Design method of Paporosky III type acetabular defect reconstruction prosthesis

Abstract

A design method of a Paporosky III-type acetabular defect reconstruction prosthesis comprises the following steps: acquiring pelvic CT images of a defective side and an uninjured side, constructing a three-dimensional pelvic model according to the pelvic CT image of the defective side, and finally adding a bone grafting cage on the surface of a prosthesis model in a second prosthesis optimization model through other eight steps to obtain the Paporosky III-type acetabular defect reconstruction prosthesis. The prosthesis designed by the design method of the Paporosky III type acetabular defect reconstruction prosthesis can reduce tissue irritation and trauma, and has the advantages of upward movement resistance, rotation resistance, high biomechanical strength, initial stability and good long-term stability.

Description

Technical Field

[0001] This invention relates to the field of acetabular defect reconstruction technology, and in particular to a design method for a Paporosky III type acetabular defect reconstruction prosthesis. Background Technology

[0002] Repairing and reconstructing Paprosky type III acetabular defects is one of the most challenging problems in joint surgery. With the rise of 3D printing technology, customized revision prostheses have provided a new solution. However, the potential mechanical mechanism between structural optimization of revision prostheses and the immediate and long-term stability of the prosthesis after reconstruction is still unclear.

[0003] Currently, there is still controversy regarding reconstruction strategies for Paprosky type III acetabular defects. Clinically used methods such as acetabular cups, metal pads, reinforced cups, cemented acetabular cups, and cage titanium mesh reconstruction have yielded unsatisfactory results for these complex acetabular defects. 3D-printed customized prostheses, as the ultimate solution for these defects, have been explored in clinical practice. However, current designs vary in quality. Key issues remain unresolved, including the number and location of screws, their direction, optimal combination of iliofemoral-pubic screws for synergistic effects, improving prosthesis anti-rotation, especially during weight-bearing, reducing prosthesis volume to avoid stress shielding while maintaining fixation strength, and balancing initial and long-term prosthesis stability. Research in this area is currently both a hot topic and a challenging area.

[0004] Therefore, it is essential to provide a design method for the Paporosky III type acetabular defect reconstruction prosthesis to address the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a design method for a Paporosky III type acetabular defect reconstruction prosthesis. The prosthesis designed using this method reduces tissue irritation and trauma, and possesses advantages such as resistance to upward displacement and rotation, high biomechanical strength, and good initial and long-term stability.

[0006] The above-mentioned objectives of the present invention are achieved through the following technical measures:

[0007] A design method for a Paporosky III type acetabular defect reconstruction prosthesis is provided, comprising the following steps:

[0008] S1. Obtain CT images of the pelvis, including the defective side and the healthy side, and construct a three-dimensional model of the pelvis based on the CT images of the defective side.

[0009] S2. Perform mesh convergence and verification analysis on the 3D pelvic model obtained in S1 to obtain the optimal mesh size, and then proceed to S3 to obtain the solidified acetabular defect pelvic model with the optimal mesh size.

[0010] S3. Based on the contralateral image of the pelvic CT image, the rotation center of the solidified acetabular defect pelvic model obtained in S2 is reconstructed, and a prosthesis model is generated. The prosthesis model includes a three-wing plate, a bone graft pad, an acetabular cup, a wear-resistant liner, and hooks to prevent the overall upward movement and rotation of the prosthesis model.

[0011] S4. Assemble the prosthesis model described in S3 and the solidified acetabular defect pelvic model described in S2 into a whole to obtain the assembled model.

[0012] S5. Generate a pin path in the assembly model that runs from the prosthesis model through the solidified acetabular defect pelvic model. The pin path is divided into multiple first pin paths and multiple second pin paths. The length of the first pin path is greater than the length of the second pin path. This yields the first prosthesis optimization model. Proceed to S6.

[0013] S6. Based on the hip joint reaction force under multiple daily activity conditions, calculate the maximum nodal force, total stiffness value and micromomentum value of each pin track. Based on the maximum nodal force, total stiffness value and micromomentum value, screen the pin tracks to obtain the optimal pin track combination. Then delete the other pin tracks except for the optimal pin track combination to obtain the second prosthesis optimization model.

[0014] S7. Optimize the second spurious model obtained in S6 using the variable density method, thereby reducing the material content of the assembly model and obtaining the third spurious model.

[0015] S8. Based on the third prosthesis optimization model obtained in S7, the prosthesis model generates different porosities according to the stress range, and the bone graft pad is a fourth prosthesis optimization model with a gradient porous structure. Proceed to S9.

[0016] S9. Add a bone graft cage to the surface of the prosthesis model in the fourth prosthesis optimization model in S8 to obtain the Paporosky III type acetabular defect reconstruction prosthesis.

[0017] Preferably, S7 specifically involves optimizing the second prosthesis optimization model obtained in S6 using Tosca's variable density method for prostheses. Specifically, the three-wing steel plate is divided into different stress grids according to the stress range, and the density value of each stress grid is different. All stress grids are arranged from high to low according to the stress range, and the density value distribution is the opposite of the stress arrangement order of the stress grids. That is, the density value of the stress grid with the maximum stress is 1, and the density value of the stress grid with the minimum stress is 0. The three-wing steel plate is then subjected to material reduction to obtain the second prosthesis optimization model.

[0018] Preferably, S8 specifically involves: dividing the bone graft block region in the third prosthesis optimization model obtained in S7 into multiple stress regions according to the stress range, arranging all stress regions from high to low according to the stress range, and ensuring that the porosity of each stress region is different, and that the porosity distribution is the opposite of the stress arrangement order of the stress regions, i.e., the stress region with the maximum stress has the lowest porosity, and the stress region with the minimum stress has the highest porosity, thus obtaining the second prosthesis optimization model in which the bone graft block has a gradient porous structure, and proceeding to S9.

[0019] Preferably, S9 specifically involves adding a bone graft cage to the surface of the bone graft pad in the fourth prosthesis optimization model of S8 to prevent dislocation of the osteogenic material, such as... Figures 7-9 The bone graft cage is located in the gap between the bone graft pad and the pelvis, resulting in the Paporosky III type acetabular defect reconstruction prosthesis.

[0020] In the prosthetic model, the acetabular cup is located inside the groove of the bone graft pad, the three-winged steel plate is integrally connected to the upper surface of the acetabular cup, the wear-resistant liner is disposed inside the groove of the acetabular cup, the hook is integrally connected to the edge of the three-winged steel plate, the three-winged steel plate covers the ilium, pubis and ischium of the solidified acetabular defect pelvic model, the hook is engaged with the obturator foramen edge of the hip bone of the solidified acetabular defect pelvic model, and the bone graft pad is located at the acetabulum of the solidified acetabular defect pelvic model.

[0021] Preferably, the three-winged steel plate covers 1 / 3 to 2 / 3 of the iliac bone in the solidified acetabular defect pelvic model and is located anterior to the gluteus minimus insertion.

[0022] Preferably, the coverage area of ​​the ischium by the aforementioned three-winged steel plate in the solidified acetabular defect pelvic model is from the acetabulum to the ischial tuberosity.

[0023] Preferably, in the solidified acetabular defect pelvic model, the coverage area of ​​the pubis by the aforementioned three-wing steel plate extends from the acetabulum to the pubic tubercle.

[0024] Preferably, the above specifically refers to: each first screw track penetrating from the acetabular cup into the interior of the solidified acetabular defect pelvic model, and the first screw track does not penetrate the outer cortex of both sides of the solidified acetabular defect pelvic model; the second screw track penetrating from the three-wing plate into the interior of the solidified acetabular defect pelvic model, and the second screw track is perpendicular to the bone surface; the first screw track and the second screw track are distributed in the ilium, pubis and ischium of the solidified acetabular defect pelvic model, and the first screw track and the second screw track are most numerous in the ilium;

[0025] S5.2 Generate different nail path combinations A with all the first nail paths and all the second nail paths, and proceed to S6. Each nail path combination A consists of N nail paths, and the number of first nail paths is the same as the number of second nail paths.

[0026] Preferably, S6 is performed by the following steps:

[0027] S6.1 Establish a three-dimensional coordinate system in the assembly model, and apply the joint reaction force of daily activity conditions from the center of the femoral head ball in the assembly model towards the acetabulum;

[0028] S6.2. Based on the hip joint reaction force under multiple daily activity conditions, the maximum nodal force of each nail track is calculated by inputting the corresponding X-axis force data, Y-axis force data, and Z-axis force data under each daily activity condition into the assembly model. The average value of the maximum nodal forces generated by all daily activity conditions in each nail track is taken as the first nodal force of the nail track. The hip joint reaction force includes resultant force data, X-axis force data, Y-axis force data, and Z-axis force data.

[0029] S6.3 Sort all needle tracks in descending order of the first node force in S6.2, and copy the first prosthesis optimization model to obtain two first prosthesis optimization models;

[0030] S6.4. In one of the first prosthesis optimization models, select the first 14 pin tracks and delete the other pin tracks to obtain a screening prosthesis optimization model; in another first prosthesis optimization model, select the first 2 first pin tracks and the first 4 second pin tracks in the iliac crest, select the first 1 first pin track and the first 3 second pin tracks in the pubis, select the first 1 first pin track and the first 3 second pin tracks in the ischium, and delete the other pin tracks to obtain another screening prosthesis optimization model;

[0031] S6.5 In the two screening prosthesis optimization models in S6.4, 9 pin tracks are used as a pin track combination. Then, based on the hip joint reaction force under multiple daily activity conditions, the total stiffness value and micromomentum of each pin track combination in the two screening prosthesis optimization models are calculated.

[0032] S6.6. Take the average of the total stiffness values ​​generated by all daily activity conditions in each spike track assembly to obtain the average total stiffness value of each spike track assembly; take the average of the micro-motion values ​​of all daily activity conditions in each spike track assembly to obtain the average micro-motion value of each spike track assembly.

[0033] S6.7. Weight the average total stiffness and average micromoment of each pin combination to obtain the index value. Select the pin combination with the best index value as the optimal pin combination. Delete other pins besides the optimal pin combination in the screening prosthesis optimization model corresponding to the optimal pin combination to obtain the third prosthesis optimization model.

[0034] Preferably, the above-mentioned daily activities include heel strike, toe push-off, normal walking, going upstairs, going downstairs, standing up, sitting down, bending knees, and standing on both feet.

[0035] Preferably, S2 specifically involves: importing the 3D pelvic model obtained in S1 into Hypermesh for mesh optimization; selecting five isolated mesh models with different mesh sizes within the range of 1mm to 4mm into Mimics software; assigning grayscale values ​​according to empirical formulas; then importing the five isolated mesh models into Abaqus software for mesh convergence analysis and model validity verification to determine the optimal mesh size for the 3D pelvic model.

[0036] Preferably, S4 is performed by the following steps:

[0037] S4.1. Import the solidified acetabular defect pelvic model from S2 into Hypermesh software, then import the optimal mesh size obtained in S2 into Hypermesh, and assemble the prosthesis model from S3 and the solidified acetabular defect pelvic model from S2 into a whole.

[0038] S4.2 Assign material properties, wherein the materials of the three-wing steel plate, the bone graft pad, the acetabular cup and the hook are all Ti6Al4V, the material of the wear-resistant liner is polyethylene, and the material of the femoral head in the solidified acetabular defect pelvic model is CoCrMo alloy; the solidified acetabular defect pelvic model adopts grayscale assignment, defines the contact relationship, constraints and boundaries between the prosthesis model and the solidified acetabular defect pelvic model, and restricts the degrees of freedom in the six directions of the sacroiliac joint, the dorsum of the ilium, and the pubic symphysis in the solidified acetabular defect pelvic model to be completely fixed.

[0039] In S5, the nail path is replaced by a beam unit, the diameter of the nail path is 6.0 mm, the length of the first nail path is 60 mm, and the length of the second nail path is 40 mm.

[0040] The present invention discloses a design method for a Paporosky III type acetabular defect reconstruction prosthesis, comprising the following steps: S1, acquiring CT images of the pelvis including the defect side and the healthy side, and constructing a three-dimensional pelvic model based on the CT image of the defect side; S2, performing mesh convergence and verification analysis on the three-dimensional pelvic model obtained in S1 to obtain an optimal mesh size, and proceeding to S3; S3, reconstructing the rotation center based on the healthy side mirror image of the pelvic CT image on the solidified acetabular defect pelvic model obtained in S2, and generating a prosthesis model, wherein the prosthesis model includes a three-winged plate, a bone graft, an acetabular cup, a wear-resistant liner, and hooks to prevent the overall upward movement and rotation of the prosthesis model; S4, assembling the prosthesis model of S3 and the solidified acetabular defect pelvic model of S2 into a whole, obtaining an assembled model; S5, generating a pin path in the assembled model that runs from the prosthesis model through the solidified acetabular defect pelvic model, wherein the pin path is divided into multiple The system consists of a first screw track and multiple second screw tracks, with the length of the first screw track being greater than the length of the second screw tracks, resulting in a first prosthesis optimization model, which proceeds to step S6. In step S6, based on the hip joint reaction forces under multiple daily activity conditions, the maximum nodal force, total stiffness, and micromomentum value of each screw track are calculated. The optimal screw track combination is obtained by filtering based on these values, and then all other screw tracks are deleted, resulting in a second prosthesis optimization model. In step S7, the second prosthesis optimization model obtained in step S6 is optimized using the variable density method, thereby reducing the material content of the assembly model, resulting in a third prosthesis optimization model. In step S8, based on the prosthesis model in the third prosthesis optimization model obtained in step S7, different porosities are generated according to the stress range, resulting in a fourth prosthesis optimization model with a gradient porous structure for the bone graft pad, which proceeds to step S9. In step S9, a bone graft cage is added to the surface of the prosthesis model in the fourth prosthesis optimization model from step S8, resulting in the Paporosky III acetabular defect reconstruction prosthesis. Compared with existing technologies, the design method of this Paporosky III acetabular defect reconstruction prosthesis has the following advantages: 1. This invention adds hooks to the prosthesis model, thereby providing advantages such as resistance to upward displacement and rotation, high biomechanical strength, and good initial and long-term stability. 2. The screw screening and analysis process of this invention incorporates multiple screw track positions, covers various screw track combinations and multiple working conditions, and considers the combined effect of screw tracks. This is more scientific and theoretically sound than existing screw track analysis methods, and has better clinical guidance value.3. This invention optimizes the macroscopic topology of the prosthesis using a variable density method, reducing the prosthesis volume to facilitate clinical implantation, minimize tissue irritation and trauma, and maintain necessary initial stability and fixation strength while reducing the overall structural stiffness of the prosthesis. It also minimizes low-stress shielding effects and ensures that micro-movements at the prosthesis-bone interface remain within a range conducive to bone ingrowth (less than 50 μm), thus improving the long-term stability of the prosthesis and preventing loosening due to long-term bone resorption, thereby guaranteeing the fixation effect. 4. Unlike traditional pads, the bone graft pad of this invention is integrally molded with the prosthesis body and structurally optimized through stress analysis. A bone grafting space is provided between the prosthesis and the pelvis. Furthermore, the bone graft pad features a gradient porous design, ensuring support strength while facilitating bone ingrowth and enhancing long-term stability. 5. The surface of the bone graft pad of this invention is enhanced with a bone graft cage, effectively preventing dislocation of the bone graft material. Attached Figure Description

[0041] The invention will be further described with reference to the accompanying drawings, but the contents of the drawings do not constitute any limitation on the invention.

[0042] Figure 1 This is a flowchart illustrating a design method for a Paporosky III type acetabular defect reconstruction prosthesis.

[0043] Figure 2 This is a schematic diagram of the assembly model after generating multiple nail tracks.

[0044] Figure 3 This is a schematic diagram of the Paporosky III type acetabular defect reconstruction prosthesis.

[0045] Figure 4 This is a schematic diagram of the Paporosky III acetabular defect reconstruction prosthesis and a solidified acetabular defect pelvic model.

[0046] Figure 5 This is a schematic diagram of the structure of the three-winged steel plate after material reduction.

[0047] Figure 6 for Figure 3 A schematic diagram of the structure of the mortar and pestle.

[0048] Figure 7 This is a schematic diagram of the acetabular cup and bone graft pad without the addition of a bone graft cage.

[0049] Figure 8 for Figure 7 A schematic diagram of the structure with added bone graft cages.

[0050] Figure 9 This is a schematic diagram of part of the internal structure of the bone graft cage.

[0051] exist Figures 1 to 9 This includes:

[0052] Bone graft pad 100

[0053] Three-wing steel plate 200, first wing 231, second wing 232, third wing 233

[0054] Acetabular cup 300, wear-resistant liner 400, hook 500, hip bone 600, pin channel 700, bone graft cage 800. Detailed Implementation

[0055] The technical solution of the present invention will be further described in conjunction with the following embodiments.

[0056] Example 1

[0057] A design method for Paporosky III type acetabular defect reconstruction prosthesis, such as Figure 1 It includes the following steps:

[0058] S1. Obtain CT images of the pelvis, including the defective side and the healthy side, and construct a three-dimensional model of the pelvis based on the CT images of the defective side.

[0059] S2. Perform mesh convergence and verification analysis on the 3D pelvic model obtained in S1 to obtain the optimal mesh size, and then proceed to S3 to obtain the solidified acetabular defect pelvic model with the optimal mesh size.

[0060] S3. Based on the contralateral image of the pelvis CT image, the rotation center of the solidified acetabular defect pelvis model obtained in S2 is reconstructed, and a prosthesis model is generated. The prosthesis model includes a three-wing steel plate 200, a bone graft pad 100, an acetabular cup 300, a wear-resistant pad 400, and a hook 500 to prevent the overall upward movement and rotation of the prosthesis model.

[0061] S4. Assemble the prosthetic model of S3 and the solidified acetabular defect pelvis model of S2 into a whole to obtain the assembled model.

[0062] S5. Generate a screw path 700 in the assembly model that runs from the prosthesis model through the solidified acetabular defect pelvic model. The screw path 700 is divided into multiple first screw paths 700 and multiple second screw paths 700, with the length of the first screw path 700 greater than the length of the second screw path 700. Then, generate different combinations of the first and second screw paths 700 and input them into S6, such as... Figure 2 ,exist Figure 2 The dashed line in the middle represents the first nail track 700, and the dot represents the second nail track 700;

[0063] S6. Based on the hip joint reaction force under multiple daily activity conditions, calculate the maximum nodal force, total stiffness value and micromomentum value of each pin track. Based on the maximum nodal force, total stiffness value and micromomentum value, screen the pin tracks to obtain the optimal pin track combination. Then delete the other pin tracks except for the optimal pin track combination to obtain the second prosthesis optimization model.

[0064] S7. Optimize the second spurious model obtained in S6 using the variable density method, thereby reducing the material content of the assembly model and obtaining the second spurious model.

[0065] S8. Based on the third prosthesis optimization model obtained in S7, the prosthesis model generates different porosities according to the stress range, and the second prosthesis optimization model with the bone graft pad 100 as a gradient porous structure is obtained, and then proceed to S9.

[0066] S9. Add a bone graft cage of 800mm to the surface of the prosthesis model in the fourth prosthesis optimization model of S8 to obtain the Paporosky III type acetabular defect reconstruction prosthesis, as follows: Figure 3 and Figure 4 .

[0067] In the prosthetic model of the present invention, the acetabular cup 300 is located inside the groove of the bone graft pad 100, the three-winged steel plate 200 is integrally connected to the upper surface of the acetabular cup 300, the wear-resistant liner 400 is disposed inside the groove of the acetabular cup 300, the hook 500 is integrally connected to the edge of the three-winged steel plate 200, the three-winged steel plate 200 covers the ilium, pubis and ischium of the solidified acetabular defect pelvic model, the hook is engaged with the obturator edge of the hip bone 600 of the solidified acetabular defect pelvic model, and the bone graft pad 100 is located at the acetabulum of the solidified acetabular defect pelvic model. In the solidified pelvic model with acetabular defects, the coverage of the iliac bone by the three-winged plate 200 is 1 / 3-2 / 3 and it lies anterior to the gluteus minimus insertion point; the coverage of the ischium by the three-winged plate 200 extends from the acetabulum to the ischial tuberosity; and the coverage of the pubis by the three-winged plate 200 extends from the acetabulum to the pubic tuberosity.

[0068] Current prostheses for reconstructing complex acetabular defects, such as the acetabular cup 300, metal pad, reinforcing cup, cemented acetabular cup 300, and Cage titanium mesh, are unsatisfactory. These prostheses suffer from poor long-term stability and are prone to long-term bone resorption leading to loosening. This invention adds a hook 500 to the prosthesis model beforehand. This hook 500 is subsequently optimized along with other prosthesis model structures, ultimately resulting in the Paporosky III acetabular defect reconstruction prosthesis also featuring the hook 500. This hook 500 prevents the Paporosky III acetabular defect reconstruction prosthesis from shifting upwards and rotating during actual use, exhibiting advantages such as high biomechanical strength and good initial and long-term stability.

[0069] It should also be noted that the pelvic CT images in S1 are in Dicom format. The pelvic CT images are then imported into Mimics software for 3D reconstruction of the pelvic model, and then generated into a 3D pelvic model using Geomagic software.

[0070] S2 specifically involves importing the 3D pelvic model obtained in S1 into Hypermesh for mesh optimization. Five isolated mesh models with different mesh sizes within the range of 1mm to 4mm are selected and imported into Mimics software. Grayscale values ​​are assigned according to empirical formulas. Then, the five isolated mesh models are imported into Abaqus software for mesh convergence analysis and model validity verification to determine the optimal mesh size for the 3D pelvic model.

[0071] It should be noted that the optimal mesh size is one with a deviation of less than 5%, and where stress, displacement, and stress energy values ​​are all optimal. Since a mesh with a deviation within 5% is generally considered sufficiently refined, convergence is successful.

[0072] It should be noted that in S3, the solidified acetabular defect pelvic model is imported into SolidWorks software. Based on the contralateral mirror image of the pelvic CT image obtained in S2, the rotation center is reconstructed from the solidified acetabular defect pelvic model. Specifically, Mimics software is used to mirror and fit the acetabular center, i.e., the rotation center, and generate a prosthesis model. This is because the rotation center cannot be determined when the defect side is severely damaged. Therefore, this invention fits the rotation center based on the contralateral side and generates an acetabular cup 300 and an anatomically matched bone graft 100 based on the contralateral rotation center to restore the healthy hemipelvic structure.

[0073] S4 is performed by the following steps:

[0074] S4.1. Import the solidified acetabular defect pelvic model from S2 into Hypermesh software, then import the optimal mesh size obtained from S2 into Hypermesh, and assemble the prosthesis model from S3 and the solidified acetabular defect pelvic model from S2 into a whole.

[0075] S4.2 Assign material properties. The materials for the three-wing steel plate 200, bone graft pad 100, acetabular cup 300, and hook 500 are all Ti6Al4V. The material for the wear-resistant liner is polyethylene. The material for the femoral head in the solidified acetabular defect pelvic model is CoCrMo alloy. The solidified acetabular defect pelvic model is assigned grayscale values. Define the contact relationship, constraints, and boundaries between the prosthesis model and the solidified acetabular defect pelvic model. The degrees of freedom in the six directions of the sacroiliac joint, iliac dorsal surface, and pubic symphysis in the solidified acetabular defect pelvic model are defined as completely fixed.

[0076] S5 of the present invention specifically refers to: each first screw channel penetrates from the acetabular cup into the interior of the solidified acetabular defect pelvic model, and the first screw channel does not penetrate the outer cortex of both sides of the solidified acetabular defect pelvic model; the second screw channel penetrates from the three-wing plate into the interior of the solidified acetabular defect pelvic model, and the second screw channel is perpendicular to the bone surface; the first screw channel and the second screw channel are distributed in the ilium, pubis and ischium of the solidified acetabular defect pelvic model, and the first screw channel and the second screw channel are most abundant in the ilium.

[0077] It should be noted that, in order to more accurately determine the optimal combination of pins, the number of first pins 700 and second pins 700 is as dense as possible. In this embodiment, 7 first pins 700 and 28 second pins 700 are generated in the iliac bone, 4 first pins 700 and 9 second pins 700 are generated in the ischium, and 2 first pins 700 and 9 second pins 700 are generated in the pubis are used as examples. Therefore, the present invention generates a total of 13 first pins 700 and 46 second pins 700.

[0078] S6 of the present invention is performed by the following steps:

[0079] S6.1 Establish a three-dimensional coordinate system in the assembly model, and apply the joint reaction force of daily activity conditions from the center of the femoral head ball in the assembly model towards the acetabulum.

[0080] S6.2. Based on the hip joint reaction force under multiple daily activity conditions, the maximum nodal force of each nail track 700 is calculated by inputting the corresponding X-axis force data, Y-axis force data and Z-axis force data under each daily activity condition into the assembly model. The average value of the maximum nodal forces generated by all daily activity conditions in each nail track 700 is taken as the first nodal force of the nail track 700. The hip joint reaction force includes resultant force data, X-axis force data, Y-axis force data and Z-axis force data.

[0081] S6.3 Sort all needle tracks in descending order of the first node force in S6.2, and copy the first prosthesis optimization model to obtain two first prosthesis optimization models;

[0082] S6.4. In one of the first prosthesis optimization models, select the first 14 pin tracks 700 and delete the other pin tracks 700 to obtain a screening prosthesis optimization model; in another first prosthesis optimization model, select the first 2 first pin tracks 700 and the first 4 second pin tracks 700 in the iliac bone, select the first 1 first pin track 700 and the first 3 second pin tracks 700 in the pubis, select the first 1 first pin track 700 and the first 3 second pin tracks 700 in the ischium, and delete the other pin tracks 700 to obtain another screening prosthesis optimization model;

[0083] S6.5 In the two screening prosthesis optimization models in S6.4, each of the nine pin channels 700 is used as a pin channel 700 combination. Then, based on the hip joint reaction force under multiple daily activity conditions, the total stiffness value and micromomentum of each pin channel 700 combination in the two screening prosthesis optimization models are calculated.

[0084] S6.6. Take the average of the total stiffness values ​​generated by all daily activity conditions in each 700-pin track combination to obtain the average total stiffness value of each 700-pin track combination; take the average of the micro-motion values ​​of all daily activity conditions in each 700-pin track combination to obtain the average micro-motion value of each 700-pin track combination.

[0085] S6.7. Weight the average total stiffness and average micromoment of each pin 700 combination to obtain the index value. Select the pin 700 combination with the best index value as the optimal pin 700 combination. Then delete the other pin 700 combinations other than the optimal pin 700 combination in the screening prosthesis optimization model corresponding to the optimal pin 700 combination to obtain the third prosthesis optimization model.

[0086] It should be noted that the two screening prosthesis optimization models in S6.5 of this invention use nine spike paths 700 as a single spike path 700 combination. Therefore, this invention can generate thousands of spike path 700 combinations. In S6, multiple daily activity conditions are calculated for each of these thousands of spike path 700 combinations. Thus, this invention can obtain the spike path 700 combination with the optimal index value from among these thousands of spike path 700 combinations. The index value of this invention is obtained by adding 0.5 times the average total stiffness and 0.5 times the average micromomentum, with the optimal index value being the minimum value. The purpose of using the screening prosthesis optimization model in S6.4 of this invention is to eliminate the bias in spike path 700 selection and avoid ignoring the combination effect.

[0087] S7 specifically involves optimizing the second prosthesis optimization model obtained in S6 using Tosca's variable density method. Specifically, the three-wing steel plate 200 is divided into different stress-bearing grids according to the stress range, with each grid having a different density value. All stress-bearing grids are arranged from highest to lowest stress range, with the density distribution reversed to the stress arrangement order. That is, the stress-bearing grid with the highest stress has a density value of 1, while the stress-bearing grid with the lowest stress has a density value of 0. Subtraction is then performed on the three-wing steel plate 200 to obtain the second prosthesis optimization model. Figure 5 This is a schematic diagram of the subtractive structure of a single three-winged plate 200 in the Paporosky III acetabular defect reconstruction prosthesis. The three wings of the three-winged plate are defined as follows: the wing fixed to the iliac bone is defined as the first wing 231, the wing fixed to the ischium as the second wing 232, and the wing fixed to the pubis as the third wing 233. Figure 5 The round hole in the middle is a 700mm nail track. Figure 6The acetabular cup 300 in the Paporosky III acetabular defect reconstruction prosthesis is similarly used in... Figure 6 The round hole in the middle is a 700mm nail track.

[0088] It should be noted that when the density value of the stress-bearing mesh is 0, the stress-bearing mesh is completely hollowed out; when the density value of the stress-bearing mesh is between 0 and 1, the stress-bearing mesh has a porous structure. This invention optimizes the structural stiffness of the prosthesis model through a variable density method, controls the micromomentum of the prosthesis model-bone interface within an ideal range, and reduces the volume of the prosthesis model, thereby reducing tissue irritation and trauma during actual use.

[0089] S8 specifically involves: dividing the bone graft pad 100 region into multiple stress regions according to the stress range in the third prosthesis optimization model obtained in S7, arranging all stress regions from high to low according to the stress range, and ensuring that the porosity of each stress region is different, and that the porosity distribution is the opposite of the stress arrangement order of the stress regions, i.e., the stress region with the maximum stress has the lowest porosity, and the stress region with the minimum stress has the highest porosity, thus obtaining the second prosthesis optimization model in which the bone graft pad 100 is a gradient porous structure, and proceeding to S9.

[0090] It should be noted that the bone graft pad 100 of this invention incorporates a gradient porous structure. This aims to ensure the support strength of the prosthesis model while simultaneously facilitating bone ingrowth and enhancing long-term stability. In other words, the porosity is minimized in the stress-bearing region with the highest stress, thus ensuring the support strength of that region. Conversely, the porosity is maximized in the stress-bearing region with the lowest stress, promoting bone ingrowth into the pores. Specifically, this invention divides the stress-bearing region into 10 areas, with porosities ranging from 10% to 80%, increasing in 7% increments. Therefore, the porosity of the stress-bearing region with the highest stress is 10%, and the porosity of the stress-bearing region with the lowest stress is 80%.

[0091] S9 specifically refers to: adding a bone graft cage 800 to the surface of the bone graft pad 100 in the fourth prosthesis optimization model of S8 to prevent dislocation of the osteogenic material, such as... Figures 7-9 The bone graft cage 800 is located in the gap between the bone graft pad 100 and the pelvis, resulting in the Paporosky III type acetabular defect reconstruction prosthesis.

[0092] It should be noted that the bone graft cage 800 of the present invention is located on both sides of the raised rib of the bone graft pad 100. This is because there is a large gap between the raised rib of the bone graft pad 100 and the pelvis, and in clinical practice, it is necessary to implant bone fragments and bone-promoting material BMP in this area. Therefore, the present invention places the bone graft cage 800 at this location.

[0093] The daily activities described in this invention include heel strike, toe push-off, normal walking, going upstairs, going downstairs, standing up, sitting down, bending knees, and standing on both feet.

[0094] It should be noted that the daily activity conditions of this invention are based on Bergmann's 2011 study. The specific resultant force data, X-axis component force data, Y-axis component force data, and Z-axis component force data for heel strike, toe push-off, normal walking, climbing stairs, descending stairs, standing up, sitting down, knee bending, and standing on both feet are shown in Table 1.

[0095] Table 1 shows the resultant force data, X-axis component force data, Y-axis component force data, and Z-axis component force data under daily operating conditions.

[0096]

[0097] Note: In the coordinate system, X points to the inside of the hip joint, Y points to the back of the hip joint, and Z points to the top of the hip joint; BW is body weight: 700N.

[0098] Compared with existing technologies, the design method of this Paporosky III acetabular defect reconstruction prosthesis has the following advantages: 1. This invention adds a 500mm hook to the prosthesis model, resulting in advantages such as resistance to upward displacement and rotation, high biomechanical strength, and good initial and long-term stability. 2. The screw selection and analysis process of this invention incorporates multiple screw path 700mm positions, covering various screw path combinations and working conditions, and considers the combined effect of screw path 700mm. This is more scientific and theoretically sound than existing screw path 700mm analysis methods, and has better clinical guidance value. 3. This invention optimizes the macroscopic topology of the prosthesis using the variable density method, which reduces the prosthesis volume to facilitate clinical implantation, reduce tissue irritation and trauma, and maintain the necessary initial fixation strength while reducing the overall structural stiffness of the prosthesis. It also reduces the low-stress shielding effect and ensures that the micro-movement of the prosthesis-bone interface is within the range conducive to bone ingrowth (less than 50μm), which is beneficial to improving the long-term stability of the prosthesis and thus avoiding long-term bone resorption leading to prosthesis loosening, thereby ensuring the fixation effect. 4. Unlike traditional pads, the bone graft pad 100 of this invention is integrally formed with the prosthesis body and is structurally optimized through stress analysis. The gap between the prosthesis and the pelvis leaves space for bone grafting. In addition, the bone graft pad 100 has a gradient porous design to ensure support strength while facilitating bone ingrowth and enhancing long-term stability. 5. The surface of the bone graft pad 100 of this invention is increased with a bone graft cage 800, which can effectively prevent the bone graft material from dislodging.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A design method for a Paporosky III type acetabular defect reconstruction prosthesis, characterized in that, Includes the following steps: S1. Obtain CT images of the pelvis, including the defective side and the healthy side, and construct a three-dimensional model of the pelvis based on the CT images of the defective side. S2. Perform mesh convergence and verification analysis on the 3D pelvic model obtained in S1 to obtain the optimal mesh size, and then proceed to S3 to obtain the solidified acetabular defect pelvic model with the optimal mesh size. S3. Based on the contralateral image of the pelvic CT image, the rotation center of the solidified acetabular defect pelvic model obtained in S2 is reconstructed, and a prosthesis model is generated. The prosthesis model includes a three-wing plate, a bone graft pad, an acetabular cup, a wear-resistant liner, and hooks to prevent the overall upward movement and rotation of the prosthesis model. S4. Assemble the prosthesis model described in S3 and the solidified acetabular defect pelvic model described in S2 into a whole to obtain the assembled model. S5. Generate a pin path in the assembly model that runs from the prosthesis model through the solidified acetabular defect pelvic model. The pin path is divided into multiple first pin paths and multiple second pin paths. The length of the first pin path is greater than the length of the second pin path. This yields the first prosthesis optimization model. Proceed to S6. S6. Based on the hip joint reaction force under multiple daily activity conditions, calculate the maximum nodal force, total stiffness value and micromomentum value of each pin track. Based on the maximum nodal force, total stiffness value and micromomentum value, screen the pin tracks to obtain the optimal pin track combination. Then delete the other pin tracks except for the optimal pin track combination to obtain the second prosthesis optimization model. S7. Optimize the second spurious model obtained in S6 using the variable density method, thereby reducing the material content of the assembly model and obtaining the third spurious model. S8. Based on the third prosthesis optimization model obtained in S7, the prosthesis model generates different porosities according to the stress range, and the fourth prosthesis optimization model with a gradient porous structure for the bone graft pad is obtained, and then proceed to S9. S9. Add a bone graft cage to the surface of the prosthesis model in the fourth prosthesis optimization model in S8 to obtain the Paporosky III acetabular defect reconstruction prosthesis.

2. The design method of the Paporosky III type acetabular defect reconstruction prosthesis according to claim 1, characterized in that, Specifically, S7 involves optimizing the second prosthesis optimization model obtained in S6 using Tosca's variable density method. Specifically, the three-wing steel plate is divided into different stress grids according to the stress range, and the density value of each stress grid is different. All stress grids are arranged from high to low according to the stress range, and the density value distribution is the opposite of the stress arrangement order of the stress grids. That is, the density value of the stress grid with the maximum stress is 1, and the density value of the stress grid with the minimum stress is 0. The three-wing steel plate is then subjected to material reduction to obtain the second prosthesis optimization model. S8 specifically involves: dividing the bone graft block region into multiple stress regions according to the stress range in the third prosthesis optimization model obtained in S7, arranging all stress regions from high to low according to the stress range, and ensuring that the porosity of each stress region is different, and that the porosity distribution is the opposite of the stress arrangement order of the stress regions, that is, the stress region with the maximum stress has the lowest porosity, and the stress region with the minimum stress has the highest porosity, thus obtaining the second prosthesis optimization model with a gradient porous structure for the bone graft block, and proceeding to S9; Specifically, S9 involves adding a bone graft cage to the surface of the bone graft pad in the fourth prosthesis optimization model of S8 to prevent dislocation of the osteogenic material. The bone graft cage is located in the gap between the bone graft pad and the pelvis, resulting in the Paporosky III type acetabular defect reconstruction prosthesis.

3. The design method of the Paporosky III type acetabular defect reconstruction prosthesis according to claim 2, characterized in that: In the prosthetic model, the acetabular cup is located inside the groove of the bone graft pad, the three-winged steel plate is integrally connected to the upper surface of the acetabular cup, the wear-resistant liner is disposed inside the groove of the acetabular cup, the hook is integrally connected to the edge of the three-winged steel plate, the three-winged steel plate covers the ilium, pubis and ischium of the solidified acetabular defect pelvic model, the hook is engaged with the obturator foramen edge of the hip bone of the solidified acetabular defect pelvic model, and the bone graft pad is located at the acetabulum of the solidified acetabular defect pelvic model.

4. The design method of the Paporosky III type acetabular defect reconstruction prosthesis according to claim 3, characterized in that: The three-winged steel plate covers 1 / 3 to 2 / 3 of the iliac bone in the solidified acetabular defect pelvic model and is located anterior to the gluteus minimus insertion. The three-winged steel plate covers the ischium from the acetabulum to the ischial tuberosity in the solidified acetabular defect pelvic model. In the solidified acetabular defect pelvic model, the coverage area of ​​the three-winged steel plate extends from the acetabulum to the pubic tubercle.

5. The design method of the Paporosky III type acetabular defect reconstruction prosthesis according to any one of claims 1 to 4, characterized in that, Specifically, S5 is as follows: each first screw path extends from the acetabular cup into the interior of the solidified acetabular defect pelvic model, and the first screw path does not penetrate the outer cortex of both sides of the solidified acetabular defect pelvic model; the second screw path extends from the three-wing plate into the interior of the solidified acetabular defect pelvic model, and the second screw path is perpendicular to the bone surface; the first screw path and the second screw path are distributed in the ilium, pubis and ischium of the solidified acetabular defect pelvic model, and the first screw path and the second screw path are most numerous in the ilium.

6. The design method of the Paporosky III type acetabular defect reconstruction prosthesis according to claim 5, characterized in that: S6 is performed by the following steps: S6.1 Establish a three-dimensional coordinate system in the assembly model, and apply the joint reaction force of daily activity conditions from the center of the femoral head ball in the assembly model towards the acetabulum; S6.

2. Based on the hip joint reaction force under multiple daily activity conditions, the maximum nodal force of each nail track is calculated by inputting the corresponding X-axis force data, Y-axis force data, and Z-axis force data under each daily activity condition into the assembly model. The average value of the maximum nodal forces generated by all daily activity conditions in each nail track is taken as the first nodal force of the nail track. The hip joint reaction force includes resultant force data, X-axis force data, Y-axis force data, and Z-axis force data. S6.3 Sort all needle tracks in descending order of the first node force in S6.2, and copy the first prosthesis optimization model to obtain two first prosthesis optimization models; S6.

4. In one of the first prosthesis optimization models, select the first 14 pin tracks and delete the other pin tracks to obtain a screening prosthesis optimization model; in another first prosthesis optimization model, select the first 2 first pin tracks and the first 4 second pin tracks in the iliac crest, select the first 1 first pin track and the first 3 second pin tracks in the pubis, select the first 1 first pin track and the first 3 second pin tracks in the ischium, and delete the other pin tracks to obtain another screening prosthesis optimization model; S6.5 In the two screening prosthesis optimization models in S6.4, 9 pin tracks are used as a pin track combination. Then, based on the hip joint reaction force under multiple daily activity conditions, the total stiffness value and micromomentum of each pin track combination in the two screening prosthesis optimization models are calculated. S6.

6. Take the average of the total stiffness values ​​generated by all daily activity conditions in each spike track assembly to obtain the average total stiffness value of each spike track assembly; take the average of the micro-motion values ​​of all daily activity conditions in each spike track assembly to obtain the average micro-motion value of each spike track assembly. S6.

7. Weight the average total stiffness and average micromoment of each pin combination to obtain the index value. Select the pin combination with the best index value as the optimal pin combination. Delete other pins besides the optimal pin combination in the screening prosthesis optimization model corresponding to the optimal pin combination to obtain the third prosthesis optimization model.

7. The design method of the Paporosky III type acetabular defect reconstruction prosthesis according to claim 6, characterized in that: The daily activities described are: heel strike, toe push-off, normal walking, going upstairs, going downstairs, standing up, sitting down, bending knees, and standing on both feet.

8. The design method of the Paporosky III type acetabular defect reconstruction prosthesis according to any one of claims 1 to 4, characterized in that, Specifically, S2 involves importing the 3D pelvic model obtained in S1 into Hypermesh for mesh optimization. Five isolated mesh models with different mesh sizes within the range of 1mm to 4mm are selected and imported into Mimics software. Grayscale values ​​are assigned according to empirical formulas. Then, the five isolated mesh models are imported into Abaqus software for mesh convergence analysis and model validity verification to determine the optimal mesh size for the 3D pelvic model.

9. The design method of the Paporosky III acetabular defect reconstruction prosthesis according to any one of claims 1 to 4, characterized in that: S4 is performed by the following steps: S4.

1. Import the solidified acetabular defect pelvic model from S2 into Hypermesh software, then import the optimal mesh size obtained in S2 into Hypermesh, and assemble the prosthesis model from S3 and the solidified acetabular defect pelvic model from S2 into a whole. S4.2 Assign material properties, wherein the materials of the three-wing steel plate, the bone graft pad, the acetabular cup and the hook are all Ti6Al4V, the material of the wear-resistant liner is polyethylene, and the material of the femoral head in the solidified acetabular defect pelvic model is CoCrMo alloy; the solidified acetabular defect pelvic model adopts grayscale assignment, defines the contact relationship, constraints and boundaries between the prosthesis model and the solidified acetabular defect pelvic model, and restricts the degrees of freedom in the six directions of the sacroiliac joint, the dorsum of the ilium, and the pubic symphysis in the solidified acetabular defect pelvic model to be completely fixed.

10. The design method of the Paporosky III acetabular defect reconstruction prosthesis according to any one of claims 1 to 4, characterized in that: In S5, the nail path is replaced by a beam unit, the diameter of the nail path is 6.0 mm, the length of the first nail path is 60 mm, and the length of the second nail path is 40 mm.

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