Femoral implant part or tibial implant part

Abstract

The invention relates to a femoral implant part (2) or tibial implant part, each made of a first plastic (10), in particular of PEEK, for an orthopedic knee joint prosthesis, wherein the femoral implant part (2) or the tibial implant part, in the implanted state, has surface regions (4) facing the femoral bone or the tibial bone, respectively, and in contact therewith; according to the invention, it is proposed that the femoral implant part (2) or the tibial implant part comprises at least one insert part (12) made of a second plastic (18), which partially forms the surface regions (4) in contact with bone and / or cement.

Description

[0001] The invention relates to a femur implant part or tibia implant part, each made of a first plastic, in particular of PEEK, for an orthopaedic knee joint prosthesis, wherein the femur implant part or the tibia implant part, in the implanted state, has surface areas facing the femur bone or the tibia bone and in contact therewith.

[0002] Femoral and tibial implant components have mostly been made of metal alloys, particularly cobalt-chromium-molybdenum alloys. For some time now, efforts have been made to manufacture these implant components from plastic, particularly PEEK (polyether ketone), which offers the advantage of a modulus of elasticity more similar to that of bone. A non-metal-based implant has also proven advantageous in preventing metal-related allergic reactions. However, some plastics, particularly load-bearing, resilient, and wear-resistant plastics such as PEEK, have the problem of poor cement or bone bonding. The present invention is therefore based on the object of improving implant components of the type mentioned above with regard to their ability to bond to bone or cement.

[0003] This object is achieved according to the invention in an implant part of the type mentioned in that the femur implant part or the tibia implant part comprises at least one insert part made of a second plastic, which partially forms the surface areas in contact with bone and / or cement.

[0004] The production of the respective implant component with an insert made of a second plastic makes it possible to select this second plastic in such a way that its ability to bond to bone can be optimized using typical bone cements. When selecting the second plastic, the primary consideration is not its load-bearing capacity and tribological properties, but rather its ability to bond, taking chemical processes into account. The invention therefore proposes that an insert made of a different second plastic be provided, which at least partially forms the surface of the implant component that bonds to the bone or cement, so that the ability of the implant component to bond can be optimized by the specific material selection of the second plastic.

[0005] According to one embodiment of the invention, the second plastic is PMMA.

[0006] Plastics of the type in question here can be processed in a variety of ways. As thermoplastics, they can be injection molded or extruded. 3D printing or filling with tribologically active components or reinforcing materials, such as carbon fibers, is also possible.

[0007] According to one embodiment of the invention, it proves to be advantageous that the femur implant part or the tibia implant part is produced as a plastic injection-molded part, wherein the at least one insert part is overmolded with the first plastic.

[0008] In a further development of this idea, it proves advantageous to form undercut areas during the overmolding of the insert in a direction orthogonal to the adjacent surface area in contact with bone or cement, which ensure permanent anchoring of the insert in the first plastic. These undercut areas effectively achieve a form-fitting integration of the insert into the first plastic of the implant component. Separation of the insert from the second plastic is thus impossible and reliably prevented due to the stability of the first plastic.

[0009] Furthermore, it proves advantageous if the insert is formed from the first plastic material so that it is flush with the surface areas in contact with the bone and / or cement. With such a flush and preferably at least partially flat design of the surface areas, the contact areas to be prepared on the bone can also be formed with the required precision to ensure a precise fit of the implant component.

[0010] According to one embodiment of the invention, it is proposed that the insert is a lattice part with webs and through-openings. The lattice part can be designed as a cross-lattice or also honeycomb-shaped, in particular with hexagonal honeycomb openings. The webs extending in the surface or plane allow the formation of a projecting connection surface towards the bone. In a further development of this idea, it proves advantageous if the webs, viewed in cross section, form undercut regions and are designed for this purpose in particular in a triangular, trapezoidal, or parallelogram shape. By appropriately orienting the triangular shape, trapezoidal shape, or parallelogram, the undercut regions can be realized in order to be able to anchor the insert securely in the material of the first plastic.

[0011] Notwithstanding this, it proves to be advantageous if the insert is extended in a plane and a thickness of the insert in the direction orthogonal to the plane is 1-4 mm.

[0012] The invention also relates to an orthopaedic knee joint prosthesis having the features of claim 9.

[0013] Further features, details and advantages of the invention emerge from the patent claims and the drawing and subsequent description of a preferred embodiment of an implant part according to the invention.

[0014] The drawing shows: Fig. 1 a perspective view (albeit schematic) of a femur implant part according to the invention; and Fig. 2 a sectional view of a grid-shaped insert (in schematic representation, not to scale), which is overmolded with plastic of the implant part; Fig. 3 a perspective view of the grid-shaped insert before overmolding with plastic.

[0015] The Fig. 1 and Fig. 2 schematically show the design of an implant part, here exemplified in the form of a femur implant part 2 according to the present invention. The perspective view of the Fig. Figure 1 shows the femoral implant component 2 from an oblique view above, i.e., with a view of surface areas 4 facing inward and facing the bone (not shown) and in contact with it. Furthermore, a centrally arranged connection area 6 can be seen for attaching additional connecting elements, such as shaft elements, to attach the implant component to the prepared femoral bone, typically using bone cement. Furthermore, the condylar surface areas 8, which extend obliquely from bottom to top, can be seen, by means of which the femoral implant component 2 can be moved back and forth during operation into sliding surface contact with the meniscus or a meniscus replacement component (not shown) of a total knee endoprosthesis.

[0016] The femur implant part 2 is formed on the basis of a first supporting plastic 10, in particular PEEK, and comprises, in surface areas 4 in contact with bone, one or more Fig. 1 shows structured inserts 12, each in the form of a grid part 14 with a grid structure of webs 16, which cross one another at an acute angle α, made of a second plastic 18, in particular and preferably of PMMA. The insert 12 is, before being embedded in the first plastic 10, in Fig. 3. The intersecting webs 16 of the lattice structure of the insert 12 form, for example, a diamond-shaped honeycomb shape. Fig. 2 shows schematically a section of the insert 12 embedded in the first plastic 10; it extends, for example, in a plane 11 orthogonal to the drawing plane of the Fig.2. It can be seen that the insert part 12 and its lattice structure and webs 16 have bevelled flanks 20 which form undercut regions 22 with material of the first plastic 10, viewed orthogonally to the plane 11, so that the insert part 12 is held in a form-fitting manner in the supporting plastic 10 of the femur implant part 2.

Claims

[1] Femur implant part (2) or tibia implant part, each made of a first plastic (10), in particular of PEEK, for an orthopaedic knee joint prosthesis, wherein the femur implant part (2) or the tibia implant part, in the implanted state, has surface areas (4) facing the femur bone or the tibia bone and in contact therewith, characterized by that the femoral implant part (2) or the tibial implant part comprises at least one insert part (12) made of a second plastic (18), which partially forms the surface areas (4) in contact with bone and / or cement. [2] Femoral implant part (2) or tibial implant part, characterized by that the second plastic is PMMA. [3] Femoral implant part (2) or tibial implant part, characterized by that it is produced as a plastic injection-molded part, wherein the at least one insert part (12) is overmolded with the first plastic (10). [4] Femoral implant part (2) or tibial implant part, characterized by that when the insert (12) is overmolded in a direction orthogonal to the adjacent surface area (4) in contact with bone or cement, undercut areas (22) are formed, which ensure a permanent anchoring of the insert (12) in the first plastic (10). [5] Femoral implant part (2) or tibial implant part, characterized by that the insert part (12) is formed flush with the surface areas (4) of the first plastic (10) that are in contact with bone and / or cement. [6] Femoral implant part (2) or tibial implant part, characterized by that the insert part (12) is a grid part (14) with webs (16) and through openings. [7] Femoral implant part (2) or tibial implant part according to claim 6, characterized bythat the webs (16) form undercut areas when viewed in cross section and are in particular triangular, trapezoidal or parallelogram-shaped. [8] Femoral implant part (2) or tibial implant part, characterized by that the insert part (12) extends in a plane (11), and a thickness of the insert part (12) in the direction orthogonal to the plane (11) is 1.0 - 4.0 mm. [9] Orthopaedic knee joint prosthesis with a femoral implant part (2), with a tibial implant part and with a meniscus replacement part, which forms a sliding partner for the femoral implant part (2) and is held on the tibia implant part, characterized by that the femur implant part (2) and / or the tibia implant part is designed according to one or more of the preceding claims.

Images