Bionic bone graft for filling long bone defect

Abstract

The application discloses an individual customized long bone defect filling biomimetic bone block, which has biological compatibility and is a topological optimization structure and comprises a support cylinder, a middle filling body and an inner filling body from outside to inside. The support cylinder is a dense cylindrical structure, has connecting parts for being connected with bone cortices at both ends of the support cylinder, and further has fusion parts at both ends of the inner wall of the support cylinder. The fusion parts are annular and are made of degradable material with a porous lattice structure, and the outer end surface of the fusion part is in contact with the end surface of the connected bone cortex. The middle filling body is arranged in the support cylinder and is filled between the two fusion parts and is made of degradable material. The inner filling body is filled in the middle filling body, and both ends of the inner filling body do not extend into the fusion part. The middle filling body and the inner filling body are stacked by a plurality of porous cell units. The dense non-degradable material and the loose porous degradable material are combined, the mechanical properties are optimized through the topological structure, the growth simulation is realized by using different lattice form characteristics, and the rapid osteogenesis is promoted.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, and in particular to a biomimetic bone graft for filling long bone defects using a custom-made method. Background Technology

[0002] In clinical practice, multiple fractures of the long bone shaft are a type of surgery with a very high difficulty in open reduction, and the usual approach is to only perform simple functional reduction. After reduction, the weight-bearing capacity of the limb will be significantly reduced.

[0003] With the rapid development of biomaterials and digital medical technology in recent years, biomimetic prostheses with porous structures have developed rapidly, bringing hope for the recovery of many patients. Existing long bone prostheses are usually custom-made. Based on the CT data of the patient's bilateral long bones, the bone model of the patient's healthy side is mirrored onto the affected side. Through registration, cutting, and trimming commands, the shape of the affected side before the disease is restored one-to-one. Finally, the final replacement prosthesis for the affected area is formed through porous editing.

[0004] Existing technologies offer various bone-filling prostheses, typically composed of a homogeneous porous structure and made of a single material, broadly categorized as metallic magnesium-titanium alloys or biodegradable materials such as polylactic acid (PLLA) or caprolactam monomer (MC). Metallic prostheses, due to their homogeneous porous structure, have a linear contact with the bone. For example, a bone-filling block disclosed in Chinese Utility Model Patent ZL202021832757.4 exhibits high specific pressure at the junction, leading to bone surface subsidence, non-union of the prosthesis and bone, and ultimately surgical failure. While biodegradable materials have a high degree of bone integration, their current manufacturing processes result in poor structural performance, making them unable to withstand significant stress. They fail to meet the strength, stiffness, and elastic modulus requirements of bone defects and negatively impact bone ingrowth and long-term osseointegration within the implant.

[0005] Therefore, a prosthesis is needed that has both good mechanical properties and strong compatibility with bone tuberculosis. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a biomimetic bone graft for filling long bone defects by combining dense non-degradable materials with loose and porous degradable materials, optimizing their mechanical properties through topological structure, and using different lattice morphology characteristics to achieve biomimetic growth and promote rapid bone formation.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A biomimetic bone graft for filling long bone defects, custom-made and biocompatible, is characterized by a multi-layered columnar structure comprising, from the outside to the inside:

[0009] The support tube is a dense cylindrical structure with connecting parts at both ends of the support tube that can be inserted into the cortical bone of the bone. It also has fusion parts at both ends of the inner wall of the support tube. The fusion parts are annular and made of a biodegradable material with a porous lattice structure. The outer end face of the fusion part is in contact with the end face of the cortical bone of the bone.

[0010] An intermediate filler, placed inside the support cylinder and filling the space between the two fusion portions, wherein the intermediate filler is made of a biodegradable material; and

[0011] The inner filler is filled within the middle filler, and its two ends do not extend into the fusion region.

[0012] Both the middle filler and the inner filler are topology-optimized structures, which are composed of multiple porous unit cells stacked together. Each porous unit cell is composed of multiple dense rods forming a hollow three-dimensional structure.

[0013] Compared to the porous unit cells in the inner filler, the porous unit cells in the inner filler have a larger volume and form thicker rods.

[0014] A further technical solution is that the end face of the fusion portion that contacts the cortical bone of the connecting bone is a granular surface.

[0015] A further technical solution is that each of the porous unit cells is a hexahedron composed of two triangular pyramids, each hexahedron is composed of six dense rods, and multiple porous unit cells are stacked on top of each other.

[0016] A further technical solution is that the biomimetic transplant bone block is integrally formed by 3D printing.

[0017] A further technical solution is that the length of the connecting part is 5 to 300 mm.

[0018] A further technical solution is that the fusion part is a topology-optimized structure, having an inner ring wall and an outer ring wall, with multiple axially spaced partitions between the inner and outer ring walls, and protruding columns on both ends of the partitions.

[0019] A further technical solution is that the outermost baffle on the proximal connection is lower than the inner and outer ring walls, and the three of them form a liquid storage tank.

[0020] A further technical solution involves having a notch on the inner ring wall of the proximal connector.

[0021] A further technical solution is that the sidewall of the filling material has a through-hole.

[0022] A further technical solution is that the pores on the fusion portion are smaller than the pores on the intermediate filler.

[0023] The beneficial effects of adopting the above technical solution are as follows:

[0024] It combines dense, non-degradable materials with loose, porous, degradable materials, optimizes their mechanical properties through topological structure, and utilizes different lattice morphology characteristics to achieve biomimetic growth and promote rapid osteogenic formation.

[0025] The support tube is made of a dense, non-degradable material with the same strength, providing overall support for the bone block and increasing the overall structural force. The two ends of the support tube are connected to the proximal and distal ends of the long bones through a socket joint, achieving stable contact between the prosthesis and the bone and ensuring the stability of the bone block position after implantation.

[0026] Furthermore, at both ends of the inner arm of the support tube, there is a biodegradable fusion section, which is a porous lattice structure that mimics cortical fusion growth. The fusion section provides surface support for the connected long bones, increases the contact area between the bone cross-section and the prosthesis, ensures uniform force distribution, and also increases the contact area between osteoblasts and nutrients, thereby ensuring stronger cell activity, making the growth and integration of the prosthesis and bone more robust, and increasing the degree of integration at the fracture ends.

[0027] The support cylinder is filled with fillers of different materials and densities.

[0028] The inner filling material is located in the center of the bone block. It has a vertically growing lattice structure designed according to the longitudinal load-bearing shape of the bone trabeculae. Each lattice is formed by stacking the tops of a spatial triangular pyramid, which can disperse the stress concentration area to various parts of the structure, greatly increasing the stability of the overall structure. It has large pores while ensuring mechanical properties, which facilitates the attachment of external biomaterials. The structure is also transparent and does not affect the blood supply inside the bone.

[0029] The middle layer filler is located within the annular cavity formed by the inner filler, support tube, and fusion section. The middle layer filler has a loose structure with certain spatial stability, providing more space for osteoblasts to reside. At the same time, the porous lattice structure can greatly increase the contact area between osteoblasts and nutrients, thereby ensuring stronger cell activity and making the prosthesis and bone grow and bond more firmly.

[0030] Furthermore, the two ends of the inner filler do not extend into the fusion zone. That is, after initial implantation, the inner filler does not come into direct contact with the bone, and will not cause bone collapse due to point contact. Instead, it integrates with the bone after the blood flows in and osteoblasts form bone, thereby improving the mechanical strength of the limb. Attached Figure Description

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0032] Figure 1 This is the intention of the bionic bone graft to be integrated with long bone as disclosed in this paper;

[0033] Figure 2 This is a schematic diagram of the structure of the bionic bone graft disclosed herein;

[0034] Figure 3 This is a schematic diagram of the cross-sectional structure of the bionic bone graft disclosed herein;

[0035] Figure 4 This is a schematic diagram of the structure of the filler in the biomimetic bone graft disclosed herein;

[0036] Figure 5 This is a schematic diagram of the structure of the filler in the biomimetic bone graft disclosed herein. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0039] like Figures 1-5 As shown, the biomimetic bone graft for filling long bone defects is a biocompatible material that will not trigger an attack by the body's immune system. The biomimetic bone graft has a multi-layered columnar structure, consisting of a support cylinder 1, a middle filler 2, and an inner filler 3 from the outside in. The entire biomimetic bone graft is manufactured using inkjet 3D printing technology (3DP) in a single piece.

[0040] The support cylinder 1 is a dense cylindrical structure that will not be absorbed or degraded. It can be made of metal materials such as pure titanium, stainless steel, cobalt-based alloys, titanium-based alloys, magnesium-titanium alloys, etc., or non-degradable polymer materials such as PA plastics, polyethylene (PE), etc.

[0041] The support cylinder 1 has connecting portions 101 at both ends that are inserted into the cortical bone of the adjacent bone. The connecting portion 101 can be a socket that encloses the cortical bone or an insertion port within the cortical bone. The connecting portion 101 primarily mates with the protrusions in the cutting area of ​​the outer wall of the bone, allowing for a more stable fit and effectively preventing bone fragment dislodgement. The length of the connecting portion 101 is 5–300 mm to ensure connection stability. The support cylinder 1 is made of a dense, non-degradable material with uniform strength, providing overall support for the bone fragment and increasing the overall structural strength. The two ends of the support cylinder 1 are connected to the proximal and distal ends of the adjacent long bones via sockets, achieving stable contact between the prosthesis and the bone and ensuring stable positioning of the bone fragment after implantation.

[0042] At both ends of the inner wall of the support cylinder 1, there are fusion portions 102. The fusion portions 102 are annular and made of a biodegradable material with a porous lattice structure. The outer end face of the fusion portion 102 contacts the end face of the bone cortex to which it is attached. The fusion portion 102 has a topology-optimized structure with an inner ring wall and an outer ring wall. There are multiple axially spaced partitions between the inner and outer ring walls. There are protruding pillars on both end faces of the partitions. The end face of the fusion portion 102 that contacts the bone cortex to which it is attached is a granular surface. Small grooves are formed between the protruding pillars and the partitions, allowing blood to enter the grooves. The blood carries osteoblasts, and where blood flows sufficiently, bone and trabecular bone structures can form in the future, thus increasing the holding force between the bone and the implant.

[0043] Furthermore, the outermost septum on the proximal connector 101 is lower than the inner and outer annular walls, and the three together form a reservoir to store blood. The blood-filled area eventually becomes the osteogenic zone. The inner annular wall of the proximal connector 101 has a notch to facilitate blood flow.

[0044] The fusion section 102 is a porous lattice structure that mimics cortical fusion growth. The fusion section 102 provides surface support for the connected long bones, increases the contact area between the bone cross-section and the prosthesis, ensures uniform stress distribution, and also increases the contact area between osteoblasts and nutrients, thereby ensuring stronger cell activity, making the growth and integration of the prosthesis and bone more robust, and increasing the degree of integration at the fracture ends.

[0045] The support cylinder 1 is filled with fillers of different materials and densities. A middle filler 2 is placed inside the support cylinder 1 and fills the space between the two fusion portions 102; the middle filler 2 is made of a biodegradable material. An inner filler 3 is filled inside the middle filler 2, but its ends do not extend into the fusion portion 102, and it will not be absorbed or degraded. The fusion portion 102 and the middle filler 2 can be made of the same material, and their absorption rates are not sequential; typically, bone formation begins to heal within two weeks.

[0046] Both the intermediate filler 2 and the inner filler 3 are topology-optimized structures, composed of multiple stacked porous unit cells. Each porous unit cell consists of multiple dense rods forming a hollow three-dimensional structure. Preferably, each porous unit cell is a hexahedron composed of two triangular pyramids, and each hexahedron consists of six dense rods, with the tops of the multiple porous unit cells stacked. Compared to the porous unit cells in the inner filler 3, the porous unit cells in the inner filler 3 have a larger volume and thicker rods.

[0047] Both the fusion section 102 and the intermediate filler 2 are made of biodegradable materials, and the materials can be the same. Their absorption rates are not sequential, and bone formation typically begins to heal after two weeks. The fusion section 102 and the intermediate filler 2 use different crystal morphologies because they take into account the direction of blood flow and the formation direction of bone trabeculae. Since bone will form where there is blood flow, the reason for making them different structures is to allow for a tighter integration with the bone after the blood has formed bone. Since it is no longer autologous bone, multiple spatial structures are necessary to better restrict the degree of freedom.

[0048] In this biomimetic bone graft, the porosity of the fusion portion 102, the intermediate filler 2, and the inner filler 3 increases sequentially. The small vertical slits in the fusion portion 102 allow blood flow to promote osteoblast differentiation into a relatively robust cortex. The intermediate filler 2, the fusion section, aims to form a trabecular structure of cancellous bone, and the ideal size for this structure is a pore size of 300µm-1mm, making this size the most suitable for the lattice structure. The inner filler 3, being a supporting structure, requires a large triangular framework for mechanical structural support. This structure also needs a certain degree of elasticity to ensure slight deformation under pressure, dispersing stress concentration. Furthermore, the long bone shaft is hollow, containing bone marrow; a large size is necessary to avoid affecting the normal function of the bone marrow, as it will revert to red bone marrow after surgery to promote bone formation, thus requiring a large filler structure.

[0049] Furthermore, the sidewall of the filler 2 has a through-hole, which serves as a nutrient pore for the biomimetic bone, facilitating the differentiation and formation of blood supply. This ensures the activity of the osteo-associated body formed within the implant later.

[0050] The inner filler 3 is located in the center of the bone block. It has a vertically growing lattice structure designed according to the longitudinal bearing shape of the bone trabeculae. Each lattice is formed by stacking the tops of a spatial triangular pyramid, which can disperse the stress concentration area to various parts of the structure, greatly increasing the stability of the overall structure. It has large pores while ensuring mechanical properties, which facilitates the attachment of external biological materials. The structure is also transparent and does not affect the blood supply inside the bone.

[0051] The middle layer filler is located within the annular cavity formed by the inner filler 3, the support cylinder 1, and the fusion part 102. The middle layer filler has a loose structure with certain spatial stability, which provides more space for osteoblasts to reside. At the same time, the porous lattice structure can greatly increase the contact area between osteoblasts and nutrients, thereby ensuring stronger cell activity and making the growth and integration of the prosthesis with the bone more solid.

[0052] Furthermore, the two ends of the inner filler 3 do not extend into the fusion portion 102. That is, after initial implantation, the inner filler 3 does not directly contact the bone, and will not cause bone collapse due to point contact. Instead, it integrates with the bone after the blood flows in and osteoblasts form bone, thereby improving the mechanical strength of the limb.

[0053] The above are merely preferred embodiments of the present invention. Any simple modifications, variations, and equivalent substitutions made by any person based on the content of the present invention shall fall within the protection scope of the invention.

Claims

1. An individualized long bone defect filling biomimetic bone graft having biocompatibility, characterized in that , the columnar structure is multi-layered, from outside to inside including: a support cylinder, which is a dense cylindrical structure, has a connecting part for connecting with the end surface of the bone cortex at both ends of the support cylinder, and has a fusion part on the inner wall of the support cylinder at both ends, the fusion part is annular, is a porous lattice structure of degradable material, the outer end surface of the fusion part is in contact with the end surface of the bone cortex, the fusion part is a topologically optimized structure, has an inner ring wall and an outer ring wall, and has a plurality of axially spaced partitions between the inner ring wall and the outer ring wall, the two end surfaces of the partitions have protruding columns, and the protruding columns and the partitions form a small groove, and blood can enter the groove; a middle filler, which is placed in the support cylinder and fills between the two fusion parts, the middle filler is a degradable material; and an inner filler, which is filled in the middle filler, and the two ends of the inner filler do not extend into the fusion part; the middle filler and the inner filler are both topologically optimized structures, which are composed of a plurality of porous cell units stacked, each porous cell unit is composed of a plurality of dense rods to form a hollow three-dimensional structure; compared with the porous cell units in the inner filler, the volume of a single porous cell unit in the middle filler is larger, and the rod is thicker.

2. The biomimetic bone graft of claim 1, wherein, The end surface of the fusion part in contact with the bone cortex is a granular surface.

3. The biomimetic bone graft of claim 1, wherein, Each of the porous cell units is composed of two triangular pyramids to form a hexahedron, each hexahedron is composed of six dense rods, and a plurality of porous cell units are stacked at the top.

4. The biomimetic bone graft of claim 1, wherein, The bionic bone graft block is integrally formed by 3D printing.

5. The biomimetic bone graft of claim 1, wherein, The length of the connecting part is 5-300mm.

6. The biomimetic bone graft of claim 1, wherein, The outermost partition on the proximal connecting part is lower than the inner ring wall and the outer ring wall, and the three form a liquid storage tank.

7. The biomimetic bone graft of claim 1, wherein, The inner ring wall of the proximal connecting part has a notch.

8. The biomimetic bone graft of claim 1, wherein, The side wall of the middle filler has a through notch.

9. The osteochondral implant of claim 1, wherein the porous layer has a porosity of about 50% to about 90%. The porosity of the fusion part is smaller than that of the middle filler.

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