Device for identifying straight line connecting specific points of object

Abstract

To provide a device for identifying a straight line connecting specific points of an object easily at a low cost which can properly determine a mechanical axis of the tibia in comparison to a conventional technique, and reduces a burden on an operator by allowing the operator to confirm the mechanical axis and confirm a portion of the bone to be cut within a same field of view.SOLUTION: A device includes multiple fixed markers 12a, 12b positioned relative to each other, a movable marker 14, movable imaging means 16, display means 16 and arithmetic processing means 16. A three-dimensional coordinate system of each fixed marker is a reference for a three-dimensional coordinates of a specific point of an object. Each fixed marker is used to determine the specific point of the object together with the movable marker. The imaging means is used to image one of the fixed markers and the movable marker simultaneously. The arithmetic processing means is used to identify a straight line connecting the specific points of the object. The display means displays at least the straight line connecting the specific points of the object.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus for identifying a straight line connecting specific points on an object, and more particularly to an apparatus for determining and displaying a more appropriate position for the mechanical axis of the tibia (tibial functional axis) required during artificial knee joint surgery. [Background technology]

[0002] In knee artificial joint surgery, when cutting the tibia, it is necessary to determine in advance a so-called mechanical axis that is displayed by connecting a first reference position located on the proximal side of the tibia (specifically, a point on the intercondylar eminence on the superior articular surface of the proximal part of the tibia including the lateral condyle and the medial condyle) and a second reference position located on the distal side of the tibia (specifically, a center point in the width direction of the distal end of the lower leg bone including the medial malleolus of the tibia and the lateral malleolus of the fibula). The mechanical axis is a reference line for determining a surface for cutting the tibia, for example, to perform high tibial osteotomy on the proximal part of the tibia. Therefore, it is important to determine the mechanical axis on the tibia.

[0003] As a technology related to tibial osteotomy, for example, Patent Document 1 discloses an optical tracking system 42 including a detection device 44 and a trackable element (e.g., a navigation marker 46) that is placed on the tracked object and can be detected by the detection device 44 (Figure 6 of Patent Document 1), and the detection device 44 is said to include a visible light-based detector that detects a pattern on the trackable element, or a stereoscopic camera pair that is sensitive to infrared light and can be positioned in the operating room where the osteotomy surgery is performed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-505326 A Summary of the Invention [Problem to be solved by the invention]

[0005] Although U.S. Patent No. 5,933,333 discloses that the optical tracking system 42 includes a detection device 44 and a navigation marker 46, which enables the detection device 44 to track the orientation of an object (e.g., the tibia) as it moves within the coordinate system of the detection device 44 to detect the movement of the object, there is no disclosure that these components 44, 46 combine to determine the mechanical axis of the tibia.

[0006] In recent years, there has been a demand for a more appropriate determination of the mechanical axis of the tibia than in the past, and there is also a strong demand for reducing the burden on the surgeon when performing osteotomy of the proximal portion of the tibia by enabling the surgeon to check both the mechanical axis and the part of the bone to be cut within the same field of view.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide an apparatus for identifying a straight line connecting specific points on an object, which can determine the mechanical axis of the tibia more appropriately than conventional apparatuses, reduces the burden on the surgeon by allowing the surgeon to check the mechanical axis and the part of the bone to be cut within the same field of view, and is also inexpensive and simple. [Means for solving the problem]

[0008] In order to solve the above problem, the device of the present invention for identifying a straight line connecting specific points of an object includes a plurality of fixed markers positioned relative to each other, a movable marker, a movable imaging means, a display means, and a calculation processing means, wherein the three-dimensional coordinate system of each of the fixed markers is a reference for the three-dimensional coordinates of the specific points of the object, each of the fixed markers is used together with the movable marker to determine the specific points of the object, the imaging means is used to simultaneously photograph one of the fixed markers and the movable marker, the calculation processing means is used to identify the specific points of the object and the straight line connecting these points, and the display means is used to display at least the straight line connecting the specific points of the object. Effect of the Invention

[0009] In the present invention, on the premise of using a mechanism as a navigation system, i.e., a simple and inexpensive mechanism including a movable imaging means, a display means, a plurality of fixed markers, a movable marker, and a calculation processing means, when determining, for example, the mechanical axis of the tibia, taking into consideration the positional relationship between the fixed markers simultaneously placed at a plurality of locations on the tibia and one movable marker sequentially placed at a position relatively close to each fixed marker, the imaging means photographs a marker unit consisting of each fixed marker and a movable marker as many times as the number of locations where the movable marker is placed, and the display means displays the marker unit as many times as the number of locations where the movable marker is placed. Next, in the present invention, the calculation processing means obtains the positions of the fixed marker and the movable marker in the three-dimensional coordinate system of the imaging means from the image data displayed in this way, and converts the position of a specific point corresponding to the movable marker into relative coordinates with respect to the fixed marker. Furthermore, in the present invention, since the positional relationship between the fixed markers is known, the position of a specific point determined using one fixed marker and a movable marker can be converted into relative coordinates with respect to the other fixed marker, and as a result, the position information of the specific point converted into relative coordinates with respect to the fixed marker is stored in the calculation processing means, specific points on the tibia are determined, and these specific points are further displayed on the display means, thereby enabling the mechanical axis of the tibia to be determined.

[0010] According to the device for identifying a straight line connecting specific points of an object of the present invention, the fixed markers and the movable markers are close to each other, and the imaging means is movable, so that the imaging means can properly capture images of each marker unit consisting of a fixed marker and a movable marker. Therefore, the mechanical axis of the tibia, for example, can be determined more properly than in the past from multiple image data, taking into account the positional relationship between the fixed markers.

[0011] Furthermore, according to the device of the present invention for identifying a straight line connecting specific points of an object, the imaging means is particularly movable, and therefore when this device is used to determine the mechanical axis of the tibia, by making at least the imaging means and the display means into the same device, the surgeon can confirm the mechanical axis and the part of the tibia to be cut within the same field of view, thereby reducing the burden on the surgeon. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a plan view showing an apparatus for identifying a line connecting specific points of an object, in particular an apparatus for determining the mechanical axis of a tibia, according to an embodiment of the present invention, in which (a) shows a removable marker positioned near a first marker fixed to the tibia, and (b) shows a removable marker positioned near a second marker fixed to the tibia. [Diagram 2] FIG. 2 is a perspective view of a system including the device shown in FIGS. 1(a) and 1(b) and a device for cutting the tibia. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In the following, a device for determining the mechanical axis of the tibia will be described in detail as a device for identifying a straight line connecting specific points of an object according to an embodiment of the present invention (hereinafter, may be referred to as the "present device"). However, the present device is not limited to a device for determining the mechanical axis of the tibia, and may include any device for identifying a straight line connecting specific points of an object. Note that the example shown below is an example in which the imaging means, display means, and arithmetic processing means are realized by the same device (for example, a smartphone with a camera (hereinafter, may be simply referred to as a "smartphone") on which an application for performing a predetermined arithmetic processing is installed).

[0014] FIG. 1 is a plan view of the present device, in particular a device for determining the mechanical axis of the tibia, in which (a) shows a removable marker positioned near a first marker fixed to the tibia, and (b) shows a removable marker positioned near a second marker fixed to the tibia.

[0015] As shown in FIGS. 1( a ) and 1 ( b ), the present device 10 includes a first marker 12 a , a second marker 12 b , a third marker 14 , and a smartphone 16 .

[0016] The first marker 12a is fixed directly to a proximal portion of the tibia T or indirectly via a marker fixing member (not shown). The first marker 12a may be fixed to the tibia T in any manner as long as the portion to be read can be read by the smartphone 16 (when photographed together with the third marker 14 as described below). The first marker 12a may be a matrix type two-dimensional code such as a QR code (registered trademark), but is not limited to these, and various markers may be used. The first marker 12a fixed to the tibia T is in a mutually fixed positional relationship with the second marker 12b (fixed to the tibia) described below.

[0017] Similarly, the second marker 12b is fixed directly to a distal portion of the tibia T or indirectly via a marker fixing member (not shown). The second marker 12b may be fixed to the tibia T in any manner as long as the portion to be read can be read by the smartphone 16 (when photographed together with the third marker 14 as described below). The second marker 12b may be, for example, a matrix type two-dimensional code such as a QR code (registered trademark), but is not limited to these, and various markers may be used. The second marker 12b fixed to the tibia T is in a mutually fixed positional relationship with the first marker 12a (fixed to the tibia) described below.

[0018] The three-dimensional coordinate system of each of the first marker 12a and the second marker 12b is the reference for the three-dimensional coordinates of a specific point used when determining the mechanical axis MA. In order to determine a specific point used when determining the mechanical axis MA, three three-dimensional coordinate systems are required: the three-dimensional coordinate system of the camera of the smartphone 16a, the three-dimensional coordinate system of each of the first marker 12a and the second marker 12b (which are fixed markers), and the three-dimensional coordinate system of the third marker 14 (which is a movable marker), and the position of the determined specific point is finally stored in the smartphone 16 as a relative coordinate with respect to the three-dimensional coordinate system of each of the first marker 12a and the second marker 12b (which are fixed markers).

[0019] An example of the three-dimensional coordinate system of the first marker 12a and the second marker 12b is a coordinate system determined by the X-axis, Y-axis, and Z-axis shown in Figures 1(a) and 1(b) and having a point near the center of either the first marker 12a or the second marker 12b as its origin. These three axes each indicate a direction projected on the screen of the smartphone 16. Specifically, the X-axis indicates a direction connecting the two markers 12a and 12b, the Z-axis indicates a direction passing through each of the markers 12a and 12b, and the Y-axis indicates a direction perpendicular to both the X-axis and the Z-axis.

[0020] The third marker 14 can be attached to any point on the tibia T, including a point on the tibia T close to the first marker 12a and a point on the tibia T close to the second marker 12b, and can be removed from any of these points. Here, the third marker 14 being attached to the tibia T means that the third marker 14 is in contact with any part of the tibia T, and it does not matter whether there is another mechanical element or the like for maintaining the contact state between the third marker 14 and the tibia T. That is, the third marker 14 may be attached by piercing the tibia T as it is with a needle-shaped tip, or the third marker 14 may simply be brought into contact with the tibia T using another mechanical element or the like.

[0021] 1(a), for example, the third marker 14 is attached directly to a proximal portion of the tibia T (specifically, a point P1 of the intercondylar eminence on the superior articular surface of the proximal portion of the tibia including the lateral condyle and the medial condyle), or indirectly attached via a marker fixing member (not shown). By attaching the third marker 14 in this manner, a first marker unit U1 is formed by the first marker 12a and the third marker 14 at the proximal portion of the tibia T.

[0022] 1(b), for example, the third marker 14 is attached directly to a point on the distal side of the tibia T (specifically, a point P2 on the medial malleolus of the tibia T that is farthest from the fibula F) or indirectly attached via a marker fixing member (not shown). By attaching the third marker 14 in this manner, a second marker unit U2 is formed by the second marker 12b and the third marker 14 at the distal part of the tibia T.

[0023] 1(b), for example, the third marker 14 is directly attached to a point on the distal side of the tibia T (specifically, the point P3 on the lateral malleolus of the fibula F that is the furthest from the tibia T) or indirectly attached via a marker fixing member (not shown) (the third marker 14 is not shown at point P3). By attaching the third marker 14 in this manner, the second marker 12b and the third marker 14 form a third marker unit U3 (not shown) at the distal part of the tibia T.

[0024] The third marker 14 may be attached in any manner to the tibia T as long as the portion to be read can be read by the smartphone 16 (when photographed together with the first marker 12a or the second marker 12b, as described below). The third marker 14 may also be a matrix type two-dimensional code such as a QR code (registered trademark), but is not limited to these and various other markers may be used.

[0025] The smartphone 16 separately photographs each of the above-mentioned first marker unit U1 (composed of a first marker 12a fixed to the proximal side of the tibia T and a third marker 14 attached nearby on the tibia T), the second marker unit U2 (composed of a second marker 12b fixed to the distal side of the tibia T and a third marker 14 attached nearby on the tibia T), and the third marker unit U3 (composed of a second marker 12b fixed to the distal side of the tibia T and a third marker 14 attached nearby on the fibula F), and displays the information thereof.

[0026] The smartphone 16 determines a first point (point P1 shown in FIG. 1(a)) at the proximal end of the tibia T and a second point (point P4 in FIG. 1(b)) at the distal end of the tibia T based on the images of the first, second, and third marker units U1, U2, and U3. The smartphone 16 then determines the mechanical axis MA based on the above two points (P1, P4), taking into consideration that the positional relationship between the first marker 12a and the second marker 12b fixed to the tibia T is fixed to each other. Various calculation processes performed in determining the mechanical axis MA can be performed, for example, by a specific application installed in the smartphone 16 and having a calculation processing function.

[0027] As described above, the examples shown above are examples in which the imaging means, display means, and arithmetic processing means are integrated into a single device (e.g., a smartphone), but other examples of this type include notebook PCs as well as smartphones. However, the present invention is not limited to these examples. In other words, the present invention also includes examples A) and B) in which these three means are shared among multiple devices as follows. A) An example in which a camera is used as an imaging means, a personal computer (hereinafter referred to as "PC") as a computing means, and a display as a display means. B) Example of using a camera as an imaging means and a notebook PC equipped with a computing means and a display means In addition, when these three means are provided by two or more devices, there are no other particular restrictions as long as each device is capable of communicating with each other via wired or wireless communication.

[0028] (Mechanism for determining the mechanical axis of the tibia T using this device) The present device 10 (specifically, a device for determining the mechanical axis MA of the tibia) including the first marker 12a, the second marker 12b, the third marker 14, and the smartphone 16 as described above operates as follows.

[0029] The first marker 12a is fixed to a predetermined position on the proximal side of the tibia T, and the second marker 12b is fixed to a predetermined position on the proximal side of the tibia T. Therefore, the first marker 12a and the second marker 12b in a state where they are fixed to the tibia T are in a fixed positional relationship with each other. That is, the first marker 12a is located at a position with a fixed direction and distance from the second marker 12b, and the second marker 12b is located at a position with a fixed direction and distance from the first marker 12a. This makes it possible to clarify the positional relationship between a point whose positional relationship with the first marker 12a is clear and a point whose positional relationship with the second marker 12b is clear.

[0030] Under such a condition, for example, first, the third marker 14 is attached to a point on the tibia T close to the first marker 12a (point P1 on the intercondylar eminence on the superior interarticular surface of the proximal part of the tibia including the lateral condyle and the medial condyle in FIG. 1(a)), and the smartphone 16 photographs the first marker unit U1 composed of the first marker 12a and the third marker 14. Next, based on information about the photographed first marker unit U1, the smartphone 16 determines the position of point P1 in space based on the position of the first marker 12a fixed to the tibia T in advance, and the point P1 is stored and displayed in the smartphone 16. As a result, the first point (i.e., point P1) on the proximal end of the tibia T is determined.

[0031] Next, the third marker 14 is removed from the point P1 and attached to a point on the tibia T close to the second marker 12b (in Figure 1(b), the point P2 on the medial malleolus of the tibia T that is farthest from the fibula F), and the smartphone 16 photographs the second marker unit U2 composed of the second marker 12b and the third marker 14 attached to point P2.

[0032] Furthermore, the third marker 14 is removed from the point P2 and attached to a point on the fibula F close to the second marker 12b (in Figure 1(b) , point P3 on the lateral malleolus of the fibula F that is farthest from the tibia T), and the smartphone 16 photographs the third marker unit U3 composed of the second marker 12b and the third marker 14 attached to point P3.

[0033] Based on the information on the second marker unit U2 and the information on the third marker unit U3 photographed in this manner, the smartphone 16 determines the positions of points P2 and P3 in space based on the position of the second marker 12b previously fixed to the tibia T as a reference, and also determines the midpoint between points P2 and P3 (point P4 in FIG. 1(b)), and point P4 is stored and displayed in the smartphone 16. In this way, a second point (i.e., point P4) at the distal end of the tibia T is determined.

[0034] Finally, based on the positions of a first point (point P1) on the proximal side of the tibia T determined based on the first marker 12a and a second point (point P4) on the distal side of the tibia T determined based on the second marker 12b, the smartphone 16 determines the mechanical axis MA of the tibia T, taking into account that the positional relationship between these markers 12a and 12b is fixed, and the mechanical axis MA is stored and displayed in the smartphone 16.

[0035] (Actions of the device 10 of the present application, etc.) The above-described device 10 of the present application is a kind of so-called navigation system, since it uses a mechanism (smartphone 16) having an imaging function, a calculation processing function, and a display function. In such a system, the imaging function is realized by the camera of the smartphone 16, the calculation processing function is realized by an application for performing calculation processing installed in the smartphone 16, and the display function is realized by the screen of the smartphone 16. In addition, when the smartphone 16 is used, a predetermined operation can be efficiently performed by a single surgeon (action 1).

[0036] Alternatively, such a navigation system may be substantially separate, on the premise that the imaging means, the arithmetic processing means, and the display means are capable of communicating with each other by wire or wirelessly, instead of the smartphone 16. As a result, by allowing these three means to be operated by different people, it is possible to achieve division of labor and to specialize the operation of the surgeon to one or two of these three means, thereby reducing the operational burden on each surgeon (effect 2).

[0037] Next, conventionally, when determining the mechanical axis of the tibia, only one fixed marker was placed on the tibia, and removable markers were sequentially attached to predetermined positions at the proximal end and distal end of the tibia, and these two types of markers were treated as one marker unit.The marker unit was photographed as many times as the number of positions at which the removable markers were placed, and the mechanical axis of the tibia was determined based on the multiple images obtained in this way.

[0038] However, when there is only one fixed marker, the fixed marker must be relatively large in order to determine the mechanical axis with high accuracy, and the imaging means must be placed at a certain distance from the fixed marker to perform imaging, which not only makes the device difficult to handle but also makes it difficult to determine the mechanical axis appropriately. In addition, since the fixed marker is relatively large, it may get in the way of surgery, which may cause a large psychological burden on the surgeon.

[0039] In contrast, the device 10 of the present application uses two relatively small fixed markers (one fixed to the proximal side of the tibia T and the other fixed to the distal side of the tibia T) on the tibia T when determining the mechanical axis of the tibia T. The device 10 of the present application also obtains the positions of the first marker 12a and the second marker 12b (which are fixed markers) and the third marker 14 (which is a movable marker) in the three-dimensional coordinate system of the smartphone 16 (which is an imaging means), and converts the position of a specific point corresponding to the third marker 14 into relative coordinates for each of the first marker 12a and the second marker 12b. Furthermore, in the present device 10, since the positional relationship between the first marker 12a and the second marker 12b is known, the positions of the specific points determined using the first marker 12a and the third marker 14, or the specific points determined using the second marker 12b and the third marker 14, can be converted into relative coordinates with respect to the second marker 12b or the first marker 12a that were not used to determine these specific points. As a result, in the present device 10, the position information of the specific points converted into relative coordinates with respect to the first marker 12a and the second marker 12b is stored in the smartphone 16 (as a computing means), and specific points on the tibia T are determined, and these specific points are further displayed on the smartphone 16, and thus the mechanical axis MA of the tibia T can be determined.

[0040] This allows the imaging means to be installed relatively close to the fixed marker for imaging, which not only has the advantage of making the device itself easier to handle, but also allows the mechanical axis to be determined more appropriately than before.Furthermore, since the fixed marker is relatively small, there is no risk of the fixed marker interfering with the surgery, which in turn has the advantage of reducing the psychological burden on the surgeon (effect 3).

[0041] Furthermore, according to the present device 10 which determines the mechanical axis of the tibia T by the above-mentioned method, since the smartphone 16 is movable, the surgeon can check the mechanical axis of the tibia T and the part of the tibia to be cut within the same field of view, thereby reducing the burden on the surgeon (effect 4).

[0042] As described above, the present device 10 allows the surgeon to perform operations efficiently using a navigation system (effect 1) or reduces the burden on the surgeon (effect 2), while simultaneously solving problems that are particularly in line with recent needs, namely, determining the mechanical axis of the tibia more appropriately than before (effect 3), and reducing the burden on the surgeon by allowing the surgeon to check the mechanical axis and the part of the bone to be cut within the same field of view (effect 4), thereby making it possible to perform osteotomy of the tibia T more easily and appropriately.

[0043] (Other Possible Forms) In the device 10 of the present application described above, the distance between the first marker 12a and the second marker 12b shown in Figs. 1(a) and 1(b) can be set to 5 cm or more and 35 cm or less.

[0044] By setting the distance to 5 cm or more, the first marker 12a and the second marker 12b fixed to the tibia T do not overlap on the screen of the smartphone 16, and both of these two markers can be clearly displayed by the smartphone 16. In contrast, considering that the length of the tibia is generally approximately 40 cm or less, by setting the distance to 35 cm or less, the first marker 12a and the second marker 12b can be reliably placed on the tibia.

[0045] Next, the distance between the first marker 12a (or the second marker 12b) and the third marker 14 shown in FIG. 1(a) and FIG. 1(b) can be 5 cm or more and 20 cm or less. When using the markers (e.g., 5 cm x 5 cm squares) that have been used so far when determining the mechanical axis in the conventional manner (the manner in which only one marker fixed to the tibia is used), it was appropriate from the viewpoint of the operability of the smartphone 16 to set the distance between these two types of markers 12a, 14 and the smartphone 16 to about 30 to 40 cm. Under such a premise, if the two types of markers 12a, 14 are changed to relatively large ones in order to determine the mechanical axis with higher accuracy, it is necessary to move the smartphone 16 relatively far from these two types of markers, and in that case, the operability of the smartphone 16 may be deteriorated. Based on this rule of thumb, assuming that markers of the same size as those used up until now will be used, and taking into consideration the operability of the smartphone 16, it is essential that the distance between the first marker 12a (or the second marker 12b) and the third marker 14 be between 5 cm and 20 cm.

[0046] Furthermore, in the present device 10 in Fig. 1(a) and the like, the first marker 12a and the second marker 12b are square, but the shape of these markers 12a and 12b is not particularly limited to a square, and they can be any shape (for example, a circle, a hexagon, an octagon, a star, etc.). Here, each of the shapes listed above is a shape that, when the markers 12a and 12b are rotated on their surfaces around the center of gravity of the markers 12a and 12b, matches the original shape multiple times during a 360° rotation, and such a shape allows suitable imaging, particularly regardless of the angular relationship between the smartphone 16 and the markers 12a and 12b.

[0047] The reason why the above-mentioned shape is preferable is as follows: The first marker 12a and the second marker 12b are both fixed to the tibia T, and once fixed, their orientation cannot be changed. In order to properly photograph each of the markers 12a and 12b, which cannot be changed in orientation, with the smartphone 16, it is necessary to appropriately adjust the position of the smartphone 16. However, if the longitudinal length and lateral length of the markers 12a and 12b are significantly different from each other, it may be difficult to adjust the position of the smartphone 16.

[0048] Furthermore, the subjects to be photographed in one go are the first (or second) marker 12a (12b) and the third marker 14 that constitute each marker unit U1, U2, U3. If the longitudinal and lateral lengths of these markers 12a, 12b are significantly different, the smartphone 16 may not be able to simultaneously and properly photograph the two types of markers 12a (12b), 14 that constitute each marker unit.

[0049] In contrast, when at least one of the first marker 12a and the second marker 12b has a shape such as a square or a circle as listed above, the longitudinal length and the transverse length of these markers 12a, 12b are equal, which not only makes it easier to adjust the position of the smartphone 16, but also enables the smartphone 16 to simultaneously and appropriately photograph the two types of markers 12a (12b), 14 that make up each of the marker units U1, U2, U3.

[0050] <System including the present device and a device for cutting the tibia> 2 is a perspective view showing a system including the present device 10 and a device 20 for cutting the tibia T. The device 20 for cutting the tibia T includes a cutting guide 22 in which a single slit is defined, a blade 24 for cutting the tibia along the slit of the cutting guide 22, a blade holding portion 26 for holding the blade 24, and a handle piece 28 connected to the blade holding portion 26. The handle piece 28 includes a main body portion 28a and a button 28b attached to the main body portion 28a, and when the button 28b is pressed, the blade 24 vibrates in its short direction (i.e., left and right).

[0051] Once the mechanical axis MA of the tibia T has been determined using the device 10 of the present application as described above, the cutting guide 22 is fixed to the tibia T so that the osteotomy angle planned by the surgeon is achieved when the tibia T is tilted in valgus, varus, or posterior tilt. Here, the osteotomy angle planned by the surgeon with respect to the cutting guide 22 is determined by the obtained mechanical axis MA.

[0052] The position information of the mechanical axis MA is stored in the smartphone 16 (as a calculation processing means) as the positions of the first marker 12a and the second marker 12b (which are fixed markers) on the three-dimensional coordinate system. The installation angle when fixing the cutting guide 22 to the tibia T is an angle obtained by converting the position information of the mechanical axis in the three-dimensional coordinate system of the first marker 12a and the second marker 12b into the position information of the mechanical axis in the three-dimensional coordinate system of the camera of the smartphone 16 (as an imaging means) and calculating the angle based on the converted mechanical axis MA.

[0053] Next, the surgeon grasps the handle piece 28, inserts the blade 24 into the slit, and while pressing the button 28b of the handle piece 28, presses the blade 24 against the tibia T to cut a predetermined portion of the tibia T. When cutting of the tibia T is completed, the surgeon stops pressing the button 28b of the handle piece 28, and pulls out the blade 24 from the slit.

[0054] According to the cutting of the tibia T described above, a more appropriate mechanical axis MA can be utilized compared to the conventional method, so that the cutting guide 22 can be fixed to the tibia T with higher accuracy, thereby achieving a higher level of cutting accuracy of the tibia T. [Explanation of symbols]

[0055] 10. Apparatus of the Present Invention 12a First Marker 12b Second Marker 14 Third Marker 16 Smartphone 20 Tibial T-cutting device 22 Cutting Guide 24 Blades 26 Blade holder 28 Handle piece 28a Main body 28b Button F fibula MA Mechanical Axis P1: A predetermined point on the superior articular surface of the proximal tibia including the lateral and medial condyles P2 The point on the medial malleolus of the tibia (T) that is farthest from the fibula (F) P3 The point of the lateral malleolus of the fibula F that is the furthest from the tibia T P4: Midpoint between points P2 and P3 (second point) T tibia X: The direction connecting the two markers 12a and 12b A direction perpendicular to both YX and Z Z: Direction passing through each marker 12a and 12b

Claims

1. An apparatus for identifying a straight line connecting specific points of an object, the apparatus comprising: a plurality of fixed markers positioned relative to one another; a movable marker; a movable imaging means; a display means; and a calculation processing means, a three-dimensional coordinate system of each of the fixed markers is a reference for three-dimensional coordinates of a specific point of the object, and each of the fixed markers is used together with the movable marker to determine the specific point of the object; The imaging means is used to simultaneously capture an image of one of the fixed markers and the movable marker, and the arithmetic processing means is used to identify a straight line connecting specific points of the object, The apparatus, wherein the display means is used to display at least straight lines connecting specific points of the object.

2. An apparatus for determining a mechanical axis of a tibia, comprising: a first marker on a proximal side and a second marker on a distal side, the first marker and the second marker on a distal side being positioned between a proximal end and a distal end of the tibia and displaced in at least a longitudinal direction of the tibia; a third marker detachable from the tibia; a movable imaging means; a display means; and a processing means, the first marker is used in conjunction with the third marker to determine a first point on the proximal end of the tibia; the second marker is used in conjunction with the third marker to determine a second point on the distal end of the tibia; the imaging means simultaneously images the first marker and the third marker, and simultaneously images the second marker and the third marker; the arithmetic processing means determines a mechanical axis connecting the first point and the second point; The apparatus of claim 1 , wherein the display means displays at least the mechanical axis of the tibia.

3. The apparatus of claim 2 , wherein the first point is determined and stored based on a position of the first marker relative to a position of the third marker.

4. The apparatus of claim 2 , wherein the second point is determined and stored based on a position of the second marker relative to a position of the third marker.

5. The device of claim 2 , wherein the distance between the first marker and the second marker is greater than or equal to 5 cm and less than or equal to 35 cm.

6. The device of claim 2 , wherein at least one of the distance between the first marker and the third marker and the distance between the second marker and the third marker is 5 cm or more and 20 cm or less.

7. A system comprising a device according to any one of claims 1 to 6 and a device for cutting the tibia.

Images