CN111400953A - Simulation system for distraction osteogenesis - Google Patents
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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
The technical field is as follows:
the invention relates to the technical field of numerical simulation, in particular to a simulation system for distraction osteogenesis.
Background art:
the distraction osteogenesis is to cut the bone through osteotomy, and utilize a distractor to apply stable and slow distraction force to the bone tissue to stimulate the regeneration and growth of tissue cells and promote the formation and mineralization of new bone in a distraction gap, thereby achieving the purpose of prolonging the bone. The biggest defect of the current clinical distraction osteogenesis is that new bones are slowly formed and mineralized, so that a distraction device has long retention time and long treatment period, and great inconvenience is brought to life and work of a patient. It is reported clinically that the fixation time of the distraction scaffold required for the treatment of bone defects of the lower limbs (femur and tibia) by distraction osteogenesis can reach 10 months to 3 years. In addition, about 35% to 68% of stretch bone surgeries have problems with delayed or no healing of the bone. Therefore, the research on how to accelerate the formation and mineralization of new bone in the distraction osteogenesis so as to shorten the treatment period has very important clinical practical value. The forming speed and mineralization speed of new distraction osteogenesis bones depend on applied distraction modes (such as distraction rate in the distraction period, distraction frequency in the distraction period, duration of the distraction period, the period of applying distraction-compression coupling stimulation in the consolidation period, the application rate of distraction-compression coupling load, the application frequency of distraction-compression coupling load, rigidity of a distractor and the like), but the selection of the current distraction modes is mostly based on the experience of a doctor, and no tool for the doctor to select the optimal distraction mode before operation exists.
The simulation of the distraction osteogenesis system simulates and displays the dynamic process of bone regeneration and osteogenesis results under the stimulation effect of the distraction force in a program mode by establishing a mechanical biological model. The computer simulation technology is applied to simulate distraction osteogenesis, different distraction combination 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 distraction osteogenesis treatment period is favorably shortened, and the incidence rate of complications is reduced.
The invention content is as follows:
the invention aims to provide a simulation system for distraction osteogenesis, which can describe the visco-elastic-plastic behavior of callus in an osteotomy region aiming at a personalized simulation model of a patient, realize the numerical analysis of tissue differentiation based on strain regulation by using fuzzy logic, reproduce the complex bone regeneration dynamic process in the distraction osteogenesis, facilitate doctors to find the optimal mechanical stimulation condition aiming at the patient, help to shorten the whole treatment time and further reduce the incidence rate of complications.
In order to achieve the aim, the invention provides a simulation system for distraction osteogenesis, which can cause different osteogenesis effects of callus areas when different distraction conditions are applied in the distraction osteogenesis implementing 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.
Further, the A1 individualized three-dimensional reconstruction module for the osteotomy region of the subject is used to obtain individualized geometric and finite element models for 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;
further, different tension load combination parameters are set through a 2. The A2 stretch parameter setting module sets parameters including: stretching rate in stretching period, stretching frequency in stretching period, duration of stretching period, stretching-compression coupling stimulation period applied in consolidation period, stretching-compression coupling load application rate, stretching-compression coupling load application frequency, rigidity of a stretching device 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 tension parameter setting module; setting material properties includes: the user material of ABAQUS is provided with cortical bone Young modulus, Poisson ratio and callus Young modulus, Poisson ratio, yield stress and viscosity coefficient (the material type is defined by a UMAT subprogram containing a viscoelastic-plastic biomechanical model), an initial stage of a callus area is assumed to be filled with connective tissue, and simulation stretching is carried out to obtain a mechanical stimulation strain state of the callus area, wherein the mechanical stimulation strain state 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. The UMAT subroutine was written by establishing biomechanical models of cortical bone and callus, and calculating viscoelastic-plastic behavior of the 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 periodUsing ndiffEqually dividing the strain sample of each stretch time period, sampling according to the maximum peak value stimulation of each sample to obtain ndiffDistortion 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.
Further, the A4 bone regeneration dynamic process simulation module obtains the distortion strain gamma of each element of the finite element model of the osteotomy region by B2 finite element analysis0And 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
Seven variables for each element 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 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) Defuzzifying 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 blood supply, the bone and the cartilage in each unit of tissue differentiationAmount of change of content Δ Ci：
In the formula CperfIs the blood supply content in each unit, CboneIs the bone content in each unit, CcartIs the cartilage content in each unit;
Cbone＝Clamellar+Cwoven
in the formula, ClamellarFor lamellar bone content in each cell, CwovenKnitting bone content for each unit;
Ci+1＝ΔCiΔt+Ci
the above formula is an iterative function, Ci+1Is the corresponding blood supply, bone or cartilage content, C, in the current time unitiAnd delta t is the time step for the corresponding blood supply, bone and cartilage content in the previous time unit.
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; updating the blood supply, bone and cartilage content of each unit in the callus region to a range of 0-Ci≤1；
2) Calling n during the entire stretch stepdiffThe sub-fuzzy logic controller is used for calculating the blood supply, the bone and the cartilage content C of each unitiA 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 iscoon＝1-Cbone-Ccart
In the formula, CcoonThe association content in each unit
Young's modulus E per unit for callus regioneleUsing:
in the formula, ElamellarYoung's modulus of lamellar bone, EwovenYoung's modulus for braided bone, EcartYoung's modulus of cartilage, EcoonThe Young's modulus of connective tissue is obtained through experiments;
poisson ratio upsilon per unit for callus regioneleUsing:
υele＝υlamellarClamellar+υwovenCwoven+υcartCcart+υcoonCcoon
in the formula, ulamellarIs the poisson ratio of lamellar bone, upsilonwovenIs a braided bone Poisson's ratio, upsiloncartIs cartilage Poisson's ratio, upsiloncoonThe poisson ratio of the connective tissue is obtained through experiments;
further, the initial bone, cartilage and blood supply content in C1 is obtained through step a1, that is, 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.
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 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.
Further, the simulation system for distraction osteogenesis 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 until the content of all unit bones at the callus position is 100% after distraction is finished, and outputs an osteogenesis result after simulation is finished.
Further, in the simulation system for distraction osteogenesis, in the iterative process, the finite element mesh repartitioning and state data mapping of the large deformation unit of the callus region in the previous analysis step caused by distraction loading are also required to be performed, and the method 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.
In the simulation system for distraction osteogenesis provided by the invention, different osteogenesis effects of callus area tissues can be caused by applying different distraction conditions according to the implementation process of distraction osteogenesis; 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; in addition, the personalized parameter setting for the patient provided by the tension parameter setting module comprises the following steps: stretching rate in stretching period, stretching frequency in stretching period, stretching period duration, strengthening period applied stretching-compression coupling stimulation period, stretching-compression coupling load application rate, stretching-compression coupling load application frequency and rigidity of a stretching device; the user can define the distraction parameters by self, so that doctors can conveniently find the optimal mechanical stimulation condition for patients, the whole treatment time is shortened, and the incidence rate of complications is reduced.
In addition, the simulation system software for distraction osteogenesis adopts a modular structure, a simulation program has good expandability, the operation and the operation are convenient, the fuzzy logic is utilized to realize the tissue differentiation based on strain regulation and control to carry out numerical analysis, the efficiency and the accuracy of system design are improved, and the simulation system software can also be used for designing other similar bone regeneration systems.
Description of the drawings:
fig. 1 is a schematic view of a distraction osteogenesis simulation system of the present invention;
FIG. 2 is a flow chart of an implementation of the distraction osteogenesis simulation system of the present invention;
FIG. 3 is a schematic diagram of the fuzzy rule established by the present invention
The specific implementation mode is as follows:
the simulation system for distraction osteogenesis according to the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.
Example 1
The embodiment provides a simulation system for distraction osteogenesis, which is used for inducing different osteogenesis effects of callus region tissues by applying different distraction conditions in the distraction osteogenesis implementing 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; as shown in figure 1, the simulation system for distraction osteogenesis comprises an A1 individualized three-dimensional reconstruction module of an osteotomy region of a subject, an A2 distraction parameter setting module, an A3 computational biomechanical analysis module of the osteotomy region, an A4 bone regeneration dynamic process simulation module and an A5 display module. A1, the individual three-dimensional reconstruction module of the osteotomy region of the system object is used for automatically segmenting and three-dimensionally reconstructing the CT image of the osteotomy region of the object to obtain an individual three-dimensional geometric model of the osteotomy region of the object, and then carrying out mesh division processing; a2, setting different mechanical loading modes for the finite element model of the individualized three-dimensional osteotomy region of the object by the system stretching parameter setting module, and using the different mechanical loading modes as the input of the A3 computational biomechanics analysis module for the osteotomy region; a3 the computational biomechanical analysis module of the osteotomy region is used for setting boundary conditions and material properties according to the loading parameters transmitted by the A2 tension parameter setting module. Setting material properties includes: setting cortical bone Young modulus, Poisson ratio and callus Young modulus, Poisson ratio, yield stress and viscosity coefficient (defining material type by UMAT subprogram containing viscoelastic-plastic biomechanical model) in user material of ABAQUS, assuming that a callus region is filled with connective tissue at an initial stage, and performing simulation tension to determine the mechanical stimulation state of the callus region; a4, wherein the simulation module of the system bone regeneration dynamic process is used for inputting the strain result obtained by finite element analysis, determining the position of the strain state on the tissue differentiation diagram by using fuzzy logic control, outputting the result of tissue type change, updating the tissue material type and reproducing the bone regeneration process of callus; a5 the system display module is used for displaying the calculation result of the distraction osteogenesis simulation system.
As shown in fig. 1-2, in the distraction osteogenesis simulation system, the setting of the required parameters by the a2 distraction parameter setting module includes: stretching rate in stretching period, stretching frequency in stretching period, stretching period duration, strengthening period applied stretching-compression coupling stimulation period, stretching-compression coupling load application rate, stretching-compression coupling load application frequency and rigidity of a stretching device; 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 biomechanics analysis module, the next analysis step is carried out, until the content of all unit bones at the callus position is 100% after tension is finished, simulation is finished, and an osteogenesis result is output. In addition, in the iterative process, the finite element mesh repartitioning and state data mapping of large deformation units of the callus region of the last analysis step caused by tension loading comprise 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.
Specifically, in the distraction osteogenesis simulation system, the individualized three-dimensional reconstruction module of the A1 object osteotomy region is used for carrying out CT scanning, obtaining a CT image of the object osteotomy region, automatically segmenting the CT image into the osteotomy region of the object, and carrying out three-dimensional reconstruction and grid division to obtain an individualized geometric and finite element model of the object osteotomy region. 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.
Specifically, in the distraction osteogenesis simulation system, the A3 osteotomy area calculation biomechanical analysis module sets boundary conditions and material properties according to loading parameters transmitted by the A2 distraction parameter setting module. Setting material properties includes: setting cortical bone young's modulus, poisson's ratio and callus young's modulus, poisson's ratio, yield stress, viscosity coefficient (material type defined by UMAT subroutine containing viscoelastic-plastic biomechanical model) in user material of ABAQUS, the callus region being assumed to be filled with connective tissue at initial stage;
b1, setting a linear elastic biomechanical model of cortical bone:
σs＝Es s(1)
in the formula, σsIs a linear elastic model stress, EsIs the modulus of elasticity of the linear elastic model,sis the linear elastic model strain;
and viscoelastic biomechanical model of callus region (bingham-maxwell viscoelastic-plastic model):
wherein
Wherein σ is a viscoelastic-plastic model stress, η is a viscosity coefficient, EfIs the elastic modulus, σ, of a viscoelastic-plastic modelyieldThe critical stress of the viscoelastic-plastic model is the strain of the viscoelastic-plastic model, and t is time.
Inputting the constitutive equations (1) and (2) obtained in the above steps into a UMAT subprogram of ABAQUS, and simulating stretch to obtain the mechanical stimulation strain state of the callus area;
b2, strain result data arrangement, comprising:
viscoelastic finite element analysis was performed in ABAQUS to obtain the strain versus time curves of the elements of the finite element model. For each stretch cycle, use ndiffSampling equidistant strain samples according to the maximum peak value stimulation of each sample to obtain ndiffA strain component for a tissue differentiation algorithm.
Wherein for each cell strain component there is:
in the formula (2)]Is the main strain of the unit,11、22、33、12、23、136 strain components found for ABAQUS;
three main strains of each unit of the finite element model are obtained through the solution of the equation:
in the formula (I), the compound is shown in the specification,1,2,3three main strains of each unit respectively;
the distortion strain of each element of the finite element model can be obtained from the main strain:
in the formula, gamma0The distortion strain suffered by each element of the finite element model;
the expansion strain of each element of the finite element model can be obtained from the main strain:
in the formula (I), the compound is shown in the specification,0is the expansion strain experienced by each element of the finite element model.
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 diagram 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. The method comprises the following steps:
c1, establishing tissue differentiation model
1) Establishing an input variable membership function;
seven variables for each element in the osteotomy region finite element model (i.e., all cortical bone and callus) were taken as inputs, including: percent bone content in a cell, percent cartilage content in a cell, strain to expansion of a cell, strain to distortion of a cell, blood supply of a cell, percent bone content in an adjacent cell, and blood supply of an adjacent cell. Wherein the initial bone, cartilage and blood supply content is obtained by step a1, i.e. using parameters corresponding to the cells in the cortical bone if the cells are in the cortical bone, and using parameters corresponding to the cells in the callus if the cells are 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, 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.
2) Establishing fuzzy control rule
Fuzzy control rules describing tissue differentiation such as angiogenesis, intramembranous ossification, chondrogenesis, endochondral ossification, and tissue destruction under mechanical stimulation (distortion strain and expansion strain) are established (for example, fuzzy control rules composed of 17 if-then languages are established), and if rule conditions exist or are met, corresponding tissue differentiation occurs, and the rules describe processes of angiogenesis, intramembranous ossification, chondrogenesis, endochondral ossification, and tissue destruction under mechanical stimulation (distortion strain and expansion strain).
If the fuzzy controller consists of 17 language if-then rules (see fig. 3), the corresponding tissue differentiation occurs if the if condition is present. These rules describe the processes of angiogenesis, intramembranous ossification, chondrogenesis, endochondral ossification and tissue destruction under mechanical stimulation (aberrant strain and swelling strain).
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;
finally outputting the blood supply change quantity of each unit, the bone content change quantity of each unit and the cartilage content change quantity of each unit through the tissue differentiation process described by the fuzzy rule.
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 differentiationi：
In the formula CperfIs the blood supply content in each unit, CboneIs the bone content in each unit, CcartIs the cartilage content in each unit;
Cbone＝Clamellar+Cwoven(9)
in the formula, ClamellarFor lamellar bone content in each cell, CwovenKnitting bone content for each unit;
Ci+1＝ΔCiΔt+Ci(10)
the above formula is an iterative function, Ci+1Is the corresponding blood supply, bone or cartilage content, C, in the current time unitiAnd delta t is the time step for the corresponding blood supply, bone and cartilage content in the previous time unit.
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: the blood supply, the bone and cartilage content of each unit in the cortical bone area are kept unchanged, and the Young modulus and Poisson ratio of the cortical bone are also unchanged; updating the blood supply, bone and cartilage content of each unit in the callus region to a range of 0-Ci≤1；
2) Calling n during the entire stretch stepdiffThe sub-fuzzy logic controller is used for calculating the blood supply, the bone and the cartilage content C of each unitiA 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 iscoon＝1-Cbone-Ccart(11)
In the formula, CcoonThe association content in each unit
Young's modulus E per unit for callus regioneleUsing:
in the formula, ElamellarYoung's modulus of lamellar bone, EwovenYoung's modulus for braided bone, EcartYoung's modulus of cartilage, EcoonThe Young's modulus of connective tissue is obtained through experiments;
poisson ratio upsilon per unit for callus regioneleUsing:
vele＝vlamellarClamellar+vwovenCwoven+vcartCcart+vcoonCcoon(13)
in the formula, vlamellarIs the lamellar Poisson's ratio, vwovenTo weave the bone Poisson's ratio, vcartIs cartilage Poisson's ratio, upsiloncoonThe poisson ratio of the connective tissue is obtained through experiments;
and finally, judging the optimal tension loading mode by comparing the osteogenesis results in the simulation calculation loaded by each combination parameter.
In the simulation system for distraction osteogenesis provided by the invention, different osteogenesis effects of callus area tissues can be caused by applying different distraction conditions according to the implementation process of distraction osteogenesis; 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; in addition, the personalized parameter setting for the patient provided by the tension parameter setting module comprises the following steps: stretching rate in stretching period, stretching frequency in stretching period, stretching period duration, strengthening period applied stretching-compression coupling stimulation period, stretching-compression coupling load application rate, stretching-compression coupling load application frequency and rigidity of a stretching device; the user can define the distraction parameters by self, so that doctors can conveniently find the optimal mechanical stimulation condition for patients, the whole treatment time is shortened, and the incidence rate of complications is reduced.
In addition, the simulation system software for distraction osteogenesis adopts a modular structure, a simulation program has good expandability, the operation and the operation are convenient, the fuzzy logic is utilized to realize the tissue differentiation based on strain regulation and control to carry out numerical analysis, the efficiency and the accuracy of system design are improved, and the simulation system software can also be used for designing other similar bone regeneration systems.
In summary, the above embodiments have described the detailed implementation configurations of the simulation system for distraction osteogenesis, but it is understood that the present invention includes but is not limited to the configurations listed in the above embodiments, and any variations on the configurations provided by the above embodiments are within the scope of the present invention. One skilled in the art can take the contents of the above embodiments to take a counter-measure.
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 ndiffEqually dividing the strain sample of each stretch time period, sampling according to the maximum peak value stimulation of each sample to obtain ndiffDistortion 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 differentiationi：
In the formula CperfIs the blood supply content in each unit, CboneIs the bone content in each unit, CcartIs the cartilage content in each unit;
Cbone＝Clamellar+Cwoven
in the formula, ClamellarFor lamellar bone content in each cell, CwovenKnitting bone content for each unit;
Ci+1＝ΔCiΔt+Ci
the above formula is an iterative function, Ci+1Is the corresponding blood supply, bone or cartilage content, C, in the current time unitiCorresponding 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≤Ci≤1；
2) Calling n during the entire stretch stepdiffThe sub-fuzzy logic controller is used for calculating the blood supply, the bone and the cartilage content C of each unitiA 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 iscoon＝1-Cbone-Ccart
In the formula, CcoonThe association content in each unit
Young's modulus E per unit for callus regioneleUsing:
in the formula, ElamellarYoung's modulus of lamellar bone, EwovenYoung's modulus for braided bone, EcartYoung's modulus of cartilage, EcoonThe Young's modulus of connective tissue is obtained through experiments;
poisson ratio upsilon per unit for callus regioneleUsing:
υele＝υlamellarClamellar+υwovenCwoven+υcartCcart+υcoonCcoon
in the formula, ulamellarIs the poisson ratio of lamellar bone, upsilonwovenIs a braided bone Poisson's ratio, upsiloncartIs cartilage Poisson's ratio, upsiloncoonThe 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.
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