WO2005089681A2 - Device for assisting a surgeon in the selection of a femoral and/or tibial implant for the preparation of a prosthesis, and implant selection method used in said device - Google Patents

Device for assisting a surgeon in the selection of a femoral and/or tibial implant for the preparation of a prosthesis, and implant selection method used in said device Download PDF

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Publication number
WO2005089681A2
WO2005089681A2 PCT/FR2005/000332 FR2005000332W WO2005089681A2 WO 2005089681 A2 WO2005089681 A2 WO 2005089681A2 FR 2005000332 W FR2005000332 W FR 2005000332W WO 2005089681 A2 WO2005089681 A2 WO 2005089681A2
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WO
WIPO (PCT)
Prior art keywords
femoral
measuring
femur
tibia
data
Prior art date
Application number
PCT/FR2005/000332
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French (fr)
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WO2005089681A3 (en
Inventor
Gérard GOVAL
François Gougeon
Original Assignee
Sofinordest, S.A.S.
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Publication of WO2005089681A2 publication Critical patent/WO2005089681A2/en
Publication of WO2005089681A3 publication Critical patent/WO2005089681A3/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
    • A61F2/4657—Measuring instruments used for implanting artificial joints
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/06—Measuring instruments not otherwise provided for
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/14—Surgical saws ; Accessories therefor
    • A61B17/15—Guides therefor
    • A61B17/154—Guides therefor for preparing bone for knee prosthesis
    • A61B17/155—Cutting femur
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/02—Surgical instruments, devices or methods, e.g. tourniquets for holding wounds open; Tractors
    • A61B17/025—Joint distractors
    • A61B2017/0268—Joint distractors for the knee
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/06—Measuring instruments not otherwise provided for
    • A61B2090/061—Measuring instruments not otherwise provided for for measuring dimensions, e.g. length
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/06—Measuring instruments not otherwise provided for
    • A61B2090/064—Measuring instruments not otherwise provided for for measuring force, pressure or mechanical tension
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/10—Computer-aided planning, simulation or modelling of surgical operations
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/45—For evaluating or diagnosing the musculoskeletal system or teeth
    • A61B5/4528—Joints
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/45—For evaluating or diagnosing the musculoskeletal system or teeth
    • A61B5/4533—Ligaments
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/38—Joints for elbows or knees
    • A61F2/3859—Femoral components
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/38—Joints for elbows or knees
    • A61F2/389—Tibial components
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
    • A61F2002/4632—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor using computer-controlled surgery, e.g. robotic surgery
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
    • A61F2/4657—Measuring instruments used for implanting artificial joints
    • A61F2002/4658—Measuring instruments used for implanting artificial joints for measuring dimensions, e.g. length
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
    • A61F2/4657—Measuring instruments used for implanting artificial joints
    • A61F2002/4666—Measuring instruments used for implanting artificial joints for measuring force, pressure or mechanical tension
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
    • A61F2002/4688—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor having operating or control means
    • A61F2002/4696—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor having operating or control means optical

Definitions

  • the present invention relates to a device for assisting surgeons in the selection of a femoral and / or tibial implant for the preparation of a knee prosthesis placement.
  • the invention also relates to a method for selecting a femoral and / or tibial implant implemented in the aforementioned device.
  • the assistance device may also facilitate the surgeon's work in choosing the ligament tension to be applied to the patient or in determining the tibial and femoral section planes on which the various elements of the knee prosthesis will be positioned.
  • the installation of a knee prosthesis presents many difficulties for the surgeon. Indeed, one of the main objectives of knee replacement surgery is to distribute the stresses that will be exerted on the prosthesis in a homogeneous manner. The surgeon must therefore take into account in particular data relating to the patient such as, in particular, the relative position of the tibia relative to the femur, or else the particular ligamentary strength of the patient. It must also take into account the geometry of the prostheses existing on the market.
  • These devices include means of spatial location in three dimensions of the femur with respect to the tibia, the assembly operating using markers placed on the patient, said markers being associated with cameras.
  • the measurements made from the positioning means are transmitted to a computer which processes the data with a view to displaying data in three dimensions to assist the surgeon in the selection of the elements of the prosthesis.
  • these devices have various drawbacks, including the fact that at no time can the ligament tension be applied to the patient.
  • these devices using optical systems are complex to implement and it is difficult to achieve, with existing optical systems, the precision required in medical applications.
  • the present invention aims to overcome the aforementioned drawbacks and for this purpose provides a device for assisting the surgeon allowing the latter to take into account the ligament tension specific to the patient.
  • the assistance device comprises: - means for storing data relating to the patient's anatomy and data relating to the femoral and tibial implants; - spacing means between the tibia and the femur allowing the tension of the internal and external ligaments; - first means of measuring the distance between the tibia and the femur; - second means for measuring the ligament tension of the internal and external ligaments; - means for transmitting the data obtained by said measuring means; means for processing the measured and / or stored data allowing the obtaining of output data relating to the ligament tension to be applied and / or to the femoral cutting plane to be produced and / or to the dimensions of the femoral and tibial implants to be selected; - means for displaying said output data.
  • the invention also relates to a method for selecting a femoral and / or tibial implant implemented in the aforementioned device in which a step is carried out: - of measuring the optimal ligament tension; - measuring the imbalance in extension; - for measuring the imbalance in flexion.
  • a step is carried out: - of measuring the optimal ligament tension; - measuring the imbalance in extension; - for measuring the imbalance in flexion.
  • the assistance device 1 comprises means 2 for storing data relating to the anatomy of the patient and data relating to the femoral and tibial implants.
  • the data relating to the patient's anatomy can be obtained by any means known to those skilled in the art and in particular by a scanner of the patient's leg or by radiographs.
  • the data relating to the patient are in particular the relative position of the tibia and the femur and in particular the angle of the distal femoral valgus (VFD). This angle VFD can advantageously be calculated from an intramedullary guide placed at a chosen HKS angle and as a function of the space measured between the condyles of the femur.
  • the storage means 2 also store the data relating to the existing femoral and / or tibial implants, this data being able to be updated as a function of the appearance of new types of implants or of dimensions of new implants. Ancillary data is also stored.
  • Said assistance device 1 also comprises spacing means 3 between the tibia and the femur allowing the tension of the internal and external ligaments.
  • the spacing means are constituted by a tensor 4 comprising at least one bracket 5 on which is fixed a tibial pad 6 and two movable arms 7,7 '.
  • the two arms 7, 7 ′ can be moved independently along at least said stem 5 by maneuvering means 8 thus making it possible to separate the two parts of the joint and to put the internal and external ligaments in tension.
  • the assistance device 1 also includes first means 9 for measuring the distance between the tibia and the femur. These first spacing measurement means 9 comprise sensors 11 arranged at the spacing means 3 making it possible to determine the distance between each movable arm 7,7 'and the tibial pad 6 making it possible to determine the corresponding distance between the tibia and the femur.
  • the assistance device 1 also includes second means for measuring the ligament tension 10 of the internal and external ligaments. Referring to FIG. 1, it can be seen that said second measurement means 10 are arranged at each arm 7, 7 ′ of the tensor 4.
  • said second measurement means 10 consist of at least two sensors force 12 distributed over the length of each arm 7,7 'making it possible to measure the force exerted on each arm 7,7' corresponding to the ligament tension of each ligament.
  • sensors 12 At the level of the force sensors 12, it will be possible to advantageously choose sensors of the Piezoelectric type or also strain gauges.
  • two force sensors 12 are used on each arm 7, 7 ′, in this way the force exerted is measured by comparing the measurements carried out by each of said sensors 12 making it possible to overcome the problems of arrows at level of each movable arm or of the point of application of the force on each arm 7.7 'relative to the condyle heads of the femur.
  • Said assistance device also comprises means for transmitting the data 13 obtained by said measuring means 9,10.
  • These data transmission means 13 are of the wired type.
  • data transmission means 13 of radioelectric type.
  • These transmission means 13 make it possible to transmit all of the measured data to processing means 14.
  • Said processing means 14 are advantageously located in a central unit 15, the latter also grouping the storage means 2.
  • Said means of processing 14 of the measured and / or stored data makes it possible to obtain output data relating to the ligament tension to be applied and / or to the femoral section planes to be produced and / or to the optimal dimensions of the femoral and tibial implants to be selected.
  • said processing means 14 use a program based on the stored data and the data measured during the various stages of the assistance process.
  • Said device also comprises means 16 for displaying said output data. These display means 16 make it possible to display the output data in particular in the form of graphics. Of course, we can also consider displaying the data only in text form.
  • the invention also relates to a method of selecting a femoral and / or tibial implant implemented in the device for assistance 1 as mentioned above.
  • this selection process the following steps are carried out: - a measurement of the optimal ligament tension; - a measure of the imbalance in extension; - a measure of the imbalance in flexion.
  • the tibia was cut according to a resection plan so as to constitute the seat of the tibial implant.
  • the step of measuring the optimal ligament tension consists in using the spacing means 3 to distend the tibia and the femur when the knee is in flexion up to a threshold value K of ligament stiffness and to measure the ligament tension corresponding to this threshold value K.
  • the method also consists in carrying out a measurement of the imbalance in extension, this step consists in distending the tibia and the femur when the knee is in extension until obtaining internally and externally the optimal ligament tension and to measure the corresponding internal YI and external YE spacings so as to determine whether the articulation, placed in extension, is tightened internally or externally or balanced.
  • a measurement of the imbalance in flexion is also carried out which consists in distending the tibia and the femur when the knee is in flexion until obtaining internally and externally the optimal ligament tension and measuring the internal spacings XI and external XE corresponding in order to determine if the joint placed in flexion is tight internally, externally or balanced.
  • the surgeon's assistance device makes it possible to display graphs corresponding to the steps of measuring imbalance in extension or in flexion and for example graphs of the type of those of FIGS. 2 to 4. It is important to note at this level that if the difference between the value XI and XE displayed is too large, the surgeon must perform internal / external balancing in flexion. Thus if XI is greater than XE plus a constant El, the surgeon will have to perform an external relaxation and in this case it will be necessary to carry out a new measurement of the imbalance in flexion. If on the other hand XI is less than XE plus this same constant El, the surgeon will have to perform an internal relaxation.
  • the surgeon will be able to compensate by a rotation of the femur if the YI value measured in the step of measuring the imbalance in extension is less than the YE value and if the difference between YE and YI is less than the difference between XE and XI.
  • a new measurement of the bending imbalance is carried out to obtain the new values XE and XI.
  • the surgeon can also perform an internal / external balancing in extension in the case where the difference between the values YI and YE are too large.
  • the set of output data is then displayed and the surgeon can either use the data directly to prepare the pose, or impose additional constraints, for example, if he wishes a particular posterior cut, in which case he introduces these constraints and relaunches. the program.
  • additional constraints for example, if he wishes a particular posterior cut, in which case he introduces these constraints and relaunches. the program.

Abstract

The invention relates to a device for assisting a surgeon in the selection of a femoral and/or tibial implant for the preparation of a knee prosthesis placement, and to the method of selecting a femoral and/or tibial implant used in said device. According to the invention, the device comprises: means (2) for storing data relating to the anatomy of the patient and data relating to femoral and tibial implants; means (3) for moving the tibia and the femur away from one another, such that the inner and outer ligaments can be placed under tension; first means (9) for measuring the distance between the tibia and the femur; second means (10) for measuring the ligament tension in relation to the inner and outer ligaments; data-transmission means (13); data-processing means (14); and means (16) for displaying the output data.

Description

DISPOSITIF D'ASSISTANCE AU CHIRURGIEN DANS LA SELECTION DON IMPLANT FEMORAL ET/OU TIBIAL POUR LA PREPARATION D'UNE PROTHESE ET PROCEDE DE SELECTION D'IMPLANT MIS EN ŒUVRE DANS LE DISPOSITIF PRECITE La présente invention concerne un dispositif d'assistance aux chirurgiens dans la sélection d'un implant fémoral et/ou tibial pour la préparation d'une pose de prothèse de genou. L'invention concerne également un procédé de sélection d'implant fémoral et/ou tibial mis en œuvre dans le dispositif précité. Le dispositif d'assistance pourra également faciliter le travail du chirurgien dans le choix de la tension ligamentaire à appliquer au patient ou encore dans la détermination des plans de coupe tibial et fémoral sur lesquels viendront se positionner les différents éléments de la prothèse du genou. Avec les techniques actuelles, la pose d'une prothèse du genou présente de nombreuses difficultés pour le chirurgien. En effet, un des principaux objectifs des opérations d'arthroplastie du genou est de répartir de manière homogène les contraintes qui s'exerceront sur la prothèse. Le chirurgien doit donc tenir compte notamment des données relatives au patient telles que, notamment, la position relative du tibia par rapport au fémur, ou encore la force ligamentaire particulière du patient. Il doit également tenir compte de la géométrie des prothèses existant sur le marché. Pour le chirurgien, une grande difficulté sera d'obtenir une fois la prothèse choisie une bonne balance ligamentaire pour le patient tant en flexion qu'en extension. Compte tenu de l'ensemble des paramètres interdépendants entrant en jeu, on comprendra que le chirurgien pourra difficilement, sans assistance, sélectionner de manière optimale les plans de coupe, la tension ligamentaire à appliquer sur des ligaments internes et externes ou encore sélectionner précisément l'implant fémoral et/ou tibial. Ceci a pour effet que lors de la pose de la prothèse du genou, le chirurgien est régulièrement obligé de procéder à des coupes supplémentaires ou à ajouter des cales pour que les éléments de la prothèse, une fois posés, permettent une articulation correcte du genou. Pour faciliter la tache du chirurgien, il a été proposé des dispositifs d'assistance au chirurgien à partir de mesures réalisées avant la pose de la prothèse. Ces dispositifs comportent des moyens de repérage spatial en trois dimensions du fémur par rapport au tibia, l'ensemble fonctionnant grâce à des marqueurs disposés sur le patient, lesdits marqueurs étant associés à des caméras. Les mesures réalisées à partir des moyens de positionnement sont transmises à un ordinateur qui traite les données en vue d'afficher des données en trois dimensions pour aider le chirurgien à la sélection des éléments de la prothèse. Ces dispositifs présentent toutefois différents inconvénients parmi lesquels le fait qu'à aucun moment on ne peut mesurer la tension ligamentaire à appliquer au patient. De plus, ces dispositifs utilisant des systèmes optiques sont complexes à mettre en œuvre et il est difficile d'atteindre, avec les systèmes optiques existants, la précision requise dans des applications médicales. La présente invention a pour but de palier aux inconvénients précités et propose à cet effet un dispositif d'assistance au chirurgien permettant à ce dernier de prendre en compte la tension ligamentaire propre au patient. Un autre but de la présente invention est de proposer un dispositif d'assistance au chirurgien permettant de mesurer avec précision les distances relatives du fémur et du tibia. Un autre objet de la présente invention est de proposer un dispositif d'assistance au chirurgien permettant à ce dernier de réaliser une balance ligamentaire équilibrée. Un autre objet de la présente invention est de déterminer et d'afficher des données de sortie relatives aux plans de coupe du tibia et du fémur. L'invention a ainsi pour objet un dispositif d'assistance au chirurgien dans la sélection d'un plan fémoral et/ou tibial pour la préparation d'une pose de prothèse de genou. Selon l'invention, le dispositif d'assistance comprend : - des moyens de stockage de données relatives à l'anatomie du patient et de données relatives aux implants fémoral et tibial ; - des moyens d'écartement entre le tibia et le fémur permettant la mise en tension des ligaments internes et externes ; - des premiers moyens de mesure de l'écartement entre le tibia et le fémur ; - des seconds moyens de mesure de la tension ligamentaire des ligaments internes et externes ; - des moyens de transmission des données obtenues par lesdits moyens de mesure ; - des moyens de traitement des données mesurées et/ou stockées permettant l'obtention de données de sortie relatives à la tension ligamentaire à appliquer et/ou au plan de coupe fémorale à réaliser et/ou aux dimensions des implants fémoral et tibial à sélectionner ; - des moyens d'affichage desdites données de sortie. L'invention vise également un procédé de sélection d'implant fémoral et/ou tibial mis en œuvre dans le dispositif précité dans lequel on réalise une étape : - de mesure de la tension ligamentaire optimale ; - de mesure du déséquilibre en extension ; - de mesure du déséquilibre en flexion. D'autres caractéristiques et avantages de l'invention apparaîtront plus clairement à la lecture de la description ci-après d'un exemple préféré de réalisation, dans lequel la description n'est donnée qu'à titre non limitatif et en références aux dessins annexés parmi lesquels : - la figure 1 représente une vue schématique du dispositif conforme à l'invention ; - les figures 2 à 6 représentent des exemples d'affichage de données de sortie pour l'assistance au chirurgien conformes à l'invention ; En se reportant à la figure 1, on voit que le dispositif d'assistance 1 comprend des moyens de stockage 2 de données relatives à l'anatomie du patient et de données relatives aux implants fémoral et tibial. Les données relatives à l'anatomie du patient pourront être obtenues par tout moyen connu de l'homme du métier et notamment par un scanner de la jambe du patient ou encore par des radiographies. Les données relatives au patient sont notamment la position relative du tibia et du fémur et notamment l'angle du valgus fémoral distal (VFD). Cet angle VFD pourra de manière avantageuse être calculé à partir d'un guide intramédulaire placé à un angle HKS choisi et en fonction de l'espace mesuré entre les condyles du fémur. Les moyens de stockage 2 stockent également les données relatives aux implants fémoral et/ou tibial existant, ces données pouvant être réactualisées en fonction de l'apparition de nouveaux types d'implants ou de dimensions d'implants nouvelles. Des données relatives aux ancillaires sont également stockées. Ledit dispositif d'assistance 1 comprend également des moyens d'écartement 3 entre le tibia et le fémur permettant la mise en tension des ligaments internes et externes. Dans le mode de réalisation préféré représenté dans la figure 1, les moyens d'écartement sont constitués par un tenseur 4 comportant au moins une potence 5 sur laquelle est fixée un patin tibial 6 et deux bras déplaçâmes 7,7'. Les deux bras 7,7' peuvent être déplacés indépendamment le long au moins de ladite potence 5 par des moyens de manœuvre 8 permettant ainsi d'écarter les deux parties de l'articulation et de mettre les ligaments internes et externes en tension. Le dispositif d'assistance 1 comprend également des premiers moyens de mesure 9 de l'écartement entre le tibia et le fémur. Ces premiers moyens de mesure de l'écartement 9 comprennent des capteurs 11 disposés au niveau des moyens d'écartement 3 permettant de déterminer la distance entre chaque bras deplaçable 7,7' et le patin tibial 6 permettant de déterminer la distance correspondante entre le tibia et le fémur. Le dispositif d'assistance 1 comprend également des seconds moyens de mesure de la tension ligamentaire 10 des ligaments internes et externes. En se reportant à la figure 1, on voit que lesdits seconds moyens de mesure 10 sont disposés au niveau de chaque bras 7,7' du tenseur 4. De manière avantageuse, lesdits seconds moyens de mesure 10 sont constitués d'au moins deux capteurs de force 12 répartis sur la longueur de chaque bras 7,7' permettant de mesurer la force exercée sur chaque bras 7,7' correspondant à la tension ligamentaire de chaque ligament. Au niveau des capteurs de force 12, on pourra choisir de manière avantageuse des capteurs du type Piezo électrique ou encore des jauges de contrainte. Dans le mode de réalisation préféré, on utilise deux capteurs de force 12 sur chaque bras 7,7', de cette manière on mesure la force exercée en comparant les mesures effectuées par chacun desdits capteurs 12 permettant de s'affranchir des problèmes de flèches au niveau de chaque bras deplaçable ou du point d'application de la force sur chaque bras 7,7' par rapport aux têtes de condyle du fémur. Cela étant, on pourra envisager dans un autre mode de réalisation du dispositif conforme à l'invention soit un nombre de capteurs 12 plus élevé pour chaque bras 7,7' soit encore un seul capteur par bras 7,7'. Ledit dispositif d'assistance comprend également des moyens de transmission des données 13 obtenues par lesdits moyens de mesure 9,10. Ces moyens de transmission de données 13 sont de type filaire. Toutefois, on pourra également envisager des moyens de transmission de données 13 de type radioélectrique. Ces moyens de transmission 13 permettent de transmettre l'ensemble des données mesurées vers des moyens de traitement 14. Lesdits moyens de traitement 14 sont de manière avantageuse situés dans une unité centrale 15, cette dernière regroupant également les moyens de stockage 2. Lesdits moyens de traitement 14 des données mesurées et/ou stockées permettent l'obtention de données de sortie relatives à la tension ligamentaire à appliquer et/ou aux plans de coupe fémorale à réaliser et/ou aux dimensions optimales des implants fémoral et tibial à sélectionner. On pourra également afficher les tensions ligamentaires attendues avec les valeurs et données de coupe et de dimensions d'implants. A cette fin, lesdits moyens de traitement 14 utilisent un programme basé sur les données stockées et les données mesurées au cours des différentes étapes du procédé d'assistance. Ledit dispositif comprend également des moyens d'affichage 16 desdites données de sortie. Ces moyens d'affichage 16 permettent d'afficher les données de sortie notamment sous forme de graphiques. Bien entendu, on pourra également envisager d'afficher les données uniquement sous forme de textes. En se reportant principalement aux figures 5 et 6, on voit des exemples de graphiques produits par lesdits moyens d'affichage 16. L'invention concerne également un procédé de sélection d'implant fémoral et/ou tibial mis en œuvre dans le dispositif d'assistance 1 tel que précité. Dans ce procédé de sélection, on réalise les étapes suivantes : - une mesure de la tension ligamentaire optimale ; - une mesure du déséquilibre en extension ; - une mesure du déséquilibre en flexion. Préalablement à la réalisation des étapes précitées, le tibia a été coupé selon un plan de résection de manière à constituer l'assise de l'implant tibial. Différentes données anatomiques ont également été mesurées et notamment l'épaisseur antéro-postérieure du fémur, l'écartement condylien et le valgus fémoral distal et l'angle HKS. L'étape de mesure de la tension ligamentaire optimale consiste à l'aide des moyens d'écartement 3 à distendre le tibia et le fémur lorsque le genou est en flexion jusqu'à une valeur seuil K de rigidité ligamentaire et à mesurer la tension ligamentaire correspondant à cette valeur seuil K. Le procédé consiste également à réaliser une mesure du déséquilibre en extension, cette étape consiste à distendre le tibia et le fémur lorsque le genou est en extension jusqu'à obtenir en interne et en externe la tension ligamentaire optimale et à mesurer les écartements interne YI et externe YE correspondant de manière à déterminer si l'articulation, placée en extension, est serrée en interne ou en externe ou équilibrée. Selon le procédé, on réalise également une mesure du déséquilibre en flexion qui consiste à distendre le tibia et le fémur lorsque le genou est en flexion jusqu'à obtenir en interne et en externe la tension ligamentaire optimale et à mesurer les écartements interne XI et externe XE correspondant de manière à déterminer si l'articulation placée en flexion est serrée en interne, en externe ou équilibrée. Le dispositif d'assistance au chirurgien permet d'afficher des graphiques correspondant aux étapes de mesure de déséquilibre en extension ou en flexion et par exemple des graphiques du type de ceux des figures 2 à 4. Il est important de noter à ce niveau que si l'écart entre la valeur XI et XE affiché est trop important, le chirurgien devra réaliser un équilibrage interne/ externe en flexion. Ainsi si XI est supérieur à XE plus une constante El le chirurgien devra réaliser un relâchement externe et il faudra dans ce cas procéder à une nouvelle mesure du déséquilibre en flexion. Si par contre XI est inférieur à XE plus cette même constante El, le chirurgien devra réaliser un relâchement interne. Il faut souligner qu'éventuellement, le chirurgien pourra compenser par une rotation du fémur si la valeur YI mesurée dans l'étape de mesure du déséquilibre en extension est inférieure à la valeur YE et si la différence entre YE et YI est inférieure à la différence entre XE et XI. Il y aura également la possibilité de compenser lorsque XI est inférieure à XE et que YI est supérieur ou égal à YE. Lorsque ces opérations sont, si nécessaires, effectuées, on procède à une nouvelle mesure du déséquilibre en flexion pour obtenir les nouvelles valeurs XE et XI. Le chirurgien peut également réaliser un équilibrage interne/externe en extension dans le cas où l'écart entre les valeurs YI et YE sont trop importantes. Pour ce faire, il effectue un relâchement interne si YI est inférieur à YE plus une constante El ou un relâchement externe si YI est supérieur à YE plus une constante E2. De la même manière que pour l'équilibrage interne/externe en flexion, il faudra réaliser une nouvelle mesure du déséquilibre en extension de manière à déterminer les nouvelles valeurs YE et YI. A partir des différentes valeurs XI, XE et YE,YI , le programme calcule ensuite des valeurs X et Y avec X = (XE + XI) / 2 et Y = (YE + YI) / 2 avec VFD égal à l'angle du valgus fémoral distal et rot égal à l'angle de rotation du fémur que le chirurgien a choisi en cas de déséquilibre original interne/externe en flexion. A partir de ces données ainsi que des données relatives aux tailles des implants ou aux épaisseurs de coupes possibles au niveau de la coupe postérieure du fémur et de la coupe distale, le programme propose par l'intermédiaire des moyens d'affichage au chirurgien différentes données pour que celui-ci puisse réaliser une pose optimale de la prothèse de genou. Le programme calcule, selon un mode préféré : - l'épaisseur de la coupe postérieure fémorale selon l'équation : CP = taille fémur - taille implant fémoral, - la taille du polyéthylène selon l'équation : P = X + CP - IFP - ET avec : CP = épaisseur de la coupe postérieure, IFP = épaisseur implant fémoral postérieur, ET = épaisseur implant tibial, - la taille de la coupe distale selon l'équation : CD = IFD + P + ET + Y avec : IFD = taille implant fémoral distal, P = épaisseur du polyéthylène, ET = épaisseur implant tibial, - l'angle de rotation du fémur, - la tension ligamentaire attendue compte tenu des valeurs des autres données affichées. L'ensemble des données de sortie est ensuite affiché et le chirurgien peut soit utiliser les données directement pour préparer la pose, soit imposer des contraintes supplémentaires, par exemple, s'il souhaite une coupe postérieure particulière, auquel cas il introduit ces contraintes et relance le programme. Bien entendu, d'autres modes de réalisation à la portée de l'homme de l'art auraient pu être envisagés sans pour autant sortir du cadre de l'invention définie par les revendications ci-après. DEVICE FOR ASSISTING A SURGEON IN THE SELECTION OF A FEMORAL AND / OR TIBIAL IMPLANT FOR THE PREPARATION OF A PROSTHESIS AND METHOD FOR SELECTING AN IMPLANT USED IN THE ABOVE DEVICE The present invention relates to a device for assisting surgeons in the selection of a femoral and / or tibial implant for the preparation of a knee prosthesis placement. The invention also relates to a method for selecting a femoral and / or tibial implant implemented in the aforementioned device. The assistance device may also facilitate the surgeon's work in choosing the ligament tension to be applied to the patient or in determining the tibial and femoral section planes on which the various elements of the knee prosthesis will be positioned. With current techniques, the installation of a knee prosthesis presents many difficulties for the surgeon. Indeed, one of the main objectives of knee replacement surgery is to distribute the stresses that will be exerted on the prosthesis in a homogeneous manner. The surgeon must therefore take into account in particular data relating to the patient such as, in particular, the relative position of the tibia relative to the femur, or else the particular ligamentary strength of the patient. It must also take into account the geometry of the prostheses existing on the market. For the surgeon, a great difficulty will be to obtain, once the prosthesis chosen, a good ligament balance for the patient both in flexion and in extension. Given all of the interdependent parameters involved, it will be understood that the surgeon will find it difficult, without assistance, to optimally select the cutting planes, the ligament tension to be apply to internal and external ligaments or else select precisely the femoral and / or tibial implant. This has the effect that when placing the knee prosthesis, the surgeon is regularly obliged to make additional cuts or to add shims so that the elements of the prosthesis, once placed, allow correct articulation of the knee. To facilitate the surgeon's task, devices have been proposed to assist the surgeon on the basis of measurements made before fitting the prosthesis. These devices include means of spatial location in three dimensions of the femur with respect to the tibia, the assembly operating using markers placed on the patient, said markers being associated with cameras. The measurements made from the positioning means are transmitted to a computer which processes the data with a view to displaying data in three dimensions to assist the surgeon in the selection of the elements of the prosthesis. However, these devices have various drawbacks, including the fact that at no time can the ligament tension be applied to the patient. In addition, these devices using optical systems are complex to implement and it is difficult to achieve, with existing optical systems, the precision required in medical applications. The present invention aims to overcome the aforementioned drawbacks and for this purpose provides a device for assisting the surgeon allowing the latter to take into account the ligament tension specific to the patient. Another object of the present invention is to provide a device for assisting the surgeon making it possible to accurately measure the relative distances of the femur and the tibia. Another object of the present invention is to provide a device for assisting the surgeon enabling the latter to produce a balanced ligament balance. Another object of the present invention is to determine and display output data relating to the cutting planes of the tibia and the femur. The invention thus relates to a device for assisting the surgeon in the selection of a femoral and / or tibial plane for the preparation of a knee prosthesis placement. According to the invention, the assistance device comprises: - means for storing data relating to the patient's anatomy and data relating to the femoral and tibial implants; - spacing means between the tibia and the femur allowing the tension of the internal and external ligaments; - first means of measuring the distance between the tibia and the femur; - second means for measuring the ligament tension of the internal and external ligaments; - means for transmitting the data obtained by said measuring means; means for processing the measured and / or stored data allowing the obtaining of output data relating to the ligament tension to be applied and / or to the femoral cutting plane to be produced and / or to the dimensions of the femoral and tibial implants to be selected; - means for displaying said output data. The invention also relates to a method for selecting a femoral and / or tibial implant implemented in the aforementioned device in which a step is carried out: - of measuring the optimal ligament tension; - measuring the imbalance in extension; - for measuring the imbalance in flexion. Other characteristics and advantages of the invention will appear more clearly on reading the description below of a preferred embodiment, in which the description is given only without limitation and with reference to the accompanying drawings. among which: - Figure 1 shows a schematic view of the device according to the invention; - Figures 2 to 6 show examples of display of output data for assistance to the surgeon according to the invention; Referring to FIG. 1, it can be seen that the assistance device 1 comprises means 2 for storing data relating to the anatomy of the patient and data relating to the femoral and tibial implants. The data relating to the patient's anatomy can be obtained by any means known to those skilled in the art and in particular by a scanner of the patient's leg or by radiographs. The data relating to the patient are in particular the relative position of the tibia and the femur and in particular the angle of the distal femoral valgus (VFD). This angle VFD can advantageously be calculated from an intramedullary guide placed at a chosen HKS angle and as a function of the space measured between the condyles of the femur. The storage means 2 also store the data relating to the existing femoral and / or tibial implants, this data being able to be updated as a function of the appearance of new types of implants or of dimensions of new implants. Ancillary data is also stored. Said assistance device 1 also comprises spacing means 3 between the tibia and the femur allowing the tension of the internal and external ligaments. In the preferred embodiment shown in Figure 1, the spacing means are constituted by a tensor 4 comprising at least one bracket 5 on which is fixed a tibial pad 6 and two movable arms 7,7 '. The two arms 7, 7 ′ can be moved independently along at least said stem 5 by maneuvering means 8 thus making it possible to separate the two parts of the joint and to put the internal and external ligaments in tension. The assistance device 1 also includes first means 9 for measuring the distance between the tibia and the femur. These first spacing measurement means 9 comprise sensors 11 arranged at the spacing means 3 making it possible to determine the distance between each movable arm 7,7 'and the tibial pad 6 making it possible to determine the corresponding distance between the tibia and the femur. The assistance device 1 also includes second means for measuring the ligament tension 10 of the internal and external ligaments. Referring to FIG. 1, it can be seen that said second measurement means 10 are arranged at each arm 7, 7 ′ of the tensor 4. Advantageously, said second measurement means 10 consist of at least two sensors force 12 distributed over the length of each arm 7,7 'making it possible to measure the force exerted on each arm 7,7' corresponding to the ligament tension of each ligament. At the level of the force sensors 12, it will be possible to advantageously choose sensors of the Piezoelectric type or also strain gauges. In the preferred embodiment, two force sensors 12 are used on each arm 7, 7 ′, in this way the force exerted is measured by comparing the measurements carried out by each of said sensors 12 making it possible to overcome the problems of arrows at level of each movable arm or of the point of application of the force on each arm 7.7 'relative to the condyle heads of the femur. However, in another embodiment of the device according to the invention, it is possible to envisage either a higher number of sensors 12 for each arm 7.7 ′ or even a single sensor per arm 7.7 ′. Said assistance device also comprises means for transmitting the data 13 obtained by said measuring means 9,10. These data transmission means 13 are of the wired type. However, it is also possible to envisage data transmission means 13 of radioelectric type. These transmission means 13 make it possible to transmit all of the measured data to processing means 14. Said processing means 14 are advantageously located in a central unit 15, the latter also grouping the storage means 2. Said means of processing 14 of the measured and / or stored data makes it possible to obtain output data relating to the ligament tension to be applied and / or to the femoral section planes to be produced and / or to the optimal dimensions of the femoral and tibial implants to be selected. We can also display the expected ligament tensions with the values and data of cut and implant dimensions. To this end, said processing means 14 use a program based on the stored data and the data measured during the various stages of the assistance process. Said device also comprises means 16 for displaying said output data. These display means 16 make it possible to display the output data in particular in the form of graphics. Of course, we can also consider displaying the data only in text form. Referring mainly to Figures 5 and 6, we see examples of graphs produced by said display means 16. The invention also relates to a method of selecting a femoral and / or tibial implant implemented in the device for assistance 1 as mentioned above. In this selection process, the following steps are carried out: - a measurement of the optimal ligament tension; - a measure of the imbalance in extension; - a measure of the imbalance in flexion. Prior to carrying out the above steps, the tibia was cut according to a resection plan so as to constitute the seat of the tibial implant. Various anatomical data were also measured, in particular the anteroposterior thickness of the femur, the condylar spacing and the distal femoral valgus and the HKS angle. The step of measuring the optimal ligament tension consists in using the spacing means 3 to distend the tibia and the femur when the knee is in flexion up to a threshold value K of ligament stiffness and to measure the ligament tension corresponding to this threshold value K. The method also consists in carrying out a measurement of the imbalance in extension, this step consists in distending the tibia and the femur when the knee is in extension until obtaining internally and externally the optimal ligament tension and to measure the corresponding internal YI and external YE spacings so as to determine whether the articulation, placed in extension, is tightened internally or externally or balanced. According to the method, a measurement of the imbalance in flexion is also carried out which consists in distending the tibia and the femur when the knee is in flexion until obtaining internally and externally the optimal ligament tension and measuring the internal spacings XI and external XE corresponding in order to determine if the joint placed in flexion is tight internally, externally or balanced. The surgeon's assistance device makes it possible to display graphs corresponding to the steps of measuring imbalance in extension or in flexion and for example graphs of the type of those of FIGS. 2 to 4. It is important to note at this level that if the difference between the value XI and XE displayed is too large, the surgeon must perform internal / external balancing in flexion. Thus if XI is greater than XE plus a constant El, the surgeon will have to perform an external relaxation and in this case it will be necessary to carry out a new measurement of the imbalance in flexion. If on the other hand XI is less than XE plus this same constant El, the surgeon will have to perform an internal relaxation. It should be noted that eventually, the surgeon will be able to compensate by a rotation of the femur if the YI value measured in the step of measuring the imbalance in extension is less than the YE value and if the difference between YE and YI is less than the difference between XE and XI. There will also be the possibility of compensating when XI is less than XE and when YI is greater than or equal to YE. When these operations are, if necessary, carried out, a new measurement of the bending imbalance is carried out to obtain the new values XE and XI. The surgeon can also perform an internal / external balancing in extension in the case where the difference between the values YI and YE are too large. To do this, it performs an internal relaxation if YI is less than YE plus a constant El or an external relaxation if YI is greater than YE plus a constant E2. In the same way as for internal / external balancing in bending, it will be necessary to carry out a new measurement of the imbalance in extension so as to determine the new values YE and YI. From the different values XI, XE and YE, YI, the program then calculates values X and Y with X = (XE + XI) / 2 and Y = (YE + YI) / 2 with VFD equal to the angle of the distal femoral valgus and rot equal to the angle of rotation of the femur that the surgeon has chosen in the event of an original internal / external imbalance in flexion. From these data as well as data relating to the sizes of the implants or the thicknesses of cuts possible at the level of the cut posterior of the femur and the distal cut, the program proposes, by means of display means to the surgeon, different data so that he can perform an optimal placement of the knee prosthesis. The program calculates, according to a preferred mode: - the thickness of the posterior femoral cut according to the equation: CP = femur size - femoral implant size, - the size of the polyethylene according to the equation: P = X + CP - IFP - AND with: CP = thickness of the posterior cut, IFP = thickness of the posterior femoral implant, ET = thickness of the tibial implant, - the size of the distal cut according to the equation: CD = IFD + P + ET + Y with: IFD = size distal femoral implant, P = thickness of the polyethylene, ET = thickness of the tibial implant, - the angle of rotation of the femur, - the expected ligament tension taking into account the values of the other data displayed. The set of output data is then displayed and the surgeon can either use the data directly to prepare the pose, or impose additional constraints, for example, if he wishes a particular posterior cut, in which case he introduces these constraints and relaunches. the program. Of course, other embodiments within the reach of ordinary skill in the art could have been envisaged without departing from the scope of the invention defined by the claims below.

Claims

REVENDICATIONS 1. Dispositif d'assistance au chirurgien dans la sélection d'un implant fémoral et/ou tibial pour la préparation d'une pose de prothèse de genou caractérisé en ce qu'il comprend : - des moyens de stockage de données (2) relatives à l'anatomie du patient et de données relatives aux implants fémoral et tibial ; - des moyens d'écartement (3) entre le tibia et le fémur permettant la mise en tension des ligaments internes et externes ; - des premiers moyens de mesure (9) de l'écartement permettant de déterminer la distance entre le tibia et le fémur ; - des seconds moyens de mesure (10) de la tension ligamentaire des ligaments internes et externes ; - des moyens de transmission (13) des données obtenues par lesdits premiers et seconds moyens de mesure (9,10) ; - des moyens de traitement (14) des données mesurées et/ou stockées permettant l'obtention de données de sortie relatives à la tension ligamentaire à appliquer et/ou au plan de coupe fémorale à réaliser et/ou aux dimensions des implants fémoral et tibial à sélectionner ; - des moyens d'affichage (16) desdites données de sortie. 2. Dispositif selon la revendication 1 caractérisé en ce que lesdits moyens d'écartement (3) sont constitués par un tenseur (4) comportant une potence (5) sur laquelle est fixée un patin tibial 6 et deux bras deplaçable (7,7') séparément le long de la potence (5) par des moyens de manœuvre (8) permettant d'écarter les deux parties de l'articulation et de mettre les ligaments en tension. 3. Dispositif selon la revendication 2 caractérisé en ce que lesdits moyens de mesure (10) sont disposés au niveau de chaque bras (7,7') du tenseur (4). 4. Dispositif selon la revendication 3 caractérisé en ce que les seconds moyens de mesure 10 sont constitués d'au moins deux capteurs (12) de force repartis sur la longueur de chaque bras (7,7') permettant de mesurer la force exercée sur chaque bras (7,7') correspondant à la tension ligamentaire. 5. Dispositif selon l'une quelconque des revendications précédentes caractérisé en ce que les moyens de transmission (13) des données sont filaires. 6. Dispositif selon l'une quelconque des revendications précédentes caractérisé en ce que les moyens d'affichage (16) permettent d'afficher les données de sortie sous forme de graphique. 7. Procédé de sélection d'implants tibial et/ou fémoral mis en œuvre dans le dispositif selon l'une quelconque des revendications 1 à 6 précédentes, caractérisé en ce qu'on effectue les étapes suivantes : - une mesure de la tension ligamentaire optimale ; - une mesure du déséquilibre en extension ; - une mesure de déséquilibre en flexion. 8. Procédé selon la revendication 8, caractérisé en ce que l'étape de mesure de la tension ligamentaire consiste à distendre le tibia et le fémur lorsque le genou est en flexion jusqu'à une valeur seuil K et à mesurer la tension ligamentaire correspondant à ladite valeur seuil K. 9. Procédé selon la revendication 8, caractérisé en ce que l'étape de mesure du déséquilibre en extension consiste à distendre le tibia et le fémur lorsque le genou est en extension jusqu'à obtenir en interne et en externe la tension ligamentaire optimale et à mesurer les écartements YI et externe YE correspondant de manière à déterminer si l'articulation placée en extension est serrée ou déséquilibrée. 10. Procédé selon l'une ou l'autre des revendications 8 et 9 caractérisé en ce que l'étape de mesure du déséquilibre en flexion consiste à distendre le tibia et le fémur lorsque le genou est en flexion jusqu'à obtenir en interne et en externe la tension ligamentaire optimale et à mesurer les écartements interne Xi et externe Xe correspondant de manière à déterminer si l'articulation placée en flexion est serrée ou équilibrée. CLAIMS 1. Device for assisting the surgeon in the selection of a femoral and / or tibial implant for the preparation of a knee prosthesis fitting, characterized in that it comprises: - data storage means (2) relating to the patient's anatomy and data relating to the femoral and tibial implants; - spacing means (3) between the tibia and the femur allowing the tension of the internal and external ligaments; - first measuring means (9) of the spacing for determining the distance between the tibia and the femur; - second means for measuring (10) the ligament tension of the internal and external ligaments; - means for transmitting (13) the data obtained by said first and second measuring means (9,10); - processing means (14) of the measured and / or stored data making it possible to obtain output data relating to the ligament tension to be applied and / or to the femoral cutting plane to be produced and / or to the dimensions of the femoral and tibial implants to select; - display means (16) of said output data. 2. Device according to claim 1 characterized in that said spacing means (3) consist of a tensor (4) comprising a bracket (5) on which is fixed a tibial pad 6 and two displaceable arms (7,7 ' ) separately along the bracket (5) by maneuvering means (8) making it possible to separate the two parts of the joint and to put the ligaments in tension. 3. Device according to claim 2 characterized in that said measuring means (10) are arranged at each arm (7,7 ') of the tensor (4). 4. Device according to claim 3 characterized in that the second measuring means 10 consist of at least two force sensors (12) spread over the length of each arm (7.7 ') to measure the force exerted on each arm (7.7') corresponding to the ligament tension. 5. Device according to any one of the preceding claims, characterized in that the transmission means (13) of the data are wired. 6. Device according to any one of the preceding claims, characterized in that the display means (16) make it possible to display the output data in the form of a graph. 7. Method for selecting tibial and / or femoral implants implemented in the device according to any one of the preceding claims 1 to 6, characterized in that the following steps are carried out: - a measurement of the optimal ligament tension ; - a measure of the imbalance in extension; - a measurement of unbalance in flexion. 8. Method according to claim 8, characterized in that the step of measuring ligament tension consists in distending the tibia and the femur when the knee is in flexion up to a threshold value K and in measuring the ligament tension corresponding to said threshold value K. 9. Method according to claim 8, characterized in that the step of measuring the imbalance in extension consists in distending the tibia and the femur when the knee is in extension until obtaining internally and externally the optimal ligament tension and measure the corresponding YI and external YE spacings so as to determine whether the articulation placed in extension is tight or unbalanced. 10. Method according to either of claims 8 and 9 characterized in that the step of measuring the imbalance in flexion consists in distending the tibia and the femur when the knee is in flexion until obtaining internally and externally the optimal ligament tension and to measure the internal spacings Xi and external Xe corresponding so as to determine if the joint placed in flexion is tight or balanced.
PCT/FR2005/000332 2004-02-23 2005-02-11 Device for assisting a surgeon in the selection of a femoral and/or tibial implant for the preparation of a prosthesis, and implant selection method used in said device WO2005089681A2 (en)

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