A bionic lantern frame composite internal fixation device and a preparation method thereof

Abstract

The application discloses a kind of bionic lantern frame composite internal fixation device and preparation method, it is related to the technical field of orthopedic medical instruments, including implant and multi-bar bridging structure, multi-bar bridging structure is made of multiple longitudinal connecting rods and horizontal locking nail, implant is made of multiple multilevel bionic structures, multilevel bionic structure includes two symmetrically arranged hexagonal upper and lower layer structures and intermediate spiral layer structure arranged between two hexagonal upper and lower layer structures.The application is inspired from macro-micro structure of honeycomb and spent horn, the multilevel bionic structure prepared by coupling bionic technology has excellent mechanical properties, strong shock absorption capacity, can effectively match the mechanical properties of natural bone, can effectively avoid secondary damage and "stress shielding" effect after implantation of patients, and the composite coating introduced by electrochemical deposition method makes up for the problems of insufficient biocompatibility, insufficient antibacterial property and weak osteogenic differentiation ability of single implant structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of orthopedic medical devices, in particular to a bionic lantern frame composite internal fixation device and a preparation method thereof. BACKGROUND

[0002] With the progress of society and the development of science and technology, life and health are increasingly valued. However, the number of cases of bone trauma and bone defect caused by factors such as traffic accidents and diseases continues to rise, especially the demand for high-performance bone implant materials and mechanical stability for long bone segmental bone defects is increasingly urgent.

[0003] In terms of bone implant materials, currently commonly used hard tissue implants (such as densified coated titanium alloy, porous titanium alloy, etc.) are widely used in the fields of orthopedics, dentistry, etc., but they are difficult to simultaneously have excellent biocompatibility, mechanical properties (especially elastic modulus) matching human bone tissue, and strong bone integration ability, which can easily cause the "stress shielding" effect, leading to inflammation and degradation of bone tissue around the implant. Natural bone tissue is a kind of biological composite material with exquisite multi-level structure, which is a composite structure of cancellous bone (porous) and cortical bone (dense) on a macroscopic scale, and has a periodic arrangement of collagen fibers and deposition of hydroxyapatite (HA) nanocrystals on a microscopic scale. Most of the existing implant structures are relatively simple, and are mostly single-scale surface modification (such as micron-level sandblasting and acid etching or deposition of nanoscale tubular structures), which cannot effectively simulate the multi-level complexity of bone tissue. Macroscopic body structures are mostly solid or simple and uniform pore structures (such as some porous titanium), which are not conducive to cell ingrowth, vascularization and nutrient transport. Therefore, there is a lack of an implant material in the prior art that can balance mechanical properties, biocompatibility, bone integration ability, and adapt to individualized bone defect morphology for precise customization to meet the growing demand for diversified and high-performance bone repair materials in clinical practice.

[0004] In terms of internal fixation devices, the current clinical commonly used internal fixation methods include intramedullary nails, steel plates and external fixation frames, but their application scenarios and biomechanical properties have deficiencies: intramedullary nails need to penetrate bone graft materials, thereby affecting their biological properties; steel plate fixation needs to be attached to the surface of bone graft materials, interfering with their biological properties, and the mechanical support for long segmental defects is insufficient; external fixation frames can avoid direct contact of the implant with the bone graft material, but have problems such as poor stability, low patient comfort, high risk of needle tract infection, etc.

[0005] Therefore, a bionic "lantern" frame composite internal fixation device combining a medical implant multi-level bionic structure with a bridging internal fixation system is proposed to solve the above problems. SUMMARY

[0006] To achieve the above object, the present application provides the following technical scheme: a bionic lantern frame composite internal fixation device, comprising an implant and a multi-rod bridging structure, the multi-rod bridging structure is composed of a plurality of longitudinal connecting rods and transverse locking nails, the implant is composed of a plurality of multi-level bionic structures, the multi-level bionic structure comprises two symmetrically arranged hexagonal upper and lower layer structures and a middle spiral layer structure arranged between the two hexagonal upper and lower layer structures, wherein the hexagonal upper and lower layer structures comprise an equilateral hexagonal frame and a wavy line structure, a plurality of wavy line structures are symmetrically arranged inside the equilateral hexagonal frame, the middle spiral layer structure is composed of a plurality of middle spiral layer unit structures arranged in a circumferential array, a support cylinder is arranged between the center positions of the two hexagonal upper and lower layer structures, both ends of the support cylinder are connected with the wavy line structures of the two hexagonal upper and lower layer structures through ribs respectively, both ends of the middle spiral layer unit structure are connected with both ends of the support cylinder respectively, and a plurality of middle layer concave support structures arranged in a circumferential array are further arranged between the two equilateral hexagonal frames, both ends of the middle layer concave support structure are connected with the two equilateral hexagonal frames respectively.

[0007] As a preferred, the wavy line structure is designed according to the following equation:

[0008] ;

[0009] Wherein, is the abscissa of the curve, is the ordinate of the curve, is the amplitude, is the angular velocity, is the phase, is the offset.

[0010] As a preferred, the middle spiral layer unit structure is designed according to the following equation:

[0011] ;

[0012] ;

[0013] Wherein, is the radius, is the coefficient, is the change angle, is the major diameter, is the minor diameter, is the degree of rotation; the equation is converted into Cartesian coordinate system as follows:

[0014] ;

[0015] ;

[0016] .

[0017] Preferably, the intermediate helical layer structure is composed of six intermediate helical layer unit structures.

[0018] Preferably, the edge length of the equilateral hexagonal frame is 1 cm, and the height is 0.2 cm; the radius of the supporting cylinder is 0.2 cm, and the rib width is 0.1 cm.

[0019] Preferably, the inner recessed support structure in the intermediate layer is designed according to the following equation:

[0020]

[0021]

[0022] wherein, is a parameter ranging from [0, 1], , is the starting point coordinate of the curve, , is the midpoint coordinate of the curve, , is the end point coordinate of the curve.

[0023] The application also provides a preparation method of the bionic lantern frame composite internal fixation device, for preparing the implant as described above, comprising the following steps:

[0024] Step 1: based on the principle of sine function and Archimedes spiral line, the modeling of multi-level bionic structure is carried out, and the model of the implant is obtained after the multi-level bionic structure is closely arrayed;

[0025] Step 2: based on the laser powder bed fusion metal additive manufacturing technology, the implant skeleton is prepared;

[0026] Step 3: the implant skeleton obtained in step 2 is immersed in a polydopamine solution, and is subjected to magnetic stirring at a temperature of 25-30℃ for 12 h, and then is taken out, washed with deionized water, and dried for standby;

[0027] Step 4: the implant treated in step 3 is immersed in an electrolyte, a platinum sheet electrode is used as a counter electrode, and electrochemical deposition is carried out under magnetic stirring to obtain a gradient coating.

[0028] ​​As preferred, in step 2, the model obtained in step 1 is saved in stl. format, imported into MaterialiseMagics software for slicing processing, and then copied into an L-PBF printing device, and TC4 spherical powder with a particle size of 15-53 μm is used for printing, and the printing parameters are as follows: laser power is 175 W, scanning speed is 1200 mm / s, scanning interval is 0.08 mm, layer thickness is 0.03 mm, scanning strategy is strip scanning, and scanning angle is 67°.

[0029] As preferred, the polydopamine solution in step 3 is prepared by dissolving dopamine hydrochloride powder in a Tris buffer solution which is previously configured and adjusted to a pH of 8.5, and the concentration of the polydopamine solution is 2 mg / ml.

[0030] As preferred, step 4 is specifically as follows:

[0031] First, the implant treated in step 3 is immersed in an electrolyte, a platinum electrode is used as a counter electrode, and electrodeposition is carried out at a magnetic stirring speed of 10 rpm for 30 min to obtain a first layer of hydroxyapatite coating, then 0.5wt% of chitosan is added to the electrolyte to continue electrodeposition for 45 min, the stirring speed is increased to 15 rpm, and then 0.03mol / L of SrCl2 is added to the electrolyte to continue electrodeposition for 60 min, so that Sr 2+ The implant is immersed in the coating to improve the antibacterial performance, and finally the implant is taken out and immediately immersed in deionized water for ultrasonic cleaning, and after cleaning, it is placed in a drying box for 24 h at a temperature of 60℃ to obtain a gradient coating.

[0032] The present application has the following beneficial effects:

[0033] The implant of the present application is different from the traditional single dense or porous titanium alloy implant, and is inspired by the macro-micro structure of honeycomb and cow horn, and has excellent mechanical properties and strong shock absorption capacity by using the multi-level biomimetic structure prepared by coupling biomimetic technology. In addition, the bone tissue is a composite structure of cancellous bone (porous) and cortical bone (dense), the upper and lower layer structure of the hexagonal structure in the multi-level biomimetic structure simulates cancellous bone, and the middle spiral layer unit structure simulates cortical bone, which can effectively match the mechanical properties of natural bone, and can effectively avoid secondary damage and "stress shielding" effect after implantation of patients.

[0034] The present application introduces a gradient nano-hydroxyapatite (HA), Sr 2+ , chitosan (CTS) composite coating in the multi-level biomimetic structure by electrochemical deposition, which makes up for the problems of insufficient biocompatibility, insufficient antibacterial property and weak osteogenic differentiation ability of single implant structure, so that the prepared multi-level biomimetic structure is more suitable for implant applications.

[0035] The application combines additive manufacturing technology with electrochemical deposition method, and coats polydopamine (PDA) material on the surface of the structure, so that the interface bonding force of the coating can be effectively enhanced, and the corrosion resistance of the multilevel biomimetic structure is improved, and the additive manufacturing technology gives the bone implant the ability of free shape rapid prototyping.

[0036] The multi-rod bridging structure of the application provides three-dimensional stability, and the design core is the 'lantern type' multi-rod support distribution of the fixed rod (i.e. the longitudinal connecting rod) in space, which spans the middle bone graft area, and the locking screw (i.e. the transverse locking nail) passes through the healthy bone tissue to stably anchor the mechanical support structure to both ends of the bone defect. The device provides a stable mechanical environment without interfering with the biological microenvironment of the bone graft area. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is a microstructure electron microscope graph of the horn of cattle consumed in the application;

[0038] Figure 2 It is a multilevel biomimetic structure design flowchart in the application;

[0039] Figure 3 It is a multilevel biomimetic structure schematic diagram in the application;

[0040] Figure 4 It is a schematic diagram of the electrodeposition coating in the application;

[0041] Figure 5 It is an implant filling schematic diagram in the application;

[0042] Figure 6 It is a whole device schematic diagram in the application.

[0043] In the figure: 3, equilateral hexagonal frame; 31, wavy line structure; 4, intermediate spiral layer unit structure; 5, intermediate spiral layer structure; 6, multilevel biomimetic structure; 61, intermediate layer inner concave support structure; 7, polydopamine solution; 8, platinum electrode; 9, electrolyte; 10, implant; 11, multi-rod bridging structure. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0045] The application will be further described in detail below according to the drawings and embodiments.

[0046] Embodiments of the application:

[0047] As shown in Figure 2 , Figure 3 , Figure 5 and Figure 6 , a bionic lantern frame composite internal fixation device comprises an implant 10 and a multi-bar bridging structure 11, the multi-bar bridging structure 11 is composed of a plurality of longitudinal connecting rods and transverse locking nails, the implant 10 is composed of a plurality of tightly arrayed multi-level bionic structures 6, the multi-level bionic structure 6 comprises two symmetrically arranged hexagonal upper and lower layer structures and a middle spiral layer structure 5 arranged between the two hexagonal upper and lower layer structures, wherein the hexagonal upper and lower layer structure comprises an equilateral hexagonal frame 3 and a wavy line structure 31, a plurality of wavy line structures 31 are symmetrically arranged inside the equilateral hexagonal frame 3, the middle spiral layer structure 5 is composed of six circumferentially arrayed middle spiral layer unit structures 4, in order to provide good support for the middle spiral layer structure 5, a support cylinder is arranged between the center positions of the two hexagonal upper and lower layer structures, the two ends of the support cylinder are connected with the wavy line structures 31 of the two hexagonal upper and lower layer structures through ribs respectively, the two ends of the middle spiral layer unit structure 4 are connected with the two ends of the support cylinder respectively, a plurality of circumferentially arrayed middle layer concave support structures 61 are arranged between the two equilateral hexagonal frames 3, the two ends of the middle layer concave support structure 61 are connected with the two equilateral hexagonal frames 3 respectively. The side length a of the equilateral hexagonal frame 3 is 1 cm, and the height is 0.2 cm; the radius b of the support cylinder is 0.2 cm, and the rib width c is 0.1 cm.

[0048] The specific design method of the hexagonal upper and lower layer structure is as follows: first, an equilateral hexagonal frame 3 is established according to the principle of honeycomb structure, then a bionic structure is extracted based on the characteristics of the cross section of the horn of a cow (i.e. the transverse cross section in Figure 1 , which is simplified to a sine curve due to its typical wavy line feature, thereby obtaining the wavy line structure 31, the wavy line structure 31 is designed according to the following equation:

[0049] ;

[0050] Wherein, is the horizontal coordinate of the curve, is the vertical coordinate of the curve, is the amplitude, is the angular velocity, is the phase, is the offset.

[0051] Based on the characteristics of the longitudinal cross section of the horn of a cow (i.e. the longitudinal cross section in Figure 1 ), it presents the characteristics of high spiral torsion, therefore, the typical Archimedes spiral equation is used to extract this feature, the middle spiral layer unit structure 4 is designed according to the following equation:

[0052] ;

[0053] ;

[0054] wherein, is the radius, is the coefficient, is the angle of change, is the major diameter, is the minor diameter, is the degree of rotation; for the purpose of facilitating the establishment of a three-dimensional model, the above equation is converted into a Cartesian coordinate equation as follows:

[0055] ;

[0056] ;

[0057] ;

[0058] By adjusting the values of and , the controllability of the intermediate spiral layer unit structure 4 can be achieved, and the parametric design of the implant 10 is also achieved.

[0059] In order to make the intermediate layer concave support structure 61 have good support stability, an excessively relatively smooth Bezier curve is used for design, and the intermediate layer concave support structure 61 is designed according to the following equation:

[0060] ;

[0061] ;

[0062] wherein, is a parameter ranging from [0, 1], , is the starting point coordinate of the curve, , is the midpoint coordinate of the curve, , is the terminal point coordinate of the curve.

[0063] Inspired by the macro-micro structure of honeycomb and cow horn, the embodiment also provides a preparation method of a bionic lantern frame composite internal fixation device, which is used for preparing the implant 10 as described above, and the reference Figures 2 to 6 includes the following steps:

[0064] Step 1, based on the principle of sine function and Archimedes spiral line, the modeling of the multi-level bionic structure 6 is carried out, and the model of the implant 10 is obtained after the multi-level bionic structure 6 is closely arrayed;

[0065] Step 2, the implant 10 skeleton is prepared by using a suitable printing strategy based on the laser powder bed fusion (L-PBF) metal additive manufacturing technology, the model obtained in step 1 is saved in stl. format, imported into Materialise Magics software for slicing processing, and then copied into the L-PBF printing equipment, and TC4 spherical powder with a particle size of 15-53 μm is used for printing, and the printing parameters are as follows: laser power is 175 W, scanning speed is 1200 mm / s, scanning interval is 0.08 mm, layer thickness is 0.03 mm, scanning strategy is strip scanning, and scanning angle is 67°;

[0066] Step 3, the implant 10 skeleton obtained in step 2 is immersed in a polydopamine solution 7, and is magnetically stirred at a temperature of 25-30 °C for 12 h, then is washed with a large amount of deionized water after being taken out, and is dried for standby use; the polydopamine solution 7 is prepared by dissolving dopamine hydrochloride powder in a Tris buffer solution which is previously configured and adjusted to a pH of 8.5, and the concentration of the polydopamine solution 7 is 2 mg / ml; after the implant 10 is treated by polydopamine, the interface bonding force of the coating can be effectively improved, the adhesion of the coating is enhanced, and the corrosion resistance is improved;

[0067] Step 4, the implant 10 treated in step 3 is first immersed in an electrolyte 9, a platinum electrode 8 is used as a counter electrode, and electrodeposition is performed at a magnetic stirring speed of 10 rpm for 30 min to obtain a first layer of hydroxyapatite (HA) coating, then 0.5 wt% of chitosan is added to the electrolyte 9, and electrodeposition is continued for 45 min at a speed of 15 rpm, then 0.03 mol / L of SrCl2 is added to the electrolyte 9, and electrodeposition is continued for 60 min, so that Sr 2+ is immersed in the coating, the antibacterial performance is improved, finally the implant 10 is taken out and immediately immersed in deionized water for ultrasonic cleaning, after cleaning, is placed in a drying box and is kept at a temperature of 60 °C for 24 h to obtain a gradient coating, and the biocompatibility is significantly improved; the electrolyte 9 used in step 4 includes deionized water, 0.1 mol / L of Ca(NO3)2·4H2O, 0.06 mol / L of NH4H2PO4, and 0.1 mol / L of NaNO3.

[0068] When the present application is used, the designed implant 10 is implanted in the bone defect site to form the "wick" structure of the bionic "lantern" frame composite internal fixation device, and the bone cement is used to connect with the two ends of the bone defect. Then, the multi-bar bridging structure 11 is used to form a three-dimensional stereoscopic support system through a plurality of longitudinal connecting rods and transverse locking nails, to accurately cross the capsule wall of the infection focus in the body to realize "extracapsular fixation", and to realize the stable fixation of the two ends of the bone defect and the bone graft area without crossing the bone graft material, thereby effectively reducing the risk of infection. In addition, by adjusting the number of bridging rods (i.e. longitudinal connecting rods) (three rods / four rods), the compression stiffness (up to the level of double steel plates) and the torsional stiffness (close to single steel plate) are optimized; the stability of the implant 10 and the comfort of the patient are improved, and the frame structure of the bionic "lantern" frame composite internal fixation device is formed.

[0069] The implant 10 of the present application is different from the traditional single dense or porous titanium alloy implant. The present application is inspired by the macro-micro structure of honeycomb and cow horn, and the multi-level bionic structure 6 prepared by coupling bionic technology has excellent mechanical properties and strong shock absorption capacity. In addition, the bone tissue is a composite structure of cancellous bone (porous) and cortical bone (dense), the upper and lower layer structure of the hexagon in the multi-level bionic structure 6 simulates cancellous bone, and the middle spiral layer unit structure 4 simulates cortical bone, which can effectively match the mechanical properties of natural bone, and can effectively avoid secondary damage and "stress shielding" effect after implantation in patients.

[0070] The present application introduces a gradient nano-hydroxyapatite (HA), Sr 2+ , chitosan (CTS) composite coating in the multi-level bionic structure 6 by electrochemical deposition method, which makes up for the problems of insufficient biocompatibility, insufficient antibacterial property and weak osteogenic differentiation ability of single implant structure, so that the prepared multi-level bionic structure 6 is more suitable for implant application.

[0071] The present application combines additive manufacturing technology with electrochemical deposition method, and coats polydopamine (PDA) material on the structure surface, which can effectively enhance the interfacial bonding strength of the coating and improve the corrosion resistance of the multi-level bionic structure 6. At the same time, the additive manufacturing technology gives the bone implant the ability of free shape rapid prototyping.

[0072] The multi-bar bridging structure 11 of the present application provides three-dimensional stability, and the core of the design is the "lantern type" multi-bar support distribution of the fixed rod (i.e. longitudinal connecting rod) in space, which spans the middle bone graft area and is anchored to the two ends of the bone defect by the locking screw (i.e. transverse locking nail) passing through the healthy bone tissue. The device provides a stable mechanical environment without interfering with the biological microenvironment of the bone graft area.

[0073] In summary, the implant 10 and the multi-bar bridging structure 11 together form a bionic "lantern" frame composite internal fixation device. After implantation, the device provides a good biological and mechanical microenvironment for the bone defect area, and can effectively promote bone repair. The application breaks through the limitations of traditional fixation path and material, and provides a new type of minimally invasive, efficient and safe internal fixation solution for bone defects.

[0074] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely divergences of the principles and spirit of the application and that numerous modifications, changes, replacements, and variations can be made thereto by those skilled in the art without departing from the principles and spirit of the application, and the scope of the application is defined by the appended claims and their equivalents.

Claims

1. A bionic lantern frame composite internal fixation device, characterized in that, The implant (10) includes an implant body (10) and a multi-rod bridging structure (11). The multi-rod bridging structure (11) consists of multiple longitudinal connecting rods and transverse locking pins. The implant body (10) consists of multiple multi-level biomimetic structures (6). The multi-level biomimetic structure (6) includes two symmetrically arranged hexagonal upper and lower layer structures and an intermediate spiral layer structure (5) arranged between the two hexagonal upper and lower layer structures. The hexagonal upper and lower layer structures include an equilateral hexagonal frame (3) and a wavy line structure (31). Multiple wavy line structures (31) are symmetrically arranged inside the equilateral hexagonal frame (3). The intermediate spiral layer structure... (5) It consists of multiple intermediate spiral layer unit structures (4) arranged in a circular array. A supporting cylinder is set between the center positions of the two hexagonal upper and lower layer structures. Both ends of the supporting cylinder are connected to the wave line structure (31) of the two hexagonal upper and lower layer structures through ribs. The two ends of the intermediate spiral layer unit structure (4) are connected to the two ends of the supporting cylinder. Multiple intermediate concave support structures (61) arranged in a circular array are also set between the two equilateral hexagonal frames (3). The two ends of the intermediate concave support structures (61) are connected to the two equilateral hexagonal frames (3).

2. The bionic lantern frame composite internal fixation device according to claim 1, characterized in that, The wavy line structure (31) is designed according to the following equation: ； wherein is the abscissa of the curve, is the ordinate of the curve, is the amplitude, is the angular velocity, is the phase at, is the offset.

3. The bionic lantern frame composite internal fixation device according to claim 2, characterized in that, The intermediate spiral layer unit structure (4) is designed according to the following equation: ； ； in, For radius, For coefficients, To change the angle, For the large diameter, For a path, Let be the degree of rotation; the equation in Cartesian coordinates is: ； ； 。 4. The biomimetic lantern frame composite internal fixing device according to claim 3, characterized in that, The intermediate spiral layer structure (5) is composed of six intermediate spiral layer unit structures (4).

5. The biomimetic lantern frame composite internal fixing device according to claim 4, characterized in that, The side length of the equilateral hexagonal frame (3) is 1cm and the height is 0.2cm; the radius of the supporting cylinder is 0.2cm and the rib width is 0.1cm.

6. The biomimetic lantern frame composite internal fixing device according to claim 5, characterized in that, The concave support structure in the intermediate layer (61) is designed according to the following equation: ； ； in, The parameter is in the range [0,1]. , Let the coordinates be the starting point of the curve. , Let these be the coordinates of the midpoint of the curve. , These are the coordinates of the endpoint of the curve.

7. A method for preparing a biomimetic lantern frame composite internal fixing device, characterized in that, The preparation of the implant (10) as described in claim 6 comprises the following steps: Step 1: Model the multi-level biomimetic structure (6) based on the sine function and the Archimedes spiral principle. After the multi-level biomimetic structure (6) is arranged in a tight array, the model of the implant (10) is obtained. Step 2: Based on laser powder bed molten metal additive manufacturing technology, prepare the implant (10) skeleton; Step 3: Immerse the implant (10) skeleton obtained in step 2 into polydopamine solution (7), stir magnetically at 25-30°C for 12 hours, take it out, rinse with deionized water, and dry for later use. Step 4: Immerse the implant (10) processed in step 3 into the electrolyte (9), use a platinum sheet electrode (8) as the counter electrode, and perform electrochemical deposition under magnetic stirring to obtain a gradient coating.

8. The method for preparing a biomimetic lantern frame composite internal fixing device according to claim 7, characterized in that, In step 2, the model obtained in step 1 is saved as an STL file, imported into Materialise Magics software for slicing, and then copied into the L-PBF printing device. TC4 spherical powder with a particle size of 15–53 μm is used for printing. The printing parameters are: laser power of 175 W, scanning speed of 1200 mm / s, scanning interval of 0.08 mm, layer thickness of 0.03 mm, scanning strategy of strip scanning, and scanning angle of 67°.

9. The method for preparing a biomimetic lantern frame composite internal fixing device according to claim 8, characterized in that, The polydopamine solution (7) in step 3 is prepared by dissolving dopamine hydrochloride powder in a pre-prepared Tris buffer solution with pH adjusted to 8.5, and the concentration of polydopamine solution (7) is 2 mg / ml.

10. The method for preparing a biomimetic lantern frame composite internal fixing device according to claim 9, characterized in that, Step 4 specifically involves: The implant (10) treated in step 3 is first immersed in the electrolyte (9), using a platinum sheet electrode (8) as a counter electrode, and electrodeposition is carried out under magnetic stirring at 10 rpm for 30 min to obtain a first layer of hydroxyapatite coating, then 0.5 wt% of chitosan is added to the electrolyte (9) and electrodeposition is continued for 45 min, the stirring speed is increased to 15 rpm, then 0.03 mol / L of SrCl2 is added to the electrolyte (9) and electrodeposition is continued for 60 min, so that Sr 2+ The implant (10) is immersed in the coating, the antibacterial performance is improved, and finally the implant (10) is taken out and immediately immersed in deionized water for ultrasonic cleaning, after cleaning, it is placed in a drying box and kept at a temperature of 60°C for 24 h to obtain a gradient coating.

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