Orthopedic knee joint prosthesis

Abstract

The invention relates to an orthopedic knee joint prosthesis (2) comprising a metallic femoral implant part (4), a metallic tiboral implant part (6), and a meniscus replacement part (8) which forms a sliding partner for the femoral implant part (4) and is held on the tiboral implant part (6), wherein the femoral implant part (4) in the implanted state has surface areas (10) facing the bone and in contact with the bone, wherein the femoral implant part (4) in the implanted state has articulating condylar surface areas (12) in sliding contact with the meniscus replacement part (8) as a sliding partner, wherein the tiboral implant part (6) in the implanted state has surface areas (16) facing the bone and in contact with the bone, and wherein the tiboral implant part (6) in the implanted state has surface areas (18) in contact with the meniscus replacement part (8).wherein the femoral implant part (4) and the tiboral implant part (6) each have surface areas (14, 20) in the implanted state that are not in contact with the bone or the meniscus replacement part, but are in contact with the soft tissue, wherein the femoral implant part (4) has at least a hardening and wear-reducing, in particular multilayer, coating (38) on the articulating condylar surface areas (12) that are in sliding contact with the sliding partner; according to the invention, it is proposed that the femoral implant part (4) and / or the tiboral implant part (6) has a three-dimensionally porous surface structure (30, 32) in the surface areas (10, 16) facing the bone to promote bone ingrowth into the implant part (4, 6),and that the femoral implant part (4) and / or the tiboral implant part (6) has a coating (52, 54) on the surface areas (14, 20) that are not in contact with the bone and not with the meniscus replacement part (8) but are in contact with soft tissue, at least in some areas, by means of which the surface roughness of these surface areas (14, 20) is reduced.

Description

[0001] The invention relates to an orthopaedic knee joint prosthesis with a metallic, in particular additively manufactured, femoral implant part, with a metallic, in particular additively manufactured, tiboral implant part, and with a meniscus replacement part, which forms a sliding partner for the femoral implant part and is held on the tiboral implant part, wherein the femoral implant part has surface areas facing the bone and in contact with the bone in the implanted state, wherein the femoral implant part has articulating condylar surface areas in sliding contact with the meniscus replacement part as a sliding partner in the implanted state, wherein the tiboral implant part has surface areas facing the bone and in the implanted state in contact with the bone, wherein the tiboral implant part has surface areas in contact with the meniscus replacement part in the implanted state, wherein the femoral implant part and the tiboral implant part, in the implanted state, each have surface areas that are not in contact with the bone and not with the meniscus replacement part, but are in contact with the soft tissue, wherein the femoral implant part has, at least in some areas, a hardening and wear-reducing, in particular multi-layered, coating on the articulating condylar surface areas in sliding contact with the sliding partner.

[0002] Such a knee joint prosthesis is previously known from EP 2 051 666 B1, which proposed forming articulating condylar surface regions of the femolar implant component that are in sliding contact with the meniscus replacement component, as well as surface regions of the tiboral implant component that are in contact with the meniscus replacement component, with a hardening and wear-reducing coating. This hardening and wear-reducing coating is particularly multi-layered and comprises, in particular, ceramic layers that prove to be particularly wear-resistant in sliding contact with corresponding articulation surfaces of the meniscus replacement component. They also prevent or reduce the release of metal ions from the interior of the femoral or tiboral implant component as a result of the articulating sliding contact.

[0003] Since then, attempts have only been made to optimize the wear resistance of surface areas of the implant components subject to stress through articulating sliding movements, including micro-movements.

[0004] The object of the present invention is to achieve, on the one hand, optimal anchoring of the metallic implant material in the bone, starting from a knee joint prosthesis of the type mentioned at the beginning, and, on the other hand, to achieve unproblematic contact with surrounding soft tissue.

[0005] This object is achieved according to the invention, starting from a knee joint prosthesis of the type mentioned at the outset, in that the femoral implant part and / or the tiboral implant part have a three-dimensional porous surface structure in the surface areas facing the bone for the bone to grow into the implant part, and in that the femoral implant part and / or the tiboral implant part has, at least in some areas, a coating on the surface areas that are not in contact with the bone and not with the meniscus replacement part but are in soft tissue contact, by means of which coating a surface roughness of these surface areas is reduced.

[0006] It is therefore proposed, on the one hand, to provide a three-dimensionally porous surface structure, in particular by metallic 3D printing, on the surface areas of the implant part in question facing the bone. On the other hand, it is proposed to provide a coating that reduces the surface roughness on the surface areas that are not in contact with the bone and not with the meniscus replacement part, but are in contact with the soft tissue. It has been found according to the invention that rough surfaces in contact with soft tissue can lead to increased cell death during relative movements to soft tissue. The present invention therefore proposes to specifically reduce the surface roughness in these surface areas of the implant parts that are in contact with soft tissue by applying a coating.The surface roughness is lower than that of the uncoated surface areas of the implant part in question and also lower than that of the surface areas of the implant part in question facing the bone. As a result, an optimization of preferably all of the aforementioned surface areas of the implant part in question is achieved with regard to their respective specific function in the implanted state of the prosthesis. In particular, the implant parts can be advantageously manufactured using additive manufacturing processes, such as metallic 3D printing, since a certain surface roughness formed in this process can be smoothed by applying the coating.

[0007] It may be found that the surface roughness of the surface areas not in contact with the bone or the meniscus replacement part, but in soft tissue contact and provided with the coating, is greater than or equal to the surface roughness of the articulating condylar surface areas in sliding contact and provided with the hardening and wear-reducing coating (claim 2). Advantageously, the surface areas in soft tissue contact in the femoral implant part and / or the tibia implant part are designed to be as smooth as possible.

[0008] It proves to be advantageous if the surface roughness of the surface areas not in contact with the bone and not with the meniscus replacement part but in contact with soft tissue and provided with the coating is at most 0.50 µm, in particular at most 0.40 µm, in particular at most 0.30 µm and in particular at least 0.10 µm, measured as Ra according to DIN / ISO 21920-3 (claim 3).

[0009] Various processes can be used to produce the coating that reduces surface roughness. It is advantageous if this coating of the surface areas not in contact with the bone or the meniscus replacement, but in contact with soft tissue, is produced using a PVD (Physical Vapor Deposition) process (claim 4). This allows a very uniform and thin coating to be produced in a process-stable manner. In particular, it is advantageous if the coating has a coating thickness of 3.5 - 6.0 µm, which can be measured and determined according to DIN / ISO 26423. Ceramic materials, such as zirconium nitride (ZrN), chromium nitride (CrN), or chromium carbonitride (CrCN), are suitable for the coating, which can preferably be multi-layered.The coating can be bonded to the implant component via an adhesion promoter layer, particularly one based on cobalt-chromium or titanium.

[0010] In an advantageous embodiment of the knee joint prosthesis according to the invention, it is provided that at least the tiboral implant part has a three-dimensionally porous surface structure in the surface areas facing the bone for bone ingrowth into the implant part, and that the tiboral implant part has, at least in some areas, a coating on the surface areas not in contact with the bone and not with the meniscus replacement part but in contact with the soft tissue, by means of which coating the surface roughness of these surface areas is reduced (claim 5). This, on the one hand, allows for secure anchoring of the tiboral implant part in the bone, and on the other hand, the surrounding soft tissue in the area of ​​the tiboral implant part is less irritated due to the smooth design of the surface in contact with the soft tissue.

[0011] The following explains the hardening and wear-reducing coating of the articulating surface areas in sliding contact with the meniscus replacement part. It proves advantageous if the hardening and wear-reducing, in particular multi-layered, coating of the articulating condylar surface areas in sliding contact comprises a ceramic surface, in particular made of or based on zirconium nitride (ZrN) (claim 6).

[0012] Furthermore, it proves to be advantageous if the hardening and wear-reducing coating of the articulating condylar surface areas in sliding contact is formed in several layers and is bonded to the implant part via an adhesion-promoting layer, in particular on a cobalt-chromium basis or on a titanium basis (claim 7).

[0013] Furthermore, it proves to be advantageous if the hardening and wear-reducing coating comprises layers based on cobalt-chromium and / or based on chromium nitride (CrN) and / or based on chromium carbonitride (CrCN) and / or based on zirconium nitride (ZrN) (claim 8).

[0014] Furthermore, it proves to be advantageous if the hardening and wear-reducing coating has a top layer based on zirconium nitride (ZrN) and inner layers based on chromium nitride (CrN) or chromium carbonitride (CrCN), wherein several inner layers based on chromium nitride (CrN) and chromium carbonitride (CrCN) can alternate (claim 9).

[0015] It is furthermore advantageous if not only articulating condylar surface areas of the femoral implant part, but also the tiboral implant part in surface areas in contact with the meniscus replacement part has a hardening and wear-reducing, in particular multi-layered, coating of the type just described in order to reduce wear due to micromovements between the meniscus replacement part and a plateau of the tiboral implant part (claim 10).

[0016] In order to bond the coating reducing the surface roughness in the soft tissue contact area, it proves to be advantageous if the coating of the surface areas not in contact with the bone and not with the meniscus replacement part but in contact with the soft tissue is bonded to the implant part via a titanium-based adhesion-promoting layer (claim 11).

[0017] It has been found according to the invention that it is possible and even advantageous if the coating of the surface areas not in contact with the bone or the meniscus replacement part but in contact with the soft tissue is the same coating as the hardening and wear-reducing coating of the articulating condylar surface areas in sliding contact (claim 12). It is conceivable that the coatings are bonded to a base material of the respective implant part via different adhesion-promoting layers. Thus, it would be conceivable for the adhesion-promoting layer in the hardening and wear-reducing coating to be cobalt-chromium-based, and for the adhesion-promoting layer in the surface roughness-reducing coating in the soft tissue contact area to be titanium-based. However, both coatings can also be bonded via the same titanium-based adhesion-promoting layer.

[0018] It is further advantageous if the meniscus replacement part has a polymer-based, in particular polyethylene-based, sliding surface that is in contact with the articulating condylar surface areas of the femoral implant part (claim 13). The meniscus replacement part can also be made entirely of polymer.

[0019] With regard to the production of the implant parts, it proves advantageous if the metallic femoral implant part and / or the metallic tiboral implant part is manufactured additively (claim 14). Additive manufacturing in the form of metallic 3D printing is suitable for the production of complex and, in particular, delicate structures that would be impossible or difficult to produce using injection molding or casting technology. With regard to the present invention, however, additive manufacturing proves advantageous in that it can be used to produce any closed and / or three-dimensionally porous structures, including surface structures. For example, in an implant part, both a preferably substantially closed articulating surface region and a three-dimensionally porous surface region in contact with the bone can be produced in the same implant part.In particular, it is conceivable that a respective implant component could be formed with a three-dimensional bar structure in the area of ​​bone contact, whereby the three-dimensional bar structure can extend inward from the outer shell to any desired depth. This allows for deep penetration of the bone tissue into the implant component, enabling a lasting, secure fit of the implant component and thus the prosthesis. A certain surface roughness inherent in 3D printing can then be reduced in the soft tissue contact area by applying a roughness-reducing coating.

[0020] The subject matter of the invention is also considered to be a respective implant part, i.e. a femoral implant part and / or a tiboral implant part, which has a three-dimensional porous surface structure in the area of ​​bone contact in the surface areas facing the bone for the bone to grow into the implant part and which has a coating at least in some areas on the surface areas not in contact with the bone and not with the meniscus replacement part but in contact with soft tissue, by means of which coating a surface roughness of these surface areas is reduced.

[0021] Further features, details and advantages of the invention emerge from the appended patent claims and from the drawing and subsequent description of an embodiment of the orthopaedic knee joint prosthesis according to the invention.

[0022] The drawing shows: Fig. 1 an exploded view of an embodiment of an orthopedic knee joint prosthesis according to the invention with a femoral implant part, a tiboral implant part and a meniscus replacement part that can be fixed to the tiboral implant part; Fig. 2 a schematic, simplified sectional view of the femoral implant part; Fig. 3 a side view of the tiboral implant part with partial cross-section; Fig. 4 a view of the tiboral implant part from above in the direction of arrow IV in Fig. 3; Fig. 5 a view from below in the direction of arrow V in Fig. 3; Fig. 6 schematically shows an additively manufactured three-dimensional porous metallic structure of an implant portion for bone tissue ingrowth; and Fig. Figure 7 schematically illustrates a multi-layer coating.

[0023] Fig. 1 shows an exploded view of an orthopedic knee joint prosthesis, designated overall by the reference numeral 2, with a femoral implant part 4, a tiboral implant part 6 and a meniscus replacement part 8, which is typically anchorable to the tiboral implant part 6.

[0024] The femoral implant part 4 comprises surface regions 10 facing a bone of the thigh (femur) (not shown) and in contact with the bone, and furthermore, articulating condylar surface regions 12 in sliding contact with the meniscus replacement part 8 as a sliding partner. Furthermore, the femoral implant part 4 comprises surface regions 14 that are not in contact with the bone and not with the meniscus replacement part 8, but are in soft tissue contact. These are surface regions 14 that are outside the articulating sliding contact with the meniscus replacement part, in particular surface regions 14 that flank the femoral implant part 4 horizontally laterally.

[0025] The tiboral implant part 6 also has surface areas 16 facing the bone of the lower leg (tibia) and in contact with the bone. Furthermore, the tiboral implant part 6 comprises surface areas 18 in contact with the meniscus replacement part 8, and finally, the tiboral implant part 6 also has surface areas 20 that are not in contact with the bone and not with the meniscus replacement part 8, but are in soft tissue contact.

[0026] One can see from the Fig. 1 to 5, the femoral implant part 4 has at least one dome- or shaft-shaped projection 22, and the tiboral implant part 6 has an elongated projection 24, each of which serves for engagement and anchoring to the femur or lower leg bone. The projection 24 of the tiboral implant part 6 is also connected to a disc-shaped plateau part 26 of the tiboral implant part 6 via cheek-shaped sections 25 extending in the vertical plane.

[0027] How best to Fig. 4, the disc-shaped plateau part 26 comprises, facing away from the bone and facing the meniscus replacement part 8, a flat recess 28 for inserting and in particular locking the area 28 of the meniscus replacement part 8 which is designed to be complementary thereto.

[0028] In the exemplary and preferred case, the femoral implant part 4 and the tiboral implant part 6 are each formed with a three-dimensional porous surface structure 30 and 32, respectively, in the region of their bone contact. In both cases, this three-dimensional porous surface structure 30 and 32 extends macroscopically over at least 0.5 mm and in particular up to 20 mm, in particular up to 15 mm and in particular up to 10 mm in the depth direction into the respective implant part 4 and 6, respectively, which are each preferably manufactured using additive manufacturing processes.

[0029] The meniscus replacement part 8 forms, as a sliding partner to the femoral implant part 4, three-dimensionally shaped sliding surface regions 34 that are essentially complementary in shape to the condylar surface regions 12 of the femoral implant part 4. These sliding surface regions 34, like the entire meniscus replacement part 8, are formed from a polymer, in particular polyethylene. To reduce frictional contact and thus wear between the condylar surface regions 12 of the femoral implant part 4 and the meniscus replacement part 8, the articulating condylar surface regions 12 that are in sliding contact with the meniscus replacement part 8 have a hardening and wear-reducing, in particular multi-layered, coating 38. This coating comprises several ceramic layers 40 and a cover layer, for example and preferably based on zirconium nitride, as well as an adhesion-promoting layer 44 and the base material of the femoral implant part 4.The hardening and wear-reducing coating 38 can be formed in detail as described in EP 2 051 666 B1, so that the relevant content of this document with regard to the structure of the hardening and wear-reducing coating is incorporated by reference into the present application.

[0030] A corresponding hardening and wear-reducing coating 50 is present on the surface area 18 of the tiboral implant part 6 that is in contact with the meniscus replacement part 8. This is advantageous because, despite the retaining connection, in particular the locking connection, between the meniscus replacement part 8 and the tiboral implant part 6, micromovements occur between these components.

[0031] With the present invention, it was discovered that surface regions of the femoral implant part 4 or the tiboral implant part 6 that are in contact with soft tissue can have a problematic effect on the soft tissue and, in the worst case, can lead to cell death if these surface regions 14 or 20 are too rough and, as a result of the articulating movement of the implant parts relative to one another, a relative movement occurs between these surface regions and the soft tissue. Therefore, the present invention proposes providing surface regions 14 of the femoral implant part 4 and surface regions 20 of the tiboral implant part 6 that are in contact with soft tissue, outside the contact area with the bone and the meniscus replacement part, with a smoothing coating 52 or 54, respectively, by means of which the surface roughness of these surface regions 14, 20 that are in contact with soft tissue is reduced.The aim is to achieve a surface that is as smooth as possible so that relative movements do not lead, or at least lead to a significantly lower introduction of frictional energy into the soft tissue, which could prove to be problematic.

[0032] It has also proven advantageous that this coating 52 or 54, which reduces the surface roughness, is only deposited on outer webs, struts or ribs of the structure during application in the PVD process in the event of an unintentional coating of three-dimensionally porous surface areas 10 or 16 in contact with bone of the implant parts 4, 6, which does not noticeably impede the anchoring of bone material in the three-dimensionally porous structure.

[0033] It was further determined that the same layer structure can be used to form the smoothing coating 52, 54, i.e., coating which reduces the surface roughness, as is used to produce the hardening and wear-reducing coating 38 and 50, respectively, of the articulating condylar surface regions 12 of the femoral implant part 4 and the surface regions 18 of the tiboral implant part 6 facing the meniscus replacement part 8.

[0034] Fig. Figure 7 shows schematically and by way of example a multi-layered coating structure, which is equally suitable for the construction of the respective hardening and wear-reducing coating 38, 50 and for the smoothing coating 52, 54. One can see a base material 60 of the respective implant part 4 or 6 and a layer thickness of only 30 to 200 x 10 -9A 1 m thick adhesion-promoting layer 62, in particular based on cobalt-chromium or titanium, is provided on top of this. Several ceramic layers 64, in particular made of two alternating materials, are provided. Finally, a ceramic surface layer 66, in particular based on zirconium nitride, is provided. As mentioned, this layer structure can be used both as a hardening and wear-reducing coating 38, 50 and as a smoothing coating 52, 54 exclusively for soft tissue contact. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 2 051 666 B1 [0002, 0029]

Claims

[1] Orthopaedic knee joint prosthesis (2) with a metallic, in particular additively manufactured, femoral implant part (4), with a metallic, in particular additively manufactured, tiboral implant part (6), and with a meniscus replacement part (8) which forms a sliding partner for the femoral implant part (4) and is held on the tiboral implant part (6), wherein the femoral implant part (4) in the implanted state has surface areas (10) facing the bone and in contact with the bone, wherein the femoral implant part (4) in the implanted state has articulating condylar surface areas (12) in sliding contact with the meniscus replacement part (8) as a sliding partner, wherein the tiboral implant part (6) in the implanted state has surface areas (16) facing the bone and in contact with the bone, wherein the tiboral implant part (6) in the implanted state has surface areas (18) in contact with the meniscus replacement part (8), wherein the femoral implant part (4) and the tiboral implant part (6) in the implanted state each have surface areas (14, 20) which are not in contact with the bone and not with the meniscus replacement part but are in contact with the soft tissue, wherein the femoral implant part (4) has, at least in some areas, a hardening and wear-reducing, in particular multi-layered, coating (38) on the articulating condylar surface regions (12) in sliding contact with the sliding partner, characterized by , that the femoral implant part (4) and / or the tiboral implant part (6) has a three-dimensionally porous surface structure (30, 32) in the surface areas (10, 16) facing the bone for the bone to grow into the implant part (4, 6), and that the femoral implant part (4) and / or the tiboral implant part (6) has, at least in some areas, a coating (52, 54) on the surface areas (14, 20) that are not in contact with the bone and not with the meniscus replacement part (8) but are in contact with soft tissue, by means of which coating a surface roughness of these surface areas (14, 20) is reduced. [2] Orthopaedic knee joint prosthesis (2) according to claim 1, characterized bythat the surface roughness of the surface areas (14, 20) which are not in contact with the bone and not with the meniscus replacement part but are in soft tissue contact and are provided with the coating (52, 54) is greater than or equal to a surface roughness of the articulating condylar surface areas (12) which are in sliding contact and are provided with the hardening and wear-reducing coating. [3] Orthopaedic knee joint prosthesis (2) according to claim 1 or 2, characterized by that the surface roughness of the surface areas (14, 20) which are not in contact with the bone and not with the meniscus replacement part (8) but are in contact with soft tissue and are provided with the coating (52, 54) is at most 0.50 µm, in particular at most 0.40 µm, in particular at most 0.30 µm and in particular at least 0.10 µm, measured as Ra according to DIN / ISO 21920-3. [4] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized by that the coating (52, 54) of the surface areas (14, 20) which are not in contact with the bone and not with the meniscus replacement part (8) but are in contact with soft tissue is produced by PVD (Physical Vapour Deposition) processes. [5] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized bythat the tiboral implant part (6) has a three-dimensionally porous surface structure (32) in the surface areas (16) facing the bone for the bone to grow into the implant part (6), and that the tiboral implant part (6) has, at least in some areas, a coating (54) on the surface areas (20) which are not in contact with the bone and not with the meniscus replacement part (8) but are in soft tissue contact, by means of which coating a surface roughness of these surface areas (20) is reduced. [6] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized by that the hardening and wear-reducing, in particular multi-layer coating (38) of the articulating condylar surface regions (12) in sliding contact comprises a ceramic surface, in particular made of or based on zirconium nitride. [7] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized by that the hardening and wear-reducing coating (38) of the articulating condylar surface regions (12) in sliding contact is multi-layered and is bonded to the implant part (4) via an adhesion-promoting layer, in particular based on cobalt-chromium or titanium. [8] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized by that the hardening and wear-reducing coating (38) comprises layers based on cobalt-chromium and / or based on chromium nitride (CN) and / or based on chromium carbonitride (CrCN) and / or based on zirconium nitride (CrN). [9] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized bythat the hardening and wear-reducing coating (38) has a cover layer based on zirconium nitride and inner layers based on chromium nitride (CN) or chromium carbonitride (CrCN), wherein inner layers based on chromium nitride (CN) and chromium carbonitride (CrCN) can alternate. [10] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized by in that the tiboral implant part (6) has a hardening and wear-reducing, in particular multi-layered, coating (50) in surface areas (18) in contact with the meniscus replacement part (8) in order to reduce wear due to micromovements between the meniscus replacement part (8) and a plateau (26) of the tiboral implant part (6). [11] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized bythat the coating of the surface areas not in contact with the bone and not with the meniscus replacement part but in contact with the soft tissue is bonded to the implant part via a titanium-based adhesive layer. [12] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized by that the coating of the surface areas (14, 20) which are not in contact with the bone and not with the meniscus replacement part (8) but are in contact with soft tissue is the same coating as the hardening and wear-reducing coating (38) of the articulating condylar surface areas (12) which are in sliding contact. [13] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized bythat the meniscus replacement part (8) has a polymer-based, in particular polyethylene-based, sliding surface which is in contact with the articulating condylar surface regions (12) of the femoral implant part (4). [14] Orthopaedic knee joint prosthesis (2) according to one or more of the preceding claims, characterized by that the metallic femoral implant part (4) and / or the metallic tiboral implant part (6) is additively manufactured.

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