FR2709662A1 - Tibial implant for knee prosthesis - Google Patents

Abstract

The tibial implant comprises a plateau (1) which is mounted in a seat, the said plateau having a flat outer compartment (1b) and an inner compartment (1c) whose rear edge (1c1) is raised in such a way as to guarantee the anterior stabilisation of the knee.

Description

 Table implant For knee prosthesis.

 The invention relates to a knee prosthesis of the sliding type comprising a femoral implant and a tibial implant.

 More particularly, the invention relates to a tibial implant comprising, in a perfectly known manner, a generally metallic tibial base receiving a polyethylene plate. The plate is intended to receive support and sliding, the condylar pads of the femoral element.

 In this type of prosthesis, where the femoral and tibial implants are not coupled, it is necessary to provide for stabilization of the implants, since very often the anterior cruciate ligaments are no longer present. To ensure this stabilization, the tibial plateau has certain arrangements capable of guiding the two implants during the rotation of the knee; resulting from the natural bending movement.

 In this regard, it is recalled that the knee flexion takes place in the sagittal plane, while the rotation takes place in a horizontal plane along a series of vertical axes.

 It also appears that during flexion, the femoral condyles roll and slide at the same time on the tibial plateau.

 It appears that this automatic rotation of the knee results in a slight external tibial rotation at the end of the extension movement, while the beginning of the flexion includes an internal tibial rotation.

 Generally, the arrangements of the tibial plateau are constituted either by hollow imprints formed in the internal and external compartments of the tibial plateau, or by two raised edges.

 However, these solutions are not entirely satisfactory.

 In the case of imprints, constraints appear, generated by the symmetry of the guidance, which goes against the natural movement of the knee, at the time of bending, which is accompanied by a rotational movement, relative to the internal compartment.

 In the case of two raised edges, the rotation is limited.

 The object of the invention is to remedy these drawbacks in a simple, safe and effective manner.

 The problem which the invention proposes to solve is to ensure the stability of the femoral implant relative to the tibial implant, at the time in particular of the rotation resulting from the flexion, taking into account the fact that there is no there is more anterior cruciate ligament.

 To solve such a problem, a tibial plateau has been designed and developed which has a flat external compartment and an internal compartment whose posterior edge is raised so as to ensure the anterior stabilization of the knee.

 More particularly, the problem posed of ensuring the anterior stability of the knee at the time of rotation, taking into account the shape of the meniscus, is resolved by the following characteristics.

 - the posterior edge is raised from a notch that presents the plate for the passage of the postero-internal cruciate ligament, and is extended on the side of the anterior face to find the shape of the meniscus.

 the posterior edge is extended over very substantially two thirds of the width of the corresponding external side.

 Another problem which the invention proposes to solve is to ensure the mXdio-lateral stability of the prosthesis, in the event of laxity of the lateral ligaments.

 To solve such a problem, the plate has, between said compartments, a profiled boss corresponding to the mass of the tibial spines to ensure the medio-lateral stability of the prosthesis. These provisions are advantageously combined with the characteristics defined above of the internal compartment.

 The boss profile is determined according to the condyle profile to fill the inter-condylar notch with functional play.

 The profile has longitudinally from the notch of the tibial plateau, an inclined edge extended by a very substantially planar reach connected to the front face of the plateau, by an edge of slight inclination.

The invention is set out below in more detail using the appended drawings, in which:
Figure 1 is a perspective view of the tibial plateau according to the invention.

 Figure 2 is a front view of the tray.

 Figure 3 is a cross-sectional view taken along line 3.3 of Figure 2.

 The tibial implant comprises a polyethylene plate (1) fixed by any known and appropriate means, in a generally metallic base. The plate (1) is asymmetrical in shape to take account of the asymmetry existing between the internal and external compartments of the tibial end. The tray also has a notch (la) for the passage of the posterior cruciate ligament.

 According to the invention, the plate (1) has an external compartment (lob) with a completely flat bearing and sliding surface.

The internal compartment (tic) of the tray has a posterior edge (here) which is raised so as to ensure the anterior stabilization of the knee.

 As shown in particular in FIG. 1, the rear edge (here) is raised from the notch (1a) and extends on the side of the internal face over very substantially two-thirds (L1) of the width (L) of the internal compartment (in).

 Advantageously, such characteristics are combined with a profiled boss (nest) formed at the level of the mass of tibial spines to ensure the medio-lateral stability of the prosthesis. This boss has a profile determined according to the profile of the condyles of the femoral element in order to fill the intercondylar notch with a functional clearance.

 The boss (nest) has longitudinally, from the notch (la), a profile formed by an inclined edge (ide) extended by a substantially planar surface (1d2) connected to the front face of the plate, by an edge of slight inclination ( lu3). The edges (ide) and (1d3) have longitudinally a concave radius of curvature.

 In the other shot, the profile takes up the physiological forms that exist on the tibia.

 Obviously, the plate (i) has all types of arrangements, cooperating with complementary fixing arrangements presented by the tibial base. Such arrangements are not described since they do not form part of the specific object of the invention.

 The advantages clearly emerge from the description, in particular the stability obtained and the stress relief at the time of rotation resulting from bending are emphasized and recalled.

Claims (1)

 R EVEN DICAT IONS -1- Tibial implant for knee prosthesis comprising a plate (1) mounted in a base, characterized in that the plate (1) has a flat external compartment (1b) and an internal compartment (lc), the posterior edge (1c1) is raised to ensure anterior stabilization of the knee. -2- Implant according to claim 1, characterized in that the posterior edge (here) is raised from a notch (la) that has the plate for the passage of the posterior cruciate ligament and is extended on the side of the anterior face to find the shape of the meniscus. -3- Implant according to claim 2, characterized in that the rear edge (here) is extended over very substantially two thirds of the width of the corresponding external side.  -4- Implant according to claim 1; characterized in that the plate (1) has between said compartments (1b) and (1c), a profiled boss (nest) corresponding to the mass of the tibial spines to ensure the mediolateral stability of the prosthesis. -5- Implant according to claim 4, characterized in that the profile of the boss (nest) is determined according to the profile of the condyles to fill the inter-condylar notch with a functional clearance. -6- Implant according to claim 5, characterized in that the profile (nest) has longitudinally from the notch (1a) of the tibial plateau, an inclined edge (ide) extended by a very substantially flat span (1d2) connected to the front face of the plate, by an edge of slight inclination (1d3).  -7- Implant according to any one of claims 1 to 6, characterized  in that the plate (1) is made of polyethylene and has arrangements  fixing cooperating with the complementary arrangements of the base  tibial.