Tibial tray shaft structure and tibial tray with artificial knee joint

Abstract

The present invention provides a tibial tray that ensures a good cemented connection between the proximal end of the tibia and the tibial tray shaft. [Solution] The present invention relates to a tibial tray 20 having a distal surface D, wherein a tibial tray shaft structure 21 extends distally DD away from the distal surface D, and the tibial tray structure 21 comprises at least three shaft wall elements 22, 23, 24, 25. The at least three shaft wall elements 22, 23, 24, 25 are arranged relative to each other such that their cross-sections in a plane perpendicular to the distal direction DD are T-shaped, Y-shaped, or X-shaped, and the area F of the cross-sections decreases strictly monotonically from the distal surface D toward the distal direction DD. The present invention also relates to an artificial knee joint.

Description

Technical Field

[0001] The present invention relates to a tibial shaft having a shaft structure with the features described in claim 1 and an artificial knee joint having the features described in claim 27.

Background Art

[0002] Arthroplasty, particularly artificial knee arthroplasty, has been known for a fairly long time. In the case of an artificial knee joint, it is known that the tibial tray portion is connected to the proximal end of the patient's tibia. The connection is made via the distal portion of the tibial tray, i.e., the tibial tray shaft.

[0003] The femoral component is connected to the distal end of the patient's femur. The tibial insert is connected to the proximal surface of the tibial tray such that after the completion of the surgery, the tibial insert is disposed between the distal surface of the femoral component and the proximal surface of the distal tray.

[0004] This type of tibial tray and tibial insert is described, for example, in European Patent No. 3626209.

[0005] In order to ensure a good cement connection between the proximal end of the tibia and the tibial tray shaft, a geometric shape of an appropriate shape such as a shape fit design is required. This is particularly important when a ceramic material is used for the tibial tray and its tibial tray shaft.

Summary of the Invention

[0006] The tibial tray having the features described in claim 1 addresses these problems.

[0007] The tibial tray has a distal surface, and the tibial tray shaft structure extends in the distal direction away from the distal surface. The tibial tray structure forms a protrusion that is inserted into the tibia.

[0008] For good fixation of the tibial tray to the bone, the tibial tray structure comprises at least three shaft wall elements arranged relative to each other such that the cross-sections of the at least three shaft wall elements in a plane perpendicular to the distal direction are T-shaped, Y-shaped, or X-shaped. The T-shaped structure comprises three shaft wall elements, two forming the transverse bar of the T-shape and one forming the longitudinal bar. The transverse and longitudinal bars are positioned at an angle of 90°.

[0009] The Y-shaped structure also comprises three shaft wall elements, but the three angles may not be 90°. In one possible embodiment, the shaft wall elements are spaced at equal intervals of 120°. Alternatively, two shaft wall elements can be spaced at 90° intervals, and the remaining third shaft wall element is spaced 135° from each of the other shaft wall elements.

[0010] The X-shaped structure comprises four shaft wall elements. The shaft wall elements are arranged around a central axis with angles between them. For example, each of the two sets of angles between the shaft wall elements can contain angles of the same size (e.g., two angles of 110° each and two angles of 70° each).

[0011] Furthermore, the cross-sectional area decreases strictly monotonically from the distal surface toward the distal end. This means that tibial tray structures generally taper distally from a broad base. Such a shape facilitates the effective insertion of the tibial tray into the tibia. The taper is continuous with the portion parallel to the distal surface.

[0012] In one embodiment, the outer rims of at least three shaft wall elements converge strictly monotonically distally toward the axis of the tibial tray structure. This configuration is also a form of taper that facilitates effective insertion of the tibial tray into the tibia.

[0013] The shape of the outer rim can be curved, for example, in a uniform curvature direction (e.g., an exponential shape). However, in one embodiment, the outer rims of at least three shaft wall elements have at least one inflection point, in particular three inflection points. This means that the direction (not just the amount) of curvature changes at least once.

[0014] The curvature of the lateral rim should not change excessively abruptly, and consequently, the change in tangential angle at the lateral rim of at least three shaft wall elements should be less than 30° over the distal 10%. In particular, the tangential angles at the lateral rim of at least three shaft wall elements within one-third of the height of the tibial tray structure measured from the distal plane must satisfy this condition. The change in gradient should be smaller in the region closest to the distal plane of the tibial shaft structure (one-third).

[0015] In a further embodiment, at least 50% of the volume of the tibial tray structure is located within one-third of the height of the tibial tray structure as measured from the distal surface.

[0016] At least one of the shaft wall elements can have a wall thickness of 1–6 mm, particularly 2–5 mm, and 1–5 mm for ceramic materials, measured at the point furthest from the axis on the distal surface.

[0017] The radius at the transition from at least one outer rim of at least three shaft wall elements to at least one side wall of at least three shaft wall elements can be in the range of 0.5 to 4 mm.

[0018] For efficient bonding with bone cement, at least one of the three shaft wall elements is provided with at least one cement-retaining structure, in particular at least one recessed structure for holding bone cement. These cement-retaining structures may preferably be located anteriorly and / or posteriorly, closer to the tibial tray.

[0019] The transition point from the lateral limb to the tibial shaft structure in the distal plane is located at least 5 mm from the lateral and / or posterior side of the distal plane. This ensures an appropriate distance from the edge of the distal plane and guarantees that the tibial shaft structure is positioned medially to the cancellous bone and lateral to the cortical bone. This distance is measured linearly from the end of the lateral limb to the edge of the distal plane.

[0020] In one embodiment, the tibial tray structure includes a surface extending between at least two outer rims of at least three shaft wall elements, or between two side walls of at least three shaft wall elements.

[0021] Since rounding of the edges can be important, the radius of at least one of the three shaft wall elements from the distal surface and / or the transition to the smooth surface may be in the range of 1 to 4 mm.

[0022] Furthermore, the axis of the tibial tray shaft structure can be located on the distal plane at 1 / 3 of the distance between the anterior and posterior rims, measured from the anterior rim. This means that the axis of the tibial tray shaft is located somewhat anteriorly than posteriorly. The axis of the tibial tray shaft is defined for X, Y, and T-shaped tibial tray shaft structures because at least three shaft wall elements converge strictly monotonically toward this axis. In certain embodiments, the distance of the axis of the tibial tray shaft structure is 5 mm, 5.67 mm, 6.33 mm, or 7 mm from the center of the distal plane. In combination with or alternatively to this, embodiments may have a tibial shaft tray structure having a height of 35 mm, 40 mm, 45 mm, or 55 mm from the distal plane. In combination with or alternatively to this, the thickness of the shaft wall elements may be 3 mm, 3.75 mm, 4.25 mm, or 5 mm.

[0023] The angles between the shaft wall elements are 90° to 180° anteriorly and 30° to 120° posteriorly. For example, a T-shaped tibial tray structure with three shaft wall elements has an anterior angle of 180° and two posterior angles of 90°. The shapes of X-shaped and Y-shaped tibial tray structures can vary within the aforementioned range.

[0024] To ensure a good mechanical connection between the tibial tray and the tibia, the tibial tray shaft structure includes at least one cement-retaining structure, particularly holes, grooves, and / or recesses without undercuts. This allows for efficient cementation of the cement-retaining structure. In particular, at least one cement-retaining structure is located within two-thirds of the vertical direction of the tibial tray shaft structure, measured distally from the distal surface, and especially within one-third. This means that it is preferable that at least one cement-retaining structure is located toward the distal surface rather than toward the distal end of the tibial tray shaft structure.

[0025] In a further embodiment, the tibial tray comprises at least one anterior fixation element, in particular exactly one, located on the anterior side of the proximal plane, the posterior side of the at least one anterior fixation element comprising a wall perpendicular to the midplane of the proximal plane in a plane parallel to the proximal plane. In particular, the at least one anterior fixation element comprises at least one channel through the at least one anterior fixation element for at least one shape-fitting element, in particular at least one cavity in the posterior wall of the at least one anterior fixation element and / or a corresponding shape-fitting element of the tibial insert, the at least one shape-fitting element of the at least one anterior fixation element being particularly located in a region where load transfer is less than 70%, in particular less than 50%, of the maximum load transfer.

[0026] At least one anterior fixing element comprises at least one guide surface for the tibial insert, which may in particular have a curved portion and / or a planar portion in the proximal direction of at least one shape-fitting element. When the tibial insert is to be fitted with the tibial tray, the projection of the tibial insert contacts the guide surface and slides along the guide surface, thereby guiding its movement during fitting so that the projection can snap into the at least one shape-fitting element. In one embodiment, at least one guide surface comprises a planar portion or is a plane inclined at an angle of 5 to 45° with respect to a horizontal plane, particularly at an angle of 30°.

[0027] In some embodiments, the tibial tray has a proximal surface, the proximal surface having at least two, in particular exactly two, central fixation elements to enable connection with a tibial insert as a further part of a prosthesis, the at least two central fixation elements projecting proximal from the proximal surface, the at least two central fixation elements being arranged symmetrically and / or parallel to a midplane of the proximal surface, the midplane being perpendicular to the proximal surface and intersecting the proximal surface midway between the two most lateral points of the proximal surface. In particular, the at least two central fixation elements are arranged symmetrically with respect to a front plane perpendicular to the midplane, the front plane passing, in particular, through the most lateral points of the proximal surface. The at least two central fixation elements may have central fixation element recesses to provide better mating with the tibial insert. At least two, or exactly two, central fixation elements may be configured as shape-fitting and / or interlocking elements.

[0028] Furthermore, an embodiment of the tibial tray may comprise at least one, particularly exactly one, posterior fixation element arranged symmetrically with respect to the intermediate plane of the proximal surface. This posterior fixation element has a posterior wall flush with the posterior rim of the tibial tray and / or a front wall arranged essentially parallel to the posterior wall of at least one anterior fixation element. The side wall and / or the front wall of the at least one posterior element can be inclined, particularly, at an angle of 0 to 45°, particularly 0 to 30°, more specifically 10° with respect to a plane perpendicular to the proximal surface, and / or the side wall and the front wall of the at least one posterior element include an undercut. This enables, for example, the formation of a posterior block having inwardly inclined side walls (i.e., side walls having an angle greater than 0°) and side walls or tongue and groove systems (undercuts) converging towards the front. Such a posterior fixation element can be used as a fulcrum when attaching the tibial insert.

[0029] The tibial tray can be manufactured completely or partially from ceramic, polymer material or metal.

[0030] Other embodiments of the tibial tray can include a proximal surface which, as a further part of the artificial knee joint, comprises at least two, particularly exactly two, central fixation elements for enabling connection with the tibial insert. The central fixation elements are projections from the proximal surface that can connect as a form fit and / or a press fit with the tibial insert.

[0031] The at least two central fixation elements are designed as projections in the proximal direction from the proximal surface, i.e., the central fixation elements generally face away from the proximal surface in the direction of the tibial insert.

[0032] At least two central fixed elements are positioned symmetrically and / or parallel to the midplane of the proximal plane, which is perpendicular to the proximal plane and intersects it midway between the two most lateral points of the proximal plane. The midplane divides the proximal plane into two lateral halves. At least two central fixed elements are oriented symmetrically and / or parallel to the midplane. In a further embodiment, at least two fixed elements are oriented asymmetrically with respect to the midplane. This may imply different angles with respect to the midplane and / or different distances from the midplane.

[0033] At least two central fixing elements are configured as cylindrical or linear projections, specifically designed for interference fits and / or shape fittings. Cylindrical means the projection has, for example, a circular or elliptical cross-section. Linear means the projection extends linearly on the proximal surface. At least one of the central fixing elements may have, for example, a linear or cylindrical shape.

[0034] In one embodiment, at least two central fixed elements are arranged symmetrically with respect to a front plane perpendicular to the midplane. The front plane divides the proximal plane into a front portion and a rear portion. In particular, the front plane can pass through the outermost lateral point of the proximal plane.

[0035] For better insertion of the tibial insert and for better fixation in vivo, the posterior wall of at least one anterior fixation element and / or the anterior wall of at least one posterior fixation element may be provided with an undercut.

[0036] In one embodiment, the heights of at least two central fixation elements, at least one anterior fixation element, and / or at least one posterior fixation element extending from the proximal plane are in the range of 1 mm to 6 mm, particularly 3 mm to 4 mm, and 5 mm, and / or the anterior and / or posterior ends of at least two central fixation elements are rounded. In particular, the heights of at least two central fixation elements, at least one anterior fixation element, and / or at least one posterior fixation element above the proximal plane are constant or vary by up to 10% from the minimum height. These features help to provide a secure connection with the tibial insert and / or enable effective assembly.

[0037] These issues are also addressed by tibial inserts designed or configured to conform to the tibial tray described in the claims.

[0038] To ensure a good connection with the tibial tray, the tibial insert may have a recess on its distal surface to align with at least one posterior fixation element. This recess has at least one stress-relieving notch at the junction of the two walls of the recess. This prevents the accumulation of mechanical stress at the sharp angle where the two walls of the recess meet.

[0039] A secure connection may be made possible by at least one shape-fitting element of the tibial insert for engaging with at least one shape-fitting element of at least one anterior fixation element of the tibial tray. This connection may also be made by a press-fit connection or a combination thereof.

[0040] These problems are also addressed by an artificial knee joint comprising a tibial tray and a tibial insert as described in the claims. The tibial insert has a light interlocking connection between it and at least two central fixation elements, at least one anterior fixation element and at least one posterior fixation element, the interlocking amount being in the range of 0 to 450 μm, and particularly in the range of 0 to 250 μm.

[0041] In a further embodiment of the artificial knee joint, there is at least one compression area between the posterior fixation element and the tibial insert, particularly created by an angular mismatch between the two walls. This allows for improved joint assembly and reduced micro-movement in the posterior portion of the joint.

[0042] Embodiments of the present invention are shown in the figure. [Brief explanation of the drawing]

[0043] [Figure 1] A perspective view of an artificial knee joint is shown. [Figure 2] This shows a perspective view of the distal surface of one embodiment of a tibial tray having a tibial tray structure with three shaft wall elements (Y-shaped structure). [Figure 3] This shows a perspective view of the distal surface of one embodiment of a tibial tray having a tibial tray structure with four shaft wall elements (X-shaped structure). [Figure 4] A diagram showing the distal view of a further embodiment of a tibial tray having a tibial tray structure with three shaft wall elements (T-shaped structure) is shown. [Figure 5] Figure 4 shows the structure of the tibial tray structure (T-shaped structure) with a cross-sectional plane in the proximal 1 / 3. [Figure 6] Figures 4 and 5 show a perspective view of the distal surface of the embodiment (T-shaped structure) shown. [Figure 6A] A diagram of the distal surface of one embodiment is shown, with an indication of the surrounding radius. [Figure 7] A side view is shown of one embodiment of a tibial tray having a tibial tray structure with three shaft wall elements (T-shaped structure) and a concave structure for bone cement. [Figure 8] This shows a perspective view of the distal surface of one embodiment of a tibial tray having a tibial tray structure with three shaft wall elements (T-shaped structure). [Figure 9] A perspective view of one embodiment of a tibial tray is shown. [Figure 9A] The same diagram as Figure 9 is shown to emphasize the reference frame. [Figure 9B]A modified form of the embodiment shown in Figure 9 is presented. [Figure 10A] A proximal view of one embodiment of a tibial tray is shown. [Figure 10B] Figure 10A shows a diagram of the distal view of the tibial insert that aligns with the tibial tray. [Figure 11] Figure 10A shows a diagram of the proximal surface of the embodiment that illustrates the interference region. [Figure 12A] The insertion of the tibial insert into the tibial tray is shown in a perspective view. [Figure 12B] Figure 12A shows a cross-sectional view of the insertion of the tibial insert into the tibial tray. [Figure 13A] A detailed front view of the first embodiment of the tibial insert is shown. [Figure 13B] A detailed front view of a second embodiment of the tibial insert is shown. [Figure 14] Figure 9 shows a perspective view of a modified form of the embodiment shown. [Figure 15A] This is a distal perspective view of the tibial shaft structure, seen from the anterior side. [Figure 15B] This is a distal perspective view of the tibial shaft structure, seen from the posterior side. [Figure 15C] This is a diagram of the proximal direction of the distal surface. [Figure 16A] This is a posterior perspective view of the proximal surface of a tibial tray having a first embodiment of the central fixation element. [Figure 16B] This is a perspective view from the anterior side of the proximal surface of a tibial tray having a first embodiment of the central fixation element. [Figure 17] This is a posterior perspective view of the proximal surface of a tibial tray having a second embodiment of the central fixation element. [Figure 18A] This is a cross-sectional view through one embodiment of a tibial tray in the anterior direction. [Figure 18B] This is a cross-sectional view through one embodiment of a posterior tibial tray. [Figure 19] A schematic diagram of line elements for generating a smooth outer rim of a wall element is shown. [Figure 20A] This shows an anterior perspective view of one embodiment of a tibial tray having a cement-retaining structure. [Figure 20B] Figure 20A shows a rear perspective view of the embodiment having a cement-holding structure. [Figure 21A] An anterior perspective view of one embodiment is shown along with a diagram of the geometric shape of the wall element in the tibial tray shaft structure. [Figure 21B] Figure 21A shows a rear perspective view of the embodiment shown. [Figure 22] A perspective view of the proximal surface of a further embodiment of a tibial tray having a guide surface on the anterior fixing element is shown. [Figure 23] The details of the connection between the rear fixing elements in one embodiment are shown. [Modes for carrying out the invention]

[0044] Figure 1 shows a posterior perspective view of the artificial ceramic knee joint 100. Figure 1 also shows the femoral portion 40, tibial insert 30, and tibial tray 20 of the metal-free artificial knee joint. Alternative embodiments are not metal-free.

[0045] Here, the complete artificial knee joint 100 is metal-free and is, for example, a combination of ceramic and polymer materials. The tibial tray 20 can be made from, for example, ceramic, and the tibial insert 30 can be made from polymer material.

[0046] The proximal position of the artificial knee joint shows a femoral portion 40, which has two condyles that fit into matching grooves on the proximal surface of the tibial insert 30 at the distal end of the femoral portion 40.

[0047] The tibial insert 30 is connected to the tibial tray 20, and the distal surface D of the tibial insert 30 faces the proximal surface P of the tibial tray 20.

[0048] Embodiments of the tibial tray 20 are described in relation to Figures 2 to 8. Embodiments of the tibial tray 10 and tibial insert 30 that can be used in relation to the embodiments of the tibial tray 20 described herein are shown in Figures 9 to 14.

[0049] Figure 2 shows a distal perspective view of one embodiment of the tibial tray 20. The shape of the distal surface D is formed substantially the same as that of the proximal side of the tibial tray 20 (see, for example, Figures 9 to 15). The tibial tray shaft structure 21 is located midway in the lateral width between points L1 and L2, i.e., at the center of the distal surface D. In the illustrated embodiment, the tibial shaft structure 21 is essentially Y-shaped (i.e., refers to a cross-section in a plane parallel to the distal surface D) with respect to axis A. The tibial tray structure 21 comprises three shaft wall elements 22, 23, and 24 arranged around axis A at an angle of 120° between the elements. One Y-shaped shaft wall element 22 is oriented toward the anterior side of the tibial tray 20, and the other two shaft wall elements 23 and 24 are oriented toward the posterior side of the tibial tray 20.

[0050] The tibial tray structure 21 extends distally DD away from the distal plane D (as shown in Figure 5, for example), and distal DD is essentially oriented laterally from the plane of the figure in Figure 2.

[0051] The distal surface D has a raised rim R that extends away from the distal surface D. The width of the plane parallel to the distal surface D is 1 to 4 mm.

[0052] The three shaft wall elements 22, 23, and 24 of the tibial tray shaft structure 21 each have an outer rim 26. The outer rim 26 is the thin surface of the shaft wall elements 22, 23, and 24. The thickness T of the shaft wall elements 22, 23, and 24, measured at the endpoint (i.e., the point furthest from axis A on the distal plane D), is 2 to 5 mm.

[0053] The outer rims 26 converge from their broad bases in the distal plane D toward the distal axis A. The convergence is strictly monotonic; that is, there are no sections of the outer rim 26 parallel to the distal plane D. In the embodiment shown in Figure 2, the slope of the outer rim 26 increases from the base, i.e., the distal plane D toward the axis. The change in slope is smooth and without twisting.

[0054] In the space defined between the shaft wall elements 22, 23, and 24, the outer rim 26 is connected by a smooth surface S, in this case a surface curved inward (i.e., toward axis A). The surface 13 itself has no twists or edges to allow for good insertion into the tibia. The transition from the smooth surface 13 to the outer rim 26 is also smooth, i.e., without twists or edges. In the illustrated embodiment, the radius R2 of this transition is 1 to 4 mm, in particular, depending on the size of the tibial tray structure 21.

[0055] The transitions from the distal surface D to the shaft wall elements 22, 23, 24 and / or the smooth wall 13 are rounded such that the radius R1 is in the range of 1 to 4 mm.

[0056] Furthermore, as shown in more detail in relation to Figure 5, the cross-sectional area of ​​the tibial shaft structure 21 in a plane C parallel to the distal plane D is maximum at its base in the distal plane D. As the tibial shaft structure 21 extends distally DD, its cross-sectional area decreases (more precisely, it decreases monotonically).

[0057] The base plate having a distal surface D has a thickness ranging from 2 mm to 6 mm, particularly in the range of 4.5 mm.

[0058] Figure 3 shows an embodiment of a tibial tray 20 comprising four shaft wall elements 22, 23, 24, and 25 in an X-shaped pattern. Two of the shaft wall elements 24 and 25 are oriented towards the anterior side of the tibial tray 20, while the other two shaft wall elements 22 and 23 are oriented towards the posterior side.

[0059] Otherwise, the geometric shape of the outer rim 26, the smooth surface 13 in the angled space between the shaft wall elements 22, 23, 24, and 25, and especially the convergence of the outer rim 26 in the distal direction D toward axis A are similar to the embodiment shown in relation to Figure 2, so you can refer to the description.

[0060] The embodiment shown in the perspective view in Figure 4 is a further variation of the embodiment shown in Figures 2 and 3. Therefore, the description given above is equally applicable.

[0061] Here, the tibial tray structure 21 has a T-shaped cross-section in a plane parallel to the distal plane D. The shaft wall elements 22 and 24 that form the horizontal bar of the T are arranged essentially parallel to each other on the anterior side, and one shaft wall element 25 that forms the vertical bar of the T is oriented perpendicular to the posterior side of the tibial tray 20.

[0062] Here too, the three shaft wall elements 22, 23, and 24 of the tibial tray structure 21 have cross-sectional areas that converge strictly monotonically toward the distal direction DD toward axis A. The lateral rims 22, 23, and 24 always have a slope greater than 0° (measured relative to the distal plane), i.e., the lateral rims do not have a trapezoidal portion. However, the lateral rim 26 has three inflection points 27 where the curvature changes.

[0063] Any change in the tangential angle over a 10% height distance of the tibial tray structure means that there is no sharp bend in the lateral rim 26. The change in gradient is smaller in the first one-third of the height of the tibial tray structure 21 as measured from the distal plane. A further definition of the lateral rim 26 is explained in relation to Figure 19.

[0064] Figure 5 shows a rear view of the embodiment shown in Figure 4. Here, a cross-sectional plane C parallel to the distal plane D is shown. Cross-sectional plane C separates the lower 1 / 3 of the tibial tray structure 21 from the upper 2 / 3. For good mechanical load distribution, at least 50% of the volume of the shaft wall elements 22, 23, and 24 is located between this cross-sectional plane C and the distal plane D, i.e., the 1 / 3 closest to the distal plane D. This also applies to the other embodiments shown in Figures 2 and 3.

[0065] Figure 6 shows the same embodiment as shown in Figures 4 and 5, namely the tibial tray structure 21 having a T-shape. In this figure, the shape of the lateral rim 26 and the rounded transition from the distal surface to the tibial tray structure 21 are clearly shown.

[0066] Figure 6A illustrates some of the geometric shapes around the tibial tray 20. The anterior radius Rant is 30mm to 60mm. The lateral radius Rlat is 15mm to 30mm, and the posterior radius Rpost is 10mm to 20mm, specifically 16mm.

[0067] Figure 7 is essentially a side view of the embodiments shown in Figures 4 to 6, so the above description is applicable. In addition to the embodiments described, this embodiment includes one or more anterior and / or posterior cement-retaining structures, in this case recessed structures 28 within the tibial tray structure 21. When the tibial tray 20 is implanted in the tibia, better fixation is achieved as bone cement enters such undercuts. In this embodiment, the recessed structure 28 is shaped like a groove essentially parallel to the distal surface. In principle, other shapes are also possible. One embodiment here is such that the cement-retaining structure 28 is oriented so that the bone cement is not easily removed when the tibial tray 20 is implanted.

[0068] Figure 8 shows a modified embodiment of the embodiments shown in Figures 4 to 7, namely a T-shaped structure such as the tibial tray structure 21. The distal surface D is provided with a recess 14. Furthermore, it is shown that the transition point of the distal surface D from the lateral rim 26 of the tibial shaft structure 21 is located at least 5 mm (D1) from the lateral and / or posterior side of the distal surface D. The intermediate planes of the shaft wall elements 22, 23 extend laterally and / or posteriorly to the distal surface D, defining the distance D1. This allows for good placement of the tibial tray structure 21 within the bone.

[0069] The following describes embodiments of the tibial tray 20 and tibial insert 30, particularly the features of the proximal surface P of the tibial tray 20 and the matching distal surface D of the tibial insert 30.

[0070] Figures 9 and 9A show a perspective view of the tibial tray 20 on the proximal plane P. In Figure 9A, the tibial tray is shown without reference numerals to reduce complexity, but it has reference planes M and N, which are used below to define the position of features on the tibial tray 20.

[0071] Referring to Figure 9A, the intermediate plane M is perpendicular to the flat proximal plane P and intersects the proximal plane P midway between the two outermost points L1 and L2 on the proximal plane P. The front plane N is perpendicular to the intermediate plane M.

[0072] In one embodiment of the tibial tray 20, the dimensions are classified into different sizes. There are eight different sizes for the distance between points L1 and L2. This is used to enable artificial knee joints 100 for patients of different sizes. The minimum distance between L1 and L2 is 60 mm. The other seven sizes have distances of 64 mm, 68 mm, 72 mm, 76 mm, 80 mm, 84 mm, and 88 mm (i.e., using increments of 4 mm). Other embodiments may use different absolute sizes and / or different increments, and the increments do not need to be identical.

[0073] In the range of the proximal plane P in the direction perpendicular to the distance between L1 and L2, the corresponding sizes 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. Other embodiments may use different absolute sizes and / or different increments, where again the increments do not have to be identical.

[0074] The proximal surface P of the tibial tray 20 is structured so that the corresponding tibial insert 30 (see, for example, Figures 1 and 13) can be securely fastened to the tibial tray 20 (see Figures 12A and 12B). The flat proximal surface P itself is polished to an average roughness of Ra=1 μm, particularly Ra=0.1 μm, and a flatness of 0.1. In other embodiments, the average roughness is less than 5 μm, particularly less than 2 μm.

[0075] Different embodiments of structures 1, 2, and 3 on a flat proximal surface P are described below. These structures provide symmetrical, flat, pegboard portions having island-like fixing elements 1, 2, and 3 for connecting a tibial insert 30 using press-fit or interlocking fit (see Figure 11).

[0076] In the embodiment shown in Figure 9, the proximal surface P comprises two central fixation elements 1. As described below, these two central fixation elements enable a secure connection with a tibial insert (see Figure 10B) as a further part of the artificial knee joint 100.

[0077] In the illustrated embodiment, the two central fixation elements 1 are linear projections that project proximally away from the proximal surface P, and as a result, they can align with the corresponding notches (or grooves) 34 of the tibial insert 30 (see Figure 10B). In other embodiments, the central fixation elements 1 may have a cylindrical shape. Other shapes and different positions of the central fixation elements 1 are shown below.

[0078] The two central fixed elements 1 are arranged symmetrically and parallel to the intermediate plane M.

[0079] In the embodiment shown in Figure 9B, the two central fixed elements 1 are still symmetrical with respect to the midplane M, but are not parallel because they are angled less than 5° with respect to the midplane M, and as a result the two linear fixed elements 1 show some convergence toward the front.

[0080] In other embodiments, the two central fixed elements 1 can be asymmetrical with respect to the intermediate plane M, but parallel to each other.

[0081] As shown in Figure 14, in different embodiments, three or more central fixed elements 1 can be used. In other respects, the embodiment in Figure 14 is equivalent to the one described in relation to Figure 9.

[0082] In the embodiment shown in Figure 9, the two central fixed elements 1 are arranged symmetrically with respect to a front plane N perpendicular to the intermediate plane M. In this embodiment, although not necessarily so, the front plane N passes through the outermost points L1 and L2 of the proximal plane P.

[0083] The two central fixed elements 1 have the shape of a parallelepiped, and the front and rear ends of the central fixed elements 1 are rounded.

[0084] In the illustrated embodiment, the two central fixation elements 1 have a height H that extends 3.8 mm from the proximal surface P of the tibial tray 20. In other artificial knee joints 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 may vary with respect to the proximal surface P. In other embodiments, the height H of at least two central fixation elements 1 on the proximal surface varies by up to 10% from the minimum height.

[0085] In the embodiment shown in Figure 9, the distance between the two central fixing elements 1 is 10.5 mm when measured between the inner walls and 15.5 mm when measured between the outer walls. Since the two central fixing elements 1 are parallel to each other, the width of each central fixing element is 2.5 mm. The distance between the central fixing elements is selected here to be as large as possible to provide a large torque and prevent shearing of the polyethylene material from the tibial insert 30. If the distance between the two central fixing elements 1 is always the same, different sized tibial inserts 30 can be used when assembling the artificial knee joint 100.

[0086] The orientation of the central fixation element 1 on the proximal surface P allows for linear guidance of the tibial insert 30 during assembly (see Figures 12A and 12B), and as a result, the central fixation element 1 may also be called a central guide rail. Furthermore, the central fixation element 1 enables improved stability against shear forces in the artificial knee joint.

[0087] The proximal surface P also includes a front fixing element 2 located on the front rim of the proximal surface P. The rear side of the front fixing element 2 includes a rear wall 4 positioned perpendicular to the midplane M of the proximal surface P. Thus, the rear wall 4 is also essentially perpendicular to the two linear central fixing elements 1. In this embodiment, the front fixing element 2 has the same height H as the central fixing element 1. In other embodiments, the heights of the front fixing element 2 and the central fixing element 1 may be different.

[0088] The anterior fixation element 2 comprises two cavities 5 in the form of channels having essentially rectangular cross-sections (i.e., the channels are open at both ends). As shown in relation to Figures 12A and 12B, these cavities are shape-fitting elements 5 that cooperate with matching shape-fitting elements 31 on the tibial insert 30. The shape-fitting elements 5 within the anterior fixation element are arranged symmetrically with respect to the midplane M.

[0089] In other embodiments, the front fixing element 2 comprises one or more shape-fitting elements 5. The cross-section of the cavity of the shape-fitting element 5 does not have to be rectangular; for example, a circular or polygonal cross-section can also be used.

[0090] In the embodiment shown in Figure 9, the anterior fixing element 2 is a single continuous element located on the anterior rim of the tibial tray 20. In other embodiments, the anterior fixing element 2 can be divided into two or more parts, for example, two elements, each of which comprises a shape-fitting element 5.

[0091] The two shape-fitting elements 5 within the front fixing element 2 are positioned in a region where the mechanical load transmission is less than 50% of the maximum load transmission. This is due to the fact that the channel-shaped shape-fitting elements 5 somewhat weaken the structure of the front fixing element 1.

[0092] A further structure on the proximal plane P is a posterior fixing element 3 positioned on the posterior rim of the proximal plane P. The posterior fixing element 3 is positioned symmetrically with respect to the intermediate plane M and comprises a posterior wall 7 flush with the posterior rim 8 of the tibial tray 20. The posterior wall 7 follows the curved shape of the posterior rim 8 of the tibial tray 20. The cross-section of the anterior fixing element 3 in a plane parallel to the proximal plane P is symmetrical with respect to the intermediate plane M. In this embodiment, the posterior fixing element 3 has the same height H as the central fixing element 1. In other embodiments, the heights of the posterior fixing element 3 and the central fixing element 1 may be different.

[0093] The embodiment shown in Figure 9 also includes a front wall 9 of the rear fixing element 3 and a rear wall 4 of the front fixing element 2. The rims of these walls 4, 9 on the proximal surfaces of the rear element 3 and the front fixing element 2 are parallel to each other. If the walls 4, 9 do not have undercuts (i.e., the walls 4, 9 are not inclined), then the walls 4, 9 themselves are parallel. Thus, the two central fixing elements 1 are oriented perpendicular to both the rear wall 4 of the front fixing element 2 and the front wall 9 of the rear fixing element 3.

[0094] The rear fixing element 3 also comprises two side walls 10 angled with respect to the front wall 9 of the rear fixing element 3. The angle α between the two side walls 10 and the front wall 9 in a plane parallel to the proximal plane P is in the range of 0° to 22°, particularly in the range of 15° to 22°. Thus, the two side walls 10 are oriented to converge in the forward direction. The overall horizontal shape of the rear fixing element 3 is approximately trapezoidal, with the longer side of the trapezoid being curved.

[0095] The two side walls 10 of the rear fixing element 3 are inclined inward, forming undercuts at angles of 1° to 45°, particularly 20° to 30°, with respect to a plane perpendicular to the proximal plane P. Therefore, the upper surface of the rear fixing element 3 is slightly larger than the base cross-section in the plane of the proximal plane.

[0096] In the embodiments described herein and best shown in Figure 12B, the front wall 9 of the rear fixing element 3 is provided with an undercut 6, which forms an angle β of 1° to 45°, particularly 30°, with respect to a plane perpendicular to the proximal surface P. In other embodiments, the undercut 6 may have at least a partially curved shape. In principle, the rear wall 4 of the front fixing element 2 may also be provided with an undercut 6.

[0097] In the embodiments discussed so far, the heights H of the fixed elements 1, 2, and 3 above the proximal surface P were the same. This does not necessarily apply to all embodiments.

[0098] The matching tibial tray 20 and tibial insert 30 are shown side by side in Figures 10A and 10B. An embodiment of the tibial tray 20 in Figure 10A has already been described in Figure 9, so refer to that description. The distal surface D of the tibial insert 30 is shown in Figure 10B. A comparison of the two parts 20 and 30 shows that the tibial insert 30 can be connected to the tibial tray 20 such that the first fixing element 1 fits into the matching notch 34 of the tibial insert 30.

[0099] The tibial insert 30 includes a recess 32 (see Figure 10B) in the distal surface D for the posterior fixation element 3 of the tibial tray 20 to which it is aligned. The recess 32 opens posteriorly so as to have only an anterior wall 35 and two lateral walls 36.

[0100] The side wall 36 of the recess 32 is angled to match the angled side wall 10 of the rear fixing element 3. At the corner where the front wall 35 and the two side walls 36 of the recess 32 intersect, a stress-relieving notch 33 is located at the joint of the two walls 35 and 36.

[0101] On the anterior side of the tibial tray insert 30 are two shape-fitting elements 31 that can be inserted into two cavities (see Figure 9) of the shape-fitting element 5 within the anterior fixing element 2.

[0102] The notches 34 and recesses 32 of the tibial tray 30 also form a matching structure, namely, some kind of morphologically fitted connection with the central fixation element 1 and posterior fixation element 3 of the tibial tray 20. However, the main function of structures 32 and 34 is to assist during assembly, as described below in relation to Figures 12A and 12B.

[0103] The connection between the tibial tray 20 and the tibial insert 30 is primarily achieved by a compression fit connection between the tibial insert 30 and at least two central fixation elements 1, where at least one anterior fixation element 2 and at least one posterior fixation element 3 have compression fits in the range of 0 μm to 450 μm, more specifically 0 μm to 250 μm, in the anterior-posterior direction. In Figure 11, the surfaces 37 for compression fits on the posterior wall 4 of the anterior fixation element 2, the inside of the central fixation element 1, and the anterior wall 9 of the posterior fixation element 3 are highlighted. While all compression fit connections can be of the same dimensions, this is not required in all embodiments. For example, the compression 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 50 to 150 μm, and / or the compression fit between the central fixation elements 1 is in the range of 50 to 100 μm. The sides of the recess 32 provide the compression fit.

[0104] Figures 12A and 12B show different diagrams illustrating the assembly of embodiments of the tibial insert 30 and the tibial tray.

[0105] Figure 12A shows a frontal perspective view with the tibial tray 20 and tibial insert 30 partially connected below. Figure 12B is a cross-sectional view showing the tibial tray 20 and tibial insert 30 in essentially the same relative position, but with the anterior fixation element 2 on the right side.

[0106] The tibial insert 30 is initially connected to a posterior fixing element 3 (see Figures 9, 10A, and 10B), which is used as a kind of fulcrum in snapping into place. Figure 12B shows an undercut 6 in the anterior wall 9 with an angle of approximately 15° to allow for secure placement of the tibial insert 30. On the anterior side (see Figure 12A) are two shape-fitting elements 31 that snap into the cavity of shape-fitting element 5 (not shown in Figure 12A).

[0107] Figure 13A shows a front view of a first embodiment of the tibial insert 30. In this embodiment, the shape of the distal surface D does not conform to the contact area; that is, the lateral rim of the tibial insert 30 is essentially a slightly inclined wall. The inclination can be 0 to 10°. At a 0° inclination, the wall is upright.

[0108] Figure 13B shows a second embodiment of the tibial insert 30, similarly in a front view. Here, the shape of the distal surface D conforms to the contact area, i.e., the outer wall is slightly inclined outward.

[0109] While the above-described ceramic knee joint 100 having a metal-free, particularly ceramic, tibial tray 20 is a preferred embodiment, the tibial tray 20 or the complete knee joint 100 may be made from or contain metal or polymer materials.

[0110] Figures 15A, 15B, and 15C show the distal surface D of the tibial tray 20. Figure 15A shows the view from the front, and Figure 15B shows the view from the back. Figure 15C shows the upper view of the distal surface D.

[0111] The tibial tray structure 21 is essentially an X-shaped structure, and the angle γ1 between the first shaft wall element 22 and the second shaft wall element 23 is different from the angle γ2 between the third shaft wall element 24 and the fourth shaft wall element 25. The angle γ1 between the first shaft wall element 22 and the second shaft wall element 23 facing posteriorly is smaller than the angle γ2 between the third shaft wall element 24 and the fourth shaft wall element 25. In the illustrated embodiment, the angle γ1 between the first shaft wall element 22 and the second shaft wall element 23 is less than 90°, i.e., 80° (see Figure 15B), and the angle γ2 between the third shaft wall element 22 and the fourth shaft wall element 23 is greater than 90°, i.e., 120°. In one embodiment, angles γ1 and γ2 are 110° and 70°, respectively.

[0112] In other embodiments, for example as shown in Figure 9, the central fixing element 1 has a shape having two axes of symmetry: an axis of symmetry along the long axis and an axis of symmetry on an axis perpendicular to this axis of symmetry. Figures 16A and 16B show embodiments of the tibial tray 20 that deviate from this pattern.

[0113] Figures 16A and 16B show an embodiment in which the central fixation element 1 has a lateral cross-section that is wider towards the anterior side than towards the posterior side. Thus, each of the long side walls of the central fixation element 1 converges toward the anterior side. The medial side walls of the central fixation element 1 are not parallel but diverge toward the posterior side of the tibial tray 20, while the lateral side walls are essentially parallel.

[0114] Figure 17 shows a deformed embodiment of the tibial tray 20 when the central fixation element 1 has a different shape. Here, as in the embodiment shown in Figure 9, the lateral side walls of the central fixation element 1 are parallel to each other and have two axes of symmetry. In the embodiment of Figure 17, the medial side wall is not linear along its entire length. Towards the anterior and posterior sides, the side walls converge and diverge towards the middle.

[0115] The front fixing element 2 in the embodiments shown in Figures 16A, 16B, and 17 has the same shape as the embodiment shown in Figure 9. However, the rear fixing element 3 in the embodiments shown in Figures 16A, 16B, and 17 has a different shape.

[0116] The side walls of the rear element 3 are inclined at an angle of 0° to 45°, particularly 0° to 30°, with respect to a plane perpendicular to the proximal plane P. Additionally or alternatively, the side walls and front walls of at least one rear element 3 are provided with undercuts.

[0117] Figures 18A and 18B show cross-sections of a front plane N (see, for example, Figure 9A) for one embodiment. Figure 18A shows a view in the front direction, i.e., the front fixing element 2 can be seen behind the central fixing element 1, which is shown in the cross-sectional view. Figure 18B shows a view in the rear direction, but on the same front plane N.

[0118] The cross-section of the central fixing element 1 shows that it has a central fixing element recess 12 (undercut) along the inner side wall at the transition to the proximal surface P. The central fixing element recess 12 is here a groove with a constant radius. In different embodiments not shown herein, the central fixing element recess 12 may also be located on or within the outer side wall of the central fixing element 1.

[0119] Figures 18A and 18B also show a cement retaining structure 28, which will be described in more detail in relation to Figures 20A and 20B.

[0120] Figure 19 shows a schematic diagram of the tibial tray structure 21 (here a T-shaped structure) in an anterior view with the distal direction facing upward. This figure is not shown as a specific embodiment of the tibial tray 20, but is intended to show how the shape of the lateral rim 26 of the lateral wall (e.g., as in Figures 4 and 5) can be generated. In this exemplary embodiment, the lateral rim 26 follows a strictly monotonic curve with an inflection point. An example of how this curve is generated is shown below. Multiple line segments M1, M2, M3, M4, and M5 are used to connect the distal plane D to the distal tip of the tibial tray shaft structure 21.

[0121] The first line segment M1 connects the distal plane D to a first point P1 within the distal plane D. The first point P1 is positioned laterally at approximately 68% of the distance from the midplane M (see Figure 9A) to the outermost point of the lateral rim. The inclination of the first line segment M1 is approximately 20°, measured from the distal plane D. In an alternative embodiment, the first point P1 is positioned laterally within the range of 55-75% of the distance from the midplane M to the outermost point of the lateral rim. In an alternative embodiment, the inclination of the first line segment M1 can also be in the range of 15-30°, measured from the distal plane D. The above embodiments can also be combined.

[0122] The second line segment M2 connects the first point P1 to the second point P2 above the distal plane D. The second point P2 is positioned perpendicularly at approximately 15% of the distance from the distal plane D to the plane parallel to the most distal point of the tibial tray shaft structure 21. The inclination of the second line segment M2 is approximately 40°, measured from the distal plane D. In an alternative embodiment, the second point P2 is positioned perpendicularly within the range of 10-20% of the distance from the distal plane D to the plane parallel to the most distal point of the tibial tray shaft structure 21. In an alternative embodiment, the inclination of the second line segment M2 can also be in the range of 30-50°, measured from the distal plane D. The above embodiments can also be combined.

[0123] The third line segment M3 connects the second point P2 to the third point P3 above the distal plane D. The third point P3 is positioned perpendicularly at approximately 33% of the distance from the distal plane D to the plane parallel to the most distal point of the tibial tray shaft structure 21. The inclination of the third line segment M3 is approximately 60°, measured from the distal plane D. In an alternative embodiment, the third point P3 is positioned perpendicularly within the range of 25-40% of the distance from the distal plane D to the plane parallel to the most distal point of the tibial tray shaft structure 21. In an alternative embodiment, the inclination of the third line segment M3 can also be in the range of 45-70°, measured from the distal plane D. The above embodiments can also be combined.

[0124] The fourth line segment M4 connects the third point P3 to the fourth point P4 above the distal plane D. The fourth point P4 is positioned perpendicularly at approximately 50% of the distance from the distal plane D to the plane parallel to the most distal point of the tibial tray shaft structure 21. The inclination of the fourth line segment M4 is approximately 50° when measured from the distal plane D. In an alternative embodiment, the fourth point P4 is positioned perpendicularly within the range of 40-60% of the distance from the distal plane D to the plane parallel to the most distal point of the tibial tray shaft structure 21. In an alternative embodiment, the inclination of the fourth line segment M4 can also be in the range of 40-60° when measured from the distal plane D. The above embodiments can also be combined.

[0125] The fifth line segment M5 connects the fourth point P4 to a point in the central structure of the tibial tray shaft 21. The inclination of the fifth line segment M5 is approximately 75° when measured from the distal plane D. In other embodiments, the inclination of the fifth line segment M5 is in the range of 50° to 80° when measured from the distal plane D. The above embodiments can also be combined.

[0126] The slopes of line segments M1, M2, M3, M4, and M5 change, and as a result, approximately halfway through, the slope of the fourth line segment M4 is steeper than the slope of the third line segment M3.

[0127] The points defining the line segments can be approximated by smooth curves, such as polynomials or spline curves, to generate the smooth outline of one of the outer limbs 26 of the tibial tray shaft structure 21. That is, all elements of the two lateral shafts of the T-structure are shown in Figure 19.

[0128] Figures 20A and 20B show a perspective view of one embodiment of the tibial tray 20. Essentially, the embodiment has the features described above, but here the T-shaped tibial shaft structure 21 is provided with a cement retaining structure 28 relatively close to the distal surface D. The anterior side, which is best seen in Figure 20A, has grooves as cement retaining structures 28 that cross two wall elements. The posterior side, which is best seen in Figure 20B, has two grooves as cement retaining structures 28, each extending across two wall elements, i.e., traversing the rounded corner between the wall elements.

[0129] The cement retaining structure 28 is designed here as a rounded groove for ease of manufacture. In other embodiments, the cement retaining structure 28 may include, or consist solely of, other shapes, such as grooves with sharp angles or holes with circular or polygonal cross-sections.

[0130] Figures 21A and 21B show modifications of the above-described embodiments, such as those shown in Figures 20A and 20B, but here an embodiment of the tibial tray 20 without the cement holding structure 28 is shown. The tibial tray shaft structure 21 comprises a vertical cylindrical base shaft structure 29 extending around the axis A of the tibial tray shaft structure 21. The diameter of this base shaft structure 29 is 5 to 8 mm, in particular depending on the size of the tibial tray 20. The diameter can vary in discrete steps, such as 5 mm, 6 mm, 7 mm, and 8 mm. The cross-section of the base shaft structure 29 does not have to be circular. Other shapes, such as elliptical or polygonal, are also possible.

[0131] As described above, three wall elements 22, 23, 24 (Y-shaped structure, T-shaped structure) or four wall elements 22, 23, 24, 25 (X-shaped structure) extend radially away from their base shaft structure 29. The angles between the wall elements 22, 23, 24, 25 are described, for example, in relation to Figures 15A, 15B, and 15C. The angular space between the wall elements 22, 23, 24, 25 is smoothly filled, for example, by curved surfaces 13 connecting adjacent wall elements 22, 23, 24, 25. Figure 21B shows a posterior view of the tibial tray 20 (T-shaped structure). The radius of the curved surface 13 close to the base shaft structure 29 is 1 to 9 mm, particularly 3 to 5 mm. Curved surfaces with similar radii are used between the wall elements of the X-shaped or Y-shaped structure.

[0132] Figure 21A shows a front view of the T-shaped structure shown in Figure 21B. Here, the cylindrical base shaft structure 29 extends forward beyond two front wall elements 22 and 23. Here, the curved surface 13 on the front side is 10 mm to 30 mm, in particular 20 mm.

[0133] These curved surfaces 13 prevent the formation of sharp angles and improve the ease of inserting the tibial tray.

[0134] Figure 22 shows the proximal surface P of the tibial tray 20, including a modified form of the design of the anterior fixation element 2 across the embodiments described above. The central fixation element 1 and the posterior fixation element 3 are described in various ways, for example in Figure 9 or Figure 16A, so you can refer to the above description.

[0135] The anterior fixation element 2 comprises two morphological fitting elements 5 for receiving the corresponding portion of the tibial insert 30 (not shown here; see Figures 12A and 12B for, for example, the snap-fitting process of the tibial tray). The morphological fitting elements 5 are essentially holes with a rectangular cross-section.

[0136] When the tibial insert 30 is inserted from above, using its posterior and posterior fixation elements 3 as pivots, the shape-fitting element 31 for anterior fixation has a shape corresponding to the shape-fitting element 5 (e.g., a rectangular hole).

[0137] To facilitate the snap-fitting of the tibial insert 30 (not shown here), a guide surface 11 is provided on the proximal surface of the anterior fixing element 5. Here, the guide surface 11 is a plane inclined at an angle of 5° to 45°, particularly 30°, with respect to the horizontal plane. Other embodiments are not shown here. The guide surface may be curved or have a flat portion.

[0138] The morphological fitting element 31 of the tibial insert 30 protrudes forward. When the tibial insert 30 is about to be snap-fitted, the morphological fitting element 31 is initially placed on top of the guide surface 11. When distal pressure is applied to the tibial insert 30, the morphological fitting element 31 is guided downward along the guide surface 11 and finally snaps into the hole that forms the morphological fitting element of the anterior fixing element 5 for secure fitting. The guide surface 11 prevents damage to the morphological fitting element 5 during insertion and facilitates secure snap-fitting.

[0139] The lateral width of the guide surface is the same as, or approximately the same as, the lateral width of the shape-fitting element 5 of the front fixing element 2.

[0140] In Figure 23, the details of the rear fixing element 3 are shown in the top view, i.e., in the direction of the proximal plane P.

[0141] The cross-section of the posterior fixation element 3 includes two side walls 10 inclined toward the midplane M. Each of the side walls 10 is angled by approximately 20° with respect to the midplane 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 here).

[0142] For example, if the side wall of the tibial insert 30, which is intended to contact or conform to the side wall 10 of the posterior fixation element 3, has a slightly different inclination than the side wall 10, an angular mismatch will occur, causing closer contact or pressure fit in some parts along the side wall 10 and a looser fit in other parts.

[0143] In the embodiment shown in Figure 23, the angle of the side wall of the posterior fixation element 3 is wider (for example, by about 1°) than the corresponding angle in the recess of the tibial insert 30. This results in a shape fit, i.e., a tighter fit in the posterior region. The interlocking region 38 within this region is shown in Figure 23. This angular mismatch not only allows for easier assembly but also reduces minute movements in the posterior region.

[0144] In other embodiments, the compression fit region 38 is created by widening the rear portion of the rear fixing element 3. [Explanation of Symbols]

[0145] 1 Central fixed element 2 Anterior fixation element 3 Posterior fixation element 4 Rear wall of front fixed element 5. Shape of the front fixing element and the fitting element 6. Undercut of the wall of the rear fixed element 7 Rear wall of the rear fixing element 8. Posterior limb of the tibial tray 9 Front wall of rear fixing element 10 Side wall of rear fixing element 11 Guide surface for tibial insert on anterior fixation element 12 Central fixed element recess 13 Curved surfaces between shaft wall elements 14. Concave on the distal surface 20 Tibial tray 21 Tibial tray shaft structure 22 First shaft wall element of tibial tray shaft structure 23. Second shaft wall element of the tibial tray shaft structure 24 Third shaft wall element of the tibial tray shaft structure 25. Fourth shaft wall element of the tibial tray shaft structure 26. Outer rim of shaft wall element 27 Inflection point on the outer rim of the shaft wall element 28. Recessed structure of shaft wall element for cement retaining structure and bone cement 29 Base shaft structure 30 Tibial Inserts 31 Shape-fitting element for front fixing element 32 Recess for rear fixing element 33 Relaxation Notch 34 Notches / grooves in tibial inserts for linear central fixation elements 35 Front wall of the recess 36 Side wall of the recess 37. Firm fitting surface 38. Interference area due to angular mismatch 40 Femoral part 100 Artificial knee joints Axial axis of the tibial tray shaft structure C section plane D. Distal surface of the tibial tray DD distal direction D1 Distance H is the height of the fixed element. Height of the tibial tray structure measured from the distal surface (L) L1 Lateral point on the proximal plane L2 lateral point on the proximal plane Midplane of the proximal surface of the M tibial tray M1 First line segment defining the outer rim of the shaft element M2 Second line segment defining the outer rim of the shaft element The third line segment defining the outer rim of the M3 shaft element. The fourth line segment defining the outer rim of the M4 shaft element. The fifth line segment defining the outer rim of the M5 shaft element. N Front plane perpendicular to the intermediate plane P Proximal surface of the tibial tray P1 is the first point of the line segment defining the outer rim of the shaft element. P2 is the second point of the line segment defining the outer rim of the shaft element. P3 The third point of the line segment defining the outer rim of the shaft element P4 The fourth point of the line segment defining the outer rim of the shaft element R distal surface rim R1 radius, R2 radius Rant anterior radius Rlat Lateral radius Rpost rear radius S smooth surface T-shaft wall element thickness α Angle between the side wall and the front wall of the front fixing element in a plane parallel to the proximal plane β Undercut angle Angle between the first and second wall structures of the γ1 tibial tray structure Angle between the third and fourth wall structures of the γ2 tibial tray structure

Claims

1. A tibial tray (20) having a distal surface (D), wherein the tibial tray structure (21) extends distally (DD) away from the distal surface (D), The tibial tray structure (21) comprises at least three shaft wall elements (22, 23, 24, 25), which are arranged relative to each other such that their cross-sections in a plane perpendicular to the distal direction (DD) are T-shaped, Y-shaped, or X-shaped. The area of ​​the cross-section decreases strictly monotonically from the distal surface (D) in the distal direction (DD). Tibial tray (20).

2. The tibial tray (20) according to claim 1, wherein the outer rims (26) of the at least three shaft wall elements (22, 23, 24, 25) converge strictly monotonically toward the axis (A) of the tibial tray shaft structure (21) in the distal direction (DD).

3. The tibial tray (20) according to claim 1 or 2, wherein the outer rim (26) of the at least three shaft wall elements (22, 23, 24, 25) has at least one inflection point (27), in particular three inflection points (27).

4. A tibial tray (20) according to at least one of claims 1 to 3, wherein the change in the tangent angle (γ) at the outer rim (26) of the at least three shaft wall elements (22, 23, 24, 25) is less than 30° over 10% of the distal direction, and in particular, the tangent angle (γ) at the outer rim (26) of the at least three shaft wall elements (22, 23, 24, 25) within 1 / 3 of the height (L) of the tibial tray shaft structure (21) measured from the distal surface (D), the tibial tray (20).

5. A tibial tray (20) according to at least one of claims 1 to 4, wherein at least 50% of the volume of the tibial tray shaft structure (21) is located within 1 / 3 of the height (L) of the tibial tray shaft structure (21) measured from the distal surface (D).

6. A tibial tray (20) according to at least one of claims 1 to 5, wherein at least one of the shaft wall elements (22, 23, 24, 25) has a wall thickness (T) of 1 to 6 mm, particularly 2 to 5 mm, and particularly 1 to 5 mm for ceramic materials, measured at the point furthest from the axis (A) on the distal surface (D).

7. A tibial tray (20) according to at least one of claims 1 to 6, wherein the radius (γ) of the transition from the outer rim (26) of at least one of the at least three shaft wall elements (22, 23, 24, 25) to the side wall of at least one of the at least three shaft wall elements is in the range of 0.5 to 4 mm.

8. A tibial tray (20) according to at least one of claims 1 to 7, wherein at least one of the at least three shaft wall elements (22, 23, 24, 25) is provided particularly on the anterior and / or posterior side with at least one recessed structure (28) for holding a cement-holding structure, particularly bone cement.

9. A tibial tray (20) according to at least one of claims 1 to 8, wherein the transition point from the lateral rim (26) to the tibial tray shaft structure (21) on the distal surface (D) is located at least 5 mm from the lateral and / or posterior side of the distal surface (D).

10. A tibial tray (20) according to at least one of claims 1 to 9, wherein the tibial tray shaft structure (21) includes a surface (S) extending between at least two of the outer rims (26) of the at least three shaft wall elements (21) or between two side walls of the at least three shaft wall elements (21).

11. A tibial tray (20) according to at least one of claims 1 to 10, wherein the radius (R1) of the transition from the distal surface (D) to at least one of the at least three shaft wall elements (22, 23, 24, 25) and / or the smooth surface (S) is in the range of 1 to 4 mm.

12. A tibial tray (20) according to at least one of claims 1 to 11, wherein the axis (A) of the tibial tray shaft structure (21) is located on the distal surface (D) at a distance of 1 / 3 of the distance between the anterior rim and the posterior rim, measured from the anterior rim.

13. In the tibial tray (20) according to at least one of claims 1 to 12, the angle (γ) between the shaft wall elements (22, 23) １ The angle between the shaft wall elements (24, 25) is 30° to 120° on the rear side, and the angle between the shaft wall elements (γ ２ ) is a tibial tray (20) with an anterior angle of 90° to 180°.

14. A tibial tray (20) according to at least one of claims 1 to 13, wherein the tibial tray shaft structure (21) comprises at least one cement retaining structure (28), in particular holes, grooves and / or recesses without undercuts.

15. The tibial tray (20) according to claim 14, wherein the at least one cement-holding structure (28) is located within two-thirds, particularly within one-third, of the vertical direction of the tibial tray shaft structure (21), measured from the distal surface (D) in the distal direction (DD).

16. A tibial tray (20) according to at least one of claims 1 to 15, wherein at least one anterior fixing element (2), in particular precisely one anterior fixing element (2), is positioned anterior to the proximal surface (P), and the posterior side of the at least one anterior fixing element (2) comprises a wall (4) perpendicular to the intermediate plane (M) of the proximal surface (P) in a plane parallel to the proximal surface (P).

17. The tibial tray (20) according to claim 16, wherein the at least one anterior fixing element (2) comprises at least one channel through the at least one anterior fixing element (2) for at least one shape-fitting element (5), particularly for at least one cavity in the posterior wall (4) of the at least one anterior fixing element (2), and / or 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 particularly positioned in a region where load transfer is less than 70%, particularly less than 50%, of the maximum load transfer.

18. The tibial tray (20) according to claim 17, wherein the at least one anterior fixing element (2) comprises at least one guide surface (11) for a tibial insert (30), in particular the guide surface (11) having a curved portion and / or a planar portion in the proximal direction of the at least one shape-fitting element (5).

19. The tibial tray (20) according to claim 18, wherein the at least one guide surface (11) includes a flat portion or is a plane inclined at an angle of 5° to 45° with respect to a horizontal plane, particularly at an angle of 30°.

20. A tibial tray (20) according to at least one of claims 1 to 19, wherein the tibial tray (20) has a proximal surface (P), the proximal surface (P) comprising at least two, in particular two, central fixation elements (1) for enabling connection with the tibial insert (30) as a further part of an artificial knee joint, the at least two central fixation elements (1) projecting proximal from the proximal surface (P) and arranged symmetrically and / or parallel to an intermediate plane (M) of the proximal surface (P), the intermediate plane (M) being perpendicular to the proximal surface (P) and intersecting the proximal surface (P) midway between two of the proximal surface (L1, L2).

21. A tibial tray (20) according to at least one of claims 1 to 20, wherein the at least two central fixing elements (1) are provided with central fixing element recesses (12).

22. A tibial tray (20) according to at least one of claims 1 to 21, wherein at least one, in particular precisely one posterior fixation element (3) is symmetrically positioned on the intermediate plane (M) of the proximal surface (P) and comprises a posterior wall (7) flush with the posterior rim (8) of the tibial tray (20) and / or comprises an anterior wall (9) positioned essentially parallel to the posterior wall (4) of the at least one anterior fixation element (2).

23. A tibial tray (20) according to claim 22, wherein the side wall (10) and / or the anterior wall (9) of the at least one posterior fixation element (3) are inclined at an angle of 0° to 45°, particularly 0° to 30°, more specifically 10°, 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 fixation element (3) are provided with an undercut.

24. A tibial tray (20) according to at least one of claims 1 to 23, wherein the at least two central fixing elements (1) are oriented symmetrically and / or parallel to the intermediate plane (M), or the at least two central fixing elements (1) are oriented asymmetrically with respect to the intermediate plane (M).

25. A tibial tray (20) according to at least one of claims 1 to 24, wherein the tibial tray (20) is manufactured entirely or partially from a ceramic, polymer material or metal.

26. An artificial knee joint (100) comprising a tibial tray (20) and a tibial insert (30) according to at least one of claims 1 to 23.

27. An artificial knee joint (100) according to claim 25, wherein there is at least one interference fit (38) region between the posterior fixation element (3) and the tibial insert (30), particularly created by an angular mismatch between two walls.

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