WO1993017638A1

WO1993017638A1 - Joint prosthesis

Info

Publication number: WO1993017638A1
Application number: PCT/AT1993/000042
Authority: WO
Inventors: Randolf Scholz; Reinhard Ehall
Original assignee: Logimed Medizinische Spezialprodukte Gesellschaft M.B.H.
Priority date: 1992-03-09
Filing date: 1993-03-09
Publication date: 1993-09-16
Also published as: HUT66221A; HU9303147D0; EP0583457A1; JPH06507567A; AT398371B; CA2102430A1; SK122693A3; ATA45792A; CZ233793A3

Abstract

A joint prosthesis (3) has two extensions (4, 5) that can be linked to bones and swivel with respect to each other around an axis bolt (6). One of the extensions (5) has a claw shaped head and the other extension (4) has a head part provided with a bearing eye that enters the claw-shaped head. The axis bolt of the joint extends through the mutually aligned bores of the claw-shaped head and bearing eye. The axis bolt (6) of the joint tapers towards one end and/or its outer diameter is reduced towards said end, which is designed as a ring-shaped snapping element that cooperates with corresponding ring-shaped snapping elements arranged on one of the mutually aligned openings of the claw-shaped head.

Description

Gel prosthesis

The invention relates to a joint prosthesis with two extensions which can be pivoted relative to one another and are to be connected to bones, in which one of the extensions has a claw-shaped head and the other extension carries a bearing part which bears a bearing eye and plunges into the claw-shaped head and in which the hinge axis extends through mutually aligned bores of the claw-shaped head and the bearing eye.

Prostheses of the type mentioned at the outset can be found, for example, in US Pat. No. 4,193,139. Another joint endoprosthesis, as can be seen, for example, from DE-A 2 351 912, is primarily designed for the elbow joint according to its structure. Overall, the majority of the prostheses that have become known to date are more or less suitable for the respective special application or for the replacement of a very specific joint.

Joint prostheses, which, like the joint prosthesis according to the present invention, are primarily intended to replace a finger joint, can be found in particular in addition to the US Pat. No. 4,193,139 mentioned at the beginning of EP-Bl 214 773. In view of the fact that they are intended for finger joints, these two known joints are limited to a uniaxial articulation of the bone parts which are to be connected to one another in an articulated manner, obviously primarily intended for use in the second joint seen from the fingertip. Due to the known construction of such joint prostheses, a relatively large length of the bone must be removed from the end face on which the joint is to be used, in order to make room for the accommodation of the joint. In such operations, a partial area of the bone on which the articular ligaments were originally able to grow is thus removed, and a new steepness must subsequently be used for the determination of Ligaments are searched for on the bone. Experience has shown that the new growth of bone ligaments at a different, than the original, natural growth site is associated with major problems.

The proposed prosthesis as mechanical joints must have not only high mechanical strength moreover still be distinguished in that they are easy to assemble in order to keep the _n erforder¬ Liche operation time corresponding to a short in the operational application or during use.

The invention now aims to provide a hinge joint, i.e. To create a joint prosthesis, in particular for use as an metacarpal joint, which is characterized by its design that only small areas of the opposing end faces of articulated bones have to be removed during installation and, in particular, removal of the end face of the bone is only necessary to the extent that the natural growth points for ligaments can be maintained intact.

Furthermore, the aim is to create a joint prosthesis of the type mentioned at the outset, which is characterized by particularly simple installation and assembly without complex instruments. To achieve this object, the joint prosthesis according to the invention essentially consists in the fact that the joint axis is formed by a bolt which tapers to one end and / or is offset to a smaller outside diameter, this end being designed as an annular latching member which cooperates with corresponding annular locking members on one of the aligned openings of the claw-shaped head. The fact that the hinge axis is designed as a locking bolt, it is possible to make the joint itself relatively small and to ensure secure anchoring of the extensions in the respective bones 5 before the joint is assembled in a simple manner and in the smallest space. For the assembly of the joint, it is sufficient, only that Pressing locking bolts into the corresponding openings, which requires a relatively small amount of space, which in turn means that the bones which are to be connected to such an artificial joint only have to be removed or removed over a short length . In addition to this latching capability, which is particularly advantageous for simple assembly, the end of the bolt can also be tapered in order to facilitate centering and insertion of the bolt, in any case the definitive installation position by latching the free end of the bolt in the corresponding latching elements of the claw ¬ shaped head. The assembly can be made considerably easier by the fact that the hinge axis has a blind hole at its end facing away from the latching members for the engagement of a tool, a particularly simple fixing of a tool for the manipulation of the relatively small hinge axis then being possible is when the training is made so that the blind hole has an internal thread. Overall, with such a design, relatively small joint axes with correspondingly small joints can be safely assembled in the smallest space due to the possibility of using a correspondingly easier-to-use tool.

With Vortei.l i.st the design of the joint prosthesis according to the invention made such that the locking members are formed by annular grooves and / or annular ribs. In order to enable elastic locking of such ring grooves with ring ribs, it is advantageously possible to use physiologically harmless plastics, whereby the assembly or the manufacture of the joint can be simplified considerably in that the mutually aligned bores of the claw-shaped head have essentially the same inside diameter and that the locking members are arranged in an insert bushing which is inserted in one of the two bores of the claw-shaped head and secured against falling out. The arrangement of the mutually aligned bores essentially with the same inner diameter makes it possible to choose correspondingly simple manufacturing tools for the extensions and the claw-shaped head, the required small tolerances subsequently being ensured by the corresponding high-precision manufactured insert parts, in particular the insert bushing. Furthermore, it is possible in this way for the extensions and the formation of the head to select appropriate high-strength materials, in particular metallic materials, and in that insert bushings with correspondingly low manufacturing tolerances and in particular insert bushes made of physiologically harmless plastics are used At the same time, the bearing longevity is significantly improved and the friction of metallic parts in particular is avoided. Such undesirable friction of metallic parts of the joints against one another, taking advantage of the self-lubricating properties of various physiologically harmless plastics, also succeeds if the design is such that the insert bush has an annular flange with an outside diameter exceeding the inside diameter of the bores, which in the Mounting position on the inside of the claw of the claw-shaped head, whereby a lateral stabilization of the joint with a correspondingly low tolerance, viewed in the direction of the bearing axis, is made possible. This effect can be further improved in that a bearing bush is inserted into the bearing eye of the head part of the second extension, which has an annular flange with the inner diameter of the receiving bore for the bearing bush exceeding the outer diameter, which can ensure that on both sides of the bearing eye Head part friction on metallic parts of the inner walls of the claws encompassing this head part can be avoided.

With regard to the use of the joint prosthesis according to the invention as a joint in the metacarpal region or in the finger region, only a hinge articulation is to be reproduced, for which the training, in particular with extensive imitation of the actual natural conditions during the movement of such wrists is advantageously taken such that the head part carrying the bearing eye carries at least one stop shoulder which interacts with the claw-shaped head of the other extension. In this way, at least one of the limit positions, for example the extended position of the joint, can be clearly delimited by a stop, without the need for another space-consuming component.

In order to ensure that the extensions are securely anchored even in the case of such a small-sized joint, the design is advantageously made such that the extensions are essentially symmetrical about their longitudinal axis that intersects the bearing axis, the extensions on their outside advantageously over the Wear circumferentially distributed, preferably sharp-edged ribs extending in the direction of their longitudinal axis. Such, in particular sharp-edged ribs favor the corresponding anchoring effect in the end region of the bone and offer a number of advantages when mounting the extensions in the bone. While in known, largely asymmetrical extensions, high demands were placed on the precision of the corresponding bone recess for rapid and reliable growth, in such largely centrically symmetrical extensions, the requirements are considerably lower

Requirements are placed on the maximum permissible tolerances of these recesses without significantly impairing the security of ingrowth. To achieve an anchoring effect, it is sufficient immediately after being pressed in

To ensure extent, the formation is advantageously made such that the sharp-edged ribs have a decreasing height in the direction of the free end of the extensions, the formation being advantageously made such that the extensions are required for the subsequent integration into the bone material wear a coating of biodegradable ceramic material. The pressing of the extensions into recesses which can be produced in a simple manner on the end faces of the bones to be articulated to one another is thereby substantially combined. fold and with less effort allows the extensions to taper to their free end substantially conical.

The invention is explained in more detail below with the aid of an exemplary embodiment shown schematically in the drawing. In this show; Fig.l schematically a section, for example by a metacarpal joint, with a built-in joint prosthesis according to the invention; 2 shows a plan view of the one extension or joint part of the joint prosthesis according to the invention which carries the claw-shaped head according to FIG. 1; 3 shows a side view of the extension or joint part in the direction of arrow III of FIG. 2; 4 shows a view in the direction of arrow IV of FIGS. 2 and 3; 5 shows a side view of the second extension or joint part carrying the bearing eye of the joint prosthesis according to the invention according to FIG. 1 in a representation analogous to FIG. 3; 6 shows a plan view of the second extension in the direction of arrow VI in FIG. 5; 7 shows a view of the bolt forming the joint axis of the joint prosthesis according to the invention; 8 shows a section through an insert bushing which can be arranged in a claw of the claw-shaped head and which carries latching members for interaction with the bolt according to FIG. 7; and FIG. 9 shows a section through a further bearing bush which can be inserted into the bearing eye of the head part of the second extension of the joint prosthesis according to the invention.

In FIG. 1, a joint prosthesis, generally designated 3, is used in two bones 1 and 2 to replace the natural joint, the joint prosthesis 3 having two extensions 4 and 5, which are inserted into recessed or hollow bone areas and further below in Detail are shown in more detail. The two extensions or joint parts 4 and 5 are pivotally hinged to one another, the pivot axis being schematically indicated by 6 in FIG. The pivot axis is formed by a bolt which can be introduced into mutually aligned bores of the extensions 4 and 5 and which is shown in more detail in FIG - 1 -

is shown. The actual joint areas of the joint prosthesis, i.e. those partial areas which protrude from bones 1 and 2 are dimensioned so short by using a bolt as a joint axis that the natural growth sites for the ligaments in the end areas of the bones do not have to be removed, the growth sites of the ligaments are indicated schematically with 7.

2 and 3 the extension or joint part 5 carrying a claw-shaped head is shown in more detail. Immediately adjacent to the extension 5, which tapers conically towards its free end 8, are two claws 9, each of which has openings 10 which are flush with one another and have essentially the same diameter. The pivot axis is again indicated at 6. The extension 5 has, in the direction of its longitudinal axis 11, distributed around the circumference, in particular sharp-edged ribs 12, as can be seen particularly clearly from FIG. The conically tapering formation of the extension can also be clearly seen from FIG.

In the assembled state, the claws 9 grip around the bearing eye 13 of the second extension or joint part 4, which is shown in detail in FIGS. 5 and 6. The extension 4 or the bearing eye 13 have an opening 14 which is aligned with the bores or openings 10 of the second extension 5 and which is likewise penetrated by the bolt shown in FIG. 7 in the assembled state. The extension shown in FIGS. 5 and 6 also has a cross section which tapers conically towards its free end 15 and is likewise formed with sharp-edged ribs 12. Overall, the two extensions or joint parts 4 and 5 are both centrally symmetrical and identical in their partial areas projecting into the bones, so that the joint can be used in both positions. The ribs 12, which are distributed around the circumference, in particular with sharp edges, are arranged in the bones in such a way that only one rib is arranged on the inside, ie on the flexion side of the joint, while the two remaining ribs shown in the illustration 12 are arranged accordingly on the outside, as is also indicated schematically in Fig.l. The ribs have, starting up from the respective free end 8 and 15, respectively increasing height, to facilitate a ^'driving the respective projections in the recesses in the bones. Overall, the ribs serve to anchor the extensions in the bones and, in particular, to prevent rotation of the joint parts therein. Furthermore, due to the presence of the ribs 12, it is not necessary to set excessively high conditions with regard to the geometric design for the recesses to be made in the bones, since the ribs can also compensate for irregular recesses in the bones due to their different heights.

In one of the claws 9, the insert bushing 16 shown in FIG. 8 is inserted into the corresponding opening 10, which has an annular flange 17, which comes into contact with the inside of the corresponding claw. Similarly, the bearing bush 18 shown in FIG. 9 is inserted into the opening or bore 14 of the bearing eye 13 of the second extension, which also has an annular flange 19 which bears against the inside of the bearing eye and thus between the bearing eye 13 and the adjacent claw 9 is arranged. Naturally, the insert bushing 16 is inserted on the second claw 9 provided.

To assemble the joint prosthesis, the bolt 20 shown in FIG. 7, which forms the joint axis, is introduced into the openings 10 and 14 of the extensions 5 and 4 or through the openings provided in the bushes 16 and 18. The bolt 20 is tapered towards one end 21 and is offset to a smaller diameter, with an annular connection at the free end 21 of the bolt 20. detent member 22 is formed in the form of an annular rib. When the bolt 20 is inserted from that side of the assembled joint prosthesis which is opposite the claws 9 having the insert bushing 16, the bolt first penetrates the first opening of the first claw 9 and then passes through the opening 23 of the bearing bushing 18 into the bearing eye and subsequently into the insert bushing 16 arranged in the second claw. As can be seen from FIG. 8, the insert bushing 16 has an annular projection 24 which is matched to the diameter of the annular rib 22 of the bolt 20, so that when completely When the hinge pin or locking pin is inserted, the ring rib 22 latches with the annular projection 24 of the insert bushing 16 and the joint is thus closed in a simple manner, ie the two extensions or hinge parts 4, 5 are pivotably articulated to one another.

For the insertion of tools, the hinge pin 20 has a blind hole 25, which is formed over a schematically indicated partial area 26 with an internal thread, so that, for example, a screw or the like. can be arranged for simple handling of the bolt or for applying the required forces, which in turn can be removed in a simple manner after the joint has been assembled.

When using the present joint prosthesis in the area of the finger or metacarpal, all that is required is a uniaxial hinge connection, in which an end position of the joint prosthesis 3 is shown in FIG. 1, with bending up to an angle of approximately 90 ° being achievable. In order to prevent excessive extension or flexion in the opposite direction, the bearing eye 13 shown in FIGS. 5 and 6 has a stop shoulder 27 which, in a stretched position, on the inner surface 28 of the extension 5 between the claws 9 in System arrives and prevents excessive diffraction beyond the stretched position. The angle beyond the distance is limited by the stop to about 10 °. Special titanium-aluminum alloys are used as materials for the joint parts, which are characterized by a low specific weight, high elasticity, high strength and excellent corrosion resistance. The bushings 16 and 18 shown in FIGS. 8 and 9 are used not only for locking the joint parts with one another, but also to prevent metallic parts from rubbing against one another. For this purpose, these insert bushings are made of a biologically well-tolerated material, which has good sliding properties and optimal damping properties with minimal abrasion. For a rapid ingrowth of the prostheses, ie in particular the extensions 4 and 5 in the bones, an appropriate biodegradable coating material is applied to the extensions 4 and 5, for example by plasma spraying, which, moreover, gives freedom from pain and thus an earlier use of the operated Allows joint. The achievable complete growth of the bone on the implanted extensions 4 and 5 results in an early and good resilience of the artificial. lend joint.

Naturally, different outer diameters of the extensions 4 and 5 can be used to adapt to different bone sizes. The conical tapering of the extensions 4 and 5 is chosen such that, in addition to the anchoring by the ribs 12, a self-locking anchoring against pulling out the extensions from the bones is effected, with an angle of inclination of about 5, for example, according to the materials used and the bone. 7 ° is selected. In the event that, in deviation from the embodiment shown with a smaller number of ribs, the length is to be found, the rib assigned to the flexion side is dispensed with due to the kinematics of the joint.

Claims

Claims:

1. Joint prosthesis (3) with two extensions (4, 5) which can be pivoted relative to one another about an axis (6) and in which one of the extensions (5) has a claw-shaped head (9) and the other Extension (4) carries a head part which bears a bearing eye (13) and plunges into the claw-shaped head and in which the joint axis (6) extends through mutually aligned bores (10, 14) of the claw-shaped head (9) and the bearing eye (13), characterized in that the hinge axis is formed by a bolt (20) which tapers to one end and / or is offset to a smaller outside diameter, this end being designed as an annular latching member (22), which cooperates with corresponding ring-shaped latching members (24) on one of the aligned openings (10) of the claw-shaped head (9).

2. A prosthetic joint according to claim 1, characterized in that the hinge axis (20) has a blind hole (25) on its end facing away from the locking members for the engagement of a tool.

3. Joint prosthesis according to claim 2, characterized in that the blind hole (25) has an internal thread (26).

4. Joint prosthesis according to claim 1, 2 or 3, characterized gekenn¬ characterized in that the latching members are formed by annular grooves and / or annular ribs (22).

5. Joint prosthesis according to one of claims 1 to 4, characterized in that the mutually aligned bores (10) of the claw-shaped head (9) have substantially the same inner diameter and that the locking members (24) are arranged in an insert bushing (16) , which is inserted in one of the two bores of the claw-shaped head (9) secured against falling out.

6. Joint prosthesis according to claim 5, characterized in that the insert bushing (16) has an annular flange (17) with the inside diameter of the bores (10) exceeding outside diameter, which in the mounting position on the inside of the claw of the claw-shaped head (9) is present.

7. Joint prosthesis according to one of claims 1 to 6, characterized in that in the bearing eye (13) of the head part of the second extension (4) a bearing bush (18) is inserted, which has an annular flange with the inner diameter of the receiving bore (14) for the Bearing bush (18) has an outer diameter exceeding.

8. Joint prosthesis according to one of claims 1 to 7, characterized in that the bearing part (13) carrying the head part carries at least one stop shoulder (27) which interacts with the claw-shaped head (9) of the other extension (5).

9. A joint prosthesis according to one of claims 1 to 8, characterized in that the extensions (4, 5) are designed to be essentially centrically symmetrical with respect to their longitudinal axis (11) intersecting the bearing axis.

10. Joint prosthesis according to claim 9, characterized in that the extensions (4,5) on their outside over the circumference in the direction of their longitudinal axis (11) extending, preferably sharp-edged ribs (18).

11. A prosthetic joint according to claim 10, characterized in that the sharp-edged ribs (12) have n decreasing height in the direction of the free end of the extensions (4, 5).

12. Joint prosthesis according to one of claims 1 to 11, characterized in that the extensions (4, 5) carry a coating made of biodegradable ceramic material.

13. Joint prosthesis according to one of claims 1 to 12, characterized in that the extensions (4,5) taper to their free end (8,15) substantially conically.