CN111400953A - Simulation system for distraction osteogenesis - Google Patents

Abstract

A simulation system for distraction osteogenesis relates to the technical field of numerical simulation. The invention can reproduce the complex bone regeneration dynamic process and the osteogenesis effect in the distraction osteogenesis, can be used for determining the distraction scheme with the optimal bone regeneration effect, and provides preoperative guidance for clinical distraction osteogenesis operation. The system comprises an individualized three-dimensional reconstruction module of an osteotomy region of a subject, a tension parameter setting module, a computational biomechanics analysis module of the osteotomy region, a bone regeneration dynamic process simulation module and a display module. The osteotomy region individualized three-dimensional reconstruction module is used for reconstructing a real geometric model of the osteotomy region on the basis of the medical image of the object. The tension parameter setting module is used for setting different tension loading modes and parameters. The osteotomy region computational biomechanics analysis module is used for establishing a biomechanics model and performing finite element analysis. The bone regeneration dynamic process simulation module is used for reproducing a bone regeneration process of the callus. The display module is used for displaying the result of the simulation calculation.

Description

A simulation system for distraction osteogenesis

Technical field:

The invention relates to the technical field of numerical simulation, in particular to a simulation system for distraction osteogenesis.

Background technique:

Distraction osteogenesis is to cut the bone through osteotomy, and use the distractor to apply stable and slow distraction to the bone tissue to stimulate the regeneration and growth of tissue cells, and promote the formation and mineralization of new bone in the distraction gap. So as to achieve the purpose of lengthening the bones. At present, the biggest drawback of distraction osteogenesis in clinical practice is the slow formation and mineralization of new bone, which leads to a long retention time of the distractor and a long treatment period, which brings great inconvenience to the life and work of patients. According to clinical reports, distraction stent fixation time required for the treatment of lower extremity (femur and tibia) bone defects by distraction osteogenesis can range from 10 months to 3 years. In addition, about 35% to 68% of distraction osteogenesis have problems such as delayed or non-union of bone union. Therefore, it is of great clinical and practical value to study how to accelerate the formation and mineralization of new bone in distraction osteogenesis to shorten the treatment period. The rate of new bone formation and mineralization during distraction osteogenesis depends on the applied distraction mode (eg, distraction rate, distraction frequency, distraction duration, and application of coupled distraction-compression stimulation during consolidation). period, traction-compression coupled load application rate, traction-compression coupled load application frequency, and stretcher stiffness, etc.), but currently, the choice of stretch mode is mostly based on doctor’s experience, and there is no one available for doctors to choose the best stretch before surgery. pattern tool.

The simulation of the distraction osteogenesis system simulates and displays the dynamic process of bone regeneration and osteogenic results under the stimulation of distraction mechanics in a procedural manner by establishing a mechanobiological model. Using computer simulation technology to simulate distraction osteogenesis, setting different distraction combined loading parameters, reproducing the complex dynamic process of bone regeneration in distraction osteogenesis, it is convenient for doctors to find the best distraction mode for clinical objects. It can shorten the period of distraction osteogenesis and reduce the incidence of complications.

Invention content:

The purpose of the present invention is to provide a simulation system for distraction osteogenesis, which can describe the viscoelastic-plastic behavior of the callus in the osteotomy area according to the patient's personalized simulation model, and use fuzzy logic to realize the tissue differentiation based on strain regulation for numerical analysis , reproduce the complex dynamic process of bone regeneration in distraction osteogenesis, facilitate doctors to find the best mechanical stimulation conditions for patients, help to shorten the entire treatment time, and thus reduce the incidence of complications.

In order to achieve the above object, the present invention provides a simulation system for distraction osteogenesis. The simulation system for distraction osteogenesis is based on the fact that during the implementation of distraction osteogenesis, applying different distraction conditions will cause different tissue in the callus area. Osteogenic effect; by simulating the bone regeneration process of distraction osteogenesis, the optimal distraction loading mode is determined according to the output osteogenesis results;

The simulation system for distraction osteogenesis includes an A1 object osteotomy area individualized three-dimensional reconstruction module, A2 distraction parameter setting module, A3 osteotomy area computational biomechanical analysis module, A4 bone regeneration dynamic process simulation module and A5 display module;

The system A1 object osteotomy area individualized 3D reconstruction module is used to automatically segment and perform 3D reconstruction of the CT image of the object osteotomy area, obtain an individualized 3D geometric model of the object osteotomy area, and then perform grid division processing;

The system A2 distraction parameter setting module is used to set different mechanical loading modes for the individualized three-dimensional osteotomy area finite element model of the object, as the input of the A3 osteotomy area computational biomechanical analysis module;

The system A3 osteotomy area computational biomechanical analysis module is used to set the loading parameters input from the A2 distraction parameter setting module, set the bone linear elastic biomechanical model and the callus area viscoelastic biomechanical model, and perform simulated distraction determination Mechanical stimulation state of the callus area;

The system A4 dynamic process simulation module of bone regeneration is used to take the strain results obtained by finite element analysis as input, use fuzzy logic control to determine the position of the strain state on the tissue differentiation map, and output the results of tissue type changes to update tissue materials type, reproducing the process of bone regeneration of callus;

The system A5 display module is used to display the calculation results of the distraction osteogenesis simulation system.

Further, the individualized three-dimensional reconstruction module of the A1 osteotomy area of the object is used to obtain an individualized geometric and finite element model of the osteotomy area of the object. The model consists of two parts: cortical bone and callus. Set the initial state of the finite element model of the osteotomy area. The initial state settings include the initial cortical bone content of 100%, the cartilage content of 0% and the blood supply of 100%, the initial callus region of 0% of bone content, 0% of cartilage content and 0% of blood supply. Save in an Excel file;

Further, different stretch-loading combination parameters were set through A2. The setting parameters of the A2 stretch parameter setting module include: stretch rate, stretch frequency, stretch duration, stretch-compression coupled stimulation period, stretch-compression coupled load application rate, stretch Coupled load application frequency and stretcher stiffness, etc.;

Further, the A3 osteotomy area computational biomechanical analysis module is used to set the boundary conditions and material properties according to the loading parameters input by the A2 distraction parameter setting module; setting the material properties includes: setting cortical bone Young's in the user material of ABAQUS Modulus, Poisson's ratio and Young's modulus of callus, Poisson's ratio, yield stress, viscosity coefficient (material type is defined by UMAT subroutine including viscoelastic-plastic biomechanical model), callus area is assumed to be filled at initial stage Connective tissue, perform simulated distraction to obtain mechanically stimulated strain states in the callus area, including:

B1. Set the viscoelastic plastic model of the callus area

A viscoelastic biomechanical model of the callus region was established using the Bingham-Maxwell viscoelastic plastic model, which consisted of a linear spring, a Newtonian stick pot and a friction element. By establishing the biomechanical model of cortical bone and callus, UMAT subprogram was written to calculate the viscoelastic-plastic behavior of callus area.

B2. Calculate the strain state of the callus area

Viscoelastic-plastic finite element analysis was performed in ABAQUS to obtain the strain curve of each element of the finite element model with time. For each stretch time period, use n _diff to equally divide the strain samples for each stretch time period, and sample by the maximum peak stimulus for each sample to obtain n _diff distortion strain γ ₀ and dilation for the tissue differentiation algorithm strain ε ₀ ;

In the formula, ε ₁ , ε ₂ , and ε ₃ are the three principal strains of each element, respectively.

Further, the A4 bone regeneration dynamic process simulation module takes the results of the distortion strain γ ₀ and the expansion strain ε ₀ of each element of the finite element model of the osteotomy area obtained from the B2 finite element analysis as input, and uses fuzzy logic control to determine the strain state in tissue differentiation. position on the map, and output the results of tissue type changes, update tissue material types, and reproduce the bone regeneration process of callus, including:

C1. Establish a tissue differentiation model

Seven variables for each element in the finite element model of the osteotomy area (i.e. all cortical bone and callus) were used as inputs, including: the percentage of bone content in the element, the percentage of cartilage content in the element, the expansion strain of the element, the Distortion strain, vascularity of cells, effect of bone content in adjacent cells and effect of blood supply to adjacent cells. Establish fuzzy rules including angiogenesis, intramembranous ossification, chondrogenesis, endochondral ossification, tissue destruction, bone maturation and bone resorption to describe the results of tissue differentiation under mechanical stimulation, and finally output the bone of each unit, Percent change in cartilage and blood vessel content.

C2. Update material properties

1) Defuzzify the fuzzy value output by the fuzzy logic control of step C1 to obtain the change amount of the output variable, thereby obtaining the change amount ΔC _i of blood supply, bone and cartilage content in each unit of tissue differentiation:

where C _perf is the blood supply content in each unit, C _bone is the bone content in each unit, and C _cart is the cartilage content in each unit;

C _bone =C _lamellar +C _woven

In the formula, C _lamellar is the lamellar bone content in each unit, and C _woven is the woven bone content in each unit;

C _i+1 =ΔC _i Δt+C _i

The above formula is an iterative function, C _i+1 is the corresponding blood supply, bone or cartilage content in the current time unit, C _i is the corresponding blood supply, bone and cartilage content in the previous time unit, Δt is the time step.

At the end of each update tissue content run, it is necessary to gradually renormalize the blood supply, bone and cartilage content C _i of each unit of the finite element model of the osteotomy area (i.e. all cortical bone and callus): for each unit of blood in the cortical bone area If the contents of blood supply, bone and cartilage remain unchanged at the initial state, the corresponding Young's modulus and Poisson's ratio of cortical bone remain unchanged; the blood supply, bone and cartilage contents of each unit in the callus area are updated and the range is 0≤C _i ≤ 1;

2) in the process of the whole stretch step, call the fuzzy logic controller n _diff times to calculate the changes of blood supply, bone and cartilage content C _i of each unit;

3) Then update the material properties of each unit in the callus area according to the content of bone, cartilage and connective tissue in each unit of the callus area;

Among them: C _coon = 1-C _bone -C _cart

In the formula, C _coon is the content of connective tissue in each unit

For the update of the Young's modulus E _ele per cell in the callus area, use:

In the formula, E _lamellar is the Young's modulus of lamellar bone, E _woven is the Young's modulus of woven bone, E _cart is the Young's modulus of cartilage, and E _coon is the Young's modulus of connective tissue, and the above-mentioned Young's modulus is determined by obtained experimentally;

For the update of the Poisson's ratio υ _ele per cell in the callus region, use:

υ _ele =υ _lamellar C _lamellar +υ _woven C _woven +υ _cart C _cart +υ _coon C _coon

In the formula, υ _lamellar is the Poisson’s ratio of lamellar bone, υ _woven is the Poisson’s ratio of woven bone, υ _cart is the Poisson’s ratio of cartilage, and υ _coon is the Poisson’s ratio of connective tissue, and the above Poisson’s ratios are obtained by experiments;

Further, the initial bone, cartilage and blood supply contents in the C1 are obtained through step A1, that is, if the unit is a unit in the cortical bone, the parameters corresponding to the unit in the cortical bone are used, and if the unit is a unit in the callus, the callus is used. The parameters corresponding to the middle element; the influence of adjacent elements is to sample the centroid of each finite element element, use the Chebyshev distance to obtain the adjacent area of each element, and then use the Gaussian kernel function to determine each phase of the adjacent area. The weight of the influence of adjacent units on it, and finally the influence of adjacent units in the adjacent area is determined by weighted average.

Further, the bone maturation and bone resorption rules in C1 are not really implemented with fuzzy logic, but as separate post-processing steps. This separation is to achieve that the different resorption rates of woven and lamellar bone have different effects on osteogenesis and are distinct from the reduction in bone content caused by the tissue destruction process.

Further, the simulation system of distraction osteogenesis takes the output result of the A4 bone regeneration dynamic process simulation module as an input, and sends it back to the A3 osteotomy area calculation biomechanical analysis module, and enters the next analysis step calculation until the distraction ends. The bone content of all units at the callus is 100%, the simulation ends and the osteogenesis results are output.

Further, in the simulation system of distraction osteogenesis, in the iterative process, it is also necessary to perform finite element mesh re-division and state data mapping on the large deformed element in the callus region of the previous analysis step due to distraction loading, including: (1 ) Reshape the deformed mesh model to generate an undivided geometric model; (2) Use the mesh size of the previous unit to mesh the new deformed geometric model to obtain a new deformed geometric model. Distortion-free grid; (3) Each new grid determines the volume of the intersecting part with each old grid according to its location, and calculates the weight of the volume of the intersecting part in the current grid; (4) Combine the old grid The current state of each cell of the grid is assigned to the corresponding cell of the new grid according to its corresponding weighted sum.

In the simulation system for distraction osteogenesis provided by the present invention, the simulation system for distraction osteogenesis is based on the fact that different distraction conditions will cause different osteogenic effects in the callus area during the implementation of distraction osteogenesis; The bone regeneration process of distraction osteogenesis is simulated and calculated, and the best distraction loading mode is determined according to the output osteogenesis results; in addition, the present invention provides personalized parameter settings for patients in the distraction parameter setting module, including: distraction period stretch rate, stretch period stretch frequency, stretch period duration, stretch-compression coupled stimulus period applied during consolidation period, stretch-compression coupled load application rate, stretch-compression coupled load application frequency, and stretcher stiffness; user can Customized stretch parameters make it easier for doctors to find the best mechanical stimulation conditions for the patient, which can help shorten the entire treatment time, thereby reducing the incidence of complications.

In addition, the simulation system software of distraction osteogenesis of the present invention adopts a modular structure, the simulation program has good scalability, and the operation is convenient, and the fuzzy logic is used to realize the numerical analysis of tissue differentiation based on strain regulation, which improves the system design. The efficiency and accuracy can also be used in other similar bone regeneration system designs.

Description of drawings:

Fig. 1 is the schematic diagram of the simulation system of distraction osteogenesis of the present invention;

Fig. 2 is the flow chart of the simulation system implementation of distraction osteogenesis of the present invention;

Fig. 3 is a schematic diagram of a fuzzy rule established by the present invention

Detailed ways:

A simulation system for distraction osteogenesis proposed by the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Example 1

The present embodiment provides a simulation system for distraction osteogenesis, and the simulation system for distraction osteogenesis may cause different osteogenic effects of callus area tissue by applying different distraction conditions during the implementation of distraction osteogenesis; By simulating the bone regeneration process of distraction osteogenesis, the optimal distraction loading mode is determined according to the output osteogenesis results; as shown in Figure 1, the simulation system of distraction osteogenesis includes the osteotomy area of the A1 object Individualized 3D reconstruction module, A2 distraction parameter setting module, A3 osteotomy area computational biomechanical analysis module, A4 bone regeneration dynamic process simulation module and A5 display module. The system object osteotomy region individualized 3D reconstruction module described in A1 is used to automatically segment and perform 3D reconstruction of the CT image of the object osteotomy region, obtain an individualized 3D geometric model of the object osteotomy region, and then perform grid division processing; The system distraction parameter setting module in A2 is used to set different mechanical loading modes for the individualized three-dimensional osteotomy area finite element model of the object, which is used as the input of the biomechanical analysis module for calculating the osteotomy area in A3; the system osteotomy area calculation in A3 The biomechanical analysis module is used to set the loading parameters input from the module according to the A2 stretch parameters, and to set the boundary conditions and material properties. Setting the material properties includes: setting the Young's modulus of cortical bone, Poisson's ratio and Young's modulus of callus, Poisson's ratio, yield stress, viscosity coefficient (via the UMAT subsection containing the viscoelastic-plastic biomechanical model) in ABAQUS's User Materials The program defines the material type), the initial stage of the callus area is assumed to be filled with connective tissue, and simulated distraction is performed to determine the mechanical stimulation state of the callus area; the dynamic process simulation module of the system described in A4 is used to simulate the strain obtained by the finite element analysis. The result is used as input, and fuzzy logic control is used to determine the position of the strain state on the tissue differentiation map, and output the result of tissue type change, update the tissue material type, and reproduce the bone regeneration process of the callus; the system display module described in A5 is used to display The calculation results of the distraction osteogenesis simulation system.

As shown in Figures 1-2, in the described distraction osteogenesis simulation system, the required parameters set by the A2 distraction parameter setting module include: distraction rate, distraction frequency, distraction period duration, period of application of distraction-compression coupled stimulation during consolidation phase, rate of distraction-compression coupled load application, frequency of distraction-compression coupled load application, and distractor stiffness; in addition, the A4 bone regeneration dynamic process needs to be The output result of the simulation module is used as input, which is returned to the A3 osteotomy area calculation biomechanical analysis module, and the next analysis step is calculated until the bone content of all units at the callus after the distraction is 100%, and the simulation ends and the osteogenesis result is output. . In addition, in the iterative process, it is also necessary to perform finite element mesh re-division and state data mapping for the large-deformed elements in the callus region of the previous analysis step due to distraction loading, including: (1) The deformed mesh model is modeled Reshape to generate an ungridded geometric model; (2) use the mesh size of the previous element to mesh the deformed new geometric model to obtain a new deformed undistorted mesh; (3) each The new grid judges the volume of the intersecting part with each old grid according to its location, and calculates the weight of the volume of the intersecting part in the current grid; (4) Calculate the current state of each unit of the old grid according to its The corresponding weighted sums are assigned to the corresponding cells of the new grid.

Specifically, in the described distraction osteogenesis simulation system, the individualized 3D reconstruction module of the osteotomy area of the A1 object is used to perform CT scanning, obtain the CT image of the osteotomy area of the object, and automatically segment the CT image into the osteotomy of the object 3D reconstruction and meshing are performed to obtain the individualized geometric and finite element model of the osteotomy area of the object. The model consists of two parts: cortical bone and callus. Set the initial state of the finite element model of the osteotomy area. The initial state settings include the initial cortical bone content of 100%, the cartilage content of 0% and the blood supply of 100%, the initial callus region of 0% of bone content, 0% of cartilage content and 0% of blood supply. Saved in an Excel file.

Specifically, in the described distraction osteogenesis simulation system, the A3 osteotomy area computational biomechanical analysis module sets the boundary conditions and material properties according to the loading parameters input from the A2 distraction parameter setting module. Setting the material properties includes: setting the Young's modulus of cortical bone, Poisson's ratio and Young's modulus of callus, Poisson's ratio, yield stress, viscosity coefficient (via the UMAT subsection containing the viscoelastic-plastic biomechanical model) in ABAQUS's User Materials procedure to define the material type), the callus area is assumed to be filled with connective tissue at the initial stage;

B1. Set the linear elastic biomechanical model of cortical bone:

σ _s =E _s ε _s (1)

where σ _s is the linear elastic model stress, E _s is the linear elastic model elastic modulus, ε _s is the linear elastic model strain;

and a viscoelastic biomechanical model of the callus region (Bingham-Maxwell viscoelastic plastic model):

in

where σ is the stress of the viscoelastic-plastic model, η is the viscosity coefficient, E _f is the elastic modulus of the visco-elastic-plastic model, σ _yield is the critical stress of the visco-elastic-plastic model, ε is the strain of the visco-elastic-plastic model, and t is the time.

Input the above-obtained constitutive equations (1) and (2) into the UMAT subroutine of ABAQUS, and simulate the distraction to obtain the mechanically stimulated strain state of the callus area;

B2. Arrangement of strain result data, including:

Viscoelastic finite element analysis was performed in ABAQUS to obtain the strain curve of each element of the finite element model with time. For each stretch cycle, n _diff equidistant strain samples were used to sample the maximum peak stimulus per sample, resulting in n _diff strain components for the tissue differentiation algorithm.

where for each element strain component is:

where [ε] is the principal strain of the element, and ε ₁₁ , ε ₂₂ , ε ₃₃ , ε ₁₂ , ε ₂₃ , and ε ₁₃ are the six strain components obtained by ABAQUS;

The three principal strains of each element of the finite element model are obtained by solving the above equations:

where ε ₁ , ε ₂ , and ε ₃ are the three principal strains of each element, respectively;

The distortion strain of each element of the finite element model can be obtained from the principal strain:

In the formula, γ ₀ is the distortion strain received by each element of the finite element model;

The expansion strain of each element of the finite element model can be obtained from the principal strain:

In the formula, ε ₀ is the expansion strain experienced by each element of the finite element model.

Specifically, in the described distraction osteogenesis simulation system, the A4 dynamic process simulation module of bone regeneration uses fuzzy logic control to determine the position of the strain state on the tissue differentiation map, output the results of tissue type changes, and update tissue materials type that reproduces the bone regeneration process of callus. include:

C1. Establish a tissue differentiation model

1), establish the input variable membership function;

Seven variables for each element in the finite element model of the osteotomy area (i.e. all cortical bone and callus) were used as inputs, including: the percentage of bone content in the element, the percentage of cartilage content in the element, the expansion strain of the element, the Distortion strain, blood supply to cells, percentage of bone content in adjacent cells, and blood supply to adjacent cells. Among them, the initial bone, cartilage and blood supply contents are obtained through step A1, that is, if the unit is a unit in the cortical bone, the parameters corresponding to the unit in the cortical bone are used, and if the unit is a unit in the callus, the parameter corresponding to the unit in the callus is used. Parameter; the influence of adjacent units is obtained by sampling the centroid of each finite element unit, using the Chebyshev distance to obtain the adjacent area of each unit, and then judging the influence of each adjacent unit in the adjacent area by the Gaussian kernel function. Finally, the influence of adjacent units in adjacent areas is determined by weighted average.

2), establish fuzzy control rules

Establish fuzzy control rules that describe tissue differentiation such as angiogenesis, intramembranous ossification, chondrogenesis, endochondral ossification and tissue destruction under mechanical stimulation (distortion strain and expansion strain) (such as establishing a 17 if-then language Fuzzy control rules), corresponding tissue differentiation occurs if the conditions of rules are present or are met, these rules describe angiogenesis, intramembranous ossification, chondrogenesis, endochondral bone under mechanical stimuli (distortion strain and expansion strain) process of transformation and tissue destruction.

For example, the fuzzy controller consists of 17 language if-then rules (see Figure 3). If the above-mentioned if-then conditions exist, the corresponding tissue differentiation will occur. These rules describe the processes of angiogenesis, intramembranous ossification, chondrogenesis, endochondral ossification and tissue destruction under mechanical stimuli (distorting and distending strain).

Rules 1 to 3 represent angiogenesis under the influence of mechanical stimulation and blood supply to adjacent regions. The blood supply is increased when there is moderate strain and not low blood supply to the adjacent area.

Rules 4 to 5 describe intramembranous ossification. Areas of low mechanical stimulation and adequate blood supply will have increased bone density if the adjacent area cells are not low in bone density.

Rules 6 to 8 describe cartilage formation. Occurs under high mechanical stimulation and is not affected by blood supply.

Rules 9 to 12 represent cartilage calcification. A higher cartilage concentration is required and is influenced by the adjacent bone concentration. Occurs under conditions of adequate blood supply and relatively high mechanical stimulation.

Rules 13 to 14 represent endochondral ossification. Occurs with moderate or high blood supply.

Rules 15 to 17 simulate tissue damage from mechanical stimulation overload.

Furthermore, an additional rule was added in fuzzy logic to describe the process of bone maturation and bone resorption.

3), establish the output variable membership function;

After the tissue differentiation process described by fuzzy rules, the change of blood supply in each unit, the change in bone content in each unit and the change in cartilage content in each unit are finally output.

C2. Update material properties

1) Defuzzify the fuzzy value output by the fuzzy logic control of step C1 to obtain the change amount of the output variable, thereby obtaining the change amount ΔC _i of blood supply, bone and cartilage content in each unit of tissue differentiation:

where C _perf is the blood supply content in each unit, C _bone is the bone content in each unit, and C _cart is the cartilage content in each unit;

C _bone =C _lamellar +C _woven (9)

In the formula, C _lamellar is the lamellar bone content in each unit, and C _woven is the woven bone content in each unit;

C _i+1 =ΔC _i Δt+C _i (10)

The above formula is an iterative function, C _i+1 is the corresponding blood supply, bone or cartilage content in the current time unit, C _i is the corresponding blood supply, bone and cartilage content in the previous time unit, Δt is the time step.

At the end of each update tissue content run, it is necessary to gradually renormalize the blood supply, bone and cartilage content C _i of each unit of the finite element model of the osteotomy area (i.e. all cortical bone and callus): for each unit of blood in the cortical bone area The contents of blood supply, bone and cartilage remain unchanged in the initial state, and the Young's modulus and Poisson's ratio of cortical bone also remain unchanged; the blood supply, bone and cartilage contents of each unit in the callus area are updated and set to the range 0≤C _i ≤ 1;

2) in the process of the whole stretch step, call the fuzzy logic controller n _diff times to calculate the changes of blood supply, bone and cartilage content C _i of each unit;

3) Then update the material properties of each unit in the callus area according to the content of bone, cartilage and connective tissue in each unit of the callus area;

Where: C _coon = 1-C _bone -C _cart (11)

In the formula, C _coon is the content of connective tissue in each unit

For the update of the Young's modulus E _ele per cell in the callus area, use:

In the formula, E _lamellar is the Young's modulus of lamellar bone, E _woven is the Young's modulus of woven bone, E _cart is the Young's modulus of cartilage, and E _coon is the Young's modulus of connective tissue, and the above-mentioned Young's modulus is determined by obtained experimentally;

For the update of the Poisson's ratio υ _ele per cell in the callus region, use:

v _ele =v _lamellar C _lamellar +v _woven C _woven +v _cart C _cart +v _coon C _coon (13)

In the formula, v _lamellar is the Poisson's ratio of lamellar bone, v _woven is the Poisson's ratio of woven bone, v _cart is the Poisson's ratio of cartilage, and υ _coon is the Poisson's ratio of connective tissue, and the above Poisson's ratios are obtained by experiments;

Finally, the optimal distraction loading mode was determined by comparing the osteogenesis results in the simulation calculation of loading with each combination of parameters.

In the simulation system for distraction osteogenesis provided by the present invention, the simulation system for distraction osteogenesis is based on the fact that different distraction conditions will cause different osteogenic effects in the callus area during the implementation of distraction osteogenesis; The bone regeneration process of distraction osteogenesis is simulated and calculated, and the best distraction loading mode is determined according to the output osteogenesis results; in addition, the present invention provides personalized parameter settings for patients in the distraction parameter setting module, including: distraction period stretch rate, stretch period stretch frequency, stretch period duration, stretch-compression coupled stimulus period applied during consolidation period, stretch-compression coupled load application rate, stretch-compression coupled load application frequency, and stretcher stiffness; user can Customized stretch parameters make it easier for doctors to find the best mechanical stimulation conditions for the patient, which can help shorten the entire treatment time, thereby reducing the incidence of complications.

In addition, the simulation system software of distraction osteogenesis of the present invention adopts a modular structure, and the simulation program has good scalability, convenient operation and operation, and uses fuzzy logic to realize the numerical analysis of tissue differentiation based on strain regulation, which improves the system design. The efficiency and accuracy can also be used in other similar bone regeneration system designs.

To sum up, the above embodiments describe in detail the implementation configuration of the simulation system for distraction osteogenesis. Of course, the present invention includes but is not limited to the configurations listed in the above embodiments, any configuration provided in the above embodiments Changes made on the basis belong to the scope of protection of the present invention. Those skilled in the art can draw inferences from the contents of the foregoing embodiments.

Claims (9)

1. The simulation system for distraction osteogenesis is characterized in that different distraction conditions are applied to cause different osteogenesis effects of callus region tissues according to the distraction osteogenesis implementation process; the optimal tension loading mode is judged according to the output osteogenesis result by performing simulation calculation on the bone regeneration process of tension osteogenesis;

the distraction osteogenesis simulation system comprises an A1 object osteotomy region individualized three-dimensional reconstruction module, an A2 distraction parameter setting module, an A3 osteotomy region computational biomechanics analysis module, an A4 bone regeneration dynamic process simulation module and an A5 display module;

the system A1 individualized three-dimensional reconstruction module of the object osteotomy region is used for automatically segmenting and carrying out three-dimensional reconstruction on a CT image of the object osteotomy region to obtain an individualized three-dimensional geometric model of the object osteotomy region, and then carrying out mesh division processing;

the system A2 stretch parameter setting module is used for setting different mechanical loading modes for the finite element model of the individualized three-dimensional osteotomy region of the object, and the mechanical loading modes are used as the input of the A3 computational biomechanics analysis module for the osteotomy region;

the system A3 osteotomy region computational biomechanics analysis module is used for setting a bone line elastic biomechanics model and a callus region viscoelastic-plastic biomechanics model according to loading parameters transmitted by the A2 stretching parameter setting module, and performing simulated stretching to determine the mechanical stimulation state of the callus region;

the system A4 bone regeneration dynamic process simulation module is used for taking a strain result obtained by finite element analysis as input, determining the position of a strain state on a tissue differentiation diagram by using fuzzy logic control, outputting a result of tissue type change, updating the tissue material type and reproducing the bone regeneration process of callus;

the system A5 display module is used for displaying the calculation result of the distraction osteogenesis simulation system.

2. The distraction osteogenesis simulation system of claim 1, wherein said a1 individual three-dimensional reconstruction module of the osteotomy region of the subject is adapted to obtain individual geometric and finite element models of the osteotomy region of the subject. The model consists of two parts: cortical bone and callus. And setting an initial state of the finite element model of the osteotomy region. The initial state settings included an initial cortical bone content of 100%, a cartilage content of 0% and a blood supply of 100%, an initial callus region bone content of 0%, a cartilage content of 0% and a blood supply of 0%, and were saved in an Excel file.

3. The distraction osteogenesis simulation system of claim 1, wherein different distraction loading combination parameters are set via a 2; the A2 stretch parameter setting module sets parameters including: the stretching rate in the stretching period, the stretching frequency in the stretching period, the duration of the stretching period, the strengthening period applied with the stretching-compression coupling stimulation period, the applying rate of the stretching-compression coupling load, the applying frequency of the stretching-compression coupling load and the rigidity of the stretching device.

4. The distraction osteogenesis simulation system of claim 1, wherein said A3 osteotomy region computational biomechanical analysis module is configured to set boundary conditions and material properties based on loading parameters received from said a2 distraction parameter setting module; setting material properties includes: the Young modulus of cortical bone, Poisson ratio and Young modulus of callus, Poisson ratio, yield stress and viscosity coefficient are set in user materials of ABAQUS, the callus area is assumed to be filled with connective tissue at the initial stage, and the mechanical stimulation strain state of the callus area is obtained by performing simulated stretching, which comprises the following steps:

b1 viscoelastic-plastic model for setting callus region

A viscoelastic biomechanical model of a callus region is established by utilizing a Bingham-Maxwell viscoelastic-plastic model, and the viscoelastic-plastic model consists of a linear spring, a Newton viscous pot and a friction piece. Compiling a UMAT subprogram by establishing a biomechanical model of cortical bone and callus, and calculating viscoelastic-plastic behavior of a callus region;

b2, calculating the strain state of the callus area

Viscoelastic-plastic finite element analysis is carried out in ABAQUS to obtain the change curve of each element strain of the finite element model along with time. For each stretch time period, use n_diffEqually dividing the strain sample of each stretch time period, sampling according to the maximum peak value stimulation of each sample to obtain n_diffDistortion strain gamma for tissue differentiation algorithm₀And strain of expansion₀；

In the formula (I), the compound is shown in the specification,₁,₂,₃three main strains of each cell.

5. The distraction osteogenesis simulation system of claim 1, wherein said a4 bone regeneration dynamic process simulation module performs B2 finite element analysis to obtain distortion strain γ of each element of the finite element model of the osteotomy region₀And strain of expansion₀And the result is used as an input, the fuzzy logic control is used for determining the position of the strain state on the tissue differentiation graph, the result of the change of the tissue type is output, the tissue material type is updated, and the bone regeneration process of the callus is reproduced, and the method comprises the following steps:

c1, establishing tissue differentiation model

Taking seven variables of each element in the finite element model of the osteotomy region as input, the method comprises the following steps: the percentage of bone content in the cell, the percentage of cartilage content in the cell, the expansion strain of the cell, the distortion strain of the cell, the vascularity of the cell, the effect of bone content in adjacent cells and the effect of blood supply to adjacent cells; establishing fuzzy rules including angiogenesis, intramembranous ossification, chondrogenesis, endochondral ossification, tissue destruction, bone maturation and bone resorption, describing tissue differentiation results under the action of mechanical stimulation, and finally outputting the percentage of content change of the bone, cartilage and blood vessels of each unit;

c2, updating material properties

1) Defuzzification is carried out on the fuzzy value output by the fuzzy logic control in the step C1 to obtain the change quantity of the output variable, thereby obtaining the change quantity delta C of the blood supply, the bone and the cartilage content in each unit of tissue differentiation_i：

In the formula C_perfIs the blood supply content in each unit, C_boneIs the bone content in each unit, C_cartIs the cartilage content in each unit;

C_bone＝C_lamellar+C_woven

in the formula, C_lamellarFor lamellar bone content in each cell, C_wovenKnitting bone content for each unit;

C_i+1＝ΔC_iΔt+C_i

the above formula is an iterative function, C_i+1Is the corresponding blood supply, bone or cartilage content, C, in the current time unit_iCorresponding blood supply, bone and cartilage contents in the previous time unit are obtained, and delta t is a time step;

at the end of each run of updating the tissue content, it is necessary to progressively update the blood supply, bone and cartilage content C of the elements of the finite element model of the osteotomy zone (i.e. all the cortical bones and callus)_iAnd (3) re-normalization: keeping the blood supply, bone and cartilage content of each unit in the cortical bone region unchanged, and keeping the Young modulus and Poisson ratio of the corresponding cortical bone unchanged; the blood supply, bone and cartilage content of each unit in the callus region are updated and ranged0≤C_i≤1；

2) Calling n during the entire stretch step_diffThe sub-fuzzy logic controller is used for calculating the blood supply, the bone and the cartilage content C of each unit_iA change in (c);

3) then updating the material properties of each unit in the callus region according to the content of bone, cartilage and connective tissue in each unit in the callus region;

wherein C is_coon＝1-C_bone-C_cart

In the formula, C_coonThe association content in each unit

Young's modulus E per unit for callus region_eleUsing:

in the formula, E_lamellarYoung's modulus of lamellar bone, E_wovenYoung's modulus for braided bone, E_cartYoung's modulus of cartilage, E_coonThe Young's modulus of connective tissue is obtained through experiments;

poisson ratio upsilon per unit for callus region_eleUsing:

υ_ele＝υ_lamellarC_lamellar+υ_wovenC_woven+υ_cartC_cart+υ_coonC_coon

in the formula, u_lamellarIs the poisson ratio of lamellar bone, upsilon_wovenIs a braided bone Poisson's ratio, upsilon_cartIs cartilage Poisson's ratio, upsilon_coonThe poisson's ratio of connective tissue, which is obtained experimentally.

6. The simulation system for distraction osteogenesis according to claim 4, wherein the initial bone, cartilage and blood supply contents in C1 are obtained by step A1, wherein the parameters corresponding to the unit in the cortical bone are used if the unit is in the cortical bone, and the parameters corresponding to the unit in the callus are used if the unit is in the callus; the influence of the adjacent units is obtained by sampling the mass center of each finite element unit, utilizing the Chebyshev distance to obtain the adjacent area of each unit, then judging the weight of the influence of each adjacent unit of the adjacent area on the adjacent unit through a Gaussian kernel function, and finally judging the influence of the adjacent units in the adjacent area through weighted average.

7. The distraction osteogenesis simulation system of claim 4, wherein said C1 bone maturation and bone resorption rules are not truly implemented with fuzzy logic, but are implemented as separate post-processing steps; this separation is to achieve different absorption rates of the woven and lamellar bones to have different effects on osteogenesis and to distinguish them from the reduction in bone content caused by the tissue destruction process.

8. The distraction osteogenesis simulation system according to claim 1, wherein the simulation system takes the output result of the A4 bone regeneration dynamic process simulation module as input, returns the input result to the A3 bone cutting area calculation biomechanics analysis module, enters the next analysis step for calculation, and outputs the result of osteogenesis after the simulation is finished and until the content of all unit bones at the callus position is 100%.

9. The distraction osteogenesis simulation system according to claim 1, wherein the iterative process further comprises the steps of performing finite element mesh repartitioning and state data mapping on large deformation units of the callus region of the previous analysis step caused by distraction loading, wherein the finite element mesh repartitioning and state data mapping comprises the following steps: (1) performing model remodeling on the deformed grid model to generate a geometric model of an undivided grid; (2) carrying out mesh division on the deformed new geometric model by using the mesh size of the previous unit to obtain a deformed new undistorted mesh; (3) judging the volume of the intersection part of each new grid and each original old grid according to the position of each new grid, and calculating the weight of the volume of the intersection part in the current grid; (4) the current state of each cell of the old grid is assigned to the corresponding cell of the new grid according to its corresponding weighted sum.

Images