EP3790510A1

EP3790510A1 - Implant for use in a wear couple including a spherical wear partner

Info

Publication number: EP3790510A1
Application number: EP19721624.5A
Authority: EP
Inventors: Mateusz Maria JUSZCZYK
Original assignee: Ceramtec GmbH
Current assignee: Ceramtec GmbH
Priority date: 2018-05-07
Filing date: 2019-05-06
Publication date: 2021-03-17
Also published as: AU2019266468A1; US20210282931A1; CA3093488A1; CN112087989A; WO2019215069A1; BR112020019206A2; KR20210006903A; JP2021522915A; JP7379379B2; CN112087989B

Abstract

The invention describes an implant for wear couples in endoprosthetics, the implant having an outer side, with an outer face, and an inner side, and a hemispherical wear region for accommodating a spherical wear partner being formed on the inner side. The aim of the invention is to reduce the height of the implant as much as possible and to ensure that, e.g., the pelvic bone does not have to be milled down as much. According to the invention, the implant is therefore designed in the form of a ring or annular structure and the outer face permits direct implantation in the body. In order to reduce friction between the spherical wear partner and the implant to a minimum, the implant has a specially designed inner geometry.

Description

Implant for the sliding combination with a spherical sliding partner

description

The invention relates to an implant for the pairing in endoprosthetics, wherein the implant has an outer side and an inner side or an inner surface and on the inner surface of a specially designed sliding portion for receiving a spherical Gleitpartners is formed. It is preferably a ceramic implant.

So far implants have been used in endoprosthetics consisting of a metal shell and a ceramic half-shell insert. The metal shell is also designed as a half shell and takes on the ceramic insert. The sliding partner, the prosthesis head, is spherical and is absorbed by the ceramic insert. Ceramic inserts for the sliding pair in hip arthroplasty are hemispherical and cover approximately 50% of the prosthetic head. The center of the sliding surface is at the level of the face of the insert or slightly above or below it. The outside of the insert is divided into several areas. The region of the outside at the equator comprises a clamping surface, which may be conical or cylindrical. By means of this clamping surface is made with a shell, usually a metal shell, an operative connection. The insert is inserted into the shell. This is done either pre-assembled after production, or only during implantation.

Another area of the outside, the back of the insert, which extends from the equator to the pole, is not in contact with the metal shell, but must have a minimum wall thickness for stability reasons.

The load transfer between femoral head and insert or hip socket in the sliding surface is in this pairing point or circular, since there is a positive clearance between the ball diameter of the prosthesis head and the calotte diameter of the insert. The load is transmitted through the femoral head axis parallel to the insert.

DE 10 2016 222 616 A1 shows an implant, comprising a ceramic ring insert, which is introduced into a metal shell and on the inside has a hemispherical sliding surface for receiving the spherical sliding partner. The depth for the metal shell with the ring insert is reduced, so that compared to the conventional Implant made of metal shell and ceramic half-shell insert a less deep cutout in the pelvic bone is needed. In addition, there are no point loads, but strip-shaped loads with lower maximum values, similar to the physiological load absorption available.

Based on this, the task was to further reduce the friction between the spherical sliding partner and the implant. Furthermore, the object was to develop the most cost-effective and easy-to-use implant for endoprosthetics, which can be implanted in a simple manner in the bone.

According to the invention this object is achieved by a half-shell, preferably annular implant according to the features of claim 1. Preferred embodiments are specified in the subclaims. Embodiments can be combined with each other as desired.

According to the invention, the implant is designed so that it is anchored directly in the bone without a metallic shell. The design of the outer surface on the outside allows on the one hand the use for cement-free direct implantation, but also the implantation by means of medical adhesives and / or cement. The implant is preferably at least partially ceramic, preferably of full ceramic design.

The implant is used according to the invention to receive a ball of a prosthetic head, a spherical sliding partner. The ball of the prosthesis head and the implant form a sliding pair. The implant is held stationary in the pelvic bone. The ball of the prosthesis head should be able to rotate in the implant. A jumping out of the ball of the prosthesis head should be avoided.

In the present case, an implant, preferably an annular implant (ring), is understood to be a body which is formed from a cross-sectional area F (see FIG. 1 b) which rotates about an axis of rotation L (see FIG. 1 b). It has a concave inner surface and an outer side. The shape of the outside may be formed differently from the shape of the inside.

The implant has a first region, comprising an end face and an inlet zone, which ensures the insertion of a ball of a prosthesis head, the spherical sliding partner in the implant and a second area, the recording the ball is limited. In one embodiment, the implant corresponds to a half-shell whose second region is closed. In a further embodiment, the implant corresponds to a ring whose second region, comprising a bottom surface and an outlet zone, is open. The circular opening of the first area, the receiving area, has a diameter which is larger than the diameter of the opening of the second area. The circular opening of the second region of the annular implant is smaller than the diameter of the spherical sliding partner to be used in order to avoid slipping out of the spherical sliding partner, hereinafter referred to as KG.

The connection between the inner surface and the outer side forms a transition and is preferably made by radii. The rounded transitions avoid sharp edges and corners, which improves the stability of the implant. In addition, this facilitates handling. These radii preferably have an amount of 0.5-2 mm. The first transition of the inner surface to the outer side in the first region of the implant comprises an end face.

In the half-shell embodiment, the outside is formed closed. The surface development of the outside can correspond to a closed circle. The second region of the implant, which is arranged opposite the first region, is closed and has a closed bottom surface. The outside of this closed bottom surface is part of the outside of the implant. The maximum distance between the first region in which the end face is arranged and the bottom surface corresponds to the height H of the half shell. The inner surface of the closed bottom surface is part of the inner surface of the implant. The inner surface of the implant has a sliding area, followed by the inner surface of the closed bottom surface. A half-shell embodiment of an implant has a first opening, an inlet zone for introducing a ball. The geometry of the inner surface of the closed bottom surface may correspond to a dome, a hemisphere or a hemispherical shape.

The annular configuration of the implant has a second opening with respect to the first region. The diameter of this second opening is smaller than the diameter of the first opening of the first area. This allows and limits the introduction of KG into the implant. The surface development of the outside of a ring insert corresponds to a ring. Due to the opening, which is arranged opposite the first region of the implant, this has a second transition between the inner surface and outside on. This is located in the second area and limits the implant in height. The transition between inner surface and outer side comprises a bottom surface. The maximum distance between the end face and the second transition, or the bottom surface corresponds to the height H of the annular implant.

The rounded first transition of the inner surface of the implant to the beginning of the sliding area is referred to as the inlet zone, the rounded second transition of the inner surface of the implant to the beginning of the sliding area is referred to as the outlet zone.

The inner surface is at least partially rotationally symmetrical. The outer side and / or surface of the implant, preferably of the annular implant, may deviate from the rotational symmetry in partial regions. The height H (see FIG. 1 b) of the implant is understood to mean its extent along the axis of rotation L. In the annular embodiment, the height H is substantially smaller compared to the half-shell design. The outside of the implant corresponds to the side facing the bone into which the implant is to be implanted. The outer surface is an area of the outside and serves to attach the implant in the bone. The size of the outer surface may match the size of the outer surface. It can also be made smaller. The outer surface can take various forms, be divided into several areas or individual areas that are related to each other or are separated from each other. The design of the individual surfaces can be the same or different.

The implant according to the invention is designed as a half-shell or as a ring so that it cooperates with balls according to the prior art, wherein the functionality is ensured. The implant has a wall thickness of at least 3 mm to ensure stability. The maximum wall thickness of the implant depends on the sintering properties of the material used and is in the range of 15 mm, preferably at most 15 mm. The height H of the annular implant is preferably 5-20 mm. Depending on the circumstances of the application, an implant with the appropriate geometric dimensions is used.

The inner surface of the implant has a sliding area on which the KG is to rotate. The sliding region of the implant is configured concave and corresponds to a partial section of a surface of a rotary body. The rotating body is a spindle torus, which is described by a circle 108 rotating about a rotation axis. The distance A of the axis of rotation to the center M7M "of the circle is smaller than the radius r of the circle describing the torus. Parallel to the axis of rotation L are the center lines L 'and L ". The torus describes inside a spindle 105 with a center M, which is located in the middle of the line, which describes the maximum longitudinal extent of the spindle 105 and lies on the axis of rotation. The intersections of the outer surface of the spindle 105 with the axis L are referred to as E and E '. The surface is the outer surface 106 of the spindle 105 thus described.

The partial section 107, which describes the sliding region of the implant, corresponds to the region between the two normal planes S and S ', which intersect the longitudinal axis L, which corresponds to the axis of rotation of the spindle torus, at the points S1 and S2. Both points of intersection are between E 'and M, ie in one half of the spindle 105 in longitudinal extent. S1 may correspond to the center M of the spindle 105. S2 is between S1 and E 'or equal to E'.

The implant thus has, in its simplest embodiment, an internal geometry which corresponds to a section of the spindle of a spindle torus, wherein the region of the inner surface which is located between the end surface and the bottom surface is concave and the geometry of the outside can deviate from the rotational symmetry. The sliding area of the inner surface is thus not hemispherical, i. does not correspond to a section of a sphere. The sliding portion corresponds to the portion 107 of the outer surface 106 of a spindle 105. The portion 107 is located in one half of the spindle 105 along its longitudinal axis and does not exceed the center M of the spindle on the longitudinal axis L of the spindle 105. In the direction of the end face, the sliding region of the implant has a maximum diameter D1 at its first opening. At the second opening, the sliding area has a minimum diameter D2. The diameter D1 of the implant is greater than the diameter D2. The diameters of the spindle 105 between D1 and D2 become smaller in the direction D2.

The internal geometry according to the invention ensures the mobility of the KG, that is to say a sphere or a spherical segment of a prosthesis head. The diameter D1 of the first opening of the implant is greater than the outside diameter of the KG introduced into the implant. The diameter D2 is smaller than the outer diameter of the KG. The smallest diameter of the inlet zone is preferably greater than D1. S2 corresponds in one embodiment to the point E '. If S2 equals E ', the implant is a half shell. In this embodiment of the half-shell implant, the diameter D2 = 0, ie there is no second opening.

In a further embodiment, the implant is a half shell and S2 is located above E 'on the axis L. In this embodiment, the inner surface is formed flattened in the region E'. This reduces the height H of the implant. In this embodiment of the half-shell implant, the geometry of the inner surface of the closed bottom surface deviates from the geometry of the spindle. It is preferably ensured that the flattened inner surface of the closed bottom surface is designed such that it does not affect the geometry of the contact line and sufficient space is provided for the KG, in order to generate no point friction. It is then a hemispherical or preferably even more flattened inner surface of the closed bottom surface.

In a preferred embodiment, S2 is above E 'on the axis L and it joins the sliding area at D2 the outlet zone. Then the implant is a ring. In the annular embodiment, D2 is smaller than the radius of the KG to be used in order to avoid falling out.

The KG thus rotates in the non-hemispherical sliding region of the inner surface, the sliding region corresponding to a partial section 107 of half of a spindle of a spindle torus in longitudinal extension.

The height H _{G of} the sliding region corresponds to at least 20% and not more than 80% of the diameter of the KG to be used and preferably 50-95% of the height H of the implant.

The height of the sliding region corresponds to the extent in the longitudinal direction, ie along the axis of rotation L. The height H _G preferably corresponds to at least 25%, particularly preferably at least 30% and preferably at most 70%, particularly preferably at most 60% of the diameter of the KG to be used. For a ring-shaped implant, the height H _{G is} in particular at most 50% of the diameter of the KG.

The KG to be used in one embodiment has a diameter of 5 to 70 mm, preferably 6 to 64 mm. KG for human joint prostheses have a diameter of 20-70 mm, preferably 22-64 mm, for animal joint prostheses KG are used with a diameter of 5 - 20 mm, preferably 6 - 19 mm. Thus, in this embodiment, an implant, in which a KG with a diameter of 5 mm is to be used, a sliding area with a height of at least 1 mm and a maximum of 4 mm.

Furthermore, in one embodiment, the height H _{G of} the sliding region (2) corresponds to at least 20%, preferably at least 35%, particularly preferably at least 50%, and at most 95% of the height H of the half-shelled or ring-shaped implant. The outlet and inlet zones of an annular implant are not part of the sliding area. The inlet zone of the semi-shelled implant as well as the inner surface of the closed bottom surface with a possibly existing flattening are not part of the sliding area. The KG preferably does not touch the inlet and the inner surface of the closed bottom surface of the half-shell implant in the mounted state.

With regard to the geometry of the spindle, the following conditions preferably apply:

• A is the distance between L and L "or the horizontal distance from the center to the axis of rotation.

• r is the radius of the circle describing the spindle torus

• r _P is the radius of the spherical sliding partner, ie the radius of the prosthetic head.

• C is the clearance and follows Formula I.

C = (rr _p ) ^* 2 (formula I)

In one embodiment, the clearance corresponds to the sum of the production-dictated maximum deviations of the extensions of the prosthesis head (of the radius r _P ) and of an implant suitable for the prosthesis head with a hemispherical sliding region. In a particular embodiment, C is> 10 μm, preferably> 25 μm, particularly preferably> 50 μm and <500 μm, preferably <350 μm and particularly preferably <280 μm.

The radius r of the circle 108 describing the spindle torus is greater than the radius r _{P of} the KG.

KG has contact with the sliding area and glides on it, preferably KG is in line contact with the sliding area of the implant.

The contact line corresponds to a circular line in the sliding region, ie in the section 107 on the outer surface 106 of the spindle 105 of the spindle torus. This line corresponds to the section line of a cutting plane 11 1 through the spindle 105 in the region between S and S '. For a fixed predetermined radius r _{P of} the prosthesis head and fixed clearance, the diameter of the ring contact or the ring contact line by changing the distance A be influenced. Thus, the angle a between the longitudinal axis L of the spindle and the straight line connecting the center of the spherical sliding partner with a point 110 on the contact line can be influenced. If a increases, the contact line is oriented in the direction of the inlet zone of the implant. If a is smaller, the contact line is oriented in the direction of the bottom surface or outlet zone. A point contact would be in a hemispheric implant if a = 0. Since the implant according to the invention has a spindle shape in the half-shell shape, the ball can not touch the point of intersection E '.

The contact line is in one embodiment of the annular implant in the lower half of the height H of the implant, i. in the half of the implant facing the second region. Seen from the bottom surface or the outlet zone, the contact line is thus in the range between 0-50% of the height. This counteracts the dislocation, the jumping out of the prosthesis head from the implant. Preferably, the contact line is between 10-40%, and more preferably between 20-30% of the width of the implant viewed from the bottom surface. This contact line spaced from the bottom surface also allows the formation of a lubricating film, e.g. from synovial fluid, which aids in the sliding of the ball in the implant.

The implant according to the invention has in its annular configuration compared to a conventional, half-shell implant a much lower height and thus a much smaller installation depth. The cutout in the bone for implantation may therefore be smaller. This allows the use of an artificial implant in very small or thin bones, especially hip bones, as they are common in adolescents or children or animals. An implant according to the invention with a reduced height allows the depth required for insertion of the implant to be reduced to a minimum.

Preferably, the concave sliding region extends over> 80%, particularly preferably over> 95%, in particular preferably over the entire inner surface of the implant, as a result of which a major part or the entire inner surface is available for the sliding pairing.

The center of the sliding area is preferably arranged on the plane of the end face, or slightly above or below it, in the range of 0 to 2 mm.

In a further embodiment of the implant according to the invention, the implant, preferably also the sliding region on a partial section of the implant along the Longitudinal axis formed extended. This means that the height H of the implant, and preferably also the height H _{G of} the sliding region, change over the circumference of the circle. The implant, preferably also the sliding region, is formed either in the direction of the prosthesis head over the end face of the implant, and / or, in the case of a ring insert, over the bottom surface of the implant, raised / extended.

This enlargement of the implant, preferably the sliding region, is referred to as a cranial extension, and comprises only a part, a portion of the peripheral surface of the implant. This reduces the tendency to dislocation. The center of rotation is preferably on or below the end face.

A cranial elevation is a section or partial section of the implant which is arranged in the region of the inlet zone. This will increase the height H of the implant. This increase also extends the sliding area in one embodiment.

A cranial extension is a section or partial section of the implant, which is arranged in the region of the outlet zone. By increasing this length, the sliding area is also increased in one embodiment.

The cranial extension of the implant is formed in one embodiment by a balcony-like projection or a shaped projection, the inside of which is a continuation of the receiving space or the inner surface of the implant described by circular lines. In this case, the projection preferably makes the surface described by these circular lines on which the cranial elevation and / or extension lie.

In another embodiment of an implant according to the invention results in that the end face is not arranged in a plane. By means of a continuous slope of the end face and / or the bottom surface (in the case of a ring implant) of the implant, the cranial extension is realized. Starting from a position on the end face (or bottom face), this end face (or bottom face) continuously rises until it reaches its highest point after 180 degrees. From this highest point, the end face (or bottom surface) then drops continuously back to its starting point. As a result, the end face or bottom surface is arranged at a shallow angle to the rotation axis R. The flat angle of the thus arranged tilted end face is 95 to 105 degrees, preferably 97 to 101 degrees, particularly preferably 99.5 degrees. The center of the sliding area lies on or below the end face. The continuous increase in Face or bottom surface can also be in an area that is less than 180 degrees done. The same applies to the descent. Rise and descent are preferably formed the same length, but may also have different lengths.

Due to the cranial extension, the maximum height H 'of the implant in the area of the cranial extension deviates from the height H of the implant without cranial enlargement. The height of the implant is H '= H + x + y. In one embodiment, the cranial extension also leads to an enlargement of the sliding region, in this case the height of the sliding region is analogously H _G '= H _G + x _G + y _G.

The maximum extent of the cranial extension is denoted by x. This is the distance between the cutting plane S 'and the point Y'. The distance x thus describes the height difference of the points X 'and Y' along the axis of rotation L.

The maximum extent of the gliding area of the cranial extension is designated by x _G.

The maximum extent of the cranial elevation is denoted by y. This is the distance between the cutting plane S and the point Y. The distance y thus describes the height difference of the points X and Y along the axis of rotation L.

The maximum extent of the sliding area of the cranial elevation is denoted by y _G and describes the height difference of the points X _G and Y _G.

If x = y = 0, there is no cranial extension.

If x> 0 and y = 0, there is a cranial extension. In a preferred embodiment, additionally x _G > 0 _.

If x = 0 and y> 0, there is a cranial increase. In a preferred embodiment, additionally y _G > 0 _.

In another embodiment, x> 0 and y> 0, where x = / F y and x _G =! + Y _G > 0.

The distances x and y are directly proportional depending on the diameter of the ball to be used of the prosthesis head and the sum of x + y is preferably 2-20 mm, more preferably 3-15 mm.

The cranial elevation follows in one embodiment of the geometry of the spindle. That is, the portion of the torus, the extended area of the implant, possibly the extended Sliding area that forms cranial elevation is a development of the geometry of the spindle.

In another embodiment, an implant with a cranial extension in the region of the cranial extension no longer has any rotational symmetry along the axis of rotation L. The radii of the implant, possibly of the sliding region, of the cranial enlargement are not oriented in one embodiment on the geometry of a spindle.

The value of the radius defining the sliding range may then differ from the value of the radius defining the increase. Preferably, the value of this radius (the

dl

Increase) smaller or equal.

The cranial elevation must always meet the condition that the spherical sliding partner can continue to be used, i. the opening has a diameter which is larger than the diameter of the KG. The cutting plane through the spindle, which is between a point X lying on the plane S and the outer surface of the spindle, and another point Y, which is opposite to X and the maximum of the cranial elevation, must have a diameter which at least corresponds to the area of the spherical sliding partner to be used. X is on the opposite side from Y, i. a straight line K from X to Y intersects L. The preferred maximum cranial elevation of the implant results from a straight line K between X and Y, if this also intersects the center of the spindle. This also preferably applies to a cranial increase in the sliding area.

Particularly preferably, Y lies on the outer surface of the spindle. The inner surface continues to correspond to a portion of a spindle, wherein the part of the implant, which surrounds the sliding completely circular, corresponds to the portion of a half of the spindle along its longitudinal axis and this part does not exceed the center of the longitudinal axis L of the spindle.

In one embodiment of the cranial extension, the radii of the implant, possibly the sliding area, of the cranial extension do not orientate themselves on the geometry of a spindle. The value of the radius defining the sliding range may then differ from the value of the radius defining the extension. Preferably, the value of this

D 2

Radius (of increase) is smaller or equal. The portion of the torus which forms the extended sliding region, in a further embodiment, a development of the geometry of the spindle.

The cranial extension must always meet the condition that the spherical sliding partner still can not fall out, i. the opening has a diameter which is smaller than the diameter of the KG. The cutting plane through the spindle, which is between a point X ', which lies on the plane S' and the outer surface of the spindle, and another point Y ', which is opposite to X' and depicts the maximum of the cranial extension, must have a Have a diameter which is smaller than the diameter of the spherical sliding partner. X 'is on the opposite side of Y', i. a straight line K 'from X' to Y 'intersects L. Particularly preferably, Y' also lies on the outer surface of the spindle.

In one embodiment, the axis of rotation L does not correspond to the axis of rotation R of the conically or cylindrically shaped outside of the insert, preferably in the case of an annular insert with a cranial extension. Preferably, the axis of rotation R intersects the axis of rotation L, particularly preferably in the region of the sliding region. Preferably, the axis of rotation R is arranged such that it is perpendicular to and intersects the straight line K ', which connects the maximum extent of the bottom surface of the annular insert with and without cranial extension in the points X' and Y '. If such an insert is inserted into a conventional shell, the cranial extension appears as a cranial elevation and the internal geometry corresponds to a tilted spindle (shown in FIG. 12).

In a preferred embodiment, the implant should meet the mechanical, biological and chemical requirements during implantation and while remaining in the human or animal body in an excellent manner. The implant is therefore preferably made of a ceramic material. For this purpose, the implant furthermore has an outer surface on the outside, which is designed so that human or animal bone cells (eg osteoblasts) or cells, which are necessary in the formation of human or animal bone tissue (ossification), find favorable conditions. The implant is preferably designed so that it can be anchored over the outer surface directly in the bone. The outer surface has means for anchoring the implant. Thus, a direct implantation of the implant in the bone is possible. The aim of such a design is the complete bony installation in human or animal bones. The outer surface of the implant is provided in a preferred embodiment with a rough surface that allows direct implantation and fixation in the bone. The rough surface supports the ingrowth of the implant into the bone and thus assumes the task of anchoring in the bone. Under rough surface is understood according to the invention an outer surface having a three-dimensional structure or roughness, in the form of elevations and depressions. These elevations and depressions have dimensions that do not change the original shape of an implant according to the invention. For example, this means that an implant with a circular outer surface, which has a rough outer surface, still has a circular shape. Incidentally, this also applies to all other forms.

The rough surface of the outer surface is achieved in one embodiment via a metallic coating of the implant and / or by applying one or more chemical compounds that promote osseointegration. The one or more chemical compounds are preferably selected from hydroxyapatite, tricalcium phosphate or other calcium phosphates and / or mixtures thereof. The metallic coating consists primarily of the materials that are conventionally used as a metal shell for prostheses. The metallic coatings are preferably titanium-containing coatings, more preferably titanium particles. The layer thickness of the metallic and / or chemical coating is 100-400 μm, preferably 175-300 μm, and has a roughness R _a (average roughness) of 15-50 μm. In order to produce the thus coated implant, the uncoated ceramic implant is initially produced and sintered in one embodiment. Subsequently, the coating is applied at least partially on the outside of the ceramic implant and thus forms an outer surface with a rough surface. The metallic and / or chemical coating is preferably applied by means of thermal spraying, particularly preferably by means of plasma spraying.

The rough surface of the outer surface is realized in a further embodiment on a porous surface on the outside. The porous surface of the outer surface allows not only the primary anchorage but also ingrowth of the bone for increased long-term stability.

It has been found that the following properties of a porous surface positively influence the ossification:

Porosities between 50% and 99%, preferably between 60% and 85%

• Interconnectivity, ie the individual pores are at least partially interconnected Pore sizes between 100 and 1000 pm,

In one embodiment, the porous surface consists of a metallic, porous layer. This metallic, porous layer preferably contains titanium particles, more preferably it consists of titanium particles. The metallic, porous layer is preferably 100-500 μm thick.

The porous surface is formed in a preferred embodiment by a porous ceramic, which is at least partially applied to the outside of the implant. The chemical composition of the porous ceramic of the implant according to the invention in a particularly preferred embodiment has the same chemical composition as the rest of the implant. As a porous surface, the porous ceramic has an arithmetic mean roughness of R _a = 10-100 μm, preferably of R _a = 20-80 μm. The porosity of the porous layer is between 50% and 99%, preferably between 60% and 85%, particularly preferably between 60 and 80%, and the pores have a pore size between 100 and 1000 μm.

Preferably, 10% -90% of the cumulative area fraction of the outer surface of the implant has pores with a size of 100-600 pm. In one particular embodiment, an implant has an outer surface in which at least 80% of the pore surface that is in contact with the bone and that has a pore size of 100-600 μm.

In general, a variety of methods and methods for producing the porous ceramics are known. These include slip-based processes in which ceramic porous layers are produced on parts or entire porous parts by means of a ceramic slurry with organic, structure-determining porosity agents or chemical ingredients. The ceramic slips are to be understood as suspensions comprising a liquid medium, a ceramic starting powder and optionally additional additives.

The porous ceramic is formed in a preferred embodiment of a ceramic foam of a ceramic solid material. In one embodiment, the implant consists of <100% of the ceramic foam. In a preferred embodiment, the ceramic foam is a mixed oxide system Al ₂ O ₃ -ZrO ₂ , especially ZTA (Zirconia Toughened Alumina) ceramics, or ceramic composites in which zirconia is the volume-nominating phase, these systems depending on the dominant phase nor chemical stabilizers or dispersoids in the form of other metal oxides or mixed oxides are added.

By using a ceramic foam, the behavior of the implant is significantly changed. At local, high loads, especially under pressure, only a locally limited defect can arise, instead of a catastrophic failure of the entire implant. The local defect, the local damage, manifests itself as fractures of the pores and is limited to the area comprising the porous foam.

The porous layer of the ceramic implant is also adhesive and cementable beyond. In this case, the porosity of the porous layer is advantageous since the implant is infiltrated with the adhesive / bone cement (> 0.5 mm deep) and then mechanically connected thereto via a chemical bond, for example toothed. As a result, connections to other materials such as non-ceramic materials such as plastics and metals are possible. If, for medical reasons, the bone structure at the site milled out for the implant is not suitable for a cement-free implantation, it is therefore possible to resort to an attachment by means of bone cement. The decision to additionally use bone cement may be made during the application. The user thus has the opportunity during the insertion of the implant to decide whether the bone structure allows a cement-free insertion or a cemented insertion is required.

The implant with an outer surface made of a porous ceramic foam is produced by various methods, preferably the production takes place directly during the production process of the ceramic implant. The direct manufacturing processes include e.g. a two-stage injection molding process, in which preferably only the first part is poured in a tool and then, in particular by suitable modification of the tool, the further part is cast, which surrounds the first part and at least partially forms the textured and / or rough outer surface of the outside , Thereafter, a co-sintering of the two parts as well as the finishing, which ensures that the pores are opened on the outer surface, in which e.g. superficially the ceramic material is applied.

An embodiment of the invention has a structured surface with recesses and / or projections on the outer surface. This structured surface corresponds to a macroscopic three-dimensional structure of the outer surface, which serves to counteract a rotation or displacement of the implant in the bone. This means that the shape of the outside is determined by the macroscopic recesses and / or projections. The macroscopic three-dimensional structure may be in the form of protrusions, serrations or waves. This ensures the permanent anchorage in the bone. The structured surface initially provides a slip-resistant, fixed connection in the bone, since the implant is held in the correct position in a first phase of the womb in the human body only by its mechanical properties. With the help of the recesses and / or projections, the implant hooks in the bone or the implant is fixed in the position in which it was used.

A wave-shaped surface here means that forms on the surface by periodically recurring local minima and maxima, a 3-dimensional structure, with equal or different distances between the minima and / or maxima and the same or different height differences between adjacent minima and maxima.

In one embodiment, the implant has an outer surface and / or outer surface with a rough surface, which is additionally structured, i. the rough, porous surface in a preferred embodiment additionally has a macroscopic, three-dimensional structure.

The outer surface, preferably the rough, particularly preferably the porous surface of the outer side, is additionally activated in a preferred embodiment in such a way that it grows cells by a biological activation applied to the outer surface and / or outer side, a layer of the amino acids, peptides and / or proteins, such as RGD peptide (Arg-Gly-Asp) and / or collagen supported.

In a particularly preferred embodiment, the ceramic implant is designed such that it has a macroscopically three-dimensionally structured, rough and / or porous and activated outer surface. In one embodiment, the outer side has differently structured and / or rough and / or porous surfaces with or without biological activation next to one another.

Preferably, the implant is executed all-ceramic. The implant according to the invention preferably consists of an oxidic ceramic. Oxide ceramics are characterized in particular by a high resistance and good compatibility with body media. Oxidic ceramics have good biocompatibilities and produce almost no allergic reactions. According to a preferred embodiment of the invention, the implant is based on oxide ceramic material systems, comprising:

• zirconia-reinforced alumina (ZTA) and all based on it

advanced ZTA systems.

• Zirconia ceramics, especially yttria-stabilized zirconia (3Y-TZP).

• Cerium-stabilized zirconium oxide (Ce-TZP), in which the stabilization of the tetragonal phase of zirconium oxide by cerium oxide takes place.

All other composite materials based on zirconium oxide, wherein the dispersoid composite component can be based on aluminates and also other stabilizers from the group of rare earths can be used, such. Gd and Sm.

The implant is preferably used with the structured and / or rough and / or porous outer surface without cement in the bone.

The implant is preferably used in hip, shoulder, elbow, toe joint or finger arthroplasty in humans or animals.

The advantages are:

• Reduced height of the implant in the annular configuration, therefore a very small cut-out in the bone is required.

• No punctiform loads, but strip-shaped loads with lower maximum values, similar to the physiological load absorption.

In comparison to a hemispheric insert, the geometry according to the invention produces a lower pressure on the contact point.

The implant with the geometry according to the invention can be combined without restriction with conventional spherical sliding partners.

The changed geometry does not adversely affect the manufacturing costs, since known manufacturing methods can be used.

• Since a metal shell for anchoring and stabilization in the bone can be dispensed with, there is a saving of material during manufacture, which results in a cost advantage.

• During the application, an implant according to the invention can be used directly or cementless or, if required, cemented, depending on the circumstances. The invention describes an implant for the sliding pairing in endoprosthetics, wherein the implant has an outer side with an outer surface and an inner side with an inner surface and a non-hemispherical sliding region for receiving a spherical sliding partner is formed on the inner surface. Thus, the depth (height) for the implant is as low as possible and a less deep cutout, for example, in the pelvic bone is necessary, the invention proposes that the implant is preferably designed as a ring or ring and the outer surface allows direct implantation into the body. In order to minimize the friction between the spherical sliding partner and the implant, a specially designed internal geometry of the implant is proposed.

In summary, the implant (1) for the sliding mating with a spherical sliding partner (5) is half-shelled or annular and has an inner surface which is designed as a sliding region (2) for receiving a spherical sliding partner (5). The sliding region (2) corresponds to a partial section of half of a spindle of a spindle torus in longitudinal extension. The height H _{G of} the sliding portion (2) corresponds to 20-80% of the diameter of the ball to be inserted, and preferably 50-95% of the height of the implant.

The implant (1) preferably has a first region for the introduction of the sliding partner, and a second region which limits the reception of the sliding partner. Furthermore, the implant has an inner surface, which is designed as a sliding region (2) for receiving a spherical sliding partner (5), an outer side (6), with an outer surface (3) with means for anchoring the implant in the bone and an end surface (9). , which represents the transition from the inside to the outside in the first region, and a bottom surface (10) which is located opposite the end surface (9) in the second region. The sliding region (2) of the implant corresponds to a partial section of half of a spindle of a spindle torus in longitudinal extent.

In the figures, selected embodiments of the annular implant according to the invention are described, showing

FIG. 1 a: an implant in side view,

FIG. 1 b: the implant according to FIG. 1 a in the annular embodiment in FIG

Cross-section,

FIG. 2 shows an exemplary embodiment of an implant according to the invention with inserted spherical KG, 3 a - c): the contact points of the spherical sliding partner in a conventional insert (A), a conventional ring insert (B) and the implant (C) according to the invention in its annular configuration,

FIG. 4 a - c): geometry of the spindle,

FIG. 5: an implant according to the invention in a preferred embodiment,

Figure 6: shows the geometry of the cranial elevation in a preferred

configuration

Figure 7: shows the geometry of the cranial extension in a preferred

Design.

Reference numeral and abbreviation list

1 implant

2 sliding area

3 outer surface, rough and / or textured surface

4 biological coating

5, 109 head, ball of the prosthesis

6 outside

9 floor area

10 face

100 contact point

101, 1 12 Ring contact, contact line

105 spindle

106 outer surface of the spindle

107 Part of the spindle

108 Circle describing the spindle torus

1 10 tangent point

1 1 1 sectional plane of the contact line

1 12 contact line

201 Range of cranial increase in gliding area

202 Area of cranial extension of the implant

205 area of bone contact

212, 212 'circle (orientation guide)

214 inlet zone

216 outlet zone

A is the distance of the axis of rotation from the center M of the circle describing the spindle torus

C clearance

D1 maximum diameter of the sliding area, arranged in the first area

D2 minimum diameter of the sliding area, arranged in the second area

E, E 'Intersection of the spindle outer surface with L

F cross-sectional area

H height of the implant

H _G height of the sliding area

K is the straight line describing the cranial enhancement

K _{G is} the straight line describing the cranial increase of the gliding area

K 'straight line describing the cranial extension

KG spherical sliding partner

L longitudinal axis of the spindle, rotation axis L ', L "to L parallel axis of the circle describing the spindle torus through the center

M center of the spindle

M ', M "Center of the circle describing the spindle torus

M _P Center of the spherical sliding partner

r Radius of the circle describing the spindle torus

r _P radius of the spherical sliding partner (KG, prosthesis head)

R axis of rotation of the outer surface

S, S 'normal planes to L

S1, S2 intersections of the normal planes S, S 'on the longitudinal axis L

X Maximum of the implant without cranial elevation in the direction of the end face

X _G Maximum of the sliding area without cranial elevation in the direction of the end face

X 'maximum of the implant without cranial extension in the direction of

floor area

x height difference of the cranial elevation

Y maximum of the implant of the cranial elevation

Y _G maximum of the sliding area of the cranial elevation

Y 'maximum of the implant of the cranial extension

y Height difference of the cranial extension

In FIGS. 1 a and 1 b, an annular implant 1 according to the invention is shown. FIG. 1 a shows this implant 1 in a view and FIG. 1 b in a section along the axis of rotation L according to FIG. 1 a. The implant 1 has an inner ring portion of a spindle, which is also referred to as (non-hemispherical, covalent) sliding region 2 or inner surface. 2, on the outside 6 of the implant 1, in a preferred embodiment, an outer surface 3 with a rough and / or structured surface is arranged, with which the implant can be anchored in the bone. The height H of the implant is represented by the dashed lines and extends from a first region with the end face 10 over a second region to the bottom surface 9. L denotes the axis of rotation. F denotes the cross-sectional area of the annular implant.

Fig. 2 shows the implant 1 according to the invention in cross section. In the implant 1, a prosthesis head 5 is inserted. On the outside 6 and the outer surface 3, a biological coating 4 may be applied in addition.

Fig. 3 a) shows schematically the most likely places of friction of a conventional insert, Fig. 3b) of a conventional ring insert and Fig. 3c) of an implant according to the invention in an annular design. In a known semicircular insert is the contact point 100 between insert and KG at the bottom of the insert. The contact between the insert and the KG (Figure 3b) in a known annular insert is located on a contact line 101. This is a linear contact to a linear friction. This line 101 is arranged in the area near the bottom surface 9. In the implant according to the invention, the correspondingly designed geometry results in that the contact line on the plane 11 1 is arranged at a distance from the bottom surface 9 in the direction of the end face 10 (FIG. 3 c).

4 shows the determination of the sliding region 2 of the implant according to the invention. Spindle torus 105 in Fig. 4a) is described by a circle 108 of radius r having a center M7M "and rotating about the axis of rotation corresponding to the longitudinal axis L of the spindle. The axes L 'and L "are parallel to L and pass through M', M". The distance between L7L "and L is smaller than the radius r. The spindle intersects the longitudinal axis L at points E and E '.

In Fig. 4b), the determination of the subsection 107 is illustrated. The section 107 is located in one half of the spindle 105 and is formed by the normal planes to L (S and S '). These intersect L in points S1 and S2 where S1 = M or S1 lies between M and S2, S2 = E 'or S2 lies between S1 and E'. Both intersections S1, S2 thus lie in one half of the spindle and do not exceed their center. The diameter D1 in the first region is greater than the diameter D2 in the second region, D1 being greater than the diameter of the KG to be used. D2 is smaller than the diameter of the KG to be inserted, which (in the case of an annular implant) prevents the KG from falling out.

In Fig. 4c) is the sectional plane 11 1 of the contact line 1 12 between the KG 109 and the implant 1 on the sliding portion 2, according to the outer surface of the spindle 106, shown schematically. The contact line 1 12 corresponds to a sectional plane 11 1 on the spherical sliding partner 109. Due to the spindle shape, the area of the end face 10 is inclined in the direction of the spherical sliding partner 109 or in the direction of the longitudinal axis L. As a result, the diameter D1 has a smaller value as compared with a diameter of a comparable hemispherical sliding portion measured at the same position. As a result, the contact line 112, on which the spherical sliding partner 109 moves, shifts in the direction of the end face 10 of the implant and away from the bottom surface 9. FIG. 5 shows the height H _{G of} the non-hemispherical sliding region 2, represented on an annularly shaped implant 1 with inserted KG with a center point M _P and a radius r _P. The sliding region 2 corresponds to a partial section 107 of half of a spindle of a spindle torus in longitudinal extension. The circular lines 212, 212 'are for orientation only. The portion 107 is limited in the region of the end face 10 by the inlet zone 214 and in the region of the bottom surface 9 through the outlet zone 216. The inlet zone 214 and the outlet zone 216 do not belong to the sliding region 2 and accordingly do not necessarily follow the spindle geometry. The clearance C corresponds to the formula C = (rr _P ) ^* 2. The KG slides on the sliding surface 2 on the circle described by the plane 1 1 1.

FIG. 6 shows the range of the cranial extension of the sliding region 201. The height y _{G of} the cranial extension extends between an intersection of the normal plane S with the end of the sliding region 2 in the direction of the inlet zone 214 and the point Y _G. The point Y _G lies on a straight line K _G which intersects L. The straight line K _G extends between the intersection point X _{G of} the normal plane S with the end of the sliding region 2 on the outer surface of the spindle 106 and the point Y _G. In this case, the points X _G and Y _{G are arranged} on a plane which extends through the end points of the sliding region 2. Both points X _G and Y _G are spaced apart. If the cranial elevation is formed symmetrically, ie the rise and the slope are the same length and extend to each 180 °, the point X _{G is arranged} opposite to the point Y _G. He is then located 180 ° from the point Y _G. In such an embodiment, a gentle increase in the cranial elevation can be realized. If the increase or the slope of the cranial increase is steeper, two points X _{G can be} provided. At these points, the slope of the cranial elevation begins or ends. Between these two points X _G , in which no cranial elevation is formed, the implant can be flat, flat without elevation or depression. In the illustrated preferred embodiment, the straight line K _G also intersects the center of the spindle and Y _G lies on the outer surface of the spindle. For the height H _{G of} the sliding area of a cranial-elevation implant, H _g '= H _G + y. The same connections can be made for the cranial extension of the implant, which is based on the height of the implant.

Fig. 7 shows the area of the cranial extension 202 of the implant. The area results between the point Y 'on a straight line K' and the cutting plane S '. The straight line K 'runs from the point X', which lies on the plane S 'and the outer surface of the spindle 106, to another point Y', which lies opposite to X 'and represents the maximum of the cranial elevation. X 'lies on the opposite side of Y', ie a straight line from X 'to Y' cuts L. For the height of the implant H '= H + x. The region 205 corresponds to the bone contact surface of the outside of the implant in the inserted state. This area is preferably parallel to the straight line K 'as shown, which shows the maximum dimensions of the implant in the area of the floor area. The axis of rotation R of this bone contact surface is thus perpendicular to the straight line K '. Such an implant then appears as an implant with a cranial elevation, the internal geometry of which is tilted away from the cranial elevation in the form of a partial section of a spindle.

Claims

claims

1. implant (1) for the sliding pair with a spherical sliding partner (5, 109), wherein the implant is half-shelled or annular and an inner surface which is formed as a sliding region (2) for receiving a spherical sliding partner (5, 109) characterized in that the sliding region (2) corresponds to a partial section (107) of half of a spindle (105) of a spindle torus in longitudinal extent, wherein the height H _{G of} the sliding region (2) 20-80% of the diameter of the ball to be inserted and / or 50-95% of the height H of the implant corresponds and wherein the maximum diameter D1 of the sliding portion (2) is greater than the diameter of the inserted spherical sliding partner (5, 109).

2. implant (1) according to claim 1, comprising a first region for insertion of the sliding partner with an end face (9), which represents the transition of the inside to the outside in the first region, and a second region which limits the inclusion of the sliding partner with a bottom surface (10) opposite the end surface (9) and an outside surface (6) having an outer surface (3) with a rough and / or textured surface for anchoring the implant in the bone.

3. according to claim 1 or 2, implant according to one of the preceding claims, wherein the implant is annular and the minimum diameter D2 of the sliding portion (2) is smaller than the diameter of the inserted spherical Gleitpartners (5, 109).

4. Implant according to one of the preceding claims, wherein the radius of the spindle torus descriptive circle r, the clearance C and the radius of the ball of the prosthesis r _P according to formula I are related.

C = (rr _p ) ^* 2 (formula I)

5. Implant according to one of the preceding claims, wherein 10 pm <C <500 pm applies.

6. Implant according to one of the preceding claims, wherein the ring insert (1), preferably the sliding region (2) is extended cranially.

An implant according to any one of the preceding claims, wherein the rough surface is a coating (4).

An implant according to any one of claims 1 to 6, wherein the rough surface is a porous surface.

Implant according to one of the preceding claims, wherein the porous surface has a porosity of between 50% and 99%, preferably between 60% and 85%, and the pores have a pore size of between 100 and 1000 μm.

10. An implant according to claim 8 or 9, wherein the porous surface is a porous ceramic.

1 1. An implant according to claim 10, wherein the porous ceramic is a porous ceramic foam.

12. Implant according to claim one of the preceding claims, wherein the implant is all-ceramic.

13. Implant according to claim 12, wherein the implant consists of a porous ceramic foam.

14. Implant according to one of the preceding claims, wherein the implant is cranially elevated (201) and / or cranially extended (202).

15. Use of an implant according to any one of the preceding claims in the hip, shoulder, elbow, finger joint or toe joint endoprosthesis.