DE2318459A1 - ARTIFICIAL JOINT REPLACEMENT MADE OF Sintered OXIDE CERAMIC - Google Patents

Description

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HANSUIiLMANN

PATENT ADVOCATE
. 406 VlERSEN 1
GLADBAOHER STK. 189

Remote call MM 2318459

Applicant: Feldmühle Plant and Production Company

with limited liability, 4 Düsseldorf-Oberkassel, Fritz-Vomfelde-Platz 4

Annex to the entry from April 9th, 1975
Pat / 12.285 / Vth-Hx.

Artificial joint replacement made of sintered oxide ceramic.

The invention relates to an artificial joint replacement for a joint socket and bone parts which are in engagement therewith such as thigh bones or joint role, in which at least the parts of the artificial joint replacement subject to friction made of sintered, wear-resistant molded bodies of high mechanical strength made of high-melting, physiological harmless metal oxides.

In the case of an artificial joint replacement for joint sockets and bone parts that are in contact with them, such as the thighbones the tight fit (hold) of the interacting parts is an essential prerequisite for functionality.

One suggestion is to move the joint head, which is in engagement with the artificial joint socket, towards a shaft attach that into the medullary canal of the femur is driven.

Al ^s material for the shank came because of their high strength so far primarily metals, primarily corrosion resistant alloys, nickel-chromium-cobalt-molybdenum-base in question. According to DOS 2 134 316, a metallic one is used

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Shank driven into the bone and by means of a Putty made of a highly polymerized acrylic resin (bone cement) attached. According to this proposal, however, do not achieve a bond between shaft and bone that always remains permanently firm over a long period of time. The mentioned. Alloys have a high corrosion resistance, but have the disadvantage that they are not directly in the Bones can be anchored, but instead require the aforementioned putty.

Due to the heat generated during the polymerization process, which can reach up to 12o ° 0, it occurs in the adjacent Tissue for protein denaturation and possible toxic damage due to the formation of monomers. Additionally arises the metallosis caused by electrolytic influences. Perform the operations described above a ^, then the implant loosens. Another disadvantage is that metallic implants have a comparatively high specific weight. aside from that a special putty must be found that combines the bone substance with the completely different metallic material Material connects satisfactorily.

However, this proposal also entails considerable difficulties for the surgeon and the patient. Around the shaft To be able to introduce it into the medullary canal, the femoral head and femoral neck must be removed from the femur, that is a relatively large proportion of the bone, so that only a small amount of bone substance remains for the occasional necessary follow-up operation is available. The large contact area between the shaft and the bone prosthesis has an even more disadvantageous effect. A large contact area always represents a large wound area with the associated increased risk of infection. In addition, there is a large area of attack on the

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Kilochen tissue before. A foreign body like an artificial joint replacement often causes receding natural bone tissue, which can extend to regression. Such a breakdown of the bone tissue inevitably leads to loosening of the joint replacement and thus to renewed complaints of the patient.

The task was therefore to create an artificial joint replacement in which the remaining bones were protected as much as possible experiences and with which a better bond to the remaining bone is achieved without additional binding agents.

This task is performed in an artificial joint replacement for the joint socket and bone parts that are in engagement with it, such as Thigh bone or joint role, in which at least the parts of the artificial joint replacement subject to friction made of sintered, wear-resistant molded bodies of high mechanical strength made of high-melting, physiological harmless metal oxides exist, solved in that with the machined leg head or the joint roller Joint head 'is directly connected and this with the also made of sintered refractory metal oxides artificial socket is engaged.

So far, the experts believe the body element can only be attached via a shaft sufficiently firmly in the thigh. As stated in D-OS 2 134 316, the shaft had to be made of metal and had to be firmly driven and cemented into the bone.

The solution at hand is therefore completely surprising who deliberately avoids attachment by a shaft in a departure from the previous direction, with the Artificial joint replacement still holds.

*) made of sintered high-melting metal oxides

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The explanation is probably that because of the material Relationship between bone and oxide ceramic implants, • especially with additional mechanical holding devices the surface of contact gradually grow together »Above In addition, there is so much muscle and tendon tension that the joint head is pulled tightly into the joint socket, see above that the union of the interacting parts by itself holds.

The considerable progress of this solution consists in the simple structural arrangement, since only two interacting Parts are available and the associated economical production. Especially in the production of moldings The uncomplicated shape is made of sintered oxide ceramic because of the material shrinkage that occurs during sintering an important role.

The solution according to the invention is more appropriate to the material, since the previously common shaft was subjected to bending stress while the joint head is only subject to compressive stress in the present case.

In contrast to the previous proposals, the advantages for the surgeon and the patient also become particularly clear emerged.

If the joint head is indirectly connected to the machined leg head or the joint roller, there is still enough Boil substance available for possible follow-up operations. At the same time is the contact area between the articular head and Bone substance limited to a minimum. In this way the wound area is significantly reduced and there is less Possibility of regression of the bone tissue. In addition, the previous impairment of the supply of the bone substance can be about lea bones! no longer occur.

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Finally, there is a decisive advantage of the invention in that the artificial joint replacement made of oxide ceramics creates a solid bond with the bone without additional binding agents enables. This eliminates the material and labor required for the binding agent.

Oxide-ceramic joint replacements also have a higher corrosion resistance than, for example, the aforementioned alloys on, so that the unwanted life effects are no more may occur. Because of its material relationship to the bone substance, oxide-ceramic joint replacements show the better composite also has better tissue compatibility.

Efforts are made to establish the connection between the surface of the bone-engaging parts and the bone to be as firm as possible. The surface of the parts that are in engagement with the bone is made of oxide ceramic additional mechanical holding means. Such retaining means can consist of barbs on the artificial joint replacement exist or have the shape of pores or simply consist of a roughening.

A porous surface of the bone-engaging parts can cause bone tissue ingrowth to a considerable extent Promote dimensions. The porosity of the surface can, for example, be increased mechanically. Appropriate But burnout materials can also be added to the shaped body before the sintering process, thereby reducing the porosity of the Surface can be controlled in a targeted manner. Although it has already been proposed to use metallic implants with a porous deposit, e.g. made of clay. Apart from the fact that a permanent metal-alumina connection always occurs at the interface Weak point, the porous, thin deposit

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tion of the tissue fluid attacking the metal of the implant cannot be prevented.

Each of a very preferred embodiment are in one Artificial joint replacement according to the invention, the parts of the joint replacement which are in engagement with the bone directly screwed to the bone in a self-tapping manner. The particular advantage here lies in addition to the use of the corrosion-resistant Oxide ceramics in that no bone cement is used and 3 additional material related to it and workload is completely eliminated. For this purpose, the joint head is provided with an internal thread. In the case of the socket the convex surface can be partially designed as a self-tapping thread. These self-tapping trained Parts are screwed onto the machined head of the leg or into the natural pan, which means that the previous one Impact and the associated impact-like stress can be completely avoided.

According to another preferred embodiment, the joint head Provide a polygonal socket to produce a form-fitting connection and milled off the square Thigh head attached. In this way, a safeguard against rotation is achieved. In addition, there is the advantage that with local regression of bone tissue there is always a flat contact surface between the articular head and femoral head and so that the position of the joint head is stabilized.

For this same reason, the joint socket can also have laterally flat surfaces arranged at an angle to one another exhibit. The anti-twist protection achieved in this way is provided on the edge of the joint socket at the open boundary edge arranged flap is reinforced. This tab enables a fastening screw to be inserted into a relative strong area of the pelvic bone.

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For sintered, wear-resistant moldings of high mechanical strength made of high-melting, physiologically harmless Metal oxides, hereinafter referred to as oxide ceramics, are the well-known high-melting, hard oxides such as zirconium oxide or titanium oxide in question. Sintered oxide ceramics are characterized in particular by very high compressive strength and excellent Wear resistance.

As an oxide ceramic material for artificial bone replacement, sintered aluminum oxide with a degree of purity of more than 97 % is preferred because of its economical production method, mechanical strength and chemical resistance at temperatures above 17oo ° C. A high-purity aluminum oxide with a density of over 3.9 g per cm and a mean parameter below 10 μm has proven particularly useful.

Often one becomes the two interacting pieces, like joint head and joint socket made of the same material. Sintered alumina having a high density can be excellent polishing. This is particularly important for those parts of the joint that are in contact, the outer surface of the spherical joint head and the concave surface of the joint socket are very important, since the aim is to minimize friction will. The joint head and the joint socket are expediently optimally fitted into one another directly after production by lapping. Polished, sintered, high density alumina has minimal abrasion, making it practical no wear of the friction surfaces is caused.

It can be useful to check the flexural, shear and flexural fatigue strength to increase the interior of the parts made of oxide ceramics with reinforcing inserts such as nets, grids, fibers, etc. Such materials are advantageously selected for these insoles, which enable a solid sintered bond to the oxide ceramic. Metals have proven their worth in the first place.

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The invention is illustrated below by means of figures and examples of a hip-thigh joint replacement described in more detail, without . that the subject matter of the invention relates to this embodiment limited:

Fig. 1 shows a synthetic joint replacement from two cooperating Parts, the joint head 4- and the joint socket 7 The joint head 4- is via a self-tapping thread 5 screwed onto the machined head 3. The femoral head 3 adjoins the femoral neck 2, both are Parts of the femur 1. The socket 7 is through a self-tapping thread 12 in the pelvic bone 6 attached and additionally fixed by a retractable screw 8.

lig. 2 shows an artificial joint replacement which, as in FIG consists of two interacting parts joint head 4 and joint socket 7.

The joint head 4 has inside to produce a form-fitting Connection with the machined leg head 3 has a square socket. The machined leg head 3 is that is, connected to the joint head 4 via flat contact surfaces 11. The joint socket 7 has laterally flat, in one Angularly arranged contact surfaces Io and is connected to the pelvic bone 6 in a form-fitting manner. Edge side the joint socket 7 has a tab 9. The socket is fixed over the tab 9 by the retractable screw 8 connected to the pelvic bone 6.

FIG. 3 shows the joint socket 7 shown in FIG. 2 Direction X. The joint socket 7 has laterally flat surfaces Io which are arranged at an angle to one another.

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All parts of the artificial joint replacement consist of high-purity, 'sintered alumina. The concave surface of the joint socket 7 and the convex surface of the joint head 4- are ground and polished.

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Claims (1)

DR RER- HANS UHLMANN ΡΑΤΠΓ! ADVOCATE FOURS 1 GLADBACHER STR. 189 J _fl ZJ 1 O 4 O 'Telephone 17081 flf Applicant: Feldmühle Plant and Production Company with limited liability, 4 Düsseldorf-Oberkassel, Fritz-Vomfelde-Platz 4 Pat / 12.285 / Tth-Hx. Claims. Artificial joint replacement for the socket and thus in Engaging bone parts such as thigh bones or joint roles, in which at least those are exposed to friction Parts of the artificial joint replacement made of sintered, wear-resistant molded bodies of high mechanical strength consist of high-melting, physiologically harmless metal oxides, characterized in that with the machined leg head (5) or the joint roller a joint head (4) 'is directly connected and this with the artificial joint socket (7), which is also made of sintered refractory metal oxides, engages stands. 2. Artificial joint replacement according to claim 1, characterized in that that the surface of the parts in engagement with the bone is made of oxide ceramic for stronger attachment these parts have additional mechanical holding means. 3 Artificial joint replacement according to one of Claims 1 and 2, characterized in that the parts of the joint replacement which are in engagement with the bone are self-tapping with the bone are screwed. 4. Artificial joint replacement according to one of claims 1 üii <§ 2, characterized in that the joint head (4) has a polygonal socket to produce a form-fitting connection having. *) made of sintered high-melting _ 2 - Metal oxides 409844/0087 5 Artificial joint replacement according to one of Claims 1 to 4, characterized in that the joint socket (7) laterally flat surfaces (Io) arranged at an angle to one another having. 6. Artificial joint replacement according to one of claims 1 to 5j characterized in that the joint socket (7) has a tab (9) on the edge. 7 '. Artificial joint replacement according to one of Claims 1 to 6, characterized in that molded bodies made of an oxide ceramic are used which consist of aluminum oxide sintered at temperatures above 1,700 ° O with a degree of purity of more than 97 % Al ^ O. 8. Artificial joint replacement according to one of claims 1 to 7 » characterized in that molded bodies made of an oxide ceramic are used which are made of sintered high-purity aluminum oxide with a density of more than 3 »9 g / cnr and a medium one Grain size below Io / um. 9. Artificial joint replacement according to one of claims 1 to 8, characterized in that the parts made of oxide ceramics for Increase in bending, shear and alternating bending strength are reinforced inside by metal. 409 8.4 4/0087