Patent Publication Number: US-10307261-B2

Title: Revision stepped tibial implant

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/186,350, filed Jun. 17, 2016, now U.S. Pat. No. 9,943,413, which is a continuation of U.S. patent application Ser. No. 15/011,402, filed Jan. 29, 2016, which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/110,410, filed Jan. 30, 2015, which are hereby incorporated by reference herein in their entireties, including but not limited to those portions that specifically appear hereinafter, the incorporation by reference being made with the following exception: In the event that any portion of the above-referenced applications are inconsistent with this application, this application supercedes the above-referenced applications. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND 
     1. The Field of the Present Disclosure 
     The present disclosure relates generally to knee joint prosthesis and more particularly to a revision tibial implant and method of utilizing and implanting the same. 
     2. Description of Related Art 
     Conventionally a knee joint prosthesis can include a femoral implant and a tibial implant. The femoral implant and tibial implant are designed to be surgically implanted into the distal end of the femur and the proximal end of the tibia, respectively. The femoral implant is further designed to cooperate with the tibial implant in simulating the articulating motion of an anatomical knee joint. 
     These femoral and tibial implants, in combination with ligaments and muscles, attempt to duplicate natural knee motion as well as absorb and control forces generated during the range of flexion. In some instances however, it may be necessary to replace or modify an existing femoral and/or tibial implant. Such replacements are generally referred to as revision implants. It may be necessary for a revision implant to eliminate one or more motions, thereby increasing the level of restraint, in order to provide adequate stability. In this way, it may be desirable to provide a cruciate retaining (CR) revision knee, a fully constrained revision knee, a posterior stabilized (PS) revision knee or a hinged revision knee for example. 
     There are also circumstances when a fixed bearing implant must be changed out for a mobile bearing implant. While this change is possible, it can create added damage and deterioration of the remaining tibial bone due to the need to remove the tibial implant to replace it. Therefore, there is a need to enable a surgeon to change or modify an existing implant from a fixed bearing to a mobile bearing (or vice versa), without removing the tibial implant from the tibial bone, thus saving the integrity of the surrounding tibial bone. 
     The features and advantages of the present 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 present disclosure without undue experimentation. The features and advantages of the present 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 side view of an embodiment of the tibial implant of the present disclosure; 
         FIG. 2  is a cross-sectional side view the embodiment of  FIG. 1 ; 
         FIG. 3  is an exploded cross-sectional side view of the embodiment of  FIG. 1 ; 
         FIG. 4  is an exploded perspective view of the embodiment of  FIG. 1 ; 
         FIG. 5  is a partial cross-sectional view of the embodiment of  FIG. 1 ; 
         FIG. 6  is a perspective view of an example of an offset ring of the present disclosure; 
         FIG. 7  is a perspective view of the stem of the present disclosure; 
         FIG. 8  is a side view of the stem of  FIG. 7 ; 
         FIG. 9  is a cross-sectional view of another embodiment of the present disclosure; 
         FIG. 10  is a perspective view of the base plate of the embodiment of  FIG. 9 ; and 
         FIG. 11  is a cross-section view of an alternative embodiment 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. 
     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. 
     Applicant has discovered a novel apparatus and method for a revision tibial implant having modularity between a fixed and mobile bearing configuration. 
     Applicant&#39;s method of initially implanting and interchanging a revision stepped tibial implant is also discussed herein below. In an exemplary method, insertion of a tibial implant is accomplished by drilling or otherwise creating a cavity in the proximal end of a tibial bone. A stem is then inserted into the cavity such that the outer surface of the stem engages and contacts the surrounding bone. 
     The stem can then be threadedly engaged with a tibial sleeve, allowing the stem to be easily assembled with, or disengaged from, the tibial sleeve. This modularity between the stem and the tibial sleeve can enable a surgeon or user to customize the sizes of a stem and a tibial sleeve to accommodate the specific needs of each particular tibial implant. 
     On the distal end of the stem is a male threaded portion which can be threadedly mated with a female threaded portion located on the distal end of the tibial sleeve. This threaded engagement enables different sized tibial sleeves to mate with a variety of different sized stems. 
     The outer surface of the tibial sleeve can include tapered steps which can improve grafting with the surrounding bone of the tibia after the tibial sleeve is inserted into the tibial and threadedly attached to the stem. This improved grafting can better secure the tibial implant in place and reduce the likelihood of complications or failure stemming from the unintentional displacement of the tibial implant. 
     The tibial sleeve, can include an annular male portion having a central bore that is coaxial with the tibial sleeve. The male end can extend from the distal end of the tibial sleeve, and receive an offset ring which is designed and configured to fit securely around and be removably fixed to the male end of the tibial sleeve, via a friction fit, cold weld or other desired securement mechanism. Thus, after the tibial sleeve is connected to the stem, the offset ring is secured around the male end of the tibial sleeve. The offset ring is cylindrical in shape, having a substantially circular cross-section, but includes a bore that is offset from the central axis of the offset ring. The offset of the bore can be substantially zero, meaning the bore can be coaxial with the central axis of the offset ring. 
     A base plate can then be connected to tibial sleeve. The base plate can include, on the distal end, a female portion that includes a counter-sunk bore configured to receive the offset ring. The outer surface of the offset ring may be configured to engage and mate with the female portion of the base plate, such that the female portion is removably fixed to the offset ring via a friction fit, cold weld or other desired securement mechanism. The offset configuration of the bore within the offset ring may enable the base plate to be axially offset with respect to the tibial sleeve and stem. The removable engagement between the base plate and the offset ring can enable a surgeon or user to remove the base plate from the tibial sleeve, and substitute a different base plate and/or offset ring, without having to remove the tibial sleeve and stem from the tibial bone. The resulting modularity between the offset ring and base plate, with respect to the tibial sleeve, can enable a surgeon or user to change or modify the size, positioning (relative to the tibial sleeve and stem), or type of base plate, without also removing tibial sleeve and stem. 
     This modularity can provide significant benefits, for example, after inserting the tibial implant, a surgeon or user can change and replace a base plate and/or offset ring if the ideal size or positioning of the base plate needs to be modified, without removing the stem and tibial sleeve from the patient which can cause unwanted damage to the tibial bone. Another example of the benefits of modularity of the base plate and offset ring with respect to the tibial sleeve can occur when changes or repairs need to be made to a preexisting tibial implant. In this case a surgeon or user can exchange the preexisting base plate with a different base plate, to accommodate a new or different condition, or repair a broken base plate, all without removing the stem and tibial sleeve, saving further damage to the tibial bone. 
     The proximal end of the base plate can be configured with a counter-sunk tray portion having a substantially planar central surface with a central bore. The tray of the base plate may be configured to receive a platform. Thus, after the base plate has been secured to the tibial sleeve (about the offset ring and male end of the tibial sleeve) a platform may be secured to the base plate. The platform can include various features or embodiments to accommodate various levels of restraint needed by a patient, for example, alternative platforms can be designed and used to accommodate a Posterior Cruciate (PS), Cruciate Retaining (CR), Constrained Condylar Knee (CCK) or a hinge type platform. 
     The platform can also include a spike that extends from a base of the platform in a proximal direction, and a post that extends in an opposite distal direction from the spike. As the platform is secured to the base plate, the post extends through the bore of the base plate, through the offset ring and into the central bore of the male end of the tibial sleeve. The central bore of the tibial sleeve can be sized to retain the post and provide strength and stability to the platform, via the post. The post is then removable from the central bore of the tibial sleeve, to enable simple and easy removal of the platform to accommodate a replacement platform, without requiring a corresponding removal of the tibial sleeve and stem. 
     The platform is configured to engage with a corresponding femoral implant (not shown), thus completing a total knee replacement implant. The disclosed tibial implant can be a fixed bearing system, where the platform is fixed to the tray, such that the platform can not rotate with respect to the tray or base plate. In the fixed bearing configuration the platform can be cold welded to the tray or fixed using another desired fixation mechanism. 
     Alternatively, the disclosed tibial implant can be a mobile bearing system, where the platform is rotatable with respect to the tray and base plate. When the post of the platform is inserted into the base plate and tibial sleeve, a bushing can be utilized to receive the post. The bushing can be inserted into the bore of the base plate and the central bore of the tibial implant. The bushing can be sized to the central bore of the tibial sleeve without any lateral movement, thus providing lateral stability to the post and platform, while still maintaining smooth rotatability of the platform with respect to the base plate and tibial sleeve. The bushing can reduce the friction of the rotating post, in a mobile bearing configuration, thus improving the life and functionality of both the post and the tibial sleeve. 
     In the disclosed method of changing or modifying a previously used tibial implant, the surgeon or user can readily remove the platform and or base plate, due to the modularity discussed above, in exchange for a different size or type of platform and/or base plate. For example, if a fixed bearing implant, according to the disclosed embodiment, was inserted into a patient&#39;s tibial bone, a surgeon could then remove the fixed bearing platform, and base plate if necessary, and replace it with a mobile bearing platform and base plate, without removing the tibial sleeve and or stem. 
     Referring to  FIGS. 1-6 , the invention includes a revision stepped tibial implant  100 . The implant  100  includes an implant stem  102  that is removably attached to a tibial sleeve  104 . As shown in  FIGS. 2 and 3 , the stem  102  can be threadedly engaged with the tibial sleeve  104  allowing the stem  102  to be easily assembled with, or disengaged from, the tibial sleeve  104 . This modularity between the stem  102  and the tibial sleeve  104  enable a surgeon or user to customize the sizes of stems  102  and tibial sleeve  104  to accommodate the specific need of each particular tibial implant. For example, the respective lengths and substantive diameters of the stem  102  and tibial sleeve  104  can be manufactured to a variety of different dimensions, enabling a surgeon to choose from an array of potential stems  102  and tibial sleeves  104 , that are all equally engagable with one another, to ensure the best or most ideal fit for an intended patient or recipient. 
     The stem  102 , as seen in further detail in  FIGS. 7 and 8 , may include a spike portion  102   a  on the distal end  105  that is substantially straight and may include a plurality of ribs  102   b  extending radially from the spike portion  102   a . This configuration of radially extending ribs  102   b  provides better fixation with surrounding bone of the tibia and reduces any tendency of the stem  102  to rotate once the stem is implanted in the tibial. On the distal end of the stem is a male threaded portion  102   c  which, as explained above, is dimensioned to threadedly mate with a female threaded portion  104   a  located on the distal end  105  of tibial sleeve  104 . This threaded engagement enables different sizes of tibial sleeves  104  to mate with a variety of different sized stems  102 . 
     The tibial sleeve  104  has a generally conical shape tapering down from the proximal end  107 , the proximal end  107  having a larger diameter than the distal end  105 . The outer surface of the tibial sleeve  104  includes a plurality of steps  104   b  that gradually reduce in diameter from the proximal end  107  of the tibial sleeve  104  to the distal end  105 . The steps  104   b  on the outer surface of the tibial sleeve  104  facilitate improved grafting with the surrounding bone of the tibia after implantation of the tibial sleeve  104 . This improved grafting can better secure the implant  100  in place and reduce the likelihood of complications or failure stemming from the unintentional displacement of the tibial implant  100 , particularly when compared to a tibial implant having a substantially smooth outer surface. 
     As shown in  FIGS. 2-5 , the tibial sleeve  104  also includes an annular male portion  106  having a central bore  108  that may be coaxial with the tibial sleeve  104 . The male end  106  extends from the proximal end  107  of the tibial sleeve  104 , but does not extend in the proximal direction beyond an outer rim  110  of the tibial sleeve  104 . The annular male portion or male end  106  may be unitary with the tibial sleeve  104 , or may otherwise be fixedly attached to the tibial sleeve  104 . A spacing between the male end  106  and the outer rim  110  creates an annular engagement groove  112 . 
     The annular groove  112  is configured to receive an ring  114 . The ring  114  may be designed and configured to fit securely around the male end  106  of the tibial sleeve  104  and be removably fixed to the male end  106  of the tibial sleeve  104 , via a friction fit, cold weld or other desired securement mechanism. 
     As shown in  FIG. 6  the ring  114  is cylindrical in shape, having a substantially circular cross-section. The offset ring also includes a bore  116  also having a substantially circular shape. The ring  114  may be an offset ring  114 , wherein the bore  116 , shown in  FIG. 6 , may be offset from the central axis, or center, of the offset ring  114 , meaning that the central axis A-A of the offset ring  114  is not coaxial with the central axis B-B of the bore  116 . The offset configuration of the bore  116  creates a first side  118  of the offset ring having a thicker (in a radial direction) cross-section that the cross-section of an opposing second side  121 . For example, the first side  118  can have a thickness (in the radial direction) that is 1-4 mm greater than the thickness (in the radial direction) of the second side  120  of the offset ring  114 . In another embodiment, the offset ring  114  may be configured with the bore  116  coaxial with the offset ring  114  itself, thus providing a symmetrical offset ring  114 . 
     As shown in  FIGS. 1-6 , a base plate  120  includes, on the distal end  123 , a female portion  122  that includes a counter-sunk bore  127  configured to receive the offset ring  114 . The outer surface of the offset ring  114  is configured to engage and mate with the female portion  122  of the base plate  120 , such that the female portion is removably fixed to the offset ring  114  via a friction fit, cold weld or other desired securement mechanism. The offset configuration of the bore  116  within the offset ring  114 , enables the base plate  120  to correspondingly be offset with respect to the tibial sleeve  104  and stem  102 . 
     The female portion  122  may be configured to receive both the offset ring  114  and the annular male portion  106  of the tibial sleeve  104 . In an embodiment, the female portion  122  may receive only the offset ring  114 . In another embodiment, the female portion  122  may receive only the annular male portion  106  of the tibial sleeve  104 . 
     As shown in  FIG. 5 , the annular engagement groove  112 , or the space provided between the annular male portion, or male end,  106  and the outer rim  110  of the tibial sleeve  104 , may be configured to receive not only the offset ring  114 , but also the female portion  122  of the base plate  120 . The annular engagement groove may comprise a distance between the male end  106  and the outer rim  110  that may vary depending on the desired application and sizes of the offset ring  114  and the base plate  120 . For example, as shown in  FIG. 5 , the annular engagement groove  112  may comprise a distance between the male end  106  and the outer rim  110  that is greater than the distance required for the offset ring  114  and the female portion  122  of the base plate  120  to fit inside the annular engagement groove  112 . The annular engagement groove  112  may be configured to accommodate an symmetrical offset ring  114 , as described above, or an offset ring  114  having a first side that is thicker than a second side, as described above. 
     The removable engagement between the base plate  120  and the offset ring  114 , can enable a surgeon or user to remove the base plate  120  from the tibial sleeve  104 , and substitute a different base plate  120  and/or offset ring  114 , without having to remove the tibial sleeve  104  and stem  102  from the tibia bone. The resulting modularity between the offset ring  114  and base plate  120 , with respect to the tibial sleeve  104 , enables the surgeon or user to change or modify the size, positioning (relative to the tibial sleeve  114  and stem  102 ), or type of base plate  120 , without also removing tibial sleeve  104  and stem  102 . 
     The proximal end  125  of the base plate  120  is configured with a counter-sunk tray portion  124 . The tray portion  124  has a substantially planar central surface  126  having a central bore  128 . The tray portion  124  also includes an outer rim  130  that extends around the perimeter of the central surface  126  and also extends in the proximal direction from the central surface  126 . The tray portion  124  of the base plate  120  is configured to receive a platform  132 . The platform  132  can be formed from a high strength plastic and can include various features or embodiments to accommodate various levels of restraint needed by a patient. For example, alternative platforms can be designed and used to accommodate a Posterior Cruciate (PS), Cruciate Retaining (CR), Constrained Condylar Knee (CCK) or hinge type platform. 
     As shown in  FIGS. 1-5 , the platform  132  can include a spike  134  that extends from a base portion  132   a  of the platform  132  in a proximal direction, and a post  136  extends in an opposite distal direction from the spike  134 . Although the base portion  132   a  of the platform can be made of a plastic material, the post  136  can be made from a metal material, for added strength, which can extend through the base portion  132   a  of the platform  132  and into the spike  134 , providing strength and support to the spike  134  during use. The spike  134  may vary in size and length depending on the level of restraint needed by the patient. Additionally, the location of the spike  134  on the platform  132  can also very, for example, the spike  134  can be offset from the center of the platform, as shown in  FIGS. 2-5 , or the spike can be centered and substantially coaxial with the post  136 . 
     The post  136  extends through the bore  128  of the base plate  120 , through the offset ring  114  and into the central bore  108  of the male end  106  of the tibial sleeve  104 . The central bore of the tibial sleeve can be sized to retain the post  136  and provide strength and stability to the platform  132 , via the post. The post  132  is removable from the central bore  108  of the tibial sleeve  104 , to enable simple and easy removal and replacement of the platform  132 , without requiring a corresponding removal of the tibial sleeve  104  and stem  102 . 
     As discussed above, the tray portion  124  of the base plate  120  is configured to receive the platform  132 , and the platform  132  is configured to engage with a corresponding femoral implant (not shown), thus completing a total knee replacement implant. The tibial implant  100  can be a fixed bearing system, where the platform  132  is fixed to the tray  124 , such that the platform can not rotate with respect to the tray  124  or base plate  120 . In the fixed bearing configuration the platform can be cold welded to the tray  124  or fixed using another desired fixation mechanism. 
     Alternatively, the tibial implant  100  can be a mobile bearing system, where the platform  132  is rotatable with respect to the tray  124  and base plate  120 . As shown  FIGS. 2-5 , the post  136  of the platform can be received within a bushing  138 , where the bushing  138  is also received within the bore  128  of the base plate  120  and the central bore  108  of the tibial implant  104 . The bushing  138  is sized to the central bore  108  of the tibial sleeve  104  without any lateral movement, thus providing lateral stability to the post  136  and platform  132 , while still maintaining smooth rotatability of the platform with respect to the base plate and tibial sleeve  104 . The bushing  138  reduces the friction of the rotating post  136 , thus improving the life and functionality of both the post  136  and the tibial sleeve  104 . 
     In alternative embodiments, a fixed bearing platform  132  can include a shorter post and a bushing  138  is unnecessary, as there is no rotation of the platform  132 . Thus, alternative tibial sleeves can also be utilized, having varying sized central bores  108  to compensate for the use of a bushing  138  in a mobile bearing configuration or the absence of a bushing  138  in a fixed bearing configuration. 
     In other exemplary embodiments and similar to the size versatility of the stem  102 , tibial sleeve  104 , and offset ring  114 , the blase plate  120  and platform  132  can also be made to different lengths, and diameters to accommodate the varying needs of patients and the necessary level of constraint needed for the tibial implant  100 . The varying sizes of all of the different components referenced above, and the above described modularity of the corresponding components, can be interchangeably mixed and matched, creating a matrix of component configurations and possibilities. Of particular benefit is the ability to change the offset ring  114 , base plate  120  and/or platform  132  without removing the stem  102  and tibial sleeve  104 , thus preserving the integrity of the tibial bone surrounding the stem  102  and tibial sleeve  104 . 
     In another exemplary embodiment, as shown in  FIGS. 9 and 10 , a tibial implant  200  is illustrated utilizing the same modularity characteristics discussed above with respect to tibial implant  100 . For example, the same stem  102  having a male threaded portion  102   c , mates with a tibial sleeve  204  via a female threaded portion  204   a . Tibial sleeve  204  has the same features as the corresponding tibial sleeve  104 , except the male end  206  of the tibial sleeve  204  does not include a central bore. However, the male end  206  of the tibial sleeve  204  is still configured to receive the offset ring  114 . The tibial implant  200  also includes a base plate  220  having the same type of female end  222  as the corresponding base plate  120 . The base plate  220  having the same type of female end  222  as the base plate  120 , illustrates the common modularity of the components described above with respect to tibial implant  100  and tibial implant  200 . 
     The base plate  220  is different from base plate  120  in that there is no bore that extends through the base plate  220 , or tray portion  124  of the base plate  120 . Instead, base plate  220  includes a substantially planar proximal surface  225  having a central depression  227 . The proximal surface can be fixed to a corresponding platform (not shown) using cement, glue or other desired adhesive of attachment mechanism. The depression  224  can receive a post extending from the platform, and the post may be shorter that the post  136  of platform  132  described above. 
     In another exemplary embodiment, as shown in  FIG. 11 , a tibial implant  300  is illustrated utilizing the same modularity characteristics discussed above with respect to tibial implant  100 . For example, the same stem  102  having a male threaded portion  102   c , mates a tibial sleeve  304  via a female threaded portion  304   a . Tibial sleeve  304  has the same features as the corresponding tibial sleeve  104 , except the male end  306  of the tibial sleeve  204  does not include a central bore, but instead includes a threaded bore  307  which is configured to threadedly mate with a set screw  309 . A male end  306  of the tibial sleeve  304  is still configured to receive the offset ring  114 , in the same way tibial sleeves  104  and  204  also receive the offset ring  114 . 
     The tibial implant  300  also includes a base plate  320  having the same type of female end  322  as the corresponding base plate  120 . The base plate  220  having the same type of female end  222  as the base plate  120 , illustrates the common modularity of the components described above with respect to tibial implant  100  and tibial implant  200 . 
     The base plate  320  is different from base plate  220  in that there is a central bore  329  that is configured to receive the set screw  307 . Thus the set screw  307  can secure the base plate  320  to tibial sleeve  304  and add strength and stability to the connection, beyond the use of a cold weld or press fit connection. Base plate  320  also includes a substantially planar proximal surface  325  having a central depression  327 . The proximal surface can be fixed to a corresponding platform (not shown) using cement, glue or other desired adhesive or attachment mechanism. The depression  324  can receive a post extending from the platform, and the post may be shorter than the post  136  of platform  132  described above. 
     The tibial sleeves and base plates of the present disclosure above may be formed of a metal material (or other desired bio compatible material) having a non-smooth surface (i.e. porous coating, trabecular metal, gription, bio-foam or any other suitable non-smooth surface) which may be ideal for an un-cemented configuration, or a substantially smooth outer surface when used in conjunction with a cement product. 
     In accordance with the features and combinations described above, a tibial implant may comprise: 
     a stem; 
     a tibial sleeve having a proximal end and a distal end, wherein the proximal end includes an annular male portion; 
     an offset ring having a central bore that is offset from the center of the offset ring, wherein the bore of the offset ring receives the annular male portion of the tibial sleeve; and 
     a base plate having a proximal end and a distal end, wherein the distal end of the base plate forms a female portion, and wherein the female portion receives both the offset ring and the male portion of the tibial sleeve. 
     The tibial sleeve including a stepped exterior surface. 
     The offset ring being removably engaged with the tibial sleeve. 
     The base plate being removably engaged with the offset ring and tibial sleeve. 
     The stem being threadedly engaged with the tibial sleeve. 
     The tibial sleeve also including an outer rim that extends from the proximal end of the tibial sleeve and surrounds the annular male portion. 
     The outer rim does not extend further in the proximal direction than the annular male portion. 
     The offset ring also includes a first side of the bore and a second side of the bore, the second side opposite the first side, wherein the first side is 1 to 4 mm thicker in a radial direction than the second side. 
     The tibial implant also includes a platform having a base portion and a post extending in a distal direction from the base portion, wherein the post extends through a bore in the base plate and a central bore in the tibial sleeve. 
     The platform being removably engaged to the base plate and tibial sleeve. 
     The platform being rotatable with respect to the base plate and tibial sleeve. 
     The platform is not rotatable with respect to the base plate and tibial sleeve. 
     In accordance with the features and combinations described above, a tibial implant may comprise: 
     a stem; 
     a tibial sleeve having a proximal end and a distal end, wherein the proximal end includes an annular male portion; 
     a base plate having a proximal end and a distal end, wherein the distal end of the base plate forms a female portion, and wherein the female portion receives the male portion of the tibial sleeve, 
     a platform having a base portion and a post extending in a distal direction from the base portion, wherein the post extends through a bore in the base plate and a central bore in the tibial sleeve. 
     In accordance with the features and combinations described above, a tibial implant may comprise: 
     a stem; 
     a tibial sleeve having a proximal end and a distal end, wherein the proximal end includes an annular male portion, the tibial sleeve also including a stepped exterior surface and an outer rim that extends from the proximal end of the tibial sleeve and surrounds the annular male portion, the outer rim not extending further in the proximal direction than the annular male portion; 
     an offset ring having a central bore that is offset from the center of the offset ring, wherein the bore of the offset ring receives the annular male portion of the tibial sleeve; 
     a base plate having a proximal end and a distal end, wherein the distal end of the base plate forms a female portion, and wherein the female portion receives both the offset ring and the male portion of the tibial sleeve; and 
     a platform having a base portion and a post extending in a distal direction from the base portion, wherein the post extends through a bore in the base plate and a central bore in the tibial sleeve; 
     wherein the offset ring is removably engaged with the tibial sleeve, and the base plate is removably engaged with the tibial sleeve. 
     In accordance with the features and combinations described above, a method of utilizing a tibial implant may comprise: 
     inserting a stem into a tibial bone; 
     inserting a tibial sleeve into the tibial bone, the tibial sleeve having a proximal end and a distal end, wherein the proximal end includes an annular male portion; 
     connecting a base plate to the tibial sleeve, the base plate having a proximal end and a distal end, wherein the distal end of the base plate forms a female portion, and wherein the female portion receives the male portion of the tibial sleeve when connected; and 
     connecting a platform to the tibial sleeve, the platform having a base portion and a post extending in a distal direction from the base portion, wherein the post extends through a bore in the base plate and a central bore in the tibial sleeve when connected. 
     The method may also include: connecting an offset ring to the tibial sleeve, the offset ring having a central bore that is offset from the center of the offset ring, wherein the bore of the offset ring receives the annular male portion of the tibial sleeve when connected. 
     The method may also include: removing the offset ring from connection with the tibial sleeve without removing the tibial sleeve from the tibial bone. 
     The method may also include: removing the base plate from connection with the tibial sleeve without removing the tibial sleeve from the tibial bone. 
     The method may also include: removing the platform from connection with the tibial sleeve without removing the tibial sleeve from the tibial bone. 
     The platform is not rotatable with respect to the base plate and tibial sleeve. 
     The method may also include: removing the platform from connection with the tibial sleeve without removing the tibial sleeve from the tibial bone; and 
     The method may also include: connecting a replacement platform to the tibial sleeve, wherein the replacement platform is rotatable with respect to the base plate and tibial sleeve. 
     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 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 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.