FR2729560A1 - Femoral wedge set for three-section knee prosthesis - Google Patents

Abstract

The wedge set comprises separate posterior (1) and distal (2) wedges of different thicknesses and adjustable so that the length and height of the wedges are constant and determined as a function of the maximum thickness. Both posterior and distal wedges are basically rectangular in shape, the posterior wedges having rounded corners, and the distal ones bevelled edges (2a, 2b) to conform to the shape of the prosthesis. Both sets of wedges have fixing projections (2e) to engage with matching recesses in the corresponding zones of the prosthesis, allowing the wedges to be fitted and removed after the prosthesis has been fitted.

Description

 Set of femoral wedges in particular. Dour three-compartment knee replacement prosthesis.

 The invention relates to the technical sector of prostheses for recovery, in particular three-compartment prostheses for knee recovery.

 By definition, a prosthesis has the function of replacing a prosthesis already implanted for some time and that it is necessary to change for various reasons. When removing the initial prosthesis, it is very common to remove the pieces of bone that adhere directly to the prosthetic implant considered or to the cement used to fix the implant. To fill these bone defects, we can use shims.

 Generally, these shims are divided into three ranges, so that the practitioner has, at his disposal, a set of distal shims, a set of posterior shims, sometimes a set of shims combining both the distal side and the posterior side.

 This results in a very large number of parts taking into account, in addition, the different thicknesses and the profile of the shims which is not suitable for the left side and the right side. This number is further increased in the case of an asymmetric prosthesis where, again, the shape of the wedges must be adapted to the inner and outer sides.

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

 The problem which the invention proposes to solve is to reduce this stock considerably, by creating wedges which are modular and capable of being adapted both for a right knee and for a left knee, and for internal or external compartments.

 To solve such a problem, a set of femoral wedges has been designed and developed in particular, for a three-part knee prosthesis, which includes independent posterior and distal wedges of different thicknesses and modular so that the length or height of the posterior (or distal) wedges is constant and determined according to the greatest thickness of the distal (or posterior) wedges.

Advantageously, the problem posed previously exposed, is solved by the following characteristics:
- the rear wedges are generally rectangular in shape and have a transverse side connecting with the lateral sides, by wide rounded edges.

 - The distal wedges are generally rectangular in shape, the lateral faces being bevelled to correspond very substantially to the internal profile of the condylar pads.

 - The lateral edges of the distal wedges have, on the anterior side of the prosthesis, chamfers, to adapt to the anatomical profile of said prosthesis.

 Another problem which the invention proposes to solve is to improve the fixing of these wedges, relative to the prosthetic implant.

 In fact, according to the prior art, the fixing of the shims, at the level of the prosthetic implant, is carried out by a system of screws.

Under these conditions, it is necessary to fix the wedges before the implantation is put in place. However, if the selected wedge does not correspond, the practitioner is obliged to proceed once again to the removal of the prosthesis in order to equip it with a new wedge. We understand that this way of proceeding is not rational.

 To remedy these drawbacks, the problem which the invention proposes to solve is to be able to insert and fix the wedges after the implantation is put in place, with the possibility of removing the wedge or wedges if necessary, without being forced to remove the recovery implant.

 To solve such a problem, each wedge has fixing arrangements cooperating with complementary arrangements formed in the thickness of the corresponding, posterior and distal parts of the internal profiles of the condylar pads, said arrangements being capable of allowing, on the one hand, I engagement and removal by the side of the shims after fitting the prosthesis and, on the other hand, the blocking in translation of said shims after fitting.

 Advantageously, the arrangements consist of bosses of conical longitudinal profile and of cross section of the dovetail type, said bosses being formed in overflow from the underside of the posterior and distal wedges, being able to be engaged in notches. complementary to the condylar pads, said notches being in communication with the outside of the prosthesis.

The invention is set out below in more detail using the appended drawings, in which:
Figure 1 is a perspective view of a rear wedge.

 Figure 2 is a perspective view of a distal wedge.

 Figures 3, 4, 5, 6, 7, 8, 9, 10 and 11 are views showing different combinations of distal and posterior wedges.

 Figure 12 is a longitudinal sectional view of a femoral implant equipped with a set of wedges according to the invention and according to a first embodiment.

 FIG. 13 is a plan view corresponding to FIG. 12.

 Figure 14 is a cross-sectional view taken along line 14.14 of Figure 12.

 Figure 15 is a longitudinal sectional view of a femoral implant equipped with a set of shims according to a preferred embodiment of the invention.

 FIG. 16 is a plan view corresponding to FIG. 15.

 The set of wedges finds a particularly advantageous application, in the case of a femoral implant (F) of a three-compartment knee prosthesis. The shape of the femoral implant (F), illustrated in the figures of the drawings, is given by way of non-limiting indication.

 According to the invention, the set of shims comprises posterior (1) and distal (2) shims independent of each other. The shims (1) and (2) are made in different thicknesses, determined to constitute a set of modular shims. For this purpose, the length (I) of the posterior wedges (1) is constant, whatever the thickness of the distal wedges (2), and is determined as a function of the greater thickness (E) of the distal wedges ( 2) or vice versa.

 We refer to Figures 3 to 1 1 which show different possible combinations of posterior (1) and distal (2) wedges.

 For example, in FIGS. 3, 4, 5, the posterior wedges are of the same thickness and are combined with distal wedges of different thicknesses "3", "6", "9" (for example). The same is true in FIGS. 6, 7, 8 and 9, 10, 11, where the rear wedges made in other thicknesses ("6" in FIGS. 6, 7, 8 and "9" in FIGS. 9, 10, 11) are combined with distal shims of different thicknesses "3", "6", "9".

 The posterior wedges (1) are of generally rectangular shape, and have a transverse side which is connected with the lateral sides by wide rounded edges (1a) and (it). The distal wedges (2) are also generally rectangular in shape. The lateral faces (2a) and (2b) are bevelled to correspond very substantially to the chamfers (a) (b) of the internal profiles of the condylar pads of the femoral implant. Similarly, the lateral edges of the distal wedges (2) have, on the anterior side of the implant, chamfers (2c) (2d), to adapt to the anatomical profile of said implant.

 The profile of these wedges (1) and (2), in combination with a distal clearance and a posterior clearance, allows their mounting both for the right knee and for the left knee, on the side of the internal compartment and the external compartment. These provisions therefore make it possible to have a reduced number of shims.

 The wedges are fixed by a complementary system of bosses and grooves shaped to allow, on the one hand, the engagement and withdrawal from the side, of said wedges after the prosthesis is put in place and, on the other hand, the blocking in translation of the shims after their installation.

 The underside of the posterior (1) and distal (2) wedges has, in overflow, a boss (tic) and (2e) capable of being engaged in complementary grooves or notches (3) (4), formed in the thickness of the corresponding part of the condylar pads.

 In a preferred embodiment, FIGS. 15 and 16, each of the bosses (lc) and (2e) and of the grooves (3) (4) has a conical longitudinal profile which tapers off from the outer side of the implant. The cross section of the bosses and grooves is of the dovetail type.

 According to an important characteristic, each groove (3) and (4) is in communication with the corresponding external edge of the femoral implant. Such arrangements allow, on the one hand, the engagement and removal from the side, of the shims (1) and (2) after the implant has been placed and, on the other hand, the blocking in translation of said shims after their installation in the groove, taking into account the conical profile.

 In fact, it suffices to present the wedge and to engage it in the corresponding notches (3a) and (4a), to ensure the locking in translation by jamming.

 In the embodiment illustrated in a variant, FIGS. 12, 13 and 14, the bosses (tic) and (2e) and the grooves (3) and (4) are rectilinear, each groove (3) and (4) is in communication with the corresponding external edge of the femoral implant, by a notch (3a) and (4a) of depth less than that of the corresponding groove. These notches (3a) and (4a) are therefore accessible from the edge of the implant. In this case, it suffices to shift the implant very slightly, so as to angularly engage the bosses (tic) and (2e) in the corresponding notches (3a) and (4a) to position said bosses in the grooves, thus ensuring the blocking in translation of the shims.

 Whatever the embodiment, by proceeding in a reverse manner, it is possible to remove, by the sides, the shim (s) when it is necessary to choose another thickness. These provisions therefore make it possible to avoid micro-movements as much as possible and above all allow the installation of wedges after impaction of the recovery implant.

 Obviously, without departing from the scope of the invention, other sectional profiles, bosses and grooves are provided, such as, for example, T-profiles.

The advantages clearly emerge from the description, in particular it is emphasized and recalled:
- the modular nature of the set of wedges making it possible to reduce their number considerably, thus facilitating the intervention of the practitioner,
- the possibility of placing and removing, by the sides, if necessary the shims, without being obliged to remove the entire implant.

Claims (4)

-1- Set of femoral wedges in particular, for three-compartment knee replacement prosthesis, characterized in that it comprises independent posterior (1) and distal (2) wedges of different thicknesses and modular so that the length (or height) (I) posterior (1) (or distal) wedges is constant and determined as a function of the greatest thickness of the distal (2) (or posterior) wedges. -2- Set of shims according to claim 1, characterized in that the rear shims (1) are of generally rectangular shape and have a transverse side connecting with the lateral sides, by wide rounded (la) (it). -3- Set of shims according to claim 1, characterized in that the distal shims (2) are of generally rectangular shape, the lateral faces (2a) (2b) being bevelled to correspond very substantially to the internal profile of the condylar pads.  4- shim set according to claim 3, characterized in that the lateral edges of the distal shims (2) have, on the anterior side of the prosthesis, chamfers (2c) (2d), to adapt to the anatomical profile of said prosthesis. The engagement and removal of the shims (1) (2) after fitting the prosthesis and, on the other hand, the blocking in translation of said shims after fitting.  -S set of shims according to claim 1, characterized in that each shim (1) (2) has fixing arrangements (tic) (2e) cooperating with complementary arrangements (3) (4) formed in the thickness of the corresponding posterior and distal parts of the inner profiles of the condylar pads, said arrangements being capable of allowing, on the one hand, -6- Set of shims according to claim 5, characterized in that the arrangements consist of rectilinear bosses (1c) (2e) formed in overflow from the underside of the posterior (1) and distal (2) shims, said bosses being able to be engaged in complementary notches (3) (4) of the condyles, said notches being in communication with the outside of the prosthesis, by means of a notch of lower depth (3a) (4a). -7- Set of shims according to claim 5, characterized in that the arrangements consist of bosses (tic) (2e) of conical longitudinal profile and cross section of the dovetail type, said bosses being formed in overflow of the underside of the posterior (1) and distal (2) wedges, being able to be engaged in complementary notches (3) (4) of the condyles, said notches being in communication with the outside of the prosthesis.  -8- Set of shims according to any one of claims 2, 3 and 4, characterized in that the shapes and profiles of the shims (1) and (2) are determined to be mounted indifferently on the right and left sides of the compartments internal or external.