixed and matched without from the spirit or scope of the present disclosure. 
     Referring to  FIG. 11 , the concave articulation surface portion  210  of the second component  200  may comprise a wall  216  defining the concave articulation surface  214  and further defining an overall area of said concave articulation surface  214 . It will be appreciated that the wall  216  may be configured and arranged to extend around at least a portion of the convex articulation surface  147  of the insert  140  of the first component  100 . The greater the surface area of the concave articulation surface  214 , which may be created and defined by the wall  216 , the more constrained the convex articulation surface  147  will be when the concave articulation surface  214  and the convex articulation surface  147  are matingly engaged. In other words, the higher the wall  216  the more force that is required for the convex articulation surface  147  of the head  146  to jump or move over the top of the wall  216 . Thus, it will be appreciated that stability of the concave-convex articulation surface interface is increased as the height of the wall  216  increases, thereby becoming more constrained. As the wall  216  increases in height, a hemispherical capture of the head  146  and the convex articulation surface  147  may occur with respect to the concave articulation surface  214 . 
     In a substantially non-constrained embodiment of the present disclosure, the wall  216  may not function to constrain the convex articulation surface  147  of the head  146  to a large degree. In other words, in the substantially non-constrained embodiment less than about twenty percent of the convex articulation surface  147  of the head  146 , when seated in the concave articulation surface  214 , is surrounded by the wall  216 . 
     In another embodiment, the wall  216  may be formed such that it may extend around the convex articulation surface  147  of the insert  140  in a semi-constrained manner. In other words, about twenty percent to about fifty percent of the convex articulation surface  147  of the head  146 , when seated in the concave articulation surface  214 , is surrounded by the wall  216  (see  FIG. 1 ). 
     It has been found to be advantageous that the wall  216  may extend around at least thirty percent of the convex articulation surface  147  of the insert  140 . As the contact interface between the convex articulation surface  147  of the liner  140  and the concave articulation surface  214  of the concave articulation surface portion  210  increases the amount of stress at the interface decreases. Thus, there is a lower potential coefficient of friction and therefore a reduction in wear debris generation at the interface. Thus, by maximizing the surface area contact between the convex articulation surface  147  and the concave articulation surface  214 , the coefficient of friction at the interface is reduced and the amount of stress at the interface is also reduced. The above advantages are made possible by the design of the present disclosure, i.e., with the convex articulation surface  147  being located on the acetabular side of the hip joint and the concave articulation surface  214  being located on the femoral side of the hip joint. 
     In another embodiment, the wall  216  may be formed such that it may extend around the convex articulation surface  147  of the head  146  of the insert  140  in a constrained manner. In other words, more than about fifty percent of the convex articulation surface  147  of the head  146 , when seated in the concave articulation surface  214 , is surrounded by the wall  216 , as illustrated in  FIG. 11 . 
     One of skill in the art can readily determine the indications of when a substantially non-constrained embodiment, a semi-constrained embodiment or a fully constrained embodiment is advantageous over the others. For example, a patient who has chronic dislocation problems is a prime candidate for a fully constrained embodiment, whereas a semi-constrained or potentially a substantially non-constrained embodiment may be used for active patients. 
     It will be appreciated that the distal stem portion  250  may be lengthened or shortened depending upon the desired outcome. In one embodiment, the distal stem portion  250  may be at least 200 mm in length and may be bowed or curved in a manner that substantially matches the shape of the medullary canal of the patient&#39;s femur. In such instances, the modular aspects of the bi-body or tri-body stems of the present disclosure may be advantageously used to increase the bony contact between the proximal stem portion  210  and the medial calcar portion of the femur. Increased bony contact by the second component may increase the overall joint stability of the entire implant. 
     If a modular distal stem portion  250  or even a component comprising both the proximal body portion  240  and the distal stem portion  250  as a single component (but that is modular with respect to the concave articulation surface portion  210 ), has been implanted in a patient&#39;s body and should the patient require a revision surgery, then the second component  200  can be utilized in a traditional hip arthroplasty. In other words, the modular concave articulation surface portion  210  can be removed from the patient leaving the distal stem portion  250 , or the proximal body portion  240  and the distal stem portion  250 , in place in the patient&#39;s femoral canal. Due to its modularity, the concave articulation surface portion  210  can be replaced with a traditional femoral neck and head. In such a case, only the acetabular component, i.e., the first component  100 , will have to be completely removed, thereby saving valuable operating time and increasing the efficacy of the second component  200  because the distal stem component  250  does not have to be removed or replaced. 
     It will be appreciated that the structure and apparatus disclosed herein regarding the second component  200  is merely one example of a means for articulating with the convex articulation surface  147  of the insert  140  in a semi-constrained manner, and it should be appreciated that any structure, apparatus or system for articulating with the convex articulation surface  147  of the insert  140  in a semi-constrained manner, which performs functions the same as, or equivalent to, those disclosed herein are intended to fall within the scope of a means for articulating with the convex articulation surface  147  of the insert  140  in a semi-constrained manner, including those structures, apparatus or systems for articulating with the convex articulation surface  147  of the insert  140  in a semi-constrained manner, which are presently known, or which may become available in the future. Anything which functions the same as, or equivalently to, a means for articulating with the convex articulation surface  147  of the insert  140  in a semi-constrained manner falls within the scope of this element. 
     It will be appreciated that the structure and apparatus disclosed herein is merely one example of a means for indexing one modular component with respect to another component, and it should be appreciated that any structure, apparatus or system for indexing one modular component with respect to another component, which performs functions the same as, or equivalent to, those disclosed herein are intended to fall within the scope of a means for indexing one modular component with respect to another component, including those structures, apparatus or systems for indexing one modular component with respect to another component, which are presently known, or which may become available in the future. Anything which functions the same as, or equivalently to, a means for indexing one modular component with respect to another component falls within the scope of this element. 
     It will be appreciated that the structure and apparatus disclosed herein is merely one example of a means for interlocking one modular component with respect to another component, and it should be appreciated that any structure, apparatus or system for interlocking one modular component with respect to another component, which performs functions the same as, or equivalent to, those disclosed herein are intended to fall within the scope of a means for interlocking one modular component with respect to another component, including those structures, apparatus or systems for interlocking one modular component with respect to another component, which are presently known, or which may become available in the future. Anything which functions the same as, or equivalently to, a means for interlocking one modular component with respect to another component falls within the scope of this element. 
     In accordance with the features and combinations described above, a useful method of restoring joint mechanics in a hip joint, may comprise the steps of: 
     (a) providing an acetabular or first component  100  comprising a convex articulation surface  147  and a femoral or second component  200  comprising a concave articulation surface  214 ; 
     (b) implanting the acetabular or first component  100  in a surgically prepared acetabulum of a patient such that the convex articulation surface  147  extends from the patient&#39;s acetabulum; and 
     (c) implanting the femoral or second component  200  in a surgically prepared proximal femur, such that the concave articulation surface  214  extends from the proximal femur in an orientation to receive the convex articulation surface  147  of the acetabular or first component  100 . 
     Those having ordinary skill in the relevant art will appreciate the advantages provide by the features of the present disclosure. For example, it is a potential feature of the present disclosure to restore the normal or natural joint mechanics using the components disclosed herein, or in other words, target restoration of the natural joint mechanics in, for example, a hip joint. Another potential feature of the present disclosure is to stabilize the joint by utilizing the device disclosed herein. It is yet another potential feature of the present disclosure to reduce stress and strains at the bearing or articulating interface between the first component  100  and the second component  200 , to thereby reduce wear debris. Another potential feature includes providing modular, indexable components to aid in correcting version, offset in a joint. 
     In the foregoing Detailed Description of the Disclosure, various features of the present disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby incorporated into this Detailed Description of the Disclosure by this reference, with each claim standing on its own as a separate embodiment of the present disclosure. 
     It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present disclosure. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present disclosure and the appended claims are intended to cover such modifications and arrangements. Thus, while the present disclosure has been shown in the drawings and described above with particularity and detail, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in number, size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein.