FR2776919A1 - TOTAL KNEE PROSTHESIS WITH HINGE - Google Patents

Abstract

Hinged total knee prosthesis (1) comprising a femoral component (2) and a tibial base (3), the femoral component (2) being mounted movable in transverse rotation with respect to a pivot member (5) which is itself mounted movable in longitudinal rotation with respect to the tibial base (3), the femoral component (2) comprising two condyles (20a, 20b) cooperating by congruent contact with a tibial plateau (4) arranged at the upper end (14) of tibial base (3). According to the invention, said total knee prosthesis (1) comprises abutment means (6) able to block the femoral component (2) in longitudinal rotation, when the knee joint is in extension.Application to the field of knee prostheses more specifically intended to be implanted when the ligament apparatus is not able to guarantee satisfactory stability to the joint.

Description

TOTAL KNEE PROSTHESIS WITH HINGE

  The present invention relates to a total knee prosthesis, called a hinge, that is to say provided with a mechanical joint connecting the femoral component to

the tibial base.

  The invention finds a particularly advantageous application in the field of knee prostheses more specifically intended to be implanted when the ligament apparatus is not able to guarantee satisfactory stability at

the joint.

  In these circumstances, in fact, it is preferable to mechanically join the femoral component and the tibial base, by means of a mobile connection.

  allowing both flexion-

  permanent extension and cohesion between

  different components of the implant.

  A first type of hinged total knee prosthesis is known from the state of the art, in which the femoral component is simply articulated on the tibial base via a transverse axis. Although rotating in bearings generally made of polyethylene, the axis is extremely stressed since it supports the various constraints transmitted by the femur to the tibia, and in particular the load and rotation constraints. he

  this results in rapid wear of the hinged system.

  In order to reduce the stresses passing through the axis of the joint, a second type of total knee prosthesis provides that the femoral component can pivot more or less longitudinally against a polyethylene disc serving as a shock absorber. For this, the axis of the hinge is extended by a rotary pivot mounted longitudinally pivoting in the tibial base. If it can be limited between two extreme angular values, the rotation in question remains nonetheless free and therefore uncontrolled. It

  therefore results in an obvious lack of stability.

  Also, the patient does not have real support points in extension, which gives him a balance

  insufficient especially when walking.

  A third type of total hinged knee prosthesis consists of resting the femoral component on a polyethylene rotary plate. The friction surface is thus advantageously divided into two interfaces, the first between the tibial plateau and the tibial base, the second between the femoral component and the tibial plateau. This again results in less wear but the instability in extension remains due to the free rotation. There is in particular a significant risk of subluxation of the rotary pivot, in

  outside of its housing in the tibial base.

  In order to progressively control the longitudinal rotation of the femoral component, a fourth type of total hinged knee prosthesis provides that the respective shapes of the condyles of the femoral component and of the cups of the tibial plateau are congruent, said femoral condyles being perfectly supported on said plateau tibial. However, this type of implant has the drawback of limiting the friction surface only at the interface between the femoral component and the tibial plateau. Consequently, the wear of the latter gradually results in a rotation of

less and less controlled.

  Also, the technical problem to be solved by the object of the present invention is to provide a total hinged knee prosthesis comprising a femoral component and a tibial base, the femoral component being mounted movable in transverse rotation relative to a pivoting member. itself mounted movable in longitudinal rotation relative to the tibial base, the femoral component comprising two condyles cooperating by congruent contact with a tibial plate disposed at the upper end of the tibial base, total knee prosthesis which would allow avoid the problems of the state of the art by offering in particular optimal stability in extension, while guaranteeing precise control of the longitudinal rotation and minimizing the risks

  wear of the various components of the joint.

  The solution to the technical problem posed consists, according to the present invention, in that the total hinged knee prosthesis comprises stop means capable of locking the femoral component in longitudinal rotation when the knee joint is in

extension.

  The invention as defined has the advantage of allowing locking in extension of the most restrictive mobility from the point of view of stability, that is to say the longitudinal rotation. The patient thus has a sufficiently stable point of support to guarantee his balance and therefore to

secure his walk.

  According to a feature of the invention, the abutment means are able to cooperate simultaneously by contact with the respective internal lateral faces of the two femoral condyles, when the knee joint is in extension. As the two surfaces in question are by nature arranged in opposition and in a manner substantially parallel to the longitudinal axis of rotation of the femoral component, the abutment means are able to block any longitudinal pivoting of said femoral component when double contact occurs, and this whatever the direction of the envisaged gyration. According to another feature of the invention, the abutment means are able to cooperate alternately by contact with the internal lateral face of one or the other of the femoral condyles, when the knee joint is in flexion. In this specific case, the absence of simultaneous double contact prohibits any total immobilization of the femoral component. The longitudinal rotation of the latter is permitted, but it is limited angularly between two extreme values corresponding to the respective abutments of each

  internal lateral face against the stop means.

  Contrary to what happens in extension, the femoral component is in no way immobilized in longitudinal rotation since it is able to pivot in one direction or the other until one of these condyles comes into contact with the stop means. In a particularly advantageous manner, the interval separating the respective internal lateral faces of the two femoral condyles is increasing from the anterior part to the posterior part of the femoral component. It follows that, for a given longitudinal angle of rotation, the difference between the condyles and the abutment means is not constant if the angle of flexion of the joint is varied. The divergence of the internal lateral faces consequently generates a variation in the amplitude of the angular displacement of the femoral component as a function of the relative position of said femoral component with respect to the tibial base. Thus, the longitudinal rotation of the femoral component is gradually released during the flexion of the joint. This allows optimal control of this mobility until the condyles can no longer come into contact with the means

  stop; rotation then becomes free.

  According to a first embodiment of the invention, the tibial plateau is mounted fixed relative to the tibial base. The stop means, intended to control the longitudinal rotation in bending and to prohibit it in extension, can in this configuration be fixed to two different types of supports. According to a first variant of the first embodiment, the abutment means are directly integral with the tibial plateau at the upper surface from which they project. These two elements can be part of a single piece, or be independent of each other but assembled together

in order to form a whole.

  According to a second variant of the first embodiment, the abutment means are integral with the tibial base. In the case where the attachment point is located on the upper surface of said tibial base, the tibial plate is advantageously provided with a housing allowing the passage of the abutment means forming a projection. This housing may have a shape and dimensions substantially complementary to the section of the stop means, without this being a

absolute obligation.

  In accordance with a second currently preferred embodiment of the invention, the tibial plateau is mounted movable in longitudinal rotation on the tibial base in order to allow a better distribution of the friction forces inherent in the longitudinal rotation of the femoral component in abutment against said tibial plateau; the contact between these two elements being perfectly congruent. These constraints are in fact exerted here between significantly larger contact surfaces than in the first embodiment, which has the advantageous consequences

  significantly reduce its effects.

  The use of a rotary plate allows the friction forces to be shared at two interfaces, the first between the tibial plate and the tibial base, the second between the femoral component

and the tibial plateau.

  In this configuration, the abutment means can only be integral with the tibial base since it is the only part of the prosthesis which is fixed relative to the tibia, and which is therefore capable of serving as an anchoring point in view of achieving immobilization in longitudinal rotation of the component

  femoral when the joint is in extension.

  In the event that the abutment means again extend from the upper surface of the tibial base, the tibial plate is advantageously provided with a housing capable of receiving said abutment means, the end of which protrudes. The shape and / or dimensions of the housing should not, however, prevent rotation of the tibial plateau. Also, its characteristics are fixed so as to allow free rotation at least over a given angular sector; the opposite ends of the housing then forming a stop to block the tibial plateau when the latter

  reaches a position considered as limit.

  In a particularly advantageous manner, the tibial plateau is mounted mobile in longitudinal rotation around the pivoting member supporting the femoral component. Thus, the distribution of friction forces between the two interfaces

  tibial plateau - tibial base and femoral component -

  tibial plateau, can be performed optimally since the tibial plateau and the femoral component have the same longitudinal axis of rotation. As these two elements cooperate more by congruent contact, any rotation of the femoral component will cause that of the tibial plateau within the limits fixed by the blocking system that together form the abutment means and the condyles of said femoral component.

  The following description next to the drawings

  attached, given by way of nonlimiting examples, will make it clear what the invention consists of and how

it can be done.

  Figure 1 is an exploded view of a prosthesis

  total knee according to the invention.

  FIG. 2 constitutes a view from above and in perspective of part of the total knee prosthesis illustrated in FIG. 1, representing in particular the nesting of the tibial base, of the tibial plateau,

  of the pivoting member and the stop means.

  Figure 3 is a perspective view in section

  partial of the total knee prosthesis in extension.

  Figure 4 shows a partial front section

  of the total knee replacement shown in Figure 3.

  Figure 5 is a perspective view of the

  total knee prosthesis in flexion.

  FIG. 6 constitutes a partial frontal section of the total knee prosthesis represented in FIG. 5. For reasons of clarity, the same elements have been designated by identical references. Likewise, only the essential elements for understanding the invention have been shown, and this without respect

  scale and schematically.

  As can be seen in FIG. 1, the total knee prosthesis 1 with hinge comprises in particular a femoral component 2, a tibial base 3, a tibial plate 4, a pivoting member 5 and abutment means 6. The femoral component 2 is mounted movable in transverse rotation relative to the pivoting member 5, by means of a pin 7 which is inserted respectively in a through bore 8 formed transversely at the upper end of said pivoting member 5 , and in two through bores 9 formed through the casing 10 of said femoral component 2. The latter have a diameter greater than that of the axis 7 so that bearings 11a, 11b made of polyethylene or metal

  biocompatible can be inserted.

  The pivoting member 5 is in turn mounted movable in longitudinal rotation relative to the tibial base 3. It therefore has a cylindrical part 12 adapted to cooperate by pivoting in a housing 13 of complementary shape, formed longitudinally to across the top 14 of

the tibial base 3.

  In this particular embodiment, the tibial plate 4 is of the rotary type, that is to say that it is mounted movable in longitudinal rotation on the tibial base 3, which is more around the pivoting member 5 via a bearing 15. The tibial plateau 4 has for this purpose a first internal housing 16 adapted to receive the bearing 15, as well as at least a portion of the shoulder 17 delimiting the housing 13 formed through the tibial base 3. It is also provided with a second internal housing 18, not visible in Figure 1 and more particularly intended to allow the passage of the stop means 6. The latter must in fact both be integral with the upper part 14 of the base tibial 3 and do

  projection on the upper surface 19 of the tibial plateau 4.

  The stop means 6 are here mounted removable relative to their support, that is to say relative to the tibial base 3 in this example. It should be noted that in the case where a tibial plate secured to the tibial base is used, the support on which the abutment means are removably mounted can be constituted directly by said tibial plate. Anyway, this specificity allows to be able to advantageously vary the section of the stop means 6, and thus to modify the amplitude of the longitudinal rotation of the femoral component 2 for a given flexion position. An increase in the width of the stop means 6 obviously results in a proportional decrease in the amplitude of the rotation, since the space between the internal lateral face 31a, 31b of each condyle 20a, 20b and the said

  stop means 6 is then restricted.

  FIG. 2 shows in more detail the arrangement of the various components of the lower part of the total knee prosthesis 1 illustrated in FIG. 1. The tibial plateau 4 extends parallel to the upper part 14 of the tibial base 3, which has for this purpose a flat profile all around the shoulders 17 and 22 intended respectively to receive the pivoting member 5 and the abutment means 6. It is only maintained in this position because of the interlocking produced with the cylindrical part 12 of said pivot member 5 and of congruence with the femoral component 2. The two condyles 20a, 20b carried by the latter are in fact able to remain in intimate contact with cups 21a, 21b formed on the upper surface 19 of the tibial plateau 4, and this

  whatever the angle of flexion envisaged.

  The longitudinal rotation of the tibial plateau 4 is in no way disturbed by the presence of the shoulder 17. It is quite different with regard to the shoulder 22, responsible for supporting the stop means 6 removably mounted on the tibial base. 3 in this exemplary embodiment. The shoulder 22 indeed delimits a housing 23 intended to receive the abutment means 6 which are thus oriented orthogonally to the upper part 14, and which are consequently able to come to bear against

the internal wall of the housing 18.

  In this particular embodiment, the abutment means 6 consist of a simple stud 24, the lower part 25 and the upper part 26 of which have respectively complementary sections

  of the housing 23 and identical to the shoulder 22.

  Immobilization of the stud 24 in the housing 23 is effected by means of a pin 27 cooperating by locking, on the one hand, with a through bore 28 formed transversely in the shoulder 22, and on the other hand, with a socket 29 embedded in a through bore 30 formed transversely in

  the lower part 25 of the pad 24.

  As can be seen in Figure 2, the stop means 6 are shaped so as to project from the upper surface 19 of the tibial plateau 4, after their passage through the thickness of said tibial plateau 4 via internal housing 18 also visible. This internal housing 18 also has formal and dimensional characteristics capable of allowing the longitudinal rotation of the tibial plateau 4, despite the presence of the shoulder 22 and the stud 24. The pivoting in question is of course limited angularly by the abutment side walls of the housing 18 with those of the means of

stop 6.

  Figures 3 and 4 show the total knee prosthesis 1 in extension. In this extreme position, the stop means 6 cooperate simultaneously by contact with the internal lateral faces 31a, 3lb respective of the two femoral condyles 20a, 20b. The contact zones in question being arranged substantially radially with respect to the longitudinal axis of rotation, they are able to tangentially oppose any gyration of the femoral component.

  2 relative to the axis of the pivoting member 5.

  The absence of play between the various surfaces concerned advantageously allows blocking

  omnidirectional of the longitudinal rotation.

  On the other hand, when the knee joint is in flexion as is the case in FIGS. 5 and 6, the stop means 6 are no longer able to cooperate by contact, except alternately with one or the other of the internal side faces 31a, 3lb. This means, in other words, that the abutment means 6 are only capable of serving as support for one condyle a, 20b at a time, and that between these two extreme cases, there is a plurality of positions for which he

  there is no contact and therefore no blocking even partial.

  When the prosthesis 1 is not in extension, there are in fact relatively large spaces between the contact surfaces concerned, that is to say the internal lateral faces 31a, 3lb and the lateral walls 32a, 32b of the means of stop 6. As shown precisely in FIG. 6, this fundamental characteristic here comes from the fact that the condyles 20a, b are divergent from the anterior part,

  to the posterior part of the femoral component 2.

  The interval separating the two internal lateral faces 31a, 3lb being increasing as one passes from the extension position to any flexion position, the clearance between each of said internal lateral faces 31a, 31b, and the corresponding side wall 32a, 32b, stop means 6 will also tend to increase gradually during a bending movement. As a result, the femoral component 2 has more and more space to pivot longitudinally. The amplitude of this movement remains limited, however, on either side of the central position illustrated in FIG. 6, by bringing each of the internal lateral faces 31a, 31b into contact with the corresponding lateral wall 32a, 32b.

stop means 6.

  In practice, the total knee prosthesis 1 has no longitudinal mobility when it is extended. The femoral component 2 is indeed immobilized in longitudinal rotation relative to the tibial base 3, by means of the stop means 6 and in a medium position with respect to the future possibilities of displacement which will appear.

  once the total knee prosthesis 1 in flexion.

  As the two condyles 20a, 20b cooperate by congruence with the two cups 21a, 21b, the femoral component 2 will in turn immobilize the tibial plateau 4 in longitudinal rotation, thus completely blocking the total knee prosthesis 1 along this same axis. The patient's knee is then perfectly

stabilized.

  As soon as a bending will start, the stop means 6 will no longer be able to remain in simultaneous contact with the two condyles 20a, 20b of which

  the internal lateral faces 31a, 31b are divergent.

  The femoral component 2 will thus be able to pivot longitudinally with increasing amplitude as the flexion increases. As in the vicinity of the extended position, the rear middle part 33 of the tibial plateau 4 is of section substantially complementary to the casing 10, any longitudinal rotation of the femoral component 2 will be transmitted to said tibial plateau 4 which will thus be pivoted. When the flexion of the total knee prosthesis 1 continues, it is essentially the congruence between the condyles 20a, 20b and the cups 21a, 21b which will be at the origin of the transmission of the rotational movement. As has been explained before, the aim here is to distribute the friction forces inherent in the longitudinal rotational movements as well as possible between the two parts of the hinge. It should be noted that the congruence between the femoral component 2 and the tibial plateau 4 will advantageously make it possible to control the progressiveness of the longitudinal rotation at any time. On the other hand, it is the stop means 6 which will be responsible for limiting the angular displacement of the femoral component 2 and of the tibial plateau 4, by bringing their side walls 32a, 32b into contact with the internal side faces 31a, 3lb respectively. and the ends of the housing 18. It is however possible to provide that the abutment means 6 cannot cooperate by contact with the condyles 20a, b of the femoral component 2, from the extended position, only to a bending position

  given, corresponding for example to 45.

  Naturally, the invention is in no way limited by the characteristics which have been specified in the foregoing, nor by the details of the modes of

  particular realization chosen to illustrate it.

  All kinds of variations can be made, especially in terms of structure and

arrangement of the stop means 6.

Claims (13)

  1. Total knee prosthesis (1) with hinge comprising a femoral component (2) and a tibial base (3), the femoral component (2) being mounted movable in transverse rotation relative to a pivoting member (5) itself even mounted movable in longitudinal rotation relative to the tibial base (3), the femoral component (2) comprising two condyles (20a, b) cooperating by congruent contact with a tibial plate (4) disposed at the upper end (14 ) of the tibial base (3), characterized in that said total knee prosthesis (1) comprises abutment means (6) capable of blocking the femoral component (2) in longitudinal rotation, when the knee joint is in extension.   2. Total knee prosthesis (1) according to claim 1, characterized in that in extension, the stop means (6) are able to cooperate simultaneously by contact with the internal lateral faces (31a, 3lb) respective of the two condyles femoral (20a, 20b).   3. Total knee prosthesis (1) according to one of   claims 1 or 2, characterized in that   bending, the stop means (6) are able to cooperate alternately by contact with the internal lateral face (31a, 31b) of one or the other of the condyles femoral (20a, 20b).   4. Total knee prosthesis (1) according to one   any one of claims 1 to 3, characterized in that   that the interval between the respective lateral internal faces (31a, 31b) of the two femoral condyles (20a, b) is increasing from the part anterior to the part   posterior of the femoral component (2).   5. Total knee prosthesis (1) according to one   any one of claims 1 to 4, characterized in that   that the abutment means (6) are able to cooperate by contact with the condyles (20a, 20b) of the femoral component (2), from the extension position to a given bending position.   6. Total knee prosthesis (1) according to claim, characterized in that the flexion position corresponds to approximately 450.   7. Total knee prosthesis according to any one   claims 1 to 6, characterized in that the   tibial plateau is mounted fixed relative to the tibial base and in that the abutment means are integral with the tibial plateau.   8. Total knee prosthesis according to any one   claims 1 to 6, characterized in that the   tibial plateau is mounted fixed relative to the tibial base and in that the abutment means are   integral with said tibial base.   9. Total knee prosthesis according to claim 8, characterized in that the tibial plateau comprises a housing intended to receive the abutment means forming   protruding from its upper surface.   10. Total knee prosthesis (1) according to one   any of claims 1 to 6, characterized in that   that the tibial plateau (4) is mounted movable in longitudinal rotation on the tibial base (3) and in that the abutment means (6) are integral with said base tibial (3).   11. Total knee prosthesis (1) according to claim 10, characterized in that the tibial plateau (4) comprises a housing (18) intended to receive the abutment means (6) projecting from its upper surface (19 ), the housing (18) being able to allow the rotation of said tibial plate (4) at   less on a given angular sector.   12. Total knee prosthesis (1) according to one of   claims 10 or 11, characterized in that the   tibial plateau (4) is mounted mobile in rotation   longitudinal around the pivoting member (5).   13. Total knee prosthesis (1) according to one   any of claims 1 to 12, characterized in   that the stop means (6) are removably mounted on their support.