Precise opening angle planning method and device and storage medium

Abstract

The invention provides a precise distraction angle planning method, which comprises the following steps of: reconstructing femur surface grid data and tibia surface grid data, marking related feature points, generating a horizontal osteotomy surface and adjusting the horizontal osteotomy surface; calculating the depth of a horizontal osteotomy surface and the vertical height between the horizontal osteotomy surface and a tibia inner and outer side platform in real time, determining a hinge point, determining a vertical osteotomy surface, simulating the state of the tibia after biplane cutting, determining a distraction angle and the like; personalized preoperative planning is implemented in a 3D space, and automatic setting of the optimal distraction angle of tibia osteotomy is ensured through preoperative personalized evaluation, so that optimal knee joint load distribution is achieved, and operation uncertainty is reduced; three-dimensional data of a tibia, such as CT or MRI, is used, osteotomy and distraction are carried out by calculating the geometrical relationship of feature points of a tibia three-dimensional image and adjusting the section of the three-dimensional image to a proper position, and the method aims at improving the accuracy of planned correction angle measurement.

Description

Technical Field

[0001] The present invention relates to the field of path planning technology, and in particular to a method, device and storage medium for precise expansion angle planning. Background Art

[0002] High Tibial Osteotomy (HTO) is a high tibial osteotomy and distraction procedure that adjusts the force line of the lower limbs. It is suitable for knee osteoarthritis with severe varus. It can reduce joint load and slow down the progression of the disease. It is also called knee-preserving treatment. The key to a successful operation is to accurately calculate the distraction angle before surgery to ensure proper correction of the mechanical axis and avoid complications caused by under- or over-correction. Therefore, personalized preoperative planning is indispensable, and the surgical plan needs to be customized according to the patient's specific condition to achieve the best mechanical adjustment and clinical effect.

[0003] Traditional HTO surgical planning relies on two-dimensional X-rays, which are complex to operate and the accuracy is limited by the doctor's personal skills, which can easily lead to poor surgical results. In contrast, robotic navigation technology has improved surgical accuracy and safety standards, but the existing planning processes are mostly based on two-dimensional planning of a single section, ignoring the complexity of three-dimensional anatomy, which affects the accuracy of surgical planning. The introduction of three-dimensional planning technology not only enhances the optimization ability of surgical strategies through all-round simulation and prediction, but also significantly reduces the geometric errors caused by projection, effectively reducing the risk of complications such as overcorrection and uneven load distribution, thereby improving the accuracy and safety of surgery and reducing postoperative complications such as overcorrection and uneven load distribution.

[0004] The existing technology has the following disadvantages: Current surgical planning usually relies on two-dimensional imaging data, such as X-rays and single-layer CT scans, but due to the lack of three-dimensional perspective, coupled with changes in the tibial projection angle and the influence of surrounding tissue occlusion, it is difficult to accurately analyze the deep structure and key anatomical landmarks of the surgical area. As a result, the accuracy of measuring the angle between the tibial mechanical axis and the proximal tibial articular surface is not high, and the plane angle measurement is very sensitive to the patient's direction. When the degree of femoral bending is too large, the rotation posture will affect the radiographic measurement. This will in turn affect the calculation of personalized correction angles and the surgical effect.

[0005] Traditional surgical planning often relies on general guidelines or doctor experience, and lacks personalized considerations for each patient's specific situation. Different patients have different bone structures, soft tissue conditions, and lower limb force lines, and a single distraction angle is difficult to meet the treatment needs of all patients. Summary of the invention

[0006] The present invention proposes a precise opening angle planning method, which solves the problems in the prior art. The technical solution of the present invention is implemented as follows:

[0007] A precise opening angle planning method comprises the following steps:

[0008] Reconstruct the femoral surface mesh data and mark relevant feature points;

[0009] Reconstruct the tibia surface mesh data and mark relevant feature points;

[0010] Generate and adjust the horizontal osteotomy surface, and calculate the vertical height between the horizontal osteotomy surface and the medial and lateral tibial platform in real time: construct a horizontal cutting plane, adjust the posture of the current horizontal osteotomy surface, and calculate the vertical height between the current horizontal osteotomy surface and the medial and lateral tibial platform according to the medial and lateral marking points of the tibial platform, the midpoint of the end of the horizontal osteotomy surface, and the intersection of the horizontal osteotomy surface and the medial entrance of the tibial surface model in real time;

[0011] Determine the horizontal osteotomy surface and the depth of the horizontal osteotomy surface: construct a horizontal cutting plane, cut the proximal and distal ends of the tibia, record the intersection of the horizontal cutting plane and the mesh data of the femoral surface in real time during the movement, and find the maximum and minimum intersection points on the intersection line parallel to the coronal plane in the x direction, which represent the coordinates of the intersection of the horizontal osteotomy surface and the medial entrance of the tibia, and the coordinates of the intersection of the horizontal osteotomy surface and the edge of the lateral tibia in three-dimensional space; when the end of the horizontal osteotomy line does not exceed the outermost point of the tibia, the depth calculation of the horizontal osteotomy surface is refreshed in real time according to the midpoint of the end of the current horizontal osteotomy surface and the point at the entrance of the horizontal osteotomy surface;

[0012] Determine the hinge point: After determining the horizontal osteotomy surface, the midpoint of the end of the horizontal osteotomy line is used as the current hinge point;

[0013] Determine the vertical osteotomy plane: take the currently determined horizontal osteotomy plane as the reference, record the direction vector on the horizontal osteotomy plane in real time in three-dimensional space as the rotation axis, use its center point as the rotation center, set the rotation angle to 110°, copy the horizontal osteotomy plane as a copy and rotate it 110° around the axis vector as the vertical osteotomy plane;

[0014] Simulate the state of the tibia after dual-plane cutting;

[0015] Determine the distraction angle: calculate the proportion of the force line in the tibial plateau, take the midpoint of the end line of the horizontal osteotomy surface as the axis point, and increase or decrease the rotation angle in sequence based on the ideal correction angle of the previous step, which is the current distraction angle result; calculate the current distraction height based on the osteotomy depth and the current distraction angle.

[0016] As a preferred technical solution, reconstructing the femoral surface mesh data includes the following steps: scanning the patient's entire lower limb simulated weight-bearing CT tomography, intercepting a three-dimensional image of the femur part, recorded as femurImage, and reconstructing the femoral surface mesh data based on femurImage, recorded as femurSurface; intercepting a three-dimensional image of the tibia part, recorded as tibiaImage, and reconstructing the femoral surface mesh data based on tibiaImage, recorded as tibiaSurface, the inner and outer points of the tibial plateau are stored in a point set named PointSet1, the first point in the point set outerTibia(x1,y1,z1) refers to the outer point of the tibial plateau, the second point in the point set inTibia(x2,y2,z2) refers to the inner point of the tibial plateau, and the edge position closest to the inner and outer platforms of the tibia is selected; the inner and outer malleolus points of the distal tibia are stored in a point set named PointSet2, the first point in the point set exPoint(x1,y1,z1) represents the outer malleolus of the tibia, and the second point in the point set inPoint(x2,y2,z2) represents the inner malleolus of the tibia.

[0017] As a preferred technical solution, the center of the femoral head is marked on the femoral side, and the inner and outer sides of the proximal tibia, the medial malleolus, and the lateral malleolus are marked on the tibial side. The method for marking the center of the femoral head is as follows: select the rotation center of the femoral head on the femoral surface grid data. If the rotation center of the femoral head is difficult to determine directly, several points can be selected on the surface of the femoral head, and the least squares method can be used to fit the center of a sphere based on these surface points as the rotation center of the femoral head.

[0018] As a preferred technical solution, the horizontal osteotomy surface and the depth of the horizontal osteotomy surface are determined by the following method:

[0019] Step 1) Use the vtkPlaneSource class to create a plane vtkPolyData data Plane1 to represent the horizontal cutting plane, cut the proximal and distal ends of the tibia, move the horizontal cutting plane to a reasonable position on the tibia surface model, and record the normal vector of Plane1 after the move and the coordinate values ​​of any point on the plane. With a1, use Create a vtkPlane class data cutPlane_1 with a1;

[0020] Step 2) Use vtk to record the intersection of cutPlane_1 and tibiaSurface at all times during the movement, and find out the maximum intersection point vergePoint(x0,y0,z0) and the minimum intersection point kerfpoint(x1,y1,z1) on the intersection line parallel to the coronal plane in the x direction, which respectively represent the intersection coordinates of the horizontal osteotomy surface and the medial entrance of the tibia in three-dimensional space, and the intersection coordinates of the horizontal osteotomy surface and the edge of the lateral side of the tibia;

[0021] Step 3) Record the midpoint of the end line of the current horizontal osteotomy surface in real time, which is the hinge point and is recorded as hingePoint(xi,yi,zi);

[0022] Step 4) The distance between the osteotomy surface entrance and the medial tibial plateau is h in calculate:

[0023] Calculate the Euclidean distance between the point inTibia(x2,y2,z2) and the point kerfPoint(x1,y1,z1):

[0024]

[0025] The height h from the end of the osteotomy surface to the lateral tibial plateau out calculate:

[0026] Calculate the Euclidean distance between the point outerTibia(x1,y1,z1) and the point vergePoint(x0,y0,z0):

[0027]

[0028] Keep the outer hinge thickness h hinge Calculate the vergePoint(x0,y0,z0) and hingePoint(x i ,y i ,z i ) is the Euclidean distance between:

[0029]

[0030] Step 5) When the end of the horizontal osteotomy line does not exceed the outermost vergePoint(x0,y0,z0) of the tibia, the current horizontal osteotomy depth depth can be calculated based on the real-time recorded midpoint of the horizontal osteotomy surface end hingePoint(xi,yi,zi) and the horizontal osteotomy surface entrance point kerfPoint(x1,y1,z1). The calculation formula is as follows:

[0031]

[0032] When the end of the horizontal osteotomy line exceeds the vergePoint(x0,y0,z0) point on the outermost side of the tibia, the current horizontal osteotomy depth can be calculated based on the real-time recorded intersection point vergePoint(x0,y0,z0) between the end of the horizontal osteotomy surface and the outermost side of the tibia and the kerfPoint(x1,y1,z1) at the entrance of the horizontal osteotomy surface. The formula is as follows:

[0033]

[0034] As a preferred technical solution, the vertical osteotomy plane is determined by the following method: taking the current horizontal osteotomy plane as a reference, recording the direction vector on the horizontal osteotomy plane in real time in three-dimensional space as the selected rotation axis, specifying the center point centerPoint(x0,y0,z0) of the horizontal osteotomy line as the rotation center, setting the rotation angle angle to 110°, and using vtkTransform to copy the horizontal osteotomy plane as a copy and rotate it 110° around the axis vector as the vertical osteotomy plane cutPlane_2.

[0035] As a preferred technical solution, the following method is used to simulate the state of the tibia after dual-plane cutting:

[0036] Step 6) Use the vtkClipPolyData method, take tibia_Surface and cutPlane_1 as its input and cutting function respectively, get the cut-removed and remaining two sets of vtkPolyData data, record the larger space volume as tibia_L, and the smaller space volume as tibia_S, and use the vtkFillHolesFilter method to fill the holes on the surfaces of tibia_L and tibia_S caused by cutting;

[0037] Step 7) Use the vtkClipPolyData method, take tibia_S and cutPlane_2 as its input and cutting function respectively, get the cut-out and remaining two sets of vtkPolyData data, record the larger space volume as tibia_P, and the smaller space volume as tibia_T. Use the vtkFillHolesFilter method to fill the holes on the surfaces of tibia_P and tibia_T caused by cutting;

[0038] Step 8) Use the vtkAppendPolyData method to merge tibia_T and tibia_L into a vtkPolyData data, recorded as tibia_D. tibia_D and tibia_P simulate the state of the patient's tibia after dual-plane cutting. The proximal and distal ends of the tibia are divided into two independent parts, and the tibial tuberosity is connected to the distal end of the tibia.

[0039] As a preferred technical solution, the proportion of the force line on the tibial plateau is calculated by the following steps:

[0040] Step 9) Based on the point set PointSet2 storing the medial and lateral malleolus of the distal tibia, calculate the center point of the medial and lateral malleolus of the distal tibia, tibiaPointCenter(x3,y3,z3); create a new node of type DataNode, named powerLine; insert the femoral head center point femurCenter(x0,y0,z0) and tibiaPointCenter(x3,y3,z3) stored in the point set Poinset1 into the point set powerLine, and use them as the starting point to construct a lower limb force line, named powerLine, and calculate the length of the lower limb force line:

[0041] L=|tibiaPointCenter-femurPoint|;

[0042] Step 10) Based on the inner and outer marking points of the proximal tibia stored in the set PointSet1, a straight line is constructed and named tibiaPlane; and the width d of the tibial plateau is calculated using the following formula:

[0043] d=|outerTibia x -inTibia x |

[0044] Step 11) The center point of the knee joint can be calculated from the medial and lateral points of the proximal tibia, which is recorded as ioPoint(xi,yi,zi);

[0045] Step 12) The straight lines powerLine and tibiaPlane are respectively transformed to a two-dimensional plane (x, z) parallel to the human coronal plane by means of geometric projection, and the intersection of the lower limb force line powerLine and tibiaPlane on the two-dimensional plane is calculated using the VTK mathematical library, recorded as IsPoint(xi,yi); the proportion of the force line on the tibial plateau can be expressed by the following formula:

[0046]

[0047] As a preferred technical solution, the ideal opening angle is determined by the following steps:

[0048] Step 13) Calculate the direction vector from the axis point H to the end point of the current force line (i.e., to the center point of the tibia and the medial and lateral ankle joints tibiaPointCenter (x3, y3, z3)): The formula can be expressed as:

[0049]

[0050] Step 14) Calculate the target from the center of the femoral head through the center of the knee joint to the ideal position, that is, the end point a' of the ideal force line. The formula can be expressed as:

[0051]

[0052] Step 15) Calculate the direction vector from the axis point H to the end point a′ of the ideal force line: The formula is as follows:

[0053]

[0054] Step 16) Calculate the angle θ between the two vectors a and b, which is the ideal correction angle. The formula is as follows:

[0055]

[0056] A precise distraction angle planning device comprises a CT tomography apparatus and an osteotomy surgical robot, and is used to execute a precise distraction angle planning method as described in any one of the above steps.

[0057] A non-temporary computer-readable storage medium, when the instructions in the storage medium are executed by a precise opening angle planning device, enables the device to execute the above-mentioned precise opening angle planning method.

[0058] Compared with the prior art, this solution has the following beneficial effects:

[0059] 1) Navigation-assisted HTO surgical planning technology integrates biomechanics and intelligent algorithms to implement personalized preoperative planning in 3D space. Through personalized preoperative evaluation, the optimal tibial osteotomy angle is automatically set to achieve the optimal knee joint load distribution and reduce surgical uncertainty.

[0060] 2) Using 3D data of the tibia, such as CT or MRI, the osteotomy and distraction are performed by calculating the geometric relationship of the feature points of the 3D image of the tibia and adjusting the cross-section of the 3D image to the appropriate position, aiming to improve the accuracy of the measurement of the planned correction angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0062] Figure 1A schematic diagram of the position of the rotation center of the femoral head of the present invention;

[0063] Figure 2 It is a schematic diagram of the positions of the medial and lateral points of the tibial plateau of the present invention;

[0064] Figure 3 It is a schematic diagram of the positions of the medial and lateral malleolus points at the distal end of the tibia of the present invention;

[0065] Figure 4 It is a schematic diagram of the horizontal osteotomy surface of the present invention;

[0066] Figure 5 It is a schematic diagram of the position adjustment of the horizontal osteotomy surface of the present invention;

[0067] Figure 6 It is a schematic diagram of the positions of the midpoint of the end of the horizontal osteotomy surface and the point at the entrance of the horizontal osteotomy surface when the end of the horizontal osteotomy line does not exceed the outermost point of the tibia in the present invention;

[0068] Figure 7 It is a schematic diagram of the positions of the intersection of the end of the horizontal osteotomy surface and the outermost point of the tibia and the point at the entrance of the horizontal osteotomy surface when the end of the horizontal osteotomy line exceeds the outermost point of the tibia according to the present invention;

[0069] Figure 8 A schematic diagram of a vertical osteotomy plane determined according to a horizontal osteotomy plane in the present invention;

[0070] Fig. 9 It is a schematic diagram of the state presented by the present invention after cutting through the horizontal osteotomy surface;

[0071] Fig.10 It is a schematic diagram of the state of the tibia after double-plane cutting according to the present invention;

[0072] Fig.11 It is a schematic diagram of the force line of the lower limbs of the present invention;

[0073] Fig.12 This is a schematic diagram of an ideal opening angle of the present invention. DETAILED DESCRIPTION

[0074] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0075] The present invention provides a method for accurate distraction angle planning, which includes the following main steps: three-dimensional reconstruction of bone model, marking of physiological feature points, osteotomy surface planning and distraction angle planning. Specifically:

[0076] 1. 3D reconstruction of bone model

[0077] Before the operation, the patient's entire lower limb was scanned with simulated weight-bearing CT tomography, and the three-dimensional image of the femur was captured, recorded as femurImage, and the femoral surface mesh data was reconstructed based on femurImage, recorded as femurSurface; the three-dimensional image of the tibia was captured, recorded as tibiaImage, and the femoral surface mesh data was reconstructed based on tibiaImage, recorded as tibiaSurface; (capturing CT images and reconstructing surface meshes are both basic operations in medical imaging).

[0078] 2. Physiological feature point marking

[0079] Before surgery, the femoral and tibia feature points were marked on the reconstructed three-dimensional model of the lower limbs to calculate the mechanical axis of the lower limbs. The center of the femoral head was marked on the femoral side, and the medial and lateral sides of the proximal tibia, the medial malleolus, and the lateral malleolus were marked on the tibial side.

[0080] 1. Femoral head rotation center: Select the femoral head rotation center point femurCenter (x0, y0, z0) on femurSurface and save it in a single point set named femurCenter. Figure 1 If the rotation center of the femoral head is difficult to determine directly, several points can be selected on the surface of the femoral head and the least squares method can be used to fit the center of the sphere based on these surface points as the rotation center of the femoral head.

[0081] 2. If Figure 2 and Figure 3 As shown, mark the following points on the tibial surface model;

[0082] The inner and outer points of the tibial plateau are stored in a point set named PointSet1 (the first point in the point set outerTibia(x1,y1,z1) refers to the outer point of the tibial plateau, and the second point inTibia(x2,y2,z2) refers to the inner point of the tibial plateau. The edge position closest to the inner and outer tibial plates is selected as much as possible).

[0083] The points of the medial and lateral malleolus of the distal tibia are stored in a point set named PointSet2 (the first point in the point set exPoint(x1,y1,z1) represents the lateral malleolus of the tibia, and the second point in the point set inPoint(x2,y2,z2) represents the medial malleolus of the tibia).

[0084] 3. Osteotomy surface planning

[0085] 1. Horizontal osteotomy surface planning

[0086] In clinical surgery, double-plane cutting is often used to preserve the integrity of the tibial tuberosity. The relative position of the double plane and the patient's tibia needs to be planned in advance. This plan will serve as a basis for the doctor to judge whether the saw blade position is correct when performing osteotomy.

[0087] like Figure 4 As shown, first use the vtkPlaneSource class to create a plane vtkPolyData data Plane1 to represent the horizontal cutting plane, cutting the proximal and distal ends of the tibia. Move the horizontal cutting plane to a reasonable position on the tibia surface model. Record the normal vector of Plane1 after the move and the coordinate values ​​of any point on the plane respectively. With a1, use Create a vtkPlane class data cutPlane_1 with a1;

[0088] 1.1. Adjustment of the horizontal osteotomy surface and calculation of osteotomy parameters (taking the right leg as an example)

[0089] like Figure 5 As shown, vtk is used to record the intersection of cutPlane_1 and tibiaSurface during the movement, and the maximum intersection point vergePoint(x0,y0,z0) and the minimum intersection point kerfpoint(x1,y1,z1) on the intersection line parallel to the coronal plane in the x direction are found, which respectively represent the intersection coordinates of the horizontal osteotomy surface and the medial entrance of the tibia in three-dimensional space, and the intersection coordinates of the horizontal osteotomy surface and the edge of the lateral side of the tibia;

[0090] The midpoint of the end line of the current horizontal osteotomy surface is recorded in real time, recorded as hingePoint(xi,yi,zi) (i.e., hinge point);

[0091] 1.2. Height h from the osteotomy entrance to the medial tibial plateau in calculate

[0092] Calculate the Euclidean distance between the point inTibia(x2,y2,z2) and the point kerfPoint(x1,y1,z1):

[0093]

[0094] 1.3. The distance between the end of the osteotomy surface and the lateral tibial plateau h out calculate

[0095] Calculate the Euclidean distance between the point outerTibia(x1,y1,z1) and the point vergePoint(x0,y0,z0):

[0096]

[0097] 1.4. Keep the thickness of the outer hinge h hinge calculate

[0098] Calculate vergePoint(x0,y0,z0) and hingePoint(x i ,y i ,z i ) is the Euclidean distance between:

[0099]

[0100] 1.5. Calculation of horizontal osteotomy depth

[0101] According to the current horizontal osteotomy surface posture adjustment, the depth calculation of the horizontal osteotomy surface is refreshed in real time;

[0102] like Figure 6 As shown in the figure, when the end of the horizontal osteotomy line does not exceed the outermost vergePoint(x0,y0,z0) of the tibia, the current horizontal osteotomy depth depth can be calculated based on the real-time recorded midpoint of the end of the horizontal osteotomy surface hingePoint(xi,yi,zi) and the entrance point of the horizontal osteotomy surface kerfPoint(x1,y1,z1). The formula is as follows:

[0103]

[0104] like Figure 7 As shown in the figure, when the end of the horizontal osteotomy line exceeds the vergePoint(x0,y0,z0) point on the outermost side of the tibia, the current horizontal osteotomy depth can be calculated based on the real-time recorded intersection point vergePoint(x0,y0,z0) between the end of the horizontal osteotomy surface and the outermost side of the tibia and the kerfPoint(x1,y1,z1) at the entrance of the horizontal osteotomy surface. The formula is as follows:

[0105]

[0106] 2. Vertical osteotomy surface planning

[0107] Based on the current horizontal osteotomy surface, the direction vector on the horizontal osteotomy surface is recorded in real time in three-dimensional space. As the selected rotation axis, specify the center point centerPoint(x0,y0,z0) of the horizontal osteotomy line as the rotation center, set the rotation angle angle to 110°, use vtkTransform, copy the horizontal osteotomy surface as the copy around the axis vector Rotate 110° to make the vertical osteotomy plane cutPlane_2, such as Figure 8 As shown;

[0108] 3. Osteotomy

[0109] Use the vtkClipPolyData method, take tibia_Surface and cutPlane_1 as its input and cutting function respectively, and get the two vtkPolyData data after cutting and removing. The larger one is recorded as tibia_L, and the smaller one is recorded as tibia_S. Use the vtkFillHolesFilter method to fill the holes on the surfaces of tibia_L and tibia_S caused by cutting. The obtained tibia_L and tibia_S are as follows Fig. 9 As shown;

[0110] Use the vtkClipPolyData method, take tibia_S and cutPlane_2 as its input and cutting function respectively, get the cut-out and remaining two sets of vtkPolyData data, record the larger space volume as tibia_P, and the smaller space volume as tibia_T. Use the vtkFillHolesFilter method to fill the holes on the surfaces of tibia_P and tibia_T caused by cutting;

[0111] Use the vtkAppendPolyData method to merge tibia_T and tibia_L into a vtkPolyData data, recorded as tibia_D. Fig. 9 As shown, tibia_D and tibia_P simulate the state of the patient's tibia after dual-plane cutting. The proximal and distal ends of the tibia are divided into two independent parts, and the tibial tuberosity is connected to the distal end of the tibia.

[0112] 4. Opening Angle Planning

[0113] 1. Calculation of the proportion of force line on tibial plateau (P)

[0114] Based on the point set PointSet2 storing the medial and lateral malleolus of the distal tibia, calculate the center point of the medial and lateral malleolus of the distal tibia, tibiaPointCenter(x3,y3,z3); create a new node of type DataNode and name it powerLine; insert the femoral head center point femurCenter(x0,y0,z0) and tibiaPointCenter(x3,y3,z3) stored in the point set Poinset1 into the point set powerLine, and use them as the starting point to construct a lower limb force line named powerLine, such as Fig.10 As shown, calculate the length of the lower limb force line:

[0115] L=|tibiaPointCenter-femurPoint|;

[0116] According to the proximal medial and lateral marker points of the tibia stored in the set PointSet1, a straight line is constructed and named tibiaPlane; and the width d of the tibial plateau is calculated as follows:

[0117] d=|outerTibia x -inTibia x |

[0118] The center point of the knee joint can be calculated from the medial and lateral points of the proximal tibia, which is recorded as ioPoint(xi,yi,zi);

[0119] The straight lines powerLine and tibiaPlane are transformed into two-dimensional planes (x, z) parallel to the coronal plane of the human body by geometric projection. The intersection of the lower limb force line powerLine and tibiaPlane on the two-dimensional plane is calculated using the VTK mathematical library, which is recorded as IsPoint(xi,yi). The proportion of the force line on the tibial plateau can be expressed by the following formula:

[0120]

[0121] 2. Calculation of ideal opening angle

[0122] like Fig.12 As shown, determine the axis point (H), which is the hinge point in the osteotomy surface planning (the end point of the horizontal osteotomy surface hingePoint (x1, y1, z1));

[0123] 2.1 Calculate the direction vector from the axis point H to the end point of the current force line: The formula can be expressed as:

[0124]

[0125] Among them, the end point of the current force line is the center point of the tibia and the medial and lateral ankle joints tibiaPointCenter(x3,y3,z3)

[0126] 2.2 Calculate the target ideal force line end point a" (i.e. from the center of the femoral head through the center of the knee joint to the ideal position), the formula can be expressed as:

[0127]

[0128] 2.3 Calculate the direction vector from the axis point H to the end point a′ of the ideal force line: The formula is as follows:

[0129]

[0130] 2.4 Calculate the angle θ between the two vectors a and b, which is the ideal correction angle. The formula is as follows:

[0131]

[0132] 3. Current opening angle calculation

[0133] Tibia_D rotates around the axis point H by angle angle, and increases or decreases by angle based on the ideal correction angle in the previous step, which is the current opening angle result;

[0134] 4. Calculation of opening height (h)

[0135] The current distraction height h can be calculated by trigonometric function from the osteotomy depth depth and the current distraction angle Angle;

[0136] h = depth*sin(angle).

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A precise opening angle planning method, characterized in that: The following steps are involved: Reconstruct the femoral surface mesh data and mark relevant feature points; Reconstruct the tibia surface mesh data and mark relevant feature points; Generate and adjust the horizontal osteotomy surface, and calculate the vertical height between the horizontal osteotomy surface and the medial and lateral tibial platform in real time: construct a horizontal cutting plane, adjust the posture of the current horizontal osteotomy surface, and calculate the vertical height between the current horizontal osteotomy surface and the medial and lateral tibial platform according to the medial and lateral marking points of the tibial platform, the midpoint of the end of the horizontal osteotomy surface, and the intersection of the horizontal osteotomy surface and the medial entrance of the tibial surface model in real time; Determine the horizontal osteotomy surface and the depth of the horizontal osteotomy surface: construct a horizontal cutting plane, cut the proximal and distal ends of the tibia, record the intersection of the horizontal cutting plane and the mesh data of the femoral surface in real time during the movement, and find the maximum and minimum intersection points on the intersection line parallel to the coronal plane in the x direction, which represent the coordinates of the intersection of the horizontal osteotomy surface and the medial entrance of the tibia, and the coordinates of the intersection of the horizontal osteotomy surface and the edge of the lateral tibia in three-dimensional space; when the end of the horizontal osteotomy line does not exceed the outermost point of the tibia, the depth calculation of the horizontal osteotomy surface is refreshed in real time according to the midpoint of the end of the current horizontal osteotomy surface and the point at the entrance of the horizontal osteotomy surface; Determine the hinge point: After determining the horizontal osteotomy surface, the midpoint of the end of the horizontal osteotomy line is used as the current hinge point; Determine the vertical osteotomy plane: take the currently determined horizontal osteotomy plane as the reference, record the direction vector on the horizontal osteotomy plane in real time in three-dimensional space as the rotation axis, use its center point as the rotation center, set the rotation angle, copy the horizontal osteotomy plane as a copy and rotate it 110° around the axis vector as the vertical osteotomy plane; Simulate the state of the tibia after dual-plane cutting; Determine the distraction angle: calculate the proportion of the force line in the tibial plateau, take the midpoint of the end line of the horizontal osteotomy surface as the axis point, and increase or decrease the rotation angle in sequence based on the ideal correction angle of the previous step, which is the current distraction angle result; calculate the current distraction height based on the osteotomy depth and the current distraction angle.

2. A precise opening angle planning method as claimed in claim 1, characterized in that: Reconstructing the surface mesh data of the femur and tibia includes the following steps: scanning the whole length of the patient's lower limbs for simulated weight-bearing CT tomography, intercepting the three-dimensional image of the femur part, recorded as femurImage, and reconstructing the surface mesh data of the femur based on femurImage, recorded as femurSurface; intercepting the three-dimensional image of the tibia part, recorded as tibiaImage, and reconstructing the surface mesh data of the femur based on tibiaImage, recorded as tibiaSurface, the inner and outer points of the tibial plateau are stored in a point set named PointSet1, the first point in the point set outerTibia(x1,y1,z1) refers to the outer point of the tibial plateau, the second point in the point set inTibia(x2,y2,z2) refers to the inner point of the tibial plateau, and the edge position closest to the inner and outer tibial platforms is selected; the inner and outer malleolus points of the distal tibia are stored in a point set named PointSet2, the first point in the point set exPoint(x1,y1,z1) represents the outer malleolus of the tibia, and the second point in the point set inPoint(x2,y2,z2) represents the inner malleolus of the tibia.

3. A precise opening angle planning method as claimed in claim 1, characterized in that: The center of the femoral head is marked on the femoral side, and the inner and outer sides of the proximal tibia, the medial malleolus, and the lateral malleolus are marked on the tibial side. The marking method for the center of the femoral head is as follows: select the rotation center of the femoral head on the femoral surface grid data. If the rotation center of the femoral head is difficult to determine directly, select several points on the surface of the femoral head and use the least squares method to fit the center of the sphere based on these surface points as the rotation center of the femoral head.

4. A precise opening angle planning method as claimed in claim 2, characterized in that: The horizontal osteotomy plane and the horizontal osteotomy plane depth are determined by the following methods: Step 1) Use the vtkPlaneSource class to create a plane vtkPolyData data Plane1 to represent the horizontal cutting plane, cut the proximal and distal ends of the tibia, move the horizontal cutting plane to a reasonable position on the tibia surface model, and record the normal vector of Plane1 after the move and the coordinate values ​​of any point on the plane. With a1, use Create a vtkPlane class data cutPlane_1 with a1; Step 2) Use vtk to record the intersection of cutPlane_1 and tibiaSurface at all times during the movement, and find out the maximum intersection point vergePoint(x0,y0,z0) and the minimum intersection point kerfpoint(x1,y1,z1) on the intersection line parallel to the coronal plane in the x direction, which respectively represent the intersection coordinates of the horizontal osteotomy surface and the medial entrance of the tibia in three-dimensional space, and the intersection coordinates of the horizontal osteotomy surface and the edge of the lateral side of the tibia; Step 3) Record the midpoint of the end line of the current horizontal osteotomy surface in real time, which is the hinge point and is recorded as hingePoint(xi,yi,zi); Step 4) The distance between the osteotomy surface entrance and the medial tibial plateau is h in calculate: Calculate the Euclidean distance between the point inTibia(x2,y2,z2) and the point kerfPoint(x1,y1,z1): The height h from the end of the osteotomy surface to the lateral tibial plateau out calculate: Calculate the Euclidean distance between the point outerTibia(x1,y1,z1) and the point vergePoint(x0,y0,z0): Keep the outer hinge thickness h hinge calculate Calculate vergePoint(x0,y0,z0) and hingePoint(x i ,y i ,z i ) is the Euclidean distance between: Step 5) When the end of the horizontal osteotomy line does not exceed the outermost vergePoint(x0,y0,z0) of the tibia, the current horizontal osteotomy depth depth can be calculated based on the real-time recorded midpoint of the horizontal osteotomy surface end hingePoint(xi,yi,zi) and the horizontal osteotomy surface entrance point kerfPoint(x1,y1,z1). The calculation formula is as follows: When the end of the horizontal osteotomy line exceeds the vergePoint(x0,y0,z0) point on the outermost side of the tibia, the current horizontal osteotomy depth can be calculated based on the real-time recorded intersection point vergePoint(x0,y0,z0) between the end of the horizontal osteotomy surface and the outermost side of the tibia and the kerfPoint(x1,y1,z1) at the entrance of the horizontal osteotomy surface. The formula is as follows:

5. A precise opening angle planning method as claimed in claim 2, characterized in that: The vertical osteotomy plane is determined by the following method: taking the current horizontal osteotomy plane as the reference, the direction vector on the horizontal osteotomy plane is recorded in real time in three-dimensional space as the selected rotation axis, the center point centerPoint(x0,y0,z0) of the horizontal osteotomy line is specified as the rotation center, the rotation angle angle is set to 110°, and vtkTransform is used to copy the horizontal osteotomy plane as a copy and rotate it 110° around the axis vector as the vertical osteotomy plane cutPlane_2.

6. A precise opening angle planning method as claimed in claim 2, characterized in that: The following method is used to simulate the state of the tibia after biplane cutting: Step 6) Use the vtkClipPolyData method, take tibia_Surface and cutPlane_1 as its input and cutting function respectively, get the cut-removed and remaining two sets of vtkPolyData data, record the larger space volume as tibia_L, and the smaller space volume as tibia_S, and use the vtkFillHolesFilter method to fill the holes on the surfaces of tibia_L and tibia_S caused by cutting; Step 7) Use the vtkClipPolyData method, take tibia_S and cutPlane_2 as its input and cutting function respectively, get the cut-out and remaining two sets of vtkPolyData data, record the larger space volume as tibia_P, and the smaller space volume as tibia_T. Use the vtkFillHolesFilter method to fill the holes on the surfaces of tibia_P and tibia_T caused by cutting; Step 8) Use the vtkAppendPolyData method to merge tibia_T and tibia_L into a vtkPolyData data, recorded as tibia_D. tibia_D and tibia_P simulate the state of the patient's tibia after dual-plane cutting. The proximal and distal ends of the tibia are divided into two independent parts, and the tibial tuberosity is connected to the distal end of the tibia.

7. The precise opening angle planning method according to claim 1, characterized in that: The proportion of the force line on the tibial plateau is calculated by the following steps: Step 9) Based on the point set PointSet2 storing the medial and lateral malleolus of the distal tibia, calculate the center point of the medial and lateral malleolus of the distal tibia, tibiaPointCenter(x3,y3,z3); create a new node of type DataNode, named powerLine; insert the femoral head center point femurCenter(x0,y0,z0) and tibiaPointCenter(x3,y3,z3) stored in the point set Poinset1 into the point set powerLine, and use them as the starting point to construct a lower limb force line, named powerLine, and calculate the length of the lower limb force line: L=|tibiaPointCenter-femurPoint|; Step 10) Based on the inner and outer marking points of the proximal tibia stored in the set PointSet1, a straight line is constructed and named tibiaPlane; and the width d of the tibial plateau is calculated using the following formula: d=|outerTibia x -inTibia x | Step 11) The center point of the knee joint can be calculated from the medial and lateral points of the proximal tibia, which is recorded as ioPoint(xi,yi,zi); Step 12) The straight lines powerLine and tibiaPlane are respectively transformed to a two-dimensional plane (x, z) parallel to the human coronal plane by means of geometric projection, and the intersection of the lower limb force line powerLine and tibiaPlane on the two-dimensional plane is calculated using the VTK mathematical library, recorded as IsPoint(xi,yi); the proportion of the force line on the tibial plateau can be expressed by the following formula:

8. The precise opening angle planning method according to claim 1, characterized in that: Determine the ideal distraction angle by following these steps: Step 13) Calculate the direction vector from the axis point H to the end point of the current force line (i.e., to the center point of the tibia and the medial and lateral ankle joints tibiaPointCenter (x3, y3, z3)): The formula can be expressed as: Step 14) Calculate the target from the center of the femoral head through the center of the knee joint to the ideal position, that is, the end point a' of the ideal force line. The formula can be expressed as: Step 15) Calculate the direction vector from the axis point H to the end point a′ of the ideal force line: The formula is as follows: Step 16) Calculate the angle θ between the two vectors a and b, which is the ideal correction angle. The formula is as follows:

9. A precise opening angle planning device, characterized in that: It comprises a CT tomograph and an osteotomy robot, which are used to execute a precise distraction angle planning method as described in any one of steps 1 to 8 above.

10. A non-temporary computer-readable storage medium, when the instructions in the storage medium are executed by a precise opening angle planning device as described in claim 9, the device is able to execute any one of the precise opening angle planning methods described in claims 1 to 8.

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