DE3917035A1 - Sliding partner for joint endoprostheses and method of producing the sliding partners for joint endoprostheses - Google Patents

Abstract

The sliding partner for joint endoprostheses which are used in orthopaedics for joint replacement is produced from a biocompatible, crosslinked polyurethane of high strength. In order to reduce the friction and wear, a granular powder of a hard, crystalline bioceramic material is added to the polyurethane. The particle size of this biocompatible ceramic powder is in the range of 50-500 mu m, and it is present in the composite for the sliding partner to the extent of 10-80%. The technique or method of producing the sliding partner is chosen such that one of the surfaces of the crystals is in each case arranged on the surface of the joint part exposed to friction tangentially relative to the surface. <IMAGE>

Description

2. Field of application of the invention

The sliding partner is part of an artificial joint that in conjunction with a second known partner for the Manufacture of joint endoprostheses in bone replacement surgery gie is used. The endoprosthesis can be made in different ways management forms, e.g. B. as a hip, knee, elbow wrist, shoulder, wrist, ankle or ligament disc endoprosthesis are used. To ensure a trouble-free long-term function of at least 20 years the joints have high operational and wear resistance and are made of a material that is biocompatible.

3. Characteristics of the known prior art

The implantation of artificial joints has changed in the last 15 Years ago developed into a standard operation in the world. In spite of all advances in the field of artificial joint replacement however, prosthesis failure still occurs after prolonged Im plantation time leading to a reoperation rate of around 12% leads. The causes for this are varied; Material problems but demonstrably play an important role in this thus require the constant search for new and better work substances (P. Eyerer: "Plastics in joint arthroplasty", Journal of materials technology 17 (1986). P. 384-391, p. 422-428, pp. 444-448).

The use of chirules, an ultra high molecular low pressure polyethylene, for the socket of the artificial hip joint (PS D 21 29 832) for example leads despite a low Rei and the low wear to release of relatively large particles of abrasion caused by the cellular Defense systems of the body are not broken down or transported away can be. This leads to a quantitative over  Exceeding the foreign material load for decompensation of the Neocapsule with the formation of a bone-dissolving granulate tissue and to loosen the joint partners. Polyethylene pans that as Screw pans are manufactured, also do not result in duration firm connection between bone and pan. Pans made of poly Because of the machining, ethylene also requires one high manufacturing costs and high costs. By using a Bioceramics for pans (PS D 23 05 333) can wear the artificial joint can be reduced. As a result of the large brittle However, these pans tend to break due to the ceramics sudden loads. Because of the low damping of the Ma terials are also subjected to shock loads directly on the Bones transferred. Ceramic pans are also very expensive because of that elaborate technological processes (forms, Sintering, grinding, polishing) are necessary.

In recent times, the use of graphite fibers with Plastic coated for the manufacture of sliding part tested (PS D 21 38 146). About practical use with however, there is no experience with this new material.

4. Purpose of the invention

The aim of the invention is to produce joint endoprosthesis to provide a biocompatible sliding partner that Connection with bioceramics as a second high-strength sliding partner and provides low-wear joints that last at least 20 years Guaranteed operational time without disruptions and the reoperations significantly reduce the rate in orthopedics.

The solution according to the invention can be used in artificial gels to replace damaged hip, knee, elbow, Shoulder, wrist and ankle joints and intervertebral discs used will.

The advantages achieved also include a clear sen Reduction of the manufacturing effort and thus the costs, since the Pro theses are to be produced by casting and since this process elaborate processing steps (machining, grinding, polishing) saves.  

5. Explain the nature of the invention

In orthopedic surgery, damaged joints of the People replaced by prostheses that have the full function of the replaced joint. To be at least 20 years old guaranteeing the duration of use are biocompa for the prostheses tible materials with high strength. The for that Articulated material pairings must have a small coefficient of friction clients own and are allowed under the specific conditions of use experienced only slight wear.

Lately, as a material for the joint ball is increasing an aluminum oxide ceramic used. As a sliding partner for this, a high molecular weight polyethylene or also selected an aluminum oxide ceramic. From experimental Research shows that the bullet even after 20 years Use time shows no wear and tear while on the polyethylene pans after about 5 years of use material arises that accumulates in the joint prosthesis and from Body must be broken down. The ceramic pans have better wear properties, but the large Hardness of the material shock loads (for example, when Traps) do not dampen and tend to break.

The object of the invention is for bioceramics to provide a sliding partner that is characterized by a large Characterized strength and in connection with the ceramic one has a low coefficient of friction and low wear. In addition, by the method chosen for the production of Prostheses significantly increase the manufacturing effort and thus the costs to reduce.

According to the invention this goal is achieved in that as part a pan made of a compo for the ceramic joint ball Sit material is used. The matrix of this material be is made of a biocompatible, cross-linked plastic. Therefore Polyurethanes are preferably used, but can also specially cleaned epoxy resins (free of epichlorohydrin) and  radiation-chemically cross-linkable, unsaturated polyester resins come into use.

Low molecular weight is used to manufacture the polyurethanes Hydroxyl compounds (e.g. trimethylolpropane, neopentylycol, Hexanediol-1.6 and butanediol-1.4) and higher molecular weight polyols (e.g. monorizinoleates of these hydroxyl compounds or poly tetrahydrofuran) used.

The matrix material is filled with high-strength minerali nice, coarsely crystalline and physiologically harmless materials brought. Suitable minerals are: a sufficient hardness of over 5 according to Mohs and a good have crystallized structure, e.g. B. quartz or silicon car bid. However, the so-called bioceramics are particularly suitable Materials that in addition to their strength and hardness on bioactive effects on the surrounding bone tissue ver add and in the physiological milieu chemical bonds to Form the surrounding resin.

These bioceramic fillers are produced by melting calcium and phosphate-containing raw materials and by introducing crystallization by introducing appropriate germs. Materials of the CaO-P ₂ O ₅ -SiO type with apatite and wollastonite crystal phases have proven to be particularly advantageous.

According to the invention, the polyol component is between 2.1 and 4.0, preferably between 3.3 and 3.6. To guarantee performance of the necessary hardness to bind the ceramic Component used polyurethane, it is necessary that Hydroxyl equivalent weight between 40 and 300 g component / Mol OH, preferably set to 120-180 g / mol.

The coarsely crystalline filler is in for 2 hours at 150 ° C. thin layer pre-dried and according to the invention in one grain size of 50-150 µm used with a share of 40-60% on the resulting composite material. It is preferably in  the isocyanate component introduced so that the filler adhering water even before the crosslinking of the polyurethane resin responds and in this way a compact when networking Shaped body is created.

While the plastic matrix of the composite material, the Festig speed of the manufactured component is achieved with the kerami the good friction and wear properties achieved. This requires that the manufacture of the corresponding sliding partner for an artificial joint in a casting process. The frictional load must be used Surface lying in the form preheated to 60 ° C below, so that the coarse crystalline filler accumulates on this surface and each one of the faces of the crystals tangent to Arrange sliding body surface.

The resin-filler mixture is cured at 80 ° C over 24 hours.

The material and method of making a suitable one Sliding partners for artificial joints have been through extensive experimental investigations found:

• - process steps for the production of the base material,
• - Check for migration according to the drug book the GDR,
• - Checking the biocompatibility of the base material,
• - Studies on friction and wear behavior the base material,
• - Try using the exercise and movement simulator Determination of the operational strength of the artificial Joints.

The suitability of the new composite material as a sliding partner in artificial Joints proven. The use of these new joints guaranteed provides trouble-free long-term function via an insert time of at least 20 years.  

6th embodiment

Fig. 1 acetabular cup for anchoring bone cement,

Fig. 2 Threaded acetabular cup for cement-free anchoring Ver,

Fig. 3 position of the mold during casting,

Fig. 4 Structure of the composite material on the sliding surface.

The explanation of the invention is based on two execution examples.

The composite material suitable as a sliding partner can be used in the cups for total hip joint endoprostheses, which are completed with a ball made of a bio-ceramic. According to embodiment 1, the socket can be designed so that it is used for anchoring with bone cement ( Fig. 1), or it can also be provided with an external thread for cement-free anchoring according to embodiment 2 ( Fig. 2).

When the pans are poured from the filled polyurethane as matrix material 1 , the casting mold is placed according to the invention in such a way that the filler 2 is arranged on the sliding surface in such a way that one surface of the crystals is tangential to the upper surface (FIGS . 3 and 4).

Claims (5)

1. sliding partner for joint endoprostheses, characterized in that it consists of a particularly low-wear and high-strength, biocompatible composite material. 2. sliding partner according to claim 1, characterized in that the Matrix of the composite material made of a cross-linked polyurethane exists to reduce wear and friction Powder made of a hard, crystalline material added becomes. 3. Process for the production of the sliding partner for articulated end prostheses, characterized in that the addition of crystalline linem material accounts for 10-80% of the sliding partner. 4. The method according to claim 3, characterized in that the Grain size of the crystalline material used Is 60-500 µm. 5. The method according to claim 3 and 4, characterized in that the crystalline of the filler on the loaded sliding surface the pair of bearings are aligned so that with each one of their faces is tangent to the surface.