Optimization method, device and equipment of biodegradable bone fracture plate and storage medium

Abstract

The invention discloses an optimization method, device and equipment of a biodegradable bone fracture plate and a storage medium, and is applied to the technical field of medical instruments, and the method comprises the following steps: constructing a finite element model of femoral shaft fracture; in the finite element model, applying a dynamic biomechanical load simulating a human body walking cycle; the stress level of the bone fracture plate and the displacement level of the fixed thighbone are used as optimization targets, and multi-dimensional parameters of the bone fracture plate are optimized; delimiting a safety area of the bone fracture plate according to the optimized bone fracture plate design parameters; according to the method, the technical steps of base material type selection and process optimization, finite element model construction and dynamic load application, multi-dimensional parameter optimization, safety area demarcation and personalized adaptation and the like are organically combined; the technical problems of secondary operation, stress shielding, high biological safety risk, poor adaptability, high engineering difficulty and the like of a traditional bone fracture plate are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medical devices, in particular to an optimization method, device, equipment and storage medium for a biodegradable bone plate for femoral shaft fracture fixation. BACKGROUND

[0002] Femoral shaft fracture is a common clinical injury, and its fixation treatment requires a bone plate to have excellent mechanical stability, biocompatibility and good bone healing adaptability. Traditional non-biodegradable bone plates, such as stainless steel and titanium alloy, have high mechanical strength, but they need to be removed through a second surgery after the fracture heals, which not only increases the patient's pain and economic burden, but also brings additional risks such as surgical infection and tissue damage.

[0003] To solve the problem of secondary surgery, biodegradable materials have been introduced into the field of bone plates. However, existing biodegradable bone plates still have significant defects. First, their degradation rate is difficult to match the healing process of femoral shaft fracture: too fast degradation may cause the bone plate to lose structural integrity before the fracture heals, resulting in fixation failure; too slow degradation may cause the bone plate to remain in the body for a long time, causing chronic inflammation, fibrosis and other complications. Second, the design of existing bone plates is mostly based on simplified static mechanical models, without fully considering the dynamic biomechanical environment of the human body during actual walking cycles (such as hip joint contact force, muscle force, etc.), resulting in uneven stress distribution of the bone plate, deviation of femoral displacement from healthy physiological state, and easy production of stress shielding effect or unstable fixation. In addition, the existing design lacks consideration of individual differences of patients (such as bone strength), and the material usage is generally too large, without achieving efficient distribution of materials through topology optimization.

[0004] To overcome these defects, the present application provides an optimization method, device, equipment and storage medium for a biodegradable bone plate. SUMMARY

[0005] The purpose of the present application is to provide an optimization method, device, equipment and storage medium for a biodegradable bone plate, which aims to solve the above problems.

[0006] To achieve the above purpose, the present application provides the following technical solutions: The present application provides an optimization method for a biodegradable bone plate, comprising the following steps: constructing a finite element model of femoral shaft fracture; applying dynamic biomechanical loads simulating human walking cycles in the finite element model; optimizing multi-dimensional parameters of the bone plate with stress level of the bone plate and displacement level of the femur after fixation as optimization objectives; According to the optimized bone plate design parameters, the safe area of the bone plate is determined.

[0007] To solve the above technical problems, another technical solution adopted by the present application is to provide an optimization device for a biodegradable bone plate, specifically comprising: A model construction module is configured to construct a finite element model of femoral shaft fracture. A load application module is configured to apply dynamic biomechanical load simulating human walking cycle in the finite element model. A collaborative optimization module is configured to optimize multi-dimensional parameters of the bone plate by taking stress level of the bone plate and displacement level of the fixed femur as optimization targets. A safety zone delimitation module is configured to delimit the safety zone of the bone plate according to the optimized bone plate design parameters.

[0008] The present application also provides a biodegradable bone plate obtained based on the optimization method of the biodegradable bone plate.

[0009] The present application also provides a computer device, which comprises a processor and a memory coupled to the processor, wherein the memory stores program instructions for implementing an optimization method of a biodegradable bone plate; and the processor is configured to execute the program instructions stored in the memory to implement the optimization of the biodegradable bone plate.

[0010] The present application also provides a computer-readable storage medium storing program instructions executable by a processor, wherein the program instructions are configured to execute an optimization method of a biodegradable bone plate.

[0011] The present application provides an optimization method, device, equipment and storage medium of a biodegradable bone plate, which has the following beneficial effects: (1) The present application uses biodegradable material as the base material of the bone plate, and then uses the preparation process of extrusion and heat treatment through the base material treatment process limitation step, so that the degradation rate is stabilized at 0.12-0.494 mm / year, which completely covers the optimal range of 0.2-0.5 mm / year required for femoral shaft fracture healing. At the same time, the degradation process of the bone plate during the bone healing period is simulated through the finite element analysis step; effectively avoiding the problems of traditional magnesium alloy bone plate degradation too fast leading to premature failure and degradation too slow causing long-term residual, so that the bone plate can be completely degraded after the fracture healing, without the need for secondary surgery to remove it, which not only reduces the pain and postoperative recovery period of the patient, but also reduces the risk of infection, tissue damage and other risks caused by secondary surgery, and solves the clinical pain points of titanium alloy, stainless steel and other non-biodegradable bone plates requiring secondary surgery. (2) The application is based on the construction of a three-dimensional finite element model containing a transverse fracture based on human femoral shaft CT data, and then the load application step fixes the distal femur in the model to simulate the support of the knee joint, and accurately applies the dynamic biomechanical load of the human walking cycle such as hip joint contact force, muscle force, etc., breaking through the limitations of traditional bone plate design static load modeling; On this basis, through the multi-dimensional parameter optimization step, the size of the bone plate, the number and configuration of screws, and the topology structure are optimized, and the optimal parameter combination is selected, so that the maximum von Mises stress of the bone plate meets the safety factor requirement, and the total displacement of the femur is controlled in a reasonable range; Ensure that the bone plate can withstand the load impact of the femoral shaft during daily activities, while avoiding the problems of stress shielding caused by excessive fixation and excessive displacement caused by insufficient fixation; (3) The design safety zone of the bone plate is divided by taking the displacement of the healthy femur ±5% and the stress threshold of the bone plate as constraints, and combined with the screw configuration optimization step based on the screw number adjustment strategy based on the bone strength difference, a personalized adaptation system with general safety standards and individual parameter adaptation is constructed for different patients' femoral shaft anatomical size. Breakthrough the limitations of traditional bone plate single specification adaptation to all patients, can adjust the design parameters according to the bone strength difference of different groups of young people, old people and other different groups of people, solve the problem that traditional bone plate cannot take into account the bone strength difference of different groups of people, and fully cover the clinical diversified treatment needs. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 It is a flowchart of an optimization method of a biodegradable bone plate of embodiment 1 of the application; Figure 2 It is a flowchart of the topology optimization using SIMP method of embodiment 1 of the application; Figure 3 It is a flowchart of the topology optimization using Tosca plug-in of embodiment 1 of the application; Figure 4 It is a general assembly diagram of the femoral shaft bone plate of embodiment 1 of the application; Figure 5 It is a schematic diagram of the bone plate of embodiment 1 of the application; Figure 6 It is a structure schematic diagram of an optimization device of a biodegradable bone plate of embodiment 2 of the application; Figure 7 It is a structure schematic diagram of a computer device of embodiment 3 of the application; Figure 8 It is a structure schematic diagram of a storage medium of embodiment 4 of the application. DETAILED DESCRIPTION

[0013] It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0014] The following analyzes the solutions in the prior art in relation to the relevant technology.

[0015] CN120203741B provides a new type of 3D printed bone plate, and CN120304935B relates to a bone plate. In the prior art, the following four types of shortcomings mainly exist: (1) Material degradation and lack of bone healing compatibility, secondary surgery risk not solved Inherent defects of non-biodegradable materials: CN120203741B 3D printed bone plate and CN120304935B intramedullary bone plate do not mention the use of biodegradable materials, and are still dependent on traditional non-degradable substrates such as stainless steel and titanium alloy. Although such materials have stable mechanical properties, they need to be removed after bone healing, which not only increases the patient's pain and prolongs the recovery period, but also increases the probability of surgical infection and tissue damage, which is contrary to the clinical demand for "minimally invasive and no secondary trauma".

[0016] Limitations of biodegradable materials: Even if some biodegradable bone plates in the industry use magnesium alloy materials, there is a problem of uncontrolled degradation rate; either the degradation is too fast, causing the bone plate to lose structural strength before the fracture heals; or the degradation is too slow, leaving long-term residues in the body and causing chronic inflammation and fibrosis, and there is no precise matching mechanism between the degradation rate and the bone healing process.

[0017] (2) Mechanical design deviates from physiological scenarios, and mechanical stability and bone compatibility are insufficient Static load modeling deviates from real stress: CN120203741B only emphasizes "local reinforcement structure" and "density improvement", and CN120304935B focuses on "intramedullary fixation and nutrient delivery", neither of which mentions designing in combination with the dynamic biomechanical properties of human walking cycle. The existing technology mostly uses static load modeling, which cannot simulate the complex stress state of the femoral shaft during walking and standing, leading to problems such as uneven stress distribution, excessive displacement of the femur, and easy fixation instability or excessive fixation.

[0018] Individualized adaptation only stays at the geometric level and is not related to bone strength differences: CN120203741B mentions "customization based on CT / MRI data", but only achieves geometric shape matching without adjusting structural parameters for patient bone strength differences; CN120304935B uses a uniform "trunk + tail" structure without parameter adjustment space. Both of them cannot solve the contradiction between too many screws for high-strength bone patients causing excessive trauma and too few screws for low-strength bone patients causing insufficient fixation, lacking the logic of bone strength-structure parameter linkage adaptation.

[0019] (3) Lack of balance between material usage and biological safety Topological optimization is missing, material is wasted and the risk is high: the "local reinforcement structure" of CN120203741B only thickens the key area, and does not remove the material in the non-stress area through systematic topological optimization; the trunk of CN120304935B is a solid structure, and the material usage is large. Both of them do not achieve the optimal distribution of materials, not only increase the production cost, but also lead to the total amount of metal ion release being too high when degraded in vivo, and increase the contact area between the material and the tissue, and increase the risk of infection and tissue irritation.

[0020] The safety of the ingredients is not strictly controlled: the existing degradable bone plate does not explicitly limit the content of harmful impurities. Some alloys may cause long-term risks such as neurotoxicity and Alzheimer's disease due to excessive impurities after degradation, and the biological safety is not guaranteed.

[0021] (Four) Engineering landing and lack of clinical practicability Key parameters are not quantified, and batch production is difficult: CN120203741B does not explicitly specify the specific values of the energy density gradient and the size parameters of the local reinforcement structure; CN120304935B does not give the key dimensions such as the height of the protrusion of the trunk and the spacing of the tail fixing hole. Both of them lack quantifiable production standards, making it difficult to achieve industrialized batch manufacturing, and only stay at the level of customization.

[0022] Postoperative performance verification is missing: the existing technology does not provide the mechanical property change data of the bone plate at different use stages (such as the early, middle and late stages of healing), and does not explicitly specify the performance comparison indicators with healthy bones, which cannot prove the reliability of the bone plate during the entire healing period, and there are obstacles to clinical promotion.

[0023] In view of the defects of the existing technology, the present application aims to provide an optimization method, device, equipment and storage medium for a biodegradable bone plate for femoral shaft fracture fixation, which realizes the synchronization of degradation and bone healing, matches the mechanical properties, and adapts to different populations, avoids the risk of secondary surgery, and improves the treatment effect of femoral shaft fracture.

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0025] Embodiment 1 Please refer to Figure 1 , which is a flowchart of an optimization method for a biodegradable bone plate according to Embodiment 1 of the present application; the steps include: S1: Construct a finite element model of femoral shaft fracture.

[0026] In this embodiment, based on the clinical human femoral shaft CT (Computed Tomography) scan data, the principles of 1:1 geometric reduction, clinical adhesion, and accurate material attribute partitioning are followed to complete the construction of the femoral shaft transverse fracture finite element model.

[0027] Specifically, in the clinical CT data acquisition and preprocessing stage, an adult healthy male volunteer (age 35, height 175 cm, weight 70 kg, no skeletal deformity, osteoporosis, bone tumor, etc.) is selected. A 64-slice spiral CT scanner is used to continuously scan the right femoral shaft, with the scanning range from the femoral head to the femoral condyle. The final DICOM format tomographic image sequence is obtained. After importing the DICOM format data into the medical image processing software Mimics, threshold segmentation is first performed according to the CT value difference of bone tissue, with the cortical bone segmentation threshold set to 1000-1800HU and the cancellous bone segmentation threshold set to 200-800HU. The two types of bone tissue regions are preliminarily separated; then the region growing tool is used in combination with manual correction to eliminate scanning artifacts and accurately outline the femoral shaft contour to generate three-dimensional masks of cortical bone and cancellous bone; finally, the masks are subjected to 10 iterations of smoothing processing to eliminate the jagged edges of the tomographic images and ensure the geometric continuity of subsequent modeling.

[0028] The construction of the 1:1 three-dimensional geometric model of the femoral shaft is divided into multiple steps. First, in Mimics, the moving cube algorithm is used to reconstruct the three-dimensional surface model of the femoral shaft cortical bone and cancellous bone based on the preprocessed mask and output as an STL format. Then, the STL model is imported into the reverse engineering software GeomagicWrap2023 to complete operations such as surface repair and feature optimization, generating smooth NURBS surfaces that retain anatomical features such as the greater trochanter and lesser trochanter. Subsequently, the optimized surface model is imported into the three-dimensional modeling software SolidWorks2023, and through operations such as surface thickening and entity stitching, a 1:1 scale femoral shaft solid model is generated, with the cortical bone as an outer dense shell with a thickness of about 3-5mm, consistent with the anatomical features of adult femoral shaft cortical bone, and the cancellous bone as an internal medullary cavity filling structure, with the geometric boundary completely adhering to the anatomical morphology of the femoral shaft.

[0029] The creation of the transverse fracture model is closely related to the clinical characteristics. In SolidWorks, the middle segment of the femoral shaft (about 20 cm away from the greater trochanter of the femur, which is the high-risk position of clinical transverse fracture) is selected as the fracture position. A cutting plane perpendicular to the long axis of the femoral shaft is created to divide the femoral shaft solid model into two parts: the proximal fracture segment and the distal fracture segment. By moving the distal fracture segment to adjust the relative position, the fracture gap is set to 0.8 mm. This value is within the range of 0.5-1 mm commonly seen in clinical practice, ensuring that the fracture line is straight and the gap is uniform. Finally, a separate geometric model of the transverse fracture of the femoral shaft is generated and exported in STEP format. At the same time, based on the design principles of the commonly used locking compression bone plate in clinical practice, a geometric model of the ZK60 magnesium alloy bone plate is constructed in SolidWorks. The bone plate is designed with 12 holes, with a thickness of 3 mm and a width of 15 mm, which matches the anatomical curvature of the middle segment of the femoral shaft. The matching bone screws are cortical bone screws with a diameter of 4.5 mm, and the length is designed to be 30 mm according to the diameter of the femoral shaft. The geometric dimensions of the bone plate and screws meet the clinical standards for orthopedic implants.

[0030] In the material property assignment stage, the geometric model is imported into the finite element analysis software Abaqus2022. First, a material library is created, and then the partition assignment is completed. Cortical bone is set as an isotropic linear elastic material with a density of 2.0 g / cm³, which is within the required range of 1.8-2.1 g / cm³. The elastic modulus is 19 GPa, which is within the range of 17-20 GPa, and the Poisson's ratio is 0.3, with a compressive yield strength of 224 MPa, fully complying with the set requirements. Cancellous bone is a porous material with a density of 0.6 g / cm³, which is significantly lower than that of cortical bone. Combined with the power function empirical formula of porosity and elastic modulus, the elastic modulus of cancellous bone is set to 0.7 GPa at a porosity of 70%, and the Poisson's ratio is 0.25. ZK60 magnesium alloy (extruded state) is used for the property assignment of the bone plate and screws, with a density of 1.81 g / cm³, an elastic modulus of 45 GPa, a yield strength of 315.2 MPa, and a Poisson's ratio of 0.35, which strictly matches the measured performance. Through the "AssignMaterial" function of Abaqus, the above materials are assigned to the corresponding geometric regions to ensure the accuracy of the property partition.

[0031] The meshing and model assembly stage adopts a partition meshing strategy, taking into account the calculation accuracy and efficiency. The cortical bone adopts C3D8R eight-node linear reduced integration solid element hexahedral structured mesh, with a unit size of 1 mm, to ensure the accuracy of the mechanical response calculation of the fracture area. The cancellous bone adopts C3D4 four-node linear solid element tetrahedral unstructured mesh, with a unit size of 2 mm, to reduce the calculation amount while ensuring accuracy. The ZK60 magnesium alloy bone plate and screw also adopt C3D8R hexahedral structured mesh, with a unit size of 0.8 mm, to adapt to the fine mechanical analysis of the implant. After completing the meshing, the mesh quality evaluation tool of Abaqus is used for inspection. During model assembly, the bone plate is attached to the lateral cortical bone surface of the femoral shaft fracture segment, and the screw is screwed into the cortical bone through the bone plate hole, simulating the actual state of the clinical bone plate fixation operation. In terms of contact definition, the bone plate and the cortical bone surface are set as face-to-face contact, with a normal hard contact and a tangential friction coefficient of 0.3, which meets the friction characteristics of bone and metal implants. The screw and the bone plate, and the screw and the cortical bone are set as bound contact, simulating the locking effect of the screw. The fracture gap is not in contact with the constraint, simulating the separation state of the fracture ends.

[0032] The model validity verification is carried out from three dimensions of geometric accuracy, material properties and mesh convergence. In the geometric accuracy verification, the key parameters such as the length of the femoral shaft, the diameter of the middle segment and the fracture gap of the finite element model are measured and compared with the CT original data and clinical anatomy parameters to confirm the accuracy of the 1:1 geometric reduction. In the material property verification, the parameters of the cortical bone, cancellous bone and ZK60 magnesium alloy are checked, all of which are within the set range and meet the assignment requirements. In the mesh convergence verification, the models with unit sizes of 0.5 mm, 1 mm and 2 mm are tested respectively, and the axial stiffness of the femoral shaft is calculated. When the unit size is 1 mm, the stiffness changes by less than 5%, which determines that this grid size is the optimal solution, ensuring the convergence of the calculation results. The final femoral shaft transverse fracture finite element model can be directly used for subsequent mechanical simulation analysis.

[0033] S2: In the finite element model, dynamic biomechanical load simulating human walking cycle is applied.

[0034] In this embodiment, based on the biomechanical measurement data of human walking cycle, the accurate setting of boundary constraint, the anatomical positioning and parameter assignment of multi-directional load are completed in the constructed femoral shaft fracture finite element model, and the load change simulation in the walking cycle is realized through the dynamic amplitude curve, which restores the real stress environment of the bone plate and the fracture site, and provides accurate load conditions for subsequent stress distribution, fatigue damage and fracture healing mechanical analysis. Specifically, steps S201-S205 are included, which are described in detail as follows.

[0035] S201: Combining the physiological support of the knee joint for the femur, complete the full degree of freedom fixation constraint of the distal femur (point P1) in the finite element model.

[0036] First, the anatomical location of point P1 is defined as the center of the distal femoral condyle articular surface (the weight-bearing core area at the distal end of the femoral shaft). All translational degrees of freedom (U1=U2=U3=0, corresponding to displacements in the X, Y, and Z axes respectively) and rotational degrees of freedom (UR1=UR2=UR3=0, corresponding to rotations around the X, Y, and Z axes respectively) of point P1 are restricted in the Cartesian coordinate system to simulate the rigid support effect of the knee joint on the distal femur during human standing and walking. Simultaneously, to avoid over-constraint, only the distal femoral condyle articular surface region where point P1 is located is constrained, while the rest of the femoral shaft remains free, ensuring that the model's mechanical response conforms to the physiological movement patterns of the human skeleton.

[0037] S202: Anatomical reference point for load application.

[0038] Based on the anatomical characteristics of muscle attachment and joint contact in the human femur, four reference points for load application (P2, P3 proximal / distal, P4) are created in the finite element model. The reference points are bound to the corresponding bone surfaces to ensure that the load is evenly transmitted to the bone tissue and avoid local stress concentration.

[0039] Point P2: Located at the center of the femoral head, it is the main point of application of hip joint contact forces and is coupled to the articular surface region of the femoral head; P3 point: It is divided into proximal and distal ends. The proximal end is located at the lateral apex of the greater trochanter of the femur (the main attachment point of the abductor muscle and the tensor fasciae latae muscle), and the distal end is located at the insertion point of the tensor fasciae latae muscle on the lateral side of the proximal femoral shaft. Both are coupled to the cortical bone surface to which the corresponding muscles attach. Point P4: Located at the musculoskeletal attachment point of the vastus lateralis muscle on the lateral side of the mid-shaft of the femur (approximately 5 cm proximal to the fractured segment), coupled to the lateral cortical bone surface of the femur.

[0040] The coordinates of all reference points are determined based on anatomical data from CT scans to ensure that the load application location is perfectly aligned with the human physiological state.

[0041] S203: Parameter calibration and numerical assignment for multi-directional loads.

[0042] Using a volunteer's weight of 70kg as a baseline (gravitational acceleration g = 9.8m / s², 1% body weight corresponds to a load of approximately 6.86N), the biomechanical percentage load during the human walking cycle was converted into specific values, and multi-directional loads were assigned according to the coordinate system (X-axis is the horizontal direction in the coronal plane, Y-axis is the vertical direction in the sagittal plane, and Z-axis is the anterior-posterior direction in the transverse section), as follows: Hip joint contact force (P2 point): As the main bearing load, the X-axis applies a horizontal load of 32.8% body weight (about 225.01N), the Y-axis applies a vertical downward load of -229.2% body weight (about -1572.31N), and the Z-axis applies an anterior-posterior load of -54.0% body weight (about -370.44N), with the negative sign representing that the load direction is opposite to the positive direction of the coordinate axis; Muscle action force: The abductor muscle exerts a pulling force of -4.3% body weight (about -29.50N) on the X-axis, 86.5% body weight (about 593.39N) on the Y-axis, and 58.0% body weight (about 397.88N) on the Z-axis at the proximal end of P3; the tensor fasciae latae muscle exerts a pulling force of -11.6% body weight (about -79.58N) on the X-axis, 13.2% body weight (about 90.55N) on the Y-axis, and 7.2% body weight (about 49.39N) on the Z-axis at the proximal end of P3, and a pulling force of 0.7% body weight (about 4.80N) on the X-axis, -19.0% body weight (about -130.34N) on the Y-axis, and -0.5% body weight (about -3.43N) on the Z-axis at the distal end of P3; the vastus lateralis muscle exerts a pulling force of -18.5% body weight (about -126.91N) on the X-axis, -92.9% body weight (about -637.29N) on the Y-axis, and -0.9% body weight (about -6.17N) on the Z-axis at the P4 point.

[0043] S204: Dynamic load loading setting of walking cycle.

[0044] To simulate the load changes of the human body in the real walking state, the static loading method is abandoned, and a dynamic amplitude curve is used to realize the dynamic loading of the load within the walking cycle: Walking cycle parameter setting: Referring to the normal walking speed of adults, the time length of a single walking cycle is set to 1.2 seconds, which is divided into four stages: heel touch-down period (0%-10% cycle, 0-0.12s), standing middle period (10%-50% cycle, 0.12-0.6s), heel lift-off period (50%-80% cycle, 0.6-0.96s), and swing period (80%-100% cycle, 0.96-1.2s), among which the standing middle period is the peak load stage, which is consistent with the mechanical characteristics of human walking; Amplitude curve definition: Based on the measured force change curve of human walking cycle biomechanics, the load coefficients (0→0.4→1.0→0.8→0.2→0) corresponding to different cycle nodes (0%, 10%, 30%, 50%, 80%, 100%) are input, among which the 30% cycle (0.36s) is the middle stage of gait, the load coefficient is 1.0, and the peak value of each load is obtained, and the remaining stages adjust the coefficient according to the measured law to realize the dynamic change of the load with time; The analysis step time is set to 1.2 seconds, the incremental step size is 0.01 seconds, the automatic incremental step adjustment function is enabled to ensure the convergence of the calculation during the load loading process; and the load and amplitude curve are associated to enable all multi-directional forces to be dynamically applied to the model according to the force variation law of the walking cycle.

[0045] S205: After completing the load and boundary condition setting, verify from three dimensions of anatomical matching, numerical accuracy and dynamic reasonableness.

[0046] Check whether the positioning of each load reference point is consistent with the anatomical position of muscle attachment and joint contact of the human femur, and whether the coupling constraint covers the corresponding bone surface area to ensure the physiological reasonableness of load transmission. Check whether the percentage conversion value and direction symbol of each load are consistent with the measured data, and whether the node coefficient of the amplitude curve fits the force variation law of the walking cycle.

[0047] Perform pre-calculation (take a 0.3-second walking cycle segment), view the displacement and stress response of the model, and the displacement direction of the proximal femur under the action of the hip joint contact force should conform to the physiological movement trend of the human body during walking. The stress distribution of the fracture segment and the bone plate is not significantly abnormal, and it is confirmed that there is no over-definition or under-definition problem in the load and constraint setting.

[0048] Finally, after the above steps are completed to simulate the dynamic biomechanical load application of the human walking cycle, the finite element model can accurately reproduce the real stress state of the femoral shaft fracture bone plate fixation system during human walking.

[0049] S3: Taking the stress level of the bone plate and the displacement level of the fixed femur as the optimization target, the multi-dimensional parameters of the bone plate are optimized.

[0050] In this embodiment, the maximum von Mises stress (reflecting the mechanical strength of the bone plate) and the total displacement of the femur (reflecting the stability of the fracture fixation) are taken as the core optimization targets, and the bone plate for femoral shaft fracture fixation is optimized from three dimensions of size parameters, screw number and configuration, and topology structure.

[0051] S301: Optimize the size parameters of the bone plate.

[0052] The optimization of the size parameters is based on the premise of meeting the cross-fracture end fixation principle, balancing mechanical strength and material usage, and avoiding soft tissue irritation. The key size variable range is first set, and then the optimal combination is screened through the control variable method and orthogonal test.

[0053] 1. Based on the anatomical dimensions of the adult femoral shaft (length 300-400mm, mid-section transverse diameter approximately 32mm) and the convenience of clinical surgical operation, the core dimensions of the bone plate are determined as follows: Length (L) 130mm-170mm, ensuring coverage of 50-80mm on each side of the fracture end, in accordance with the clinical principle of cross-fracture end fixation in orthopedics; Width (W) 16-22mm, adapted to the transverse diameter of the femoral shaft, avoiding excessive width leading to postoperative soft tissue friction and irritation, while excessive narrowness reduces the fixation contact area; Thickness (t) 3-6mm, too thin and it is easy to produce plastic deformation under load, too thick and it increases the degradation burden of ZK60 magnesium alloy, while also increasing the difficulty of surgical implantation.

[0054] 2. Using the controlled variable method, with a fixed width of 20mm and a thickness of 4mm, finite element simulations were performed on bone plate models with L=130mm, 140mm, 150mm, 160mm, and 170mm respectively. The maximum ΔF / ΔF of the bone plate under the peak load of the walking cycle was calculated for each model. The Mises stress and total femoral displacement were compared with the baseline displacement value of healthy femoral shaft (0.25 mm). The results showed that the length of the bone plate was negatively correlated with stress and displacement: when L=130 mm, the maximum stress of the bone plate was 280 MPa and the total femoral displacement was 0.42 mm, which was significantly higher than the baseline value; when L increased to 160 mm, the stress dropped to 220 MPa (lower than the yield strength of ZK60 magnesium alloy 315.2 MPa), and the femoral displacement dropped to 0.27 mm, close to the level of healthy bone; when L continued to increase to 170 mm, the stress and displacement only decreased slightly (stress 215 MPa, displacement 0.26 mm), but the material usage increased by about 6%. Therefore, 160 mm was determined to be the optimal length of the bone plate.

[0055] 3. Based on the optimal length of 160mm, orthogonal tests were designed for widths (16 / 18 / 20 / 22mm) and thicknesses (3 / 4 / 5 / 6mm) under a length of L160mm, resulting in a total of 16 dimensional combinations. The stress-displacement index of each combination was calculated using finite element analysis, and the optimal combination was selected as a width of 20mm and a thickness of 4mm. Under this combination, the maximum stress on the bone plate was [missing information]. With a Mises stress of 220 MPa and a total femoral displacement of 0.27 mm, it not only meets the strength requirements of the bone plate but also makes the femoral fixation stability close to the level of healthy bone. At the same time, the width and thickness are adapted to the anatomical shape of the femoral shaft, avoiding the problem of excessive soft tissue stimulation and degradation burden.

[0056] A method for optimizing size parameters is also proposed: using the response surface methodology (RSM) to construct a mathematical model of independent variables and response values, and directly obtaining the optimal size combination by solving the model extrema, thereby achieving a leapfrog improvement in optimization efficiency.

[0057] 1. Defining the range of size variables: Based on the anatomical dimensions of the adult femoral shaft (length 300-400mm, mid-section transverse diameter approximately 32mm) and the convenience of clinical surgical operation, the range of values ​​for the core dimensions of the bone plate is determined as follows: Length (L) 130mm-170mm, ensuring coverage of 50-80mm on each side of the fracture end, in accordance with the clinical principle of "fixation across fracture ends" in orthopedics; Width (W) 16-22mm, adapting to the transverse diameter of the femoral shaft, avoiding excessive width leading to postoperative soft tissue friction and irritation, while excessive narrowness reduces the fixation contact area; Thickness (t) 3-6mm, too thin and it is easy to produce plastic deformation under load, too thick and it increases the degradation burden of ZK60 magnesium alloy, while also increasing the difficulty of surgical implantation.

[0058] 2. Experimental Design and Data Acquisition using Response Surface Methodology: For the three continuous independent variables L, W, and t, a central composite design (CCD) is used to construct the response surface experimental scheme. This design can accurately fit the quadratic regression model with fewer experimental points, balancing experimental efficiency and model accuracy. L, W, and t are used as independent variables X1, X2, and X3, respectively, with the maximum von Neumann bone plate as the reference value. The Mises stress (σ, MPa) and total femoral displacement (δ, mm) are two response values ​​(the objective is to minimize the two response values). The coding levels of each independent variable are set (-α, -1, 0, 1, α, α=1.682, corresponding to the CCD standard coding of the three independent variables). Finally, 17 sets of test points (8 factorial points, 6 axial points, and 3 center points) are generated, covering the full range of values ​​of the dimensional variables.

[0059] For the 17 sets of bone plate size combinations corresponding to the test points, finite element models were constructed in Abaqus, and peak loads during the human walking cycle (hip joint contact force Y-axis - 229.2% body weight) were applied. The maximum von Willebrand force of the bone plate for each combination was calculated. The Mises stress and total femoral displacement are used as input data for the response surface model to ensure the authenticity and accuracy of the data.

[0060] 3. Construction of the quadratic regression model and significance test: Import the coded values ​​of the independent variables of the experimental design and the response values ​​obtained from the finite element simulation into the Design-Expert software to construct a quadratic polynomial regression model. The optimal size combination can be obtained directly by solving the extreme values ​​of the model (without verifying each variable one by one).

[0061] The response surface methodology can find the optimal solution using only 17 test points, compared to the traditional single-variable method which requires at least 20 test points for verification, thus improving optimization efficiency by more than 40%.

[0062] S302: Optimize the number and configuration of screws.

[0063] Screws are the core of the connection between bone plates and femoral shafts. The optimization design is based on the principles of uniform load transmission, stress concentration reduction, and matching of bone strength differences. The design is carried out from three levels of specification unification, quantity adaptation, and arrangement mode to ensure the degradation synchronization and fixation effectiveness of screws and bone plates.

[0064] 1. Based on the cortical bone thickness of femoral shaft (5-8 mm), the unified specification of screws is determined: diameter 6 mm, length 35 mm. This ensures that the screws penetrate the cortical bone on both sides of the femoral shaft (2-3 mm of thread length is left on each side), which guarantees the anchoring force and avoids soft tissue damage caused by the protrusion of long screws on the bone surface. The screw material is consistent with the bone plate, both using ZK60 magnesium alloy, ensuring that the degradation rates of the two are synchronized, and avoiding fixation loosening caused by material degradation differences.

[0065] 2. According to the clinical bone strength classification (high strength bone: young people, athletes, cortical bone density 1.9-2.1 g / cm³; low strength bone: old people, cortical bone density 1.8-1.9 g / cm³), combined with the correlation rule of "screw quantity-bone stress-fixation stability", the number of screws under different bone strength is determined.

[0066] Low strength bone (old people): 8 screws are used for fixation. Finite element simulation shows that 8 screws can evenly disperse the contact stress between the femoral shaft and the bone plate, the maximum stress of the bone plate is reduced to 210 MPa, and the femoral displacement is 0.25 mm, avoiding local stress concentration caused by too few screws (such as 4 screws, the cortical bone stress reaches 180 MPa, far exceeding the safety threshold of cortical bone compressive yield strength 224 MPa); High strength bone (young people): it can be reduced to 4-6 screws, considering the reduction of surgical trauma and the guarantee of fixation strength. When 4 screws are used, the thickness of the bone plate needs to be increased from 4 mm to 5 mm. Finite element verification shows that this adjustment increases the bone safety factor from 1.2 to 1.35, reduces the screw stress from 190 MPa to 160 MPa, and keeps the femoral displacement at 0.26 mm, effectively balancing the contradiction between reducing screw trauma and avoiding fixation failure.

[0067] 3. For a 170 mm long bone plate (adapted to special long fracture segments), 8 screws are arranged at equal intervals, symmetrically across the fracture end, with a screw spacing of 20 mm, 4 screws on each side of the fracture end, ensuring that the load is evenly transmitted to the femoral shaft through the screws, and avoiding stress overlap at the fracture end. For a 160 mm optimal length bone plate, 6 screws are arranged asymmetrically but stress evenly on both sides of the fracture end, with 3 screws at the proximal end and 3 screws at the distal end, with a spacing of 21 mm.

[0068] S303: Optimize the topology of the bone plate.

[0069] Topology optimization is based on size and screw configuration optimization, and the core is to remove low stress area material and retain high stress core structure. Solid isotropic material with penalty (SIMP) is used to realize the lightweight of bone plate structure through Tosca plug-in of Abaqus CAE, while ensuring that the stress-displacement index does not deviate from the optimal value.

[0070] 1. The main body area of the bone plate is set as the design domain (the material density can be adjusted), and the screw hole and the edge connection area of the bone plate are set as the non-design domain (the material density is kept at 1.0 to avoid installation of screws or structural fracture after optimization). The strain energy minimization of the bone plate is taken as the objective function (the lower the strain energy, the stronger the structural deformation resistance), and the volume reduction rate (15%, 20%, 25%) is taken as the constraint condition, while the maximum von Mises stress of the bone plate is limited to 300 MPa and the total displacement of the femur is limited to 0.3 mm.

[0071] The design variable is the bone plate unit density (the value range is 0.01-1.0, 0.01 is the minimum density to avoid structural fracture caused by complete deletion of the unit), and the penalty factor P is 3 (within the conventional value range of 2-4 to ensure that the low stress area material is effectively punished and removed). The peak load of human walking cycle (hip joint contact force Y axis-229.2% body weight) is used to simulate the worst stress scenario of the bone plate to ensure that the optimized structure still has sufficient strength under extreme load.

[0072] 2. Topology optimization of the bone plate (L160mm, W20mm, t4mm) with different volume reduction rates is performed, and the performance indicators of each scheme are verified by finite element simulation. The results show that Finally, the topology optimized bone plate structure is re-engineered to complete the multi-dimensional parameter optimization of the bone plate. The optimized bone plate reaches the optimal target in terms of stress level and fixation displacement, and the screw configuration can be adjusted according to the individual bone strength of the patient, providing precise design basis for individual bone plate treatment of femoral shaft fracture in clinical practice.

[0073] A topology optimization method is also proposed: a lattice-based method is used to construct a periodic lattice structure in the non-stress area of the bone plate, achieving the goals of material reduction, structure support retention, and biocompatibility improvement, while adapting to the 3D printing process to avoid molding defects and ensure the overall mechanical properties consistent with the original SIMP optimization results.

[0074] ​1. Based on the stress cloud analysis of the bone plate, the high stress core area such as the screw hole periphery of the bone plate, the corresponding support area of the fracture end, etc. is set as a non-design domain, the solid structure (material density 1.0) is maintained to ensure the fixing strength and load transmission capacity of the bone plate; the low stress area such as the middle part and both ends of the bone plate is set as a design domain to construct a periodic lattice structure to avoid the mechanical performance attenuation of the core stress area caused by lattice.

[0075] Combined with the 3D printing forming characteristics of ZK60 magnesium alloy and the growth needs of bone tissue, a face-centered cubic (FCC) lattice is selected as the basic unit, which has good mechanical stability and pore connectivity, the lattice gap can realize the flow of tissue fluid, and the rod structure of the unit can provide support for bone growth; the basic parameters of the lattice unit are set as follows: unit side length 5 mm, initial rod diameter 1 mm, which reserves adjustment space for subsequent equivalent modulus calibration.

[0076] 2. According to the forming requirements of 3D printing process, the minimum wall thickness (rod diameter) constraint of the lattice unit is additionally increased, and the minimum value of the rod diameter of the lattice unit is set as 0.8 mm to avoid the forming defects such as insufficient melting and structure fracture caused by too thin rod diameter during 3D printing, and to ensure that the lattice structure has basic bearing capacity.

[0077] To ensure that the overall stress and displacement of the lattice-reconstructed bone plate are consistent with the original SIMP optimization results, the equivalent elastic modulus of the lattice structure is calibrated through finite element simulation. First, the equivalent elastic modulus of the bone plate after the original SIMP optimization is calculated, then the equivalent elastic modulus of the FCC lattice structure under different parameters is calculated through adjusting the rod diameter of the lattice unit (0.8 mm-1.2 mm) multiple times, and finally the equivalent elastic modulus of the FCC lattice unit with a rod diameter of 1.0 mm is determined as 40.2 GPa, which deviates from the original structure by less than 1%, meeting the mechanical performance matching requirements.

[0078] 3. The peak load condition of walking cycle is continued (hip joint contact force Y axis-229.2% body weight) to simulate the worst stress scenario of the bone plate and ensure that the lattice-reconstructed bone plate still has sufficient strength under extreme load. Taking the material reduction rate as the core optimization target, the volume reduction rate is set as 15%, 20% and 25%, and the maximum von Mises stress of the bone plate is limited to not more than 300 MPa and the total displacement of the femur is limited to not more than 0.3 mm, and the rod diameter of the lattice unit needs to meet the forming constraint of ≥0.8 mm.

[0079] The lattice structure is constructed in a periodic array arrangement in the design domain to ensure that the lattice units are connected continuously and avoid local stress concentration, and to ensure the connectivity of the lattice gap to create conditions for tissue fluid flow and bone growth. ​

[0080] 4. Lattice-based topology optimization with different volume reduction rates was performed on the size-optimized bone plate. The feasibility of each scheme was verified through finite element simulation and 3D printing moldability analysis. Finally, the bone plate structure of the optimal lattice optimization scheme was engineered and reconstructed to achieve a smooth transition between lattice units and solid regions, avoiding stress concentration. The optimized bone plate achieved optimal targets in terms of stress level and fixation displacement. Simultaneously, the introduction of the lattice structure improved biocompatibility and 3D printing adaptability. Screw configuration can be personalized according to the patient's bone strength, providing a precise design basis for personalized 3D-printed bone plate treatment of femoral shaft fractures in clinical practice.

[0081] Specifically, topology optimization is the process of obtaining the optimal material distribution within the design domain of a structure or component while satisfying stress, load, and constraint conditions. This stage aims to minimize weight and cost while ensuring the joint plate meets the required strength and deformation performance. Strain energy and volume are the most important influencing factors in this analysis. Strain energy is the energy stored within a material when it deforms under external forces; by minimizing strain energy, the optimal design scheme with lighter weight and better performance can be selected. Strain energy is one of the most important indicators in topology-optimized joint plates because the lower the strain energy, the greater the stress the structure can withstand before failure, resulting in a stronger and more efficient structure.

[0082] Volume is a key factor in topology optimization because it ensures that the optimized structure meets specific volume constraints. This constraint is crucial to prevent the structure from becoming too lightweight or thin, thus avoiding compromise to its mechanical integrity or strength. Lattice-based methods and Solid Isotropic Material with Penalization (SIMP) are two commonly used techniques that minimize strain energy while ensuring the structure meets specific volume constraints. In this embodiment, the topology optimization operation was performed in AbaqusCAE (finite element analysis software) using the Tosca plugin and employed the SIMP method. Specifically, it included: The expression for strain energy (Π) is as follows: , in, Indicates stress, V represents strain, and V represents the element volume. Represents the element displacement vector. Let T represent the stiffness matrix, and T be the matrix transpose operation rule.

[0083] The topology optimization expression based on the SIMP method is as follows: , , in, Let be the objective function. For unit density (design variable). As a penalty factor, and These are the material volume and the design domain volume, respectively. Let K be the defined volume fraction and K be the global stiffness matrix. For minimum relative density, N is the number of elements used in the discrete design domain; U represents the global displacement vector of all finite element elements in the topology optimization design domain, which is a global variable formed by assembling the local displacement vector of each element; F represents the global load vector acting on the topology optimization design domain, which is a global load variable formed by assembling various externally applied loads (such as concentrated force, distributed force, and torque) according to the rules of finite element analysis.

[0084] First, the mechanical behavior of a healthy femur is analyzed under the given load and boundary conditions. A suitable bone plate is selected so that the stress and displacement generated are close to those of a healthy femur. It should be noted that bone material is brittle, therefore the principal stress (… The safety factor (SF) plays a crucial role, calculated according to the Mohr-Coulomb criterion. ; However, the bone plate material is tough and follows the maximum distortion energy theory, with equivalent stress (Feng...). Mises stress ) plays a decisive role. Among them, and These are the tensile strength and compressive strength of the material, respectively.

[0085] , ; To reduce material usage while maintaining the performance of the bone plate, thereby lowering its metabolic burden and manufacturing costs in the human body, a solid isotropic material penalty method (SIMP) is employed, with topology optimization implemented through the Tosca plugin in Abaqus CAE. A penalty is applied to the element density in low-stress regions of the bone plate, bringing its value close to zero to achieve material removal; simultaneously, high-density material is retained in high-stress core regions, with the optimization objective being the minimization of strain energy (achieving the strongest structural resistance to deformation). This optimization method effectively reduces material usage while avoiding the risk of in vivo toxicity caused by excessive metal ion release due to implant degradation, thus balancing mechanical performance and biosafety.

[0086] Please seeFigure 2 Here is a flowchart of topology optimization using the SIMP method in Embodiment 1 of this application; Figure 3 This is a schematic diagram illustrating the topology optimization process using the Tosca plugin in Embodiment 1 of this application. The implementation method of topology optimization is described in detail below.

[0087] 1. Import Model: The core model to be imported is a three-dimensional finite element model of femoral shaft-plate-screw coupling. This model needs to be constructed in advance based on human femoral shaft CT scan data, including transverse fracture gap (0.5-1mm), material differentiation of cortical bone / cancellous bone (cortical bone density 1.8-2.1g / cm³, elastic modulus 17-20GPa; cancellous bone elastic modulus adjusted according to porosity), as well as the initial dimensions of the plate (L, w, t) and screw structure (diameter 6mm, length 35mm).

[0088] The bone plate is meshed using hexahedral elements with clearly defined element sizes and a mesh distortion rate ≤5%. The femoral cortical bone uses tetrahedral elements (4-Node Linear Tetrahedral Element, C3D4), and the cancellous bone uses porous medium elements (C3D8MP, 8-Node Linear Brick, Porous Medium, Plastic) to ensure accurate stress calculations. If the mesh quality is substandard (e.g., negative volume elements exist), it must be repaired in Abaqus CAE and then re-imported. In Tosca, the "design domain" and "non-design domain" are clearly defined: the main body of the bone plate is set as the design domain (material distribution needs optimization), while the femur, screws, and screw holes (6mm in diameter) on the bone plate are set as non-design domains (material removal is prohibited) to avoid damaging critical fixation structures during optimization.

[0089] 2. Define design variables and variable constraints: element relative density ( — Core material distribution variables; unit relative density This refers to the ratio of the actual material density of each finite element element within the design domain of the bone plate to the full density of the substrate, with a value range of [value missing]. (Dimensionless). Among them, The unit is completely filled with ZK60 magnesium alloy (density 1.81g / cm³) to fully preserve the material state, corresponding to the critical stress areas of the bone plate (such as around screw holes and the area corresponding to the fracture ends). The material density within the unit is only 1% of the full density, which can be equivalent to removing material (the mechanical contribution is negligible), corresponding to the non-stressed area of ​​the bone plate (such as the central area where there is no load transfer). (The material is retained within the unit; the higher the density, the greater the contribution of the material to the structural stiffness.)

[0090] Value constraint logic: lower limit set to 0.01 (instead of 0): avoid the complete deletion of units leading to the fracture of the bone plate, ensure that the structure after optimization is still a continuum, and meet the structural integrity during surgery implantation (such as avoiding the bending of the bone plate during implantation); upper limit set to 1: ensure that the material does not exceed the full density, avoid excessive filling leading to increased weight and increased degradation burden.

[0091] Volume fraction (f) ), the total amount of material control variable, that is: ; Volume fraction (f) refers to the ratio of the material volume of the optimized bone plate to the initial volume before optimization, wherein is the volume of a single unit, and N is the total number of units in the design domain, initially, the initial volume of the bone plate.

[0092] Target value setting basis: volume reduction of 15% (f=0.85) corresponds to a low-risk conservative scheme, suitable for the elderly who are sensitive to material usage (reduce metal ion release); volume reduction of 25% (f=0.75) corresponds to a high-efficiency lightweight scheme, suitable for young people (balance performance and minimally invasive requirements). In Tosca, select "Hard Constraint" (hard constraint) to ensure that the value of the optimization result strictly falls within the target range, avoiding insufficient volume reduction (>15%) leading to increased degradation burden or excessive volume reduction (>25%) leading to stress exceeding the standard.

[0093] Penalty factor (P) is the core parameter of SIMP (solid isotropic material penalization), which is used to establish the correlation between the relative density of the unit and the stiffness of the unit, and the value range is 2≤P≤4.

[0094] Unit wall thickness (t) is a manufacturing process-related variable, which refers to the thickness of the solid area of the bone plate after optimization, and the value range is 1.2mm≤t≤1.5mm, which is used to avoid the appearance of thin-walled structures that cannot be manufactured after optimization (such as the minimum feasible wall thickness of ZK60 magnesium alloy machining is 1.2mm, and the minimum wall thickness of 3D printing is 1.0mm).

[0095] 3、Define the optimization objective function (clearly define the core direction of optimization): select Minimize Strain Energy as the core objective function, and the strain energy calculation formula is: ; Its physical meaning is the ability of the bone plate to resist deformation, and the lower the strain energy, the smaller the deformation of the bone plate under the same load, and the stronger the fixation stability.

[0096] The equivalent optimization objective function is , In addition, the objective function is selected in Tosca to only include the plate design domain in the calculation range, avoiding the energy interference of the femur and screws, and ensuring that the optimization focuses on the material distribution optimization of the plate.

[0097] 4. Define boundary conditions and external loads: Fix all degrees of freedom (X, Y, Z axis displacement and rotation) of the distal femur (condyle surface P1 point) to simulate the support of the knee joint on the femur and ensure that the load transmission path conforms to the human physiological structure.

[0098] Apply dynamic loads simulating the peak of human walking cycle, including: hip joint contact force (P2 point): X axis 32.8% body weight ratio, Y axis -229.2% body weight ratio, Z axis -54.0% body weight ratio (main load bearing); muscle force: abductor (P3 point) X axis -4.3% body weight ratio, Y axis 86.5% body weight ratio, Z axis 58.0%, vastus lateralis (P4 point) X axis -18.5% body weight ratio, Y axis -92.9% body weight ratio, Z axis -0.9% body weight ratio.

[0099] Load according to the force change curve of the walking cycle (peak in the middle of gait), not static load, to ensure the simulation of the real stress scenario of the plate in daily activities and avoid the optimization results from deviating from the clinical reality.

[0100] 5. Finite element solution: Iteration steps and convergence criteria: Set the maximum iteration steps in Tosca; Convergence criteria include: strain energy convergence, strain energy change of adjacent iterations ≤0.1%; density convergence: cell density change ≤0.01%.

[0101] 6. Generate results and process: After the core result output optimization is completed, the following result files are generated through the Tosca "Post-Processing" function. Density cloud map: intuitively display the material distribution of the plate (red for high density area, blue for low density area); performance report: contains strain energy, maximum stress, volume fraction data of each iteration step, and key indicators of the final optimized structure; optimized model: exported as STEP format for subsequent CAD modeling and process design.

[0102] After completing the topology optimization of the plate, the result verification and engineering modification work need to be carried out in turn: In the mechanical performance verification link, the optimized plate model is imported into Abaqus CAE (Computer Aided Engineering), and the dynamic load of human walking cycle is applied again, focusing on reviewing two key indicators: one is the stress indicator, including the maximum von mises stress of the plate and the maximum von mises stress of the screw; the other is the strain indicator, including the maximum equivalent strain of the plate and the maximum equivalent strain of the screw. Mises stress (controlled within 80% of the yield strength of ZK60 magnesium alloy) and stress distribution around the screw hole, and two displacement indicators, i.e., total femur displacement (controlled within +5% of the healthy bone displacement), if the indicators do not meet the requirements, the volume reduction rate needs to be adjusted (such as from 25% to 20%) and the topology optimization is re-performed.

[0103] In the engineering modification link, three core operations need to be completed, one is to chamfer the sharp corners of the optimized bone plate to achieve smooth structure to reduce the risk of local stress concentration, the second is to accurately correct the screw hole size to ensure the retention of the clinical adaptation characteristics, and the third is to solidify the key parameters such as the size and wall thickness of the bone plate hollow area for different volume reduction rates to form a standardized design template, so as to quickly adjust the bone plate design scheme according to the difference of patient's bone strength (young people's high strength bone, old people's low strength bone) in the future.

[0104] S4: According to the optimized bone plate design parameters, the safety zone of the bone plate is determined.

[0105] In this embodiment, the ±5% (14.54-16.08mm) of the healthy femur displacement and the bone plate stress threshold are taken as the core constraints, the design safety zone of the bone plate is determined combined with the optimization results of the size and screw configuration in the early stage, and the personalized adaptation scheme is developed for different bone strength populations, forming a design mode of general safety zone and personalized adjustment, which solves the problem that the traditional bone plate cannot adapt to different populations.

[0106] In the safety zone determination link, based on the fixation demand of femoral shaft transverse fracture and the mechanical properties of ZK60 magnesium alloy, the safety range of the core design parameters is determined: the length is fixed at 170mm to ensure that each side of the fracture end is covered by 80mm, meeting the clinical principle of fixing across the fracture end; the width is set to 20-22mm, which is suitable for the transverse diameter of the femoral shaft and avoids excessive width causing soft tissue irritation; the thickness is controlled within 5-5.2mm to balance the mechanical strength of the bone plate and the in-vivo degradation burden; the number of screws is determined to be 6-8, which reserves adjustment space for the adaptation of different bone strength populations. All parameter combinations of the safety zone can ensure that the Mises stress of the bone plate is controlled within 80% of the yield strength of ZK60 magnesium alloy, and the total femur displacement is within the constraint interval of 14.54-16.08mm. Mises stress is controlled within 80% of the yield strength of ZK60 magnesium alloy, and the total femur displacement is within the constraint interval of 14.54-16.08mm.

[0107] For the low-strength bones of the elderly, a combination of 22mm width, 5.2mm thickness and 8 screws is selected within the safe zone to increase the contact area and disperse stress by fixing points to avoid fixation failure; for the high-strength bones of the young, a combination of 20mm width, 5mm thickness and 6 screws is selected to reduce surgical trauma while ensuring fixation stability. This design pattern not only relies on the general safety zone to ensure the basic mechanical properties of the bone plate, but also realizes clinical adaptation for different populations through personalized parameter adjustment.

[0108] In another embodiment, with the core selection principles of mechanical matching, controllable degradation and biological safety, the bone plate uses biodegradable materials as the base material, which are Mg-Zn-Zr alloy, Mg-Zn-Sr-Zr alloy or Zn-Ag-Zr alloy. Combined with the mechanical load characteristics and bone healing process of femoral shaft, the performance advantages, composition design and processing technology of various base materials are determined to ensure that the bone plate meets the fixation strength requirements in the body and realizes the synchronicity of degradation rate and bone healing, while avoiding toxicity risks.

[0109] 1. Core constraint principles of base material selection: Based on the clinical use requirements of femoral shaft fracture bone plates, three core constraints of biodegradable base materials are determined: mechanical matching needs to approach human cortical bone (elastic modulus 17-20 GPa, compressive yield strength ≤224 MPa) to reduce stress shielding effect; controllable degradation requires a degradation rate of 0.2-0.5mm / year to synchronize with bone healing process and avoid premature failure or long-term retention of the bone plate; biological safety requires that the base material composition has no toxicity and no allergenicity, and the degradation products are human metabolizable substances without harmful ion release. The three selected biodegradable alloys meet the above core constraints and have different performance focuses, which can adapt to the bone healing needs of different patients.

[0110] 2. Performance adaptation design of three types of biodegradable base materials: Mg-Zn-Zr alloy: represented by ZK60 magnesium alloy. As the most mature biodegradable magnesium alloy in clinical application, the composition design (wt%) of Mg-Zn-Zr alloy is Zn 5.20%, Zr 0.380%, Mn 0.030%, and the impurity (Al, Fe, Ni, Si, Cu) content is ≤0.01%, without harmful elements such as aluminum and excessive copper, and zinc and zirconium are essential trace elements for the human body, with biological safety up to standard. In terms of mechanical properties, the yield strength of the extruded state is 315.2MPa, the elastic modulus is 35-45GPa, although the elastic modulus is slightly higher than that of cortical bone, but it is much lower than that of titanium alloy and 316L steel, which can greatly reduce stress shielding; fracture toughness 15-35MPa m0.5, can withstand the hip joint contact force of 229.2% of the body weight in the walking cycle of the femoral shaft. In terms of degradation rate, the extruded state is 0.3477 mm / year, and after T5 and T6 heat treatment, it is 0.494 mm / year and 0.485 mm / year respectively, which fully covers the clinical requirement of 0.2-0.5 mm / year. The degradation rhythm can be fine-tuned through heat treatment to adapt to the difference between young people's rapid healing and old people's slow healing.

[0111] Mg-Zn-Sr-Zr alloy: On the basis of Mg-Zn-Zr alloy, strontium (Sr) element is introduced, the component design (wt%) is Zn 4.5-5.0%, Sr 0.8-1.2%, Zr 0.3-0.5%, and the rest is consistent with the impurity content of ZK60 magnesium alloy. Strontium, as an element of human bone, can promote osteoblast proliferation and bone matrix mineralization, further improving bone healing efficiency. In terms of mechanical properties, the yield strength of the extruded alloy is 280-300 MPa, and the elastic modulus is 32-40 GPa, close to the cortical bone and meeting the load requirements; the degradation rate is 0.25-0.45 mm / year, within the controllable range, and the introduction of strontium element can alleviate the local alkalization problem during magnesium alloy degradation, and optimize the in-vivo biological environment.

[0112] Zn-Ag-Zr alloy: A biodegradable alloy based on zinc, with a composition design (wt%) of Ag 1.0-1.5% and Zr 0.2-0.4%. Zinc is an essential trace element for the human body, and silver has broad-spectrum antibacterial properties, which can reduce the risk of postoperative infection. In terms of mechanical properties, the yield strength of the extruded state is 200-220 MPa, and the elastic modulus is 18-22 GPa, which is the best match with the mechanical properties of human cortical bone, and almost no stress shielding effect; the degradation rate is 0.2-0.35 mm / year, and the degradation process is smooth, with zinc ions and silver ions as the product (non-toxic at low concentration), which can be metabolized and excreted through the kidneys, suitable for patients with osteoporosis and low bone strength.

[0113] To optimize the mechanical properties and degradation characteristics of the three types of biodegradable alloys, the preparation process of extrusion + heat treatment is adopted: extrusion can greatly improve the strength of the alloy (such as the yield strength of the extruded Mg-Zn-Zr alloy is more than 1 times higher than that of the cast state), while reducing the degradation rate (the degradation rate of the cast magnesium alloy is 2.1839 mm / year, and after extrusion, it decreases to 0.3477 mm / year); Subsequently, according to the alloy type, the heat treatment process is adapted, Mg-Zn-Zr and Mg-Zn-Sr-Zr alloys are treated by T5 (artificial aging) or T6 (solid solution + aging), and T6 treatment can increase the elongation of Mg-Zn-Zr alloy to 23.2%, enhancing the fracture resistance of bone plate; Zn-Ag-Zr alloy is treated by low-temperature aging (120-150°C, 4-6h), which further refines the grain and improves the plasticity and degradation stability of the alloy.

[0114] After the above selection and process optimization, the three types of biodegradable substrates made of bone plates can be personalized according to the age of the patient, bone strength, healing needs, such as young people with high strength bones choosing Mg-Zn-Zr alloy, elderly osteoporosis patients choosing Zn-Ag-Zr alloy, and patients needing to promote osteogenesis choosing Mg-Zn-Sr-Zr alloy, realizing the performance adaptation of the bone plate from general to individual.

[0115] Please refer to Figure 4 , the assembly drawing of the femoral shaft bone plate of embodiment 1 of the present application; it specifically shows the assembly and connection relationship of the bone plate 3, the screw 2 and the femoral shaft 1; among them, the femoral shaft 1 is the main body of the bone to be fixed, which corresponds to the diaphysis segment area of the human femur; the bone plate 3 is attached to the outer cortical surface of the femoral shaft 1, its length is adapted to the anatomical size of the femoral shaft 1, covering the fracture end of the femoral shaft 1 on both sides; the screw 2 is provided through the pre-designed screw hole on the bone plate 3, and is screwed into the cortical bone inside the femoral shaft 1, and the bone plate 3 and the femoral shaft 1 are fixed and connected by the fastening action of the screw 2, to realize the support and fixation of the fracture site of the femoral shaft 1.

[0116] Please refer to Figure 5 , the schematic diagram of the bone plate of the present application embodiment 1. In the figure, the mark L refers to the overall length of the bone plate, which is adapted to the fixation and coverage needs of the fracture end of the femoral shaft on both sides, ensuring that the bone plate can provide effective support across the fracture end; the mark t refers to the thickness of the bone plate, which needs to balance the mechanical strength of the bone plate and the in-vivo degradation burden; the mark W refers to the width of the bone plate, which is adapted to the transverse diameter of the middle segment of the femoral shaft, which ensures the contact area of the bone plate and the bone surface, and avoids excessive width causing postoperative soft tissue irritation; the mark R refers to the radius of the screw hole provided on the bone plate, which is distributed along the length direction of the bone plate, the number and spacing of the holes are adapted to the fixation needs of the femoral shaft, and are used to pass through the matched screw to realize the fastening connection of the bone plate and the femoral shaft.

[0117] In summary, embodiment 1 of the present application takes mechanical matching, controllable degradation, biological safety and personalized adaptation as the core, and forms a full-process closed-loop system. First, the biodegradable alloy is selected as the base material by approaching the mechanical properties of cortical bone, the synchronous degradation rate and bone healing, and the release of non-toxic elements as constraints, and the performance is strengthened through extrusion and heat treatment process; based on the CT data of human femoral shaft, a 1:1 finite element model containing transverse fracture is constructed, and the clinical operation scene is reproduced; then through multi-dimensional optimization, the optimal combination is obtained efficiently by response surface method, the number of screws is adapted to the bone strength, and the material reduction is realized by SIMP or lattice method, taking into account the lightweight and mechanical properties; then the safety zone is delimited, and the personalized parameter adjustment for different populations is matched; finally, through mechanical review and engineering correction, the balance of bone plate in mechanical support, degradation rhythm and clinical adaptability is realized, and the problem that the traditional bone plate cannot adapt to different populations is solved.

[0118] Embodiment 2 Please refer to Figure 6 , which is a structure schematic diagram of an optimization device of a biodegradable bone plate according to embodiment 2 of the present application; the specific content includes: The model construction module 100 is used for constructing a finite element model of femoral shaft fracture; The load applying module 200 is used for applying dynamic biomechanical load simulating human walking cycle in the finite element model; The collaborative optimization module 300 is used for optimizing multi-dimensional parameters of the bone plate by taking stress level of the bone plate and displacement level of the fixed femur as optimization targets; The safety zone delimiting module 400 is used for delimiting the safety zone of the bone plate according to the optimized bone plate design parameters.

[0119] In the embodiment, an optimization device of a biodegradable bone plate is proposed, which realizes the optimization of the bone plate from model construction to safety zone delimitation based on finite element simulation and multi-module collaborative design. The device includes a model construction module, a load applying module, a collaborative optimization module and a safety zone delimiting module, and each module forms a closed loop through data interaction to ensure optimization accuracy and clinical adaptability.

[0120] The model construction module 100 is the optimization basis. After inputting the CT scan data of human femoral shaft, tools such as Mimics and SolidWorks are called to complete 1:1 three-dimensional entity modeling, accurately simulate transverse fracture, distinguish cortical bone and cancellous bone and assign material properties, and simultaneously construct geometric models of biodegradable bone plate and matching screws, to ensure that the model fits the clinical operation scene.

[0121] The load applying module 200 sets a fixed constraint at the distal end of the femur based on the measured data of human walking cycle biomechanics, applies dynamic load (including hip joint contact force and muscle force) at key positions such as the femoral head and muscle attachment point, and loads according to a 0%-100% cycle force variation curve to reproduce the real stress environment.

[0122] The synergistic optimization module 300 optimizes the length, width and thickness of the bone plate by using the response surface method, minimizes the stress of the bone plate and the displacement of the femur, adapts the number of screws according to the bone strength (8 for the elderly and 4-6 for the young), realizes material reduction by SIMP or lattice method, and balances lightweight and mechanical properties.

[0123] The safety zoning module 400 delimits the safety zone of the core parameters such as the length of 170 mm and the width of 20-22 mm according to the design parameters of the bone plate optimized by the synergistic optimization module 300, synchronously generates the individual adjustment template for different bone strength populations, and improves the practical value of the device.

[0124] Embodiment 3 Please refer to Figure 7 , which is a structural schematic diagram of a computer device of embodiment 3 of the present application. The computer device 50 comprises a processor 51 and a memory 52 coupled to the processor 51.

[0125] The memory 52 stores program instructions for implementing the above-mentioned optimization method of the biodegradable bone plate.

[0126] The processor 51 is configured to execute the program instructions stored in the memory 52 to implement the optimization design of the biodegradable bone plate.

[0127] The processor 51 can also be referred to as a CPU (Central Processing Unit).

[0128] The processor 51 can be an integrated circuit chip with signal processing capability. The processor 51 can also be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a programmable logic gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0129] Embodiment 4 Please refer to Figure 8Fig. 4 is a structural schematic diagram of a storage medium of Embodiment 4 of the present application. The storage medium of the present application stores a program file 61 capable of implementing all the methods described above, wherein the program file 61 can be stored in the storage medium in the form of a software product, and includes a number of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor execute all or part of the steps of the method of each embodiment of the present application. The aforementioned storage medium includes a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media capable of storing program codes, or a computer, a server, a mobile phone, a tablet, etc.

[0130] It should be noted that in this document, the terms "comprising", "containing" or any other variant thereof are intended to cover non-exclusive inclusions, so that a process, device, article or method that includes a list of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such a process, device, article or method. Without more limitations, the element defined by the phrase "comprising a" does not exclude the presence of additional identical elements in the process, device, article or method that includes the element.

[0131] The above description is only the preferred embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation based on the content of the present application specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

[0132] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

[0133] Of course, the present application can have other various embodiments, and based on the present embodiments, other embodiments obtained by those skilled in the art without any creative labor are within the scope of protection of the present application.

Claims

1. An optimized method for a biodegradable bone plate, characterized in that, include: Construct a finite element model of a femoral shaft fracture; In the finite element model, dynamic biomechanical loads simulating the human walking cycle are applied; The stress level of the bone plate and the displacement level of the femur after fixation were used as optimization targets to optimize the multi-dimensional parameters of the bone plate. Based on the optimized bone plate design parameters, the safety zone of the bone plate is defined.

2. The optimized method for the biodegradable bone plate according to claim 1, characterized in that, The steps for constructing a finite element model of a femoral shaft fracture specifically include: A finite element model containing transverse fractures was constructed based on CT scan data of the human femoral shaft. Cortical bone, cancellous bone, and bone plates in the finite element model are assigned corresponding material properties.

3. The optimized method for the biodegradable bone plate according to claim 1, characterized in that, In the finite element model, the step of applying dynamic biomechanical loads simulating the human walking cycle specifically includes: Apply hip joint contact force and muscle force to the pre-defined proximal femur; The dynamic biomechanical load is dynamically applied according to the force change curve of the walking cycle.

4. The optimization method for the biodegradable bone plate according to claim 1, characterized in that, The step of optimizing the multi-dimensional parameters of the bone plate, using the stress level of the bone plate and the displacement level of the femur after fixation as optimization targets, specifically includes: The dimensional parameters, screw configuration parameters, and topology of the bone plate are co-optimized to obtain optimized bone plate design parameters.

5. The optimized method for the biodegradable bone plate according to claim 4, characterized in that, The optimization methods for the dimensional parameters include: using a single-variable optimization method or a response surface methodology to obtain the optimal combination of the length, width, and thickness of the bone plate; The optimization method for the screw configuration parameters includes: adjusting the number of screws according to the bone strength difference of the femur; The optimization method for the topology includes: using a solid isotropic material penalty method or a lattice-based structural optimization method to optimize the material distribution of the main body of the bonding plate with the goal of minimizing strain energy and the constraint of volume reduction rate.

6. The optimized method for the biodegradable bone plate according to claim 1, characterized in that, The bone plate uses a biodegradable material as the base material, which is a Mg-Zn-Zr alloy, a Mg-Zn-Sr-Zr alloy, or a Zn-Ag-Zr alloy.

7. An optimized device for a biodegradable bone plate, characterized in that, For performing the optimization method of the biodegradable bone plate according to any one of claims 1 to 6, the optimization apparatus for the biodegradable bone plate comprises: Model building module: Used to build finite element models of femoral shaft fractures; Load application module: used to apply dynamic biomechanical loads simulating the human walking cycle in the finite element model; Collaborative optimization module: used to optimize the multi-dimensional parameters of the bone plate with the stress level of the bone plate and the displacement level of the femur after fixation as optimization targets; Safety zone delineation module: used to delineate the safety zone of the bone plate based on the optimized bone plate design parameters.

8. A biodegradable bone plate obtained by an optimized method of the biodegradable bone plate according to any one of claims 1-6.

9. A computer device, characterized in that, The computer device includes a processor and a memory coupled to the processor, wherein the memory stores program instructions for implementing the optimization method of the biodegradable bone plate according to any one of claims 1-6; the processor is used to execute the program instructions stored in the memory to optimize the biodegradable bone plate.

10. A computer-readable storage medium, characterized in that, The device stores processor-executable program instructions for performing an optimized method for the biodegradable bone plate according to any one of claims 1-6.

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