FR2686792A1 - Single-compartment knee prosthesis in three parts, including a femoral condyle, a tibial plate and a tibial block - Google Patents

Abstract

The invention relates to a single-compartment knee prosthesis including a femoral condyle (17) provided with anchoring means (20-23) allowing it to be sealed (cemented) in a condyle of the femur, a tibial plate (1) provided with anchoring means (2) allowing it to be sealed in the upper end of a tibia, and a tibial block (10) made of plastic, including a sliding surface (10a) for the femoral condyle (17) and means of removable fixation on the tibial plate (1). The anchoring means of the tibial plate (1) include an anchoring stud (2) extending under the bearing face of the said tibial plate, in the front half of its bearing face, the said anchoring stud being inclined backwards so that its longitudinal axis defines an angle lying substantially between 20 and 40@ with an axis which is orthogonal with respect to the said bearing face.

Description

UNICOMPARTMENTAL THREE-PART KNEE PROSTHESIS
INCLUDING A FEMORAL CONDYLE, A TIBIAL TRAY
AND A TIBIAL SKATE
L1 in vent i relates to a unicompartmental knee prosthesis in three parts, comprising a femoral conayle, a tibial plateau and a tibial pad.

Such prostheses are currently known and in particular described in French patents
FR 2,589,719 and European EP 32,828. They are made up
- a femoral condyle provided with anchoring means allowing it to be sealed in the condyle of the femur,
a tibial plate comprising a lower face for bearing on an upper end of the tibia having been excised, and anchoring means making it possible to seal it in said upper end of the tibia,
- And a tibial pad comprising a sliding surface for the femoral condyle and removable fixing means on the tibial plateau.

 Compared to conventional prostheses comprising a femoral condyle and a tibial element provided with a sliding surface in one piece with the tibial plateau, the advantage of these resin prostheses in the removable character of the tibial pad.

 Indeed, and in the first place, this skate is put in place at the end of the intervention after sealing the femoral condyle and the tibial plateau. Therefore, its thickness can be easily changed if necessary. In addition, it is possible, before the installation of this pad, to remove any excess cement at the posterior level in order to avoid the bending defects which are generated by the fragments of posterior cement which cannot be removed. with a pre-assembled classic tibial plateau.

 In addition, the removable nature of this pad makes it easy to replace it without having to intervene on the femoral condyle and the tibial plateau.

 The present invention relates to a unicompartmental knee prosthesis, of the type described above, and has the main objective of providing an improved prosthesis designed so that the establishment of the tibial plateau is facilitated and the risks of loosening of said plateau limited.

 Another objective of the invention is to provide a unicompartmental knee prosthesis whose placement and removal of the tibial pad is carried out in a simple and rapid manner, with however the guarantee of perfect immobilization of this pad relative to the tibial plateau once said pad in place.

 Another objective is to provide a unicompartmental knee prosthesis solving problems of conflict with the lateral lateral ligaments and the cruciate ligaments.

 Another object of the invention is to provide a unicompartmental knee prosthesis whose femoral condyle requires only a simple excision of the femoral condyle.

 (To facilitate understanding and simplify the terminology, the prosthesis will be described and defined below, assuming it in its implantation position).

 To this end, the invention relates to a unicompartmental knee prosthesis comprising three distinct elements, a femoral condyle provided with anchoring means making it possible to seal it in a condyle of the femur, a tibial plateau provided with a lower face bearing on an upper end of a tibia having been excised, and anchoring means making it possible to seal it in said upper end of a tibia, and a tibial pad of a plastic material, comprising a sliding surface for the femoral condyle and fixing means removable on the tibial plateau.

 According to the invention, this prosthesis is characterized in that the means for anchoring the tibial plateau comprise an anchoring stud extending under the bearing face of said tibial plateau, in the front half of this bearing face, said anchoring stud being inclined rearward so that its longitudinal axis defines an angle i substantially between 20 and 40 degrees with an axis orthogonal to said bearing face.

 In addition to the advantages of a unicompartmental knee prosthesis in three parts listed in the preamble of the present aemanee, the prosthesis according to the invention has, in addition, a tibial plate whose placement is facilitated by the position and the 'tilt to the anchor pad. Indeed, this position and this inclination facilitate the drilling operation to be performed in the upper end of the tibia in order to receive the anchoring pad. In addition, they virtually eliminate any risk of damage to the condylar part during this piercing operation.

 Furthermore, once the tibial plateau is in place, the inclination and the position of the anchoring stud limit the risks of loosening by avoiding any risk of vertical tilting and lateral rotation.

 According to a preferred embodiment, the anchoring stud of the tibial plateau has a cylindrical shape. The drilling to receive this anchoring pad can thus be carried out with a calibrated drill bit of suitable dimensions to minimize the possiDle of the amount of sealing cement and thus limit the risks of cracking or breaking of the cement.

According to another characteristic of the invention
- the tibial plateau has an upper face with a peripheral rim,
- the tibial pad consists, depending on its thickness, of two superimposed parts separated by a shoulder intended to come to rest on the peripheral rim of the tibial plateau: a lower part of magnifications adapted to be housed in the volume delimited by the peripheral rim of the plateau tibial, and an upper part of the same dimensions as the external dimensions of said tibial plateau.

In addition, and preferably, the anchoring stud of the tibial plateau is provided with a bore
Eye of axis orthogonal to the upper face of said plate,
said bore emerging at said upper face, while the tibial pad has a lower face provided, projecting, with a stud arranged to be housed in the blind bore of the tibial plateau.

 These provisions facilitate the installation of the tibial pad which can be put in place by sliding and pressing by means of a single finger, while guaranteeing against any risk of escape of this pad from the housing formed by the peripheral edge of the tibial plateau.

 Furthermore, according to another characteristic of the invention, the rim peripheral to the tibial plateau has two notches formed respectively at the front end and the rear end of said tibial plateau, and the lower part of the tibial pad has two adapted tenons to lodge each one respectively in one of the notches of the peripheral edge of the tibial plateau.

 The first notch formed towards the front of the initial plate allows easy removal, if necessary at the tibial pad. The second disposed towards the rear allows to remove any excess cement at the posterior level.

 According to another characteristic of the invention, the tibial plateau and the tibial pad have, in plan view, the shape of a D inscribed in a circle, said D being truncated so as to have two parallel longitudinal sides connecting two arcs of a circle forming the front and rear sides of said tibial plateau and pad.

 This characteristic shape of the tibial plateau and pad makes it possible to resolve the problems of conflict with the external lateral ligaments and the cruciate ligaments and thus to eliminate the pains at these levels and the risks of rupture of said ligaments.

 Furthermore, the femoral condyle preferably comprises 2 anchoring means comprising an anchoring stud extending on the contact face of this element with a femoral condyle, substantially recessed in the rear half of this contact face.

 This arrangement of the anchoring pad makes it possible to position the latter substantially in the axis of the load transfer line between the femur and the tibia. In addition, it allows easier placement of the femoral condyle and eliminates any possible tilting movement.

 According to another characteristic of the invention, the femoral conayle comprises, towards its front end, a return having a flat internal face parallel to the axis of the anchoring stud, adapted to come to adjust against a flat surface conjugate to ' a condyle of femur having undergone an adequate excision.

 In addition, according to a preferred embodiment, the femoral condyle has a contact surface curved longitudinally and transversely so as to conform to the shape of a femoral condyle, said femoral condyle being provided laterally with two longitudinal edges delimiting a width suitable for house a femoral condyle.

 Such a femoral condyle adapted to exactly match the shape of a femoral condyle arises simply by resurfacing the end of the femur. The only excision to be carried out consists of a cut which makes it possible to set up the femoral condyle by presenting it in a very practical way, parallel to the axis of the femur.

Other characteristics, objects and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings which represent, by way of non-limiting example, a preferred embodiment. On these drawings which form an integral part of this description:
FIGS. 1a, 1b and 1c are perspective views of the three elements, respectively the femoral condyle, tibial pad and tibial plateau, making up a unicompartmental knee prosthesis according to the invention,
FIG. 2 is a view in partial section through a longitudinal plane A of a tibial plateau according to the invention,
FIG. 3 is a top view of this tibial plateau,
- Figure 4 is a bottom view,
FIG. 5 is a view below of a tibial pad according to the invention,
FIG. 6 is a front view thereof,
FIG. 7 is a side view thereof,
FIG. 8 is a side view of a femoral condyle according to the invention,
FIG. 9 is a partial sectional view thereof through a longitudinal plane B,
FIG. 10 is a view in partial section thereof through a transverse plane C,
- And Figure 11 is a top view.

 The prosthesis shown in the figures is a unicompartmental knee prosthesis composed of three distinct elements: a tibial plateau, a tibial pad and a femoral condyle. This prosthesis can be implanted with or without cement. In the latter case, the surfaces intended to come into contact with the bone are covered with a layer of hydroxyapatite or of a similar material intended to promote bone growth.

 The first element of this prosthesis, the tibial plateau 1, shown in Figures 1 and 2 to 4, is made of a biocompatible metal.

 This plate 1 has, seen in plan, the shape of a D inscribed in a circle, said D being truncated so as to comprise two parallel longitudinal sides la, lb connecting the front sides îc and rear îd having the shape of an arc of circle.

 The tibial plateau 1 comprises, firstly, an anchoring stud 2 of cylindrical shape extending under its underside of support le. This anchoring pad 2 is inclined rearward so that its longitudinal axis substantially defines an angle o (30 degrees with an axis orthogonal to the face a'ui support.

 It is furthermore arranged, at its junction with the face with the support, at a distance from the front end of the latter sensiDlement equivalent to a quarter of the length of the tibial plateau 1.

 Furthermore, the anchoring stud 2 has a peripheral surface provided with longitudinal ridges 3 distributed around the periphery of said surface. The purpose of these streaks is to allow air backflow and any excess cement during the placement of the tibial plateau 1.

 This anchoring stud 2 is finally provided with a blind bore 4 formed in the axis of the latter orthogonally with respect to the upper face 1f of the tibial plateau 1, said bore emerging at the level of this upper face 1f.

 The tibial plateau 1 further comprises a grooved support face consisting of a plurality of studs 5 aligned longitudinally and transversely, said studs being separated by longitudinal and transverse grooves 6.

 This tibial plateau 1 finally has an upper face 1f provided with a peripheral rim 7 with a height of the order of 2 mm. This peripheral rim 7 is interrupted at the level of the front side lc and of the rear side ld of the tibial plateau 1 by two notches 8, 9. These notches have the role of allowing, for the front notch 8, easy removal of the tibial pad, and for the rear notch 9, the removal of any excess posterior cement.

 The second element of this prosthesis, the tibial pad 10, shown in Figures 1b and 5 to 7, is made of high density polyethylene. This tibial pad is intended to be removably secured to the tibial plateau 1, and has a concave upper face 10a of sliding for the femoral condyle.

 This tibial pad has, seen in plan, the same shape as that of the tibial plateau 1, that is to say that of a D inscribed in a circle (as shown in FIG. 5), truncated so as to present two parallel longitudinal sides .

This tibial pad consists, depending on its thickness, of two superimposed parts 11, 12 separated by a shoulder 13
- A lower part 11 of dimensions adapted to be accommodated in the volume delimited by the peripheral rim 7 of the tibial plateau 1, the thickness of this lower part 11 corresponding to the height of the peripheral rim 7 so that the shoulder 13 comes rest on this ledge 7,
- And an upper part 12 of the same dimensions as the external dimensions of the tibial plateau 1, and the thickness of which varies according to the models ae so as to allow this thickness to be adjusted according to needs.

 In addition, the lower part 11 of this tibial pad has two studs 14, 15 adapted to be housed each in a notch 8, 9 of the tibial plateau so as to ensure the continuity of the peripheral rim 7 of this plateau.

 The tibial pad 10 finally has a lower face 10b protruding from a stud 16 arranged to be housed in the blind bore 4 of the tibial plateau 1.

 The last element of this prosthesis, the femoral condyle 17, shown in FIGS. 1a and 8 to 11, is made of a biocompatible material and comprises a lower face 17a convex longitudinally and transversely, sliding on the tibial pad 10.

 Conversely, the upper face 17b of this femoral condyle, intended to come into contact with a femoral condyle, is curved longitudinally and transversely so as to conform to the shape of this femoral condyle. This upper face 17b is further delimited laterally by two longitudinal edges 18a, 18b defining a width adapted to accommodate a femoral condyle.

 Towards its front end, this upper face 17b comprises, moreover, a return 19 having a flat internal face 19a adapted to come to fit against a condyle of femur having undergone for this purpose beforehand a conjugate cut of said face.

 The femoral condyle 17 further comprises an anchoring stud 20 extending projecting from the upper face 17b, substantially set back in the rear half of this upper face.

 This anchoring stud 20 has a cylindrical shape has several annular grooves 21 allowing good anchoring of the cement for better holding of the condyle as soon as it is put in place.

 The femoral condyle 17 finally comprises two anchoring pins 22, 23 arranged on either side of the anchoring stud 20, along the longitudinal axis of said condyle, and the role of which is to avoid any instability of the condyle.

Claims (14)

 1 / - Unicompartmental knee prosthesis comprising three aistinct elements, a femoral condyle (17) provided with anchoring means (20-23) making it possible to seal it in a condyle of the femur, a tibial plateau (1) provided with a face lower (the) bearing on an upper end of a tibia having been excised, and anchoring means (2) allowing it to be sealed in said upper end ae tibia, and a tibial pad (10) made of a plastic material, comprising a sliding surface (1osa) for the femoral condyle (1.7) and means (11, 16) for removable attachment to the tibial plateau (1), said unicompartmental prosthesis being characterized in that the means for anchoring the tibial plateau (1) comprise an anchoring stud (2) extending under the bearing face (le) of said tibial plateau, in the front half of this bearing face, said anchoring stud being inclined towards the rear so that its longitudinal axis defines an angle (o () substantially understood is between 20 and 40 degrees with an axis orthogonal to said bearing face.  2 / - Unicompartmental knee prosthesis according to claim 1, characterized in that the longitudinal axis of the anchoring stud (2) to the tibial plateau (1) defines an angle substantially equal to 30 degrees with an axis orthogonal to the bearing surface (le) of said tibial plateau.  3 / - Unicompartmental knee prosthesis according to one of claims 1 or 2, characterized in that the anchoring stud (2) of the tibial plateau (1) is disposed, at its junction with the bearing face ( read), at a distance from the front end of said face substantially equivalent to a quarter of the length of the tibial plateau (1).  4 / - Unicompartmental knee prosthesis according to one of the preceding claims, characterized in that the anchoring stud (2) of the tibial plateau (1) has a cylindrical shape.  5 / - Unicompartmental knee prosthesis according to one of the preceding claims, characterized in that the anchoring stud (2) of the tibial plateau (1) has a peripheral surface provided with longitudinal grooves (3) distributed around the periphery of said area.  6 / - Unicompartmental knee prosthesis according to one of the preceding claims, characterized in that  the tibial plateau (1) has an upper face (1f) with a peripheral rim (7),  - the tibial pad (10) consists, depending on its thickness, of two superimposed parts separated by a shoulder (13) intended to come to rest on the peripheral rim (7) of the tibial plateau (1): a lower part (11) of dimensions adapted to fit in the volume delimited by the peripheral rim (7) to the tibial plateau (1), and an upper part (12) of the same dimensions as the external dimensions of said tibial plateau (1).  7 / - Unicompartmental knee prosthesis according to claim 6, characterized in that  the peripheral rim (7) of the tibial plateau (1) has two notches (8, 9) formed respectively at the front end and the rear end of said tibial plateau,  - The lower part (11) of the tioial pad (10) has two pins (14, 15) adapted to be housed each in one of the notches (8, 9) respectively at the peripheral rim (7) of the tibial plateau (1).  8 / - Unicompartmental knee prosthesis according to one of the preceding revenaications, in which the tibial plateau (1) has a grooved support face (the) consisting of a plurality of studs (5) aligned longitudinally and transversely, said studs being separated by longitudinal and transverse grooves (6).  9 / - Unicompartmental knee prosthesis according to one of the preceding claims, characterized in that the tibial plateau (1) and the tibial pad (10) have, seen in plan, the shape of a D inscribed in a circle, said D being truncated so as to have two longitudinal sides (la, 1D) parallel connecting two arcs of a circle forming the front (lc) and rear (nest) sides of said tibial plateau and pad.  10 / - Unicompartmental knee prosthesis according to one of the preceding claims, characterized in that  the anchoring stud (2) of the tibial plateau (1) is provided with a blind bore (4) of axis orthogonal to the upper face (1f) of said plateau, said bore emerging at said upper face,  - The tibial pad (10) has a lower face (10b) provided, projecting, with a stud (16) arranged to be housed in the blind bore (4) of the tibial plate (1).  11 / - Unicompartmental knee prosthesis according to one of the preceding claims comprising a femoral condyle (17) provided with an upper surface (17b) in contact with a conjugate shape of a femoral condyle, characterized in that the means of anchoring of said femoral condyle comprise an anchoring stud (20) extending over the contact face (17b) substantially recessed in the rear half of this contact face.  12 / - Unicompartmental knee prosthesis according to claim 11, characterized in that the femoral condyle (17) comprises two anchoring pins (22, 23) arranged on either side of the anchoring stud (20), according to a longitudinal axis of said condyle.  13 / - Unicompartmental knee prosthesis according to one of claims 11 or 12, characterized in that the femoral condyle (17) comprises, towards its front end, a return (19) having a flat internal face (19a) parallel to the 'axis of the anchoring stud (20), adapted to come to adjust against a flat surface combined with a femoral condyle having undergone adequate excision.  14 / - Unicompartmental knee prosthesis according to one of claims 11 to 13, characterized in that the femoral condyle (17) has a contact surface (17b) curved longitudinally and transversely so as to follow the shape of a condyle of femur, said femoral condyle being provided laterally with two longitudinal edges (18a, 18b) delimiting a width a adapted to accommodate a femoral condyle.