DD272603B3 - WEAR-RELIABLE SLIDE PARTNERS FOR A CERAMIC JOINT DENTURE THRESHOLD AND METHOD FOR THE MANUFACTURE THEREOF - Google Patents

Description

For this 1 page drawings

The invention relates to low-wear sliding partner for a ceramic Gelenkendoprothesenteil according to the preamble of claim 1 and a method for producing the same.

Artificial joint implantation has become a standard surgical procedure in the world over the past 15 years. Despite all the advances in the art of artificial joint replacement, prosthesis failure still occurs after prolonged implantation, resulting in a reoperation rate of about 12%. The causes are manifold; However, material problems play a significant role and thus require the constant search for new and better materials (P.Eyerer: "Plastics in joint endoprosthesis", Journal of Materials 17 (1986)., Pp. 384-391, pp. 422-428) , Pp. 444-448).

In general, the use of composite materials in bone prosthetics is known. Thus, US Pat. No. 3,314,420 proposes a porous ceramic body coated with a resin. Body tissue grows into the pores in particular. From DE-PS 2620907 composite materials are known which can be used in dental prosthetics, in which ceramic particles are embedded in a plastic matrix, but the ceramic particles have a high resorbability in the body medium. It has also been attempted (EP-A 0269745) to coat porous ceramic bodies with metals or ceramic layers and to use the structure enclosed in a PTFE membrane as the bone growth stabilizing part in the restoration of bone defects.

The use of chirulas, an ultra-high molecular weight low density polyethylene, for the acetabulum of the hip joint (DE-OS 2129832), for example, despite a low coefficient of friction and low wear results in the release of relatively large abrasive particles that are not degraded or removed by the body's cellular defense systems can be. This leads to a quantitative Überi sion of the foreign material burden for decompensation of the neocapsule with the formation of a bone-dissolving granule tissue and loosening of the joint partner. Polyethylene pans, which are manufactured as threaded cups, also do not give a permanent bond between bone and pan. Pans made of polyethylene also require a high because of the machining

Production costs and high costs. By using a bioceramic for pans (OE-OS 2305333), the wear of the artificial joint can be reduced. Due to the great brittleness of the ceramic, however, these pans tend to break under sudden loads. Because of the low attenuation of the material also shock-like loads are transmitted directly to the bone.

Ceramic pans are also very expensive, since expensive technological processes (molding, sintering, grinding, polishing) are necessary for their production.

From DE-OS 3722111 polyurethane is known as plastic and from the publication SPRECHSAAL, 117.1984 p.196 finally triazine resin-Xarbonfaser-Varbundwerkstoffe as Endoprothesenmaterialien.

Recently, the use of graphite fibers which are coated with plastic, for the production of sliding partners has been tested (DE-2138146). However, there is no experience of practical use with this new material. The aim of the invention is to provide a biocompatible sliding partner for the production of Gelenkendnprothesen that provides high-strength and low-wear joints in conjunction with bioceramics as the second sliding, which guarantee a long service life without interference and significantly reduce the rate of reoperation in orthopedics.

The solution according to the invention is applicable to artificial joints which are used to replace damaged hip, knee, elbow, shoulder, hand and ankle joints and intervertebral discs.

The advantages achieved also include a significant reduction in manufacturing costs and thus the cost, since the prostheses are to be prepared by pre-casting and because this method saves complex processing steps (machining, grinding, polishing).

In orthopedic surgery, damaged joints of the human are replaced by prostheses, which must take over the full function of the replaced joint. In order to guarantee the longest possible duration of use, biocompatible materials with high strength are to be used for the prostheses. The material pairings chosen for the joint must have low coefficients of friction and may experience only slight wear under the specific conditions of use. Recently, an alumina ceramic is increasingly used as a material for the ball joint. As a sliding partner for the pan, a high molecular weight polyethylene or alumina ceramic is also selected. Experimental studies show that the ball does not show any wear even after a long period of use, whereas after 5 years of use the polyethylene pans develop fine flaky wear material which accumulates in the joint prosthesis and has to be broken down by the body. The pans made of ceramics have better wear properties, but because of the high hardness of the material they can not cope with shock loads (for example when falling) and tend to break.

The invention has for its object to provide for the bioceramics a sliding partner, which is characterized by a high strength and in conjunction with the ceramic has a small coefficient of friction and low wear. In addition, the production costs and thus the costs must be significantly reduced by the selected method for producing the prostheses.

According to the invention, this object is achieved in that the fillers are enriched in the surface of the sliding partner loaded by friction with the ceramic joint endoprosthesis part and the crystals of the filler on the loaded surface of the sliding partner are aligned such that they are arranged tangentially to the surface with one of their surfaces are. The matrix of this material consists of a biocompatible, cross-linked plastic. For this purpose, preferably polyurethanes are used, but it is also possible to use specially purified epoxy resins (epichlorohydrin-free) and radiation-crosslinkable, unsaturated polyester resins.

The polyurethanes are prepared by using low molecular weight hydroxyl compounds (for example trimethylolpropane, neopentyl glycol, 1,6-hexanediol and 1,4-butanediol) and relatively high molecular weight polyols (for example monorizinoleates of these hydroxyl compounds or polytetrahydrofuran).

For filling high-strength, mineral, coarsely crystalline and physiologically harmless materials are brought into the matrix material. Suitable fillers are minerals that have a sufficient hardness of more than 5 to Mohs and a well crystallized microstructure, z. As quartz or silicon carbide. Particularly suitable, however, are the so-called bioceramic materials which, in addition to their strength and hardness, additionally have bioactive effects on the surrounding bone tissue and form chemical bonds to the surrounding resin in the physiological milieu. These bioceramic fillers are prepared by melting calcium and phosphate-containing starting materials and by initiating crystallization by introducing appropriate nuclei. Particularly advantageous materials have ve η CaO-P ₂ O ₅ -SiO-TyP proven with apatite and wollastonite crystal phases.

According to the invention, the polyol component is adjusted between 2.1 and 4.0, preferably between 3.3 and 3.6. To ensure the necessary hardness of the polyurethane used to bond the ceramic component, it is necessary that the hydroxyl equivalent weight between 40 and 300 g component / mole OH, preferably to 120-180g / mol, is set.

The coarsely crystalline filler is pre-dried for 2 hours at 150 ° C. in a thin layer and used according to the invention in a particle size of 50-150 μm with a proportion of 40-60% by weight of the resulting composite material. It is preferably introduced into the isocyanate component, so that the water adhering to the filler reacts before the crosslinking of the polyurethane resin and in this way forms a compact shaped body during the crosslinking.

While the plastic matrix of the composite material effects the strength of the manufactured component, the ceramic filler achieves good friction and wear properties. For this it is necessary that the production of the corresponding sliding partner for an artificial joint is successful in a casting process. In this case, the surface must be due to friction in the preheated to 60 ° C Fenn down, so that the coarsely crystalline filler accumulates on this surface and arranges each one of the surfaces of the crystals tangent to Gleitkörperoberfläche. The curing of the resin-filler mixture is carried out at 80 ⁰ C for 24 hours.

The material and the method for producing a suitable sliding joint for artificial joints were found by extensive experimental investigations:

- process steps for the production of the base material,

- examination for migration in accordance with the Pharmacopoeia of the former GDR,

- testing the biocompatibility of the base material,

- Studies on the friction and Verschlaißverhalten of the base material,

- Experiment with the load and motion simulator to determine the fatigue strength of artificial joints.

With the experimental investigations, the suitability of the new composite material as a sliding partner in artificial joints was demonstrated. The use of these new joints guarantees a trouble-free long-term function over a long set-up time.

Embodiment show

1: acetabular cup for anchoring with bone cement, FIG. 2: screwable acetabulum for cementless anchoring, FIG. 3: position of the mold during casting, FIG. 4: construction of the composite material on the sliding surface.

The explanation of the invention is based on two embodiments.

The use of the composite material suitable as a sliding partner can be carried out in the cups for hip total endoprostheses, which are completed with a ball made of a bioceramic. According to embodiment 1, the pan can be designed so that it is used for anchoring with bone cement (Figure 1), or it can be provided according to Embodiment 2 with an external thread for cementless anchoring (Figure 2).

When casting the pans from the filled polyurethane as the matrix material 1, the mold according to the invention is provided so that the filler 2 au * the sliding surface so arranged that each surface of the crystals is tangent to the surface (Figure 3 and 4).

Documents considered:

DE-PS 2620907 DE 3722410, A1 DE-OS 2305333 DE-OS 2138146 DE-OS 2129832 US-PS 4676799 US-PS 3314420 DE-Z: Speech room 117.1984 S. 196-201

Claims (7)

1. Low-wear sliding partner for a ceramic Gelenkendoprothesenteil, wherein the sliding partner consists of high-strength, biocompatible composite material having as a matrix a biocompatible, crosslinked plastic, are embedded in the high-strength, mineral, coarsely crystalline and physiologically harmless fillers, characterized in that a) the fillers are enriched in the surface of the sliding partner loaded by friction with the ceramic joint endoprosthesis part, and b) the crystals of the filler are aligned on the loaded surface of the sliding partner so that they are each arranged with one of their surfaces tangent to the surface. 2. Verschleißarrrtf ^r '.Üleitpartner according to claim 1, characterized in that the matrix plastic is a polyurethane > -A. 3. Low-wear sliding partner according to one of the preceding claims, characterized in that the crystalline filler is quartz, silicon carbide or a bioceramic material, which consists of calcium and phosphate-containing starting materials. 4. Low-wear sliding partner according to claim 3, characterized in that the bioceramic material of the CaO-P ₂ O ₅ -SiO type and having apatite and / or wollastonite crystal phases. 5. Low-wear sliding partner according to one of the preceding claims, characterized in that the grain size of the crystalline filler is 50 to 500pm, preferably 50 to 150mm. 6. A method for producing a low-wear sliding partner for a ceramic Gelenkendoprothesenteil, wherein the sliding partner consists of high-strength, biocompatible composite material having as a matrix a biocompatible, crosslinked plastic, are embedded in the high-strength, mineral coarsely crystalline and physiologically harmless fillers, characterized in that a) the pre-dried filler is added to the matrix plastic prior to its crosslinking in an amount of between 10 and 80% by weight, based on the total amount of the sliding partner, b) the mixture obtained in a) is poured into a preheated mold, wherein the surface of the sliding partner to be loaded by friction in use is arranged in the mold at the bottom and c) cross-linking and curing the mixture. 7. A process for producing a low-wear sliding partner according to claim 6, characterized in that the plastic used is a polyurethane whose isocyanate component is added to the predried filler before crosslinking.