WO1999030672A2

WO1999030672A2 - Coating material for prostheses and prosthetic parts

Info

Publication number: WO1999030672A2
Application number: PCT/EP1998/008184
Authority: WO
Inventors: Wilhelm Aicher; Kurt E. Geckeler; Wolfgang KÜSSWETTER
Original assignee: Eberhard-Karls-Universität Tübingen Universitätsklinikum; ZIRNGIBL, Friedrich, E.
Priority date: 1997-12-15
Filing date: 1998-12-14
Publication date: 1999-06-24
Also published as: EP1039939A2; WO1999030672A8; WO1999030672A3; DE19755334A1

Abstract

A coating material for prostheses is characterized such that it is made of an organic polymeric material which forms a solid composite with the material of which the prosthesis is produced, and that the organic polymeric material is chemically modified such that a growth of bone cells thereon is increased with regard to the prosthetic material.

Description

Coating material for prostheses and prosthesis parts

The invention relates to a coating material for prostheses and a prosthesis part.

In the case of endoprostheses, a rough distinction is made between cemented prostheses and cementless implanted prostheses. In the cemented prosthesis, a prosthesis section is firmly connected to the wall of a cavity created in a bone using a cement layer. With cementless implants, bone material grows against the surface of the prosthesis. The prostheses are made from a metal, usually titanium, in view of their high mechanical strength. However, osteogenic cells in the bone material adhere less well to metal surfaces. It has therefore already been proposed to provide the surface of prostheses or implants made of metal with an outer layer of hydroxylapatite. Hydroxyapatite is an inorganic material related to bone material, which has a favorable influence on the waxing-up kinetics of the implant. The rapid growth of osteogenic cells on the coated prosthesis surface accelerates the mobilization of patients after operations.

However, prostheses coated with hydroxyapatite have the disadvantage that cracks or surface detachments can occur between the mineral outer layer and the metallic base body of the prosthesis. This has a negative effect on the strength of the corresponding implants in the bone.

It has also become known to coat prostheses with plastic materials, for example with Teflon.

However, plastic materials of this type do not promote the growth of bone cells, but rather display a more inert, some even a non-biocompatible behavior.

It is therefore an object of the present invention to provide a prosthetic part which can be permanently implanted in a body and which ensures rapid growth of osteogenic cells.

According to the invention, the object is achieved in the case of a coating material in that it is formed from an organic polymer material which has a firm bond with the al forms from which the prosthesis is made, and that the organic polymer material is chemically modified such that an increase in bone cells thereon is increased compared to the prosthesis material.

In the case of a prosthesis part, the object is achieved in that the outer layer consists of such a coating material.

It has surprisingly been found that special organic polymers have good adhesion to metallic surfaces or to the surfaces of ceramic materials or plastic composite materials and that, if chemically modified, they promote the growth of osteogenic cells thereon. This ensures that, on the one hand, there is a firm, intimate bond between the coating material and the base of the prosthesis, and at the same time, due to the rapid and intensive growth, there is an intimate bond between the bone material in which the prosthesis is inserted and the outer surface of the prosthesis. This creates a permanently mechanically robust and stable bond between the outside of the prosthesis and the body materials that grow quickly and well, namely osteogenic cells.

In one embodiment of the invention, the coating material is selected from the materials epoxy resins, epoxy resins modified with acetethylamine or chromosulfuric acid, glutardialdehyde, polyvinyl acetates, polyacrylonitriles, polyhydroxybutyrates, polyacrylates, polyoxymethylenes, polystyrenes, polyethylenes, polyethylenes, paraffins, polymethylols , Acetyl celluloses, nitrocelluloses, polyvinylpyrrolidones. These materials are outstandingly suitable as coating materials for the common materials from which base bodies of prosthesis parts are made, but these materials can also serve as base bodies themselves. These materials can already be modified in such a way that an increase in bone cells is increased, or they must be additionally modified in order to increase this increase even further.

In a further embodiment of the invention, the chemical modification is carried out by introducing functional groups into the polymer materials.

This is one way of carrying out the modification by introducing groups which promote the growth of the bone cells by means of chemical reactions.

This chemical modification can take place wet-chemical or plasma-chemical.

In a further embodiment of the invention, the modification is carried out by including biocompatible materials in the polymer material.

This measure has the advantage that the polymer material as such essentially serves to form the firmly adhering bond with the base of the prosthesis. The biocompatible materials enclosed in the polymer material then promote ingrowth into the organism. It is particularly advantageous if the enclosed materials are osteocompatible, they then specifically promote the growth of bone cells on the prosthesis material.

In a particularly preferred embodiment, the coating material is an epoxy resin which is modified with 0.01 to 1.0 mol / mol, preferably with 0.3 to 0.8 mol / mol, most preferably with 0.5 mol / mol acetethylamines.

A prosthesis part which is coated with such materials ensures sufficient mechanical stability and a rapid and firmly adhering growth of the bone cells on the prosthesis.

The free surface of the outer layer of the prosthesis part can be treated by a plasma discharge, in particular with a treatment plasma that contains oxygen. The surface can also be treated with microwaves.

In a further embodiment of the invention, the outer layer can carry a surface layer made of a material which is selected from the group of hydroxyapatite, proteins, in particular albumin, trypsin, pepsin, collagen.

This measure has the advantage that a particularly tissue-friendly surface is present at the immediate interface with the growing bone material and thus an increase in the outer layer is further promoted by interposing this surface layer. In a further embodiment of the invention, this surface layer is treated by plasma discharge.

This measure has the advantage that the additional treatment of the surface layers results in further promotion of rapid and intensive growth.

A particularly intimate bond with the coating materials results when the prosthesis base body is made of metal, preferably titanium, a ceramic material or a fiber / plastic composite material.

However, some of the polymer polymers selected have such a high mechanical stability in themselves that they can be used as basic prosthesis bodies.

In this case, the prosthesis itself is formed from the materials that also build the coating material. In order to promote the growth, only the outside has to be modified or activated accordingly.

This can be done by including appropriate biocompatible or osteocompatible substances. It is also possible to produce a base body from a not yet chemically modified organic polymer material, which is then coated with a corresponding coating material that is chemically modified to grow.

It goes without saying that the features mentioned above and those yet to be explained not only in the respectively specified combination but also in other combinations or can be used alone without leaving the scope of the present invention.

The invention is described and explained in more detail below on the basis of exemplary embodiments with reference to the drawing. Show it:

Figure 1: a side view of a femoral stem prosthesis; and

Figure 2: a transverse section through the shaft portion of the prosthesis shown in Figure 1 after insertion or ingrowth in a femur on an enlarged scale.

In Figure 1, a total of 10 femoral stem prosthesis is designated. It consists of a prosthesis part 12 cast from metal, which in the exemplary embodiment shown has an essentially rectangular transverse cross section, is curved like a sickle and tapers towards the free end. The prosthesis part 12 carries, via a molded pin 14, a joint ball 16 made of ceramic with a polished surface.

As shown in the enlarged detail, the prosthesis part 12 consists of a titanium prosthesis base body 18, to which an outer layer 20 made of an organic plastic material is applied.

The outer layer 20 is in the vicinity of its surface by a TCPL treatment (tissue culture plasma treatment; Low pressure plasma treatment) has been treated. This treatment gives the surface chemical modifications and reactive centers as well as biocompatible behavior.

This part of the outer layer 20 is shown in the drawing as a separate intermediate layer 22. A surface layer 24, which likewise consists of a plastic material, is applied to the intermediate layer 22. The surface layer 24, in turn, has received an edge layer 26 by a further TCPL treatment, which has similar physical properties as the intermediate layer 22.

Possible materials for the outer layer 20 are: epoxy resins, epoxy resins which are modified with 0.1 to 1.0 mol / mol acetethylamine (AEM), preferably 0.3 to 0.8 mol / mol AEM, again preferably contain about 0.5 mol / mol AEM; Epoxy resins modified with chromosulfuric acid (CrSS); Glutardialdehyde (GDA); Polyvinyl acetates (PVAC), polyacrylonitriles (PAN); Polyhydroxybutyrates (PHB); Polycarbonate (PA); Polyoxymethylene (POM); Polyacrylates (PA); Polyvinylchloride (PVC); Polyethylenes (PE); Acetyl celluloses; Nitrocelluloses; Polyethylene glycol 400 diacryl (PEG4-D); Methyl methacrylate (PMMA); Polyvinyl pyrolidone (PVP).

Suitable materials for the surface layer 24 are initially the materials already listed in connection with the outer layer 20 (applied as a thinner layer), furthermore the following particularly tissue-friendly, in particular bone-friendly, materials: hydroxyapatite; Proteins, especially albumin, trypsin, pepsin, collagen. The free surface of the outer layer 20 (and possibly the surface layer 24) is preferably modified by a TCPL action. This consists in subjecting the surface to a plasma treatment, the plasma being enriched with, for example, 20-50% oxygen.

FIG. 2 shows in the right half the prosthesis part 12 immediately after insertion into a cavity 32 created in the cancellous bone 28 of a femur 30. The left half of FIG. 2 shows the conditions after the prosthesis part 12 has grown in. The one between the wall of the cavity Intermediate spaces 32 and the outer surface of the prosthesis part 12 are filled with regrown cancellous tissue 34 (shown more densely dotted). This adheres firmly to the surface of the prosthesis part, so that the prosthesis part is firmly connected to the femur 30.

An in vitro test of the various above Organic polymers for their biocompatibility with bone cells were carried out as follows:

Normal cell culture petri dishes (surface-treated molded parts made of polystyrene (PS)) were coated on the inside with the polymer or the polymers to be tested (outer layer 20 and surface layer 24). The surface of the layer was subjected to the secondary treatment described above (e.g. plasma, acid).

The dishes prepared in this way were additionally UV-sterilized and inoculated with SAOS-2 osteosarcoma cells. The cells were in normal full medium, enriched with serum (20% FCS in Doubl. mod. ass. Medium (DMEM)) with antibiotics and vitamin additives for 7 days at 37 ° C and 5% C0 ₂ incubated. The vitality of the cells after incubation was measured in the MTT assay (formazan formation). In the MTT assay, the number of cells is measured via the metabolic enzyme dehydrogenase produced by the mitochondria. This catalyzes with a test substance contained in the assay in such a way that a color change is obtained. Its intensity is a measure of the vitality of the cells and indirectly the number of cells.

The highest cell growth is obtained on a pure polystyrene layer treated with TCPL. Based on this material, the table growth shown with other materials is shown in the table below:

Table:

Relative cell growth of SAOS-2 osteosarcoma cells on different plastic layers

External surface comments relative

Layer layer cell growth (in%) S TPCL 100

PS untreated 35

EPO Hydroxyapatite 90

EPO Albumin 35

EPO trypsin 23

EPO pepsin 10

EPO Albumin 10

EPO Collagen 18

EPO CrSS 32 External surface comments relative

Layer layer cell growth (in%)

EPO 0.5 x AEM 90

EPO 2 x AEM 5

EPO 75

GDA albumin 25

GDA Trypsin 90

GDA pepsin 95

PVAC 45

PAN 45

PHB 38

Polyacrylate 18

POM 30

PA 6 37

PVC 8

PE 45

PEG4-D 8

PMMA 30 PVP 10

The table above clearly shows that the plasma treatment of surfaces on which cells are supposed to settle significantly promotes cell growth (comparison of untreated and treated polystyrene).

This plasma chemical surface modification can partly be replaced by using moderately polar plastics. Even such cells can still achieve cell growth of 80% of that of plasma-treated polystyrene, which means that these plastics are around 30% higher than untreated polystyrene.

Claims

claims

1. Coating material for prostheses, characterized in that it is formed from an organic polymer material which forms a firm bond with the material from which the prosthesis is made, and that the organic polymer material is chemically modified such that an increase in bone cells thereon compared to the prosthetic material is increased.

2. Coating material according to claim 1, characterized in that it is selected from the following materials, namely epoxy resins, epoxy resins modified with acetethylamine or chromosulfuric acid; Glutardialdehyde; Polyvinyl acetates; Polyacrylonitriles, polyhydroxybutyrates; Polyacrylates, polyoxymethylenes, polystyrenes, polymethylenes, polyethylenes, paraffins, polymethylmetacrylates, acetylcelluloses, nitrocelluloses, polyvinylpyrrolidones.

3. Coating material according to claim 1 or 2, characterized in that the chemical modification is carried out by introducing functional groups into the organic polymer materials.

4. Coating material according to one of claims 1 to 3, characterized in that it is modified by wet chemistry.

5. Coating material according to one of claims 1 to 3, characterized in that it is modified by plasma chemistry.

6. Coating material according to one of claims 1 to 5, characterized in that biocompatible materials are included in the polymer material.

7. Coating material according to claim 6, characterized in that osteocompatible materials are included in the polymer material.

8. Coating material according to one of claims 2 to 7, characterized in that it has an epoxy resin which is modified with 0.1 to 1.0 mol / mol of acetethylamine groups.

9. Coating material according to claim 8, characterized in that it has an epoxy resin which is modified with 0.3 to 0.8 mol / mol of acetethylamine groups.

10. Coating material according to claim 8, characterized in that it is an epoxy resin which is modified with 0.5 mol / mol acetethylamine groups.

11. prosthesis part, with a base body (18) and an outer layer (20) carried by this, characterized in that the outer layer (20) consists of a coating material according to one of claims 1 to 10.

12. Prosthesis part according to claim 11, characterized in that the free surface of the outer layer (20) is treated by a plasma discharge.

13. Prosthesis part according to claim 12, characterized in that the treatment plasma contains oxygen.

14. Prosthesis part according to one of claims 11 to 13, characterized in that the surface of the outer layer (20) is treated with microwaves.

15. Prosthesis part according to one of claims 11 to 14, characterized in that the outer layer (20) carries a surface layer (24) made of a material which is selected from the group of hydroxyapatite, proteins, in particular albumin, trypsin, pepsin, collagen.

16. Prosthesis part according to claim 15, characterized in that the surface layer (24) is treated by plasma discharge.

17. A prosthesis part according to one of claims 11 to 16, characterized in that the prosthesis base body (18) consists of metal, preferably titanium, a ceramic material or a fiber / plastic composite material which is coated with the coating material.

18. Prosthesis part according to one of claims 11 to 16, characterized in that the prosthesis base is also constructed from the coating material.

19. The prosthesis part according to claim 18, characterized in that the prosthesis base consists of the not yet chemically modified organic polymer material.