New knee prosthesis

Abstract

New knee prosthesis The invention relates to a support element (100) for a femoral implant of a total knee prosthesis, which is intended to be positioned on the tibia side and comprising an upper surface (41) on which are arranged 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 entire generatrix a convex external profile and, with in a horizontal plane, the lateral flank (209) of the boss (20) which has a radius of curvature which is greater than the radius of curvature of the medial flank, thus than any corresponding total knee replacement. Figure for abstract: 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 particular field a new knee prosthesis. Prior art

[0002] In the field of knee prostheses, many previous proposals have already been made. The most common models of knee prostheses, commonly called sliding prostheses, comprise a femoral implant which covers, after resection, the superficial bony surfaces of the lower end of the femur, a tibial implant which covers, after resection, the superficial bony surfaces of the upper end of the tibia. These prostheses preserve the lateral ligaments, the joint capsule, the tendons of the periarticular muscles, as well as 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 existing between the tibia and the femur which has become diseased. Knee prostheses aim to meet a certain number of requirements, which are, in particular: - a tribological requirement: they must undergo a minimum of wear in use; - a kinematic requirement: the functioning 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 comprise at the level of the femoral implant two bumps called lateral condyle and medial condyle and an anterior articular surface called trochlea articulated with the patella. The two condyles are separated by a part corresponding to a lack of material, called 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 supported on the upper surface of the tibia after resection, supporting an articular insert intended to articulate with the femoral implant. The shapes of the articular insert differ from one type of prosthesis to another and characterize the functioning of the prosthesis. The bearing surface for the femoral implant, whether on the tibial implant (two-part prosthesis) or on the articular insert (three-part prosthesis) generally comprises two hollow cavities, called lateral and medial.

[0005] It is on the bearing surface for the femoral implant and its articulation with the femoral implant that innovations most often concern. Also, in order to allow a more or less physiological movement of the joint, several solutions have been proposed in the state of the art.

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

[0007] In a particular configuration of knee prosthesis with insert, proposed in application WO 2010 / 001010 by some of the inventors of the present invention, the insert comprises on its upper face between the two medial and lateral cavities which are symmetrical, a central saddle-shaped bump (or more precisely a hyperbolic paraboloid), 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 which is itself symmetrical, with respect to a sagittal plane. This symmetry does not allow the rotational movement to be guided according to physiology and causes stress on the insert. These effects required releasing the rotation between the lower face of the insert and the upper face of the tibial plateau which supports it.The rotation thus obtained is symmetrical around a central vertical axis, which is different from the asymmetrical physiological functioning of a natural knee and therefore of an optimal knee prosthesis.

[0008] Indeed, in its physiological functioning, the movement of the condyles during knee flexion is done asymmetrically. During natural knee flexion, the medial condyle moves little back and forth in the medial glenoid cavity on which it rests, while the contact zone of the lateral condyle describes an arc of a circle and moves back and forth in the lateral cavity.

[0009] In addition, prostheses of this type with a mobile insert (known as a mobile plate) carry a high risk of excessive rotation and therefore of dislocation. Indeed, this type of prosthesis provides mediolateral stability, but does not provide or provides little anteroposterior stability (from front to back) and no rotational stability at all, the insert being able to rotate 360° around its keel and give rise to dislocations, either by excess external rotation or by excess internal rotation (the opposite of physiological).

[0010] Other knee prosthesis configurations have been proposed in the prior art. Application US 2017 / 0189195, in particular, proposes complex profiles of the medial condyle or the lateral condyle which engage in corresponding cavities on the tibial implant, said cavities having a complementary profile to ensure stability and to allow asymmetrical and variable rotations to be obtained depending on the flexion angles of the knee. A first embodiment detailed in claim 1 of application US 2017 / 0189195 uses a femoral element of particular shape, with at the medial condyle, two different convex profiles 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 element of particular shape, with at the lateral condyle, two different convex profiles 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. Certain implementations of this second embodiment propose a spherical medial condyle shape in a spherical medial cavity generating a rotation of 360° by definition (of the sphere in sphere type).These configurations generate a transition from one radius of curvature to another with a staircase effect, as well as a possibility of catching due to the angles and flats between neighboring radii of curvature as shown in Figure 9 of this document.

[0011] The present invention aims to propose a new knee prosthesis and a support element for the corresponding femoral implant, which do not have the previously mentioned disadvantages of the known prostheses of the prior art. The knee prosthesis and the support element for the femoral implant according to the invention aim to meet, simultaneously, the following three requirements: - the stability requirement: the femoral implant and the support surface must maintain contact by remaining superimposed on each other, without the condyles of the femoral implant leaving their virtual envelope, neither in a mediolateral displacement, nor in an anteroposterior displacement, nor in the direction of excessive rotation in the horizontal plane; - the kinematic requirement: when the natural knee moves from full extension (knee straight) to full flexion (knee bent to the maximum), the contact surface of the lateral femoral condyle in the lateral cavity of the insert moves back and forth along an arc of about 20° + / -5°, whereas, advantageously, the medial femoral condyle moves only a few millimeters back and forth (4 to 5 mm at most) 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, it describes, in addition to its rotation around its transverse axis, a so-called asymmetric rotation around a vertical axis which crosses the medial cavity; - the tribological requirement: in order to reduce the pressure per unit of surface and therefore the wear of the prosthesis elements, there must be surface contact between the femoral implant and the support surface which decreases during knee flexion.

[0012] The invention particularly aims to improve comfort for the person wearing the prosthesis, by promoting unconstrained kinematics of functioning of the prosthesis, which best meets all physiological and tribological requirements, but which also ensures good stability of the prosthetic joint. Statement 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 an upper surface on which are arranged 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 on the upper surface between the two cavities, which is inserted into the intercondylar notch when the femoral implant is resting on the upper surface of the support element.The support element according to the invention is characterized in that, in a horizontal plane, said dent extends along a curved generatrix having a concavity oriented towards the medial cavity of said support element, said dent having a lateral flank and a medial flank connected by a vertex which together define, along the entire length of the generatrix of the dent, a section whose external profile is convex and, in particular, in an arc of a circle, with in a horizontal plane, the lateral flank of the dent having a radius of curvature which is greater than the radius of curvature of the medial flank of the dent. The invention relates to any support element of this type.

[0014] In the context of the invention, by medial flank of the dent, 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 Rrnmin of the medial flank and the maximum radius of curvature Rlmax of the lateral flank each have their center which is located on the side of the medial cavity; According to particular embodiments, these centers are located in the medial cavity, in an area which extends from the center of the medial cavity to the peripheral edge of the medial cavity opposite the bump.

[0016] According to a first variant embodiment of a support element according to the invention, the medial and lateral flanks have parallel curvatures, which correspond to concentric arcs of a circle, the upper surface of the support element has a maximum width located on a medio-lateral axis A2 and an antero-posterior axis A1 extends perpendicular to the medio-lateral axis A2 by intersecting the medio-lateral axis A2 in its middle A, with the medio-lateral axis A2 which intersects the peripheral edges of the medial and lateral cavities opposite the denture, respectively at points M and L, with AM=AL=Lmax, the centers of the radii of curvature of the medial flank and the lateral flank being the same 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: - Rmmin of the medial flank 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 variant embodiment of a support element according to the invention, the maximum width 1b of the section of the bossing decreases along its generator from the anterior part towards the posterior part of the support element. This contributes, in particular, to limiting the forward movement of the femoral implant during knee flexion. Thus, the anteroposterior stability of the knee prosthesis is further promoted, as well as the backward rolling 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 medio-lateral axis A2 and an antero-posterior axis Al extends perpendicular to the medio-lateral axis A2 by intersecting the medio-lateral axis A2 in its middle A and the medio-lateral axis A2 intersecting the peripheral edges of the medial and lateral cavities opposite the denture, respectively at points M and L, with AM=AL=Lmax. According to this second embodiment variant, advantageously, the centers of the radii of curvature of the medial flank and the lateral flank are different, the centers of the radii of curvature (and therefore Rmmin and Rlmax) of the medial flank and the lateral flank being located in a square of l / 4Lmax on the side with M which is the center of the square.By way of illustration, one of the centers of the radii of curvature of the medial flank and the lateral flank (in particular Rmmin and Rlmax) is on an axis A'2 offset and parallel 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 Rmmin 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 embodiment, given by way of example, the minimum radius of curvature Rrnmin of the medial flank may have its center Cl in M ​​on the medio-lateral axis A2, and the maximum radius of curvature Rlmax of the lateral flank can have its center C2 on the axis A'2, with the axis A'2 being located between the medio-lateral axis A2 and the anterior part of the support element, with the distance dc between the medio-lateral axis A2 and the axis A'2 being equal to Lmax / 8 + / - 2mm, or the maximum radius of curvature Rlmax of the lateral flank has its center C2 on the medio-lateral axis A2 in 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 being located between the medio-lateral 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 being equal to Lmax / 8 + / - 2mm.

[0021] Whatever the embodiment variant 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 antero-posterior axis A1 or the upper surface of the support element may have a circumference which has a non-symmetrical shape with respect to the antero-posterior axis A1, with, in particular, a lateral circumference smaller than the medial circumference.

[0022] Advantageously, and whatever the embodiment variant of the support element according to the invention, the medial cavity seen from above has an ovoid shape with a small medio-lateral axis and a large anteroposterior axis and / or the medial cavity and the lateral cavity define cavities with a concave external profile. Such choices of cavity make it possible to better adapt to the shape of the most common condyles.

[0023] According to particular embodiments of the support element according to the invention, the bump is raised towards the front part and / or towards the 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 whatever the embodiment variant of the support element according to the invention, there is no flatness or angulation between the bump and the medial and lateral cavities.

[0025] Conventionally in total knee prostheses 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, if necessary after resection. In particular, said articular insert may comprise a lower face intended to be placed on the tibial implant, in particular by reversible fitting, in a housing located on the upper surface of the tibial implant.

[0026] According to another of its aspects, 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 has two condyles, called the medial condyle and the lateral condyle, delimiting between them an intercondylar notch, the external profiles of the two condyles which face the bearing element being convex in shape, - the femoral implant being adapted to the bearing element, so that when the femoral implant is resting on the upper surface of the bearing 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 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 bearing element are configured so that when the femoral implant is bearing on the upper surface of the bearing 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 portion of the medial condyle which delimits the intercondylar notch and between the lateral flank of the boss and the portion of the lateral condyle which delimits the intercondylar notch.

[0027] In the context of the invention, when the femoral implant is in a support position on the upper surface of the support 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 zone of the lateral condyle in the lateral cavity from the anterior part to the posterior part of the support element, which corresponds to a displacement over a portion of an arc of a circle.

[0028] Any total knee prosthesis that corresponds to this definition which has a guiding and stabilizing bossing is part of the invention. The displacement of the contact zone of the lateral condyle in the lateral cavity advantageously corresponds to a displacement, in particular, over 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 zone 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 movement, the femoral implant moves in rotation around a transverse axis and the lateral condyle experiences a movement with, on the one hand, a rotation along a horizontal axis, called transverse, and a rotation along a vertical rotation axis which crosses the medial cavity. Thus, the flexion movement 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 knee of the patient on which the knee prosthesis is to be implanted.

[0032] According to an alternative 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 support position of the femoral implant on the upper surface of the support element, when the latter moves in flexion from an extension position to a maximum flexion position.

[0033] According to the first variant 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 section of the bulge decreases along its generator from the anterior part towards the posterior part of the support element and, due to the congruent shapes of the external profiles of the bulge and the intercondylar notch, the maximum width of the intercondylar notch decreases from the anterior part towards 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 generator of which is a spiral, in particular the lateral condyle has an external profile in the sagittal plane, the generator of which is a logarithmic type spiral which is inscribed in 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 generator of the external profile of the lateral condyle. This makes it possible, in particular, 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 previous ones, the medial cavity seen from above has an ovoid shape with a small medio-lateral axis and a large anteroposterior axis and has in the sagittal plane passing through its large anteroposterior 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 in the cavity and limiting its displacement when the femoral implant is in the support position on the upper surface of the support element and moves in rotation (also called flexion displacement) from an extension position to a maximum flexion position.

[0036] In particular, in the knee prostheses according to the invention, the section of the denture has a convex external profile with a radius of curvature R20 and the section of the notch has a concave external profile with a radius of curvature RIO, with the radii of curvature R20 and RIO which are substantially identical, with sufficient clearance to avoid tightening between the femoral implant and the support element at the level of the dent. "substantially identical" means that it is a fit with play because there must be no tightening. The space between the dent and the intercondylar notch is, in particular, between 1 and 2 mm, knowing that the weight of the patient and therefore the pressure can reduce the play.

[0037] Advantageously in the context 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 boss.

[0038] In particular, at each degree of flexion between the extension position and the maximum flexion position of the femoral implant, the contact zones of the two condyles in the two cavities are connected by an isthmus corresponding to the contact surface between the bump and the intercondylar notch of the femoral implant. In practice, when the knee prosthesis is implanted in the body of a subject, the contact zones 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 weight of the subject.

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

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

[0041] The 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, the knee prostheses according to the invention also comprise a tibial implant intended to be placed on the end of the tibia, if necessary after resection and the support element is an articular insert intended to be interposed between the femoral implant and the tibial implant. The articular insert may be movable in rotation about an axis perpendicular to the support plate of the tibial implant. But, advantageously, said articular insert will be fixed to the tibial implant, the fixing being able to be done by any suitable attachment means, in particular by removable fitting such as a direct assembly of the elastic fitting type or an indirect assembly using in particular screwing. According to a particular embodiment, the tibial implant comprises on its upper surface, a housing and the articular insert comprises a lower face intended to be placed by reversible fitting in said housing.

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

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

[0044] [Fig.2A] [Fig.2A] represents a schematic perspective view from below of an example of a femoral implant of a knee prosthesis according to the invention, which comprises two medial and lateral condyles delimiting between them an intercondylar notch which constitutes an opening between the two condyles. In this case, the intercondylar notch has a parallel edge and is adapted to a support element as shown in [Fig.4D] and the condyles are connected to each other only by a connection 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 similar to [Fig.2A], but illustrates another femoral implant variant in which the intercondylar notch forms a seamless connecting bridge with the two condyles, which extends from the anterior portion of the femoral implant to its posterior portion. In this case, in each bearing position, the intercondylar notch has an external profile which faces the bearing element whose shape is congruent with the external profile of the boss of the bearing element of [Fig.l]. This view is enlarged compared to that shown in [Fig.3]. The intercondylar notch has diverging edges towards the anterior portion of the implant and is adapted to a bearing element as shown in [Fig.l].

[0046] [Fig.3] [Fig.3] is a schematic perspective view, from the anterior part of the prosthesis, representing the femoral implant in the support position on the support element, when the prosthesis is in the extension 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 zone (shown in gray) between the femoral implant and the support element, depending on the support position re shown in [Fig.3], but according to a view from the posterior part of the support element. The gray area schematically represents the location of the contact zone between the two parts, when the intercondylar notch forms a seamless connecting bridge with the two condyles, which extends from the anterior part of the femoral implant to its posterior part.

[0048] [Fig.4B] [Fig.4B] is a schematic 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 gray area schematically represents the location of the contact zone between the bump and the intercondylar notch, when the latter forms a seamless connecting bridge with the two condyles, which extends 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 bump.

[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 and the axes A1 and A2 and the distance Lmax, in particular. In this exemplary 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 dent which has an identical section along its generatrix. References 208 and 209 here represent the sides of the dent, at the level of the widest part of the dent, that is to say at the base of its section, which corresponds to the change in curvature corresponding to the start 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 dent decreases along its generator from the front part towards the rear part of the support element.

[0052] [Fig.4F] [Fig.4F] is a view similar to [Fig.4E], which corresponds to another exemplary embodiment of a support element according to the invention, in which the maximum width 1b of the section of the dent decreases along its generator from the front part towards 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 support position on the support element, when the prosthesis is in the flexion position corresponding to an angle of approximately 120° between the femur and the tibia.

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

[0055] [Fig.6B] [Fig.6B] is a schematic sectional view along the horizontal plane shown in [Fig.3], of the prosthesis shown in [Fig.5] (therefore in the maximum flexion position), from a top view. The gray area schematically represents the location of the contact zone between the bump and the intercondylar notch, when the latter forms a seamless connecting bridge with the two condyles, which extends 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 bump. What is dotted corresponds to the position of [Fig.4B].

[0056] [Fig.7] [Fig.7] is a schematic sectional view of the knee prosthesis of the previous figures when the latter is in the extension position, according to a sagittal plane taken 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 greater clarity.

[0057] [Fig.8] [Fig.8] is a schematic 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 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. To facilitate understanding, the femoral implant and the bearing element are shown slightly apart. The gray area schematically represents the location of the contact zone between the femoral implant and the bearing element, when the latter are in contact with each other, in the case where the intercondylar notch forms a bridge which extends from one to the other of the condyles and extends from the anterior part to the posterior part of the femoral implant.

[0059] [Fig.9B] [Fig.9B] is a schematic 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 bearing element, when the latter are in contact with each other, in the case where the intercondylar notch forms a bridge which extends from one to the other of the condyles and extends from the anterior part to the posterior part of the femoral implant. To facilitate understanding, the femoral implant and the bearing element are shown at a distance and the contact zone shown in shade.

[0060] [Fig.9C] [Fig.9C] is a schematic sectional view of [Fig.7], according to the plan frontal IXC shown in [Fig.6B], when the knee prosthesis is in the flexion position corresponding to an angle of 120°, with the femoral implant and the support element in contact with each other. To facilitate understanding, the femoral implant and the support element are shown at a distance and the contact area shown in gray, in the case where the intercondylar notch forms a bridge which extends from one to the other of the condyles and extends from the anterior part 52 to the posterior part 53 of the femoral implant 2.

[0061] [Fig.10A] [Fig.10A] is a schematic view along a sagittal plane, of the medial condyle conforming to [Fig.8] in contact with the medial cavity, when the knee prosthesis is in the extension position.

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

[0063] [Fig. 11 A] [Fig. 11 A] is a schematic view along a sagittal plane 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] [Fig. 1 IB] is a schematic view along a sagittal plane, of the lateral condyle conforming to [Fig.8] in contact with the lateral cavity, analogous to [Fig.10A], but when the knee prosthesis is in the maximum flexion position, corresponding to an angle of approximately 120°.

[0065] [Fig. 12] [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 embodiments

[0066] A knee prosthesis is intended to be implanted in an individual to replace his knee damaged by the disease. Also, the different elements of the latter are defined with reference to its use, that is to say during the operation 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 of a subject respectively. The femoral implant is intended to be adapted after resection on the lower femoral epiphysis. The bearing element is intended 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, in this case, it will correspond to an articular insert positioned between the femoral implant and a tibial implant and it is the tibial implant which will be adapted on the upper tibial epiphysis.Conventionally, in the field of knee prostheses, the following denominations are: used: - the extension position, corresponds to the case where the knee prosthesis is in a position which corresponds to the knee stretched, 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°; - the flexion positions correspond to the case where the knee is bent, that is to say that the femur and the tibia which come, respectively, in extension of the femoral implant and the support 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 face 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 rear face of the individual; - The parts (cavity, condyle, etc.), called medial, of the prosthesis correspond to the parts which will be positioned on the crotch side of the individual and the parts (cavity, condyle, etc.), called lateral, of the prosthesis correspond to the parts which will be positioned on the outside of the individual's leg; - The sagittal and frontal planes are understood in the anatomical sense. Also, a sagittal plane extends perpendicular 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 perpendicular 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 towards the outside of the part considered (femoral implant, support element), a concave profile or shape means a profile or shape that is curved towards the inside of the part considered (femoral implant, support element). Furthermore, when it is a question of a concave or convex profile or shape, this excludes points of change of curvature. Furthermore, the notion of concavity or convexity can correspond to a variable radius of curvature, but advantageously, 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 is apparent from the figures and, in particular, from [Fig. 3], the subject of the invention relates to a total knee prosthesis 1 conventionally comprising a femoral implant 2 and a support element 100 which will be positioned on the tibia side. The support element 100 is also the subject of the invention. In the description which follows, the emphasis will be placed on the specific features of the invention, and only the upper part of the support element will be shown. be represented, knowing 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 will be positioned on the tibia, most often after resection. In the knee prostheses according to the invention, conventionally, the femoral implant and the tibial implant are both preferably made of a biocompatible stainless metal alloy, and the articular insert will generally be made of a plastic material, such as polyethylene. However, one or more elements of the prosthesis may also be made of alumina or alumina and zirconia ceramic, or biocompatible resins for example. Preferably, the support element will constitute an articular insert which will be placed on a tibial implant, which allows better attachment to the tibia bone.If the joint insert is made of a plastic material, generally high-density polyethylene enriched with Vitamin E, the tibial implant and the femoral implant will generally be metallic. If the joint insert is made of ceramic, the femoral implant will then advantageously be made of ceramic.

[0069] Conventionally, the femoral implant 2 has, in side view as partially shown in Figures 3, 5 and 12, in particular, a substantially non-symmetrical U-shape between the branches of which is delimited a housing 500 for fixing on the lower epiphysis of the femur, in particular by fitting together two projecting lugs 600, visible in Figures 7, 9B and 12. Such lugs are optional, the positioning and fixing of the femoral implant 2 on the epiphysis of the femur being able to be done by elastic force fitting or by cementing.

[0070] As is apparent from [Fig.2A], the femoral implant 2 comprises on a lower face 700 which faces the support element 100, two condyles, respectively a medial condyle 8 and a lateral condyle 9, delimiting between them an intercondylar notch 10 which delimits a space existing between the two condyles. As is visible in [Fig.2A], but is more apparent in [Fig. 12], which illustrates another embodiment, in a conventional manner, at the level of the anterior part 52 of the femoral implant 2, a femoral trochlea 110 extends in the anterior extension of the two condyles 8, 9 respectively medial and lateral and comprises two medial 120 and lateral 130 trochlea cheeks 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 extension 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 void of material which corresponds to the intercondylar notch 10. The medial condyle 8 and the lateral condyle 9 delimit the intercondylar notch 10, at the level of their parts 108 and 109, respectively. The medial condyle 8 and the lateral condyle 9 are only connected at the level of the anterior part 52 of the femoral implant 2. The connection between the medial condyle 8 and the lateral condyle 9, located in the anterior part 52 of the femoral implant 2, is made at the level of the lower part of the trochlear groove 150, and more precisely at the level of the condylotrochlear groove 160.

[0072] It is also possible for the intercondylar notch 10 to connect seamlessly with the two medial and lateral condyles 8 and 9 and form a connecting bridge 170 which extends from one to the other of the condyles and extends from the anterior portion 52 (more precisely from the condylotrochlear groove 160) to the posterior portion 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 of concave shape. This is evident, however, in [Fig.9B], which shows a 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, along 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 is apparent from [Fig.l], the support element 100 comprises an upper surface 41, in which two cavities are arranged: 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, whatever the vertical plane considered. The two medial 18 and lateral 19 cavities are separated by a boss 20 which extends from the anterior part 42 to the posterior part 43 of the support element 100, taking a curved shape. Thus, the bump 20 is located in the central part of the support element 100. The bump 20 connects seamlessly with the two medial 18 and lateral 19 cavities. The bump 20 has, when viewed from above, a curvature 180 oriented towards the medial cavity 18.In other words, in a horizontal plane or in top view, the medial flank 208 (located on the medial cavity 18 side) of the bump 20 has a concave profile, and the lateral flank 209 (located on the lateral cavity 19 side) has a convex profile. In a horizontal plane or in top view, the bump 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, an external profile of convex shape. The medial flank 208 and the lateral flank 209 have, in a horizontal plane, an external profile in the form of an arc of a circle, with the lateral flank 209 having a radius of curvature greater than the radius of curvature 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 ensure the reception of 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 a contact between the medial cavity 18 and the medial condyle 8, on the one hand and a contact between the lateral cavity 19 and the lateral condyle 9, on the other hand, there is also a 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 boss 20 and the part 109 of the lateral condyle 9 which delimits the intercondylar notch 10, as can be seen in [Fig.4A]. [Fig.4A] represents the contact zone 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 extended position as shown in [Fig.3]. [Fig.4B], which is a schematic sectional view at the base of the section of the boss 20 (section IVB of [Fig.3]), highlights the contact zones 183 and 193, between the medial and lateral flanks 208 and 209 of the boss 20 and the parts 108 and 109 of the medial and lateral condyles 8 and 9 which delimit the intercondylar notch 10. During the relative movement in flexion of the femoral implant 2 with respect to the support element 100, these contact zones 183 and 193 move, but there is always contact and this in any flexion position, 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 19 which delimits the intercondylar notch 10, which allows the guidance and control of the movement of the lateral condyle 9, in the lateral cavity 19.

[0075] The boss 20 has a section (cross-section, i.e. a section taken in a vertical plane which is perpendicular to its generator) whose external profile facing the femoral implant 2 is convex.

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

[0077] In particular, this external profile 201 of the bump 20 has the shape of an arc of a circle. In other words, the bump 20 is a half-torus or a portion of a half-torus which is curved and whose section can be constant or variable. If the section is constant, the medial flank 208 and the lateral flank 209 form arcs of concentric circles. Such an embodiment is illustrated in [Fig.4D].

[0078] To understand [Fig.4D], it is first appropriate to refer to [Fig.4C], which shows 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 medio-lateral axis A2 and an antero-posterior axis A1 extends perpendicular to the medio-lateral axis A2 by intersecting the medio-lateral axis A2 in its middle A. The medio-lateral 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.In the illustrated example A1 and A2 are perpendicular and the circumference of the upper surface 41 is symmetrical with respect to the axis A1. The point a is located on the axis A2, in the medial cavity 18, at a distance 3Lmax / 4 from M, the point y is located on the axis A2, in the medial cavity 18, at a distance 7Lmax / 8 from M, the point ô is located on the axis A2, in the lateral cavity 19, at a distance 9Lmax / 8 from M and the point [3 is located on the axis A2, in the lateral cavity 19, at a distance 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] [Fig.4D] shows a schematic view of an embodiment of the dent 20 in which the medial 208 and lateral 209 flanks have parallel curvatures in a horizontal plane, which therefore correspond to concentric arcs of a circle. It can thus be considered that the section of the dent 20 is identical along its generator. In [Fig.4D], the medial 208 and lateral 209 flanks which are visible are represented at the level of the base of the section of the dent 20, that is to say at the level of the change in curvature corresponding to the start of each medial 18 and lateral 19 cavity. Thus, at this level the medial flank 208 has its minimum radius of curvature Rmmin and the lateral flank 209 has its maximum radius of curvature Rlmax. In the illustrated example, the center of the minimum radius of curvature Rmmin 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 merged with M.The minimum radius of curvature Rm min of the medial flank 208 is between the distance separating the points M and a and the distance separating the points M and y and the maximum radius of curvature Rlmax of the lateral flank 209 is between the distance separating the points M and ô and the distance separating the 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, 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 boss 20 and the part 109 of the lateral condyle 9 which delimits the intercondylar notch 10 when the femoral implant is in the 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 movement. Thus, in the case of a support element 100 having a bossing with parallel medial 208 and lateral 209 flanks (as in [Fig.4D]), a suitable femoral implant 2 will have an intercondylar notch 10 delimited by condyle portions 108 and 109 which, in a horizontal plane, extend according to concentric arcs of a circle. Such an example of a femoral implant 2 is shown in [Fig.2A].

[0081] [Fig.4E] shows a schematic view of another embodiment of the dent 20 in which the medial 208 and lateral 209 flanks have non-parallel curvatures in a horizontal plane, and which correspond to a reduction in the width 1b of the dent 20 of the anterior part 42, towards the posterior part of the support element 100. The width 1b of the dent is taken according to the section of the dent, therefore perpendicular to its generator 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 in 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 medio-lateral 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 being equal to Lmax / 8, in this example.

[0082] [Fig.4F] shows a schematic view of another embodiment of the boss 20 in which the medial 208 and lateral 209 flanks have non-parallel curvatures in a horizontal plane, and which correspond to a reduction in the width 1b of the boss 20 of 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 Rm min of the medial flank 208 has its center Cl at M on the medio-lateral 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 relative to the latter. The axis A'2 is located between the medio-lateral axis 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 flanks 208 and lateral flanks 209 diverging towards the anterior part 42 of the support element 100. The width of the intercondylar notch 10 and its shape being adapted to those of the boss 20 to allow 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 boss 20 and the part 109 of the lateral condyle 9 which delimits the intercondylar notch 10 when the femoral implant is in the support position on the upper surface 41 of the support 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 movement, in the case of a support element whose bossing has medial 208 and lateral 209 flanks 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 which diverge towards the anterior part 52 of the femoral implant 2. Such an example of a femoral implant 2 is presented in [Fig.2B].

[0084] The geometry choices for the support element 100 illustrated by Figures 4A to 4F are given purely for illustrative purposes 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 which it is to be implanted. The presence of a central boss 20 which extends 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 which has a radius of curvature which is 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 bump 20 and the intercondylar notch 10 are chosen to ensure contact between the bump 20 and the medial 8 and lateral 9 condyles at the level of this intercondylar notch 10, throughout the flexion movement when the femoral implant 2 is in the support 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, the guidance of the movement of the femoral implant 2 during this flexion is possible with a displacement of the contact zone 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 over a portion of an arc of a circle.

[0085] Advantageously, the medial cavity 18 has, in top view, an ovoid shape, as illustrated in FIGS. 4A, 4B, 4D to 4F, 6A and 6B, the major axis of the ovoid extending along the anteroposterior axis of the medial cavity 18. The lateral cavity 19 has, for its part, generally, in top view, a crescent-type shape, as highlighted in FIGS. 4A, 4B, 4D to 4F, 6A and 6B.

[0086] As is apparent from these figures, in top view, the upper surface 41 of the support element 100 has the shape of a bean whose concave zone 44 is located at the level of the posterior part 43. The concave zone 44 particularly promotes the preservation of the posterior cruciate ligament where appropriate. The posterior end of the bossing 20 is therefore located at the level of this concave zone 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 a contact between the medial cavity 18 and the medial condyle 8, a contact between the lateral cavity 19 and the lateral condyle 9 and a contact between the bossing 20 and the intercondylar notch 10. Figures 3 and 5 show the femoral implant of [Fig.2B] resting on the surface 41 of the support element 100 of [Fig.l], in two different positions, respectively in the extension position (0° angle) and in the maximum flexion position (120° angle) of the knee prosthesis.

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

[0089] As is apparent 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 medial condyle 8 side) of the intercondylar notch 10 has a concave profile, in a horizontal plane and the lateral leg 109 (located on the lateral condyle 9 side) has a convex profile. In particular, as is apparent from Figures 9A to 9C, the external profile of the bump 20 corresponds exactly but in a hollow and mirrored manner to the external profile of the intercondylar notch 10 which separates the medial 8 and lateral 9 condyles. In particular, as is apparent from [Fig.9B], in a plane extending perpendicular to the generatrix of the bump, the convex external profile 201 of the bump 20 and the concave external profile 101 of the intercondylar notch 10 form arcs of circles with radii of curvature R20 and R10 respectively which are substantially identical.

[0090] Furthermore, the movement of the lateral condyle 9 in the lateral cavity 19 is accompanied by a rotation of the latter around its transverse axis, during the flexion of the prosthesis. Thus, during the flexion movement of the femoral implant 2, the path of a point which follows 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 boss 20 and the concave external profiles 101a and 101b of the intercondylar notch 10 are not arcs of a circle, but have an ovoid shape, because the section is not taken perpendicular to the generatrix of the boss 20.

[0091] According to the invention, it is the curvature of the boss 20 and the contact zones 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 kinematics 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 a bearing of the surface of the intercondylar notch 10, on the surface of the bulge 20, or more precisely with a bearing at least between the medial flank 208 of the bulge 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 bulge 20 and the part 109 of the lateral condyle 9 which delimits the intercondylar notch 10, on the other hand.This ensures both guidance and stability of the femoral element during its relative rotational movement, with guidance and stability not being dissociated. [Fig.9B] highlights the congruent nature of the two external profiles of the intercondylar notch 10 and the bump 20 and the fact that the latter are in contact, according to a continuous contact ensured over the entire intercondylar notch 10 and the bump 20. In the example illustrated in [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 bump 20 is made 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 makes it possible to ensure an asymmetrical rotation of the two medial 8 and lateral 9 condyles: the curved boss 20 makes it possible to guide the rotational movement of the femoral implant 2, the medial condyle 8 and the lateral condyle 9 following the guidance of the intercondylar notch 10 on the curved boss 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 the support 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 their shape, or even their congruence, ensure the guidance of the movement of the femoral implant 2 during this rotation with a displacement of the contact zone 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 of a vertical axis which is located on the medial cavity side 18 and can cross the medial cavity 18.

[0094] In particular, the contact area of ​​the lateral condyle 9 in the lateral cavity 19 is moves along a curved path, as is apparent 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 sectional view which therefore highlights the contact zones 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 gray, 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, which respectively present a top view of the surface 41 and a top sectional view which therefore highlights the contact zones 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 is shown in gray, when the intercondylar notch 10 is full and forms a connecting bridge 170 between the two condyles.

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

[0096] The boss 20, by 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 rotating 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 is evident, in particular, from Figures 3 to 6.

[0097] Thus, unlike the solutions proposed in particular in document US 2017 / 0189195, it is not the cooperation of the cavities and the condyles which ensures the guiding 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 the apex 210 of the boss 20. This further facilitates the control of the movement of the femoral implant 2. The congruence is assessed in each position of the femoral implant 2 bearing on the surface 41 of the bearing element 100. That is to say that at each position of movement in flexion from the extension position to the maximum flexion position, there is contact between the intercondylar notch 10 and the boss 20, at the lateral flanks 208 and medial 209 and summit 210 when the intercondylar notch 10 is full.However, there is play between the two parts, and in particular at the level of the boss 20, to avoid tightening 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 is no stop 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 8 and medial 9 condyles each have a profile that is convex at all points, that is to say that they do not include a sudden change in curvature defining two different convex profiles, as is the case, in particular, in application US 2017 / 0189195. Likewise, the two medial 18 and lateral 19 cavities each have a profile which is concave at all points, that is to say that they do not include a sudden change in curvature defining two different concave profiles, as, in particular, is the case in application US 2017 / 0189195.

[0098] The curved boss 20 and the fact that the external profile of the intercondylar notch 10 matches the external profile of the curved boss 20, at least at the level of the lateral 208 and medial 209 flanks 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 on which they come into abutment.

[0099] Along its generator, the maximum width 1b of the section of the boss 20 can be constant along the entire length of the boss. It is also possible, as in the example illustrated in FIGS. 1 to 10B, that the width 1b decreases from the anterior portion 42 to the posterior portion 43 of the support element 100. In this case, in the case of congruent shapes of the external profiles of the boss 20 and the intercondylar notch 10, the width of the intercondylar notch 10 also decreases from the anterior portion 52 to the posterior portion 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 towards 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 is evident in particular from FIGS. 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 to the other of the medial 18 and lateral 19 cavities, 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 respectively of the two medial 8 and lateral 9 condyles in the two medial 18 and lateral 19 cavities 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 precisely, the isthmus 202 is an isthmic surface which follows the external profile of the hump and therefore extends, not only on the summit 210 of the latter, but also on its medial 208 and lateral 209 flanks.

[0101] Furthermore, the contact area between the denture 20 and the intercondylar notch 10 moves back and forth on the denture when the knee prosthesis 1 bends from its fully extended position (0° angle) to its maximum flexion position (120° angle or more). The contact is made on the flanks of the denture (medial contact area 183 at the medial flank 208 and lateral contact area 193 at the lateral flank 209), with a back and forth movement of the contact area 193 on the lateral flank 209 of the denture 20. The contact may extend to the apex 210 of the denture 20, when the intercondylar notch 10 forms a connecting bridge 170.

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

[0103] As illustrated in [Fig.8], according to a preferred embodiment, the lateral 8 and medial 9 condyles have, in the sagittal plane, an external profile which is a turn whose radius decreases continuously. In particular, the lateral condyle 9 has an external profile 92 in the sagittal plane, which is a turn of the logarithmic type. The external profile 82 in the sagittal plane of the medial condyle 8 is a turn whose radius is of lesser decrease. In the sagittal plane, the external profile 92 of the lateral condyle 9 is inscribed in the external profile 82 of the medial condyle 8 whose generating spiral has a radius with a lower decrease than that of the generator 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 small medio-lateral axis and a large antero-posterior axis. Preferably, this medial cavity 18 has, in the sagittal plane, an antero-posterior curvature corresponding to the shape of the medial condyle 8 when the knee prosthesis is in extension. Advantageously and as illustrated in [Fig. 10A], the external profile 181 of the medial cavity 18 matches 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 extended knee corresponding to an angle between the femur and the tibia of 0°).

[0105] There is thus no anteroposterior mobility in the medial cavity 18 when the knee is stretched in full extension. In this position, according to a sagittal section shown in [Fig.10A] extending along the major axis of the medial cavity 18, contact with the medial condyle 8 is made over the entire surface of the cavity. [Fig.10B] which represents a section similar to that of [Fig.10A], but when the knee prosthesis is in a flexion position corresponding to an angle of 120° shows that the medial condyle 8 moves little in the medial cavity 18. This movement which takes place from the posterior part 43, towards the anterior part 42, or from the anterior part 42, towards 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 small displacement is allowed by the fact that the medial cavity has the negative shape of the medial condyle 8 when the knee is stretched to 0°, but as the radius of the spiral of the medial condyle 8 decreases slightly during flexion, it will find itself in a cavity with an anteroposterior diameter greater than it from a degree of flexion of 45°. The presence of this play provides greater comfort to the patient.

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

[0107] Conversely, the contact area 192 of the lateral condyle 9 in the lateral cavity 19 moves greatly back and forth, as is evident from the comparison: - of [Fig. 11 A] which shows 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] Concerning the lateral condyle 9 and the lateral cavity 19, there is no constraint in terms of choice of the radii of curvature. In particular, as is the case in the figures, the concavity of the lateral cavity 19 may be less significant 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 symmetrical appearance in a mirror.

[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 comprises at least one support plate 21 intended to rest by its lower surface 212 on the end of the tibia, if necessary after resection.

[0111] The insert 4 which corresponds to a support element 100 according to the invention, for its part, is supported 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 done by reversible interlocking, in particular according to an elastic snap-fastening, 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 comprises a medullary anchor rod 240 extending from the lower face 212 of the plate 21 and intended to come to rest against a resected epiphyseal surface of the tibia (not shown).

Claims

Claims

1. Support element (100) for a femoral implant (2) of a total knee prosthesis (1), said femoral implant (2) comprising two condyles (8, 9), called medial condyle (8) and lateral condyle (9) delimiting between them an intercondylar notch (10), the external profiles (82, 92) of the two condyles (8, 9) being convex in shape, said support element (100) being intended to be positioned on the tibia side and comprising an upper surface (41) on which are arranged 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 on the upper surface (41) between the two cavities (18, 19), which is inserted into the intercondylar notch (10) when the femoral implant (2) is supported on the upper surface (41) of the support element (100), characterized in that, in a horizontal plane,said dent (20) extends along a curved generatrix having a concavity (180) oriented towards the medial cavity (18) of said support element (100), said dent (20) having a lateral flank (209) and a medial flank (208) connected by a vertex (210) which together define, along the entire generatrix of the dent (20), a section whose external profile is convex and, in particular, in an arc of a circle, with in a horizontal plane, the lateral flank (209) of the dent (20) which has a radius of curvature which is greater than the radius of curvature of the medial flank (208) of the dent (20).,

2. Support element (100) according to claim 1, characterized in that the minimum radius of curvature Rrnmin of the medial flank (208) and the maximum radius of curvature Rlmax of the lateral flank (209) each have their center (Cl, C2) which is located in the medial cavity (18), in a zone which extends from the center (Cm) of the medial cavity (18) to the peripheral edge (308) of the medial cavity (18) opposite the bump (20).

3. Support element (100) according to claim 1 or 2, characterized in that the medial (208) and lateral (209) flanks of the boss (20) have parallel curvatures, which correspond to concentric arcs of a circle, the upper surface (41) of the support element (100) having a maximum width located on a medio-lateral axis A2 and an anteroposterior axis A1 extending perpendicular to the medio-lateral axis A2 by intersecting the medio-lateral axis A2 in its middle A and the medio-lateral axis A2 intersecting the peripheral edges (308 and 309) of the medial (18) and lateral (19) cavities opposite the bump (20), respectively at points M and L, with AM=AL=Lmax, the centers of the radii of curvature of the medial flank (208) and of the lateral flank (209) being merged 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.

4. Support element (100) according to claim 1 or 2, characterized in that the maximum width 1b of the section of the denture (20) decreases along its generator from the front part (42) towards the rear part (43) of the support element (100).

5. Support element (100) according to claim 4, characterized in that, in top view, the upper surface (41) of the support element (100) having a maximum width located on a medio-lateral axis A2 and an antero-posterior axis A1 extending perpendicular to the medio-lateral axis A2 by intersecting the medio-lateral axis A2 in its middle A and the medio-lateral axis A2 intersecting the peripheral edges (308 and 309) of the medial (18) and lateral (19) cavities opposite the bossing (20), respectively at points M and L, the center of the radii of curvature of the medial flank (208) and of the lateral flank (209) being located in a square of l / 4Lmax on the side with M which is the center of the square.

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

7. Support element (100) according to any one of claims 1 to 6, characterized in that the upper surface (41) of the support element (100) has a circumference which has a symmetrical shape with respect to the antero-posterior axis A1.

8. Support element (100) according to any one of claims 1 to 6, 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 antero-posterior axis A1, with a lateral circumference smaller than the medial circumference.

9. Support element (100) according to any one of claims 1 to 8, characterized in that the medial cavity (18) seen from above has an ovoid shape with a small medio-lateral axis and a large antero-posterior axis.

10. Support element (100) according to any one of claims 1 to 9, characterized in that the boss (20) is raised towards the front part (42) and / or towards the rear part (43) of the support element (100).

11. Support element (100) according to any one of claims 1 to 10, characterized in that there is no flattening or angulation between the bump (20) and the medial (18) and lateral (19) cavities.

12. Support element (100) according to any one of claims 1 to 11, characterized in that it 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, if necessary after resection, said articular insert (4) comprising a lower face (45) intended to be placed on the tibial implant (3), in particular, by reversible fitting into a housing (211) located on the upper surface of the tibial implant (3).

13. Total knee prosthesis (1) comprising a femoral implant (2) and a bearing element (100) for the femoral implant (2) as defined in any one of claims 1 to 12, wherein: - the femoral implant (2) comprises two condyles (8, 9), called medial condyle (8) and lateral condyle (9) delimiting between them an intercondylar notch (10), the external profiles of the two condyles (8, 9) which face the bearing element (100) being convex in shape, - the bearing element (100) as defined in any one of claims 1 to 11, the femoral implant (2) being adapted to the bearing element, so that when the femoral implant (2) is bearing on the su- upper (41) of the support element (100), there is a contact between the medial cavity (18) and the medial condyle (8), a contact between the lateral cavity (19) and the lateral condyle (9) and a contact, at the same time, between the medial flank (208) of the bump (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 boss and the condyles (8, 9) at the intercondylar notch (10) ensuring, when the femoral implant is in the support position on the upper surface (41) of the support 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 zone (192) 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 over a portion of an arc of a circle.;

14. Prosthesis according to claim 13, 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).

15. Prosthesis according to claim 14, characterized in that in a frontal plane, when the femoral implant (2) is in the support position on the upper surface (41) of the support 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).

16. Prosthesis according to claim 15, characterized in that the support element (100) is in accordance with claim 4, that is to say that the maximum width 1b of the section of the boss (20) is decreasing along its generator from the anterior part (42) towards 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) towards the posterior part (53) of the femoral implant (2).

17. Prosthesis according to one of claims 13 to 16, characterized in that the section of the bump (20) has a convex external profile (201) with a radius of curvature R20 and the section of the intercondylar notch (10) has a concave external profile (101) with a radius of curvature RIO, with the radii of curvature R20 and RIO which are substantially identical, with sufficient clearance to avoid tightening between the femoral implant (2) and the support element (100) at the level of the bump (20).

18. Prosthesis according to one of claims 13 to 17, 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).

19. Prosthesis according to any one of claims 13 to 18, characterized in that the condyles (8, 9) have an external profile (82, 92) in the sagittal plane, the generator of which is a spiral, in particular the lateral condyle (9) has an external profile (92) in the sagittal plane, the generator of which is a logarithmic spiral which is inscribed in the external profile (82) in the sagittal plane of the medial condyle (8) the generating spiral of which has a radius with a smaller decrease than that of the generator of the external profile (92) of the lateral condyle (9).

20. Prosthesis according to any one of claims 13 to 19, characterized in that the support element (100) is in accordance with claim 9, that is to say that the medial cavity (18) seen from above has an ovoid shape with a small medio-lateral axis and a large anteroposterior axis and has in the sagittal plane passing through its large 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 extended position.

21. Prosthesis according to one of claims 13 to 20, characterized in that it also comprises a tibial implant (3) intended to be placed on the end of the tibia, if necessary after resection, and the support element (100) is in accordance with claim 12 and is an articular insert (4) intended to be interposed between the femoral implant (2) and the tibial implant (3).

22. Prosthesis according to claim 21, characterized in that the tibial implant (3) comprises on its upper surface, a housing (211) and the articular insert (4) comprises a lower face (45) intended to be placed by reversible fitting in said housing (211).

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