Porous tibial prosthesis with gradient porous structure and preparation method thereof

Abstract

The invention discloses a porous tibial prosthesis with a gradient porous structure and a preparation method of the porous tibial prosthesis. Comprising a tray and a handle part, the handle part comprises an internal discrete gradient porous core body and an external solid shell, and a plurality of circular windows are further formed in the solid shell; the preparation method comprises the following steps: establishing a basic digital model of the tibia support prosthesis by using three-dimensional modeling software; importing the basic digital model into implicit modeling software, generating a three-period minimal curved surface lattice structure in the internal space of the solid shell, and forming a digital model of the discrete gradient porous core body; performing Boolean union operation on the generated discrete gradient porous core digital model and the entity shell digital model to obtain a complete prosthesis digital model; a metal additive manufacturing technology is adopted, medical titanium alloy powder is used as a raw material, and a prosthesis digital model is integrally printed and formed. According to the method, the advantages of parameterized CAD software and implicit modeling software are combined, and efficient and accurate design of the complex gradient porous structure prosthesis is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to a porous tibial prosthesis with gradient porous structure and a preparation method thereof. BACKGROUND

[0002] Artificial knee replacement is an effective means for treating end-stage knee arthritis and other diseases. The long-term stability of the tibial prosthesis, as the core component, is crucial. Currently, most commercial tibial prostheses are solid structures or uniform porous structures, and the elastic modulus of their materials (such as titanium alloy) is much higher than that of human tibia (about 110 GPa, which is much higher than that of human tibia (about 0.1-1.5 GPa for cancellous bone and about 10-20 GPa for cortical bone)), resulting in a serious "stress shielding" effect. The load is mainly borne by the high-stiffness prosthesis, and the surrounding bone is absorbed and atrophied due to insufficient mechanical stimulation, eventually leading to loosening and sinking of the prosthesis.

[0003] To solve the stress shielding, the prior art proposes a method of designing a uniform porous structure in the prosthesis stem. However, the uniform porous structure cannot achieve precise matching with the bone modulus, and while reducing the distal stress shielding, it may weaken the proximal load-bearing capacity, resulting in performance compromise. In addition, the exposed porous structure is easily damaged during surgical implantation, and has high frictional resistance, affecting the initial stability. SUMMARY

[0004] The purpose of the present application is to provide a porous tibial prosthesis with gradient porous structure that can achieve stiffness gradient transition and balance implant safety and long-term biological integration. Another purpose of the present application is to provide a preparation method of the porous tibial prosthesis.

[0005] Technical solution: The porous tibial prosthesis with gradient porous structure according to the present application comprises a tray and a stem fixed to the tray, wherein the stem comprises a discrete gradient porous core inside and a solid shell outside.

[0006] Further, the tray has an asymmetric kidney-shaped profile matching the tibial plateau; the stem is fixed below the tray.

[0007] Further, the discrete gradient porous core adopts a three-dimensional porous structure of Gyroid three-periodic minimal surface unit, and the relative density thereof includes three discrete gradient changes along the axial direction: a proximal high-density zone at a distance of 0-14 mm from the bottom surface of the tray; a middle middle-density zone at a distance of 14-27 mm; and a distal low-density zone at a distance of 27-40 mm.

[0008] Further, the relative densities of the three gradient zones are set to 55%, 40%, and 25%, respectively. Each zone has a uniform porous structure, and the zones are connected by a 1mm transition unit.

[0009] Further, the solid shell is wrapped outside the discrete gradient porous core, and the thickness is 1 mm; through the segmented array and Boolean subtraction operation, a circular window with a diameter of 2.5 mm is opened on the solid shell, and the window of the circular window exposes the internal three-dimensional porous structure.

[0010] Further, the distribution of the circular window is as follows: The distal handle region: 6 windows are uniformly distributed in the circumferential direction, 4 rows are arranged in the axial direction, and a total of 24 windows are arranged, with a row spacing of about 3.3 mm; The middle region: 6 windows are uniformly distributed in the circumferential direction, 3 rows are arranged in the axial direction, and a total of 18 windows are arranged, with a row spacing of about 4.5 mm; The proximal handle region: 4 windows are uniformly distributed in the circumferential direction, 2 rows are arranged in the axial direction, and a total of 8 windows are arranged, with a row spacing of about 10 mm.

[0011] Further, the minimum solid spacing between all windows is ≥1.2 mm.

[0012] Further, the distribution density of the circular window in the distal end region of the handle is higher than that in the proximal end region.

[0013] Further, the distal end face of one end of the tray of the handle is a closed solid structure.

[0014] Further, the preparation method of the porous tibial prosthesis with a gradient porous structure is as follows: (1) A three-dimensional modeling software is used to establish a basic digital model of a tibial tray prosthesis, including the initial structure of the tray and the solid shell of the handle with preset circular windows; (2) The basic digital model is imported into an implicit modeling software, and a three-period minimum surface lattice structure is generated in the internal space of the handle solid shell based on the preset discrete gradient parameters, forming a digital model of a discrete gradient porous core; (3) The generated digital model of the discrete gradient porous core and the digital model of the solid shell are subjected to accurate Boolean set operation to ensure that the internal lattice structure and the window on the shell are completely penetrated, and a complete prosthesis digital model is obtained; (4) A metal additive manufacturing technology is used, and medical titanium alloy powder is used as raw material to integrally print the prosthesis digital model.

[0015] Beneficial effects: Compared with the prior art, the present application has the following remarkable advantages: 1. Excellent biomechanical compatibility: through the axial discrete gradient porous structure, the stepwise matching of the prosthesis stem stiffness and the human tibial bone modulus is realized, the stress shielding effect is effectively reduced while the structural bearing capacity is ensured, and the design and manufacturing are more simple and reliable; 2. Synergistic stability mechanism: the solid shell ensures the structural integrity and surgical feasibility of the prosthesis during implantation and provides initial stability; and the gradient distribution of the window provides a channel for the bone to grow into the internal porous structure, and excellent long-term stability is achieved through biological integration; 3. Integrated forming manufacturing: through parameterized design and metal additive manufacturing technology, the integrated manufacturing of the complex discrete gradient porous structure and the solid shell is realized, avoiding the interface failure risk of traditional combined structure; 4. High design flexibility and process feasibility: the number of discrete gradients, the density values of each region and the window distribution can be personalized according to the specific conditions of the patient, and the discrete gradient model has higher process stability and controllability during preparation, and has wide clinical application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a schematic diagram of the overall structure of the present application; Figure 2 is a longitudinal sectional view of the stem part in the present application; Figure 3 is a schematic diagram of the relative density of the stem part gradient porous structure in the present application along the axial stepwise change curve; Figure 4 is a schematic diagram of the distribution of the window on the stem part shell in the present application (dense at the distal end, sparse at the proximal end); In the figure: 1 is a tray, 2 is a stem, 2-1 is a discrete gradient porous core, 2-2 is a solid shell, 2-3 is a circular window, and 2-4 is a distal end face. DETAILED DESCRIPTION

[0017] The specific technical solutions of the present application will be further described in detail below in combination with specific examples.

[0018] As shown in the figure, the porous tibial prosthesis with gradient porous structure described in the present embodiment comprises a tray 1 and a stem 2; the contour of the tray 1 is an asymmetric kidney shape based on the anatomical morphology of the tibial plateau; Figures 1-4 The stem 2 is a circular truncated cone body, fixedly connected below the tray 1, which comprises an internal discrete gradient porous core 2-1 and an external solid shell 2-2; ​The discrete gradient porous core 2-1 (internal core) adopts a three-dimensional porous structure of Gyroid three-periodic minimal surface unit, and the relative density thereof presents at least three discrete gradient step changes along the axial direction of the shank 2, so that the equivalent elastic modulus of the shank 2 presents a step decrease from the proximal end to the distal end: wherein the distance from the bottom surface of the tray 1 is 0-14 mm, which is the proximal end high-density area, and the relative density is set to 55%; 14-27 mm is the middle section medium-density area, and the relative density is set to 40%; 27-40 mm is the distal end low-density area, and the relative density is set to 25%; the internal part of each area is a uniform porous structure, and the connection between the areas is realized through a 1 mm transition unit.

[0019] According to the homogenization method, the equivalent elastic modulus is correspondingly decreased from about 10 GPa at the proximal end to about 5 GPa at the middle section, and then to about 1.5 GPa at the distal end.

[0020] The outer part of the shank 2 is a solid shell 2-2 with a thickness of 1 mm; it is wrapped outside the discrete gradient porous core 2-1; a plurality of circular windows 2-3 with a diameter of 2.5 mm are opened on the shell 2-2 through a segmented array and a Boolean subtraction operation, and the distribution follows a strict gradient strategy; The circular windows 2-3 expose the internal three-dimensional porous structure; The distal shank area: 6 windows are uniformly distributed in the circumferential direction, and 4 rows are arranged in the axial direction, totaling 24 windows, and the row spacing is about 3.3 mm; The middle section area: 6 windows are uniformly distributed in the circumferential direction, and 3 rows are arranged in the axial direction, totaling 18 windows, and the row spacing is about 4.5 mm; The proximal shank area: 4 windows are uniformly distributed in the circumferential direction, and 2 rows are arranged in the axial direction, totaling 8 windows, and the row spacing is about 10 mm.

[0021] The minimum solid spacing between all windows is ensured to be not less than 1.2 mm to ensure the structural integrity of the shell.

[0022] The distal end surface 2-4 of the shank 2 is a closed solid structure, which is used for effective load transmission and prevents soft tissue invasion.

[0023] The distribution density of the windows in the distal end area of the shank 2 is higher than that in the proximal end area.

[0024] The steps of the preparation method are as follows: Step one: first, a model of the tray 1 with an asymmetric kidney-shaped contour is established in SolidWorks according to the anatomical morphology of the tibial platform, and a basic solid model of the shank 2 is established, and a shell with windows (circular windows 2-3) that meet the gradient distribution requirements is formed on the shank 2 solid by stretching and cutting, etc. Step two: import the model established in SolidWorks into nTopology software in STEP format; define the lattice types of the three regions of the proximal end, the middle and the distal end of the handle 2 as Gyroid curved surface respectively through the TPMS lattice module in nTopology, and set the corresponding relative density parameters to generate a lattice structure with three gradient changes along the axial direction; Step three: through the Boolean operation function in nTopology, ensure that the gradient lattice structure generated inside is accurately aligned with and penetrates through the pre-set window on the shell to form an integrated digital model of the complete prosthesis internal porous structure and the external solid shell and window; and export it in STL or 3MF format.

[0025] Step four: using selective laser melting technology, using Ti-6Al-4V ELI medical titanium alloy powder as raw material, under the optimized process parameters, the prosthesis is integrally printed.

[0026] The present application combines the advantages of parameterized CAD software and implicit modeling software, realizes efficient and accurate design of complex gradient porous structure prosthesis, and provides a feasible technical path for personalized medical treatment.

Claims

1. A porous tibial prosthesis with a gradient porous structure, characterized in that, It includes a tray (1) and a handle (2) fixed to the tray (1), the handle (2) including an inner discrete gradient porous core (2-1) and an outer solid shell (2-2).

2. The porous tibial prosthesis with a gradient porous structure according to claim 1, characterized in that, The tray (1) has an asymmetrical kidney-shaped profile that matches the tibial plateau; the handle (2) is fixed to the underside of the tray (1).

3. The porous tibial prosthesis with a gradient porous structure according to claim 1, characterized in that, The discrete gradient porous core (2-1) adopts a three-dimensional porous structure of Gyroid three-period minimal surface unit. Its relative density includes three discrete gradient changes along the axial direction: the near end high density area is 0-14mm from the bottom surface of the tray (1); the middle section medium density area is 14-27mm; and the far end low density area is 27-40mm.

4. The porous tibial prosthesis with a gradient porous structure according to claim 3, characterized in that, The relative densities corresponding to the three gradient regions are set to 55%, 40%, and 25%, respectively. Each region has a uniform porous structure, and the regions are connected by a 1mm transition unit.

5. The porous tibial prosthesis with a gradient porous structure according to claim 1, characterized in that, The solid shell (2-2) covers the outside of the discrete gradient porous core (2-1) and has a thickness of 1 mm. Through segmented array and Boolean subtraction operation, a circular window (2-3) with a diameter of 2.5 mm is opened on the solid shell (2-2), and the window of the circular window (2-3) exposes the internal three-dimensional porous structure.

6. The porous tibial prosthesis with a gradient porous structure according to claim 5, characterized in that, The circular windows (2-3) are distributed as follows: Distal shank area: 6 windows are evenly distributed circumferentially and arranged in 4 rows axially, for a total of 24 windows, with a row spacing of approximately 3.3 mm; Central area: 6 windows are evenly distributed around the perimeter and arranged in 3 rows along the axis, for a total of 18 windows, with a row spacing of approximately 4.5 mm; Near the handle area: 4 windows are evenly distributed circumferentially and arranged in 2 rows axially, for a total of 8 windows, with a row spacing of about 10mm.

7. The porous tibial prosthesis with a gradient porous structure according to claim 6, characterized in that, The minimum physical spacing between all windows is ≥1.2mm.

8. The porous tibial prosthesis with a gradient porous structure according to claim 5, characterized in that, The distribution density of the circular window (2-3) in the distal region of the handle (2) is higher than that in the proximal region.

9. The porous tibial prosthesis with a gradient porous structure according to claim 1, characterized in that, The distal end face (2-4) of the handle (2) away from the tray (1) is a closed solid structure.

10. The method for preparing the porous tibial prosthesis with a gradient porous structure according to any one of claims 1-9, characterized in that, The preparation steps are as follows: (1) Use three-dimensional modeling software to establish the basic digital model of the tibial support prosthesis, including the initial structure of the tray (1) and the handle (2) with a preset circular window (2-3) and the solid shell (2-2); (2) Import the basic digital model into the implicit modeling software. Based on the preset discrete gradient parameters, generate a three-period minimal surface lattice structure in the internal space of the solid shell (2-2) of the handle (2) to form a digital model of the discrete gradient porous core (2-1). (3) Perform a precise Boolean union operation on the digital model of the generated discrete gradient porous core (2-1) and the digital model of the solid shell (2-2) to ensure that the internal lattice structure and the window on the shell are completely connected, and obtain a complete digital model of the sculpt. (4) Using metal additive manufacturing technology, medical titanium alloy powder is used as raw material to integrally print the digital model of the prosthesis.

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