Surgery support device for determining a virtual rotation center of a femur and a system including the device

Abstract

To provide a surgical operation support device which can properly determine the rotation center position of the femur in comparison to a conventional technique, and reduces the burden on an operator by allowing the operator to confirm a mechanical axis and confirm a portion of the bone to be cut within the same field of view.SOLUTION: Two candidate points (R1, R2) for the virtual rotation center of the femur (F) are determined by arithmetic processing means (14) on the basis of the internal rotation position (R01) and the external rotation position (R02) of the reference position (R0). For each of the two candidate points, an index based on the internal rotation position and external rotation position of the candidate point is determined by the arithmetic processing means. If the index of the candidate point for which the index is more suitable is within a prescribed range, this candidate point is determined by the arithmetic processing means as the virtual rotation center of the femur. If the indices of the two candidate points are outside the prescribed range, two new candidate points (R3, R4) are determined by the arithmetic processing means on the basis of the internal rotation position and external rotation position of the candidate point for which the index is more suitable.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a surgical support device for determining a virtual rotation center of the femur, which determines and displays a more appropriate position for the femoral rotation center (hereinafter sometimes simply referred to as the "rotation center") used to determine the mechanical axis required during knee artificial joint surgery, and a system including this device. [Background technology]

[0002] In knee artificial joint surgery, when cutting the femur, it is necessary to determine in advance the so-called mechanical axis, which is displayed by connecting the rotation center (hip joint center) located on the proximal side of the femur and the knee joint center located on the distal side of the femur. The mechanical axis is a reference line for determining the plane for cutting the femur in order to properly fit a femoral component into the distal part of the femur, for example. Therefore, it is important to determine the rotation center of the femur in order to determine the mechanical axis.

[0003] As a technique for determining the rotation center of the femur, for example, Patent Document 1 discloses a femoral head center location identifying device that identifies the position of the femoral head center (corresponding to the above-mentioned rotation center) of a patient in a plane parallel to the frontal plane during total knee joint replacement surgery. In Patent Document 1, the distance from the rotation axis to the marker in a direction parallel to the frontal plane is the same as the distance from the distal end of the femur to the femoral head center, which is measured in advance, and the rotation axis is located at the distal end of the femur, so that when the rotating arm is rotated to mark an arc on a marking plate with a marker, the arc passes through a point opposite the femur center. Therefore, according to Patent Document 1, when the hip joint is internally or externally rotated to position the femur at a first position and a second position that are spaced apart from each other, and a first arc and a second arc are marked on a marking plate at these positions, the first arc and the second arc will intersect at a point opposite the center of the femoral head, and the position of the center of the femoral head can be identified in a plane parallel to the frontal plane from this intersection. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-029769 A Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of Patent Document 1 aims to identify the center of rotation of the femur as accurately as possible while keeping surgical costs low, but in recent years there has been a strong demand to determine the center of rotation even more accurately.

[0006] In recent years, there has also been a strong desire to reduce the burden on the surgeon when performing distal femur osteotomy by allowing 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 objective to provide a surgical support device and a system including this device that can determine the position of the center of rotation of the femur more appropriately than before, and that reduces the burden on the surgeon by allowing him or her to check the mechanical axis and the part of the bone to be cut within the same field of view. [Means for solving the problem]

[0008] In order to solve the above problems, a surgery support device according to the present invention comprises: A surgical support device for determining a virtual rotation center of a femur, comprising: A marker whose position relative to the pelvis is fixed, an imaging means for capturing an image including the marker, the imaging means being fixed in position relative to the femur; A display means for displaying the image; a calculation processing means for detecting a plurality of images of the marker captured during rotation of the imaging means, and determining a reference position of the virtual rotation center based on the plurality of images; Equipped with two candidate points for the virtual center of rotation are determined by the arithmetic processing means based on an internal rotation position and an external rotation position of the reference position photographed by internally rotating and externally rotating the imaging means around the longitudinal axis of the femur; For each of the two candidate points, an index based on an internal rotation position and an external rotation position of the candidate point photographed by internally rotating and externally rotating the imaging means around the longitudinal axis of the femur is determined by the arithmetic processing means; If the index of the candidate point with the more suitable index is within a predetermined range, the candidate point with the more suitable index is determined as the virtual rotation center of the femur by the arithmetic processing means; If the indicators of both of the two candidate points are outside the specified range, two new candidate points for the virtual rotation center, which are corrected positions of the candidate point for which the indicator is more suitable, are determined by the calculation processing means based on the internal rotation position and the external rotation position of the candidate point for which the indicator is more suitable. Effect of the Invention

[0009] In the present invention, on the premise of using a type of navigation system, i.e., a mechanism including an imaging means, a display means, and a calculation processing means, when determining the virtual rotation center of the femur, a plurality of points are set based on the pelvis, and the reference position of the virtual rotation center of the femur is determined based on these points, and the reference position is further corrected so as to approach the true rotation center, thereby making it possible to determine the virtual rotation center of the femur more appropriately than in the past. In addition, in the present invention, the marker is installed with a fixed positional relationship with the pelvis, and the imaging means is installed with a fixed positional relationship with the femur, so that the degree of freedom of change in the relative position between the imaging means and the marker to be photographed is reduced, making it possible to more appropriately photograph the marker, and thus making it possible to more appropriately determine the rotation center of the femur. Furthermore, in the present invention, the imaging means is tied to the femur to be cut and fixed near the femur, so that the surgeon can check the mechanical axis with the virtual rotation center of the femur as an end point and the part of the femur to be cut in the same field of view, thereby reducing the burden on the surgeon. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing a surgery support device 10 of the present invention, and in particular shows the manner in which a smartphone 14 is rotated when determining the reference position of a virtual rotation center of a femur F. [Diagram 2] Figure 2 is an oblique view showing the surgical support device 10 of the present invention viewed from the distal side of the femur F, and in particular shows the rotational manner of the smartphone 14 when determining a candidate point for the virtual rotation center of the femur F based on the reference position R0. [Diagram 3] FIG. 3 is a schematic diagram showing an example of a method for determining a candidate point, in which a trajectory (arc) of the reference position R0 is determined based on a position R01 after internal rotation and a position R02 after external rotation of the reference position R0, and a candidate point (center of a circle) R1 for the virtual rotation center of the femur F is determined based on this trajectory. [Figure 4] FIG. 4 is a schematic diagram showing candidate points R1 and R2 for the virtual rotation center of the femur determined by the calculation processing means based on position R01 after internal rotation and position R02 after external rotation of the reference position R0, and new candidate points R3 and R4 when these candidate points R1 and R2 are not determined as the virtual rotation center. [Diagram 5] FIG. 5 is a schematic diagram showing a mechanical axis MA connecting a virtual rotation center Cf of the femur F determined using the surgery support device 10 of the present invention and a knee joint center Ck. [Figure 6] FIG. 6 is a schematic diagram showing a system including an apparatus 20 for cutting a femur F whose mechanical axis MA has been determined. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <Surgical support device> FIG. 1 is a perspective view showing a surgery support device for determining a virtual rotation center of a femur according to an embodiment of the present invention (hereinafter, sometimes referred to as the "surgery support device of the present application"), and in particular, a diagram showing a rotation state of a smartphone 14 when determining a reference position R0 of a virtual rotation center of a femur F. Note that the figure shows an example of a right femur. As shown in FIG. 1, the surgery support device 10 of the present application includes a marker 12 and a smartphone 14. Here, the smartphone 14 has a function of an imaging means by its camera, a function of a display means by its display screen, and further has a function of a calculation means by an application installed therein. Therefore, the surgery support device 10 of the present application is substantially equipped with an imaging means, a display means, and a calculation means.

[0012] The marker 12 is fixed to an arbitrary portion of the pelvis P, for example, near the pelvis P adjacent to the proximal end of the femur F as shown in FIG. 1, via a marker fixing member, or directly near the pelvis P (ilium). The marker 12 may be fixed to the pelvis P in any manner as long as the portion to be read can be read by the smartphone 14. The marker 12 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 adopted. The marker 12 may be, for example, a square so that it can be read accurately and easily by the smartphone 14.

[0013] The smartphone 14 can be fixed to any site on the distal end side of the femur F, for example, at the very distal end of the femur F. Fixing of the smartphone 14 to the femur F can be achieved, for example, by a smartphone holder 16 and a cutting guide 18 as shown in FIG. 1. The smartphone 14 may be fixed to the femur F in any manner as long as the part that performs reading faces the marker 12. In the example shown in FIG. 1, the smartphone 14 is used as a device equipped with an imaging means, a display means, and a calculation processing means, but any device that includes the functions of these means can be used instead of the smartphone 14.

[0014] In this embodiment, the imaging means, the display means, and the arithmetic processing means are integrated by the smartphone 14, but the imaging means, the display means, and / or the arithmetic processing means can be provided separately. Here, the display means is a means for displaying an image captured by the imaging means, a result of arithmetic processing by the arithmetic processing means, and the like. The arithmetic processing means is a means for detecting a plurality of images of the marker captured by a predetermined first operation (rotation, described later) of the imaging means, performing a predetermined operation based on these images to determine a reference position R0 of the virtual rotation center of the femur, detecting a plurality of images related to the position after the movement of the reference position R0 captured by a predetermined second operation (internal rotation and external rotation, described later) of the imaging means, performing a predetermined operation based on these images to correct the reference position R0 so as to approach the position of the true rotation center, thereby determining the virtual rotation center of the femur F. Furthermore, in addition to the above-mentioned roles, the arithmetic processing means also has a function of checking how many degrees the femur F has rotated around its longitudinal axis during internal rotation and external rotation, described later, and this function is also displayed on the display means. Here, the longitudinal axis of the femur F refers to the straight line obtained by connecting the imaginary center of the femoral head and the center of the knee joint, that is, the mechanical axis MA.

[0015] The imaging means may be disposed in the same manner as described above for the smartphone 14, whether the imaging means is provided integrally with the display means and / or the arithmetic processing means or provided separately. In contrast, the display means and / or the arithmetic processing means, when provided separately from the imaging means, may be directly or indirectly disposed on the pelvis P or the femur F, but may also be disposed in other positions (i.e., positions spaced apart from the pelvis P or the femur F). Note that it is sufficient for these three means to be capable of communicating with other means separate from themselves, either wired or wirelessly, and no other restrictions are imposed on these three means.

[0016] Based on the above, examples of combinations of an imaging means, a display means, and a calculation processing means include the following examples in addition to the present example in which all of them are contained within the smartphone 14. A) An example in which a single-lens reflex camera is used as an imaging means, a personal computer (hereinafter referred to as "PC") is used as a computing means, and a display is used as a display means. B) An example in which a single-lens reflex camera is used as the imaging means, and a notebook PC is used as both the computing means and the display means.

[0017] The surgery support device 10 of the present invention, which includes the marker 12 and the smartphone 14 (which incorporates an imaging means, a display means, and a calculation processing means) described above, will be described in further detail.

[0018] The surgical support device 10 of the present application is a device that can determine the reference position R0 of the virtual rotation center of the femur F, and then corrects the reference position R0 so as to approach the true rotation center of the femur F, thereby more appropriately determining the virtual rotation center of the femur F than conventional devices.

[0019] The surgical support device 10 of the present application is configured to be used in two separate steps: In the first step, a reference position R0 of a virtual center of rotation of the femur F is determined, and in the second step, the virtual center of rotation is determined.

[0020] (First step) The first step is to determine the reference position R0 of the virtual center of rotation of the femur F by rotating the femur F to which the smartphone 14 is attached in three dimensions around its true center of rotation as a fulcrum, from a state in which the smartphone 14 is photographing the marker 12 and the pelvis P to which the marker 12 is attached is fixed.

[0021] Here, the marker 12 is fixed to an arbitrary portion of the pelvis P, and therefore the position of the marker 12 is fixed relative to the pelvis P. In contrast, the smartphone 14 is fixed to an arbitrary portion on the distal end side of the femur F, and therefore the position of the smartphone 14 is fixed relative to the femur F.

[0022] Under these conditions, the smartphone 14 is positioned so that the marker 12 shown in Fig. 1 and the true center of rotation of the femur F are both within the display screen of the smartphone 14. Here, the true center of rotation of the femur F refers to the center of rotation of the femur F in a state in which the pelvis P is fixed when the hip joint, which is the joint between the pelvis P and the femur F, moves.

[0023] Next, the femur F to which the smartphone 14 is attached is rotated with its true center of rotation as a fulcrum. The femur F can be rotated, for example, in the directions of the arrows shown in Fig. 1 (upward A11, downward A12, leftward A13, rightward A14), but can be rotated in any direction without being limited to these directions. The femur F can be rotated manually, or by using a femur rotation tool (not shown) attached to the femur F.

[0024] In this specification, the coordinate system is based on the camera of the smartphone 14. Therefore, when the camera of the smartphone 14 moves by rotating the femur F as described above, the marker 12 fixed to the pelvis P appears to move from the camera. In contrast, even if the camera of the smartphone 14 moves, the femur F to which the camera is attached appears to be stationary from the camera.

[0025] Rotation of the femur F also rotates the smartphone 14 attached to the femur F. Here, rotation of the smartphone 14 refers to moving the smartphone 14 relative to the marker 12 (i.e., the pelvis P) so that the center of the lens of the camera of the smartphone 14 moves three-dimensionally while keeping the smartphone 14 fixed to the femur F. In the example shown in Fig. 1, the center of the lens of the camera moves three-dimensionally so as to describe a sphere with the true center of rotation of the femur F as a fulcrum and the line segment connecting this true center of rotation and the center of the lens of the camera of the smartphone 14 as a radius.

[0026] When the smartphone 14 is rotated, the position of the marker 12 is stored and displayed on the smartphone 14 for each predetermined amount of rotation of the smartphone 14. The predetermined amount of rotation of the smartphone 14 can be determined by a predetermined moving distance and / or a predetermined moving time of the center of the lens of the camera. When the number of markers 12 displayed on the smartphone 14 reaches, for example, 300, the above rotation of the femur F is terminated.

[0027] By not making this predetermined amount of rotation too small, the positions of the markers 12 displayed on the smartphone 14 do not overlap excessively, and it is possible to easily determine the reference position R0 described below. On the other hand, by not making this predetermined amount of rotation too large, it is not necessary to rotate the smartphone 14 excessively when storing and displaying the positions of a predetermined number of markers 12 (for example, 300 points) on the smartphone 14, and it is possible to reduce the burden on the surgeon.

[0028] In this way, when the positions of the markers 12, for example, 300 points, are stored and displayed on the smartphone 14, a calculation processing means (i.e., various applications with calculation processing functions installed in the smartphone 14) determines a reference position R0, and the reference position R0 is stored and displayed on the smartphone 14.

[0029] The reference position R0 can be determined, for example, as follows. That is, assuming that multiple positions (e.g., 300 points) of the markers 12 displayed on the smartphone 14 are near the surface of a specific sphere, the arithmetic processing means in the smartphone determines the radius and center of this sphere using the least squares method or the like. Next, the arithmetic processing means determines the center of this sphere as the reference position R0 of the virtual rotation center of the femur F, and the reference position R0 is stored and displayed in the smartphone 14.

[0030] (Second step) The second step is a step in which the smartphone 14 is photographing the reference position R0 of the virtual rotation center of the femur F obtained in the first step and the pelvis P to which the marker 12 is attached is fixed, and then the femur F to which the smartphone 14 is attached is rotated (i.e., internally and externally) around its longitudinal axis to determine the virtual rotation center of the femur.

[0031] 2 is a perspective view showing the present surgery support device 10 when the femur F is viewed from the distal side, and in particular shows the rotational state of the smartphone 14 when determining a candidate point for the virtual rotation center of the femur F based on the reference position R0. Note that FIG. 2 also shows the right femur, like FIG. 1.

[0032] In the second step, the smartphone 14 is first positioned so that the marker 12 is located toward the center of the display screen of the smartphone 14 .

[0033] Next, the femur F to which the smartphone 14 is attached is internally and externally rotated around its longitudinal axis. The external and internal rotation of the femur F is performed in the directions of the arrows shown in Fig. 2 (internal rotation direction A21, external rotation direction A22). The internal and external rotation of the femur F can be performed manually, but can also be performed by attaching a femur rotation (internal and external rotation) instrument (not shown) to the femur F and using this instrument.

[0034] When the femur F internally and externally rotates, the smartphone 14 attached to the femur F also internally and externally rotates. Here, the internal rotation of the smartphone 14 refers to moving the camera lens center of the smartphone 14 closer to the median plane of the human body so as to move the camera lens center two-dimensionally within a plane perpendicular to the longitudinal axis of the femur F while keeping the smartphone 14 fixed to the femur F. In contrast, the external rotation of the smartphone 14 refers to moving the camera lens center of the smartphone 14 away from the median plane of the human body so as to move the camera lens center two-dimensionally within a plane perpendicular to the longitudinal axis of the femur F while keeping the smartphone 14 fixed to the femur F.

[0035] For example, in the example shown in Figure 2, the center of the lens of the camera of the smartphone 14 fixed to the femur F can be moved two-dimensionally by the action of the center of the lens of the camera tracing a circle toward the median plane (rotating in the direction of arrow A21 in the same figure) and the action of the center of the lens of the camera tracing a circle away from the median plane (rotating in the direction of arrow A22 in the same figure).

[0036] As a rough guide, the smartphone 14 is rotated internally until the internal rotation angle of the femur displayed on the smartphone 14 reaches 10°. Similarly, as a rough guide, the smartphone 14 is rotated externally until the external rotation angle of the femur displayed on the smartphone 14 reaches 10°. The range of internal and external rotation of the smartphone 14 corresponds to the range in which the patient's femur is preferably rotated during surgery. That is, if the internal and external rotation angles are excessively small, there is a risk that the accuracy of determining the virtual rotation center of the femur will be low. In the case of a human femur, the rotation angle is realistically about ±10°, and in reality, the internal and external rotation angles may be ±9° or ±11°.

[0037] During internal and external rotation of the smartphone 14, the position of the reference position R0 after the movement is stored and displayed on the smartphone 14 for each predetermined amount of rotation of the smartphone 14. The predetermined amount of rotation of the smartphone 14 can be determined by a predetermined movement distance and / or a predetermined movement time of the lens center of the camera. By not making this predetermined amount of rotation excessively small, the positions of the reference position R0 displayed on the smartphone 14 after the movement do not overlap excessively, and it is possible to easily determine the virtual rotation center of the femur F, which will be described later. On the other hand, by not making this predetermined amount of rotation excessively large, it is not necessary to rotate the smartphone 14 excessively when storing and displaying the positions of a predetermined number (for example, 40 points) of reference positions R0 after the movement on the smartphone 14, and the burden on the surgeon can be reduced.

[0038] The internal rotation and external rotation are performed until the number of positions displayed after the reference position R0 has been moved reaches a predetermined number. When the above-mentioned predetermined amount of rotation of the smartphone 14 is relatively small, it is sufficient to perform the internal rotation and external rotation once each. In contrast, when the above-mentioned predetermined amount of rotation of the smartphone 14 is relatively large, the internal rotation and external rotation can be performed multiple times in succession, for example, internal rotation, external rotation, internal rotation, external rotation, until the number of positions displayed after the reference position R0 has been moved reaches a predetermined number. The internal rotation and external rotation are terminated when the number of positions displayed on the smartphone 14 after the reference position R0 has been moved reaches a predetermined number (for example, when it reaches 40).

[0039] 3 is a schematic diagram showing an example of a method for determining a candidate point, in which a trajectory (arc) of the reference position R0 is obtained based on a position R01 after internal rotation and a position R02 after external rotation of the reference position R0, and a candidate point (center of a circle) R1 of the virtual rotation center of the femur F is further obtained based on this trajectory. Note that this figure assumes a case viewed from the camera of the smartphone 14, that is, a case in which a plane perpendicular to the optical axis of the camera of the smartphone 14 is used as a reference.

[0040] In determining the candidate points for the virtual center of rotation of the femur F shown in Figure 3, first, an arc CA with positions R01 and R02 as its two ends is determined based on multiple points that exist between position R01 after internal rotation of the reference position R0 and position R02 after external rotation. This is because previous research has shown that most figures with positions R01 and R02 as their two ends are circular arcs.

[0041] Next, assuming that the central angle of this arc CA (the sum of the internal rotation angle and external rotation angle described above) is 20°, the center of a circle including this arc CA is determined as shown in Fig. 3, and this is set as a candidate point R0' for the virtual rotation center of the femur F. Here, the reason why the central angle of the arc CA is set to 20° is because it coincides with the preferable range for internally and externally rotating the patient's femur during surgery, similar to the reason for the rotation range of the smartphone 14 described above.

[0042] The above-described determination of candidate points for the virtual center of rotation of the femur F is premised on the premise that most of the figures having both ends, position R01 after internal rotation of the reference position R0 and position R02 after external rotation, form a circular arc. However, recent further research has revealed that when the reference position R0 is relatively far from the true center of rotation, the figures having both ends, position R01 and position R02, form a circular arc, but when the reference position R0 is very close to the true center of rotation, the figures having both ends, position R01 and position R02, do not form a circular arc.

[0043] For this reason, the inventors have concluded that it is appropriate to use the method described below instead of the method shown in Figure 3 described above, so that the candidate points for the virtual rotation center of the femur F in the present invention can be determined appropriately regardless of the distance between the reference position R0 and the true rotation center.

[0044] 4 is a schematic diagram showing candidate points R1 and R2 of the virtual rotation center of the femur determined by the arithmetic processing means based on the position R01 after internal rotation and the position R02 after external rotation of the reference position R0, and new candidate points R3 and R4 when these candidate points R1 and R2 are not determined as the virtual rotation center. Note that in this figure, as in FIG. 3, it is assumed that the view is taken from the camera of the smartphone 14, that is, the plane perpendicular to the optical axis of the camera of the smartphone 14 is used as the reference.

[0045] As shown in Fig. 4, when the reference position R0 is rotated internally and externally and the end points R01 and R02 after the movement are determined, the arithmetic processing means included in the smartphone 14 regards two arcs C1 and C2 between the end points R01 and R02. This is because, when the reference position R0 is actually very close to the true rotation center, it is unclear on which side the center of the arc should be when the figure with the end points R01 and R02 as both ends is regarded as an arc. Furthermore, the arithmetic processing means determines the center of each arc C1 and C2 as the candidate points R1 and R2 for the virtual rotation center of the femur F, assuming that the central angle (the sum of the above-mentioned internal rotation angle and external rotation angle) of these arcs C1 and C2 is 20°.

[0046] Next, which of the candidate points R1 and R2 for the virtual rotation center of the femur is to be set as the virtual rotation center of the femur F will be described in detail.

[0047] For each of the candidate points R1 and R2, the same internal rotation and external rotation operations as those performed for the reference position R0 are performed, and as shown in Figure 4, a position R11 after internal rotation and a position R12 after external rotation are determined for the candidate point R1, and a position R21 after internal rotation and a position R22 after external rotation are determined for the candidate point R2.

[0048] Here, the following indicators are determined based on the position R11 after internal rotation and the position R12 after external rotation of candidate point R1, and the position R21 after internal rotation and the position R22 after external rotation of candidate point R2 due to the internal and external rotation of the camera lens of smartphone 14. Index for candidate point R1: Dimension of triangle with one side made up of position R11 after internal rotation and position R12 after external rotation Index for candidate point R2: Dimension of triangle with one side made up of R21 after internal rotation and R22 after external rotation

[0049] For example, a specific example of the index for the candidate point R1 is the sum of the lengths of the sides of a triangle T1 with vertices R1, R11, and R12 shown in FIG. 4, and a specific example of the index for the candidate point R2 is the sum of the lengths of the sides of a triangle T2 with vertices R2, R21, and R22 shown in FIG. 4. Note that the above triangles T1 and T2 are both assumed to have the same internal rotation angle and external rotation angle from the candidate points R1 and R2. However, if the internal rotation angle and external rotation angle are different, such as if the internal rotation angle from the candidate point R1 is 11° and the external rotation angle is 9°, the exact center position (in this case, the position of 1° of internal rotation) when considering the internal rotation and external rotation comprehensively is set as the vertex of the triangle T1 instead of the candidate point R1. This idea is because if two of the three vertices of a triangle are relatively close to each other, the above index becomes less meaningful.

[0050] Once these indices have been determined, the smartphone 14 uses a calculation processing means to check whether the indices for each of the candidate points R1 and R2 are within a predetermined reference value range.

[0051] There is no particular restriction on the sum of the lengths of the three sides of the triangle for the above index, for example. This is because the standard of the index (the range of the sum of the lengths of the three sides of the triangle) varies depending on the purpose of use of the machine that uses the present invention, and it is meaningful to have the function of presenting the index so that the purpose of use can be changed.

[0052] The arithmetic processing means determines whether or not the index for candidate point R1 and the index for candidate point R2 are within the range of reference values, and if at least one of the indexes is within the range of reference values, determines the candidate point with the more suitable index value as the virtual rotation center of the femur F, and this information is stored and displayed on the smartphone 14. In the example shown in Fig. 4, the sum of the lengths of the three sides of triangle T1 is smaller than that of triangle T2, so the arithmetic processing means determines candidate point R1 as the virtual rotation center of the femur F only when the sum of the lengths of the three sides of triangle T1 is within a specific range.

[0053] In response to this, the calculation processing means determines whether or not the index for candidate point R1 and the index for candidate point R2 are within the range of reference values, and if both indexes are outside the range of reference values, new candidate points R3 and R4 are determined by the calculation processing means based on the position R11 after internal rotation and the position R12 after external rotation of the candidate point with the more suitable index value (in the example shown in Figure 4, candidate point R1), and this information is stored and displayed on the smartphone 14.

[0054] The new candidate points R3 and R4 are determined based on the position R11 after internal rotation and the position R12 after external rotation of candidate point R1, in the same way that candidate points R1 and R2 were determined based on the position R01 after internal rotation and the position R02 after external rotation of the reference position R0.

[0055] The above operations are repeated until a candidate point whose index is within a predetermined range appears. The above example is merely one example of determining the final candidate point (an example using the above index). Other examples of determining the final candidate point include determining the index based on the ratio between the distance from the camera of the smartphone 14 and the index value, rather than the index value itself, and determining based on the amount of change in the index value, rather than the index value itself. In practice, these examples can be appropriately adopted to avoid infinitely repeating the above process without the index reaching a specific standard.

[0056] (effect, etc.) The surgical support device 10 of the present application described above is based on the premise of using a type of navigation system, i.e., a mechanism including an imaging means, a display means, and a calculation processing means, and when determining the virtual rotation center of the femur F, multiple points are set based on the pelvis P, and a reference position R0 of the virtual rotation center of the femur F is determined based on these points. Furthermore, by correcting this reference position R0 so as to approach the true rotation center, the virtual rotation center of the femur F can be determined more appropriately than in the conventional method (effect 1).

[0057] In addition, in the present surgical support device 10, the marker 12 is placed in a fixed position relative to the pelvis P, and the imaging means (smartphone 14) is placed in a fixed position relative to the femur F. This reduces the degree of freedom for changes in the relative position between the imaging means and the marker to be photographed, making it possible to more appropriately photograph the marker 12, and ultimately to more appropriately determine the center of rotation of the femur F (effect 2).

[0058] Furthermore, in the present surgical support device 10, the imaging means is linked to the femur F to be cut and fixed near the femur F, so that the surgeon can check the mechanical axis with the virtual rotation center of the femur F as its end point and the part of the femur F to be cut within the same field of view, thereby reducing the burden on the surgeon (effect 3).

[0059] As described above, according to the surgical support device 10 of the present application, the above-mentioned actions 1 to 3 are combined to simultaneously solve problems that are particularly in line with recent needs, namely, determining the position of the center of rotation of the femur F more appropriately than before, and reducing the burden on the surgeon by allowing him or her to check the mechanical axis and the part of the bone to be cut within the same field of view, thereby making it possible to perform osteotomy of the femur F more appropriately and easily.

[0060] (Other Additional Embodiments) The above is an embodiment in which the candidate points R1 and R2 are determined from the reference position R0 to determine the virtual rotation center of the femur F, but there are cases where the reference position R0 itself is very close to the true rotation center. This is the case where the distance between the end points R01 and R02 shown in FIG. 3 is very short. In such a case, on the premise that it is confirmed that the sum of the lengths of the three sides of a triangle having a line segment connecting the position R01 after internal rotation and the position R02 after external rotation of the reference position R0 shown in FIG. 4 is within a range of a predetermined reference value, instead of determining the candidate points R1 and R2 by the arithmetic processing means, the arithmetic processing means determines that the reference position R0 is the virtual rotation center of the femur F, and this information is stored and displayed on the smartphone 14.

[0061] An example of the above triangle is triangle T0 with vertices R0, R01, and R02 shown in Fig. 4, but the sum of the lengths of the three sides of this triangle is not particularly limited. This is because the criteria for the above index (the range of the sum of the lengths of the three sides of the above triangle) differs depending on the purpose of use of the machine that uses the present invention, and the function of presenting the above index makes it meaningful to be able to change the purpose of use.

[0062] (Mechanical Axis) 5 is a schematic diagram showing a mechanical axis MA connecting a virtual rotation center Cf of the femur F determined using the surgery support device 10 of the present invention and a knee joint center Ck. Here, the knee joint center Ck is a center of rotation between the distal condyle of the femur F and the knee joint center Ck. It is located in the fossa and serves as the distal starting point of the mechanical axis MA, the reference axis for the osteotomy angle. In addition, the mechanical axis MA serves as a reference line for determining the plane along which the femur F is to be cut in order to properly fit a femoral component into the distal portion of the femur F, for example.

[0063] <System including the present surgical support device and a device for cutting the femur> FIG. 6 is a schematic diagram showing a system including an apparatus 20 for cutting the femur F for which the mechanical axis MA has been determined. It is assumed that this system includes the above-mentioned surgical support apparatus 10 of the present application. When cutting the femur F, a cutting block 18a included in the above-mentioned cutting guide 18 and having one slit formed therein is used. The apparatus 20 for cutting the femur F includes a blade 24 for cutting the femur F along the slit of the cutting block 18a, a blade holding part 26 for holding the blade 24, and a handle piece 28 connected to the blade holding part 26. The handle piece 28 includes a main body 28a and a button 28b attached to the main body 28a, and when the button 28b is pressed, the blade 24 vibrates in its short direction.

[0064] Once the mechanical axis MA of the femur F has been determined using the support device 10 of the present invention as described above, the cut block 18a is aligned with and fixed to the femur F so that the bone cutting angle planned by the surgeon is achieved when the femur F is tilted in valgus, varus, or posterior inclination. Here, the bone cutting angle planned by the surgeon with respect to the cut block 18a is determined by the obtained mechanical axis MA.

[0065] The position information of the mechanical axis MA is stored in the smartphone 14 (as a calculation processing means) as the position on the three-dimensional coordinate system of the marker 12 shown in Figures 1 and 2. The installation angle when fixing the cut block 18a to the femur F is an angle obtained by converting the position information of the mechanical axis MA in the three-dimensional coordinate system of the marker 12 into position information of the mechanical axis MA in the three-dimensional coordinate system of the camera of the smartphone 14 (as an imaging means) and calculating the angle based on the converted mechanical axis MA.

[0066] Next, the surgeon grasps the handle piece 28 and inserts the blade 24 into the slit of the cut block 18a (inserting it from the front into the plane of the paper in the example shown in FIG. 6), and while pressing the button 28b of the handle piece 28, presses the blade 24 against the femur F to cut a predetermined portion of the femur. When cutting of the femur F is completed, the surgeon stops pressing the button 28b of the handle piece 28 and pulls the blade 24 out of the slit.

[0067] According to the cutting of the femur F as described above, a more appropriate mechanical axis MA can be utilized than in the past, so that the cut block 18a can be fixed to the femur F with higher precision, and thus a higher level of cutting precision of the femur F can be achieved. [Explanation of symbols]

[0068] 10 Proposed surgical support device 12 Markers 14 Smartphone 16 Smartphone holder 18 Cutting Guide 18a Cut Block 20 Femur cutting device 24 Blades 26 Blade holder 28 Handle piece 28a Main body 28b Button A11, A12, A13, A14, A21, A22 Arrows A21 Internal rotation direction A22 External rotation direction CA, C1, C2 Arcs Cf Virtual rotation center of femur F Ck knee joint center F Femur MA Mechanical Axis P Pelvis R0 Reference position R01 Position after internal rotation of reference position R02 Position after external rotation from reference position R0´, R1, R2 Candidate points for the virtual rotation center of the femur R11 Position of candidate point R1 after internal rotation R12 Position of candidate point R1 after external rotation R21 Position of candidate point R2 after internal rotation R22 Position of candidate point R2 after external rotation R3, R4 New candidate points for the virtual rotation center of the femur T0 Triangle with three vertices R0, R01, and R02 T1 A triangle with three vertices R1, R11, and R12 T2 A triangle with vertices R2, R21, and R22

Claims

1. A surgical support device for determining a virtual rotation center of a femur, comprising: A marker whose position relative to the pelvis is fixed, an imaging means for capturing an image including the marker, the imaging means being fixed in position relative to the femur; A display means for displaying the image; a calculation processing means for detecting a plurality of images of the marker captured during rotation of the imaging means, and determining a reference position of the virtual rotation center based on the plurality of images; Equipped with two candidate points for the virtual center of rotation are determined by the arithmetic processing means based on an internal rotation position and an external rotation position of the reference position photographed by internally rotating and externally rotating the imaging means around the longitudinal axis of the femur; For each of the two candidate points, an index based on an internal rotation position and an external rotation position of the candidate point photographed by internally rotating and externally rotating the imaging means around the longitudinal axis of the femur is determined by the arithmetic processing means; If the index of the candidate point having the more suitable index is within a predetermined range, the candidate point having the more suitable index is determined as the virtual rotation center of the femur by the arithmetic processing means; A surgical support device in which, if the index of either of the two candidate points is outside a predetermined range, two new candidate points of the virtual rotation center, which are corrected positions of the candidate point for which the index is more suitable, are determined by the calculation processing means based on the internal rotation position and the external rotation position of the candidate point for which the index is more suitable.

2. The surgery support device according to claim 1 , wherein the two new candidate points are repeatedly determined by the arithmetic processing means until the index for either of the two new candidate points falls within a predetermined range.

3. The surgery support device according to claim 1 , wherein the index is determined based on a dimension of a triangle having a line segment connecting the internal rotation position and the external rotation position of the two candidate points as one side.

4. 2. The surgical support device according to claim 1, wherein when the sum of the lengths of the sides of a triangle having a line segment connecting the internal rotation position and the external rotation position of the reference position as one side is within a predetermined range, instead of the two candidate points being determined by the arithmetic processing means, the arithmetic processing means determines the reference position as a virtual rotation center of the femur.

5. The surgery support device according to claim 1 , wherein a mechanical axis connecting a virtual rotation center of the femur and a center of a knee joint is determined and displayed.

6. A system comprising a surgical assistance device according to any one of claims 1 to 5 and a device for cutting a femur.

Images