AU2012213931A1

AU2012213931A1 - A method of fabricating a personalized positioning guide

Info

Publication number: AU2012213931A1
Application number: AU2012213931A
Authority: AU
Inventors: Gregory Biette; Christophe Bussiere; Franck Cladiere; Patrick Coipeau; Richard Elhage; Stephane Fournol; Sebastien Martres; Xavier Roussignol; Francois Xavier Verdot
Original assignee: I M A G E
Current assignee: Image
Priority date: 2011-08-29
Filing date: 2012-08-14
Publication date: 2013-03-21
Anticipated expiration: 2032-08-14
Also published as: EP2564802A1; BR102012021584A2; FR2979223A1; AU2012213931B2; FR2979223B1

Abstract

The invention relates to a method of fabricating a personalized positioning guide (10) for positioning at least one member on a distal end (I) of a femur or on a proximal end of a tibia of a patient, the method including the step (200) of modeling the desired end as a three-dimensional virtual model on the basis of at least one medical image of said end. According to the invention, the method comprises the steps of: - positioning (300) a three-dimensional predetermined virtual positioning guide relative to the virtual model of the end; . virtually removing (400) from the predetermined virtual positioning guide any portion thereof that is intersected by the virtual model of the end in order to obtain a personalized virtual positioning guide; and - fabricating (500) the personalized positioning guide by powder sintering on the basis of the personalized virtual positioning guide. Fig.1 20a p 20b Take a medical 100 J image of the end 20d Model the end 200 as a virtual 3D model 20c Position a 3D predetermined 300 virtual positioning guide Virtually remove any intersected portion 400 to obtain a personalized virtual positioning guide Fig.2 Fabricate the personalized 500 positioning guide

Description

AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION INVENTION TITLE: A METHOD OF FABRICATING A PERSONALIZED POSITIONING GUIDE The following statement is a full description of this invention, including the best method of performing it known to us:- A METHOD OF FABRICATING A PERSONALIZED POSITIONING GUIDE FIELD OF THE INVENTION [0001] The invention relates to a method of fabricating a personalized positioning guide. [0002] In the present application, reference is made to a conventional anatomical reference system in which the patient is standing and facing an observer. In this reference system, the distal end of a femur designates the end of the femur that is associated with a knee and the proximal end of a tibia designates the end of the tibia that is associated with a knee. BACKGROUND OF THE INVENTION [0003] Implanting a total knee prosthesis is intended to restore a joint between a femur and a tibia of a patient. [0004] In order to be able to implant the total prosthesis, a surgeon needs to prepare the distal end of the femur and the proximal end of the tibia respectively to receive the femoral portion and the tibial portion of the total prosthesis. For this purpose, the surgeon performs various resections on the two above-mentioned ends. [0005] In order for a knee prosthesis to be painless and trouble-free for a patient, it needs to reproduce as accurately as possible the knee that it replaces. It is therefore essential to make the various resections very accurately so as to position the total knee prosthesis as well as possible. [0006] In order to assist the surgeon in making the various resections, there exist cutting guides that enable the actions of the surgeon to be guided. Positioning members are used to arrange the cutting guides temporarily on the ends that are to be prepared, where such positioning members may be pins that have previously been implanted in said ends. For this purpose, there exist pin positioning guides that assist a surgeon in drilling the ends for receiving the pins. These positioning guides are matched to the patient in 2 order to enable the pins to be positioned in a manner that is specific to the patient so that the resections made are matched as well as possible to the anatomy of the patient. OBJECT OF THE INVENTION [0007] An object of the invention is to propose a method of fabricating a personalized positioning guide for positioning at least one positioning member, which method can be implemented simply and quickly. BRIEF SUMMARY OF THE INVENTION [0008] In order to achieve this object, the invention provides a method of fabricating a personalized positioning guide for positioning at least one member on a distal end of a femur or on a proximal end of a tibia of a patient, the method including the step of modeling the desired end as a three-dimensional virtual model on the basis of at least one medical image of said end. According to the invention, the method comprises the steps of: positioning a three-dimensional predetermined virtual positioning guide relative to the virtual model of the end; virtually removing from the predetermined virtual positioning guide any portion thereof that is intersected by the virtual model of the end in order to obtain a personalized virtual positioning guide; and fabricating the personalized positioning guide by powder sintering on the basis of the personalized virtual positioning guide. [0009] The inventors have observed that it is much easier to make a positioning guide that matches the anatomy of a patient by using the method of the invention than, for example, by determining a personalized virtual positioning guide solely on the basis of the outside surface of the virtual model of the end.

3 BRIEF DESCRIPTION OF THE DRAWING [0010] The invention can be better understood in the light of the following description of a particular non-limiting implementation of the invention described with reference to the accompanying figures, in which: [0011] Figure 1 is a diagrammatic three-dimensional view of the distal end of a femur on which there is arranged a personalized positioning guide for pins fabricated using the method of the invention, four pins being ready to be positioned on said end; and [0012] Figure 2 is a flow chart showing the various steps in fabricating the personalized positioning guide shown in Figure 1. DETAILED DESCRIPTION OF THE INVENTION [0013] With reference to Figures 1 and 2, the fabrication method of the invention is implemented in this example to fabricate a personalized positioning guide 10 for positioning at least one pin on the distal end I of a femur. As shown in Figure 1, the personalized positioning guide 10 is for use in positioning four pins 20a, 20b, 20c, and 20d on the distal end 1 of the femur. [0014] In a first step 100, at least one medical image is taken of the distal end I of the femur. For example, the medical image may be obtained by magnetic resonance imaging (MRI). [0015] In a second step 200, and in known manner, on the basis of the medical image, the distal end I of the femur is modelled as a virtual model in three dimensions. [0016] Thereafter, in a third step 300, a three-dimensional virtual predetermined positioning guide is positioned relative to the virtual model of the distal end I of the femur. [0017] In a preferred implementation, the method of the invention includes the step of selecting the predetermined virtual positioning guide from a list of virtual positioning guides, each of which is adapted to a category of people to be found in a population 4 sample. By way of example, these categories may be characterized by any of the following parameters singly or in combination: a person's sex, height, weight, ... . [0018] The predetermined virtual positioning guide for fitting is thus selected from the list from parameters specific to the patient, said parameters enabling the patient to be assigned to one of said categories. Preferably, the virtual positioning guide is selected automatically. [0019] Advantageously, the predetermined virtual positioning guide is then already substantially matched to the anatomy of the distal end I of the femur. [0020] In a fourth step 400, once the predetermined virtual positioning guide has been positioned relative to the virtual model of the end 1, any portion of the predetermined virtual positioning guide that is intersected by the virtual model of the end I is determined. Thereafter said intersected portion(s) is virtually removed from the predetermined virtual positioning guide so as to obtain a personalized positioning guide. The fourth step 400 thus makes it possible to refine the matching of the predetermined virtual positioning guide to the anatomy of the distal end I of the femur. [0021] In a last step 500, and in known manner, the personalized positioning guide 10 is then fabricated on the basis of the personalized virtual positioning guide by means of a powder sintering operation. [0022] Naturally, the invention is not limited to the implementation described, and variants may be applied thereto without going beyond the ambit of the invention as defined by the claims. [0023] In particular, although in this example the distal end 1 of the patient's femur is modelled as a virtual model in three dimensions on the basis of a medical image obtained by MRI, the distal end I could be modelled from a greater number of images and/or on the basis of medical images obtained by other kinds of medical examination such as X-rays, scanning, or joint scanning.

5 [0024] The fabrication method of the invention makes it possible to fabricate personalized positioning guide of types other than that shown. The predetermined virtual positioning guide may for example be selected as a function of the looked-for type of personalized positioning guide. For example, the method of the invention may also be implemented for fabricating a personalized guide for positioning pins for the proximal end of a tibia. In addition, although the personalized positioning guide in this example can be used for guiding the positioning of four pins, the method of the invention can also be implemented for fabricating a personalized positioning guide that is deigned in operation to guide some other number of pins, e.g. only one pin. (0025] Although the predetermined virtual positioning guide in this example is selected from a list and from parameters specific to the patient, the predetermined virtual positioning guide could be selected in other ways. For example, one or more measurements may be taken from the medical image (e.g. antero-posterior ratio, medio lateral ratio, ...). The predetermined virtual positioning guide is then selected as a function of said measurement(s). [0026] In addition, the predetermined virtual positioning guide may be selected by a surgeon instead of being selected automatically. [0027] The method of the invention may include steps other than those described. For example, between the fourth step 400 of removing the intersected portion(s) and the step 500 of fabrication, the method of the invention may include a step in which the personalized virtual positioning guide is retouched, automatically or by the surgeon, so as to match it even better to the anatomy of the patient. In this step, account may be taken for example of the antero-posterior ratio and/or of the medio-lateral ratio, of a study concerning the positions of the femur relative to the tibia throughout a bending movement of the associated knee, ... . [0028] Although the positioning guide described above is for positioning at least one pin, the positioning guide may be intended for positioning positioning members of other kinds such as, for example: nails, screws, threaded rods, ... . The term "positioning 6 member" should be understood as covering any means enabling a guide or the like to be held on a bone. [0029] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. [0030] The reference to any prior art in this specification is not and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge in Australia.

Claims

1. A method of fabricating a personalized positioning guide for positioning at least one member on a distal end of a femur or on a proximal end of a tibia of a patient, the method including the step of modeling the desired end as a three-dimensional virtual model on the basis of at least one medical image of said end, the method wherein it includes the steps of: . positioning a three-dimensional predetermined virtual positioning guide relative to the virtual model of the end; - virtually removing from the predetermined virtual positioning guide any portion thereof that is intersected by the virtual model of the end in order to obtain a personalized virtual positioning guide; and - fabricating the personalized positioning guide by powder sintering on the basis of the personalized virtual positioning guide.

2. A fabrication method according to claim 1, including the step of selecting the predetermined virtual positioning guide from a list of virtual positioning guides in which each guide is adapted to a category of people present in a population sample.

3. A fabrication method according to claim 1, in which the medical image used for modeling the end is derived from magnetic resonance imaging.