A positioning method of uterine cardinal ligament and sacral ligament and a pelvic floor finite element evolution model construction method

Abstract

The application discloses a positioning method of uterine cardinal ligament and sacral ligament and a pelvic floor finite element evolution model construction method, and belongs to the field of two-dimensional digital modeling and biomechanics research. According to the pelvic floor anatomy structure, the starting point and the ending point of the cardinal ligament and the sacral ligament in the two-dimensional finite element model are determined, and a distributed nonlinear hyperelastic spring group is proposed to simulate the suspension mechanical properties of the cardinal ligament and the sacral ligament. An organ tissue proportional damage simulation method and a proportional damage expression are proposed, the nonlinear material stress-strain curve of the pelvic floor organ tissue is multiplied by a proportional damage factor to simulate the mechanical properties of the pelvic floor organ damage. A concentrated load application method and a concentrated force-displacement expression of the initial shape feature are proposed to simulate the initial genital cleft and the uterine-vaginal angle. The evolution model can intuitively show the mechanical changes and shape feature change trends of the pelvic floor from the initial injury to the severe prolapse, and provides a basis for the reconstruction surgery design of the pelvic organ prolapse.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional digital modeling and biomechanics research. It is mainly a method for locating the cardinal ligament and sacral ligament of the uterus and constructing a finite element evolution model of the pelvic floor. Specifically, it is a method for accurately locating and mechanically simulating the complex three-dimensional cardinal ligament and sacral ligament of the pelvic floor in a two-dimensional finite element model, while simulating the proportional damage and initial shape and position characteristics of organs and tissues, and constructing a finite element evolution model of the pelvic floor. Technical Background

[0002] Pelvic organ prolapse (POP) is a condition in which tissues and organs protrude from the vaginal opening due to weakened support from the pelvic floor muscles and skeletal system. POP can be classified by location into anterior vaginal wall prolapse, uterine prolapse, and posterior vaginal wall prolapse. Bladder prolapse accounts for 34.3% of all prolapse cases, uterine prolapse for 14.2%, and rectocele for 18.6%. A survey of POP cases among rural women in China found an overall prevalence of 9.21%, making it a prevalent disease affecting women. In the process of digital modeling and analysis of the pelvic floor, due to the complex multi-factor combined damage, changes in shape and position, and the significant influence of the hyperelastic mechanical properties of ligaments and soft tissues, there are currently no effective methods for locating the cardinal ligament and sacroiliac ligament, nor are there accurate mechanical simulation methods for these organs. Furthermore, the lack of simulation methods for soft tissue injury mechanics and initial shape and position characteristics has resulted in slow progress in pelvic floor biomechanics research. Summary of the Invention

[0003] The technical problem this invention aims to solve is to provide a method for locating the cardinal ligament and sacrosacral ligament and constructing a finite element model of pelvic floor evolution. The method for locating the initiation and termination of the cardinal and sacrosacral ligaments is simple, efficient, and requires minimal manual processing, while ensuring the biomechanical function of the cardinal and sacrosacral ligaments within the two-dimensional pelvic floor system. The method employs a proportional damage simulation approach for pelvic floor organs and tissues, avoiding numerous complex in vivo / ex vivo material mechanics experiments for soft tissue injuries, thus enabling rapid and effective analysis of the damage mechanics behavior of organs and tissues damaged by multiple factors. The method utilizes a concentrated force load application approach, which allows for convenient and quick setting of different initial pelvic floor features without relying on MRI images of different clinical patients. This method can be applied to the construction of a two-dimensional pelvic floor evolution model and biomechanical analysis, providing effective assistance in simulating the process of pelvic floor prolapse evolution.

[0004] The technical solution adopted in this invention is: a method for locating the cardinal ligament and sacrosacral ligament and constructing a finite element model of pelvic floor evolution, the specific steps of which are as follows:

[0005] Step 1: Obtain a set of two-dimensional midsagittal and cross-sectional images with clear organ outlines based on MRI images of the pelvic floor of healthy women, and use them as important materials for constructing a two-dimensional pelvic floor finite element model;

[0006] Step 2: Based on the midsagittal plane two-dimensional image selected in Step 1, a two-dimensional pelvic floor finite element model without prolapse is established using finite element software. The starting and ending points of the cardinal ligament and sacral ligament in the two-dimensional pelvic floor finite element model are determined according to the pelvic floor anatomy and the midsagittal plane two-dimensional image. Based on the pelvic floor anatomy principles and the cardinal ligament, combined with the cross-sectional image set, a distributed nonlinear hyperelastic spring assembly is used to represent the cardinal ligament and sacral ligament in the two-dimensional pelvic floor finite element model.

[0007] Step 3: In the finite element software, a method for simulating proportional damage to organs and tissues and a proportional damage expression are proposed. By multiplying the nonlinear material stress-strain curves corresponding to each organ and tissue in the pelvic floor by a given proportional damage factor, the mechanical properties of the organs are reduced to simulate the damage to the mechanical properties of the pelvic floor organs.

[0008] Step 4: Based on clinical statistics and mechanical equivalence methods of the initial shape and position characteristics of the pelvic floor, a concentrated load application method and a concentrated force-displacement expression for the initial shape and position characteristics are proposed. The initial genital cleft and uterus-vaginal angle are simulated using concentrated force loads on a two-dimensional pelvic floor finite element model to analyze the changing trend of shape and position characteristics of the pelvic floor due to the decline in tissue mechanical properties. Combined with the proportional damage simulation method in Step 3, a pelvic floor finite element evolution model is constructed.

[0009] Specifically, the positioning and parameter setting method of this invention is applicable to the positioning of two-dimensional models of different types of pelvic floor cardinal ligaments and sacroiliac ligaments, including normal pelvic floor systems without prolapse, abnormally prolapsed pelvic floor systems, pelvic floor systems in a resting state, and pelvic floor systems under VALSALVA movements. This method can accurately position the cardinal and sacroiliac ligaments while maintaining the accuracy of finite element analysis as much as possible. Similarly, the proportional damage simulation method and initial shape and position feature construction method mentioned in this invention are not limited to the hyperelastic material and pelvic floor two-dimensional model mentioned in this invention.

[0010] Specifically, the steps in step 2 are as follows:

[0011] 2.1) Locate the origin of the sacral ligament using the medical imaging software Mimics:

[0012] Origin: Using medical imaging software Mimics, the origin of the sacral ligament is located on the sacrospinous ligament-coccygeal muscle complex on the 2nd to 3rd sacral vertebrae from the bottom to the top of the cross-sectional image set. Due to individual physiological differences, the origin of the sacral ligament may be located on the sacrum, piriformis muscle, sciatic foramen region or ischial spine in some patients. This origin is used as the origin of the sacral ligament.

[0013] End point: Generally located at the cervix or vagina, the specific location of which is determined by the MRI image of the individual patient. This point serves as the endpoint of the sacral ligament.

[0014] 2.2) Locate the origin of the cardinal ligament of the uterus using the medical imaging software Mimics:

[0015] Origin: Using the medical imaging software Mimics, the point at the top of the greater sciatic foramen on the ipsilateral pelvic side wall, at the sacroiliac joint, is located in the cross-sectional images. This point is the origin of the cardinal ligament of the uterus.

[0016] End point: The cardinal ligament inserts into the cervix or posterolateral aspect of the vagina; this insertion point is considered the end point of the cardinal ligament.

[0017] 2.3) Based on the starting point and ending point determined in the above steps, and combined with the two-dimensional image of the midsagittal plane, the cardinal ligament and sacral ligament of the uterus in the two-dimensional pelvic floor finite element model are equivalently represented by an approximately parallel distributed nonlinear hyperelastic spring group.

[0018] Specifically, the steps in step 3 are as follows:

[0019] 3.1) Material samples were taken from each pelvic floor organ and tissue, and uniaxial tensile tests were performed on them.

[0020] 3.2) Nonlinear material stress-strain data for each healthy organ obtained from uniaxial tensile tests were imported into finite element software and fitted into nonlinear curves for Mooney-Rivlin, Ogden, Yeoh, and Neo-Hookean hyperelastic materials. Different hyperelastic material models were selected according to different organs.

[0021] 3.3) A proportional damage simulation method and proportional damage expression are adopted, introducing a proportional damage coefficient K. The dataset of stress-strain nonlinear curves for each organ is multiplied by the corresponding proportional damage coefficient K (0.05, 0.25, 0.5, 0.75, corresponding to organ damage degrees of 95%, 75%, 50%, and 25%, respectively) to simulate the damage degree of pelvic floor organ tissues. The smaller the proportional damage coefficient K, the lower the tensile stiffness of the material and the lower the material properties. Damage degree K * The relationship with the proportional damage coefficient K is as follows:

[0022] K * =1-K,0<K<1 (1).

[0023] Specifically, the steps in step 4 are as follows:

[0024] 4.1) In the two-dimensional pelvic floor finite element model, a concentrated load method and a concentrated force-displacement expression are used to apply a concentrated horizontal force load to the nodes at the fundus of the uterus to simulate the abnormal initial shape and position characteristics of the uterus-vaginal angle in an upright mid-position uterus and a retroverted retroverted uterus. Different concentrated force-angle expressions can be obtained by fitting curves for different two-dimensional pelvic floor finite element models. The fitted expression is as follows:

[0025] θ = 28.3 + 6139.1F v (2)

[0026] Where θ is the uterine-vaginal angle, in degrees (°), F v The concentrated force applied at the fundus of the uterus is measured in Newtons.

[0027] 4.2) In the two-dimensional pelvic floor finite element model, a concentrated load application method and a concentrated force-displacement expression are used to apply concentrated force loads to the nodes at the vaginal base to simulate the widening of the reproductive tract cleft in the physiological pelvic floor. Different concentrated force-displacement expressions can be obtained by fitting curves for different two-dimensional pelvic floor finite element models. The relationship between the reproductive cleft and the concentrated force can be fitted to an approximately linear relationship, and the fitted expression is:

[0028] D GH =0.0189+3.96F u (3)

[0029] Where D GH F represents the width of the reproductive slit, in meters. u The concentrated force applied to the bottom of the posterior vaginal wall is measured in Newtons.

[0030] Specifically, the finite element software described is Ansys.

[0031] The beneficial effects of this invention are:

[0032] (1) This invention takes the healthy pelvic floor system of women without a history of pelvic organ prolapse as the research object, obtains its MRI images, and constructs a physiological pelvic floor without pelvic organ prolapse using computer-aided design software, finite element analysis software, combined with uniaxial tensile data, statistical data, etc. By mechanically altering the initial shape and position characteristics of the pelvic floor and organ damage, a two-dimensional finite element evolution model of the pelvic floor with initial damage characteristics is obtained. This model can simulate the evolution process from an initially damaged pelvic floor to a prolapsed pelvic floor under the influence of multiple factors (such as abdominal pressure, anorectal pressure, and urine pressure). In this process, the influence of each factor on the degree of pelvic floor prolapse can be studied in detail, and the changing law of pelvic floor prolapse can be obtained.

[0033] (2) This invention provides a method for locating the starting points of the cardinal ligament and the sacral ligament. Combined with MRI images, the cardinal ligament and the sacral ligament can be quickly located in two-dimensional midsagittal images, providing an accurate starting point for the two-dimensional equivalent of the ligament and ensuring that the ligament can play its important biomechanical role in the two-dimensional equivalent process.

[0034] (3) This invention proposes a mechanically equivalent method for constructing the initial shape and position of the pelvic floor. Research suggests that the initial shape and position characteristics affect the stability of the pelvic floor system. By applying concentrated forces to alter the initial shape and position characteristics of the pelvic floor finite element system, the influence of different physiological angles and different reproductive tract openings on pelvic organ prolapse can be studied. This means that corresponding two-dimensional pelvic floor finite element models can be constructed for clinical cases to find personalized treatment plans, which is of great significance for reducing postoperative pain and improving treatment efficiency. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the implementation of the present invention;

[0036] Figure 2 It is the location of the origin and insertion points of the cardinal ligament and the sacroiliac ligament on an MRI image;

[0037] Figure 3 It is a simple two-dimensional representation of the cardinal ligament and sacroiliac ligament of the uterus on an MRI image;

[0038] Figure 4 This is a two-dimensional equivalent schematic diagram of the cardinal ligament and sacrosacral ligament on a two-dimensional finite element model of the pelvic floor.

[0039] Figure 5 These are the stress-strain curves of the levator ani muscle under different degrees of injury.

[0040] Figure 6 It is a two-dimensional finite element model of the physiological pelvic floor system and changes in its initial shape and position characteristics.

[0041] Note: Figure 2 (a) is the origin of the cardinal ligament and the endpoint of the cardinal ligament-sacral ligament junction; Figure 2 (b) is the origin of the sacral ligament; Figure 6 (a) Represents the physiological pelvic floor and the two concentrated force loading locations that alter its shape and position. Figure 6 (b) indicates a situation where the pelvic floor system simultaneously experiences widening of the reproductive cleft and changes in the uterine-vaginal angle. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0043] Example 1: As Figure 1-6 As shown, a method for locating the cardinal ligament and sacrosacral ligament and constructing a finite element model of pelvic floor evolution is described, with the following steps:

[0044] Step 1: Select a young, healthy female volunteer with no history of pelvic organ prolapse and obtain informed consent before undergoing an MRI scan. Scan the subject using a 3T MRI scanner while she is supine. MRI images are continuously acquired in the axial, coronal, and sagittal planes. The field of view is 20 cm × 20 cm, the slice interval is 1 mm, and the slice thickness is 4 mm. Based on these MRI images, a set of two-dimensional midsagittal and transverse images with clear organ outlines is obtained. A two-dimensional pelvic floor finite element model, including the uterus, vagina, bladder, urethra, rectum, and sacrum / coccyx, is then constructed using principles of pelvic floor anatomy.

[0045] Step 2: Open the woman's MRI image using Mimics, and determine the origin and insertion points of the cardinal ligament and sacroiliac ligament on the cross-sectional image set based on organ characteristics and organ relationships. Figure 2 And a simple two-dimensional characterization of the cardinal ligament and sacroligament was performed. Figure 3 Two-dimensional solid models and two-dimensional finite element models without prolapse were established using computer-aided design software and finite element software. The starting and ending points of the cardinal and sacroiliac ligaments in the two-dimensional finite element model of the pelvic floor were determined based on the pelvic floor anatomy. Based on the mechanical equivalence method, the principles of pelvic floor anatomy, and the tensile test parameters of the cardinal and sacroiliac ligaments, combined with two-dimensional images in the midsagittal plane, a distributed nonlinear hyperelastic spring system was used to represent the cardinal and sacroiliac ligaments in the two-dimensional pelvic floor finite element model.

[0046] ( Figure 4 ).

[0047] The specific steps are as follows:

[0048] 2.1) Locating the origin of the sacrosacral ligament: Using medical imaging software Mimics, the location of the sacrospinous ligament-coccygeal muscle complex on the lateral wall of the pelvis, at the 2nd to 3rd sacral vertebrae from the bottom, is determined in a set of transverse images. This location is then used as the origin of the sacrosacral ligament. The precise location of the origin is confirmed by combining transverse and coronal MRI images at the same horizontal plane. Due to individual physiological differences, in some patients, the origin may be located on the sacrum, piriformis muscle, sciatic foramen region, or on the ischial spine; this point is the origin of the sacrosacral ligament distribution.

[0049] 2.2) Locating the endpoint of the sacral ligament: Using the medical imaging software Mimics, the cervix or upper part of the vagina is located in the cross-sectional image set. The specific endpoint is determined by the insertion trace of the sacral ligament in the coronal, cross-sectional and midsagittal two-dimensional images of the specific patient's MRI. This point is taken as the endpoint of the sacral ligament.

[0050] 2.3) Locating the origin of the cardinal ligament: Using medical imaging software Mimics, the location at the top of the greater sciatic foramen on the ipsilateral pelvic side wall, at the sacroiliac joint, is used as the origin of the cardinal ligament. The exact location of the cardinal ligament is determined by combining the transverse and coronal MRI images at the same horizontal plane. This point is the origin of the cardinal ligament.

[0051] 2.4) Locating the endpoint of the cardinal ligament: Using medical imaging software Mimics, the cervix or the upper posterolateral part of the vagina is located in the cross-sectional images. In most patients, the sacral ligament connects with the cardinal ligament at its endpoint, forming a sacral ligament-cardinal ligament combination. The specific endpoint is determined by the insertion trace of the sacral ligament in the coronal, transverse, and midsagittal MRI images of the individual patient; this point is considered the endpoint of the cardinal ligament.

[0052] 2.5) Based on the above starting point and the principle of mechanical projection synthesis, the connection between the cardinal ligament and the sacral ligament in the two-dimensional pelvic floor finite element model is simulated using the combine14 spring damping element in the finite element software ANSYS, combined with the two-dimensional image of the midsagittal plane.

[0053] Step 3: In the finite element software, the mechanical properties of the organs are reduced by multiplying the stress-strain curves of the materials corresponding to each tissue and organ in the pelvic floor by a given factor (percentage), thus simulating the loss of mechanical properties of the organs damaged in the pelvic floor.

[0054] The specific steps are as follows:

[0055] 3.1) Material samples were taken from each pelvic organ and subjected to uniaxial tensile tests to obtain the force-displacement curves of the sampled materials from each pelvic organ.

[0056] 3.2) The stress-strain data obtained from uniaxial tensile tests of each healthy organ in the pelvic floor were imported into the finite element software ANSYS and fitted as nonlinear curves of the Mooney-Rivlin, Ogden, Yeoh, and Neo-Hookean hyperelastic material models.

[0057] The strain energy function of the Mooney-Rivlin model is expressed as follows:

[0058]

[0059]

[0060] Among them W Mooney-rivlin Corresponding to its strain energy function, D1, C 10 C 01 These are the parameters of Mooney-Rivlin hyperelastic material, where ν is the Poisson's ratio and J is the weight of the material. MRI1 and I2 are the incompressible parameters of the Mooney-Rivlin model material, and the invariants of the right Cauchy-Green deformation tensor.

[0061] The strain energy function of the Ogden model is expressed as follows:

[0062]

[0063] Among them W Ogden This is the strain energy function of the Ogden material model, where N is the model order and u is the strain energy function. i α i These are the parameters of Ogden hyperelastic material, D ogden It is an incompressible parameter. This refers to the reduction of principal elongation, and the relationship between the reduction of principal elongation and the following formula is expressed:

[0064]

[0065] Where J is the ratio of the deformed volume to the undeformed volume of the material, and λ1, λ2, and λ3 are the principal elongations in the three directions of the strain tensor.

[0066] The strain energy function of the Yeoh material model is expressed as follows:

[0067]

[0068] Where D Yeoh C i0 These are the corresponding material parameters. These are the principal strain invariants in uniaxial tension, and their relationship is expressed as:

[0069]

[0070] Where λ is the principal expansion ratio of the maximum hyperelastic material.

[0071] The strain energy expression for the Neo-Hookean material model is:

[0072]

[0073] Where u is the initial shear modulus, D1 is the material incompressibility parameter, and I is the strain tensor invariant. If the material is assumed to be incompressible, then J = 1, and the second term is 0.

[0074] Based on the strain energy function, the uniaxial tensile results of organs, the mechanical behavior of different tissues and organs, and the deformation range described by different hyperelastic constitutive models, appropriate material models are selected for different pelvic floor organs.

[0075] 3.3) The stress-strain datasets for each organ are multiplied by a corresponding proportional damage coefficient K to simulate the degree of damage to the pelvic floor organs. A smaller proportional damage coefficient K indicates lower tensile stiffness and lower material properties. In this embodiment, damage simulations were performed on the levator ani muscle at 95%, 75%, 50%, and 25% damage levels, with damage degree K... * The relationship with the proportional damage coefficient K is as follows:

[0076] K * =1-K,0<K<1 (1).

[0077] Figure 5 Taking the proportional damage of the levator ani muscle as an example, the stress-strain data of the levator ani muscle material were multiplied by 0.05, 0.25, 0.5, and 0.75 to obtain stress-strain curves of the levator ani muscle with damage levels of 95%, 75%, 50%, and 25%.

[0078] Step 4: Based on clinical statistical data of the initial shape and position characteristics of the pelvic floor, and using statistical data and mechanical equivalence methods, simulate the initial reproductive cleft and uterus-vaginal angle of the two-dimensional pelvic floor finite element model under concentrated force loads to simulate the changing trend of pelvic floor shape and position characteristics caused by the decline in tissue mechanical properties. Set F... u F v These are the concentrated forces that change the width of the genital slit and the angle between the vagina and uterus, respectively. Their direction and location of action are as follows: Figure 6 (a).

[0079] The specific steps are as follows:

[0080] 4.1) In the finite element software ANSYS, a concentrated horizontal force load is applied to the nodes at the fundus of the uterus in the finite element model to simulate the situation when the uterus-vaginal angle is in an abnormal position (the uterus is not approximately parallel to the horizontal). Different concentrated force-angle expressions can be obtained by fitting curves. In this embodiment, the expression obtained after fitting discrete points is as follows:

[0081] θ = 28.3 + 6139.1F v (2)

[0082] Where θ is the uterine-vaginal angle, in degrees (°), F v The concentrated force applied at the fundus of the uterus is measured in Newtons.

[0083] 4.2) In the finite element software ANSYS, a concentrated horizontal force load is applied to the bottom of the vagina in the finite element model to simulate the genital slit. In this implementation case, the approximate linear relationship between the genital slit and the concentrated force can be obtained through discrete point fitting:

[0084] D GH =0.0189+3.96Fu (3)

[0085] Where D GH F represents the width of the reproductive slit, in meters. u The concentrated force applied to the bottom of the posterior vaginal wall is measured in Newtons.

[0086] 4.3) Through the above two steps, a preliminary pelvic floor finite element model showing changes in shape and position characteristics can be constructed based on the physiological morphology of the pelvic floor in a two-dimensional finite element model, such as... Figure 6 (b)

[0087] It should be noted that the method of this invention is applicable to the localization of the cardinal ligament and sacrosacral ligament in healthy women and the simulation of pelvic organ injuries in healthy women. The methods for locating the cardinal and sacrosacral ligaments, simulating proportional injuries, and constructing pelvic floor morphology mentioned in this invention are not limited to the aforementioned patients, organs, and injury proportions; they can be applied to MRI images of other patients where applicable to construct two-dimensional finite element evolution models.

[0088] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. The present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for locating the cardinal ligament and sacrosacral ligament and constructing a finite element model of pelvic floor evolution, characterized in that: The steps are as follows: Step 1: Obtain a set of two-dimensional midsagittal and transverse images with clear organ outlines based on MRI images of the pelvic floor of healthy women. Step 2: Based on the midsagittal plane two-dimensional image selected in Step 1, a two-dimensional pelvic floor finite element model without prolapse is established using finite element software. The starting and ending points of the cardinal ligament and sacral ligament in the two-dimensional pelvic floor finite element model are determined according to the pelvic floor anatomy and the midsagittal plane two-dimensional image. Based on the pelvic floor anatomy principles and the cardinal ligament, combined with the cross-sectional image set, a distributed nonlinear hyperelastic spring assembly is used to represent the cardinal ligament and sacral ligament in the two-dimensional pelvic floor finite element model. Step 3: In the finite element software, the organ tissue proportional damage simulation method and proportional damage expression are used. By multiplying the nonlinear material stress-strain curves corresponding to each organ tissue in the pelvic floor by a given proportional damage factor, the mechanical properties of the organs are reduced to simulate the damage to the mechanical properties of the pelvic floor organs. Step 4: Based on the clinical statistics and mechanical equivalence methods of the initial shape and position characteristics of the pelvic floor, the concentrated load application method and concentrated force-displacement expression of the initial shape and position characteristics are used to simulate the initial reproductive cleft and uterus-vaginal angle of the two-dimensional pelvic floor finite element model with concentrated force loads to analyze the changing trend of the shape and position characteristics of the pelvic floor due to the decline of tissue mechanical properties. Combined with the proportional damage simulation method in Step 3, a pelvic floor finite element evolution model is constructed. The specific steps of step 3 are as follows: 3.1) Material samples were taken from each pelvic floor organ tissue, and uniaxial tensile tests were performed on them; 3.2) Nonlinear material stress-strain data of each healthy organ obtained by uniaxial tensile test were imported into finite element software and fitted into nonlinear curves of Mooney-Rivlin, Ogden, Yeoh, and Neo-Hookean hyperelastic materials, respectively. Different hyperelastic material models were selected according to different organs. 3.3) A proportional damage simulation method and proportional damage expression are adopted, introducing a proportional damage coefficient K. The stress-strain curve datasets of each organ are multiplied by the corresponding proportional damage coefficient K to simulate the degree of damage to pelvic floor organ tissues. The smaller the proportional damage coefficient K, the lower the tensile stiffness of the material, the lower the material properties, and the greater the degree of damage. * The relationship with the proportional damage coefficient K is as follows: 。 2. The method for locating the cardinal ligament and sacrosacral ligament of the uterus and constructing a finite element model of pelvic floor evolution according to claim 1, characterized in that: The specific steps of step 2 are as follows: 2.1) Locate the origin of the sacral ligament distribution using the medical imaging software Mimics: Origin: Using the medical imaging software Mimics, the origin of the sacrospinous ligament is located on the sacrospinous ligament-coccygeal muscle complex on the 2nd to 3rd sacral vertebrae from the bottom to the top of the cross-sectional image set. Endpoint: Located in the cervix or vaginal apex region. The location of the endpoint is determined by the specific patient's MRI images. This region serves as the endpoint of the distribution of the sacroligament. 2.2) Locate the starting point of the cardinal ligament distribution using the medical imaging software Mimics: Origin: Using the medical imaging software Mimics, the point at the top of the greater sciatic foramen on the ipsilateral pelvic side wall, at the sacroiliac joint, is located in the cross-sectional images. This point is the origin of the cardinal ligament of the uterus. End point: The cardinal ligament terminates at the cervix or posterolateral aspect of the vagina, and this point is considered the endpoint of the cardinal ligament. 2.3) Based on the starting point and ending point determined in the above steps, and combined with the two-dimensional image of the midsagittal plane, the cardinal ligament and sacral ligament of the uterus in the two-dimensional pelvic floor finite element model are equivalently represented by an approximately parallel distributed nonlinear hyperelastic spring group.

3. The method for locating the cardinal ligament and sacrosacral ligament of the uterus and constructing a finite element model of pelvic floor evolution according to claim 1, characterized in that: The specific steps of step 4 are as follows: 4.1) In the two-dimensional pelvic floor finite element model, a concentrated load method and a concentrated force-displacement expression are used to apply a concentrated horizontal force load to the nodes at the fundus of the uterus to simulate the abnormal initial shape and position characteristics of the uterus-vaginal angle in an upright mid-position uterus and a retroverted retroverted uterus. Different concentrated force-angle expressions are obtained by fitting curves for different two-dimensional pelvic floor finite element models. The fitted expression is as follows: ； Where θ is the uterine-vaginal angle, in degrees (°), F v The concentrated force applied at the fundus of the uterus is measured in Newtons. 4.2) In the two-dimensional pelvic floor finite element model, a concentrated load application method and a concentrated force-displacement expression are used to apply concentrated force loads to the nodes at the vaginal base to simulate the widening of the reproductive tract cleft in the physiological pelvic floor. Different concentrated force-displacement expressions are obtained by fitting curves for different two-dimensional pelvic floor finite element models. The relationship between the reproductive cleft and the concentrated force is fitted to an approximately linear relationship, expressed as: ； Where D GH F represents the width of the reproductive slit, in meters. u The concentrated force applied to the bottom of the posterior vaginal wall is measured in Newtons.

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