HUT66221A - Joint prosthesis - Google Patents

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

BACKGROUND OF THE INVENTION The present invention relates to a joint prosthesis with two protrusions that can be pivotally rotated about one axis and which can be inserted into bone, one of which extends into a fork-shaped head and the other into an eye-shaped head inserted between branches of a fork-shaped head. through axial bore holes in the head and eye-shaped head.

Such a prosthesis is described in US-PS 4,193,139. Another joint endoprosthesis, for example, as disclosed in DE-A-2 351 912, is intended primarily for elbow joints. Most of the known prostheses are suitable for special purposes and for replacing certain joints.

In addition to the aforementioned US-PS 4,193,139, prostheses intended primarily for replacement of finger joints

EP-B1 214 773. These two known solutions, given that they serve to replace the finger joints, are limited to the uniaxial articulation of the bones to be connected to each other and are used primarily at the second joint from the finger tip. However, due to the known construction of such joint prostheses, a relatively long portion of the bone end where the joint is implanted must be removed to provide adequate space for the joint. Thus, in such operations, a portion of the bone is removed, which could have been pulled on by the articular ligaments and, as a result,

-3 new space for fixing the tapes. Experience has shown that the re-growth of bone straps to the non-original, natural site of growth has led to significant problems.

In addition to its high mechanical strength, the joint used as a prosthesis must also be easy to assemble to minimize the time required for surgical installation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an articulated joint, particularly a center joint, which is a joint prosthesis which, due to its construction, requires only a short section of the bones of the opposing articulated bones at insertion, retention. It is a further object of the present invention to provide a joint prosthesis that enables installation and assembly without complicated tools.

SUMMARY OF THE INVENTION An object of the present invention is to provide a joint prosthesis with two protrusions that can be pivoted about each other about an axis, one of which extends in a fork-shaped head, the other in a forearm-shaped head inserted between branches of a fork-shaped head. the axis of the joint passes through axial bores formed in the fork-shaped head and in the eye-shaped head, wherein the joint axis is formed as a taper tapering at one end and / or shrinking to a smaller diameter, at which end a locking ring is formed locking engagement with one of the annular bores of one of the axial bores formed as locking members. By designing the joint axis as a pin, it is possible for the joint itself to be relatively small in size and for the joint to be securely anchored in the affected bone before the joint is started in a simple, small space. In fact, to assemble the joint, it is sufficient to insert the pin forming the shaft into the appropriate holes, which requires relatively little space, which means that only a small part of the bones to which such an artificial joint is attached is removed or removed. For this particularly advantageous locking for easy assembly, the end of the shaft-forming pin may be tapered, thereby facilitating the centering and insertion of the pin and finally locking its definitive mounting position with the locking elements of the fork-head. The assembly can also be significantly facilitated by having a socket hole for receiving a tool on the front face of the articulation shaft relative to the locking elements, in which the tool is fastened in a particularly simple manner and thus allows manipulation of the relatively small articulation axis. The socket hole may be provided with an internal thread for receiving the tool. The

-5crew-in, properly handled tool enables the insertion of a small shaft into the joints of the small joint, which requires only a small amount of space.

A preferred embodiment of the joint prosthesis according to the invention is that the locking elements are designed as annular grooves and / or annular ribs. In order to provide elastic locking with such annular grooves and annular ribs, physiologically compatible plastics may be used on the locking members, thereby substantially simplifying the assembly and fabrication of the joint, since arranged in a insert sleeve which is securely inserted in one of the forks to prevent it from falling out, the common axle bore holes of the forks have substantially the same internal diameter allowing the use of simple tools for forming the projections and the fork-shaped head manufactured parts, in particular the insert sleeves, can be secured. It is also advantageous to select materials of high strength, in particular metal materials, to suit the projections and the head. By making the liner sleeves of physiologically compatible plastics with sufficiently low tolerances, the life of the bearing of the pivot bearing is significantly increased and at the same time the metal formation can be avoided · · · · · · · · · · · · · · · · · ·· · ¹

-6 friction between parts. Such undesirable friction between the metal parts of the joint, due to the self-lubricating properties of physiologically compatible plastics, can also be avoided by the fact that the insert sleeve is provided with an annular rim whose outer diameter is greater than the diameter of the holes in the forks. This flange of the insert sleeve lies on the inner surface of the fork branch of the fork-shaped head, thereby allowing lateral stabilization of the joint with a sufficiently small tolerance towards the eye formed in the other head. This situation can be further improved by inserting an insert sleeve in the eye formed in the head portion of the other projection, which is provided with an annular rim, the outer diameter of the rim being larger than the inside diameter of the opposed opening. This ensures that there is no metallic friction between the two sides of the eye-shaped head and the forks that surround it.

In view of the fact that the joint prosthesis of the present invention is used as a joint, particularly in the center of the hand and the fingers, it should be designed to rotate a pivot about an axis and thus be designed to mimic the natural hand movements. Accordingly, the eye-shaped head portion is provided with at least one stop shoulder which cooperates with the other fork-shaped head. With this solution, it is possible to provide at least one of the borderline positions, for example, the elongated, non-bent position of the joining members, · 4 · 4 · · 4 · · · · · · *

-7 collision limitation without the need for an additional bulky component.

In order to provide anchorage of the projections for such a small wrist, it is preferable to have a design in which the projections are substantially centrally symmetrical about their longitudinal axis intersecting the pivot axis and are circumferentially circumferentially circumferential. These edged ribs provide proper anchorage in the bone and offer a number of benefits when mounting the projection into the bone. While the known, largely asymmetric, protrusions have extremely high requirements for accuracy for rapid and reliable growth of bone, the use of the essentially centrally trained protrusions of the present invention in terms of the maximum allowable tolerances for bone construction requires significantly less growth would be endangered. In order to obtain an adequate anchoring effect immediately after insertion, a training is provided whereby the ribs are formed with a decreasing height towards the free end of the projections, and a training according to which the projections are biologically beneficial is preferred. are fitted with a removable ceramic coating. Inserting the projections into the cavities of the bones to be interconnected in a straightforward manner is made possible by · · • «

-8 much simpler and requires only a small amount of effort to taper the projections towards their free end.

The invention will now be described in more detail with reference to the drawings, in which an exemplary embodiment is provided. The attached drawings show

Fig. 1 is a schematic, sectional view of a medial sacroiliac joint with a joint prosthesis according to the invention.

Fig. 2 is a plan view of a fork-head extension of the joint prosthesis of Fig. 1,

Figure 3 is a side view of the hinge portion of Figure 2 a

From arrow III, a

Fig. 4 is a view of Figs. 2 and 3 in the direction of arrow IV, i

Figure 5 is a side elevation view of another projection or joint portion of the joint prosthesis of the present invention, ending in a bearing view;

Figure 6 is a plan view of the hinge of Figure 5 a

VI arrow direction, a

Figure 7 is a view of the pin forming the articulation axis of the joint prosthesis of the present invention, a

Figure 8 is a sectional view of a sleeve insert inserted into a fork branch of a fork-shaped head, a

Fig. 9 is another sleeve insert that can be inserted into a bore of a bearing-shaped head.

• · 4 • 4

44444 · ······ · ··· ♦ ·

Fig. 1 illustrates a joint prosthesis 3 inserted into the bones 1 and 2 to replace a natural joint, wherein the joint prosthesis 3 has two projections 4 and 5 which can be inserted into hollow or hollow bones and will be described in detail below. The two projections 4 and 5 are pivotally disposed relative to one another. The axis of the articulation is located in the axial bores formed in the heads connected to the ends of the projections 4, 5. The position of the axis of the joint prosthesis is schematically illustrated by the centerline 6. The shaft formed as a pin is shown in greater detail in Figure 7. The joint portion of the articular prosthesis, i.e., the part that protrudes from the bones 1 and 2, can be scaled so short using the tapered axis that no need for stripping at the ends of the bones. The locations of the tapes 7 are shown in Figure 1. Figures 2 and 3 illustrate a projection 5 ending in a fork-shaped head. A fork-shaped head having two fork branches 9 is connected to the other end of the projection 5, which is tapered towards the free end 8. The forks are provided with holes 10 having a common axis of substantially the same diameter. The articulation axis is indicated by the centerline 6 in Figures 1 and 2. The projection 5 is provided with ribs 12 in the direction of its longitudinal axis 11, which are particularly visible in FIG. Figure 4 also shows the thinning of the projection 5 towards the end 8.

When assembled, the fork tines 9 encircle the projections 13 which form a joint at the junction of the forehead. ·

-105. and Figure 6. The eye 13 is formed by an opening 14 in the same axis as the holes 10 in the forks 9, which, when assembled, passes through the pin illustrated in FIG. The projections shown in Figures 5 and 6 also have a tapered cross-section towards the end 15 and are also formed with ribs 12 having a sharp edge. The protruding portions of each of the protrusions 4, 5 are symmetrically, centrally and identically centered, allowing the artificial joint to be inserted in both positions. The joint prosthesis is inserted into the bones such that one of the ribs on the circumference of the projections 4, 5 is oriented in the direction of flexion of the joint, while the other two face outwards, as shown in Figure 1. The ribs are descending in the direction of the free ends 8, 15 of the projections 4, 5 to facilitate insertion of the projections 4, 5 into bone cavities. The ribs are a

4, 5 is used to fix the protrusions in the bones, in particular to prevent rotation of the joints. In addition, the ribs 12 do not require high geometric accuracy for the voids to be formed in the bones, since the ribs, due to their variable height, can compensate for irregularities in the bone voids.

In a bore 10 formed in one of the fork branches 9 an a

The insert sleeve 16 shown in Fig. 8 is provided with a flange 17 which lies on the inside of the fork branch 9. Likewise, the insert sleeve 18 is also inserted into the opening 14 of the eye 13, which also has an insert.

It is provided with a flange 19 which lies on the inside of the eye 13 and is thus arranged between the eye 13 and the adjacent fork branch 9. Of course, the insert sleeve 16 is inserted into the second fork branch 9.

When the joint prosthesis is assembled, the pin 20 illustrated in Figure 7 is inserted through the bore 10 and the opening 10 of the projections 5 and the insertion lugs 16 and 18, which form the axis of the joint prosthesis. One end 21 of the pin 20 is tapered to form a locking ring 22 in the form of an annular rib at a portion adjacent the end 21 of the tapered section. The pin 20 is inserted into the assembled joint prosthesis through the fork branch 9 opposite the fork branch 9 in which the insert sleeve 16 is located. Thus, the pin 20 first passes through the first fork branch 9 and then through the opening 23 of the insert sleeve 18 located opposite to it and finally into the insert sleeve 16 in the other fork branch 9. As shown in Figure 8, the insert sleeve 16 has an annular protrusion 24 that fits the diameter of the locking ring 22 of the pin 20, so that when the pin 20 is fully inserted, the locking ring 22 and the annular projection 24 of the insert sleeve 16 the projections 4, 5 are pivotally connected to each other.

For use of the tools, the pin 20 is formed with a sack hole 25 provided with an internal thread on a section 26 schematically depicted. Thus, for example, a chess * 9 • ·

-12var or a similar tool allows you to exert the required force on the pin or simply handle the pin, and the tool can be easily removed after assembly.

By using the joint prosthesis of the invention, a uniaxial hinge connection is formed on the finger or midbone portions, with one end position illustrated in Figure 1 and wherein, with respect to folding, an approx. An angle of 90 ° can be provided. In order to avoid excessive straightening or folding in the opposite end position, the eye 13, as illustrated in Figures 5 and 6, is provided with an abutment pin 27 which, when extended, abuts the inner face 28 of the projection 5 between the forks 9, over-bending shall not occur. The angle of bending beyond the straightened position due to impact may not exceed 10 °.

The material used for the joints is special titanium - aluminum alloys, which are extremely suitable for this purpose due to their low specific gravity, high elasticity and high strength and excellent corrosion resistance. The liners illustrated in Figures 8 and 9 not only serve to lock parts of the joint prosthesis by locking, but also to prevent friction of the metallic members. To this end, the insert sleeves are made of a material that meets biological requirements and has good slip properties and optimal (sound) damping properties.

-13delkezik. For rapid proliferation of the joint prosthesis, particularly the 4 and 5 protrusions, the injections 4 and 5 can be provided with a biologically degradable coating on the protrusions which, in addition, has analgesic properties and enables the operative joint to be used as soon as possible. The implanted protrusions 4 and 5, which are well and fully integrated into the bones, allow early use and remarkable load capacity of the artificial joint.

Of course, depending on the different bone sizes, protrusions 4 and 5 of different diameters can be used. The tapering of the projections 4 and 5 must be selected so that, in addition to the anchoring effect of the ribs 12, a self-locking anchorage is created which prevents the projections 4, 5 from being pulled out of the bones. Therefore, it is preferable to select a taper angle of 5-7 ° according to the implanted material and bone. If, in contrast to the illustrated embodiment, the use of fewer ribs proves sufficient, the ribs in the bending direction may be omitted based on the joint kinematics.

Claims (13)

Patent Claims 1. A joint prosthesis with two protrusions pivotable about one axis and inserted into bone, one of the projections terminating in a fork-shaped head and the other in an eye-shaped head inserted between the branches of a fork-shaped head and wherein the axis of the articulated joint and passing through axial bore holes in the eye-shaped head, characterized in that the joint axis is in the form of a pin (20) tapered at one end and / or reduced to a smaller diameter, wherein at this end (21) is a locking ring (22). is formed which engages in locking engagement with the annular protrusions (24) of one of the axial bores (10) formed on the forks (9) of the fork-shaped head. A joint prosthesis according to claim 1, characterized in that the end face of the articulated shaft formed as a pin (20) opposite to the formed end of the locking ring (22) is provided with a socket hole (25) for receiving a tool. The joint prosthesis according to claim 2, characterized in that the cod hole (25) has a section (26) with an internal thread. 4. A joint prosthesis according to any one of claims 1 to 3, characterized in that the locking elements are designed as annular grooves and / or locking rings (22). 5. A joint prosthesis according to any one of claims 1 to 3, characterized in that the axial bore (10) of the fork arms (9) have substantially the same diameter and the locking annular protrusion (24) is arranged in a insert sleeve (16) is securely inserted. A joint prosthesis according to claim 5, characterized in that the insert sleeve (16) is provided with a flange (17) having an outer diameter greater than the diameter of the bore (10), which when mounted lies on the inner surface of the fork branch (9) of the fork head. up. 7. A joint prosthesis according to any one of claims 1 to 5, characterized in that a liner (18) is provided in the opposite face (13) of the other projection (4) having an outer diameter (19) larger than the opening (14) of the eye (13). ). 8. A joint prosthesis according to any one of claims 1 to 3, characterized in that the head portion formed by the eye (13) has at least one stop shoulder (27) which is formed on the fork-shaped head of the other projection (5). 9. A joint prosthesis according to any one of claims 1 to 4, characterized in that the projections (4, 5) are substantially centrally symmetrical to their longitudinal axis (11) intersecting the articulated axis. 10. The joint prosthesis of claim 9, wherein .... characterized in that the projections have ribs (12) on their outer surface distributed in a circumferential, preferably longitudinal, direction. A joint prosthesis according to claim 10, characterized in that the ribs (12) are formed at a decreasing height towards the free end of the projections (4, 5). 12. A joint prosthesis according to any one of claims 1 to 3, characterized in that the projections (4, 5) are coated with a biodegradable ceramic material. 13. A joint prosthesis according to any one of claims 1 to 3, characterized in that the projections are tapered to their free end (8, 15).