DE2318396A1 - ARTIFICIAL JOINT REPLACEMENT MADE OF Sintered OXIDE CERAMIC - Google Patents

Description

Artificial joint replacement made of sintered oxide ceramic The invention relates to an artificial joint replacement consisting of at least two interacting pieces like the shaft piece and joint socket, in the case of frictionally stressed parts of sintered wear-resistant moldings of high mechanical strength made from high-melting consist of physiologically harmless metal oxides.

Prostheses as a replacement for a joint consist of at least two functionally cooperating pieces, e.g. a shaft piece and a joint socket. The shaft piece has, at the end protruding from the bone, a joint head which can be rotated is stored in the joint socket. The joint head is fixed in place by a shaft Bone anchored, the production of a connection that meets all requirements between the bone and the shaft is an essential prerequisite for the firm hold of the Shank piece forms.

The material used for the shaft so far has been used because of its high strength primarily metals, mainly corrosion-resistant alloys based on nickel-chromium-cobalt-molybdenum in question.

According to DOS 2 134 316, a metallic shaft is inserted into the bone driven in and using a putty made from a highly polymerized acrylic resin (bone cement) attached. According to this proposal, it is not possible to achieve a bond that is always over remains permanently firm for a long time. The alloys mentioned have a high Corrosion resistance, but have the disadvantage that they are not directly in the bone can be anchored, but need the already mentioned putty for this.

Due to the heat generated during the polymerization process, which can be up to 1200C, protein denaturation occurs in the adjacent tissue and possible toxic damage due to the formation of monomers. In addition, the Metallosis caused by electrolytic influences. Kick the above processes described, then it comes to loosening of the implant.

Another disadvantage is that metallic implants are a comparatively have a high specific weight. In addition, a special putty must be found the bone substance with the completely different metallic metal Material connects satisfactorily.

The task was therefore to create a lighter implant, which, in addition to high strength, has good tissue compatibility and without additional binding agent enables a better bond with the surrounding bone.

According to the invention, this object is achieved in the case of an artificial joint replacement from at least two interacting pieces, such as the shaft piece and the socket, in which the frictionally stressed parts of sintered, wear-resistant molded bodies high mechanical strength from high-melting, physiolo-existing, gically harmless Metal oxides are dissolved by having all of the bone engaging part of the gel replacement consist of sintered oxide ceramic.

The invention is illustrated below using the example of a hip-thigh joint replacement described, but can be used in the same way for other implants, the other joints correspond.

For sintered, wear-resistant moldings with high mechanical strength made of high-melting, physiologically harmless metal oxides, hereinafter referred to as oxide ceramics called, come the well-known high-melting, hard oxides such as zirconium oxide or titanium oxide in question. Sintered oxide ceramic has a sufficiently high Firmness on. However, it is essential that an oxide-ceramic implant has a higher Corrosion resistance than, for example, the aforementioned alloys and thereby the undesirable side effects do not occur or occur to a much lesser extent. Oxide ceramic implants have a lower specific weight than metallic ones Implants on.

Because of their material relationship to the bone substance, oxide ceramics are Implants have a better tolerance and also allow a better Connection to the bone.

Initially, sintered oxide ceramics were introduced for the shaft the prejudices of the medical community against a relatively brittle material opposite to. As stated in DOS 2 154 516, there was the opinion of the experts that the shaft could only be made of metal to prevent the blows from being driven in endure in the bones. The present technical solution is all the more surprising Problem. The reason for the particularly good suitability of sintered, dense oxide ceramics is probably due to the fact that with such a high density due to the solid grain bond there is also a high material strength, which is necessary for use as a joint replacement is of paramount importance.

As an oxide ceramic material for the shaft piece is because of its economic production method, mechanical strength and chemical resistance at temperatures above 17000C sintered alumina with a Purity of more than 97% preferred. A high-purity has proven particularly successful 5 aluminum oxide with a density above 5.9 g / cm and an average grain size below 10 / um.

Often one becomes the two interacting pieces, like shaft piece and joint socket made of the same material. Sintered aluminum oxide high density is excellent for polishing. This is especially for the contacting parts of the joint, the outer surface of the spherical The joint head and the concave surface of the joint socket are very important, as one is possible low friction is aimed at. The joint head and the joint socket are useful Immediately after production by lapping, they are optimally matched to one another. Polished, sintered High density alumina has minimal abrasion, which means virtually none Wear of the friction surfaces is caused.

It can be useful to check the flexural, shear and flexural fatigue strength the parts made of oxide ceramics inside by reinforcing rope layers such as nets, grids, Fibers and the like to increase.

Such materials are advantageously selected for these insoles, which enable a solid sintered bond to the oxide ceramic. Have proven themselves in primarily metals.

The aim is to make the connection between the surface of the parts in engagement with the bone and the bone as firm as possible. Additional mechanical holding means on the surface of the implant make a particular contribution to this. Such holding means can be raised, for example in the form of barbs, Shape of pores hQhQn or simply consist of a roughening.

A porous surface of the parts in engagement with the bone can promote the ingrowth of bone tissue to a considerable extent. The porosity the surface can e.g. be enlarged mechanically. Can expediently but also Burnout substances are added to the molded body before the sintering process and thereby the porosity of the surface can be controlled in a targeted manner. True was already proposed to use metallic implants with a porous deposit, e.g. from To provide clay. Apart from the fact that there is a permanent metal-alumina connection always has a weak point at the interface, can through the porous, thin Deposition does not attack the tissue fluid on the metal of the implant be prevented.

According to a preferred embodiment, an artificial Joint replacement according to the invention, the parts that are in engagement with the bone of the joint replacement screwed directly to the bone in a self-tapping manner. Of the The main advantage here is the use of corrosion-resistant oxide ceramics in the fact that no bone cement is used and the additional associated therewith Material and labor are completely eliminated. The shaft itself can be connected to a Threads are provided. In the case of the socket, the convex surface can be partially be designed as a self-tapping thread. These self-tapping trained Parts are screwed into the cancellous bone, which means that it is hammered in and with it associated shock loads can be avoided.

Complicated moldings, such as artificial joint replacements made from oxide ceramics are difficult to manufacture in one piece. An additional problem is that during the operation there is little room for the introduction of the joint replacement is available. To remedy these difficulties is in a further advantageous Execution of the shaft piece composed of shaft and joint head. This embodiment has the advantage of a simple structural design and a related one simple manufacturing.

It is also advantageous if the shaft piece in addition to the shaft and the joint head still has a shaft neck, attached to the shaft and expedient is additionally fixed. In this way there is the additional advantage that During the operation, the shaft that has just formed is only inserted into the bone can be. Only after the stem is firmly anchored1 does the stem neck open the shaft attached and fixed.

The connection between the shaft and the joint head is advantageous via an attachment on the shaft neck. Such an approach can intervene in the joint head and thus form a particularly durable form-fitting twist. The fixation between The attachment and joint head can be made in different ways, e.g. by gluing. Particularly The connection is firm when the joint head is in contact with the neck of the shaft is screwed.

The interface through the natural femoral neck shows depending on the cutting angle a different bevel. In order to be able to support the joint head evenly, become conical after an appropriate training on the approach of the shaft neck Intermediate pieces pushed on.

It can also be advantageous if the joint socket can be lowered by means of Screws is also fixed in the pelvic bone. This is where the im Pelvic bones self-tapping screwed joint socket to a very considerable extent consolidated.

To the high bending, shear and alternating bending strength of metallic Materials in an advantageous manner with the high corrosion resistance of oxide ceramics to combine, the joint replacement parts according to the invention can be used inside Including a gain, e.g. made of metal or fiber-reinforced composites, be hollow. Also come here for such a massive Reinforcement only takes into account all those parts that are not directly related to the bone are engaged. For example, the core of the shaft or the inside of the shaft neck be reinforced by metal. The connection between reinforcement and oxide ceramics can be done with a two-component adhesive.

According to a further preferred embodiment, the connection between the individual parts of the joint replacement made of oxide ceramic molded bodies Reinforced by a physiologically harmless putty and secured against twisting.

It is advantageous to use a putty that is specific to the one used Oxide ceramic is matched. This cementing comes naturally within the meaning of the invention only for ceramic surfaces under each other that are not directly related to the Bones are engaged.

The invention is illustrated below with reference to that shown in the figure Embodiment described without affecting the invention on this example limited.

The figure shows an artificial joint replacement consisting of two interacting Pieces, the sheep 5 and the socket 14.

The shaft piece 2 has a joint head 10 and a shaft 3, which are connected to one another via the shaft neck 8.

The shaft 3 is at its lower end for attachment ## 1e in the thigh bone 1 provided with a self-tapping thread 4 and has at its upper end a pin 6.

The key surface is on the shaft 3 as a gripping surface for the key 5 attached. In addition, longitudinal grooves 17 are provided to accommodate a socket wrench arranged.

The shaft neck 8 is plugged from pin 6 of the shaft 3 and fixed by the nut 7. The approach 9 of the shaft neck 8 engages positively into the joint head 10. The link head 10 is screwed onto the attachment 9.

To achieve a uniform support of the joint head 10 on the cut surface of the femur 1 are conical on the extension 9 Spacer 11 and a beveled spacer 12 pushed on.

The joint socket 14 is by a self-tapping thread 16 in the Pelvis bone 13 attached. The joint socket is secured by retractable screws 15 14 additionally fixed.

All parts are made of high-purity, sintered aluminum oxide. the concave surface of the joint socket 14 and the convex surface of the joint head 10 are sin sanded and polished.

Claims (1)

Claims Artificial joint replacement from at least two interacting pieces, such as the shaft piece and socket, in which the parts subjected to friction from sintered, wear-resistant molded bodies of high mechanical strength made of high-melting, consist of physiologically harmless metal oxides, characterized in that all parts of the joint replacement that are in engagement with the bone are made of sintered Oxide ceramics exist. 2. Artificial joint replacement according to claim 1, characterized in that that moldings made of an oxide ceramic are used, which are made from at temperatures Alumina sintered above 1700 C with a purity of more than 97 % Al205 exist. 5. Artificial joint replacement according to one of claims 1 and 2, characterized characterized in that moldings are used from an oxide ceramic, which is made of sintered high-purity aluminum oxide with a density of over 5.9 g / cm3 and an average grain size is less than 10 / um. 4. Artificial joint replacement according to one of claims 1 to), characterized characterized in that the parts made of oxide ceramics to increase the bending, shear and Flexural fatigue strength are reinforced inside by metal. 5. Artificial joint replacement according to one of claims 1 to 4, characterized gekennzeidrnet that the surface of the parts in engagement with the bone has additional mechanical holding means for stronger fastening of these parts. 6. Artificial joint replacement according to one of claims 1 to 4, characterized characterized in that the parts of the joint replacement that are in engagement with the bone are screwed directly to the bone in a self-tapping manner. 7. Artificial joint replacement according to one of claims 1 to 6, characterized characterized in that the shaft piece (2) is composed of the shaft (3) and joint head (10) is. 8. Artificial joint replacement according to one of claims 1 to 7, characterized characterized in that the shaft piece (2) consists of a shaft (5) with a self-tapping thread (4), shaft neck (8) and joint head (10) is assembled. 9. Artificial joint replacement according to one of claims 1 to 8, characterized characterized in that the shaft neck (8) is pushed onto the shaft (3) and fixed is. 10. Artificial joint replacement according to one of claims 1 to 9, characterized characterized in that the connection between the shaft (3) and joint head (10) over an approach (9) takes place on the shaft neck (8). 11. Artificial joint replacement according to one of claims 1 to 10, characterized characterized in that the joint head (10) with the shoulder (9) of the shaft neck (8) is screwed. 12. Artificial joint replacement according to one of claims 1 to 11, characterized characterized in that to achieve uniform support of the joint head (io) on the separating surface spacers and washers (left, 12) on the shoulder (9) of the shaft neck (8) are pushed on. 13. Artificial joint replacement according to one of claims 1 to 12, characterized characterized in that the shaft () is hollow inside for receiving a reinforcement is trained. 14. Artificial joint replacement according to one of claims 1 to 1), characterized characterized in that the connection between the individual parts of the joint replacement made of oxide ceramic moldings with a physiologically harmless one Putty is reinforced and secured against twisting. Blank page