Orthopedic knee joint prosthesis

Abstract

The present invention relates to an orthopedic knee joint prosthesis (2) having a metal femoral implant portion (4), a metal tibial implant portion (6), and a meniscus replacement portion (8). According to the present invention, the femoral implant portion (4) and in particular the tibial implant portion (6) are additively manufactured by metal 3D printing, and the femoral implant portion (4) and / or the tibial implant portion (6) have a three-dimensional porous surface structure (30, 32) formed by 3D printing in the surface regions (10, 16) facing the bone, thereby enabling bone to integrate with the implant portion (4, 6). Furthermore, the femoral implant portion (4) and / or the tibial implant portion (6) have a coating (52, 54) on at least a portion of the surface regions (14, 20) that do not come into contact with bone or the meniscus replacement portion (8) but come into contact with soft tissue, thereby reducing the surface roughness of these surface regions (14, 20).

Description

Technical Field

[0001] The present invention relates to an orthopedic knee joint prosthesis having a metallic femoral implant part, a metallic tibial implant part, and a meniscus replacement part held by the tibial implant part and forming a sliding partner with the femoral implant part. The femoral implant part has a surface area that faces and contacts the bone in the implanted state, and the femoral implant part has an articular granular surface area that slidably contacts the meniscus replacement part, which is the sliding partner, in the implanted state. The tibial implant part has a surface area that faces and contacts the bone in the implanted state, and the tibial implant part has a surface area that contacts the meniscus replacement part in the implanted state. Each of the femoral implant part and the tibial implant part has a surface area that does not contact either the bone or the meniscus replacement part but contacts soft tissue in the implanted state. The femoral implant part has, at least in part, a hardening and wear reduction coating (particularly a multi-layer coating) in the articular granular surface area that slidably contacts the sliding partner.

[0002] Such a knee joint prosthesis is already known from EP2051666B1, and it has been proposed to form a hardening and wear reduction coating on the articular granular surface area of the femoral implant part that slidably contacts the meniscus replacement part and on the surface area of the tibial implant part that contacts the meniscus replacement part. This hardening and wear reduction coating is a multi-layer coating and particularly has a ceramic layer that exhibits particularly high wear resistance against sliding contact with the corresponding articular surface of the meniscus replacement part. They also prevent or reduce the release of metal ions from the inside of the femoral implant part or the tibial implant part due to articular sliding contact.

[0003] Previously, attempts have focused solely on optimizing the wear resistance of the surface area of ​​the implant portion that is subjected to stress from joint sliding movements (including micro-movements). Similar knee joint prostheses are disclosed in US8,642,112B2. In that disclosure as well, a hardening and wear-reducing coating is applied to the joint sliding surface. A separate porous layer is attached to the implant portion to form a three-dimensional porous surface structure that faces and contacts the bone. In one embodiment, a highly porous open-cell biomaterial having the form of a mesh carbon foam is mentioned. [Overview of the Initiative]

[0004] The objective of the present invention is to optimally fix a metal implant material to bone and to achieve problem-free contact with surrounding soft tissues, based on the above-described type of knee joint prosthesis.

[0005] This objective is achieved by the present invention, which is based on the aforementioned type of knee joint prosthesis. In the present invention, the femoral implant portion and especially the tibial implant portion are additively manufactured by metal 3D printing. The femoral implant portion and / or tibial implant portion have a three-dimensional porous surface structure formed by metal 3D printing in the surface region facing the bone, thereby enabling bone to integrate with the implant portion. The femoral implant portion and / or tibial implant portion have a coating in at least a portion of the surface region that does not come into contact with bone or the meniscus replacement portion but comes into contact with soft tissue, thereby reducing the surface roughness of these surface regions.

[0006] On the one hand, it is proposed to create a three-dimensional porous surface structure on the surface region of the implant facing the bone using metal 3D printing. On the other hand, it is proposed to apply a coating to reduce the surface roughness of the surface region that does not come into contact with bone or the meniscus replacement but does come into contact with soft tissue. According to the present invention, it has been found that if the surface in contact with soft tissue is rough, many cells die when relative movement occurs with the soft tissue. Therefore, the present invention proposes to reduce the surface roughness of the surface region of the implant that comes into contact with soft tissue by applying a coating, thereby reducing irritation to the surrounding soft tissue. The surface roughness is lower than the surface roughness of the uncoated surface region of the 3D printed implant, and also lower than the surface roughness of the surface region of the implant facing the bone. This optimizes, preferably all of the above-mentioned surface regions of the implant with respect to each specific function when the prosthesis is implanted. To do this, advantageously, the implant is manufactured using an additive manufacturing process with metal 3D printing, and the surface roughness generated in this process can be smoothed by applying a coating. This coating, applied to the surface area in contact with soft tissue, can reduce or prevent the tendency for bone to integrate with the implant, particularly in areas near joints and at the transition to the resection surface, thereby preventing or reducing undesirable heterotopic ossification. Since bone integrates particularly well with titanium, this is especially advantageous for implants made of titanium or titanium alloy.

[0007] The coating has the advantage of preventing or reducing the formation of bacterial biofilms by using appropriate materials such as zirconium nitride (ZrN). Such biofilm formation can lead to infections requiring further surgery, for example.

[0008] The surface roughness of the coated surface area, which does not come into contact with bone or the meniscus replacement but does come into contact with soft tissue, may be greater than or equal to the surface roughness of the articular condyle surface area, which comes into sliding contact and is coated with a hardened, wear-reducing coating. Advantageously, the surface areas of the femoral implant and / or tibial implant that come into contact with soft tissue are designed to be as smooth as possible.

[0009] When the surface roughness of a coated surface area that does not come into contact with bone or the meniscus replacement but does come into contact with soft tissue is measured as Ra according to DIN / ISO 21920-3, it is advantageous for the maximum to be 0.50 μm, particularly 0.40 μm, particularly 0.30 μm, and for the minimum to be 0.04 μm, particularly 0.05 μm, and particularly 0.10 μm.

[0010] Various methods can be used to form coatings that reduce surface roughness. It is advantageous for coatings applied to surface areas that do not come into contact with bone or meniscus replacement tissue but do come into contact with soft tissue to be formed by a PVD (Physical Vapor Deposition) process. This allows for the formation of a very uniform and thin coating in a process-stable manner. It is particularly advantageous for the coating thickness to be 3.5 to 6.0 μm when measured and specified in accordance with DIN / ISO 26423. Ceramic materials such as zirconium nitride (ZrN), chromium nitride (CrN), and chromium carbonitride (CrCN) are particularly suitable for the coating, and a multilayer structure is preferred. The coating may be bonded to the implant via an adhesion-promoting layer (particularly a cobalt-chromium or titanium-based adhesion-promoting layer).

[0011] In an advantageous embodiment of the knee joint prosthesis according to the present invention, at least the tibial implant portion has a three-dimensional porous surface structure in the surface region facing the bone, thereby enabling bone to integrate with the implant portion. The tibial implant portion also has a coating in at least a portion of the surface region that does not come into contact with the bone or the meniscus replacement portion but comes into contact with soft tissue, thereby reducing the surface roughness of these surface regions. This not only ensures that the tibial implant portion is securely fixed to the bone, but also reduces irritation to the soft tissue surrounding the tibial implant portion because the surface in contact with soft tissue is smooth.

[0012] The following describes hardening and wear-reducing coatings applied to the articular condylar surface region that slides against the meniscus replacement portion. It is advantageous for the hardening and wear-reducing coating (especially multilayer coatings) applied to the articular condylar surface region that slides against it to be made of zirconium nitride (ZrN) or to have a zirconium nitride-based ceramic surface.

[0013] Furthermore, it is advantageous if the hardening and wear-reducing coating applied to the articular condylar surface region that comes into sliding contact is formed from multiple layers and bonded to the implant via an adhesion-promoting layer (particularly a titanium-based adhesion-promoting layer).

[0014] Furthermore, it is advantageous for the hardening and wear-reducing coating to have a chromium nitride (CrN) layer and / or a chromium carbonitride (CrCN) layer and / or a zirconium nitride (ZrN) layer.

[0015] Furthermore, it is advantageous for the hardening and wear-reducing coating to have a zirconium nitride (ZrN)-based surface layer and a chromium nitride (CrN)-based or chromium carbonitride (CrCN)-based internal layer, and the chromium nitride (CrN)-based internal layer and the chromium carbonitride (CrCN)-based internal layer may be arranged alternately.

[0016] Furthermore, in order to reduce wear caused by micro-movements between the meniscus replacement portion and the plateau of the tibial implant portion, it is advantageous for both the tibial implant portion and the articular condylar surface region of the femoral implant portion to have the aforementioned type of hardening and wear-reducing coating (especially multilayer coating) on ​​the surface region that comes into contact with the meniscus replacement portion.

[0017] To bond a surface roughness-reducing coating to a soft tissue contact area, it is advantageous for the coating, applied to a surface area that does not come into contact with bone or the meniscus replacement but does come into contact with soft tissue, to be bonded to the implant via a titanium-based adhesion-promoting layer.

[0018] According to the present invention, the coating applied to the surface region that does not come into contact with bone or the meniscus replacement but does come into contact with soft tissue may be the same coating as the hardening and wear-reducing coating applied to the articular condyle-like surface region that comes into sliding contact with the bone, and it has been found that this is advantageous. Each coating can be bonded to the substrate of the implant portion via various adhesion-promoting layers. For example, the adhesion-promoting layer of the hardening and wear-reducing coating may be cobalt-chromium-based or titanium-based, and the adhesion-promoting layer of the surface roughness-reducing coating in the soft tissue contact region may be titanium-based. However, both coatings may be bonded via the same titanium-based adhesion-promoting layer.

[0019] Furthermore, it is advantageous if the meniscus replacement portion has a polymer-based (particularly polyethylene-based) sliding surface that contacts the articular condylar surface region of the femoral implant. The entire meniscus replacement portion may also be made of polymer.

[0020] Regarding the manufacturing of implant portions, it is advantageous for metal femoral implant portions and metal tibial implant portions to be additively manufactured. Additive manufacturing by metal 3D printing is suitable for manufacturing complex and particularly delicate structures that are difficult or impossible to manufacture by injection molding or casting techniques. However, with respect to the present invention, additive manufacturing is advantageous in that it can manufacture any closed structure and / or three-dimensional porous structure (including surface structure). For example, the implant portion may be designed to have both a preferably substantially closed joint surface area and a three-dimensional porous surface area that contacts the bone. In this case, the three-dimensional porous surface area of ​​the implant portion can be formed by additive manufacturing by metal 3D printing without adding another porous layer to the implant portion. In particular, the bone contact area of ​​the implant portion may be formed by a three-dimensional bar structure, and the three-dimensional bar structure may extend inward from the outer shell surface to any depth. In this case, bone tissue can penetrate deep into the implant portion, and the implant portion and, consequently, the prosthesis can be securely fixed over the long term. The inherent surface roughness in 3D printing can be reduced by applying a roughness-reducing coating to the soft tissue contact area.

[0021] It is particularly advantageous if the metal femoral implant portion and / or metal tibial implant portion are additively manufactured from titanium or a titanium alloy. Because bone readily integrates with surfaces formed of titanium or titanium alloys, titanium or titanium alloys are suitable for directly forming surface areas that face and contact the bone. For this purpose, the natural surface roughness produced by 3D printing is even more advantageous. In particular, α-type or β-type titanium alloys (e.g., Ti6-Al4-V or Ti-24Nb-4Zr-8Sn) may be used as the titanium alloy.

[0022] By applying a pre-formed coating to the articular condylar surface region, the tribological properties of the titanium surface can be improved, and in the soft tissue contact region, as described above, undesirable bone grafting can be prevented or suppressed.

[0023] The subject of the present invention is a femoral implant part and / or a tibial implant part, each implant part having a three-dimensional porous surface structure in the bone contact region within the surface region facing the bone, enabling bone ingrowth with the implant part, and having a coating in the surface region that does not contact the bone or the meniscus replacement part but contacts soft tissue, thereby reducing the surface roughness of these surface regions.

[0024] Further features, details, and advantages of the present invention will become apparent in the following description of embodiments according to the present invention, the appended claims, the drawings, and an orthopedic knee joint prosthesis.

Brief Description of the Drawings

[0025] [Figure 1] A perspective exploded view of an orthopedic knee joint prosthesis according to an embodiment of the present invention, the orthopedic knee joint prosthesis having a femoral implant part, a tibial implant part, and a meniscus replacement part that can be fixed to the tibial implant part. [Figure 2] A schematic simplified cross-sectional view of the femoral implant part. [Figure 3] A side view of the tibial implant part, with a part shown in cross-section. [Figure 4] A view of the tibial implant part from above in the direction of arrow IV in FIG. 3. [Figure 5] A view of the tibial implant part from below in the direction of arrow V in FIG. 3. [Figure 6] Schematically shows an additively manufactured three-dimensional porous metal structure of the implant part region for integration with bone tissue. [Figure 7] Schematically shows a multi-layer coating.

Modes for Carrying Out the Invention

[0027] The femoral implant portion 4 has a surface area 10 that faces and contacts the femoral bone (femur) (not shown), and further has an articular condyle-like surface area 12 that slides against the meniscus substitute portion 8, which is its sliding counterpart. Furthermore, the femoral implant portion 4 has a surface area 14 that does not contact the bone or the meniscus substitute portion 8, but does contact soft tissue. The surface area 14 is located outside the articular sliding contact with the meniscus substitute portion, and is particularly the portion that protrudes from the femoral implant portion 4 in the horizontal direction.

[0028] The tibial implant portion 6 also has a surface area 16 that faces and contacts the bone of the lower leg (tibia). Furthermore, the tibial implant portion 6 has a surface area 18 that contacts the meniscus replacement portion 8, and the tibial implant portion 6 also has a surface area 20 that does not contact the bone or the meniscus replacement portion 8 but contacts soft tissue.

[0029] As can be seen from Figures 1 to 5, the femoral implant portion 4 has at least one dome-shaped or shaft-shaped projection 22, and the tibial implant portion 6 has an elongated projection 24, each of which is for engagement and fixation with the femur or tibia. The projection 24 of the tibial implant portion 6 is connected to the disc-shaped plateau portion 26 of the tibial implant portion 6 via a cheek-shaped portion 25 that extends along a vertical plane.

[0030] As best shown in Figure 4, the disc-shaped plateau 26 has a flat recess 28 on the opposite side of the bone and on the meniscal replacement 8 side, the recess 28 for inserting (particularly locking) the corresponding region 28 of the meniscal replacement 8.

[0031] In the illustrated preferred example, the femoral implant portion 4 and the tibial implant portion 6 are designed to have three-dimensional porous surface structures 30 and 32 in the bone contact area. These three-dimensional porous surface structures 30 and 32 extend macroscopically to at least 0.5 mm, and especially to a maximum of 20 mm, especially to a maximum of 15 mm, and especially to a maximum of 10 mm, in the depth direction toward the interior of the corresponding implant portions 4 and 6, and each implant portion 4 and 6 is manufactured by an additive manufacturing process.

[0032] The meniscus substitute portion 8 forms a three-dimensional sliding surface region 34 that is substantially complementary in shape to the articular condylar surface region 12 of the femoral implant portion 4, and acts as a sliding counterpart to the femoral implant portion 4. The sliding surface region 34, like the entire meniscus substitute portion 8, is composed of a polymer (particularly polyethylene). To reduce frictional contact and wear between the articular condylar surface region 12 of the femoral implant portion 4 and the meniscus substitute portion 8, the articular condylar surface region 12 that slides in contact with the meniscus substitute portion 8 has a hardened / wear-reducing coating (particularly a multilayer coating) 38. This coating has multiple ceramic layers, a surface layer which is preferably made of zirconium nitride, and an adhesion-promoting layer on the substrate of the femoral implant portion 4 (illustrated below with respect to Figure 7). The hardened / wear-reducing coating 38 may be formed as detailed in EP 2 051 666 B1, the details of the structure of the hardened / wear-reducing coating in that document are incorporated into this application by reference.

[0033] The surface area 18 of the tibial implant portion 6 that is in contact with the meniscus replacement portion 8 is provided with a corresponding hardening and wear-reducing coating 50. Although the meniscus replacement portion 8 and the tibial implant portion 6 are held together (particularly locked together), micro-movements occur between them, so the above arrangement is advantageous.

[0034] In this invention, it has been found that the surface areas of the femoral implant portion 4 and the tibial implant portion 6 that come into contact with soft tissue may have adverse effects on the soft tissue. When the implant portions move together, these surface areas move relative to the soft tissue, and if the surface areas 14 and 20 are too rough, in the worst case, it may lead to cell death. Therefore, this invention proposes applying smoothing coatings 52 and 54 to the surface area 14 of the femoral implant portion 4 that comes into contact with soft tissue and the surface area 20 of the tibial implant portion 6 that does not come into contact with the bone and meniscus replacement portion, respectively, in order to reduce the surface roughness of the surface areas 14 and 20 that come into contact with soft tissue. The objective is to achieve the smoothest possible surface so that frictional energy is not introduced into the soft tissue due to relative movement, or to significantly reduce such introduction.

[0035] Furthermore, it is advantageous that the surface roughness reduction coatings 52 and 54 are formed only on the web, struts, and ribs on the outside of the structure during the PVD process. Even if the three-dimensional porous surface regions 10 and 16 of the implant parts 4 and 6 that come into contact with the bone are mistakenly coated, this does not significantly hinder the adhesion of bone tissue to the three-dimensional porous structure.

[0036] Furthermore, it was found that smoothing coatings (i.e., surface roughness reduction coatings) 52 and 54 can be formed using the same layer configuration as the hardening / wear reduction coatings 38 or 50 provided on the articular condylar surface region 12 of the femoral implant portion 4 and the surface region 18 of the tibial implant portion 6 that face the meniscus replacement portion 8.

[0037] Figure 7 schematically shows, as an example, a multilayer coating structure equally suitable for constructing the corresponding hardening / wear reduction coatings 38, 50 and the smoothing coatings 52, 54. The substrate 60 of the corresponding implant portion 4 or 6 and the adhesion-promoting layer 62 (particularly a titanium-based layer) are shown, with the thickness of the adhesion-promoting layer being particularly 30-200 × 10 -9The thickness is approximately m. Multiple ceramic layers 64 (particularly layers made of two alternating materials) are provided on top of this layer. Finally, a ceramic surface layer 66 (particularly a zirconium nitride-based layer) is provided. As described above, this layer structure can be used for both hardening and wear-reducing coatings 38, 50 and smoothing coatings 52, 54 that come into contact only with soft tissue.

Claims

1. An orthopedic knee joint prosthesis (2) having a metal femoral implant portion (4), a metal tibial implant portion (6), and a meniscus substitute portion (8) that forms a sliding mating surface with the femoral implant portion (4) and is held by the tibial implant portion (6), The femoral implant portion (4) has a surface region (10) that faces and contacts the bone when implanted. The femoral implant portion (4) has an articular condyle-like surface region (12) that slides against the meniscus replacement portion (8), which is the sliding mating surface in the implanted state. The tibial implant portion (6) has a surface region (16) that faces and contacts the bone in the transplanted state, The tibial implant portion (6) has a surface region (18) that contacts the meniscus replacement portion (8) in the transplanted state, Each of the aforementioned femoral implant portion (4) and tibial implant portion (6) has a surface area (14, 20) that, in the transplanted state, does not come into contact with the bone or the meniscus replacement portion but comes into contact with soft tissue. The femoral implant portion (4) has a hardening and wear-reducing coating, particularly a multilayer coating (38), on at least a portion of the articular condyle-like surface region (12) that slides against the sliding mating surface. The femoral implant portion (4) and, in particular, the tibial implant portion (6) are manufactured by metal 3D printing. The femoral implant portion (4) and / or the tibial implant portion (6) have a three-dimensional porous surface structure (30, 32) formed by 3D printing in the surface regions (10, 16) facing the bone, thereby enabling the bone to integrate with the implant portion (4, 6). The femoral implant portion (4) and / or the tibial implant portion (6) are characterized in that at least a portion of the surface areas (14, 20) that do not come into contact with the bone or the meniscus substitute portion (8) but come into contact with soft tissue have a coating (52, 54) thereby reducing the surface roughness of these surface areas (14, 20). Orthopedic knee joint prosthesis (2).

2. The surface roughness of the surface region (14, 20) where the coating (52, 54) is provided, which does not come into contact with the bone or the meniscus substitute but comes into contact with soft tissue, is characterized in that it comes into sliding contact with the joint condyle surface region (12) where the hardening and wear-reducing coating is provided, and is therefore greater than or equal to the surface roughness of the joint condyle surface region (12) where the hardening and wear-reducing coating is provided. The orthopedic knee joint prosthesis (2) according to claim 1.

3. The surface roughness of the surface region (14, 20) where the coating (52, 54) is provided, which does not come into contact with the bone or the meniscus substitute portion (8) but comes into contact with soft tissue, is characterized in that, when measured as Ra in accordance with DIN / ISO 21920-3, it is at a maximum of 0.50 μm, particularly at a maximum of 0.40 μm, particularly at a maximum of 0.30 μm, and at a minimum of 0.04 μm, particularly at a minimum of 0.05 μm, particularly at a minimum of 0.10 μm. The orthopedic knee joint prosthesis (2) according to claim 1 or 2.

4. The coating (52, 54) on the surface region (14, 20) that does not come into contact with the bone or the meniscus substitute portion (8) but comes into contact with soft tissue is formed by a PVD (physical vapor deposition) process. An orthopedic knee joint prosthesis (2) according to one or more of claims 1 to 3.

5. The tibial implant portion (6) has a three-dimensional porous surface structure (32) in the surface region (16) facing the bone, thereby enabling the bone to integrate with the implant portion (6). The tibial implant portion (6) is characterized in that at least a portion of the surface area (20) that does not come into contact with the bone or the meniscus substitute portion (8) but comes into contact with soft tissue has a coating (54) that reduces the surface roughness of these surface areas (20). An orthopedic knee joint prosthesis according to one or more of claims 1 to 4 (2).

6. The hardening and wear-reducing coating, particularly the multilayer coating (38), on the joint condylar surface region (12) that is in sliding contact is characterized in that it is made of zirconium nitride or has a zirconium nitride-based ceramic surface. An orthopedic knee joint prosthesis according to one or more of claims 1 to 5 (2).

7. The hardening and wear-reducing coating (38) on the joint condylar surface region (12) that is in sliding contact is formed of multiple layers, and is characterized in that it is bonded to the implant portion (4) via a chromium-based or titanium-based adhesion-promoting layer. An orthopedic knee joint prosthesis according to one or more of claims 1 to 6 (2).

8. The hardening and wear-reducing coating (38) is characterized by having a chromium nitride (CrN)-based layer and / or a chromium carbonitride (CrCN)-based layer and / or a zirconium nitride (ZrN)-based layer. An orthopedic knee joint prosthesis according to one or more of claims 1 to 7 (2).

9. The hardening and wear-reducing coating (38) has a zirconium nitride-based surface layer and a chromium nitride (CrN)-based or chromium carbonitride (CrCN)-based internal layer. The material is characterized in that chromium nitride (CrN)-based inner layers and chromium carbonitride (CrCN)-based inner layers can be arranged alternately. An orthopedic knee joint prosthesis according to one or more of claims 1 to 8 (2).

10. The tibial implant portion (6) is characterized in that, in order to reduce wear caused by micro-movements between the meniscus substitute portion (8) and the plateau (26) of the tibial implant portion (6), it has a hardened and wear-reducing coating, particularly a multilayer coating (50), on the surface region (18) that is in contact with the meniscus substitute portion (8). An orthopedic knee joint prosthesis according to one or more of claims 1 to 9 (2).

11. The coating in the surface region that does not come into contact with the bone or the meniscus replacement portion but comes into contact with soft tissue is characterized in that it is bonded to the implant portion via a titanium-based adhesion-promoting layer. An orthopedic knee joint prosthesis according to one or more of claims 1 to 10 (2).

12. The coating in the surface regions (14, 20) that do not come into contact with the bone or the meniscus substitute portion (8) but come into contact with soft tissue is characterized in that it is the same coating as the hardening and wear-reducing coating (38) in the articular condyle surface region (12) that comes into sliding contact with the bone. An orthopedic knee joint prosthesis according to one or more of claims 1 to 11 (2).

13. The meniscus replacement portion (8) is characterized by having a polymer-based, particularly polyethylene-based, sliding surface that contacts the articular condylar surface region (12) of the femoral implant portion (4). An orthopedic knee joint prosthesis according to one or more of claims 1 to 12 (2).

14. The metal femoral implant portion (4) and / or the metal tibial implant portion (6) are characterized in that they are additively manufactured from titanium or a titanium alloy. An orthopedic knee joint prosthesis according to one or more of claims 1 to 13 (2).

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