MXPA00009124A - Composition, manufacturing, and use of silicon nitride as a biomaterial for medical purpose - Google Patents

Abstract

The invention refers to the composition, manufacturing and usage of silicon nitride as a biomaterial for medical usage as a surface carrying, orthopaedic biomaterial for wearing surfaces in artificial joints, for example the hip and the knee joint. The manufacturing is performed by preparing and mixing a mixture of powder containing 70-100 volume%silicon nitride with the addition of 0-30 volume%of one or a combination of the following materials:zirconium dioxide, yttrium dioxide, titanium dioxide, calcium oxide, silicon carbide and mullite. From the mixture a body is formed which is subjected to a high pressure greater than 50 MPa and temperatures between 500-3000°C under sintering (HIP). The material can be used for one, both or all the wearing surfaces in an artificial joint.

Description

COMPOSITION, MANUFACTURE AND USE OF SILICON NITRIDE AS BIOMATERIAL FOR MEDICAL PURPOSE FIELD OF THE ART The present invention relates to the composition, manufacture, use and function of silicon nitride for medical purposes, for example, as a bio-material for wearing surfaces in artificial joints. Patients with joints destroyed due to fractures or degenerative joint diseases suffer from pain of the joint involved, for example, the hip joint. In order to relieve pain it is necessary, in addition to using agents that mitigate pain, to surgically change the joint involved. Another alternative is to replace the joint involved with an artificial joint where articulating surfaces are fabricated from a biomaterial. The biomaterial must be durable against wear since a joint receives a heavy load. It is necessary to select a biomaterial that meets these requirements in such a way that the life of the prosthesis can exceed the life expectancy of the patient. Today, approximately 10% of hip prostheses must be replaced within 10 years of implantation due to wear and loosening caused by particles that originate from the surfaces of the joint. It is difficult to find new biomaterials with the necessary characteristics for their implantation in humans. Ceramic materials or substances, and particularly structural ceramic materials are generally considered highly resistant against corrosion and erosion. This is true of many oxides, nitrides, carbides and borides. The materials are totally inactive, that is, they do not cause any reaction directly or indirectly with the surrounding tissue, and therefore they are suitable as orthopedic implants. Silicon nitride is a ceramic substance of that type. The silicon nitride and mixtures in powder form can be pressed under a high temperature and high pressure, which is known as isotactic pressing (HIP), into a preformed porous body consisting of the powder material. Silicon nitride is also a ceramic material that has extraordinary characteristics as a biological material and is extremely well tolerated by the biological organism. In addition, the material has a high coefficient of resistance, which means that it has a high resistance to wear. Compared to other ceramics (see table below), silicon nitride has excellent characteristics as a prosthesis material for implant.

The invention is defined as a method of using a ceramic substance of this type or its mixtures as a biomaterial in a biological environment. More specifically, the invention can be defined as a form of use of such a ceramic substance in the form of silicon nitride as a base, and mixtures thereof, as a support material / wear surface, for example, in prostheses to be used for implant biological in humans and / or animals. A biomaterial refers in this context to a material or substance that can be sustained by biological tissues without causing significant rejection. A support material refers to a material that functions as a joint surface in an artificial joint, for example, in the hip or knee, see figures 1 and 2 below. Biological use refers to the fact that the prosthesis is surgically implanted or carried by a biological organism. STATE OF THE ART When silicon nitride is used as a biomaterial in the tissues of biological organisms, rejection has no relevance since the biological organism holds the foreign material well and the material can therefore be used as an implant.

Silicon nitride is formed by isotactic pressing, at high temperature and high pressure, on a joint surface, for example, the joint surfaces of the hip and the knee. In order to acquire a sufficient quality of the wear surface it is necessary to meet certain biological requirements. Through the Swedish patent application 90.04134-4 (KN 7334 SE) it is known how to carry out the isotactic pressing of ceramic materials to the highest degree of pore quality. We refer to the following publications: T. Mukarami and N. Ohtsuki, Bioceramics, Ishiyaku Euroamérica, 224-46, 1989; P. Ku ar et al .. Adv. In Bio. Eng. 9, 373-8, 1990; H. Oonis i et al. Bioceramics, Ishiyaku Euro America, 272-7, 1989; H. McKellop et al .. JBMR 15, 619-53, 1981; B. Weight an and D. Light, Bio aterials 7, 20-9, 1986; L. Zichner, Trans Soc. Biomaterials Imp. Retrieval Symp. P. 22, 1988. DESCRIPTION OF THE INVENTION The purpose of the present invention is to solve the problems mentioned above, which involve the loosening of the prosthesis in biological organisms, including the human being, as a result of an increased wear of the joint surface of the teeth. Mechanical prosthesis joints. According to the present invention, silicon nitride is used which, in comparison with other ceramics, resists wear and has excellent characteristics for implantation in the form of prostheses, as shown in the following table: TABLE Characteristics Alumina Zirconia Silicon Nitride Resistance to 600 1000 900 bent (MPa) Resistance in 3-4 > í 4.5 the fracture (MPa / m2) Hardness (Gpa) 22 12 19 The articulation surfaces are manufactured from silicon nitride and / or their mixtures by isotactic pressing under high temperatures, high pressures and sintering, where: 1. Silicon nitride as base and its mixtures (see below) create the prerequisites for a wear resistant material that is suitable for articulation support components in prostheses for biological organisms, including humans. 2. The powder material from which the object consists of a ceramic material, nitride ^ Hitáilta tfiwta, silicon, but may also be composed of intermetallic compounds or compounds consisting of mixtures of metallic materials and ceramics. 3. A joint surface, both articulation surfaces or the entire articulation surface in the same artificial joint are manufactured from the mixture in accordance with the following example. 4. The minimum porosity of the joint surface through the use of HIP for its manufacture limits wear. 5. The polished surface contributes to decreased wear. 6. The specific microstructure of the joint surface increases the liquid film between the joint surfaces in order to limit the wear through increased lubrication of the body fluid. 7. The processing of the articulation surface causes a lower risk of cavities or cracks formation. 8. The angular movement of the circulation influences the wear, and the manufacture of small components such as, for example, a hip with a small prosthesis head (ball) that can have 22 mm or less in diameters of silicon nitride and / or mixtures of the biomaterials mentioned below. 9. Special methods of disinfection that avoid the risk of infection of the biological organism.

The invention is especially valuable for the fabrication of surfaces in artificial joints for which good surface characteristics, such as hardness and wear resistance, are necessary requirements, and when surface defects such as irregularities, cracks, etc. are present. They can not be tolerated. Examples of products with such requirements are articulation surfaces, that is, both the prosthesis head (ball) and what is known as the socket (socket), in hip prostheses, articulation surfaces, that is, both the thigh bone (femoral) as the shin bone (tibia) in knee prostheses and joint surfaces, for example, in the shoulder, ankle, etc., where the characteristics of the joint surface is a decisive factor and where the nitride of silicon and / or mixtures of the biomaterials mentioned below constitute the body of the prosthesis. BRIEF DESCRIPTION OF THE DRAWINGS A currently preferred variant of the present invention will now be described with reference to the drawings, wherein Figure 1 shows the wear surfaces in an artificial hip joint; Figure 2 shows the wear surfaces in an artificial knee joint;Figure 3 shows the wear surfaces in an artificial shoulder joint; Figure 4 shows the components of an artificial hip joint; and Figure 5 shows the components in an artificial knee joint. DETAILED DESCRIPTION OF THE MANUFACTURE Below are a couple of examples of compositions of suitable materials and suitable characteristics of materials. Example 1 shows silicon nitride mixed with 2% by volume of yttrium dioxide and the following data are obtained: Example 1 Characteristic Value Fold resistance (3 pt.) 1000 MPa eibull module () 22 Fracture strength 4.5 MPa / m2 Tension exponent > 100 Hardness 19 Gpa Example 2 shows the silicon nitride mixed with 10% by volume of aluminum oxide in the form of short fibers, which results in the following data: Example 2 Characteristic Value Fold resistance (3 pt.) 930 MPa Module Weibull () 23 Fracture Resistance 6.5 MPa / m2 Tension Exponent > 100 Hardness 20 Gpa The manufacture of the material is carried out by preparing a powder mixture according to one of the examples above with silicon nitride as a base or by adding other biomaterials having the desired characteristics. The mixture is formed in a body and sintered under high pressure (greater than 50 MPA, particularly pressures greater than 150 MPa, but not greater than 350 MPa) and high temperature (500-3000 ° C) in accordance with the HIP method. The HIP method is the appropriate method, since the porosity is a decisive factor for the wear, for example of the articulation surfaces. After cooling, the surfaces are polished, cleaned and disinfected before medical use. When the material has been consolidated, there is no chemical reaction. To reduce the wear on the joint surfaces of the mechanical joint to be used for implanting, a special method of medical material polishing that complies with Class III is necessary. With reference to the following figures, some examples of the use of biomedical material in relation to different artificial joints are shown.

Figure one demonstrates an example of a hip prosthesis head and socket, where the articulation surfaces are made of silicon nitride or mixtures thereof in accordance with one of the above examples. The ball has a diameter of 22 mm, but it can be larger or smaller. The ball is spherical with a conical fit to be fixed on the neck of the body of the prosthesis. The construction is suitable for artificial hip joints in general. Figure 2 demonstrates a knee prosthesis consisting of a thigh bone (femur) and a shin bone (tibia) made of silicon nitride or mixtures thereof and fixed on the thigh bone and shin bone, respectively. The sizes vary according to the weight and size of the patient. The construction is suitable for artificial knee prostheses in general. The figure shows an example of a shoulder prosthesis in the form of a prosthesis ball and its socket, made of silicon nitride or its mixtures. Figure 4 shows the assembly of the components in an artificial hip joint consisting of a shaft, ball and socket, where the components bearing the articulation surface are composed of silicon nitride or its mixtures. A corresponding view, from the side and from the front, of an artificial knee joint appears in figure 5. Even in this case the components bearing the joint surface, ie the bone, thigh and bone of pimple, are made of silicon nitride or their mixtures. The invention is not limited to the designs described above which may vary within the framework of the patent description. One, both or all of the wear surfaces in an artificial joint can be composed of one or more materials according to the invention. The invention is not limited to the hip, knee or man but can also be used for other types of joints such as elbow, ankle, finger, and other possible joints.

Claims (1)

CLAIMS A method for the manufacture of a joint prosthesis, for example, a hip or knee joint prosthesis, a ceramic material with a high tolerance to tension and a high tolerance to tissues for medical use as a surface that carries an orthopedic biological material for the wearing surfaces of the artificial joint prosthesis, which is characterized by the following: 1.1 the preparation / mixing of a powder composition containing silicon nitride as a base consisting of 70 to 100% by volume of silicon nitride with the addition of 0 to 30% by volume of one of the following materials or a combination of the following materials: zirconium dioxide, yttrium dioxide, titanium dioxide, calcium oxide, silicon carbide and / or 0 to 20% by volume of short fibers of aluminum oxide, silicon carbide and mulite, or independent mixtures thereof, 1.2 form the body of joint prostheses n of the mixture, 1.3 submit the prosthesis body at high pressures between 50 MPa and 350 MPa and temperatures between 500 and 3000 ° C by isotactic pressing and sintering (HIP) in order to acquire a desirable porosity of the body, after which,

1.4 the body is cooled and the wear surfaces are polished to minimize wear and are clinically decontaminated before medical use. A method according to claim 1, characterized by the formation of silicon nitride and its mixtures in a body of different sizes and different shapes in joint prostheses such as, for example, a hip joint ball, a hip joint socket , a knee joint wear surface, etc. A method according to claim 2, characterized by the use of the biomaterial in one, both or all of the wear surfaces of an artificial joint prosthesis. A joint prosthesis, for example, a hip or knee joint prosthesis, made of a ceramic material with a high tolerance to tension and tolerance of tissue for medical use as a surface bearing an orthopedic biomaterial for wearing surfaces in artificial joint prosthesis, characterized in that the prosthesis body material is a composition of a powder containing silicon nitride as a base, consisting of 70 to 100% by volume of silicon nitride with the addition of 0 to 30% in volume of one of the following materials or a combination of the following materials: zirconium dioxide, yttrium dioxide, titanium dioxide, calcium oxide, silicon carbide and / or from 0 to 20% by volume of short fibers of aluminum oxide, silicon carbide and mulite, or separate mixtures of these, so that the mixture of material is formed on the body of joint prosthesis in question ny is subjected to a high pressure comprised within a range of 50 MPa to 350 MPa and temperatures between 500 and 3000 ° C by means of isotactic pressing and sintering (HIP) to achieve a desired porosity of the body and wearing surfaces Polished body to minimize wear. A prosthesis according to claim 4, characterized in that the body is formed, for example, as a hip joint head, a hip joint socket or a knee joint wear surface. A prosthesis according to claim 5, characterized in that one or both or all of the wear surfaces are made of said composition of ceramic powder material.