Bone fixing plate with double effects of promoting osteogenesis and gradient degradation

Abstract

The utility model relates to the technical field of bone fixing plates, and particularly discloses a bone fixing plate with double effects of promoting osteogenesis and gradient degradation. The bone fixing plate comprises a first high polymer material layer, a first biodegradable magnesium alloy layer, a second high polymer material layer, a biodegradable zinc alloy layer, a third high polymer material layer, a second biodegradable magnesium alloy layer and a fourth high polymer material layer which are sequentially stacked. The bone fixing plate with the double effects of promoting osteogenesis and gradient degradation, provided by the utility model, has remarkable advantages in mechanical property, degradation effect and osteogenesis promoting effect.

Description

Technical Field

[0001] This utility model relates to the field of bone fixation plate technology, and in particular to a bone fixation plate with dual effects of promoting bone growth and gradient degradation. Background Technology

[0002] Bone fixation plates play a crucial role in fracture treatment and bone grafting, but current technologies have several shortcomings that limit their clinical application. First, many traditional fixation plate materials lack biocompatibility, easily triggering inflammation or rejection reactions, thus affecting bone healing. Second, the mechanical properties of traditional fixation plate materials are insufficient to withstand large loads, potentially leading to insecure fixation and consequently affecting treatment outcomes. Furthermore, the degradation rate of existing fixation plates often does not match the rate of bone healing, resulting in implant residue, necessitating secondary surgery, and increasing patient suffering and financial burden.

[0003] Currently, clinically approved biodegradable orthopedic implants are mainly polylactic acid (PLA), polylactic acid-glycolic acid copolymer (PLGA), and PLA / phosphate composites. Their mechanical properties do not meet practical application requirements. Furthermore, these materials create a low-pH, acidic microenvironment around the implant in the fracture area, easily inducing secondary fractures and local inflammation, severely affecting osteoblast bioactivity. In addition, due to the mismatch between the hydrophobicity and low degradation rate of these materials and the rate of new bone formation during the healing process, they may take more than three years to completely disappear. Meanwhile, the application potential of biodegradable magnesium alloys and zinc alloys as orthopedic implants has attracted widespread attention and exploration from colleagues worldwide. Biodegradable magnesium and zinc alloys have many advantages, such as high tensile strength (200–400 MPa) and stiffness, meeting mechanical strength requirements and load-bearing applications. Moreover, as essential elements of the human body, they possess excellent biocompatibility. Furthermore, Mg... 2+ Magnesium-based orthopedic devices, by stimulating osteoblasts and chondrocytes to promote bone formation, hold great potential in the field of bone fixation plate technology. However, magnesium-based orthopedic devices corrode too quickly, easily losing structural integrity in the early stages, resulting in insufficient mechanical support. Zinc-based orthopedic devices, on the other hand, corrode too slowly and have a relatively high density. Therefore, further improvements are needed before they can be applied in large-scale clinical trials.

[0004] To address the above shortcomings, it is of great significance to provide a novel bone fixation device with excellent comprehensive performance. Utility Model Content

[0005] In view of this, the present invention provides a bone fixation plate with dual effects of promoting bone growth and gradient degradation, aiming to overcome the shortcomings of the prior art, improve the bone fixation effect, and meet clinical needs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A bone fixation plate with dual effects of promoting bone growth and gradient degradation, the bone fixation plate comprising a first polymer material layer, a first biodegradable magnesium alloy layer, a second polymer material layer, a biodegradable zinc alloy layer, a third polymer material layer, a second biodegradable magnesium alloy layer, and a fourth polymer material layer stacked sequentially.

[0008] Preferably, the first polymer material layer 1, the second polymer material layer 3, the third polymer material layer 5, and the fourth polymer material layer 7 are independently polylactic acid, polycaprolactone, magnesium-doped polylactic acid, or magnesium-doped polycaprolactone.

[0009] Preferably, the layers of the bone fixation plate form a mechanically interlocking structure.

[0010] Preferably, the total thickness of the bone fixation plate is 2.5 mm, and the thickness ratio of the first polymer material layer, the first biodegradable magnesium alloy layer, the second polymer material layer, the biodegradable zinc alloy layer, the third polymer material layer, the second biodegradable magnesium alloy layer, and the fourth polymer material layer is 0.3:0.4:0.15:0.8:0.15:0.4:0.3.

[0011] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0012] This invention provides a bone fixation plate with dual effects of promoting bone growth and gradient degradation. The bone fixation plate comprises a first polymer material layer, a first biodegradable magnesium alloy layer, a second polymer material layer, a biodegradable zinc alloy layer, a third polymer material layer, a second biodegradable magnesium alloy layer, and a fourth polymer material layer, stacked sequentially. The biodegradable zinc alloy layer, serving as the middle layer of the bone fixation plate, possesses high strength, excellent mechanical properties, and a long degradation cycle, effectively supporting and fixing the bone. The first and second biodegradable magnesium alloy layers have good mechanical properties and suitable degradation cycles, providing effective support and fixation of the bone within a short period. The polylactic acid and polycaprolactone used in the first and fourth polymer material layers are FDA-approved and biosafety compliant. The incorporation of a certain amount of magnesium microparticles into the first and fourth polymer material layers contributes to the bone-promoting effect. The second and third polymer material layers effectively bind the various alloy layers. The bone fixation plate provided by this invention has significant advantages in mechanical properties, degradation effect, and bone-promoting effect. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the bone fixation plate of the present invention, which has the dual effects of promoting bone growth and gradient degradation.

[0015] Figure 2 for Figure 1 Enlarged diagram of A in the middle; Figure 2 In the diagram, 1 is the first polymer material layer, 2 is the first biodegradable magnesium alloy layer, 3 is the second polymer material layer, 4 is the biodegradable zinc alloy layer, 5 is the third polymer material layer, 6 is the second biodegradable magnesium alloy layer, and 7 is the fourth polymer material layer.

[0016] Figure 3 This is a schematic diagram of the bone fixation plate of the present invention, which has the dual effects of promoting bone growth and gradient degradation. Figure 3 In the diagram, 1 is the first polymer material layer, 2 is the first biodegradable magnesium alloy layer, 3 is the second polymer material layer, 4 is the biodegradable zinc alloy layer, 5 is the third polymer material layer, 6 is the second biodegradable magnesium alloy layer, and 7 is the fourth polymer material layer.

[0017] Figure 4 This is a schematic diagram of the bending strength of the bone fixation plate with the dual effects of promoting bone growth and gradient degradation in Example 1 (stain—strain, stress—stress);

[0018] Figure 5 This is a schematic diagram of cell activity of the bone fixation plate with dual effects of promoting bone growth and gradient degradation in Example 1 (Merge - mixture). Detailed Implementation

[0019] The technical solutions in the embodiments of this utility model will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0020] As a preferred embodiment of this utility model, such as Figure 1 , Figure 2As shown, this utility model provides a bone fixation plate with dual effects of promoting bone growth and gradient degradation, comprising a first polymer material layer 1, a first biodegradable magnesium alloy layer 2, a second polymer material layer 3, a biodegradable zinc alloy layer 4, a third polymer material layer 5, a second biodegradable magnesium alloy layer 6, and a fourth polymer material layer 7 stacked sequentially.

[0021] As a preferred embodiment of this utility model, the biodegradable zinc alloy layer 4 was purchased from Suzhou Jingjun New Materials Co., Ltd.; the biodegradable zinc alloy layer 4, as the middle layer of the bone fixation plate, has high strength, excellent mechanical properties, and a long degradation cycle, and can effectively support and fix the bone.

[0022] As a preferred embodiment of this utility model, the first biodegradable magnesium alloy layer 2 and the second biodegradable magnesium alloy layer 6 were purchased from Suzhou Jingjun New Materials Co., Ltd.; the first biodegradable magnesium alloy layer 2 and the second biodegradable magnesium alloy layer 6 have good mechanical properties, a suitable degradation cycle, and can support and fix the bones within an effective time.

[0023] In this invention, the first polymer material layer 1, the second polymer material layer 3, the third polymer material layer 5, and the fourth polymer material layer 7 are independently polylactic acid, polycaprolactone, magnesium-doped polylactic acid, or magnesium-doped polycaprolactone.

[0024] In this invention, the mass fraction of magnesium in magnesium-doped polylactic acid is preferably 1-5%, more preferably 2-4%, and even more preferably 3%; the mass fraction of magnesium in magnesium-doped polycaprolactone is preferably 1-5%, more preferably 2-4%, and even more preferably 3%; incorporating a certain amount of magnesium particles into the first and fourth polymer layers has a bone-promoting effect; and when the mass fraction of magnesium is within the above range, the magnesium particles can be uniformly dispersed in the polymer matrix; for magnesium-doped polylactic acid and magnesium-doped polycaprolactone, a magnesium mass fraction of 3% has the best bone-promoting effect, while also possessing good biocompatibility, meeting the requirements of implantable medical devices.

[0025] In a preferred embodiment of this invention, polylactic acid (PLA) was purchased from Nature Works, USA, model number 3051D, with a number-average molecular weight of 80,000; polycaprolactone (PCT) was purchased from Solvay, USA, with a number-average molecular weight of 80,000. Both PLA and PCT are FDA certified and have biocompatibility. The magnesium in the magnesium-doped PLA and PCT is spherical magnesium powder with a D50 of 26.8 μm, purchased from Tangshan Weihua Magnesium Powder Co., Ltd. The magnesium-doped PLA and PCT are prepared using conventional techniques in the art.

[0026] In a preferred embodiment of this invention, before preparing the bone fixation plate, the first biodegradable magnesium alloy layer 2, the biodegradable zinc alloy layer 4, and the second biodegradable magnesium alloy layer 6 are independently surface-treated. The purpose of the surface treatment is to enhance the interfacial bonding between the layers and to provide functional ions or active groups. Different surface treatment processes can be adopted for different layers to achieve ion gradient release effect and gradient controllable degradation effect. The surface treatment methods include micro-arc oxidation or chemical modification. The reagents used in the chemical modification method include hydrofluoric acid, dopamine, or γ-aminopropyltriethoxysilane. The surface treatment is completed using conventional techniques in the art.

[0027] In a preferred embodiment of this invention, the layers of the bone fixation plate form a mechanically interlocking structure. Specifically, the first biodegradable magnesium alloy layer 2, the biodegradable zinc alloy layer 4, and the second biodegradable magnesium alloy layer 6 are drilled. The shape and size of the drill holes are conventionally selected by those skilled in the art based on specific performance requirements. During the drilling process, computer-aided design (CAD) and finite element analysis (FEA) techniques are combined to achieve a balance between optimal mechanical properties and biocompatibility. The purpose of the drilling is to form a mechanically interlocking structure between the layers, thereby improving the bonding strength between the layers and facilitating the positioning and fixation of screws during surgery, thus improving the stability and durability of the implant.

[0028] As a preferred embodiment of this utility model, such as Figure 3 As shown, the first biodegradable magnesium alloy layer 2, the biodegradable zinc alloy layer 4, and the second biodegradable magnesium alloy layer 6 are drilled, and multiple circular through holes are uniformly distributed on the first biodegradable magnesium alloy layer 2, the biodegradable zinc alloy layer 4, and the second biodegradable magnesium alloy layer 6.

[0029] In a preferred embodiment of this utility model, the first biodegradable magnesium alloy layer 2, the biodegradable zinc alloy layer 4, and the second biodegradable magnesium alloy layer 6 are drilled, and then the layers are stacked and hot-pressed to obtain a bone fixation plate. The hot-pressing is carried out using conventional techniques in the art. After drilling, the surface of the alloy layer has circular holes. The two polymer materials located above and below the alloy layer melt during the hot-pressing process, penetrate into the holes of the alloy, and solidify to form protrusions. These protrusions are then bonded together through the pores of the alloy layer to form a single unit, thus "locking" the alloy plate and achieving mechanical locking.

[0030] In a preferred embodiment of this utility model, the total thickness of the bone fixation plate is 2.5 mm, and the thickness ratio of the first polymer material layer, the first biodegradable magnesium alloy layer, the second polymer material layer, the biodegradable zinc alloy layer, the third polymer material layer, the second biodegradable magnesium alloy layer, and the fourth polymer material layer is preferably 0.3:0.4:0.15:0.8:0.15:0.4:0.3.

[0031] Example 1

[0032] A laser engraving machine was used to engrave magnesium alloy plates and zinc alloy plates respectively, resulting in two 60*12*0.4mm (length*width*height) magnesium alloy plates (the first biodegradable magnesium alloy layer 2 and the second biodegradable magnesium alloy layer 6, respectively) and one 60*12*0.8mm (length*width*height) zinc alloy plate (i.e., biodegradable zinc alloy layer 4). Each of the three plates independently contains five equally spaced parallel circular through holes with a radius of 1.5mm.

[0033] 35 mL of polylactic acid (PLA) solution (containing magnesium, PLA, and dichloromethane, with a total mass concentration of PLA and magnesium of 0.125 g / mL and a mass ratio of PLA and magnesium to magnesium of 100:3) was poured into a 180 mm × 130 mm tray and placed in a fume hood for evaporation for 24 h to obtain a magnesium-doped PLA film with a thickness of 0.15 mm. This film was then cut into two sheets of 60 * 12 mm (length * width) and placed in a 50 °C oven for 6 h to dry completely (i.e., the second polymer layer 3 and the third polymer layer 5). With other conditions unchanged, the volume of PLA solution was changed to 70 mL to obtain a magnesium-doped PLA film with a thickness of 0.3 mm. After processing, the first polymer layer 1 and the fourth polymer layer 7 were obtained.

[0034] Following the order of first polymer material layer 1, first biodegradable magnesium alloy layer 2, second polymer material layer 3, biodegradable zinc alloy layer 4, third polymer material layer 5, second biodegradable magnesium alloy layer 6, and fourth polymer material layer 7, the layers are stacked in an orderly manner, wrapped with aluminum foil sprayed with dry release agent, and the sample is placed in a mold. Under the conditions of 175℃ and 5MPa, it is hot-pressed for 15 minutes to obtain a bone fixation plate with the dual effects of promoting bone growth and gradient degradation, measuring 60mm*12mm*2.5mm (length*width*height).

[0035] The flexural strength of the bone fixation plate with dual effects of promoting bone growth and gradient degradation, prepared in this embodiment, was tested using an electronic universal testing machine manufactured by Xin Sansi Experimental Equipment Co., Ltd. Referring to the GB / T3356-1999 testing standard, the loading rate was set to 2 mm / min, and the fracture point was defined as the load value being less than 50% of the previous value. A schematic diagram of the flexural strength of the bone fixation plate with dual effects of promoting bone growth and gradient degradation in this embodiment is shown below. Figure 4 As shown. From Figure 4 As can be seen, compared with pure PLA sheet (bending strength 40-65MPa), the bone fixation plate prepared in this embodiment has a bending strength exceeding 200MPa.

[0036] Hank's solution was used in the in vitro degradation test. The bone fixation plate prepared in this embodiment, which exhibits both bone-promoting and gradient degradation effects, was used in the test. The bone fixation plate and Hank's solution were prepared at a ratio of at least 1g:30mL and placed in plastic test tubes for degradation. The degradation phases were divided into 1, 2, 4, 6, 8, and 10 weeks, and the degradation temperature was set at 37℃. After the degradation tests of 1, 2, 4, 6, 8, and 10 weeks were completed, the degraded samples were taken out, washed, and their flexural strength was tested and compared with that before degradation. The final test results showed that the flexural strength of the bone fixation plate prepared in this embodiment remained at approximately 80% of its initial value after 10 weeks of degradation.

[0037] The cytotoxicity of the bone fixation plate with dual effects of promoting bone growth and gradient degradation prepared in this embodiment was investigated by co-culturing MC3T3-E1 cells with the material extract. Double fluorescence staining of live and dead cells was performed using a combination of Calcein AM and PI, resulting in a schematic diagram of cell viability of the bone fixation plate with dual effects of promoting bone growth and gradient degradation in this embodiment. Figure 5 As shown. From Figure 5 As can be seen, the bone fixation plate prepared in this embodiment exhibits more significant cell proliferation and maintains higher cell activity compared to pure PLA.

[0038] The above description is merely a preferred embodiment of the present utility model and does not constitute any limitation on the technical scope of the present utility model. Therefore, any minor modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model shall still fall within the scope of the technical solution of the present utility model.

Claims

1. A bone fixation plate having a dual effect of promoting bone and gradient degradation, characterized in that, The bone fixation plate with the dual effects of promoting bone and gradient degradation comprises a first high polymer material layer, a first biodegradable magnesium alloy layer, a second high polymer material layer, a biodegradable zinc alloy layer, a third high polymer material layer, a second biodegradable magnesium alloy layer and a fourth high polymer material layer which are sequentially stacked.

2. The bone fixation plate with dual effects of promoting bone and gradient degradation of claim 1, wherein, The first high polymer material layer 1, the second high polymer material layer 3, the third high polymer material layer 5 and the fourth high polymer material layer 7 are independently polylactic acid, polycaprolactone, magnesium-doped polylactic acid or magnesium-doped polycaprolactone.

3. A bone fixation plate with dual effects of promoting bone and gradient degradation according to claim 1 or 2, characterized in that, The layers in the bone fixation plate form a mechanical interlocking structure.

4. The bone fixation plate with dual effects of promoting bone and gradient degradation of claim 3, wherein, The total thickness of the bone fixation plate is 2.5 mm, and the thickness ratio of the first high polymer material layer, the first biodegradable magnesium alloy layer, the second high polymer material layer, the biodegradable zinc alloy layer, the third high polymer material layer, the second biodegradable magnesium alloy layer and the fourth high polymer material layer is 0.3:0.4:0.15:0.8:0.15:0.4:0.3.

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