FR2812540A1 - TWO-COMPARTMENTAL KNEE PROSTHESIS - Google Patents

Abstract

Bicompartmental sliding knee prosthesis comprising a femoral implant and a tibial implant: - the femoral implant (1) comprises two internal (la) and external (1b) condylar pads joined at the level of the median intercondylar notch by a solid part ( 1 C); - the condylar pads (1a, 1b) are profiled at the posterior level to envelop the bone condyles; - the condylar pads 1a, 1b) are united, at the anterior level, directly by the solid part (1c), without forming a trochlea; - the condylar pads have, at the level of the notch, posterior-stabilized guidance arrangements (1d) cooperating with complementary arrangements (2a) of part of the tibial implant; - the tibial implant has a tibial plate (2) in polyethylene mounted with limited displacement capacity in rotation in a horizontal plane, in a fixed metal tibial base (3); - the internal (1a) and external (1b) condylar pads present, seen in plan, a symmetrical profile with respect to the median axis of the implant, so that the internal condylar pad (la) for a right knee represents the external condylar pad (1b) for a left knee, and vice versa .

Description

The invention relates to the technical sector of implants

  orthopedics including knee prostheses.

  More particularly, the invention relates to a two-compartment anatomical knee sliding prosthesis comprising an implant.

femoral and a tibial implant.

  On an anatomical level, the knee joint consists of three compartments, namely: - an internal femoro-tibial compartment, - an external finoro-tibial compartment,

  - a femoro-patellar compartment.

  It turns out that osteoarthritis of the knee does not necessarily concern these

  three compartments, but is most often limited to the femoral-

  iibial, without reaching the femoro-patellar compartment. However, it appears that the total sliding knee prostheses, whatever their embodiments, are shaped to replace the three compartments, including the fenoro-patellar compartment, even if the latter is

perfectly saM.

  By experience, it turns out that in 80% of cases, the compartment

  femoro-patellar is healthy, while it was prosthetic.

  I1 as a result of mechanical complications, following a patellar stroke defect, patellar instability, subluxation, dislocation or

  fatigue fracture of the prosthetic patella, a rupture of the patellar tendon, or a rupture of the quadricepital tendon.

  These complications of the fenoro-patellar extensor represent 50% of the causes of revision of a knee prosthesis.

  To remedy these drawbacks, the Applicant of the present has proposed a solution according to which the femoral implant has two condylar pads inserted at the level of the median intercondylar notch by a solid part, said pads being profiled at the posterior level to envelop the 5 bony condyles, being united at the anterior level directly by the solid part without forming a trochlea. This absence of trochlea makes it possible to carry out a

  much more closed femoral implant to fully adapt to the bone anatomy, as well as the functional anatomy of the knee.

  1 0 From this basic conception, the problem which the invention proposes to solve is to make an original two-compartment prosthesis,

  anatomical, postero-stabilized, with high flexion and a rotating rotary plate.

  To solve such a problem, an anatomical knee-sliding knee prosthesis comprising a femoral implant and a tibial implant has been designed and developed, according to which: - the femoral implant comprises two internal and external condylar pads joined at the level of the intercondylar midline notch with a solid part; - the condylar pads are profiled at the posterior level to wrap the bony condyles; the condylar pads are joined at the anterior level directly by the solid part, without forming a trochlea; - the condylar pads have at the level of the ecbancrure posterior stabilized guide arrangements cooperating with complementary arrangements of part of the tibial implant; - the tibial implant has a tibial polyethylene plate mounted with limited displacement capacity in rotation in a horizontal plane, in a fixed metal tibial base. - the internal and external condylar pads have, in plan, a symmetrical profile with respect to the median axis of the implant, so that the internal condylar pad for a right knee represents the external condylar pad for

a left knee and vice versa.

  The invention is set out below in more detail with the aid of the figures of the accompanying drawings, in which: - Figure 1 is a schematic longitudinal section view of the two-compartment prosthesis according to the invention; - Figures 2 and 3 are side views of the femoral implant;

  - Figure 4 is a plan view of the femoral implant.

  The anatomical bicompartmental knee prosthesis comprises a femoral implant (1) mounted in abutment and sliding on a mobile tibial plateau

  (2) a tibial base (3), fixed, by any known and appropriate means.

  The femoral implant (1) comprises two internal (la) and external (lb) condylar pads joined at the level of the intercondylar midline notch.

a full part (lc).

  The condylar pads (la, lb) have, at the level of the notch, posterior stabilized guide arrangements (ld) capable of cooperating with complementary arrangements (2a) which present part of the tibial implant.

  in particular the tibial plateau (2) advantageously made of polyethylene.

  The tibial plateau (2) is mounted with limited displacement capacity in rotation in a horizontal plane in the metal tibial base (3). For example, the tibial plateau (2) may have an overflow from its underside, a median stud (2b) capable of being engaged in a cylindrical well (3a) of the tibial indemnbase (3). Also note that the tibial plateau (2) and the tibial base (3), may have additional arrangements for angular indexing.

in rotation of the plate.

  According to an important characteristic of the invention, the internal and external condylar pads (la) and (lb) are profiled at the posterior level to wrap the bony condyles which are joined at the anterior level directly

  by the solid part (lc), without forming a trochlea.

  Thus, the condylar pads (la) and (lb) have at the posterior level an external curvature (le) capable of completely enveloping the face.

posterior of the bony condyles.

  Each of the internal and external condylar pads (la) and (lb) have, on the internal side, a series of cut sides delimiting plane bearing surfaces

  (a), (b), (c), (d). These bearing surfaces are intended to cooperate with the femoral bone cuts obtained by any known and appropriate means.

  The bearing surface (a), considered from the anterior edge of the femoral implant, is located in a vertical plane corresponding substantially to that of the mechanical axis of the femur, in a knee extension position. The horizontal surface (a) is extended by the surface (b) which is inclined, constituting a connection surface oriented at an obtuse angle of approximately 20,130 with respect to said surface (a). The inclined surface (b) is extended by the surface (c) which is oriented substantially perpendicular to the surface (a). The

  surface (d) is located in the extension of surface (c), being oriented in a substantially symmetrical manner with respect to the inclined connection surface (b). The two surfaces (b) and (d) are substantially perpendicular to one another.

  As shown in particular in FIGS. 2 and 3, the internal (la) and external (lb) condylar pads, seen in plan, have a symmetrical profile with respect to the median axis of the implant, so that the internal condylar pad (la) for a right knee represents the external condylar pad for a left knee and vice versa The external edges (lai) and (lbl) of each condylar pad converge at the posterior level in the direction of the mnedian axis of the implant. Conversely, the internal edges (1a2) and (lb2) of each condylar pad form, at the posterior level, a radius of curvature oriented by a

  diverging from the center line of the implant.

  The advantages are apparent from the description.

Claims (1)

  -1- Anatomical bicompartmental knee prosthesis comprising a femoral implant and a tilbial implant: - the femoral implant (1) comprises two internal (la) and external (lb) condylar pads joined at the intercondylar midline by a solid part (l); - the condylar pads (la, lb) are profiled at the posterior level to wrap the bony condyles; - the condylar pads (la, lb) are joined, at the anterior level, directly by the solid part (lc), without forming a trochIée; - the condylar pads (la, lb) have, at the level of the notch, posterior stabilized guide arrangements (ld) cooperating with complementary arrangements (2a) of a part of the tibial implant; - The tibial implant has a tibial plate (2) made of polyethylene mounted with limited displacement capacity in rotation in a horizontal plane, in a fixed metallic fibial base (3); - the internal (la) and external (lb) condylar pads, seen in plan, have a symmetrical profile with respect to the median axis of the implant, so that the internal condylar pad (la) for a right knee represents the external condylar pad (lb) for a left knee, and vice versa -2- Two-compartment prosthesis according to claim 1, characterized in that   the outer edges of each condylar pad (la, lb) converge, at the posterior level, in the direction of the median axis of the implant.   -3- BicompartimentaJe prosthesis according to claim 1, characterized in that the internal edges of each condylar pad (la, lb) form, at the posterior level,   a radius of curvature oriented in a divergent manner relative to the median axis of the implant.   -7 -4- Two-compartment prosthesis according to claim. 1, characterized in that the complementary arrangements (ld-2a) for post-stabilized guide of the implant   Tibial are formed at the level of the rotary fibial plateau (2).