DE102020116929A1 - Endoprosthesis, method for the production thereof and use of an endoprosthesis - Google Patents

Abstract

An endoprosthesis (1) for at least partially replacing a joint (5) of a mammal, a method for producing an endoprosthesis (1) and a special use of an endoprosthesis (1) are described. The endoprosthesis (1) has an attachment area (2) for direct or indirect attachment to or in a bone (6) of the mammal and a sliding surface (3) which is set up to surround a joint gap (7) of an at least partially artificial joint (5) and to form a sliding pair (8) with at least one artificial or natural joint component comprises a metal, and that the sliding surface (3) is arranged on the prosthesis base body (4) and comprises a ceramic material at least in regions.

Description

The invention relates to an endoprosthesis for at least partial replacement of a joint of a person or an animal, a method for its production and particularly suitable uses of the endoprosthesis. The endoprosthesis has an attachment area for direct or indirect attachment to or in a bone of a person or an animal and a sliding surface which is designed to delimit a joint gap of an at least partially artificial joint and a sliding pairing with at least one artificial or natural joint component to build.

An endoprosthesis, also known as a joint replacement, is an implant that remains in a person or animal for as long as possible and completely or partially replaces a damaged joint. In addition to hip endoprostheses, endoprostheses are now also available for knee joints, shoulder joints and, in some cases, for ankle joints, elbow joints and finger joints. In veterinary medicine, artificial hip joints in particular are used for dogs and cats.

A hip endoprosthesis is usually used to replace the femoral head and acetabulum. If the patient suffers from osteoarthritis of the hip or femoral head necrosis, the entire joint is regularly replaced, as the femoral head and socket are often equally damaged. Even after a femoral neck fracture, in most cases the broken thigh bone and the acetabulum are replaced at the same time, since the remaining acetabular cartilage would be damaged in the long run if the femoral head was only replaced. In many cases, as part of an operation on the thigh side, after the femoral head has been removed, a more or less long shaft is inserted into the medullary canal of the bone, onto which the artificial femoral head or hip ball is finally placed. Another form of an artificial hip joint, on the other hand, only replaces the worn surfaces of the femoral head and acetabulum and is known as a surface replacement prosthesis or cap prosthesis. The aim of modern endoprosthesis care is to reduce pain and increase the patient's quality of life, while ensuring the longest possible service life for the implant, that is, the implant remains in the body without complications. For this reason, the strength of the individual components of an endoprosthesis and their secure connection with the bone with low wear and tear, body compatibility and minimization of impermissible stresses in the bone are essential quality features of an implant.

the DE 44 37 479 A1 describes endoprostheses that are suitable for replacing a damaged knee or hip joint. It is essential to the technical solution described that a base body to be attached to a bone or to be introduced into a cavity in a bone is provided, which has a sliding surface to simulate the joint and projections to improve the retention in or on a bone. Here, the projections are knife-like and each have sharp edges protruding from the base body, which cut into the bone provided for attachment when the endoprosthesis provided with the projections is introduced. In this way, relative movements between the base body and the bone provided for the fastening are to be largely prevented and the area provided for the growth of the bone is to be enlarged.

In general, with orthopedic endoprostheses or implants that are in contact with a bone, for example on the femoral condyles or in the medullary canal of the thigh bone, complications can be attributed to the material properties of the endoprostheses and have a negative impact on their service life. Endoprostheses which are at least partially attached to the bone and which also have a sliding surface in the area of the joint are often made of special metal alloys, for example cobalt-chromium alloys, the wear particles of which can lead to significant biologically undesirable tissue reactions and, as a result, cause implant failure. For this reason, ceramic endoprostheses are sometimes used, which are primarily characterized by better compatibility in the body, the so-called biocompatibility, and low wear rates.

A corresponding ceramic endoprosthesis is from the DE 10 2011 005 424 A1 known. The ceramic endoprosthesis described has a prosthesis body which is formed from an aluminum oxide or zirconium dioxide ceramic, which can be stabilized with yttrium oxide, magnesium oxide or other oxides. A porous, rough ceramic layer consisting of one or more granulate layers is applied to the surface of the ceramic endoprosthesis on the bone side. According to a described embodiment, to produce the ceramic layer, ceramic granules are mixed as a suspension to form a slip, applied in this form to the basic prosthesis body and solidified by sintering in a furnace.

However, due to the comparatively high rigidity of a ceramic, the use of ceramic endoprostheses can lead to a so-called stress shielding or so-called stress shielding in the case of cement-free anchoring in the adjacent bone. Tension shielding means that the bone adjoining the artificial joint no longer absorbs the tensions that are usually introduced into the bone by a natural joint, so that the bone density in the fastening area of the artificial joint decreases over time, for example due to bone remodeling processes, and the risk of a aseptic loosening of the implant.

Based on the endoprostheses known from the prior art and the problems described above, the invention is based on the object of developing the endoprostheses used in such a way that, on the one hand, abrasion on the sliding surfaces of the joint replacement is at least largely avoided or at least significantly reduced and on the other hand, an endoprosthesis in the area in which it is attached to a bone has at least a bone-like rigidity. Here, above all, a physiological load introduction corresponding to the natural joint should be made possible and thus stress shielding or so-called stress shielding in the case of cement-free anchoring should be prevented or at least considerably reduced.
Furthermore, the technical solution to be specified should enable the connection of an endoprosthesis to the bone of a patient using the already known connection techniques. It should therefore be possible to fix the endoprosthesis with a bone cement as well as cement-free fixation. In addition, the components used should be biocompatible, i.e. compatible with regard to use in the human or animal body, and guarantee the longest possible service life for an endoprosthesis in the body.

The aforementioned object is achieved with an endoprosthesis according to claim 1 and a method for producing an endoprosthesis according to claim 10. Furthermore, special uses of an endoprosthesis designed according to the invention are specified in claims 15 and 16. Advantageous embodiments of the invention are the subject matter of the dependent claims and are explained in more detail in the following description with partial reference to the figures.

The invention relates to an endoprosthesis for at least partial replacement of a joint of a mammal with an attachment area for direct or indirect attachment to or in a bone of the mammal and with a sliding surface which is designed to delimit a joint gap of an at least partially artificial joint and with at least to form a sliding pair with an artificial or natural component of the joint. According to the invention, the endoprosthesis is characterized in that the fastening area is part of a prosthesis base body, which at least partially comprises a polymer or a metal, in particular a soft metal with a bone-like elasticity, and that the sliding surface is arranged on the prosthesis base body and at least in some areas comprises a ceramic material. The endoprosthesis according to the invention is thus characterized in that a prosthesis base body made of a composite material is provided, which in relation to the implantation position on the bone side is a polymer or a plastic material or a soft metal, e.g. titanium or tantalum, and in the area of the sliding surface, which after Implantation is part of a sliding pair, has a ceramic material. In this context, it is generally conceivable that the prosthesis base body is designed in one piece, for example as a cover for a bone surface with a bone-side fastening area, or in several parts, for example with a shaft for fastening in the bone onto which a hip ball is attached.

Furthermore, it is conceivable that the material on the bone side, in particular plastic material or soft metal, e.g. titanium or tantalum, is at least partially connected to the ceramic material and / or at least partially a further material is provided between these materials. The bone-side material, in particular a polymer or plastic material or soft metal, is advantageously selected or structured in such a way that it has the same or at least similar rigidity to the bone to which the endoprosthesis is to be attached, so that a stiffness that is the same as that of the natural Joint-appropriate, physiological load introduction enables and thus a voltage shield, so the so-called stress shielding, is prevented or at least reduced.

The main advantage of using a ceramic material in the area of the sliding surface is that a sliding surface is provided which is characterized by low abrasion and whose abrasive particles are more biologically compatible than metal particles, for example. This reduces the risk of adverse tissue reactions that can lead to implant failure.

An endoprosthesis embodied according to the invention, which has a soft material on the bone side, such as a polymer or a soft metal, for example titanium or tantalum, and a hard ceramic material on the sliding surface, can advantageously be carried out both with the aid of a bone cement Anchored in the bone and implanted without cement. It is always essential to the invention that the basic prosthesis body of an endoprosthesis has at least two materials, namely at least in the attachment area via which the endoprosthesis is attached to or in a bone, an at least partially bone-like soft material, such as a polymer or a soft metal, e.g. titanium or tantalum and has at least one ceramic material in the area of a sliding surface, which after implantation forms a sliding pair with a further joint component.

According to the invention, soft metal is understood to mean any metal, in particular non-ferrous metal, and / or any metal alloy, which has a Mohs hardness of a maximum of 6.6. Titanium, tantalum, aluminum and / or zirconium are particularly suitable for use in the basic prosthesis body. Furthermore, it is advantageous if the metal used is elastic in such a way that its elasticity comes as close as possible to that of a bone. A metal is preferably used which, at a temperature of 20 ° C., has a modulus of elasticity of 70 to 187 GPa, preferably 100 to 130 GPa and very particularly preferably about 110 GPa. In particular, titanium and tantalum can preferably be used.

In a particular embodiment of the invention it is provided that the material consists of oxide ceramics. It is also conceivable that the ceramic material is a dispersion ceramic, such as aluminum oxide-reinforced zirconium dioxide or zirconium dioxide-reinforced aluminum oxide, whereby it is also generally conceivable that the zirconium dioxide with or without yttrium oxide, in particular without Y ₂ O ₃ stabilize. It is also conceivable that the ceramic material has at least one non-oxide ceramic, for example Si ₃ N ₄ or SiC. In principle, other biocompatible ceramics are also suitable, provided they are compatible with the patient and have good sliding properties.

With regard to the material used at least for the fastening area of the prosthesis base body, preferably for the entire prosthesis base body on which a sliding layer comprising ceramic material is arranged, in particular a polymer or a soft metal, e.g. titanium or tantalum, it is advantageous if this has a stiffness and / or a modulus of elasticity (E-module) which are at least similar to the corresponding properties of the adjacent bone after implantation. In this way, even after the endoprosthesis according to the invention has been implanted, the natural stresses occur in the stressed bone, so that there is little or no stress shielding, as sometimes occurs after implantation of the known endoprostheses in the area of the endoprosthesis anchors. Tension shielding is mainly caused by the use of stiff implant materials, whereby a reduction in tension in the bone compared to the natural joint situation leads to a decrease in bone density and thus the bone substance, so that ultimately the risk of aseptic loosening of the adjacent endoprosthesis and failure of the endoprosthesis, for example a hip cap endoprosthesis of a hip joint.

According to a particular embodiment of the invention, the material on the bone side, which at least partially forms the basic prosthesis body, has a polyetheretherketone (PEEK) and / or an ultra-high molecular weight polyethylene (UHMW-PE). Alternatively, soft metals such as tantalum or titanium with a corresponding porous structure can be used as the material on the bone side. It is essential for the material used in each case that stresses that occur when the artificial joint replacement is loaded are introduced into the bone attached to the endoprosthesis, as is the case in a natural joint. The bone adjoining the endoprosthesis is thus stressed in the usual way even after a joint has been replaced, so that a decrease in bone density in the area of the bone adjoining the endoprosthesis can be prevented or at least minimized.

In principle, other biocompatible polymers are also suitable, provided they are well tolerated by the patient, have the required strength and at least bone-like properties when absorbing stress.

Another embodiment of the invention provides that the plastic material has fibers and / or particles to improve the strength. In this context it is conceivable that at least one polymer arranged in the fastening area of the prosthesis main body is reinforced with fibers and / or particles, e.g. made of carbon. In this way, the strength properties of the basic prosthesis body, and in particular those of the fastening area of an endoprosthesis designed according to the invention, can be adapted as required to the stresses to be expected in each case.

Furthermore, it is conceivable that the fastening area of an endoprosthesis designed according to the invention has a special surface coating and / or surface structure at least on an outer surface facing the bone to which the endoprosthesis is fastened. Preferably the Surface coating over a material that promotes the growth of the bone on the attachment area of the endoprosthesis. It is particularly advantageous if the surface coating has titanium, a titanium plasma and / or calcium phosphates. A surface structure that favors the growth of the adjacent bone can also be produced by means of a subtractive machining process, for example by grinding, honing or lapping, and / or by targeted surface etching.

According to a further preferred embodiment, the endoprosthesis has at least one substance, in particular an active substance, for example an antibiotic, which is released in the patient's body over a longer period of time after implantation. An endoprosthesis according to the invention can thus preferably be used as part of a drug delivery system.

In principle, the fastening area on its surface facing the bone to which the endoprosthesis component is to be fastened can be designed in such a way that it is fastened to the femoral head with the aid of a bone cement. Alternatively, it is conceivable to design the fastening area in such a way that cement-free fastening of the endoprosthesis in the surrounding bone is possible. It is also conceivable that the fastening area in relation to the bone to which the endoprosthesis is to be fastened is designed with an oversize, so that fastening takes place by way of a press-in process.

In a particular embodiment of the invention, the prosthesis base body and the fastening area are made in one piece, in particular from the same polymer material, with a sliding surface having ceramic material being arranged at least in one area on the surface. The fastening area is preferably part of an anchoring element and is designed in such a way that the endoprosthesis can be fastened to or in a bone.

Alternatively, it is conceivable that the prosthesis base body is made in several parts and the fastening area is part of an anchoring element that is to be fastened in or on a bone and that has a connection structure to which at least one second element of the prosthesis base body is fastened directly or indirectly, for example can be plugged on , wherein the ceramic sliding surface is arranged on the at least one second element.

It is again essential to the invention that the prosthesis base body has on the one hand the material on the bone side, which forms a load-bearing, forces and / or stress-absorbing base structure, and on the other hand has a sliding surface arranged thereon, which has a ceramic material. For an implantation, an endoprosthesis is thus provided which has a composite material which is formed by a material provided on the bone side that has at least partially bone-like properties and a sliding surface that is applied at least in sections and that has a ceramic material.

The sliding surface can be applied to the basic prosthesis body by means of a coating process and subsequent tempering or sintering. It is also conceivable to fasten the sliding surface to the basic prosthesis body with the aid of suitable connecting elements, for example with screws, rivets and / or clamping elements. According to a particular embodiment of the invention, the sliding surface is attached to the basic prosthesis body by pressing or by gluing.

In addition to a special endoprosthesis, the invention also relates to a method for producing an endoprosthesis which is suitable for at least partially replacing a joint of a mammal and which has an attachment area for direct or indirect attachment to or in a bone of the mammal and via a sliding surface that is set up to limit the joint gap of an at least partially artificial joint and to form a sliding pair with at least one artificial or natural joint component. The fastening area in turn makes it possible to fasten the endoprosthesis to a bone adjacent to the joint. In contrast, the sliding surface is part of a sliding pair that is formed by two parts of the replaced joint that can be moved relative to one another. When the joint moves, there is usually a relative movement between the sliding surface of the endoprosthesis designed according to the invention and at least one further natural or artificial component of the joint. As an example, reference is made here to the femoral head, which is arranged in the hip joint so as to be movable relative to the acetabulum. In the hip joint, the sliding surface of the femoral head and the surface of the acetabulum thus form a sliding pair that delimits the joint space, which in the natural joint is filled by the synovial fluid and also enclosed by the joint capsule.

• - formgebende Erzeugung eines Prothesengrundkörpers, der über den Befestigungsbereich verfügt, aus einem ersten Werkstoff, der wenigstens ein Polymer oder ein Metall, insbesondere ein weiches Metall mit einer knochenähnlichen Elastizität, aufweist, sowie
• - formgebende Erzeugung der Gleitfläche aus einem zweiten Werkstoff der, wenigstens teilweise keramisches Material aufweist, und Verbinden der Gleitfläche mit einem Oberflächenbereich des Prothesengrundkörpers, wobei es denkbar ist, dass die formgebende Erzeugung der Gleitfläche, insbesondere die Herstellung einer finalen Form, Oberflächeneigenschaft, Festigkeit und/oder Härte, zumindest teilweise vor, während oder nach dem Verbinden der Gleitfläche mit dem Prothesengrundkörper erfolgt.

The method according to the invention is characterized by the following steps:

• - shaping production of a prosthesis base body, which has the fastening area, from a first material which has at least one polymer or a metal, in particular a soft metal with a bone-like elasticity, and
• - shaping production of the sliding surface from a second material which has at least partially ceramic material, and connecting the sliding surface to a surface area of the prosthesis main body, it being conceivable that the shaping production of the sliding surface, in particular the production of a final shape, surface property, strength and / or hardness takes place at least partially before, during or after the connection of the sliding surface to the prosthesis main body.

With the aid of the method according to the invention, an endoprosthesis can thus be produced which is at least partially made on the bone side from a polymer or a soft metal bone-side material and which has a fastening area for fastening to an adjacent bone after implantation and a sliding surface that has special sliding properties with comparatively high abrasion resistance at the same time.
According to the invention, soft metal is understood to mean any metal, in particular non-ferrous metal, and / or any metal alloy, which has a Mohs hardness of a maximum of 6.6. Titanium, tantalum, aluminum and / or zirconium are particularly suitable for use in the basic prosthesis body. Furthermore, it is advantageous if the metal used is elastic in such a way that its elasticity comes as close as possible to that of a bone. A metal is preferably used which, at a temperature of 20 ° C., has a modulus of elasticity of 70 to 187 GPa, preferably 100 to 130 GPa and very particularly preferably about 110 GPa. In particular, titanium and tantalum can be used with preference.

In a special embodiment it is provided that the sliding surface is glued, screwed and / or pressed onto the basic prosthesis body. It is essential in each case that a firm connection is created between the basic prosthesis body and the sliding surface. In this context, it is conceivable that the basic prosthesis body on which the sliding surface is arranged consists entirely of the polymer or soft metal provided according to the invention, such as titanium and / or tantalum. In this case it is advantageous if the endoprosthesis produced according to the invention has essentially two materials, namely on the one hand a polymer or soft metal to form a load-bearing structure and on the other hand a ceramic material for the sliding surface.

A further development of the invention provides that the shaping production of the ceramic sliding surface takes place at least partially by producing a shaped blank from at least one ceramic raw material and then heating the shaped blank. The heating takes place here preferably in the form of a sintering process, so that a completely hardened ceramic is produced. In this case, when producing the sliding surface, a so-called green compact or green body is preferably first produced, which can be processed with all known methods if necessary to produce the final shape, surface property, strength and / or hardness. In this context, the use of at least one subtractive or one additive method step is conceivable. It is therefore conceivable to produce a corresponding sliding surface by using a turning or milling process or also by means of additive manufacturing, for example by 3D printing. As an alternative or in addition, it is of course conceivable to process an already cured ceramic material, which is to form the sliding surface of an endoprosthesis designed according to the invention, using a subtractive processing method such as turning, milling, grinding, honing or lapping.

A further embodiment of the invention provides that the fastening area is provided, at least in sections, with a surface coating which has titanium, a titanium plasma and / or calcium phosphate. The fastening area is preferably coated with a titanium plasma spray, all of the aforementioned surface coatings having the advantage of promoting the growth of a bone onto the endoprosthesis adjoining it. Applying a surface coating is therefore useful when the endoprosthesis is implanted without bone cement.

Furthermore, the invention also relates to an artificial joint or a joint replacement with at least one endoprosthesis, which is designed according to the invention and according to at least one of the embodiments described above and / or is produced using the method according to the invention. An endoprosthesis designed or manufactured according to the invention is particularly suitable for use in a hip cap endoprosthesis. In this context, it is conceivable in a particularly advantageous manner that an endoprosthesis designed according to the invention at least partially covers the surface of a damaged hip ball, the basic prosthesis body having at least one polymer or soft metal, such as titanium or tantalum, on which the bone is located remote side is at least partially a sliding surface that has at least one ceramic material. On the side facing the bone, a fastening area is provided on an inside, which is designed in the form of the hip ball surface and is clamped to it during the implantation. Incidentally, there is a stem with a Shank provided, which is introduced into a bore in the natural hip ball and is used to center the endoprosthesis and thus to align the endoprosthesis relative to the hip ball. The polymer or soft metal with elasticity that is as bone-like as possible is selected in such a way that its stiffness and / or modulus of elasticity corresponds at least approximately to that of the adjacent bone.

• 1: Schematische Gegenüberstellung von Schaft- und Kappen-Hüft-Endoprothese,
• 2: Schematische Gegenüberstellung von Kappen-, Kurzschaft-, und Geradschaft-Hüft-Endoprothese sowie
• 3: Schnittdarstellung einer erfindungsgemäß ausgeführten Hüftkappen-Endoprothese.

In the following, the invention is explained in more detail without restricting the general inventive concept on the basis of exemplary embodiments with reference to the figures. Show:

• 1 : Schematic comparison of stem and cap-hip endoprosthesis,
• 2 : Schematic comparison of cap, short stem and straight stem hip endoprosthesis as well
• 3 : Sectional view of a hip cap endoprosthesis designed according to the invention.

In the following, the invention is described on the basis of the special embodiment of an endoprosthesis which is used for hip endoprostheses, in particular for hip cap endoprostheses. However, the invention is not restricted to this embodiment, but can also be used for other endoprostheses. 1 shows a comparison of stem and cap hip prostheses as they are known from the prior art. In addition to this shows 2 a comparison of cap, short-stem and straight-stem hip endoprostheses, which are also known from the prior art.

In 1 a) a straight stem hip endoprosthesis is shown schematically. The lower part of the endoprosthesis 1 , which is connected to a femur during an implantation, has a shaft 10, which is anchored in the medullary canal of a femur, and an artificial femoral head 11, which is attached to the shaft 10 and replaces the natural femoral head. Also shows 1 a) an artificial, at least almost hemispherical acetabulum 12, which replaces the natural acetabulum. Artificial acetabular cups 12 that are inserted with bone cement are often made of polyethylene. Artificial acetabular cups 12, which are used without bone cement, are often of modular construction and have an additional shell 13, usually made of titanium, into which bone initially grows after it has been pressed in, and into which an acetabular cup 12, also called an inlay, is made of plastic or ceramic is used. In some cases, artificial acetabular cups that have been inserted without cement must be additionally anchored with the help of screws.

1b) shows a cap hip prosthesis. In contrast to shaft endoprostheses, when a cap endoprosthesis is implanted, both the femoral neck and the natural femoral head are largely preserved. The femoral head is covered with the aid of a cap 14 due to damage present in this area, the caps used in the solutions known from the prior art being designed as metal caps, in particular made of cobalt-chromium alloys. A comparatively thin and short stem with a shaft serves as a centering pin that is inserted into a hole in the femoral head and is intended to ensure the best possible alignment of the cap. A connection to the endoprosthesis 1 with the bone or anchoring takes place through a clamp connection between the fastening area 2 forming, a cap interior on the outside surrounding the inner surface of the cap and the femoral head introduced into the interior. The clamping effect is supported by the fact that the cross section of the open interior decreases from the cap opening along the stem in the direction of the sliding surface. An acetabular cup 12 is inserted into the hip bone. The cap 14 attached to the natural femoral head is thus part of a basic prosthesis body 4th the fastening area that is intended for anchoring and is clamped to the bone 2 and a sliding surface disposed on the cap surface 3 having. After the implantation, the sliding surface forms 3 with an artificial acetabulum 12 a sliding pairing 8th who have a joint space 7th at least partially limited.
In the 1 b) The cap hip endoprosthesis shown is also referred to as a surface replacement endoprosthesis.

2 shows again in addition to 1 the three main types of hip replacement used. In 2 a) a cap hip endoprosthesis is shown again. It is essential here that the femoral head is covered by a cap 14, which with its fastening area 2 forming inner surface is clamped on the femoral head and properly aligned with the help of the stem-shaped centering pin introduced into a bore. 2 B) shows a short-shaft hip prosthesis. This endoprosthesis has a comparatively short shaft 10, which is in the thigh bone 6th protrudes. In contrast to the cap hip prosthesis, this one has an endoprosthesis 1 however, via a spherical artificial femoral head 11 which is attached to the shaft 11. The short shaft 11 protrudes into the thigh bone in this way 6th that part of the femoral neck is preserved. If a replacement operation is necessary, there is thus more healthy bones 6th to disposal. For this reason, short-shaft implants are also called bone-saving. Such short-shaft hip prostheses are mainly used in younger people Patients are used for whom a later change operation is relatively likely due to their age.

Further shows 2 c) an endoprosthesis designed as a straight stem hip prosthesis 1 that have a comparatively long, in the thigh bone 6th used shaft 10 has, the inside of a thigh bone 6th is anchored. The shaft 10 serves to anchor the endoprosthesis in the medullary canal of the femur 6th and disposes of the bones in his 6th protruding area usually via a conical fastening structure onto which the artificial femoral head 12 is attached.

If the femoral head moves in the hip joint relative to the acetabulum, there is a risk of material wear and tear over a longer period of time. In the natural hip joint, the mechanical properties of the cartilage ensure a high load-bearing capacity for decades without significant wear and tear. When using artificial joint replacements, it is therefore of crucial importance that suitable materials and material pairings are used in order to minimize wear and tear on the endoprostheses used and to create a joint situation that is as natural as possible. This is where the invention comes into play.

3 shows an endoprosthesis designed according to the invention 1 , in which case it is a cap 14 for covering a damaged femoral head of a hip joint 5 acts. 3 shows the hip cap 14 in a sectional view and in view “A” a detailed view of a section of the hip cap 14. The cap 14 has a prosthesis main body 4th made of a plastic material or a soft metal, such as titanium or tantalum, on the one sliding surface 3 , which comprises a ceramic material, is applied. A polyetheretherketone (PEEK) or an ultra-high molecular weight polyethylene (UHMW-PE) is particularly suitable as a plastic material. The sliding surface 3 has a ceramic material, which can be a dispersion ceramic, such as alumina-reinforced zirconia or zirconia-reinforced alumina.

Essential to the endoprosthesis shown 1 is that the prosthesis main body 4th on the side intended for attachment to a bone via an attachment area 2 which is in one piece with the basic prosthesis body 4th is executed. According to the embodiment shown, the fastening area 2 in the form of an at least partially spherical shell-shaped inner surface which is placed on the femoral head and clamped to it. The stem, which is arranged centrally on the inside of the cap and which is also part of the basic prosthesis body, is inserted into a hole in the femoral head and is used for the correct alignment of the endoprosthesis 1 . In this context, it is conceivable that the fastening takes place without cement or with the aid of a bone cement applied at least in certain areas to the outside of the femoral head. When the endoprosthesis designed as a cap 14 is fastened without cement on the natural femoral head, the fastening area is located on the bone side 2 a surface coating 9 showing an increase in the area of attachment 2 surrounding bone 6th favored.

The sliding surface provided on the joint side 3 that are applied to the prosthesis base body, which has a polymer or a soft metal 4th is applied, has a ceramic material. Ceramic material in this case has the advantage that abrasion is minimized and abraded particles are largely bioinert, so that they do not cause any tissue damage in the patient's body. The sliding surface containing a ceramic material 3 is on the prosthesis body 4th , which has a plastic material, in particular a plastic material reinforced with carbon fibers, or soft metal, has been glued on. In the detailed view “A”, the transition between the basic prosthesis body is clear 4th forming material and the applied to it, the sliding surface 3 forming ceramic material.

By using ceramic material for the sliding surface 3 become the abrasion properties of the endoprosthesis 1 improved, while due to the use of a soft, structured material, in particular a plastic or a soft metal, such as titanium or tantalum, for the basic prosthesis body 4th the mechanical stability of the endoprosthesis 1 , here a cap 14 for a femoral head, is increased. By providing a soft, structured material for the basic prosthesis body 4th this has a bone-like stiffness, which enables a load application that corresponds to or at least comes close to that in a natural joint. For this reason, for the basic prosthesis body 4th a material is selected whose modulus of elasticity is at least almost the same as that of the modulus of elasticity and / or the stiffness of the adjacent bone after implantation 6th is equivalent to. This avoids or at least minimizes voltage shielding, so-called stress shielding, which leads to a decrease in bone density in the area of the implant attachment when endoprostheses known from the prior art are used. This is achieved by reducing the load on the natural bone after the implantation of an endoprosthesis designed according to the invention 1 at least almost corresponds to that with natural load application.

Furthermore, by providing a suitable surface coating 9 , here a coating with a titanium plasma spray and, if necessary, a supplementary structuring of the surface, a thigh bone growing on the fastening area 2 of the main body of the prosthesis 4th , which is rod-shaped or shaft-shaped in this case, favors.

In the 3 The endoprosthesis shown, designed according to the invention, here a cap 14 for covering a damaged femoral head, is characterized above all by the fact that a joint situation that at least mimics the natural conditions can be produced and thus a comparatively long service life of an endoprosthesis with this endoprosthesis 1 can be achieved. Aseptic loosening due to a decrease in bone density in the anchoring area of an endoprosthesis 1 Can occur in the bone due to the in the attachment area 2 suitable material used.

In the 3 shown, designed as a cap 14 for a femoral head endoprosthesis 1 represents part of an artificial joint for at least partial replacement of a hip joint. In addition to that in 3 Shown special cap 14 for a femoral head, if necessary, an acetabular cup is inserted into the hip bone, so that the sliding surface 3 a sliding pair 8th forms with the artificial acetabulum, with a relative movement occurring between the acetabulum and the femoral head covered by the cap 14 when the hip joint moves.

List of reference symbols

1

Endoprosthesis

2

Attachment area

3

Sliding surface

4th

Basic body of the prosthesis

5

joint

6th

bone

7th

Joint space

8th

Sliding pair

9

Surface coating

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 4437479 A1 [0004]
• DE 102011005424 A1 [0006]

Claims (16)

Endoprosthesis (1) for at least partial replacement of a joint (5) of a mammal with an attachment area (2) for direct or indirect attachment to or in a bone (6) of the mammal and with a sliding surface (3) which is designed around a To limit the joint gap (7) of an at least partially artificial joint (5) and to form a sliding pairing (8) with at least one artificial or natural joint component, characterized in that the fastening area (2) is part of a prosthesis base body (4) which at least partially comprises a polymer or a metal, and that the sliding surface (3) is arranged on the prosthesis base body (4) and at least in some areas comprises a ceramic material. Endoprosthesis after Claim 1 , characterized in that the ceramic material has an oxide ceramic or non-oxide ceramic, in particular Si ₃ N ₄ or SiC. Endoprosthesis after Claim 1 or 2 , characterized in that the polymer has fibers and / or particles. Endoprosthesis according to one of the preceding claims, characterized in that the metal at a temperature of 20 ° C has a modulus of elasticity of 70 to 187 GPa, preferably 100 to 130 GPa and very particularly preferably about 110 GPa. Endoprosthesis according to one of the preceding claims, characterized in that the polymer comprises a polyetheretherketone (PEEK) and / or an ultra-high molecular weight polyethylene (UHMW-PE). Endoprosthesis according to one of the preceding claims, characterized in that the fastening area (2) has, at least in sections, a surface coating (9) and / or a surface structure which favors the growth of the bone (6). Endoprosthesis after Claim 6 , characterized in that the surface coating (9) comprises titanium, titanium plasma and / or calcium phosphate. Endoprosthesis according to one of the preceding claims, characterized in that the fastening area (2) has at least one fastening element, at least in sections. Endoprosthesis according to one of the preceding claims, characterized in that the prosthesis base body (4) and the fastening area (2) are made in one piece. A method for producing an endoprosthesis (1) which is suitable for at least partially replacing a joint (5) of a mammal and which has an attachment area (2) for direct or indirect attachment to or in a bone (6) of the mammal and via a Sliding surface (3) which is designed to limit the joint gap (7) of an at least partially artificial joint (5) and to form a sliding pairing (8) with at least one artificial or natural joint component, characterized by the steps: shaping production of a prosthesis base body (4), which has the fastening area (2), from a first material which has at least one polymer or metal, shaping production of the sliding surface (3) from a second material which is at least partially ceramic material, before, during and / or after establishing a connection between the basic prosthesis body (4) and the sliding surface (3). Procedure according to Claim 10 , characterized in that the sliding surface (3) is glued, screwed and / or pressed onto the basic prosthesis body (4). Procedure according to Claim 10 or 11th , characterized in that the shaping production of the sliding surface (3) takes place at least partially by producing a shaped blank from at least one ceramic raw material and then heating the shaped blank. Method according to one of the Claims 10 until 12th , characterized in that the shaping production of a basic prosthesis body (4) with the fastening area (2) takes place at least partially by a subtractive and / or an additive manufacturing process. Method according to one of the Claims 10 until 13th , characterized in that the fastening area (2) is provided at least in sections with a surface coating (9) which has titanium, a titanium plasma and / or calcium phosphate. Artificial joint or joint replacement with at least one endoprosthesis (1) according to one of the Claims 1 until 9 . Hip cap endoprosthesis for at least regionally covering a femoral head surface with at least one endoprosthesis (1) according to one of the Claims 1 until 9 , in which the fastening area (2) on one of the femoral head surface to be covered facing inner surface of the Endoprosthesis (1) is arranged, which is at least partially adapted to the shape of the femoral head surface.

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