A self-adaptive bionic cancellous bone defect prosthesis and its design method

Abstract

A self-adaptive bionic cancellous bone defect prosthesis and a design method thereof belong to the technical field of medical prostheses. The prosthesis consists of a bio-interface gradient microporous structure portion and a main bionic truss support structure portion. The bio-interface gradient microporous structure portion is arranged at both ends of the main bionic truss support structure portion and is mainly used to reconstruct bone defects. Through the established linear relationship between CT grayscale value and bone density-elastic modulus, the main truss portion is bionicly designed with the same arrangement direction and morphology as human trabeculae, adaptively matching the mechanical conduction of the bone structure, reducing the stress shielding effect, and simultaneously matching the prosthesis's various complex mechanical working conditions, reducing the risk of prosthesis failure, and extending the prosthesis's service life.

Description

Technical Field

[0001] The present invention relates to the technical field of medical prostheses, and in particular to a self-adaptive bionic cancellous bone defect prosthesis and a design method thereof. Background Art

[0002] Approximately 4 million patients suffer from large segmental bone defects in my country each year, primarily due to high-energy injuries (such as falls from height and traffic accidents) and pathological bone destruction (such as bone tumors and chronic osteomyelitis). Their treatment remains a major challenge in orthopedic clinical practice. The current mainstream treatment approach is repair and reconstruction with solid titanium alloy prostheses. However, the intrinsic elastic modulus of titanium alloy (110 GPa) is significantly higher than that of cortical bone (10-30 GPa), triggering a severe stress shielding effect and leading to bone resorption rates exceeding 35% at the prosthesis-bone interface. Therefore, reducing the elastic modulus of prostheses through porous designs such as microporous or truss structures is the current primary improvement approach. Currently, prosthesis designs often utilize homogenized porous structures or topological optimization methods based on finite element stress / volume response. While conventional homogenized microporous designs can significantly reduce elasticity, they suffer from insufficient mechanical strength, resulting in local mechanical mismatch. While porous structures designed using finite element stress / volume response topology optimization methods can achieve macroscopic mechanical strength requirements, existing stress / volume response optimization models rely on in vitro loading simulations and fail to reflect the dynamic mechanical conduction characteristics of the body. This can lead to deviations between the orientation of the prosthesis' micropores or trusses and the principal stress trajectory of the bone, hindering functional bone remodeling. Therefore, there is an urgent need to develop a new bone defect prosthesis that matches mechanical conduction and can meet the needs of a variety of complex mechanical conditions.

[0003] Patent document 202411381537.7 discloses a "Method for Designing a Variable-Density Porous Bone Prosthesis Based on Bone Density Distribution." This method produces a microporous prosthesis with small pores. If the elastic modulus approaches that of bone, this inevitably leads to reduced strength. Furthermore, this method involves a CAD modeling approach, where a large grid is created. Micropores are then created within the prosthesis using Boolean operations. Some of the pores are reduced in size, inevitably leading to Boolean edge distortion. Micropores make it difficult to achieve both an elastic modulus close to that of bone and sufficient mechanical strength.

[0004] Wolff's law, a cornerstone theory in bone biomechanics, clearly states that there is a dynamic adaptive relationship between the morphological structure of bone tissue and the distribution of mechanical loads. Through the continuous remodeling process of bone resorption and deposition, parameters such as the orientation of trabecular bone and cortical bone thickness are highly aligned with the direction and magnitude of the principal stresses. This law reveals that bone tissue regulates cellular activity by sensing local stress stimuli, forming a microstructure adapted to the mechanical environment. Furthermore, trabeculae grow directional along the direction of the principal stresses, forming efficient mechanical conduction pathways and achieving an optimal balance between lightweight structure and load-bearing performance. Therefore, bone tissue structure is the most reliable biomimetic reference for prosthetic design.

[0005] There is ample evidence that CT grayscale values and bone density are linearly related. Therefore, extracting the host bone density gradient field from CT grayscale values can reflect the cumulative effect of historical mechanical stimulation on bone tissue, embodying the dual-driven mechanism of "anatomical structure and mechanical environment." Therefore, by establishing a cross-scale mapping model of grayscale value, elastic modulus, and stress stimulation, this invention achieves an engineered expression of Wolff's law, addressing the shortcomings of current prosthesis design.

[0006] In summary, a self-adaptive bionic cancellous bone defect prosthesis and its design method can meet the requirements of various complex mechanical working conditions of the prosthesis, reduce the risk of prosthesis failure, and extend the service life of the prosthesis. Summary of the Invention

[0007] In response to the shortcomings of existing bone defect prostheses and their design technologies, the present invention proposes a self-adaptive bionic cancellous bone defect prosthesis and its design method, which is mainly used to reconstruct bone defects. Through the established linear relationship between CT grayscale value and bone density-elastic modulus, the truss part of the main body with the same arrangement direction and morphology as the human trabeculae is bionic designed, adaptively matching the mechanical conduction of the bone structure, reducing the stress shielding effect, and at the same time matching the various complex mechanical working conditions of the prosthesis, reducing the risk of prosthesis failure, and extending the service life of the prosthesis.

[0008] A self-adaptive bionic cancellous bone defect prosthesis comprises a biological interface gradient microporous structure part and a main body bionic truss support structure part, wherein the biological interface gradient microporous structure part is arranged at both ends of the main body bionic truss support structure part.

[0009] The biointerface gradient microporous structure part and the main bionic truss support structure part are bionic trabecular structures or bionic glass sponge structures or Thiessen polygon structures or TPMS structures.

[0010] The bone defect prosthesis material is Ti6Al4V.

[0011] A method for designing a self-adaptive bionic cancellous bone defect prosthesis, wherein the bone defect prosthesis is a 3D printing integrated molding design, includes the following four steps.

[0012] Step 1: Construct a 3D anatomical model of the bone defect area based on the patient's CT data, including the following steps:

[0013] (1) Collect CT data of patients with bone defects and import the CT data into medical 3D reconstruction software, such as Mimics, in Dicom format;

[0014] (2) Reconstruct the 3D bone model in medical 3D reconstruction software, divide the defect area, and export its STL model;

[0015] (3) Import the divided defect STL model into 3D modeling software, such as Rhino, Solidwork, Magics, etc., to design the 3D structure of the prosthesis;

[0016] (4) The three-dimensional structure of the prosthesis is divided into the main body and the bone interface connection part. The main body prepares for the subsequent truss structure design, and the bone interface connection part prepares for the subsequent microporous structure design.

[0017] Step 2: Mirror the contralateral side and extract the spatial coordinate points of the model on the healthy side and their corresponding CT grayscale value distribution matrix, including the following steps:

[0018] (1) Divide the exported main body into body units and import the body unit structure into Mimics software;

[0019] (2) Using the mirror tool, mirror the unit structure to the healthy side and fit it to match the contralateral bone structure;

[0020] (3) Assign parameters to the volume unit according to the CT grayscale value and export the assigned point cloud data;

[0021] (4) Import the assigned volume unit information into post-processing software, such as Matlab software, to extract the three-dimensional coordinates of the corresponding spatial coordinate points and the corresponding grayscale value information.

[0022] Step 3: Based on the grayscale value-bone density-elastic modulus mapping relationship model, the geometric parameters of the truss unit are dynamically adjusted through a gradient parameter matching algorithm, including spatial density distribution, beam diameter gradient change, and porosity distribution. An optimization iterative algorithm is used to generate a mechanically conductive adaptive truss structure that matches the host bone elastic modulus distribution. The following steps are included:

[0023] (1) Based on the existing grayscale value-bone density-bone elastic modulus assignment formula, a mapping relationship model is established, and the appropriate assignment formula is selected according to the different elastic moduli of the bone site where the bone defect is located;

[0024] (2) Based on the corresponding formula of the spatial density distribution, beam diameter gradient change and porosity change of the existing truss structure and the elastic modulus of the titanium alloy truss structure, a grayscale value-bone density-bone elastic modulus-titanium alloy elastic modulus matching response is established;

[0025] (3) Import the spatial coordinate points and their grayscale value data of the volume unit into the computational design software, such as ntop, Grasshopper, Matlab, etc., and establish the connection between the spatial coordinate points and their grayscale value data of the volume unit and the truss design;

[0026] (4) Use computer language to automatically generate the main truss structure based on the grayscale value changes.

[0027] The change in truss density is affected by the grayscale value. High-density trusses are selected where the grayscale value is high, and low-density trusses are selected where the grayscale value is low. Therefore, the relationship between CT grayscale value - bone density - elastic modulus - truss density is generated.

[0028] Step 4: Set interface gradient micropores according to the change of interface grayscale value, integrate the optimized truss structure with the interface gradient micropore structure, and output the final prosthesis model, including the following steps:

[0029] (1) Import the bone interface connection part into the prosthesis design software, such as Rhino, Solidwork, Magics, etc., and match it with the main truss part;

[0030] (2) Extract the spatial coordinate points and grayscale values of the prosthesis-bone connection interface. Based on steps 2 and 3, set a gradient microporous structure based on grayscale value response to achieve the change of microporous structure parameters with grayscale value.

[0031] (3) In the prosthesis design software, the microporous part connecting the bone interface and the truss part are integrated together using the Boolean addition operation to complete the design of the prosthesis shape;

[0032] (4) Screw channels and auxiliary bone plates are set according to the fixation requirements of prostheses in different positions. Among them, pelvic prostheses need to add sacral dorsal bionic axis joint fixation, long bone shaft prostheses need to add bilateral bone plates and reserve intramedullary nail channels, and the proximal / distal ends of long bones need to add bone plates and reserve prosthesis stem channels.

[0033] The self-adaptive bionic cancellous bone defect prosthesis produced by 3D printing using the above method is connected to the human body's own pelvis through screws.

[0034] Beneficial effects of the present invention:

[0035] 1. The present invention is designed based on CT grayscale value drive. By establishing a cross-scale mapping model of grayscale value-bone density-elastic modulus, the prosthesis truss structure is dynamically matched with the mechanical conduction characteristics of the host bone. While ensuring strength, it can significantly reduce the stress shielding effect of traditional titanium alloy prostheses.

[0036] 2. The main bionic truss structure of the present invention simulates the mechanical conduction path of trabecular bone, combined with the interface gradient microporous structure, taking into account both macroscopic bearing strength and microscopic bone ingrowth requirements, and solving the problems of insufficient mechanics of homogeneous porous structures or topological optimization deviating from the in vivo mechanical environment.

[0037] 3. The present invention mirrors the healthy side bones based on the patient's CT data, extracts the three-dimensional coordinates and grayscale value distribution, realizes personalized prosthesis design, and accurately matches the anatomical morphology and mechanical environment.

[0038] 4. The present invention provides a new bionic prosthesis that conforms to the mechanical conduction distribution characteristics of the human body and its design method, which can meet the mechanical requirements of bone defect prostheses under complex load conditions and improve their interface bone integration ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is an overall design pattern diagram of an embodiment of the present invention.

[0040] Figure 2 Schematic diagram of the overall structure of an embodiment of the present invention.

[0041] Figure 3 Schematic diagram of the overall installation of an embodiment of the present invention.

[0042] Figure 4 Schematic diagram of the structure of trusses with different densities according to an embodiment of the present invention.

[0043] Figure 5 Schematic diagram of Thiessen polygons selected for the microporous structure of an embodiment of the present invention.

[0044] Figure 6 Schematic diagram of the design process of an embodiment of the present invention. DETAILED DESCRIPTION

[0045] See also Figures 1 to 6 Shown is an embodiment of the present invention.

[0046] A self-adaptive bionic cancellous bone defect prosthesis comprises a biological interface gradient microporous structure part 1 and a main bionic truss support structure part 2, wherein the biological interface gradient microporous structure part 1 is arranged at both ends of the main bionic truss support structure part 2.

[0047] The biointerface gradient microporous structure part 1 and the main bionic truss support structure part 2 are Thiessen polygon structures. The bone defect prosthesis material is Ti6Al4V.

[0048] The self-adaptive bionic cancellous bone defect prosthesis described in this embodiment is a 3D printing integrated molding design, which includes the following four steps.

[0049] Step 1: Construct a 3D anatomical model of the bone defect area based on the patient's CT data, including the following steps:

[0050] (1) Collect CT data of patients with bone defects and import the CT data into Mimics medical 3D reconstruction software in Dicom format;

[0051] (2) Reconstruct the bone 3D model in Mimics medical 3D reconstruction software, divide the defect area, and export its STL model;

[0052] (3) Import the segmented defect STL model into the 3D modeling software Solidwork to design the 3D structure of the prosthesis;

[0053] (4) The three-dimensional structure of the prosthesis is divided into the main body and the bone interface connection part. The main body prepares for the subsequent truss structure design, and the bone interface connection part prepares for the subsequent microporous structure design.

[0054] Step 2: Mirror the contralateral side and extract the spatial coordinate points of the model on the healthy side and their corresponding CT grayscale value distribution matrix, including the following steps:

[0055] (1) Divide the exported main body into body units and import the body unit structure into Mimics software;

[0056] (2) Using the mirror tool, mirror the unit structure to the healthy side and fit it to match the contralateral bone structure;

[0057] (3) Assign parameters to the volume unit according to the CT grayscale value and export the assigned point cloud data;

[0058] (4) The assigned volume unit information is imported into the post-processing Matlab software to extract the three-dimensional coordinates of the corresponding spatial coordinate points and the corresponding grayscale value information.

[0059] Step 3: Based on the grayscale value-bone density-elastic modulus mapping relationship model, the geometric parameters of the truss unit are dynamically adjusted through a gradient parameter matching algorithm, including spatial density distribution, beam diameter gradient change, and porosity distribution. An optimization iterative algorithm is used to generate a mechanically conductive adaptive truss structure that matches the host bone elastic modulus distribution. The following steps are included:

[0060] (1) Based on the existing grayscale value-bone density-bone elastic modulus assignment formula, a mapping relationship model is established, and the appropriate assignment formula is selected according to the different elastic moduli of the bone site where the bone defect is located;

[0061] (2) Based on the corresponding formula of the spatial density distribution, beam diameter gradient change and porosity change of the existing truss structure and the elastic modulus of the titanium alloy truss structure, a grayscale value-bone density-bone elastic modulus-titanium alloy elastic modulus matching response is established;

[0062] (3) Import the spatial coordinate points and their grayscale value data of the volume unit into the Matlab computational design software, and establish the connection between the spatial coordinate points and their grayscale value data of the volume unit and the truss design;

[0063] (4) Use computer language to automatically generate the main truss structure based on the grayscale value changes.

[0064] The change in truss density is affected by the grayscale value. High-density trusses are selected where the grayscale value is high, and low-density trusses are selected where the grayscale value is low. Therefore, the relationship between CT grayscale value - bone density - elastic modulus - truss density is generated.

[0065] Step 4: Set interface gradient micropores according to the change of interface grayscale value, integrate the optimized truss structure with the interface gradient micropore structure, and output the final prosthesis model, including the following steps:

[0066] (1) Import the bone interface connection part into the prosthesis design software Rhino and match it with the main truss part;

[0067] (2) Extract the spatial coordinate points and grayscale values of the prosthesis-bone connection interface. Based on steps 2 and 3, set a gradient microporous structure based on grayscale value response to achieve the change of microporous structure parameters with grayscale value.

[0068] (3) In the prosthesis design software, the microporous part connecting the bone interface and the truss part are integrated together using the Boolean addition operation to complete the design of the prosthesis shape;

[0069] (4) Screw channels and auxiliary bone plates are set according to the fixation requirements of prostheses in different positions. Among them, pelvic prostheses need to add sacral dorsal bionic axis joint fixation, long bone shaft prostheses need to add bilateral bone plates and reserve intramedullary nail channels, and the proximal / distal ends of long bones need to add bone plates and reserve prosthesis stem channels.

[0070] The self-adaptive bionic cancellous bone defect prosthesis produced by 3D printing using the above method is connected to the human body's own pelvis via screws 3.

[0071] The truss used in the present invention has large holes, and the inner beams of the main part of the bracket are thickened. In terms of the appearance of the prosthesis structure, a truss prosthesis is generated according to the grayscale value - elastic modulus - hole density and beam diameter algorithm; the truss has large holes, and by increasing the diameter of the main beam, it can better ensure that the elastic modulus is reduced to close to that of the bone while meeting the mechanical properties.

Claims

1. A method for designing a self-adaptive bionic cancellous bone defect prosthesis, wherein the self-adaptive bionic cancellous bone defect prosthesis comprises a biointerface gradient microporous structure portion (1) and a main bionic truss support structure portion (2), wherein the biointerface gradient microporous structure portion (1) is arranged at both ends of the main bionic truss support structure portion (2); and is characterized in that: The bone defect prosthesis is a 3D printing integrated molding design, which includes the following steps: Step 1: Construct a three-dimensional anatomical model of the bone defect area based on the patient's CT data; Step 2: Mirror the contralateral side and extract the spatial coordinate points of the model on the healthy side and their corresponding CT grayscale value distribution matrix; Step 3: Based on the grayscale value-bone density-elastic modulus mapping relationship model, a gradient parameter matching algorithm is used to dynamically adjust the geometric parameters of the truss unit, including spatial density distribution, beam diameter gradient change, and porosity distribution. An optimization iterative algorithm is then used to generate a mechanically conductive adaptive truss structure that matches the host bone elastic modulus distribution. Step 4: Set interface gradient micropores according to the change of interface grayscale value, integrate the optimized truss structure with the interface gradient micropore structure, and output the final prosthesis model; The step 1 comprises the following steps: (1) Collect CT data of patients with bone defects and import the CT data into medical 3D reconstruction software in Dicom format. (2) Reconstruct the 3D bone model in medical 3D reconstruction software, divide the defect area, and export its STL model; (3) Import the segmented defect STL model into 3D modeling software to design the 3D structure of the prosthesis; (4) The three-dimensional structure of the prosthesis is divided into the main body and the bone interface connection part. The main body is prepared for the subsequent truss structure design, and the bone interface connection part is prepared for the subsequent microporous structure design; The step 2 comprises the following steps: (1) Divide the exported main body into body units and import the body unit structure into Mimics software; (2) Using the mirror tool, mirror the unit structure to the healthy side and fit it to match the contralateral bone structure; (3) Assign parameters to the volume unit according to the CT grayscale value and export the assigned point cloud data; (4) Import the assigned volume unit information into the post-processing software to extract the three-dimensional coordinates of the corresponding spatial coordinate points and the corresponding grayscale value information; The step three comprises the following steps: (1) Based on the existing grayscale value-bone density-bone elastic modulus assignment formula, a mapping relationship model is established, and the appropriate assignment formula is selected according to the different elastic moduli of the bone site where the bone defect is located; (2) Based on the corresponding formula of the spatial density distribution, beam diameter gradient change and porosity change of the existing truss structure and the elastic modulus of the titanium alloy truss structure, a grayscale value-bone density-bone elastic modulus-titanium alloy elastic modulus matching response is established; (3) Import the spatial coordinate points and their grayscale value data of the volume unit into the computational design software, and establish the connection between the spatial coordinate points and their grayscale value data of the volume unit and the truss design; (4) Using computer language to automatically generate the main truss structure based on grayscale value changes; The step 4 comprises the following steps: (1) Import the bone interface connection part into the prosthesis design software and match it with the main truss part; (2) Extract the spatial coordinate points and grayscale values of the prosthesis-bone connection interface. Based on steps 2 and 3, set a gradient microporous structure based on grayscale value response to achieve the change of microporous structure parameters with grayscale value. (3) In the prosthesis design software, the microporous part connecting the bone interface and the truss part are integrated together using the Boolean addition operation to complete the design of the prosthesis shape; (4) Screw channels and auxiliary bone plates are set according to the fixation requirements of prostheses in different positions. Among them, pelvic prostheses need to add sacral dorsal bionic axis joint fixation, long bone shaft prostheses need to add bilateral bone plates and reserve intramedullary nail channels, and the proximal / distal ends of long bones need to add bone plates and reserve prosthesis stem channels.

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