Tibial trays, tibial inserts and knee prostheses

Abstract

A tibial tray, a tibial insert and a knee prosthesis are provided. [Solution] The tibial tray 20 has a proximal surface P with at least two central fixation elements 1, in particular exactly two central fixation elements 1, which enable connection with a tibial insert 30, which is a further component of the knee prosthesis 100. The at least two central fixation elements 1 are protruding parts in the proximal direction from the proximal surface P. The at least two central fixation elements 1 are arranged symmetrically with respect to a median plane M of the proximal surface P and / or parallel to the median plane M of the proximal surface P. The median plane M is perpendicular to the proximal surface P and intersects with the proximal surface P in the middle between the two most lateral points L1, L2 of the proximal surface P.

Description

[Technical field]

[0001] The present invention relates to a tibial tray having the features of claim 1, a tibial insert having the features of claim 13, and an artificial knee joint having the features of claim 16. [Background technology]

[0002] Joint replacement procedures, and in particular knee replacement procedures, have been known for some time. In a knee replacement procedure, it is known that a tibial tray component is coupled to a proximal end of a patient's tibia. A femoral component is coupled to a distal end of the patient's femur. A tibial insert is coupled to a proximal surface of the tibial tray. Thus, after the surgical procedure is completed, the tibial insert is located between the distal surface of the femoral component and the proximal surface of the distal tray.

[0003] For example, EP 3 626 209 B1 describes a tibial tray and a tibial insert of this type. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] European Patent No. 3626209 Summary of the Invention [Problem to be solved by the invention]

[0005] Proper geometrical features, such as form-fitting features, are necessary to ensure a good connection between the proximal end of the tibia and the tibial tray stem, especially when ceramic materials are used for the tibial tray and its tibial tray stem.

[0006] Additionally, it is difficult to combine a tibial tray with a mating tibial insert without localized mechanical loading exceeding certain design limits, especially when ceramic materials are used for the tibial tray. [Means for solving the problem]

[0007] A tibial tray having the features of claim 1 solves these problems.

[0008] The tibial tray comprises a proximal surface with at least two central fixation elements, in particular exactly two central fixation elements, which allow connection with a further part of the knee joint, the tibial insert, which are protrusions from the proximal surface that can be connected as a form-fit and / or friction lock (press fit) with the tibial insert.

[0009] The at least two central fixation elements are configured as proximal protrusions from the proximal surface, i.e., the central fixation elements are generally oriented away from the proximal surface in the direction of the tibial insert.

[0010] The at least two central fixation elements are oriented symmetrically with respect to and / or parallel to a median plane of the proximal surface, the median plane being perpendicular to the proximal surface and intersecting the proximal surface midway between the two most lateral points of the proximal surface. The median plane divides the proximal surface into two lateral halves. The at least two central fixation elements are oriented symmetrically with respect to and / or parallel to the median plane.

[0011] The at least two central fixation elements are configured as cylindrical or linear protrusions, in particular configured for a press fit. Cylindrical means that the protrusions have a cross section, e.g. circular, elliptical, etc. Linear means that the protrusions extend in a straight line on the proximal surface. One or more of the central fixation elements may be, for example, linear or cylindrical in shape.

[0012] In one embodiment, the at least two central fixation elements are arranged symmetrically with respect to a frontal plane perpendicular to the median plane and dividing the proximal surface into an anterior and a posterior part, and in particular the frontal plane may pass through the most lateral points of the proximal surface.

[0013] The proximal surface may include additional structure beyond the central fixation element.

[0014] In one embodiment, at least one anterior fixation element, in particular exactly one anterior fixation element, is provided on the anterior side of the proximal surface, the posterior side of which has a wall perpendicular to the median plane of the proximal surface in a plane parallel to the proximal surface.

[0015] The at least one anterior fixation element also has at least one form-fitting element for the corresponding form-fitting element of the tibial insert, in particular at least one cavity in the rear wall of the at least one anterior fixation element and / or at least one groove in the at least one anterior fixation element. That is, the cavity and the groove are examples of form-fitting elements that can be mated with the corresponding form-fitting element (e.g., protrusion, etc.) of the tibial insert to be connected to the tibial tray. The at least one form-fitting element of the at least one anterior fixation element can be arranged, for example, in an area where the load transfer is less than 70%, in particular less than 50% of the maximum load transfer. The load transfer (pressure, torque, etc.) can be calculated under various conditions. In general, certain areas of the structure are subject to higher loads than other areas. In some areas, the load transfer is transferred at a clearly defined maximum value. Areas where the load transfer is less than 50% of this maximum value are candidates for the location of the at least one form-fitting element.

[0016] In one embodiment, at least one posterior fixation element, in particular exactly one posterior fixation element, may be arranged symmetrically with respect to the median plane of the proximal surface, with a posterior wall flush with the posterior edge of the tibial tray and / or with an anterior wall parallel to the posterior wall of the at least one anterior fixation element, which may provide some anterior connection elements for the tibial insert. In one embodiment, the at least one posterior fixation element may have two side walls, each of which is at an angle α in a plane parallel to the proximal surface with respect to a plane perpendicular to the anterior wall. The angle may be in the range of 5 to 85°, in particular in the range of 40 to 50°.

[0017] In one embodiment, the at least one posterior element has a sidewall inclined at an angle of 1 to 25°, in particular 3 to 10°, relative to a plane perpendicular to the proximal surface, which allows for example the formation of a posterior block with inwardly inclined sidewalls, anteriorly converging sidewalls, etc. Such a posterior fixation element can be used as a fulcrum for mounting the tibial insert.

[0018] The wall behind the at least one anterior fixation element and / or the wall in front of the at least one posterior fixation element can also have an undercut, in particular an undercut that may form an angle β of 10 to 30°, in particular 15°, with a plane perpendicular to the proximal surface, i.e. structures on the proximal surface may have an undercut, in particular an undercut for better retention during assembly.

[0019] In one embodiment, the height of the at least two central fixation elements and / or the at least one anterior fixation element and / or the at least one posterior fixation element extending from the proximal surface is in the range of 1 mm to 6 mm, in particular 3 mm to 4.5 mm, and / or the anterior and / or posterior ends of the at least two central fixation elements are rounded. In particular, the height of the at least two central fixation elements and / or the height of the at least one anterior fixation element and / or the height of the at least one posterior fixation element on the proximal surface is constant or varies within 10% from a minimum height. These features help to ensure connection with the tibial insert and / or allow for effective assembly.

[0020] In another embodiment, the at least one anterior fixation element has at least one guiding surface for the tibial insert, in particular having a curved and / or planar portion at least in the proximal direction of the form-fitting element, which can facilitate the movement of the tibial insert during assembly, i.e. when the form-fitting parts are mated together.

[0021] The at least two central fastening elements may also comprise a central fastening element recess.

[0022] In one embodiment, to ensure a secure connection, the side walls and the front wall of the at least one posterior element are inclined at an angle of 0 to 25°, in particular 0 to 10°, relative to a plane perpendicular to the proximal surface and / or the side walls and the front wall of the at least one posterior element have an undercut.

[0023] The tibial tray embodiments are constructed in whole or in part from ceramics, polymeric materials, or metals.

[0024] The above problems are further solved by a tibial insert designed or configured to mate with the presently claimed tibial tray.

[0025] The tibial insert may include a recess on a distal surface for mating with at least one posterior fixation element to ensure a good connection with the tibial tray, the recess having at least one stress relief notch at the intersection of two walls of the recess, thereby preventing mechanical stress from accumulating at a sharp corner where the two walls of the recess meet.

[0026] A secure connection may be provided by at least one form-fitting element of the tibial insert engaging the at least one form-fitting element of the at least one anterior fixation element of the tibial tray.

[0027] The above problem is further solved by an artificial knee joint comprising a tibial tray according to the present invention, which corresponds to the tibial insert according to the present invention, between which a light press-fit connection, in particular a press-fit having a press-fit in the range of 0 to 250 μm, is generated.

[0028] In a further embodiment of the knee prosthesis, at least one press-fit area is created between the posterior fixation element and the tibial insert, in particular at least one press-fit area formed by an angular mismatch between the two walls, which improves the assembly of the joint and reduces micro-movements between the posterior parts of the joint.

[0029] The drawings illustrate embodiments of the present invention. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a perspective view of an artificial knee joint. [Diagram 2] FIG. 1 is a perspective view of one embodiment of a tibial tray. [Figure 2A] FIG. 3 is a diagram showing the reference system in FIG. 2. [Figure 2B] FIG. 3 shows a modification of the embodiment of FIG. 2. [Figure 3A] 1 is a view of a proximal surface of one embodiment of a tibial tray. [Figure 3B] FIG. 3B is a view of the distal surface of a tibial insert that mates with the tibial tray shown in FIG. 3A. [Figure 4] FIG. 3B illustrates a press-fit portion of the proximal surface of the embodiment shown in FIG. 3A. [Figure 5A] 13 is a perspective view showing a state in which the tibial insert is fitted to the tibial tray. FIG. [Figure 5B] 5B is a cross-sectional view of FIG. 5A in which the tibial insert is fitted to the tibial tray. [Figure 6A] FIG. 2 is a detailed front view showing the tibial insert of the first embodiment. [Figure 6B] FIG. 13 is a detailed front view showing the tibial insert of the second embodiment. [Figure 7] FIG. 3 is a perspective view showing a modified example of the embodiment shown in FIG. [Figure 8A] FIG. 2 is a posterior perspective view of the proximal surface of a tibial tray with a central fixation element of the first embodiment. [Figure 8B]1 is an anterior perspective view of a proximal surface of a tibial tray with a central fixation element of a first embodiment. FIG. [Figure 9] FIG. 2 is a posterior perspective view of the proximal surface of a tibial tray with a central fixation element of a second embodiment. [Figure 10] 13 is a perspective view of a proximal surface of a further embodiment of a tibial tray comprising a guiding surface on an anterior fixation element; FIG. [Figure 11] FIG. 13 shows details of the connection between the posterior fixation elements in one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Fig. 1 is a perspective view of a ceramic knee prosthesis 100 from a posterior position. Fig. 1 illustrates the femoral component 40, tibial insert 30, and tibial tray 20 of the non-metallic knee prosthesis. The total knee prosthesis 100 is non-metallic, for example, a combination of ceramic and polymeric materials. The tibial tray 20 can be made of ceramic, for example, and the tibial insert 30 can be made of polymeric material.

[0032] The femoral component 40 is depicted in a proximal position within the knee prosthesis, with the two condyles at the distal end of the femoral component 40 mating with corresponding grooves in the proximal surface of the tibial insert 30 .

[0033] A tibial insert 30 is coupled to the tibial tray 20 such that a distal surface D of the tibial insert 30 opposes a proximal surface P of the tibial tray 20 .

[0034] The following describes embodiments of the tibial tray 20 and tibial insert 30, and in particular the features of the proximal surface P of the tibial tray 20 and the mating distal surface D of the tibial insert 30.

[0035] 2 and 2A are perspective views of the proximal surface P of the tibial tray 20. FIG 2A illustrates the tibial tray without reference numbers to reduce complexity, and with the addition of reference planes M and N. Hereinafter, the reference planes M and N will be used to define the location of each feature on the tibial tray 20.

[0036] 2A, the median plane M is perpendicular to the planar proximal surface P and intersects the proximal surface P midway between the most lateral points L1, L2 of the proximal surface P. The frontal plane N is perpendicular to the median plane M.

[0037] In one embodiment, the tibial tray 20 is provided with a set of dimensions. Eight different distances between points L1 and L2 are provided, allowing the knee prosthesis 100 to be adapted for a variety of patient sizes. The minimum distance between L1 and L2 is 60 mm. The remaining seven distances are 64 mm, 68 mm, 72 mm, 76 mm, 80 mm, 84 mm, and 88 mm (i.e., in 4 mm increments). In other embodiments, other absolute dimensions and / or other increments may be used, and the increments may not be the same.

[0038] The corresponding dimensions of the proximal surface P in the direction perpendicular to the distance between L1 and L2 are 38.7 mm, 41.3 mm, 43.9 mm, 46.5 mm, 49.0 mm, 51.6 mm, 54.2 mm, and 56.8 mm. Again, other absolute dimensions and / or other increments may be used in alternative embodiments, and the increments may not be the same.

[0039] The proximal surface P of the tibial tray 20 is configured (see FIGS. 5A and 5B) such that a corresponding tibial insert 30 (see, e.g., FIGS. 1, 6, etc.) can be securely fastened and fixed to the tibial tray 20. The planar proximal surface P itself is polished to an average roughness Ra=0.1 μm and a flatness of 0.1. In another embodiment, the average roughness is less than 5 μm, in particular less than 2 μm.

[0040] Next, various embodiments of structures 1, 2, 3 on the planar proximal surface P will be described, which provide island-like fixation elements 1, 2, 3 on a symmetrical and flat platform for the connection of a tibial insert 30 by means of a press fit (see FIG. 4).

[0041] In the embodiment shown in Fig. 2, the proximal surface P is provided with two central fixation elements 1 which, as will be explained below, allow a secure connection with a further part of the knee prosthesis 100, the tibial insert (see Fig. 3B).

[0042] In the illustrated embodiment, the two central fixation elements 1 are linear projections that project proximally away from the proximal surface P so as to mate with corresponding grooves 34 in the tibial insert 30 (see FIG. 3B). In another embodiment, the central fixation element 1 may be cylindrical in shape.

[0043] The two central fixing elements 1 are provided symmetrically with respect to the median plane M and parallel to the median plane M.

[0044] 2B, the two central fixing elements 1 are symmetrical with respect to the median plane M, but are inclined by less than 5° with respect to the median plane M. Therefore, these two linear fixing elements 1 cannot be said to be parallel because they converge to some extent toward the front side.

[0045] As an alternative embodiment, the two central fixation elements 1 can be asymmetric with respect to the median plane M, but parallel to each other.

[0046] In an alternative embodiment, more than two central fixing elements 1 can be used, as shown in figure 7. Otherwise, the embodiment of figure 7 does not differ from the embodiment described in connection with figure 2.

[0047] In the embodiment shown in Fig. 2, two central fixation elements 1 are provided symmetrically with respect to a front surface N perpendicular to the median plane M. In this embodiment, the frontal plane N passes through the most lateral points L1, L2 of the proximal surface P, but this is not necessarily the case.

[0048] The two central fixing elements 1 are in the form of a parallelepiped. The front and rear ends of the central fixing elements 1 are rounded.

[0049] In the illustrated embodiment, the height H of the two central fixation elements 1 extending from the proximal surface P of the tibial tray 20 is 3.8 mm. In other knee prosthesis 100, the height H can be up to 6 mm. In the illustrated embodiment, the height H of the central fixation elements 1 is constant. In other embodiments, the height H can vary relative to the proximal surface P. In other embodiments, the height H of the at least two central fixation elements 1 on the proximal surface varies within 10% of a minimum height.

[0050] In the embodiment shown in Fig. 2, the distance between the inner walls of the two central fixing elements 1 is 10.5 mm, and the distance between the outer walls is 15.5 mm. Since the two central fixing elements 1 are parallel to each other, the width of each central fixing element is 2.5 mm. Here, the distance between the central fixing elements is selected as wide as possible so that the torque is large and the polyethylene material of the tibial insert 30 does not shear. By making the distance between the two central fixing elements 1 common to all, it is possible to assemble the artificial knee joint 100 even with tibial inserts 30 of different sizes.

[0051] Such an orientation of the central fixation element 1 on the proximal surface P allows for linear guidance of the tibial insert 30 during assembly (see FIG. 5). The central fixation element 1 can therefore also be referred to as a central guide rail. The central fixation element 1 also allows for increased stability against shear forces in the artificial knee joint.

[0052] The proximal surface P further comprises an anterior fixation element 2 provided at the front edge of the proximal surface P. The rear side of the anterior fixation element 2 has a rear wall 4 provided perpendicular to the median plane M of the proximal surface P. That is, the rear wall 4 is also approximately perpendicular to the two linear central fixation elements 1. The anterior fixation element 2 in this embodiment has the same height H as the central fixation element 1.

[0053] The anterior fixation element 2 has two cavities 5 in the form of grooves, i.e. grooves open at both ends, of approximately rectangular cross section. As shown in relation to figure 5, these cavities are form-fitting elements 5 which cooperate with corresponding form-fitting elements 31 in the tibial insert 30. The form-fitting elements 5 in said anterior fixation element are arranged symmetrically with respect to the median plane M.

[0054] In alternative embodiments, the anterior fixation element 2 may have only one or more form-fitting elements 5. The cavity of the form-fitting element 5 may not have a rectangular cross-section, for example rounded or polygonal cross-sections may be used.

[0055] 2, the anterior fixation element 2 is a continuous element at the anterior edge of the tibial tray 20. In alternative embodiments, the anterior fixation element 2 may be divided into two or more sections, for example, two elements each having a form-fitting element 5.

[0056] The two form-fitting elements 5 of the front locking element 2 are arranged in a region where the mechanical load transfer is less than 50% of the maximum load transfer, because the groove-like form-fitting elements 5 weaken the structure of the front locking element 1 somewhat.

[0057] A further structure on the proximal surface P is a posterior fixation element 3 located at the posterior edge of the proximal surface P. The posterior fixation element 3 is symmetrical about the median plane M and has a posterior wall 7 that is flush with the posterior edge 8 of the tibial tray 20. The posterior wall 7 follows the curvilinear shape of the posterior edge 8 of the tibial tray 20. A cross section of the anterior fixation element 3 in a plane parallel to the proximal surface P is symmetrical about the median plane M. The posterior fixation element 3 in this embodiment has the same height H as the central fixation element 1.

[0058] The embodiment shown in figure 2 further comprises a front wall 9 parallel to the rear wall 4 of the front fixation element 2. That is to say, the two central fixation elements 1 are oriented perpendicular to the rear wall 4 of the front fixation element 2 and the front wall 9 of the rear fixation element 3.

[0059] The posterior fixation element 3 further has two side walls 10 which are inclined with respect to the front wall 9 of the posterior fixation element 3. The angle α between the two side walls 10 and the front wall 9 in a plane parallel to the proximal surface P is in the range of 5 to 85°, in particular in the range of 40 to 50°. That is to say, the two side walls 10 are oriented convergingly in the forward direction. The overall horizontal shape of the posterior fixation element 3 is approximately trapezoidal with curved long sides.

[0060] The two side walls 10 of the posterior element 3 are inclined inwards by an angle of 1 to 25°, in particular 3 to 10°, relative to a plane perpendicular to the proximal surface P. That is to say, the top surface of the posterior fixation element 3 is slightly smaller than its bottom cross section in the plane of said proximal surface.

[0061] In the embodiment described herein, best illustrated in Fig. 5B, the anterior wall 9 of the posterior fixation element 3 has an undercut 6 which forms an angle β of 10 to 30°, in particular 15°, with a plane perpendicular to the proximal surface P. In another embodiment, the undercut 6 may at least partially have a curved shape. In principle, it is also possible for the posterior wall 4 of the anterior fixation element 2 to have an undercut.

[0062] In the embodiments described so far, the heights H of the anchoring elements 1, 2, 3 on the proximal surface P are the same. This does not have to be the case in all embodiments.

[0063] Figures 3A and 3B show the mating tibial tray 20 and tibial insert 30 side-by-side. The embodiment of the tibial tray 20 in Figure 3A has already been described in Figure 2, so please refer to the corresponding description. Figure 3B shows the distal surface D of the tibial insert 30. Comparing the two parts 20, 30, it can be seen that the tibial insert 30 can be connected to the tibial tray 20 such that the first fixation element 1 fits into a corresponding groove 34 in the tibial insert 30.

[0064] The tibial insert 30 comprises a recess 32 in its distal surface D for a corresponding posterior fixation element 3 of the tibial tray 20. The recess 32 is open towards the posterior side and therefore only has an anterior wall 35 and two side walls 36.

[0065] The side walls 36 of the recess 32 are inclined to mate with the inclined side walls 10 of the rear fixation element 3. At the corner where the front wall 35 of the recess 32 meets the two side walls 36, a stress relief notch 33 is provided at the intersection of the two walls 35, 36.

[0066] The anterior side of the tibial tray insert 30 is provided with two form-fitting elements 31 which can be inserted into two cavities of the form-fitting element 5 in the anterior fixation element 2 (see FIG. 2).

[0067] Additionally, the groove 34 and recess 32 of the tibial tray 30 form a form-fitting connection with the corresponding structures of the tibial tray 20, i.e., the medial fixation element 1 and the posterior fixation element 3. However, the primary function of the structures 32, 34 is to aid in assembly, as will be described below in conjunction with Figures 5A and 5B.

[0068] The connection between the tibial tray 20 and the tibial insert 30 is mainly caused by a light press-fit connection between the tibial insert 30 and the at least two central fixation elements 1, at least one anterior fixation element 2 and at least one posterior fixation element 3, in particular a light press-fit connection having a press-fit in the range of 0-250 μm in the anterior-posterior direction. In FIG. 4, the surfaces 37 used for the press-fit on the posterior wall 4 of the anterior fixation element 2, on the medial side of the central fixation element 1 and on the anterior wall 9 of the posterior fixation element 9 are highlighted. It is possible, but not necessary in all embodiments, that all the press-fit connections are of the same size. For example, the press-fit between the posterior wall 4 of the anterior fixation element 2 and the anterior wall 9 of the posterior fixation element 3 is in the range of 25-125 μm and / or the press-fit between the central fixation elements 1 is in the range of 0-100 μm.

[0069] 5A and 5B illustrate the assembly of an embodiment of a tibial insert 30 with an embodiment of a tibial tray from different perspectives.

[0070] Figure 5A is a front perspective view of the tibial insert 30 partially connected to the underlying tibial tray 20. Figure 5B is a cross-sectional view of the tibial tray 20 and tibial insert 30 with the anterior fixation element 2 now to the right, with the tibial tray 20 and tibial insert 30 in substantially the same relative positions.

[0071] The tibial insert 30 is first connected with the posterior fixation element 3 (see Figs. 2, 3A and 3B), which serves as a kind of fulcrum for the fitting into place. Fig. 5B depicts an undercut 6 in the anterior wall 9 with an angle of about 15°, which ensures the positioning of the tibial insert 30. Two form-fitting elements 31 are depicted on the anterior side (see Fig. 5A), which fit into the cavities of the form-fitting element 5 (not shown in Fig. 5A).

[0072] 6A is a front view of the tibial insert 30 according to the first embodiment. In this embodiment, the distal surface D is not contoured to the footprint, i.e., the outer edge of the tibial insert 30 is in effect a slightly inclined wall. The inclination can be between 0 and 10°. When the inclination is 0°, the wall is straight.

[0073] 6B is a front view of the tibial insert 30 according to the second embodiment, in which the distal surface D is shaped to match the footprint, i.e., the outer wall is gently angled outward.

[0074] In an embodiment different from that shown in Figure 2, the central fixation element 1 has a shape with two axes of symmetry, one along the long axis and one perpendicular to that axis. Figures 8A and 8B show an embodiment of the tibial tray 20 that deviates from this pattern.

[0075] 8A and 8B depict an embodiment in which the central fixation elements 1 are wider anteriorly than posteriorly in transverse cross section, i.e., the longitudinal side walls of each central fixation element 1 converge toward the anterior side. The lateral side walls of the central fixation elements 1 are generally parallel, while the medial side walls are not parallel but diverge toward the posterior side of the tibial tray 20.

[0076] Figure 9 shows an alternative embodiment of the tibial tray 20, in which the shape of the central fixation element 1 is changed. Here, the outer side walls of the central fixation elements 1 are parallel to each other and have two axes of symmetry, as in the embodiment shown in Figure 2. In the embodiment of Figure 9, the inner side walls are not straight along their entire length. They converge towards the anterior and posterior sides, but diverge towards the center.

[0077] The anterior fixation element 2 of the embodiment shown in Figures 8A, 9B and 9 has a similar shape to the embodiment shown in Figure 2. However, the embodiment shown in Figures 8A, 8B and 9 has a different shape for the posterior fixation element 3.

[0078] The side walls of the posterior element 3 are inclined at an angle of 0 to 25°, in particular 0 to 10°, to a plane perpendicular to the proximal surface P. Additionally or alternatively, at least one of the side walls of the posterior element and / or the front wall may have an undercut.

[0079] 10 shows a proximal surface P of a tibial tray 20 in which the structure of the anterior fixation element 2 is modified from that of the previously described embodiment. The central fixation element 1 and the posterior fixation element 3 are as described in, for example, FIGS. 2 and 8A, so please refer to the previous descriptions.

[0080] The anterior fixation element 2 has two form-fitting elements 5 that receive corresponding portions of the tibial insert 30 (not shown in the figure; see, for example, Figures 5A and 5B for the fitting process of the tibial tray). The form-fitting elements 5 are essentially holes with a rectangular cross section.

[0081] Since the tibial insert 30 is inserted from above using its rear portion and the posterior fixation device 3 as fulcrums, the form-fitting element 31 used for anterior fixation has a shape that corresponds to the form-fitting element 5 (e.g., a rectangular hole portion, etc.).

[0082] A guide surface 11 is provided on the proximal surface of the anterior fixation device 5 to facilitate fitting of the tibial insert 30 (not shown in the figure). Here, the guide surface 11 is a plane inclined at an angle of 5° to 45°, particularly 30°, with respect to the horizontal plane.

[0083] The form-fitting element 31 of the tibial insert 30 protrudes in the anterior direction. When the tibial insert 30 is to be fitted, the form-fitting element 31 is first placed on top of the guiding surface 11. When a distal pressure is applied to the tibial insert 30, the form-fitting element 31 is guided downward along the guiding surface 11 until it finally fits into the hole forming the form-fitting element of the anterior fixation element 5, thereby ensuring a secure fit. The guiding surface 11 prevents lateral slippage and facilitates a secure fit.

[0084] The lateral width of said guiding surface is the same or approximately the same as the lateral width of the form-fitting element 5 of the anterior locking element 2 .

[0085] FIG. 11 shows a detailed plan view of the posterior fixation element 3, ie in the direction of the proximal surface P.

[0086] The cross section of the posterior fixation element 3 includes two side walls 10 that are inclined toward the median plane M. Each side wall 10 is inclined at about 20° with respect to the median plane M. In the illustrated embodiment, there is an intentional angular mismatch between the side walls 10 of the posterior fixation element 3 and the corresponding side walls of the tibial insert 30 (not shown in this figure).

[0087] For example, if the side wall of the tibial insert 30 that is intended to contact or form-fit with the side wall 10 of the posterior fixation element 3 is angled slightly differently than the side wall 10, an angular mismatch will result in closer contact or a more forceful fit (press fit) in some areas along the side wall 10 and a looser fit in other areas.

[0088] In the embodiment shown in Figure 11, the angle of the side walls of the posterior fixation element 3 is wider (e.g., by about 1°) than the corresponding angle of the recess in the tibial insert 30. This creates a form-fit, i.e., a tighter fit, in the posterior section. Figure 11 shows a press-fit area 38 in this section. This angular mismatch not only facilitates assembly, but also limits microscopic movement between the posterior sections.

[0089] In another embodiment, the press-fit area 38 is formed by expanding the rear portion of the rear fixation element 3 .

[0090] While the ceramic knee joint 100 described above with a non-metallic (particularly ceramic) tibial tray 20 is a preferred embodiment, the tibial tray 20 and / or the total knee joint 100 can be made of a metal or polymeric material or can contain these materials. [Explanation of symbols]

[0091] 1 Central fixed element 2 Anterior fixation element 3 Posterior fixation element 4 Rear wall of the front fixing element 5. Form-fitting element of front fixing element 6 Undercut in the wall of the rear fixing element 7 Rear wall of rear fixing element 8 Posterior edge of tibial tray 9 Front wall of rear fixing element 10 Side wall of rear fixation element 11 Guide Surface 12 Central fixing element recess 20 Tibial Tray 30 Tibial Insert 31 Form-fitting element for front fixing element 32 Recess for rear fixing element 33 Relief cutout 34 Groove in tibial insert for straight central fixation element 35 Front wall of recess 36 Recess side wall 37 Press-fit surface 38 Press-in area 40 Femoral component 100 Artificial knee joint D Distal surface of the tibial insert H Height of the fixed element L1 Lateral point of proximal surface Lateral point of proximal surface of L2 M Median plane of the proximal surface of the tibial tray N Frontal plane perpendicular to the median plane P Proximal surface of tibial tray α the angle between the side wall of the anterior fixation element and a plane perpendicular to the anterior wall, in a plane parallel to the proximal surface β Undercut angle

Claims

1. Tibial tray (20), It has a proximal surface (P) which is equipped with at least two central fixation elements (1) that enable connection to a tibial insert (30), which is a further component of the artificial knee joint, A tibial tray (20) wherein the at least two central fixing elements (1) are proximal projections from the proximal surface (P), and the at least two central fixing elements (1) are provided symmetrically with respect to the median plane (M) of the proximal surface (P) and / or parallel to the median plane (M) of the proximal surface (P), the median plane (M) is perpendicular to the proximal surface (P) and intersects the proximal surface (P) at the midpoint between the two most lateral points (L1, L2) of the proximal surface (P).

2. The tibial tray (20) according to claim 1, wherein one or more of the at least two central fixing elements (1) is a cylindrical projection or a linear projection from the proximal surface (P).

3. The tibial tray (20) according to claim 1 or 2, wherein the at least two central fixing elements (1) are provided symmetrically with respect to a frontal plane perpendicular to the median plane (M).

4. The tibial tray (20) according to claim 1, wherein at least one anterior fixing element (2) is provided on the anterior side of the proximal surface (P), and the posterior side of the at least one anterior fixing element (2) has a wall (4) perpendicular to the median plane (M) of the proximal surface (P) in a plane parallel to the proximal surface (P).

5. The tibial tray (20) according to claim 4, wherein the at least one anterior fixing element (2) has at least one shape-fitting element (5) for a corresponding shape-fitting element (31) of the tibial insert (30), and the at least one shape-fitting element (5) of the at least one anterior fixing element (2) is positioned in a region where load transfer is less than 70% of the maximum load transfer.

6. In the tibial tray (20) according to claim 4, at least one posterior fixation element (3) is provided symmetrically with respect to the median plane (M) of the proximal surface (P), and the posterior fixation element (3) has a posterior wall (7) that is flush with the posterior edge (8) of the tibial tray (20), and / or has an anterior wall (9) provided parallel to the posterior wall (4) of the at least one anterior fixation element (2), and / or The at least one rear fixing element (3) has two side walls (10), and the angle (α) between each of these side walls (10) and a plane perpendicular to the front wall (9) is in the range of 5 to 85° in a plane parallel to the proximal surface (P), and / or The side wall (10) of at least one rear element (3) is inclined at an angle of 1 to 25° with respect to a plane perpendicular to the proximal surface (P), and / or A tibial tray (20) wherein the posterior wall (4) of at least one anterior fixing element (2) and / or the anterior wall (9) of at least one posterior fixing element (3) have undercuts (6) that form an angle (β) of 10 to 30° with a plane perpendicular to the proximal surface (P).

7. In the tibial tray (20) according to claim 6, the height (H) of the at least two central fixation elements (1) and / or the at least one anterior fixation element (2) and / or the at least one posterior fixation element (3) from the proximal surface (P) is in the range of 1 mm to 6 mm, and / or the anterior and / or posterior ends of the at least two central fixation elements (1) are rounded and / or A tibial tray (20) in which the height (H) of the at least two central fixation elements (1) and / or the height of the at least one anterior fixation element (2) and / or the height of the at least one posterior fixation element (3) on the proximal surface (P) is constant or varies within 10% of the minimum height.

8. The tibial tray (20) according to claim 4, wherein the at least one anterior fixing element (2) has at least one guide surface (11) for the tibial insert (30).

9. The tibial tray (20) according to claim 1, wherein at least two central fixing elements have central fixing element recesses (12).

10. The tibial tray (20) according to claim 6, wherein the side wall (10) and the anterior wall (9) of the at least one posterior element (3) are inclined at an angle of 0 to 25° with respect to a plane perpendicular to the proximal surface (P), and / or the side wall (10) and the anterior wall (9) of the at least one posterior element (3) have an undercut.

11. The tibial tray (20) according to claim 1, wherein the tibial tray (20) is manufactured in whole or in part from ceramics, polymer materials, or metal.

12. A tibial insert (30) configured to fit with the tibial tray (20) described in claim 1.

13. The tibial insert (30) according to claim 12, wherein the tibial insert (30) has a recess (32) on its distal surface (D) that fits with at least one posterior fixation element (3), and the recess (32) has at least one stress relief notch (33) at the intersection of two walls (35, 36), The tibial insert (30) comprises at least one shape-fitting element (31) that engages with at least one shape-fitting element (5) of at least one anterior fixing element (2) of the tibial tray (20).

14. The tibial tray (10) according to claim 1, The tibial insert (30) according to claim 12, An artificial knee joint (100) equipped with this.

15. In the artificial knee joint (100) according to claim 14, a light press-fit connection is made between the tibial insert (30) and the at least two central fixation elements (1), the at least one anterior fixation element (2), and the at least one posterior fixation element (3), and / or An artificial knee joint (100) wherein at least one press-fit (38) region is formed between the posterior fixing element (3) and the tibial insert (20).

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