A bionic knee joint testing device based on medical image personalized reconstruction

Abstract

The application discloses a kind of based on medical image individualized reconstruction's bionic knee joint testing device, belong to humanoid test technical field, with bionic knee joint matrix, the matrix includes femoral end interface, middle rotating shaft, pedestal and tibial end interface, the middle rotating shaft includes mutually perpendicular and arranged horizontal rotating cylinder and vertical rotating shaft, horizontal rotating shaft is arranged in the horizontal rotating cylinder;The horizontal rotating shaft end is provided with first bearing, first bearing is fixedly connected with femoral end interface, and simulation cartilage is arranged in the lower end of first bearing and femoral end interface connection position;The middle part of the pedestal has through-hole, and vertical rotating shaft is placed in the through-hole;Simulation meniscus is arranged on the upper end of the pedestal, and the upper surface of simulation meniscus is in contact with the lower surface of simulation cartilage;The lower side of the pedestal is connected with tibial end interface.The bionic knee joint pressure measuring dummy disclosed by the application can realize human knee physiological level coupling motion simulation.

Description

Technical Field

[0001] This invention relates to a bionic knee joint testing device based on personalized reconstruction of medical images, belonging to the field of humanoid testing technology. Background Technology

[0002] Existing knee prostheses still have significant limitations in simulating the complex kinematics and biomechanics of real knee joints, making it difficult to meet the growing clinical demand for personalized medicine and precise functional reconstruction. Specifically, existing technologies have the following main shortcomings:

[0003] First, in terms of individual anatomical adaptation, existing prosthetic systems are mostly designed based on standardized parameters, which makes it difficult to accurately reproduce the anatomical differences in three-dimensional shape, radius of curvature and relative spatial position of the femoral condyle, tibial plateau and other structures of different patients, making it difficult for the prosthesis to reproduce the complex movement trajectory of the real knee joint.

[0004] Second, in terms of kinematic simulation, the movement of a real knee joint involves the coordinated compound movement of the femoral condyle rotating around its coronal axis and the tibial plateau rotating around its vertical axis. The dynamic coupling mechanism of the two rotation centers is complex, and existing prosthesis designs often fail to accurately reproduce the instantaneous trajectory and coupling relationship of this dual-center coordinated movement, resulting in deviations between the kinematic performance and physiological state of the knee joint during flexion, extension, internal and external rotation and anterior and posterior translation.

[0005] Third, in terms of material mechanical properties, the key mechanical parameters such as the elastic modulus, damping characteristics and friction coefficient of existing articular cartilage substitutes are difficult to be specifically adjusted as needed, resulting in the inability to accurately simulate the prosthesis during the simulation process.

[0006] Fourth, in terms of functional monitoring and simulation verification, existing prostheses lack a system for real-time synchronous measurement of intra-articular contact pressure distribution, triaxial acceleration and angular velocity, making it impossible to achieve online closed-loop verification of experimental data and finite element simulation results. As a result, it is impossible to obtain data on the actual mechanical environment within the joint, which limits the optimization of prosthesis design and the accurate assessment of postoperative function.

[0007] Fifth, in terms of soft tissue interaction modeling, existing prosthetic systems do not adequately consider the nonlinear stiffness effects of active contraction of ligaments, joint capsules and muscles around the knee joint. It is difficult to simulate the regulatory effects of these active and passive soft tissue constraints on joint motion stability, load transfer and joint contact characteristics in prosthetic design, thus affecting the functional adaptability and safety of the prosthesis under dynamic loads.

[0008] In summary, existing knee joint prostheses have significant shortcomings in areas such as individualized anatomical adaptation, reconstruction of multi-center motion coupling mechanisms, individualized customization of material mechanical properties, real-time monitoring and simulation verification of intra-articular contact pressure, and integration of soft tissue active dynamic effects. These shortcomings restrict their further application in meeting highly personalized needs and achieving precise biomechanical functional reconstruction. Therefore, it is necessary to conduct more in-depth research on existing bionic knee joint pressure measurement dummies in order to solve the above problems. Summary of the Invention

[0009] To overcome the aforementioned problems, in-depth research was conducted, and a bionic knee joint testing device based on personalized reconstruction from medical images was proposed. This device features a bionic knee joint matrix, which includes a femoral end interface 1, a mid-section rotation axis 2, a base 3, and a tibial end interface 4.

[0010] The central rotating shaft 2 includes a horizontal rotating cylinder 21 and a vertical rotating shaft 22 arranged perpendicularly to each other. A horizontal rotating shaft 23 is provided in the horizontal rotating cylinder 21, so that the horizontal rotating shaft 23 can rotate relative to the vertical rotating shaft 22.

[0011] The horizontal rotation shaft 23 is provided with a first bearing 231 at its end. The first bearing 231 is fixedly connected to the femoral end interface 1. Simulated cartilage 5 is provided at the lower end of the connection position between the first bearing 231 and the femoral end interface 1.

[0012] The base 3 has a through hole in the middle, and the vertical rotation shaft 22 is placed in the through hole, so that the vertical rotation shaft 22 can rotate and move up and down relative to the base 3.

[0013] A simulated meniscus 6 is provided on the upper end of the base 3, and the upper surface of the simulated meniscus 6 is in contact with the lower surface of the simulated cartilage 5.

[0014] The base 3 is connected to the tibial end interface 4 at its lower part.

[0015] In a preferred embodiment, the tibial end interface 4 includes a connecting column 41 and a connecting flange 42. The connecting column 41 is a hollow column that is fixedly connected to the base 3. A second bearing 221 is provided at the lower end of the vertical rotation shaft 22. The second bearing 221 is located in the cavity of the connecting column 41, and the vertical movement of the vertical rotation shaft 22 is limited by the length of the cavity of the connecting column 41.

[0016] In a preferred embodiment, the shape of the contact surface between the simulated cartilage 5 and the simulated meniscus 6 is made based on human magnetic resonance imaging data.

[0017] In a preferred embodiment, the simulated cartilage 5 is made of an isotropic linear elastic material with an elastic modulus of 4-6 MPa and a Poisson's ratio of 0.45-0.47.

[0018] The simulated meniscus 6 is made of isotropic linear elastic material with an elastic modulus of 50-70MPa and a Poisson's ratio of 0.48-0.50.

[0019] In a preferred embodiment, the lower part of the femoral end interface 1 has a connector 11, which is sleeved on the first bearing 231 to achieve a fixed connection between the first bearing 231 and the femoral end interface 1.

[0020] In a preferred embodiment, thin-film sensors are attached to the surfaces of the simulated cartilage 5 and the simulated meniscus 6.

[0021] In a preferred embodiment, a plurality of springs 7 are provided between the base 3 and the femoral end interface 1.

[0022] In a preferred embodiment, the elasticity of the spring and the installation angle are obtained by the following method:

[0023] S1. Establish the relationship between joint rotation angle and spring deformation;

[0024] S2, Obtain the equivalent torque of the joint after torque balance;

[0025] S3. Based on the joint rotation angle, spring deformation, and joint equivalent torque, establish an optimization objective function, set constraint terms, and use optimization methods to solve for the spring stiffness and installation angle.

[0026] In a preferred embodiment, the relationship between the joint angle and the spring deformation is expressed as follows:

[0027]

[0028] in, Indicates the first spring deformation amount Indicates the first The length of the spring after deformation Indicates the first The length of the spring before deformation This indicates the distance between the upper end of the spring and the main axis of the joint's rotation center. Let X be the angle of rotation of the joint around the X, Y, and Z axes. Indicates the first The initial installation azimuth angle of the spring. This represents the projected length between the upper and lower ends of the spring along the Z-axis.

[0029] In a preferred embodiment, the equivalent torque generated by all springs at the joint is:

[0030]

[0031] in, , , Let the equivalent torques of all springs be defined in the X, Y, and Z axes. For the first The stiffness of a spring. , , For the first The amount of deformation of a spring in the X, Y, and Z axes.

[0032] The beneficial effects of this invention include:

[0033] (1) It can realize 6 degrees of freedom of motion, realizing human physiological-level coupled motion simulation;

[0034] (2) Based on human MRI data, simulated cartilage and simulated meniscus are made to achieve personalized customization and improve the reliability of experimental data;

[0035] (3) It can be used to study the effects of muscle action on joint mechanics;

[0036] (4) All components can be quickly disassembled, adjusted, and replaced to achieve accurate simulation of different individuals;

[0037] (5) Equipped with a thin film sensor and an accelerometer to verify the inter-joint contact pressure, concentrated load and physiological motion state, it can accurately measure detailed mechanics indicators during knee joint movement. Attached Figure Description

[0038] Figure 1 The diagram shows the overall structure of the bionic knee joint testing device based on personalized reconstruction of medical images according to a preferred embodiment of the present invention.

[0039] Figure 2 A schematic diagram of the mid-rotation axis structure of a bionic knee joint testing device based on personalized reconstruction of medical images, according to a preferred embodiment of the present invention, is shown.

[0040] Figure 3 A schematic diagram of the mid-rotation axis structure of a bionic knee joint testing device based on personalized reconstruction of medical images, according to a preferred embodiment of the present invention, is shown.

[0041] Figure 4 A schematic diagram of the tibial end interface structure of a bionic knee joint testing device based on personalized reconstruction of medical images according to a preferred embodiment of the present invention is shown.

[0042] Figure 5A schematic diagram of the bionic knee joint femoral end interface structure of a bionic knee joint testing device based on personalized reconstruction of medical images according to a preferred embodiment of the present invention is shown.

[0043] Figure 6 A schematic diagram of the coordinate system constructed in a bionic knee joint testing device based on personalized reconstruction of medical images according to a preferred embodiment of the present invention is shown.

[0044] Figure 7 This diagram illustrates the establishment of a spatial rectangular coordinate system during the acquisition of the elasticity of the bionic knee joint spring and the installation angle in a bionic knee joint testing device based on personalized reconstruction of medical images, according to a preferred embodiment of the present invention.

[0045] Explanation of icon numbers

[0046] 1-Femoral end interface;

[0047] 2-Central rotating axis;

[0048] 3-Base;

[0049] 4-Tibial end interface;

[0050] 5-Simulated cartilage;

[0051] 6-Simulated meniscus;

[0052] 7-Spring;

[0053] 11-Connector;

[0054] 21-Horizontal rotating cylinder;

[0055] 22 - Vertical rotation axis;

[0056] 23 - Horizontal rotation axis;

[0057] 41-Connecting column;

[0058] 42-Connecting flange;

[0059] 221 - Second bearing;

[0060] 231 - First bearing. Detailed Implementation

[0061] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more apparent.

[0062] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0063] According to the present invention, a bionic knee joint testing device based on personalized reconstruction of medical images has a bionic knee joint matrix, the matrix including a femoral end interface 1, a central rotation axis 2, a base 3, and a tibial end interface 4, as shown below. Figure 1 As shown,

[0064] The central rotating shaft 2 includes a horizontally rotating cylinder 21 and a vertically rotating shaft 22 arranged perpendicularly to each other, such as Figure 2 , Figure 3 , Figure 4 As shown, a horizontal rotating shaft 23 is provided in the horizontal rotating cylinder 21, so that the horizontal rotating shaft 23 can rotate relative to the vertical rotating shaft 22.

[0065] The horizontal rotation shaft 23 is provided with a first bearing 231 at its end. The first bearing 231 is fixedly connected to the femoral end interface 1. Simulated cartilage 5 is provided at the lower end of the connection position between the first bearing 231 and the femoral end interface 1.

[0066] The base 3 has a through hole in the middle, and the vertical rotation shaft 22 is placed in the through hole, so that the vertical rotation shaft 22 can rotate and move up and down relative to the base 3.

[0067] A simulated meniscus 6 is provided on the upper end of the base 3, and the upper surface of the simulated meniscus 6 is in contact with the lower surface of the simulated cartilage 5.

[0068] The base 3 is connected to the tibial end interface 4 at its lower part;

[0069] According to the present invention, the horizontal rotation axis 23 provides rotation simulation between the femur and tibia, and the vertical rotation axis 22 provides micro-rotation simulation of the tibia in the vertical direction and vertical stretching simulation between the femur and tibia, providing a total of 6 micro-degrees of freedom in horizontal / vertical / rotation, thereby realizing human physiological-level coupled motion simulation.

[0070] In a preferred embodiment, such as Figure 3As shown, the vertical rotation axis 22 does not intersect with the horizontal rotation cylinder 21, forming an eccentric T-shaped component. This eccentric structure can simulate the physiological characteristic of the human knee joint's rotation center shifting with the flexion angle during flexion and extension. Furthermore, by setting the eccentric structure, when the femoral end rotates around the horizontal rotation axis, its instantaneous rotation center relative to the tibia exhibits a non-fixed position change, thus more realistically reproducing the complex coupled motion characteristics exhibited by the real knee joint during flexion, extension, internal and external rotation, and anterior and posterior sliding, improving the accuracy of biomimetic kinematic simulation.

[0071] Preferably, the inner side of the horizontal rotating cylinder 21 is provided with a groove to provide axial assembly positioning space for the horizontal rotating shaft 23, and at the same time provide space for bearing installation, lubrication medium distribution or assembly tolerance compensation, thereby improving the stability and repeatability of the rotational motion.

[0072] Preferably, the top end of the horizontal rotating cylinder 21 is provided with a through hole, which is used to install fasteners, adjusting tools or calibration components, so as to facilitate the assembly, disassembly or maintenance of the relative position between the horizontal rotating shaft 23 and the vertical rotating shaft 22, and also to facilitate the calibration of the joint movement state or the replacement of components during the experiment.

[0073] In a preferred embodiment, the tibial end interface 4 includes a connecting column 41 and a connecting flange 42, such as Figure 4 As shown,

[0074] The connecting column 41 is a hollow column, which is fixedly connected to the base 3. A second bearing 221 is provided at the lower end of the vertical rotation shaft 22. The second bearing 221 is located in the cavity of the connecting column 41, and the vertical movement of the vertical rotation shaft 22 is limited by the length of the cavity of the connecting column 41.

[0075] Preferably, the relative position between the connecting column 41 and the base 3 is adjustable, thereby making the lower limit position of the vertical rotation axis 22 adjustable, and thus realizing the adjustment of the pressure between the simulated cartilage 5 and the simulated meniscus 6 in a static state.

[0076] In one embodiment, the connecting column 41 and the base 3 are connected by bolts. The connecting column 41 is provided with bolt holes, and the base 3 is provided with strip-shaped through holes, so that the relative position between the connecting column 41 and the base 3 is adjustable.

[0077] In this invention, the specific shape of the connecting flange 42 is not limited, as long as it can be connected to the tibia of the pressure testing dummy or to other testing devices.

[0078] In this invention, the specific shape of the femoral end interface 1 is not limited, and those skilled in the art can freely set it according to actual needs.

[0079] In a preferred embodiment, the shape of the contact surface between the simulated cartilage 5 and the simulated meniscus 6 is made based on human magnetic resonance imaging data to achieve accurate reproduction of individual anatomical differences.

[0080] Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging technique that uses cross-sectional scanning to create three-dimensional images. By assigning density to voxel points, the mass, center of mass, and moment of inertia of the body segments can be calculated, allowing the fabricated simulated cartilage and meniscus to have personalized body segment parameters similar to those of the real human body.

[0081] Preferably, the simulated cartilage 5 is made of an isotropic linear elastic material with an elastic modulus of 4-6 MPa and a Poisson's ratio of 0.45-0.47. More preferably, the elastic modulus is 5 MPa and the Poisson's ratio is 0.46.

[0082] Preferably, the simulated meniscus 6 is made of an isotropic linear elastic material with an elastic modulus of 50-70 MPa and a Poisson's ratio of 0.48-0.50. More preferably, the elastic modulus is 59 MPa and the Poisson's ratio is 0.49.

[0083] Numerous experiments have shown that the simulated cartilage 5 and simulated meniscus 6 within the above parameter range can match the real human body. Through finite element analysis, the difference rate between the simulated cartilage meniscus and the real human body is less than 5%.

[0084] In a preferred embodiment, such as Figure 5 As shown, the lower part of the femoral end interface 1 has a connector 11, which is sleeved on the first bearing 231 to realize the fixed connection between the first bearing 231 and the femoral end interface 1.

[0085] More preferably, the upper end of the simulated cartilage 5 is provided with a fixing hole, and the connector 11 is provided with a corresponding threaded hole, so that the simulated cartilage 5 can be stably attached to the lower end of the femoral end interface 1.

[0086] In a preferred embodiment, thin-film sensors are attached to the surfaces of the simulated cartilage 5 and the simulated meniscus 6 to measure the intra-articular contact pressure in real time.

[0087] Thin-film sensors have the characteristics of high sampling rate, thin sensing sheet thickness, short response time, and strong flexibility. They can fit the contact surface of the knee joint and work with dummy knee joint components containing anatomical structures to measure knee joint contact pressure. The detection results are used to verify the contact pressure between joints, thereby improving the accuracy of simulation.

[0088] In a preferred embodiment, a plurality of springs 7 are provided between the tibial end interface 4 and the femoral end interface 1.

[0089] The spring simulates ligament stiffness. The upper end of the spring is connected to the femoral interface, and the lower end is connected to the tibia interface. The preload is adjusted by a knob to simulate the rotational stiffness caused by different muscle contraction torques, effectively simulating the real degree of freedom of human joints and reflecting the rotational stiffness of joints.

[0090] Preferably, there are three springs 7, located to the left, right, and forward of the bionic knee joint base. The springs located on either side of the knee joint (left and right) are used to represent the joint rotational stiffness caused by active muscle contraction.

[0091] Experiments have shown that the stiffness and installation angle of the spring significantly affect the accuracy of the simulation. Selecting the appropriate spring stiffness and installation angle for accurate simulation is one of the key problems that this invention aims to solve.

[0092] Preferably, multiple through holes are provided on the femoral end interface 1, and the upper end of the spring is connected by bolts.

[0093] Preferably, the connecting flange 42 is provided with multiple through holes for fixing the lower end of the spring.

[0094] In this invention, the elasticity of the spring and the installation angle are obtained by the following method:

[0095] S1. Establish the relationship between joint rotation angle and spring deformation;

[0096] S2, Obtain the equivalent torque of the joint after torque balance;

[0097] S3. Based on the joint rotation angle, spring deformation, and joint equivalent torque, establish an optimization objective function, set constraint terms, and use optimization methods to solve for the spring stiffness and installation angle.

[0098] In S1, a spatial rectangular coordinate system is established with the center of knee joint rotation as the origin. The Z-axis is along the main axis of the knee joint, and the planes containing the X and Y axes coincide with the center of knee joint rotation. Figure 6 As shown.

[0099] When the joint rotates around the X-axis Rotate around the Y-axis Rotate around the Z-axis When the spring rotates with the joint, the coordinates of the upper end of the spring are transformed by the spatial rotation matrix. At a small angle, the coordinates of the upper end of the spring are:

[0100]

[0101] in, , , For the first The coordinates of the upper end of the spring, For the first The initial azimuth angle of the lower end of the spring, i.e. the first... One spring installation angle.

[0102] The length of the spring after deformation is:

[0103]

[0104] The relationship between the joint rotation angle and the spring deformation is expressed as follows:

[0105]

[0106] in, Indicates the first spring deformation amount Indicates the first The length of the spring after deformation Indicates the first The length of the spring before deformation This indicates the distance between the upper end of the spring and the main axis of the joint's rotation center. Let X be the angle of rotation of the joint around the X, Y, and Z axes. Indicates the first The initial installation azimuth angle of the spring. This represents the projected length between the upper and lower ends of the spring along the Z-axis.

[0107] In S2, the torque of the spring force about the X, Y, and Z axes needs to be balanced with the equivalent external torque generated by the joint movement in order to simulate the joint capsule constraint.

[0108] Among them, the The torque of the spring on the X-axis Represented as:

[0109]

[0110] No. The torque of the spring on the Y-axis Represented as:

[0111]

[0112] No. The torque of the spring on the Z-axis Represented as:

[0113]

[0114] Then the equivalent torque produced by all springs at the joint is:

[0115]

[0116] in, , , Let the equivalent torques of all springs be defined in the X, Y, and Z axes. For the first The stiffness of a spring. , , For the first The amount of deformation of a spring in the X, Y, and Z axes.

[0117] In S3, the optimization objective function is set as the weighted sum of squared errors between the equivalent torque and the desired torque:

[0118]

[0119] in, , , The weighting coefficients are configurable and satisfy the following conditions: + + =1, , , Let be the desired torque in the X, Y, and Z axes.

[0120] The desired torque is the theoretical torque that the joint needs to withstand during actual movement.

[0121] Preferably, the constraints include stiffness constraints, initial azimuth angle constraints, small deformation angle constraints, and spring deformation constraints.

[0122] Preferably, the stiffness constraint is expressed as:

[0123]

[0124] It is used to represent a constraint with non-negative stiffness and physical realizability.

[0125] The initial azimuth constraint is expressed as follows:

[0126]

[0127] It is used to indicate that the azimuth angle is reasonably distributed on the circumference, avoiding interference between multiple springs.

[0128] The small deformation angle constraint is expressed as follows:

[0129]

[0130] This is to ensure that the spring deforms at a small angle, which conforms to the actual human body.

[0131] The spring deformation constraint is expressed as follows:

[0132]

[0133] in, To allow for setting parameters, typically, .

[0134] Spring deformation constraints can prevent the spring from undergoing plastic deformation that exceeds its allowable elongation.

[0135] Preferably, the constraints further include knee joint biomechanical statistical constraints:

[0136]

[0137] in, , The upper and lower bounds are set. .

[0138] In this invention, no limitation is placed on the optimization method. Those skilled in the art can use any known method, such as: Sequential Quadratic Programming (SQP), Interior Point Method, Genetic Algorithm (GA), Particle Swarm Optimization (PSO), and Levenberg-Marquardt Algorithm (LM).

[0139] According to the present invention, after obtaining the spring stiffness, an alloy spring or polymer elastomer with corresponding stiffness is selected or customized and installed on the bionic knee joint substrate according to the determined installation angle, so as to achieve that the ligament equivalent torque of the bionic knee joint is highly matched with that of the real human body under different movement postures, thereby improving the reliability of the dummy joint.

[0140] Example

[0141] Example 1

[0142] Adopting such Figure 1 The bionic knee joint shown was used in a simulation experiment. This bionic knee joint includes a femoral end interface 1, a middle rotation axis 2, a base 3, and a tibial end interface 4.

[0143] The central rotating shaft 2 includes a horizontal rotating cylinder 21 and a vertical rotating shaft 22 arranged perpendicularly to each other. A horizontal rotating shaft 23 is provided in the horizontal rotating cylinder 21, so that the horizontal rotating shaft 23 can rotate relative to the vertical rotating shaft 22.

[0144] The horizontal rotation shaft 23 is provided with a first bearing 231 at its end. The first bearing 231 is fixedly connected to the femoral end interface 1. Simulated cartilage 5 is provided at the lower end of the connection position between the first bearing 231 and the femoral end interface 1.

[0145] The base 3 has a through hole in the middle, and the vertical rotation shaft 22 is placed in the through hole, so that the vertical rotation shaft 22 can rotate and move up and down relative to the base 3.

[0146] A simulated meniscus 6 is provided on the upper end of the base 3, and the upper surface of the simulated meniscus 6 is in contact with the lower surface of the simulated cartilage 5.

[0147] The base 3 is connected to the tibial end interface 4 at its lower part.

[0148] The equivalent torque generated by all springs at the joint is:

[0149]

[0150] Finite element method (FEM) simulation analysis was used to verify the accuracy and effectiveness of the simulation of the device's kinematic and mechanical response.

[0151] Magnetic resonance imaging (MRI) data of the knee joints of healthy adult volunteers were acquired using a Philips Achieva 3.0T TX imaging system. The scanning magnetic field strength was 3.0T, and proton-suppressed fat volumetric imaging sequences were used with a repetition time of 1300. The echo time is 32.7 seconds. The scanned layer thickness was 0.498 mm. No gap, scanning field of view is 220. Three-dimensional reconstruction of the femur, tibia, cartilage, meniscus, and major ligaments was performed. Using the 3D modeling software MIMICS v17.1 (Materialise Inc., Leuven, Belgium), the geometric contours of the femur, tibia, meniscus, and cartilage (from sagittal images), as well as the major ligaments such as the cruciate ligaments and collateral ligaments (from axial images), were extracted. A 3D geometric model of the knee joint, including the femur, femoral cartilage, tibia, tibial cartilage, meniscus, anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, and lateral collateral ligament, was established. Subsequently, the 3D geometric models of each tissue were imported into the mesh generation software Hypermesh v10 (Altair Engineering, Michigan, US) for mesh generation, and then assembled using the finite element software ABAQUS v6.10 (Dassault Systemes Simulia Corp., Providence, RI, USA) to obtain a complete 3D geometric model of the human tibiofemoral joint. Figure 7As shown, a complete finite element model of the human knee joint is established.

[0152] Based on the same medical imaging data and material parameters, a corresponding finite element model of a bionic knee joint testing device was established, in which the geometry and material properties of the simulated cartilage and simulated meniscus are consistent with those of the real human body.

[0153] The relevant parameters of all tissue material properties in the finite element model of the bionic knee joint testing device are shown in Table 1.

[0154] Table 1

[0155]

[0156] Where D represents the derivative of the bulk modulus of the material, and C1, C2, C3, C4, and C5 represent the parameters of the Neo-hookean model. It represents the elongation rate when the fibers in a ligament are stretched.

[0157] Under the same boundary conditions, typical motion loads, including a 3000 N normal load and a 656 N tangential load, were applied to the model to simulate the stress on the knee joint during motion. Simulation results show that under the above load conditions, the tibia in the finite element model of the human knee-tibiofemoral joint moved by 2.85 mm, 1.76 mm, and 1.22 mm in the anterior, proximal, and lateral directions, respectively. These displacements are within the normal physiological range of the human knee joint. Simultaneously, the tibia rotated outward and inward by 0.3° and 1.32°, respectively.

[0158] Analysis of the stress on various tissues of the joint showed that:

[0159] The maximum equivalent stress of the femoral cartilage is approximately 3.1 MPa;

[0160] The maximum equivalent stress of tibial cartilage is approximately 3.4 MPa;

[0161] The stress in the posterior corner region of the meniscus is significantly higher than that in other regions, with a maximum value of approximately 40 MPa.

[0162] The stress concentration area and stress distribution characteristics are consistent with the typical stress patterns of the human knee joint in existing biomechanical studies.

[0163] Comparative analysis between the finite element model of the bionic knee joint testing device and the finite element model of the human knee joint revealed that the peak deviation of the contact pressure in the main load-bearing area of ​​the present invention is less than 5%, and the overall pressure distribution difference rate is no more than 5%, indicating that the device can accurately reproduce the mechanical response characteristics of the real human knee joint.

[0164] Impact tests were used to verify the measurement stability and consistency of the device under dynamic operating conditions.

[0165] The impact absorption performance of hockey knee braces was tested under falling weight impact test conditions. The hockey knee brace was worn on a simulated lower limb segment, ensuring the impact head was collinear with the anterior-posterior axis of the knee joint. A falling weight impact test bench was used, with the impact head held by a pneumatic clamp, raised to a predetermined height, and then released to impact the hockey knee brace. The impact height was determined based on an impact energy of 15J. A single-axis force sensor was fixed along the lower leg axis, angular velocity sensors were fixed on the thigh and lower leg segments respectively, and a thin-film sensor was placed in the femoral and tibial contact areas of the knee joint. The peak angular velocity of the lower leg, peak angular velocity of the thigh, peak normal force of the knee joint, and maximum pressure on the knee joint surface were measured. The falling weight impact test bench conformed to GB / T The platform required by 40926.2-2021 uses the 50th percentile male body parameters for the lower limb segments of the dummy. The thigh and calf are determined based on the actual inertial parameters of the test subject. The knee joint contains the main anatomical structure of the human knee joint and is wrapped in silicone with a density and hardness similar to human skin. The impact head is either cylindrical or conical. The drop hammer impact test device includes a vertical guide rail and an impact head mounting bracket, which enables vertical movement on the vertical guide rail and allows the impact head to have different impact energies. The lower limb segments of the dummy are placed flat on the impact platform. The data acquisition system includes a single-axis force sensor placed along the lower leg axis, with a force sensor range of 2000N, a test accuracy of ≤1%, and a maximum acquisition frequency of not less than 2 kHz; an angular velocity sensor fixed on the thigh and lower leg, with an angular velocity sensor range of 150°, a test accuracy of ≤1%, and a maximum acquisition frequency of not less than 2 kHz; and a thin-film sensor placed in the contact area between the femur and tibia of the knee joint, with a thin-film sensor range of 5 MPa, a test accuracy of ≤1%, and a maximum acquisition frequency of not less than 500 Hz.

[0166] The trends of various pressure distribution indicators of the thin-film pressure sensor in the experiment were consistent with the results of finite element simulation.

[0167] The results of the peak normal force measurement of the knee joint are shown in Table 2.

[0168] Table 2

[0169]

[0170] As shown in Table 2, under the same impact energy, knee brace 1 exhibits significantly higher angular velocities in both the thigh and lower leg compared to knee brace 2, and its peak normal force is also significantly higher, indicating a significant difference between knee brace 1 and knee brace 2. Further analysis of the specific data reveals that under the same energy impact, knee brace 2 protects the thigh and lower leg with a slower change in angular velocity, which is more beneficial for protecting the lower limbs from a sports environment perspective. From the perspective of normal force, under the same energy impact, knee brace 1's normal force is significantly higher than that of knee brace 2, indicating that knee brace 2 provides better protection against external impacts. This is also verified by the pressure distribution diagram from the thin-film pressure sensor, which shows that knee brace 1 protects the knee joint with greater pressure, while knee brace 2 protects the knee joint with less pressure, making knee brace 2 more effective in protecting the knee joint.

[0171] Combining the finite element simulation results and the impact test results, we can conclude that:

[0172] The bionic knee joint testing device in this embodiment can accurately simulate the kinematic behavior and mechanical response of the human knee joint under exercise conditions. Its contact pressure distribution and key mechanical indicators are highly consistent with those of the real human knee joint, verifying the effectiveness of the technical solution of the present invention in terms of simulation accuracy, measurement stability and engineering application feasibility.

[0173] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this invention, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0174] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0175] The present invention has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present invention based on these embodiments, all of which fall within the scope of protection of the present invention.

Claims

1. A bionic knee joint testing device based on personalized reconstruction of medical images, comprising a bionic knee joint matrix, characterized in that, The base includes a femoral end interface (1), a central rotation axis (2), a base (3), and a tibial end interface (4). The central rotating shaft (2) includes a horizontal rotating cylinder (21) and a vertical rotating shaft (22) arranged perpendicularly to each other. A horizontal rotating shaft (23) is provided in the horizontal rotating cylinder (21) so that the horizontal rotating shaft (23) can rotate relative to the vertical rotating shaft (22). The horizontal rotating shaft (23) is provided with a first bearing (231) at its end. The first bearing (231) is fixedly connected to the femoral end interface (1). Simulated cartilage (5) is provided at the lower end of the connection position between the first bearing (231) and the femoral end interface (1). The base (3) has a through hole in the middle, and the vertical rotation shaft (22) is placed in the through hole, so that the vertical rotation shaft (22) can rotate and move up and down relative to the base (3); A simulated meniscus (6) is provided at the upper end of the base (3), and the upper surface of the simulated meniscus (6) is in contact with the lower surface of the simulated cartilage (5); The base (3) is connected to the tibial end interface (4) below; Multiple springs (7) are provided between the base (3) and the femoral end interface (1), and the elasticity and installation angle of the springs are obtained by the following method: S1. Establish the relationship between joint rotation angle and spring deformation; S2, Obtain the equivalent torque of the joint after torque balance; S3. Based on the joint rotation angle, spring deformation, and joint equivalent torque, establish an optimization objective function, set constraint terms, and use optimization methods to solve for the spring stiffness and installation angle. The relationship between the joint rotation angle and the spring deformation is expressed as follows: ； in, Indicates the first spring deformation amount Indicates the first The length of the spring after deformation Indicates the first The length of the spring before deformation This indicates the distance between the upper end of the spring and the main axis of the joint's rotation center. Let X be the angle of rotation of the joint around the X, Y, and Z axes. Indicates the first The initial installation azimuth angle of the spring. This represents the projected length of the spring between its upper and lower ends along the Z-axis. The equivalent torque generated by all springs at the joint is: ； in, , , Let the equivalent torques of all springs be defined in the X, Y, and Z axes. For the first The stiffness of a spring. , , For the first The amount of deformation of a spring in the X, Y, and Z axes.

2. The bionic knee joint testing device based on personalized reconstruction of medical images according to claim 1, characterized in that, The tibial end interface (4) includes a connecting column (41) and a connecting flange (42). The connecting column (41) is a hollow column, which is fixedly connected to the base (3). A second bearing (221) is provided at the lower end of the vertical rotation shaft (22). The second bearing (221) is located in the cavity of the connecting column (41), and the vertical movement of the vertical rotation shaft (22) is limited by the length of the cavity of the connecting column (41).

3. The bionic knee joint testing device based on personalized reconstruction of medical images according to claim 1, characterized in that, The shapes of the contact surfaces of the simulated cartilage (5) and simulated meniscus (6) are made based on human magnetic resonance imaging data.

4. The bionic knee joint testing device based on personalized reconstruction of medical images according to claim 1, characterized in that, The simulated cartilage (5) is made of isotropic linear elastic material with an elastic modulus of 4-6 MPa and a Poisson's ratio of 0.45-0.

47. The simulated meniscus (6) is made of isotropic linear elastic material with an elastic modulus of 50-70 MPa and a Poisson's ratio of 0.48-0.

50.

5. The bionic knee joint testing device based on personalized reconstruction of medical images according to claim 1, characterized in that, The femoral end interface (1) has a connector (11) at its lower part. The connector (11) is sleeved on the first bearing (231) to achieve a fixed connection between the first bearing (231) and the femoral end interface (1).

6. The bionic knee joint testing device based on personalized reconstruction of medical images according to claim 1, characterized in that, Thin-film sensors are attached to the surfaces of the simulated cartilage (5) and the simulated meniscus (6).

Images