Talus prosthesis with flexible joint surface buffer layer and preparation method thereof

Abstract

The present invention relates to a talar prosthesis with a flexible joint surface buffer layer and a preparation method thereof, belonging to the field of artificial prosthesis technology, and solving the problem of cartilage degeneration caused by neglecting the missing space of the cartilage layer and the direct contact of hard materials with adjacent cartilage in existing full talar prostheses. The preparation method comprises the following steps: reconstructing a talar prosthesis model based on the CT data of the patient's healthy side talus; generating a macroscopic mechanical interlocking structure at the edges of the talonavicular, tibiotalar and subtalar joint contact areas; 3D printing the talar prosthesis model to obtain a hard base; using 3D printing to manufacture the injection molds corresponding to each contact area; injecting a flexible buffer material into the cavity of the injection mold, cooling and solidifying to form a flexible buffer layer with an integrated structure with the hard base; and obtaining a talar prosthesis with a flexible joint surface buffer layer. The present invention can compensate for the missing space of cartilage and reduce the risk of surgical injury. At the same time, the flexible buffer layer can protect the adjacent cartilage, reduce the risk of degeneration, and ensure long-term prognosis.

Description

Technical Field

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

[0002] Avascular necrosis of the talus is a disease caused by pathological factors that temporarily or permanently interrupt the blood supply to the bone area, and patients often experience severe pain. If not treated in time, the lesion can easily lead to collapse of the joint surface, subsequently developing into arthritis, and ultimately leading to disability and loss of mobility. Currently, the treatment of this disease still faces many challenges. Non-surgical treatment options are limited and have poor efficacy, while common surgical options including talar decompression, tibiotalar fusion, and total ankle replacement all have problems such as unsatisfactory surgical results, loss of ankle joint mobility, and a high incidence of complications.

[0003] With the development of 3D printing technology, the use of 3D-printed, personalized talar prostheses for total talar replacement surgery has gained increasing attention. This technology allows the production of prostheses with anatomical morphology that is highly similar to the native talus and closely matches the adjacent joint, thereby preserving ankle joint motion, improving quality of life, and reducing complication rates. Currently, the most common design for total talar prostheses involves reconstructing the unaffected talus using 3D CT and performing mirror-image optimization. However, the natural tibiotalar joint's cushioning layer is cartilage, which is difficult to visualize on CT images. Therefore, a method of proportionally enlarging the size of the total talar prosthesis is currently common to compensate for the spatial loss of the talar cartilage layer and thus maintain joint stability. However, this method of proportionally enlarging the prosthesis also enlarges non-essential structures, potentially requiring a larger surgical incision during implantation, increasing the surgical difficulty and operational risk.

[0004] In addition, current 3D-printed personalized full-talar prostheses mostly use additive manufacturing technology, and commonly used materials include metals, alloys, ceramics, polyetheretherketone and other uniform materials. However, 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] In response to the problems that the existing full talar prosthesis design does not take into account the spatial loss of the talar cartilage layer and the direct contact between the hard material prosthesis and the adjacent cartilage, which leads to cartilage degeneration and increased risk of poor prognosis, the present invention provides a talar prosthesis with a flexible articular surface buffer layer and a preparation method thereof.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A talar prosthesis with a flexible joint surface buffer layer, the talar prosthesis comprising a 3D-printed hard base and three flexible buffer layers injection-molded from a flexible buffer material, wherein a flexible buffer layer is respectively provided on the contact areas of the hard base corresponding to the talonavicular joint, the tibiotalar joint and the subtalar joint, and macro-mechanical interlocking structures are respectively provided at the edges of the talonavicular joint contact area, the tibiotalar joint contact area and the subtalar joint contact area, wherein the flexible buffer layer is interlocked with the hard base via the macro-mechanical interlocking structures to form an integrated structure.

[0008] At the same time, the present invention also provides a method for preparing a talar prosthesis with a flexible joint surface buffer layer, the preparation method comprising the following steps:

[0009] Step 1: Reconstruct a talar prosthesis model using 3D reconstruction software based on CT data of the patient's unaffected talus, and determine the positions and shapes of the areas corresponding to the three flexible buffer layers on the talar prosthesis model. The areas corresponding to the three flexible buffer layers are the talonavicular joint contact area, the tibiotalar joint contact area, and the subtalar joint contact area.

[0010] Step 2: generating macro-mechanical interlocking structures at the edges of the talonavicular joint contact area, the tibiotalar joint contact area, and the subtalar joint contact area, respectively, wherein the macro-mechanical interlocking structures are T-slot structures or slot structures, and the T-slot structures or slot structures extend toward the interior of the talar prosthesis model;

[0011] Step 3: 3D printing the talar prosthesis model having the macro-mechanical interlocking structure to obtain a hard base of the talar prosthesis;

[0012] Step 4: Using 3D printing to manufacture injection molds corresponding to the talonavicular joint contact area, the tibiotalar joint contact area, and the subtalar joint contact area after the macro-mechanical interlocking structure is generated, and the bottom edge morphology of each injection mold matches the edge geometry of the corresponding area;

[0013] Step 5: After placing the injection mold on the hard substrate and making the injection mold fit tightly with the corresponding area, injecting a flexible cushioning material into the cavity of the injection mold, the flexible cushioning material covers the area where the injection mold fits and fills all the macro-mechanical interlocking structures on the area, and after the flexible cushioning material cools and solidifies, the flexible cushioning layer is formed as an integrated structure with the hard substrate, and the flexible cushioning layer and the hard substrate are locked with each other through the macro-mechanical interlocking structure;

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

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

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

[0017] The present invention provides a flexible cushioning layer with similar functions to natural cartilage (covering the tibiotalar, talonavicular, and subtalar articular surfaces), directly compensating for the missing cartilage space in the talus. This eliminates the need to enlarge the overall size of the prosthesis, thus avoiding the increase in surgical incision and operational risks caused by unnecessary structural expansion.

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

[0019] Compared to the currently common full talar prosthesis designed with uniform hard materials, the flexible buffer layer of the present invention can protect the cartilage adjacent to the prosthesis while ensuring that the size of the talar prosthesis is similar to that of the healthy side talus. 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.

[0020] (3) Improve joint stability:

[0021] The present invention reconstructs a talar prosthesis model based on CT data of the patient's healthy side talus, which can maintain an anatomical morphology that is highly similar to the autologous talus. At the same time, it combines a flexible buffer layer designed in different regions to optimize the matching degree with adjacent joints, thereby improving joint stability.

[0022] (4) Integrated structural design:

[0023] By adopting a macro-mechanical interlocking structure of T-slots or card slots, the flexible buffer layer is locked with the hard base to prevent delamination or displacement after implantation of the prosthesis and ensure long-term mechanical reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 – Figure 6 The schematic diagrams of the structure of the talar prosthesis with a flexible articular surface cushioning layer are shown in six orthogonal perspectives (top view, bottom view, left view, right view, front view and back view);

[0025] Figure 7 This is a flow chart of the preparation method according to an embodiment of the present invention;

[0026] Figure 8 Sagittal cross-section of the talar prosthesis when a T-slot structure is used for the macro-mechanical interlocking structure;

[0027] Figure 9 Sagittal cross-section of the talar prosthesis when a slot structure is used as the macromechanical interlocking structure.

[0028] Explanation of the accompanying reference numerals: 1. Hard base; 2-1. Flexible buffer layer of talonavicular joint; 2-2. Flexible buffer layer of tibiotalar joint; 2-3. Flexible buffer layer of subtalar joint; 3. T-slot structure; 4. Slot structure. DETAILED DESCRIPTION

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

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

[0031] Specifically, the talar prosthesis of this embodiment includes a hard base 1 and three flexible buffer layers, wherein the hard base 1 is manufactured by 3D printing, and its 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 a talonavicular joint flexible buffer layer 2-1, a tibiotalar joint flexible buffer layer 2-2 and a subtalar joint flexible buffer layer 2-3, and the three flexible buffer layers are all obtained by injection molding of flexible buffer materials, and their materials can be any one of materials including ultra-high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (HXLPE), polycarbonate polyurethane (PCU), polyurethane (PU), etc.

[0032] The talonavicular joint flexible buffer layer 2-1, the tibiotalar joint flexible buffer layer 2-2, and the subtalar joint flexible buffer layer 2-3 respectively cover the contact areas corresponding to the talonavicular joint, tibiotalar joint, and subtalar joint on the hard base 1. Macro-mechanical interlocking structures are provided at the edges of the talonavicular joint contact area, the tibiotalar joint contact area, and the subtalar joint contact area. These macro-mechanical interlocking structures can adopt T-slot structures or card slot structures. Each flexible buffer layer is interlocked with the hard base 1 through the T-slot structure or card slot structure to form an integrated structure. At the same time, the macro-mechanical interlocking structure can also be combined with a biocompatible adhesive to ensure the overall stability of the prosthesis. The macro-mechanical interlocking structure is pre-planned using computer graphics design software during the prosthesis design stage to meet the requirements of the 3D printing process.

[0033] In this embodiment, each flexible cushioning layer is designed to protrude outward from the surface of the hard base 1 to a certain thickness and extend inward to a certain depth. The outward protrusion thickness, i.e., the thickness of the flexible cushioning layer, is determined based on the patient's unaffected joint space measurement and is generally 1 mm to 1.5 mm. The inward extension depth is flexibly selected within a range of 0 to 9 mm, depending on the patient's specific condition and the selected material.

[0034] See also Figure 7Another embodiment of the present invention provides a method for preparing a talar prosthesis having a flexible joint surface buffer layer. The method is used to prepare the talar prosthesis described in the above embodiment. Specifically, the method comprises the following steps:

[0035] Step 1: Based on the CT data of the patient's healthy side talus, a talar prosthesis model was reconstructed using 3D reconstruction software, and the positions and shapes of the areas corresponding to the three flexible buffer layers on the talar prosthesis model were determined. The areas corresponding to the three flexible buffer layers were the talonavicular joint contact area, the tibiotalar joint contact area, and the subtalar joint contact area.

[0036] The talar prosthesis is individually designed based on the CT data of the patient's unaffected talus to maximize ankle function. The process of reconstructing the talar prosthesis model using 3D reconstruction software in step 1 specifically includes the following steps:

[0037] Step 1.1: First, in Mimics software, obtain a talus mask based on the CT data of the patient's unaffected talus and perform 3D reconstruction to obtain the geometric shape of the talus;

[0038] Step 1.2: The talar prosthesis model for total talar replacement was then determined in Geomagic software through mirroring and model optimization. Model optimization included removing abnormal holes and protrusions, appropriately reducing the posterior process of the talus, and reserving space for the flexible cushioning layer.

[0039] If the CT data of the patient's healthy side talus is available, it will be used for mirror reconstruction to prepare the talar prosthesis model; if the patient has necrosis on both sides and cannot provide a reference, the talar shape of the population in the patient's area will be statistically analyzed, and based on the statistical data of the talar shape of the population in the patient's area and combined with the CT data of the patient's talus, a design will be made to reconstruct the talar prosthesis model.

[0040] Step 2: Generate macro-mechanical interlocking structures at the edges of the talonavicular joint contact area, tibiotalar joint contact area, and subtalar joint contact area on the talar prosthesis model. The macro-mechanical interlocking structures are T-shaped groove structures (such as Figure 8 As shown) or slot structure (as Figure 9 As shown), the T-slot structure or the card slot structure extends to the inside of the talar prosthesis model to ultimately achieve an integrated stable structure between the flexible buffer layer and the hard base 1. The width of the notch in the T-slot 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 solidified. The hook portion of the card slot structure is in the form of an inverted buckle, and a stable connection can be formed between the inverted hook and the solidified flexible buffer layer to prevent the flexible buffer layer from falling out. At this point, a talar prosthesis model with a macroscopic mechanical interlocking structure is obtained.

[0041] Step 3: Perform 3D printing on the talar prosthesis model obtained in step 2 to obtain a hard base 1 of the talar prosthesis.

[0042] The material of the hard substrate 1 may include but is not limited to cobalt-chromium-molybdenum alloy, bioceramics, titanium alloy, polyetheretherketone (PEEK) and the like, preferably cobalt-chromium-molybdenum alloy.

[0043] In order to further improve the stability between the flexible buffer layer and the hard substrate 1, a combination of macro-mechanical interlocking structure and micro-mechanical interlocking structure is adopted, that is, the surface of the hard substrate 1 in contact with the flexible buffer material is processed, including but not limited to any one or more of sandblasting, laser etching or acid etching treatment to form a rough surface to enhance mechanical interlocking.

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

[0045] Specifically, after step 2, the talar prosthesis model has generated a macroscopic mechanical interlocking structure in the talonavicular joint contact area, the tibiotalar joint contact area and the subtalar joint contact area. 3D printing is used to manufacture the injection molds corresponding to the talonavicular joint contact area, the tibiotalar joint contact area and the subtalar joint contact area, respectively, and the bottom edge morphology of each injection mold matches the edge geometry of the corresponding contact area, thereby ensuring that the flexible buffer material can just cover the corresponding contact area during injection molding.

[0046] Step 5: Taking the talonavicular joint flexible cushioning layer 2-1 as an example, during injection molding, the injection mold corresponding to the talonavicular joint contact area is first placed on the talonavicular joint contact area on the hard base 1, and the injection mold is tightly fitted to the corresponding area surface. Then, a flexible cushioning material is injected into the cavity of the injection mold, completely covering the area where the injection mold fits and filling all macro-mechanical interlocking structures in this area. After the flexible cushioning material wraps around and covers the talonavicular joint contact area, the flexible cushioning material cools and solidifies to form the talonavicular joint flexible cushioning layer 2-1, which is an integrated structure with the hard base 1. The talonavicular joint flexible cushioning layer 2-1 and the hard base 1 are interlocked by the macro-mechanical interlocking structure. The injection molding process of the tibiotalar joint flexible cushioning layer 2-2 and the subtalar joint flexible cushioning layer 2-3 is similar to that of the talonavicular joint flexible cushioning layer 2-1 and will not be repeated here.

[0047] In this embodiment, the flexible cushioning material can be 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 used on the hard base side, thereby achieving a smooth transition in elastic modulus across the entire talar prosthesis.

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

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

[0051] For talar prostheses using PCU or PU as cushioning materials, the elastic modulus can be adjusted over a wide range of 11 MPa to 1 GPa by adjusting the ratio of the hard and soft segments of the material. Biomechanical simulation tests indicate that the optimal elastic modulus should be less than 96.94 MPa.

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

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

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

[0055] The present invention provides a flexible cushioning layer with similar functions to natural cartilage (covering the tibiotalar, talonavicular, and subtalar articular surfaces), directly compensating for the missing cartilage space in the talus. This eliminates the need to enlarge the overall size of the prosthesis, thus avoiding the increase in surgical incision and operational risks caused by unnecessary structural expansion.

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

[0057] Compared to the currently common full talar prosthesis designed with uniform hard materials, the flexible buffer layer of the present invention can protect the cartilage adjacent to the prosthesis while ensuring that the size of the talar prosthesis is similar to that of the healthy side talus. 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.

[0058] (3) Improve joint stability:

[0059] The present invention reconstructs a talar prosthesis model based on CT data of the patient's healthy side talus, which can maintain an anatomical morphology that is highly similar to the autologous talus. At the same time, it combines a flexible buffer layer designed in different regions to optimize the matching degree with adjacent joints, thereby improving joint stability.

[0060] (4) Integrated structural design:

[0061] By adopting a macro-mechanical interlocking structure of T-slots or card slots, the flexible buffer layer is locked with the hard base to prevent delamination or displacement after implantation of the prosthesis and ensure long-term mechanical reliability.

[0062] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a talar prosthesis with a flexible joint surface buffer layer, characterized in that: The preparation method comprises the following steps: Step 1: Reconstruct a talar prosthesis model using 3D reconstruction software based on CT data of the patient's unaffected talus, and determine the positions and shapes of the areas corresponding to the three flexible buffer layers on the talar prosthesis model. The areas corresponding to the three flexible buffer layers are the talonavicular joint contact area, the tibiotalar joint contact area, and the subtalar joint contact area. Step 2: generating macro-mechanical interlocking structures at the edges of the talonavicular joint contact area, the tibiotalar joint contact area, and the subtalar joint contact area, respectively, wherein the macro-mechanical interlocking structures are T-slot structures or slot structures, and the T-slot structures or slot structures extend toward the interior of the talar prosthesis model; Step 3: 3D printing the talar prosthesis model having the macro-mechanical interlocking structure to obtain a hard base of the talar prosthesis; Step 4: Using 3D printing to manufacture injection molds corresponding to the talonavicular joint contact area, the tibiotalar joint contact area, and the subtalar joint contact area after the macro-mechanical interlocking structure is generated, and the bottom edge morphology of each injection mold matches the edge geometry of the corresponding area; Step 5: After placing the injection mold on the hard substrate and making the injection mold fit tightly with the corresponding area, injecting a flexible buffer material into the cavity of the injection mold, the flexible buffer material covers the area where the injection mold fits and fills all the macro-mechanical interlocking structures on the area, and after the flexible buffer material cools and solidifies, the flexible buffer layer with an integrated structure with the hard substrate is formed, and the flexible buffer layer and the hard substrate are locked with each other through the macro-mechanical interlocking structure, and the flexible buffer layer has a gradually changing elastic modulus, and the elastic modulus on the joint surface side is lower than the elastic modulus on the hard substrate side; Step 6: After removing the injection mold, a talar prosthesis with a flexible joint surface buffer layer is obtained.

2. The method for preparing a talar prosthesis with a flexible joint surface buffer layer according to claim 1, characterized in that: The talar shape statistics of the population in the patient's area are used to replace the CT data of the patient's healthy side talus in step 1 and then reconstruct the talar prosthesis model.

3. The method for preparing a talar prosthesis with a flexible joint surface buffer layer according to claim 1 or 2, characterized in that: The process of reconstructing the talar 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 patient's unaffected talus and perform 3D reconstruction to obtain the geometric shape of the talus; Step 1.2: In Geomagic software, the talar prosthesis model is determined by mirroring and model optimization processing, wherein the model optimization processing includes removing abnormal holes and protrusions, appropriately reducing the posterior process of the talus, and reserving space required for the flexible buffer layer.

4. The method for preparing a talar prosthesis with a flexible joint surface buffer layer according to claim 1 or 2, characterized in that: After step 3 and before step 5, the following steps are further included: The surface of the hard substrate in contact with the flexible buffer material is sandblasted, laser etched or acid-etched to form a rough surface.

5. The method for preparing a talar prosthesis with a flexible joint surface buffer layer according to claim 1 or 2, characterized in that: The material of the hard 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 polyethylene, highly cross-linked polyethylene, polycarbonate polyurethane and polyurethane.

6. The method for preparing a talar prosthesis with a flexible joint surface buffer layer according to claim 5, characterized in that: When the flexible buffer material is polycarbonate polyurethane or polyurethane, the macro-mechanical interlocking structure adopts a T-slot structure; when the flexible buffer material is ultra-high molecular polyethylene or highly cross-linked polyethylene, the macro-mechanical interlocking structure adopts a slot structure.

7. The method for preparing a talar prosthesis with a flexible joint surface buffer layer according to claim 5, characterized in that: When the flexible buffer material is polycarbonate polyurethane or polyurethane, the elastic modulus of the flexible buffer material ranges from 11 MPa to 1 GPa.

8. The method for preparing a talar 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.

9. A talar prosthesis with a flexible joint surface buffer layer, characterized in that: The talar prosthesis is prepared by the preparation method according to any one of claims 1 to 8, and includes a 3D-printed hard base and three flexible buffer layers injection-molded by flexible buffer materials. A flexible buffer layer is respectively provided on the contact areas of the hard base corresponding to the talonavicular joint, the tibiotalar joint and the subtalar joint, and macro-mechanical interlocking structures are respectively provided at the edges of the talonavicular joint contact area, the tibiotalar joint contact area and the subtalar joint contact area. The flexible buffer layer is interlocked with the hard base through the macro-mechanical interlocking structure to form an integrated structure.

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