Patent Publication Number: US-2015081028-A1

Title: Adaptor for modular joint prostheses

Description:
CLAIM OF PRIORITY 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/879,435, filed on Sep. 18, 2013, the benefit of priority of which is claimed hereby, and which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Joint replacement procedures are commonly performed to alleviate pain and loss of function in injured and diseased joints. A human knee is a joint, for example, connects a femur to a tibia (sometimes referred to as the thigh bone and the shin bone, respectively). The knee allows for pivoting between the femur and the tibia. The pivoting has a pivot axis aligned with the medial-lateral direction. Some types of injury, disease, or degeneration can produce pain and/or restricted motion in the knee joint. One treatment for certain types of damage to a knee joint is surgery. For relatively mild knee damage, the knee may be repaired. For more severe damage, the knee may be replaced. 
     In total knee replacement surgery, all of the articulating elements within the knee joint are replaced. During the surgery, a distal end (sometimes referred to as an inferior end or a bottom end) of the femur is cut to a particular shape, and then a femoral implant is attached to the cut distal end of the femur. The femoral implant typically includes a pair of convex condylar surfaces. The condylar surfaces are shaped to slide within corresponding concave bearing indentations on a tibial bearing surface. The tibial bearing surface is typically formed from a hard plastic, which allows the condylar surfaces to slide in the indentations with reduced friction. 
     In some surgical cases, there has been a loss of bone at the distal portion of the femur and/or the proximal portion of the tibia. In order to compensate for the missing bone, a bone augments can be employed along with the other components of the prosthesis. The augments can be attached between an epiphyseal replacement portion (e.g. the articulating portion) and a diaphyseal anchoring portion (e.g. the stem) of the joint replacement prosthesis. 
     Modular prosthetic components are useful, at least in part, because they allow the surgeon to assemble components in a variety of configurations at the time of surgery to meet specific patient needs relative to size and geometry. For example, modular femoral components can include separate stem and articulating condylar components that can be assembled in a variety of configurations. Likewise, modular tibial components can include separate convex tibial bearing components, tibial platforms, and stems, which can be assembled in a variety of configurations. The use of augments in prosthetic systems can complicate modularity, as surgeons may wish to mix and match augments and femoral and tibial prosthetic components from different surgical kits and from different manufacturers. 
     SUMMARY 
     Examples according to this disclosure are directed to an adaptor that can be inseparably coupled to a bone augment and which is configured to be connected, at one end of the adaptor, to an epiphyseal replacement portion and, in some cases, is configured to be connected, at the other end of the adaptor, to a diaphyseal anchoring portion of a modular joint replacement prosthesis. 
     Modular joint replacement prostheses can increase the adaptability of a prosthesis system to varying degrees of damage and/or disease to the joint, which may, in turn, improve surgical outcomes. Modular joint replacement systems generally include a prosthesis for each bone of the joint. Each prosthesis can include separate epiphyseal replacement portions and diaphyseal anchoring portions. Example epiphyseal replacement portions include a proximal femoral component in a hip prosthesis, a distal femoral component in a knee prosthesis, a proximal tibial component in a knee prosthesis, and a distal humeral component in a shoulder prosthesis. The diaphyseal anchoring portions can include an intramedullary stem configured to be implanted within a medullary cavity of the diaphysis of a bone of the joint. The epiphyseal portions can include multiple components or sections. For example, a proximal femoral component can include a neck and/or body interposed between the intramedullary stem and a femoral head. 
     Joint replacement prosthesis may also include bone augments, which are configured to compensate for bone loss that occurs as the result of damage and/or disease to the joint and/or as the result of the surgical procedure to replace or repair the joint. Bone augments can be adapted for different portions of a bone. For example, joint prostheses can include one or both of metaphyseal and diaphyseal augments. In any case, the augments are generally arranged between the epiphyseal replacement portions and diaphyseal anchoring portions of a modular joint replacement prosthesis. 
     The use of augments in prosthetic systems can complicate modularity, as surgeons may wish to mix and match augments and femoral and tibial prosthetic components from different surgical kits and from different manufacturers. As such, examples according to this disclosure are directed to an adaptor that can be inseparably coupled to a bone augment and which is configured to be connected to an epiphyseal replacement portion and to a diaphyseal anchoring portion of a modular joint replacement prosthesis. 
     One example according to this disclosure includes an adaptor for a modular prosthetic device configured to partially or completely replace a human joint. The adaptor includes a tapered outer surface and first and second ends. The tapered outer surface is configured to be received within a cavity of an augment. The cavity includes a tapered inner surface. The tapered outer surface of the adaptor and the tapered inner surface of the central cavity of the augment are configured to interlock the adaptor and the augment. The first end of the adaptor is configured to be coupled to an epiphyseal component of the modular prosthetic device. The second end of the adaptor is configured to be coupled to an intramedullary stem of the modular prosthetic device. 
     In other examples, the augment and the adaptor can be coupled to one another by mechanisms other than interlocking tapered surfaces. For example, the augment and adaptor can be press or interference fit to one another. Regardless of how the two components are connected, the augment and adaptor are configured to be generally inseparable and the adaptor is configured to be connected, at one end, to an epiphyseal replacement portion and, at the other end, to a diaphyseal anchoring portion of a modular joint replacement prosthesis. In one example, the augment and adaptor are inseparably coupled to one another and the adaptor is configured to be connected, at one end, to a number of different epiphyseal replacement portions and, at the other end, to a number of different diaphyseal anchoring portions. 
     The details of examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of examples according to this disclosure will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  schematically depicts an example modular knee repair or replacement prosthesis including a bone augment adaptor in accordance with this disclosure. 
         FIGS. 2A and 2B  depict elevation and section views, respectively, of a distal femoral prosthesis including an example adaptor in accordance with this disclosure. 
         FIG. 3  depicts an example proximal tibial prosthesis including another example adaptor in accordance with this disclosure. 
         FIGS. 4A and 4B  depict the adaptor, bone augment, and bushing of the proximal tibial prosthesis of  FIG. 3  in greater detail. 
         FIG. 5  is a flowchart depicting an example method in accordance with this disclosure. 
         FIG. 6  depicts a section view of a distal femoral prosthesis including another example adaptor in accordance with this disclosure. 
         FIG. 7  depicts a section view of another example adaptor in accordance with this disclosure. 
         FIG. 8  schematically depicts an example modular knee repair or replacement prosthesis including adaptors in accordance with this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     As noted above, examples according to this disclosure are directed to adaptors that can be inseparably coupled to a bone augment and which are configured to be connected, at one end of the adaptor, to an epiphyseal replacement portion and, in some cases, at the other end of the adaptor, to a diaphyseal anchoring portion of a modular joint replacement prosthesis. 
     One example of a joint prosthesis is a knee repair or replacement prosthesis, which can include a femoral prosthesis and/or a tibial prosthesis. The femoral prosthesis can include an epiphyseal replacement portion including a pair of convex condylar surfaces that can slide within corresponding concave bearing indentations on a tibial bearing surface of the tibial prosthesis. The condylar component of the femoral prosthesis can be coupled to an intramedullary stem, which extends proximally from the condylar component, and attaches to a cut distal end of the femur. The tibial bearing surface of the tibial prosthesis can be disposed on a proximal side of a tibial platform. An intramedullary stem extends distally from the tibial platform, and attaches to a cut proximal end of the tibia. 
     One example according to this disclosure includes an adaptor for such a knee prosthesis. The adaptor includes a tapered outer surface and first and second ends. The tapered outer surface of the adaptor is configured to be received within a cavity of a bone augment. The bone augment could be, e.g., a diaphyseal or metaphyseal femoral augment that augments the cut proximal end of the femur to which the prosthesis is attached. The cavity of the augment includes a tapered inner surface. For example, the femoral augment can include a central bore that includes a tapered profile along a portion or all of the axial length of the bore. The tapered outer surface of the adaptor and the tapered inner surface of the central cavity of the augment are configured to interlock the adaptor and the augment. 
     The first end of the adaptor is configured to be coupled to an epiphyseal component of the knee repair or replacement prosthesis. For example, the first end of the adaptor can be coupled to a distal femoral component, which includes medial and lateral condyles. The second end of the adaptor is configured to be coupled to an intramedullary stem of the knee repair or replacement prosthesis, which is configured to be affixed within the medullary cavity of the femur. 
     As used herein, “proximal” refers to a direction generally toward the torso of a patient, and “distal” refers to the opposite direction of proximal, i.e., away from the torso of a patient. “Anterior” refers to a direction generally toward the front of a patient or knee, and “posterior” refers to the opposite direction of anterior, i.e., toward the back of the patient or knee. In the context of a prosthesis alone, such directions correspond to the orientation of the prosthesis after implantation, such that a proximal portion of the prosthesis is that portion which will ordinarily be closest to the torso of the patient, the anterior portion closest to the front of the patient&#39;s knee, etc. 
     Similarly, knee and other prostheses and augments in accordance with the present disclosure may be referred to in the context of a prosthesis coordinate system including three mutually perpendicular reference planes, referred to herein as the transverse, coronal and sagittal planes of the knee prosthesis. Upon implantation and with a patient in a standing position, a transverse plane of the knee prosthesis is generally parallel to an anatomic transverse plane, i.e., the transverse plane is inclusive of imaginary vectors extending along medial/lateral and anterior/posterior directions. Coronal and sagittal planes of the knee prosthesis are also generally parallel to the coronal and sagittal anatomic planes in a similar fashion. Thus, a coronal plane of the prosthesis is inclusive of vectors extending along proximal/distal and medial/lateral directions, and a sagittal plane is inclusive of vectors extending along anterior/posterior and proximal/distal directions. As with anatomic planes, the sagittal, coronal and transverse planes of a knee prosthesis are mutually perpendicular to one another. For purposes of the present disclosure, reference to sagittal, coronal and transverse planes is with respect to a knee prosthesis unless otherwise specified. 
       FIG. 1  schematically depicts example modular knee repair or replacement prosthesis  100 , which includes bone augment adaptors in accordance with this disclosure. In  FIG. 1 , knee prosthesis  100  includes distal femoral prosthesis  102  and proximal tibial prosthesis  104 . Distal femoral prosthesis  102  includes epiphyseal replacement portion  106  including medial and lateral condyles  108 ,  110 , respectively. Distal femoral prosthesis  102  also includes diaphyseal bone augment  112 , intramedullary stem  114 , and adaptor  116 . Diaphyseal augment  112  is interposed between epiphyseal replacement portion  106  and intramedullary stem  114 . Adaptor  116  is arranged within and coupled to a central cavity of augment  112 . The proximal end of adaptor  116  is connected to intramedullary stem  114  and the distal end is connected to epiphyseal replacement portion  116 . 
     Proximal tibial prosthesis  104  includes epiphyseal replacement portion  118  including tibial bearing  120  and platform  122 . Tibial prosthesis  104  also includes augment  124  and intramedullary stem  126 . The distal side of tibial bearing  120  is connected to the proximal side of platform  122 . Although not shown in  FIG. 1 , platform  122  can include a protrusion extending distally into a central cavity of augment  124 . Bone augment  124  is interposed between platform  122  and intramedullary stem  126 . Intramedullary stem  126  can extend through the central cavity of augment  124  to connect to platform  122 . 
     Portions or all of distal femoral prosthesis  102  and proximal tibial prosthesis  104  can be fabricated from a variety of biologically compatible materials and by a variety of processes including machining, casting, forging, compression molding, injection molding, sintering, and/or other suitable processes. In some examples, all of the portions of femoral prosthesis  102  and/or tibial prosthesis  104  are fabricated from the same material, while, in other examples, different portions of the prostheses are fabricated from different materials. In one example, one or more portions of femoral prosthesis  102  and/or tibial prosthesis  104  are fabricated from metals, polymers, ceramics, and/or other suitable materials. For example, one or more portions of femoral prosthesis  102 , including adaptor  116 , and/or tibial prosthesis  104  may be made of a cobalt-chromium alloy. Other metals suitable for femoral prosthesis  102 , including adaptor  116 , and/or tibial prosthesis  104  (including in combination with cobalt and/or chrome) include titanium, aluminum, vanadium, molybdenum, hafnium, nitinol, molybdenum, tungsten, nickel, tantalum, and stainless steel. 
     The example of  FIGS. 1  is described with reference to adaptor  112  in accordance with this disclosure included in distal femoral prosthesis  102 . However, in other examples, an adaptor in accordance with this disclosure could also be included in a modular tibial prosthesis like proximal tibial prosthesis  104 . For example, tibial prosthesis  104  could include an adaptor that is arranged within and coupled to the central cavity of augment  124 . In such an example, proximal end of the tibial adaptor could be connected to intramedullary stem  126  and the distal end could be connected to epiphyseal replacement portion  118 . 
     In practice, knee prosthesis  100  is configured to be implanted in a patient to alleviate damage and/or disease of the patient&#39;s knee. Distal femoral prosthesis  102  is implanted in the distal end of a femur of the patient and replaces the epiphyseal portion of the femur, including the articulating medial and lateral condyles. Tibial prosthesis  104  is implanted in the proximal end of a tibia of the patient and replaces the epiphyseal portion of the tibia, including the articular surfaces of the tibia bearing the condyles. 
     Medial and lateral condyles  108 ,  110  of epiphyseal replacement portion  116  each include convex bearing surfaces that are configured to approximate the condyles of the patient&#39;s femur. Tibial bearing  120  includes concave bearing surfaces with which the convex surfaces of condyles  108  and  110  are configured to articulate. 
     Intramedullary stem  114  anchors distal femoral prosthesis  102  to the patient&#39;s femur by being affixed to the medullary cavity of the femur. Similarly, intramedullary stem  126  anchors tibial prosthesis  104  to the patient&#39;s tibia by being affixed to the medullary cavity of the tibia. 
     Diaphyseal femoral bone augment  112  of distal femoral prosthesis  102  and tibial bone augment  124  of tibial prosthesis  104  are configured to compensate for bone loss that occurs as the result of damage and/or disease to the joint and/or as the result of the surgical procedure to replace or repair the joint. Bone augments can be adapted for different portions of a bone. For example, although not illustrated in  FIG. 1 , distal femoral prosthesis  102  can include a metaphyseal bone augment in addition to diaphyseal augment  112 . Such a metaphyseal bone augment could be arranged between diaphyseal augment  112  and medial and lateral condyles  108 ,  110 , respectively. 
     Bone augments  112  and  124  can be made of a porous bone ingrowth material that provides a scaffold for bone ingrowth on multiple surfaces. In some cases, the surfaces of augments  112  and  124  present large, three-dimensional areas of bone ingrowth material to the surrounding healthy bone for long-term fixation of the augment to the bone of the joint. 
     Augments  112  and  124  can be formed from one or multiple pieces of highly porous biomaterial. A highly porous metal structure can incorporate one or more of a variety of biocompatible metals. Such structures are particularly suited for contacting bone and soft tissue, and in this regard, can be useful as a bone substitute and as cell and tissue receptive material, for example, by allowing tissue to grow into the porous structure over time to enhance fixation (i.e., osseointegration) between the structure and surrounding bodily structures. In some examples, an open porous metal structure may have a porosity as low as 55%, 65%, or 75% or as high as 80%, 85%, or 90%, or within any range defined between any pair of the foregoing values. An example of an open porous metal structure is produced using Trabecular Metal™ Technology available from Zimmer, Inc., of Warsaw, Ind. Trabecular Metal™ is a trademark of Zimmer, Inc. Such a material may be formed from a reticulated vitreous carbon foam substrate which is infiltrated and coated with a biocompatible metal, such as tantalum, by a chemical vapor deposition (“CVD”) process in the manner disclosed in detail in U.S. Pat. No. 5,282,861 and in Levine, B. R., et al., “Experimental and Clinical Performance of Porous Tantalum in Orthopedic Surgery”, Biomaterials 27 (2006) 4671-4681, the disclosures of which are expressly incorporated herein by reference. In addition to tantalum, other biocompatible metals may also be used in the formation of a highly porous metal structure such as titanium, a titanium alloy, cobalt chromium, cobalt chromium molybdenum, tantalum, a tantalum alloy, niobium, or alloys of tantalum and niobium with one another or with other metals. It is also within the scope of the present disclosure for a porous metal structure to be in the form of a fiber metal pad or a sintered metal layer, such as a Cancellous-Structured Titanium™ (CSTi™) layer. CSTi™ porous layers are manufactured by Zimmer, Inc., of Warsaw, Ind. Cancellous-Structured Titanium™ and CSTi™ are trademarks of Zimmer, Inc. 
     Generally, a highly porous metal structure will include a large plurality of metallic ligaments defining open voids (i.e., pores) or channels therebetween. The open spaces between the ligaments form a matrix of continuous channels having few or no dead ends, such that growth of soft tissue and/or bone through open porous metal is substantially uninhibited. Thus, the open porous metal may provide a lightweight, strong porous structure which is substantially uniform and consistent in composition, and provides a matrix (e.g., closely resembling the structure of natural cancellous bone) into which soft tissue and bone may grow to provide fixation of the implant to surrounding bodily structures. According to some aspects of the present disclosure, exterior surfaces of an open porous metal structure can feature terminating ends of the above-described ligaments. Such terminating ends can be referred to as struts, and they can generate a high coefficient of friction along an exposed porous metal surface. Such features can impart an enhanced affixation ability to an exposed porous metal surface for adhering to bone and soft tissue. Also, when such highly porous metal structures are coupled to an underlying substrate, a small percentage of the substrate may be in direct contact with the ligaments of the highly porous structure, for example, approximately 15%, 20%, or 25%, of the surface area of the substrate may be in direct contact with the ligaments of the highly porous structure. 
     An open porous metal structure may also be fabricated such that it comprises a variety of densities in order to selectively tailor the structure for particular orthopedic applications. In particular, as discussed in the above-incorporated U.S. Pat. No. 5,282,861, an open porous metal structure may be fabricated to virtually any desired density, porosity, and pore size (e.g., pore diameter), and can thus be matched with the surrounding natural tissue in order to provide an improved matrix for tissue ingrowth and mineralization. In some examples, an open porous metal structure may be fabricated to have a substantially uniform porosity, density, and/or void (pore) size throughout, or to comprise at least one of pore size, porosity, and/or density being varied within the structure. For example, an open porous metal structure may have a different pore size and/or porosity at different regions, layers, and surfaces of the structure. The ability to selectively tailor the structural properties of the open porous metal, for example, enables tailoring of the structure for distributing stress loads throughout the surrounding tissue and promoting specific tissue ingrown within the open porous metal. 
     In other examples, an open porous metal structure may comprise an open cell polyurethane foam substrate coated with Ti-6Al-4V alloy using a low temperature arc vapor deposition process. Ti-6Al-4V beads may then be sintered to the surface of the Ti-6Al-4V-coated polyurethane foam substrate. Additionally, another example of an open porous metal structure may comprise a metal substrate combined with a Ti-6Al-4V powder and a ceramic material, which is sintered under heat and pressure. The ceramic particles may thereafter be removed leaving voids, or pores, in the substrate. An open porous metal structure may also comprise a Ti-6Al-4V powder which has been suspended in a liquid and infiltrated and coated on the surface of a polyurethane substrate. The Ti-6Al-4V coating may then be sintered to form a porous metal structure mimicking the polyurethane foam substrate. Further, another example of an open porous metal structure may comprise a porous metal substrate having particles, comprising altered geometries, which are sintered to a plurality of outer layers of the metal substrate. Additionally, an open porous metal structure may be fabricated according to electron beam melting (EBM) and/or laser engineered net shaping (LENS). For example, with EBM, metallic layers (comprising one or more of the biomaterials, alloys, and substrates disclosed herein) may be coated (layer by layer) on an open cell substrate using an electron beam in a vacuum. Similarly, with LENS, metallic powder (such as a titanium powder, for example) may be deposited and coated on an open cell substrate by creating a molten pool (from a metallic powder) using a focused, high-powered laser beam. 
       FIGS. 2A and 2B  depict elevation and section views, respectively of an example distal femoral prosthesis  200  including adaptor  202  in accordance with this disclosure. As noted above, the use of bone augments in prosthetic systems can complicate modularity, as surgeons may wish to mix and match augments and femoral and tibial prosthetic components from different surgical kits and from different manufacturers. As such, examples according to this disclosure are directed to an adaptor, e.g., adaptor  202 , which can be inseparably coupled to a bone augment and which is configured to be connected to an epiphyseal replacement portion and to a diaphyseal anchoring portion of a modular joint replacement prosthesis. 
     In the example of  FIGS. 2A and 2B , adaptor  202  is inseparably coupled to bone augment  204 . Bone augments and adaptors in accordance with this disclosure are described as being “inseparably” coupled to one another. In this disclosure, an adaptor and augment are inseparably coupled in the sense that the two components are generally used during a surgical procedure as a single component, where the adaptor and augment are not adjustable relative to one another and where the two components are not disconnected. Thus, while it may be possible to physically separate the augment and adaptor, the two components are configured to be inseparable and used as a single component during a joint repair or replacement procedure. The adaptor can be configured to be a generic adaptor. For example, the two ends of the adaptor can be configured to be connected to different epiphyseal replacement portions and different diaphyseal anchoring portions, respectively, of a modular joint replacement prosthesis. In this manner, a bone augment including an inseparable generic adaptor can be mixed and matched with different prosthetic components, e.g. femoral or tibial, including, e.g., from different surgical kits and from different manufacturers. 
     Referring to  FIGS. 2A , distal femoral prosthesis  200  includes epiphyseal replacement portion  206  and intramedullary stem  208 . Epiphyseal replacement portion  206  includes shaft  210  and condylar portion  212  with a medial and a lateral condyle. Bone augment  204  includes thru hole  214  and slot  216 . Thru hole  214  can be a threaded hole configured to receive set screw  218 . Slot  216  can be configured to provide clearance to insert and tighten set screw  220 , which is received in a threaded hole in shaft  210  of epiphyseal replacement portion  206 . The proximal end of adaptor  202  is coupled to intramedullary stem  208 . The distal end of adaptor  202  is coupled to epiphyseal replacement portion  206 . The interconnection between adaptor  202  and augment  204  and adaptor  202  and epiphyseal replacement portion  206  and stem  208  is illustrated in greater detail in  FIG. 2B . 
     Referring to  FIG. 2B , adaptor  202  is inseparably coupled to augment  204 . In the example of  FIG. 2B , adaptor  202  and augment  204  are coupled by a taper-lock, which is also referred to as a self-locking taper. Adaptor  202  interlocks with augment  204  by means of a male taper formed on outer surface  222  of adaptor  202  mated with a complementary female taper formed on inner surface  224  of augment  204 . 
     Adaptor  202  is connected to epiphyseal replacement portion  206  and intramedullary stem  208 . For example, distal end of adaptor  202  is connected to epiphyseal replacement portion  206  and proximal end of adaptor  202  is connected to stem  208 . Distal end of adaptor  202  includes a shaft that defines outer surface  226 . Inscribed in outer surface  226  is channel  228 . Shaft  210  of epiphyseal replacement portion  206  includes a bore that defines inner surface  230 . Outer surface  226  of adaptor  202  defines a male taper that is configured to be received by and interlocked with a female taper defined by inner surface  230  of the bore of shaft  210 . 
     Proximal end of adaptor  202  includes a bore that defines inner surface  232 . The distal end of intramedullary stem  208  includes tapered portion  234 . Inscribed in tapered portion  234  of stem  208  is channel  228 . Inner surface  332  of adaptor  202  defines a female taper that is configured to receive and interlocked with a male taper defined by tapered portion  234  of stem  208 . 
     To ensure a secure fit between adaptor  202  and augment  204  and between adaptor and epiphyseal replacement portion  206  and stem  208 , the taper angle can be chosen to be within the range of self-locking tapers. In one example, the angle, t, of the male taper of adaptor  202  relative to the female taper of augment  204  is in a range from about 1 to about 35 arcminutes, or, from about 1/60 degrees to about 35/60 degrees. In one example, a total included taper angle (both sides of the taper-lock) of adaptor  202  and any of bone augment  204 , epiphyseal replacement portion  206 , and stem  208  in the range of from about 6 degrees to about 19 degrees can be employed. Other particular taper configurations can also be employed to inseparably couple adaptor  202  and augment  204  and to connect adaptor  202  and epiphyseal replacement portion  206  and stem  208 . 
     In the example of  FIGS. 2A and 2B , adaptor  202  is inseparably coupled to augment  204  and connected to epiphyseal replacement portion  206  and stem  208  via a taper-lock. As noted, however, other mechanisms may be employed to connect adaptor  202 , augment  204 , epiphyseal replacement portion  206 , and/or stem  208 . For example, adaptor  202  can be inseparably coupled to augment  204  using a press or interference fit. In one example, adaptor  202  is interference fit with augment  204 . For example, adaptor  202  and augment  204  can be interference fit to one another using thermal expansion of one or both of the components. This type of coupling may also be referred to as a shrink-fit. In one example employing an interference fit, the phenomenon of thermal expansion is employed to couple adaptor  202  and augment  204  by heating or cooling one of the components before assembly and then allowing the heated/cooled component to return to an ambient temperature after assembly. 
     In some examples, the taper-lock between adaptor  202  and augment  204  and between adaptor  202  and epiphyseal replacement portion  206  and/or stem  208  can be augmented by surface features on the male and/or female taper. For example, outer surface  222  that forms the male taper of adaptor  202  may include surface features that enhance the interlock between adaptor  202  and augment  204 . In one example, complementary inner surface  224  of augment  204  may include a shallow female thread and outer surface  222  of adaptor  202  may be texturized such that the roughness of surface  222  is configured to engage the female thread inscribed in inner surface  224  of augment  204 . 
     Additionally, in some cases the taper-lock, press fit, and/or interference fit between adaptor  202  and augment  204  can be augmented by additional coupling mechanisms. In one example, adaptor  202  and augment  204  are taper-locked to one another and subsequently welded or adhered to one another to complete the coupling of the two components. 
     The taper-lock described above between adaptor  202  and epiphyseal replacement portion  206  and stem  208  may not be configured to provide a permanent connection between components. In some cases, the taper-lock may be configured to allow a surgeon to connect adaptor  202  and epiphyseal replacement portion  206  and stem  208  and position the components relative to one another. However, the taper-lock may not be configured to be strong or durable enough to provide a permanent connection between the components. 
     In some examples, therefore, the connections between adaptor  202  and epiphyseal replacement portion  206 , and between adaptor  202  and stem  208  can be achieved or augmented by set screws  218  and  220 , respectively. For example, set screw  218  is threaded to augment  204  and is driven through a hole in adaptor  202  into channel  236  in tapered portion  234  of stem  208  to secure the adaptor and the stem together. The set screw  218  can function to inhibit relative axial movement between adaptor  202  and stem  208 , as well as inhibiting relative rotation between the two components. Similarly, set screw  220  is threaded to shaft  210  of epiphyseal replacement portion  206  and is driven through shaft  210  into channel  228  in adaptor  202 . The set screw  220  can function to inhibit relative axial movement between adaptor  202  and epiphyseal replacement portion  206 , as well as inhibiting relative rotation between the two components. 
     Adaptor  202  can be fabricated from a variety of biologically compatible materials, e.g., including the materials described above with reference to adaptor  116 . For example, adaptor  202  can be fabricated from a cobalt-chromium alloy. 
     Augment  204  can be fabricated from bone ingrowth materials such as those described above with reference to bone augments  112  and  124 . For example, augment  204  can be fabricated from one or multiple pieces of highly porous biomaterial with a porosity as low as 55%, 65%, or 75% or as high as 80%, 85%, or 90%. An example of such a material is produced using Trabecular Metal™ Technology generally available from Zimmer, Inc., of Warsaw, Ind. 
       FIG. 3  depicts an example proximal tibial prosthesis  300  including another example adaptor  302  in accordance with this disclosure. In the example of  FIG. 3 , adaptor  302  is inseparably coupled to augment  304  via bushing  306 . Tibial prosthesis includes adaptor  302 , augment  304 , bushing  306 , platform  308 , and stem  310 . 
     In some cases, attaching augment  304  to bushing  306 , rather than directly to adaptor  302 , can assist in situating augment  304  in the more proximal, metaphyseal region of the tibia after the adaptor  302 , augment  304 , and bushing  306  have been inserted. In some situations, this region is more likely to sustain cavitary damage during revisions. Therefore, bushing  306  can act as a connector between augment  304  and adaptor  302 . In some examples, the shape of the bushing  306  is designed to frictionally (press) fit with adaptor  302  with concurrent assembly and weldment of both parts; being adaptable to augment  304 , such that adaptor  302 , augment  304 , and bushing  306  can be eventually permanently attached together; and clear the entire platform  308 . After coupling bushing  306  and adaptor  302  the two components effectively become one component. However, bushing  306  and adaptor  302  can be machined separately to simplify the manufacturing process and reduce associated costs. 
     In one example, proximal tibial prosthesis  300  can includes an epiphyseal replacement portion including tibial platform  308  that is configured to be connected with a tibial bearing (not shown). The tibial bearing mounted to tibial platform  308  forms a concave bearing surface against which the convex condyler surfaces of the patient&#39;s femur or a femoral prosthetic are configured to slide. Tibial prosthesis  300  also includes augment  304  and intramedullary stem  310 . Bone augment  304  is interposed between platform  308  and intramedullary stem  310 . Adaptor  302  is arranged within and coupled to a central cavity of augment  304 . The proximal end of adaptor  302  is connected to tibial platform  308  and the distal end is connected to intramedullary stem  310 . Intramedullary stem  310  is configured to be inserted within a medullary cavity of the diaphysis of a bone of the patient&#39;s knee joint. 
       FIGS. 4A and 4B  depict adaptor  302 , augment  304 , and bushing  306  in greater detail. In  FIGS. 4A and 4B , adaptor  302  is inseparably coupled to augment  304  via bushing  306 . For example, bushing  306  is coupled to adaptor  302  and augment  304  is coupled to bushing  306 . The connections between adaptor  302 , augment  304 , and bushing  306  can be achieved with a variety of mechanisms including those described above with reference to  FIGS. 1-2B , e.g., taper-lock, press fit, interference fit, weldment, and the like. 
     In one example, adaptor  302  and bushing  306  are coupled by a taper-lock. For example, adaptor  302  can interlock with bushing  306  by means of a male taper formed on shoulder  400  of adaptor  302  mated with a complementary female taper formed on inner surface  402  of bushing  306 . In another example, shoulder  400  and inner surface  402  can be press or interference fit to one another to couple adaptor  302  to bushing  306 . 
     Adaptor  302  and bushing  306  can be fabricated from a variety of biologically compatible materials, e.g., including the materials described above with reference to adaptor  116 . For example, adaptor  302  and bushing  306  can be fabricated from a cobalt-chromium alloy. 
     Augment  304  can be fabricated from bone ingrowth materials such as those described above with reference to bone augments  112  and  124 . For example, augment  304  can be fabricated from one or multiple pieces of highly porous biomaterial with a porosity as low as 55%, 65%, or 75% or as high as 80%, 85%, or 90%. An example of such a material is produced using Trabecular Metal™ Technology generally available from Zimmer, Inc., of Warsaw, Ind. 
     Bushing  306  can also be connected to augment  304  by a taper-lock. For example, bushing  306  can interlock with augment  304  by means of a male taper formed on outer surface  404  of bushing  306  mated with a complementary female taper formed on inner surface  406  of augment  304 . In another example, outer surface  404  and inner surface  406  can be press or interference fit to one another to couple bushing  306  to augment  304 . 
     Adaptor  302  is configured to be connected to tibial platform  308  and intramedullary stem  310 . For example, the proximal end of adaptor  302  can be connected to platform  308  and the distal end of adaptor  302  can be connected to stem  310 . The proximal end of adaptor  302  includes a shaft that defines outer surface  408 . Inscribed in outer surface  408  is channel  410 . In one example, platform  308  can include a distally extending protrusion, e.g., a shaft including a bore. The proximal end of adaptor  302  can be configured to be received in the bore of the shaft of platform  308 . For example, outer surface  408  of adaptor  302  can define a male taper that is configured to be received by and interlocked with a female taper defined by an inner surface of the bore of shaft extending distally from tibial platform  308 . 
     Proximal end of adaptor  302  includes a bore that defines inner surface  412 . In one example, the distal end of intramedullary stem  310  can includes a tapered portion that is configured to with inner surface  412  of adaptor  302 . For example, inner surface  412  of adaptor  302  can define a female taper that is configured to receive and interlocked with a male taper defined by the tapered portion of stem  310 . 
     In other examples, other mechanisms may be employed to connect adaptor  302  to platform  308  and/or stem  310 . For example, adaptor  302  can be coupled to platform  308  and/or stem  310  using a press or interference fit. In one example, adaptor  302  is interference fit with platform  308  and/or stem  310 . For example, adaptor  302  and platform  308  can be interference fit to one another using thermal expansion of one or both of the components. In one example employing an interference fit, the phenomenon of thermal expansion is employed to couple adaptor  302  and platform  308  by heating or cooling one of the components before assembly and then allowing the heated/cooled component to return to an ambient temperature after assembly. 
     In some examples, the taper-lock between any of adaptor  302 , augment  304 , bushing  306 , platform  308 , and/or stem  310  can be augmented by surface features on the male and/or female taper. For example, outer surface  408  that forms the male taper of adaptor  302  may include surface features that enhance the interlock between adaptor  302  and platform  308 . 
     The taper-lock described above between adaptor  302 , platform  308 , and stem  310  may not be configured to provide a permanent connection between components. In some cases, the taper-lock may be configured to allow a surgeon to connect adaptor  302  and platform  308  and stem  310  and position the components relative to one another. However, the taper-lock may not be configured to be strong or durable enough to provide a permanent connection between the components. 
     In some examples, therefore, the connections between adaptor  302  and platform  308 , and between adaptor  302  and stem  310  can be achieved or augmented by one or more set screws or other appropriate fastening mechanisms. For example, a set screw can be threaded to hole  414  in adaptor  302  into a channel inscribed in the tapered portion of stem  310  to secure the adaptor and the stem together. The set screw can function to inhibit relative axial movement between adaptor  302  and stem  310 , as well as inhibiting relative rotation between the two components. Similarly, a set screw can be threaded to a hole in the distally extending shaft of platform  308  and can be driven into channel  410  in adaptor  302 . The set screw can function to inhibit relative axial movement between adaptor  302  and tibial platform  308 , as well as inhibiting relative rotation between the two components. Hole  416  in augment  304  can be configured to provide clearance for accessing the set screw threaded into platform  308  and configured to engage channel  410 . 
       FIG. 5  is a flowchart depicting an example method in accordance with this disclosure. The method of  FIG. 5  includes inseparably coupling an adaptor to a bone augment ( 500 ), connecting a first end of the adaptor to an epiphyseal component of a prosthetic device ( 502 ), and connecting a second end of the adaptor to an intramedullary stem of the prosthetic device ( 504 ). In one example, the adaptor and the bone augment are inseparably coupled to one another before a procedure to implant the prosthetic device to partially or completely replace a human joint. The first and second ends of the adaptor can then be connected to the epiphyseal component and the stem, respectively, during the procedure. 
     For example, the adaptor and augment are inseparably coupled such that the two components are generally used during the surgical procedure as a single component, where the adaptor and augment are not adjustable relative to one another and where the two components are not disconnected. Thus, while it may be possible to physically separate the augment and adaptor, the two components are configured to be inseparable and used as a single component during a joint repair or replacement procedure. 
     In one example, the adaptor includes a tapered outer surface, which is configured to be received within a cavity of the bone augment. The bone augment can be, e.g., a diaphyseal or metaphyseal femoral augment that augments the cut proximal end of the femur to which the prosthesis is attached. The cavity of the augment includes a tapered inner surface. For example, the femoral augment can include a central bore that includes a tapered profile along a portion or all of the axial length of the bore. The tapered outer surface of the adaptor and the tapered inner surface of the central cavity of the augment are configured to interlock the adaptor and the augment. 
     The adaptor can be configured to be a generic adaptor. For example, the two ends of the adaptor can be configured to be connected to different epiphyseal replacement portions and different diaphyseal anchoring portions, respectively, of a modular joint replacement prosthesis. During the surgical procedure, the first end of the adaptor is configured to be coupled to an epiphyseal component of the knee repair or replacement prosthesis. For example, the first end of the adaptor can be coupled to a distal femoral component, which includes medial and lateral condyles. The second end of the adaptor is configured to be coupled to an intramedullary stem of the knee repair or replacement prosthesis, which is configured to be affixed within the medullary cavity of the femur. 
     Due to a number of factors including circumstances encountered during surgery and individual patient anatomy, it may not be possible or appropriate to employ an intramedullary stem component that is inserted into and affixed within the intramedullary canal of a patient&#39;s bone in a joint repair/replacement procedure.  FIGS. 6 and 7  depict two examples of representative devices in accordance with this disclosure that can be employed in such circumstances, or, as appropriate, in other circumstances. 
       FIG. 6  depicts a section view of a distal femoral prosthesis  600  including an example adaptor  602  in accordance with this disclosure. The example of  FIG. 6  is similar to the example of  FIGS. 2A and 2B , except the prosthesis does not include an intramedullary stem. In the example of  FIG. 6 , adaptor  602  is inseparably coupled to bone augment  604 . Distal femoral prosthesis  600  includes epiphyseal replacement portion  606 . Epiphyseal replacement portion  606  includes shaft  610  and condylar portion  612  with a medial and a lateral condyle. Bone augment  604  may include a slot and/or thru hole (not shown) similar in structure and function to slot  216  and thru hole  214  of the example of  FIGS. 2A and 2B . The distal end of adaptor  602  is coupled to epiphyseal replacement portion  606 . The proximal end of adaptor  602  is in the form of a truncated shaft, which extends a relatively short distance past the proximal end of augment  604 . 
     The materials employed for components of distal femoral prosthesis  600  can be similar to those described above with reference to distal femoral prosthesis  200  of  FIGS. 2A and 2B . Additionally, the interconnection between adaptor  602  and augment  604  and adaptor  602  and epiphyseal replacement portion  606  can be similar in function and structure as that described above with reference to the example of  FIGS. 2A and 2B . For example, adaptor  602  is inseparably coupled to augment  604 . In the example of  FIG. 6 , adaptor  602  and augment  604  are coupled by a taper-lock, which is also referred to as a self-locking taper. Adaptor  602  interlocks with augment  604  by means of a male taper formed on outer surface  622  of adaptor  602  mated with a complementary female taper formed on inner surface  624  of augment  604 . 
     Adaptor  602  is connected to epiphyseal replacement portion  606 . For example, distal end of adaptor  602  is connected to epiphyseal replacement portion  606 . Distal end of adaptor  602  includes a shaft that defines outer surface  626 . Inscribed in outer surface  626  is channel  628 , which can be configured, for example, to receive a set screw through holes/slots in augment  604  and shaft  610  of epiphyseal replacement portion  606 . Shaft  610  of epiphyseal replacement portion  606  includes a bore that defines inner surface  630 . Outer surface  626  of adaptor  602  defines a male taper that is configured to be received by and interlocked with a female taper defined by inner surface  630  of the bore of shaft  610 . 
     As noted above, in the example of  FIG. 6 , distal femoral prosthesis  600  does not include and adaptor  602  does not connect to an intramedullary stem. Instead, the proximal end of adaptor  602  is in the form of a truncated shaft, which extends a relatively short distance past the proximal end of augment  604 . The example of  FIG. 6  can be employed in situations in which it may not be possible or appropriate to employ an intramedullary stem component that is inserted into and affixed within the intramedullary canal of a patient&#39;s bone in a joint repair/replacement procedure. 
       FIG. 7  depicts another example adaptor  702  in accordance with this disclosure. The example of  FIG. 7  is similar to the example of  FIGS. 3-4B , except the tibial prosthesis used with the depicted adaptor  702  and augment  704  does not include and the adaptor  702  is not connected to an intramedullary stem. In the example of  FIG. 7 , adaptor  702  is inseparably coupled to augment  704  via bushing  706 . The tibial prosthesis employed with adaptor  702  and augment  704  can be similar in structure and function to the prosthesis of  FIG. 3  without the intramedullary stem. 
     Adaptor  702  is inseparably coupled to augment  704  via bushing  706 . For example, bushing  706  is coupled to adaptor  702  and augment  704  is coupled to bushing  706 . The connections between adaptor  702 , augment  704 , and bushing  706  can be achieved with a variety of mechanisms including those described above with reference to  FIGS. 1-2B , e.g., taper-lock, press fit, interference fit, weldment, and the like. 
     In one example, adaptor  702  and bushing  706  are coupled by a taper-lock. For example, adaptor  702  can interlock with bushing  706  by means of a male taper formed on shoulder  708  of adaptor  702  mated with a complementary female taper formed on inner surface  710  of bushing  706 . In another example, shoulder  708  and inner surface  710  can be press or interference fit to one another to couple adaptor  702  to bushing  706 . 
     Bushing  706  can also be connected to augment  704  by a taper-lock. For example, bushing  706  can interlock with augment  704  by means of a male taper formed on outer surface  712  of bushing  706  mated with a complementary female taper formed on inner surface  714  of augment  704 . In another example, outer surface  712  and inner surface  714  can be press or interference fit to one another to couple bushing  706  to augment  704 . 
     Adaptor  702  is configured to be connected to a tibial platform similar to platform  308  of the example of  FIG. 3 . For example, the proximal end of adaptor  702  can be connected to the tibial platform. The distal end of adaptor  702 , as noted, is not connected to an intramedullary stem and terminates at the distal end of bushing  706 . The proximal end of adaptor  702  includes a shaft that defines outer surface  716 . Inscribed in outer surface  716  is channel  718 , which can be used, for example, to receive a set screw as described above with reference to the examples of  FIGS. 3-4B . In one example, the platform of the tibial prosthesis (e.g., platform  308  from the example of  FIG. 3 ) can include a distally extending protrusion, e.g., a shaft including a bore. The proximal end of adaptor  702  can be configured to be received in the bore of the shaft of platform of the tibial prosthesis. For example, outer surface  716  of adaptor  702  can define a male taper that is configured to be received by and interlocked with a female taper defined by an inner surface of the bore of the shaft extending distally from the tibial platform. 
       FIG. 8  schematically depicts example modular knee repair or replacement prosthesis  800 , which includes bone augment adaptors in accordance with this disclosure. In  FIG. 8 , prosthesis  800  includes distal femoral prosthesis  802  and tibial prosthesis  804  coupled to one another by a single integral or multiple connected fusion shaft(s)  806 . Femoral prosthesis  802  includes adaptor  808  inseparably coupled to augment  810 . Adaptor  808  is connected, at the proximal end, to stem  812 , and is connected, at the distal end, to fusion shaft  806 . Tibial prosthesis includes adaptor  814  inseparably coupled to augment  816  via bushing  818 . Adaptor  814  is connected, at the proximal end, to fusion shaft  806 , and is connected, at the distal end, to stem  820 . 
     The example of  FIG. 8  combines a femoral prosthesis similar to the example of  FIGS. 2A and 2B  and a tibial prosthesis similar to the example of  FIGS. 3-4B , except that knee repair or replacement prosthesis  800  is non-articulating. In other words, prosthesis  800  does not include the articulating components like the condyler epiphyseal distal femoral component or the tibial platform of the examples of  FIGS. 1-4B . Example prosthesis  800  may be employed in situations in which it may be necessary to essentially fuse the proximal (femur) and distal (tibia) portions of a patient&#39;s leg at the knee. The structure, arrangement, function, and materials of the components of prosthesis  800  can be similar to the examples described above with reference to  FIGS. 1-5 . However, the distal and proximal ends of adaptors  808  and  814  are respectively connected to fusion shaft  806 , instead of being connected to respective articulating epiphyseal components of a femoral and tibial prosthesis. 
     Various examples have been described. These and other examples are within the scope of the following claims.