DE2728427C2 - Knee joint endoprosthesis - Google Patents

Description

40

The invention relates to a knee joint endoprosthesis according to the preamble of claim, as is known from DE-OS 25 49 819.

In this known knee joint endoprosthesis, the femur part is in the thigh bone with a fastening stem provided, its axis in the vertical, longitudinal center plane of the joint space lay. As a result, the kneecap embedded in the patella ligament was unable to move naturally at the top outside curved inwards and downwards unimpeded.

The object of the invention is therefore to provide the knee joint endoprosthesis of the type mentioned at the beginning to be trained in such a way that the kneecap embedded in the patella ligament can move naturally from above outside must be curved inwards and downwards.

This object is achieved in that the stem of the femur part from the vertical central longitudinal plane of the middle bar of the tibia part between the runners of the femur part to the outside to the outer runners in a perpendicular Level is offset.

This solution ensures that a limited rotational movement of the in each flexion position of the joint Tibiate parts is reached to the femur part corresponding to the healthy knee joint, and that the femur part a can perform limited forward movement in relation to the tibial part, which is also the case in the healthy knee joint is available. Due to the physiological sequence of movements that can be achieved in the prosthesis parts Overstretching of the muscular knee extensor apparatus avoided.

This solution is also used when the clamping straps of the kneecap have elongated and leads to the fact that the patella guideway is practically relocated inwards due to the displacement of the handle is. This means that the kneecap acts as the outer boundary of the guideway through the outer runner pressed inside into the guideway, so that the kneecap has no problem with sideways evasion is led

The invention is explained below with reference to the drawing explained it shows

F i g. 1 the femoral part of a left knee joint prosthesis in side view

F i g. 2 the femur part in top view.

F i g. 3 the femur part, seen in the direction of the arrow yderFig. 1,

F i g. 4 shows a section along line 18 of FIG. 2 or 3.

F i g. 5 the femur part, seen in the direction of the arrow XderFig. 1.

According to DE-OS 25 49 819, there is the femur part a knee joint endoprosthesis from the two runners 136 and 13c sliding on the tibia part, the are bridged by the front part of a bridge 14 with a flat surface. Those facing each other Surfaces of the runners 136 and 13c are provided with guide grooves 15 open at one end for engagement a guide pin of the tibia part is provided, as can be seen from DE-OS 25 49 819

The front part of the bridge 14 and the front parts of the runners 136 and 13c form the guideway for the nichr. shown kneecap.

To match the kneecap movement to the natural kneecap movement coming from the top outside takes place arcuately downward and inward, the stem 6 is in the thigh bone with its axis the vertical longitudinal plane 17 of the central web, which is laid through the joint gap 16 from front to back, is somewhat arranged offset to the outside to the outer runner 13c in the vertical plane 18. Since now the inner Femur part 136 is at a greater distance from axial plane 18 than outer femur part 13c. can the Kneecap on the front surface of the bridge 14 and the front surface of the two runners 136 and 13c of FIG slide above outside arcuately downward and inward into the joint space 16, so that the natural Movement of the kneecap is achieved and thus a lateral evasion and strains of the kneecap ligament or increased wear and tear can be eliminated.

For this purpose 2 sheets of drawings

Claims (1)

Claim: Knee joint endoprosthesis, consisting of a tibial part to be anchored by a stem with a central bar and fluted sliding surfaces on both sides of this, and a femoral part (2) also to be anchored by a stem, which is supported by two runners (13 , 13a, 136, 13c) , the tibia and femur part (2) being movably connected to one another by a pin lying transversely to the bar eccentrically to the tibial stem, which is eccentrically against the curvature of the sliding surface (12) backwards in the bar in its longitudinal axis is inserted so that the ends of the pin approximately parallel to the 'internal runner surface, at the rear end upwardly open guide grooves (15) engage in the runners (136, i3c) with play and that the web and the distance between the runners (136,13c, l are designed to be wider towards the rear, characterized in that the stem (6) of the femoral part (2) from the vertical middle length ngsplane (17) of the central web of the tibia part between the runners (136, 13c) of the femoral part (2) is offset outwards to the outer runner (13ς) in the vertical plane (18).