Ceramic Part Having At Least One Ceramic Foam for Medical Applications

Abstract

The invention relates to the use of ceramic parts that at least partly consist of a ceramic foam in the field of medical technology.

Claims

1. Ceramic part for medical applications which consists of a porous region and optionally a dense region, wherein the porous region consists of a ceramic foam being formed by an oxide-ceramic material or a non-oxide-ceramic material.

2. Ceramic part for medical applications according to claim 1, wherein the ceramic foam is selected from the Al.sub.2O.sub.3ZrO.sub.2 mixed-oxide system or ceramic composite materials in which zirconia constitutes the volume-dominant phase.

3. Ceramic part for medical applications according to claim 1, wherein a pore size of the porous region is between a few 10 m and 1 mm.

4. Ceramic part for medical applications according to claim 1, wherein the porous region has a porosity of from 20 to 95%.

5. Ceramic part for medical applications according to claim 1, wherein the ceramic part is an implant.

6. Ceramic part for medical applications according to claim 5, wherein fastening means can be inserted into the porous region of the implant.

7. Ceramic part for medical applications according to claim 6, wherein the fastening means include screws, pins, and nails.

8. Ceramic part for medical applications according to claim 6, wherein the fastening means have a diameter of up to 5 mm.

9. Ceramic part for medical applications according to claim 5, wherein the porous region can be machined.

10. Ceramic part for medical applications according to claim 9, wherein the machining is carried out by grinding and/or drilling and/or nailing and/or screwing and/or pressing.

11. Ceramic part for medical applications according to claim 1, wherein the porous region can be connected to a non-ceramic material.

12. Ceramic part for medical applications according to claim 11, wherein the porous region and the non-ceramic material are connected by plastics infiltration and/or by bonding.

13. Use of the ceramic part according to claim 1 for implants for applications in human medicine or veterinary medicine.

14. Use of the ceramic part according to claim 13 for medical applications as an implant that has a component size having wall thicknesses of from 0.3 to 30 mm.

15. Use of the ceramic part according to claim 13 for medical applications as a vertebral implant and/or in the field of partial resurfacing and/or as a bone replacement material.

16. Ceramic part for medical applications according to claim 3, wherein the pore size of the porous region is between 50 m and 1 mm.

17. Ceramic part for medical applications according to claim 16, wherein the pore size of the porous region is between 100 and 700 m.

18. Ceramic part for medical applications according to claim 4, wherein the porous region has a porosity of from 55 to 85%.

Description

[0028] Examples of ZTA ceramics in which alumina constitutes the volume-dominant phase are:

[0029] A ceramic material which consists of 60 to 98 vol. % of an alumina/chromium oxide mixed crystal in the form of a matrix material that may contain 0.8 to 32.9 vol. % of one or more other mixed crystals, selected from mixed crystals according to one of the general formulas Lao.sub.9Al.sub.11.76-xCr.sub.xO.sub.19, Me.sup.1Al.sub.11-xCr.sub.xO.sub.17, Me.sup.2Al.sub.12-xCr.sub.xO.sub.19, Me.sup.2Al.sub.12-xCr.sub.xO.sub.19 or Me.sup.3Al.sub.11-xCr.sub.xO.sub.18, with Me1 representing an alkali metal, Me.sup.2 representing an alkaline earth metal, Me.sup.2 representing cadmium, lead or mercury and Mea representing a rare earth metal oxide, and x representing a value of from 0.0007 to 0.045, and consists of 2 to 40 vol. % of zirconium dioxide embedded in the matrix material, which may contain, as stabilizing oxides, greater than 10 to 15 mol. % of one or more 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.

[0030] A ceramic material made up of alumina in the form of a ceramic matrix having zirconia dispersed therein and optionally other aggregates or phases, with the alumina proportion being at least 65 vol. % and the zirconia proportion being 10 to 35 vol. %, the zirconia being present in the tetragonal phase in a proportion of 80 to 99%, preferably 90 to 99%, based on the total zirconia content, and the stabilization of the tetragonal phase of the zirconia taking place predominantly mechanically rather than chemically, the total content of chemical stabilizers being <0.2 mol. %, with preferably no chemical stabilizers being used. This material preferably contains another dispersoid phase, the volume fraction of the dispersoids forming the dispersoid phase being up to 10 vol. %, preferably 2 to 8 vol. %, particularly preferably 3 to 6 vol. %. In principle, according to the invention, all substances that are chemically stable, do not dissolve in the alumina or zirconia during the production of the composite material by sintering at high temperatures, and allow micro-deformations at a microscopic level due to its crystal structure can be used as dispersoids. According to the invention, it is possible to both add dispersoids and to form the dispersoids in situ when producing the composite material according to the invention. Examples of dispersoids that are suitable according to the invention are strontium aluminate (SrAl.sub.12O.sub.16) or lanthanum aluminate (LaAl.sub.11O.sub.18).

[0031] An example of ceramic composite materials in which zirconia constitutes the volume-dominant phase is a ceramic material, a ceramic zirconia matrix, and at least one secondary phase dispersed therein, the zirconia matrix forming a proportion of at least 51 vol. % of the composite material, and the secondary phase forming a proportion of 1 to 49 vol. % of the composite material, the zirconia being present in the tetragonal phase in a proportion of 90 to 99%, preferably 95 to 99%, based on the total zirconia content, and Y2O3, CeO2, Gd2O3, Sm2O3 and/or Er2O3 being contained as chemical stabilizers, the total content of chemical stabilizers being <12 mol. % based on the total zirconia content, and the secondary phase being selected from one or more of the following compounds: strontium hexaaluminate aluminate (SrAl.sub.12O.sub.16), lanthanum aluminate (LaAl.sub.11O.sub.18), hydroxyapatite (Ca.sub.10(PO.sub.4).sub.6(OH).sub.2), fluorapatite Ca.sub.10(PO.sub.4).sub.6F.sub.2), tricalcium phosphate (Ca.sub.3(PO.sub.4).sub.2), spinel (MgAl.sub.2O.sub.4), alumina (Al.sub.2O.sub.3), yttrium aluminum garnet (Y.sub.3AL.sub.6O.sub.12), mullite (Al.sub.6Si.sub.2O.sub.13), zircon (ZrSiO.sub.4), quartz (SiO.sub.2), talc (Mg.sub.3Si.sub.4O.sub.10(OH).sub.2), kaolinite (Al.sub.2Si.sub.2O.sub.6(OH).sub.4), pyrophyllite (Al.sub.2Si.sub.4O.sub.10(OH).sub.2), potassium feldspar (KAISi.sub.3O.sub.8), leucite (KAISi.sub.2O.sub.6) and lithium metasilicate (Li.sub.2SiO.sub.3); strontium hexaaluminate, lanthanum aluminate, hydroxyapatite, fluorapatite, spinel, alumina, and zircon are preferred, and strontium hexaaluminate is particularly preferred.

[0032] The average particle size (D50) of the ceramic starting powder can be determined by laser diffraction and according to the invention is preferably in the range of from 0.01 to 50 m, particularly preferably in the range of from 0.1 to 5 m.

[0033] The particle size in the sintered structure is usually in a similar range of from 0.01 to 50 m or particularly preferably in the range of from 0.1 to 5 m in the structure, determined by means of the linear intercept technique in accordance with DIN EN ISO 13383-1 (2016-11).

[0034] The ceramic part for medical applications according to the invention consists at least of a porous region and optionally a dense region, the porous region that consists of a ceramic foam preferably having a density in the range of from 0.5 to 2.5 g/cm.sup.3, particularly preferably 0.8 to 1.8 g/cm.sup.3. The strength of the porous region of the part is preferably in the range of from 5 to 300 MPa, particularly preferably in the range of from 20 to 150 MPa.

[0035] The thermal conductivity of the ceramic part is preferably <10 W/km and is thus in a similar range to that of the thermal conductivity of natural tissue. As a result, altered sensitivity to cold and heat due to the use of an implant is reduced for the user or patient, and is preferably completely eliminated.

[0036] By using a structure according to the invention that comprises a ceramic foam, the behavior of this structure is significantly altered. In the event of local, high loads, predominantly under pressure, a locally restricted defect therefore occurs, rather than a catastrophic failure of the entire implant. The local damage manifests in the form of fractures in the pore webs and is restricted to the region containing the porous foam. Here, the cracks are prevented from propagating more widely since this material has a low fracture toughness (<1 MPa). It contains pores, which counteract cracks from continually propagating to new boundaries. Owing to this locally restricted material behavior, the material of the porous region becomes compacted, with it being possible for deformation energy to be dissipated and applied stresses to also be distributed and relieved thereby.

[0037] This material behavior of a part according to the invention allows for machining methods, e.g. drilling, nailing, screwing, rasping, or abrasive cutting. This makes it possible to fix a part according to the invention in position using fastening means such as screws, nails, pins, etc. These fastening means can be inserted into the region formed by the porous ceramic foam without the part being damaged, which impairs the use thereof.

[0038] As a result, the part according to the invention, in particular the porous region made of the ceramic foam, not only encourages the natural tissue to grow in, but also contributes to the fixing before and during the operation, i.e. a connection to the body or other implant material is made possible. The ceramic part of the present invention and its porous region preferably can be screwed, i.e. screws can be inserted, can be nailed, i.e. it is possible to tap in or press in nails, and can be drilled, i.e. holes can be made, as a result of which other form-fitting and/or force-locking connections (e.g. by pins) and stitching are also made possible. The above-mentioned fixing means may have a diameter of up to 5 mm, preferably of up to 3 mm.

[0039] Furthermore, the ceramic component and its porous region can also be bonded and can be welded (Bone Welding). Both in bonding and in Bone Welding, the porosity of the part according to the invention and its porous region is advantageous, since the implant can be infiltrated by the process material (>0.5 mm deep) and is then also mechanically connected thereto or interlocked therewith, in addition to the chemical bond. As a result, connections to other materials, for example non-ceramic materials such as plastics materials and metals, are also made possible. The different methods for joining the different materials can be carried out within applications, for example during insertion as part of an operation, or separately therefrom, in advance, when producing a component or a part of a system.