AU2021223178A1 - Coated implant and method of making the same - Google Patents

Abstract

An orthopaedic knee implant (10) includes a femoral component (12) having a metallic substrate (60) and a metallic coating (58). A method for making a femoral component of an orthopaedic knee implant is also disclosed.

Description

COATED IMPLANT AND METHOD OF MAKING THE SAME

[OOOl] This application claims priority to U.S. Provisional Application Serial No. 62/978,539, filed February 19, 2020, the contents of which are incorporated herein by reference.

CROSS-REFERENCE SECTION

[0002] Cross reference is made to copending U.S. Application Serial No. ##/###,###, (Attorney Docket No. 265280-333150, DSP6174USNP1) and International Application Serial No. PCT/AA2021/XXXXXX, (Attorney Docket DSP6174USPCT1) titled “COATED IMPLANT AND METHOD OF MAKING THE SAME,” each of which is hereby incorporated by reference.

TECHNICAL FIELD

[0003] The present disclosure relates generally to an implantable orthopaedic prosthesis, and more particularly to a femoral component of an implantable orthopaedic prosthesis.

BACKGROUND

[0004] Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged natural joint is replaced by a prosthetic joint. A typical knee prosthesis includes a patella prosthetic component, a tibial tray, a femoral component, and a tibial bearing positioned between the tibial tray and the femoral component. Femoral components are designed to be attached to a surgically-prepared distal end of a patient’s femur. Tibial trays are designed to be attached to a surgically-prepared proximal end of a patient’s tibia.

[0005] The femoral component and the tibial tray can be made of biocompatible materials such as metal alloys of cobalt-chrome. The tibial bearing component disposed between the femoral component and the tibial tray can be formed from a plastic material like polyethylene. However, cobalt alloys tend to be expensive, and accordingly, a need exists for a component made from a non-cobalt metal material and a method of manufacturing the same. For example, a need exists for a femoral component of a knee prosthesis out of a non-cobalt metal material and a method for manufacturing the same.

SUMMARY

[0006] According to an aspect of the disclosure, an orthopaedic implant includes a femoral component. The femoral component may be configured to be coupled to the distal end of a patient’s femur. The femoral component may include a substrate comprising a titanium alloy. Illustratively, the substrate may have a condylar surface that is curved in a sagittal plane and a bone -facing surface positioned opposite the condylar surface. An articular layer may be disposed on the condylar surface. The articular layer may comprise a first layer comprising niobium, zirconium, titanium, tantalum, platinum, molybdenum, or combinations thereof, a second layer comprising an alloy or a ceramic, and a third layer comprising titanium zirconium nitride, zirconium oxide, niobium oxide, zirconium oxynitride, niobium oxynitride, or a combination thereof. The first layer may extend between and interconnect the second layer and the condylar surface. The second layer may extend between and interconnect the first layer and the third layer. The third layer may form an outer articular surface of the femoral component.

[0007] In some embodiments, the first layer may have a coefficient of thermal expansion in at least one direction of about 7. 1 x 10^-6/°K to about 7.5 x 10-⁶/°K.

[0008] In some embodiments, the third layer may comprise at least about 90% monoclinic zirconium oxide. In some embodiments, the third layer may have a thickness of about 100 nm to about 5 pm.

[0009] In some embodiments, the second layer may comprise at least about 95% zirconium niobium alloy. In some embodiments, the second layer may have a thickness of about 3 pm to about 8 pm.

[0010] In some embodiments, the first layer may comprise at least about 95% niobium. In some embodiments, the first layer may have a thickness of about 0.5 pm to about 2 pm.

[0011] Illustratively, the femoral component may include a bone-engaging layer disposed on the bone-facing surface. In some embodiments, the bone- engaging layer may be porous.

[0012] According to another aspect, a process for forming a femoral component of an orthopaedic knee implant includes depositing a first layer comprising niobium, zirconium, titanium, tantalum, platinum, molybdenum, combinations thereof or ceramics thereof, on a condylar surface of a substrate comprising. The substrate may comprise titanium. The condylar surface may be curved in a sagittal plane. In some embodiments, the process includes depositing a second layer that may comprise an alloy of zirconium and niobium on the first layer.

[0013] In some embodiments, the first layer may comprise at least about 90% niobium. In some embodiments, the first layer may have a thickness of about 0.5 pm to about 2.5 pm.

[0014] In some embodiments, the second layer may comprise at least about 95% of an alloy of zirconium and niobium. In some embodiments, the second layer may have a thickness of about 3 pm to about 8 pm.

[0015] In some embodiments, the process may include oxidizing a portion of the second layer to form a third layer. In some embodiments, the third layer may comprise zirconium oxide, niobium oxide, zirconium oxynitride, niobium oxynitride, or a combination thereof.

[0016] In some embodiments, the third layer may comprise at least about 95% zirconium oxide. In some embodiments, the third layer may have a thickness of about 4 pm to about 5 pm.

[0017] In some embodiments, the step of oxidizing may be performed in an environment comprising about 97.5% argon and about 2.5% oxygen.

[0018] In some embodiments, the step of oxidizing may be performed at a temperature of about 500 °C to about 600 °C.

[0019] In some embodiments, the process may include depositing a third layer on the second layer.

[0020] According to another aspect of the disclosure, an orthopaedic implant includes a femoral component. The femoral component may be configured to be coupled to the distal end of a patient’s femur. The femoral component may include a substrate comprising a titanium alloy. Illustratively, the substrate may have a condylar surface that is curved in a sagittal plane and a bone-facing surface positioned opposite the condylar surface. An articular layer may be disposed on the condylar surface. The articular layer may comprise inner layer comprising niobium, zirconium, titanium, tantalum, platinum, molybdenum, or combinations thereof, and an outer layer comprising titanium zirconium nitride, zirconium oxide, niobium oxide, zirconium oxynitride, niobium oxynitride, or a combination thereof. The inner layer may extend from the condylar surface. The outer layer may form an outer articular surface of the femoral component.

[0021] In some embodiments, the articular layer may include an intermediate layer comprising an alloy or a ceramic.

[0022] In some embodiments, the atomic percent of zirconium in the outer layer may be 50 At% to 80 At%. In some embodiments, the atomic percent of zirconium in the outer layer is 30 At% to 85 At%.

BRIEF DESCRIPTION

[0023] The detailed description particularly refers to the following figures, in which:

[0024] FIG. 1 is an exploded perspective view of an orthopaedic knee prosthesis, showing from top to bottom a femoral component, a tibial bearing, and a tibial tray;

[0025] FIG. 2 is a cross-sectional view of the femoral component and the tibial bearing of FIG. 1 along the sagittal plane, taken generally along line 2-2 of FIG. 1, as viewed in the direction of the arrows, note the porous-metal coating is not shown in cross section in FIG. 2 for clarity of description;

[0026] FIG. 3 is an enlarged cross-sectional view taken from FIG. 2 as indicated by the encircled area; and

[0027] FIG. 4 is an illustrative diagrammatic view of a process for forming the articular layer of the femoral component of FIGS. 1-3.

DETAILED DESCRIPTION

[0028] While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0029] Terms representing anatomical references, such as anterior, posterior, medial, lateral, superior, inferior, etcetera, may be used throughout the specification in reference to the orthopaedic implants or orthopaedic prostheses described herein as well as in reference to the patient’s natural anatomy. Such terms have well-understood meanings in both the study of anatomy and the field of orthopaedics. Use of such anatomical reference terms in the written description and claims is intended to be consistent with their well- understood meanings unless noted otherwise. [0030] Referring now to FIG. 1, in one embodiment, an orthopaedic knee prosthesis 10 includes a femoral component 12, a tibial bearing 14, and a tibial tray 16. The femoral component 12 is configured to articulate with the tibial bearing 14, which is configured to be coupled with the tibial tray 16. In the illustrative embodiment of FIG. 1, the tibial bearing 14 is embodied as a rotating or mobile tibial bearing and is configured to rotate relative to the tibial tray 16 during use. However, in other embodiments, the tibial bearing 14 may be embodied as a fixed tibial bearing, which may be limited or restricted from rotating relative to the tibial tray 16.

[0031] The tibial tray 16 is configured to be secured to a surgically-prepared proximal end of a patient’s tibia (not shown). The tibial tray 16 may be secured to the patient’s tibia via use of bone cement or other attachment methods. The tibial tray 16 includes a platform 18 having a top surface 20 and a bottom surface 22. Illustratively, the top surface 20 is generally planar. The tibial tray 16 also includes a stem 24 extending downwardly from the bottom surface 22 of the platform 18. A cavity or bore 26 is defined in the top surface 20 of the platform 18 and extends downwardly into the stem 24. The bore 26 is formed to receive a complimentary stem 36 of the tibial bearing 14 as discussed in more detail below.

[0032] As discussed above, the tibial bearing 14 is configured to be coupled with the tibial tray 16. The tibial bearing 14 includes a platform 30 having an upper bearing surface 32 and a bottom bearing surface 34. In the illustrative embodiment wherein the tibial bearing 14 is embodied as a rotating or mobile tibial bearing, the bearing 14 includes a stem 36 extending downwardly from the bottom surface 34 of the platform 30. When the tibial bearing 14 is coupled to the tibial tray 16, the stem 36 is received in the bore 26 of the tibial tray 16. In use, the tibial bearing 14 is configured to rotate about an axis defined by the stem 36 relative to the tibial tray 16. In embodiments wherein the tibial bearing 14 is embodied as a fixed tibial bearing, the bearing 14 may or may not include the stem 36 and/or may include other devices or features to secure the tibial bearing 14 to the tibial tray 16 in a non-rotating configuration.

[0033] The upper bearing surface 32 of the tibial bearing 14 includes a medial bearing surface 42 and a lateral bearing surface 44. The medial and lateral bearing surfaces 42, 44 are configured to receive or otherwise contact corresponding medial and lateral condyles 52, 54 of the femoral component 12 as discussed in more detail below. As such, each of the bearing surfaces 42, 44 has a concave contour.

[0034] The femoral component 12 is configured to be coupled to a surgically-prepared surface of the distal end of a patient’s femur (not shown). The femoral component 12 may be secured to the patient’s femur via use of bone adhesive or other attachment methods. The femoral component 12 includes a pair of medial and lateral condyles 52, 54. The condyles 52, 54 are spaced apart to define an intracondyle notch 56 therebetween. In use, the condyles 52, 54 replace the natural condyles of the patient’s femur and are configured to articulate on the corresponding bearing surfaces 42, 44 of the platform 30 of the tibial bearing 14.

[0035] The illustrative orthopaedic knee prosthesis 10 (sometime referred to as an “implant”) of FIG. 1 is embodied as a posterior cruciate-retaining knee prosthesis. That is, the femoral component 12 is embodied as a posterior cruciate-retaining knee prosthesis and the tibial bearing 14 is embodied as a posterior cruciate-retaining tibial bearing 14. However, in other embodiments, the orthopaedic knee prosthesis 10 may be embodied as a posterior cruciate- sacrificing knee prosthesis.

[0036] Referring now to FIGS. 1 and 2, the femoral component 12 is configured to articulate on the tibial bearing 14 during use. Each condyle 52, 54 of the femoral component 12 includes an outer articular surface 50, which is convexly curved in the sagittal plane and configured to face the respective bearing surface 42, 44 of the tibial bearing 14.

[0037] As shown in FIG. 2, the femoral component 12 includes a substrate 60 and an articular layer 58. Illustratively, the articular layer 58 is disposed on the substrate 60 and is configured to interact with the tibial bearing 14. In some embodiments, the femoral component 12 includes a bone-engaging layer 62 located opposite the articular layer 58 to locate the substrate 60 therebetween. The bone-engaging layer 62 is configured to interact with a surgically prepared femur of a patient.

[0038] The substrate 60 comprises a condylar surface 66 and a bone-facing surface 64, as shown in FIG. 2. The condylar surface 66 is curved in a sagittal plane and is configured to locate the articular layer 58 on the substrate 60. The bone-facing surface 64 is positioned opposite the condylar surface 66 and is arranged to face a surgically-prepared distal end of a patient’s femur.

[0039] FIGS. 1 and 2 show a cementless embodiment of the femoral component 12 where the bone-engaging layer 62 is configured to be implanted in the absence of cement between the femoral component 12 and the surgically- prepared distal end of a patient’s femur. In some embodiments, the bone- engaging layer 62 comprises titanium. It should be appreciated that the bone- engaging layer 62 could be a separately-applied coating such as Porocoat® Porous Coating, which is commercially available from DePuy Synthes of Warsaw, Indiana.

[0040] In some embodiments, the bone-engaging layer 62 can be defined by a porous three-dimensional structure formed by a plurality of interconnected struts. In one example, the plurality of interconnected struts form a plurality of geometric structures, which, in the illustrative embodiment, are rhombic trigonal trapezohedrons. It should be appreciated that such geometric structures may vary to fit the needs of a given design. Further, it should be appreciated that the bone-engaging layer 62 may be formed form any other alternative geometry suitable to fit the needs of a given design.

[0041] In some embodiments, the bone-engaging layer 62 is formed from a metal powder. Illustratively, the metal powder may include, but is not limited to, titanium, titanium alloys, stainless steel, cobalt chrome alloys, tantalum, niobium, or combinations thereof. The bone-engaging layer 62 has a porosity suitable to facilitate bony ingrowth into the bone-engaging layer 62 of the femoral component 12 when implanted into the surgically-prepared surface of the distal end of a patient’s femur.

[0042] In the illustrative embodiment described herein, the bone-engaging layer 62 is additively manufactured directly onto the bone-facing surface 64 of the femoral component 12. In such an embodiment, the two structures - i.e., the femoral component 12 and bone-engaging layer 62 - may be manufactured contemporaneously during a common additive manufacturing process. For example, the two structures may be manufactured contemporaneously in a single 3D printing operation that yields a common, monolithic metallic component including both structures. Alternatively, the bone-engaging layer 62 could be manufactured as a separate component that is secured to the bone- facing surface 64 of the femoral component 12.

[0043] In alternative embodiments, the femoral component 12 is configured to attach to the surgically-prepared distance end of a patient’s femur using cement. In some embodiments, the femoral component 12 comprises a cement reservoir disposed (not shown) on the bone-facing surface 64. In some embodiments, the bone adhesive is disposed on the bone-facing surface 64. In some embodiments, the bone adhesive comprises bone cement. In some embodiments, the bone-facing surface 64 is configured to receive a bone adhesive.

[0044] In some embodiments, the substrate 60 is metallic. In some embodiments, the substrate 60 comprises a metal alloy. In some embodiments, the substrate 60 comprises a titanium alloy. In some embodiments, the substrate 60 comprises titanium and vanadium. In some embodiments, the substrate 60 comprises titanium, aluminum, and vanadium. In some embodiments, the substrate 60 comprises Ti-6A1-4V. In some embodiments, the substrate 60 consists essentially of Ti-6A1-4V. In some embodiments, the substrate 60 has a coefficient of thermal expansion (CTE) of about 8.2 x 10^-6/°K to about 9 x 10^-6/°K. In some embodiments, the substrate 60 comprises Ti-6A1- 4V and has a coefficient of thermal expansion (CTE) of about 8.2 x 10^-6/°K to about 9 x 10^-6/°K

[0045] Referring now to FIGS. 2 and 3, the articular layer 58 is disposed on the condylar surface 66. The articular layer 58 is located opposite the bone- facing surface 64 to locate the substrate 60 therebetween. The articular layer 58 is configured to interact with the bearing surfaces 42, 44 and to articulate with the tibial bearing 14.

[0046] The articular layer 58 can have a number of layers as described herein. The layers of the articular layer 58 may be each constructed with a material which possesses mechanical properties favorable for use in the construction of the articular layer 58 (e.g., enhanced wear resistance and/or corrosion resistance).

[0047] In some embodiments, the articular layer 58 cooperates with the substrate 60 to minimize scratching of the outer articular surface 50. In some embodiments, the articular layer 58 cooperates with the substrate 60 to minimize cohesive chipping of the femoral component 12. In some embodiments, the articular layer 58 cooperates with the substrate 60 to provide sufficient toughness to minimize or avoid fracturing.

[0048] Referring now to FIG. 3, the articular layer 58 comprises an inner layer 68, an intermediate layer 70, and an outer layer 72. The outer layer 72 of the articular layer 58 is constructed with a material which possesses mechanical properties favorable for use in the construction of the articular layer 58 (e.g., enhanced wear and/or corrosion resistance). The inner layer 68, on the other hand, is constructed of a material which possesses mechanical properties favorable for use in securing the articular layer 58 to the substrate 60. In some embodiments, the articular layer 58 may include only an inner layer and an outer layer.

[0049] It should be appreciated that, as used herein, the term “layer” is not intended to be limited to a “thickness” of material positioned proximate to another similarly dimensioned “thickness” of material, but rather is intended to include numerous structures, configurations, and constructions of material. For example, the term “layer” may include a portion, region, or other structure of material, which is positioned proximate to another portion, region, or structure of differing material. For example, although the interface between the intermediate layer 70 and the outer layer 72 is shown to be uniform in FIG. 3, in some embodiments the interface is irregular such that the intermediate layer 70 and the outer layer 72 do not have a uniform thickness. In some embodiments, a “layer” is formed by modifying a surface or a portion of an existing layer. For example, in some embodiments, the outer layer 72 is formed from oxidizing an outer portion of the intermediate layer 70. In alternative embodiments, a “layer” is formed by providing additional material to an existing surface. For example, in some embodiments, the inner layer 68 is formed by depositing a material onto the condylar surface 66.

[0050] The articular layer 58 in the illustrative embodiment shown in FIG. 3 comprises an inner layer 68, an intermediate layer 70, and an outer layer 72. The inner layer 68 is disposed on the condylar surface 66. The outer layer 72 is arranged to form the outer articular surface 50 of the femoral component 12. The intermediate layer 70 extends between and interconnects the inner layer 68 and the outer layer 72.

[0051] The inner layer 68 extends between and interconnects the intermediate layer 70 and the condylar surface 66. The inner layer 68 includes an inner surface 74 and an outer surface 76. The inner surface 74 is located between the outer surface 76 and the condylar surface 66. The outer surface 76 of the inner layer 68 is located between the inner surface 74 of the inner layer 68 and the intermediate layer 70. In some embodiments, the inner layer 68 is configured to minimize delamination of the articular layer 58 from the femoral component 12.

[0052] The inner layer 68 may have a particular thickness as measured from the condylar surface 66. In some embodiments, the inner layer 68 may be present at a thickness in the nanoscale to the micron scale. In some embodiments, the inner layer 68 is about 0.5 nm to about 10 nm or about 0.5 nm to about 3 nm. In some embodiments, the inner layer 68 has a thickness of about 0.10 pm to about 2 pm. In some embodiments, the inner layer 68 has a thickness of about 200 nm to about 1 pm. In some embodiments, the inner layer 68 has a thickness of at least about 0.10 pm, at least about 0.20 pm, at least about 0.30 pm, at least about 0.5 pm, at least about 1 pm, at least about 1.5 pm, or at least about 2 pm.

[0053] The inner layer 68 can include metals, alloys, ceramics, or other suitable material to provide mechanical properties favorable for use in securing the articular layer 58 to the substrate 60. For example, the composition of the inner layer 68 can be selected to minimize cohesive chipping of the articular layer 58 after an oxidation step of the intermediate layer 70. In illustrative embodiments, the inner layer 68 comprises niobium, zirconium, titanium, tantalum, molybdenum, platinum, hafnium, combinations thereof, or any other suitable metal. Illustratively, a ceramic may comprise a metal and a nitride, a carbide, an oxide, or combinations thereof. In some embodiments, the inner layer 68 comprises niobium. In some embodiments, the inner layer 68 comprises at least about 90% niobium. In some embodiments, the inner layer 68 comprises at least about 95% niobium. In some embodiments, the inner layer 68 comprises at least about 90% of zirconium, titanium, tantalum, molybdenum, platinum, or combinations thereof. In some embodiments, the inner layer 68 comprises at least about 95% of zirconium, titanium, tantalum, molybdenum, platinum, or combinations thereof.

[0054] In some embodiments, the inner layer 68 has a particular coefficient of thermal expansion (CTE). In some embodiments, the CTE of the inner layer 68 is between the CTE of the substrate 60 and the intermediate layer 70. In some embodiments, the CTE of the inner layer 68 is about 6 x 10^-6/°K to about 8 x 10^-6/°K or about 7. 1 x 10^-6/°K to about 7.5 x 10^-6/°K. In some embodiments, the inner layer 68 has a CTE of about 7.1 x 10^-6/°K, about 7.2 x 10^-6/°K, about 7.3 x 10^-6/°K, about 7.4 x 10^-6/°K, or about 7.5 x 10^-6/°K.

[0055] In the illustrative embodiment, the intermediate layer 70 extends between and interconnects the inner layer 68 and the outer layer 72. The intermediate layer 70 comprises an inner surface 78 and outer surface 80. The inner surface 78 of the intermediate layer 70 is located between the inner layer 68 and the outer surface 80 of the intermediate layer 70. The outer surface 80 of the intermediate layer 70 is located between the inner surface 78 of the intermediate layer 70 and the outer layer 72. In other embodiments, the outer articular surface 50 does not have an outer layer 72 and the outer surface 80 of the intermediate layer 70 forms the outer articular surface 50 [0056] In some embodiments, the intermediate layer 70 has a thickness of about 1 μm to about 8 μm . In some embodiments, the intermediate layer 70 has a thickness of at least about 1 μm , at least about 2 μm , at least about 3 μm , at least about 5 μm , at least about 6 μm , at least about 7 μm , or at least about 8 μm .

[0057] The intermediate layer 70 can include metals, alloys, ceramics, or other suitable material to enhance wear and oxidation resistance. For example, the intermediate layer 70 may comprise niobium, zirconium, titanium, tantalum, molybdenum, combinations thereof, or any other suitable metal. In some embodiments, intermediate layer 70 comprises a ceramic comprising niobium, zirconium, titanium, tantalum, molybdenum, combinations thereof, or any other suitable metal. Illustratively, a ceramic may comprise a metal and a nitride, a carbide, an oxide, or combinations thereof. For example, the intermediate layer 70 can comprise a ceramic such as niobium nitride, zirconium nitride, or a combination thereof.

[0058] In some embodiments, the intermediate layer 70 comprises a zirconium alloy. In some embodiments, the intermediate layer 70 comprises an alloy of zirconium and niobium. In some embodiments, the intermediate layer 70 comprises at least about 97.5% zirconium. In some embodiments, the intermediate layer 70 comprises at least about 2.5% niobium. In some embodiments, the intermediate layer 70 comprises at least about 95% of an alloy of zirconium and niobium. In some embodiments, the intermediate layer 70 comprises Zr-2.5Nb. In some embodiments, the intermediate layer 70 consists essentially of Zr-2.5Nb. In some embodiments, the CTE of the intermediate layer 70 in each direction may be in a range of about 5 x 10^-6/°K to about 5.9 x 10^{_ 6}/°K. In some embodiments, the intermediate layer 70 comprises an alloy of zirconium and niobium and may have a CTE in each direction of about 5 x 10^{_ 6}/° K to about 5.9 x 10^-6/°K.

[0059] In some illustrative embodiments, the outer layer 72 is configured to form the outer articular surface 50 of the femoral component 12. The outer layer 72 comprises an inner surface 82 and an outer surface 84. The inner surface 82 of the outer layer 72 is located between the intermediate layer 70 and the outer surface 84 of the outer layer 72. The outer surface 84 of the outer layer 72 forms an outer surface 84 of the femoral component 12. Illustratively, the outer surface 84 of the outer layer 72 forms the outer articular surface 50 of the femoral component 12 and is configured to interact and rotate about the tibial bearing 14, as shown in FIG. 2.

[0060] In some examples, the outer layer 72 can be formed by depositing the outer layer or by thermal growth through oxidation of a portion of the intermediate layer 70. In some embodiments, the outer layer 72 has a thickness of at least about 0.2 pm, at least about 0.5 pm, at least about 1 pm, at least about 2 pm, at least about 3 pm, at least about 4 pm, at least about 5 pm, or at least about 6 pm. [0061] In an illustrative embodiment, the outer layer 72 is formed by oxidizing at least part of the intermediate layer 70. For example, the outer surface 80 of the intermediate layer 70 can be oxidized to thermally grow the outer layer 72. Illustratively, the thermal growing may occur by oxygen inserting into the lattice of portions, for example an outer portion, of the intermediate layer 70 to form an oxide. In some embodiments, the outer layer 72 comprises a ceramic. In illustrative embodiments, the ceramic of the outer layer 72 is an oxide of the composition of the intermediate layer 70. In some embodiments, the outer layer 72 comprises an oxide of a niobium and zirconium alloy. In some embodiments, the outer layer 72 comprises zirconium oxide. In some embodiments, the outer layer 72 comprises titanium zirconium nitride. In some embodiments, the outer layer 72 comprises niobium oxide. In some embodiments, the outer layer 72 comprises zirconium oxide and niobium oxide. In some embodiments, the outer layer 72 comprises monoclinic zirconium oxide. In some embodiments, the outer layer 72 comprises at least about 90% zirconium oxide. In some embodiments, the atomic percent of zirconium in the outer layer may be 50 At% to 80 At%. In some embodiments, the atomic percent of zirconium in the outer layer is 30 At% to 85 At%. In some embodiments, the outer layer 72 comprises at least about 90% monoclinic zirconium oxide. In some embodiments, the outer layer 72 may comprise zirconium oxynitride and niobium oxynitride.

[0062] In some embodiments, the inner layer 68 comprises niobium, the intermediate layer 70 comprises an alloy of zirconium and niobium, and the outer layer 72 comprises zirconium oxide. [0063] Referring now to FIG. 4, the femoral component 12 of an orthopaedic knee prosthesis 10 may be formed through a process 100. In some embodiments, the process 100 comprises a first depositing step 110 of depositing the inner layer 68, a second depositing step 120 of depositing the intermediate layer 70, and an oxidizing step 130. In some embodiments, the process 100 comprises a first depositing step of depositing an inner layer including a metal such as, for example, titanium, and a second depositing step of depositing an outer layer including a ceramic such as, for example, titanium zirconium nitride. In some embodiments, the process 100 does not include an oxidizing step 130 after the second depositing step 120. In illustrative embodiments, the process 100 includes the steps of preparing the substrate 60 for the step of depositing 110. In some embodiments, the process 100 includes finishing steps after the step of oxidizing 130 such as polishing. In some illustrative embodiments, the process 100 includes preparing the substrate 60 for the deposition of the aforementioned layers.

[0064] In some embodiments, the first depositing step 110 deposits the inner layer 68 and forms the inner layer 68 on the condylar surface 66 of the substrate 60. In some embodiments, the first depositing step 110 is performed by physical vapor deposition (PVD), which may be performed using a magnetron sputter system. In other embodiments, PVD may be performed using HiPIMS, Ion Beam Assisted Deposition (IBAD) or Ion Beam Emitted Deposition (IBED), or other deposition systems. In other embodiments, the first depositing step 110 may be performed by chemical vapor deposition (CVD) when depositing, for example, zirconium, niobium, tantalum, or ceramics thereof. [0065] In some embodiments, the second depositing step 120 forms the intermediate layer 70 on the outer surface 76 of the inner layer 68. In some embodiments, second depositing step 120 is performed by physical vapor deposition (PVD). In some embodiments, the step of depositing 120 is performed by a magnetron sputter system. In other embodiments, the second depositing step 120 may be performed by chemical vapor deposition (CVD).

[0066] In some embodiments, the oxidizing step 130 oxidizes at least a portion of the intermediate layer 70. In some embodiments, the oxidizing step 130 is performed as described in U.S. Patent Nos. 6,447,550 and U.S. Patent No. 5,324,009, the entirety of each of which is expressly incorporated herein by reference. In some embodiments, the oxidizing step 130 oxidizes at least a portion of the outer surface 80 of the intermediate layer 70. In some embodiments, the oxidizing step 130 oxidizes at least a portion of the zirconium alloy of the intermediate layer 70 into zirconium oxide. In some embodiments, the oxidizing step 130 oxidizes at least a portion of the zirconium -niobium alloy of the intermediate layer 70 into zirconium oxide. In some embodiments, the oxidizing step 130 oxidizes the zirconium-niobium alloy of the intermediate layer 70 into monoclinic zirconium oxide.

[0067] In some embodiments, the oxidizing step 130 is performed by heating an environment comprising oxygen. In some embodiments, the environment is at a temperature of least 500°C or about 540°C. In some embodiments, the environment is at a temperature of about 500°C to about 600°C. In an illustrative embodiment, the environment comprises about 2.5% oxygen in argon. In some embodiments, the oxidizing step 130 is performed for about 5 hours. In some embodiments, the environmental may include a partial vacuum and temperatures up to about 1,000°C.

[0068] In alternative embodiments, instead of the oxidizing step 130, the process 100 comprises a step of depositing the outer layer 72 (not shown). The step of depositing the outer layer 72 can be performed by physical vapor deposition (PVD), which may be performed using a magnetron sputter system. In other embodiments, PVD may be performed using HiPIMS, IBAD, or other deposition systems. In some embodiments, the step of depositing the outer layer 72 deposits a ceramic layer, for example a layer of zirconium oxide. In some embodiments, the step of depositing the outer layer 72 deposits a ceramic layer, for example a layer of titanium zirconium nitride onto an inner layer of titanium. [0069] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.

[0070] There are a plurality of advantages of the present disclosure arising from the various features of the method, apparatus, and system described herein. It will be noted that alternative embodiments of the method, apparatus, and system of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of the method, apparatus, and system that incorporate one or more of the features of the present invention and fall within the spirit and scope of the present disclosure as defined by the appended claims.

Claims (23)

1. An orthopaedic knee implant comprising: a femoral component configured to be coupled to the distal end of a patient’s femur, the femoral component comprising:

(i) a substrate comprising a titanium alloy, the substrate having (a) a condylar surface that is curved in a sagittal plane and (b) a bone- facing surface positioned opposite the condylar surface; and

(ii) an articular layer disposed on the condylar surface, the articular layer comprising (a) a first layer comprising niobium, zirconium, titanium, tantalum, platinum, molybdenum, or combinations thereof, (b) a second layer comprising an alloy or a ceramic, and (c) a third layer comprising titanium zirconium nitride, zirconium oxide, niobium oxide, zirconium oxynitride, niobium oxynitride, or a combination thereof, wherein (i) the first layer extends between and interconnects the second layer and the condylar surface, (ii) the second layer extends between and interconnects the first layer and the third layer, and (iii) the third layer forms an outer articular surface of the femoral component.

2. The implant of claim 1, wherein the first layer has a coefficient of thermal expansion in at least one direction of about 7. 1 x 10^-6/°K to about 7.5 x 10^-6/°K.

3. The implant of claim 1, wherein the third layer comprises at least about 90% monoclinic zirconium oxide.

4. The implant of claim 3, wherein the third layer has a thickness of about 100 nm to about 5 pm.

5. The implant of claim 1, wherein the second layer comprises at least about 95% zirconium niobium alloy.

6. The implant of claim 5, wherein the second layer has a thickness of about 3 pm to about 8 pm.

7. The implant of claim 1, wherein the first layer comprises at least about 95% niobium.

8. The implant of claim 7, wherein the first layer has a thickness of about 0.5 pm to about 2 pm.

9. The implant of claim 1, wherein the femoral component comprises a bone-engaging layer disposed on the bone-facing surface.

10. The implant of claim 9, wherein the bone-engaging layer is porous.

11. A process for forming a femoral component of an orthopaedic knee implant, the process comprising: depositing a first layer comprising niobium, zirconium, titanium, tantalum, platinum, molybdenum, combinations thereof or ceramics thereof, on a condylar surface of a substrate comprising titanium, wherein the condylar surface is curved in a sagittal plane; and depositing a second layer comprising an alloy of zirconium and niobium on the first layer.

12. The process of claim 11, wherein the first layer comprises at least about 90% niobium.

13. The process of claim 12, wherein the first layer has a thickness of about 0.5 pm to about 2.5 pm.

14. The process of claim 11, wherein the second layer comprises at least about 95% of an alloy of zirconium and niobium.

15. The process of claim 14, wherein the second layer has a thickness of about 3 pm to about 8 pm.

16. The process of claim 11, comprising oxidizing a portion of the second layer to form a third layer comprising zirconium oxide, niobium oxide, zirconium oxynitride, niobium oxynitride, or a combination thereof.

17. The process of claim 16, wherein the third layer comprises at least about 95% zirconium oxide.

18. The process of claim 16, wherein the third layer has a thickness of about 4 pm to about 5 pm.

19. The process of claim 16, wherein the step of oxidizing is performed in an environment comprising about 97.5% argon and about 2.5% oxygen.

20. The process of claim 16, wherein the step of oxidizing is performed at a temperature of about 500 °C to about 600 °C.

21. The process of claim 11, comprising depositing a third layer on the second layer.

22. An orthopaedic knee implant comprising: a femoral component configured to be coupled to the distal end of a patient’s femur, the femoral component comprising:

(i) a substrate comprising a titanium alloy, the substrate having (a) a condylar surface that is curved in a sagittal plane and (b) a bone- facing surface positioned opposite the condylar surface; and

(ii) an articular layer disposed on the condylar surface, the articular layer comprising (a) an inner layer comprising niobium, zirconium, titanium, tantalum, platinum, molybdenum, or combinations thereof, and (b) a outer layer comprising titanium zirconium nitride, zirconium oxide, niobium oxide, zirconium oxynitride, niobium oxynitride, or a combination thereof, wherein (i) the inner layer extends from the condylar surface, and (ii) the outer layer forms an outer articular surface of the femoral component.

23. The orthopaedic knee implant of claim 22, wherein the articular layer further comprises an intermediate layer comprising an alloy or a ceramic, the intermediate layer being positioned between the inner layer and the outer layer.