CN111400953B - Simulation system for distraction osteogenesis - Google Patents
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Abstract
A traction and tension osteogenesis simulation system relates to the technical field of numerical simulation. The invention can reproduce the complex bone regeneration dynamic process and the bone regeneration effect in the distraction osteogenesis, can be used for determining the optimal distraction scheme of the bone regeneration effect, and provides preoperative guidance for the clinical distraction osteogenesis. The system comprises an object osteotomy region individuation three-dimensional reconstruction module, a stretching parameter setting module, an osteotomy region calculation biomechanical analysis module, a bone regeneration dynamic process simulation module and a display module. The personalized three-dimensional reconstruction module of the osteotomy region is used for reconstructing a real geometric model of the osteotomy region on the basis of the medical image of the object. The stretching parameter setting module is used for setting different stretching loading modes and parameters. The osteotomy region computational biomechanical analysis module is used for establishing a biomechanical model and performing finite element analysis. The bone regeneration dynamic process simulation module is used for reproducing the bone regeneration process of the poroma. The display module is used for displaying the simulation calculation result.
Description
Technical field:
the invention relates to the technical field of numerical simulation, in particular to a traction and expansion osteogenesis simulation system.
The background technology is as follows:
the distraction osteogenesis is to cut bones through osteotomy, and apply stable and slow distraction force to bone tissues by using a distractor to stimulate regeneration and growth of tissue cells, promote formation and mineralization of new bones in a distraction gap, thereby achieving the purpose of extending bones. The biggest defect of the existing clinical distraction osteogenesis is that new bones are formed and mineralized slowly, so that the distractor has long retention time and long treatment period, and great inconvenience is brought to life and work of patients. It has been reported clinically that the fixation time of a distraction scaffold required for the treatment of lower extremity (femur and tibia) bone defects can reach 10 months to 3 years. In addition, about 35% -68% of the distraction osteogenesis procedures have problems such as delayed or non-healing bone healing. Therefore, it is of great clinical utility to investigate how to accelerate new bone formation and mineralization in distraction osteogenesis and thus shorten the treatment cycle. The speed of the formation and mineralization of new bone after distraction osteogenesis depends on the applied distraction mode (such as the rate of distraction Zhang Qi, the distraction frequency of Zhang Qi, the duration of the distraction period, the period of the consolidation period during which distraction-compression coupling stimulation is applied, the rate of the application of distraction-compression coupling load, the frequency of the application of distraction coupling load, and the rigidity of the distractor), but the selection of the distraction mode is currently based on the experience of doctors, and there is no tool for the doctors to select the optimal distraction mode before surgery.
The traction and tension osteogenesis system simulation simulates and displays the dynamic process and the osteogenesis result of bone regeneration under the action of traction and tension biological stimulation in a program mode by establishing a mechanical biological model. The method has the advantages that the computer simulation technology is applied to simulate the distraction osteogenesis, different distraction combined loading parameters are set, the complex bone regeneration dynamic process in the distraction osteogenesis is reproduced, a doctor can conveniently find the optimal distraction mode aiming at a clinical object, the reduction of the distraction osteogenesis treatment period is facilitated, and the incidence rate of complications is reduced.
The invention comprises the following steps:
the invention aims to provide a traction osteogenesis simulation system which can describe the viscoelastic-plastic behavior of osteotomy region callus aiming at a personalized simulation model of a patient, realize the tissue differentiation based on strain regulation and control by using fuzzy logic to carry out numerical analysis, reproduce the complex bone regeneration dynamic process in traction osteogenesis, facilitate doctors to search the optimal mechanical stimulation condition aiming at the patient, and help to shorten the whole treatment time and further reduce the occurrence rate of complications.
In order to achieve the above-mentioned purpose, the present invention provides a stretch-to-bone simulation system, which applies different stretch-to-bone conditions to cause different osteogenic effects of tissue in callus areas according to the stretch-to-bone implementation process; by carrying out simulation calculation on the bone regeneration process of the distraction osteogenesis, judging the optimal distraction loading mode according to the output osteogenesis result;
the traction and tension osteogenesis simulation system comprises an A1 object osteotomy region individuation three-dimensional reconstruction module, an A2 traction and tension parameter setting module, an A3 osteotomy region calculation biomechanical analysis module, an A4 bone regeneration dynamic process simulation module and an A5 display module;
the system A1 is characterized in that an object osteotomy region individuation three-dimensional reconstruction module is used for automatically dividing and reconstructing a CT image of the object osteotomy region to obtain an individuation three-dimensional geometric model of the object osteotomy region, and then conducting grid division;
the system A2 stretching parameter setting module is used for setting different mechanical loading modes for the finite element model of the object individuation three-dimensional osteotomy region and is used as the input of the A3 osteotomy region calculation biomechanical analysis module;
the system A3 osteotomy region computational biomechanics analysis module is used for setting a bone line elastic biomechanics model and a poroma region viscoelastic plastic biomechanics model according to the loading parameters transmitted by the A2 stretching parameter setting module, and simulating stretching to determine the mechanical stimulation state of the poroma 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 chart by using fuzzy logic control, outputting a result of tissue type change, updating the tissue material type and reproducing the bone regeneration process of poroma;
the system A5 display module is used for displaying the calculation result of the distraction osteogenesis simulation system.
Further, the A1 object osteotomy region individuation three-dimensional reconstruction module is used for obtaining an object osteotomy region individuation geometric and finite element model. 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 setting comprises an initial cortical bone content of 100%, a cartilage content of 0% and a blood supply of 100%, an initial callus area bone content of 0%, a cartilage content of 0% and a blood supply of 0%, and storing the initial cortical bone content, the cartilage content of 0% and the blood supply of 0% in an Excel file;
further, different tension loading combination parameters are set through A2. The A2 stretching parameter setting module setting parameters comprise: a stretch Zhang Qi stretch rate, a stretch Zhang Qi stretch frequency, a stretch period duration, a consolidation period applied stretch-pressure coupled stimulation period, a stretch-pressure coupled load application rate, a stretch-pressure coupled load application frequency, a stretch stiffness, and the like;
further, the A3 osteotomy region computational biomechanics analysis module is used for setting boundary conditions and material properties according to the loading parameters transmitted by the A2 stretching parameter setting module; the setting of the material properties includes: setting the cortical bone young modulus, poisson ratio and callus young modulus, poisson ratio, yield stress, viscosity coefficient (defined material type by UMAT subroutine comprising viscoelastic biomechanical model) in ABAQUS's user material, the initial stage of the callus region is assumed to be filled with connective tissue, and simulated stretch is performed to obtain the mechanically stimulated strain state of the callus region, comprising:
b1, setting a viscoelastic-plastic model of a callus area
A viscoelastic biomechanical model of the callus area was established using a Bingham-Max Wei Nian elastoplastic model consisting of a linear spring, newton's visco-kettle and a friction member. The viscoelastic-plastic behavior of the callus area was calculated by creating a biomechanical model of cortical bone and callus, programming a UMAT subroutine.
B2, calculating the strain state of the callus area
And performing viscoelastic-plastic finite element analysis in ABAQUS to obtain the strain change curve of each unit of the finite element model with time. For each stretch time period n is used diff Equally dividing strain samples of each stretching time period, sampling according to maximum peak stimulation of each sample to obtain n diff Distortion strain gamma for tissue differentiation algorithm 0 And expansion strain ε 0 ；
Wherein ε 1 ,ε 2 ,ε 3 Three main strains for each cell, respectively.
Further, the A4 bone regeneration dynamic processThe simulation module analyzes the B2 finite element to obtain the distortion strain gamma of each unit of the finite element model of the osteotomy region 0 And expansion strain ε 0 The result is used as input, the fuzzy logic control is used for determining the position of the strain state on the tissue differentiation chart, and the result of the change of the tissue type is output, the tissue material type is updated, and the bone regeneration process of the poroma is reproduced, which comprises the following steps:
c1, establishing a tissue differentiation model
Seven variables for each cell in the osteotomy region finite element model (i.e., all cortical bone and callus) were taken as inputs, including: 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 the adjacent cell and the effect of blood supply in the adjacent cell. Fuzzy rules including angiogenesis, intramembranous ossification, cartilage generation, endochondral ossification, tissue destruction, bone maturation and bone resorption are established to describe the results of tissue differentiation under mechanical stimulation, and finally the percentage of changes in bone, cartilage and vascular content of each unit is output.
C2, updating material properties
1) Deblurring the fuzzy value output by the fuzzy logic control in the step C1 to obtain the change quantity of output variables, thereby obtaining the change quantity delta C of blood supply, bone and cartilage contents in each unit of tissue differentiation i ：
C in the formula perf For the blood supply content in each unit, C bone For bone content in each unit, C cart Cartilage content in each unit;
C bone ＝C lamellar +C woven
wherein C is lamellar For lamellar bone content in each cell, C woven Braiding bone content for each cell;
C i+1 ＝ΔC i Δt+C i
the above is an iterative function, C i+1 For the corresponding blood supply, bone or cartilage content in the current time unit, C i For the corresponding blood supply, bone and cartilage contents in the previous time unit, Δt is the time step.
At the end of each tissue content update run, the finite element model of the osteotomy region (i.e. all cortical bone and callus) needs to be progressively fed with blood, bone and cartilage content C i And (5) renormalizing: for each unit blood supply, bone and cartilage content in the cortical bone region, keeping the initial state unchanged, and keeping the Young modulus and Poisson ratio of the corresponding cortical bone unchanged; updating blood supply, bone and cartilage contents of each unit in poroma region to be in the range of 0-C i ≤1；
2) Invoking n during the whole stretch step diff Sub-fuzzy logic controller to calculate blood supply, bone and cartilage content C of each unit i Is a variation of (2);
3) Updating the material properties of each unit of the callus area according to the contents of bones, cartilages and connective tissues in each unit of the callus area;
wherein C is coon ＝1-C bone -C cart
Wherein C is coon For connective tissue content in each unit
Young's modulus E for each unit of callus area ele Is updated using:
wherein E is lamellar Young's modulus of lamellar bone, E woven To weave bone Young's modulus E cart Young's modulus of cartilage, E coon Is the Young's modulus of connective tissue, all of which are experimentally obtained;
poisson ratio v per unit for callus area ele Is updated using:
υ ele ＝υ lamellar C lamellar +υ woven C woven +υ cart C cart +υ coon C coon
in the formula, v lamellar Is the lamellar Poisson's ratio, v woven To weave the Poisson's ratio, v cart Is the Poisson's ratio of cartilage, v coon The poisson ratio is connective tissue poisson ratio, and the poisson ratios are all obtained through experiments;
further, the initial bone, cartilage and blood supply content in the C1 is obtained by the step A1, that is, if the unit is a unit in cortical bone, the parameter corresponding to the unit in cortical bone is adopted, and if the unit is a unit in poroma, the parameter corresponding to the unit in poroma is adopted; the influence of each adjacent unit is that the centroid of each finite element unit is sampled, the Chebyshev distance is utilized to obtain the adjacent area of each unit, then the weight of each adjacent unit of the adjacent area on the influence is judged through a Gaussian kernel function, and finally the influence of the adjacent unit in the adjacent area is judged through weighted average.
Further, the bone maturation and bone resorption rules in C1 are not actually implemented with fuzzy logic, but 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 is distinguished from the reduction in bone content caused by the tissue destruction process.
Further, the simulation system for stretching and osteogenesis takes the output result of the A4 bone regeneration dynamic process simulation module as input, returns to the A3 bone cutting area computational biomechanical analysis module, enters the next analysis step for calculation until the content of all unit bones at the poroma is 100% after stretching is finished, and the simulation is finished and the osteogenesis result is output.
Furthermore, in the stretch-bone simulation system, the finite element mesh repartition and state data mapping of the large deformation unit caused by the stretch-load of the last analysis step callus area are required to be performed in the iterative process, and the method comprises the following steps: (1) Performing model remodeling on the deformed grid model to generate an undivided geometric model; (2) Grid division is carried out on the deformed new geometric model by utilizing the grid size of the previous unit, so that a deformed new undistorted grid is obtained; (3) Judging the volume of the intersection part of each new grid and each old grid according to the position of each new grid, and calculating the weight of the volume of the intersection part to the current grid; (4) The current state of each cell of the old grid is assigned to the corresponding cell of the new grid in accordance with its corresponding weighted sum.
In the traction and osteogenesis simulation system provided by the invention, different traction conditions are applied to cause different osteogenesis effects of tissues in a callus area according to the traction and osteogenesis implementation process; by carrying out simulation calculation on the bone regeneration process of the distraction osteogenesis, judging the optimal distraction loading mode according to the output osteogenesis result; in addition, the invention provides personalized parameter settings for a patient at the stretch parameter setting module comprising: a stretch Zhang Qi stretch rate, a stretch Zhang Qi stretch frequency, a stretch period duration, a consolidation period applied stretch-pressure coupled stimulation period, a stretch-pressure coupled load application rate, a stretch-pressure coupled load application frequency, and a stretch stiffness; the user can customize the stretching parameters, so that a doctor can conveniently find the optimal mechanical stimulation condition for the patient, the whole treatment time is shortened, and the occurrence rate of complications is reduced.
In addition, the simulation system software for stretching and osteogenesis adopts a modularized structure, and the simulation program has good expandability, is convenient to operate and operate, realizes numerical analysis on tissue differentiation based on strain regulation by using fuzzy logic, improves the efficiency and accuracy of system design, and can be also used for other similar bone regeneration system designs.
Description of the drawings:
FIG. 1 is a schematic diagram of a distraction osteogenesis simulation system of the present invention;
FIG. 2 is a flow chart of an embodiment of a distraction osteogenesis simulation system of the present invention;
FIG. 3 is a schematic diagram of a fuzzy rule established in the present invention
The specific embodiment is as follows:
a distraction osteogenesis simulation system according to the present invention will be described in further detail with reference to the drawings and the accompanying examples.
Example 1
The embodiment provides a traction and osteogenesis simulation system, wherein the traction and osteogenesis simulation system can cause different osteogenesis effects of tissues in a callus area by applying different traction and osteogenesis conditions according to the traction and osteogenesis implementation process; by carrying out simulation calculation on the bone regeneration process of the distraction osteogenesis, judging the optimal distraction loading mode according to the output osteogenesis result; as shown in FIG. 1, the traction and expansion osteogenesis simulation system comprises an A1 object osteotomy region individuation three-dimensional reconstruction module, an A2 traction and expansion 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 object osteotomy region individuation three-dimensional reconstruction module is used for automatically dividing and reconstructing a CT image of the object osteotomy region to obtain an individuation three-dimensional geometric model of the object osteotomy region, and then conducting grid division; the system stretching parameter setting module is used for setting different mechanical loading modes for the finite element model of the object individuation three-dimensional osteotomy region and is used as input of the A3 osteotomy region calculation biomechanical analysis module; and A3, the system osteotomy region computational biomechanics analysis module is used for setting boundary conditions and material properties according to the loading parameters transmitted by the A2 stretching parameter setting module. The setting of the material properties includes: setting a cortical bone Young modulus, a Poisson ratio, a callus Young modulus, a Poisson ratio, a yield stress and a viscosity coefficient (the type of materials is defined by UMAT subroutine comprising a viscoelastic plastic biomechanical model) on an ABAQUS user material, wherein the initial stage of the callus area is assumed to be filled with connective tissues, and carrying out simulated stretch to determine the mechanical stimulation state of the callus area; the system bone regeneration dynamic process simulation module A4 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 chart by using fuzzy logic control, outputting a result of tissue type change, updating the tissue material type and reproducing the bone regeneration process of poroma; and A5, the system display module is used for displaying the calculation result of the distraction osteogenesis simulation system.
As shown in fig. 1 to 2, in the distraction osteogenesis simulation system, the setting module of the A2 distraction parameter sets required parameters including: a stretch Zhang Qi stretch rate, a stretch Zhang Qi stretch frequency, a stretch period duration, a consolidation period applied stretch-pressure coupled stimulation period, a stretch-pressure coupled load application rate, a stretch-pressure coupled load application frequency, and a stretch stiffness; in addition, in the iterative process of the system, the output result of the A4 bone regeneration dynamic process simulation module is required to be used as input, and is transmitted back to the A3 bone cutting area calculation biomechanical analysis module to enter the next analysis step for calculation until the bone content of all units in the poroma after the stretching is finished is 100%, and the simulation is finished and the osteogenesis result is output. In addition, in the iterative process, finite element mesh repartition and state data mapping are needed to be carried out on the large deformation unit of the callus area caused by stretching and loading in the last analysis step, and the method comprises the following steps: (1) Performing model remodeling on the deformed grid model to generate an undivided geometric model; (2) Grid division is carried out on the deformed new geometric model by utilizing the grid size of the previous unit, so that a deformed new undistorted grid is obtained; (3) Judging the volume of the intersection part of each new grid and each old grid according to the position of each new grid, and calculating the weight of the volume of the intersection part to the current grid; (4) The current state of each cell of the old grid is assigned to the corresponding cell of the new grid in accordance with its corresponding weighted sum.
Specifically, in the stretch-draw osteogenesis simulation system, the personalized three-dimensional reconstruction module of the A1 object osteotomy region is used for CT scanning, CT images of the object osteotomy region are obtained, the CT images are automatically segmented into the osteotomy region of the object, three-dimensional reconstruction and grid division are carried out, and the personalized geometric and finite element model of the object osteotomy region is obtained. The model consists of two parts: cortical bone and callus. And setting an initial state of the finite element model of the osteotomy region. Initial status settings included an initial cortical bone content of 100%, cartilage content of 0% and blood supply of 100%, initial callus area bone content of 0%, cartilage content of 0% and blood supply of 0%, and they were saved in an Excel file.
Specifically, in the distraction osteogenesis simulation system, the A3 osteotomy region computational biomechanics analysis module sets boundary conditions and material properties according to the loading parameters transmitted by the A2 distraction parameter setting module. The setting of the material properties includes: setting cortical bone young's modulus, poisson's ratio and callus young's modulus, poisson's ratio, yield stress, viscosity coefficient (defined material type by UMAT subroutine containing viscoelastic-plastic biomechanical model) in ABAQUS user material, callus area initial stage is assumed to be filled with connective tissue;
b1, setting a linear elastic biomechanical model of cortical bone:
σ s ＝E s ε s (1)
in sigma s Stress of elastic model of line E s Modulus of elasticity, ε, of linear elastic model s Strain for the line elastic model;
and viscoelastic biomechanical model of callus area (bingham-maxwell Wei Nian elastoplastic model):
wherein the method comprises the steps of
Wherein sigma is the stress of the viscoelastic-plastic model, eta is the viscosity coefficient, E f For the elastic modulus, sigma, of the viscoelastic-plastic model yield The strain is the critical stress of the viscoelastic-plastic model, epsilon is the strain of the viscoelastic-plastic model, and t is the time.
Inputting the constitutive equations (1) and (2) into a UMAT subroutine of ABAQUS, and simulating stretching to obtain a mechanical stimulation strain state of a callus area;
b2, finishing strain result data, including:
and performing viscoelastic finite element analysis in ABAQUS to obtain a time-dependent strain curve of each unit of the finite element model. For each stretch cycle, n is used diff Sampling the equidistant strain samples according to the maximum peak stimulation of each sample to obtain n diff And a strain component for the tissue differentiation algorithm.
Wherein for each element strain component there is:
in [ epsilon ]]Epsilon as the principal strain of the unit 11 、ε 22 、ε 33 、ε 12 、ε 23 、ε 13 6 strain components determined for ABAQUS;
solving the equation to obtain three main strains of each unit of the finite element model:
wherein ε 1 ,ε 2 ,ε 3 Three main strains of each cell respectively;
the distortion strain of each unit of the finite element model can be obtained from the main strain:
wherein, gamma 0 The distortion strain is applied to each unit of the finite element model;
the expansion strain of each unit of the finite element model can be obtained from the main strain:
wherein ε 0 Is the expansion strain to which each unit of the finite element model is subjected.
Specifically, in the distraction osteogenesis simulation system, an A4 bone regeneration dynamic process simulation module; and determining the position of the strain state on the tissue differentiation chart by using fuzzy logic control, outputting the result of the change of the tissue type, updating the tissue material type, and reproducing the bone regeneration process of the callus. Comprising the following steps:
c1, establishing a tissue differentiation model
1) Establishing an input variable membership function;
seven variables for each cell in the osteotomy region finite element model (i.e., all cortical bone and callus) were taken as inputs, including: 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 blood supply of the cell, the percentage of bone content in the adjacent cell, and the blood supply of the adjacent cell. Wherein, the initial bone, cartilage and blood supply content is obtained by the step A1, namely, if the unit is the unit in the cortical bone, the parameter corresponding to the unit in the cortical bone is adopted, and if the unit is the unit in the poroma, the parameter corresponding to the unit in the poroma is adopted; the influence of the adjacent units is obtained by sampling the centroid of each finite element unit and utilizing Chebyshev distance, the weight of each adjacent unit in the adjacent area on the influence is judged through Gaussian kernel function, and finally the influence of the adjacent units in the adjacent area is judged through weighted average.
2) Establishing fuzzy control rules
Establishing fuzzy control rules describing angiogenesis, intramembranous ossification, cartilage generation, endochondral ossification and tissue destruction under mechanical stimulus (distortion strain and expansion strain), and if the rules exist or are met, corresponding tissue differentiation occurs, wherein the rules describe the processes of angiogenesis, intramembranous ossification, cartilage generation, endochondral ossification and tissue destruction under mechanical stimulus (distortion strain and expansion strain).
If the fuzzy controller consists of 17 language if-then rules (see FIG. 3), if the above-mentioned if condition exists, the corresponding tissue differentiation occurs. These rules describe the processes of angiogenesis, intramembranous ossification, chondrogenesis, endochondral ossification and tissue destruction under mechanical stimuli (distortional and expansive strains).
Rules 1 to 3 represent angiogenesis under mechanical stimulation and adjacent regional blood supply effects. When there is moderate strain and a non-low adjacent area of blood supply, the blood supply increases.
Rules 4 to 5 describe intramembranous ossification. If the adjacent area unit bone concentration is not low, the bone concentration in the area of low mechanical stimulation and adequate blood supply will increase.
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 affected by the adjacent bone concentration. In cases where the blood supply is adequate and the mechanical stimulus is relatively high.
Rules 13 to 14 represent endochondral ossification. Occurs in medium or high blood supplies.
Rules 15 to 17 simulate tissue destruction caused by mechanical stimulation overload.
In addition, an additional rule is added to the fuzzy logic to describe the process of bone maturation and bone resorption.
3) Establishing an output variable membership function;
and finally outputting the blood supply change amount of each unit, the bone content change amount of each unit and the cartilage content change amount of each unit through the tissue differentiation process described by the fuzzy rule.
C2, updating material properties
1) Deblurring the fuzzy value output by the fuzzy logic control in the step C1 to obtain the change quantity of output variables, thereby obtaining the change quantity delta C of blood supply, bone and cartilage contents in each unit of tissue differentiation i ：
C in the formula perf For the blood supply content in each unit, C bone For bone content in each unit, C cart Cartilage content in each unit;
C bone ＝C lamellar +C woven (9)
wherein C is lamellar For lamellar bone content in each cell, C woven Braiding bone content for each cell;
C i+1 ＝ΔC i Δt+C i (10)
the above is an iterative function, C i+1 For the corresponding blood supply, bone or cartilage content in the current time unit, C i For the corresponding blood supply, bone and cartilage contents in the previous time unit, Δt is the time step.
At the end of each tissue content update run, the finite element model of the osteotomy region (i.e. all cortical bone and callus) needs to be progressively fed with blood, bone and cartilage content C i And (5) renormalizing: for each unit blood supply, bone and cartilage content in the cortical bone region, the initial state is unchanged, and the Young modulus and Poisson's ratio of the cortical bone are also unchanged; updating blood supply, bone and cartilage contents of each unit in poroma region to be in the range of 0-C i ≤1；
2) Invoking n during the whole stretch step diff Sub-fuzzy logic controller to calculate blood supply, bone and cartilage content C of each unit i Is a variation of (2);
3) Updating the material properties of each unit of the callus area according to the contents of bones, cartilages and connective tissues in each unit of the callus area;
wherein C is coon ＝1-C bone -C cart (11)
Wherein C is coon For connective tissue content in each unit
Young's modulus E for each unit of callus area ele Is updated using:
wherein E is lamellar Young's modulus of lamellar bone, E woven To weave bone Young's modulus E cart Young's modulus of cartilage, E coon Is the Young's modulus of connective tissue, all of which are experimentally obtained;
poisson ratio v per unit for callus area ele Is updated using:
v ele ＝v lamellar C lamellar +v woven C woven +v cart C cart +v coon C coon (13)
in the formula, v lamellar For lamellar Poisson's ratio, v woven To weave the Poisson's ratio, v cart Is the Poisson's ratio of cartilage, v coon The poisson ratio is connective tissue poisson ratio, and the poisson ratios are all obtained through experiments;
and finally, judging the optimal tension loading mode by comparing the osteogenesis results in the simulation calculation of loading of each combination parameter.
In the traction and osteogenesis simulation system provided by the invention, different traction conditions are applied to cause different osteogenesis effects of tissues in a callus area according to the traction and osteogenesis implementation process; by carrying out simulation calculation on the bone regeneration process of the distraction osteogenesis, judging the optimal distraction loading mode according to the output osteogenesis result; in addition, the invention provides personalized parameter settings for a patient at the stretch parameter setting module comprising: a stretch Zhang Qi stretch rate, a stretch Zhang Qi stretch frequency, a stretch period duration, a consolidation period applied stretch-pressure coupled stimulation period, a stretch-pressure coupled load application rate, a stretch-pressure coupled load application frequency, and a stretch stiffness; the user can customize the stretching parameters, so that a doctor can conveniently find the optimal mechanical stimulation condition for the patient, the whole treatment time is shortened, and the occurrence rate of complications is reduced.
In addition, the simulation system software for stretching and osteogenesis adopts a modularized structure, and the simulation program has good expandability, is convenient to operate and operate, realizes numerical analysis on tissue differentiation based on strain regulation by using fuzzy logic, improves the efficiency and accuracy of system design, and can be also used for other similar bone regeneration system designs.
In summary, the foregoing embodiments describe the implementation configuration of the distraction osteogenesis simulation system in detail, and of course, the present invention includes, but is not limited to, the configurations listed in the foregoing implementation, and any modifications based on the configurations provided in the foregoing embodiments are within the scope of the present invention. One skilled in the art may recognize that the above embodiments are illustrative.
Claims (8)
1. The simulation system for the stretch-forming is characterized in that in the simulation system for the stretch-forming, different stretch-forming conditions are applied to cause different osteogenesis effects of tissues in a callus area according to the stretch-forming implementation process, and the optimal stretch-loading mode is determined according to the output osteogenesis result by performing simulation calculation on the bone regeneration process of the stretch-forming;
the traction and tension osteogenesis simulation system comprises an A1 object osteotomy region individuation three-dimensional reconstruction module, an A2 traction and tension parameter setting module, an A3 osteotomy region calculation biomechanical analysis module, an A4 bone regeneration dynamic process simulation module and an A5 display module;
the system A1 is characterized in that an object osteotomy region individuation three-dimensional reconstruction module is used for automatically dividing and reconstructing a CT image of the object osteotomy region to obtain an individuation three-dimensional geometric model of the object osteotomy region, and then conducting grid division;
the system A2 stretching parameter setting module is used for setting different mechanical loading modes for the finite element model of the object individuation three-dimensional osteotomy region and is used as the input of the A3 osteotomy region calculation biomechanical analysis module;
the system A3 osteotomy region computational biomechanics analysis module is used for setting a bone line elastic biomechanics model and a poroma region viscoelastic plastic biomechanics model according to the loading parameters transmitted by the A2 stretching parameter setting module, and simulating stretching to determine the mechanical stimulation state of the poroma 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 chart by using fuzzy logic control, outputting a result of tissue type change, updating the tissue material type and reproducing the bone regeneration process of poroma;
the system A5 display module is used for displaying the calculation result of the distraction osteogenesis simulation system;
the A3 osteotomy region computational biomechanics analysis module is used for setting boundary conditions and material properties according to the loading parameters transmitted by the A2 stretching parameter setting module; the setting of the material properties includes: setting the Young modulus, poisson's ratio and the Young modulus, poisson's ratio, yield stress and viscosity coefficient of the cortical bone in the user material of ABAQUS, wherein the initial stage of the callus area is assumed to be full of connective tissue, and carrying out simulated stretching to obtain the mechanical stimulation strain state of the callus area, wherein the method comprises the following steps:
b1, setting a viscoelastic-plastic model of a callus area
Establishing a viscoelastic biomechanical model of the callus area by using a Bingham-Max Wei Nian elastoplastic model, wherein the viscoelastic biomechanical model consists of a linear spring, a Newton visco-kettle and a friction piece, and calculating the viscoelastic-plastic behavior of the callus area by establishing a biomechanical model of cortical bone and callus, and writing a UMAT subroutine;
b2, calculating the strain state of the callus area
Performing viscoelastic-plastic finite element analysis in ABAQUS to obtain a time-dependent strain change curve of each unit of the finite element model; for each stretch time period n is used diff Equally dividing strain samples of each stretching time period, sampling according to maximum peak stimulation of each sample to obtain n diff Distortion strain gamma for tissue differentiation algorithm 0 And expansion strain ε 0 ；
Wherein ε 1 ,ε 2 ,ε 3 Three main strains for each cell, respectively.
2. A distraction osteogenesis simulation system according to claim 1, wherein the A1 object osteotomy region individualization three-dimensional reconstruction module is adapted to obtain an object osteotomy region individualization geometric and finite element model, the model being composed of two parts: cortical bone and callus, initial state settings were made on the osteotomy zone finite element model, the initial state settings including an initial cortical bone content of 100%, cartilage content of 0% and blood supply of 100%, initial callus zone bone content of 0%, cartilage content of 0% and blood supply of 0%, and they were saved in an Excel file.
3. A distraction osteogenesis simulation system according to claim 1, wherein different distraction loading combination parameters are set by A2; the A2 stretching parameter setting module setting parameters comprise: a stretch Zhang Qi stretch rate, a stretch Zhang Qi stretch frequency, a stretch period duration, a consolidation period applied stretch-pressure coupled stimulation period, a stretch-pressure coupled load application rate, a stretch-pressure coupled load application frequency, and a stretch stiffness.
4. The simulation system for distraction osteogenesis according to claim 1, wherein the A4 bone regeneration dynamic process simulation module analyzes B2 finite elements to obtain distortion strain γ of each element of the finite element model of the osteotomy region 0 And expansion strain ε 0 The result is used as input, the fuzzy logic control is used for determining the position of the strain state on the tissue differentiation chart, and the result of the change of the tissue type is output, the tissue material type is updated, and the bone regeneration process of the poroma is reproduced, which comprises the following steps:
c1, establishing a tissue differentiation model
Taking as input seven variables for each element in the osteotomy region finite element model, comprising: 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 the adjacent cell and the effect of blood supply in the adjacent cell; establishing fuzzy rules comprising angiogenesis, intramembranous ossification, cartilage generation, endochondral ossification, tissue destruction, bone maturation and bone resorption, describing the result of tissue differentiation under the action of mechanical stimulation, and finally outputting the percentage of the change of the contents of bone, cartilage and blood vessels of each unit;
c2, updating material properties
1) Outputting the fuzzy logic control of the step C1Defuzzifying the fuzzy value to obtain the change quantity of output variable, so as to obtain the change quantity delta C of blood supply, bone and cartilage contents in every unit of tissue differentiation i ：
C in the formula perf For the blood supply content in each unit, C bone For bone content in each unit, C cart Cartilage content in each unit;
C bone ＝C lamellar +C woven
wherein C is lamellar For lamellar bone content in each cell, C woven Braiding bone content for each cell;
C i+1 ＝ΔC o Δt+C i
the above is an iterative function, C i+1 For the corresponding blood supply, bone or cartilage content in the current time unit, C i For the corresponding blood supply, bone and cartilage contents in the previous time unit, Δt is the time step;
at the end of each tissue content updating operation, the blood supply, bone and cartilage contents C of each unit of the finite element model of the osteotomy region are required to be gradually changed i And (5) renormalizing: for each unit blood supply, bone and cartilage content in the cortical bone region, keeping the initial state unchanged, and keeping the Young modulus and Poisson ratio of the corresponding cortical bone unchanged; updating blood supply, bone and cartilage contents of each unit in poroma region to be in the range of 0-C i ≤1；
2) Invoking n during the whole stretch step diff Sub-fuzzy logic controller to calculate blood supply, bone and cartilage content C of each unit i Is a variation of (2);
3) Updating the material properties of each unit of the callus area according to the contents of bones, cartilages and connective tissues in each unit of the callus area;
wherein C is coon ＝1-C bone -C cart
Wherein C is coon In each unit ofConnective tissue content
Young's modulus E for each unit of callus area ele Is updated using:
wherein E is lamellar Young's modulus of lamellar bone, E woven To weave bone Young's modulus E cart Young's modulus of cartilage, E coon Is the Young's modulus of connective tissue, all of which are experimentally obtained;
poisson ratio v per unit for callus area ele Is updated using:
υ ele ＝v lamellar C lamellar +υ woven C woven +υ cart C cart +υ coon C coon
in the formula, v lamellar Is the lamellar Poisson's ratio, v woven To weave the Poisson's ratio, v cart Is the Poisson's ratio of cartilage, v coon The poisson ratio was found experimentally for connective tissue.
5. The distraction osteogenesis simulation system of claim 4, wherein the initial bone, cartilage and blood supply content of C1 is obtained by step A1, wherein parameters corresponding to cells in cortical bone are used if the cells are cells in cortical bone, and parameters corresponding to cells in callus are used if the cells are cells in callus; the influence of each adjacent unit is that the centroid of each finite element unit is sampled, the Chebyshev distance is utilized to obtain the adjacent area of each unit, then the weight of each adjacent unit of the adjacent area on the influence is judged through a Gaussian kernel function, and finally the influence of the adjacent unit in the adjacent area is judged through weighted average.
6. A distraction osteogenesis simulation system according to claim 4, wherein the bone maturation and resorption rules in C1 are not really implemented with fuzzy logic, but 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 is distinguished from the reduction in bone content caused by the tissue destruction process.
7. The simulation system of stretch osteogenesis according to claim 1, wherein the simulation system of stretch osteogenesis takes the output result of the A4 bone regeneration dynamic process simulation module as input, returns to the A3 bone cutting area computational biomechanical analysis module, enters the next analysis step for calculation until the content of all unit bones at the poroma is 100% after the stretch is finished, and the simulation is finished and the osteogenesis result is output.
8. A distraction osteogenesis simulation system according to claim 1, wherein the distraction osteogenesis simulation system further requires finite element mesh repartition and state data mapping of large deformation cells of a previous analysis callus area due to distraction loading during iteration, comprising the steps of: (1) Performing model remodeling on the deformed grid model to generate an undivided geometric model; (2) Grid division is carried out on the deformed new geometric model by utilizing the grid size of the previous unit, so that a deformed new undistorted grid is obtained; (3) Judging the volume of the intersection part of each new grid and each old grid according to the position of each new grid, and calculating the weight of the volume of the intersection part to the current grid; (4) The current state of each cell of the old grid is assigned to the corresponding cell of the new grid in accordance with its corresponding weighted sum.
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