DE4434806A1 - Prosthesis for knee joints - Google Patents

Abstract

The prosthesis has a femur part (1) which comprises a housing type of coupling component (3) with a polyethylene insert (4) fixed within it, which has a bearing section (5) with straight sides and a load bearing tangential section (6). The coupling component is connected by screws (7) with an insert sleeve (8) which acts to implant the device in the femur. An articulation component (9) has two curved articulation faces (10) which extend on either side of the coupling. A square section coupling pin (11) with a ball joint (12) locates within the correspondingly square shaped bearing section of the coupling component. The tibia part (2) comprises a support section (14) on which is moulded a polyethylene sliding face (15) for the articulation component and an extension (16) with a conical bore (19) at its lower end. An anchor component (21) is secured in the conical bore with a screw thread (23).

Description

The invention is directed towards a prosthetic knee joint 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 part of the articulation surface resting on the sliding plate, the Tibial plateau part and the femoral part via an axially displaceable Coupling pins are connected to each other, which in the tibia part a vertical axis and horizontally pivoted in the femoral part is.

The goal of a complete knee replacement with a prosthesis is restore the function of the joint as much as possible. Here must be the kinematics and biomechanics of the roll-slide rotation be taken into account. A knee joint prosthesis must prove this reconstruction process and the stress caused by tilting, Thrust and rotation without damage to the bone bed and for the cape catch the belt apparatus.

For this purpose, prostheses are known in which the tibia-plateau part and the femur are not coupled. These prostheses or artificial joints are on the operational maintenance, the physiological tension and thus on the undisturbed function of the entire capsular ligament apparatus. Overstressing individual parts of the belt guide occurs band insufficiencies, instabilities and consecutive prostheses are not uncommon loosening up. The ligaments of the knee joint are also advanced tener destruction preoperatively often so inoperative that instabilities  and the failure of the artificial joint is already predetermined. Most of time force the size and shape of the artificial joints to partial resections of the central Band shares, so that then the shear stress by the Kunstge steering is not caught with sufficient certainty. Despite this systembe The disadvantages of uncoupled joints are certain for certain Use cases, especially if functionality is still available of the capsular ligament apparatus, sometimes preferred because of a relatively natural one Movement is possible.

On the other hand, coupled articulations are known, such as z. B. in the generic DE 41 02 509 A1 are described. Known such Prostheses may not be very complicated th, physiologically predetermined roll-slide-rotary movements of the knee kes follow, so that with each step the coupling of the joint to one temporally and locally punctual loading of the anchorage and thus too Overloads. This also loosens the implant conditional parts.

From the foregoing it follows that both coupled and un Coupled joints have certain advantages and disadvantages with the greater or lesser degrees of freedom of the two joint types connected are.

Proceeding from this, the object of the invention is a prothe to create a system that is not a coupled or uncoupled system is executed and accordingly the surgeon gives freedom, considering all the boundary conditions of the individual case to select the joint that appears to be optimal. Beyond that the joint can be assembled from individual components, so that the Operator on the selection of a coupled or uncoupled system also has the option of a whole or partial joint sentence, regardless of the medical decision of the Operators can always work with the same components, so that a rational production of the same in large quantities possible is.  

This object is achieved in that the femur End of the coupling pin is rectangular in cross section and has a bearing approach, which is anchored in the femur res engages bearing part, which has a corresponding rectangular Cross section and a corresponding circular segment-shaped bearing section. This bearing section can become tangential Connect the stop section, which is in the extended state of the knee Stop and abutment serves to absorb force.

The embodiment of the invention realizes a ho horizontal swiveling movement according to the bending movement of the knee allows steering, the coupling pin simultaneously in the bearing cut is rotatably mounted with respect to a vertical pivot axis. On the other hand, it is possible for the femur part designed in this way also without To use coupling pins with full functionality.

In a further embodiment of the invention it is provided that the femur side bearing part has a housing-like coupling shaft, in which chem a plastic, in particular polyethylene insert is arranged in which the bearing section is formed. It is accordingly on the one hand technically easy to work out the shapes of the bearing part, and on on the other hand, an optimal sliding behavior between the coupling pin and La to achieve no recess.

It is advantageously provided that the coupling shaft with an expansion sleeve se is connectable, the connection through from the inside of the Coupling shaft brought in screws can be realized. The The expansion sleeve is used to anchor the bone in the femur.

The coupling shaft can in turn be connected to the articulation surface be connected, which in turn is the use of the femur Part of the prosthesis also possible without a coupling pin.

In a further embodiment of the invention it is provided that the tibiasei term part of the coupling pin is cylindrical and the sliding plate and  Carrying plate penetrating into a corresponding recess in a the support plate connected insert engages. This is a ver binding that enables a swiveling movement. Although the coupling pin in the femur-side bearing section itself rotatably intervenes, can be limited by the formation of bevels Possibility of pivoting, for example +/- 4 °, also provided on the femur side his.

The base plate is advantageously attached to an anchoring part attachable and by means of one at the upper end of the anchoring part formed threaded hole and one inserted through the recess Screw connectable with this.

Finally, it can be provided that the anchoring part has conical upper section and the approach of the support plate a corresponding conical lower recess so that when tightening the screw is under tension.

From a medical point of view, the configurations described above lead to the following, summarized options:

A knee joint prosthesis is initially used as a pri in 80% of all indications implanted in prosthesis. As already explained at the beginning, assume that in patients under 75 years of age the capsular ligament apparatus is still essentially functional.

In 20% of the indications for artificial knee prostheses are precautionary rigid axis-guided knee prostheses are used. The corresponding Caution arises from the fear that in older patients over time, d. H. within a period of 2 to 5 years, the capsular ligament apparatus is becoming increasingly inadequate and a so-called "Schlotter knee" arises, which leads to failure of the knee joint. It a rigid knee joint prosthesis is used for precautionary reasons set, although this is not yet mandatory at the time of the operation would be offered.  

According to the conventional state of the art, the clinician had to choose len between a hinge knee prosthesis in the form of a rigid, axially guided knee joint, a rotating knee prosthesis, one Axis-guided hinge knee joint with lateral rotation movement is seen, and a knee joint prosthesis with a firmly cast-on guide sign.

The disadvantage of these known knee joint prostheses is that that once a selection regarding a particular type of prosthesis must be met without subsequent correction options stand. Exactly this limitation is with the Ent invention winding eliminated.

According to the invention, a knee joint prosthesis is provided which can be used as a primary prosthesis and on the other hand with few additional parts as a modular revision knee prosthesis inter can be expanded operationally without problems.

For example, if the surgeon is looking for an uncoupled prosthesis decides and cemented both components firmly and then with the trial reduction of the knee joint reveals that the capsular ligament device does not have the desired stability, so far only existed Possibility to increase the platform sliding surface and thus the band structure better preload. This has the disadvantage of being a leg extension occurs and the joint gap is pulled apart, which causes increased thrust and shear forces.

In contrast, the configuration according to the invention makes it possible to on the one hand, both fixed cemented components without changing let and starting with an emerging insufficiency the capsule apparatus with a box chisel the place for the coupling chisel shaft, then the pre-assembled coupling mechanism inserted and with a clamping screw using a Screwdriver is clamped with a torque limiter. After the one Bring the polyethylene insert into the coupling pin into the tibia  plateau inserted, the plateau sliding surface pressed in again and that Knee joint retracted.

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

In addition to the situation described above, it is also possible that the knee joint prosthesis is implanted as a primary prosthesis and only after Several years of wearing it is found that the capsular ligament apparatus has become so insufficient that a revision operation is undertaken must become.

Because of the configuration according to the invention, it is then possible that Open knee joint and, as with the intraope described above corrective correction, with the box chisel space for the coupling shaft to create and use the coupling mechanism.

The advantage is thus achieved that a stable one with only a few interventions Knee joint function can be established, it is also possible Optional replacement of femoral or tibial components. All components fit due to the modular design according to the invention to each other.

In contrast, in such a situation, a prosthesis must be used state of the art of the surgeon possibly stuck compo Tear out what you always want to avoid, and an axis implant the guided hinge joint. This makes it a big operation required, as such, and by becoming completely necessary new knee prosthesis, considerable costs.

In contrast, in the solution according to the invention there is only an onset of Coupling modules required.

From the above it is clear that the core of the fiction Appropriate solution is that a primary knee prosthesis for ver  is provided in every situation, i.e. intraoperatively or too any later time, as a coupled prosthesis modular can be continued without having to explant fixed implants sen. This saves time and money and the prothe Changing the sen is much more bearable for the patient.

In the following the invention is illustrated by a preferred embodiment game described in connection with the drawing. Show:

Fig. 1 shows a part-sectional view of a prosthesis assembly according to the invention,

Fig. 2 is an opposite order Figure 1 rotated through 90 ° sectional view.,

Fig. 3 is a Fig. 1 corresponding sectional view of the prosthesis to 118 ° abgewin kelten according to the invention,

Fig. 4 is a Fig. 1 corresponding sectional view of the 4 ° hyperextension th prosthesis,

Fig. 5 and 6, Figs. 1 and 2 are corresponding views without coupling pin FIG.

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

FIG. 9 shows a representation corresponding to FIG. 7 (reduced) in the manner of an exploded representation.

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

The femur part 1 is formed by a housing-like, a Ausneh definition defining coupling shaft 3 , in which a polyethylene insert 4 is arranged, which has a bearing section 5 . The bearing section 5 is formed in this embodiment in the form of a circular section, with a serving as a stop and force transmission surface Tan potential section 6 .

The coupling shaft 3 is connected via screws 7 to an expansion sleeve 8 , which is used for implantation in the femur. With the coupling shaft 3 , an articulation surface part 9 is connected, which has two curved articulation surfaces 10 , which extend on both sides of the coupling shaft.

In the bearing section 5 engages a coupling pin 11 , which has at its upper end a kind of joint ball 12 , which corresponds in its Krümmungsra dius with the circular section-shaped bearing section 5 and to which a tangential section 13 connects, the course of which approximately the tangential section 6 in the connection speaks to the storage section 5 ent.

The tibia part 2 comprises a support plate 14 for a slide plate 15 made of polyethylene. An attachment 16 adjoins the support plate 14 and has a cylindrical recess 17 , into which a cylindrical lower section 18 of the coupling pin 11 engages in a form-fitting, pivotable manner.

On the underside of the extension 16 , a conical recess 19 is formed, into which a conical section 20 of an anchoring part 21 engages with anchoring ribs 22 which are star-shaped in cross section.

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

FIGS. 3 and 4 illustrate the movement possibilities of he inventive prosthesis assembly with the coupling pin 11, whereas the Figs. 5 and 6 show that the most important components in particular the manufacture technically complex articulating surface portion corresponding to the free choice of the surgeon can be used 11 without coupling studs.

In the second embodiment shown in FIGS . 7 to 9, 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 1 a is formed by a cross-section substantially L-shaped coupling shaft 3 a, in which a cross-section also approximately L-shaped polyethylene insert 4 a is arranged, which has a bearing section 5 a. The bearing section 5 a is not circular section-shaped in this embodiment, but open to one side, in the drawing on the left, so that not a fixed horizontal pivot axis is created for the joint, but to a certain extent also a translatory movement of the Swiveling movement can be superimposed, which simulates the degrees of freedom of a natural knee joint. At the Lagerab section 5 a, a tangential section 6 a joins as a stop and power transmission surface.

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

In the bearing section 5 a engages a coupling pin 11 a, which comprises a cylindrical lower section 18 a and a joint section 12 a, wherein the joint section 12 a is offset relative to the cylindrical section 18 a with respect to the longitudinal axis Y or is designed as an offset, the section 12 a extends after this offset also substantially in the direction of the longitudinal axis Y and has a rounded, ball-like end, which is essentially guided on the La gerabschnitt 5 a.

The section 12 a has a rectangular configuration in cross section (just like the section 12 in the first embodiment), so that, as is particularly clear from FIG. 8, it is guided in the polyethylene insert 4 a in a rotationally fixed manner. In other words, the width of the section 12 a corresponds essentially to the width of the polyethylene insert 4 a.

The tibia part 2 a comprises a support plate 14 a for a slide plate 15 a made of polyethylene. At the support plate 14 a follows a shoulder 16 a, which has a cylindrical recess 17 a, in which the cylindrical portion 18 a of the coupling pin 11 a engages pivotally.

On the underside of the projection 16 a, a recess 19 a with an internal thread 25 a is formed, into which a section 20 a with an external thread 26 a of an anchoring part 21 a can be screwed. If an anchoring part 21 a is not required, this recess can be closed by a screw. The approach 16 a is connected to the anchoring part 21 a before the operation and both parts are used together. A polyethylene insert 27 a is provided between the lower end 18 a of the coupling pin 11 a and the anchoring part 21 a.

Claims (7)

1. Knee joint prosthesis comprising a tibial plateau part with an anchoring section in the bone and a support plate for a sliding plate made of plastic and / or a femur part with an articulation surface part lying on the sliding plate, the tibial plateau part and the femur part via one axially displaceable coupling pins can be connected to one another, which is pivotally mounted in the tibia part about a vertical axis and horizontally in the femur part, characterized in that the end of the coupling pin ( 11 ) on the femur side is rectangular in cross section and has a bearing attachment (joint ball 12 ) which engages in a bearing part ( 4 ) which can be anchored in the femur bone and which has a corresponding rectangular cross section and a bearing section ( 5 ). 2. Knee joint prosthesis according to claim 1, characterized in that the femur-side bearing part ( 4 ) has a housing-like coupling shaft ( 3 ) in which a plastic, in particular polyethylene insert ( 4 ') is arranged, in which the bearing section ( 5 ) is trained. 3. Knee joint prosthesis according to claim 2, characterized in that the coupling shaft ( 3 ) with an expansion sleeve ( 8 ) can be connected. 4. Knee joint prosthesis according to claim 2, characterized in that the coupling shaft ( 3 ) is connected to the articulation surface part ( 9 ). 5. Knee joint prosthesis according to claim 1, characterized in that the part of the coupling pin ( 11 ) on the Tibias side is cylindrical and the slide plate ( 13 ) and support plate ( 14 ) penetrating into a corresponding recess ( 17 ) of an approach to the support plate ( 14 ) ( 16 ) engages. 6. Knee joint prosthesis according to claim 5, characterized in that the extension ( 17 ) of the support plate ( 14 ) can be placed on an anchoring part ( 21 ) and by means of a threaded bore ( 23 ) at the upper end of the anchoring part ( 21 ) and one through the recess ( 17 ) inserted screw ( 24 ) can be connected to this. 7. Knee joint prosthesis according to claim 6, characterized in that the anchoring part ( 21 ) has a conical upper section ( 20 ) and the shoulder ( 16 ) of the support plate ( 14 ) has a corresponding conical lower recess ( 19 ).