Fiducial marker device used in the field of orthopaedic surgery for spatially locating surgical instruments

Abstract

The invention relates to a fiducial marker device (2) used in the field of orthopaedic surgery which uses, for spatially locating surgical instruments, an augmented reality system comprising at least two fiducial markers (3), e.g. each of which is an "ArUco" marker, carried by a plate (10), wherein one is able to be rigidly attached, directly or indirectly, to bone material or to a surgical instrument and the other is rigidly attached to a surgical instrument to be positioned or to be guided in its movement relative to the first. The invention also relates to a camera associated with software for detecting and identifying the markers (3). Each "ArUco" marker ((33)), which is used to identify the instrument and to pre-position same, is supplemented by the display, on the periphery of the "ArUco" marker ((33)), of additional patterns (4) which physically represent detectable and identifiable marker points (40).

Description

[0001] DESCRIPTION

[0002] Locator marker device, used in the field of orthopedic surgery for the spatial localization of surgical instruments.

[0003] The present invention relates to a locating marker device, used in the field of orthopedic surgery and more particularly, but not limited to, for arthroplasty, using for the navigation of surgical instruments, an augmented reality system comprising on the one hand at least two locating markers each of the so-called "Arüco" type for example and carried by a plate, one of which can be fixedly secured, directly or indirectly, to the bone material or to a surgical instrument, the other secured to a surgical instrument to be positioned or guided in its movement relative to the first, and on the other hand a camera associated with software for detecting and identifying said markers.

[0004] It should be noted that in this application reference will only be made to “Arüco” type markers, knowing of course that markers of other types may also be used.

[0005] The locating marker device according to the invention thus relates to the field of surgical navigation, which allows the surgeon to benefit, throughout the intervention, from visual assistance, to have in real time not only a three-dimensional image of the positioning, at the level of the intervention zone, of instruments or prosthetic elements, but also to access the clinical values ​​which allow the surgeon to precisely orient the prosthetic components, namely essentially angles of varus, valgus, flexion and slope, as well as distances such as cutting thicknesses, joint spacings, and ligament tensions. Today, the methods of instrument navigation for orthopedic surgery are varied, the majority of these solutions are composed of a system for acquiring, visualizing and processing data.

[0006] Most of the systems used are bulky and expensive but they provide remarkable precision, less than a millimeter.

[0007] Also known, according to another approach, is the surgical navigation system for total knee arthroplasty, developed by the present Applicant, described in document US 2023 / 0052103, which has the advantage of using only a pair of augmented reality glasses, so as to remain compact and low cost.

[0008] This solution, however, has the disadvantage of being less precise, and in particular of not allowing a pose estimation error of less than 1 millimeter to be achieved.

[0009] The present invention aims to overcome this drawback by proposing a tracking marker device, usable in a compact and inexpensive system, using easily portable and lightweight equipment such as augmented reality glasses.

[0010] The locating marker device according to the invention, used in the field of orthopedic surgery and more particularly, but not limited to, for arthroplasty, using for the spatial localization of surgical instruments, an augmented reality system comprising on the one hand at least two locating markers each of the so-called “Arüco” type for example and carried by a plate, one being able to be fixedly secured, directly or indirectly, to the bone material or to a surgical instrument, the other secured to a surgical instrument to be positioned or guided in its movement relative to the first, and on the other hand a camera associated with software for detecting and identifying said markers, and it is characterized in that each “Arüco” type marker, which serves to identify the instrument and to preposition it, is completed by the representation, on the periphery of said “Arüco” type marker,additional patterns which materialize detectable and identifiable reference points, which make it possible to refine the positioning of said instrument initially obtained with said “Arüco” type marker.,

[0011] This marker device allows to achieve higher precision without having to change the base of the detection system used, nor the size of the devices already proven and marketed.

[0012] This new design of marker devices makes it possible to improve and stabilize the pose estimation for the navigation of surgical instruments. Indeed, with such marker devices, it is possible, while of course respecting specific conditions, in particular resolution and exposure, to envisage an error in the estimation of the pose of the instruments of less than a millimeter, which makes it possible to carry out critical acquisitions for surgery, such as, for example, but not limited to, the acquisition of point anatomical landmarks, or the measurement of resection thicknesses, in the context of knee arthroplasty.

[0013] To date, there is no system with submillimeter precision with a portable platform that detects reusable instruments using a smartphone-quality monocamera, for example, even if it is placed behind the transparent visor of a surgical suit.

[0014] According to an additional characteristic of the marker device according to the invention, the additional patterns are in the form of isolated islands arranged externally to the centrally positioned Arüco type marker.

[0015] According to a variant of the marker device according to the invention, the additional patterns are in the form of a belt which surrounds the centrally positioned Arüco type marker. According to another additional characteristic of the marker device according to the invention, the additional patterns consist of sets of black squares or rectangles distributed in a checkerboard or similar arrangement, and whose junctions by two corners form the detectable and identifiable reference points.

[0016] From a structural point of view, the plates that support the marker devices are preferably made of metal or ceramic, or any other material capable of withstanding an autoclave washing cycle without deterioration of the marking, which marking is preferably carried out by laser, so as to maintain a very flat surface, so as not to introduce shadows and bias when estimating the installation.

[0017] From a functional point of view, the first steps of the system are identical to those of the state of the art using ArUco marker devices. They consist of using a dictionary of ArUco markers to differentiate the instruments used in the operating protocol, the determination of the position and orientation of the markers allows to define the global position of the instrument thanks to the intrinsic parameters of the camera as well as the very precise geometric description of the dimensions of the instrument, obtained by metrological measurements.

[0018] The next step is to use the position of the landmarks materialized by the additional patterns to refine the pose.

[0019] The advantages and characteristics of the marker device according to the invention will emerge more clearly from the description which follows and which refers to the appended drawing, which represents a non-limiting embodiment thereof.

[0020] In the attached drawing: Figure 1 represents a partial perspective view of a marker device according to the invention, Figure 2 represents a diagram describing the ArUco marker detection algorithm, - Figure 3 illustrates a step of the identification method,

[0021] - figure 4 illustrates another step of this same process,

[0022] - figures 5a, 5b, 5c and 5d, represent variants of visuals of a marker device according to the invention.

[0023] With reference to figure 1, we can see a support 1 for a location marker according to the invention, which comprises a plate 10 associated with a support element 11, seen partially, a rod for example, intended for fixing directly or indirectly to bone material, or to a surgical instrument, the free end of which, not shown, is intended to be shaped according to its destination.

[0024] On the upper face 12 of the plate 10 is the marker 2 according to the invention, two parts of which are to be distinguished, namely centrally a marker 3 of the so-called ArUco type, and externally to this marker 3, patterns 4, in this case portions of a checkerboard.

[0025] Referring to Figure 2, we can see a diagram describing, in a known manner, the algorithm for detecting marker 3.

[0026] The process of identifying marker 3 is set up when an image is acquired, the latter is thresholded to extract the regions of interest that may contain marker 3. Each region of interest is filtered to keep only the elements having four sides as well as a relevant size. The next step consists of extracting the internal pattern from the remaining regions of interest and comparing it to an ArUco marker present in the dictionary as shown in Figure 3.

[0027] When the ArUco marker is identified, it is recorded, and the position of each of its four corners 30, visible in Figure 4, is refined.

[0028] This allows you to first place marker 2.

[0029] The next step consists of refining the pose of the marker 2 using, according to the invention, the checkerboard-type patterns 4. In Figure 4, it can be seen that, in addition to the corners 30 of the marker 3, the intersections 40 of the black squares of the checkerboard-shaped patterns are materialized, which makes it possible to interpolate these intersections 40 from the first pose of the marker 2 using the marker 3. Knowing the position of the intersections 40 relative to the marker 3, as well as the pose of the marker 2, the position of each intersection 40 in the image plane can be calculated.

[0030] After calculating their theoretical positions, the position of the 40 intersections is refined and filtered to ensure that each intersection is correctly detected / positioned.

[0031] The final step is the addition of the intersections 40 detected for the installation of marker 2: the four corners 30 of marker 3 will be completed by the intersections 40, in this case sixteen, of patterns 4, in order to refine the installation.

[0032] In fact, the corners of the 4-sided checkerboard patterns provide better contrast for subpixel corner refinement, compared to a two-sided corner like those used with ArUco markers.

[0033] Referring now to figures 5a, 5b, 5c and 5d, we can see, without limitation, variants of embodiment of the patterns 4.

[0034] The present invention has the advantage of making it possible to envisage carrying out the navigation of reusable surgical instruments with a portable platform, of the smart glasses type, with submillimeter precision.

[0035] The applications of this technology are not limited to total knee arthroplasty surgeries, they can also be extended to other uses, even non-medical ones.

[0036] In addition, the present invention also maintains the objective of not requiring consumables, since the markers are preferably made of ceramic associated with metal, as regards the plate 10 and the support 11, which allows cleaning in an autoclave without degradation of the navigation precision. For existing systems, such as for example that described in document US 2023 / 0052103, the basic technology is identical, the detection system is not modified, a simple update of the navigation software with a modification of the tools is sufficient to implement the present invention. Surgeons already accustomed to the basic technology can maintain the usage habits and are not disoriented by a new mode of use.

[0037] Of course, even if the marker device according to the invention is preferably usable with a pair of augmented reality glasses, stereoscopic or not, it is perfectly usable with more cumbersome equipment, in particular with dynamic and static instruments, with a computer vision system.

Claims

CLAIMS 1) A locating marker device (2), used in the field of orthopedic surgery and more particularly, but not limited to, arthroplasty, using for the spatial localization of surgical instruments, an augmented reality system comprising on the one hand at least two locating markers (3) each of the so-called “Arüco” type for example and carried by a plate (10), one of which can be fixedly secured, directly or indirectly, to the bone material or to a surgical instrument, the other secured to a surgical instrument to be positioned or guided in its movement relative to the first, and on the other hand a camera associated with software for detecting and identifying said markers (3), characterized in that each “Arüco” type marker (3), which serves to identify the instrument and to preposition it, is completed by the representation, on the periphery of said “Arüco” type marker (3),additional patterns (4) which materialize detectable and identifiable reference points (40), which make it possible to refine the positioning of said instrument initially obtained with said marker (3) of the “Arüco” type., 2) Marker device (2) according to claim 1, characterized in that the additional patterns (4) are in the form of isolated islands arranged externally to the centrally positioned Arüco type marker (3). 3) Marker device (2) according to claim 1, characterized in that the additional patterns (4) are in the form of a belt which surrounds the centrally positioned Arüco type marker (3). 4) Marker device (2) according to claim 1 or claim 2, characterized in that the additional patterns (4) consist of sets of black squares or rectangles distributed in a checkerboard or similar arrangement, and whose junctions by two corners form the detectable and identifiable reference points.

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