FI115029B - Joint prosthesis - Google Patents

Description

115029

artificial joints

The invention relates to an artificial joint as defined in the preamble of claim 1.

Diamond and diamond-like membranes have 5 characteristics that resemble those of traditional natural diamonds. Such features include e.g. hardness, low coefficient of friction and good wear resistance. The diamond coating is stable in all bases and acids. Due to their above properties, diamond-like coatings and films are well suited to demanding corrosion and wear conditions, e.g., artificial joints.

The current form of hip replacement surgery was described in 1961. Since then, surgery has become more common-15 nowadays and around 800,000 hip replacements are performed each year worldwide. Around 2.3 million artificial joints are performed worldwide each year, of which 1.6 million are artificial or artificial knees. For example, the first 20 years of hip replacement joint adhesion are generally good and within 10 years about 10-13% of re-operations have been performed and probably more than twice as many detachments. After ten years, the frequency of artificial joint release increases sharply, and after one year most of the artificial joints have been detached.

.. 25 In addition to wear and tear on the artificial joint, the problem is the different elasticity of the artificial joint • ·· and bone.

Good adhesion of the artificial joint is referred to as osseointegration. It requires that:. the implant interface forms macromolecules of an adhesive cellular medium that attaches the implant to the bone. So far, these media are not well known. One major difficulty is that even the best metallic artificial materials dissolve at least: • slightly in body fluids (e.g., CoCrMo dissolves at about 50/35 nm / year), which prevents the formation of a stable adhesive layer at the bone-artificial joint interface. Ke-frames (e.g., Αΐ5θ3 and Y-ZrO2) do not dissolve in the body 2 115029 of the body, but they are brittle and are generally not suitable for bone-bonding parts of the artificial joints due to their poor elasticity.

Efforts have been made to reduce release by developing titanium-based, partially rosin-based, artificial joint components that adhere to bone without methylmethacrylate medium. Titanium has excellent elasticity and tissue compatibility properties in the kappa form, but due to its softness, the movement between bone and 10 implants over time removes huge amounts of generally smaller microns of titanium, which macroscopically stains the lymphoid tissue and initiates the process. This eh-15 camshaft has been used e.g. coating the jagged gripping surfaces of the artificial hip cup portion and the stem portion with hydroxyapatite, which, however, tends to be resorbed over a long period of time, resulting in adhesion failure.

It is an object of the present invention to overcome the above drawbacks.

In particular, it is an object of the invention to provide an artificial joint whose diamond coating enhances bone adhesion. Because the diamond is biocompatible: · 25 materials, it adheres well to the bone after surgery and does not cause rejection. A stable adhesive layer is formed between the bone and the tympanic membrane, which is not destroyed by tissue reactions.

It is a further object of the invention to provide; 30 reveals an artificial joint whose diamond coating protects against artificial corrosion and wear.

It is a further object of the invention to provide: · an artificial joint whose diamond coating is flexible and withstands the stresses occurring in use on parts of the artificial joint.

The artificial joint according to the invention is characterized by the features * * * as set forth in claim 1.

3, 115029

According to the invention, the diamond coating is amorphous and contains predominantly carbon, of which at least 30% of the bonds are diamond-like sp3 bonds.

The artificial joint coating is an amorphous diamond-5 or diamond-like membrane. The coating consists predominantly of carbon and a significant proportion, over 30%, of the carbon bond contains diamond-like sp3 bonds. The coating covers at least a portion of the artificial joint that is in contact with body tissues and / or fluids. 10 The amorphous coating film is dense because it is non-crystalline and has no grain boundaries or pores. The wear resistance of the coating is improved by increasing the proportion of carbon sp3 bonds. Some coated artificial joints preferably have at least 70% carbon-15 bonds having diamond-like sp3 bonds.

In one embodiment of the artificial joint, the diamond coating has a thickness of at least 100 nm, preferably 500 to 1000 nm. In some coating applications, the coating may also be significantly thicker, up to tens of micrometres in length.

In one embodiment of the artificial joint, an intermediate layer is formed between the surface to be coated and the diamond coating to improve adherence of the diamond coating. The coating consists of at least one layer. The coating may be applied without an interlayer, i.e. an interlayer, or over a suitable interlayer and / or mixing layer. In most cases, the coating is applied over the interlayer. The layers may be made of a plurality of layers of various materials and / or mixtures thereof. Suitable interlayer metals for adhesion and corrosion include Cr, Ta and Pt. The interlayer materials used in the coating withstand the corrosive environment of the body.

The coated artificial joint consists of a bone attachment part, i.e. a shaft part, and a more or less attachment end of the V * attachment part, a 'U spherical ball part and a cup part. The artificial joint of the invention may be, for example, a hip, knee, fingers, wrist, elbow, shoulder or jaw. Synthetic joint materials known in the art can be used in artificial joints. The artificial joint members 5 may be made of metal, ceramic or plastic and combinations thereof. Examples of metals used in artificial joints are Ti, Al, V, Cr, Co and / or Mo. The artificial joint attachment surface is a flat or most porous roughened 10 or jagged metal surface made of metal powder or spheres.

A diamond or diamond-like coating can be applied to the artificial joint surface by a variety of methods. In the case of the examples described below, the amorphous diamond coating (also referred to in the literature as diamond-like coating, diamond-like carbon DLC and ta-C, tetrahedral amorphous carbon) was grown by the pulsed plasma arc discharge method of PVD. The advantage of the method is e.g. good coating adherence, low coating temperature (near room temperature), and high quality coating with almost natural diamond properties. The method: * can coat coatings up to several micrometers thick on most solids. Other similar methods of coating amorphous diamond films include ion beam deposition and laser ablation. In addition, there are many different methods based on chemical gas phase (CVD) cultivation, which, however, most often require a significantly higher coating temperature and, for example, the coating of ferrous alloys is generally unsuccessful.

The diamond coated surface of the artificial joint 35 does not wear much due to mechanical movement or corrosion, whereby the amount of loose particles is significantly reduced and bone adhesion is improved and the adhesion layer between the artificial joint and bone is stable. The tissue compatibility of any detachable particles is also better than with existing materials. This results in a reduction in the need for re-surgery.

The invention will now be described in detail by way of example with reference to the accompanying drawing, in which Fig. 1 shows a first embodiment of an artificial joint of the invention, i.e. a rabbit hip implant used in animal experiments 3 is a sectional view showing an artificial joint according to the invention! a third embodiment, i.e., a metal portion of the knee-joint joint perforation, and Figure 4 schematically shows an IV-20 IV of Figure 3.

Example. A.,.

In this example, the coated te column column part 1 was tested in rabbits. The shaft portion 1 of the artificial hip is shown in Figure 1. The shaft portion 1 is made of Ti-25 alloy (Ti6Al4V) and the shaft is either smooth or porous. In the test, 10 smooth and 10! , porous shaft portions with an amorphous diamond coating · '' throughout about 300-1000 nm using a pulsed plasma arc discharge I * '30 method. At the same time, the spherical joint spherical part 6 was also coated. Prior to coating, commercially available implants were washed with acetone and ethanol and purified just prior to coating by Ar-'ion-sputtering. Implant adhesion was tested by operating diamond-coated half-prostheses on New Zealand White rabbits. After a 52-week follow-up beach, rabbits were sacrificed and prostheses with surrounding tissue were taken for test. On the basis of the samples, the diamond-coated implants were well adhered to and showed no signs of foreign material at the bone-implant interface.

5

Example 2

Figure 2 shows a human modular hip joint joint consisting of an attachment part 1, an arm conical attachment head 10, a 5 attachment ball part 6 and a UHMWPE plastic cup part 7. The arm part is made of a titanium alloy (Ti6Al4V) with an upper arm the most important point for adhesion, the rough part is made by coating it with granular Ti-15 Danish metal. It is also possible to completely coat the shaft with granular titanium metal. The stem is commercially manufactured (Biomet). The stem was coated as in Example 1500 with a 1000 to 1000 nm amorphous diamond coating. The coating has been tested for corrosion resistance and corrosion and worked well. The conical end of the arm portion to which the ball attaches was also coated with the above coating, whereby the attachment point was protected from corrosion. Such a shaft is also suitable for use in clinical trials with a population of about 25 squares, which allows the implant to be tested for adhesion and movement under real conditions.

• »!; ·. Example 3.

30 Figure 3 shows a metal part of the femoral side of the knee joint. The bone of this metal part ;;; the engaging surface 1 has a spherical shape

CoCr powder coating. Here, too, the adhesion can be improved with a diamond 35 coating. The coating may be carried out either without the interlayer or with a suitable interlayer or mixing layer 4. Suitable metals for the intermediate layer 4 in the case of CoCr-7 115029 based artificial joints are, for example, Cr and Ta. Based on the corrosion tests, the coating sticks well and also protects the backing material against corrosion.

5

Example 4.

Hip and knee artificial joints and balls or specimen plates made of CoCrMo alloy, stainless steel 10 AISI316L or AISI420, Ti6Al4V alloy or alumina were used in the experiment.

Prior to coating, the samples were mechanically polished and polished with a diamond paste to obtain a surface roughness of Ra = 10 nm (center line Avera-15 ge), washed with acetone and ethanol, dried, placed in a coating chamber (100 μΡη) and purified just prior to coating by Ar ionization. A 10-100 nm dense intermetallic layer was formed on the implant surface using a pulsed plasma arc purge extrusion method. In some cases, diamond plating with high ion energy (140 eV) resulted in extremely good adhesion without the interlayer. The carbon sp3 bonds of the coating had a proportion of less than 50% with high ion energy. The optimum coating quality (80% I.25 sp3) was achieved when the coating was continued with lower ion plasma energies. However, this high quality film has a high internal tension, for example a 2 μτη: η diamond coating on a silicon substrate destroys silicon at a depth of 25 μm and peel off the surface. Thus, good bonding generally requires a proper interlayer and / or the initiation of a high diamond coating; energy.

· 'Pulsed plasma arc discharge process', · coated films are extremely clean. 35, the diamond coating has a hydrogen content of less than 0.1 at.% (FRES method) and a total purity of more than 99 at.%.

8 115029

The corrosion resistance of coated artificial joints was already improved by up to 3,600 times with a thin coating. The most significant improvement was achieved by coating the Ti6Al4V alloy.

In the experiment, diamond coatings were also prepared on a Si substrate by a pulsed plasma macar discharge discharge method using different pulses: (a) high quality diamond coatings (sp3 content <80%) were obtained using a short pulse (30 μβ); b) Using 10 long pulses (1 ms), medium quality diamond coatings were obtained (sp3 ratio> 70%); c); and d) Medium quality diamond coatings were obtained using a long pulse and N-gas ignition (sp3 content <54%). The wear resistance of the coatings decreased with the decrease of sp3 15.

The effect of the surface roughness of the mating material on the wear and friction of UHMWPE was investigated with diamond-coated and uncoated spheres and test balls made of alumina-20 and AISI420. Both the friction coefficient and the abrasion coefficient decreased significantly as the roughness decreased. For example, when coating the AISI420 spherical beads with about 500 nm diamond coating film and polishing some of the beads with 1/4 μπι diamond paste, the surface roughness decreased: ·· 25 from 46 nm to 7 nm and the wear of the UHMWPE cup member decreased by about 30%. On thicker and rough surfaces, the effect of surface roughness was even greater. Coatings also reduced significantly, up to 50-600 times. . UHMWPE wear.

30 The examples and inventors above. on the basis of studies carried out to date ;; the shape of the artificial joint can be pinched with a highly adherent diamond blade * ,! layer pulsed plasma arc method. The mantle-coated surface is well-resistant and is an excellent material for bone tissue. The coating] does not alter the elastic properties of the artificial joint and withstands the mechanical stresses encountered in the use of the typically used metal artificial parts of the joint. Any particles that may come off the coating are also biocompatible in bone. Therefore, the coating of diamond-bonded, non-cemented artificial joints with non-cemented, non-cemented artificial methacrylate, seems to be a valid solution based on clinical trials. In addition, the tantalum coating, based on our laboratory tests 10, provides significant advantages in terms of low friction coefficient and good abrasion resistance also on the sliding surfaces of artificial joints. The coating significantly reduces, for example, the wear of high molecular weight polyethylene 15 (UHMWPE), which is typically used as a counterpart for the metal part of artificial joints.

The coating used according to the invention improves the adhesion of the artificial joints in use. Compared to the lifetime of currently used artificial joints, the lifetime of diamond-coated artificial joints with respect to adhesion is significantly longer. The required surface properties, biocompatibility, corrosion and abrasion resistance of artificial joints are better than those of the materials currently in use.

According to the inventors' researches, it is also possible to use plastics for use in machine joint joints with a diamond coating, but they require the use of laminate structures or composites based on whiskers or fibers.

It will be apparent to one skilled in the art that various embodiments of the invention are not limited solely to the above examples, but may alternate; the claims set forth below; framework I>

Claims (9)

115029 10 7 An artificial joint comprising a bone attachment portion (1), a sliding surface portion (2) having a joint sliding surface, an intermediate layer (4) formed on the surface of the attachment portion, the sliding surface portion, and / or the other portion to improve adhesion of the diamond coating; ti-mantle coating (3) formed on the surface of the intermediate layer (4) by a pulsed arc discharge method and / or ion beam, characterized in that the intermediate layer (4) contains chromium (Cr), tantalum (Ta) and / or platinum (Pt). metal, and that the diamond coating (3) is amorphous and / or nanocrystalline and contains predominantly carbon, of which at least 30% of the bonds are diamond-like sp3 bonds. Artificial joint according to Claim 1, characterized in that at least 70% of the carbon bonds in the diamond coating (3) are diamond-like sp 3 bonds. Te-2 0 machine joint according to claim 1 or 2, characterized in that the diamond coating (3) has a thickness of at least 100 nm. Artificial joint, characterized in that the diamond coating '(3) is formed by a separated pulsed plasma arc discharge method, preferably using a short pulse, such as a 30 μβ-.η pulse. A process according to any one of claims 1-4; an artificial joint, characterized in that the sliding surface part (2) comprises a ball part (6); that the bone attachment part (1) has an attachment head (5) for attaching the ball part (6); and that the diamond coating (3) is formed on the surface of the mounting head (5). An artificial joint according to claim 5, characterized in that the artificial joint comprises a cup part · ···, 35 (7) adapted to receive the ball part (6); and that the diamond coating (3) is formed on the sliding surface of the sphere. 115029 Artificial joint according to one of Claims 1 to 6, characterized in that the fastening part (1) is made of metal, collector, plastic and / or composite thereof. An artificial joint according to claim 7, characterized in that the fastening part (1) comprises titanium (Ti), aluminum (Al), vanadium (V), chromium (Cr), cobalt (Co) and / or molybdenum (Mo). An artificial joint according to any one of claims 1 to 8, characterized in that the artificial joint is a hip, knee or finger joint. »'» · • · • · 1 # t> i * 115029