DE102013104388A1 - Application-specific coating and structuring of implantable prostheses using laser techniques - Google Patents

Abstract

The invention relates to an implantable prosthesis (1) with at least one socket (3), a ball part (2) and a shaft (4), the socket (3) having an essentially spherical receptacle for the ball part (2) , wherein at least part of the receptacle of the pan (3) and / or the ball head (2) has a layer deposited using the PLD process.

Description

The invention relates to implantable prostheses, such as hip or knee prostheses, and to a method for producing such prostheses by structuring the surface of these prostheses.

Numerous prostheses which have a structured surface are known from the prior art. For example, there are acetabular cups which have a shell of pure titanium or a titanium alloy, such as TiAl6v4, which are positioned as screw or pressfit cups in the hipbone. The surface of such acetabular cups is often roughened in the range of 4 to 6 micrometers according to the prior art.

In order to enable a better ingrowth of such prostheses in the bone of a patient, according to another known from the prior art, it is proposed to provide the prostheses with a calcium phosphate coating of about 20 microns with a surface roughness of 40 to 80 microns for TiAlGv4.

It is also proposed in the art to introduce in this acetabulum a shell of highly cross-linked polyethylene or a ceramic inlay. The inner surface is a spherical surface with minimal surface roughness. In such a shell usually a standard ball head made of alumina ceramic is introduced, which is placed on the shaft by means of a cone. The ceramic heads are also available as a variant with titanium sleeve.

A shell of highly cross-linked polyethylene is produced according to the prior art under the influence of gamma radiation. The gamma radiation penetrates the entire structure and hardens the entire structure. As a result, however, the shell also loses elasticity, which is undesirable.

It is also proposed in the prior art to apply to the shaft of a prosthesis, which is often made of titanium, for better growth of the bone (osteointegration) a hydroxyl apatite coating having a roughness of 20 to 50 micrometers. It is proposed that the coating extends to about ¾ of the shaft from the upper end (near the ball head) seen from the shaft.

The roughness on the then non-hydroxyl apatite coated lower end is 4 to 6 microns, with the stem provided with a standard cone. Such a shaft is intended for a cementless insertion.

From the prior art, the mating of a cobalt-chromium-molybdenum head with a polyethylene shell and the use of a shaft made of this material are provided.

Serious deficiencies for all these prostheses known from the prior art are the fracture of individual components, the formation of inflammations due to the abrasion of the polyethylene shell and the increase in chromium and cobalt ions in the body fluid. Increased metal ions can also trigger allergy to the components in question.

The use of a cobalt-chromium-molybdenum (Co-Cr-Mo) shaft generally does not result in significantly increased metal ion concentration.

The abrasion of the polyethylene shell arises both in a ceramic ball head and in a metal ball head.

By the movement of the metal ball head in cooperation with the synovial fluid, individual atoms are released from the metal compound, which can enter the body fluid (synovial fluid, blood, lymph) as ions.

Also ceramic-ceramic friction pairings and highly cross-linked polyethylene ZrO ceramic friction pairings (shell, ball head) have become known from the prior art, which produce no wear or very little abrasion, because the ZrO ceramic is very smooth and hard and has a low friction.

The object of the invention is thus to reduce the problems arising from the prior art, to turn it off or to offer an alternative to existing proposals.

According to the invention this object is achieved with a prosthesis according to claim 1 and a method for producing such prostheses according to claim 11.

Accordingly, the prosthesis according to the invention has at least one pan, a ball part and a shaft, wherein the pan has a substantially spherical trained receptacle for the ball part and wherein at least a part of the surface of the ball part and / or the inner surface of the receptacle via a or several deposited by the PLD process layers, so-called functional layers has. Preferably, other surfaces of the prosthesis are wholly or partially provided with such a layer or with such layers.

According to one embodiment, at least one of the layers consists of aluminum oxide, zirconium (II) oxide, titanium, silver, hydroxyl apatite or TiAl6v4 or contains one of these substances or alloys. Preferably, both the ball part, as well as the receptacle of the pan is formed of titanium and has coatings.

One advantage of the invention is that in a particularly favorable manner, even implantable prostheses known from the prior art can be transformed into the article according to the invention by deposition and optionally structuring.

According to a particularly preferred embodiment, the ball part and / or the receptacle of the pan has tetrahedral bound amorphous carbon layers (ta-C). According to a further embodiment, this tetrahedral bonded amorphous carbon layer is silver doped. The ta-C is preferably arranged in several layers on a ball part formed from titanium and / or a receptacle of the pan formed from titanium. The coating makes it possible to produce the wall of the pan particularly thin. Preferably, the radius of the ball part is only smaller by a maximum of 8.5 mm than the outer radius of the pan, more preferably even only by a maximum of 7.5 mm smaller and even more preferably only by a maximum of 5 mm smaller.

According to one embodiment, the pan is constructed in two parts with an inner and an outer shell, wherein the inner shell is formed from a thermoplastic material, which is then particularly preferably coated with functional layers. Preferably, to improve the property of the thermoplastic for the prosthesis, the plastic is crosslinked by means of electron beams. In this case, the crosslinking is controlled so that only the upper layer is correspondingly hard and the existing elasticity of the plastic is substantially retained.

The abrasion is essentially a consequence of the forces and the friction occurring. Of course, the load peaks are attenuated by the cartilaginous layer in the socket and the ball head (each 3 to 4 mm) and by synovial fluid. For this reason, an advantageous embodiment of the prosthesis has a bivalve structure of the cup with an inner shell, which is preferably anchored during the implantation process in an outer shell of the pan, for example by a snap connection.

According to this advantageous embodiment, a damping device is particularly preferably provided in the joint, which absorbs the recording of load peaks that would otherwise be absorbed by a cartilage layer. Such a damping device can be formed either by the inner shell, which is at least partially flexible, it can also be provided according to various embodiments, a gel damping or it can be provided compressible means in the outer shell. Due to the two-shell design at the same time an uncomplicated installation and accurate alignment of the recording of the pan allows.

According to various embodiments, the surface of the implantable prosthesis is coarse and / or nanostructured, at least in some areas. Preferably, the prosthesis has a longitudinal corrugation over 50-100% of the total length of the shaft, wherein a strip spacing of 0.5 to 1.5 mm, a strip width of 0.5 to 15 mm and a survey between 0.3 and 0, 5 microns are provided.

Preferably, the original surface is - particularly preferably in addition to the longitudinal corrugations - structured so that a coarse structure between 10 to 500 microns in the surface is present. Such a structure can be produced, above all, with a femtosecond laser by way of laser ablation.

In addition, parts of the prosthesis, in particular the outer side of the socket and the shaft, are enlarged by a factor of 2 to 4 by rearrangement (ripple formation). Also the ripple formation can be procedurally well implemented with a femtosecond laser.

According to a particularly preferred embodiment, at least parts of the prosthesis are provided with a plurality of layers, which were preferably applied by means of the PLD method and have corresponding properties. As one of the layers, silver is preferably provided according to an embodiment which is concealed by one or more layers or partially concealed and exerts antibiotic properties. To apply a layer, the laser pulse method PLD is used, whereby a layer with a thickness of about 10 nanometers is produced and is relaxed by means of a second laser.

Subsequently, the next layer is generated. By combining multiple layers with a ripple structure, an embodiment is provided in which "buried" layers are made partially effective or long term.

In the production of these layer structures, two to three substances can be deposited simultaneously be stored or stored in alternating order one above the other. This makes it possible to introduce silver as a layer or in a layer as an antibiotic. The layer may also be buried by one or more other layers applied. Thus, according to one embodiment, the layers can be stored one on top of the other by a distance of 10 to 15 times and are firmly adhered to the base material due to the kinetic energy introduced. Preferably, the majority of these layers are formed of ta-C and in between, according to different embodiments, one or more layers of, for example, silver or another metal or alloy may be arranged. If the base material of the prosthesis or of the prosthesis part permits this, the first layer is formed by the base material, by means of laser pulses in the range of 7 to 15 μm, preferably 10 μm, the base material being melted and smoothed. Then the low-wear layers are applied.

In a particular embodiment wherein at least 3 layers are provided for at least a partial surface of the prosthesis, the second layer is formed from the smoothed surface of the first layer by additionally microcuring it in a range of 3 to 5 μm by means of laser pulses. On the hardened layer, a firmly adhering, low-wear third layer is applied, which has a layer thickness of 1 to 2 μm, preferably 1.5 μm.

Preferably, one or more ta-C layers (diamond-like carbon structure) having a layer thickness of 1 to 1.5 micrometers are applied to the ball part.

This layer reaches Vickers hardness of about 4000 to 5000 HV and is thus twice as hard as a Zirkonoxydschicht. It is firmly adherent and low friction and very smooth and leads to a substantial extension of the durability of the system.

In the case of a ball part made of metal, a barrier action results, so that no metal ions are released from the ball part via abrasion or joint lubrication. In order to prevent an ion release in a shaft made of Cr-Co-Mo it is coated with a layer of pure titanium or TiAl6v4 and provided with the corresponding structures for the cement-free installation.

In order to protect inflammation-prone patients against inflammation in the long term, it is proposed to provide all surfaces not involved in the prosthetic function with a silver-doped ta-C layer. These are the inside of the acetabulum, the top of the acetabulum, and the transition from the cone to the stem. At the same time, a silver doping of the ta-C spherical part coating can be provided for these patients. This allows the use of metal prostheses for allergy patients.

Preferably, the outermost, structured layer of the prosthesis is constructed at least in a partial region of diamond, titanium, or similar biocompatible hard materials. This layer can also be produced by introducing titanium into a boundary region of the underlying, preferably micro-hardened, layer.

This surface layer of the ball portion and / or the inner surface of the receptacle of the pan is preferably structured by means of laser pulses, preferably with a period of between 400 and 800 nanometers and more preferably between 500 and 700 nanometers and even more preferably in about 600 nanometers and a depth of preferably 200 to 500 nm. It has surprisingly been found that this structuring significantly reduces the friction. For this purpose, a diode laser with a wavelength between 400 and 800 nanometers is preferably used.

On the surface of the prosthesis, which is intended for incorporation into the body tissue, structuring in the range of 53 to 75 nanometers is particularly preferably used. This is preferably produced by means of a UV laser by wavelengths between 154 and 248 nanometers and has the characteristic structure for this. It has been found that with the said wavelengths a good random distribution of the elevations and depressions results.

This causes the endothelial cells to settle particularly well on the surface

As a structure, according to various embodiments, a ripple structure, a riffle structure, a double ripple structure or an interrupted double ripple structure are provided. Preferably, the double ripple structure is V-shaped. But even a broken double ripple structure or a simple ripple structure can be designed in accordance with V-shaped embodiments according to further embodiments.

Between the ball part and the inner surface of the receptacle of the pan and / or between the inner and the outer shell, according to one embodiment, a suitable damping layer is applied. The same applies according to a further embodiment for the inner and the outer shell. The damping layer can act shock-absorbing. Preferably, the damping layer is applied with a layer thickness of preferably 0.2 to 0.5 mm.

In the embodiments in which a third layer has a ripple, double ripple or discontinuous double rippled structure, a self-stabilizing lubricating layer forms during further use. Even with substantially punctiform damage to the structured surface, a self-lubricating layer forms again through the materials and structures provided in the course of the further movement.

Another, self-inventive aspect of the invention relates to a device for aligning and transferring the socket of an implantable prosthesis, with a handle, a surface for seating on the end face of the wall of the pan, at least one impact surface and means for centering the impact surface with respect to the wall of the pan.

Further details of the invention will become apparent from the drawings with reference to the description.

In this case, the feature combinations disclosed in the described embodiments should not limit the invention, but also the features of the different embodiments are combined.

In the drawings show:

1 a representation of an inventive hip joint in a single-shell design,

2 a representation of an inventive hip joint in two-shell design,

3 a schematic representation of the layer structure of the prosthesis in cross section

4 a device for transferring the cup of an implantable prosthesis into a bone structure from three perspectives

LIST OF REFERENCE NUMBERS

1

Implantable prosthesis

2

spherical part

3

Pan with receptacle

4

shaft

5

Inner shell made of PET

6

Layer of ta-C

7

Layer from AG

8th

Layer of ta-C

9

Area of a ripple structure

10

Device for transferring a socket of a prosthesis

11

Handle

12

seating surface

13

centering

14

Centered clubface

1 shows an implantable prosthesis 1 in a first embodiment with a simple shell design. The prosthesis has a shaft 4 on which a ball part 2 is arranged and a pan 3 which has a receptacle with a spherical inner surface for receiving the ball part 2 , As shown here, the shaft has a structuring which securely holds the prosthesis in the bone of a patient. The ball part 2 is exactly like the inner surface of the pan 3 formed of titanium and has a plurality of successively spent on the surface by means of PLD process ta-C layers, and an AG layer.

2 shows a second embodiment of the inventive prosthesis 1 , Here is a clam shell embodiment of the pan 3 is provided, because in it is an attachable by snap connection inner shell 5 made of PET. It is on the inner surface of the PET shell 5 a titanium layer and other ta-C layers applied. The ball part 2 also has a plurality of stacked ta-C layers.

3 shows the outer 3 layers of the ball part of the inventive prosthesis 1 , where the outermost layer 6 consists of ta-C and an AG layer 7 concealed, which in turn sits on a ta-C layer. In the area 9 There is a ripple structure that partially exposes the silver layer through the amorphous structure.

4a shows the insertion and adjustment tool from a bottom view. On the left side there is a handle 11 on which distally a seating surface 12 is arranged, with which the tool on the front side of the wall of the pan 3 can be placed. With the help of the centering means 13 can be the centered clubface with regard to the spherical recording of the pan 3 or center its wall. Will be on the centered area 14 in 4c beaten, the pan is driven evenly. Shall the pan 3 to be driven somewhat obliquely further, one uses one of the side or above and below the centered clubface 14 arranged further playing surfaces. 4b shows that the handle 11 to better handle bent at the proximal end.

Claims (11)

Implantable prosthesis ( 10 ), with at least one pan ( 3 ), a ball part ( 2 ) and a shaft ( 4 ), characterized in that the pan ( 3 ) formed over a substantially spherical Holder for the ball part ( 2 ), wherein a part of the receptacle and / or the ball part ( 2 ) has a functional layer deposited by the PLD method. Implantable prosthesis ( 1 ) according to claim 1, characterized in that the ball part ( 2 ) has tetrahedral bonded amorphous carbon layers. Implantable prosthesis ( 1 ) according to one of claims 1 or 2, characterized in that at least part of the surface is provided with silver-doped tetrahedral bound amorphous carbon layers. Implantable prosthesis ( 1 ) according to one of claims 1 to 3, characterized in that the at least part of the surface with alumina, zirconium (II) oxide, titanium, silver, TiAl6v4 Implantable prosthesis ( 1 ) according to one of the preceding claims, which has a bivalve pan ( 3 . 5 ) with an inner ( 5 ) and an outer shell ( 3 ), wherein the inner shell ( 5 ) is at least partially formed of a thermoplastic which has been modified by means of electron beams to have a hard outer highly crosslinked layer and an elastic inner structure. Implantable prosthesis ( 1 ) according to claim 5, characterized in that the two-shell design of the pan ( 3 . 5 ) fulfills a damping function. Implantable prosthesis ( 1 ) according to one of the preceding claims, characterized in that at least on a partial region of the prosthesis ( 1 ) Is laser structured. Implantable prosthesis ( 1 ) according to claim 7, characterized in that the shaft over at least 1/3 of its length has a longitudinal corrugation, which has a strip spacing of 0.5 to 1.5 mm, a strip width of 0.5 to 15 mm and a survey between 0 , 3 and 0.5 micrometers. Implantable prosthesis ( 1 ) according to one of claims 7 or 8, characterized in that at least a part of the surface of the prosthesis has a producible by laser ablation by femtosecond laser in the range between 10 to 500 micrometers structuring Implantable prosthesis ( 1 ) according to one of the preceding claims, which has a ripple structure on at least a part of the surface, the surface in this partial area of the prosthesis ( 1 ) has a surface enlarged by a factor of 2 to 4. Method for producing an implantable prosthesis ( 1 ) according to claim 1, comprising the steps of - using a conventional prosthesis consisting of at least one pan ( 3 ), a ball part ( 2 ) and a shaft ( 4 ) and a substantially spherical trained receptacle of the pan ( 3 ) for the ball part ( 2 ), - applying at least one metal layer of pure titanium and a diamond layer on the surface of the ball part ( 2 ) using the PLD method - Simultaneous or downstream structuring of the metal layer by means of laser.

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