FR2813780A1 - Procedure and instrument for determining theoretical articulation interline of knee joint for prosthesis - Google Patents

Abstract

The instrument for determining at least one point on the theoretical articulation interline of a resectioned femoral epiphysis consists of a movable body (10) with a flat reference face (11) for placing against the anterior cortex of the bone epiphysis, and a mounting (15) for accessories (20) such as a micrometer gauge with a moving branch (25) and curved tip (26, 27), or a graduated slider with a plate in a plane perpendicular to its axis.

Description

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The present invention relates to the field of orthopedic surgery of the skeleton, more particularly of the rehabilitation surgery of the joints of the lower limbs and, more particularly, of the rehabilitation of the knees.

We know that, due to decay, malformation, wear, it becomes necessary to intervene surgically on the knee joint to restore the good functionality of the joint.

In some cases, this intervention can be reduced to the installation of a partial prosthesis but in most cases it is necessary to perform an intervention aimed at implanting a total prosthesis, that is to say involving all the compartments. knee.

These interventions can be considered as standard practice and give results which are generally satisfactory, even very satisfactory, for relatively long periods.

In some cases, whether it is the implantation of a single or multi-compartment prosthesis, it is necessary to resect more or less strongly the distal epiphysis of the femur so as to ensure a good adaptation of the prosthesis, so that it it can cooperate optimally with the prosthetic part implanted on the tibial plateau.

Despite the very satisfactory results which can be observed, it sometimes appears that implantation of prostheses requires, in a relatively short time, a new intervention of a complementary nature or of restoration.

In such a case, the first prosthesis dated must be removed and then leaves apparent the resected distal epiphysis which generally has to be resected again to admit the implantation of a rehabilitation or resumption prosthesis.

In such a situation, the difficulty that the orthopedic surgeon must overcome is that of being able to determine the theoretical articular line space of the knee joint, so as to choose the prosthesis which, by its geometric and dimensional characteristics, is found. better suited to reestablish, by cooperation with the tibial plateau, the maintenance of this fundamental articular spacing in order to preserve articular characteristics which are in optimal relation with the initial anatomical articulation and the various characteristics

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 geometric, including angular, bone segments constituting the limb to be rehabilitated.

However, as the distal epiphysis of the femur has already been resected and requires, or requires, a new resection intervention, the determination of the theoretical joint space becomes impossible by the absence of a reference term to be considered in relation to the tibial plateau.

The risk is then to consider the installation of a single- or multi-compartment prosthesis whose geometrical and dimensional characteristics do not correspond to the anatomical requirement and which, consequently, do not respect the theoretical joint space and lead to the definition of a prosthetic joint which is not in exact agreement with the anatomical requirements of the subject fitted.

So far, it can be considered that this particular anatomical problem, if it is not overlooked, has not been the subject of any provision aimed at solving it in a satisfactory and practical manner.

It is precisely an object of the invention to propose a method for determining at least one point of the theoretical joint space of a knee from the resected distal epiphysis of the femur, method of determination which presents the characteristic of meeting the above needs and being able to be implemented for the implantation of a knee prosthesis uni- or multicompartmental, indifferently.

To achieve the above objective, the method according to the invention is characterized in that it consists, from a profile plane of the resected femur, taken parallel to the sagittal plane and in a state of extension of the limb inferior a) to determine, from the anterior cortex of the femur, a reference line merged with said cortex and extending beyond the resected epiphysis of said femur placed in anatomical alignment position in extension with respect to the tibia , b) to draw a line perpendicular to the reference line and passing through the isometric point projecting on the bottom of the notch naturally separating the posterior condyles,

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 c) to measure the distance a included on this line between the reference line and the isometric point, d) to draw, starting from the isometric point, the line called BLUMENSATT which is tangent to the bottom of the intercondylar notch and which s 'extends beyond the resected epiphysis of the femur to cut the reference line at an angle a close to 30, e) to transfer, from the isometric point, on the BLUMENSATT line a distance b which is either equal to a, that is equal to acos30 and which defines on this line an intersection constituting a point pi of the joint line of the knee in the extended position.

The subject of the invention is also an ancillary material designed to allow the determination of at least one point of the theoretical joint space from the resected epiphysis of a femur, with a view to choosing the single or multi-compartment femoral prosthesis best suited to respecting this theoretical line spacing.

To this end, the ancillary equipment according to the invention is characterized in that it consists of - a removable fixing body # defining a plane reference face intended to be placed in abutment on the anterior cortex of the resected epiphysis of the femur, # and comprising a removable fitting end piece of an accessory, - of a set of measuring accessories comprising # a palm adaptable on the end piece and comprising a movable branch in a direction orthogonal to the flat face au- beyond the plane of which it extends and which forms at the end a terminal part, curved in the direction of the plane of said planar face, # and a graduated slide adjustable adaptably on the end piece to extend beyond the resected epiphysis of the femur and carrying a determination plate occupying a plane perpendicular to the axis of the slide and extending beyond the plane passing through the plane reference face.

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 Various other characteristics will emerge from the description given below with reference to the appended drawings which show, by way of nonlimiting examples, embodiments and implementation of the subject of the invention.

Figs. 1 and 2 are diagrams illustrating the different operating phases of the process according to the invention.

Fig. 3 is a perspective of a part of ancillary equipment for implementing the method.

Fig. 4 is a perspective of another part of said material.

Fig. 5 is a schematic elevation showing the implementation of the material. Fig. 6 is a schematic elevation showing an alternative embodiment of said equipment.

The object of the invention aims to solve the problem which can be considered as partially illustrated by FIG. 1 showing a femur 1 whose distal epiphysis 2 has undergone a resection, shown diagrammatically by the broken line 3, to allow the fitting of a knee rehabilitation prosthesis in cooperation with a tibial plateau, whether or not fitted, which 'is not shown in fig. 1.

When, for reasons of recovery, it is necessary to proceed with the removal of this first prosthesis, it can be admitted that the epiphysis then presents itself in its conformation on the basis of resection 3, which generally requires to be continued to admit the correct implantation of a recovery prosthesis.

In such a case, the normal external anatomy of the epiphysis 2, as illustrated in phantom, is no longer available, so that the problem which arises for the surgeon is that, after new resection, to choose the correct single- or multi-compartment prosthesis which should be adapted on the newly resected epiphysis 2 to respect the theoretical joint line with respect to the tibial plateau.

The method of the invention aims to offer this possibility of determination, so that the surgeon can choose the type of femoral prosthesis best suited to respecting the theoretical anatomical configuration.

To ensure the determination of at least one point of the theoretical joint space, the method according to the invention consists in taking into account a profile plane of the resected femur as it appears in FIG. 1, which profile is taken parallel to the

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 sagittal plane of the femur 1 placed in a state of relative extension of the lower limb, for example from a conventional radiography, so that its theoretical geometric axis such as A can be considered to be more or less aligned with the theoretical axis B of the tibia not shown.

The method of the invention consists in determining, from such a profile plane, a reference line L1 defined in the extension of the anterior cortex 4 of the femur 1 and extending beyond the resected epiphysis 2 The method then consists in drawing on the profile plane, a line LZ which is perpendicular to the reference line L1 and which passes through the isometric point 5 projecting on the bottom of the intercondylar notch 6 naturally separating the posterior condyles represented for mixed line memory by the reference 7 but which in practice is lacking due to the resection carried out for the installation of the previous prosthesis.

In the above state, the method of the invention then consists in taking the measurement of the distance a taken on the line LZ and comprised between the isometric point 5 and the reference line L1.

The method of the invention then consists, from the profile plane, in drawing the line known as BLUMENSATT L3 which, from isometric point 5, is naturally tangent to the bottom of the intercondylar notch 6. Line L3 s' extends beyond the resected epiphysis 2 of the femur and cuts the reference line L1 at an angle a close to 30 which represents an approximate anatomical constant observable in all subjects within a few degrees.

According to a provision of the invention, the method then consists in transferring, from isometric point 5 and on line L3, a distance b equal to a, so as to define a point of intersection p, which turns out to be a point of the knee joint space in position of extension relative to the tibial plateau.

According to an alternative embodiment, the method consists in drawing a line L4 passing through the isometric point 5 and parallel to the reference line L ,, and in measuring on this line a distance corresponding to the measurement acos30, so as to determine a point 8 from which a line LS is drawn perpendicular to the line L4 and to the reference line L1. Line LS intersects line L3 exactly at point pi which determines the point of the theoretical joint space of the knee joint and

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 allows the surgeon to choose the type of prosthesis best suited and adaptable on the resected epiphysis 2 of the femur 1.

In a development of the invention, the method consists, in a second phase, in considering the determination of a point of the joint space in a flexed position of the knee joint as illustrated in FIG. 2 showing a state of flexion at 90 in consideration of the axes A and B.

In this second operational phase and always starting from a profile plane of the resected femur considered parallel to the sagittal plane, the method consists in preserving the course of the line L1, as said previously, as well as that of the line L2 which is however extended, beyond isometric point 5, opposite line L1.

The method then consists in drawing, from the isometric point 5 and on the extension L2, a distance c equal to '/ z of a and which defines on the line L2 an intersection point p2 which constitutes the point of the line spacing theoretical knee joint in flexed position which can be materialized by a line L6 parallel to the line L1 and passing through the point p2.

The implementation of this second phase of the method according to the invention makes it possible to have two points which materialize, in the absence of any reference and on a theoretical appraisal diagram, the theoretical joint spacing of the knee joint concerned considered in extension position and in flexion position.

These two points of determination turn out to be sufficient to provide the surgeon with the reference considerations allowing him to make the choice of the unicompartmental or pluricompartmental prosthesis best suited to the implant recovery required to reconstruct the artificial joint of the dilapidated knee.

The invention also relates to ancillary equipment intended to allow the practical determination of at least one point of the theoretical joint space of a knee whose distal epiphysis of the femur is in the state of resection along the line 3 as a result of the previous implantation of a first single or multi-compartment prosthesis which should be replaced.

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 For the implementation of the above method, the ancillary equipment according to the invention comprises, as illustrated by the fig. 3, a body 10 for removable attachment to the femur 1 and, more particularly in relation to the anterior cortex 4 of the latter for which the body 1 delimits a flat reference face 11. The attachment body 10 can have any shape in plan adapted geometrical and include removable bone fixing means involving, for example, conventional screws which are mounted while being engaged in holes 12 which the body 10 presents.

In consideration of an implantation on a femur, the body 10 comprises a so-called high part 13 and a so-called low part 14 which is provided with a mounting end piece 15 forming an integral part with the body 10 or attached to the latter in particular by the 'through at least one screw 16.

The means for fixing the end piece 15 on the body 10 must be considered as being assembled to ensure the establishment of an anchoring free from any degree of freedom.

The nozzle 15 defines a housing 17 capable of ensuring the removable adaptation of an accessory 20 for measuring and determining the geometric considerations previously stated. In the example according to fig. 3, the accessory 20 is constituted by a palm including a rigid and fixed branch 21 which is adapted in the housing 17 in which it can be immobilized, both angularly and axially, by means of a blocking member 22. The fixed branch 21 of the palm bears a measuring vernier 23 capable of being moved by means of a button 24 so as to slide, in a direction perpendicular to the plane reference face 11, a movable branch 25 s' extending beyond the plane passing through the face 11 and comprising an end portion 26 oriented in the direction of said plane. The end portion 26 is preferably provided with an end tip 27 called a palpation.

The vernier 23 is provided with a graduated scale 28 which can be moved in relation to an index or mark 29 and which is chosen to provide a distance measurement, for example but not exclusively established on the basis of a metric submultiple.

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 Fig. 4 shows that the ancillary equipment can also admit the adaptation of a second accessory 20 which comprises a slide 30 provided with a graduated rule 31 and which can be immobilized angularly and axially in the housing 17 of the end piece 15 by the intermediate of the blocking member 22. The graduated rule 31 can be appreciated in position with respect to a fixed reference such as an index or a mark which can, if necessary, be constituted by a flat face such as the face 15a of the end piece 15. The slide 30 can therefore be adjusted in relative displacement on the axis zx 'defining the housing 17. The graduated rule 31 determines a displacement factor which is preferably chosen in correspondence with the rule 28 of the vernier 30 by being affected by a transposition factor which is for example acos30.

The slide 30 is provided, at its end part extending beyond the part 14 of the body 10, with a plate 32 called determination plate which can be constituted by a simple plate or if necessary by a U-shaped plate as illustrated in fig. 4, so as to allow indifferent use for determining a point of the joint space in the case of fitting a unicompartmental or pluricompartmental recovery prosthesis.

The use of ancillary equipment according to fig. 3 and 4 for carrying out the process described with reference to FIGS. 1 and 2, consists in adapting, as shown in fig. 5, the body 10 by the flat reference face 11 on the anterior cortex 4 of the femur 2 by means, for example, of two screws 33.

The body 10 is then provided with the accessory 20 constituted by the palm which is mounted in the endpiece 15 by the fixed branch 21 so as to substantially place the tip 27 of the movable branch 25 in alignment with the isometric point 5.

In this situation, the vernier 23 is operated by the button 24 so as to bring a surface contact between the tip 27 and the isometric point 5, which makes it possible to determine the measurement a comprised between said isometric point 5 and the anterior cortex 4 The appreciation of this measurement is carried out by reading the vernier 23 which provides a precise indication of the measurement of the distance a.

By deduction and at this stage of the commissioning of the ancillary equipment, the practitioner can assess the positioning of the point p2 from the measurement offered by

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 the vernier 23 to which it is advisable to add half of the distance a as previously mentioned.

At this stage of the determination, as illustrated in FIG. 6, the palm 20 is removed from the end piece 15 to be replaced by the second accessory according to FIG. 4, which is mounted in the housing 17 by the slide 30 which is adjusted by means of the graduated rule 31 so as to reveal, with respect to the index 15a, the measurement corresponding to that provided by the vernier 23 and which is transposed to correspond to the application of the acos30 factor.

The position of the graduated rule is maintained by means of the blocking member 22, so that the pallet 32 occupies the plane passing through the line LS providing the reference for the point of determination of the articular spacing of the joint knee in the extended position.

By this means the practitioner is able to determine the choice of prosthesis and this choice can be supplemented by the transposed knowledge of reading the vernier 23 providing the overall measurement of the distances a and c.

According to an alternative embodiment illustrated in FIG. 5, the vernier 23 called "main" is associated with a vernier 34 called "secondary" which allows, by an eyepiece or the like 35, to determine an axis yy 'parallel to the cortex 4 and which can be placed at a distance al equal to 1/3 of the overall distance a from line L1 or cortex 4 to determine the optimal location of the medullary axis of the femur.

The invention is not limited to the examples described and shown since various modifications can be made thereto without departing from its scope.

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Claims (10)

 CLAIMS 1- Method for determining at least one point of the theoretical joint space of a knee from the resected distal epiphysis of the femur, with a view to choosing the type of femoral prosthesis best suited to respecting this spacing , characterized in that it consists, from a profile plane of said resected femur, taken parallel to the sagittal plane and in a state of extension of the lower limb a) to be determined, from the anterior cortex of the femur, a reference line (L1) merged with said cortex (4) and extending beyond the epiphysis (2) resected from said femur placed in position of anatomical alignment in extension with respect to the tibia, b) to draw a line (L2) perpendicular to the reference line and passing through the isometric point (5) projecting from the bottom of the notch (6) naturally separating the posterior condyles, c) measuring the distance (a) included on this line between line of reference and the isometric point, d) to draw, starting from the isometric point, the line (L3) called of BLUMENSATT which is tangent to the bottom of the intercondylar notch and which extends beyond the resected epiphysis of femur to cut the reference line at an angle (oc) close to 30, e) to transfer, from the isometric point, on the BLUMENSATT line a distance (b) which is either equal to a, or equal to acos30 and which defines on this line an intersection constituting a point (pi) of the joint line of the knee in the extended position. 2 - Method according to claim 1, characterized in that it consists in drawing, from the isometric point (5), a line (L4) parallel to the line (L1), to transfer on this line a distance equal to acos30 to define a point of intersection (8) then to draw, from this point (8), a line (L5) perpendicular to the line (L4) and which comes to cut the line (L3) with which it determines the point (pi). <Desc / Clms Page number 11>  3 - Method according to claim 1 or 2, characterized in that it consists, in an additional step and in consideration of a profile plane of the resected femur, parallel to the sagittal plane and in a state of flexion at 90 of the lower limb - to extend the line (L2) perpendicular to the line (L1) and passing through the isometric point (5), beyond said point, - to draw from said isometric point a distance (c) equal to a / 2 which defines on said extension an intersection constituting the point (P2) of the knee joint space in the flexion position. 4 - Method according to claim 3, characterized in that it consists in drawing through the point (P2) a line parallel (L6) to the reference line and which materializes the position of the joint space plane in the position of knee flexion. 5 - Method according to one of claims 1 to 4, characterized in that it is used for the determination of the joint space in order to choose a unicompartmental femoral prosthesis. 6 - Method according to one of claims 1 to 4, characterized in that it is used for determining the joint space in order to choose a total femoral prosthesis. 7 - Ancillary equipment for the determination of at least one point of the theoretical joint line of the resected epiphysis of a femur with a view to choosing the femoral prosthesis best suited to respecting this line spacing, characterized in that it consists of - a removable fixing body (10) # defining a flat reference face (11) intended to be placed in abutment on the anterior cortex (4) of the resected epiphysis (2) of the femur, # and comprising an end piece (15) for detachably mounting an accessory (20), - a set of measuring accessories comprising # a palm adaptable on the end piece and comprising a branch (25) movable in a direction orthogonal to the face plane beyond the plane of which it extends and which forms an end part <Desc / Clms Page number 12>  terminal (26), (27) curved in the direction of the plane of said planar face, and a graduated slide (30) adaptably adjustable on the end piece to extend beyond the resected epiphysis of the femur and carrying a determination plate (32) occupying a plane perpendicular to the axis of the slide and extending beyond the plane passing through the plane reference face. 8 - ancillary equipment according to claim 7, characterized in that the mounting tip defines a housing (17) capable of receiving either the fixed branch (21) of the palm, or the slide (30) in a position of angular and axial immobilization adjustable by means of an adjustment member (22) adapted to the end piece. 9 - Ancillary equipment according to claim 7 or 8, characterized in that the palm comprises a vernier (23) for measuring the distance between the plane of the reference plane face (11) and that passing through the curved end part of the mobile arm of the palm and in that the slide (30) has a graduated rule (31) established on the basis of a correspondence with the measuring vernier including a transposition factor acos30. 10 - Ancillary equipment according to one of claims 7 to 9, characterized in that the palm comprises a vernier (34) said secondary relative to the vernier (23) said main, in the same direction as the latter, maneuverable independently and capable of determine, compared to the same reference plane, a fraction of the measurement established by the main vernier.