EP2413816A1

EP2413816A1 - Ceramic cutting template

Info

Publication number: EP2413816A1
Application number: EP10713617A
Authority: EP
Inventors: Roman Preuss; Heinrich Wecker; Matthias Eschle
Original assignee: Ceramtec GmbH
Current assignee: Ceramtec GmbH
Priority date: 2009-04-01
Filing date: 2010-04-01
Publication date: 2012-02-08
Also published as: CN102448385A; DE102010003605A1; JP2012522711A; WO2010112588A1; JP5762397B2; KR20120022853A; US20120123421A1

Abstract

The invention relates to a cutting template or a cutting block, preferably to a cutting template or a cutting block for use in medical technology.

Description

Cutting template made of ceramic

The present invention is a cutting template or a saw block, preferably a cutting template or a saw block for use in medical technology.

For each knee TEP implantation, a so-called incision template or saw block is fixed on the femur. With this cutting template, three cuts are normally made to adapt the femoral surface to the geometry of the femoral component. For each cut there is a guide in the cutting template (3 or 4 cuts in 1 template). In this guide, the cut is performed with an oscillating saw blade. The saw blades and the cutting templates are today basically made of biocompatible metal alloys.

Depending on the manufacturer, the guide rails in the saw block have a width of 1, 2 - 1, 5 mm. Due to the oscillation of the saw blade and the friction occurring between saw blade and guide rail, high metal abrasion occurs on the side of the guide rail. This abrasion does not or can only be removed from the wound inadequately intraoperatively. Thus, this abrasion can turn into the cause of infections and, above all, lead to allergic reactions of the patient. For this reason, it is essential to reduce this abrasion in principle, but in particular if an implant reaction is to be avoided by the use of a ceramic femoral component in the potential allergic person.

According to current knowledge, the majority of the metal abrasion caused by the wear of the guide rails in the cutting template. After approx. 20 - 40 times the use of a cutting template in the context of knee TEP implantations, the guide rails are enlarged by approx. 0.5-1.5 mm

Guide column on. As a result, the guidance accuracy of the cut significantly. The consequences for the surgeon are corresponding, a precise cutting of the saw blade is no longer possible, alignment and flatness of the cut surfaces of the femur are increasingly deviating. This leads to larger gaps between cut surfaces and femoral component. These gaps must be filled intraoperatively by a larger than usual volume of bone cement, which can have a negative impact on the lifetime of the system.

The object underlying the present invention was to eliminate the disadvantages of the cutting templates / saw blocks of the prior art, and in particular:

> to reduce metal abrasion, whereby a reduction of metal abrasion by up to 90% compared to the previous metal solutions should be sought;

> extend the service life of a cutting template and thus save costs;

> to reduce the risk of allergies and the risk of infections.

The inventive task was surprisingly by a

Cutting template / a Sägeblock ceramic (hereinafter, the terms sintered body or sintered body are used for the inventive cutting template / saw block according to the invention) with the features of the independent claims. Preferred embodiments can be found in the subclaims. It was surprisingly found that the

Solving the pending tasks requires sintered body with a very special composition. In addition to the conversion gain achieved by the incorporation of a stabilizing oxide-containing zirconium dioxide in a ceramic matrix, according to a first embodiment the invention provides as matrix a mixed crystal of aluminum oxide / chromium oxide. Of

Furthermore, the invention provides that the zirconium matrix embedded in the matrix dioxide and the mixed oxide forming the mixed crystal together with the aluminum oxide in a certain molar ratio to one another. This measure makes it possible to achieve the required hardness values even with higher zirconium dioxide contents, which may be required to obtain a particularly good fracture toughness. On the other hand, at low

Zirconium dioxide shares also relatively low levels of chromium oxide are present, whereby an embrittlement of the material is counteracted.

The statement that the zirconia and chromium oxide containing the stabilizing oxides should be present in a certain molar ratio, inevitably results in certain ratios for the other components, since e.g. with decreasing proportion of zirconium dioxide, the proportions of the stabilizing oxides, based on the sintered molded body decrease, while on the other hand, the proportion of alumina increases. Based on the aluminum oxide of the sintered body, the chromium oxide is in a weight of 0.004 to

6.57 wt .-%, but it must not be forgotten that chromium oxide and the stabilizing oxides containing zirconia are in the indicated molar ratio. Of the stabilizing oxides, the cerium oxide has been found to be most preferred.

According to a further advantageous embodiment, the proportion of the matrix material on Sinterform body is at least 70 vol .-% - and is made of an aluminum oxide / chromium oxide mixed crystal with a chromium oxide content of 0.01 to 2.32 wt .-%, based on alumina, with from 2 to 30% by volume of zirconia incorporated into the matrix, and the zirconia contains from 0.27 to 2.85 mole percent yttria, based on the mixture of zirconia and yttria, and the zirconia does not exceed 2 micrometers average grain size predominantly in the tetragonal modification. An amount of 0.27 to 2.85 mol% of yttria, based on the mixture of zirconia and yttrium oxide, corresponds to 0.5 to 5.4 wt%.

Yttrium oxide, based on zirconium dioxide. In such a sintered body - A -

Between the yttria-containing zirconia and chromium oxide is a molar ratio of 370: 1 to 34: 1 before.

According to a further particularly preferred embodiment of the invention, the matrix material consisting of an aluminum oxide / chromium oxide mixed crystal and a further mixed crystal of the formula Cr _x _-x SrAli2 Oi9, wherein x has a value from 0.0007 to 0.045. In this embodiment as well, which otherwise corresponds to the first embodiment, the toughening effect of the zirconia incorporated in the mixed-crystal matrix is increased, while the addition of chromium can counteract a decrease in the hardness values caused by the zirconium dioxide content. Surprisingly, it was found that in the presence of strontium oxide platelets form in the structure, which he general formula SrAli _2- χCr _x Oi ₉ correspond. The additionally formed by the addition of strontium oxide mixed crystal of the formula SrAli _2- χCr _x Oi9 has the additional effect that it gives the sintered body even at a higher temperature, a further improved toughness. The wear resistance of these sintered bodies under the influence of elevated temperature is therefore also improved. Also in this embodiment, the cerium oxide has been found to be particularly suitable. Platelets also form if the matrix does not contain Cr ₂ θ ₃ .

According to a further embodiment, the wear resistance of the sintered shaped bodies can still by the incorporation of 2 to 25 VoI .-% of one or more carbides, nitrides or carbonitrides of the metals of the 4th and 5th subgroup of the Periodic Table of the Elements (PSE) - based on the Matrix material - to be improved in these. Preferably, the proportion of these hard materials is 6 to 15 vol .-%. In particular, titanium nitride, titanium carbide and titanium carbonitride are suitable.

According to a particularly preferred further embodiment of the invention, the molar ratio of the zirconium containing the stabilizing oxides is umdioxids to chromium oxide as a function of the zirconia present in the sintered shaped bodies according to the invention are adjusted so that at low zirconia shares also small quantities of chromium oxide are present. In particular, an adjustment of the molar ratio zirconium dioxide: chromium oxide has proven to be in the range of

2 to 5% by volume of zirconia 1,000: 1 to 100: 1

> 5 - 15% by volume zirconium dioxide 200: 1 to 40: 1

> 15-30% by volume zirconia 100: 1 to 20: 1

> 30-40 vol% zirconia 40: 1 to 20: 1

is.

To ensure that the zirconium dioxide is present predominantly in the tetragonal modification, according to the invention the adjustment of a particle size of the zirconium dioxide not exceeding 2 μm is required. In addition to the admissible amounts of zirconium dioxide in cubic modification up to an amount of 5% by volume, even small quantities of the monoclinic modification are permitted, but these should also have a maximum amount of max. 5% by volume and are preferably less than 2% by volume, very particularly preferably less than 1% by volume, so that preferably more than 90% by volume are present in the tetragonal modification.

Since the sintered molded article contains only in an unavoidable manner entrained impurities other than the components specified in the claims, which according to a further preferred embodiment of the invention is not more than 0.5 vol .-%, the sintered molded body consists only of the alumina-chromium oxide mixed crystal or containing the stabilizing oxides in the presence of strontium oxide and chromium oxide, in this solid solution and the mixed crystal of the formula SrAli _2- χCr _x Oi9 and from and embedded in the matrix of said mixed crystals zirconium koniumdioxid. Other phases, such. As grain boundary phases formed in the combined use of alumina and magnesium oxide or other crystalline phases, as in the known from the prior art additives of substances such as YNbO ₄ or YTaO. ₄ arise and have a not sufficiently high softening point, are not available in the sintered body according to the invention. Also known from the prior art oxides of Mn, Cu, Fe, which also lead to the formation of further phases, cause a reduced softening point and have a low edge strength result. The use of these materials is therefore excluded in the invention.

Preferably, the zirconia is present in an amount of not more than 30% by volume. Preferably, the zirconia is also not present in an amount of less than 15% by volume. If there are between 15 and 30% by volume of zirconium dioxide, the molar ratio between the zirconium dioxide and chromium oxide containing the stabilizing oxides is very particularly preferably between 40: 1 and 25: 1.

According to a further very particularly preferred embodiment, the proportion of zirconium dioxide present in tetragonal modification is more than 95% by volume, with only up to 5% by volume being present in total in the cubic and / or monoclinic modification. Very particular preference is given to maintaining a particle size of the incorporated zirconium dioxide in the range of 0.2 to 1, 5 microns. In contrast, an average grain size of the alumina / chromium oxide mixed crystal in the range of 0.8 to 1, 5 microns has been found to be particularly suitable. If, in addition, carbides, nitrides and carbonitrides of the metals of the 4th and 5th subgroups of the PSE are used, they are used in a particle size of 0.8 to 3 μm. The grains of the mixed crystal of the formula SrAli _2- χCr _x Oi 9 have a length / thickness ratio in the range from 5: 1 to 15: 1. Its maximum length is 12 μm, its maximum thickness 1.5 μm. It has surprisingly been found that corresponding platelets can be produced in the microstructure not only with strontium oxide but also with certain other oxides. The prerequisite for platelet formation is the formation of a hexagonal crystal structure of the "in situ" platelets to be formed. If the material system Al ₂ θ3-Cr ₂ θ 3 -ZrO ₂ -Y ₂ θ 3 (CeO ₂ ) is used as the matrix, the following platelets can be formed "in situ" using a wide variety of oxides. On alloying of alkali metal oxides, the corresponding Al _kal-Aln-x Cr _x 0i ₇ form - in alloying of alkaline earth metal oxides, the corresponding ErdalkaliAli _2-x Cr _x Oi9 -Platelets form, on alloying of CdO, PbO, HgO the corresponding (Cd, Pb or HgAli _2-x Cr _x Oi9) -Platelets and alloying of the corresponding rare earth oxides, rare Erdaln _-x Cr _x Oi8 -Platelets. La ₂ θ3 may also form the compound La ₀ , 9Aln, ₇ 6-χCr _x Oi9. Platelets also form when the matrix does not contain Cr ₂ θ ₃ . The platelets forming then, without the presence of strontium oxide, correspond to the general ones

Formulas: AlkaliAlnOu, alkaline earthAl ₁₂ Oi ₉ , (Cd, Pb or HgAli ₂ Oi ₉ ) or rare earth Al ₂ Oi ₈ .

According to the invention the matrix material in a preferred Ausgestal- contains tung an aluminum oxide / chromium oxide mixed crystal and an additional mixed crystal according to one of the general formulas Me ¹ AI n _-x Cr _x 0i _7, Me ² AI i _2-x Cr _x 0 ₁ 9, Me ² Ali _2-x Cr _x Oi 9 or Me ³ Al n _-x Cr _x 0i8 where Me ^{1 is} an alkali metal, Me ^{2 is} an alkaline earth metal, Me ^{2 is} cadmium, lead or mercury and Me ^{3 is} a rare earth metal. Likewise added to the matrix material can be mixed crystal La ₀ , 9Aln, ₇ 6-χCr _x Oi9. x can assume values of 0.0007 to 0.045.

The inventively provided "in situ" Plateletverstärkung also occurs when the matrix does not contain Cr ₂ θ3. This is provided according to the invention in particular when a drop in the hardness values does not disturb. The ones without

Cr ₂ θ ₃ forming platelets then correspond to the general formulas Me ¹ Ah 1O17, Me ² Ali ₂ Oi ₉ , Me ² Ali ₂ Oi ₉ or Me ³ Ali ₂ Oi ₈ . Even with these sintered shaped bodies, the same preferred embodiments can be provided, as with the sintered shaped bodies containing Cr ₂ Os in the matrix material. In that regard, made for the sintered molded body with Cr ₂ θ ₃ in the matrix material further above statements in an analogous manner to the sintered body without

Cr ₂ θ3 in the matrix material too.

The Vickers hardness of the sintered shaped bodies according to the invention is greater than 1750 [HVo.δ], but is preferably more than 1,800 [HVo.s].

The microstructure of the sintered body according to the invention is free of microcracks and has a degree of porosity of not more than 1.0%. The sintered body may further include whiskers, but not silicon carbide.

The sintered shaped body preferably contains none of the substances frequently used as grain growth inhibitors, such as. B. magnesium oxide.

The term "mixed crystal" used in the claims and in the description is not to be understood as meaning a single crystal, rather it means a solid solution of chromium oxide in aluminum oxide or strontium aluminate.

During sintering, the stabilizer oxides dissolve in the ZrO ₂ lattice and stabilize its tetragonal modification. To produce the sintered shaped bodies and to obtain a structure free of further undesirable phases, it is preferred to use high-purity raw materials, ie alumina and zirconium dioxide with a purity of more than 99%. Preferably, the degree of impurities is still much lower. In particular, SiO ₂ contents of more than 0.5% by volume, based on the finished sintered body, are undesirable. Excluded from this rule is the inevitable presence of hafnium oxide in a small amount of up to 2% by weight within the zirconium dioxide.

The sintered shaped body according to the invention is produced by pressure-free sintering or hot pressing of a mixture of aluminum oxide / zirconium dioxide / chromium oxide and stabilizing oxides or a mixture of these components is used which additionally contains strontium oxide or alternatively an alkali oxide instead of strontium oxide. an alkaline earth oxide, CdO, PbO, HgO, a rare earth oxide or La2θ3 and / or one or more nitrides, carbides and carbonitrides of the 4th and 5th subgroup of the PSE are added.

Exemplary offsets are given in Table 1. The addition of yttrium oxide and chromium oxide can also be in the form of yttrium chromium oxide (YCrOs), while the addition of strontium oxide can preferably be carried out in the form of strontium salts, in particular as strontium carbonate (SrCOs). The place of the strontium oxide usable alkali, alkaline earth, cadmium, lead,

Mercury, rare earth oxides or the lanthanum oxide may preferably be added in the form of their salts, in particular as carbonates. But also the addition of ternary compounds that decompose and rearrange during sintering is possible. Various ceramic mixtures were prepared by mixed grinding. To the milled mixtures was added a temporary binder and the mixtures were then spray dried. Subsequently, green bodies were pressed from the spray-dried mixtures and these were sintered under standard conditions, for example either sintered or presintered without pressure and subjected to a gas pressure sintering process under argon.

The term pressureless sintering includes both sintering under atmospheric conditions, as well as under inert gas or in a vacuum. Preferably, the molded body is first pre-sintered without pressure to 90 to 95% theoretical density and then by hot isostatic pressing or gas recompressed inside the pressure. The theoretical density can thereby be increased to a value of more than 99.5%.

An alternative way of producing the green bodies is achieved directly from the suspension. For this purpose, the mixture with a solids content of over

50 vol .-% ground in an aqueous suspension. The pH of the mixture should be adjusted to 4 - 4.5. After grinding, urea and an amount of the enzyme urease, which is capable of breaking down the urea, are added before this suspension is poured into a mold. Enzyme-catalyzed urea decomposition shifts the pH of the suspension to 9, with the suspension coagulating. The green body thus produced is dried after demolding and sintered. The sintering process can take place without pressure, but pre-sintering, followed by subsequent hot isostatic re-compaction, is also possible. Further details of this process (DCC process) are disclosed in WO 94/02429 and in WO 94/24064, to which reference is expressly made.

In the production of the ceramics based on the mentioned multicomponent systems, a number of factors can acquire a significant importance. In particular, in the preparation of the powder mixtures, the dispersion and grinding can have a special influence on the properties of the ceramic according to the invention. The grinding process and the grinding unit itself can affect the result. The solids content of the millbase used may additionally contribute to the dispersion.

In the following examples, the influence parameters and their effect on the mechanical properties are described in more detail. For the individual experiments, the following solid combination has been used: Al ₂ O ₃ 73.11% by weight

ZrO ₂ 23.57% by weight

La ₂ O ₃ 2.48% by weight

YCrO ₃ 0.84% by weight

For the experiments V1-V4, a 60% by weight slip was used. In experiment V5, the solids content was reduced to 55% by weight. To carry out Experiment V1, a vibratory mill was used. Experiments V2 and V3 were carried out on a laboratory attritor mill; at V2 was milled for 1 h, the grinding time at V3 was 2 h. In Run V4, an amount of 30 kg was treated in a through-feed mill. The experiment V5 was carried out in the laboratory attritor with a grinding time of 2 h.

The results of the strength tests for the individual experiments are shown below:

Table 1

La ₂ O ₃ ; ^** He ₂ O ₃ ; ^*** BaO; ^**** Dy ₂ O ₃

With the teaching of the invention, the metal abrasion is reduced by up to 90% compared to the previous cutting templates or saw blocks made of metal. The service life of the cutting template or the saw block according to the invention in use is significantly prolonged, since only slight wear of the cutting template occurs. This reduces the costs. In addition, the risk of allergies or the allergic reactions of patients and the risk of infections are reduced.

Preferably, the cutting template is used in medical technology, in particular in operations for processing a bone, preferably in a knee-TEP implantation.

The advantages of the ceramic cutting template according to the invention or of the ceramic from which it is made are: > The cutting template has an extremely low abrasion.

> The material is biocompatible.

> If the cutting template according to the invention is labeled with a laser, it is very clearly visible and readable and can thus reduce incorrect handling when using the cutting template.

> The cutting template has good tribological properties.

Figures 1 to 4 show a cutting template 1 of ceramic according to the invention in different views. FIG. 5 shows images of the shape and intraoperative use of a conventional metal cutting template.

In the figures 1 to 4 a cutting template 1 according to the invention is shown, which is also referred to as a saw block. Such a cutting template 1 serves to guide a surgical saw blade during the implantation of an artificial knee joint.

The cutting template consists of a base body 2, which is provided with slot-like recesses 3 for the implementation and precise guidance of a plate-shaped saw blade, wherein the slot-like recesses 3 has opposing guide surfaces 4. At these guide surfaces 4, the saw blade (see Figure 5) is applied during the sawing process. In the base body 2 through holes 5 are introduced, which serve for screwing the cutting template 1 on the femur.

In the context of the present invention, the terms sintered body / sintered body denote a ceramic in the form of or for use as a cutting template or saw block.

Claims

claims

1. Cutting template of: a) 60 to 98 vol .-% of a matrix material, formed from an aluminum oxide / chromium oxide mixed crystal, b) 2 to 40 vol .-% embedded in the matrix material zirconia, the c) as stabilizing oxides more than 10 to 15 mol% of one or more of the oxides of cerium, praseodymium and terbium with respect to the mixture of zirconia and stabilizing oxides, wherein d) the amount of stabilizing oxides added is such that the

Z) the zirconium dioxide is present predominantly in the tetragonal modification and e) the molar ratio between the zirconium dioxide and chromium oxide containing the stabilizing oxides is from 1000: 1 to 20: 1, f) the proportions of all components supplement to 100% by volume of the sintered compact.

2. Cutting template of: a) at least 70% by volume of a matrix material formed from an aluminum oxide / chromium oxide mixed crystal having a chromium oxide content of 0.01 to 2.32% by weight, based on aluminum oxide, b) 2 up to 30% by volume of zirconia incorporated in the matrix material, containing c) from 0.27 to 2.85 mole% yttria, based on the mixture of zirconia and yttria, the amount of yttria added being such that the zirconia is predominantly is present in the tetra- gonal modification and d) the molar ratio between the zirconia and chromium oxide containing the stabilizing oxides is from 1000: 1 to 20: 1, and e) the proportions of all the components add up to 100% by volume of the cutting template.

3. A cutting template according to claim 2, wherein the molar ratio between the stabilizing oxides containing zirconia and chromium oxide is 370: 1 to 34: 1.

4. Cutting template of: a1) 60 to 98 vol .-% of a matrix material, this up to a2) 67.1 to 99.2 vol .-% of an alumina / chromium oxide mixed crystal a3) up to 0.8 to 32 , 9 Vol .-% of a further mixed crystal, which consists of at least one mixed crystal according to one of the general formulas SrAl 12-XCr _x O ig, Lao, 9Aln, 76-χCr _x Oi9, Me ¹ Al n _-x Cr _x Oi ₇ , Me ² Al i _2-x Cr _x 0i ₉ ,

Me ² Ali _2-x Cr _x Oi 9 and / or Me ³ Aln _-x Cr _x Oi ₈ where Me ^{1 is} an alkali metal, Me ^{2 is} an alkaline earth metal, Me ^{2 is} cadmium, lead or mercury and Me ³ represents a rare earth metal and x corresponds to a value of 0.0007 to 0.045 and b) the matrix material contains 2 to 40% by volume of tetragonal stabilized zirconium dioxide embedded in the matrix material and c) the proportions of the components amount to 100% by volume Complete the cutting template.

5. cutting template according to claim 4, characterized in that as

Stabilizing agent for the zirconium oxide is used 2 to 15 mol% of one or more of the oxides of cerium, praseodymium and terbium and / or 0.2 to 3.5 mol% yttrium oxide, based on the mixture of zirconium dioxide and stabilizing oxides, wherein the addition amount of stabilizing oxides is chosen so that the zirconium dioxide is present predominantly in the tetragonal modification and the proportion of cubic modification, based on zirconia, is 0 to 5% by volume.

6. Cutting template according to claim 4 or 5, characterized in that the molar ratio between the stabilizing oxides containing zirconia and chromium oxide is from 1000: 1 to 20: 1.

7. Cutting template according to one or more of claims 1 to 6, characterized in that the zirconium dioxide has a 2 microns not exceeding grain size.

8. Cutting template according to one or more of claims 1 to 7, characterized in that the matrix material also still 2 to 25 vol .-%; one or more of the carbides, nitrides and carbonitrides of the fourth and fifth subgroups of the PSE - based on

Matrix material - contains.

9. Cutting template of: a) 60 to 85% by volume of a matrix material formed from an aluminum oxide / chromium oxide mixed crystal and from 2 to 25% by volume of one or more of the carbides, nitrides and carbonitrides of the metals of the fourth b) more than 15 to 40% by volume of zirconium dioxide embedded in the matrix material, c) as stabilizing oxides more than 10 to 15% by mole of one or more of the oxides of cerium, praseodymium and terbium and / or 0.2 to 3.5 mol% of yttria, based on the mixture of zirconia and stabilizing oxides, wherein d) the addition amount of the stabilizing oxides is selected so that the zirconia is predominantly in the tetragonal modification and e) the molar ratio between the zirconia and chromium oxide containing the stabilizing oxides is 100: 1 to 20: 1, f) the proportions of all components complement 100% by volume of the sintered body, g) the zirconium dioxide is 2 μm does not exceed grain size.

10. Cutting template according to one of claims 1 to 9, characterized in that the molar ratio of the stabilizing oxides containing zirconium dioxide to chromium oxide in the range of

2 to 5% by volume zirconia 1, 000: 1 to 100: 1

> 5 - 15% by volume zirconium dioxide 200: 1 to 40: 1

> 15-30% by volume zirconia 100: 1 to 20: 1

> 30-40 vol% zirconia 40: 1 to 20: 1

lies.

1 1. Cutting template according to one or more of claims 1 to 10, characterized in that no more than 30 vol .-% zirconia are included.

12. Cutting template according to one or more of claims 1 to 1 1, characterized in that the zirconium dioxide to at least

95 vol .-% has the tetragonal modification.

13. Cutting template according to one or more of claims 1 to 12, characterized in that the zirconium dioxide is present in total to 0 to 5 vol .-% in the cubic and / or monoclinic modification.

14. Cutting template according to one or more of claims 1 to 13, characterized in that the average grain size of the AIuminium oxide / chromium oxide Mischkhstalls from 0.6 to 1, 5 microns.

15. Cutting template according to one or more of claims 1 to 14, characterized in that the grain size of the zirconium dioxide is between 0.2 and 1, 5 microns.

16. Cutting template according to one or more of claims 1 to 14, characterized in that not more than 0.5 vol .-% unavoidable

Impurities, based on the sintered body are included.

17. Cutting template according to one or more of claims 1 to 14, characterized in that the hardness according to Vickers [Hv 0.5]> 1 .800.

18, the cutting template with a matrix material, characterized in that the matrix material of at least one of the platelets by any of general formulas SrAli2 _-x Cr _x Oi9, Lao, 9Aln, 76-χCr _x Oi9, Me ¹ AInOi _7, Me ² Ah ₂ Oi ₉ , Me ² Ah ₂ Oi ₉ and / or Me ³ Ah ₂ Oi ₈ , where Me ¹ for a

Alkali metal, Me ² for an alkaline earth metal, Me ² for cadmium, lead or mercury and Me ³ for a rare earth metal and the matrix material contains tetragonal stabilized zirconia.

19. A method for producing a cutting template according to one or more of claims 1 to 18, characterized in that a mixture, the alumina, zirconia, chromium oxide, tetragonal zirconia stabilizing oxides and at least one oxide selected from strontium oxide, alkali oxides, alkaline earth oxides, CdO, PbO , HgO, rare earth oxides and / or La ₂ Os contains, ground, added to the ground mixture a temporary binder, this mixture sprayed is dried, are pressed from this mixture green body and these are sintered under standard conditions.

20. The method according to claim 19, characterized in that the green body is pre-sintered to a density of 90-95% without pressure and then subjected to a hot isostatic recompression.

20. A method for producing a cutting template according to one or more of claims 1 to 18, characterized in that a mixture comprising alumina, chromium oxide, tetragonal zirconia, optionally stabilizing oxides and at least one oxide selected from strontium oxide, alkali oxides, alkaline earth oxides, CdO, PbO , HgO, rare earth oxides and / or La ₂ θ ₃ , is milled in aqueous suspension having a solids content of more than 50 vol .-% while maintaining a pH of 4 to 4.5, then with urea and

Urease is added, poured into a mold and removed after a subsequent coagulation and sintered or pre-sintered and hot isostatically recompressed.

21 Use of the cutting template according to one of claims 1 to 18 in medical technology, in particular in operations for processing a bone.

22 Use of the cutting template according to one of claims 1 to 18 in a knee TEP implantation.