New knee prosthesis

Abstract

Novel Knee Prosthesis The invention relates to a support element (100) for a femoral implant of a total knee prosthesis, intended to be positioned on the tibia side and comprising an upper surface (41) on which are formed a medial cavity (18) for receiving the medial condyle and a lateral cavity (19) for receiving the lateral condyle, said cavities (18, 19) being separated by a boss (20) located on the upper surface (41) between the two cavities (18, 19), which extends in a horizontal plane along a curved generatrix having a concavity (180) oriented towards the medial cavity (18), said boss (20) having along its generatrix a convex external profile and, in a horizontal plane, the lateral flank (209) of the boss (20) having a radius of curvature that is greater than the radius of curvature of the medial flank, as well as any prosthesis corresponding total knee. Figure for the abbreviation: Fig. 1.

Description

Title of the invention: New knee prosthesis technical field

[0001] The present invention relates to the field of joint prostheses, and more particularly in this specific field, to a new knee prosthesis. Prior art

[0002] In the field of knee prostheses, numerous prior proposals have already been made. The most common models of knee prostheses, commonly called sliding prostheses, comprise a femoral implant which, after resection, covers the superficial bone surfaces of the lower end of the femur, and a tibial implant which, after resection, covers the superficial bone surfaces of the upper end of the tibia. These prostheses preserve the lateral ligaments, the joint capsule, the tendons of the periarticular muscles, and the patella, the articular surface of which is generally replaced; the cruciate ligaments are generally removed. Knee prostheses are therefore intended to replace the natural joint between the tibia and the femur when it has become diseased.Knee prostheses are designed to meet a number of requirements, including: - a tribological requirement: they must undergo minimal wear in use; - a kinematic requirement: the function of the prosthesis must be as close as possible to the kinematics of the normal knee in order to be comfortable for the patient in all physical activities.

[0003] These prostheses generally have two bosses at the femoral implant, called the lateral condyle and the medial condyle, and an anterior articular surface called the trochlea, which articulates with the patella. The two condyles are separated by a portion corresponding to a lack of material, called the intercondylar notch.

[0004] Thus, in general, a knee prosthesis comprises three parts: a femoral implant fitted onto the lower end of the femur after resection, a fixed tibial implant resting on the upper surface of the tibia after resection, supporting an articular insert designed to articulate with the femoral implant. The shapes of the articular insert differ from one type of prosthesis to another and characterize the function of the prosthesis. The bearing surface for the femoral implant, whether it is on the tibial implant (two-part prosthesis) or on the articular insert (three-part prosthesis), generally has two recessed cavities, called the lateral and medial cavities.

[0005] Innovations most often focus on the bearing surface for the femoral implant and its articulation with the femoral implant. Therefore, in order to allow a Regarding joint movement, which is more or less physiological, several solutions have been proposed based on the current state of technology.

[0006] In common configurations, the bearing surface includes, between the two cavities, a vertical cylindrical piece intended to bear against a bar located between the two condyles of the femoral implant, which acts as a cam and is intended to guide the movement of the femoral implant from front to back, during the bending of the knee (flexion movement, causing the tibia, relative to the femur, to pass from an angle of 0° to an angle corresponding to the maximum flexion, of the order of 120° or more).

[0007] In a particular configuration of a knee prosthesis with an insert, proposed in application WO 2010 / 001010 by some of the inventors of the present invention, the insert has, on its upper surface between the two symmetrical medial and lateral cavities, a central saddle-shaped (or more precisely, hyperbolic paraboloid) boss, which is itself symmetrical with respect to a sagittal plane. Similarly, the condyles of the femoral implant are symmetrical and separated by an intercondylar notch that is itself symmetrical with respect to a sagittal plane. This symmetry prevents the rotational movement from being guided according to physiology and results in stress on the insert. These effects necessitated freeing up rotation between the lower surface of the insert and the upper surface of the tibial plateau that supports it.The rotation thus obtained is symmetrical around a central vertical axis, which differs from the asymmetrical physiological functioning of a natural knee and therefore of an optimal knee prosthesis.

[0008] Indeed, in its physiological function, the movement of the condyles during knee flexion occurs asymmetrically. During natural knee flexion, the medial condyle moves little from front to back in the medial glenoid cavity on which it rests, while the contact area of ​​the lateral condyle describes an arc and moves from front to back in the lateral cavity.

[0009] Furthermore, prostheses of this type with a mobile insert (known as a mobile-plate prosthesis) carry a high risk of excessive rotation and therefore dislocation. Indeed, this type of prosthesis provides mediolateral stability, but offers little or no anteroposterior (front-to-back) stability and no rotational stability at all, as the insert can rotate 360° around its keel and lead to dislocations, either through excessive external rotation or excessive internal rotation (the opposite of physiological rotation).

[0010] Other knee prosthesis configurations have been proposed in the prior art. US patent application 2017 / 0189195, in particular, proposes complex profiles of the medial or lateral condyle that engage in corresponding cavities on the tibial implant, said cavities having a complementary profile to ensure stability and allow for asymmetrical and variable rotations depending on the knee flexion angles. A first embodiment detailed in claim 1 of US application 2017 / 0189195 uses a femoral component of particular shape, with two different convex profiles at the medial condyle, and a tibial implant with a bearing surface at the medial cavity having two concave profiles complementary to the convex profiles of the medial condyle. A second embodiment detailed in claim 8 uses another femoral component of particular shape, with two different convex profiles at the lateral condyle, and a tibial implant with a bearing surface at the lateral cavity having two concave profiles complementary to the convex profiles of the lateral condyle. Some implementations of this second embodiment feature a spherical medial condyle within a spherical medial cavity, generating a 360° rotation by definition (of the sphere-within-a-sphere type). These configurations create a step-like transition from one radius of curvature to another, and also allow for snagging due to the angles and flats between adjacent radii of curvature, as shown in Figure 9 of this document.

[0011] The present invention aims to provide a new knee prosthesis and a corresponding support element for the femoral implant, which do not present the aforementioned drawbacks of prostheses known in the prior art. The knee prosthesis and the support element for the femoral implant according to the invention are designed to simultaneously meet the following three requirements: - the requirement of stability: the femoral implant and the bearing surface must maintain contact by remaining superimposed on each other, without the condyles of the femoral implant coming out of their virtual envelope, neither according to a mediolateral displacement, nor according to an anteroposterior displacement, nor in the direction of an excessive rotation in the horizontal plane; - the kinematic requirement: when the natural knee moves from full extension (straight knee) to full flexion (maximum knee flex), the contact surface of the lateral femoral condyle in the lateral cavity of the insert moves from front to back along an arc of approximately 20° + / -5°, whereas, advantageously, the medial femoral condyle moves only a few millimeters from front to back (4 to 5 mm maximum) in the medial cavity of the insert. The femoral implant of the present invention has kinematics close to the rotation of the physiological knee and, thus, in addition to its rotation around its transverse axis, it describes an asymmetrical rotation around a vertical axis that passes through the medial cavity; - the tribological requirement: in order to reduce the pressure per unit area and therefore the wear of the prosthesis elements, there must be a surface contact between the femoral implant and the bearing surface which decreases during knee flexion.

[0012] The invention has in particular the objective of improving the comfort for the person wearing the prosthesis, by promoting an unconstrained kinematics of operation of the prosthesis, which best fulfills all the physiological and tribological requirements, but which also ensures the good stability of the prosthetic joint. Description of the invention

[0013] In this context, the present invention relates to a support element for a femoral implant of a total knee prosthesis, said femoral implant comprising two condyles, called medial condyle and lateral condyle, delimiting between them an intercondylar notch, the external profiles of the two condyles being convex in shape, said support element being intended to be positioned on the tibia side and comprising a superior surface on which are provided a medial cavity for receiving the medial condyle and a lateral cavity for receiving the lateral condyle, said medial and lateral cavities being separated by a boss extending over the superior surface between the two cavities, which inserts into the intercondylar notch when the femoral implant is supported on the superior surface of the support element.The support element according to the invention is characterized in that, in a horizontal plane, said boss extends along a curved generatrix having a concavity oriented towards the medial cavity of said support element, said boss having a lateral flank and a medial flank connected by a vertex which together define, along the entire generatrix of the boss, a section whose external profile is convex and, in particular, arc-shaped, with, in a horizontal plane, the lateral flank of the boss having a radius of curvature that is greater than the radius of curvature of the medial flank of the boss. The invention relates to any support element of this type.

[0014] In the context of the invention, by medial flank of the boss, we mean its flank located on the side of the medial cavity, the other flank located on the side of the lateral cavity, being called lateral flank.

[0015] In particular, the minimum radius of curvature Rmmin of the medial flank and the maximum radius of curvature Rlmax of the lateral flank each have their center located on the side of the medial cavity; According to particular embodiments, these centers are located in the medial cavity, in an area extending from the center of the medial cavity to the peripheral edge of the medial cavity opposite the hump.

[0016] According to a first embodiment of a support element according to the invention, the medial and lateral sides have parallel curvatures, which correspond to concentric circular arcs, the upper surface of the support element has a maximum width located on a mediolateral axis A2, and an anteroposterior axis A1 extends perpendicularly to the mediolateral axis A2, intersecting the mediolateral axis A2 at its middle A, with the mediolateral axis A2 which intersects the peripheral edges of the medial and lateral cavities opposite the hump, respectively at points M and L, with AM=AL=Lmax, the centers of the radii of curvature of the medial and lateral flanks being coincident and located, in particular, on the axis A2 and on a segment [M - 2 mm ; M + 2 mm], the minimum radius of curvature Rmmin of the medial flank and the maximum radius of curvature Rlmax of the lateral flank being, preferably, defined as follows: - The medial flank length (Rmmin) is between 3Lmax / 4 + / - 2mm and 7Lmax / 8 + / - 2mm and is preferably equal to 7Lmax / 8 + / - 2mm, - Rlmax of the lateral flank is between 9Lmax / 8 + / - 2mm and 5Lmax / 4 + / - 2mm and is, preferably, equal to 9Lmax / 8 + / - 2mm.

[0017] In particular, the centers of the radii of curvature Rmmin and Rlmax of the medial flank and the lateral flank are M.

[0018] According to a second embodiment of a support element according to the invention, the maximum width 1b of the hump section decreases along its generatrix from the anterior to the posterior part of the support element. This contributes, in particular, to limiting the forward displacement of the femoral implant during knee flexion. Thus, the anteroposterior stability of the knee prosthesis is further enhanced, as well as the backward roll during knee flexion, known as "roll-back".

[0019] In top view, the upper surface of the support element has a maximum width located on a mediolateral axis A2 and an anteroposterior axis A1 extending perpendicularly to the mediolateral axis A2, intersecting the mediolateral axis A2 at its midpoint A and the mediolateral axis A2 intersecting the peripheral edges of the medial and lateral cavities opposite the boss, respectively at points M and L, with AM=AL=Lmax. According to this second embodiment, advantageously, the centers of the radii of curvature of the medial and lateral sides are different, the centers of the radii of curvature (and therefore Rmmin and Rlmax) of the medial and lateral sides lying within a square of side length l / 4Lmax, with M being the center of the square.For illustrative purposes, one of the centers of the radii of curvature of the medial flank and the lateral flank (in particular Rrnmin and Rlmax) is on an axis A'2 offset and parallel with respect to the axis A2 and the other is on the axis A2 and located, preferably, on a segment [M - 2 mm ; M = 2 mm], the minimum radius of curvature Rmmn of the medial flank and the maximum radius of curvature Rlmax of the lateral flank being, preferably, defined as follows: - Rmmin of the medial flank which is between 3Lmax / 4 + / - 2mm and 7Lmax / 8 + / - 2mm and is, preferably, equal to 7Lmax / 8 + / - 2mm, - Rlmax of the lateral flank which is between 9Lmax / 8 + / - 2mm and 5Lmax / 4 + / - 2mm and is, preferably, equal to 9Lmax / 8 + / - 2mm.

[0020] According to particular embodiments of this second variant, given by way of example, the minimum radius of curvature Rmmin of the medial flank may have its center Cl at M on the mediolateral axis A2, and the maximum radius of curvature Rlmax of the lateral flank may have its center C2 on the axis A'2, with the axis A'2 located between the mediolateral axis A2 and the anterior part of the support element, with the distance dc between the mediolateral axis A2 and the axis A'2 being equal to Lmax / 8 + / - 2 mm, or the maximum radius of curvature Rlmax of the lateral flank has its center C2 on the mediolateral axis A2 at M, and the minimum radius of curvature Rmmin of the medial flank has its center Cl on the axis A'2, with the axis A'2 located between the mediolateral axis A2 and the posterior part of the support element, with the distance dc between the medio-lateral axis A2 and the axis A'2 which is equal to Lmax / 8 + / - 2mm.

[0021] Regardless of the embodiment of the support element according to the invention, the upper surface of the support element may have a circumference which has a symmetrical shape with respect to the anteroposterior axis Al or the upper surface of the support element may have a circumference which has a non-symmetrical shape with respect to the anteroposterior axis Al, with, in particular, a lateral circumference smaller than the medial circumference.

[0022] Advantageously, and regardless of the embodiment of the support element according to the invention, the medial cavity viewed from above has an ovoid shape with a mediolateral minor axis and an anteroposterior major axis, and / or the medial and lateral cavities define cavities with a concave external profile. Such cavity choices allow for better adaptation to the shape of the most common condyles.

[0023] According to particular embodiments of the support element according to the invention, the boss is raised towards the front and / or rear part of the support element. In particular, the upper surface of the support element according to the invention may have the shape of a saddle.

[0024] Advantageously, and regardless of the embodiment of the support element according to the invention, there is no flatness or angulation between the boss and the medial and lateral cavities.

[0025] As is conventional in total knee replacements proposed in the prior art, the support element according to the invention may constitute an articular insert intended to be interposed between the femoral implant and a tibial implant intended to be placed on the end of the tibia, where applicable after resection. In particular, said articular insert may have an inferior face intended to be placed on the tibial implant, notably by reversible interlocking, in a recess located on the superior surface of the tibial implant.

[0026] According to another aspect of it, the invention relates to a total knee prosthesis comprising a femoral implant and a support element according to the invention for the femoral implant, in particular in which: - the femoral implant comprises two condyles, called the medial condyle and the lateral condyle, delimiting between them an intercondylar notch; the external profiles of the two condyles facing the bearing element are convex in shape, - the femoral implant being adapted to the support element, so that when the femoral implant is supported on the upper surface of the support element, there is contact between the medial cavity and the medial condyle, contact between the lateral cavity and the lateral condyle and contact, at the same time, between the medial flank of the boss and the part of the medial condyle which delimits the intercondylar notch and between the lateral flank of the boss and the part of the lateral condyle which delimits the intercondylar notch.Thus, the femoral implant and the support element are configured so that when the femoral implant is supported on the upper surface of the support element, there is contact between the medial cavity and the medial condyle, contact between the lateral cavity and the lateral condyle, and contact both between the medial flank of the boss and the part of the medial condyle that delimits the intercondylar notch and between the lateral flank of the boss and the part of the lateral condyle that delimits the intercondylar notch.

[0027] In the context of the invention, when the femoral implant is in a bearing position on the upper surface of the bearing element and moves in flexion from an extension position to a maximum flexion position, the contact between the boss and the condyles at the level of the intercondylar notch ensures the guidance of the movement of the femoral implant during this flexion with a displacement of the contact area of ​​the lateral condyle in the lateral cavity from the anterior part to the posterior part of the bearing element, which corresponds to a displacement over a portion of an arc of a circle.

[0028] Any total knee prosthesis that meets this definition and has a guiding and stabilizing hump is part of the invention. The displacement of the contact area of ​​the lateral condyle in the lateral cavity advantageously corresponds, in particular, to a displacement along a portion of a circular arc corresponding to an angle of approximately 20° + / - 5°.

[0029] In particular, the portion of the arc of a circle, on which the contact area of ​​the lateral condyle in the lateral cavity moves, has its center which is located on the medial cavity side in the medial cavity, or even outside the latter.

[0030] Thus, during flexion, the femoral implant rotates around a transverse axis, and the lateral condyle undergoes a displacement with, on the one hand, a rotation around a horizontal, or transverse, axis and, on the other hand, a rotation around an axis of rotation vertical which passes through the medial cavity. Thus, the flexion displacement of the femoral implant is close to that of the physiological knee.

[0031] By "approximately" 20°+ / -5°, we mean an angle of 15°+ / -2° to 25°+ / -2°. The value of this angle will, in particular, depend on the size of the implant, which corresponds to the size of the patient's knee into which the knee prosthesis will be implanted.

[0032] According to an embodiment of the knee prostheses according to the invention, in a frontal plane, the external profile of the intercondylar notch is congruent with the external profile of the boss, and this in any bearing position of the femoral implant on the upper surface of the bearing element, when the latter moves in flexion from an extension position to a maximum flexion position.

[0033] According to the first embodiment of the support element according to the invention, the knee prosthesis according to the invention comprises a support element whose maximum width 1b of the hump section is decreasing along its generatrix from the anterior part to the posterior part of the support element and, due to the congruent shapes of the external profiles of the hump and the intercondylar notch, the maximum width of the intercondylar notch is decreasing from the anterior part to the posterior part of the femoral implant.

[0034] According to preferred embodiments of the knee prostheses according to the invention, the condyles have an external profile in the sagittal plane, the generatrix of which is a spiral; in particular, the lateral condyle has an external profile in the sagittal plane, the generatrix of which is a logarithmic spiral inscribed within the external profile in the sagittal plane of the medial condyle, the generating spiral of which has a radius with a smaller decrease than that of the generatrix of the external profile of the lateral condyle. This allows, in particular, for: -to make knee flexion easier and more comfortable by reducing tension on the lateral ligaments, - facilitate rotation of the external condyle in extreme flexion corresponding to an angle of 120° or more, which is a great advantage for kneeling.

[0035] According to other preferred embodiments of the knee prostheses according to the invention, which can be combined with the preceding ones, the medial cavity viewed from above has an ovoid shape with a mediolateral minor axis and an anteroposterior major axis, and has, in the sagittal plane passing through its anteroposterior major axis, a curvature corresponding in the same plane to that of the medial condyle segment in contact with said medial cavity when the femoral implant is in the extension position. This has, in particular, the advantage of containing the movement of the condyle within the cavity and limiting its displacement when the femoral implant is in a bearing position on the upper surface of the bearing element and moves in rotation (also called flexion displacement) from an extension position to a maximum flexion position.

[0036] In particular, in knee prostheses according to the invention, the hump section has a convex external profile with a radius of curvature R20 and the notch section has a concave external profile with a radius of curvature RIO, with the radii of curvature R20 and RIO being substantially identical, with sufficient clearance to prevent clamping between the femoral implant and the support element at the hump. By "substantially identical," it is understood that it is a fit with clearance, as there must be no clamping. The space between the hump and the intercondylar notch is, in particular, between 1 and 2 mm, bearing in mind that the patient's weight and therefore the pressure can reduce the clearance.

[0037] Advantageously within the framework of the invention, in the knee prostheses according to the invention, the contact between the support element and the femoral implant is made along a continuous zone which extends at the level of the upper surface of the support element, from one of the cavities to the other, passing through the bump.

[0038] In particular, at each degree of flexion between the extension position and the maximum flexion position of the femoral implant, the contact areas of the two condyles in the two cavities are connected by an isthmus corresponding to the contact surface between the boss and the intercondylar notch of the femoral implant. In practice, when the knee prosthesis is implanted in a subject's body, the contact areas of the two condyles in the two cavities are generally ovoid, from the extension position to a flexion position corresponding to an angle of 100°, or even 120° or more, depending on the pressure exerted on the femoral implant. The pressure exerted on the femoral implant is, in particular, a function of the subject's weight.

[0039] According to embodiments of the support elements and knee prostheses according to the invention, the hump is raised towards the anterior and / or posterior part of the support element. By way of illustration, it is possible for the intercondylar notch and the hump of the support element to have external profiles with congruent shapes, which fall within two hyperbolic paraboloids. In particular, the hump of the support element may fall within a hyperbolic paraboloid curved in the horizontal plane in the shape of a crescent with medial concavity, the external profiles of the hump and the intercondylar notch having congruent shapes of hyperbolic paraboloids curved with medial concavity.

[0040] According to another embodiment of the support elements and knee prostheses according to the invention, the hump extends along a generatrix contained in a plane. In other words, the hump is, in this case, not raised either towards the anterior or the posterior part of the support element.

[0041] Knee prostheses according to the invention can take different forms. In particular, the support element is an articular insert intended to be interposed between the femoral implant and a tibial implant. Thus, in general, knee prostheses According to the invention, the components also include a tibial implant intended to be placed on the end of the tibia, possibly after resection, and a joint insert intended to be interposed between the femoral and tibial implants. The joint insert may be rotationally mobile about an axis perpendicular to the bearing surface of the tibial implant. Advantageously, the joint insert is fixed to the tibial implant, with the fixation being achieved by any suitable means of attachment, in particular by a removable socket such as a direct assembly of the elastic socket type or an indirect assembly, notably using screws. In a particular embodiment, the tibial implant includes a housing on its upper surface, and the joint insert has an inferior face intended to be placed by reversible insertion into said housing.

[0042] According to other embodiments, the support element may directly constitute the tibial implant. In this case, the support element will most often include, in its lower part, a bearing surface intended to rest on the end of the tibia, if necessary after resection. Brief description of the drawings

[0043] [Fig-1] Fig. 1 is a schematic perspective view of a support element of a right knee prosthesis according to the invention, highlighting the curved nature of the hump extending between the two medial and lateral cavities.

[0044] [Fig. 2A] [Fig. 2A] shows a schematic bottom perspective view of an example of a femoral implant of a knee prosthesis according to the invention, which comprises two medial and lateral condyles defining between them an intercondylar notch that constitutes an opening between the two condyles. In this case, the intercondylar notch has parallel edges and is adapted to a support element as shown in [Fig. 4D], and the condyles are connected to each other only by a link located in the anterior part of the femoral implant, at the level of the lower part of the trochlea, and more precisely at the level of the condylotrochlear groove.

[0045] [Fig. 2B] [Fig. 2B] is a view analogous to [Fig. 2A], but illustrates another variant of the femoral implant in which the intercondylar notch forms a seamless connecting bridge with both condyles, extending from the anterior to the posterior part of the femoral implant. In this case, in each weight-bearing position, the intercondylar notch has an external profile facing the bearing element, the shape of which is congruent with the external profile of the boss on the bearing element shown in [Fig. 1]. This view is enlarged compared to that shown in [Fig. 3]. The intercondylar notch has edges that diverge towards the anterior part of the implant and is adapted to a bearing element as shown in [Fig. 1].

[0046] [Fig.3] Fig.3 is a schematic perspective view from the front part of the prosthesis, representing the femoral implant in the bearing position on the bearing element, when the prosthesis is in the extended position.

[0047] [Fig. 4A] [Fig. 4A] is a schematic perspective view similar to [Fig. 1] of the support element of [Fig. 3], highlighting the contact area (shown in shaded gray) between the femoral implant and the support element, according to the support position shown in [Fig. 3], but viewed from the posterior part of the support element. The shaded area schematically represents the location of the contact area between the two parts, where the intercondylar notch forms a seamless connecting bridge with the two condyles, extending from the anterior part of the femoral implant to its posterior part.

[0048] [Fig. 4B] [Fig. 4B] is a schematic cross-sectional view along the horizontal plane shown in [Fig. 3], of the prosthesis in the position shown in [Fig. 3], from a top view. The shaded area schematically represents the location of the contact zone between the boss and the intercondylar notch, when the latter forms a seamless connecting bridge with the two condyles, extending from the anterior part of the femoral implant to its posterior part, knowing that in reality this contact zone follows the external profile of the boss.

[0049] [Fig. 4C] Fig. 4C is a schematic top view of an example of the upper surface of a support element according to the invention, showing its circumference, the axes A1 and A2, and the distance Lmax, in particular. In this embodiment, the circumference of the support element is symmetrical with respect to the axis A1.

[0050] [Fig. 4D] Fig. 4D is a schematic top view of an example of the upper surface of a support element according to the invention, showing a boss that has an identical cross-section along its generatrix. Reference numerals 208 and 209 represent the flanks of the boss at its widest point, i.e., at the base of its cross-section, which corresponds to the change in curvature at the beginning of the cavities.

[0051] [Fig.4E] Fig.4E is a view similar to Fig.4D, but which corresponds to an embodiment of a support element according to the invention, in which the maximum width 1b of the section of the boss is decreasing along its generatrix from the front part to the rear part of the support element.

[0052] [Fig.4F] [Fig.4F] is a view analogous to [Fig.4E], which corresponds to another example of an embodiment of a support element according to the invention, in which the maximum width 1b of the section of the boss is decreasing along its generatrix from the front part to the rear part of the support element.

[0053] [Fig. 5] [Fig. 5] is a schematic perspective view from the front part of the prosthesis, representing the femoral implant in the bearing position on the element support, when the prosthesis is in a flexed position corresponding to an angle of approximately 120° between the femur and the tibia.

[0054] [Fig.6A] [Fig.6A] is a schematic perspective view similar to [Fig.4A] of the support element of [Fig.5], highlighting the contact area (represented in grey) between the femoral implant and the support element, according to the support position shown on [Fig.5] (flexion corresponding to an angle of approximately 120° between the femur and the tibia), when the intercondylar notch forms a seamless connecting bridge with the two condyles, extending from the anterior part of the femoral implant to its posterior part.

[0055] [Fig. 6B] [Fig. 6B] is a schematic cross-sectional view along the horizontal plane shown in [Fig. 3] of the prosthesis shown in [Fig. 5] (i.e., in the position of maximum flexion), from a top view. The shaded area schematically represents the location of the contact zone between the boss and the intercondylar notch, when the latter forms a seamless connecting bridge with the two condyles, extending from the anterior to the posterior part of the femoral implant, bearing in mind that in reality this contact zone follows the external profile of the boss. The dashed line corresponds to the position of [Fig. 4B].

[0056] [Fig.7] Fig.7 is a schematic cross-sectional view of the knee prosthesis of the previous figures when the latter is in extension position, according to a sagittal plane made at the level of the medial condyle and the medial cavity; the femoral implant and the support element are shown at a distance from each other for clarity.

[0057] [Fig.8] Fig.8 is a schematic cross-sectional view along a sagittal plane showing highlighting the spiral character of the external profiles of a medial condyle and a lateral condyle according to one of the preferred embodiments of the invention.

[0058] [Fig. 9A] [Fig. 9A] is a schematic cross-sectional view of the knee prosthesis shown in exploded view in [Fig. 7], along the frontal plane IXA shown in [Fig. 4B], when the knee prosthesis is in the extended position, with the femoral implant and the bearing element in contact with each other. For ease of understanding, the femoral implant and the bearing element are shown slightly apart. The shaded area schematically represents the location of the contact zone between the femoral implant and the bearing element when they are in contact with each other, in the case where the intercondylar notch forms a bridge extending from one condyle to the other and from the anterior to the posterior part of the femoral implant.

[0059] [Fig. 9B] [Fig. 9B] is a schematic cross-sectional view of the knee prosthesis shown in exploded view in [Fig. 7], along the frontal plane IXB shown in [Fig. 4B], when the knee prosthesis is in the extended position, with the femoral implant and the bearing element in contact with each other. The shaded area schematically represents the location of the contact zone between the femoral implant and The support element, when the two are in contact, is shown in the case where the intercondylar notch forms a bridge extending from one condyle to the other and from the anterior to the posterior part of the femoral implant. For ease of understanding, the femoral implant and the support element are shown at a distance, and the contact area is shown in gray.

[0060] [Fig. 9C] [Fig. 9C] is a schematic cross-sectional view of [Fig. 7], along the frontal plane IXC shown in [Fig. 6B], when the knee prosthesis is in a flexed position corresponding to an angle of 120°, with the femoral implant and the bearing element in contact with each other. For ease of understanding, the femoral implant and the bearing element are shown at a distance and the contact area is shown in gray, in the case where the intercondylar notch forms a bridge extending from one condyle to the other and from the anterior part 52 to the posterior part 53 of the femoral implant 2.

[0061] [Fig.1OA] The [Fig.1OA] is a schematic view along a sagittal plane, of the medial condyle conforming to the [Fig.8] in contact with the medial cavity, when the knee prosthesis is in the extension position.

[0062] [Fig.1OB] The [Fig.1OB] is a schematic view along a sagittal plane, of the medial condyle conforming to the [Fig.8] in contact with the medial cavity, analogous to the [Fig.1OA], but when the knee prosthesis is in the position of maximum flexion, corresponding to an angle of approximately 120°.

[0063] [Fig. 11 A] [Fig. 11 A] is a schematic sagittal view of the condyle lateral conforming to [Fig.8] in contact with the lateral cavity, when the knee prosthesis is in the extension position.

[0064] [Fig. 1 IB] The [Fig. 1 IB] is a schematic view along a sagittal plane, of the lateral condyle conforming to the [Fig.8] in contact with the lateral cavity, analogous to the [Fig.1OA], but when the knee prosthesis is in the position of maximum flexion, corresponding to an angle of approximately 120°.

[0065] [Fig. 12] The [Fig. 12] is a schematic perspective view of a prosthesis according to the invention in which the support element is an articular insert interposed between the femoral implant and a tibial implant. Description of the implementation methods

[0066] A knee prosthesis is intended to be implanted in an individual to replace a knee damaged by disease. Its various components are defined by reference to its use, that is, during the functioning of the prosthetic knee once the femoral implant is positioned on the end of the femur and the bearing element on the end of the tibia, respectively. The femoral implant is designed to be adapted after resection on The lower femoral epiphysis. The bearing element is designed to be adapted, directly or indirectly, after resection on the upper tibial epiphysis. When the bearing element is adapted indirectly after resection on the upper tibial epiphysis, it will correspond to an articular insert positioned between the femoral implant and a tibial implant, and it is the tibial implant that will be adapted to the upper tibial epiphysis. Conventionally, in the field of knee prostheses, the following terms are used: - the extension position corresponds to the case where the knee prosthesis is in a position that corresponds to the straight knee, that is to say that the femur and the tibia which come, respectively, in extension of the femoral implant and the support element form an angle of 0°; - Flexion positions correspond to the case where the knee is bent, that is to say, the femur and tibia, which respectively extend from the femoral implant and the supporting element, form a non-zero angle. The maximum flexion position generally corresponds to an angle equal to or greater than 120°; - the anterior part of the prosthesis (and therefore the anterior parts of the femoral implant and the support element) corresponds to the part which is positioned, when the prosthesis is implanted in an individual, towards the front of the individual; the posterior part of the prosthesis (and therefore the posterior parts of the femoral implant and the support element) corresponds to the part which is positioned, when the prosthesis is implanted in an individual, towards the back of the individual; - The medial parts (cavity, condyle ...) of the prosthesis correspond to the parts that will be positioned on the inner thigh side of the individual and the lateral parts (cavity, condyle ...) of the prosthesis correspond to the parts that will be positioned on the outer side of the individual's leg; - The terms sagittal and frontal planes are used in an anatomical sense. A sagittal plane extends perpendicularly to a frontal plane. A sagittal plane extends between the anterior and posterior parts of the prosthesis, while a frontal plane extends between the lateral and medial ends of the prosthesis. A horizontal or transverse plane extends perpendicularly to the sagittal and frontal planes.

[0067] In the context of the invention, a convex profile or shape means a profile or shape that is curved outwards from the part in question (femoral implant, support element), and a concave profile or shape means a profile or shape that is curved inwards from the part in question (femoral implant, support element). Furthermore, when referring to a concave or convex profile or shape, this excludes points of change in curvature. Moreover, the concept of concavity or convexity can correspond to a variable radius of curvature, but in a way that advantageous, the radius of curvature will be constant and said curved profile or said concave or convex shape will correspond to an arc of a circle.

[0068] As can be seen from the figures, and in particular from [Fig. 3], the object of the invention relates to a total knee prosthesis 1 conventionally comprising a femoral implant 2 and a support element 100 which is positioned on the tibia. The support element 100 is also the object of the invention. In the following description, emphasis will be placed on the specific features of the invention, and only the upper part of the support element will be shown, it being understood that the lower part may correspond to that conventionally present in a tibial implant (forming the support element on its own) or to that conventionally present in an articular insert cooperating with a tibial implant, which is positioned, on the tibia, most often after resection.In knee prostheses according to the invention, conventionally, the femoral and tibial implants are both preferably made of a biocompatible, stainless metal alloy, and the joint insert is generally made of a plastic material, such as polyethylene. However, one or more components of the prosthesis may also be made of alumina ceramic or alumina and zirconia, or of biocompatible resins, for example. Preferably, the support element is a joint insert that is placed on a tibial implant, thus allowing for better fixation to the tibia. If the joint insert is made of a plastic material, generally high-density polyethylene enriched with vitamin E, the tibial and femoral implants are generally metallic. If the joint insert is ceramic, the femoral implant is then advantageously also ceramic.

[0069] In a conventional manner, the femoral implant 2 has, in side view as partially shown in Figures 3, 5 and 12, in particular, a substantially asymmetrical U-shaped form between the arms of which is delimited a housing 500 for fixation on the lower epiphysis of the femur, in particular by interlocking two protruding lugs 600, visible in Figures 7, 9B and 12. Such lugs are optional, the placement and fixation of the femoral implant 2 on the epiphysis of the femur being able to be done by elastic force interlocking or by cementation.

[0070] As can be seen in [Fig. 2A], the femoral implant 2 has, on its lower face 700 facing the support element 100, two condyles, respectively a medial condyle 8 and a lateral condyle 9, delimiting between them an intercondylar notch 10 which defines a space existing between the two condyles. As can be seen in [Fig. 2A], but is more apparent in [Fig. 12], which illustrates another embodiment, conventionally, at the anterior part 52 of the femoral implant 2, a femoral trochlea 110 extends in the anterior continuation of the two condyles 8, 9, respectively medial and lateral, and has two trochlear cheeks, medial 120 and lateral 130, extending the external profile of the condyles 8, 9 respectively medial and lateral. The two trochlear cheeks 120, 130 are joined by a trochlear groove 150 extending in the anterior continuation of the intercondylar notch 10.

[0071] In the example shown in [Fig. 2A], the medial condyle 8 and the lateral condyle 9 are separated by a gap corresponding to the intercondylar notch 10. The medial condyle 8 and the lateral condyle 9 define the intercondylar notch 10 at their respective parts 108 and 109. The medial condyle 8 and the lateral condyle 9 are connected only at the anterior part 52 of the femoral implant 2. The connection between the medial condyle 8 and the lateral condyle 9, located at the anterior part 52 of the femoral implant 2, occurs at the lower part of the trochlear groove 150, and more precisely at the condylotrochlear groove 160.

[0072] It is also possible that the intercondylar notch 10 connects seamlessly with the two medial and lateral condyles 8 and 9 and forms a connecting bridge 170 which extends from one condyle to the other and from the anterior part 52 (more precisely from the condylotrochlear groove 160) to the posterior part 53 of the femoral implant 2. Such an embodiment is shown in [Fig. 2B]. Although it is not very visible in this figure, the external profile 101 of the intercondylar notch 10 which faces the support element 100 is concave in shape. This is evident, however, in [Fig.9B], which presents a cross-sectional view in a frontal plane of the femoral implant 2, opposite the support element 100. The two medial and lateral condyles 8, 9 of the femoral implant 2 form bumps.They are shaped in such a way that their section, according to a sagittal plane, has the shape of a spiral, the radius of curvature of which decreases from the anterior part 52 of the femoral implant 2 forming the femoral trochlea 110 towards the posterior part 53 of the femoral implant 2. .

[0073] As can be seen from [Fig. 1], the support element 100 has an upper surface 41, in which two cavities are formed: a medial cavity 18 for receiving the medial condyle 8 and a lateral cavity 19 for receiving the lateral condyle 9. Each of the cavities has a concave profile, regardless of the vertical plane considered. The two cavities, medial 18 and lateral 19, are separated by a boss 20 which extends from the anterior part 42 to the posterior part 43 of the support element 100, taking on a curved shape. Thus, the boss 20 is located in the central part of the support element 100. The boss 20 connects without discontinuity with the two cavities medial 18 and lateral 19. The boss 20 has, in top view, a curvature 180 oriented towards the medial cavity 18.In other words, in a horizontal plane or in a top view, the medial flank 208 (located on the side of the medial cavity 18) of the boss 20 has a concave profile, and the lateral flank 209 (located on the side of the lateral cavity 19) has a convex profile. In a horizontal plane or in a top view, the boss 20 therefore extends. along a curved generatrix whose concavity is oriented towards the medial cavity 18. In particular, the medial flank 208 and the lateral flank 209 are connected by a vertex 210, and the medial flank 208, the lateral flank 209, and the vertex 210 together form, in a sagittal plane, a convex external profile. The medial flank 208 and the lateral flank 209 have, in a horizontal plane, an external profile in the form of an arc, with the lateral flank 209 having a radius of curvature greater than that of the medial flank 208. The radius of curvature will depend on the width of the implant. The length of each flank 208 and 209 is different and depends on the radius of the profile of said flank.

[0074] The boss 20 will receive the intercondylar notch 10. That is to say, it is configured so that when the femoral implant 2 is supported on the support element 100, with contact between the medial cavity 18 and the medial condyle 8, on the one hand, and contact between the lateral cavity 19 and the lateral condyle 9, on the other hand, there is also contact both between the medial flank 208 of the boss 20 and the part 108 of the medial condyle 8 which delimits the intercondylar notch 10 and between the lateral flank 209 of the boss 20 and the part 109 of the lateral condyle 9 which delimits the intercondylar notch 10, as can be seen on the [Fig. 4A]. [Fig. 4A] represents the contact area between the femoral implant 2 of [Fig. 2B] and the support element 100 shown in [Fig. 1], when the femoral implant 2 is supported on the support element 100 in the extension position as shown in [Fig. 3]. [Fig.Figure 4B], which is a schematic cross-sectional view at the base of the hump 20 (section IVB of [Fig. 3]), highlights the contact areas 183 and 193, between the medial and lateral flanks 208 and 209 of the hump 20 and the portions 108 and 109 of the medial and lateral condyles 8 and 9 that define the intercondylar notch 10. During the relative flexion of the femoral implant 2 with respect to the bearing element 100, these contact areas 183 and 193 shift, but contact always exists, in any flexion position, between the medial flank 208 of the hump 20 and the portion 108 of the medial condyle 8 that defines the intercondylar notch 10, and between the flank lateral 209 of the bump 20 and part 109 of the lateral condyle 19 which delimits the intercondylar notch 10, which allows to ensure the guidance and control of the movement of the lateral condyle 9, in the lateral cavity 19. .

[0075] The hump 20 has a section (transverse straight section, that is to say a section taken in a vertical plane which is perpendicular to its generatrix) whose external profile facing the femoral implant 2 is convex.

[0076] As is more apparent in [Fig. 9B], which is a cross-sectional view along a frontal plane, the respective external profiles 181 and 191 of the two medial 18 and lateral 19 cavities are concave, and the external profile 201 of the boss 20 is convex and forms an arc of a circle. Thus, the boundary between the boss 20 and Each cavity can be defined as the point of change of convex / concave curvature. Within the scope of the invention, there is no flattening or angulation between the bump 20 and the medial 18 and lateral 19 cavities.

[0077] In particular, this external profile 201 of the boss 20 has the shape of a circular arc. In other words, the boss 20 is a semi-torus or a portion of a semi-torus that is curved and whose cross-section may be constant or variable. If the cross-section is constant, the medial flank 208 and the lateral flank 209 form concentric circular arcs in a horizontal plane. Such an embodiment is illustrated in [Fig. 4D].

[0078] To understand [Fig.4D], it is necessary first to refer to [Fig.4C], which presents a schematic top view of the circumference of the upper surface 41 of the support element 100. The upper surface 41 has a maximum width located on a mediolateral axis A2 and an anteroposterior axis Al extends perpendicularly to the mediolateral axis A2, intersecting the mediolateral axis A2 at its midpoint A. The mediolateral axis A2 intersects the peripheral edges 308 and 309 of the medial cavities 18 and lateral cavities 19 opposite the boss 20, respectively at points M and L, with AM=AL=Lmax.In the illustrated example, A1 and A2 are perpendicular and the circumference of the upper surface 41 is symmetric with respect to the axis AL. Point a is located on the axis A2, in the medial cavity 18, at a distance of 3Lmax / 4 from M, point y is located on the axis A2, in the medial cavity 18, at a distance of 7Lmax / 8 from M, point ô is located on the axis A2, in the lateral cavity 19, at a distance of 9Lmax / 8 from M and point [3 is located on the axis A2, in the lateral cavity 19, at a distance of 5Lmax / 4 from M. The geometric center of the medial cavity 18 is denoted Cm and the geometric center of the lateral cavity 19 is denoted Cl.

[0079] Figure 4D presents a schematic view of an embodiment of the boss 20 in which the medial 208 and lateral 209 flanks have parallel curvatures in a horizontal plane, which therefore correspond to concentric circular arcs. The cross-section of the boss 20 can thus be considered identical along its generatrix. In Figure 4D, the visible medial 208 and lateral 209 flanks are shown at the base of the cross-section of the boss 20, that is, at the change in curvature corresponding to the beginning of each medial 18 and lateral 19 cavity. Thus, at this point, the medial 208 has its minimum radius of curvature Rmmin and the lateral 209 has its maximum radius of curvature Rlmax. In the illustrated example, the center of the minimum radius of curvature Rrnmin of the medial flank 208 and the center of the maximum radius of curvature Rlmax of the lateral flank 209 respectively named Ci and C2 are coincident with M.The minimum radius of curvature Rmmin of the medial flank 208 is between the distance separating points M and a and the distance separating points M and y and the maximum radius of curvature Rlmax of the . lateral flank 209 is included between the distance separating points M and ô and the distance separating points M and [3.

[0080] The width of the intercondylar notch 10 and its shape are adapted to those of the boss 20 to allow contact, both, between the medial flank 208 of the boss 20 and the part 108 of the medial condyle 8 which delimits the intercondylar notch 10 and between the lateral flank 209 of the boss 20 and the part 109 of the lateral condyle 9 which delimits the intercondylar notch 10 when the femoral implant is in a bearing position on the upper surface 41 of the bearing element 100 and moves in flexion from an extension position to a maximum flexion position, and thus ensure the guidance of the movement of the femoral implant 2, during this femoral displacement. Thus, in the case of a support element 100 having a hump with parallel medial flanks 208 and lateral flanks 209 (as in the [Fig.[4D]), a suitable femoral implant 2 will have an intercondylar notch 10 delimited by parts 108 and 109 of condyles which, in a horizontal plane, extend along concentric arcs. Such an example of a femoral implant 2 is shown in [Fig. 2A].

[0081] Fig. 4E presents a schematic view of another embodiment of the hump 20 in which the medial flanks 208 and lateral flanks 209 have non-parallel curvatures in a horizontal plane, and which correspond to a decrease in the width 1b of the hump 20 from the anterior part 42, towards the posterior part of the support element 100. The width 1b of the hump is taken according to the section of the hump, therefore perpendicular to its generatrix and corresponds to the width at the level of the base of the section (which is therefore the maximum width of said section). In the example illustrated in this figure, the maximum radius of curvature Rlmax of the lateral flank 209 has its center C2 on the medio-lateral axis A2 at M, and the minimum radius of curvature Rrnmin of the medial flank has its center Cl on an axis A'2 parallel to the axis A2, but offset from the latter.The axis A'2 is located between the mediolateral axis A2 and the posterior part of the support element, with the distance dc between the mediolateral axis A2 and the axis A'2 being equal to Lmax / 8, in this example.

[0082] Figure 4F presents a schematic view of another embodiment of the hump 20 in which the medial 208 and lateral 209 flanks have non-parallel curvatures in a horizontal plane, corresponding to a decrease in the width 1b of the hump 20 from the anterior part 42 towards the posterior part of the support element 100. In the example illustrated in this figure, the minimum radius of curvature Rrnmin of the medial flank 208 has its center C1 at M on the mediolateral axis A2, and the maximum radius of curvature Rlmax of the lateral flank 209 has its center C2 on an axis A'2 parallel to the axis A2, but offset from the latter. The axis A'2 is located between the medio- lateral A2 and the anterior part 42 of the support element, with the distance dc between the medio-lateral axis A2 and the axis A'2 which is equal to Lmax / 8, in this example.

[0083] In these two embodiments of Figures 4E and 4F, the boss has medial 208 and lateral 209 flanks diverging towards the anterior part 42 of the support element 100. The width and shape of the intercondylar notch 10 are adapted to those of the boss 20 to allow contact both between the medial flank 208 of the boss 20 and part 108 of the medial condyle 8 which delimits the intercondylar notch 10, and between the lateral flank 209 of the boss 20 and part 109 of the lateral condyle 9 which delimits the intercondylar notch 10 when the femoral implant is in a bearing position on the upper surface 41 of the support element 100 and moves in flexion from a position extension up to a position of maximum flexion, and thus ensure the guidance of the movement of the femoral implant 2, during this femoral displacement,In the case of a support element whose boss has medial flanks 208 and lateral flanks 209 diverging towards the anterior part 42 of the support element 100, a suitable femoral implant 2 will also have an intercondylar notch 10 delimited by parts 108 and 109 of condyles that diverge towards the anterior part 52 of the femoral implant 2. Such an example of a femoral implant 2 is shown in [Fig. 2B].

[0084] The geometric choices for the support element 100 illustrated in Figures 4A to 4F are given for illustrative purposes only, and many other construction choices can be adopted by those skilled in the art, depending on the size of the prosthesis adapted to the size and weight of the patient on whom it is to be implanted. The presence of a central boss 20 extending in a horizontal plane along a curved generatrix with a concavity 180 oriented towards the medial cavity 18 of the support element 100, with the lateral flank 209 of the boss 20 having a radius of curvature greater than the radius of curvature of the medial flank 208 of the boss 20, cooperates with the intercondylar notch 10 to guide the movement of the lateral condyle 9 in the lateral cavity 19.The dimensions of the central boss 20 and the intercondylar notch 10 are chosen to ensure contact between the boss 20 and the medial condyle 8 and lateral condyle 9 at the level of this intercondylar notch 10, throughout the flexion movement when the femoral implant 2 is in a bearing position on the upper surface 41 of the support element 100 and moves in flexion from an extension position to a maximum flexion position. Thus, guiding the movement of the femoral implant 2 during this flexion is possible with a displacement of the contact area of ​​the lateral condyle 9 in the lateral cavity 19 from the anterior part 42 to the posterior part 43 of the support element 100, which corresponds to a displacement along a portion of a circular arc.

[0085] Advantageously, the medial cavity 18 has, in top view, an ovoid shape, as illustrated in figures 4A, 4B, 4D to 4F, 6A and 6B, the long axis of the ovoid extending along the anteroposterior axis of the medial cavity 18. The lateral cavity 19, on the other hand, generally has, in top view, a crescent-type shape, as shown in figures 4A, 4B, 4D to 4F, 6A and 6B.

[0086] As can be seen from these figures, in top view, the upper surface 41 of the support element 100 is kidney-shaped, with the concave area 44 located at the level of the posterior part 43. The concave area 44 particularly helps to preserve the posterior cruciate ligament, if necessary. The posterior end of the hump 20 is therefore located at the level of this concave area 44.

[0087] There is cooperation between the upper surface 41 of the support element 100 and the lower face 700 of the femoral implant 2. When the femoral implant 2 is supported on the upper surface 41 of the support element 100, there is contact between the medial cavity 18 and the medial condyle 8, contact between the lateral cavity 19 and the lateral condyle 9 and contact between the boss 20 and the intercondylar notch 10. Figures 3 and 5 show the femoral implant of [Fig.2B] supported on the surface 41 of the support element 100 of [Fig.1], in two different positions, respectively in the extension position (angle 0°) and in the maximum flexion position (angle 120°) of the knee prosthesis.

[0088] In the example illustrated in these figures, the bump 20 and the intercondylar notch 10 have congruent shapes which fit together with play, as can be seen from figures 9A to 9C. But, the principle of the invention is the same without this congruity, given that the guidance is ensured by the contact maintained throughout the flexion movement between the medial flank 208 of the bump 20 and the part 108 of the medial condyle 8 which delimits the intercondylar notch 10, on the one hand, and between the lateral flank 209 of the bump 20 and the part 109 of the lateral condyle 9 which delimits the intercondylar notch 10, on the other hand.

[0089] As can be seen from [Fig.2A] and [Fig.2B], the intercondylar notch 10, when viewed from below, has a curvature oriented towards the medial condyle 8. In other words, the medial leg 108 (located on the side of the medial condyle 8) of the intercondylar notch 10 has a concave profile in a horizontal plane and the lateral leg 109 (located on the side of the lateral condyle 9) has a convex profile. In particular, as shown in Figures 9A to 9C, the external profile of the boss 20 corresponds exactly, but in relief and mirrored, to the external profile of the intercondylar notch 10 that separates the medial condyle 8 and the lateral condyle 9. In particular, as shown in [Fig. 9B], in a plane extending perpendicularly to the generatrix of the boss, the convex external profile 201 of the boss 20 and the concave external profile 101 of the intercondylar notch 10 form arcs of circles with radii of curvature R20 and RIO respectively which are substantially identical.

[0090] Furthermore, the displacement of the lateral condyle 9 within the lateral cavity 19 is accompanied by a rotation of the latter around its transverse axis during flexion of the prosthesis. Thus, during the flexion of the femoral implant 2, the path of a point following the intercondylar notch 10 is shorter than the path followed by a point located on the lateral condyle 9 resting in the lateral cavity 19. In Figures 9A and 9C, the convex external profiles 201a and 201b of the hump 20 and the concave external profiles 101a and 101b of the intercondylar notch 10 are not arcs of circles, but have an ovoid shape, because the section is not taken perpendicular to the generatrix of the hump 20.

[0091] According to the invention, it is the curvature of the hump 20 and the contact areas between the latter and the intercondylar notch 10 which ensure, on the one hand, the stability of the prosthesis and on the other hand a kinematic conforming to the natural movement of the knee, when the constituent elements (femoral implant 2 and support element 100, in particular) of the knee prosthesis 1 according to the invention pass from an extension position to a flexion position, and this up to a maximum flexion position.According to the invention, in any position of the knee prosthesis 1, the femoral implant 2 bears on the upper bearing surface 41 of the bearing element 100, with the surface of the intercondylar notch 10 bearing on the surface of the hump 20, or more precisely with at least one bearing between the medial flank 208 of the hump 20 and the part 108 of the medial condyle 8 which delimits the intercondylar notch 10, on the one hand, and between the lateral flank 209 of the hump 20 and the part 109 of the lateral condyle 9 which delimits the intercondylar notch 10, on the other hand. This ensures both the guidance and stability of the femoral element during its relative rotational movement, with guidance and stability not being dissociated. The [Fig.9B] highlights the congruent nature of the two external profiles of the intercondylar notch 10 and the boss 20 and the fact that the latter are in contact, according to a continuous contact ensured over the entire intercondylar notch 10 and the boss 20. In the example illustrated on [Fig.2B] and figures 9A to 9C, in particular, the support and therefore the contact between the two external profiles of the intercondylar notch 10 and the boss 20 takes place both at the level of the parts 108 and 109 of the condyles delimiting the intercondylar notch 10, and at the level of the apex 210 of the external profile of the intercondylar notch 10. .

[0092] The curved boss 20 ensures asymmetrical rotation of the two condyles, medial 8 and lateral 9: the curved boss 20 guides the rotational movement of the femoral implant 2, the medial condyle 8, and the lateral condyle 9. the guidance of the intercondylar notch 10 on the curved hump 20, in the manner of a monorail train which follows the curvature of its central rail.

[0093] Thus, when the femoral implant 2 is in a bearing position on the upper surface 41 of the support element 100 and moves in rotation (flexion movement) from an extension position illustrated in [Fig. 3] to a maximum flexion position illustrated in [Fig. 5], the intercondylar notch 10 and the boss 20, by virtue of their shape and even their congruity, ensure the guidance of the movement of the femoral implant 2 during this rotation with a displacement of the contact area of ​​the lateral condyle 9 in the lateral cavity 19 from the anterior part 42 to the posterior part 43 of the support element 100. Thus, during the movement of the knee prosthesis 1 according to the invention, the lateral condyle 9 of the femoral implant 2 describes, in addition to its rotation around its transverse axis, a rotation around a vertical axis which is located on the medial cavity side 18 and can pass through the medial cavity 18.

[0094] In particular, the contact area of ​​the lateral condyle 9 in the lateral cavity 19 moves along a curved trajectory, as can be seen from the comparison: - of figures 4A and 4B, on the one hand, which respectively present a top view of the surface 41 and a top cross-sectional view which therefore highlights the contact areas 183 and 193 of the bump 20 and the intercondylar notch 10 between the medial flank 208 of the bump 20 and the medial leg 108 of the intercondylar notch 10 and between the lateral flank 209 of the bump 20 and the lateral leg 109 of the intercondylar notch 10, when the knee prosthesis is in extension; The contact surface 300 with the femoral implant 2 is shown in grey, when the intercondylar notch 10 is full and forms a connecting bridge 170 between the two condyles and Figures 6A and 6B, on the other hand, respectively show a top view of surface 41 and a top cross-sectional view, thus highlighting the contact areas 183 and 193 of the boss 20 and the intercondylar notch 10 between the medial flank 208 of the boss 20 and the medial leg 108 of the intercondylar notch 10, and between the lateral flank 209 of the boss 20 and the lateral leg 109 of the intercondylar notch 10, when the knee prosthesis is in maximum flexion. The contact surface 300 with the femoral implant 2, when the intercondylar notch 10 is full and forms a connecting bridge 170 between the two condyles, is shown in gray.

[0095] In particular, it is clear from these figures that the displacement of the contact area 192 of the lateral condyle 9 in the lateral cavity 19 can take the form of a portion of a circular arc corresponding to an angle of approximately 20° + / - 5°. The center of this circular arc is located in the medial cavity 18. It should be noted that, given that the lateral condyle 9 moves within the lateral cavity 19, the transverse axis around which the implant femoral 2 moves in rotation, is not fixed and experiences a planar movement in a horizontal plane.

[0096] The boss 20, by virtue of its curvature oriented towards the medial cavity 18 (concave medial profile and convex lateral profile, in top view), ensures the guidance of the femoral implant 2, when the latter is in rotation around its transverse axis and allows an asymmetrical displacement of the condyles 8 and 9. Indeed, between the extension position and the maximum flexion position of the prosthesis, the contact zone 182 of the medial condyle 8 moves only a few millimeters from front to back or from back to front in the medial cavity 18, while the contact zone 192 of the lateral condyle 9 moves along a curved trajectory, in the lateral cavity 19, and this from the anterior part 42, towards the posterior part 43 of the support element 100, as can be seen, in particular, from figures 3 to 6.

[0097] Thus, contrary to the solutions proposed in particular in US patent 2017 / 0189195, it is not the cooperation of the cavities and the condyles that ensures the guidance of the rotation, but the central boss 20 which cooperates with the intercondylar notch 10 of the femoral implant 2. According to certain embodiments, the central boss 20 and the intercondylar notch 10 can be congruent at both the lateral 208 and medial 209 flanks and at the apex 210 of the boss 20. This further facilitates the control of the displacement of the femoral implant 2. The congruence is assessed in each position of the femoral implant 2 bearing on the surface 41 of the support element 100.That is to say, at each flexion position from the extension position to the maximum flexion position, there is contact between the intercondylar notch 10 and the boss 20, at the lateral 208 and medial 209 flanks and at the apex 210 when the intercondylar notch 10 is full. However, a gap is present between the two parts, and in particular at the boss 20, to prevent clamping between the two parts. It should also be noted that in the knee prostheses 1 of the invention, and as illustrated in the figures, there are no stops in the medial 18 and lateral 19 cavities. There are also no flats or angulations in the medial 18 and lateral 19 cavities.The lateral condyle 8 and medial condyle 9 each have a profile that is convex at all points, that is to say, they do not include an abrupt change in curvature defining two different convex profiles, as is the case, in particular, in US application 2017 / 0189195. Similarly, the two cavities, medial 18 and lateral 19, each have a profile that is concave at all points, that is to say, they do not include an abrupt change in curvature defining two different concave profiles, as is the case, in particular, in US application 2017 / 0189195.

[0098] The curved boss 20 and the fact that the external profile of the intercondylar notch 10 follows the external profile of the curved boss 20, at least at the level of the lateral flanks 208 and medial flanks 209 of the boss 20 during the flexion movement of the femoral implant 2, allows both transverse stabilization, anteroposterior stabilization and rotational stabilization, the medial condyle 8 and the lateral condyle 9 (or more precisely its part 109 which constitutes a leg of the intercondylar notch 10) of the femoral implant 2 being blocked in rotation by their contact with the anterior and posterior parts of the medial flanks 208 and 209 of the curved boss 20 against which they come to rest.

[0099] Along its generatrix, the maximum width 1b of the section of the hump 20 can be constant throughout the hump. It is also possible, as in the example illustrated in Figures 1 to 10B, for the width 1b to decrease from the anterior part 42 to the posterior part 43 of the support element 100. In this case, if the external profiles of the boss 20 and the intercondylar notch 10 are congruent, the width of the intercondylar notch 10 also decreases from the anterior part 52 to the posterior part 53 of the femoral implant 2. To allow flexion movement, when it is full and forms a connecting bridge 170 between the two condyles, the height of the intercondylar notch 10 will also increase from the anterior part 52 to the posterior part 53 of the femoral implant 2.

[0100] Advantageously, in certain embodiments of the invention where the intercondylar notch 10 is solid, and as can be seen in particular from Figures 4A and 6A, the contact between the support element 100 and the femoral implant 2 is made along a continuous zone 300 which extends at the level of the upper surface 41 from one of the medial 18 and lateral 19 cavities to the other, passing through the boss 20. In particular, at each degree of flexion between the extension position and the maximum flexion position of the femoral implant 2, the contact zones 182 and 192 of the two condyles, medial 8 and lateral 9 respectively, in the two cavities, medial 18 and lateral 19, are connected by an isthmus 202 corresponding to the contact surface between the boss 20 and the intercondylar notch 10. of the femoral implant.More specifically, the isthmus 202 is an isthmic surface which follows the external profile of the hump and therefore extends not only over the apex 210 of the latter, but also over its medial 208 and lateral 209 flanks.

[0101] Furthermore, the contact area between the hump 20 and the intercondylar notch 10 moves from front to back on the hump when the knee prosthesis 1 bends from its fully extended position (0° angle) to its maximum flexed position (120° angle or more). The contact occurs on the flanks of the hump (medial contact area 183 at the level of the medial flank 208 and lateral contact area 193 at the level of the lateral flank 209), with a front-to-back displacement of the contact area 193 on the lateral flank 209 of the hump 20. The contact can extend to the top 210 of the hump 20, when the intercondylar notch 10 forms a connecting bridge 170.

[0102] The surface area of ​​this contact zone 300, which is continuous, decreases from the extension position to the maximum flexion position. In particular, in the maximum flexion position, the contact surface of the lateral condyle 9 in the lateral cavity 19 is smaller, and may even, in certain configurations, take the form of an almost linear surface.

[0103] As illustrated in [Fig. 8], according to a preferred embodiment, the lateral condyle 8 and medial condyle 9 have, in the sagittal plane, an external profile that is a spiral whose radius decreases continuously. In particular, the lateral condyle 9 has an external profile 92 in the sagittal plane, which is a logarithmic spiral. The external profile 82 in the sagittal plane of the medial condyle 8 is a spiral whose radius decreases less sharply. In the sagittal plane, the external profile 92 of the lateral condyle 9 is inscribed within the external profile 82 of the medial condyle 8, whose generating spiral has a radius that decreases less sharply than that of the generating spiral of the external profile 92 of the lateral condyle 9.

[0104] In the illustrated examples, the medial cavity 18 has an ovoid shape, with a mediolateral short axis and an anteroposterior long axis. Preferably, this medial cavity 18 has, in the sagittal plane, an anteroposterior curvature corresponding to the shape of the medial condyle 8 when the knee prosthesis is in extension. Advantageously, and as illustrated in [Fig. 1OA], the external profile 181 of the medial cavity 18 conforms to the shape of the external profile 82 of the medial condyle 8 with which it is in contact when the knee prosthesis is in extension (straight, straight knee corresponding to an angle between the femur and tibia of 0°).

[0105] Thus, there is no anteroposterior movement in the medial cavity 18 when the knee is fully extended. In this position, according to a sagittal section shown in [Fig. 1OA] extending along the long axis of the medial cavity 18, contact with the medial condyle 8 occurs over the entire surface of the cavity. [Fig. 1OB], which represents a section similar to that of [Fig. 1OA], but with the knee prosthesis in a flexed position corresponding to an angle of 120°, shows that the medial condyle 8 moves very little within the medial cavity 18. This movement, which occurs from the posterior part 43 to the anterior part 42, or from the anterior part 42 to the posterior part 43, is advantageously 3 to 5 mm at most.This mobility corresponds to the difference between the anteroposterior diameter of the external profile 181 of the medial cavity 18 and the radius of curvature of the spiral corresponding to the external profile 82 of the medial condyle 8, in this position. This slight displacement. This is permitted by the fact that the medial cavity has the negative shape of the medial condyle 8 when the knee is extended at 0°, but since the radius of the spiral of the medial condyle 8 decreases slightly during flexion, it will be located in a cavity with an anteroposterior diameter larger than itself from a degree of flexion of 45°. The presence of this play provides greater comfort to the patient.

[0106] Moreover, for a given angle of flexion, in the sagittal plane, the curvatures of the external profiles 82 and 92 of the medial condyle 8 and lateral condyle 9 are inscribed in the curvatures of the external profiles 181 and 191 of the corresponding cavities 18 and 19, which means that the contact areas 182 and 192 between condyles and cavities are surfaces which gradually decrease during flexion from 0 to 120° as the radius of the turns of the medial condyle 8 and lateral condyle 9 decreases in the sagittal plane.

[0107] Conversely, the contact area 192 of the lateral condyle 9 in the lateral cavity 19 moves greatly from front to back, as can be seen from the comparison: - of [Fig.1 IA] which presents a view along a sagittal plane of the lateral condyle 9 in the lateral cavity 19, when the knee prosthesis 1 is in extension; and - of [Fig.1 IB] which presents a view along a sagittal plane of the lateral condyle 9 in the lateral cavity 19, when the knee prosthesis 1 is in maximum flexion.

[0108] Regarding the lateral condyle 9 and the lateral cavity 19, there are no constraints in terms of the choice of radii of curvature. In particular, as shown in the figures, the concavity of the lateral cavity 19 may be less than that of the medial cavity 18.

[0109] It should be noted that the support elements 100 and femoral implants 2 illustrated in the figures correspond to prostheses for a right knee. The support elements 100 and femoral implants 2 for a left knee correspond to their mirror image.

[0110] In [Fig. 12] the other parts of a knee prosthesis 1 according to the invention are shown, in the case of a knee prosthesis in which the support element is an articular insert 4. In such a case, the support element 100 which is an articular insert 4 is interposed between the femoral implant 2 and a tibial implant 3. The tibial implant 3 has at least one support plate 21 intended to rest by its lower surface 212 on the end of the tibia, where appropriate after resection.

[0111] The insert 4, which corresponds to a support element 100 according to the invention, bears by a lower face 45 on the upper surface of the plate 21 of the tibial implant 3. The assembly between the two can be made by reversible interlocking, in particular by means of an elastic snap-fit, in a housing 211, located on the upper surface of the plate 21 as shown in [Fig.12].

[0112] The tibial implant 3, for its part, also includes a medullary anchoring rod 240 extending from the lower face 212 of the plateau 21 and intended to rest against a resected epiphyseal surface of the tibia (not shown).

Claims

1. Demands Total knee prosthesis (1) comprising a femoral implant (2) and a support element (100) for the femoral implant (2), wherein: - the femoral implant (2) comprises two condyles (8, 9), referred to as the medial condyle (8) and the lateral condyle (9), delimiting between them an intercondylar notch (10), the external profiles of the two condyles (8, 9) facing the support element (100) being convex, - the support element (100) is intended to be positioned on the tibia side and comprises a superior surface (41) on which are formed a medial cavity (18) for receiving the medial condyle (8) and a lateral cavity (19) for receiving the lateral condyle (9), said cavities (18, 19) being separated by a boss (20) extending over the superior surface (41) between the two cavities (18, 19), said bump (20) fitting into the intercondylar notch (10) when the femoral implant (2) is resting on the upper surface (41) of the support element (100),with the medial cavity (18) viewed from above, which has an ovoid shape with a minor mediolateral axis and an anteroposterior major axis, characterized in that, in a horizontal plane, said boss (20) extends along a curved generatrix having a concavity (180) oriented towards the medial cavity (18) of said support element (100), said boss (20) having a lateral flank (209) and a medial flank (208) connected by a vertex (210) which together define, along the generatrix of the boss (20), a section whose external profile is convex and, in particular, arc-shaped, with, in a horizontal plane, the lateral flank (209) of the boss (20) having a radius of curvature that is greater than the radius of curvature of the medial flank (208) of the boss (20), with the presence of no flat surfaces or with no angulation between the hump (20) and the medial (18) and lateral (19) cavities, the femoral implant (2) being adapted to the support element,so that when the femoral implant (2) is supported on the upper surface (41) of the support element (100), there is contact between the medial cavity (18) and the medial condyle (8), contact between the lateral cavity (19) and the lateral condyle (9), and contact, at the same time, between the medial flank (208) of the boss (20) and the part (108) of the medial condyle (8) which delimits the intercondylar notch (10), and between the lateral flank (209) of the bump (20) and the part (109) of the lateral condyle (9) which delimits the intercondylar notch (10); the contact between the bump and the condyles (8, 9) at the level of the intercondylar notch (10) ensuring, when the femoral implant is in a bearing position on the upper surface (41) of the bearing element (100) and moves in flexion from an extension position to a maximum flexion position, the guidance of the movement of the femoral implant (2) during this flexion with a displacement of the contact area (192) of the lateral condyle (9) in the lateral cavity (19) from the anterior part (42) to the posterior part (43) of the bearing element (100), which corresponds to a displacement over a portion of an arc of a circle.

2. Prosthesis (1) according to claim 1, characterized in that the medial (208) and lateral (209) flanks of the boss (20) have parallel curvatures, corresponding to concentric arcs of circles, the upper surface (41) of the support element (100) having a maximum width located on a mediolateral axis A2 and an anteroposterior axis A1 extending perpendicularly to the mediolateral axis A2 by intersecting the mediolateral axis A2 at its midpoint A, and the mediolateral axis A2 intersecting the peripheral edges (308 and 309) of the medial (18) and lateral (19) cavities opposite the boss (20), respectively at points M and L, with AM=AL=Lmax, the centers of the radii of curvature of the medial flank (208) and the lateral flank (209) being coincident and located on the axis A2 and on a segment [M - 2 mm;M + 2 mm], the minimum radius of curvature Rmmin of the medial flank (208) and the maximum radius of curvature Rlmax of the lateral flank (209) being defined as follows: - Rmmin of the medial flank (208) which is between 3Lmax / 4 + / -2mm and 7Lmax / 8 + / - 2mm and is, preferably, equal to 7Lmax / 8 + / -2mm, - Rlmax of the lateral flank (209) which is between 9Lmax / 8 + / - 2mm and 5Lmax / 4 + / - 2mm and is, preferably, equal to 9Lmax / 8 + / - 2mm.;

3. Prosthesis (1) according to claim 1, characterized in that the maximum width 1b of the section of the boss (20) is decreasing along its generatrix from the anterior part (42) to the posterior part (43) of the support element (100).

4. Prosthesis (1) according to claim 3, characterized in that, in top view, the upper surface (41) of the support element (100) having a maximum width located on a mediolateral axis A2 and an anteroposterior axis Al extending perpendicularly to the mediolateral axis A2 by cutting the mediolateral axis A2 at its midpoint A and the mediolateral axis A2 cutting the peripheral edges (308 and 309) of the medial (18) and lateral (19) cavities opposite the boss (20), respectively at points M and L, the center of the radii of curvature of the medial flank (208) and the lateral flank (209) being located in a square of l / 4Lmax side with M which is the center of the square.

5. Prosthesis (1) according to claim 4, characterized in that the minimum radius of curvature Rmmin of the medial flank (208) has its center Cl on the mediolateral axis A2 at M, and the maximum radius of curvature Rlmax of the lateral flank (209) has its center C2 on the axis A'2, with the axis A'2 being located between the mediolateral axis A2 and the anterior part (42) of the support element (100), with the distance dc between the mediolateral axis A2 and the axis A'2 being equal to Lmax / 8 + / - 2mm, or alternatively the maximum radius of curvature Rlmax of the lateral flank (209) has its center C2 on the mediolateral axis A2 at M, and the minimum radius of curvature Rmmn of the medial flank (208) has its center Cl on the axis A'2, with the axis A'2 which is located between the mediolateral axis A2, and the posterior part (43) of the support element (100), with the distance dc between the mediolateral axis A2 and the axis A'2 which is equal to Lmax / 8 + / - 2mm.

6. Prosthesis (1) according to any one of claims 1 to 5, characterized in that the upper surface (41) of the support element (100) has a circumference which has a symmetrical shape with respect to the anteroposterior axis Al.

7. Prosthesis (1) according to any one of claims 1 to 5, characterized in that the upper surface (41) of the support element (100) has a circumference which has a non-symmetrical shape with respect to the anteroposterior axis Al, with a lateral circumference smaller than the medial circumference.

8. Prosthesis (1) according to any one of claims 1 to 7, characterized in that the bump (20) is raised towards the anterior part (42) and / or towards the posterior part (43) of the support element (100).

9. Prosthesis (1) according to any one of claims 1 to 8, characterized in that the support element (100) constitutes an articular insert (4) intended to be interposed between the femoral implant (2) and a tibial implant (3) intended to be placed on the end of the tibia, where appropriate after resection, said articular insert (4) having an inferior face (45) intended to be placed on the tibial implant (3), in particular, by reversible fitting into a housing (211) located on the superior surface of the tibial implant (3).

10. Prosthesis according to any one of claims 1 to 9, characterized in that in a frontal plane, the external profile (101) of the intercondylar notch (10) is concave in shape, and the intercondylar notch (10) forms a connecting bridge (170) without discontinuity with the two condyles (8, 9), which extends from the anterior part (52) of the femoral implant (2) to its posterior part (53).

11. Prosthesis according to claim 10, characterized in that in a frontal plane, when the femoral implant (2) is in a bearing position on the upper surface (41) of the bearing element (100) and moves in flexion from an extension position to a maximum flexion position, the external profile (101) of the intercondylar notch (10) is congruent with the external profile of the boss (20).

12. Prosthesis according to claim 11, characterized in that the support element (100) conforms to claim 3, i.e. that the maximum width 1b of the section of the boss (20) is decreasing along its generatrix from the anterior part (42) to the posterior part (43) of the support element (100) and, due to the congruent shapes of the external profiles of the boss (20) and the intercondylar notch (10), the maximum width of the intercondylar notch (10) is decreasing from the anterior part (52) to the posterior part (53) of the femoral implant (2).

13. Prosthesis according to any one of claims 1 to 12, characterized in that the section of the boss (20) has a convex external profile (201) of radius of curvature R20 and the section of the intercondylar notch (10) has a concave external profile (101) of radius of curvature RIO, with the radii of curvature R20 and RIO being substantially identical, with sufficient clearance to avoid clamping between the femoral implant (2) and the support element (100) at the level of the bump (20).

14. Prosthesis according to any one of claims 1 to 13, characterized in that the contact between the support element (100) and the femoral implant (2) is made along a continuous zone (300) which extends at the level of the upper surface (41) of the support element (100), from one to the other of the cavities (18, 19), passing through the boss (20).

15. Prosthesis according to any one of claims 1 to 14, characterized in that the condyles (8, 9) have an external profile (82, 92) in the sagittal plane, the generatrix of which is a spiral.

16. Prosthesis according to any one of claims 1 to 15, characterized in that the medial cavity (18) has in the sagittal plane passing through its long anteroposterior axis a curvature corresponding in the same plane to that of the medial condyle segment in contact (8) with said medial cavity (18) when the femoral implant (2) is in the extension position.

17. Prosthesis according to any one of claims 1 to 16, characterized in that it also comprises a tibial implant (3) intended to be placed on the end of the tibia, where appropriate after resection, and the support element (100) conforms to claim 9 and is an articular insert (4) intended to be interposed between the femoral implant (2) and the tibial implant (3).

18. Prosthesis according to claim 17, characterized in that the tibial implant (3) comprises on its upper surface, a housing (211) and the articular insert (4) has an inferior face (45) intended to be placed by reversible fitting into said housing (211).

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