DE3049219A1 - Alloplastics endoprosthesis component - has annular grooves in fixing surface at acute angles to plane of cap mouth - Google Patents

Abstract

The alloplastics endoprosthesis component is partic. in the form of a femoral cap or socket for a two-shell internal artificial hip joint, having a fixing surface with grooves, secured by a thin layer of cement. The fixing surface (3) has annular grooves (4), whose extended planes form acute angles (5) with the plane (2) of the cap or socket mouth and also with each other. The acute angles can be between 10 and 45 deg., and there can be from 2 to 5 annular grooves, each of them enclosing the pole of the component.

Description

Alloplastic endoprosthesis part, in particular

Femoral valve or socket of a double-shell hip joint endoprosthesis The invention relates to an alloplastic endoprosthesis part, in particular the femoral cap or socket of a double-shell hip joint endoprosthesis with a by means of a thin cement layer to be fastened, grooves having fastening surface.

The aim is to care for diseased human hip joints resect as little bone as possible.

This requires the subsequent use of the thinnest possible cement layers for fastening the endoprosthesis to the bone. For better anchoring of the endoprosthesis surface structures of the endoprosthesis attachment surface in different Forms known.

On the one hand, there are surface structures of the endoprosthesis fastening surfaces known from the formation of more or less strong elevations. E.g. Prosthetic joint sockets are known with a hemispherical shell resting on their Have several annular ribs on the outside, DE-PS 20 39 731. Are known also shell-shaped pans for a prosthesis, DE-OS 28 57 297, where on the outside the pan has several elastic projections that extend over the envelope surface protrude from the outside of the pan. There are also femoral head valves in the form of a half-ball known to have a surface unevenness on the mounting surface, in particular have an elevation in the form of a rib with a triangular cross-section, DE-OS 25 12 407. The ribs, evenly distributed over the circumference, run meridially from the Vertex to edge. The purpose of these solutions, namely the better anchoring as well as the linking of larger relative movements is only possible temporarily achieved. The sharp-edged shape of the ribs results in a notch effect the breakage of the cement layer in the area of the ribs facilitates.

Because the cement layer is divided into individual strips or areas by the ribs is, after the onset of loosening, increasingly stronger cement abrasion occurs. To At a further stage, coarse pieces of bone cement can be sheared off can have a destructive effect on the bone surface.

It is also known to use the load-bearing mounting surfaces on all sides to provide limited projections, the projections are preferably spherical, DE-OS 28 19 178. This surface structure allows im In contrast to the arrangement of ribs, largely closed or network-like thin Cement layers. However, it is disadvantageous that these spherical surface structures even more than it already applies to the ribs, only on mounting surfaces of Metal prostheses can be applied, as this requires casting or

Must use welding or soldering processes.

On the other hand, alloplastic endoprosthesis parts are known the fastening surface have depressions for the purpose of surface structuring. So prosthetic joint sockets are already known in which the shell on their Outer surface has grooves, U.S. Patent 2,668,531, to make them immovable in acrylic cement to embed, which in an responding prepared cavity in the bone material is introduced. The grooves are preferably formed in the shape of a shell.

There is also a hip joint cap known, DE-CM 77 14 799, in which the inner surface is a grid, consisting of parallel, Lich-crossing grooves, preferably with angled cross-sectional figure, up. In addition, the inner surfaces can have several have meridial grooves that are wider than the grooves. The grooves run Mexican, while a group of gluten meet vertically on the grooves, while the other set runs approximately meridially.

It has been shown that surface structures that have become known are not universally applicable that in particular for ceramic materials such as Aluminum oxide, carbon, graphite or silicon carbide-carbon composites there are no optimal solutions. In the case of endoprosthesis parts made of ceramic materials Elevations are inexpedient for manufacturing reasons.

The present invention is accordingly based on the object cin To create endoprosthesis part with a fastening surface having grooves, which a firm and permanent bond even when using thin layers of cement guaranteed without affecting the mechanical connection of the cement layer and without increased abrasion in the event of an undesired loosening of the bond respectively. Important requirements to be met are good security against rotation, simple ones Creatability, design independent of the material and the lowest possible weakening the endoprosthesis strength.

To solve this problem it is provided according to the invention that the mounting surface has annular grooves whose imaginary extension planes with the socket or cap entry level and include acute angles with each other.

The angle is usually 10 to 45 to the depth of the adhesive surface As high a number of intersecting grooves as possible should be provided.

On the other hand must the increasing weakening of the prosthesis strength as well as the higher costs with increasing number of ring grooves are taken into account. Arrangements with 2 to 5 ring grooves have proven to be advantageous. An advantageous one Arrangement is that each individual annular groove the pole of the endoprosthesis part encloses.

The grooves are usually rounded in their base.

The ratio of width to depth of the groove is preferably 5: 1 to 1: 1, the depth of the groove o, 4 to 2 now, with the particularly preferred <; t-en tJ'eilc is 1 mm.

The inventive design of the fastening surface leads despite their simplicity to significant advantages.

Due to the arrangement of the ring grooves at an acute angle from 1o to The prosthesis suffers from material weakening at 45 ° to the socket or cap entry plane only in those directions in which the main stresses do not occur. Voltage peaks namely occur in hemispherical structures such as the pan and cap predominantly in a meridial manner and circumferential direction.

It should be emphasized that due to the specific arrangement of the grooves adequate protection against twisting and loosening is achieved. For stability the cement layer, depressions in the fastening surface are more favorable than elevations, since no notch effect is exerted on the cement layer. The rounding of the grooves on the other hand, it minimizes the notch effect on the prosthesis material.

the erfindungsge is (; design is in all known Protlesenworksttoffen, such as metal, plastic or ceramic material can be used. Particularly beneficial she has found herself with prostheses made of ceramic material such as carbon, graphite, silicon carbide or silicon carbide-carbon composite.

The surface structuring according to the invention has become meridial here and / or circumferentially arranged grooves, rows of holes and staggered ones Rows of holes shown superior, as a clear one with the same groove or hole depth lower prosthesis weakening was noticeable. The prosthesis strength of an inventive The prosthesis is only slightly less than the strength of a prosthesis without surface structuring. This surprising result is confirmed by comparative measurements.

Surface structuring Twist Trigger Break Safe Safe load is kN 1. without e - - 87 grooves arranged maridally + - 50 3. moridially arranged row of wells + - 50 4th circumferentially arranged rings - + 81 5. meridially arranged grooves and + + 52 circumferentially arranged rings against each other offset depressions + - 64 7. Three intersecting annular grooves, as + t 84 according to the invention Solution + good - less satisfactory The table shows the breaking loads that when attempting to push off caps made of silicon carbide-carbon composite material were obtained. The outer diameter of the cap was 44 mm and the wall thickness 5 mm. The depth of the surface structures 1 mm, the cross section of the depressions corresponded to a semicircle.

The invention is referred to below using an exemplary embodiment further explained on a drawing.

Fig. 1 shows a side view of a cup-shaped according to the invention Joint socket.

The joint socket 1 has a socket entrance plane 2, 2a, an inner, sliding surface, not shown, as well as an outer fastening surface 3. in the Fastening surface 3 are 3 ring grooves 4a, 4b and 4c let in, the imaginary with the Extension of the socket entrance plane 2a as well as acute angles between each other (5a, 5b).

FIG. 2 shows a plan view of the pan according to FIG. 1.

Three annular grooves (4a, 41>, 4c) emerge from the fastening surface in this way 3 arranged so that each individual ring groove closes the pole (, 11111-.

Only one embodiment is shown here, but it could also considerably more ring grooves, which also do not have to all enclose the pole attached to the mounting surface.

On the representation of a femoral cap, the inner surface of which the The attachment surface to the bone could be dispensed with, since the top view of Fig. 2 also shows the situation in the case of the cap, with 1 then the inner Bc-E (stigungsflticlle wcjre.

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Claims (7)

P a t e n t a n s p r ii c 1 h - to e 1. Alloplastic endoprosthesis part, in particular the femoral cap or socket of a double-shell hip joint endoprosthesis, with a grooves to be fastened by means of a thin layer of cement Fastening surface, d u r g e k e n n n z e i c h u c L, that the Ucf estigungsf Lache (3) has annular grooves (4), dereti imaginary extension planes (4 /) with the Pan or Include the cap entry level (2) as well as acute angles (5) below each other. 2. Endoprosthesis part according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the acute angle (5) between 10 ° and 45 is. 3. Endoprosthesis part according to claim 1 or 2, d a d u r c h g e k e n n z e i c h n e t that the number of annular grooves is 2 to 5. 4. Endoprosthesis part according to claim 1 to 3, d a d u r c h g e k e n n z e i c h n e t that each individual ring nut (4) the pole (6) of the endoprosthesis part (1) encloses. 5. Endoprosthesis part according to claim 1 to 4, d a d u r c h g e k e n n z e i h n e t that the annular grooves (4) are rounded in their base. 6. Endoprosthesis part according to claim 1 to 5, d a d u r c h g e k e It is noted that the ratio of width to depth of the groove is 5: 1 to 1 : 1 is. 7. Endoprosthesis part according to claim 1 to 6, d a d u r c h g e k e It is noted that the depth of the groove is 0.4 to 2 mm.