IMPROVED ANKLE PROSTHESIS

Abstract

- Improved ankle prosthesis. - The invention relates to an ankle prosthesis (100), comprising a tibial component (300) intended to be attached to the lower end of a patient's tibia, a talar component (200) intended to be attached to the talus of the patient's foot and having a superior talar face (201) defining a first articular surface (202), and an intermediate component (400) designed to be interposed between the talar component (200) and the tibial component (300), said intermediate component (400) comprising an intermediate inferior face defining a second articular surface designed to cooperate with said first articular surface (202). - Ankle prostheses. - Figure 1.

Description

Title of the invention: IMPROVED ANKLE PROSTHESIS

[0001] The invention relates to the general field of ankle prostheses, that is to say implantable devices intended for the replacement of ankle joints, in particular in the context of orthopedic treatment.

[0002] The invention relates more specifically to an ankle prosthesis, comprising a talar component which has a superior talar face defining a first articular surface and which extends between an anterior talar border and an opposite posterior talar border along a first average direction, said first articular surface being curved along said first average direction.

[0003] In order to treat certain bone pathologies of the ankle, such as osteoarthritis, which leads to degradation or disappearance of the articular cartilage, arthrodesis of the ankle joint is a known procedure. Such an arthrodesis aims to limit, or even completely block, ankle mobility through osteosynthesis, in order to eliminate the joint pain experienced by the patient. While arthrodesis of the ankle joint is generally successful, its main drawback lies precisely in the suppression of joint mobility, which must then be compensated for as much as possible by the other joints of the patient's leg. A long period of adaptation is therefore necessary for the patient to regain satisfactory mobility after the operation.Furthermore, the blockage of the ankle joint creates high mechanical stresses on neighboring joints, which are then exposed to a high risk of premature degeneration.

[0004] This is why it has been proposed, in certain cases, to perform ankle arthroplasty as an alternative to arthrodesis, that is to say, the replacement of the damaged ankle joint with a prosthetic, artificial joint.

[0005] An ankle prosthesis consisting of several components has thus been introduced, namely a talar component and a tibial component, respectively intended to be attached to the talus and the tibia, and a plastic pad which is intended to be interposed between the talar component and the tibial component and to articulate in contact with the talar component.

[0006] Unlike conventional arthrodesis, the use of such a known prosthesis allows the patient to maintain good ankle mobility, thus facilitating walking, and to preserve the various joints of the patient's foot and leg. However, it has been observed that such a known ankle prosthesis can still be improved, particularly with regard to the reproducibility of natural movements. ankle complexes and their range of motion.

[0007] The objects assigned to the present invention are therefore aimed at remedying the various disadvantages listed above and at proposing a new ankle prosthesis with improved kinematics, more respectful of the natural movements of the ankle, and promoting a return for the patient to easy and comfortable locomotion.

[0008] Another object of the invention aims to provide a new ankle prosthesis whose installation is both quick, easy and particularly non-traumatic for the patient.

[0009] Another object of the invention aims to provide a new ankle prosthesis, robust and resistant, and whose hold in the patient's body is particularly reliable.

[0010] Another object of the invention aims to provide a new ankle prosthesis whose manufacture is relatively easy.

[0011] Another object of the invention aims to propose a new ankle prosthesis that reduces the cost of the surgical procedure for fitting the prosthesis.

[0012] Another object of the invention aims to propose a new ankle prosthesis that reduces the risk to the patient's health associated with the fitting of the prosthesis and with therapy.

[0013] Another object of the invention aims to provide a new ankle prosthesis that allows the patient to be treated with a bone pathology in a particularly effective and rapid manner.

[0014] The objects assigned to the invention are reached with the aid of an ankle prosthesis, comprising a talar component which has a superior talar face defining a first articular surface and which extends between an anterior talar border and an opposite posterior talar border in a first average direction, said first articular surface being curved in said first average direction, said prosthesis being characterized in that said first articular surface comprises a first curved part and a second curved part, each extending in said first average direction, said first curved part having a first curvature and said second curved part having a second curvature, said first and second curvatures being different.

[0015] Other features and advantages of the invention will become apparent and will be further detailed upon reading the following description, with reference to the accompanying drawings, given solely by way of illustrative and non-limiting example, in which:

[0016] [Fig-1] and [Fig.2] illustrate, from different perspective views, a method of rea preferential lization of the prosthesis according to the invention, wherein the latter comprises, in addition to a talar component, a tibial component and an inter- component median;

[0017] [Fig.3], [Fig.4] and [Fig.5] illustrate, according to medial views, three spatial configurations that the prosthesis of figures 1 and 2 is likely to affect according to the relative orientation of the left foot and tibia of a patient, namely respectively to a position of plantar flexion ([Fig.3]), a so-called neutral position ([Fig.4]) and a position of dorsiflexion ([Fig.5]);

[0018] [Fig.6] and [Fig.7] illustrate, respectively according to perspective views from above and below, the talar component of the prosthesis of figures 1 and 2;

[0019] [Fig.8] and [Fig.9] illustrate, respectively in top view and bottom view, the talar component of figures 6 and 7;

[0020] [Fig. 10] illustrates, according to an anteroposterior cross-sectional view, the talar component of figures 6 to 9;

[0021] [Fig. 11] and [Fig. 12] illustrate, respectively according to perspective views from above and below, the tibial component of the prosthesis of figures 1 and 2;

[0022] [Fig. 13] and [Fig. 14] illustrate, respectively in top view and bottom view, the tibial component of figures 11 and 12;

[0023] [Fig. 15] illustrates, according to an anteroposterior cross-sectional view, the tibial component of figures 11 to 14;

[0024] [Fig. 16] and [Fig. 17] illustrate, respectively according to perspective views from above and below, the intermediate component of the prosthesis of figures 1 and 2;

[0025] [Fig. 18] and [Fig. 19] illustrate, respectively, in top and bottom view, the intermediate component of figures 16 and 17.

[0026] The invention relates to an ankle prosthesis 100, a preferred embodiment of which is illustrated in Figures 1 and 2. Said prosthesis 100 is a device that can be surgically implanted in the body of a human or animal patient, and is intended to replace a given ankle joint. Advantageously, said prosthesis 100 is designed to completely replace the ankle joint in question (total ankle replacement, TAR). As such, the prosthesis 100 according to the invention is designed to be inserted and interposed between a lower end of a tibia and a corresponding talus of the patient's foot.Advantageously, the tibia and talus in question will have undergone, prior to the implantation of the prosthesis 100 according to the invention in the patient's body, adequate preparation, for example by removing cartilaginous elements and cutting bones, so as to eliminate all or part of the natural articular surfaces of the tibio-tarsal joint to be replaced.

[0027] The prosthesis 100 illustrated as an example in Figures 1 to 5 is intended to be fitted to the left foot of a patient. Obviously, the invention also covers a prosthesis intended to be fitted to a foot patient's right. Advantageously, this would be defined by symmetry, with respect to the sagittal plane of the patient, of the prosthesis 100 illustrated in the figures.

[0028] According to the invention, said prosthesis 100 comprises a talar component 200, a preferred embodiment of which is illustrated in Figures 6 to 10, and which is advantageously intended to be attached to the talus of the patient's foot. The talar component 200 has a superior talar surface 201, which defines a first articular surface 202 of the prosthesis 100. As illustrated, said superior talar surface 201 extends between an anterior talar border 203 and an opposing posterior talar border 204 along a first mean A-A' direction and, preferably, between a lateral talar border 205 and an opposing medial talar border 206 along a second mean B-B' direction, orthogonal to said first mean A-A' direction. Advantageously, said first mean A-A' direction may correspond to a first mean anteroposterior direction in normal use of the prosthesis 100.The said second average direction B-B' may then advantageously correspond to a first average latero-medial direction. Advantageously, the said lateral talar border 205 and a medial talar border 206 are rounded, chamfered.

[0029] It should be noted here that the terms "posterior," "anterior," "medial," and "lateral" are preferentially used in this description to describe elements or features related to their respective orientation relative to the patient's body, in normal use of the prosthesis 100. Thus, the term "medial" is preferentially used to designate an element of the prosthesis 100 intended to be positioned and oriented on the side closest to the mediosagittal (or median) axis of the patient's body, in other words, the side facing the inside of the patient's foot and leg. In contrast, the term "lateral" is used in relation to the side furthest from the mediosagittal axis. Following the same logic, the terms "posterior" and "anterior" preferably refer, respectively, to a rearward and forward positioning relative to the patient's frontal plane.

[0030] According to the preferred embodiment illustrated in the figures, the talar component 200 also comprises an inferior talar face 207, opposite said superior talar face 201, and which is advantageously connected to the latter at said anterior talar border 203 and posterior talar border 204. Said inferior talar face 207 is preferably intended to be positioned in contact with or on a specially prepared area of ​​the patient's talus (or astragalus). Preferably, the inferior talar face 207 is defined by contiguous first and second substantially flat portions ([Fig. 7]), which extend generally along respective intersecting planes, for example, at an elevation angle of 30° of the first flat portion relative to the second flat portion. The first flat portion preferably forms an anterior portion of the inferior talar face 207, while the The second flat portion, which extends along a substantially horizontal plane in normal use of the prosthesis 100 according to the invention, advantageously forms a central and posterior portion of the inferior talar surface 207. A chamfer can be provided at the junction of said first and second flat portions. Such a design of the inferior talar surface 207, particularly simple, limits the number and complexity of the bone cuts required (in this case, two) for the prior preparation of the talus and facilitates the placement of the talar component 200 in the patient's body.

[0031] As illustrated, the talar component 200 may also include a medial talar face 208 and an opposing lateral talar face 209, which respectively connect the lateral talar border 205 and the medial talar border 206 to said inferior talar face 207. Preferably, said medial talar face 208 and lateral talar face 209 are generally convex outwards from the talar component 200, in order to best respect the natural anatomical conformation of the area of ​​the talus at the level of which the talar component 200 is intended to be placed.

[0032] Preferably, the prosthesis 100 according to the invention comprises a tibial component 300 (Figures 11 to 15), intended to be attached to a lower end of the patient's tibia. Said tibial component 300 has a superior tibial face 301 and an opposing inferior tibial face 302. As illustrated, said inferior tibial face 302 extends preferably, on the one hand, between an anterior tibial border 303 and an opposing posterior tibial border 304, preferably along a third average direction C-C', and, on the other hand, between a lateral tibial border 305 and an opposing medial tibial border 306, preferably along a fourth average direction D-D', orthogonal to said third direction C-C' average.

[0033] Advantageously, said third average C-C' direction may correspond to a second average anteroposterior direction in normal use of the prosthesis 100. Said fourth average D-D' direction may then advantageously correspond to a second average lateromedial direction. Said second average anteroposterior direction and second average lateromedial direction of the tibial component 300 are advantageously parallel, respectively, to said first average anteroposterior direction and first average lateromedial direction of the talar component 200, in normal use of the prosthesis 100.

[0034] In the preferred embodiment illustrated in the figures, the upper tibial face 301 and the lower tibial face 302 extend respectively along substantially parallel mean extension planes, said tibial component 300 being generally in the form of a plate. Said upper tibial face 301 is preferably intended to be positioned in contact with or on a specially prepared area of ​​the tibia. As illustrated, the tibial component 300 can It also comprises a medial tibial surface 307 and an opposing lateral tibial surface 308, which respectively connect the lateral tibial border 305 and the medial tibial border 306 to the inferior tibial surface 302. Advantageously, the medial tibial border 306 is substantially straight and the medial tibial surface 307 is substantially flat (Figures 11 to 14), so that the surgeon can precisely position the tibial component 300 within the patient's body by aligning the medial tibial surface 307 along a straight cut made at the level of the medial malleolus. This advantageously reduces the areas of uncovered bone cuts, which could promote the formation of geodes or cysts.In addition, the tibial component 300 may include an anterior tibial face 309 and an opposing posterior tibial face 310, which respectively connect the anterior tibial border 303 and the posterior tibial border 304 to said superior tibial face 301.

[0035] Preferably, said talar component 200 and / or said tibial component 300 are respectively a single piece of a biocompatible and wear-resistant material. Advantageously, said talar component 200 and / or said tibial component 300 are made of a metallic material, for example, a chromium-cobalt alloy (CrCo), stainless steel, or titanium. According to one embodiment, said talar component 200 and said tibial component 300 are respectively a cast part. According to an alternative embodiment, said talar component 200 and said tibial component 300 are respectively a machined part. Obviously, other suitable materials may be considered, such as, for example, a ceramic material, as well as other manufacturing methods (injection molding, casting, sintering, etc.).

[0036] Advantageously, the lower talar face 207 of the talar component 200 and / or the upper tibial face 301 of the tibial component 300 may be provided with a special surface coating (for example in porous titanium or in hydroxyapatite), or may have been subjected to a special mechanical treatment (sandblasting, grooving, etc.), in order to promote the bone attachment of the talar component 200 to the talus and / or of the tibial component 300 to the corresponding tibia.

[0037] Preferably, the prosthesis 100 according to the invention also includes an intermediate component 400 (or pad, or insert) (Figures 16 to 19), which is designed to be intercalated between said talar component 200 and said tibial component 300, as illustrated by example in Figures 1 to 5.

[0038] Said intermediate component 400 comprises an intermediate upper face 401, preferably intended to come into contact with the tibial lower face 302 of the tibial component 300, and an opposing intermediate lower face 402, which is preferably intended to come into contact with the talar upper face 201 of the talar component 200. Said intermediate lower face 402 advantageously defines a second articular surface 403 of the prosthesis 100, designed to cooperate with said first articular surface 202 defined by the superior talar face 201 of the talar component 200.

[0039] Preferably, said intermediate upper face 401 extends, on the one hand, between a first intermediate anterior border 404 and an opposite first intermediate posterior border 405 (for example, along a fifth average E-E' direction) and, on the other hand, between a first intermediate lateral border 406 and an opposite first intermediate medial border 407 (for example, along a sixth average F-F' direction, orthogonal to said fifth average E-E' direction). Said intermediate lower face 402, for its part, preferably extends, on the one hand, between a second intermediate anterior border 408 and an opposite second intermediate posterior border 409, along said fifth average E-E' direction and, on the other hand, between a second intermediate lateral border 410 and an opposite second intermediate medial border 411, along said sixth average F-F' direction.Said second intermediate anterior edge 408 and said second intermediate posterior edge 409 may be advantageously chamfered, as illustrated, to limit the risks of irritation or damage to the surrounding soft tissues, in use of the prosthesis 100.

[0040] The intermediate component 400 may also include an intermediate medial face 412 and an opposing intermediate lateral face 413, which respectively connect the intermediate lateral border 406 and the intermediate medial border 407 to said intermediate superior face 401. Advantageously, the intermediate medial face 412 is substantially flat, for reasons substantially identical to those set forth above in connection with the tibial medial face 307 of the tibial component 300, while the intermediate lateral face 413 may be generally convex, with a concavity oriented towards said intermediate medial face 412. In addition, the intermediate component 400 may include an intermediate anterior face 414 and an opposing intermediate posterior face 415, which respectively connect the intermediate anterior border 404 and the intermediate posterior border 405 to said intermediate superior face 401.

[0041] As illustrated in Figures 3 to 5, the intermediate component 400 is capable of moving by sliding in contact on the talar component 200 in an average anteroposterior direction and, in particular, in an overall posteroanterior (i.e. from back to front) course between the posterior talar border 204 (plantar flexion, [Fig.3]) and the anterior talar border 203 (dorsiflexion, [Fig.5]), passing through an interim position called neutral ([Fig.4]), depending on the inclination affected by the patient's foot with respect to his tibia.

[0042] Preferably, said intermediate component 400 is a single-piece part made of a material having a low coefficient of friction, for example a plastic material such as high-density polyethylene (HDPE). It may be, for example, of a machined or molded part.

[0043] Alternatively, the prosthesis 100 could not include an intermediate component 400, the lower tibial face 302 then being designed to define by itself a second articular surface intended to cooperate directly with the first articular surface 202 defined by the upper talar face 201 of the talar component 200.

[0044] According to the invention, and as can be seen in particular in [Fig. 6], said first articular surface 202 is curved, convex, along said first mean direction A-A'. Conversely, the second articular surface 403 defined by the intermediate lower face 402 of the talar component 400 is preferably curved along said fifth mean direction E-E'. Said first articular surface 202 is preferably overall convex (i.e., with a concavity oriented towards the lower talar face 207 of the talar component 200), while the second articular surface 403 is overall concave. According to an alternative embodiment (not illustrated), a reversed configuration could be envisaged without departing from the scope of the invention, the first articular surface 202 being overall concave, while the second articular surface 403 is overall convex.

[0045] Advantageously, said first articular surface 202 (and, preferably, said second articular surface 403) more specifically (each) has the general average shape of a substantially frustoconical (fictitious) surface fraction derived from a fictitious cone, which surface is preferably oriented so that its longer base is directed towards the lateral malleolus and its shorter base is directed towards the medial malleolus of the foot in question. Thus, when the intermediate component 400 moves in frictional contact relative to the talar component 200, through the cooperation of said first 202 and second 403 articular surfaces, the intermediate component 400 does not describe a strictly anteroposterior or posteroanterior trajectory, but rather a more or less curved trajectory.The patient's foot is thus advantageously guided laterally (mediolateral direction) in dorsiflexion and, conversely, medially (lateral direction) in plantar flexion. This best reproduces the natural physiological kinematics of the ankle joint.

[0046] Alternatively, said first 202 and second 403 joint surfaces could each have the general average shape of a (fictitious) cylindrical surface fraction, so as to define on the contrary a joint kinematics in which the intermediate component 400 moves along a substantially anteroposterior or posteroanterior trajectory.

[0047] According to the invention, said first articular surface 202 comprises at least two distinct curved surface parts, namely at least a first curved part 202A and a second curved part 202B, each extending along said first mean direction A-A', said first curved part 202A having a first curvature and said second curved part 202B having a second curvature, along said first mean direction A-A'.

[0048] Thus, when viewed in cross-section in a plane parallel to said first mean direction A-A' and orthogonal to said second mean direction B-B' ( [Fig. 10]), said first articular surface 202 is described by at least two distinct curvilinear portions (respectively designated on [Fig. 10] by the same references 202A and 202B as for the corresponding first and second curved parts), each preferably forming an arc whose concavity is preferably directed towards the inferior talar face 207, said curvilinear portions having centers of curvature (possibly mean) distinct from each other.

[0049] According to a preferred embodiment, said first 202A and second 202B curved portions of the first articular surface 202 are respectively generally assimilable to a first and a second (fictitious) substantially frustoconical surface fractions, said first and second surface fractions preferably originating respectively from a first and a second fictitious, virtual cones, having respectively a first and a second axis of rotation. Advantageously, the value of the half-angle at the apex of each of said first and second fictitious cones is 8°. The choice of this particular configuration helps to best reproduce the natural kinematics of the anatomical ankle.

[0050] Alternatively, said first 202A and second 202B curved parts of the first articular surface 202 could be respectively globally assimilated to a first and a second fractions of substantially cylindrical surfaces, said first and second fractions of surfaces preferably being respectively derived from a first and a second fictitious cylinders, respectively having a first and a second axis of rotation.

[0051] In other words, if said first articular surface 202 has, as introduced above, the general average shape of a (fictitious) substantially frustoconical surface fraction derived from a fictitious (or cylindrical) cone, this general average shape is more precisely defined, within the meaning of the invention, by the combination of at least a first and a second distinct fractions of substantially frustoconical (or cylindrical) surfaces. Each of these substantially frustoconical surfaces is preferably oriented so that its longer base is directed towards the lateral malleolus and its shorter base is directed towards the medial malleolus of the foot in question. Thus, the first fraction of frustoconical surface corresponding to The first curved section 202A has a radius of curvature that varies, in a latero-medial direction of the aforementioned second mean direction B-B', decreasing between a large radius Ri of curvature and a small radius ri of curvature. The second frustoconical surface fraction, corresponding to the second curved section 202B, has a radius of curvature that varies, in a latero-medial direction of the aforementioned second mean direction B-B', decreasing between a large radius R2 of curvature and a small radius r2 of curvature.

[0052] Alternatively, in the case where said first 202A and second 202B curved parts are globally assimilable to a first and a second fractions of substantially cylindrical surfaces, the latter may respectively have a radius of curvature R\, R'2 which is constant along said second average direction B-B'.

[0053] According to the invention, said first and second curvatures are different, so that one of said first 202A and second 202B curved parts is therefore more curved, that is to say more strongly curved, than the other.

[0054] According to the preferred embodiment envisaged above, in which said first 202A and second 202B curved parts of the first articular surface 202 are respectively globally assimilable to a first and a second fractions of (fictitious) substantially frustoconical surfaces, such a difference in curvature can be translated by the fact that the first fraction of frustoconical surface has a large radius Ri of curvature and a small radius ri of curvature which are respectively different from the respective large radius R2 of curvature and small radius r2 of curvature of the second fraction of frustoconical surface (Ri R2 and ri r2).According to the alternative variant in which the said first 202A and second 202B curved parts are respectively globally assimilable to a first and a second fractions of substantially cylindrical surfaces, such a difference in curvature may result in the first cylindrical surface fraction having a radius R of curvature different from the respective radius of curvature R'2 of the second cylindrical surface fraction.

[0055] It follows that the first articular surface 202, defined by the superior talar face 201, advantageously does not have the exact and perfect shape of a portion of a frustoconical (or cylindrical, as considered above as an alternative) surface, but rather has a particular localized variation in its average general curvature along said first average direction A-A'. The general kinematics of the prosthesis 100 is then not defined by a single rotation, but by at least two rotations along different radii, corresponding to at least two spatial configurations of the foot relative to the tibia. It is thus possible to generate a complex joint movement, with differentiated axes of rotation. the prosthetic joint between a plantar flexion position and a dorsiflexion position, and to approach even more closely the natural kinematic behavior of an anatomical ankle.

[0056] In the preferred embodiment illustrated in the figures, said first curved portion 202A and said second curved portion 202B define (or contribute to defining at least in part) respectively an anterior portion and a posterior portion of said first articular surface 202. As such, said first curved portion 202A extends preferably between the anterior talar border 203 and the posterior talar border 204 of the superior talar face 201 of the talar component 200, and preferably still, from said anterior talar border 203 (or at least from the immediate vicinity thereof) towards said posterior talar border 204. Said second curved portion 202B then extends respectively between said first curved portion 202A and said posterior talar border 204.Preferably, said second curved part 202B is contiguous to said first curved part 202A and extends the latter to said posterior talar border 204 (or at least to the immediate vicinity of the latter). Thus, when viewed in cross-section in a plane parallel to the first mean direction A-A' and orthogonal to the second mean direction B-B' ([Fig. 10]), said first articular surface 202 is described by at least two distinct and abutting curvilinear portions, each preferably forming an arc, and preferably connecting the anterior talar border 203 to the posterior talar border 204.

[0057] Said first curved part 202A then advantageously corresponds to a part of the first articular surface 202 with which the second articular surface 403 of the intermediate component 400 will cooperate, in the dorsiflexion configuration of the patient's foot ([Fig.5]), while said second curved part 202 corresponds to another part of the first articular surface 202 with which said second articular surface 403 of the intermediate component 400 will cooperate, in the plantarflexion configuration of the patient's foot ([Fig.3]).

[0058] Advantageously, said first and second curvatures, as well as the relative positioning of said first and second axes of rotation, shall be chosen so as to ensure a regular and harmonious transition between said first 202A and second 202B curved parts of the first articular surface 202.

[0059] Preferably, said first and second substantially truncated conical surface fractions meet in a contact plane inclined at an angle between 10° and 30°, and preferably about 20°, in the direction of said anterior talar edge 203 relative to a vertical plane containing said second axis of rotation, said contact plane containing said first and second axes of rotation. Indeed, it has been observed that this provides an excellent compromise between the increased angular range of motion and the intrinsic stability of the prosthesis.

[0060] Preferably, said first curvature of the first curved part 202A is greater than said second curvature of the second curved part 202B, that is to say that said first curved part 202A of the first articular surface 202 affects, along the first average direction A-A', a greater curvature than that respective of said second curved part 202B of the first articular surface 202 (Ri < R2 and ri < r2, or R' ! < R'2).

[0061] In the preferred case mentioned above, where said first curved part 202A and second curved part 202B respectively define an anterior and a posterior portion of the first articular surface 202, the latter advantageously exhibits a more pronounced curvature in its anterior portion than in its posterior portion. Such a configuration proves particularly advantageous, since it allows the patient to dorsiflex with a greater angular range of motion, without the patient's talus being displaced in an anteroposterior direction, that is, backwards. Equipped with the prosthesis 100 according to the invention, the patient will thus be able to flex their foot more easily, for example, during the phase of walking when the foot leaves the ground at the end of a step, or when attempting to climb the steps of a staircase.

[0062] However, one could possibly consider an inverted configuration, in which said first curvature is less than said second curvature, so that the anterior portion of the first articular surface 202 has a less pronounced curvature than the respective curvature of the posterior portion of said first articular surface 202.

[0063] Preferably, said first curvature is constant or variable (along the first mean direction A-A'), while said second curvature is constant (along the first mean direction A-A'). Such a variable first curvature may advantageously correspond to a particular embodiment in which the general shape of the first curved part 202A is itself globally defined by the combination of a plurality n of distinct fractions of substantially truncated conical or cylindrical surfaces (and not by the single first fraction mentioned above), which fractions would have small rn and large Rn radii (or radii R'n) of different curvatures (and therefore of the same different curvatures), advantageously decreasing along said first mean direction A-A'.

[0064] In the preferred case where the first curved part 202A defines an anterior portion of the first articular surface 202 and where said same curvatures vary in increasing direction towards the anterior tibial border 203, the implementation of such a first variable curvature advantageously makes it possible to further improve the amplitude of the angular movement offered by the prosthesis 100 in dorsiflexion.

[0065] Intra-articular forces, which may be exerted at the interface of the first 202 and second 403 articular surfaces, being more important in the plantar flexion phase than in the dorsiflexion phase, said second curved part 202B is preferentially designed and dimensioned so that it advantageously presents a greater surface area than the respective surface area of ​​said first curved part 202A. This ensures better absorption of intra-articular forces in plantar flexion, which improves both the stability and the lifespan of the prosthesis 100.

[0066] Preferably, the first articular surface 202 forms a prosthetic bicondylar surface, and comprises: - a lateral talar zone 210L, which extends between said anterior talar border 203 and said posterior talar border 204 along said first mean direction A-A', and between said lateral talar border 205 and said medial talar border 206 along said second mean direction B-B', and - a medial talar zone 210M, which extends between said anterior talar border 203 and said posterior talar border 204 along said first direction A-A' average, and between said lateral talar zone 210L and said medial talar border 206 along said second direction B-B' average.

[0067] Preferably, as illustrated in particular in Figures 6 and 8, said lateral talar zone 210L and medial talar zone 210M extend respectively from said anterior talar border 203 (or at least from its immediate vicinity) to said posterior talar border 204 (or at least to its immediate vicinity). Said lateral talar zone 210L then comprises a first lateral region 211L of said first curved portion 202A and a second lateral region 212L of said second curved portion 202B. Said medial talar zone 210M comprises respectively a first medial region 211M of said first curved portion 202A and a second medial region 212M of said second curved portion 202B.As illustrated in the figures, the second lateral region 212L and second medial region 212M then preferably extend the said first lateral region 21 IL and first medial region 21 IL respectively, along the first mean A-A' direction. Advantageously, the said lateral talar zone 210L and medial talar zone 210M thus form respectively lateral and medial prosthetic condyle parts continuous along the first mean A-A' direction.

[0068] Advantageously, said first articular surface 202 also comprises a central talar area 210C, which is interposed between said lateral talar area 210L and said medial talar area 210M. As illustrated in the figures, said central talar area 210C extends, along said first mean direction A-A', from said anterior talar border 203 (or at least from its immediate vicinity) towards the posterior talar border 204, and advantageously comprises a first central region 21 IC of said first part curve 202A.

[0069] Particularly advantageously, said central talar zone 21 OC also comprises a second central region 213C, curved, which extends said first central region 21 IC towards the posterior talar border 204. However, said second central region 213C preferably does not, as such, constitute a central region of the second curved portion 202B. Indeed, said second central region 213C advantageously has a third curvature, along the first mean direction A-A', which is different from said second curvature of the second curved portion 202B. Said second curved portion 202B is then discontinuous along the second mean direction B-B'.In this case, and particularly according to the preferred embodiment illustrated in the figures in which the first curvature of the first curved part 202A is greater than the second curvature of the second curved part 202B, the third curvature of the second central region 213C is advantageously greater than the second curvature. Thus, the second central region 213C is therefore more strongly curved than the surrounding second lateral region 212L and second medial region 212M. For example, the third curvature may be identical to the first curvature, the second central region 213C being continuous with the first central region 211C.

[0070] As can be seen in particular from Figures 6 and 8, said second central region 213C then advantageously materializes a central posterior depression 214 in the middle envelope of said first articular surface 202. In addition, said central talar zone 210C of the first articular surface 202 may not extend to the posterior talar border 204 of the superior talar surface 201. The space thus formed between said central talar zone 210C and said posterior talar border 204 may be left free or, on the contrary, may preferably be filled by a complementary portion 215 of the superior talar surface 201 which is solid, and for example flat, so as to avoid the formation of an uncovered bone cut zone.

[0071] According to the preferred embodiment illustrated in the figures, said second articular surface 403, which is defined by the intermediate lower face 402 of the intermediate component 400, advantageously comprises an intermediate lateral zone 416L, an intermediate medial zone 416M, and preferably also an intermediate central zone 416C, the latter being intercalated between the two preceding ones.

[0072] Extending each between said second intermediate anterior border 408 and second intermediate posterior border 409 along said fifth average E-E' direction, said intermediate lateral zone 416L, intermediate medial zone 416M and intermediate central zone 416C are respectively intended to cooperate with said talar lateral zone 210L, talar medial zone 210M and central zone talar 210C of said first articular surface 202. Preferably, said intermediate lateral zone 416L and intermediate medial zone 416M advantageously have, along said average fifth direction E-E', curvatures respectively conjugate to the curvatures of said second lateral region 212L and second medial region 212M of the second curved part 202B of said first articular surface 202. Said intermediate central zone 416C advantageously has, along said average fifth direction E-E', a curvature conjugate to the curvature of said first central region 21 IC of the first curved part 202A of said first articular surface 202.

[0073] Preferably, and as can be seen in particular in Figures 6 to 8, said central talar zone 210C has a convex curvature along said second mean direction B-B', said lateral talar zone 210L and medial talar zone 210M having respectively a concave curvature along said second mean direction B-B'. Conversely, the intermediate medial zone 416M and the intermediate lateral zone 416L are advantageously convex along said sixth mean direction F-F', while the central intermediate zone 416C is concave along this same direction F-F' ([Fig. 17]).

[0074] Thus, in the plantar flexion position ([Fig.3]) of the patient's foot, said intermediate lateral zone 416L and intermediate medial zone 416M can advantageously rest respectively in surface contact against said second lateral region 212L and second medial region 212M of the second curved part 202B of the first articular surface 202.

[0075] In the dorsiflexed position ([Fig.5]), said intermediate central zone 416C can advantageously rest in surface contact with the first central region 21 IC of the first curved part 202A of the first articular surface 202. On the other hand, said intermediate lateral zone 416L and intermediate medial zone 416M cannot then, preferably, rest in surface contact against said first lateral region 21 IL and first medial region 21 IM of the first curved part 202A of the first articular surface 202, due to their different respective curvatures.

[0076] Thus, the cooperation of said first and second articular surfaces is advantageously not perfectly congruent. In the dorsiflexed position, the intermediate component 400 advantageously remains free to slide and tilt slightly, laterally or medially, around an equilibrium position. In the case of lateral tilting, the intermediate lateral zone 416L of the second articular surface 403 can advantageously come into linear contact against the first lateral region 21IL of the first curved part 202A of the first articular surface 202 defined by the superior talar face 201 of the talar component 200. Conversely, in the case of a medial tilt, the intermediate medial zone 416M of said second articular surface 403 can advantageously come into linear contact against the first medial region 21 IM of the first curved part 202A of the first articular surface 202. In addition, in the position of dorsiflexion, the intermediate component 400 then advantageously presents a certain limited latitude of rotation around a vertical axis.

[0077] By allowing the intermediate component 400 to retain slight translational mobility in a mediolateral direction and rotational mobility around a vertical axis, such a configuration advantageously helps to limit the risk of loosening of the talar component 200 and tibial component 300 under the effect of mechanical stresses exerted on the prosthesis 100 during its normal use. This configuration also advantageously compensates, to some extent, for a slight misalignment of the talar component 200 and tibial component 300, thereby facilitating the surgeon's insertion of the prosthesis 100 into the patient's body.

[0078] Since the central intermediate zone 416C preferably has, in accordance with the foregoing, a greater curvature than the respective lateral intermediate zone 416L and medial intermediate zone 416M, it can then define, near the second posterior intermediate border 409, a protrusion 417 that projects from the surface of the inferior intermediate face 402 ([Fig. 17]). In order to avoid any mechanical interaction between said protrusion 417 and the first articular surface 202, said central posterior depression 214 (formed by the second central region 213C of the central talar zone 210C, as mentioned above) is advantageously left empty. Thus, in the plantar flexion position, said protrusion 417 can advantageously disappear into said central posterior depression 214.

[0079] According to one embodiment (not shown in the figures), the tibial component 300 is designed to be movable relative to the intermediate component 400, the tibial component 300 and the intermediate component 400 not being mechanically connected to each other. In this case, the lower tibial face 302 and the upper intermediate face 401 are preferably substantially flat and smooth, so that the tibial component 300 and the intermediate component 400 can come into planar surface contact with each other.In normal use of the prosthesis 100, the tibial component 300 and the intermediate component 400 are thus in contact with each other, and are mobile relative to each other according to three degrees of freedom, namely according to a translation in the average anteroposterior direction, a translation in the average mediolateral direction, and a rotation around an axis orthogonal to the contact plane of said inferior tibial face 302 and superior intermediate face 401 between them.

[0080] According to another embodiment, illustrated in Figures 1 to 5, said tibial component 300 is designed to be fixed, i.e., joined, to said intermediate component 400, so as to advantageously eliminate any degree of freedom between the tibial component 300 and the intermediate component 400. Such joining of the latter makes it possible to advantageously improve the stability of the prosthetic joint. Preferably, said tibial component 300 and intermediate component 400 are designed to be fixed to each other by means of respective first and second complementary joining elements, preferably again by means of a dovetail joint.

[0081] According to the preferred embodiment illustrated in the figures, the lower tibial face 302 of the tibial component 300 is advantageously provided with a groove 311, for example with a trapezoidal cross-section, which advantageously forms said first joining element (or female dovetail joint). The intermediate upper face 401 of the intermediate component 400 is conversely advantageously provided with a tenon 418, which forms said second joining element (or male dovetail joint). As illustrated by example in Figures 16 and 18, said tenon 418 projects from the surface of said intermediate upper face 401 and has a shape and dimensions complementary to those of said groove 311.

[0082] Preferably, said groove 311 extends longitudinally along said third average direction C-C', from the anterior tibial face 309 of the tibial component 300, at which point it opens, towards the posterior tibial face 310, and this over at least half of the average distance separating said anterior tibial face 309 and posterior tibial face 310 (Figures 12 and 14). Advantageously, said tenon 418 extends longitudinally along said fifth average direction E-E', from the intermediate anterior face 414 of the intermediate component 400, towards the intermediate posterior face 415 of the latter. Preferably, the length of said tenon 418 is less than the respective length of said groove 311 (Figures 16 and 18).

[0083] Said groove 311 is thus advantageously designed and configured to receive said tenon 418 with a tight sliding motion, said lower tibial face 302 and upper intermediate face 401 being held pressed against each other. Such a relative dovetail joint thus advantageously prevents at least any mediolateral translation and any rotation of the intermediate component 400 relative to the tibial component 300. Advantageously, said tenon 418 may be provided, at its posterior end, with lateral slopes 419A, 419B (or chamfers) designed to facilitate and guide the insertion of the tenon 418 into the groove 311 during the relative jointing of the tibial component 300 and the intermediate component 400.

[0084] Obviously, a reversed configuration could very well be envisaged, The lower tibial face 302 being provided with the tenon, the intermediate upper face 401 being reciprocally provided with the groove. Any other suitable means of reciprocal fastening, employing first and second means of fastening different from those described above, could also be employed.

[0085] Furthermore, it may advantageously be provided that, for different sizes of tibial component 300 and intermediate component 400, the dimensions of said groove 311 and said tenon 418 are respectively identical. It will then be advantageously possible to offer the surgeon a prosthetic kit comprising a range of talar components 200, tibial components 300, and intermediate components 400, respectively of different sizes to adapt to the morphology of the patient being treated, while ensuring compatibility between a tibial component 300 and an intermediate component 400, which correspond to prostheses of different sizes.

[0086] In the preferred case of such a dovetail joint, said tibial component 300 and intermediate component 400 further preferably comprise, respectively, first and second complementary stop elements designed to limit or block the anteroposterior (i.e., front-to-back) translation of the intermediate component 400 relative to the tibial component 300, said first and second stop elements being advantageously distinct from said first and second complementary fastening elements. In other words, the limitation (and preferably the blocking) of the anteroposterior translation is advantageously not ensured (or, at least, not exclusively) by the dovetail joint itself, but by the cooperation of said first and second complementary stop elements.This advantageously avoids the need for mechanical stresses applied to the tibial component 300 in use of the prosthesis 100 to be transferred by the groove 311 and tenon 418 alone.

[0087] Preferably, said first and second stop elements comprise respectively a rim 312 positioned at least at the level of the posterior tibial edge 304 of the inferior tibial face 302 of the tibial component 300, and a clearance 420 provided at the level of the intermediate upper face 401 of the intermediate component 400 (for example, at the level of the first posterior intermediate edge 405) and with a profile complementary to that of said rim 312. Said clearance 420 is thus designed and configured to receive said rim 312, said inferior tibial face 302 and intermediate upper face 401 being advantageously in planar contact with each other. The cooperation of said rim 312 and clearance 420 thus limits, and preferably blocks, the travel anteroposterior of tenon 418 in groove 311. Obviously, stop elements of different design could be implemented.

[0088] According to the preferred embodiment illustrated in the figures, said rim 312 is po positioned at the level of the aforementioned posterior tibial border 304, lateral tibial border 305, and medial tibial border 306 of the inferior tibial surface 302 of the tibial component 300, and advantageously extends substantially continuously along the aforementioned borders 304, 305, and 306. This border 312 preferably has a rectangular cross-section, whether constant or not. Conversely, the clearance 420 is preferably provided at the level of the first intermediate posterior border 405, first intermediate lateral border 406, and first intermediate medial border 407 of the superior intermediate surface 401 of the aforementioned intermediate component 400, advantageously extending substantially continuously along the aforementioned borders 405, 406, and 407.

[0089] The implementation of such complementary rim 312 and clearance 420 advantageously semi-peripheral, and their cooperation when the intermediate component 400 is fixed to the tibial component 300, thus makes it possible not only to limit the risk of shearing of the tenon 418 in said groove 311, but also to advantageously limit the risk of deformation of the intermediate component 400 by thinning under the effect of the compressive force exerted on the latter by the tibial component 300 in normal use of the prosthesis 100. The life of the intermediate component 400 is thus significantly improved, which makes it possible to limit the risk of having to carry out a subsequent surgical operation to replace it.

[0090] Preferably, in order to also block any postero-anterior translation (i.e. from back to front) of the intermediate component 400 relative to the tibial component 300, when the latter are fixed to each other, said tibial component 300 and intermediate component 400 are advantageously respectively provided with first 313A, 313B and second 421A, 421B complementary locking means.

[0091] As illustrated in Figures 12 and 14, said first locking means 313A, 313B may, for example, take the form of sawtooth notches 313A, 313B formed in the rim 312 of the lower tibial face 302, for example symmetrically at the level of the lateral tibial border 305 and the medial tibial border 306 of said tibial component 300. Conversely, said second locking means 421A, 421B may, for example, take the form of lugs 421A, 421B of complementary shapes to said sawtooth notches 313A, 313B, arranged at the level of the clearance 420 of the intermediate component 400 (Figures 16 to 18). The tibial component 300 and the intermediate component 400 can thus be locked to each other by clipping, the local elastic deformation of the material forming the tibial component 300 allowing the engagement of the lugs 421A, 421B of the latter in the corresponding notches 313A, 313B of the tibial component 300.Obviously, other suitable additional locking means may be considered in place of those which come first 313A, 313B and second 421 A, 421B. to be described.

[0092] Preferably, the tibial component 300 is designed to be removably attached to the intermediate component 400, in particular to allow the replacement of the intermediate component 400 in the event of its deterioration (wear, deformation, etc.). In this case, the first 313A, 313B and second 421A, 421B supplementary locking means will be designed to allow reversible locking of the tibial component 300 and the intermediate component 400 to each other. For this purpose, the intermediate component 400 may, for example, be provided with recesses 422A, 422B formed in the upper intermediate face 401 in the immediate vicinity of the lugs 421A, 421B forming said second locking means 421A, 421B, and designed to receive the end of an external instrument (not shown, for example, a flathead screwdriver).The action of this external instrument, for example by lever effect or by rotation, will advantageously allow a local elastic deformation of the material forming the intermediate component 400 and a decoupling of the notches 313A, 313B and lugs 421 A, 421B, thus allowing the separation of the talar component 300 and intermediate component 400. .

[0093] Advantageously, the talar component 200 is provided on its inferior talar face 207 with at least one talar anchoring means 216A, designed to anchor the talar component 200 in the bone mass of the talus concerned. Preferably projecting from the inferior talar face 207 of the talar component 200, said talar anchoring means 216A is advantageously designed to be housed, during the placement of the talar component 200 in the patient's body, in a corresponding recess (or hole) previously made (or during the placement of the talar component 200) by the surgeon in the bone mass of the talus. As illustrated in particular in figures 7 and 9, the talar component 200 is equipped with two talar anchoring means 216A, 216B, formed by two talar studs 216A, 216B, for example cylindrical with rounded head, which protrude from the lower talar face 207 of the talar component 200.Preferably, said talar pads 216A, 216B extend obliquely towards the posterior talar border 204. Obviously, other suitable types, shapes and configurations of talar anchorage means 216 may be considered.

[0094] In order to ensure excellent mechanical resistance of said talar anchoring means 216A, particularly in fatigue, the latter is preferably connected to the inferior talar face 207, at its base, by a talar fillet 217A, i.e., by a curved surface, or by one or more ribs. In the preferred embodiment illustrated in the figures, each of the talar anchoring means 216A, 216B is thus advantageously connected to the inferior talar face 207 by a respective talar fillet 217A, 217B. However, it has been observed that the presence of such The 217A, 217B chamfer can prove problematic during the placement of the talar component 200 in the patient's body, for example by impaction, because such a chamfer 217A, 217B then protrudes from the surface of the inferior talar face 207. Indeed, the drill bits usually available for creating recesses in the bone do not easily allow for the creation of a countersink that could accommodate the 217A, 217B chamfer. The implementation of such a 217A, 217B chamfer can be particularly unfavorable in the case, considered above, where the inferior talar face 207 has a surface coating, since the presence of this coating tends, depending on its thickness, to amplify the prominence of said 217A, 217B chamfer, and thus to further hinder the placement of said talar component 200.

[0095] To overcome this drawback, said lower talar face 207 is advantageously provided with at least one talar recess 218A, from the bottom of which said at least one talar anchoring means 216A projects from said lower talar face 207. In the preferred embodiment illustrated in the figures, said lower talar face 207 is advantageously provided with a plurality of talar recesses 218A, 218B from the respective bottoms of which said talar pads 216A, 216B project from said upper tibial face 301. As illustrated in the figures, said talar recess 218A, 218B is advantageously dimensioned so that said fillet 217A, 217B is entirely contained within said talar recess 218A, 218B and therefore does not project from the surface of the inferior talar surface 207.

[0096] Thus, said talar component 200 can be placed in a relatively simple and precise manner at the level of the talus, the lower talar face 207 being able to come into perfect surface contact with the corresponding area of ​​the talus, and this without requiring specific tools for drilling the bone mass.

[0097] Advantageously, the tibial component 300 is provided on its upper tibial face 301 with at least one tibial anchoring means 314A, designed to anchor the tibial component 300 in the bone mass of the tibia concerned. Preferably projecting from the upper tibial face 301 of the tibial component 300, said tibial anchoring means 314A is advantageously designed to be housed, during the placement of the tibial component 300 in the patient's body, in at least one corresponding recess (or hole) previously made (or during the placement of the tibial component 300) by the surgeon in the bone mass of the tibia.

[0098] As illustrated in particular in Figures 11 to 13 and 15, the tibial component 300 is preferably provided with a plurality of tibial anchoring means 314A, 314B, 314C, 314D, for example formed of two cylindrical tibial studs 314A, 314B with rounded heads, which project from said upper tibial face 301 in the vicinity of the anterior tibial edge 303, and two wings tibial wings 314C, 314D, which protrude from said superior tibial face 301 in the vicinity of the posterior tibial border 304. Preferably, said tibial wings 314C, 314D have sharp, even cutting, edges to promote their penetration into the bone mass of the tibia. Advantageously, said tibial pads 314A, 314B and said tibial wings 314C, 314D extend at an angle towards the posterior tibial border 304. The angle of inclination of said tibial pads 314A, 314B and said tibial wings 314C, 314D will be advantageously chosen to facilitate the introduction of the tibial component 400 into the patient's body and its placement on the patient's tibia, while minimizing the necessary joint distraction. Of course, other suitable types, shapes, and configurations of tibial anchorage means 314A, 314B, 314C, 314D may be considered.

[0099] Preferably, in a manner substantially comparable to what has been described above in connection with said at least one talar anchoring means 216A of the talar component 200, said at least one tibial anchoring means 314A is preferably connected to the upper tibial face 301, at the level of its base, by a tibial fillet 315A. The said upper tibial face 301 is then advantageously provided with at least one tibial cup 316A, from the bottom of which said at least one tibial fixing means 314A projects from said upper tibial face 301. In the preferred embodiment illustrated in the figures, each of the tibial pads 314A, 314B and each of the tibial wings 314C, 314D is thus advantageously connected to the upper tibial face 301 by a respective tibial fillet 315A, 315B, 315A, 315B.The said upper tibial face 301 is then advantageously provided with a plurality of tibial cups 316A, 316B, 316A, 316B from the respective bottom of which the said tibial pads 314A, 314B and the said tibial wings 314C, 314D project from the said upper tibial face 301. .

[0100] As illustrated in Figures 7 and 9, the lateral talar border 205 and the medial talar border 206 of the talar component 200 are preferably provided respectively with a lateral talar notch 219L and a medial talar notch 219M, advantageously positioned symmetrically in the vicinity of the anterior talar border 203. Said lateral talar notch 219L and said medial talar notch 219M are advantageously designed to cooperate with an external instrument (not shown, for example a flat screwdriver), to allow the removal of the talar component 200, for example in the event of unsatisfactory positioning or in the event of a medical complication justifying the removal of all or part of the prosthesis 100.

[0101] Similarly, the lateral tibial border 305 and the medial tibial border 306 of the tibial component 300 may advantageously be provided respectively with a lateral tibial notch 317L and a medial tibial notch 317M, advantageously positioned symmetrically in the vicinity of the anterior tibial border 303 (figures 11, 12 and 14).

Claims

Demands

1. Ankle prosthesis (100), comprising: - a tibial component (300) intended to be attached to a lower end of a patient's tibia; - a talar component (200) intended to be attached to the talus of a patient's foot and which includes a superior talar face (201) defining a first articular surface (202); - an intermediate component (400) designed to be interposed between said talar component (200) and said tibial component (300), said intermediate component (400) comprising an intermediate lower face (402) defining a second articular surface (403) designed to cooperate with said first articular surface (202), said ankle prosthesis (100) being characterized in that said tibial component (300) comprises a superior tibial face (301) and an opposing inferior tibial face (302), said inferior tibial face (302) extending on the one hand between an anterior tibial border (303) and an opposing posterior tibial border (304), and on the other hand, between a lateral tibial border (305) and an opposing medial tibial border (306), said tibial component (300) being provided with a plurality of tibial anchoring means (314A, 314B, 314C, 314D) formed of two cylindrical tibial studs (314A, 314B) with rounded heads, which project from said superior tibial face (301) in the vicinity of the anterior tibial border (303), and two tibial wings (314C, 314D), which protrude from said upper tibial face (301) in the vicinity of the posterior tibial border (304).

2. Prosthesis (100) according to the preceding claim, wherein the talar component (200) has a lower talar face (207) opposite said upper talar face (201), said talar component (200) being provided, at the level of said lower talar face (207), with at least one talar anchoring means (216A), said lower talar face (207) being provided with at least one talar cup (218A) from the bottom of which said talar anchoring means (216A) protrudes from said lower talar face (207).

3. Prosthesis (100) according to any one of the preceding claims, wherein each of the tibial pads (314A, 314B) and each of the tibial wings (314C, 314D) is connected to the upper tibial face (301) by a respective tibial fillet (315A, 315B, 315A, 315B), said upper tibial face (301) being provided with a plurality of tibial cups (316A, 316B, 316A, 316B) from the respective bottom of which said tibial pads (314A, 314B) and said tibial wings (314C, 314D) project from said upper tibial face (301).

4. Prosthesis (100) according to any one of the preceding claims, wherein said superior talar face (201) extends between an anterior talar border (203) and an opposite posterior talar border (204) along a first average direction (A-A'), said first articular surface (202) being curved along said first average direction (A-A') and comprising a first curved portion (202A) and a second curved portion (202B), said first curved portion (202A) and said second curved portion (202B) defining respectively an anterior portion and a posterior portion of said first articular surface (202).

5. Prosthesis (100) according to the preceding claim, wherein said first curved part (202A) having a first curvature and said second curved part (202B) having a second curvature, said first and second curvatures being different, said first curvature preferably being greater than said second curvature.

6. Prosthesis (100) according to the preceding claim, wherein said first articular surface (202) comprises a central talar area (210C), which is intercalated between a lateral talar area (210L) and a medial talar area (210M) of said first articular surface (202), and which comprises a first central region (21 IC) of said first curved portion (202A) and a second central region (213C) which extends said first central region (21 IC) and has a third curvature which is greater than said second curvature.

7. Prosthesis (100) according to the preceding claim, wherein said superior talar face (201) extends between a lateral talar border (205) and an opposing medial talar border (206) along a second average direction (B-B'), said central talar zone (210C) having a convex curvature along said second average direction (B-B'), said lateral talar zone (210L) and medial talar zone (210M) respectively exhibiting a concave curvature along said second mean direction (B-B').

8. Prosthesis (100) according to the preceding claim, wherein said second articular surface (403) comprises an intermediate lateral zone (416L), an intermediate medial zone (416M) and an intermediate central zone (416C), respectively intended to cooperate with said lateral talar zone (210L), medial talar zone (210M) and central talar zone (210C) of said first articular surface (202).

9. Prosthesis (100) according to the preceding claim, wherein said intermediate central zone (416C) has a curvature conjugate to the curvature of said first central region (21 IC) of the first curved part (202A) of said first articular surface (202).

10. Prosthesis (100) according to the preceding claim, wherein said intermediate lateral zone (416L) and intermediate medial zone (416M) having curvatures respectively conjugate to the curvatures of said second lateral region (212L) and second medial region (212M) of the second curved part (202B) of said first articular surface (202).

11. Prosthesis (100) according to the preceding claim, wherein said intermediate lateral zone (416L) and intermediate medial zone (416M) rest respectively in surface contact against said second lateral region (212L) and second medial region (212M) of the second curved part (202B) of the first articular surface (202) in plantar flexion position of the patient's foot, said intermediate central zone (416C) resting in surface contact with the first central region (21 IC) of the first curved part (202A) of the first articular surface (202) in dorsiflexion position.

12. Prosthesis (100) according to any one of the preceding claims, wherein said upper tibial face (301) and said lower tibial face (302) extend respectively along substantially parallel mean extension planes.

13. Prosthesis (100) according to the preceding claim, wherein said inferior tibial face (302) extends on the one hand between said anterior tibial border (303) and said opposite posterior tibial border (304) along a third mean direction (C-C') and, on the other hand, between said lateral tibial border (305) and said opposite medial tibial border (306) along a fourth mean direction (D-D'), which is orthogonal to said third direction (C-C') average.

14. Prosthesis (100) according to the preceding claim, wherein the tibial component (300) comprises a medial tibial face (307) and an opposite lateral tibial face (308), which respectively connect the medial tibial border (306) and the lateral tibial border (305) to said superior tibial face (301).

15. Prosthesis (100) according to the preceding claim, wherein said medial tibial edge (306) is substantially straight and said medial tibial face (307) is substantially flat, so that a surgeon can precisely position said tibial component (300) in the patient's body, by aligning said medial tibial face (307) along a straight cut made at the level of an internal malleolus.

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