Bone grafting scaffold design method based on cell fluidics

Abstract

The invention relates to the technical field of medical instrument design, and discloses a cell element fluidics-based bone grafting scaffold design method, which is characterized in that near-physiological fluid simulation is carried out on a preliminarily designed bone grafting scaffold, including instantaneous fluid environment simulation and steady-state fluid environment simulation on the bone grafting scaffold; therefore, the regulation and control effect of the basic design input parameters in the preliminary design on the internal fluid of the bone grafting scaffold is verified so as to determine cell element fluid mechanics output parameters, and the fluid flow direction and tissue growth and distribution in the bone grafting scaffold are evaluated according to the obtained cell element fluid mechanics output parameters. And further iteratively optimizing the osteogenesis blood supply state in the bone grafting scaffold, so that the osteogenesis speed in the bone grafting scaffold is accelerated, and the osteogenesis quality and strength are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of medical device design, and particularly to a design method of a bone graft scaffold based on cellular fluidics. Background Art

[0002] In orthopedic surgeries and bone repairs, bone graft scaffolds are a common type of implant material used to provide support for bone tissue growth and reconstruction at sites with bone tissue defects. Traditional bone graft scaffolds can be classified into autologous bone, allogeneic bone, xenogeneic bone, and synthetic bone based on materials, and include block-shaped bone graft scaffolds and granular bone graft scaffolds in terms of external structure. They promote bone ingrowth and improve the osteogenic effect inside the bone graft scaffold by providing certain physical support at the bone defect site and enhancing the biocompatibility of the material. The conditions for bone regeneration include the fluid characteristics inside the bone graft scaffold, which can affect the blood supply and tissue growth distribution inside the scaffold.

[0003] Whether traditional scaffolds use natural porous structure materials or synthetic porous structure materials, they generally have random and uncontrollable external shapes and internal structures, resulting in uncontrollability in terms of the mechanical mechanics and fluid characteristics of the scaffolds. Poor mechanical properties and insufficient blood supply may lead to low osteogenic efficiency at the implantation site, resulting in slow osteogenesis speed, insufficient osteogenesis amount, and poor quality of new bone inside traditional bone graft scaffolds, prolonging the patient's recovery time. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of slow osteogenesis speed, poor osteogenesis quality, and low strength in traditional bone graft scaffolds in the prior art, and thus provide a design method of a bone graft scaffold based on cellular fluidics.

[0005] To solve the above technical problem, the technical solution of the present invention is as follows:

[0006] A design method of a bone graft scaffold based on cellular fluidics, comprising the following steps:

[0007] Preliminary design: Based on the principle of cellular fluidics and the biomechanical environment required for bone regeneration, determine the basic design input parameters, and preliminarily design a bone graft scaffold according to the basic design input parameters;

[0008] Near-physiological fluid bionics: Through near-physiological fluid simulation of the bone graft scaffold, the near-physiological fluid simulation includes transient fluid environment simulation and steady-state fluid environment simulation, to verify the internal fluid regulation effect of the basic design input parameters on the bone graft scaffold, and determine the cellular fluid mechanics output parameters;

[0009] Mechanical performance optimization, regulating the fluid flow direction, tissue growth and distribution inside the bone graft scaffold according to the output parameters of the cellular fluid mechanics to optimize the osteogenic blood supply state inside the bone graft scaffold;

[0010] Iterative update design, optimizing the evaluation of the osteogenic blood supply state inside the bone graft scaffold to optimize and adjust the basic design input parameters.

[0011] According to some embodiments of the present invention, the basic design input parameters include cellular topological structure, cellular strut diameter, cellular support shell thickness and cellular size.

[0012] According to some embodiments of the present invention, in the transient fluid environment, under the action of the surface tension, the fluid depth climbs upward from the bottom of the bone graft scaffold; the transient fluid environment simulation is suitable for simulating the flow condition when the blood in the bone graft scaffold is initially in contact with the cellular structure at the initial stage of implantation, providing a reference for the initial conditions of the osteogenic blood supply state;

[0013] In the steady-state fluid environment, the bone graft scaffold is completely immersed in the fluid; the steady-state fluid environment is suitable for simulating the flow state when the blood in the bone graft scaffold is completely in contact with the cellular structure at the later stage of implantation, providing a reference for the osteogenic biomechanical conditions in the stable state.

[0014] According to some embodiments of the present invention, the steps of the transient fluid environment simulation are as follows:

[0015] Establish a simulation three-dimensional model according to the anatomical structure constraints and clinical requirements of the bone graft scaffold;

[0016] Set the near-physiological simulation boundary condition initialization adjustment, fluid material properties and air material properties according to the anatomical structure constraints and clinical requirements of the bone graft scaffold;

[0017] Based on the Young-Laplace formula, calculate the capillary pressure difference caused by the fluid surface tension of the bone graft scaffold, and the calculation formula is as follows:

[0018]

[0019] Δp is the pressure difference between the interfaces, γ is the surface tension coefficient, R 1 and R 2 are the principal radii of curvature;

[0020] Based on the Jurin's law, calculate the lifting height of the fluid inside the bone graft scaffold under capillary action, and the calculation formula is as follows:

[0021]

[0022] h is the height of the liquid in the tube, γ is the surface tension coefficient of the liquid, θ is the contact angle between the liquid and the tube wall, ρ is the density of the liquid, R is the radius of the tube, and g is the acceleration due to gravity;

[0023] Based on the Navier-Stokes equations, the fluid flow state is determined, and the formula is as follows:

[0024]

[0025] ρ is the fluid density, V is the velocity vector, f is the external force per unit volume of the fluid, p is the pressure, and μ is the dynamic viscosity;

[0026] According to the capillary pressure difference, the lifting height of the fluid in the bone graft scaffold, and the fluid flow state, transient fluid simulation output results are obtained.

[0027] According to some embodiments of the present invention, the transient fluid simulation output results include: the relative lifting height of the fluid under the action of the surface tension, the fluid flow velocity, and the flow path of the fluid induced by the cell structure.

[0028] According to some embodiments of the present invention, the transient fluid environment simulation steps are as follows:

[0029] According to the anatomical structure constraints and clinical requirements of the bone graft scaffold, a simulation three-dimensional model is established;

[0030] According to the anatomical structure constraints and clinical requirements of the bone graft scaffold, near-physiological simulation boundary conditions and fluid material properties are set;

[0031] Based on Darcy's law, the permeability of the bone graft scaffold is calculated, and the formula is:

[0032]

[0033] K is the permeability, L is the height of the scaffold, μ is the fluid dynamic viscosity, A is the cross-sectional area of the scaffold, and ΔP is the pressure gradient formed when the fluid flows through the scaffold at a velocity Q;

[0034] Steady-state fluid simulation output results are obtained.

[0035] According to some embodiments of the present invention, the steady-state fluid simulation output results include: the permeability of the bone graft scaffold, the wall shear stress of the bone graft scaffold under the steady-state fluid environment, and the fluid flow diffusion degree under the steady-state fluid.

[0036] According to some embodiments of the present invention, the simulation boundary conditions include fluid inlet conditions, fluid outlet conditions, the direction of gravity, and the contact angle between the surface material of the bone graft scaffold and the fluid;

[0037] The initialization conditions include an initial fluid domain and an initial gas domain;

[0038] The fluid material property is set as blood, and the gas material property is set as air.

[0039] According to some embodiments of the present invention, the bone graft scaffold design method based on cellular fluidics can be applied to the design and preparation of massive bone graft scaffolds, granular bone graft scaffolds or chain bone graft scaffolds.

[0040] According to some embodiments of the present invention, the evaluation and analysis of the transient fluid simulation output results and the steady-state fluid simulation output results include:

[0041] Set the fluid lifting height threshold, fluid flow velocity threshold and fluid flow path range of the bone graft scaffold in the transient fluid simulation; set the permeability threshold of the bone graft scaffold in the steady-state fluid simulation, the wall shear stress threshold range of the bone graft scaffold and the fluid flow diffusion threshold range;

[0042] Simulate to obtain the transient fluid simulation output results and the steady-state fluid simulation output results; compare the obtained transient fluid simulation output results with the preset fluid lifting height threshold, the fluid flow velocity threshold and the fluid flow path range to obtain the evaluation result of the transient fluid simulation output results;

[0043] Compare the obtained steady-state fluid simulation output results with the preset permeability threshold of the bone graft scaffold, the wall shear stress threshold range of the bone graft scaffold and the fluid flow diffusion threshold range to obtain the evaluation result of the steady-state fluid simulation output results.

[0044] The technical solution of the present invention has the following advantages:

[0045] The bone graft scaffold design method based on cellular fluidics provided by the present invention performs near-physiological fluid biomimicry on the preliminarily designed bone graft scaffold, including transient fluid environment simulation and steady-state fluid environment simulation of the bone graft scaffold, so as to verify the internal fluid regulation effect of the basic design input parameters in the preliminary design, determine the output parameters of cellular fluid mechanics, and judge the fluid flow direction and tissue growth and distribution inside the bone graft scaffold according to the obtained output parameters of cellular fluid mechanics. If the osteogenic blood supply state inside the bone graft scaffold is not satisfied, the design input parameters of the scaffold will be iteratively optimized until a better result is achieved, thereby accelerating the osteogenic speed inside the bone graft scaffold and improving the osteogenic quality and strength. Description of the Drawings

[0046] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0047] Figure 1 It is a schematic flow chart of a bone graft scaffold design method based on cell fluidics provided in some embodiments of the present invention;

[0048] Figure 2 It is a schematic diagram of the expected fluid selective flow path in the bone graft scaffold in some embodiments of the present invention;

[0049] Figure 3 It is the design and fluid simulation analysis of a granular bone graft scaffold in some embodiments of the present invention. Specific Embodiments

[0050] The following will clearly and completely describe the technical solutions of the present invention with reference to the drawings. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0051] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0052] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0054] Referring to Figure 1 As shown, in some embodiments of the present invention, the present invention provides a method for designing a bone graft scaffold based on cellular fluidics, comprising the following steps:

[0055] Preliminary design: Based on the principles of cellular fluidics and the biomechanical environment required for bone regeneration, determine the basic design input parameters, and preliminarily design the bone graft scaffold according to the basic design input parameters;

[0056] Near-physiological fluid bionics: Through near-physiological fluid simulation of the bone graft scaffold, the near-physiological fluid simulation includes transient fluid environment simulation and steady-state fluid environment simulation, to verify the internal fluid regulation effect of the basic design input parameters on the bone graft scaffold, and determine the cellular fluid mechanics output parameters;

[0057] Mechanical performance optimization: According to the cellular fluid mechanics output parameters, regulate the fluid flow direction and tissue growth and distribution inside the bone graft scaffold, so as to optimize the osteogenic blood supply state inside the bone graft scaffold;

[0058] Iterative update design: Optimize and evaluate the osteogenic blood supply state inside the bone graft scaffold, so as to optimize and adjust the basic design input parameters.

[0059] Specifically, through near-physiological fluid bionics of the preliminarily designed bone graft scaffold, including transient fluid environment simulation and steady-state fluid environment simulation of the bone graft scaffold, thereby verifying the internal fluid regulation effect of the basic design input parameters in the preliminary design on the bone graft scaffold, to determine the cellular fluid mechanics output parameters, regulate the fluid flow direction and tissue growth and distribution inside the bone graft scaffold according to the obtained cellular fluid mechanics output parameters, further optimize the osteogenic blood supply state inside the bone graft scaffold, thereby accelerating the osteogenic speed inside the bone graft scaffold and improving the osteogenic quality and strength.

[0060] It can be understood that when performing iterative update design, optimize and evaluate the osteogenic blood supply state inside the bone graft scaffold, so as to optimize and adjust the basic design input parameters; specifically, when the cellular fluid mechanics output parameters evaluate the fluid flow direction and tissue growth and distribution inside the bone graft scaffold and determine that the osteogenic blood supply state of the optimized bone graft scaffold cannot be satisfied, then further optimize and change the basic design input parameters;

[0061] When the cellular fluid mechanics output parameters evaluate the fluid flow direction and tissue growth and distribution inside the bone graft scaffold and determine that the osteogenic blood supply state of the optimized bone graft scaffold can be satisfied, then determine the optimal basic design input parameters and terminate the iterative design.

[0062] In some embodiments of the present invention, the basic design input parameters include cellular topology, cellular strut diameter, cellular support shell thickness, and cellular size.

[0063] Specifically, in some embodiments of the present invention, the basic output parameters of the bone graft scaffold are as follows: the unit cell topology is a hollow regular tetrahedron, the strut diameter is 0.1 mm, and the unit cell size (circumscribed sphere diameter) is 1 mm.

[0064] In some embodiments of the present invention, in a transient fluid environment, under the action of surface tension, the fluid depth climbs upward from the bottom of the bone graft scaffold; the transient fluid environment simulation is suitable for simulating the flow condition when the blood in the bone graft scaffold initially contacts the unit cell structure at the initial stage of implantation, so as to provide a reference for the initial conditions of the osteogenic blood supply state.

[0065] In a steady-state fluid environment, the bone graft scaffold is completely immersed in the fluid; the steady-state fluid environment is suitable for simulating the flow state when the blood in the bone graft scaffold is in full contact with the unit cell structure at the later stage of implantation, so as to provide a reference for the osteogenic biomechanical conditions in the stable state.

[0066] In some embodiments of the present invention, the steps of the transient fluid environment simulation are as follows:

[0067] Establish a simulation three-dimensional model according to the anatomical structure constraints and clinical requirements of the bone graft scaffold.

[0068] Set the near-physiological simulation boundary condition initialization adjustment, fluid material properties, and air material properties according to the anatomical structure constraints and clinical requirements of the bone graft scaffold.

[0069] Based on the Young-Laplace formula, calculate the capillary pressure difference caused by the fluid surface tension of the bone graft scaffold. The calculation formula is as follows:

[0070]

[0071] Δp is the pressure difference between the interfaces, γ is the surface tension coefficient, R 1 and R 2 are the principal radii of curvature.

[0072] Based on the Jurin's law, calculate the lifting height of the fluid in the bone graft scaffold under capillary action. The calculation formula is as follows:

[0073]

[0074] h is the height of the liquid in the tube, γ is the surface tension coefficient of the liquid, θ is the contact angle between the liquid and the tube wall, ρ is the density of the liquid, R is the radius of the tube, and g is the acceleration due to gravity.

[0075] Based on the Navier-Stokes equation, determine the fluid flow state. The formula is as follows:

[0076]

[0077] ρ is the fluid density, V is the velocity vector, f is the external force per unit volume of the fluid, p is the pressure, and μ is the dynamic viscosity;

[0078] According to the capillary pressure difference, the lifting height of the fluid in the bone graft scaffold, and the fluid flow state, the transient fluid simulation output results are obtained.

[0079] In some embodiments of the present invention, the transient fluid simulation output results include: the relative lifting height of the fluid under the action of surface tension, the fluid flow velocity, and the fluid flow path induced by the unit cell structure.

[0080] In some embodiments of the present invention, the steps of the transient fluid environment simulation are as follows:

[0081] According to the anatomical structure constraints and clinical requirements of the bone graft scaffold, a simulation three-dimensional model is established;

[0082] According to the anatomical structure constraints and clinical requirements of the bone graft scaffold, near-physiological simulation boundary conditions and fluid material properties are set;

[0083] Based on Darcy's law, the permeability of the bone graft scaffold is calculated, and the formula is:

[0084]

[0085] K is the permeability, L is the height of the scaffold, μ is the fluid dynamic viscosity, A is the cross-sectional area of the scaffold, and ΔP is the pressure gradient formed when the fluid flows through the scaffold at a velocity Q;

[0086] The steady-state fluid simulation output results are obtained.

[0087] In some embodiments of the present invention, the steady-state fluid simulation output results include: the permeability of the bone graft scaffold, the wall shear stress of the bone graft scaffold in the steady-state fluid environment, and the fluid flow diffusion degree in the steady-state fluid, as Figure 2 shown.

[0088] In some embodiments of the present invention, the simulation boundary conditions include the fluid inlet condition, the fluid outlet condition, the gravity direction, and the contact angle between the surface material of the bone graft scaffold and the fluid;

[0089] The initial conditions include the initial fluid domain and the initial gas domain;

[0090] The fluid material property is set to blood, and the gas material property is set to air.

[0091] In some embodiments of the present invention, the bone graft scaffold design method based on unit cell fluidics can be applied to the design and preparation of massive bone graft scaffolds, granular bone graft scaffolds, or chain-type bone graft scaffolds.

[0092] Specifically, for transient fluid simulation, an ordered stacking model of multiple bone graft scaffold particles is established. An initial air boundary of 0.1 mm is established on the outer periphery of the scaffold sidewall. An initial blood liquid surface and a pressure fluid inlet are established vertically below the gravity direction, and the top is the fluid outlet. The laminar flow method is used to analyze the fluid flow state, and the phase field method is used to track the gas-liquid two-phase interface. The solid-liquid contact angle of the scaffold surface is set to 60°. The liquid material property is set as blood, and the gas material property is set as air. Based on the transient Navier-Stokes equation, a transient fluid simulation of liquid lifting driven by surface tension is carried out.

[0093] For steady-state fluid simulation: A natural stacking model of multiple scaffold particles is established. A fluid boundary of 0.1 mm is established on the outer periphery of the scaffold sidewall. A fluid velocity inlet is set at the bottom, and the top is the fluid outlet. The fluid material property is set as the blood fluid property. Based on the steady-state Navier-Stokes equation, a steady-state fluid mechanics analysis is carried out, and the scaffold permeability is calculated based on Darcy's law according to the analysis results.

[0094] As Figure 3 shown, the optimized design is determined: On the basis of the aforementioned hollow regular tetrahedron unit cell structure, internal struts are added to connect the centroid of the tetrahedron and the midpoint of the side line. The diameter of the outer side line strut is 0.15 mm, the diameter of the internal strut is 0.1 mm, and the unit cell size (diameter of the circumscribed sphere) is 1 mm.

[0095] In some embodiments of the present invention, the output results of the transient fluid simulation and the steady-state fluid simulation are evaluated and analyzed, including:

[0096] Set the fluid lifting height threshold, fluid flow velocity threshold, and fluid flow path range of the bone graft scaffold in the transient fluid simulation; set the permeability threshold of the bone graft scaffold, the range of the wall shear stress threshold of the bone graft scaffold, and the range of the fluid flow diffusion threshold in the steady-state fluid simulation;

[0097] The output results of the transient fluid simulation and the steady-state fluid simulation are obtained through simulation; the obtained output results of the transient fluid simulation are compared with the preset fluid lifting height threshold, fluid flow velocity threshold, and fluid flow path range to obtain the evaluation result of the output results of the transient fluid simulation;

[0098] The obtained output results of the steady-state fluid simulation are compared with the preset permeability threshold of the bone graft scaffold, the range of the wall shear stress threshold of the bone graft scaffold, and the range of the fluid flow diffusion threshold to obtain the evaluation result of the output results of the steady-state fluid simulation.

[0099] Refer to Figure 3As shown, transient fluid simulation and steady-state fluid simulation were performed on the optimized bone graft scaffold again. By comparing the simulation results, the optimization results were determined: After transient fluid simulation, the liquid level rising speed of the preliminary design model before optimization was 0.1015 m / s, and the final relative rising height was 0.933. The blood fluid tended to adsorb on the scaffold frame; the liquid level rising speed of the optimized design model was 0.1172 m / s, and the final relative rising height was 0.935. The blood fluid tended to adsorb on the scaffold frame and inside the scaffold. After steady-state fluid simulation, the average wall shear stress of the preliminary design model before optimization was 0.014 Pa, and the permeability was 1.62×10 －9 m 2 , and the fluid tended to form concentrated flow among the larger scaffold voids; the average wall shear stress of the optimized design model was 0.024 Pa, and the permeability was 6.32×10 －10 m 2 . Due to the addition of internal struts, the fluid flow became more dispersed and balanced. In summary, the optimized granular bone graft scaffold has stronger fluid adsorption ability and is more conducive to inducing blood supply in the initial stage of osteogenesis; under the condition of providing a more suitable fluid biomechanical environment in the later stage of osteogenesis, it is more conducive to guiding the adhesion and diffusion of blood and cells, achieving the optimization effect.

[0100] Obviously, the above embodiments are only examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A bone graft scaffold design method based on cellular fluid dynamics, characterized in that: The following steps are involved: Preliminary design: determining basic design input parameters based on the principles of cellular fluid mechanics and the biomechanical environment required by the bone regeneration environment, and preliminarily designing the bone graft scaffold according to the basic design input parameters; Near-physiological fluid bionics, by performing near-physiological fluid simulation on the bone graft scaffold, the near-physiological fluid simulation includes transient fluid environment simulation and steady-state fluid environment simulation, to verify the effect of the basic design input parameters on the internal fluid regulation of the bone graft scaffold, and determine the cell fluid mechanics output parameters; Mechanical performance optimization, evaluating the fluid flow direction and tissue growth and distribution inside the bone graft scaffold according to the cell fluid mechanics output parameters, so as to determine the bone-forming blood supply status in the bone graft scaffold; The design is iteratively updated to optimize and evaluate the bone formation blood supply status in the bone graft scaffold to optimize and adjust the basic design input parameters.

2. The bone graft scaffold design method based on cellular fluid dynamics according to claim 1, characterized in that: The basic design input parameters include cell topology, cell pillar diameter, cell support shell thickness and cell size.

3. The bone graft scaffold design method based on cellular fluid dynamics according to claim 1, characterized in that: In the transient fluid environment, under the action of the surface tension, the depth of the fluid rises upward from the bottom of the bone graft scaffold; the transient fluid environment simulation is suitable for simulating the flow condition of the blood in the bone graft scaffold when it initially contacts the cellular structure at the initial stage of implantation, so as to provide a reference for the initial condition of the osteogenic blood supply state; In the steady-state fluid environment, the bone graft scaffold is completely immersed in the fluid; the steady-state fluid environment is suitable for simulating the flow state in which the blood and the cellular structure in the bone graft scaffold are in complete contact in the late stage of implantation, so as to provide a reference for the biomechanical conditions of bone formation in a stable state.

4. The method for designing a bone graft scaffold based on cellular fluid dynamics according to claim 3, characterized in that: The transient fluid environment simulation steps are as follows: Establishing a simulated three-dimensional model according to the anatomical constraints and clinical needs of the bone graft scaffold; According to the anatomical constraints of the bone graft scaffold and clinical needs, setting the initialization adjustment of the near-physiological simulation boundary conditions, the fluid material properties and the air material properties; Based on the Young-Laplace formula, the capillary pressure difference of the bone graft scaffold caused by the surface tension of the fluid is calculated as follows: Δp is the pressure difference between the interfaces, γ is the surface tension coefficient, R1 and R2 are the main curvature radii; Based on the Lin's law, the lifting height of the fluid in the bone graft scaffold under the capillary action is calculated as follows: h is the height of the liquid in the tube, γ is the surface tension coefficient of the liquid, θ is the contact angle between the liquid and the tube wall, ρ is the density of the liquid, R is the radius of the tube, and g is the acceleration due to gravity; Based on the Navier-Stokes equation, the fluid flow state is determined as follows: ρ is the fluid density, V is the velocity vector, f is the external force per unit volume of fluid, p is the pressure, and μ is the dynamic viscosity; According to the capillary pressure difference, the lifting height of the fluid in the bone grafting support, and the fluid flow state, a transient fluid simulation output result is obtained.

5. The method for designing a bone graft scaffold based on cellular fluid dynamics according to claim 4, characterized in that: The transient fluid simulation output results include: the relative lifting height of the fluid under the action of the surface tension, the fluid flow velocity, and the flow path of the fluid under the induction of the cell structure.

6. The method for designing a bone graft scaffold based on cellular fluid dynamics according to claim 4, characterized in that: The steady-state fluid environment simulation steps are as follows: Establishing a simulated three-dimensional model according to the anatomical constraints and clinical needs of the bone graft scaffold; According to the anatomical constraints and clinical requirements of the bone graft scaffold, near-physiological simulation boundary conditions and fluid material properties are set; Based on Darcy's law, the permeability of the bone graft scaffold is calculated as follows: K is the permeability, L is the height of the support, μ is the fluid dynamic viscosity, A is the cross-sectional area of ​​the support, and ΔP is the pressure gradient formed when the fluid flows through the support at a speed of Q; Get steady-state fluid simulation output.

7. The method for designing a bone graft scaffold based on cellular fluid dynamics according to claim 6, characterized in that: The steady-state fluid simulation output results include: the permeability of the bone graft scaffold, the shear stress of the bone graft scaffold wall under the steady-state fluid environment, and the fluid flow diffusion degree under the steady-state fluid.

8. The method for designing a bone graft scaffold based on cellular fluid dynamics according to claim 7, characterized in that: The simulation boundary conditions include fluid inlet conditions, fluid outlet conditions, gravity direction, and contact angle between the surface material of the bone grafting stent and the fluid; The initialization conditions include an initial fluid domain and an initial gas domain; The material property of the fluid is set to blood, and the material property of the gas is set to air.

9. The method for designing a bone graft scaffold based on cellular fluid dynamics according to claim 1, characterized in that: The method can be applied to the design and preparation of block-shaped bone graft scaffolds, granular bone graft scaffolds or chain-shaped bone graft scaffolds.

10. The method for designing a bone graft scaffold based on cellular fluid dynamics according to claim 6, characterized in that: The transient fluid simulation output result and the steady-state fluid simulation output result are evaluated and analyzed, including: Setting the fluid lifting height threshold, fluid flow velocity threshold and fluid flow path range of the bone graft scaffold in transient fluid simulation; setting the permeability threshold of the bone graft scaffold in steady-state fluid simulation, the bone graft scaffold wall shear stress threshold range and fluid flow diffusion threshold range; Simulate and obtain transient fluid simulation output results and steady-state fluid simulation output results; compare the obtained transient fluid simulation output results with the preset fluid lifting height threshold, the fluid flow velocity threshold and the fluid flow path range; to obtain an evaluation result of the transient fluid simulation output results; The obtained steady-state fluid simulation output result is compared with the preset permeability threshold of the bone graft scaffold, the bone graft scaffold wall shear stress threshold range and the fluid flow diffusion threshold range to obtain an evaluation result of the steady-state fluid simulation output result.

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