METHOD FOR MANUFACTURING A COMPLEX SUBSTITUTE OBJECT FROM A REAL OBJECT

Abstract

The present invention relates to a method for manufacturing a complex substitute object intended to supplement or replace a real object in a given state, potentially a damaged state, in particular a trapeziometacarpal prosthesis intended to replace the trapezoid bone of a human being suffering from rhizarthrosis. The present invention also relates to a trapeziometacarpal prosthesis that can be obtained by the manufacturing method according to the invention.

Claims

1. A method for manufacturing a complex substitute object having at least one functional zone and intended to complement or replace a real object, said method comprising the following steps: A. acquisition of a three-dimensional image of said real object taking the form of a point cloud, said three-dimensional image is then digitized; B. from said digitized three-dimensional image, reconstruction, using drawing or computer-assisted design software, of a three-dimensional model of the real object; C. from said three-dimensional model, programming of the driving of a numerically-controlled machine tool in order to manufacture said complex substitute object; D. additive manufacturing of said complex object by the numerically-controlled machine tool; said method being characterized in that the step A is performed on said real object that is in a damaged state specific to a given deformation, and in that said method comprises, between the steps A and B, the following substeps: a1) definition of invariant topological and morphological parameters of the real object, from which a template is defined; a2) determination of the functional surfaces and of the filling surfaces of the real object in the undamaged state; a3) determination of the deformation-sensitive topological and morphological parameters of the real object in the damaged state and identification of their variations, at its so-called functional surfaces; and also characterized in that the step B further comprises the following substeps: b1) adaptation of the template to said three-dimensional image defined in the step A, using drawing or CAD software, to obtain a specific model; b2) on said specific model, precise reconstruction of the functional surfaces in the damaged state from the functional surfaces defined in the step a2) and approximate reconstruction of the filling surfaces in the damaged state from the functional surfaces defined in the step a2), to obtain a reconstructed three-dimensional image in the damaged state; b3) precise reconstruction, on said reconstructed three-dimensional image in the damaged state, of the functional surfaces in the undamaged state, by modification of the values of the deformation-sensitive topological and morphological parameters defined in the step a3) so that they correspond to an absence of deformation, to obtain a reconstructed three-dimensional image in the undamaged state; b4) from said reconstructed three-dimensional image in the undamaged state, precise definition of the zones of interest of the complex object to be reconstructed, to extract therefrom a functional digital file comprising only said zones of interest and a filling digital file comprising the zones other than the zones of interest; b5) reconstruction from the functional and filling files of a closed volume model of said object to be reconstructed, which is formatted as a neutral file suited to additive manufacturing.

2. The method as claimed in claim 1, whereby the step B further comprises, at the end of the step b5), a step b6) of global or localized smoothing of said closed volume model.

3. The method as claimed in claim 2, whereby the step b6) is performed by a surface or volume method.

4. The method as claimed in claim 1, whereby, during the step A, there is a formatting of said three-dimensional image into a neutral format compatible with drawing or computer-assisted design software.

5. The method as claimed in claim 1, whereby the complex object to be manufactured is an arch support or a dental, auditory or bone prosthesis, for a human or animal body.

6. The method as claimed in claim 5, whereby the real object is a trapezium bone, for the manufacture of a trapeziometacarpal prosthesis,

7. The method as claimed in claim 4, whereby the zones of interest of the trapezium bone are the articular surfaces with the scaphoid, the trapezoid, the first metacarpal and the second metacarpal.

8. The method as claimed in claim 6, whereby the step D of additive manufacturing is performed based on a powder of biocompatible materials.

9. A trapeziometacarpal prosthesis obtained by the manufacturing method as defined as claimed in claim 6.

Description

[0045] Other advantages and particular features of the present invention will emerge from the following description, given as a nonlimiting example and with reference to the attached figures:

[0046] FIG. 1 is a plan view of a skeleton of a hand comprising a trapeziometacarpal prosthesis according to the invention;

[0047] FIG. 2 is a detail and side view of the prosthesis of FIG. 1;

[0048] FIG. 3 is a three-dimensional view of the implantation of the prosthesis of FIG. 1, in which only the first metacarpal and the trapezoid of the skeleton of the hand being represented;

[0049] FIG. 4 shows where the trapeziometacarpal articulation is located in the hand of a patient;

[0050] FIG. 5 comprises two series of 3D images obtained by MRI then segmentation of the trapeziometacarpal articulation of the hands of two patients suffering from rhizarthrosis, one for the left hand of the two patients (FIG. 5a) and the other for the right hand of these two patients (FIG. 5b);

[0051] FIG. 6 shows the topological and morphological parameters that are constantly present from one trapezium bone to another;

[0052] FIGS. 7a to 7p show the variations of these topological and morphological parameters of a trapezium bone;

[0053] FIGS. 8a to 8c show the changing convex and concave curvatures of the contact surface with the first metacarpal according to the arthrosic state of the articulation;

[0054] FIGS. 9a to 9g show the steps A to b6 of digital reconstruction of a trapezium bone that has not undergone deformation linked to rhizarthrosis, in accordance with the method according to the invention, in which the step b5) of reconstruction of a closed volume model of the substitute object to be manufactured is produced by a surface method (called Poisson reconstruction: see FIG. 9f) or by a volume method, called filling by voxels (that is to say digital cubes: see FIG. 9g);

[0055] FIG. 10 shows the template of a trapezium bone and all of the points and the curves defining it;

[0056] FIG. 11 shows the changes in the smoothing of the closed volume model until the disappearance of the sharp angles is obtained while retaining the integrity of the parameters of a previously defined healthy trapezium bone;

[0057] FIG. 12 shows the different elements of the trapeziometacarpal prosthesis to be added (1111) or to be extracted (1111);

[0058] FIG. 13 shows the steps C and D of the method according to the invention in the context of the manufacture of a trapeziometacarpal prosthesis, from the creation of the closed volume model of the trapezium bone to be reconstructed up to the additive manufacture and the final smoothing (respectively steps 13d and 13e) culminating in the prosthesis of the trapezium bone, which is finally implanted in the hand of a patient at the trapeziometacarpal articulation (13f);

[0059] FIG. 14 shows that the properties of mobility of the hand are retained after a prosthetic arthroplasty operation with the prosthesis of the trapezium bone according to the invention;

[0060] FIG. 15 shows the different steps A and B of reconstruction of a cup from a deformed cup.

[0061] FIGS. 1 to 15 are described in more detail in the example which follows, given by way of indication, and which illustrates the invention, but without limiting the scope thereof.

EXAMPLE

Devices and Instrumentation

[0062] Comparator (measurement apparatus): (North and Rutledge, 1983);

[0063] Stereophotogrammetry (SPG) on bones of cadavers (25 m resolution) (Ateshian, 1992; Xu, 1998);

[0064] Segmentation of CT scan 0.6250.30.3 mm resolution) (Conconi, 2014; Halilaj, 2014b);

[0065] 3D laser scan (LS) (Kovler, 2004; Markze, 2012) Micro-CT system on bones of cadavers (0.38 m resolution);

[0066] Image segmentation software: OSIRIX, MATERIALIZE;

[0067] Software for formatting segmented images in STL file format: OSIRIX MATERIALIZE;

[0068] STL file visualization software: MESCHLAB;

[0069] Computer-assisted design software: CATIA V5.

MATERIALS

Real Objects

[0070] trapezium bones of two male patients suffering from rhizarthrosis, respectively aged 61 years (patient 1) and 66 years (patient 2), whose sick hand is shown in FIGS. 5a and 5b (example 1), [0071] deformed cup (example 2).

Objects to Be Modeled

[0072] trapezium bones of trapeziometacarpal prostheses schematically represented in FIGS. 1 to 3 and shown in the photographs of FIGS. 13d and 13e (example 1), [0073] non-deformed cup (example 2).

Object to Be Reconstructed

[0074] trapezium bone of trapeziometacarpal prostheses schematically represented in FIGS. 1 to 3 and shown in the photographs of FIGS. 13d and 13e. [0075] Material used for the additive manufacture of the prosthesis: CrCoMo, TA6V.

[0076] Referring to FIGS. 1 to 3 (relating to the example 1), a trapeziometacarpal prosthesis 1 that can be obtained according to the invention will be described. This trapeziometacarpal prosthesis here comprises a prosthetic trapezium 111, a metacarpal pin 117 and an anchoring screw 113. It is intended to be fitted between the first metacarpal 214 and the trapezoid 212 of a patient. The prosthetic trapezium 111 is anchored on the trapezoid 212 with the anchoring screw 113. In the embodiment illustrated in FIGS. 1 to 3, the metacarpal pin 117 comprises two parts, here added to one another: a base 115 and a head 116.

[0077] The object to be reconstructed, namely the cup, is described in example 2 and illustrated in FIG. 15.

Example 1

Production of a Trapeziometacarpal Prosthesis According to the Method of the Invention

1.1 Acquisition of Segmented Three-Dimensional Images of the Trapezium Bones (Step A of the Method According to the Invention)

[0078] The hand of the patient is scanned by MRI or by tomography, then transformed into point clouds (STL format). The technical characteristics of the medical imaging and of the extraction as point cloud (sequences, weighting, contrast) are chosen so as to discretize the cortical part of the bones (FIGS. 5a and 5b).

[0079] A digital STL file is extracted, then the identified points defining the template are adapted to the model of the patient in a CAD or mesh editing software. The software MESHLAB, a software of open source type, for 3D mesh editing makes it possible, for its part, to visualize the STL files.

[0080] When the model is highly arthrosic and damaged, and the template cannot be entirely matched to the patient, the points of unmatched markers are predicted by a healthy bone database. Moreover, the template makes it possible to eliminate the non-anatomical protuberances and roughnesses that are highly present in a bone with an advanced arthrosic state.

1.2 Determination of the Topological and Morphological Parameters that are Constantly Present From One Real Object to Another to Obtain a Template (Step A of the Method According to the Invention)

[0081] FIG. 6 shows the topological and morphological parameters that are constantly present from one trapezium bone to another.

[0082] In the biomechanical model of a trapezium bone, three types of marker points are distinguished: [0083] the anatomic marker points (411), defined by experts and corresponding to points that have a biological significance; [0084] the marker pseudo points (412), which are constructed on an object, on a line or between marker points.

[0085] Following the reconstruction, common characteristics are revealed (illustrated in FIGS. 7a to 7p): [0086] presence of 4 visible articulation surfaces: [0087] trapezoid (TPZ) 421, [0088] metacarpal 1 (M1) 422, [0089] metacarpal 2 (M2) 423, [0090] scaphoid (SCP) 424 including 2 planes (SCP and M2), and [0091] the articulation M1 (422) in saddle form.

[0092] The choice is therefore focused on highlighting these characteristics.

1.3 Determination of the Variable Topological and Morphological Parameters that are Sensitive to Arthrosis (Steps a1 to a3 of the Method According to the Invention)

[0093] FIGS. 7a to 7p show all of the measurements performed on these marker points in order to know their variability as a function of the arthrosic state. The parameters relating to the contact surface with the first metacarpal are highly sensitive to the arthrosic state (431).

[0094] Moreover, FIGS. 8a to 8c show more specifically that the concave (441) and convex (442) curvatures of the contact surface with the first metacarpal vary as a function of the arthrosic state of the articulation. The curvatures are concave are highly pronounced for a healthy subject (4411) and weakly pronounced in the arthrosic state (4412). Conversely, the convex curvatures are highly pronounced in the arthrosic state (4422) and weakly pronounced for a healthy subject. The healthy concave curvatures (4411) decrease along the radioulnar line but are stable for an arthrosic subject (4412). The healthy convex curvatures (4421) increase along the radioulnar line but decrease slightly for an arthrosic subject (4412).

1.4 Reconstruction, Using Drawing Software, of a Three-Dimensional Model of a Trapezium Bone not Having Undergone Deformation Linked to the Rhizarthrosis Corresponding to the Trapezium Bones of the Sick Patients (Step B of the Method According to the Invention)

[0095] FIGS. 9a to 9f show the different steps of reconstruction of a three-dimensional model of a trapezium bone that has not undergone deformation linked to rhizarthrosis.

[0096] More specifically, these figures show in detail:

[0097] the placement (FIG. 9a3: result of the placement) of the template (of FIG. 9a2) on the 3D digital model of the trapezium bone of the patient (FIG. 9a1),

[0098] the identification of the values of the morphological parameters that do not agree with the specifications of a healthy trapezium bone (FIG. 9b),

[0099] the identification of the zones of interest and filling zones (FIG. 9c),

[0100] the modification of the values of the parameters so that they agree with the specifications of a healthy trapezium bone (FIG. 9d),

[0101] the extraction of the zones of interest and filling zones as meshed digital model with sufficient accuracy relative to the tolerances demanded (FIG. 9e),

[0102] the reconstruction of a closed 3D model by surface method (Poisson reconstruction: FIG. 9f) or volume method (filling by voxels: FIG. 9g).

1.5 Creation by 3D Printing of a Trapezium Bone From the Three-Dimensional Model Obtained in Example 4 (Steps C And D of the Method According to the Invention)

[0103] FIG. 14 shows that the properties of mobility of the hand are conserved after a prosthetic arthroplasty operation with the prosthesis of the trapezium bone according to the invention. All of the movements relating to the trapeziometacarpal articulation have been correctly realized, including the retropulsion (91), antipulsion (92), abduction (93), adduction (94) and circumduction movements according to their respective extent.

Example 2

Reconstruction, Using Drawing Software, of a Three-Dimensional Model of a Cup That has Not Undergone Deformation From a Deformed Cup (Steps A And B of the Method According to the Invention)

[0104] FIG. 15 shows the succession of the steps performed for this purpose from:

[0105] 1. a deformed cup;

[0106] 2. creation of a digital point cloud acquired by laser robot arm;

[0107] 3. creation of a configurable meshed model (in the form of an stl file suited to 3D printing), with unconnected (noncontiguous) zones of the real morphology, [0108] 3.1: by Poisson reconstruction, or [0109] 3.2: by voxelization and smoothing;

[0110] 4. creation of a configurable meshed model (in the form of an stl file suited to 3D printing) with unconnected (noncontiguous) zones of the undeformed morphology, [0111] 4.1: by Poisson reconstruction, or

[0112] 4.2: by voxelization and smoothing.