FR2824260A1 - Tibial section for prosthetic knee joint has base and face plates connected by inter engaging surfaces and with locking key - Google Patents

Abstract

The tibial section for a knee joint prosthesis has fixings between the joint face section (7) and the base (6). The fixings have anchors (1) and indexing surfaces (11) formed on the base and face section to interengage. There are locking key inserts (111) between the base plate (8) and the face plate. The locking key inserts can compensate for play in the joint.

Description

minimum section () equal to 10 mm.

  The present invention relates to the field of bone prostheses and it relates, more particularly, to that of knee prostheses, more especially multi-compartmental. In the above technical field, it has long been known to propose artificial articular systems aiming to replace the natural articulation constituted by the low epiphyseal conformation of the femur, by the complementary high epiphyseal conformation of the tibia and by the femoro element patélaire. All of the proposals known up to now, whether or not routinely implemented, are based on a constitution of such an artificial articular system from two main elements, intended to be respectively adapted, after bone resection, on the low epiphyseal conformation of the femur and on the

  complementary upper epiphyseal conformation of the tibia.

  The invention relates, more specifically, to the proposals relating to articulation elements intended to be implanted on the epiphyseal conformation

upper shin.

  The anatomical conformation of the upper epiphysis of the tibia naturally provides a counterpart to the femoral condyles, so as to have a complementarity of articular surfaces capable of ensuring the complex function of flexion-extension, with partial internal or external rotation of the knee, between the shin and

  the femur of a human lower limb.

  For this purpose, the natural joint has, in the tibial plateau, two glenes associated with menisci and in which are supported, under the control of two crossed ligaments and two groups of lateral ligaments, the surfaces

  condylar joints of the lower epiphysis of the femur.

  When implanting a prosthesis, it is necessary to practice, as regards the upper epiphysis of the tibia, a more or less significant resection of the tibial plateau, to replace the two glenes of this plateau, artificial elements intended

  to perform the same function vis-à-vis the femoral condyles.

  As a rule, such a function is assumed by implanting after resection a tibial prosthetic element, comprising a base intended to be adapted and inserted on the tibial resection cut, by suitable means which may be simple screws, a kind of short extension. or, again, a long tail

  introduced into the medullary canal, with or without the presence of intermediate cement.

  Such a base is intended to support a shoe, generally made of plastic, such as high density polyethylene, offering, by its upper face, the

  nocessar surface in support of the femoral condyle (s).

  Being a complex joint, such as the knee, in which it can be considered that no movement can be qualified as pure, it appears essential to be able to adapt the pad on the base, so as to avoid any possibility of

relative displacement.

  To this end, it is usual to make the base so that it has a peripheral rim delimiting a kind of housing in which the shoe can be fitted, or even snapped. Because of the naturally reduced space existing between the femoral and tibial ends opposite even after resection, and especially in order to make the latter as small as possible, it is necessary to give the skate and the base, at least as regards the plate of the latter, the smallest possible thickness. It follows, therefore, that the

  relative height of the nesting or snap rim is reduced accordingly.

  If a proposal of the above type appears suitable to assume the function of immobilizing the skate on the base, however, it turns out

  unsatisfactory in practice, due to the following disadvantages.

  Due to the low height, the interlocking and snap-on of the skate cannot be ensured in a permanent way, due to fatigue and structural constraints

  which are imposed on the artificial joint thus constituted.

  This results in time, the birth of wear games which go against the desired objective which is to avoid the possible relative displacement of the shoe generating the release of wear particles which induce biological reactions. (osteolysis). Furthermore, in the case of implantation, when the natural joint always benefits from the existence and functionality of the cruciate ligaments, it has been found that, in the event that a rupture of the latter occurs then in the time, a certain laxity arose with, as a consequence, support from

  femoral condyles on the peripheral borders of the glenoid muscles of the skate.

  Given the relatively small thickness of the latter, these successive supports produce local wear or dogradation of the pad, then causing the femoral condyles to bear on and to constrain the twisting of the socket and

latching of the base.

  An artificial joint system subjected to such functional conditions quickly reaches a state of deterioration, requiring the intervention of an intervention

of recovery.

  There is therefore a need to be able to overcome these major drawbacks, so as to give an artificial articular system of the type mentioned above, anatomically satisfactory operating characteristics and, above all, for increased implantation times, in order to avoid subjecting each implanted subject to long, delicate, costly and subject to

sensitive rehabilitation.

  It is precisely the object of the invention to meet such a need, by proposing an improved tibial prosthetic element, for knee prosthesis, which will involve means of structural connection between the pad and the base, which are able to meet the requirement to prohibit relative movement of the skate relative to the base, but also to satisfy the need to be able to respond positively to this requirement under acceptable functional conditions, even in the case o , later after the implantation intervention, the cruciate ligaments, still present at the time of the intervention, are found later ...

detenores, your broken.

  To achieve the above objectives, the improved tibial prosthetic element for knee prosthesis, of the type comprising, on the one hand, a shoe shaped to cooperate with the femoral condyles, on the other hand, an adaptation base on a tibial plate resected and which comprises a plate provided with means of insertion on said plate and, moreover, means of immobilization between the plate and the pad is characterized in that the means of immobilization comprise: anchoring and indexing provided additionally on the plate and the pad, A and locking means by keying between said plate and said pad.

  Various other characteristics emerge from the description given below in

  reference to the accompanying drawings which show, by way of nonlimiting examples,

  embodiments and implementation of the subject of the invention.

  Fig. 1 is a perspective illustrating the means of the invention in relation to a schematic representation of the femoral and tibial epiphyses concerned. The ffg. 2 and 3 are perspectives, seen from different angles, illustrating constructive arrangements characteristic of one of the constituent parts of

the tibial prosthetic element.

  Figs. 4 and 5 are two perspectives, seen from different angles, illustrating the constructive characteristics of a second component part of the element

tibial prosthesis.

  The B'g. 6 is a perspective view, on a larger scale, of a third

  constituent part of the improved tibial prosthetic element according to the invention.

  The ffg. 7 is a perspective illustrating a phase of assembling the parts

  constitutive of the tibial prosthetic element.

  The fg. 8 and 9 are perspectives highlighting constructive characteristics after final assembly of the component parts of the element

tibial prosthesis.

  The ffg. 1 shows the reali sati on it part of the prosthetic element that tibl al according to the invention, in the context of an implantation on the upper epiphysis 1 of a tibia 2,

  so as to offer a functional counterpart to the condyles 3 of an associated femur 4.

  According to the illustration presented, the prosthetic element is analyzed as being an adaptation of total prosthesis involving a tibial prosthetic element which

  comprises, in an ordinary manner, a base 6 intended to support a shoe 7.

  The base 6 is formed by a plate 8 associated with insertion means on

  the equal tibial plateau. Such means can be formed in the usual way.

  in particular by holes 9 for the passage of fixing screws and / or also by the presence of a short or long extension, such as 10, protruding from the

underside of plate 8.

  In known manner, the pad 7 is in the form of a relatively thick mass, the upper surface of which presents, on either side of an inter-condylar eminence 11, two support zones Z for the femoral condyles 3 , such areas may be flat or on the contrary offer conformations

analogous to natural glenes.

  According to the invention, the structure of the tibial prosthetic element involves means for immobilizing the pad 7 on the base 6, such immobilizing means being intended to respond positively to the previously stated objectives. The immobilization means within the meaning of the invention comprise, between the plate and the shoe, complementary anchoring means I, indexing II and

locking III.

  The anchoring means I, as can be appreciated by FIG. 1 and more precisely still by FIGS. 2 and 5, include, as regards the base 6, one and preferably two hooks 15 placed in relation to the perimeter edge of the plate 8 to rise from the upper surface of the latter. The hook (s) 15 are placed in relation to the rear part 16 of the perimeter edge of the plate 8 and are provided in a symmetrical arrangement on either side of a sagittal plane of symmetry P-P '. Also preferably, the hooks 15 are implanted or arranged or provided so as to be placed in relation to a clearance 17 which is formed in the plate 8 to reserve a passage for the cruciate ligaments, when the latter remain present despite the intervention of implantation of a prosthesis. Also preferably, the hooks 15 are as slightly as possible apart on either side of the sagittal plane P-P ', so as to be located at best outside of the plumb of the contact zones between the femoral condyles and

  pad 7 during flexion / extension movements.

  According to the example, the hooks 15 are thus placed in the vertical extension

  parallel edges of dogagement 17.

  Each hook 15 comprises a foot 18 rising from the plate and which is surmounted by a head 19 extending at right angles to the foot and in the direction

  of a front part 20 of the perimeter edge of the plate.

  The anchoring means I also involve, as regards the pad 7, a notch 21, called the engagement, of the hook (s) 15. The notch 21 is formed in relation to the perimeter edge of the pad which has a clearance 22 adapted to receive the foot 18 of the hook (s) 15. The notch 21 is. preferably arranged in the thickness of the pad and in relation to the posterior part of the perimeter edge of the latter. The notch 21 is also arranged to be able to accommodate the heads 19 and can therefore have a specific conformation to each of them or,

  on the contrary, a common conformation, as shown in fig. 5.

  In the preferred embodiment, as illustrated by fg. 1, the notch 21 is common to the two hooks 15 and is made, for this reason, in relation

  of symmetry with the plane P-P 'considered specific to skate 7.

  The indexing means II, as they appear in FIG. 1 and more particularly still by FIGS. 3 and 4 include, with regard to the base 6, two studs 25 rising from the upper surface of the plate 8 to be placed in relation to the front part 20 of the perimeter edge of the latter. Preferably, the studs 25 are arranged symmetrically, on either side of the sagittal plane of symmetry P-P ', to be, moreover, placed in opposition

hooks 15.

  1S The indexing means II involve, as regards the shoe 7, two housings 30 for receiving the pads 25. These housings 30 are arranged in correspondence of the two pads 25, that is to say to open on the underside of pad 7, as appears more particularly in fg. 4, also being

  accessible from the front part of the perimeter edge of said pad.

  In the preferred embodiment, the two housings 30 are thus arranged at equal distance and on either side, symmetrically with respect to the sagittal plane

of P-P 'symmetry.

  The locking means III are partly delimited additionally in the shoe 7 and in the studs 25 and additionally comprise a key

  blocking and locking indicated as a whole by reference 35.

  The means III therefore comprise, in the shoe 7, a groove 36 which is delimited substantially at mid-thickness of the shoe 7, so as to pass through the housings 30. This groove 36 is therefore formed in the front part of the perimeter edge and has the characteristic of having two ends 36a and 36b (fig. 4), open on the perimeter edge of the pad 7. The groove 36 is also characterized by the existence of a rectilinear bottom 37 whose general direction is

orthogonal to the plane P-P '.

  The means III also involve a notch 40 presented opposite by each stud 25 and which is delimited to face the groove 36, so as to coincide with the latter in the assembled state of the pad and the base, like this will be seen later. The notches 40 are provided to present a symmetry of position and structure, in relation to the groove 36 which is also, as mentioned above, established symmetrically with respect to the plane of symmetry

sagittal P-P '.

  It must therefore be considered that the notches 40 are oriented towards the rear part of the perimeter edge of the plate 8, while each stud 25 lO has, on its part corresponding to the front edge, a notch 41 whose function

appears in the following.

  The means III involve, as said previously, an additional member constituted by the key 35 which is in the form of a key comprising a so-called rear edge 45 rectilinear, and a so-called front edge 46 formed by a ramp 47 called engagement, arising from a terminal part 48, called the introductory part, which has a wedge shape, the large base of which is oriented towards the second terminal part 49 of the key. The so-called front edge 46 also includes, following the ramp 47, a straight span 50 which is parallel to the rear edge 45, so as to give the key a constant width l which is slightly greater than the sum depths of groove 3 6 and a

notch 40.

  The key 35 is provided with a flexible locking branch 51 which extends from the terminal part 49 at a distance and in front of the bearing surface 50 towards which its

end forms a beak 52.

  The various technical means which have just been described are intended to ensure, within the meaning of the invention, an assembly of the pad 7 on the upper surface of the plate 8, so that this pad is immobilized against any relative displacement

  untimely compared to the base 6.

  The assembly is carried out by proceeding as follows notably starting from fig. 7. The shoe 7 is placed in superposition with respect to the plate 8, then is inclined relatively by a certain angular measurement in the direction of the arrow f so as to allow the relative engagement of the hooks 15 in the dogagement 22, so as to make it possible, by a relative sliding of the pad 7 in the direction of the posterior edge

  of the plate 8, the penetration of the heads 19 into the notch 21.

  Such engagement is made possible by bringing the shoe 7 substantially parallel to the plate 8, so that, simultaneously, the pads 25 engage

  in the corresponding housing (s) 30.

  Taking into account the constructive characteristics as recalled above, in this state of pre-assembly, the groove 36 and the notches 40 are placed in coincidence in the same plane, so as to delimit together a kind of

  slide open at both ends 36a and 36b.

  In the pre-assembly state thus obtained, the key or key 35 can then be introduced into the slide by the terminal part of introduction 4 8, engaged by one of the open ends 36a or 36b. The key is engaged by being oriented so

  that the rear edge 45 comes to cooperate with the bottom 37 of the groove 36.

  The progressive introduction of the key, in the direction of the arrow f2 according to FIG. 7, has the effect of making the engagement ramp 47 cooperate with the notch 40 of the stud 35 close to the open engagement end in order, in a way, to relatively preposition the pad 7 and the base 6. The pursuit of the introduction of the key 35 in the direction of the arrow f2 exerts, by the ramp 47, an application pressure of the pad 7 against the hooks 15 then, then, constrained, by compression, the material constituting the pad 7 for obtain the forced engagement of the key body comprised between the edge 45 and the bearing surface 50. The compression stress is limited to the elastic domain and achieves the coop eration of the rear edge 45 with the bottom 37 and that of the

carried 50 with the notches 40.

  At the end of introduction, the flexible branch 51 surrounds the stud 25 corresponding to the chosen introduction section 36a or 36b, so that the spout 52

  come and engage behind the notch 41, as it appears in fig. 9.

  In this state, the key 45 assumes a function of compressing the material of the pad, which makes it possible to achieve play compensation, while ensuring the immobilization of the pad 7 in a determined position, firm with respect to the base 6, in relation to the cooperation of the hooks 15 with the notch 21, of a

  part, and that of the studs 25 with the indexing housings 30.

  Due to the symmetrical arrangement of the hooks 15 and the studs 25 and the relative length of the key body and the flexible branch 51, the key 35 can be engaged either by the end 36a or 36b of the insertion slide, to assume the same immobilization function with clearance compensation and locking by cooperation of the flexible branch 51 with the notch 41 of the corresponding stud. It should be noted that, if necessary, the practitioner can be led to remove the key 35, by simply acting by lever action on the spout 52, to bend the locking branch 51 by bending and allow the key to slide. 35 off

  of the slide in the opposite direction to that of arrow f2.

  The technical means recommended according to the present invention make it possible to produce a firm, resistant assembly without relative play, between the shoe 7 and the base 6, with the possibility of making a last minute change, replacement or adaptation between the any of the constituent parts of

  the prosthetic element, namely the pad 7 or the base 6.

  Furthermore, as appears more particularly from the examination of FIGS. 8 and 9, the means according to the invention make it possible to completely eliminate the nesting and snap-fit rim usually presented by the plate 8 in traditional constructions and which turns out, in the event of subsequent rupture of the cruciate ligaments, responsible for an irreversible deterioration, necessarily leading to the

  need for recovery intervention.

  The invention is not imitated to the examples described and represented because various es

  changes can be made without departing from its scope.

Claims (14)

  1 - Improved tibial prosthetic element for knee prosthesis, of the type comprising, on the one hand, a pad (7) shaped to cooperate with the femoral condyles, on the other hand, an emb as e (6) of adaptation on a p tib i al re required and which comprises a plate (8) provided with means (10) for insertion on said plate and, moreover, means of immobilization between the plate and the shoe, characterized in that that the immobilization means comprise: À of anchoring means (I) and of indexing (II) p revisited co mp elementarily on the plate and the pad, À and locking means (III) by keying between said plate and said skate.   2 - tibial prosthetic element according to claim 1, characterized in that the   locking means (III) by keying are of the backlash compensation type.   3 - tibial prosthetic element according to claim 1, characterized in that the anchoring means (I) comprise: À in relation to the rear part of the perimeter edge of the plate (8), at least one hook (15) s' elevating from the upper face of said plate, A and in relation to the corresponding part of the perimeter edge of the shoe (7),   a notch (21) for engaging the hook.   204 - Tibial prosthetic element according to claim 3, characterized in that the anchoring means (I) comprise a notch (21) of engagement formed in   the thickness of the pad to be common to two hooks.   - Tibial prosthetic element according to claim 3 or 4, characterized in that the anchoring means (I) comprise two hooks (15) placed symmetrically   on either side of the sagittal plane of symmetry (P-P ').   6 - tibial prosthetic element according to claim 3, 4 or 5, characterized in that the hooks (15) are placed on either side of a recess (17) formed   in the plate for the passage of the cruciate ligaments.   7 - tibial prosthetic element according to claim 3, 4, 5 or 6, characterized in that each hook (15) comprises a foot (18) rising from the upper face of the plate and which is surmounted by a head (19) extending at right angles to the foot and towards the front part of the perimeter edge of the plate. 8 - tibial prosthetic element according to claim l, characterized in that the means of age index (II) c include in relation to the anterior part of the perimeter edge of the plate, two studs (25) projecting from the face upper of said plate while being located in opposition to the anchoring hook (s), A and in relation to the corresponding part of the perimeter edge of the pad,   two housings (30) for receiving said pads.   9 - tibial prosthetic element according to claim 8, characterized in that the indexing means (II) comprise two studs (25) placed symmetrically by   relation to the sagittal plane of symmetry (P-P ').   - Tibial prosthetic element according to claim 1 or 2, characterized in that the locking means by keying comprise: 15. a slide delimited in association by the pad and the base placed in as s emb lé state by the coop eration of the means anchoring (I) and indexing (II),   a removable key (35) which can be engaged in said slide.   11 - tibial prosthetic element according to claim 10, characterized in that the slide is delimited in a substantially average plane of the thickness of the pad, and in a direction perpendicular to the sagittal plane so as to have two open ends (36a, 36b).   12 - Tibial prosthetic element according to claim 10 or 11, characterized in   that the slide is symmetrical with respect to the sagittal plane.   13 - tibial prosthetic element according to claim 10, 11 or 12, characterized in that the slide is delimited in relation to the anterior part of the edge perimeter of said element.   14 - tibial prosthetic element according to claim 13 characterized in that the slide is delimited by: a rectilinear groove (36) formed in the thickness of the pad (7) in relation to the anterior part of the perimeter edge of said pad to cross the or the housings (30) for receiving the stud (s) (25), a notch (40) presented opposite by the stud (s) to accommodate   the rainare in the assembled state of the shoe and the base.   - Tibial prosthetic element according to claim 10, characterized in that the key (35) has a straight rear edge (45) bearing against the bottom (37) of the groove (36) and a front b ord (46) defined by an inclined ramp (4 7) engaging leading to an end (48) of introduction of said key and which is connected, opposite said end, to a straight bearing (50) parallel to the rear edge (45) with which it gives the key body a width (1) which is logically   greater than the sum of the depth of the groove (36) and a notch (40).   16 - Tibial prosthetic element according to claim 10 or 15, characterized in that the key (35) comprises, opposite the insertion end, a flexible locking branch (51) extending opposite - screw and away from the scope (50) and   the end part (52) of which is able to cooperate with a stud (25).   17 - tibial prosthetic element according to claim 16, characterized in that the flexible 1S branch (51) externally covers the stud in the state of engagement of the key in the slide and in that the terminal part of said branch comprises   a spout engaged, in said state, behind a notch (41) presented by the stud (25).   18- Tibial prosthetic element according to claim 10, 15, 16 or 17, characterized in that the key and the flexible branch have lengths such that the engagement of said key can intervene by one or the other of the open ends of the slide to ensure the cooperation of the flexible branch with one