Calculation method and system for optimal placement orientation of acetabular cup in total hip joint surgery

Abstract

The invention discloses a calculation method and system for the optimal placement orientation of an acetabular cup in a total hip joint operation, and belongs to the field of surgical instruments. The calculation method comprises the steps that CT data of a patient is obtained, a three-dimensional model is constructed, point locations in the three-dimensional model are recognized, a three-dimensional coordinate system is established according to a pelvis mark point and a femoral head rotation center point, and the optimal placement orientation of the acetabular cup is calculated; and determining the initial position of femoral motion according to the femoral head rotation center point and the femoral mark point. And drawing a space femoral neck movement range according to the femoral form and a preset hip joint movement range. The centroid of the curved surface is calculated based on the space femoral neck movement range, the rotation center point of the femoral head serves as the starting point and extends towards the centroid to form a ray, and the orientation of the ray in three-dimensional coordinates serves as the optimal placement orientation of the acetabular cup. According to the method, the individualized thighbone shape and the joint movement range of a patient are considered, the optimal acetabulum orientation is given according to different prostheses, and a definite operation target and guidance are given to an operator, so that the dislocation risk after hip replacement is reduced, and the acetabular cup placement reliability is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the field of surgical instruments, and particularly relates to a calculation method and system for the optimal placement orientation of an acetabular cup during total hip arthroplasty. Background Art

[0002] Total hip arthroplasty (THA) is considered one of the most effective and safest surgeries for treating hip diseases, relieving patient pain, and restoring function. More than one million hip replacement surgeries are performed globally each year to treat hip diseases such as severe hip osteoarthritis, osteonecrosis of the femoral head, and congenital hip dysplasia. The placement orientation of the acetabular prosthesis has long been considered an important factor affecting the success rate of THA surgery. Poor placement orientation of the acetabular prosthesis results in increased prosthesis wear, edge loading, and impingement rate, which may lead to a series of complications such as osteolysis and dislocation. In terms of artificial joint dislocation, the initially recognized Lewinnek and combined anteversion concept was considered unreliable after a large number of clinical practices. Even when the placement positions of the acetabular prosthesis were within the above-mentioned safe zone, a large number of dislocation cases still occurred. With the enhancement of computer simulation capabilities, new concepts such as the "combined sagittal plane index" and the "functional safe zone" have been successively proposed, but these methods have not been widely recognized. In such a clinical dilemma and demand, this application combines the personalized pelvic and femoral morphology of the patient and the range of joint motion required for daily activities, proposes the theory that there is an optimal orientation for the placement of the acetabular cup, and develops a calculation method for the optimal placement orientation of the acetabular cup based on the patient's preoperative CT and digital models of daily joint motion. Summary of the Invention

[0003] The technical objective of the present invention is to provide a calculation method and system for the optimal placement orientation of an acetabular cup during total hip arthroplasty to achieve the optimal placement of the acetabular cup during total hip arthroplasty.

[0004] To solve the above problems, the technical solution of the present invention is as follows: A calculation method for the optimal placement orientation of an acetabular cup during total hip arthroplasty, comprising the following steps: Obtain the CT data of the patient and construct a three-dimensional model, identify the pelvic landmark points, femoral landmark points, femoral head center point, and femoral head rotation center point in the three-dimensional model, establish a three-dimensional coordinate system based on the pelvic landmark points and the femoral head rotation center point, and determine the initial position of femoral movement based on the femoral head rotation center point and the femoral landmark points; Draw the spatial femoral neck movement range according to the femoral anteversion angle, femoral neck shaft angle, and the preset hip joint movement range, specifically by drawing the movement surface of the intersection point of the femoral neck and the femoral shaft of the femur in the three-dimensional model; Calculate the centroid of the femoral neck surface based on its range of motion in space. Starting from the center of rotation of the femoral head, extend a ray in the direction of the centroid. The orientation of the ray in the three-dimensional coordinate system is used as the optimal placement orientation of the acetabular cup. Furthermore, output the abduction angle and anteversion angle of the acetabulum as a reference for acetabular cup placement.

[0005] Among them, in the step of constructing the three-dimensional model, the pelvic landmark points include the left anterior superior iliac spine point, the right anterior superior iliac spine point, and the midpoint of the pubic symphysis on both sides of the pelvis, and the femoral landmark points include the lateral femoral condyle point and the medial femoral condyle point. Establish a three-dimensional coordinate system with the plane determined by the left anterior superior iliac spine point, the right anterior superior iliac spine point, and the midpoint of the pubic symphysis as the coronal plane. Take the midpoint of the connection line between the lateral femoral condyle point and the medial femoral condyle point as the center of the knee joint. Connect the center of the knee joint with the center of rotation of the femoral head to form the femoral connection line. When the femoral connection line is perpendicular to the cross-section, the position of the femur at this time is the initial position of femoral movement.

[0006] Among them, the specific steps for drawing the range of motion of the femoral neck in space are as follows: Define the joint movement of the femur, and construct rotation matrices for the flexion-extension movement, abduction-adduction movement, and internal rotation-external rotation movement of the femur respectively. 、 and ; Combine the constructed rotation matrices in sequence to obtain the final rotation matrix: Calculate the spatial position of the femoral neck based on the final rotation matrix and the center point of the femoral head: Among them, is the position coordinate of the center point of the femoral head when the femur is in the initial position, ; By changing the anteversion angle and neck-shaft angle of the femur, combined with the rotation matrix, obtain the calculation results of the acetabular center line coordinates at different angles; According to the above calculation results, draw the three-dimensional range of motion of the femoral neck at different femoral anteversion angles and neck-shaft angles to obtain a three-dimensional point cloud map.

[0007] Among them, defining the joint movement of the femur specifically means: Realize the flexion-extension movement of the femur through rotation around the global x-axis, satisfying the following formula: Among them, is the flexion-extension angle of the femur; Realize the abduction-adduction movement of the femur through rotation around the global y-axis, satisfying the following formula: Among them, is the abduction - adduction angle of the femur; The internal rotation - external rotation movement of the femur is achieved by rotating around the global z - axis and satisfies the following formula: Among them, is the internal - external rotation angle of the femur.

[0008] Among them, the calculation of the centroid is specifically as follows: All the point coordinates of the femoral neck in the three - dimensional point cloud map are represented as (X, Y, Z), and the mean values of the X, Y, and Z coordinates of all points are calculated. Its calculation formula is: Among them, is the coordinate corresponding to the point , is the mass corresponding to the point , is the th coordinate in the three - dimensional point cloud map.

[0009] Among them, the acetabular abduction angle is the angle between the ray projected onto the coronal plane and the sagittal plane; the acetabular anteversion angle is the angle between the ray projected onto the transverse plane and the coronal plane.

[0010] A calculation system for the optimal placement orientation of the acetabular cup during total hip arthroplasty, comprising: An input module, configured to input the CT data of the patient and the parameters of the prosthesis to be implanted; A three - dimensional simulation module, configured to construct a three - dimensional model based on the input CT data, identify the pelvic landmark points, femoral landmark points, femoral head center point, and femoral head rotation center point in the three - dimensional model, establish a three - dimensional coordinate system based on the pelvic landmark points and the femoral head rotation center point, and determine the initial position of the femoral movement according to the femoral head rotation center point and the femoral landmark points; draw the spatial femoral neck movement range according to the femoral anteversion angle, femoral neck - shaft angle, and the preset hip joint movement range, specifically draw it with the movement surface of the intersection of the femoral neck and the femoral shaft in the three - dimensional model; A calculation module, configured to calculate the centroid of its surface based on the spatial femoral neck movement range, extend a ray from the femoral head rotation center point in the direction of the centroid, and use the orientation of the ray in the three - dimensional coordinates as the optimal placement orientation of the acetabular cup; An output module, configured to display and output the acetabular abduction angle and acetabular anteversion angle under the optimal placement orientation of the acetabular cup as a reference.

[0011] Preferably, the three-dimensional simulation module is further configured to establish a three-dimensional coordinate system using the plane determined by the left anterior superior iliac spine point, the right anterior superior iliac spine point and the midpoint of the pubic symphysis of the pelvic landmarks as the coronal plane; The midpoint of the line connecting the lateral femoral condyle and the medial femoral condyle of the femoral landmark point is the center of the knee joint. The knee joint center is connected to the rotation center of the femoral head to form a femoral line. When the femoral line is perpendicular to the cross section, the position of the femur at this time is the initial position of the femoral movement.

[0012] Preferably, the three-dimensional simulation module is further configured to draw the spatial femoral neck range of motion. Define the joint motion of the femur, and construct rotation matrices for the flexion-extension motion, abduction-adduction motion, and internal rotation-external rotation motion of the femur , and ; Combine the constructed rotation matrices in order to get the final rotation matrix: The spatial position of the femoral neck is calculated based on the final rotation matrix and the center point of the femoral head: in, is the position coordinate of the center point of the femoral head when the femur is in the initial position, ; By changing the femoral anteversion angle and neck-shaft angle and combining the rotation matrix, the calculation results of the acetabulum centerline coordinates at different angles are obtained; According to the above calculation results, the three-dimensional motion range of the femoral neck under different femoral anteversion angles and neck-shaft angles is drawn to obtain a three-dimensional point cloud map.

[0013] Preferably, the three-dimensional simulation module is further configured to define the joint movement of the femur, The flexion and extension of the femur is achieved by rotating around the global x-axis, satisfying the following formula: in, is the flexion and extension angle of the femur; The abduction-adduction motion of the femur is achieved by rotating around the global y-axis, satisfying the following formula: in, is the abduction-adduction angle of the femur; The internal rotation and external rotation of the femur are achieved by rotating around the global z-axis, satisfying the following formula: in, is the internal and external rotation angle of the femur.

[0014] Preferably, the calculation module is further configured to calculate the centroid. Represent all the point coordinates of the femoral neck in the three-dimensional point cloud map as (X, Y, Z), and calculate the mean values of the X, Y, and Z coordinates of all the points. The calculation formula is: Wherein, is the coordinate corresponding to the point , is the mass corresponding to the point , is the th coordinate in the three-dimensional point cloud map.

[0015] Due to the adoption of the above technical solutions, the present invention has the following advantages and positive effects compared with the prior art: By inputting the CT parameters of the patient himself and the parameters of the prosthesis to be implanted, and performing analysis and calculation, the present invention takes into account the personalized femoral morphology and joint range of motion of the patient, gives the optimal acetabular orientation according to different prostheses, and gives clear surgical goals and guidance to the surgeon, thereby reducing the risk of dislocation after hip replacement and greatly improving the reliability of the acetabular cup placement. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention.

[0017] Figure 1 is a schematic flow chart of a method for calculating the optimal placement orientation of the acetabular cup during total hip arthroplasty of the present invention; Figure 2 is a schematic position diagram of the landmark points at the pelvis of the present invention; Figure 3 is a schematic position diagram of the landmark points at the femur and the center point of the femoral head of the present invention; Figure 4 is a schematic position diagram of the center point of the acetabulum of the present invention; Figure 5 is a schematic diagram of the femoral anteversion angle of the present invention; Figure 6 is a schematic diagram of the femoral neck shaft angle of the present invention; Figure 7 is a schematic diagram of the three-dimensional cloud point map formed by the femoral neck under the three-dimensional motion range of the present invention; Figure 8 is a schematic diagram of the acetabular abduction angle and the acetabular anteversion angle output by the present invention. Detailed implementation manners

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will describe the specific implementation manners of the present invention with reference to the accompanying drawings. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings, and other implementation manners can also be obtained.

[0019] To make the drawings concise, only the parts related to the present invention are schematically shown in each drawing, and they do not represent the actual structure of the product. Additionally, to make the drawings concise and easy to understand, in some drawings, for components with the same structure or function, only one of them is schematically shown, or only one of them is marked. In this article, "one" not only means "only this one", but also means "more than one" situation.

[0020] The following further details a calculation method and system for the optimal placement orientation of the acetabular cup during total hip arthroplasty proposed by the present invention in combination with the accompanying drawings and specific embodiments. According to the following description and the claims, the advantages and features of the present invention will be clearer.

[0021] Embodiment 1 Refer to Figures 1 to 8 , this embodiment provides a calculation method for the optimal placement orientation of the acetabular cup during total hip arthroplasty, which mainly includes the following steps: First, step S1: It is necessary to obtain the CT data of the patient and construct a three-dimensional model. The imported CT data is required to be from the anterior superior iliac spine to the tibial tubercle, including both hip and knee joints, and can be used to determine the femoral anteversion angle. By identifying the pelvic landmark points, femoral landmark points, femoral head center point, and femoral head rotation center point (i.e., Figure 4 the acetabular center point), as Figure 2 shown, the pelvic landmark points include the left anterior superior iliac spine point, right anterior superior iliac spine point, and the midpoint of the pubic symphysis on both sides of the pelvis; as Figure 3 shown, the femoral landmark points include the lateral femoral condyle point and the medial femoral condyle point. A three-dimensional coordinate system is established with the anterior pelvic plane as the coronal plane. The anterior pelvic plane is determined by the left anterior superior iliac spine point, right anterior superior iliac spine point, and the midpoint of the pubic symphysis. Further, the femoral head rotation center point is selected as the origin of this three-dimensional coordinate system. Preferably, the midpoint of the line connecting the lateral femoral condyle point and the medial femoral condyle point is the knee joint center. Connect the knee joint center with the femoral head rotation center point to form a femoral line. When this femoral line is perpendicular to the cross-section, the position of the femur at this time is the initial position of femoral movement, with 0° of anteversion, 0° of adduction, and 0° of internal rotation.

[0022] Then enter the next step, step S2: Draw the spatial range of femoral neck movement according to the femoral morphology and the preset hip joint range of motion. The femoral morphology includes the femoral anteversion angle and the femoral neck shaft angle, as Figure 5 and Figure 6 shown, where the specific angle of the femoral neck shaft angle is related to the selected femoral prosthesis model. The range of motion of the femur relative to the pelvis can be: extension (-) - flexion (+): -30° to +110°; abduction (-) - adduction (+): -35° to +30°; external rotation (-) - internal rotation (+): -45° to +45°. The above angles are preferred ranges, but are not limited thereto. According to the differences in the femoral anteversion angle and the femoral neck shaft angle, the movement surface of the intersection of the femoral neck and the femoral shaft in the three-dimensional model is drawn.

[0023] Among them, the specific steps for drawing the spatial range of femoral neck movement are: Define the joint movement of the femur through three basic rotational movements, namely flexion-extension movement, abduction-adduction movement, and internal rotation-external rotation movement.

[0024] For the flexion-extension movement, the flexion-extension movement of the femur is achieved by rotating around the global x-axis ( ), satisfying the following formula: Among them, is the flexion-extension angle of the femur, with a range of -30° to +110°.

[0025] For the abduction-adduction movement, the abduction-adduction movement of the femur is achieved by rotating around the global y-axis ( ), satisfying the following formula: Among them, is the abduction-adduction angle of the femur, with a range of -35° to +30°; For the internal rotation-external rotation movement, the internal rotation-external rotation movement of the femur is achieved by rotating around the global z-axis ( ), satisfying the following formula: Among them, is the internal-external rotation angle of the femur, with a range of -45° to +45°.

[0026] Then, since the movement of the femur is obtained by sequentially combining three rotation matrices, namely flexion-extension movement, abduction-adduction movement, and internal rotation-external rotation movement, the final rotation matrix is obtained: Further, considering the influence of the femoral anteversion angle and the femoral abduction angle on the acetabular center line, it is necessary to calculate the position of the femoral neck from the origin (the center point of the femoral head) to a new position. At this time, using the final rotation matrix, the spatial position of the femoral neck can be obtained: Among them, is the coordinate of the center point of the femoral head when the femur is in the initial position, .

[0027] Then, by changing the femoral anteversion angle and the femoral abduction angle and combining with the rotation matrix, the calculation results of the acetabular center line coordinates at different angles can be obtained. Each set of femoral anteversion angle and femoral abduction angle will generate a new acetabular center line coordinate.

[0028] According to the above calculation results, the three-dimensional motion range of the femoral neck at different femoral anteversion angles and femoral abduction angles is drawn, and finally a three-dimensional point cloud map is output, as shown in Figure 7 , showing the change of the position of the femoral neck in space.

[0029] Finally, step S3: Refer to Figure 8 , calculate the centroid of its surface based on the spatial motion range of the femoral neck, extend a ray from the center point of the femoral head rotation in the direction of the centroid, and use the orientation of the ray in the three-dimensional coordinates as the best placement orientation of the acetabular cup. Furthermore, output the acetabular abduction angle and the acetabular anteversion angle as the reference for acetabular cup placement, giving clear surgical goals and guidance to medical staff. Among them, the acetabular abduction angle is the angle between the projection of the ray on the coronal plane and the sagittal plane, and the acetabular anteversion angle is the angle between the projection of the ray on the transverse plane and the coronal plane.

[0030] Among them, the centroid is the geometric center of the object. Mathematically, it is the weighted average of the positions of all mass elements of the object. For an object distributed in three-dimensional space, the coordinates of its centroid are . Therefore, represent all the point coordinates of the femoral neck in the three-dimensional point cloud map as (X, Y, Z), and calculate the average value of the X, Y, and Z coordinates of all points, which is its centroid. The calculation formula is: Among them, is the coordinate corresponding to the point , is the mass corresponding to the point , is the th coordinate in the three-dimensional point cloud map, and in this embodiment, it can be assumed that the mass of each point is equal and can be simplified to 1, without considering the mass. Therefore, the calculation of the centroid is actually the average value of all point coordinates.

[0031] Embodiment 2 This embodiment also provides a calculation system for the optimal placement orientation of the acetabular cup during total hip arthroplasty, which generally includes: an input module, a three-dimensional simulation module, a calculation module, and an output module.

[0032] The input module is used to input the CT data of the patient and the parameters of the prosthetic femur to be implanted.

[0033] The three-dimensional simulation module is used to construct a three-dimensional model based on the input CT data, identify the pelvic landmark points, femoral landmark points, femoral head center point, and femoral head rotation center point in the three-dimensional model, establish a three-dimensional coordinate system based on the pelvic landmark points and the femoral head rotation center point, and determine the initial position of femoral movement according to the femoral head rotation center point and the femoral landmark points; according to the femoral anteversion angle, femoral neck-shaft angle, and the preset hip joint range of motion, draw the spatial femoral neck range of motion, specifically by drawing the motion surface of the intersection of the femoral neck and the femoral shaft of the femur in the three-dimensional model.

[0034] Preferably, the three-dimensional simulation module further establishes a three-dimensional coordinate system with the plane determined by the left anterior superior iliac spine point, right anterior superior iliac spine point, and the midpoint of the pubic symphysis of the pelvic landmark points as the coronal plane; Taking the midpoint of the line connecting the lateral femoral condyle point and the medial femoral condyle point of the femoral landmark points as the knee joint center, connecting the knee joint center with the femoral head rotation center point to form a femoral line, when the femoral line is perpendicular to the cross-section, the position of the femur at this time is the initial position of femoral movement.

[0035] Preferably, the three-dimensional simulation module is used to draw the spatial femoral neck range of motion, specifically as follows: Define the joint movement of the femur, and construct rotation matrices 、 and respectively for the flexion-extension movement, abduction-adduction movement, and internal rotation-external rotation movement of the femur; Combine the constructed rotation matrices in sequence to obtain the final rotation matrix: Calculate the spatial position of the femoral neck based on the final rotation matrix and the femoral head center point: wherein, is the position coordinate of the femoral head center point when the femur is in the initial position, ; By changing the femoral anteversion angle and the neck-shaft angle of the femur, and combining with the rotation matrix, obtain the calculation results of the acetabular center line coordinates at different angles; According to the above calculation results, draw the three-dimensional range of motion of the femoral neck at different femoral anteversion angles and neck-shaft angles to obtain a three-dimensional point cloud map.

[0036] Preferably, the three-dimensional simulation module is also used to define the joint movement of the femur. The flexion and extension movement of the femur is achieved by rotating around the global x-axis and satisfies the following formula: where is the flexion and extension angle of the femur; The abduction-adduction movement of the femur is achieved by rotating around the global y-axis and satisfies the following formula: where is the abduction-adduction angle of the femur; The internal-external rotation movement of the femur is achieved by rotating around the global z-axis and satisfies the following formula: where is the internal-external rotation angle of the femur.

[0037] The calculation module is used to calculate the centroid of the surface of the femoral neck based on the spatial range of femoral neck movement. Starting from the center point of femoral head rotation, a ray is extended in the direction of the centroid, and the orientation of the ray in the three-dimensional coordinates is used as the optimal placement orientation of the acetabular cup.

[0038] Preferably, the calculation module specifically calculates the centroid as follows: All the point coordinates of the femoral neck in the three-dimensional point cloud diagram are represented by (X, Y, Z), and the mean values of the X, Y, and Z coordinates of all points are calculated. The calculation formula is: where is the coordinate corresponding to point , is the mass corresponding to point , is the th coordinate in the three-dimensional point cloud diagram.

[0039] The output module is used to display and output the acetabular abduction angle and acetabular anteversion angle under the optimal placement orientation of the acetabular cup as a reference, providing clear surgical goals and guidance to medical staff.

[0040] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, provided that these changes fall within the scope of the claims of the present invention and their equivalent technologies, they still fall within the protection scope of the present invention.

Claims

1. A method for calculating the optimal orientation of an acetabular cup during total hip arthroplasty, characterized in that: The steps include: Acquire the patient's CT data and construct a three-dimensional model, identify the pelvic landmarks, femoral landmarks, femoral head center points and femoral head rotation center points in the three-dimensional model, establish a three-dimensional coordinate system based on the pelvic landmarks and the femoral head rotation center points, and determine the initial position of the femoral movement based on the femoral head rotation center points and the femoral landmarks; According to the femoral anteversion angle, the femoral neck-shaft angle and the preset hip joint range of motion, the spatial femoral neck range of motion is drawn, specifically, the motion surface of the intersection of the femoral neck and the femoral shaft of the femur in the three-dimensional model is drawn; The center of mass of the curved surface of the femoral neck is calculated based on the spatial range of motion of the femoral neck. A ray is formed by extending toward the center of mass with the rotation center of the femoral head as the starting point. The orientation of the ray in the three-dimensional coordinate is used as the optimal orientation for the acetabulum, and then the acetabular abduction angle and the acetabular anteversion angle are output as a reference for the placement of the acetabulum.

2. The method for calculating the optimal orientation of the acetabular cup during total hip arthroplasty according to claim 1, characterized in that: In the step of constructing a three-dimensional model, the pelvic landmarks include the left anterior superior iliac spine point, the right anterior superior iliac spine point and the midpoint of the pubic symphysis located on both sides of the pelvis, and the femoral landmarks include the lateral femoral condyle point and the medial femoral condyle point; Establishing the three-dimensional coordinate system with the plane defined by the left anterior superior iliac spine point, the right anterior superior iliac spine point and the midpoint of the pubic symphysis as the coronal plane; The midpoint of the line connecting the lateral femoral condyle and the medial femoral condyle is taken as the knee joint center. The knee joint center is connected to the rotation center of the femoral head to form a femoral line. When the femoral line is perpendicular to the cross section, the position of the femur at this time is the initial position of the femoral movement.

3. The method for calculating the optimal orientation of the acetabular cup during total hip arthroplasty according to claim 2, characterized in that: The specific steps for drawing the range of motion of the femoral neck in space are: Define the joint motion of the femur, and construct rotation matrices for the flexion-extension motion, abduction-adduction motion, and internal rotation-external rotation motion of the femur , and ; Combine the constructed rotation matrices in order to get the final rotation matrix: The spatial position of the femoral neck is calculated based on the final rotation matrix and the center point of the femoral head: in, is the position coordinate of the center point of the femoral head when the femur is in the initial position, ; By changing the femoral anteversion angle and neck-shaft angle and combining the rotation matrix, the calculation results of the acetabulum centerline coordinates at different angles are obtained; According to the above calculation results, the three-dimensional motion range of the femoral neck under different femoral anteversion angles and neck-shaft angles is drawn to obtain a three-dimensional point cloud map.

4. The method for calculating the optimal orientation of the acetabular cup during total hip arthroplasty according to claim 3, characterized in that: The joint motion of the femur is defined as: The flexion and extension of the femur is achieved by rotating around the global x-axis, satisfying the following formula: in, is the flexion and extension angle of the femur; The abduction-adduction motion of the femur is achieved by rotating around the global y-axis, satisfying the following formula: in, is the abduction-adduction angle of the femur; The internal rotation and external rotation of the femur are achieved by rotating around the global z-axis, satisfying the following formula: in, The internal and external rotation angle of the femur.

5. The method for calculating the optimal orientation of the acetabular cup during total hip arthroplasty according to claim 3, characterized in that: The calculation of the center of mass is as follows: The coordinates of all points of the femoral neck in the three-dimensional point cloud are expressed as (X, Y, Z), and the mean values ​​of the X, Y, and Z coordinates of all points are calculated. The calculation formula is: in, For point The corresponding coordinates, For point The corresponding quality, is the first coordinates.

6. The method for calculating the optimal orientation of the acetabular cup during total hip arthroplasty according to claim 1, characterized in that: The acetabular abduction angle is the angle between the ray projected onto the coronal plane and the sagittal plane; the acetabular anteversion angle is the angle between the ray projected onto the transverse plane and the coronal plane.

7. A system for calculating the optimal orientation of the acetabular cup during total hip arthroplasty, characterized in that: include: An input module, configured to input CT data of the patient and parameters of the prosthesis to be implanted; The three-dimensional simulation module is configured to construct a three-dimensional model according to the input CT data, identify the pelvic landmarks, femoral landmarks, femoral head center points and femoral head rotation center points in the three-dimensional model, establish a three-dimensional coordinate system according to the pelvic landmarks and the femoral head rotation center points, determine the initial position of the femoral movement according to the femoral head rotation center points and the femoral landmarks; draw the spatial femoral neck range of motion according to the femoral anteversion angle, the femoral neck shaft angle and the preset hip joint range of motion, and specifically draw the motion surface of the intersection of the femoral neck and the femoral shaft of the femur in the three-dimensional model; A calculation module is configured to calculate the centroid of the curved surface of the femoral neck based on the range of motion of the femoral neck in space, and to extend a ray toward the centroid from the rotation center point of the femoral head as a starting point, and the orientation of the ray in the three-dimensional coordinate is used as the optimal orientation of the acetabular cup; The output module is configured to display the acetabular abduction angle and the acetabular anteversion angle under the optimal placement direction of the acetabular cup as a reference.

8. The calculation system for the optimal placement orientation of the acetabular cup during total hip arthroplasty according to claim 7, characterized in that: The three-dimensional simulation module is further configured to establish the three-dimensional coordinate system by taking the plane defined by the left anterior superior iliac spine point, the right anterior superior iliac spine point and the midpoint of the pubic symphysis of the pelvic landmark as the coronal plane; The midpoint of the line connecting the lateral femoral condyle point and the medial femoral condyle point of the femoral landmark point is taken as the knee joint center. The knee joint center is connected to the rotation center point of the femoral head to form a femoral line. When the femoral line is perpendicular to the cross section, the position of the femur at this time is the initial position of the femoral movement.

9. The calculation system for the optimal placement orientation of the acetabular cup during total hip arthroplasty according to claim 8, characterized in that: The three-dimensional simulation module is further configured to draw the spatial femoral neck range of motion, Define the joint motion of the femur, and construct rotation matrices for the flexion-extension motion, abduction-adduction motion, and internal rotation-external rotation motion of the femur , and ; Combine the constructed rotation matrices in order to get the final rotation matrix: The spatial position of the femoral neck is calculated based on the final rotation matrix and the center point of the femoral head: in, is the position coordinate of the center point of the femoral head when the femur is in the initial position, ; By changing the femoral anteversion angle and neck-shaft angle and combining the rotation matrix, the calculation results of the acetabulum centerline coordinates at different angles are obtained; According to the above calculation results, the three-dimensional motion range of the femoral neck under different femoral anteversion angles and neck-shaft angles is drawn to obtain a three-dimensional point cloud map.

10. The calculation system for the optimal placement orientation of the acetabular cup during total hip arthroplasty according to claim 9, characterized in that: The three-dimensional simulation module is further configured to define the joint motion of the femur, The flexion and extension of the femur is achieved by rotating around the global x-axis, satisfying the following formula: in, is the flexion and extension angle of the femur; The abduction-adduction motion of the femur is achieved by rotating around the global y-axis, satisfying the following formula: in, is the abduction-adduction angle of the femur; The internal rotation and external rotation of the femur are achieved by rotating around the global z-axis, satisfying the following formula: in, The internal and external rotation angle of the femur.

11. The calculation system for the optimal placement orientation of the acetabular cup during total hip arthroplasty according to claim 9, characterized in that: The calculation module is further configured to calculate the centroid, The coordinates of all points of the femoral neck in the three-dimensional point cloud are expressed as (X, Y, Z), and the mean values ​​of the X, Y, and Z coordinates of all points are calculated. The calculation formula is: in, For point The corresponding coordinates, For point The corresponding quality, is the first coordinates.

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