Ligament isometric analysis method, device and system

Abstract

The invention provides a ligament isometric analysis method, device and system. The ligament isometric analysis method comprises the steps that the center position of a femoral head is determined according to a position set of a femoral positioning device in the femoral rotation process, and the center position of an ankle joint is determined according to the medial malleolus position and the lateral malleolus position; in the knee bending movement process of the knee joint, the obtained femoral ligament dead point position, the obtained intercondylar fossa vertex position, the obtained tibia ligament dead point position, the obtained tibia plateau center position, the obtained femoral head center position and the obtained ankle joint center position under the local coordinate system are converted into a global coordinate system; determining a knee bending angle according to the vertex position of the intercondylar fossa, the central position of the tibial plateau, the central position of the femoral head and the central position of the ankle joint under the global coordinate system, and determining the ligament length according to the stop position of the femoral ligament and the stop position of the tibial ligament under the global coordinate system to obtain a ligament length difference value; and constructing a ligament isometric curve with the ligament length difference value changing along with the knee bending angle. The accuracy of determining the position of the ligament stop point can be improved.

Description

Technical Field

[0001] This application relates to the technical field of ligament analysis. Specifically, it relates to a method, device, and system for analyzing ligament isometry. Background Art

[0002] The anterior cruciate ligament is mainly responsible for the stability of knee joint movement and prevents the anterior displacement of the tibia relative to the femur. Injury to the anterior cruciate ligament may lead to the loss of knee joint stability, affecting motor ability and daily activities. Anterior cruciate ligament reconstruction surgery is a common knee surgery, mainly used to repair ligament injuries or ruptures caused by sports injuries or other reasons. In anterior cruciate ligament reconstruction surgery, the positions of the bone tunnels in the femur and tibia determine the key to the success of the surgery, especially the position of the ligament insertion point.

[0003] In existing anterior cruciate ligament reconstruction surgeries, doctors determine the position of the ligament insertion point under arthroscope based on their own experience, thereby determining the length of the graft. However, the method of manually determining the position of the ligament insertion point is affected by many factors, and it is easy to have inaccurate positions of the ligament insertion point, resulting in the graft being too long or too short. A graft that is too long cannot provide sufficient tension, and a graft that is too short will cause intercondylar fossa collision, resulting in a low surgical success rate. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a method, device, and system for analyzing ligament isometry, which can pre-evaluate the rationality of the ligament insertion point by simulating the ligament isometry curve, improve the accuracy of determining the position of the ligament insertion point, and help improve the surgical success rate.

[0005] In a first aspect, an embodiment of this application provides a method for analyzing ligament isometry, the method including: Determine the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, and the set of knee joint registration point positions in the image coordinate system according to the original image data of the knee joint; Determine the position of the femoral head center according to the set of positions of the femoral positioning device during femoral rotation, and determine the position of the ankle joint center according to the obtained positions of the medial malleolus and lateral malleolus; According to the registration relationship between the image coordinate system and the local coordinate system, the positions of the femoral ligament insertion point, the apex position of the intercondylar fossa, the tibial ligament insertion point, and the center position of the tibial plateau in the image coordinate system are transformed from the image coordinate system to the local coordinate system. According to the mapping relationship between the global coordinate system and the local coordinate system, the center position of the femoral head and the center position of the ankle joint in the global coordinate system are transformed from the global coordinate system to the local coordinate system; wherein, the registration relationship is determined according to the position set of the knee joint positioning device and the position set of the knee joint registration points, and the center position of the tibial plateau is determined according to the position of the medial edge point of the tibial plateau and the position of the lateral edge point of the tibial plateau; During the process of the knee joint performing a flexion movement, the positions of the femoral ligament insertion point, the apex position of the intercondylar fossa, the tibial ligament insertion point, the center position of the tibial plateau, the center position of the femoral head, and the center position of the ankle joint in the local coordinate system obtained are transformed from the local coordinate system to the global coordinate system; According to the apex position of the intercondylar fossa, the center position of the tibial plateau, the center position of the femoral head, and the center position of the ankle joint in the global coordinate system, the flexion angle during the flexion movement of the knee joint is determined. According to the positions of the femoral ligament insertion point and the tibial ligament insertion point in the global coordinate system, the ligament lengths corresponding to different flexion angles are determined, and the ligament length differences corresponding to different flexion angles are obtained by comparing with the reference ligament length; Construct an isometric curve of the ligament with the ligament length difference changing with the flexion angle, so as to evaluate the rationality of the ligament insertion point according to the isometric curve of the ligament.

[0006] In an optional embodiment, the knee joint positioning device includes a femoral positioning device and a tibial positioning device. The femoral positioning device is fixed on the femur, and the tibial positioning device is fixed on the tibia; The determination of the positions of the femoral ligament insertion point, the apex position of the intercondylar fossa, the tibial ligament insertion point, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, and the position set of the knee joint registration points in the image coordinate system according to the original image data of the knee joint includes: According to the original image data of the knee joint, the positions of the femoral ligament insertion point, the apex position of the intercondylar fossa, the tibial ligament insertion point, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, the femoral registration point position set, and the tibial registration point position set in the image coordinate system are determined; The transformation of the positions of the femoral ligament insertion point, the apex position of the intercondylar fossa, the tibial ligament insertion point, and the center position of the tibial plateau in the image coordinate system from the image coordinate system to the local coordinate system according to the registration relationship between the image coordinate system and the local coordinate system, and the transformation of the center position of the femoral head and the center position of the ankle joint in the global coordinate system from the global coordinate system to the local coordinate system according to the mapping relationship between the global coordinate system and the local coordinate system includes: According to the femoral registration relationship between the image coordinate system and the local femoral coordinate system, the positions of the femoral ligament insertion points and the apex position of the intercondylar fossa are transformed from the image coordinate system to the local femoral coordinate system. According to the tibial registration relationship between the image coordinate system and the local tibial coordinate system, the positions of the tibial ligament insertion points and the center position of the tibial plateau are transformed from the image coordinate system to the local tibial coordinate system; according to the femoral mapping relationship between the global coordinate system and the local femoral coordinate system, the center position of the femoral head in the global coordinate system is transformed from the global coordinate system to the local femoral coordinate system. According to the tibial mapping relationship between the global coordinate system and the local tibial coordinate system, the center position of the ankle joint in the global coordinate system is transformed from the global coordinate system to the local tibial coordinate system; wherein, the femoral registration relationship is determined according to the position set of the femoral positioning device and the position set of the femoral registration points, and the tibial registration relationship is determined according to the position set of the tibial positioning device and the position set of the tibial registration points; During the flexion movement of the knee joint, the positions of the femoral ligament insertion points, the apex position of the intercondylar fossa, the tibial ligament insertion points, the center position of the tibial plateau, the center position of the femoral head, and the center position of the ankle joint in the local coordinate system are transformed from the local coordinate system to the global coordinate system, including: During the flexion movement of the knee joint, according to the femoral mapping relationship between the global coordinate system and the local femoral coordinate system, the positions of the femoral ligament insertion points, the apex position of the intercondylar fossa, and the center position of the femoral head in the local femoral coordinate system are transformed from the local femoral coordinate system to the global coordinate system. According to the tibial mapping relationship between the global coordinate system and the local tibial coordinate system, the positions of the tibial ligament insertion points, the center position of the tibial plateau, and the center position of the ankle joint in the local tibial coordinate system are transformed from the local tibial coordinate system to the global coordinate system.

[0007] In an optional embodiment, the femoral registration relationship and the tibial registration relationship are determined through the following steps: According to the poses returned by the femoral positioning device and the tibial positioning device, the femoral transformation matrix and the tibial transformation matrix are calculated respectively; According to the femoral transformation matrix and the position set of the femoral positioning device, the mapped femoral position set of the femoral positioning device in the local femoral coordinate system is determined; according to the tibial transformation matrix and the position set of the tibial positioning device, the mapped tibial position set of the tibial positioning device in the local tibial coordinate system is determined; According to the mapped femoral position set and the position set of the femoral registration points, a femoral registration matrix is constructed to represent the femoral registration relationship through the femoral registration matrix; according to the mapped tibial position set and the position set of the tibial registration points, a tibial registration matrix is constructed to represent the tibial registration relationship through the tibial registration matrix; and, determining the femoral mapping relationship and the tibial mapping relationship through the following steps: Calculating a femoral transformation matrix based on the pose returned by the femoral positioning device, so as to characterize the femoral mapping relationship through the femoral transformation matrix; Calculating a tibial transformation matrix based on the pose returned by the tibial positioning device, so as to characterize the tibial mapping relationship through the tibial transformation matrix.

[0008] In an optional embodiment, the determining the femoral head center position according to the position set of the femoral positioning device during the femoral rotation process and determining the ankle joint center position according to the obtained medial malleolus position and lateral malleolus position includes: Obtaining the three-dimensional position coordinates of the femoral positioning device during the femoral rotation process to form a position set; Determining the femoral head center position according to the position set by using the random sample consensus algorithm; Calculating the ankle joint center position according to the obtained medial malleolus position and lateral malleolus position by using the midpoint formula.

[0009] In an optional embodiment, the determining the femoral ligament insertion point position, the intercondylar fossa vertex position, the tibial ligament insertion point position, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, the femoral registration point position set and the tibial registration point position set in the image coordinate system according to the original image data of the knee joint includes: Determining a femoral segmentation model and a tibial segmentation model according to the original image data of the knee joint; Obtaining the femoral ligament insertion point position and the intercondylar fossa vertex position in the image coordinate system from the femoral segmentation model, and obtaining the tibial ligament insertion point position, the medial edge point position of the tibial plateau and the lateral edge point position of the tibial plateau in the image coordinate system from the tibial segmentation model; Selecting feature points on the surface of the femoral segmentation model to form a femoral registration point position set, and selecting feature points on the surface of the tibial segmentation model to form a tibial registration point position set.

[0010] In an optional embodiment, the determining the knee flexion angle during the knee flexion movement according to the intercondylar fossa vertex position, the tibial plateau center position, the femoral head center position and the ankle joint center position in the global coordinate system, and determining the ligament lengths corresponding to different knee flexion angles according to the femoral ligament insertion point position and the tibial ligament insertion point position in the global coordinate system, so as to obtain the ligament length differences corresponding to different knee flexion angles by comparing with the reference ligament length, includes: Determining the femoral mechanical axis according to the femoral head center position and the intercondylar fossa vertex position in the global coordinate system, and determining the tibial mechanical axis according to the tibial plateau center position and the ankle joint center position in the global coordinate system; Calculate the knee flexion angle during the knee flexion movement using the vector angle formula based on the femoral mechanical axis and the tibial mechanical axis; Calculate the ligament lengths corresponding to different knee flexion angles using the three-dimensional distance formula based on the positions of the femoral ligament insertion points and the tibial ligament insertion points in the global coordinate system; Calculate the differences between the ligament lengths corresponding to different knee flexion angles and the reference ligament length corresponding to the specified knee flexion angle to obtain the ligament length differences corresponding to different knee flexion angles.

[0011] In an optional embodiment, constructing an isometric curve of the ligament with the change of the knee flexion angle to evaluate the rationality of the ligament insertion point according to the isometric curve of the ligament includes: Construct an isometric curve of the ligament with the change of the knee flexion angle; If the ligament length difference is within the preset length difference range, determine that the ligament insertion point is reasonable.

[0012] In a second aspect, an embodiment of the present application further provides an isometric analysis device for ligaments, and the device includes: A data acquisition module, configured to determine a set of positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, and the knee joint registration point in the image coordinate system according to the original image data of the knee joint; A first processing module, configured to determine the position of the femoral head center according to the set of positions of the femoral positioning device during the femoral rotation, and determine the position of the ankle joint center according to the obtained positions of the medial malleolus and the lateral malleolus; A coordinate system alignment module, configured to convert the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, and the center position of the tibial plateau in the image coordinate system from the image coordinate system to the local coordinate system according to the registration relationship between the image coordinate system and the local coordinate system, and convert the positions of the femoral head center and the ankle joint center in the global coordinate system from the global coordinate system to the local coordinate system according to the mapping relationship between the global coordinate system and the local coordinate system; wherein, the registration relationship is determined according to the set of positions of the knee joint positioning device and the set of knee joint registration points, and the center position of the tibial plateau is determined according to the medial edge point position and the lateral edge point position of the tibial plateau; A coordinate system conversion module, configured to convert the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, the center position of the tibial plateau, the femoral head center position, and the ankle joint center position in the obtained local coordinate system from the local coordinate system to the global coordinate system during the knee flexion movement of the knee joint; A second processing module, configured to determine the knee flexion angle during the knee flexion movement according to the positions of the intercondylar fossa vertex, the center position of the tibial plateau, the center position of the femoral head, and the center position of the ankle joint in the global coordinate system, and determine the ligament lengths corresponding to different knee flexion angles according to the positions of the femoral ligament insertion point and the tibial ligament insertion point in the global coordinate system, so as to obtain the ligament length differences corresponding to different knee flexion angles by comparing with the reference ligament lengths; An isometry analysis module, configured to construct an isometry curve of the ligament with the change of the knee flexion angle, so as to evaluate the rationality of the ligament insertion point according to the isometry curve of the ligament.

[0013] In a third aspect, an embodiment of the present application further provides a ligament isometry analysis system, which is applied to the ligament isometry analysis method as described above. The system includes: a vision device, a knee joint positioning device, a mobile positioning device, and a processing device. The vision device is configured to collect the position set of the knee joint positioning device and the position information of the mobile positioning device, and the vision device is connected to the processing device.

[0014] In an optional embodiment, the knee joint positioning device includes a femoral positioning device and a tibial positioning device. The femoral positioning device is fixed on the femur, and the tibial positioning device is fixed on the tibia.

[0015] The ligament isometry analysis method provided by the embodiment of the present application at least has the following technical effects: First, through coordinate system alignment, and then analyzing the position changes obtained during the knee flexion movement in the local coordinate system, the dynamic changes of the ligament insertion point during the knee movement can be accurately captured. By simulating the dynamic changes during the knee flexion movement, an isometry curve of the ligament with the change of the knee flexion angle is constructed, and the rationality of the ligament insertion point is evaluated through the isometry curve of the ligament, improving the accuracy of determining the position of the ligament insertion point, thereby ensuring the reasonable position of the ligament insertion point, and contributing to improving the success rate of anterior cruciate ligament reconstruction surgery.

[0016] To make the above objects, features, and advantages of the present application more obvious and understandable, the following specific embodiments are given, and detailed descriptions are made in conjunction with the accompanying drawings as follows. Description of the Drawings

[0017] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1Flow chart of a method for analyzing ligament isometry provided by an embodiment of the present application; Figure 2 Schematic diagram of femoral rotation provided by an embodiment of the present application; Figure 3 Schematic diagram of the knee flexion angle provided by an embodiment of the present application; Figure 4 Schematic diagram of a ligament isometry curve provided by an embodiment of the present application; Figure 5 Flow chart of another method for analyzing ligament isometry provided by an embodiment of the present application; Figure 6 Schematic structural diagram of a ligament isometry analysis device provided by an embodiment of the present application; Figure 7 Schematic structural diagram of a ligament isometry analysis system provided by an embodiment of the present application; Figure 8 Schematic structural diagram of an electronic device provided by an embodiment of the present application. Detailed implementation manners

[0019] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part rather than all of the embodiments of the present application. Components of the embodiments of the present application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. Based on the embodiments of the present application, every other embodiment obtained by those skilled in the art without creative efforts belongs to the scope of protection of the present application.

[0020] It has been found through research that the anterior cruciate ligament is mainly responsible for the stability of knee joint movement and prevents the tibia from moving forward relative to the femur. Injury to the anterior cruciate ligament may lead to the loss of knee joint stability, affecting motor ability and daily activities. Anterior cruciate ligament reconstruction surgery is a common knee surgery, mainly used to repair ligament injuries or ruptures caused by sports injuries or other reasons. In anterior cruciate ligament reconstruction surgery, the positions of the bone tunnels in the femur and tibia are the key to the success of the surgery, especially the position of the ligament insertion point. In existing anterior cruciate ligament reconstruction surgeries, doctors determine the position of the ligament insertion point under arthroscope based on their own experience, thereby determining the length of the graft. However, the method of artificially determining the position of the ligament insertion point is affected by many factors, and it is easy to have inaccurate positions of the ligament insertion point, resulting in the graft being too long or too short. A graft that is too long cannot provide sufficient tension, and a graft that is too short will cause impingement in the intercondylar fossa, resulting in a low surgical success rate.

[0021] Based on this, the embodiments of the present application provide a method for analyzing ligament isometry, which can pre-evaluate the rationality of the ligament insertion point by simulating the ligament isometry curve of the ligament, improve the accuracy of determining the position of the ligament insertion point, and contribute to improving the surgical success rate.

[0022] Please refer to Figure 1 , Figure 1 which is a flowchart of a method for analyzing ligament isometry provided by the embodiments of the present application. As Figure 1 shown in S101. Determine the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, and the set of knee joint registration point positions in the image coordinate system according to the original image data of the knee joint; S102. Determine the position of the femoral head center according to the set of positions of the femoral positioning device during femoral rotation, and determine the position of the ankle joint center according to the obtained positions of the medial malleolus and lateral malleolus; S103. According to the registration relationship between the image coordinate system and the local coordinate system, convert the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, and the center position of the tibial plateau in the image coordinate system to the local coordinate system, and according to the mapping relationship between the global coordinate system and the local coordinate system, convert the positions of the femoral head center and the ankle joint center in the global coordinate system to the local coordinate system; wherein, the registration relationship is determined according to the set of positions of the knee joint positioning device and the set of knee joint registration point positions, and the center position of the tibial plateau is determined according to the medial edge point position and the lateral edge point position of the tibial plateau; S104. During the process of knee flexion, convert the positions of the femoral ligament insertion point, the apex position of the intercondylar fossa, the tibial ligament insertion point, the center position of the tibial plateau, the center position of the femoral head, and the center position of the ankle joint obtained in the local coordinate system to the global coordinate system; S105. Determine the knee flexion angle during the process of knee flexion according to the apex position of the intercondylar fossa, the center position of the tibial plateau, the center position of the femoral head, and the center position of the ankle joint in the global coordinate system. Determine the ligament lengths corresponding to different knee flexion angles according to the positions of the femoral ligament insertion point and the tibial ligament insertion point in the global coordinate system, and obtain the ligament length differences corresponding to different knee flexion angles by comparing with the reference ligament length; S106. Construct an isometric curve of the ligament with the change of the knee flexion angle according to the ligament length differences, so as to evaluate the rationality of the ligament insertion point based on the isometric curve of the ligament.

[0023] In the above steps S101 to S106, by first aligning the coordinate systems and then analyzing the changes in each position obtained during the knee flexion movement in the local coordinate system, the dynamic changes of the ligament insertion points during the knee movement can be accurately captured. By simulating the dynamic changes during the knee flexion movement, an isometric curve of the ligament with the change of the knee flexion angle is constructed. By analyzing the isometric curve of the ligament, the rationality of the ligament insertion point is evaluated, the accuracy of determining the position of the ligament insertion point is improved, and thus the position of the ligament insertion point is ensured to be reasonable, which helps to improve the success rate of anterior cruciate ligament reconstruction surgery.

[0024] The above steps will be described in detail through specific embodiments as follows: In step S101, based on the original image data of the knee joint, determine the positions of the femoral ligament attachment points, the vertex position of the intercondylar fossa, the tibial ligament attachment points, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, and the set of knee joint registration point positions in the image coordinate system. Here, the original image data of the knee joint can be the image information of the knee joint part obtained by means of CT scanning, etc., which contains the morphological structure information of bones such as the femur and tibia; the femoral ligament attachment point is the attachment point position of the anterior cruciate ligament on the femur, and its accurate position is crucial for anterior cruciate ligament reconstruction surgery; the vertex of the intercondylar fossa is the vertex position of the intercondylar fossa of the femur, which is an important reference point in surgical planning; the tibial ligament attachment point is the attachment point position of the anterior cruciate ligament on the tibia, which together with the femoral ligament attachment point determines the length and tension of the ligament; the medial edge point and the lateral edge point of the tibial plateau are specific position points on the edge of the tibial plateau, which are used to determine the center position of the tibial plateau; the set of knee joint registration point positions is a set of a series of feature points selected on the knee joint image, which is used for subsequent registration operations between the image and the physical object. Exemplarily, the original image data of the knee joint can be obtained by a high-precision CT scanner, which can provide high-resolution images and clearly show the detailed structure of the bones. For example, before actual surgical planning, the patient first undergoes a CT scan of the knee joint, and the scanning device will image the knee joint from multiple angles, and finally obtain the original image data containing a large number of feature points. In an alternative embodiment, the set of knee joint registration point positions can select some obvious bony landmark points on the surfaces of the femur and tibia, such as protrusions, depressions, etc. For example, several representative protrusion points are selected on the surface of the femur as registration points, and these points are easy to identify on the CT image and can also accurately find the corresponding positions on the actual bone. In practical applications, taking the anterior cruciate ligament reconstruction surgical planning as an example, first obtain the original CT scan image data of the patient's knee joint, and then professional medical image processing software can be used to mark the positions of the femoral ligament attachment points, the vertex position of the intercondylar fossa, the tibial ligament attachment points, the medial edge point position of the tibial plateau, and the lateral edge point position of the tibial plateau on the image, and at the same time select a suitable set of knee joint registration point positions to provide basic data for subsequent analysis and surgical planning. Through the above processing, the positions of the femoral ligament attachment points, the vertex position of the intercondylar fossa, the tibial ligament attachment points, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, and the set of knee joint registration point positions in the image coordinate system can be obtained.

[0025] In step S102, determine the center position of the femoral head according to the set of positions of the femoral positioning device during the rotation of the femur, and determine the center position of the ankle joint according to the obtained medial malleolus position and lateral malleolus position. In this step, the femoral positioning device is fixed on the femur and is used to assist in determining the position information of the femur, and it will generate a series of position change data during the rotation of the femur. Such as Figure 2As shown, the center position of the femoral head is the center point of femoral rotation. The set of positions of the femoral positioning device during femoral rotation refers to the set composed of the position information of the femoral positioning device at different times when the femur rotates around the center of the femoral head. The medial malleolus position and the lateral malleolus position are the ankle prominence positions formed at the lower ends of the tibia and fibula on the medial and lateral sides respectively, and are used to determine the center position of the ankle joint. In an alternative embodiment, the femoral positioning device can be a device with multiple reflective marker points, and the positions of these marker points in space can be tracked in real time through devices such as an optical locator. For example, in a femoral rotation experiment, the femoral positioning device is fixed on the femur. As the femur rotates, the optical locator continuously collects the position information of the marker points, thereby obtaining the set of positions of the femoral positioning device during femoral rotation. Further, the random sample consensus (RANSAC) algorithm can be used to determine the center position of the femoral head. That is, multiple points are randomly selected from the set of positions of the femoral positioning device, and the center position of the femoral head is determined by means of spherical fitting. Assuming that these points are on the sphere with the center of the femoral head as the center of the sphere, through continuous iterative calculation, a relatively accurate center position of the femoral head is finally obtained.

[0026] Specifically, the three-dimensional position coordinates of the femoral positioning device during femoral rotation are obtained to form a set of positions; that is, during the process of simulating knee flexion movement, the visual device continuously tracks the positions of the marker points on the femoral positioning device, and the three-dimensional coordinates (x, y, z) of the marker points recorded at each moment are added to the set of positions. Among them, the visual device can be an optical locator. According to the set of positions, the random sample consensus algorithm is used to determine the center position of the femoral head.

[0027] For example, with the center of the femoral head as the center, the femur is slowly and smoothly rotated, and the set of positions of the femoral positioning device is collected in the global coordinate system. , according to the random sample consensus algorithm, four non-coplanar points in G are selected. , from the standard equation of the sphere (where (a, b, c) is the center of the sphere and r is the radius) is expanded to obtain , let , to obtain a system of linear equations , solve this system of equations to obtain (a, b, c, d), and then according to , the radius r of the circle is obtained. For all data points, calculate the distance error to the sphere: , if < preset threshold, it is marked as an inlier. Iterate the above steps. If the inlier ratio exceeds the set threshold (such as 95%) or reaches the maximum number of iterations , (where p is the expected success probability, w is the proportion of inliers, and k is the minimum number of samples), the iteration can be terminated, and finally the center (a, b, c) of the circle is obtained as the position of the femoral head center, denoted as .

[0028] The above method can effectively exclude the interference of outliers and accurately find the inliers that conform to the spherical model (i.e., conform to the femoral rotation characteristics) from the noisy data, so as to more accurately determine the position of the femoral head center.

[0029] In an alternative embodiment, the positions of the medial malleolus and the lateral malleolus can be obtained by moving a positioning device (such as a probe with a sensor). For example, in the preoperative preparation stage, the position coordinates of the medial malleolus and the lateral malleolus are measured separately using the moving positioning device, and then the center position of the ankle joint is calculated using the midpoint formula. Exemplarily, the position of the medial malleolus is collected using the moving positioning device in the global coordinate system , the position of the lateral malleolus , and according to the formula the center position of the ankle joint is obtained, where t is a constant value. For example, t can be set to 0.46.

[0030] In practical applications, during the preoperative planning of anterior cruciate ligament reconstruction surgery, the femoral positioning device is fixed on the patient's femur to simulate the rotation process of the femur during knee joint movement. The position set of the femoral positioning device is collected using an optical positioning instrument, and then the position of the femoral head center is calculated by the random sample consensus algorithm; at the same time, the positions of the medial malleolus and the lateral malleolus are measured using the moving positioning device, and then the center position of the ankle joint is determined using the midpoint formula, providing key position information for subsequent knee joint movement analysis.

[0031] In step S103, according to the registration relationship between the image coordinate system and the local coordinate system, the positions of the femoral ligament insertion point, the apex position of the intercondylar fossa, the tibial ligament insertion point, and the center position of the tibial plateau in the image coordinate system are converted from the image coordinate system to the local coordinate system. According to the mapping relationship between the global coordinate system and the local coordinate system, the center position of the femoral head and the center position of the ankle joint in the global coordinate system are converted from the global coordinate system to the local coordinate system. Among them, the registration relationship is determined according to the position set of the knee joint positioning device and the position set of the knee joint registration points, and the center position of the tibial plateau is determined according to the position of the medial edge point of the tibial plateau and the position of the lateral edge point of the tibial plateau. Here, the image coordinate system is a coordinate system established based on the acquired original knee joint image, which is used to describe the positions of various points in the image. The global coordinate system is a unified coordinate system, which is used to describe the position and motion state of the entire knee joint in space. In the embodiment of the present application, it is established based on the visual device, that is, the global coordinate system can also be defined as the visual device coordinate system, that is, the world coordinate system. The local coordinate system is a relative coordinate system established for facilitating the accurate analysis of various parts of the knee joint, specifically including the femoral local coordinate system established relative to the femur and the tibial local coordinate system established relative to the tibia. The registration relationship refers to the transformation relationship between the image coordinate system and the local coordinate system. Through this relationship, the position information in the image can be accurately converted into the actual knee joint local coordinate system, and it can be calculated by a certain algorithm, such as the registration algorithm. The mapping relationship refers to the conversion relationship between the global coordinate system and the local coordinate system, which is used to unify the position information under different coordinate systems.

[0032] Exemplarily, the iterative closest point (ICP) algorithm or the like can be used to calculate the registration relationship. For example, according to the position set of the knee joint positioning device and the position set of the knee joint registration points, the ICP algorithm is continuously iteratively calculated to find the optimal rotation and translation parameters, so as to determine the registration relationship between the image coordinate system and the local coordinate system.

[0033] Optionally, the center position of the tibial plateau is determined according to the position of the medial edge point of the tibial plateau and the position of the lateral edge point of the tibial plateau. Specifically, the position of the medial edge point of the tibial plateau is obtained and the position of the lateral edge point of the tibial plateau , and by calculating the center position of the tibial plateau is obtained .

[0034] Exemplarily, the knee joint positioning device can be fixed on the knee joint. The visual device acquires the set of positions of the knee joint positioning device and performs registration in combination with the set of knee joint registration point positions. Specifically, the knee joint positioning device can include a femur positioning device and a tibia positioning device, which are respectively fixed on the femur and the tibia and are used to provide the position information of the femur and the tibia in space.

[0035] Furthermore, when performing the anterior cruciate ligament reconstruction surgical plan, first determine the image coordinate system, the global coordinate system, and the local coordinate system. Then, according to the set of positions of the knee joint positioning device and the previously determined set of knee joint registration point positions, use the registration algorithm to calculate the registration relationship between the image coordinate system and the local coordinate system. Furthermore, convert key positions such as the femur ligament insertion position and the apex position of the intercondylar fossa from the image coordinate system to the local coordinate system. According to the mapping relationship between the global coordinate system and the local coordinate system, convert the femoral head center position and the ankle joint center position in the global coordinate system from the global coordinate system to the local coordinate system to prevent the movement of the knee joint position or the visual device during the acquisition and registration process.

[0036] In step S104, during the knee joint flexion movement, convert the femur ligament insertion position, the apex position of the intercondylar fossa, the tibia ligament insertion position, the center position of the tibial plateau, the femoral head center position, and the ankle joint center position in the local coordinate system obtained to the global coordinate system.

[0037] Among them, during the knee joint flexion movement, by real-time collecting the coordinates of each key position point of the knee joint in the local coordinate system and using the mapping relationship between the global coordinate system and the local coordinate system, convert these coordinates to the global coordinate system to analyze the movement state of the knee joint and the relationship between each position point as a whole. In an optional implementation manner, during the knee joint flexion movement, use the visual device installed on the operating table to real-time monitor the pose change of the knee joint positioning device, so as to obtain the latest coordinates of each key position point in the local coordinate system. For example, before the operation, when the doctor manually operates the patient's knee joint to perform flexion and extension movements, the visual device will continuously collect the pose information of the femur positioning device and the tibia positioning device, and then determine the coordinates of each position point in the femur local coordinate system and the tibia local coordinate system. [[ID= twelve]]

[0038] Exemplarily, when converting the coordinates in the local coordinate system to the global coordinate system, according to the previously determined mapping relationship between the global coordinate system and the local coordinate system, the coordinates can be transformed using a transformation matrix. For example, for the femur ligament insertion position coordinates in the femur local coordinate system, multiply them by the corresponding femur transformation matrix to obtain its coordinates in the global coordinate system.

[0039] In step S105, the flexion angle during the knee flexion movement is determined based on the positions of the intercondylar fossa vertex, the center of the tibial plateau, the center of the femoral head, and the center of the ankle joint in the global coordinate system. The ligament lengths corresponding to different flexion angles are determined based on the positions of the femoral ligament insertion point and the tibial ligament insertion point in the global coordinate system, and the ligament length differences corresponding to different flexion angles are obtained by comparing with the reference ligament length. Here, the flexion angle refers to the change in the angle between the femur and the tibia when the knee joint makes a flexion movement. The ligament length refers to the distance between the femoral ligament insertion point and the tibial ligament insertion point at different flexion angles. The reference ligament length is a preset standard length value, and usually, the ligament length at a specific flexion angle (such as 90 degrees) can be selected as the reference. In an alternative embodiment, the flexion angle can be determined according to the vector angle formula. Specifically: the femoral mechanical axis is determined based on the position of the center of the femoral head and the position of the intercondylar fossa vertex in the global coordinate system, and the tibial mechanical axis is determined based on the position of the center of the tibial plateau and the position of the center of the ankle joint in the global coordinate system; based on the femoral mechanical axis and the tibial mechanical axis, the flexion angle during the knee flexion movement is calculated using the vector angle formula.

[0040] That is to say, the vector formed by the position of the center of the femoral head and the position of the intercondylar fossa vertex is used as the direction vector of the femoral mechanical axis, and the vector formed by the position of the center of the tibial plateau and the position of the center of the ankle joint is used as the direction vector of the tibial mechanical axis. The flexion angle of the knee joint is determined by calculating the angle between these two vectors.

[0041] Exemplarily, as Figure 3 shown, define the position of the center of the femoral head in the global coordinate system , the position of the intercondylar fossa vertex in the global coordinate system , then the femoral mechanical axis , define the midpoint position of the tibial plateau in the global coordinate system as , the midpoint position of the ankle joint in the global coordinate system , then the tibial mechanical axis , from the vector angle formula , the calculated flexion angle is . In an alternative embodiment, the ligament length differences corresponding to different flexion angles can be determined using the three-dimensional distance formula. Specifically: based on the positions of the femoral ligament insertion point and the tibial ligament insertion point in the global coordinate system, the ligament lengths corresponding to different flexion angles are calculated using the three-dimensional distance formula; the differences between the ligament lengths corresponding to different flexion angles and the reference ligament length corresponding to the specified flexion angle are calculated to obtain the ligament length differences corresponding to different flexion angles.

[0042] Exemplarily, define the position of the femoral ligament insertion point in the global coordinate system as , the position of the tibial ligament insertion point in the global coordinate system is , the ligament length , when the angle is 90 degrees, the ligament length is is the reference ligament length, and the ligament length difference .

[0043] That is, given the three-dimensional coordinates of the femoral ligament attachment point and the tibial ligament attachment point corresponding to different knee flexion angles in the global coordinate system, the distance between the two points is calculated through the three-dimensional distance formula, so as to obtain the ligament length at this knee flexion angle; then, the difference is taken from the reference ligament length to obtain the ligament length difference corresponding to different knee flexion angles. In step S106, an isometric curve of the ligament with the change of the knee flexion angle is constructed to evaluate the rationality of the ligament attachment point according to the isometric curve of the ligament. Among them, the isometric curve of the ligament with the change of the knee flexion angle is a curve constructed with the knee flexion angle as the horizontal axis and the ligament length difference as the vertical axis, which is used to intuitively display the change of the ligament length when the knee joint is at different knee flexion angles. Evaluating the rationality of the ligament attachment point means judging whether the currently set positions of the femoral ligament attachment point and the tibial ligament attachment point are reasonable and whether they can ensure the isometry of the ligament during the movement of the knee joint by analyzing the isometric curve of the ligament.

[0044] For example, control the knee joint to perform a flexion movement between 30 degrees and 120 degrees of knee flexion, and collect the knee flexion angle and the ligament length set , when the knee flexion angle is 90 degrees, the reference ligament length is denoted as , generate a set of knee flexion angles and ligament length differences , and draw an isometric curve of the ligament.

[0045] In an optional embodiment, a preset length difference range can be set to evaluate the rationality of the ligament attachment point. Specifically, step S105 specifically includes: constructing an isometric curve of the ligament with the change of the knee flexion angle; if the ligament length difference is within the preset length difference range, it is determined that the ligament attachment point is reasonable. Exemplarily, during the flexion movement of the knee joint, the data set changing with the knee flexion angle θ can be obtained, with the knee flexion angle θ as the horizontal axis,[[]] the length difference as the vertical axis, draw an isometric curve of the ligament. As shown in Figure 4 , if the ligament length difference is between (-2 mm, 2 mm), it is considered that the isometry of the ligament is good at this time, and the position of the ligament attachment point is reasonable, and the next operation can be carried out; if it exceeds this range, the doctor needs to adjust the position of the ligament attachment point according to experience or further analysis.

[0046] Furthermore, after obtaining the ligament length difference data at different knee flexion angles, a professional software can be used to construct an isometry curve of the ligament. Doctors or researchers can evaluate the rationality of the ligament insertion point by observing the curve shape and analyzing whether the ligament length difference is within the preset length difference range. If the ligament insertion point is unreasonable, the position of the ligament insertion point in the surgical plan is readjusted to ensure that the ligament during the surgery has good isometry biomechanically, thereby improving the success rate of anterior cruciate ligament reconstruction surgery.

[0047] Please refer to Figure 5 , Figure 5 which is a flowchart of another method for analyzing ligament isometry provided by an embodiment of the present application. As Figure 5 shown, the method provided by the embodiment of the present application includes: S501. Determine the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, the femoral registration point position set, and the tibial registration point position set in the image coordinate system according to the original image data of the knee joint; S502. Determine the position of the femoral head center according to the position set of the femoral positioning device during the femoral rotation, and determine the position of the ankle joint center according to the obtained positions of the medial malleolus and the lateral malleolus; S503. According to the femoral registration relationship between the image coordinate system and the femoral local coordinate system, convert the positions of the femoral ligament insertion point and the vertex position of the intercondylar fossa from the image coordinate system to the femoral local coordinate system. According to the tibial registration relationship between the image coordinate system and the tibial local coordinate system, convert the positions of the tibial ligament insertion point and the center position of the tibial plateau from the image coordinate system to the tibial local coordinate system; according to the femoral mapping relationship between the global coordinate system and the femoral local coordinate system, convert the position of the femoral head center in the global coordinate system from the global coordinate system to the femoral local coordinate system. According to the tibial mapping relationship between the global coordinate system and the tibial local coordinate system, convert the position of the ankle joint center in the global coordinate system from the global coordinate system to the tibial local coordinate system; wherein, the femoral registration relationship is determined according to the position set of the femoral positioning device and the femoral registration point position set, and the tibial registration relationship is determined according to the position set of the tibial positioning device and the tibial registration point position set; S504. During the knee flexion movement of the knee joint, according to the femoral mapping relationship between the global coordinate system and the femoral local coordinate system, convert the obtained positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, and the femoral head center in the femoral local coordinate system from the femoral local coordinate system to the global coordinate system. According to the tibial mapping relationship between the global coordinate system and the tibial local coordinate system, convert the obtained positions of the tibial ligament insertion point, the center position of the tibial plateau, and the ankle joint center in the tibial local coordinate system from the tibial local coordinate system to the global coordinate system; S505. Determine the knee flexion angle during the knee flexion movement based on the positions of the intercondylar fossa vertex, the center of the tibial plateau, the center of the femoral head, and the center of the ankle joint in the global coordinate system. Determine the ligament lengths corresponding to different knee flexion angles based on the positions of the femoral ligament insertion point and the tibial ligament insertion point in the global coordinate system, and obtain the ligament length differences corresponding to different knee flexion angles by comparing with the reference ligament length. S506. Construct an isometric curve of the ligament with the change of the knee flexion angle to evaluate the rationality of the ligament insertion point according to the isometric curve of the ligament.

[0048] Among them, the above steps S502, S505, and S506 can refer to steps S102, S105, and S106, and can achieve the same technical effects, which will not be elaborated here.

[0049] In step S501, the original image data is usually the CT scan data of the knee joint. The three-dimensional models of the femur and tibia are separated from the CT data through image processing algorithms (such as threshold segmentation, region growing, level set algorithm). The anatomical landmark points required for surgical planning are accurately located from the segmented models, and these points are all in the global coordinate system.

[0050] Here, step S501 specifically includes: determining the femur segmentation model and the tibia segmentation model according to the original image data of the knee joint; obtaining the position of the femoral ligament insertion point and the position of the intercondylar fossa vertex in the image coordinate system from the femur segmentation model, and obtaining the position of the tibial ligament insertion point, the position of the medial edge point of the tibial plateau, and the position of the lateral edge point of the tibial plateau in the image coordinate system from the tibia segmentation model; selecting feature points on the surface of the femur segmentation model to form a set of femoral registration point positions, and selecting feature points on the surface of the tibia segmentation model to form a set of tibial registration point positions.

[0051] Among them, the position of the femoral ligament insertion point and the position of the intercondylar fossa vertex in the image coordinate system can be directly obtained from the femur segmentation model, and the position of the tibial ligament insertion point, the position of the medial edge point of the tibial plateau, and the position of the lateral edge point of the tibial plateau in the image coordinate system can be directly obtained from the tibia segmentation model. On the surfaces of the femur segmentation model and the tibia segmentation model, a number of feature points (such as protrusions, depressions, or regions with obvious curvature changes on the bone surface) are manually or automatically selected to form a set of femoral registration point positions and a set of tibial registration point positions respectively.

[0052] In step S503, according to the femoral registration relationship between the image coordinate system and the local femoral coordinate system, the positions of the femoral ligament insertion points and the vertex position of the intercondylar fossa are transformed from the image coordinate system to the local femoral coordinate system. According to the tibial registration relationship between the image coordinate system and the local tibial coordinate system, the positions of the tibial ligament insertion points and the center position of the tibial plateau are transformed from the image coordinate system to the local tibial coordinate system. According to the femoral mapping relationship between the global coordinate system and the local femoral coordinate system, the center position of the femoral head in the global coordinate system is transformed from the global coordinate system to the local femoral coordinate system. According to the tibial mapping relationship between the global coordinate system and the local tibial coordinate system, the center position of the ankle joint in the global coordinate system is transformed from the global coordinate system to the local tibial coordinate system. Among them, the femoral registration relationship is determined according to the position set of the femoral positioning device and the position set of the femoral registration points, and the tibial registration relationship is determined according to the position set of the tibial positioning device and the position set of the tibial registration points.

[0053] Here, the local femoral coordinate system refers to the coordinate system fixed to the femur, the origin can be the center position of the femoral head, and the coordinate axis direction can be aligned with the mechanical axis of the femur; the local tibial coordinate system refers to the coordinate system fixed to the tibia, the origin can be the center position of the ankle joint, and the coordinate axis can be aligned with the mechanical axis of the tibia.

[0054] Specifically, the positions of the femoral ligament insertion points and the vertex position of the intercondylar fossa in the local femoral coordinate system are fixed, and the positions of the tibial ligament insertion points and the center position of the tibial plateau in the local tibial coordinate system are fixed. Furthermore, to prevent the knee joint position or the vision device from moving during the acquisition and registration process, the positions of the femoral ligament insertion points and the vertex position of the intercondylar fossa are transformed from the image coordinate system to the local femoral coordinate system, and the positions of the tibial ligament insertion points and the center position of the tibial plateau are transformed from the image coordinate system to the local tibial coordinate system, so that these feature points are not affected by individual body position changes.

[0055] In an optional embodiment, according to the poses returned by the femoral positioning device and the tibial positioning device, the femoral transformation matrix and the tibial transformation matrix are calculated respectively. According to the position set of the femoral positioning device, the femoral transformation matrix and the position set of the femoral registration points, the femoral registration matrix is constructed. According to the position set of the tibial positioning device, the tibial transformation matrix and the position set of the tibial registration points, the tibial registration matrix is constructed.

[0056] Specifically, the femoral registration relationship and the tibial registration relationship are determined through the following steps: Calculate the femoral transformation matrix and the tibial transformation matrix respectively according to the poses returned by the femoral positioning device and the poses returned by the tibial positioning device; determine the mapped femoral position set of the femoral positioning device in the femoral local coordinate system according to the femoral transformation matrix and the position set of the femoral positioning device; determine the mapped tibial position set of the tibial positioning device in the tibial local coordinate system according to the tibial transformation matrix and the position set of the tibial positioning device; construct a femoral registration matrix according to the mapped femoral position set and the femoral registration point position set to represent the femoral registration relationship through the femoral registration matrix; construct a tibial registration matrix according to the mapped tibial position set and the tibial registration point position set to represent the tibial registration relationship through the tibial registration matrix; and determine the femoral mapping relationship and the tibial mapping relationship through the following steps: Calculate the femoral transformation matrix according to the pose returned by the femoral positioning device to represent the femoral mapping relationship through the femoral transformation matrix; calculate the tibial transformation matrix according to the pose returned by the tibial positioning device to represent the tibial mapping relationship through the tibial transformation matrix.

[0057] That is to say, when determining the femoral registration relationship, the tibial registration relationship, the femoral mapping relationship and the tibial mapping relationship, it mainly depends on the pose and position set data returned by the positioning devices (femoral positioning device, tibial positioning device). Calculate the femoral transformation matrix through the pose returned by the femoral positioning device, and then combine its position set to determine the mapped femoral position set in the femoral local coordinate system. The mapped femoral position set and the femoral registration point position set construct the femoral registration matrix to represent the femoral registration relationship; similarly, perform the same operation on the tibial positioning device to determine the tibial registration relationship. When determining the mapping relationship, directly calculate the transformation matrix according to the poses returned by the femoral positioning device and the tibial positioning device respectively, and use this matrix to represent their respective mapping relationships.

[0058] The determination of the above registration relationship and mapping relationship can accurately convert the image coordinate system and the local coordinate system, and the global coordinate system and the local coordinate system, which helps to realize the accurate analysis of ligament isometry.

[0059] Exemplarily, the femoral registration point position set and the tibial registration point position set . The pose returned by the positioning device (femoral positioning device, tibial positioning device), obtain the corresponding rotation matrix according to the unit quaternion, and the translation vector . Obtain the transformation matrix from the rotation matrix and the translation vector, and further, the femoral transformation matrix can be determined according to the pose , similarly, according to the pose returned by the tibia positioning device the tibia transformation matrix can be determined . In the global coordinate system, collect the position set of the femur positioning device and the position set of the tibia positioning device . According to the femur mapping relationship between the global coordinate system and the femur local coordinate system, convert the position set of the femur positioning device to the femur local coordinate system to obtain the mapped femur position set . According to the tibia mapping relationship between the global coordinate system and the tibia local coordinate system, convert the position set of the tibia positioning device to the tibia local coordinate system to obtain the mapped tibia position set . According to and , the femur registration matrix can be obtained by using the registration algorithm. According to and , the tibia registration matrix can be obtained by using the registration algorithm.

[0060] For the positions of the femoral ligament insertion point and the apex of the intercondylar fossa in the image coordinate system, through the femur registration matrix, convert the positions of the femoral ligament insertion point and the apex of the intercondylar fossa to the femur local coordinate system. For the positions of the tibial ligament insertion point and the center of the tibial plateau in the image coordinate system, through the tibia registration matrix, convert the positions of the tibial ligament insertion point and the center of the tibial plateau to the tibia local coordinate system; for the position of the femoral head center in the global coordinate system, according to the femur mapping relationship between the global coordinate system and the femur local coordinate system, convert the position of the femoral head center to the femur local coordinate system. For the position of the ankle joint center in the global coordinate system, according to the tibia mapping relationship between the global coordinate system and the tibia local coordinate system, convert the position of the ankle joint center to the tibia local coordinate system.

[0061] Here, when converting from the image coordinate system to the local coordinate system (femur local coordinate system and tibia local coordinate system), calculate according to the coordinate transformation formula . Among them, represents the position coordinate in the local coordinate system, represents the position coordinate in the image coordinate system, represents the registration matrix, including the femur registration matrix and the tibia registration matrix . When converting from the global coordinate system to the local coordinate system (femur local coordinate system and tibia local coordinate system), calculate according to the coordinate transformation formula . Among them, represents the position coordinate in the global coordinate system, represents the transformation matrix, including the femur transformation matrix and the tibia transformation matrix 。

[0062] Convert from the local coordinate systems (the femoral local coordinate system and the tibial local coordinate system) to the global coordinate system, and calculate according to the coordinate transformation formula wherein, represents the inverse transformation of the transformation matrix, including the inverse transformation of the femoral transformation matrix and the inverse transformation of the tibial transformation matrix 。

[0063] During preoperative planning, the coordinates of the femoral ligament insertion point position and the intercondylar fossa vertex position in the image coordinate system are converted into the coordinates in the femoral local coordinate system through the femoral registration matrix; the coordinates of the tibial ligament insertion point position and the tibial plateau center position in the image coordinate system are converted into the coordinates in the tibial local coordinate system through the tibial registration matrix. The coordinates of the femoral head center position in the global coordinate system are converted into the coordinates in the femoral local coordinate system through the femoral transformation matrix, and the coordinates of the ankle joint center position in the global coordinate system are converted into the coordinates in the tibial local coordinate system through the tibial transformation matrix.

[0064] The embodiment of the present application realizes the accurate mapping of anatomical structures in different coordinate systems through the registration matrix and the transformation matrix, avoiding the positioning error caused by the coordinate system difference.

[0065] In step S504, during the knee flexion movement, according to the femoral mapping relationship between the global coordinate system and the femoral local coordinate system, the femoral ligament insertion point position, the intercondylar fossa vertex position, and the femoral head center position in the femoral local coordinate system obtained are converted from the femoral local coordinate system to the global coordinate system. According to the tibial mapping relationship between the global coordinate system and the tibial local coordinate system, the tibial ligament insertion point position, the tibial plateau center position, and the ankle joint center position in the tibial local coordinate system obtained are converted from the tibial local coordinate system to the global coordinate system.

[0066] Specifically, for the femoral ligament insertion point position, the intercondylar fossa vertex position, and the femoral head center position in the femoral local coordinate system, combined with the femoral transformation matrix, the femoral ligament insertion point position, the intercondylar fossa vertex position, and the femoral head center position are converted to the global coordinate system through the inverse transformation. For the tibial ligament insertion point position, the tibial plateau center position, and the ankle joint center position in the tibial local coordinate system, combined with the tibial transformation matrix, the tibial ligament insertion point position, the tibial plateau center position, and the ankle joint center position are converted to the global coordinate system through the inverse transformation.

[0067] Furthermore, during knee flexion, dynamic points in the femoral and tibia local coordinate systems are converted to the global coordinate system to uniformly observe the relative motion of the femur and tibia. The femoral and tibia local coordinate systems rotate and translate with movement (for example, the femur rotates around the center of the knee joint during knee flexion). Therefore, local coordinates (such as the center of the femoral head) must be converted to global coordinates to track their actual positions in space.

[0068] The ligament isometric analysis method provided in the embodiment of the present application can accurately evaluate the rationality of the ligament attachment points through precise determination of key positions of the knee joint, coordinate system conversion, and data calculation and analysis. It effectively solves the problem of poor surgical results caused by inaccurate determination of the ligament attachment point positions in anterior cruciate ligament reconstruction surgery in the prior art, improves the accuracy and reliability of surgical planning, and thus improves the success rate of anterior cruciate ligament reconstruction surgery.

[0069] Based on the same inventive concept, a ligament isometric analysis device corresponding to the ligament isometric analysis method is also provided in the embodiment of the present application. Since the principle of solving the problem by the device in the embodiment of the present application is similar to the above-mentioned ligament isometric analysis method in the embodiment of the present application, the implementation of the device can refer to the implementation of the method, and the repeated parts will not be repeated.

[0070] See also Figure 6 , Figure 6 This is a schematic diagram of the structure of a ligament isometric analysis device provided in an embodiment of the present application. Figure 6 As shown in , the apparatus 600 includes: The data acquisition module 601 is used to determine the femoral ligament insertion point position, the intercondylar notch vertex position, the tibial ligament insertion point position, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, and the knee joint registration point position set in the image coordinate system based on the original image data of the knee joint; A first processing module 602 is configured to determine the center position of the femoral head based on the acquired position set of the femoral positioning device during the femoral rotation process, and determine the center position of the ankle joint based on the acquired medial and lateral malleolus positions; A coordinate system alignment module 603 is configured to convert the femoral ligament insertion point, intercondylar notch apex, tibial ligament insertion point, and tibial plateau center position in the image coordinate system from the image coordinate system to the local coordinate system based on a registration relationship between the image coordinate system and the local coordinate system; and to convert the femoral head center position and ankle joint center position in the global coordinate system from the global coordinate system to the local coordinate system based on a mapping relationship between the global coordinate system and the local coordinate system; wherein the registration relationship is determined based on a set of knee joint positioning device positions and a set of knee joint registration point positions, and the tibial plateau center position is determined based on the medial edge point position and the lateral edge point position of the tibial plateau; A coordinate system conversion module 604 is configured to convert the positions of the femoral ligament insertion point, the apex position of the intercondylar fossa, the tibial ligament insertion point, the center position of the tibial plateau, the center position of the femoral head, and the center position of the ankle joint obtained in the local coordinate system to the global coordinate system during the knee flexion movement of the knee joint. A second processing module 605 is configured to determine the knee flexion angle during the knee flexion movement of the knee joint according to the apex position of the intercondylar fossa, the center position of the tibial plateau, the center position of the femoral head, and the center position of the ankle joint in the global coordinate system, and determine the ligament lengths corresponding to different knee flexion angles according to the positions of the femoral ligament insertion point and the tibial ligament insertion point in the global coordinate system, so as to obtain the ligament length differences corresponding to different knee flexion angles by comparing with the reference ligament lengths. An isometry analysis module 606 is configured to construct an isometry curve of the ligament length difference changing with the knee flexion angle, so as to evaluate the rationality of the ligament insertion point according to the isometry curve of the ligament.

[0071] The ligament isometry analysis device provided by the embodiment of the present application can accurately capture the dynamic changes of the ligament insertion point during the knee joint movement by first aligning the coordinate systems and then analyzing the position changes obtained during the knee flexion movement of the knee joint in the local coordinate system. By simulating the dynamic changes during the knee flexion movement of the knee joint, an isometry curve of the ligament length difference changing with the knee flexion angle is constructed, and the rationality of the ligament insertion point is evaluated through the isometry curve of the ligament, so as to improve the accuracy of determining the position of the ligament insertion point, and further ensure the reasonable position of the ligament insertion point, which is helpful to improve the success rate of anterior cruciate ligament reconstruction surgery.

[0072] Please refer to Figure 7 , Figure 7 which is a schematic structural diagram of a ligament isometry analysis system provided by an embodiment of the present application. As shown in Figure 7 In the figure, the system includes: a vision device 1, a knee joint positioning device, a mobile positioning device 4, and a processing device 5. The vision device 1 is configured to collect the position set of the knee joint positioning device and the position information of the mobile positioning device 4, and the vision device 1 is connected to the processing device 5.

[0073] Specifically, the knee joint positioning device includes a femoral positioning device 2 and a tibial positioning device 3. The femoral positioning device 2 is fixed on the femur, and the tibial positioning device 3 is fixed on the tibia.

[0074] Optionally, the vision device 1 is used to monitor the knee joint positioning device and the mobile positioning device 4, and then collect the position set of the knee joint positioning device and the position information of the mobile positioning device 4. Further, the knee joint positioning device is subdivided into a femoral positioning device 2 and a tibial positioning device 3, and the vision device is used to collect the position set of the femoral positioning device 2 and the position set of the tibial positioning device 3. The vision device 1 is usually a device based on optical principles, such as an optical locator.

[0075] Specifically, both the femoral positioning device 2 and the tibial positioning device 3 are devices with optical marker points. These optical marker points can be accurately identified and tracked by the vision device 1. In practical applications, the femoral positioning device 2 is stably fixed on the femur. Exemplarily, a Kirschner wire can be used to achieve a firm connection, so as to ensure that the femoral positioning device 2 remains relatively stationary with respect to the femur during knee joint movement, thereby truly reflecting the position and attitude changes of the femur. Similarly, the tibial positioning device 3 is fixed on the tibia and is used to collect the position information of the tibia.

[0076] Optionally, the mobile positioning device 4 is mainly used to collect the position information of some specific parts, such as the positions of the medial malleolus point and the lateral malleolus point. It can be a handheld positioning device with sensors, such as an electromagnetic locator, an optical positioning probe, etc. During the operation, the operator can hold the mobile positioning device 4 and bring its probe into contact with or close to parts such as the medial malleolus and the lateral malleolus. The mobile positioning device 4 can obtain the three-dimensional coordinate information of the medial malleolus point and the lateral malleolus point through the internal sensors. The mobile positioning device 4 is provided with optical marker points so that the vision device can collect the position information of the mobile positioning device 4 through vision recognition technology. Further, the processing device 5 receives the data from the vision device 1. The processing device 5 can be a device with strong data processing capabilities such as a computer or a server. It stores, analyzes, and calculates the received data, and performs a series of complex operation tasks such as determining the position of the femoral head center using the random sample consensus algorithm, performing coordinate transformation according to the registration relationship, calculating the ligament length difference, and constructing the ligament isometry curve. Finally, it outputs an evaluation result on the rationality of the ligament insertion point.

[0077] The ligament isometry analysis system provided by the embodiments of the present application can comprehensively and accurately obtain the overall positions of the femur and the tibia, as well as the positions of key anatomical points. The data is more comprehensive and accurate, and it can complete complex knee joint position information analysis tasks in a short time. At the same time, it ensures the accuracy of the analysis results. By using the vision device and positioning devices (such as the femoral positioning device 2, the tibial positioning device 3, and the mobile positioning device 4) to simulate the isometry curve of the ligament, the feasibility of the bone tunnel plan can be analyzed, which helps the doctor adjust the bone tunnel plan, improves the efficiency and quality of the surgical plan, and ensures the success of the surgery.

[0078] Please refer to Figure 8 ,Figure 8 The following is a schematic structural diagram of an electronic device provided by an embodiment of the present application. As Figure 8 shown in the figure, the electronic device 800 includes a processor 801, a memory 802, and a bus 803.

[0079] The memory 802 stores machine-readable instructions executable by the processor 801. When the electronic device 800 runs, the processor 801 communicates with the memory 802 through the bus 803. When the machine-readable instructions are executed by the processor 801, the steps of the ligament isometry analysis method in the method embodiments as described above Figure 1 and Figure 5 shown can be executed. For the specific implementation manner, reference can be made to the method embodiments, which will not be elaborated here.

[0080] The embodiment of the present application also provides a computer-readable storage medium. A computer program is stored on the computer-readable storage medium. When the computer program is run by a processor, the steps of the ligament isometry analysis method in the method embodiments as described above Figure 1 and Figure 5 shown can be executed. For the specific implementation manner, reference can be made to the method embodiments, which will not be elaborated here.

[0081] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments, which will not be elaborated here.

[0082] In several embodiments provided by the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. The device embodiments described above are only illustrative. For example, the division of the units is only a logical function division, and there can be other division methods in actual implementation. For another example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the couplings, direct couplings, or communication connections shown or discussed with each other can be through some communication interfaces. The indirect couplings or communication connections of the devices or units can be in electrical, mechanical, or other forms.

[0083] The units described as separate components may or may not be physically separated. The components shown as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0084] In addition, in each embodiment of the present application, each functional unit can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit.

[0085] If the above-mentioned function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a non-volatile computer-readable storage medium executable by a processor. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present application. The foregoing storage medium includes: various media that can store program codes such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical discs.

[0086] Finally, it should be noted that: the above-mentioned embodiments are only specific implementation manners of the present application, used to illustrate the technical solutions of the present application, rather than limiting it. The protection scope of the present application is not limited thereto. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: any person skilled in the art within the technical scope disclosed in the present application can still modify the technical solutions recorded in the foregoing embodiments, or can easily think of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes, or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for analyzing ligament isometry, characterized in that The method includes: Based on the original image data of the knee joint, determining the positions of the femoral ligament insertion points, the vertex position of the intercondylar fossa, the tibial ligament insertion points, the medial edge points of the tibial plateau, the lateral edge points of the tibial plateau, and the set of knee joint registration points in the image coordinate system; Determining the position of the femoral head center according to the set of positions of the femoral positioning device during femoral rotation, and determining the position of the ankle joint center according to the obtained positions of the medial malleolus and the lateral malleolus; According to the registration relationship between the image coordinate system and the local coordinate system, converting the positions of the femoral ligament insertion points, the vertex position of the intercondylar fossa, the tibial ligament insertion points, and the center position of the tibial plateau in the image coordinate system to the local coordinate system, and according to the mapping relationship between the global coordinate system and the local coordinate system, converting the positions of the femoral head center and the ankle joint center in the global coordinate system to the local coordinate system; wherein, the registration relationship is determined according to the set of positions of the knee joint positioning device and the set of knee joint registration points, and the center position of the tibial plateau is determined according to the medial edge points of the tibial plateau and the lateral edge points of the tibial plateau; During the knee joint flexion movement, converting the positions of the femoral ligament insertion points, the vertex position of the intercondylar fossa, the tibial ligament insertion points, the center position of the tibial plateau, the femoral head center position, and the ankle joint center position in the obtained local coordinate system to the global coordinate system; Determining the flexion angle during the knee joint flexion movement according to the vertex position of the intercondylar fossa, the center position of the tibial plateau, the femoral head center position, and the ankle joint center position in the global coordinate system, and determining the ligament lengths corresponding to different flexion angles according to the positions of the femoral ligament insertion points and the tibial ligament insertion points in the global coordinate system, so as to obtain the ligament length differences corresponding to different flexion angles by comparing with the reference ligament length; Constructing an isometric curve of the ligament with the change of the flexion angle of the ligament length difference, so as to evaluate the rationality of the ligament insertion points according to the isometric curve of the ligament; 2. The method according to claim 1, wherein The knee joint positioning device includes a femoral positioning device and a tibial positioning device, the femoral positioning device is fixed on the femur, and the tibial positioning device is fixed on the tibia; The determining the positions of the femoral ligament insertion points, the vertex position of the intercondylar fossa, the tibial ligament insertion points, the medial edge points of the tibial plateau, the lateral edge points of the tibial plateau, and the set of knee joint registration points in the image coordinate system based on the original image data of the knee joint includes: Based on the original image data of the knee joint, determining the positions of the femoral ligament insertion points, the vertex position of the intercondylar fossa, the tibial ligament insertion points, the medial edge points of the tibial plateau, the lateral edge points of the tibial plateau, the set of femoral registration points, and the set of tibial registration points in the image coordinate system; According to the registration relationship between the image coordinate system and the local coordinate system, the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, and the center position of the tibial plateau in the image coordinate system are transformed from the image coordinate system to the local coordinate system. According to the mapping relationship between the global coordinate system and the local coordinate system, the center position of the femoral head and the center position of the ankle joint in the global coordinate system are transformed from the global coordinate system to the local coordinate system, including: According to the femoral registration relationship between the image coordinate system and the femoral local coordinate system, the positions of the femoral ligament insertion point and the vertex position of the intercondylar fossa are transformed from the image coordinate system to the femoral local coordinate system. According to the tibial registration relationship between the image coordinate system and the tibial local coordinate system, the positions of the tibial ligament insertion point and the center position of the tibial plateau are transformed from the image coordinate system to the tibial local coordinate system; According to the femoral mapping relationship between the global coordinate system and the femoral local coordinate system, the center position of the femoral head in the global coordinate system is transformed from the global coordinate system to the femoral local coordinate system. According to the tibial mapping relationship between the global coordinate system and the tibial local coordinate system, the center position of the ankle joint in the global coordinate system is transformed from the global coordinate system to the tibial local coordinate system; wherein, the femoral registration relationship is determined according to the position set of the femoral positioning device and the position set of the femoral registration points, and the tibial registration relationship is determined according to the position set of the tibial positioning device and the position set of the tibial registration points; During the process of knee flexion, the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, the center position of the tibial plateau, the center position of the femoral head, and the center position of the ankle joint in the local coordinate system obtained are transformed from the local coordinate system to the global coordinate system, including: During the process of knee flexion, according to the femoral mapping relationship between the global coordinate system and the femoral local coordinate system, the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, and the center position of the femoral head in the femoral local coordinate system obtained are transformed from the femoral local coordinate system to the global coordinate system. According to the tibial mapping relationship between the global coordinate system and the tibial local coordinate system, the positions of the tibial ligament insertion point, the center position of the tibial plateau, and the center position of the ankle joint in the tibial local coordinate system obtained are transformed from the tibial local coordinate system to the global coordinate system.

3. The method according to claim 2, characterized in that The femoral registration relationship and the tibial registration relationship are determined through the following steps: According to the poses returned by the femoral positioning device and the poses returned by the tibial positioning device, the femoral transformation matrix and the tibial transformation matrix are calculated respectively; According to the femoral transformation matrix and the position set of the femoral positioning device, the mapped femoral position set of the femoral positioning device in the femoral local coordinate system is determined; According to the tibial transformation matrix and the position set of the tibial positioning device, the mapped tibial position set of the tibial positioning device in the tibial local coordinate system is determined; According to the mapped femoral position set and the position set of the femoral registration points, a femoral registration matrix is constructed to represent the femoral registration relationship through the femoral registration matrix; Construct a tibia registration matrix based on the set of mapped tibia positions and the set of tibia registration point positions, so as to characterize the tibia registration relationship through the tibia registration matrix; And determine the femoral mapping relationship and the tibia mapping relationship through the following steps: Calculate a femoral transformation matrix according to the pose returned by the femoral positioning device, so as to characterize the femoral mapping relationship through the femoral transformation matrix; Calculate a tibia transformation matrix according to the pose returned by the tibia positioning device, so as to characterize the tibia mapping relationship through the tibia transformation matrix.

4. The method according to claim 1, wherein The determining the center position of the femoral head according to the set of positions of the femoral positioning device during the femoral rotation and determining the center position of the ankle joint according to the obtained medial malleolus position and lateral malleolus position includes: Obtain the three-dimensional position coordinates of the femoral positioning device during the femoral rotation to form a set of positions; Determine the center position of the femoral head according to the set of positions by using the random sample consensus algorithm; Calculate the center position of the ankle joint according to the obtained medial malleolus position and lateral malleolus position by using the midpoint formula.

5. The method according to claim 2, wherein The determining the positions of the femoral ligament insertion points, the vertex position of the intercondylar fossa, the positions of the tibial ligament insertion points, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, the set of femoral registration point positions and the set of tibia registration point positions in the image coordinate system according to the original image data of the knee joint includes: Determine a femoral segmentation model and a tibia segmentation model according to the original image data of the knee joint; Obtain the positions of the femoral ligament insertion points and the vertex position of the intercondylar fossa in the image coordinate system from the femoral segmentation model, and obtain the positions of the tibial ligament insertion points, the medial edge point position of the tibial plateau and the lateral edge point position of the tibial plateau in the image coordinate system from the tibia segmentation model; Select feature points on the surface of the femoral segmentation model to form a set of femoral registration point positions, and select feature points on the surface of the tibia segmentation model to form a set of tibia registration point positions.

6. The method according to claim 1, wherein The determining the flexion angle during the knee flexion movement according to the vertex position of the intercondylar fossa, the center position of the tibial plateau, the center position of the femoral head and the center position of the ankle joint in the global coordinate system, and determining the ligament lengths corresponding to different flexion angles according to the positions of the femoral ligament insertion points and the tibial ligament insertion points in the global coordinate system, so as to obtain the ligament length differences corresponding to different flexion angles by comparing with the reference ligament length includes: Determine the femoral mechanical axis according to the center position of the femoral head and the vertex position of the intercondylar fossa in the global coordinate system, and determine the tibial mechanical axis according to the center position of the tibial plateau and the center position of the ankle joint in the global coordinate system; Calculate the flexion angle during the knee flexion movement by using the vector included angle formula according to the femoral mechanical axis and the tibial mechanical axis; Calculate the ligament lengths corresponding to different flexion angles by using the three-dimensional distance formula according to the positions of the femoral ligament insertion points and the tibial ligament insertion points in the global coordinate system; Calculate the differences between the ligament lengths corresponding to different flexion angles and the reference ligament length corresponding to the specified flexion angle respectively to obtain the ligament length differences corresponding to different flexion angles.

7. The method according to claim 1, characterized in that The constructing an isometric ligament curve of the ligament length varying with the flexion angle to evaluate the rationality of the ligament insertion points according to the isometric ligament curve includes: Construct a ligament isometry curve showing the change in ligament length difference with the knee flexion angle; If the ligament length difference is within the preset length difference range, it is determined that the ligament insertion point is reasonable.

8. A ligament isometry analysis device, characterized in that, The device includes: A data acquisition module for determining the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, the medial edge point position of the tibial plateau, the lateral edge point position of the tibial plateau, and the set of knee joint registration point positions in the image coordinate system based on the original image data of the knee joint; A first processing module for determining the position of the femoral head center according to the set of positions of the femoral positioning device during femoral rotation, and determining the position of the ankle joint center according to the obtained positions of the medial malleolus and the lateral malleolus; A coordinate system alignment module for converting the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, and the tibial plateau center position in the image coordinate system to the local coordinate system according to the registration relationship between the image coordinate system and the local coordinate system, and converting the positions of the femoral head center and the ankle joint center in the global coordinate system to the local coordinate system according to the mapping relationship between the global coordinate system and the local coordinate system; wherein, the registration relationship is determined according to the set of positions of the knee joint positioning device and the set of knee joint registration point positions, and the tibial plateau center position is determined according to the medial edge point position and the lateral edge point position of the tibial plateau; A coordinate system conversion module for converting the positions of the femoral ligament insertion point, the vertex position of the intercondylar fossa, the tibial ligament insertion point, the tibial plateau center position, the femoral head center position, and the ankle joint center in the local coordinate system to the global coordinate system during the knee flexion movement of the knee joint; A second processing module for determining the knee flexion angle during the knee flexion movement of the knee joint according to the vertex position of the intercondylar fossa, the tibial plateau center position, the femoral head center position, and the ankle joint center in the global coordinate system, and determining the ligament lengths corresponding to different knee flexion angles according to the positions of the femoral ligament insertion point and the tibial ligament insertion point in the global coordinate system, so as to obtain the ligament length differences corresponding to different knee flexion angles by comparing with the reference ligament length; An isometry analysis module for constructing a ligament isometry curve showing the change in ligament length difference with the knee flexion angle to evaluate the reasonableness of the ligament insertion point according to the ligament isometry curve.

9. A ligament isometry analysis system, characterized in that, Applied to the ligament isometry analysis method according to any one of claims 1 to 7, the system includes: a visual device, a knee joint positioning device, a mobile positioning device, and a processing device, wherein the visual device is used to collect the set of positions of the knee joint positioning device and the position information of the mobile positioning device, and the visual device is connected to the processing device.

10. The system according to claim 9, wherein The knee joint positioning device includes a femoral positioning device and a tibial positioning device, the femoral positioning device is fixed on the femur, and the tibial positioning device is fixed on the tibia.

Images