Contalar prosthesis with flexible articular surface buffer layer and preparation method of contalar prosthesis

Abstract

The invention relates to a talus prosthesis with a flexible articular surface buffer layer and a preparation method of the talus prosthesis, belongs to the technical field of artificial prostheses, and solves the problem of cartilage degeneration caused by neglecting cartilage layer space deficiency and direct contact of a hard material with adjacent cartilages in the existing full talus prosthesis. The preparation method comprises the following steps: reconstructing a talus prosthesis model based on uninjured side talus CT (Computed Tomography) data of a patient; macroscopic mechanical interlocking structures are generated on the edges of the contact areas of the talonavicular joint, the tibia joint and the subtalar joint respectively; performing 3D printing on the talus prosthesis model to obtain a hard substrate; injection molds corresponding to the contact areas are manufactured through 3D printing; a flexible buffer material is injected into a cavity of the injection mold, and a flexible buffer layer of an integrated structure with the hard substrate is formed after cooling and curing; the talus prosthesis with the flexible articular surface buffer layer is obtained. According to the invention, cartilage deletion space can be compensated, the risk of surgical injury is reduced, the flexible buffer layer can protect adjacent cartilages, the risk of degeneration is reduced, and the long-term prognosis effect is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial prostheses, and particularly to a talus prosthesis with a flexible articular surface buffer layer and a preparation method thereof. Background Art

[0002] Avascular necrosis of the talus is a disease caused by temporary or permanent interruption of blood supply to the bone area due to pathological factors, and patients often suffer from severe pain. If not treated in time, the lesion is likely to cause collapse of the articular surface, and then develop into arthritis, which may ultimately lead to disability and loss of mobility. At present, the treatment of this disease still faces many challenges. Non-surgical treatment options are limited and the curative effect is not good, while common surgical procedures such as talus decompression, tibio-talo-calcaneal fusion, and total ankle arthroplasty all have problems such as unsatisfactory surgical results, loss of ankle joint mobility, and a relatively high incidence of complications.

[0003] With the development of 3D printing technology, total talus replacement using 3D printed personalized talus prostheses has gradually attracted attention. This technology can prepare a prosthesis with an anatomical shape similar to that of the autologous talus in height and ensure its matching with adjacent joints as much as possible, so as to retain the motor function of the ankle joint, improve the quality of life, and reduce the incidence of complications. At present, the common design scheme of total talus prostheses is to reconstruct the healthy-side talus through three-dimensional CT and perform mirror optimization. However, the buffer layer of the natural tibio-talar joint is cartilage, and cartilage is difficult to display in CT images. Therefore, at present, the method of enlarging the size of the total talus prosthesis in equal proportion is often used to compensate for the space loss of the talus cartilage layer, so as to maintain joint stability. However, this method of enlarging the prosthesis size in equal proportion will also enlarge the unnecessary structures of the prosthesis, which may require a larger surgical incision during implantation, increasing the surgical difficulty and operation risk.

[0004] In addition, current 3D printed personalized total talus prostheses mostly adopt additive manufacturing processes, and common materials include homogeneous materials such as metals, alloys, ceramics, polyether ether ketone, etc. However, the direct contact between this hard material and adjacent cartilage may cause cartilage degeneration and increase the risk of poor prognosis. Summary of the Invention

[0005] Aiming at the problems in the existing design of total talus prostheses that do not consider the space loss of the talus cartilage layer and the cartilage degeneration and increased risk of poor prognosis caused by the direct contact between the hard material prosthesis and adjacent cartilage, the present invention provides a talus prosthesis with a flexible articular surface buffer layer and a preparation method thereof.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A talus prosthesis with a flexible joint surface buffer layer, the talus prosthesis comprising a 3D printed rigid substrate and three flexible buffer layers injection molded from a flexible buffer material. A respective one of the flexible buffer layers is provided on the contact areas of the rigid substrate corresponding to the talonavicular joint, the tibio-talar joint, and the subtalar joint. Macroscopic mechanical interlocking structures are respectively provided at the edges of the talonavicular joint contact area, the tibio-talar joint contact area, and the subtalar joint contact area. The flexible buffer layer is locked with the rigid substrate through the macroscopic mechanical interlocking structure and forms an integrated structure.

[0008] Meanwhile, the present invention also provides a preparation method for a talus prosthesis with a flexible joint surface buffer layer, the preparation method comprising the following steps:

[0009] Step 1: Based on the CT data of the healthy side talus of the patient, a talus prosthesis model is reconstructed using three-dimensional reconstruction software, and the positions and shapes of the areas corresponding to the three flexible buffer layers on the talus prosthesis model are determined. The areas corresponding to the three flexible buffer layers are respectively the talonavicular joint contact area, the tibio-talar joint contact area, and the subtalar joint contact area;

[0010] Step 2: Macroscopic mechanical interlocking structures are respectively generated at the edges of the talonavicular joint contact area, the tibio-talar joint contact area, and the subtalar joint contact area. The macroscopic mechanical interlocking structure is a T-shaped groove structure or a card slot structure, and the T-shaped groove structure or the card slot structure extends towards the inside of the talus prosthesis model;

[0011] Step 3: The talus prosthesis model with the macroscopic mechanical interlocking structure is 3D printed to obtain the rigid substrate of the talus prosthesis;

[0012] Step 4: Injection molds corresponding to the talonavicular joint contact area, the tibio-talar joint contact area, and the subtalar joint contact area after generating the macroscopic mechanical interlocking structure are respectively manufactured by 3D printing, and the bottom edge morphology of each injection mold matches the edge geometric morphology of the corresponding area;

[0013] Step 5: After placing the injection mold on the rigid substrate and making the injection mold closely fit the corresponding area, a flexible buffer material is injected into the cavity of the injection mold. The flexible buffer material covers the area where the injection mold fits and fills all the macroscopic mechanical interlocking structures on this area. After the flexible buffer material cools and solidifies, the flexible buffer layer that forms an integrated structure with the rigid substrate is formed. The flexible buffer layer and the rigid substrate are locked with each other through the macroscopic mechanical interlocking structure;

[0014] Step 6: After removing the injection mold, a talus prosthesis with a flexible joint surface buffer layer is obtained.

[0015] The beneficial effects of the present invention are as follows:

[0016] (1) Solve the problem of cartilage layer deficiency:

[0017] By providing a flexible buffer layer (covering the tibial-talar, talonavicular, and subtalar joint surfaces) similar in function to natural cartilage, the present invention directly compensates for the lack of cartilage space in the talus, eliminating the need to increase the overall size of the prosthesis and avoiding the enlargement of the surgical incision and increased operating risks caused by the expansion of unnecessary structures.

[0018] (2) Protect adjacent cartilage and reduce the risk of degeneration:

[0019] Compared with currently common total talus prostheses designed with a uniform rigid material, while ensuring that the size of the talus prosthesis is similar to that of the healthy-side talus, the flexible buffer layer of the present invention can protect the cartilage adjacent to the prosthesis. The flexible buffer layer replaces the traditional rigid material to directly contact the cartilage adjacent to the prosthesis, reducing mechanical friction and stress concentration, significantly reducing the risk of postoperative cartilage degeneration and poor prognosis, and ensuring long-term prognosis.

[0020] (3) Improve joint stability:

[0021] Based on the CT data of the healthy-side talus of the patient, the present invention reconstructs the talus prosthesis model, which can maintain an anatomical shape similar to the height of the autologous talus. At the same time, combined with the flexible buffer layer designed in regions, the matching degree with adjacent joints is optimized, thereby improving joint stability.

[0022] (4) Integrated structure design:

[0023] By using a macroscopic mechanical interlocking structure such as a T-shaped groove or a clamping groove to lock the flexible buffer layer to the rigid substrate, the prosthesis is prevented from delaminating or shifting after implantation, ensuring long-term mechanical reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 – Figure 6 Respectively show the schematic structural diagrams of the talus prosthesis with a flexible joint surface buffer layer from six orthogonal perspectives (top view, bottom view, left view, right view, front view, and rear view);

[0025] Figure 7 Is the flowchart of the preparation method described in the embodiment of the present invention;

[0026] Figure 8 Is the sagittal cross-sectional view of the talus prosthesis when the macroscopic mechanical interlocking structure adopts a T-shaped groove structure;

[0027] Figure 9 Is the sagittal cross-sectional view of the talus prosthesis when the macroscopic mechanical interlocking structure adopts a clamping groove structure.

[0028] Description of reference numerals: 1, hard substrate; 2-1, flexible buffer layer of talonavicular joint; 2-2, flexible buffer layer of tibio-talar joint; 2-3, flexible buffer layer of subtalar joint; 3, T-slot structure; 4, card slot structure. Detailed implementation manners

[0029] The technical solution of the present invention will be described in detail below in conjunction with the drawings and preferred embodiments.

[0030] See Figures 1 - 6 , an embodiment of the present invention provides a talus prosthesis with a flexible joint surface buffer layer manufactured by 3D printing and injection molding, which greatly reduces the risk of degeneration of adjacent cartilage of the prosthesis.

[0031] Specifically, the talus prosthesis of this embodiment includes a hard substrate 1 and three flexible buffer layers. The hard substrate 1 is manufactured by 3D printing, and the material can be selected from any one of materials including but not limited to cobalt-chromium-molybdenum alloy, bioceramics, titanium alloy, polyetheretherketone (PEEK), etc.; the three flexible buffer layers are respectively the flexible buffer layer 2-1 of the talonavicular joint, the flexible buffer layer 2-2 of the tibio-talar joint, and the flexible buffer layer 2-3 of the subtalar joint. The three flexible buffer layers are all obtained by injection molding with flexible buffer materials, and the material can be any one of ultra-high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (HXLPE), polycarbonate polyurethane (PCU), polyurethane (PU), etc.

[0032] The flexible buffer layer 2-1 of the talonavicular joint, the flexible buffer layer 2-2 of the tibio-talar joint, and the flexible buffer layer 2-3 of the subtalar joint respectively cover the contact areas on the hard substrate 1 corresponding to the talonavicular joint, the tibio-talar joint, and the subtalar joint. And at the edges of the contact area of the talonavicular joint, the contact area of the tibio-talar joint, and the contact area of the subtalar joint, there are respectively provided macroscopic mechanical interlocking structures, which can adopt T-slot structures or card slot structures. Each flexible buffer layer is locked with the hard substrate 1 through the T-slot structure or the card slot structure to form an integrated structure. At the same time, the macroscopic mechanical interlocking structure can also cooperate with a biocompatible adhesive to ensure the overall stability of the prosthesis. The macroscopic mechanical interlocking structure is pre-planned through computer graphics design software at the prosthesis design stage to meet the requirements of the 3D printing process.

[0033] Each flexible buffer layer in this embodiment is designed to protrude a certain thickness outward on the surface of the hard substrate 1 and extend a certain depth inward at the same time. Among them, the thickness of the protrusion outward, that is, the thickness of the flexible buffer layer, is determined according to the measurement result of the joint space of the healthy side of the patient, generally 1 mm to 1.5 mm; the depth of the inward extension is flexibly selected within the range of 0 to 9 mm according to the specific situation of the patient and the selected material.

[0034] See Figure 7, Another embodiment of the present invention provides a method for preparing a talus prosthesis with a flexible joint surface buffer layer, and this preparation method is used to prepare the talus prosthesis as described in the foregoing embodiments. Specifically, this preparation method includes the following steps:

[0035] Step 1: Based on the CT data of the healthy side talus of the patient, use 3D reconstruction software to reconstruct the talus prosthesis model, and determine the positions and shapes of the regions corresponding to the three flexible buffer layers on the talus prosthesis model. The regions corresponding to the three flexible buffer layers are the talonavicular joint contact region, the tibio-talar joint contact region, and the subtalar joint contact region, respectively.

[0036] The talus prosthesis is designed individually based on the CT data of the healthy side talus of the patient to restore the ankle joint function of the patient to the greatest extent. The process of reconstructing the talus prosthesis model using 3D reconstruction software in Step 1 specifically includes the following steps:

[0037] Step 1.1: First, in Mimics software, obtain the talus mask based on the CT data of the healthy side talus of the patient and perform 3D reconstruction to obtain the geometric shape of the talus.

[0038] Step 1.2: Subsequently, in Geomagic software, through mirroring and model optimization processing, determine the talus prosthesis model for total talus replacement surgery. The model optimization processing includes removing abnormal holes and protrusions, moderately reducing the posterior process of the talus, and reserving the space required for the flexible buffer layer, etc.

[0039] If the CT data of the healthy side talus of the patient is available, use it for mirror reconstruction to prepare the talus prosthesis model; if necrosis occurs in both sides of the patient and no reference can be provided, statistically analyze the talus shape of the population in the patient's area, and based on the statistical data of the talus shape of the population in the patient's area and combined with the CT data of the patient's talus, design and reconstruct the talus prosthesis model.

[0040] Step 2: Generate a macroscopic mechanical interlock structure at the edges of the talonavicular joint contact region, the tibio-talar joint contact region, and the subtalar joint contact region on the talus prosthesis model respectively. This macroscopic mechanical interlock structure is a T-shaped groove structure (as shown in Figure 8 ), or a card slot structure (as shown in Figure 9 ), and the T-shaped groove structure or the card slot structure extends towards the inside of the talus prosthesis model to finally realize an integrated stable structure between the flexible buffer layer and the rigid substrate 1. The width of the groove opening in the T-shaped groove structure is smaller than the width of the groove bottom to ensure a stable connection with the flexible buffer layer after the flexible material is cured. The hook part of the card slot structure is in an inverted form, and a stable connection can be formed between the inverted hook and the cured flexible buffer layer to prevent the flexible buffer layer from coming off. Thus, a talus prosthesis model with a macroscopic mechanical interlock structure is obtained.

[0041] Step 3: 3D print the talus prosthesis model obtained in Step 2 to obtain the rigid base 1 of the talus prosthesis.

[0042] The material of the rigid base 1 can be selected from, but not limited to, materials such as cobalt-chromium-molybdenum alloy, bioceramics, titanium alloy, polyetheretherketone (PEEK), etc., and cobalt-chromium-molybdenum alloy is preferred.

[0043] To further improve the stability between the flexible buffer layer and the rigid base 1, a combination of a macroscopic mechanical interlocking structure and a microscopic mechanical interlocking structure is adopted, that is, the surface of the rigid base 1 in contact with the flexible buffer material is treated, including but not limited to any one or several of sandblasting, laser etching or acid etching treatment, to form a rough surface to enhance mechanical interlocking.

[0044] Step 4: In this step, according to the morphology of the talonavicular joint contact area, tibio-talar joint contact area and subtalar joint contact area in the talus prosthesis model, the molds required for the injection molding of the flexible buffer layer are designed to produce the flexible buffer layer.

[0045] Specifically, after Step 2, the talus prosthesis model has generated a macroscopic mechanical interlocking structure in the talonavicular joint contact area, tibio-talar joint contact area and subtalar joint contact area. The injection molds corresponding to the talonavicular joint contact area, tibio-talar joint contact area and subtalar joint contact area are respectively manufactured by 3D printing, and the bottom edge morphology of each injection mold matches the edge geometric morphology of the corresponding contact area, so as to ensure that the flexible buffer material can just cover the corresponding contact area during injection molding.

[0046] Taking the talonavicular joint flexible buffer layer 2-1 as an example, during injection molding, first place the injection mold corresponding to the talonavicular joint contact area on the talonavicular joint contact area of the rigid base 1 and make the injection mold closely fit the surface of the corresponding area; then inject the flexible buffer material into the cavity of the injection mold, and the flexible buffer material completely covers the area where the injection mold fits and fills all the macroscopic mechanical interlocking structures on this area; after the flexible buffer material wraps and covers the talonavicular joint contact area, wait for the flexible buffer material to cool and solidify to form the talonavicular joint flexible buffer layer 2-1 with an integrated structure with the rigid base 1. The talonavicular joint flexible buffer layer 2-1 and the rigid base 1 are locked to each other through the macroscopic mechanical interlocking structure. The injection molding processes of the tibio-talar joint flexible buffer layer 2-2 and the subtalar joint flexible buffer layer 2-3 are similar to that of the talonavicular joint flexible buffer layer 2-1 and will not be elaborated here.

[0047] In this embodiment, the flexible buffer material can be either a material with a uniform elastic modulus or a material with a gradually varying elastic modulus. When using a material with a gradually varying elastic modulus, a material with a lower elastic modulus is used on the joint surface side, while a material with a higher elastic modulus is selected on the hard substrate side, so as to achieve a smooth transition of the elastic modulus of the entire talar prosthesis.

[0048] The flexible buffer material can be ultra-high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (HXLPE), polycarbonate polyurethane (PCU), polyurethane (PU), etc., and PCU is preferred.

[0049] When the flexible buffer material is polycarbonate polyurethane (PCU) or polyurethane (PU), the macro mechanical interlocking structure preferably adopts a T-shaped groove structure.

[0050] When the flexible buffer material is ultra-high molecular weight polyethylene (UHMWPE) or highly cross-linked polyethylene (HXLPE), the macro mechanical interlocking structure preferably adopts a card slot structure.

[0051] For the talar prosthesis with PCU or PU as the buffer material, by adjusting the ratio of the hard segment to the soft segment of the material, a wide range of elastic modulus regulation is achieved, and the regulation range is from 11 MPa to 1 GPa. Through biomechanical simulation tests, the preferred elastic modulus should be lower than 96.94 MPa.

[0052] Step 6: After the flexible material is cured, remove the injection mold to obtain a talar prosthesis with a flexible joint surface buffer layer.

[0053] The beneficial effects of a talar prosthesis with a flexible joint surface buffer layer and its preparation method proposed by the present invention are as follows:

[0054] (1) Solve the problem of cartilage layer deficiency:

[0055] By setting a flexible buffer layer (covering the tibio-talar, talo-navicular, and subtalar joint surfaces) similar to the function of natural cartilage, the present invention directly compensates for the cartilage space deficiency of the talus, without the need to overall enlarge the size of the prosthesis, and avoids the increase of the surgical incision and operation risk caused by the expansion of unnecessary structures;

[0056] (2) Protect adjacent cartilage and reduce the risk of degeneration:

[0057] Compared with the currently common total talar prosthesis designed with a uniform hard material, while ensuring that the size of the talar prosthesis is similar to that of the healthy side talus, the flexible buffer layer of the present invention can protect the cartilage adjacent to the prosthesis. The flexible buffer layer replaces the traditional hard material and directly contacts the cartilage adjacent to the prosthesis, reducing mechanical friction and stress concentration, significantly reducing the risk of postoperative cartilage degeneration and poor prognosis, and ensuring long-term prognosis effects;

[0058] (3) Improve joint stability:

[0059] Based on the CT data of the healthy-side talus of the patient, the present invention reconstructs the talus prosthesis model, which can maintain an anatomical shape highly similar to that of the autologous talus. At the same time, combined with the flexural buffer layer designed in sub-regions, it optimizes the matching degree with adjacent joints, thereby improving joint stability;

[0060] (4) Integrated structure design:

[0061] By adopting a macroscopic mechanical interlocking structure such as a T-shaped groove or a clamping groove to lock the flexural buffer layer and the rigid substrate, it prevents delamination or displacement after prosthesis implantation and ensures long-term mechanical reliability.

[0062] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0063] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A preparation method of a talus prosthesis with a flexible joint surface buffer layer, characterized in that, The preparation method includes the following steps: Step 1: Based on the CT data of the healthy-side talus of the patient, use three-dimensional reconstruction software to reconstruct a talus prosthesis model, and determine the positions and shapes of the regions corresponding to the three flexible buffer layers on the talus prosthesis model. The regions corresponding to the three flexible buffer layers are the talonavicular joint contact region, the tibio-talar joint contact region, and the subtalar joint contact region, respectively; Step 2: Generate macroscopic mechanical interlocking structures at the edges of the talonavicular joint contact region, the tibio-talar joint contact region, and the subtalar joint contact region respectively. The macroscopic mechanical interlocking structure is a T-shaped groove structure or a card slot structure, and the T-shaped groove structure or the card slot structure extends into the interior of the talus prosthesis model; Step 3: 3D print the talus prosthesis model with the macroscopic mechanical interlocking structure to obtain the rigid substrate of the talus prosthesis; Step 4: Use 3D printing to manufacture the injection molds corresponding to the talonavicular joint contact region, the tibio-talar joint contact region, and the subtalar joint contact region after generating the macroscopic mechanical interlocking structures respectively, and the bottom edge morphology of each injection mold matches the edge geometric morphology of the corresponding region; Step 5: After placing the injection mold on the rigid substrate and making the injection mold fit tightly with the corresponding region, inject the flexible buffer material into the cavity of the injection mold. The flexible buffer material covers the region where the injection mold fits and fills all the macroscopic mechanical interlocking structures on this region. After the flexible buffer material cools and solidifies, a flexible buffer layer integrated with the rigid substrate is formed. The flexible buffer layer and the rigid substrate are locked to each other through the macroscopic mechanical interlocking structure; Step 6: Remove the injection mold to obtain a talus prosthesis with a flexible joint surface buffer layer.

2. The preparation method of a talus prosthesis with a flexible joint surface buffer layer according to claim 1, characterized in that, Replace the CT data of the healthy-side talus of the patient in Step 1 with the talus shape statistical data of the population in the area where the patient is located, and then reconstruct the talus prosthesis model.

3. The preparation method of a talus prosthesis with a flexible joint surface buffer layer according to claim 1 or 2, characterized in that, The process of reconstructing the talus prosthesis model using three-dimensional reconstruction software in Step 1 includes the following steps: Step 1.1: In Mimics software, obtain a talus mask based on the CT data of the healthy-side talus of the patient and perform three-dimensional reconstruction to obtain the geometric shape of the talus; Step 1.2: In Geomagic software, determine the talus prosthesis model through mirroring and model optimization processing. The model optimization processing includes removing abnormal holes and protrusions, moderately reducing the posterior process of the talus, and reserving the space required for the flexible buffer layer.

4. A preparation method of a talus prosthesis with a flexible joint surface buffer layer according to claim 1 or 2, characterized in that, Before Step 5 and after Step 3, the following steps are also included: Perform sandblasting, laser etching, or acid etching on the surface of the rigid substrate that contacts the flexible buffer material to form a rough surface.

5. The preparation method of a talus prosthesis with a flexible joint surface buffer layer according to claim 1 or 2, characterized in that, The flexible buffer layer has a gradually changing gradient of elastic modulus, and the elastic modulus on the joint surface side is lower than that on the rigid substrate side.

6. The preparation method of a talus prosthesis with a flexible joint surface buffer layer according to claim 1 or 2, characterized in that, The material of the rigid substrate is any one of cobalt-chromium-molybdenum alloy, bioceramics, titanium alloy, and polyetheretherketone; The flexible buffer material is any one of ultra-high molecular weight polyethylene, highly cross-linked polyethylene, polycarbonate polyurethane, and polyurethane.

7. The preparation method of a talus prosthesis with a flexible joint surface buffer layer according to claim 6, characterized in that, When the flexible buffer material is polycarbonate polyurethane or polyurethane, the macroscopic mechanical interlocking structure adopts a T-shaped groove structure; when the flexible buffer material is ultra-high molecular weight polyethylene or highly cross-linked polyethylene, the macroscopic mechanical interlocking structure adopts a card slot structure.

8. The preparation method of a talus prosthesis with a flexible joint surface buffer layer according to claim 6, characterized in that, When the flexible buffer material is polycarbonate polyurethane or polyurethane, the elastic modulus range of the flexible buffer material is from 11 MPa to 1 GPa.

9. The preparation method of a talus prosthesis with a flexible joint surface buffer layer according to claim 1 or 2, characterized in that, The thickness of the flexible buffer layer is 1 mm to 1.5 mm.

10. An astragalus prosthesis with a flexible joint surface buffer layer, characterized in that, Prepared by the preparation method according to any one of claims 1 to 9, the talus prosthesis includes a 3D printed hard substrate and three flexible buffer layers injection-molded from a flexible buffer material. A flexible buffer layer is respectively provided on the contact areas corresponding to the talonavicular joint, the tibio-talar joint and the subtalar joint on the hard substrate, and macroscopic mechanical interlocking structures are respectively provided at the edges of the talonavicular joint contact area, the tibio-talar joint contact area and the subtalar joint contact area. The flexible buffer layer is locked with the hard substrate through the macroscopic mechanical interlocking structure and forms an integrated structure.

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