Design method of talus prosthesis

Abstract

The invention discloses a design method of a talus prosthesis in the technical field of medical instruments, which comprises the following steps of: 1, scanning an ankle joint through CT (Computed Tomography), and collecting original data of the ankle joint; 2, preparing a three-dimensional ankle joint building system, wherein an information acquisition unit is preset in the three-dimensional ankle joint building system; 3, performing finite element analysis on the ankle joint three-dimensional digital model; 4, the influence coefficient of cartilage and ligament on the stability and stress distribution of the talus is judged; the parts, with the influence coefficient higher than a preset value, in the cartilage and the ligament are completely cut off, the thickness of the parts, with the influence coefficient lower than the preset value, in the cartilage and the ligament is increased in a gradient mode, the influence coefficient of the parts on the talus prosthesis in the state is calculated, and the thickness state with the lowest influence coefficient is selected and output as the final design scheme. The ankle joint of a patient is modeled, and then the mechanical behaviors of the talus in the ankle joint under various conditions are simulated and analyzed through finite element analysis.

Description

Technical Field

[0001] The invention relates to the technical field of medical devices, in particular to a design method for a talar prosthesis. Background Art

[0002] A talar prosthesis is an artificial substitute used to replace the talus that has been damaged due to disease, injury or aging. The talus is a key structure connecting the foot and lower limbs, with a complex anatomical structure and important biomechanical functions. When the talus is severely injured or diseased, such as avascular necrosis, nonunion of fractures or bone tumors, traditional treatments may not be able to effectively restore its function. At this time, a talar prosthesis replacement is needed to restore the stability and function of the ankle joint.

[0003] The main purpose of talar prosthesis design is to restore normal ankle function and stability. By accurately simulating the anatomical morphology and biomechanical properties of the talus, the prosthesis is able to provide similar support and range of motion after replacement, allowing patients to regain the ability to walk, run, jump and other daily activities.

[0004] The current existing talar prosthesis design method designs the talar prosthesis by building a three-dimensional model of the ankle joint, but there are still problems with the biocompatibility and wear possibility of the implant material. Therefore, it is necessary to propose a talar prosthesis design method. Summary of the invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide a design method of a talar prosthesis, by modeling the patient's ankle joint, and then simulating and analyzing the mechanical behavior of the talus in the ankle joint under various conditions through finite element analysis. The finite element analysis is used to evaluate the structural integrity of the prosthesis and its interaction with surrounding bones and tissues in detail, and the finite element analysis helps to predict stress distribution and identify potential failure or excessive wear points. Finally, the finite element analysis is also used to provide insights into the performance of the prosthesis under different load conditions to assist in the design of the talar prosthesis.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A method for designing a talar prosthesis comprises: step 1: collecting original data of a healthy ankle joint by CT scanning;

[0007] Step 2: Prepare a 3D ankle joint construction system. The 3D ankle joint construction system is preset with an information acquisition unit. The information acquisition unit is used to collect the original data of the ankle joint collected by CT. The 3D ankle joint construction system is used to construct a 3D digital model of the ankle joint including the talus, tibia, calcaneus, cartilage and surrounding ligament tissue according to the original data of the ankle joint.

[0008] Features:

[0009] Step 3: Perform finite element analysis on the three-dimensional digital model of the ankle joint. The cartilage and ligament tissues on the talus in the three-dimensional digital model of the ankle joint are removed in proportion, and the three-dimensional digital model of the ankle joint with the cartilage and ligament tissue removed is imported into the engineering simulation software for finite element analysis. The engineering simulation software has preset mechanical performance parameters of the talus, tibia, calcaneus, cartilage and ligament tissues. The mechanical performance parameters are the average values ​​of several healthy ankle joints sampled and measured in the laboratory. The simulation analysis includes talus stability analysis and stress distribution analysis;

[0010] Step 4: Based on the results of the talar stability analysis and stress distribution analysis in step 3, determine the influence coefficient of cartilage and ligament on talar stability and stress distribution. The influence coefficient is used to map the difference between talar stability and stress distribution after cartilage and ligament resection and a healthy ankle joint. The portion of cartilage and ligament with an influence coefficient higher than the preset value is completely removed. For the portion of cartilage and ligament with an influence coefficient lower than the preset value, the thickness is gradually increased and the influence coefficient on the talar prosthesis is calculated. The thickness state with the lowest influence coefficient is selected as the final design solution.

[0011] The principle of the basic scheme is: by collecting the original data of the healthy ankle joint from the CT scan, a 3D digital model of the ankle joint is established, and by performing finite element analysis on the 3D digital model of the ankle joint, the 3D digital model of the ankle joint is divided into a finite number of small units, and the physical behavior in each unit is analyzed to form a mechanical analysis of the entire 3D digital model of the ankle joint. By judging the influence coefficient of cartilage and ligament on the stability and stress distribution of the talus, the part with an influence coefficient higher than the preset value is completely removed, and for the part below the preset value, the thickness is increased gradually and the influence coefficient on the talar prosthesis is calculated under its state.

[0012] The beneficial effects of the basic scheme are: 1. Among multiple design schemes, the optimal scheme can be screened out through finite element analysis, thereby improving the performance and quality of the talar prosthesis and reducing material waste and manufacturing costs.

[0013] 2. Finite element analysis can help engineers evaluate the risks and problems that talar prostheses may encounter during use, such as stress concentration, fatigue damage, etc., so that they can take measures to improve them in advance.

[0014] Furthermore, in step 2, the talus, tibia, calcaneus, cartilage and surrounding ligament tissues are distinguished by adjusting the grayscale threshold during the construction of the three-dimensional digital model of the ankle joint.

[0015] The beneficial effect of the basic scheme is that different tissues have different grayscale values ​​in CT scans. By adjusting the grayscale threshold, hard bone tissues such as the talus, tibia, and calcaneus and soft tissues such as surrounding ligaments can be accurately distinguished. This helps to more accurately restore the true structure of the ankle joint during the 3D modeling process.

[0016] Furthermore, in step 2, the initially constructed three-dimensional digital model of the ankle joint is subjected to surface optimization and detail processing to remove noise and check for distorted or missing surfaces.

[0017] The beneficial effect of the basic solution is: During the 3D scanning and modeling process, noise points or noise surfaces may be generated due to factors such as equipment accuracy and environmental interference. These noises may have an adverse effect on subsequent analysis and application. Through surface optimization, these noises can be effectively removed to make the model smoother and clearer.

[0018] Furthermore, in step 2, the shape, size and material properties of the talar prosthesis are designed based on the three-dimensional digital model of the ankle joint after surface optimization and detail processing.

[0019] The benefit of the basic solution is that by referring to the 3D digital model with optimized surface and detailed processing, it can be ensured that the shape and size of the talar prosthesis closely matches the actual anatomy of the patient.

[0020] Furthermore, in step three, the three-dimensional digital model of the ankle joint is assembled and error-checked, and then imported into engineering simulation software for simulation analysis.

[0021] The benefits of the basic solution are: simulation analysis can simulate various conditions in the real working environment, accurately predict the performance of the model, discover potential problems in advance and optimize the design. Based on the results of simulation analysis, multiple design iterations can be quickly performed to optimize product structure, material selection, etc. until the best performance is achieved.

[0022] Furthermore, in step three, a static analysis module is created through engineering simulation software, tetrahedral meshing is used, and the number of meshes is adjusted.

[0023] The beneficial effect of the basic scheme is that in static analysis, stress distribution is one of the key information. By adjusting the number of grids, it is possible to ensure that there is sufficient grid density in key areas (such as stress concentration points) to more accurately simulate and analyze stress distribution.

[0024] Furthermore, in the bone stability analysis and stress distribution analysis, fixed constraints were inserted into the upper ends of the tibia and fibula of the three-dimensional digital model of the ankle joint to apply pressure to the foot.

[0025] The beneficial effects of the basic scheme are: the upper ends of the tibia and fibula are the main load-bearing bones of the lower limbs, and their fixed constraints can simulate the relatively stable state of the lower limb bones during activities such as standing and walking. This fixation method helps to more accurately simulate the stress conditions of the ankle joint and surrounding structures in a real environment. By applying pressure to the foot, the impact force on the foot in different situations (such as walking, running, jumping, etc.) can be simulated. This pressure simulation helps to analyze the stability of the ankle joint under different loads, stress distribution, and possible injury mechanisms.

[0026] Furthermore, the maximum equivalent stress and deformation results are inserted into the bone stability analysis and stress distribution analysis.

[0027] The beneficial effects of the basic scheme are: the maximum equivalent stress is an important indicator for evaluating whether a structure will yield or fail under a specific load. The maximum equivalent stress value obtained through simulation analysis can be compared with the yield strength of the design material to determine the safety performance of the model in actual use. The deformation result is an important indicator for evaluating the ability of a structure to resist deformation under load. The deformation results obtained through simulation analysis can understand the deformation of the model under different loads, thereby evaluating its stiffness performance.

[0028] Furthermore, in step four, the final design is to remove all ligaments and adopt a cartilage thickness state of 0.5 mm.

[0029] The benefits of the basic solution are: the cartilage cover can simulate the cartilage tissue on the surface of the natural talus, providing better biocompatibility between the prosthesis and the surrounding tissue. The stress distribution of adding a 0.5 mm cartilage cover is most similar to that of a normal ankle joint.

[0030] Furthermore, after the design is completed, in vitro experimental verification is carried out, including mechanical property testing, biocompatibility assessment, and durability testing to ensure the feasibility of the design solution and the accuracy of the simulation.

[0031] The beneficial effects of the basic scheme are: through mechanical property testing, the stress distribution, deformation and load-bearing capacity of talar prostheses with cartilage covering layers of different thicknesses under simulated loads can be evaluated, thereby verifying whether the design meets the expected mechanical requirements. Good biocompatibility helps the fusion and healing of the prosthesis with surrounding tissues and improves the treatment effect. By evaluating the biocompatibility of cartilage covering layers of different thicknesses, the optimal design scheme can be selected to better promote the recovery of joint function. Through durability testing, the performance changes of different materials during long-term use can be understood, so as to select more suitable materials for the manufacture of prostheses. This helps to improve the durability and service life of the prosthesis. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 11 is a diagram of the steps of a method for designing a talar prosthesis in an embodiment of the present invention.

[0033] Figure 2 A detailed step diagram of model construction for a design method of a talar prosthesis in an embodiment of the present invention.

[0034] Figure 3 1 is a finite element analysis refinement step diagram of a design method for a talar prosthesis in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following is further described in detail through specific implementation methods:

[0036] Embodiment 1:

[0037] Basically as attached Figure 1 -Attached Figure 3 Shown: A method for designing a talar prosthesis, comprising: step 1: collecting original data of the ankle joint by scanning a healthy ankle joint through CT, wherein spiral CT is preferably used.

[0038] Step 2: Prepare a 3D ankle joint construction system. The 3D ankle joint construction system is pre-set with an information acquisition unit. The information acquisition unit is used to collect the original data of the ankle joint collected by CT. The 3D ankle joint construction system is used to construct a 3D digital model of the ankle joint including the talus, tibia, calcaneus, and surrounding ligament tissues based on the original data of the ankle joint. In the process of constructing the 3D digital model of the ankle joint, the talus, tibia, calcaneus, cartilage, and surrounding ligament tissues are distinguished by adjusting the grayscale threshold. The surface of the initially constructed 3D digital model of the ankle joint is optimized and detailed, noise is removed, and distorted or missing surfaces are checked. The shape, size, and material properties of the talus prosthesis are designed based on the 3D digital model of the ankle joint after surface optimization and detail processing.

[0039] Features:

[0040] Step 3: Assemble and check the model for errors, and then import it into the engineering simulation software for simulation analysis. Finite element analysis is performed on the three-dimensional digital model of the ankle joint. The cartilage and ligament tissues on the talus in the three-dimensional digital model of the ankle joint are removed in proportion, and the three-dimensional digital model of the ankle joint with the cartilage and ligament tissue removed is imported into the engineering simulation software for finite element analysis. The engineering simulation software presets the mechanical properties parameters of the talus, tibia, calcaneus, cartilage and ligament tissues. The mechanical properties parameters are the average values ​​of several healthy ankle joints sampled and measured in the laboratory. The simulation analysis includes talus stability analysis and stress distribution analysis; a static analysis module is created through the engineering simulation software, and tetrahedral meshing is used to adjust the number of meshes. In the bone stability analysis and stress distribution analysis, fixed constraints are inserted into the upper ends of the tibia and fibula of the three-dimensional digital model of the ankle joint to apply pressure to the foot. The maximum equivalent stress and deformation results are inserted into the bone stability analysis and stress distribution analysis.

[0041] Step 4: According to the results of the talus stability analysis and stress distribution analysis in step 3, determine the influence coefficient of cartilage and ligament on talus stability and stress distribution. The influence coefficient is used to map the difference between talus stability and stress distribution after cartilage and ligament removal and healthy ankle joint. The cartilage and ligament parts with influence coefficients higher than the preset value are completely removed; for the cartilage and ligament parts with influence coefficients lower than the preset value, the thickness is increased gradually and the influence coefficient on the talus prosthesis is calculated. The thickness state with the lowest influence coefficient is selected as the final design solution. The final design solution is to remove all ligaments and use a cartilage thickness state of 0.5 mm.

[0042] After the design is completed, in vitro experimental verification is carried out, including mechanical property testing, biocompatibility assessment and durability testing, to ensure the feasibility of the design scheme and the accuracy of the simulation.

[0043] The specific implementation process is as follows: First, use CT to perform a high-resolution scan of the healthy ankle joint, ensuring that the scanning layer thickness is thin enough to obtain clear DICOM format raw data.

[0044] Then the CT data in DICOM format were imported into Mimics software to establish a preliminary 3D digital model of the ankle joint. The talus, tibia, calcaneus, cartilage and ligament tissue were distinguished by setting an appropriate grayscale threshold. The "New Mask" function in the 3D digital model was used to generate a mask covering a specific area based on the grayscale value, and the 3D models of each part were gradually extracted.

[0045] After establishing the 3D digital model of the ankle joint, the extracted talus, tibia and calcaneus models can be smoothed to remove noise and redundant parts. Then, Geomagic software can be used to further refine the model surface, fill holes, round corners and remove noise to ensure the accuracy and smoothness of the model. Finally, the optimized model can be saved in STL format and imported into SolidWorks for assembly.

[0046] In SolidWorks, according to the anatomical structure, tools such as "Sketch" and "Lofted Boss" were used to draw and create ligament models, including the anterior talofibular ligament, posterior talofibular ligament, calcaneofibular ligament, etc.

[0047] In SolidWorks, the talus, tibia, calcaneus and ligaments were assembled accurately to ensure that the parts were in the correct position without overlap or misalignment. Finally, the "interference check" function was used to detect and correct potential assembly problems.

[0048] Import the assembled ankle 3D model into Ansys Workbench in an appropriate format (such as IGES or STP) for finite element analysis. First, you need to set the material properties, including elastic modulus, Poisson's ratio and other parameters of materials such as bones, cartilages, and ligaments. Then you can use tetrahedral meshes to divide the model, paying special attention to refinement in key areas (such as ligament connections and talar prosthesis contact surfaces). Then you can set fixed constraints on the upper ends of the tibia and fibula of the model to simulate the in vivo fixation state. Apply loads to the model that are consistent with actual walking or activity conditions, such as pressure, torque, etc.

[0049] Then you can create a static analysis module to simulate the model, remove the ligament tissue around the talus, and perform a talar stability analysis in the process, observe and record the stress and deformation of the model. The results showed that the sequential removal of the surrounding ligaments, including the lateral ligament, medial ligament, and talonavicular ligament, had no significant effect on the stability of the talar prosthesis. The stress value ranged from 2.2257MPa to 3.0218MPa, and the displacement value was stable at around 1.6611mm to 2.2119mm. By removing the cartilage and performing a talar stability analysis in the process, it was found that different cartilage thicknesses had a significant effect on the stability of the talar prosthesis.

[0050] Then, cartilage covering layers of different thicknesses can be designed and covered on the surface of the talar prosthesis to ensure that the covering layer fits tightly to the surface of the prosthesis without any gaps. Simulation analysis is performed on each thickness of the cartilage covering layer to observe and record the stress distribution and deformation of the talar prosthesis at different thicknesses.

[0051] The analysis results were compared with the stress distribution of the normal ankle joint to evaluate the effect of different thicknesses of cartilage covering on prosthesis performance. The results showed that adding a 0.5 mm cartilage covering resulted in a stress distribution most similar to that of a normal ankle joint, improving prosthesis performance.

[0052] Therefore, the final design was to remove all the ligaments and use a talar prosthesis with a cartilage thickness of 0.5 mm.

[0053] Through mechanical property tests, the load-bearing capacity, stiffness and other properties of the prosthesis are evaluated. Biocompatibility assessment is conducted to observe the interaction between the prosthesis and the surrounding tissues and evaluate its safety and long-term stability. Durability tests are conducted to simulate the wear and aging process under long-term use and evaluate the service life of the prosthesis.

[0054] The following is the experimental data:

[0055] Table 1. Summary of talar prosthesis +0 mm displacement and contact stress

[0056]

[0057] Table 2. Summary of talar prosthesis +0.5 mm displacement and contact stress

[0058]

[0059]

[0060] Table 3. Summary of talar prosthesis +1 mm displacement and contact stress

[0061]

[0062] Table 4. Summary of talar prosthesis +1.5 mm displacement and contact stress

[0063]

[0064] Table 5. Summary of talar prosthesis +2 mm displacement and contact stress

[0065]

[0066] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0067] The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for designing a talar prosthesis, comprising: Step 1: Scan the healthy ankle joint through CT to collect the original data of the ankle joint; Step 2: Prepare a 3D ankle joint construction system. The 3D ankle joint construction system is preset with an information acquisition unit. The information acquisition unit is used to collect the original data of the ankle joint collected by CT. The 3D ankle joint construction system is used to construct a 3D digital model of the ankle joint including the talus, tibia, calcaneus, cartilage and surrounding ligament tissue according to the original data of the ankle joint. Features: Step 3: Perform finite element analysis on the three-dimensional digital model of the ankle joint. The cartilage and ligament tissues on the talus in the three-dimensional digital model of the ankle joint are removed in proportion, and the three-dimensional digital model of the ankle joint with the cartilage and ligament tissue removed is imported into the engineering simulation software for finite element analysis. The engineering simulation software has preset mechanical performance parameters of the talus, tibia, calcaneus, cartilage and ligament tissues. The mechanical performance parameters are the average values ​​of several healthy ankle joints sampled and measured in the laboratory. The simulation analysis includes talus stability analysis and stress distribution analysis; Step 4: Based on the results of the talar stability analysis and stress distribution analysis in step 3, determine the influence coefficient of cartilage and ligament on talar stability and stress distribution. The influence coefficient is used to map the difference between talar stability and stress distribution after cartilage and ligament resection and a healthy ankle joint. The portion of cartilage and ligament with an influence coefficient higher than the preset value is completely removed. For the portion of cartilage and ligament with an influence coefficient lower than the preset value, the thickness is gradually increased and the influence coefficient on the talar prosthesis is calculated. The thickness state with the lowest influence coefficient is selected as the final design solution.

2. The method for designing a talar prosthesis according to claim 1, characterized in that: In step 2, the talus, tibia, calcaneus, cartilage and surrounding ligament tissues are distinguished by adjusting the grayscale threshold during the construction of the three-dimensional digital model of the ankle joint.

3. The design method of the talar prosthesis according to claim 2, characterized in that: In step 2, the initially constructed 3D digital model of the ankle joint is subjected to surface optimization and detail processing to remove noise and check for distorted or missing surfaces.

4. The method for designing a talar prosthesis according to claim 3, characterized in that: In step 2, the shape, size, and material properties of the talar prosthesis were designed based on the three-dimensional digital model of the ankle joint after surface optimization and detail processing.

5. The method for designing a talar prosthesis according to claim 4, characterized in that: In step three, the three-dimensional digital model of the ankle joint is assembled and error-checked, and then imported into the engineering simulation software for simulation analysis.

6. The method for designing a talar prosthesis according to claim 5, characterized in that: In step three, a static analysis module is created through engineering simulation software, tetrahedral meshing is used, and the number of meshes is adjusted.

7. The method for designing a talar prosthesis according to claim 6, characterized in that: In the bone stability analysis and stress distribution analysis, fixed constraints were inserted into the upper ends of the tibia and fibula of the 3D digital model of the ankle joint to apply pressure to the foot.

8. The method for designing a talar prosthesis according to claim 7, characterized in that: Insert maximum equivalent stress and deformation results into bone stability analysis and stress distribution analysis.

9. The method for designing a talar prosthesis according to claim 8, characterized in that: In step 4, the final design is to remove all ligaments and use a cartilage thickness of 0.5 mm.

10. The method for designing a talar prosthesis according to claim 9, characterized in that: After the design is completed, in vitro experimental verification is carried out, including mechanical property testing, biocompatibility assessment and durability testing, to ensure the feasibility of the design scheme and the accuracy of the simulation.

Images