WO2003028586A2

WO2003028586A2 - Endoprosthesis for a knee joint

Info

Publication number: WO2003028586A2
Application number: PCT/CH2002/000483
Authority: WO
Inventors: Willi Horber; André Bähler
Original assignee: Willi Horber; Baehler Andre
Priority date: 2001-09-28
Filing date: 2002-09-03
Publication date: 2003-04-10
Also published as: EP1432365A2; WO2003028586A3

Abstract

According to the invention, two guideways (13, 33), which co-operate with a guide body (21, 41) for guiding a sliding displacement between a tibia platform (11) and an intermediate plate (49) lying on the latter, permit the bearing part (49) to be introduced into the tibia platform (11) in two insertion positions. In a first insertion position (fig. 2) for a knee joint with intact cruciate ligaments, the guideways (13, 33) and guide body (21, 41) permit both a translational and a rotational displacement of the bearing part (49) on the tibia platform (11), whereas in a second insertion position (fig. 1) for a knee joint comprising incapacitated cruciate ligaments, only a rotation of the bearing part (49) is possible.

Description

Endoprosthesis for a knee joint

The invention relates to an endoprosthesis for a knee joint according to the preamble of claim 1, with a femoral joint part which has condylar skids and fastening means for anchoring the femur joint part in the femur, a tibia part which has a tibia plateau and fastening means for anchoring the tibia part in the tibia the tibial plateau on which the bearing part slidably lies, which has concave bearing shells for receiving the sliding runners of the femoral joint part, and cooperating guides on the tibial plateau and bearing part, for guiding the sliding movement of the bearing part on the tibial plateau.

When the healthy knee flexes, the femoral condyles on the articular surface of the tibial plateau shift from ventral to dorsal as a result of a translational movement guided by the cruciate ligaments. In addition, there is also the possibility of increasing rotation of the tibia about its longitudinal axis in the knee joint, which is blocked by the tension of the cruciate ligaments when the knee is extended.

If the cruciate ligaments, in particular the posterior one of a knee joint to be replaced by a prosthesis, are still functional, it is advantageous to use such a prosthesis that allows both a translational and a rotational movement. In the case of inoperative cruciate ligaments, however, the translation movement can no longer be controlled. It is then advisable to use a prosthesis that does not have the option of translation and only allows a rotational movement in addition to the flexion and extension function.

In both cases, modern prostheses have a bearing body which is guided on the tibia part so as to be able to articulate the femoral part of the joint prosthesis. The tibia part and the femoral part can be identical in both cases. This enables both parts to be implanted in the corresponding bones in advance and only then to decide on the basis of the ligament condition which type of function, translation and rotation, or just rotation, is most suitable for the patient. The disadvantage of such known prostheses is that for the two types of function Different guides are provided, which not only require two different bearing parts but also an additional guide part in the tibia part for the type of function that allows translation and rotation.

It is therefore an object of the invention to propose a knee joint prosthesis in which both types of function are possible without different bearing parts, each with a different type of guide and without an additional guide part on the tibia part for translation.

This object is achieved according to the invention by the characterizing features of patent claim 1, namely in that the one, unchangeable guide on the tibia part interacts with two selectable guides of the bearing part in such a way that, in a first position of use, the first guide of the bearing part only has a first function, namely translation and rotation of the bearing part about a first axis of rotation, which is directed perpendicular to the tibial plateau, and that in a second position of use, the second guidance of the bearing part only a second function, namely only one rotation of the bearing part relative to the tibia part about a second axis of rotation, which is perpendicular facing the Tibial Plateau.

The two different guides on the bearing part can be arranged side by side or one behind the other or overlapping in areas. It is also possible to design the guide parts in such a way that they are arranged in two use positions rotated by 180 degrees with respect to one another.

In principle, it is possible to design the outer (outline) shape of the bearing part as well as the arrangement and configuration of the bearing shells on the top of the bearing part independently of the respective position of use. However, it is also possible to form a purpose-specific design of the top side on two different bearing parts, but with the same guide arrangement on the underside, depending on the respective use position. The location of the first axis of rotation with respect to the tibia part advantageously coincides with the location of the second axis of rotation. This is the case at least in the flexion position of the knee.

The first axis of rotation can be displaceable together with the translation movement. However, it can also be immovable and remain in the same place during a translation.

The direction of the translational movement can be independent of the rotational position of the guide on the bearing part with respect to the guide on the tibial plateau. However, it can also depend on the rotational position of the bearing part relative to the tibial plateau. The axes of rotation can be arranged on a central axis of the tibia part extending from anterior to posterior, as well as outside of such.

For guiding the translation, two parallel legs are advantageously provided in one guide at a distance of 2R and in the other guide a guide body with at least two concentric circular sections with radius R, which cooperate with the guide legs.

For guiding the rotation, a convex circular path in one guide and a concave circular guide cooperating with the circular path in the other guide are advantageously provided, which cooperate over at least one angular range to the extent of the rotational latitude desired for the prosthesis. The guide body advantageously has the convex circular path.

A boundary track with at least one circular section on a radius S is advantageously present on the one guide, and a boundary guide cooperating with the circular sections of the boundary track at a distance from S to the center of the radius R is present on the other.

Boundary path and boundary guide can be designed such that in the first position, ie when the first function type is activated, translation and Rotation, when the knee is stretched, the rotation is restricted or prevented, similar to the case with a healthy knee.

On a guide part, a first guide surface lying on a rotation surface about a rotation axis lying perpendicular to the tibial plateau and a second guide surface concentrically thereto are advantageously formed. On the other guide part, a third guide surface cooperating with the first guide surface is formed with a radius corresponding to the radius of the first guide surface, and a fourth guide surface interacting with the second guide surface. In both positions of use, this allows rotation about an axis perpendicular to the tibial plateau, which rotation is advantageously guided by the concentric guide surfaces in the flexion position of the joint with a flat support. The rotation can be limited. Between the interacting pairs of contact surfaces, a movement space is advantageously formed in the anterior-posterior direction, which is available in the first position of use, which enables translation and rotation. In the second operating position, which only allows one rotation, this movement space is expediently not available. In the latter case, the two pairs of contact surfaces, each with the play technically necessary for the rotation, are necessarily in contact with one another.

Both pairs of contact surfaces are advantageously formed by a guide track and the lateral surface of a guide body arranged in the guide track. At least one guide track has two parallel guide legs, and the guide body arranged in this guide track has lateral surfaces which interact with the guide track. These lateral surfaces lie on a circular line, the diameter of which corresponds to the distance between the guide legs. In the case of pairs of contact surfaces interacting in the manner of a dovetail or other undercutting or not only cylindrical guide surfaces, more than a single diameter is of course matched to more than a single distance. The guide body and the guideway can be graduated one above the other or integrated into one another. If a second, narrow guideway for the second, smaller guiding body, which is arranged in the first guideway, is formed in a first, larger guiding body arranged in a first wide guideway, the construction height can be minimized, since it only constitutes a single guiding body height.

However, if a second smaller guide body is formed on a first larger guide body and a second narrow guide path for the second guide body is formed in a first wide guide track for the second guide body, the strength of the first guide body is not reduced by a recess incorporated therein.

The guideway having parallel guide legs advantageously has a semicircular closure adjoining these parallel guide legs anteriorly and / or posteriorly. As a result, stop forces occur flat in the end position of the translation. However, the termination can also be straight, ridge-like, polygonal or otherwise suitable.

In order to prevent the bearing part from lifting off from the tibia part, means can be provided, e.g. a dovetail-like or undercut configuration of the interacting pairs of contact surfaces, or roofs arranged on the outside or similar suitable devices.

Advantageous embodiments emerge from the subclaims and the exemplary embodiments shown only schematically. It shows

Figure 1: a first embodiment with a guide body in the

Rotational position used in a guideway, Figure 2: the first embodiment with the guide body in the translational position used in the guideway and in the extension position,

Figure 3: the first embodiment with the guide body in the

Translation position used in the guideway and in flexion position, FIG. 4: a second exemplary embodiment with a guide body in the translation position inserted in a guide track and in the extension position,

FIG. 5: the second exemplary embodiment with the guide body inserted in the translation position in the guide track and in the flexion position,

FIG. 6: the second exemplary embodiment according to FIG. 5, but with a shape variant of the boundary path,

FIG. 7: a third exemplary embodiment with a guide body in the rotational position used in a guide track,

FIG. 8: the third exemplary embodiment with the guide body in the translation position inserted in the guide track and in the extension position,

FIG. 9: the third exemplary embodiment with the guide body inserted in the translation position in the guide track and in the flexion position,

FIG. 10: a fourth exemplary embodiment with a guide body in the rotational position used in a guide track,

FIG. 11: the fourth exemplary embodiment with the guide body inserted in the translation position in the guide track and in the extension position,

FIG. 12: the fourth exemplary embodiment with the guide body inserted in the translation position in the guide path and in the flexion position,

Figure 13: a fifth embodiment with a second guideway incorporated into a first guideway, the guide body being inserted in the flexion position of the translation position.

FIG. 14: the sixth embodiment with the guide body in the extension position,

FIG. 15: a sixth exemplary embodiment with a guide body, the shape of which deviates from the circular shape,

FIG. 16: a seventh exemplary embodiment with a guide body deviating from the circular shape with a guide track incorporated therein,

FIG. 17: a view of an endoprosthesis with a guide track formed in the guide body, Figure 18: a view of an endoprosthesis with stepped one above the other

Guideways, Figure 19: an eighth embodiment with the bearing part in the rotational position, Figure 20: a ninth embodiment with the bearing part in the rotational position, Figure 21: a tibia plateau in supervision, with a single guide pin, suitable for the bearing parts according to Figures 22 and 26, 22: a bearing part with two guides arranged one behind the other in the anterior-posterior direction, FIG. 23: a tibial plateau with an eccentric guide pin, FIG. 24: bearing part with two guides arranged side by side, FIGS. 25 and 26: tibial plateau and the associated bearing part of another

Embodiment Figures 27 and 28: Tibial plateau and bearing part with inserted in the bearing part

Limiting part.

1 to 12, 16 and 17 show a first type of exemplary embodiment in which an outer guideway 13, 33 interacts with a large guiding body 21, 41 in which an inner guideway 33, 13 is recessed, which has a smaller one Guide body 41.21 cooperates. Under

Guideway is understood to mean a guide with mutually facing guide surfaces, by a guide body a guide with mutually facing guide surfaces.

In each of these exemplary embodiments, a guide track 33, 13 is arranged within a guide body 41, 21, which is guided in a guide track 13, 33 that limits the relative movement between the bearing part and the tibial plateau 11. One guideway is also referred to below as boundary path 13 because it limits the movement guided by the other guideway. The limiting path 13 interacts with a guide body, which is accordingly called the limiting body 21 below. In the top view, anterior or ventral is shown at the bottom and posterior or dorsal at the top.

Figures 1 to 3 show a first embodiment. In a tibial plateau 11, a recess 17 forming a boundary path 13 is formed, which is circular and whose center coincides approximately with the center of the tibial plateau 11 and has a first radius 15. A limiting body 21 is movably arranged within the limiting path 13 forming the edge of the depression 17. This is horseshoe-shaped with a circular section with a second radius S as the outer contour surface 23, and a semicircle 27 with a third radius R and then two parallel legs 31 as the inner contour line. The inner contour surface of the horseshoe-shaped limiting body 21 forms a guide track 33 for a guide body 41. The guide body 41 has a circular outline. The lateral surface 45 of the guide body 41 lies on a fourth radius 43, which corresponds to the third radius R of the guide track 33 with the tolerance required for sliding. The guide body 41 is arranged in a stationary manner with respect to the boundary track 13 on the tibial plateau 11.

The outline of a bearing part 49 is shown elliptically and dotted. This bearing part forms a meniscus part displaceably arranged on the tibial plateau 11, on the underside of which the limiting body 21 is arranged in a stationary manner. Opposing the limiting body 21, the bearing shells interacting with the femoral condyles are formed on the upper side of the bearing part 49 or on this articulation body.

In FIG. 1, the limiting body 21 is inserted into the limiting path 13 in a first position. In this position, it can be rotated about the center 29 of the fourth radius 43 and, depending on the angle of rotation, can be displaced by a small amount parallel to the legs 31 up to the limiting path 13. In a region relevant to the rotation of the knee around the central position of the limiting body 21 shown in FIG. 1, this displacement is negligible. In FIG. 2, however, the limiting body 21 is inserted into the limiting path 13 rotated by 180 degrees and consequently has a displaceability, the extent of which relative displacement the articulation surfaces of the natural knee involved in flexion and extension is simulated. This displacement is shown in FIGS. 2 and 3. FIG. 3 shows the position of the limiting body 21 in the limiting path 13 during flexion, in which a rotation about a rotation axis directed perpendicular to the tibia plateau 11 and passing through the center 29 of the fourth radius 43 is possible without hindrance. FIG. 2 shows the position at extension in which rotation is prevented or is only possible together with a posterior translation. The boundary path 13 and the outer contour surface 23 of the boundary body 21 form a first contact surface pair 51 which limits the movement, but which also acts as a leader during rotation. The guide track 33 and the outer surface 45 of the guide body 41 form a second pair of contact surfaces 53 guiding the movement.

Figures 4 and 5 show a second embodiment. In this case, a first pair of contact surfaces 51 is formed between the edge of the depression 17, which, as in the first exemplary embodiment, forms a boundary path 13, and the contour surface 23 of the boundary body 21. The delimitation body 21 has a circular contour surface 23. The delimitation path 13 is an oval with a longitudinal direction anterior-posterior. The oval is somewhat wider than the diameter of the limiting body 21. An oval guideway 33 with parallel legs 31 is formed in the interior of the limiting body 21, in which a circular guiding body 41 with a diameter which corresponds to the width of the oval of the guideway 33 is arranged , The lateral surface 45 of the guide body 41 is formed concentrically with the posterior semicircle of the boundary path 13. In addition to a translation of the limiting body 21 along its parallel legs 31, this design also enables it to rotate about the center of the guide body 41. In the extended position of the knee (FIG. 4), the limiting body 21 is advanced anteriorly. If the boundary path 13 and the contour surface 23 of the first guide body 21 touch, practically no rotation is possible without simultaneous translation. As the distance between the contact surfaces 13, 23 of the first pair of contact surfaces 51 increases, the range of rotation of the limiting body 21 increases up to the width of the oval of the limiting path 13 in order to be unlimited in the flexion position (FIG. 5). However, if the bearing part 49 and thus the limiting body 21 are inserted into the recess 17 in a position rotated by 180 degrees (not shown), only rotation is possible and translation by the two pairs of contact surfaces 51, 53 is prevented.

FIG. 6 shows a variant of the second exemplary embodiment, in which, however, the boundary track 13 is bulged laterally to create more space for the translation of the boundary body 21 in the rotational position, and has anterior and posterior circular sections 65 that correspond to the radius S of the contour surface 23 of the Boundary body 21 correspond in order to allow a flat contact of the boundary body in the two extreme positions.

A third exemplary embodiment is shown schematically in FIGS. 7 to 9. FIG. 7 shows the use position, which only allows rotation, FIG. 8 the function type translation and rotation in the extension position, FIG. 9 the same, but in the flexion position.

In this third example, a recess 17 is also incorporated, the edge of which, however, does not form a boundary track but a guide track 33. The function of this guideway 33 corresponds to that of the guideway 33 in the first and second exemplary embodiments. A circular delimitation body 21 is arranged in a fixed position in the recess 17. A guide body 41 is movably arranged in the guide track 33 and around the limiting body 21. A limiting path 13 cooperating with the limiting body 21 is formed in this. The function of this boundary path 13 corresponds to that of the boundary path 13 in the first exemplary embodiment. In contrast to the limiting body 21 in the preceding exemplary embodiments, the limiting body 21 is arranged in a stationary manner on the tibial plateau 11, while the guiding body 41 cooperating with the guideway 33 is displaceably mounted.

To put it simply, a first pair of contact surfaces 51 consisting of the boundary track 13 and a surface area 23 of the interacting with it delimits Limiting body 21 the freedom of movement of the bearing part 49 on the tibial plateau 11, while a second pair of contact surfaces 53, consisting of the guide track 33 and the lateral surface 45 of the first guide body 41, guides the movement. For this purpose, the guideway 33 has two parallel legs 31, and the guide body 41 has two opposite circular sections, which cooperate with the parallel legs 31 and lie on a circle with a diameter corresponding to the distance between the legs 31.

In the exemplary embodiment according to FIGS. 7 to 9, the recess 17, the edge of which forms the guideway 33, is worked into the tibial plateau 11 from anterior. The edge of the depression 17 forming the guideway 33 has a semicircle 27 with a radius R dorsally, to which two parallel legs 31 then extend. The outer surface 45 of the guide body 41 cooperating with the guide track 33 has a radius corresponding to the radius R of the guide track 33. As a result, at least two line contacts between the surfaces 31, 33, 45 of this second contact surface pair 53 are ensured, so that a movement of the guide body 41 is always guided.

An oval limiting path 13 is incorporated in the guide body 41, within which the stationary limiting body 21 is arranged. The limiting path 13 could also be circular, for a limitation of the movement of the guide body 41 based on the first exemplary embodiment. Owing to the oval design, the degree of rotation in the almost extension position (FIG. 8) is less than in the case of a circular design of the boundary track 13. The boundary surface of the boundary track 13 can, however, also have other shapes, as is shown with the aid of other exemplary embodiments.

FIGS. 10 to 12 show, as a fourth exemplary embodiment, a kind of reversal of the third exemplary embodiment, in which the depression 17 is open towards the posterior. An advantage of this is the large contact surface arranged anteriorly between the guide body 41 and the guide track 33, which minimizes the surface pressure which is generated by the large thrust forces acting from posterior to anterior, for example when walking up stairs. Since with the simple reversal of the In the third exemplary embodiment, there is no limitation of the rotation in the extension position, but would be present in the flexion position, this limitation is solved differently in the fourth exemplary embodiment. The guide body 41 has an extension 61 projecting beyond the circle radius. A recess 63 corresponding to the extension 61 is provided posteriorly in the guideway 33. The extension and recess can make up part of the depth of the depression 17 or take up the entire depth. In the use position, which only allows rotation, according to FIG. 10, the extension 61 is directed posteriorly and does not hinder the rotation in the area essential for the knee function. In the operating position, which permits translation and rotation, according to FIGS. 11 and 12, with the knee flexed and the guide body 41 displaced dorsally (FIG. 11), the rotation is not impeded by the extension 61, but by the limiting body 21 and the limiting path 13 inside of the guide body 41 limited. In the extension position (FIG. 12), on the other hand, the extension 61 engages in the recess 63 and prevents rotation that would otherwise be possible around the delimiting body 21 which is arranged around the circular and concentric to the semicircle of the guideway 33.

An advantageous fifth exemplary embodiment is shown in FIGS. 13 and 14. In this case, the limiting body 21 is arranged in a stationary manner on the guide body 41. In a recess 17 in the tibial plateau 11, a bore 27 is provided, the cylindrical wall of which forms a boundary track 13 which interacts with the contour surface 23 of the boundary body 21 which is "fish-blown" in one section. The radii of the "fish bubble" and bore 27 correspond to each other. The guide body 41 is circular with a diameter that corresponds to the width of the oval guide track 33 and is guided in the guide track 33. In a flexion position (FIG. 13), the delimiting body 21 and the guiding body 41 are arranged posteriorly and touch the delimiting path 13 or the guiding path 33 posteriorly. In this position, rotation is unimpeded. The contour surface 23 of the boundary body 21 slides along the bore 27 forming the boundary path 13. At the same time, translation from posterior to anterior is possible. In an extreme position with the knee in extension (FIG. 14), the limiting body 21 and the guide body 41 are advanced anteriorly and their contact surfaces 23, 45 are in flat contact with the one hand Boundary path 13 and on the other hand the anterior semicircle of the guideway 33. A flat contact is thus ensured anteriorly and posteriorly.

In the extension position, rotation is not possible, since neither the guide track 33 allows the guide body 41 arranged therein to pivot about the center of the bore 27, nor does the boundary track 13 allow the limit member to pivot about the center of the lateral surface 45 of the guide body 41. In a middle position between the extension position and the flexion position, however, rotation about the center of the guide body 41 is possible, since the longest dimension of the fish-bubble shape of the limiting body 21 is shorter than the diameter of the bore 27.

However, if the guide body 41 and the delimitation body 21 are rotated by 180 degrees, the contour surface 23 of the delimitation body 21 that is present anteriorly on the delimitation surface 13 prevents translation in the anterior direction.

FIGS. 15 and 16 show a sixth and seventh exemplary embodiment. These prove that the boundary path 13 does not have to have circular shapes. The desired functions can still be reached. In FIG. 15, which shows the first position of use for translation and rotation, a depression 17 is embedded in the tibial plateau 11 with two rectilinear edges which converge from posterior to anterior and serve as a delimitation path 13. In this recess 17, an elongated hole 27 is made, in which a circular guide body 41 is guided. This is arranged on a delimitation body 21, the contour surface 23 of which has circular sections 71 which are concentric with the lateral surface 45 of the guide body 41 in order to allow rotation, and in some cases has straight-line sections 73 which, in an extension position, touch the delimitation track 33 flatly. However, if the guide body 41 together with the limiting body 21 is inserted rotated by 180 degrees, then the circular section 71 of the limiting body 21 touches the limiting path 13 and the guide body 41 is in contact with the guide path 33 posteriorly, so that only rotation is possible. In the seventh exemplary embodiment according to FIG. 16, which shows the second operating position, which only allows rotation, the guide body 41 is arranged within a guide track 33 formed in the limiting body 21 and stationary in the recess 17. Here a similar geometry of the first contact surface pair 51 is possible as in the sixth exemplary embodiment. In contrast to this, however, in the seventh exemplary embodiment, the circular section 71 of the contour surface 23 is arranged concentrically to the semicircle of the oval guideway 33 in the limiting body 21.

17 and 18 show two basic configurations of the tibial plateau 11 and the bearing part 49. Figure 17 corresponds in principle to a front view of the exemplary embodiments of FIGS. 1-12 and 16, in which a guide body 41 is arranged in a fixed manner in the tibia plateau in the depression 17, while the limiting body 21 has a recess 75 on the underside of the bearing part 49 Edge forms the guideway 33 and receives the guide body 41. The reversal of the boundary path 13 and guideway 33 is also possible here. The guideway and guide body are dovetail-shaped to prevent the bearing part from lifting off the tibia part. In the bearing part 49, bearing shells 85 are embedded on the upper side, which articulate with the condylar skids 83 of the femoral joint part 84.

FIG. 18 essentially corresponds to a front view of the exemplary embodiments from FIGS. 13-15, in which a bore 27 is made in the recess 17 receiving the guide body 41, which receives the limiting body 21 which is arranged in a stationary manner on the guide body 41. Alternatively, the boundary track 13 can also be formed by the edge of the depression 17, the guide track 33 then being formed by the edge of the bore 27.

FIG. 18 also shows that the bearing shells 85 for receiving the condylar skids 83 can be formed in separate articulation bodies 81. These articulation bodies are then let into the bearing part 49 and are not displaceable relative to the latter. In order to prevent the bearing part from lifting off, hook-shaped projections 19 of the tibial plateau 11 grip the lateral edge of the bearing part 49 on the left and right. FIG. 19 shows an eighth exemplary embodiment in which the bearing part 49 is designed in the form of glasses and a web 91 with two concentric edges connects the two bearing shells 85 around a circular guide body 41. The inner concave circular path is part of the guideway 33 with two parallel legs 31. The outer convex circular path forms the boundary path 13, which together with a peg-like boundary body 21, which can also have a different shape, prevents displacement in the dorsal direction and rotation limited by end stops 93.

FIG. 20 shows a ninth exemplary embodiment which likewise has both a guide track 33 and a limiting track 13 on the bearing part 49, which each cooperate with a guide body 41 or limiting body 21 protruding like a pin from the tibial plateau 11. While the limiting body 21 is arranged dorsally in the ninth embodiment, it is arranged ventrally in the tenth.

Both the eighth and the ninth exemplary embodiment have the advantage that the tibial plateau 11 has no depression 17, which simplifies production, since the guide body 41 and the limiting body 21 can be inserted subsequently. In both exemplary embodiments, the bearing part can be used in an operating position rotated by 180 degrees. In contrast to the illustration, translation is possible.

A tibial plateau 11 with two matching bearing parts 49 is shown schematically in FIGS. 21, 22 and 24. The tibial plateau 11 has a cylindrical, circular guide pin 41 which fits from below into a guide 33.95 in the bearing part 49. In the bearing part 49 according to FIG. 22, two different guides 33, 95 are arranged one behind the other. The rear guide 95 has a concave circular path, which encompasses an angular range of well over 180 degrees and thus forms a rotational guide together with the guide pin. The front guide 33 has a translation guide with two parallel guide legs 31. The guide pin 41 can either be engaged with the rear guide 95 to inhibit translation, or it can be engaged with the front guide 33 to allow translation. The guides 33.95 are on a central axis of the bearing part 49.

24, the guides are arranged side by side on one side of the central axis. The guideway 33 does not necessarily have to run parallel to the central axis, but can also converge towards it, and one of the guides can also be arranged on the central axis.

A tibial plateau 11 with an eccentrically arranged guide pin 41 is shown in FIG. This is advantageous if the bearing part of FIG. 24 is in two mirror-image versions with respect to the arrangement of the guides. The function type (rotation and translation, or only rotation) can then be selected with the corresponding mirror-image bearing part.

FIGS. 25 and 26 show a further exemplary embodiment with a tibia plateau 11 and a bearing part 49 to be arranged thereon. The two guides 33, 101 in the bearing part 49 are arranged one inside the other. In contrast to the bearing part according to FIG. 22, two different guides are also provided on the tibia plateau 11 for the two function types. In a guide body 41 with a circular, cylindrical shape there is a bore 99 which can cooperate with a pin 101 in the bearing part. The pin 101 is arranged within the guideway 33 in the bearing part 49. In one insert control, the pin 101 engages in the bore 99 and thus prevents the translational movement, while together with the bore 99 it guides the rotational movement. In the other insert control it is arranged dorsally of the guide body 41 and limits the translational movement. The bore 99 is not arranged centrally in the guide body 41, but is offset to the rear. As a result, the control unit in which translation is prevented almost corresponds to the other control unit in flexion control.

A final exemplary embodiment is shown in FIGS. 27 and 28. A strong guide pin 41 is arranged on the tibia plateau 11. In the storage section 49 is a guide track 33 with two paraUelen guide legs 31 and two semicircular terminations excluded. In the guideway 33, the guide pin 41 is translationally displaceable. So that this translation can be prevented, a limiting part 103, on which the limiting path 13 is arranged, can be inserted into the bearing part 49 or into the translation guide 33. This shortens the guideway 33 to a circular rotation guide 95.

Claims

claims

1. Endoprosthesis for a human knee joint, with

a femur joint (84), which has condylar skids (83) and fastening means for anchoring the femur joint (84) in the femur,

a tibia part (12), which has a tibia plateau (11) and fastening means for anchoring the tibia plate (12) in the shin,

a bearing part (49) slidably resting on the tibia plateau (11), which has concave bearing shells (85) for receiving the sliding runners (83) of the femoral joint part (84),

- And cooperating guides on the tibial plateau (11) and bearing plate (49), for guiding the sliding movement of the bearing plate (49) on the tibial plateau (11), characterized in that the one guide on the tibial plate (12) with two selectable guides for the bearing plate (49 ) interacts in such a way that, in a first function, a first guide (33, 45) of the bearing part (49) both translates and rotates the bearing part (49) about a first axis of rotation directed perpendicular to the tibia plateau (11) with respect to the tibia part (12 ), and that, in a second function, a second guide (13, 23, 95, 101) of the bearing part only rotates the bearing part (49) relative to the tibia part (12) by a second one

Rotation axis allowed, which is directed perpendicular to the tibia plateau (11).

2. Endoprosthesis according to claim 1, characterized in that for the second type of function, a limiting path (13) is arranged on a limiting part (103) which can be inserted into the guideway (33).

3. Endoprosthesis according to claim 1, characterized in that two guides (13, 33, 95) are formed on the same bearing part and the guides on the bearing part (49) interact differently with the guides on the tibial plateau (11) in two different insert control units, in such a way

that both a translation and a rotation about a first axis of rotation, which is directed perpendicular to the tibial plateau (11), are carried out in the first operational control, - And that in the second operational control a translation is prevented and a rotation is guided around an immovable second rotation axis, which is directed perpendicular to the tibial plateau (11).

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4. Endoprosthesis according to one of claims 1 to 3, characterized in that two guides on the Lagerteü (49) are arranged one behind the other.

5. Endoprosthesis according to one of claims 1 to 3, characterized in that two guides on the Lagerteü (49) are arranged side by side.

). Endoprosthesis according to one of claims 1 to 3 in conjunction with claim

5, characterized in that, for the selection of the function type, two guides on the bearing part (49) are arranged on two different bearing parts mirror-image to one another.

Endoprosthesis according to one of claims 1 to 6, characterized in that the guides on the bearing part (49) are overlapped in regions overlapping.

8. Endoprosthesis according to one of claims 1 to 3, characterized in that the one guide on the bearing part (49) is arranged within the second guide available on the bearing part.

9. Endoprosthesis according to one of claims 1 to 8, characterized in that one of the two types of functions in each of one another in one of two

180 ° rotated use positions of the bearing part (49) is effective.

10. Endoprosthesis according to one of claims 1 to 9, characterized in that a limiting path (13) is present which allows the first function in the first operational control of the bearing element (49) and in the second

Operational control only allows the second type of function.

11. Endoprosthesis according to claim 10, characterized in that the limiting path (13) is closed.

12. Endoprosthesis according to claim 10, characterized in that the limiting path (13) is open anteriorly and / or posteriorly.

13. Endoprosthesis according to one of claims 1 to 3, characterized in that the location of the first axis of rotation with respect to the tibia (12), at least in the flexion control of the knee, coincides with the location of the second axis of rotation.

14. Endoprosthesis according to one of claims 1 to 13, characterized in that the first axis of rotation is displaceable together with the translational movement.

15. Endoprosthesis according to one of claims 1 to 13, characterized in that the first axis of rotation is immovable.

16. Endoprosthesis according to one of claims 1 to 15, characterized in that the direction of the translational movement is independent of the rotational position of the

Guided tour on the camp (49) with regard to the guided tour on the tibial plateau (11).

17. Endoprosthesis according to one of claims 1 to 15, characterized in that the direction of the translational movement is variable with a rotation of the bearing part with respect to the tibial plateau (11).

18. Endoprosthesis according to one of claims 1 to 17, characterized in that the axes of rotation are arranged perpendicularly on a central axis of the tibial plateau (11) extending in the direction of anterior-posterior.

19. Endoprosthesis according to one of claims 1 to 17, characterized in that at least one of the axes of rotation is arranged outside a central axis of the tibial plateau (11).

20. Endoprosthesis according to one of claims 1 to 19, characterized in that for guiding the translation in one guide (33) two paraüele legs (31) at a distance of 2R and in the other guide a guide body (41) with at least two concentric circular sections (45) with the radius R, which cooperate with the guide legs (31), are present.

21. Endoprosthesis according to one of claims 1 to 20, characterized in that a convex circular guide (45) in one for guiding the rotation

Guide (41) and a concave circular path (33) cooperating with the circular guide (45) are present in the other guide, which cooperate at least over an angular range α.

22. Endoprosthesis according to one of claims 1 to 21, characterized in that in the first insert control the rotation in extension control of the knee is restricted or preferably prevented.

23. Endoprosthesis according to one of claims 1 to 22 in conjunction with claims 10 and 11, characterized in that the guide body (41) has the convex circular guide (45).

24. Endoprosthesis according to claim 23, characterized in that on one guide a boundary track (13) with at least one circular section on a radius S and on the other one with the circular sections of

Boundary path (13) interacting boundary guide (23) is present at a distance from S to the center of the radius R.

25. Endoprosthesis according to one of claims 1 to 24, characterized in that the shape of the bearing shells (85) on the operational control of the

Lagerteüs (49) is matched.