CN112220588B - Method and system for generating controllable gradient bone tissue engineering scaffold - Google Patents
Method and system for generating controllable gradient bone tissue engineering scaffold Download PDFInfo
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- CN112220588B CN112220588B CN202011101516.7A CN202011101516A CN112220588B CN 112220588 B CN112220588 B CN 112220588B CN 202011101516 A CN202011101516 A CN 202011101516A CN 112220588 B CN112220588 B CN 112220588B
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/28—Bones
- A61F2/2846—Support means for bone substitute or for bone graft implants, e.g. membranes or plates for covering bone defects
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2/3094—Designing or manufacturing processes
- A61F2/30942—Designing or manufacturing processes for designing or making customized prostheses, e.g. using templates, CT or NMR scans, finite-element analysis or CAD-CAM techniques
Abstract
The invention discloses a method and a system for generating a controllable gradient bone tissue engineering scaffold. The method comprises the following steps: determining the external shape outline of the bone tissue engineering scaffold; generating a plurality of discrete points in the external shape outline of the bone tissue engineering scaffold, and screening the generated discrete points according to the gradient distribution of the Young modulus of the skeleton at the lesion part to obtain screened discrete points; generating three-dimensional Voronoi polyhedrons with coincident faces by taking each screened discrete point as a core; carrying out reduction treatment on the three-dimensional voronoi polyhedron to obtain a closed polyhedron; translating each surface of the closed polyhedron for a preset distance to obtain an entity with a gap inside; and generating the bone tissue engineering scaffold by adopting a Boolean operation method according to the external shape outline of the bone tissue engineering scaffold and the entity with the gap in the interior. By adopting the method and the system, the matching degree of the Young modulus of the bone tissue engineering scaffold and the natural skeleton of the human body can be improved.
Description
Technical Field
The invention relates to the technical field of medical bone tissue engineering scaffolds, in particular to a method and a system for generating a controllable gradient bone tissue engineering scaffold.
Background
Bone fracture is a very common disorder. The symptoms of the fracture are many, the mild bone damages are less, the operation treatment is not needed, and the severe bone damages and loss of a large section of bone can be caused. When the bone injury is serious, the bone is difficult to cure and is possibly accompanied by nonunion symptoms, which causes great trouble to the treatment and recovery of fracture patients. For fracture symptoms which are difficult to cure and have obvious gaps at fracture ends, substances for forming bones and inducing the formation of the bones must be supplemented to shorten the healing time, promote the healing of the fractures and achieve the aim of surgical treatment. Autologous bone is the "gold standard" for bone graft material, but is undoubtedly responsible for secondary trauma and injury, pain, etc. at the site of bone supply, and is extremely limited in number. Allogenic and xenogenic bones are at increased risk for rejection and disease transmission.
The bone tissue engineering scaffold is the most widely and mature method for treating fracture and promoting bone healing. The revascularization process of the implanted cancellous bone is fast, the implanted bone around the fracture can be changed into a live bone firstly, the cortical bone with poor or no blood supply in the middle can recover the blood supply slowly or can heal slowly through the creeping substitution process, which is equivalent to that the outer callus welds 2 fracture broken ends firstly to provide initial stability. The bone grafting shortens the healing time and accelerates the bone healing through the effects of compensating the bone defect, recovering the normal length of the bone, bone induction effect, bone conduction effect, promoting revascularization of the fractured end and the like.
An excellent bone tissue engineering scaffold should not only fit with natural bone in external macroscopic contour, but also have the function of conducting bone force, have good biocompatibility and good circulation, can help blood supply to meet the transportation requirement of nutrient substances, and more importantly, have approximate Young's modulus at the contact part with the natural bone to reduce the occurrence of stress shielding.
Most of the existing bone tissue engineering scaffolds have a single and unchangeable Young modulus, and the internal structural units are mostly in a regular shape. The regular structural units can cause the implant to have obvious difference in mechanical properties when the implant is stressed from different parts and different directions, and cause excessive deformation or damage of the implant in the direction with poor bearing capacity, thereby affecting the treatment effect. More importantly, when applied to the clinical treatment of fracture, the bone tissue engineering scaffold which does not have the same gradient Young's modulus as the natural human bone is not matched with the Young's modulus of the natural bone of the human body, and stress shielding occurs, so that the natural bone or the implant is damaged by abrasion more quickly.
Disclosure of Invention
The invention aims to provide a method and a system for generating a controllable gradient bone tissue engineering scaffold, which can improve the matching degree of the Young modulus of the bone tissue engineering scaffold and a natural skeleton of a human body.
In order to achieve the purpose, the invention provides the following scheme:
a bone tissue engineering scaffold generation method, comprising:
obtaining bone parameters of a lesion part; the parameters of the bone of the lesion part comprise the gradient distribution of the Young modulus of the bone of the lesion part and the external shape profile of the bone of the lesion part;
determining the external shape contour of the bone tissue engineering scaffold according to the external shape contour of the bone of the lesion part;
generating a plurality of discrete points in the external shape outline of the bone tissue engineering scaffold, and screening the generated discrete points according to the gradient distribution of the Young modulus of the skeleton at the lesion part to obtain screened discrete points;
generating a three-dimensional Voronoi polyhedron with mutually overlapped surfaces by taking each screened discrete point as a core;
carrying out reduction treatment on the three-dimensional voronoi polyhedron to obtain a closed polyhedron;
translating each surface of the closed polyhedron for a preset distance to obtain an entity with a gap inside;
and generating the bone tissue engineering scaffold by adopting a Boolean operation method according to the external shape contour of the bone tissue engineering scaffold and the entity with the gap in the interior.
Optionally, the screening the generated multiple discrete points according to the gradient distribution of the young's modulus of the bone at the lesion site to obtain the screened discrete points specifically includes:
acquiring an x-axis coordinate, a y-axis coordinate and a z-axis coordinate of the discrete point;
mapping the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point to a (0,1) interval to obtain three mapping values;
determining a function according to the gradient distribution of the Young modulus of the skeleton at the lesion part, and respectively inputting three mapping values into the function to obtain three output values;
comparing each output value with a preset value to obtain a comparison value; if the output value is smaller than the preset value, the comparison value is 1; if the output value is greater than or equal to the preset value, the comparison value is 0;
performing OR operation on the three comparison values to obtain an operation value; if the operation value is 1, deleting the corresponding discrete point; if the operation value is 0, reserving the corresponding discrete point;
judging whether all discrete points are screened; if so, deleting one of the discrete points in the reserved discrete points, the distance between any two discrete points of which is less than the threshold value, and obtaining the screened discrete points; if not, acquiring the next discrete point, and then returning to the step of acquiring the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point.
Optionally, the generating the bone tissue engineering scaffold by using a boolean operation method according to the external shape profile of the bone tissue engineering scaffold and the entity with the gap inside, and then further includes:
determining the Young modulus of the generated bone tissue engineering scaffold;
and storing the Young modulus of the generated bone tissue engineering scaffold, the screened discrete points, materials and preset distances corresponding to the generated bone tissue engineering scaffold into a database.
Optionally, the generating a three-dimensional voronoi polyhedron with mutually overlapped surfaces by using each screened discrete point as a core specifically includes:
and generating three-dimensional Venuo polyhedrons with coincident faces by taking each screened discrete point as a core and utilizing rhino software.
The invention also provides a bone tissue engineering scaffold generation system, comprising:
the lesion site bone parameter acquisition module is used for acquiring lesion site bone parameters; the parameters of the bone of the lesion part comprise the gradient distribution of the Young modulus of the bone of the lesion part and the external shape profile of the bone of the lesion part;
the external shape contour determining module of the bone tissue engineering scaffold is used for determining the external shape contour of the bone tissue engineering scaffold according to the external shape contour of the bone of the lesion part;
the discrete point screening module is used for generating a plurality of discrete points in the external shape outline of the bone tissue engineering scaffold, and screening the generated discrete points according to the gradient distribution of the Young modulus of the skeleton of the lesion part to obtain the screened discrete points;
the three-dimensional voronoi polyhedron generating module is used for generating three-dimensional voronoi polyhedrons with coincident surfaces by taking each screened discrete point as a core;
the three-dimensional Voronoi polyhedron is subjected to reduction treatment to obtain a closed polyhedron;
the translation module is used for translating each surface of the closed polyhedron for a preset distance to obtain an entity with a gap inside;
and the bone tissue engineering scaffold generating module is used for generating the bone tissue engineering scaffold by adopting a Boolean operation method according to the external shape contour of the bone tissue engineering scaffold and the entity with the gap in the interior.
Optionally, the discrete point screening module specifically includes:
the coordinate acquisition unit is used for acquiring the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point;
the mapping unit is used for mapping the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point to a (0,1) interval to obtain three mapping values;
the function calculation unit is used for determining a function according to the gradient distribution of the Young modulus of the skeleton at the lesion part and respectively inputting the three mapping values into the function to obtain three output values;
the comparison unit is used for comparing each output value with a preset value to obtain a comparison value; if the output value is smaller than the preset value, the comparison value is 1; if the output value is greater than or equal to the preset value, the comparison value is 0;
the OR operation unit is used for carrying out OR operation on the three comparison values to obtain an operation value; if the operation value is 1, deleting the corresponding discrete point; if the operation value is 0, reserving the corresponding discrete point;
the judging unit is used for judging whether all the discrete points are screened; if yes, executing an output unit; if not, acquiring the next discrete point, and then executing the coordinate acquisition unit;
the output unit is used for deleting one of the two discrete points with the distance smaller than the threshold value, and then outputting the screened discrete points.
Optionally, the system further includes:
the Young modulus determining module is used for determining the Young modulus of the generated bone tissue engineering scaffold;
and the storage module is used for storing the Young modulus of the generated bone tissue engineering scaffold, the screened discrete points, materials and preset distances corresponding to the generated bone tissue engineering scaffold into a database.
Optionally, the three-dimensional voronoi polyhedron generating module specifically includes:
and the three-dimensional voronoi polyhedron generating unit is used for generating the three-dimensional voronoi polyhedron with the overlapped surfaces by using rhino software by taking each screened discrete point as a core.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a method and a system for generating a controllable gradient bone tissue engineering scaffold, which are used for acquiring bone parameters of a lesion part; determining the external shape outline of the bone tissue engineering scaffold according to the external shape outline of the bone of the lesion part; generating a plurality of discrete points in the external shape outline of the bone tissue engineering scaffold, and screening the generated discrete points according to the gradient distribution of the Young modulus of the skeleton at the lesion part to obtain screened discrete points; generating three-dimensional Voronoi polyhedrons with coincident faces by taking each screened discrete point as a core; carrying out reduction treatment on the three-dimensional voronoi polyhedron to obtain a closed polyhedron; translating each surface of the closed polyhedron for a preset distance to obtain an entity with a gap inside; and generating the bone tissue engineering scaffold by adopting a Boolean operation method according to the external shape outline of the bone tissue engineering scaffold and the entity with the gap in the interior. The method screens the generated multiple discrete points according to the gradient distribution of the Young modulus of the skeleton at the lesion part, and can realize more effective control on the discrete points, thereby improving the matching degree of the Young modulus of the bone tissue engineering scaffold and the natural skeleton of the human body.
In addition, the number and distribution of the discrete points are controlled through functions, so that the discrete points have certain gradient density distribution in an external shape outline, the randomness of the generation positions under the control of the gradient density can be kept, the minimum distance between the points is controlled, the flexibility of the generation of the bone tissue engineering support is greatly improved, the growth mode of the human bone is simulated to a great extent, the gradient distribution of the simulated natural human bone on the elastic modulus is met, and the phenomenon that the natural bone or the implant is quickly worn and damaged due to stress shielding caused by the fact that the Young modulus of the bone tissue engineering support is not matched with that of the natural bone of the human body is avoided.
According to the invention, the Young modulus of the generated bone tissue engineering scaffold, the screened discrete points, materials and preset distances corresponding to the generated bone tissue engineering scaffold are stored in the database, so that the individualized bone tissue engineering scaffold design time for different patients is reduced, the efficiency is improved, and the possibility of delaying the treatment occasion is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a flow chart of a method for generating a controllable gradient bone tissue engineering scaffold according to an embodiment of the present invention;
FIG. 2 is a structural diagram of a scaffold generation system for bone tissue engineering with controllable gradient according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating the steps of generating a scaffold for bone tissue engineering according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of an optimized design of a structure according to an embodiment of the present invention;
fig. 5 is a schematic diagram of a method for controlling the number and distribution of random points in the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a method and a system for generating a controllable gradient bone tissue engineering scaffold, which can improve the matching degree of the Young modulus of the bone tissue engineering scaffold and a natural skeleton of a human body.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Examples
Fig. 1 is a flowchart of a method for generating a controllable gradient bone tissue engineering scaffold according to an embodiment of the present invention, and as shown in fig. 1, the method for generating a controllable gradient bone tissue engineering scaffold includes:
step 101: obtaining bone parameters of a lesion part; the lesion bone parameters include a gradient distribution of young's modulus of the lesion bone and an outer shape profile of the lesion bone.
Step 102: and determining the external shape contour of the bone tissue engineering scaffold according to the external shape contour of the bone of the lesion site.
Step 103: generating a plurality of discrete points in the external shape outline of the bone tissue engineering scaffold, and screening the generated discrete points according to the gradient distribution of the Young modulus of the bone of the lesion part to obtain the screened discrete points.
acquiring an x-axis coordinate, a y-axis coordinate and a z-axis coordinate of the discrete point;
mapping the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point to a (0,1) interval to obtain three mapping values;
determining a function according to the gradient distribution of the Young modulus of the skeleton at the lesion part, and respectively inputting the three mapping values into the function to obtain three output values; for example, the function is f (x) ═ x2-x。
Comparing each output value with a preset value to obtain a comparison value; if the output value is smaller than the preset value, the comparison value is 1; if the output value is greater than or equal to the preset value, the comparison value is 0;
performing OR operation on the three comparison values to obtain an operation value; if the operation value is 1, deleting the corresponding discrete point; if the operation value is 0, keeping the corresponding discrete point;
judging whether all discrete points are screened; if so, deleting one of the discrete points in the reserved discrete points, the distance between any two discrete points of which is less than the threshold value, and obtaining the screened discrete points; if not, acquiring the next discrete point, and then returning to the step of acquiring the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point.
Step 104: and generating a three-dimensional Veno polyhedron with mutually overlapped surfaces by taking each screened discrete point as a core.
and (4) generating a three-dimensional Veno polyhedron with mutually overlapped surfaces by using rhino software by taking each screened discrete point as a core.
Step 105: and carrying out reduction treatment on the three-dimensional voronoi polyhedron to obtain a closed polyhedron.
Step 106: and (4) translating each surface of the closed polyhedron for a preset distance to obtain an entity with a gap inside.
Step 107: and generating the bone tissue engineering scaffold by adopting a Boolean operation method according to the external shape outline of the bone tissue engineering scaffold and the entity with the gap in the interior.
Step 108: determining the Young's modulus of the generated bone tissue engineering scaffold.
Step 109: and storing the Young modulus of the generated bone tissue engineering scaffold, the screened discrete points, materials and preset distances corresponding to the generated bone tissue engineering scaffold into a database.
Fig. 2 is a structural diagram of a controllable gradient bone tissue engineering scaffold generation system in the embodiment of the invention. As shown in fig. 2, a controllable gradient bone tissue engineering scaffold generation system comprises:
a lesion bone parameter acquiring module 201, configured to acquire a lesion bone parameter; the lesion bone parameters include a gradient distribution of young's modulus of the lesion bone and an outer shape profile of the lesion bone.
And the external shape outline determining module 202 of the bone tissue engineering scaffold is used for determining the external shape outline of the bone tissue engineering scaffold according to the external shape outline of the bone of the lesion site.
The discrete point screening module 203 is configured to generate a plurality of discrete points within the outer shape profile of the bone tissue engineering scaffold, and screen the generated plurality of discrete points according to the gradient distribution of the young's modulus of the bone at the lesion site to obtain the screened discrete points.
The discrete point screening module 203 specifically includes:
the coordinate acquisition unit is used for acquiring the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point;
the mapping unit is used for mapping the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point to a (0,1) interval to obtain three mapping values;
the function calculation unit is used for determining a function according to the gradient distribution of the Young modulus of the skeleton at the lesion part and respectively inputting the three mapping values into the function to obtain three output values;
the comparison unit is used for comparing each output value with a preset value to obtain a comparison value; if the output value is smaller than the preset value, the comparison value is 1; if the output value is greater than or equal to the preset value, the comparison value is 0;
the OR operation unit is used for carrying out OR operation on the three comparison values to obtain an operation value; if the operation value is 1, deleting the corresponding discrete point; if the operation value is 0, keeping the corresponding discrete point;
the judging unit is used for judging whether all the discrete points are screened; if yes, executing an output unit; if not, acquiring the next discrete point, and then executing a coordinate acquisition unit;
and the output unit is used for deleting one of the two discrete points with the distance smaller than the threshold value in the reserved discrete points and then outputting the screened discrete points.
And a three-dimensional voronoi polyhedron generating module 204, configured to generate a three-dimensional voronoi polyhedron having overlapped surfaces with each other by using each screened discrete point as a core.
The three-dimensional voronoi polyhedron generating module 204 specifically includes:
and the three-dimensional voronoi polyhedron generating unit is used for generating the three-dimensional voronoi polyhedron with the overlapped surfaces by using rhino software by taking each screened discrete point as a core.
The downsizing processing module 205 is configured to perform downsizing processing on the three-dimensional voronoi polyhedron to obtain a closed polyhedron.
And the translation module 206 is configured to translate each surface of the closed polyhedron by a preset distance to obtain an entity with a gap inside.
The bone tissue engineering scaffold generating module 207 is configured to generate a bone tissue engineering scaffold by using a boolean operation method according to an external shape profile of the bone tissue engineering scaffold and an entity having a void inside.
And a young modulus determining module 208 for determining the young modulus of the generated bone tissue engineering scaffold.
And the storage module 209 is used for storing the young modulus of the generated bone tissue engineering scaffold, the screened discrete points, materials and preset distances corresponding to the generated bone tissue engineering scaffold into a database.
For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The invention further discloses a generation method of the controllable gradient bone tissue engineering scaffold, which comprises the following steps:
the bone tissue engineering scaffold is used as an implant to be implanted into a bone fracture pathological change part, and not only needs to meet the requirement of being matched with a human bone in the outline shape, but also needs to ensure good contact performance of a contact surface and good cell compatibility, and is beneficial to controlling the growth of cells. The performance requirements for bone tissue engineering scaffolds can be divided into mechanical and biological performance requirements. The mechanical property requirements mainly comprise Young modulus, material density and Poisson ratio, and the biological property requirements mainly comprise pore size and distribution, structural surface roughness, cell compatibility and pore connectivity. The method provided by the invention can consider the Young modulus, density distribution, Poisson ratio, the size and distribution of pores and the connectivity of the pores in the structure by designing the bone tissue engineering scaffold structure. And young's modulus, pore size and distribution, pore connectivity are important goals for design. The bone tissue engineering scaffold was designed and manufactured as follows, as shown in fig. 3.
The method comprises the following steps: and (4) collecting parameters of bones of the lesion part. In order to determine parameters required by design, the acquisition modes mainly include three types: medical scanning, case analysis, attribute requirement analysis. The approximate external structural size and porosity distribution of the bone tissue engineering scaffold are determined from medical scanning of the diseased bone by CT, X-ray, MRI, etc. The pathological analysis can help to determine the pathological part to obtain an accurate external shape profile of the bracket, and can also obtain the gradient distribution condition of the Young modulus of the bone and determine the size and the distribution of the Young modulus of the contact surface by analyzing the original healthy bone and the biomechanical property of the bone.
Step two: analyzing the target performance requirement of the bone tissue engineering scaffold. And analyzing the target performance required to be designed according to the performance parameters acquired in the step one. The target properties considered by the invention are mainly the external shape outline of the bone tissue engineering scaffold, the gradient distribution of Young modulus, the size and distribution of pores and the connectivity among pores related to blood supply.
Step three: designing and processing the bone tissue engineering scaffold. Firstly, materials are selected, and the materials need to have good biological shape and appearance, so that the occurrence of rejection reaction in a human body is avoided. In order to reduce trauma associated with secondary surgery, the desired material needs to be somewhat biodegradable. The structure with pores inside has a young's modulus generally smaller than that of the dense structure of the raw material, so that a material with a young's modulus larger than that of bone, such as a metal material of magnesium alloy, titanium alloy, etc., is selected. The schematic diagram of the optimized design of the structure is shown in fig. 4, and the optimization steps are as follows:
step1, determining the external shape contour of the bone tissue engineering scaffold according to the required external contour shape obtained by the analysis in the step two, wherein the surrounding space of the external shape contour is used as a design space;
step2, controlling the number and distribution of discrete points according to the distribution of the Young modulus gradient obtained in the step two;
step3, generating a series of three-dimensional voronoi polyhedrons by taking each discrete point as a core, wherein the polyhedrons have coincident faces, each core corresponds to one voronoi polyhedron, and the distance from any point in the polyhedrons to the core is smaller than the distance from the point to other core points;
step4, each face of the polyhedron deviates a certain distance h towards the inner direction of the polyhedron to form a closed polyhedron with the same shape and smaller volume;
step5, translating the small closed polyhedron for a distance h in the direction of each surface, and generating a solid between the translated surface and the surface of the small polyhedron, so as to obtain the whole solid volume with a rod-shaped gap inside;
step6, subtracting the solid obtained in step5 from the whole volume of the bone tissue engineering scaffold by Boolean operation to obtain the bone tissue engineering scaffold solid with a rod-shaped bone trabecular structure and interconnected pores, and smoothing.
And Step7, simulating and verifying the tension and compression resistance, the impact resistance, the fatigue resistance, the fluid circulation and the like of the obtained bone tissue engineering scaffold by using simulation software. The processing mode depends on an additive manufacturing technology, the additive manufacturing technology which can be adopted for the metal material is Selective Laser Melting (SLM), and the structure manufactured by the method has high dimensional precision and high mechanical strength and meets the design requirement; for non-metallic materials, photocuring molding (SLA) can be adopted, and the method has the advantages of high precision, short period and high efficiency.
Step four: and (6) testing and verifying. And C, performing a mechanical performance experiment and a biological performance experiment on the bone tissue engineering scaffold structure model entity obtained in the third step. The mechanical property experiment mainly comprises the experimental analysis of the Young modulus, the deformation property, the tensile and compressive strength and the fatigue strength of the contact surface; the biological performance test comprises a cell culture test, an animal implantation test and the like.
As shown in FIG. 5, for step2 of the structure design process of step three, the present invention provides a method for controlling the number and distribution of random points in the design space:
1. randomly generating n discrete points in a designated volume;
2. respectively extracting the x coordinate, the y coordinate and the z coordinate of all discrete points;
3. mapping the coordinate values to (0,1) intervals respectively;
4. for controlling points with high flexibility by setting expressions or graphical functionsDistributing; for example, the function is f (x) ═ x2-x；
5. Taking the mapping value as input, and obtaining the output of the three groups of value domains between (0,1) through the function in the step 4;
6. generating a group of random number sequences with the number of n in the interval (0, 1);
7. comparing the output with the corresponding value in the random number array, obtaining 1 when the value is smaller than the corresponding value, obtaining 0 when the value is other than the corresponding value, and finally respectively obtaining three groups of arrays only with 0 and 1;
8. integrating the three groups of data by using OR logic, and carrying out OR logic operation on the corresponding three numbers to obtain a group of data;
9. deleting the point corresponding to the value 1 in the previous step from the original discrete points;
10. and defining the minimum distance between any two points, and deleting the points with short distances, so as to obtain a discrete point set with certain gradient distribution and density.
In the structural design process of the third step, a database containing the corresponding relationship between the Young modulus and three variables of discrete point number, material and offset can be established preferentially. According to the data of the database, the distribution of core points does not need to be adjusted in the whole design space, after the Young modulus required by each partial region is determined, the corresponding core point number and the offset can be directly appointed in the corresponding region, and different Young moduli can be obtained in different regions.
The invention provides a method for constructing the database, which comprises the following steps:
1. setting a cuboid made of a material a and having a volume of V, and randomly generating N discrete points in the cuboid;
2. generating a Thiessen polyhedron with mutually overlapped surfaces by taking each discrete point as a core;
3. each Thiessen polyhedron is shifted for a certain distance h towards the inner direction of the polyhedron to form a closed polyhedron with the same shape and smaller volume;
4. translating each surface direction of the small polyhedron by a distance h, and generating an entity between the translated surface and the surface of the small polyhedron, so as to obtain the whole entity volume with a rod-shaped gap inside;
5. subtracting the solid obtained in the step4 from the whole volume of the cuboid by Boolean operation to obtain a rod-shaped bone trabecula structure and a bracket structure with interconnected pores (the pore part of the final structure is the solid volume in the step4, and the final solid part is the rod-shaped pore in the step 4);
6. obtaining the relation between the corresponding point number N, the offset h, the material a and the corresponding Young modulus through experimental tests, and calculating the porosity;
7. the point number N, the offset h and the material a are respectively changed once by using a control variable method to obtain the corresponding Young modulus, so that a database containing three variables of discrete point number, material and offset and the corresponding relation of the Young modulus can be obtained, and the corresponding relation of the porosity and the Young modulus is deduced from the database to be used as a reference evaluation structure.
The method provided by the invention is realized by a function formula or a graph function and the like on the control of random point distribution, so that the design is more flexible and adjustable, and more adjustable variability is provided for the gradient change design of the bone tissue engineering bracket in a three-dimensional space; by limiting the minimum distance between two points, the possibility of failure of the offset operation is reduced, the adjustable range of the offset is enlarged, and the possibility of problems in the design process is greatly reduced. The whole structure is smooth, the possibility of stress concentration is reduced, the stability of the structure is improved, and the possibility of damage to the structure is reduced. The invention provides a method for establishing a database, which greatly reduces the time of a design process, improves the efficiency, reduces the total treatment time and reduces the possibility of delaying the treatment time. The method of the invention ensures the mutual communication among the pores and ensures the communication of the pores to a greater extent.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In summary, this summary should not be construed to limit the present invention.
Claims (8)
1. A method for generating a bone tissue engineering scaffold, comprising:
obtaining bone parameters of a lesion part; the parameters of the bone of the lesion part comprise the gradient distribution of the Young modulus of the bone of the lesion part and the external shape profile of the bone of the lesion part;
determining the external shape contour of the bone tissue engineering scaffold according to the external shape contour of the bone of the lesion part;
generating a plurality of discrete points in the external shape outline of the bone tissue engineering scaffold, and screening the generated discrete points according to the gradient distribution of the Young modulus of the skeleton at the lesion part to obtain screened discrete points;
generating a three-dimensional Voronoi polyhedron with mutually overlapped surfaces by taking each screened discrete point as a core;
carrying out reduction treatment on the three-dimensional voronoi polyhedron to obtain a closed polyhedron;
translating each surface of the closed polyhedron for a preset distance to obtain an entity with a gap inside;
and generating the bone tissue engineering scaffold by adopting a Boolean operation method according to the external shape contour of the bone tissue engineering scaffold and the entity with the gap in the interior.
2. The method for generating a scaffold for bone tissue engineering according to claim 1, wherein the step of screening the generated plurality of discrete points according to the gradient distribution of the young's modulus of the bone at the lesion site to obtain the screened discrete points specifically comprises:
acquiring an x-axis coordinate, a y-axis coordinate and a z-axis coordinate of the discrete point;
mapping the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point to a (0,1) interval to obtain three mapping values;
determining a function according to the gradient distribution of the Young modulus of the skeleton at the lesion part, and respectively inputting three mapping values into the function to obtain three output values;
comparing each output value with a preset value to obtain a comparison value; if the output value is smaller than the preset value, the comparison value is 1; if the output value is greater than or equal to the preset value, the comparison value is 0;
performing OR operation on the three comparison values to obtain an operation value; if the operation value is 1, deleting the corresponding discrete point; if the operation value is 0, reserving the corresponding discrete point;
judging whether all discrete points are screened; if so, deleting one of the discrete points in the reserved discrete points, the distance between any two discrete points of which is less than the threshold value, and obtaining the screened discrete points; if not, acquiring the next discrete point, and then returning to the step of acquiring the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point.
3. The method for generating a scaffold for bone tissue engineering according to claim 2, wherein the generating of the scaffold for bone tissue engineering by using a boolean operation method is performed based on the external shape profile of the scaffold for bone tissue engineering and the entity having the void inside, and further comprises:
determining the Young modulus of the generated bone tissue engineering scaffold;
and storing the Young modulus of the generated bone tissue engineering scaffold, the screened discrete points, materials and preset distances corresponding to the generated bone tissue engineering scaffold into a database.
4. The method for generating scaffold for bone tissue engineering according to claim 3, wherein said generating three-dimensional Veno polyhedron having overlapped surfaces with each other with each said screened discrete point as core specifically comprises:
and generating three-dimensional Venuo polyhedrons with coincident faces by taking each screened discrete point as a core and utilizing rhino software.
5. A bone tissue engineering scaffold creation system, comprising:
the lesion site bone parameter acquisition module is used for acquiring lesion site bone parameters; the parameters of the bone of the lesion part comprise the gradient distribution of the Young modulus of the bone of the lesion part and the external shape profile of the bone of the lesion part;
the external shape contour determining module of the bone tissue engineering scaffold is used for determining the external shape contour of the bone tissue engineering scaffold according to the external shape contour of the bone of the lesion part;
the discrete point screening module is used for generating a plurality of discrete points in the external shape outline of the bone tissue engineering scaffold, and screening the generated discrete points according to the gradient distribution of the Young modulus of the skeleton of the lesion part to obtain the screened discrete points;
the three-dimensional voronoi polyhedron generating module is used for generating three-dimensional voronoi polyhedrons with coincident surfaces by taking each screened discrete point as a core;
the three-dimensional Voronoi polyhedron is subjected to reduction treatment to obtain a closed polyhedron;
the translation module is used for translating each surface of the closed polyhedron for a preset distance to obtain an entity with a gap inside;
and the bone tissue engineering scaffold generating module is used for generating the bone tissue engineering scaffold by adopting a Boolean operation method according to the external shape contour of the bone tissue engineering scaffold and the entity with the gap in the interior.
6. The bone tissue engineering scaffold generation system according to claim 5, wherein said discrete point screening module specifically comprises:
the coordinate acquisition unit is used for acquiring the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point;
the mapping unit is used for mapping the x-axis coordinate, the y-axis coordinate and the z-axis coordinate of the discrete point to a (0,1) interval to obtain three mapping values;
the function calculation unit is used for determining a function according to the gradient distribution of the Young modulus of the skeleton at the lesion part and respectively inputting the three mapping values into the function to obtain three output values;
the comparison unit is used for comparing each output value with a preset value to obtain a comparison value; if the output value is smaller than the preset value, the comparison value is 1; if the output value is greater than or equal to the preset value, the comparison value is 0;
the OR operation unit is used for carrying out OR operation on the three comparison values to obtain an operation value; if the operation value is 1, deleting the corresponding discrete point; if the operation value is 0, reserving the corresponding discrete point;
the judging unit is used for judging whether all the discrete points are screened; if yes, executing an output unit; if not, acquiring the next discrete point, and then executing the coordinate acquisition unit;
the output unit is used for deleting one of the two discrete points with the distance smaller than the threshold value, and then outputting the screened discrete points.
7. The bone tissue engineering scaffold generation system according to claim 6, further comprising:
the Young modulus determining module is used for determining the Young modulus of the generated bone tissue engineering scaffold;
and the storage module is used for storing the Young modulus of the generated bone tissue engineering scaffold, the screened discrete points, materials and preset distances corresponding to the generated bone tissue engineering scaffold into a database.
8. The bone tissue engineering scaffold generation system according to claim 7, wherein said three-dimensional voronoi polyhedron generation module specifically comprises:
and the three-dimensional voronoi polyhedron generating unit is used for generating the three-dimensional voronoi polyhedron with the overlapped surfaces by using rhino software by taking each screened discrete point as a core.
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