FR2632516A1 - Single-compartment knee prosthesis comprising a tibial plate with metal seat - Google Patents

Abstract

The invention relates to a single-compartment knee prosthesis cosisting of a metal femoral prosthesis which matches the elliptical anatomy of the condyle and is articulated on a tibial prosthesis 4 which matches the shape of a semicylindrical plate divided into two separate thicknesses, one 4a of which, called the seat, is manufactured from metal material and is used as an anchoring support on the tibia, and the other 4b of which, called the bearing, is manufactured from a polymer material and is used as a support surface for the condyle prosthesis. This prosthesis is noteworthy in that the seat 4a and the bearing 4b of the aforementioned tibial plate 4 are provided, on their contact faces, with tenon 5b and mortice 5a assembly means allowing fitting and/or removal of bearings 5b on the same seat 4a. The tenon and mortice parts of the said assembly means are obtained preferably from semicylindrical thicknesses which are concentric with the semicylindrical plate of the tibial prosthesis 4. Applications: single-compartment knee prostheses with a tibial plate.

Description

MONOCOMPARTIMENTAL KNEE PROSTHESIS COMPRISING A TIBIAL TRAY A
METAL SEAT
The present invention relates to the surgical field and relates more specifically to internal prostheses which employ osteosynthesis material making it possible to reproduce the shape and, if possible, the function of bone fragments of the human skeleton.

 The invention relates more particularly to a monocompartmental knee prosthesis of the type of this constituted by a metallic femoral prosthesis adopting the elliptical anatomy of the femoral condyle and articulated on a tibial prosthesis adopting the shape of a semi-cylindrical plate having a superior surface. concave.

 A prosthesis of this kind has already been described and represented in French patent application n. 2,575,920. This knee prosthesis is made up of a condylar element, a metal plate or armor cup intended to maintain a tibial element made of very high density polyethylene. This armor cup, of variable height, comprises in the bottom, grooves cooperating with an orthopedic cement and a Longitudinal window intended to receive hooking pins adapted to hang the element -tibial to your armor cup and to anchor this Tibial element in the upper part of the tibia. The purpose of this prosthesis is to ensure protection of the tibial plateau, limiting the phenomena of resection, the amount of orthopedic cement used while allowing without problem the reimplantation of other prostheses.

 However, such a tibial prosthesis has a major drawback since the cup and the tibial element are both anchored in the upper part of the tibia. Also, it follows that # the tibial element is subjected, via the shielding cup, to the aforesaid tibia by an orthopedic cement. Therefore, the replacement of the tibial element requires the removal and installation of the armor cup.

 One of the main objectives of the invention is to obviate this drawback by proposing a new concept of tibial prosthesis of the Celtic type adopting the shape of a semi-cylindrical plate divided into two distinct thicknesses, one of which will be called "seat". "in the context of the present invention, is shaped in a metallic material (such as stellite) and serves as an anchoring support for the prosthesis on the tibia and the other of which, which will be called" bearing ", is shaped in a polymer material (such as very high density polyethylene RCH 1000) and serves as a (preferentially highly concave) support surface for the condylar prosthesis; Which is also shaped in stellite or in another equivalent alloy such as that sold under the trade name "HS 21".

 According to the invention, this tibial prosthesis is remarkable in that the seat and the bearing of the aforesaid tibial plateau are provided, on their contacting surfaces, with tenon and mortise assembly means allowing the installation and / or removal of bearings on the same seat.

Advantageously, these tenon and mortise assembly means allow a removable fixing of the bearing on a seat anchored by an orthopedic cement on the upper part of the tibia. We understand the advantage of the removable nature of the bearing, which undergoes a phenomenon of notable wear under the effect of repeated movements of articulation of the femoral prosthesis in abutment on the concave visible face of said bearing. In addition, it is thus possible to use only one seat height, since the height of the entire semi-cylindrical plate can be modulated only by acting on different thicknesses of bearings.

According to a preferred embodiment of the invention, the above tenon is shaped on the underside of the bearing while the mortise is shaped on the upper face of the seat. Both are made by semi-cylindrical thicknesses concentric with the semi-cylindrical plate. The fact of having the tenon and the mortise concentrically to the tibial plateau makes it possible to consolidate the connection of the seat and the landing since the latter undergoes efforts
Lateral and axial under the effect of the articulation movements of the femoral condylar prosthesis.

 According to another preferred embodiment of the invention, the edges of the tenon and the mortise are preformed in a conjugate manner to allow a force fitting of the first into the second, by exerting a simple axial pressure on the two. Thus, the edges of the tenon and the mortise adopt in section, either a trapezoidal shape or a shape of a ring shaped at mid-height.

 Although the main aspects of the invention considered to be new have been expressed above, more details concerning a preferred embodiment of a tibial prosthesis respecting the fundamental concepts of the invention will be better understood by referring to the description below and the accompanying drawings illustrating this embodiment.

On these drawings
Figure 1 is a front view of a knee portion provided with a monocomponent prosthesis.

 Figure 2 is a side view of the knee of Figure 1.

 Figure 3 is an exploded perspective view of a tibial plateau according to the invention.

 FIG. 4 is a view in vertical section along A of the plate of FIG. 3.

 FIG. 5 is a view in vertical section along B of the plate of FIG. 3.

 Figure 6 is a vertical sectional view along A of the plate of Figure 3, comprising a variant in terms of the shape of the assembly mortise.

Figure 7 is a vertical sectional view along B of the tray of Figure 3, with the same variant au of the shape of the mortise illustrated in Figure 6
Figures 1 and 2 illustrate the region of a knee comprising the joint of the femur 1 with the tibia 2, in front of which is the kneecap and behind which pass the vessels and nerves of the leg. The articular surface of the femur 1 is formed of two convex condyles internal la and external lb hinging with the tibial plates 2a and 2b.

 The present invention relates to arthroplasty interventions aimed at rendering its functional value at the knee joint, in particular in the present case for restoring the articular surfaces by a monocompartmental prosthesis comprising a femoral prosthesis 3 articulated on a tibial prosthesis 4 .

 The femoral prosthesis 3 is shaped in a metallic material such as the stellite and adopts the elliptical anatomy of the internal condyle la.

 The tibial prosthesis 4, illustrated in more detail in the drawings of FIGS. 3, 4 and 5, takes the form of a semi-cylindrical plate divided into two distinct thicknesses 4a and 4b, the first of which (4a) is called "seat" and of which La second (4b) is called "landing".

The seat 4a is shaped in stellite and serves as an anchoring support for the bearing 4b on the tibia 2. The bearing 4b is shaped in high density polyethylene RCH 1000 and serves as a support surface for the condylar prosthesis 3. A For this purpose, the upper surface of the bearing 4b of the tibial prosthesis 4 is concave, thus facilitating the articulation movements of the condylar prosthesis 3. In the present description, the material and the handling manipulations of these two condylar prostheses 3 and tibial 4 will not be developed since they do not add anything to the good understanding of the invention, they can be produced conventionally by a skilled person specialized in the technique in question.

 The object of the present invention relates essentially to the production of the tibial prosthesis and more particularly to the removable factor of the connection between the seat 4a and the bearing 4b of said prosthesis.

 To achieve this result, the seat 4a is shaped on its upper face, with a mortise Sa adopting a semi-cylindrical configuration concentric with the semi-cylinder forming said seat. Halfway up this mortise Sa, note the presence of a ring 5a 'recessed.

 In a combined manner, the bearing 4b comprises a corresponding tenon part 5b, constituted by a semi-cylindrical thickness concentric with the semi-cylinder of the bearing 4b. On your height of this tenon, note the presence of a ring 5b 'formed in relief and intended to cooperate with the ring 5a' of the mortise Sa of the seat 4a.

The elastic nature of the material (polyethylene) constituting the bearing 4b, then allows, under the effect of an axial pressure (arrow P) exerted on your concave upper face of the bearing 4b, a force fit of the stud 5b inside of mortise Sa with commitment of
The ring 5b 'protruding inside the ring 5a' recessed. It is understood that the assembly pin 5b - mortise Sa maintains the bearing 4b relative to the seat 4a and that the assembly ring 5b 'ring 5a' ensures the retention of the post in the mortise.

 According to another form of embodiment of the invention, the annular shape of the edges of the tenon 5b and of the mortise Sa can both be replaced by a trapezoidal shape.

According to another embodiment of the invention, the edges of the post 5b can take an annular shape and those of the mortise
Its trapezoidal shape, like those shown in the drawings of Figures 6 and 7.

According to a particularly advantageous characteristic of
The invention aims to strengthen the sealing of the seat 4a on the tibial plateau 2a, the underside of the latter is provided with dovetail notches 6 arranged radially. The shape and arrangement of these notches 6 consolidate the sealing of the seat 4a on the tibial plateau 2a. The number of these radial cuts is correlated to the diameter of said tibial plateau.

This tibial prosthesis 4 offers great advantages insofar as the operations for removing and installing the tibial plate 4 can only be summed up by replacing the bearing 4b. Indeed, to replace it, it suffices to exert on the bearing 4b an axial pressure opposite to the arrow P, and this by means of a blade-shaped lever bearing for example on the upper face of L ' seat 4a, to release the post 5b from its housing inside your mortise Sa. Then simply position the new bearing 4b above the seat 4a and exert a new axial pressure in the direction of the arrow P to engage the new post 5b in the mortise Sa of
Seat 4a.

 It is understood that the tibial plateau, which has just been described and shown above, was for the purpose of disclosure rather than limitation. Of course, various modifications, modifications and improvements could be made to the example above, without however departing from the scope of the invention taken in its broadest aspects and spirit.

 In order to allow a better understanding of the drawings, a list of references with their Captions is listed below.

1 femur
the internal condyle
lb External condyle
2 Tibia
2a Internal tibial plateau
2b External tibial plateau
3 Femoral prosthesis
4 Tibial prosthesis
4a Seat of the tibial prosthesis 4
4b Landing of the tibial prosthesis 4
Sa Mortise of the seat 4a
Sa 'Ring behind the mortise
Her
5b Landing pin 4b
Sb 'Ring protruding from the post 5b
6 Radial notch of the seat 4a
Arrow P ................... Axial pressure

Claims (7)

CHARACTERIZED BY THE FACT THAT the seat (4a) and the bearing (4b) of the aforementioned tibial plate (4) are provided, on their contacting surfaces, with tenon (5b) and mortise (5a) assembly means allowing the installation and / or removal of bearings (5b) on the same seat (4a).  CLAIMS 1. Monocompartmental knee prosthesis constituted by a metallic femoral prosthesis (3) adopting the elliptical anatomy of the condyle (la) and articulated on a tibial prosthesis (4) adopting the shape of a semi-cylindrical plate divided into two distinct thicknesses one of which (4a), called the seat, is shaped in a metallic material and serves as an anchoring support on the tibia (2) and the other (4b), called the bearing, is shaped in a polymer material and serves as a surface support for the condylar prosthesis (3),  2. Prosthesis according to claim 1, CHARACTERIZED BY THE FACT THAT the tenon (5b) is shaped on the underside of the bearing (4b) and the mortise (Sa) is shaped on the top face of the seat (4a).  3. Prosthesis according to claim 1, CHARACTERIZED BY THE FACT THAT the tenon (5b) and mortise (5a) parts are obtained by semi-cylindrical thicknesses concentric with the semi-cylindrical plate of the tibial prosthesis (4).  4. Prosthesis according to claim 1, CHARACTERIZED BY THE FACT THAT the edges of the tenon (5b) and of the mortise (5a) are preformed in a combined way to allow a force fitting of the first in the second, under the effect of an axial pressure (arrow P).  5. Prosthesis according to claim 4, CHARACTERIZED BY THE FACT THAT the edges of the tenon (5b) and of the mortise (5a) are shaped so as to adopt, in section, a trapezoidal shape.  6. Prosthesis according to claim 4, CHARACTERIZED BY THE FACT THAT the edges of the tenon (5b) and the mortise (Sa) are shaped so as to adopt in section, the shape of a ring (5b ', 5a') arranged at mid-height.  7. Prosthesis according to one that any of claims 1 to 6, CHARACTERIZED BY THE FACT THAT the means for anchoring the seat (4a) of the plate on the tibia (Z) consist of notches (6) with tail 'radially arranged.