DE4434806B4 - knee prosthesis - Google Patents

Abstract

knee prosthesis comprising a tibial plateau portion having an anchoring portion in the bone and a support plate for a slide plate made of plastic and / or a femoral component with a resting on the sliding plate Articulating surface portion, the tibial plateau part and the femur part being axially displaceable Coupling pins are connected to each other, which in the tibial component pivotable about a vertical axis and in the femoral part horizontally is stored, characterized in that the femurseitige end of the coupling pin (11) formed rectangular in cross-section is and has a bearing approach (flexible disc 12), which engages in an anchored in the femur bearing part (4), which a corresponding rectangular cross-section and a circular section-shaped bearing portion (5), wherein the tibial side part of the coupling pin (11) is cylindrical and the sliding plate (13) and support plate (14) passing through in a corresponding recess (17) one with the support plate (14) associated approach (16).

Description

The The invention is directed to a knee joint prosthesis comprising a Tibial plateau part with an anchoring section in the bone and one Support plate for a slide plate made of plastic and / or a femur part with a on the slide plate resting articulation surface part, wherein the tibial plateau part and the femdom over an axially displaceable coupling pin connected to each other which are in the tibial component about a vertical axis and in the Femoral part is mounted horizontally pivotable.

The Goal of a complete Knee replacement by a prosthesis is the function of the joint as far as possible restore. It must considered the kinematics and biomechanics of the rolling-sliding rotary motion become. A knee joint prosthesis needs such a movement process understand and the load by tilting, thrust and rotation without harm to the bone camp and for capture the capsule ligament.

For this Prostheses are known in which tibial plateau part and femur part are not coupled. These prostheses or artificial joints are on the surgical preservation, the physiological tension and thus on the undisturbed Instructed function of the entire capsular ligament apparatus. By overuse individual parts of the tape guide not infrequently occur Bandinsuffizienzen, instabilities and consecutive prosthetic loosening up. Also, the bands of the Knee joint with advanced destruction preoperative often so dysfunctional that instabilities and thus the failure of the art joint are already predetermined. Most of time force size and shape of the artificial joints to partial resections of the central parts of the band, so afterwards the shear stress due to the artificial joint is not sufficiently secure is caught. Despite these systemic disadvantages of uncoupled Joints become such for certain applications, especially in the presence of functional ability of the capsular ligament, sometimes preferred, because a relatively natural Movement possible is.

On the other hand, coupled artificial joints are known as z. B. in the generic DE 41 02 509 A1 to be discribed. Known such prostheses may not sufficiently follow the very complicated, physiologically predetermined rolling-sliding rotational movements of the knee joint, so that at each step, the coupling of the joint leads to a temporally and locally punctiform loading of the anchorage and thus overloading. This also relaxation of the implanted parts are conditional.

From the EP 0 519 873 A2 a knee joint prosthesis is known in which the femurseitige end of the coupling pin is rectangular in cross-section and which has a bearing lug which engages in an anchored in the femur bearing part with a corresponding bearing portion. In this known knee joint prosthesis, however, the sliding plate can move on the support plate when the coupling pin rotates about its vertical axis.

Out The above shows that both coupled and uncoupled Joints have certain advantages and disadvantages, with the larger or lower degrees of freedom of the two joint types are connected.

Of these, Based on the object of the invention, a prosthesis system which is not a priori as coupled or uncoupled System running and accordingly gives the surgeon the freedom, weighing all Randbediungen of the individual case the optimal appearing joint select. About that In addition, the joint should be assembled from individual components so that the surgeon over the selection of a coupled or uncoupled system also the possibility has to do a whole or partial joint replacement, wherein independently from the medical Decision of the surgeon worked with the same components can be, so that a rational production of the same in large quantities is possible.

These Task is inventively characterized solved, that the femurseitige end of the coupling pin in cross-section rectangular is formed and a bearing approach in the form of a flexible disc which, in an anchored in the femur bearing part engages, which has a corresponding rectangular cross-section and has a corresponding circular section-shaped bearing section, wherein the tibial side part of the coupling pin is cylindrical and the sliding plate and support plate passing through in a corresponding Recess engages a connected to the support plate insert.

hereby a connection is enabled that a pivoting movement possible power. Although the coupling pin in the femurseitigen bearing section rotatably engaged, can through the formation of bevels a limited possibility of swiveling for example, +/- 4 ° also femursitig be provided. At this bearing section can tangentially Connect stop section, in the extended state of the knee as a stop and abutment serves to absorb power.

By the embodiment of the invention will the realization of a horizontal pivoting movement accordingly allows the flexion movement of the knee joint, wherein the coupling pin simultaneously in the bearing portion rotatably relative to a vertical pivot axis is stored. On the other hand, it is possible that designed so Femdom also without coupling pin at full functionality to use.

In Another embodiment of the invention is provided that the femurseitige Bearing part a box-like Coupling shaft, in which a plastic, in particular Polyethylene insert, is arranged, in which the bearing portion is formed is. Accordingly, it is on the one hand technically simple, the forms to work out the bearing part, and on the other hand, an optimal To achieve sliding behavior between coupling pin and bearing recess.

With Advantage is provided that the coupling shaft connectable with an expansion sleeve is, with the connection through from the inside of the coupling shaft ago introduced screws can be realized. The expansion sleeve is used anchoring in the femoral bone.

Of the Coupling shaft can in turn with the articulation surface part connected, which in turn the use of the femurseitigen prosthetic part also possible without coupling pin.

advantageously, is the approach of the support plate placed on an anchoring part and by means of a trained at the upper end of the anchoring part Tapped hole and a screw inserted through the recess connectable with this.

Finally, can be provided that the anchoring part has a cone-shaped upper Section and the approach of the support plate has a corresponding conical lower recess, so when tightening the screw a Tension occurs.

From a medical point of view, the embodiments described above lead to the following possibilities, summarized again:
A knee joint prosthesis is initially implanted in 80% of all indications as a primary prosthesis. It is, as already explained, assume that in patients under 75 years of capsule ligament apparatus is still essentially functional.

at 20% of the indications for artificial knee prostheses As a precaution rigid axial guided knee joint prostheses are used. The appropriate caution results from the fact that one fears that in older ones Patients over time, d. H. within a period of two to five Years ago, the capsule ligament becomes increasingly inefficient and one so-called "Schlotterknie" arises, which leads to failure of the knee joint leads. So it will be for reasons the precaution used a rigid knee joint prosthesis, though At the moment of the operation this would not be mandatory.

To the conventional one Prior art had to So choose the clinician between a hinged knee prosthesis in the form of a rigid, axle-guided knee joint, a rotary knee joint prosthesis, wherein a hinge knee joint achsgeführt is provided with lateral rotational movement, and a knee joint prosthesis with firmly molded guide shield.

Of the Disadvantage of these known knee joint prostheses is therefore that that once made a choice regarding a particular type of prosthesis must become, without subsequent correction options existed. Exactly this restriction is eliminated with the development according to the invention.

According to the invention is a Knee joint prosthesis available put, which as a primary prosthesis can be used and on the other hand with a few additional parts as a modular revision knee prosthesis interoperatively without problems can be extended expanded.

If For example, the surgeon for an uncoupled prosthesis decides and cemented both components firmly and then at the trial replacement of the knee joint it turns out that the capsular ligament apparatus does not have the desired stability, previously only the option the plateau guidance surface to increase and thus better bias the band structure. This brings the disadvantage with that one leg extension occurs and the joint space is pulled far apart, causing increased Shear and shear forces are conditional.

By means of the embodiment according to the invention, it is possible, on the one hand, to leave both firmly cemented components without change and, on that basis, to chisel out the space for the coupling shaft with a box chisel that shows off the insufficiency of the capsule apparatus, in which case the preassembled coupling mechanism is inserted and used with a clamping screw a screwdriver with torque limiter is clamped. After inserting the polyethylene insert of the coupling pin is inserted into the tibial plateau insert the plateau guide surface and fix the knee joint.

This leads to, that it can be realized, from an uncoupled to a coupled knee joint prosthesis with all degrees of freedom of an uncoupled knee joint prosthesis but with thrust and lateral kinking be prevented.

Next The situation described above, it is also possible that the knee joint prosthesis as a primary prosthesis is implanted and detected only after several years wearing time will that the capsule ligament has become so inefficient that made a revision operation must become.

by virtue of the embodiment of the invention is it possible then to open the knee joint and, as with the intraoperative correction described above, with the box chisel Room for the Coupling shaft to create and use the coupling mechanism.

It So the advantage is achieved that with few interventions a stable knee joint function can be made, it also possible is to optionally renew femoral or tibial components. All components fit together due to the modular construction according to the invention.

In contrast, must at a such situation with a prosthesis according to the prior art the surgeon if necessary tear out stuck components what you always want to avoid and an axle-guided Implant hinge joint. This is a big operation necessary, as such, and by the need for a completely new knee prosthesis, considerable costs.

In contrast, is in the inventive solution only an insertion of the coupling modules required.

Out It will therefore be apparent from the foregoing that the essence of the solution according to the invention is that one Primary knee joint prosthesis to disposal is placed in any situation, ie intraoperatively or too any later Time when coupled prosthesis can be modularly expanded, without having to explant implants. This is a time and cost savings and the prosthesis change is for the patient far more bearable.

following The invention is based on a preferred embodiment in connection closer to the drawing described. Showing:

1 a partial section of a prosthesis arrangement according to the invention,

2 one around 1 90 ° rotated sectional view,

3 a 1 corresponding sectional view of the 118 ° angled prosthesis according to the invention,

4 a 1 Corresponding sectional view of the prosthesis extended by 4 °,

5 and 6 the 1 and 2 corresponding representations without coupling pins,

7 and 8th 1 and 2 corresponding representations of a second preferred embodiment and

9 a 7 corresponding representation (reduced) in the manner of an exploded view.

A prosthesis shown in the drawing comprises a femoral component 1 and a tibia part 2 ,

The femur judgment 1 is formed by a box-like, a recess defining coupling shaft 3 in which a polyethylene insert 4 is arranged, the one bearing section 5 having. The storage section 5 is formed in this embodiment, a circular segment-shaped, with serving as a stop and force transmission surface Tangentialabschnitt 6 followed.

The coupling shaft 3 is about screws 7 with an expansion sleeve 8th connected, which serves the implantation in the femur bone. With the coupling shaft 3 is an articulation surface part 9 connected, which has two curved articulation surfaces 10 has, which extend on both sides of the coupling shaft.

In the storage section 5 engages a coupling pin 11 a, at its upper end a kind of joint ball 12 having, in its radius of curvature with the circular section bearing portion 5 coincides and to which a tangential section 13 connects, the course about the tangential section 6 following the storage section 5 equivalent.

The tibia part 2 includes a support plate 14 for a sliding plate 15 made of polyethylene. To the support plate 14 closes an approach 16 on, which is a cylindrical recess 17 in which a cylindrical lower portion 18 of the coupling pin 11 positively engages pivotally engages.

At the bottom of the neck 16 is a conical recess 19 formed into which a conical section 20 an anchoring part 21 with in cross-section star-like anchoring ribs 22 intervenes.

In the cone section 20 of the anchoring part 21 is a threaded hole 23 formed into a screw 24 engages, whose head is at the bottom of the recess 17 supported.

The 3 and 4 illustrate the possibilities of movement of a prosthesis assembly according to the invention with coupling pins 11 whereas the 5 and 6 show that the most important components in particular the manufacturing technically complex articulation surface part according to the free decision of the surgeon without coupling pin 11 can be used.

In the in the 7 to 9 In the second embodiment shown, the parts corresponding to the first embodiment are identified by the same reference numerals using the suffix "a".

Also in the second embodiment, the femoral part becomes 1a formed by a cross-sectionally substantially L-shaped coupling shaft 3a , in which also in cross-section also approximately L-shaped polyethylene insert 4a is arranged, the one bearing section 5a having. The storage section 5a is not circular segment-shaped in this embodiment, but to one side, in the drawing left, open, so that not a well-defined horizontal pivot axis is created for the joint, but to some extent, a translational movement of the pivoting movement can be superimposed, which reproduces the degrees of freedom of a natural knee joint. To the storage section 5a closes as a stop and power transmission a tangential section 6a at.

The coupling shaft 3a is about screws 7a with an expansion sleeve 8a or with a corresponding anchoring part connected to the implantation in the femur bone. With the coupling shaft 3a is an articulation surface part 9a connected, which has two curved articulation surfaces 10a having, which on both sides of the coupling shaft 3a extend.

In the storage section 5a engages a coupling pin 11a one, which has a cylindrical lower section 18a and a joint section 12a comprising, wherein the hinge portion 12a opposite the cylindrical section 18a offset relative to the longitudinal axis Y or is formed as a bend, wherein the section 12a extending following this bend also substantially in the direction of the longitudinal axis Y and having a rounded, ball-like end, which substantially at the bearing portion 5a is guided.

The section 12a has a rectangular configuration in cross-section (as does the section) 12 in the first embodiment), so that it, in particular from 8th becomes clear in the polyethylene use 4a rotatably guided. In other words, the width of the section corresponds 12a essentially the width of the polyethylene insert 4a ,

The tibia part 2a includes a support plate 14a for a sliding plate 15a made of polyethylene. To the support plate 14a closes an approach 16a on, which is a cylindrical recess 17a in which the cylindrical portion 18a of the coupling pin 11a pivotally engaged.

At the bottom of the neck 16a is a recess 19a with an internal thread 25a formed into a section 20a with external thread 26a an anchoring part 21a can be screwed. If an anchoring part 21a is not needed, this recess can be closed by a screw. The approach 16a becomes with the anchoring part 21a connected before surgery and both parts are used together. A polyethylene insert 27a is between the lower end 18a of the coupling pin 11a and the anchoring part 21a intended.

Claims (6)

Knee joint prosthesis comprising a tibial plateau portion with an anchoring portion in the bone and a support plate for a slide plate made of plastic and / or a femur part with a resting on the slide articulation surface part, wherein the tibial plateau part and the femur part via an axially displaceable coupling pin with each other are connectable, which is mounted in the tibial component about a vertical axis and in the femoral part horizontally pivotable, characterized in that the femoralitige end of the coupling pin ( 11 ) is rectangular in cross-section and a bearing approach (flexible disc 12 ), which in a fixable in the femur bearing part ( 4 ), which has a corresponding rectangular cross-section and a circular section-shaped bearing section ( 5 ), wherein the tibiaseitige part of the coupling pin ( 11 ) is cylindrical and the sliding plate ( 13 ) and support plate ( 14 ) passing through into a corresponding recess ( 17 ) one with the support plate ( 14 ) ( 16 ) intervenes. Knee joint prosthesis according to claim 1, characterized in that the femurseitige bearing part ( 4 ) a box-like coupling shaft ( 3 ), in which a plastic, in particular polyethylene insert ( 4 ' ), in which the bearing section ( 5 ) is trained. Knee joint prosthesis according to claim 2, characterized in that the coupling shaft ( 3 ) with an expansion sleeve ( 8th ) is connectable. Knee joint prosthesis according to claim 2, characterized in that the coupling shaft ( 3 ) with the articulation surface part ( 9 ) connected is. Knee joint prosthesis according to claim 1, characterized in that the neck ( 17 ) of the support plate ( 14 ) to an anchoring part ( 21 ) and by means of a at the upper end of the anchoring part ( 21 ) formed threaded hole ( 23 ) and through the recess ( 17 ) screw ( 24 ) is connectable with this. Knee joint prosthesis according to claim 5, characterized in that the anchoring part ( 21 ) has a cone-shaped upper portion ( 20 ) and the approach ( 16 ) of the support plate ( 14 ) a corresponding conical lower recess ( 19 ).