Application of bone filling mesh bag with double material filling structure in vertebral body augmentation

Abstract

The application provides a bone filling net bag with a double-material filling structure, which comprises an inner layer net bag and an outer layer net bag wrapped outside the inner layer net bag; a first filling cavity is formed in the inner layer net bag, and the first filling cavity is used for filling polymethyl methacrylate bone cement; an annular gap between the inner layer net bag and the outer layer net bag forms a second filling cavity, and the second filling cavity is used for filling artificial bone material; a connecting pipe is arranged on the outer surface of the inner layer net bag, the connecting pipe is connected with the first filling cavity and the second filling cavity, and is used for guiding the polymethyl methacrylate bone cement to enter the second filling cavity from the first filling cavity. The synergistic design of the structure and the material enables the implanted body to form a gradient composite interface of 'bone cement-artificial bone-host bone' in microcosm, realizes the unity of immediate stability and long-term fusion in macrocosm, and reduces the risk of postoperative implant loosening and re-fracture.

Description

Technical Field

[0001] This invention relates to the field of orthopedic implant technology, specifically to the application of a bone-filled mesh bag with a dual-material filling structure in vertebral body reinforcement. Background Technology

[0002] As people age, the incidence of osteoporotic vertebral compression fractures (OVCF) is increasing year by year in the elderly population. Traditional surgical treatment methods mainly involve injecting bone cement (such as polymethyl methacrylate, PMMA) to fill the vertebral body, which has the advantages of quickly improving vertebral stability and relieving pain. However, its long-term efficacy faces certain challenges: 1. Poor biocompatibility of bone cement: As a foreign substance, PMMA has relatively poor biocompatibility. Over time, stress concentration and micromovement may occur at the interface between bone cement and bone tissue. These factors may lead to gradual absorption and degeneration of surrounding bone tissue, ultimately increasing the risk of postoperative refracture. In addition, since PMMA cannot be absorbed by bone tissue, it will remain in the body as a foreign body for a long time, which may lead to a decrease in local bone density and affect the bone healing process. 2. Weak bond between bone cement and bone tissue: PMMA mainly provides support through physical bonding with the surface of bone tissue, but it does not chemically bond with bone tissue and lacks bone regeneration capacity. Therefore, although PMMA injection provides immediate stability, the bond between the PMMA material and bone tissue may gradually loosen over time, leading to decreased vertebral stability and an increased risk of refracture. 3. Material deterioration under long-term load: Prolonged weight-bearing and activity can cause microcracks in the PMMA material and even mechanical fatigue, gradually weakening its role as a supporting material. Furthermore, since PMMA is non-degradable in vivo, it may hinder normal bone cell growth and bone regeneration, further affecting fracture repair. 4. Pyrolysis of PMMA: The pyrolysis generated during PMMA injection (approximately 50-70°C) may adversely affect surrounding bone tissue. Pyrolysis may cause localized bone necrosis, affecting bone healing. Although this effect is relatively mild initially, it may lead to further damage to bone structure during long-term treatment. 5. Lack of self-repair capability: As an artificial material, PMMA cannot participate in the bone healing process and therefore cannot provide the self-repair function of natural bone tissue. Once microcracks or fractures occur in the vertebral body, PMMA cannot restore its function through self-repair.

[0003] Calcium phosphate, calcium sulfate, and other artificial bone materials have certain clinical application value in the treatment of osteoporotic vertebral compression fractures (OVCF), especially in preventing bone cement leakage and improving the biocompatibility between bone cement and bone tissue. However, using artificial bone materials such as calcium phosphate and calcium sulfate alone for vertebral body filling often faces some significant clinical challenges: 1. Poor immediate stability: Artificial bone materials such as calcium phosphate and calcium sulfate harden slowly after injection, usually failing to provide immediate stability to the fracture area quickly. In patients with vertebral compression fractures, especially in the acute phase, the stability of the fracture area is crucial for relieving pain and preventing further bone damage. Relying solely on artificial bone materials not only fails to effectively provide fracture stability in the short term after surgery but may also lead to delayed pain relief and affect the recovery process. 2. Delayed bone healing: Although artificial bone materials such as calcium phosphate and calcium sulfate can promote bone healing, their own bone regeneration capacity is relatively limited, especially in patients with osteoporosis. Osteoporosis leads to the destruction of trabecular bone structure and a decrease in bone density, which slows down the natural healing process of the fracture area. While calcium phosphate and calcium sulfate can provide some scaffolding for bone tissue, they do not possess the special function of stimulating rapid bone regeneration and repair. Their degradation rate also does not perfectly match the patient's bone healing speed, potentially leading to long-term weak bone structure and increasing the risk of refracture. 3. Incomplete bone stability during artificial bone degradation: Artificial bone materials such as calcium sulfate and calcium phosphate gradually degrade after implantation, releasing calcium and phosphorus for bone healing. However, this degradation process is gradual, and the degradation rate does not perfectly match the patient's fracture healing progress. During the transition period of degradation, the artificial bone material loses some structural support, potentially leading to insufficient stability in the fracture area and affecting long-term efficacy. Furthermore, the formation of voids after degradation may gradually weaken vertebral stability, resulting in a weak bone structure and increasing the risk of postoperative refracture. 4. Poor immediate pain relief: Although the injection of calcium sulfate and calcium phosphate helps bone healing, due to their slow hardening rate, patients often do not receive sufficient stability support immediately after surgery, resulting in inadequate pain relief. For patients with osteoporotic vertebral compression fractures, immediate stability at the fracture site is crucial. Failure to effectively control pain in the short term will significantly delay postoperative recovery. 5. Insufficient mechanical properties of artificial bone: Artificial bone materials such as calcium sulfate and calcium phosphate have relatively weak mechanical properties, especially under heavy loads, and may not provide sufficient support. In the vertebrae of osteoporotic patients, due to their already low bone density and fragile bone, simple artificial bone filling may not be able to effectively withstand the long-term load from the spine, leading to further damage to the vertebral structure. Compared with natural bone, artificial bone has lower mechanical strength and elastic modulus, and poorer compatibility with surrounding bone tissue, increasing instability during treatment.6. Inability to resolve long-term refracture: While using artificial bone materials such as calcium sulfate and calcium phosphate can promote bone healing to some extent, these materials themselves do not possess sufficient strength to support the long-term recovery of bone density in osteoporosis patients. Therefore, under prolonged loads, vertebral bodies may refracture, especially when the load is excessive or the patient's activity level is inappropriate. This problem is particularly severe in elderly patients because osteoporosis makes it difficult to restore bone density, and the rate of degradation of artificial bone is often disproportionate to the healing process of bone tissue.

[0004] Using PMMA or artificial bone materials such as calcium phosphate and calcium sulfate alone is not effective in treating osteoporotic vertebral compression fractures. However, most bone-filled mesh bags on the market are hollow, large sac-like structures that can usually only inject a single material, failing to simultaneously achieve both immediate stability and long-term efficacy. There is an urgent need for an innovative bone-filled mesh bag that can combine immediate effectiveness with long-term stability. Summary of the Invention

[0005] The purpose of this invention is to provide a bone filling mesh bag with a dual-material filling structure. By combining the short-term stability of PMMA with the long-term bone healing effect of artificial bone materials, this invention can effectively overcome the problem of poor long-term efficacy of PMMA as a single material.

[0006] To achieve the above objectives, the present invention first provides the following technical solution: A bone-filled mesh bag with a dual-material filling structure, the bone-filled mesh bag including an inner mesh bag and an outer mesh bag covering the outside of the inner mesh bag; The inner mesh bag forms a first filling cavity, which is used to fill polymethyl methacrylate bone cement; the annular gap between the inner mesh bag and the outer mesh bag forms a second filling cavity, which is used to fill artificial bone material. The outer surface of the inner mesh bag is provided with a connecting tube, which connects the first filling cavity and the second filling cavity and is used to guide the polymethyl methacrylate bone cement from the first filling cavity into the second filling cavity.

[0007] As a preferred embodiment of the present invention, the bone filling mesh bag is provided with an injection interface assembly, the injection interface assembly including a first injection channel communicating with the second filling cavity and a second injection channel communicating with the first filling cavity.

[0008] The first and second injection channels are arranged side-by-side to form a dual-lumen injection interface, or they are separately arranged and connected to the corresponding filling cavities via independent catheters. Therefore, either an integrated dual-lumen interface structure or a separate independent interface structure can be used to accommodate different surgical instruments and implantation paths.

[0009] As a preferred embodiment of the present invention, the wall thickness of the inner mesh bag is 0.05–0.30 mm; The outer mesh bag has a wall thickness of 0.10–0.50 mm.

[0010] As a preferred embodiment of the present invention, the aperture of the inner mesh bag is smaller than that of the outer mesh bag.

[0011] Preferably, the inner mesh bag has a mesh size of 0.05–0.30 mm, and the outer mesh bag has a mesh size of 0.30–1.50 mm.

[0012] The outer mesh bag adopts a non-uniform pore size design; the pore size of the mesh bag in the load-bearing area is smaller than that in the bone-attaching area. The smaller pore size in the load-bearing area is used to maintain the structural stability after filling, while the larger pore size in the bone-attaching area is used to promote contact between the artificial bone material and the surrounding cancellous bone and promote bone ingrowth.

[0013] As a preferred embodiment of the present invention, the inner mesh bag is made of one or more of PET, PEEK or polyurethane materials.

[0014] As a preferred embodiment of the present invention, the outer mesh bag is made of one or a mixture of several of polylactic acid, polycaprolactone, polylactic acid-glycolic acid copolymer, and polyglycolic acid.

[0015] As a preferred embodiment of the present invention, the artificial bone material is one or a mixture of several of calcium sulfate, calcium phosphate, β-tricalcium phosphate, and hydroxyapatite.

[0016] As a preferred embodiment of the present invention, the connecting tube is distributed along the circumference and / or axial direction of the inner mesh bag, and the connecting tube is a hollow tube structure with an internal hollow structure and open at both ends.

[0017] The cross-sectional shape of the connecting pipe can be circular, elliptical, or polygonal; preferably, the cross-sectional shape of the connecting pipe is hexagonal.

[0018] The connecting tube and the inner mesh bag can be integrally formed, or they can be fixedly connected by hot melting, bonding, welding, weaving or sleeve connection.

[0019] As a preferred embodiment of the present invention, the radial design distance between the outer surface of the inner mesh bag and the inner surface of the outer mesh bag is 1 to 4 mm.

[0020] During the filling process, the connecting tube can support the gap between the inner mesh bag and the outer mesh bag to maintain the spatial shape of the second filling cavity.

[0021] To achieve the above objectives, the present invention also provides the following technical solution: An application of the bone-filled mesh bag described in any one of the above claims in vertebral body reinforcement includes: First, artificial bone material is injected into the second filling cavity through the first injection channel. The artificial bone material fills the second filling cavity and seeps into the surrounding cancellous bone through the pores of the outer mesh bag. Then, polymethyl methacrylate (PMMA) bone cement is injected into the first filling cavity through the second injection channel. After the PMMA bone cement fills the first filling cavity, it enters the second filling cavity along the connecting tube and fills the gaps between the artificial bone materials. Finally, it forms a stable interface with the cancellous bone through the pores of the outer mesh bag.

[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention, through a dual-cavity partitioned structure constructed from an inner and outer mesh bag, combined with the directional connectivity provided by a connecting tube, fundamentally resolves the contradiction between the inability of a single material or single-layer mesh bag to simultaneously achieve both mechanical and biological performance. Specifically, the polymethyl methacrylate (PMMA) bone cement in the first filling cavity provides immediate high-modulus support post-surgery, effectively restoring vertebral height and alleviating pain; the artificial bone material in the annular second filling cavity establishes a long-term biological fixation interface through direct contact with cancellous bone and subsequent degradation into osteoblasts. The connecting tube, as a controlled communication channel between the first and second filling cavities, guides the PMMA bone cement directionally from the first filling cavity into the second filling cavity, filling the gaps between the artificial bone materials; simultaneously, the connecting tube also enhances the overall mechanical integrity of the mesh bag. The inner mesh bag has a smaller pore size than the outer mesh bag, which helps limit the disordered leakage of polymethyl methacrylate (PMMA) bone cement through the inner mesh bag wall, allowing it to mainly enter the second filling cavity through the connecting tube. The non-uniform pore size design of the outer mesh bag further optimizes the material leakage behavior, maintaining structural strength in the load-bearing area and promoting contact and bone ingrowth between the artificial bone material and cancellous bone in the bone-attaching area. This synergistic design of structure and materials enables the implant to form a gradient composite interface of "bone cement-artificial bone-host bone" at the microscopic level, achieving a balance between immediate stability and long-term fusion at the macroscopic level, reducing the risk of postoperative implant loosening and refracture. Attached Figure Description

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this 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 this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0025] Figure 1 This is a schematic diagram of the overall cross-sectional structure of the bone-filled mesh bag according to an embodiment of the present invention; Figure 2 This is a partial cross-sectional view and a schematic diagram of the filling principle of the inner mesh bag connecting tube according to an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of the dual-cavity injection interface structure according to an embodiment of the present invention.

[0027] Among them, 10-injection interface assembly; 11-first injection channel; 12-second injection channel; 20-inner mesh bag; 21-first filling cavity; 30-outer mesh bag; 31-second filling cavity; 32-pores of outer mesh bag; 40-connecting tube. Detailed Implementation

[0028] 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 embodiments of the present invention, and not all embodiments. 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.

[0029] In a typical embodiment of this application, a bone-filled mesh bag with a dual-material filling structure is provided. The bone-filled mesh bag includes an inner mesh bag 20 and an outer mesh bag 30 covering the outer side of the inner mesh bag 20. The inner mesh bag 20 forms a first filling cavity 21, which is used to fill polymethyl methacrylate bone cement; the annular gap between the inner mesh bag 20 and the outer mesh bag 30 forms a second filling cavity 31, which is used to fill artificial bone material. The outer surface of the inner mesh bag 20 is provided with a connecting tube 40, which connects the first filling cavity 21 and the second filling cavity 31 and is used to guide polymethyl methacrylate bone cement from the first filling cavity 21 into the second filling cavity 31.

[0030] The present invention constructs a dual-cavity structure by means of an inner mesh bag 20 and an outer mesh bag 30, which are independent of each other but connected by a connecting tube 40. This allows the high mechanical strength polymethyl methacrylate bone cement and the bioactive artificial bone material to be spatially distributed in sections, which not only ensures immediate support for the vertebral core but also provides a bone ingrowth interface in the periphery.

[0031] As a preferred embodiment of the present invention, the bone filling mesh bag is provided with an injection interface assembly 10, which includes a first injection channel 11 communicating with the second filling cavity 31 and a second injection channel 12 communicating with the first filling cavity 21.

[0032] like Figure 3 As shown, the first injection channel 11 and the second injection channel 12 can be arranged side by side to form a dual-lumen injection interface; in other embodiments, the first injection channel 11 and the second injection channel 12 can also be arranged separately and connected to the corresponding filling cavity through independent catheters.

[0033] By using separate injection channels to inject the two materials separately, it is possible to avoid the mixing of artificial bone material and polymethyl methacrylate bone cement before entering the corresponding cavity, thus ensuring the functional integrity of the filling material in each cavity and improving the controllability of intraoperative operation.

[0034] As a preferred embodiment of the present invention, the inner mesh bag 20 has a wall thickness of 0.05 to 0.30 mm, and the outer mesh bag 30 has a wall thickness of 0.10 to 0.50 mm.

[0035] The radial design spacing between the outer surface of the inner mesh bag 20 and the inner surface of the outer mesh bag 30 is 1–4 mm. The radial design spacing refers to the preset spacing between the outer surface of the inner mesh bag 20 and the inner surface of the outer mesh bag 30 in the unfolded state of the bone-filled mesh bag, which is used to form the second filling cavity 31.

[0036] The connecting tube 40 can support and maintain the radial design spacing during the filling process, preventing the inner mesh bag 20 from over-expanding and squeezing the second filling cavity 31 when polymethyl methacrylate bone cement is injected.

[0037] As a preferred embodiment of the present invention, the aperture of the inner mesh bag 20 is smaller than that of the outer mesh bag 30; Preferably, the inner mesh bag 20 has a mesh diameter of 0.05–0.30 mm, and the outer mesh bag 30 has a mesh diameter of 0.30–1.50 mm.

[0038] The outer mesh bag 30 adopts a non-uniform pore size design. The pores 32 of the outer mesh bag include the bearing area pores located in the bearing area and the bone-attaching area pores located in the bone-attaching area, wherein the pore size of the bearing area pores is smaller than the pore size of the bone-attaching area pores.

[0039] Smaller pores in the load-bearing area help maintain the strength of the mesh structure and reduce the risk of rapid material leakage; larger pores in the bone-attaching area facilitate contact between the artificial bone material and the surrounding cancellous bone, and provide a channel for the ingrowth of new bone tissue.

[0040] As a preferred embodiment of the present invention, the inner mesh bag 20 is made of one or more of PET, PEEK or polyurethane materials.

[0041] As a preferred embodiment of the present invention, the outer mesh bag 30 is made of one or a mixture of several of polylactic acid, polycaprolactone, polylactic acid-glycolic acid copolymer, and polyglycolic acid.

[0042] As a preferred embodiment of the present invention, the artificial bone material is one or a mixture of several of calcium sulfate, calcium phosphate, β-tricalcium phosphate, and hydroxyapatite.

[0043] As a preferred embodiment of the present invention, the connecting tube 40 is distributed along the circumference and / or axial direction of the inner mesh bag 20, and the connecting tube 40 is a hollow tube structure with an internal hollow structure and open at both ends.

[0044] The cross-sectional shape of the connecting pipe 40 can be circular, elliptical, or polygonal; preferably, the cross-sectional shape of the connecting pipe 40 is hexagonal. Multiple connecting pipes 40 can be distributed in a regular array, an alternating array, or a gradient array.

[0045] The connecting tube 40 and the inner mesh bag 20 can be integrally formed, or they can be fixedly connected by hot melting, bonding, welding, weaving or sleeve connection.

[0046] The connecting tube 40 not only serves as a directional flow channel for polymethyl methacrylate bone cement to enter the second filling cavity 31, but also supports the gap between the inner mesh bag 20 and the outer mesh bag 30, and enhances the overall shear and compression resistance of the double mesh bags.

[0047] Furthermore, the present invention also provides a method for using the bone-filled mesh bag in vertebral body reinforcement, comprising: Step S1: First, inject artificial bone material into the second filling cavity 31 through the first injection channel 11, so that the artificial bone material fills the second filling cavity 31 and seeps into the surrounding cancellous bone through the pores 32 of the outer mesh bag. Step S2: Then inject polymethyl methacrylate bone cement into the first filling cavity 21 through the second injection channel 12; Step S3: After the polymethyl methacrylate bone cement fills the first filling cavity 21, it enters the second filling cavity 31 along the connecting tube 40 and fills the gaps in the artificial bone material. Finally, it forms a stable interface with the cancellous bone through the pores 32 of the outer mesh bag.

[0048] The above-mentioned application method establishes a peripheral bone integration foundation by first filling with artificial bone material through a specific injection sequence. The subsequently injected polymethyl methacrylate bone cement provides core support and enters the gaps between the artificial bone material through the connecting tube 40 to form an interlocking structure, thereby achieving a dual stabilization mechanism of mechanical anchoring and biological fixation.

[0049] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0050] Example 1 like Figure 1 and Figure 2 As shown, this embodiment provides a bone-filled mesh bag with a dual-material filling structure, which constitutes the basic architecture of the present invention. The bone-filled mesh bag includes an inner mesh bag 20 and an outer mesh bag 30 covering the outer side of the inner mesh bag 20. The inner mesh bag 20 and the outer mesh bag 30 are spatially coaxially arranged. A first filling cavity 21 is formed inside the inner mesh bag 20 for filling with polymethyl methacrylate (PMMA) bone cement, and the gap between the inner mesh bag 20 and the outer mesh bag 30 forms an annular second filling cavity 31 for filling with artificial bone material. The centrally located first filling cavity 21 provides high-modulus immediate mechanical support through the PMMA bone cement, while the surrounding second filling cavity 31 serves as a bioactive interface, allowing the artificial bone material to contact the host cancellous bone to promote long-term osseointegration.

[0051] To achieve orderly interaction between the two materials within the dual-cavity structure, the inner mesh bag 20 is equipped with a connecting tube 40 that connects the first filling cavity 21 and the second filling cavity 31. The connecting tube 40 is not merely a simple fluid passage, but is configured as the sole material exchange channel between the first filling cavity 21 and the second filling cavity 31. Specifically, the wall of the inner mesh bag 20 is constructed to act as a barrier against polymethyl methacrylate (PMMA) bone cement, forcing the bone cement injected into the first filling cavity 21 to flow directionally into the second filling cavity 31 only through the pre-designed connecting tube 40. This structural design effectively prevents disordered leakage of bone cement through the micropores of the inner mesh bag wall, thus ensuring that the distribution of bone cement in the second filling cavity 31 is controllable and uniform, rather than randomly dispersed. Simultaneously, this also prevents the artificial bone material injected into the second filling cavity 31 earlier from invading the first filling cavity 21, ensuring the purity and mechanical properties of the core support.

[0052] Further integration Figure 2As shown in the partial cross-sectional view, the connecting tube 40 also plays a crucial role in mechanical reinforcement. Specifically, the connecting tube 40 maintains a predetermined spacing between the inner mesh bag 20 and the outer mesh bag 30 in the radial direction, preventing the inner mesh bag 20 from over-expanding and compressing or even emptying the second filling cavity 31 during high-pressure bone cement injection, thus ensuring the capacity and thickness uniformity of the artificial bone material. In the axial direction, the connecting tube 40 is similar to the web member in a truss structure, effectively transferring and distributing the axial load borne by the first filling cavity 21 to the outer mesh bag 30 and the surrounding bone tissue, significantly improving the shear resistance and compressive stability of the overall mesh bag device. This "structure-function" dual-binding design allows the connecting tube 40 to simultaneously solve the two technical problems of fluid control and mechanical support. It should be noted that, although Figure 2 The schematic diagram illustrates a specific form of the connecting pipe 40, but the present invention does not limit its specific cross-sectional shape, length or arrangement. For example, the connecting pipe 40 can be cylindrical, prismatic or corrugated, and its distribution can be a regular array or a gradient arrangement adapted to stress distribution. As long as it can achieve the connection of the two cavities and provide corresponding support, it is within the protection scope of the present invention.

[0053] like Figure 3 As shown, the bone-filled mesh bag is provided with a dual-cavity injection port 10. The dual-cavity injection port 10 includes a first injection channel 11 communicating with the second filling cavity 31 and a second injection channel 12 communicating with the first filling cavity 21. The first injection channel 11 and the second injection channel 12 are isolated from each other within the dual-cavity injection port 10 and open in their respective cavities. The first injection channel 11 is used to introduce artificial bone material into the second filling cavity 31, and the second injection channel 12 is used to introduce polymethyl methacrylate bone cement into the first filling cavity 21. This physically isolated flow channel design can prevent the two materials from mixing prematurely before injection or at the interface, avoiding abnormal injection resistance, blockage of the connecting tube 40, or blockage of the outer mesh bag pores 32 due to changes in rheological properties, thereby ensuring the functional integrity of the dual-material partitioned filling structure.

[0054] To balance the flexibility and restraint of the mesh bags, this embodiment precisely defines the wall thicknesses of the inner mesh bag 20 and the outer mesh bag 30. Specifically, the wall thickness of the inner mesh bag 20 is 0.05–0.30 mm, and the wall thickness of the outer mesh bag 30 is 0.10–0.50 mm. In the filled state, the radial distance between the inner mesh bag 20 and the outer mesh bag 30 is set to 1–4 mm. In a preferred specific example, the wall thickness of the inner mesh bag 20 is selected as 0.1 mm, the wall thickness of the outer mesh bag 30 is selected as 0.2 mm, and the radial distance after filling is controlled to approximately 2 mm. This parameter combination allows the inner mesh bag 20 to have good compliance when injected with high-viscosity bone cement, while simultaneously providing sufficient radial restraint force for the outer mesh bag 30 to prevent excessive expansion or rupture under high-pressure injection. Regarding the distance between the inner and outer layers, a range of 1 to 4 mm ensures that there is sufficient artificial bone material in the second filling cavity 31 to form an effective bone-inducing layer, while avoiding excessive thickness in the outer periphery that could lead to excessive stretching of the vertebral body and thus the risk of cortical bone fracture.

[0055] As a key improvement of this invention, the pore size of the inner mesh bag 20 is smaller than that of the outer mesh bag 30. This allows the inner mesh bag 20 to restrict the disordered extravasation of polymethyl methacrylate (PMMA) bone cement through the wall surface and directs the bone cement primarily into the second filling cavity 31 via the connecting tube 40. The pore size of the outer mesh bag 30 ranges from 0.30 to 1.50 mm; in embodiments where the outer mesh bag 30 employs a non-uniform pore size design, the pore size in the bearing area is smaller than that in the bone-attaching area. Figure 1 and Figure 2 As shown, in the load-bearing region where axial loads are primarily borne, smaller pore sizes maintain intracapsular pressure and reduce the rapid loss of artificial bone material; in the osteophyte region where it directly contacts the host cancellous bone, larger pore sizes provide a physical pathway for the ingrowth of new bone tissue. This pore size configuration achieves spatial decoupling and synergy between mechanical support and biological fixation.

[0056] Furthermore, the structural layout of the connecting tubes 40 has also been specifically optimized. The connecting tubes 40 are spaced apart circumferentially and axially, and are hollow internally with open ends, serving as flow-guiding support tubes. The connecting tubes 40 can be integrally formed with the inner mesh bag 20, or they can be fixedly connected to the inner mesh bag 20 through methods such as hot-melt bonding, adhesive bonding, or weaving. Figure 2 As can be seen, multiple connecting tubes 40 form a multi-point interconnected structure on the surface of the inner mesh bag 20, allowing polymethyl methacrylate bone cement to simultaneously and from the first filling cavity 21 into the second filling cavity 31 at multiple points, avoiding stress imbalance caused by uneven local filling. The connecting tubes 40 can be circular, elliptical, polygonal, or other cross-sectional shapes that can achieve flow guidance, and their arrangement can be a regular array, or a spiral, radial, or gradient density distribution. As long as the connecting tubes 40 can achieve directional communication between the first filling cavity 21 and the second filling cavity 31 and provide corresponding support, they are all within the protection scope of this invention.

[0057] This embodiment further defines the material system of the bone-filled mesh bag to construct a ternary synergistic mechanism of a bio-inert core, a biodegradable shell, and active artificial bone material. Specifically, the inner mesh bag is made of one or more of PET, PEEK, or polyurethane materials. This material selection is not an arbitrary, conventional substitution, but a targeted design based on the functional positioning of the inner mesh bag as a permanent container for polymethyl methacrylate (PMMA) bone cement. PET (polyethylene terephthalate), PEEK (polyetheretherketone), and polyurethane all possess excellent bioinertness, hydrolysis resistance, and long-term fatigue resistance, enabling them to maintain mechanical stability for decades in the complex physiological environment of the body. This ensures that the PMMA bone cement within the first filling cavity remains in a controlled encapsulation state, preventing bone cement release or displacement due to cyst aging and rupture. In contrast, if the inner mesh bag is made of biodegradable material, as the material degrades and loses strength, the high-modulus bone cement core inside will lose its radial restraint, making it highly susceptible to micromovement or even penetration of the capsule wall and injury to surrounding tissues under long-term alternating loads on the spine. If ordinary nylon or similar materials are used, their long-term hydrolysis resistance is insufficient, potentially leading to brittle fracture after several years. Therefore, the bioinertness and mechanical durability of the inner layer material are the cornerstones of ensuring the safety of the implant throughout its entire lifespan. In a preferred specific example, the inner mesh bag can be made of medical-grade PET filaments, with a tensile breaking strength greater than 50N, and a strength retention rate of over 90% after immersion in simulated body fluids for 12 months, sufficient to withstand the high-pressure injection during vertebroplasty and the long-term axial compression loads after surgery.

[0058] Unlike the permanent inner mesh bag, the outer mesh bag is made of a biodegradable or absorbable biocompatible polymer material, which can be selected from one or a mixture of several of polylactic acid (PLA), polycaprolactone (PCL), polyvinyl alcohol (PVA), polylactic-co-glycolic acid copolymer (PLGA), and polyglycolic acid (PGA). The outer material is designed to transform from a "temporary barrier" to an "osteogenic scaffold," and its degradation rate can be controlled by molecular weight, crystallinity, copolymerization ratio, or degree of cross-linking to match its degradation cycle with the rate of new bone replacement in the host. In the early stages of implantation, the outer mesh bag provides mechanical strength to maintain the shape of the second filling cavity and prevent disordered leakage of bone cement. Over time, the outer mesh bag gradually softens or is absorbed, and the physical space freed up in situ provides a channel for the ingrowth of new bone trabeculae, thereby improving the potential for insufficient osseointegration caused by long-term foreign body reactions with traditional non-degradable mesh bags.

[0059] To further enhance the biological activity of the second filling cavity, the artificial bone material is one or a mixture of several of the following: calcium sulfate, calcium phosphate, β-tricalcium phosphate, and hydroxyapatite. These inorganic non-metallic materials not only occupy space as filling media but also participate in the bone repair process as active carriers for osteoconduction or osteoinduction. Specifically, calcium sulfate has high solubility and ion release rate, enabling rapid release of calcium ions to create a local osteogenic microenvironment, making it suitable as an initiator of early osteogenesis; while hydroxyapatite (HA) has a chemical composition highly similar to the natural bone mineral phase, exhibiting excellent osteoconductivity and long-term stability, making it suitable as a durable scaffold for new bone deposition; β-tricalcium phosphate (β-TCP) falls between the two, possessing both moderate degradability and osteogenic activity. In practical applications, the ratio can be flexibly adjusted according to the patient's bone condition and healing expectations. For example, for elderly patients with severe osteoporosis and weak osteogenic capacity, an artificial bone material composed of a 7:3 mixture of β-TCP and HA can be used. The rapid degradation of β-TCP creates space for new bone growth, while HA particles are retained as a long-term mineralization core. For younger patients or those with smaller bone defects, the proportion of calcium sulfate can be increased to accelerate early fusion. More importantly, when the subsequently injected polymethyl methacrylate (PMMA) bone cement seeps into the second filling cavity through the connecting tube, the liquid bone cement fills the tiny gaps between the artificial bone particles, solidifying to form a microscopic interlocking composite of "artificial bone particles-bone cement matrix." This composite structure not only mechanically resembles reinforced concrete, significantly improving the overall compressive strength and shear resistance of the second filling cavity, but also biologically retains the surface activity of the artificial bone material, allowing new bone tissue to crawl and grow along the surface of the artificial bone particles and eventually penetrate the pores of the outer mesh bag to establish a strong bony connection with the host cancellous bone. This ternary synergistic design at the material level fundamentally overcomes the shortcomings of single materials or simple mixed materials in achieving both immediate mechanical support and long-term biological integration.

[0060] Example 2 This embodiment provides a method for applying bone-filled mesh bags in vertebral body reinforcement, as described in the previous embodiments. This method is not a simple material filling operation, but rather a gradient composite interface construction process based on a specific time-dependent characteristic. Specifically, the application method includes steps S1 and S2, which, by strictly controlling the injection sequence of two heterogeneous materials, form a stable structure with a gradient distribution of mechanical properties and biological activity in situ within the vertebral body.

[0061] In step S1, artificial bone material is first injected into the second filling cavity 31 through the dual-cavity injection interface 10 and the first injection channel. Combined with... Figure 2As shown, the artificial bone material enters the annular space between the inner mesh bag 20 and the outer mesh bag 30 through the first injection channel of the dual-cavity injection interface 10. With continuous application of injection pressure, the artificial bone material not only fills the second filling cavity 31, but also actively penetrates into the trabecular gaps of the surrounding cancellous bone through the outer mesh bag pores 32 of the outer mesh bag 30 under pressure. The artificial bone particles embed into the host bone gaps, forming a preliminary mechanical interlocking and chemical induction interface, while also reserving interconnected pore channels for the subsequent infiltration of polymethyl methacrylate bone cement. If this step is omitted or postponed, the outer mesh bag 30 may directly adhere to the vertebral body wall during subsequent high-pressure injection due to a lack of internal support, causing the outer mesh bag pores 32 to be closed and losing its bone ingrowth capacity.

[0062] Following step S2, polymethyl methacrylate (PMMA) bone cement is injected into the first filling cavity 21 through the second injection channel via the dual-cavity injection port 10. When the liquid PMMA bone cement is injected into the first filling cavity 21 via the second injection channel 12, as the pressure within the first filling cavity 21 increases, the PMMA bone cement does not randomly penetrate the dense wall of the inner mesh bag 20. Instead, it is forcibly guided to the connecting tube 40 and flows directionally along the connecting tube 40 into the second filling cavity 31, which has been pre-filled with artificial bone material. During this process, the liquid bone cement, like grout, fills the gaps between the artificial bone particles and the gaps between the artificial bone and the outer mesh bag 30. After the bone cement solidifies, an interlocking composite of "PMMA matrix - artificial bone particles" is formed within the second filling cavity 31. This composite ultimately forms a stable interface with the cancellous bone through the gaps in the outer mesh bag 30. From the perspective of mechanical transmission path, this gradient interface achieves a smooth transition of modulus: the high-modulus polymethyl methacrylate core provides immediate strength, the interlocking composite in the middle layer acts as a stress buffer zone, and the outermost artificial bone-host bone interface undertakes the biological fixation function, effectively avoiding the stress concentration and adjacent segment fracture risk caused by the sudden change in modulus in traditional single bone cement filling.

Claims

1. A bone-filled mesh bag with a dual-material filling structure, characterized in that, The bone-filled mesh bag includes an inner mesh bag and an outer mesh bag covering the outside of the inner mesh bag; The inner mesh bag forms a first filling cavity, which is used to fill polymethyl methacrylate bone cement; the annular gap between the inner mesh bag and the outer mesh bag forms a second filling cavity, which is used to fill artificial bone material. The outer surface of the inner mesh bag is provided with a connecting tube, which connects the first filling cavity and the second filling cavity and is used to guide the polymethyl methacrylate bone cement from the first filling cavity into the second filling cavity.

2. The bone-filled mesh bag as described in claim 1, characterized in that, The bone-filling mesh bag is provided with an injection interface assembly, which includes a first injection channel communicating with the second filling cavity and a second injection channel communicating with the first filling cavity. The first injection channel and the second injection channel are arranged side by side to form a dual-lumen injection interface, or they are arranged separately and connected to the corresponding filling cavity through independent catheters.

3. The bone-filled mesh bag according to claim 1, characterized in that, The inner mesh bag has a wall thickness of 0.05–0.30 mm; The outer mesh bag has a wall thickness of 0.10–0.50 mm.

4. The bone-filled mesh bag according to claim 1, characterized in that, The inner mesh bag has a smaller aperture than the outer mesh bag; Preferably, the inner mesh bag has a mesh size of 0.05–0.30 mm, and the outer mesh bag has a mesh size of 0.30–1.50 mm. The outer mesh bag adopts a non-uniform aperture design, wherein the aperture of the mesh bag in the bearing area is smaller than that in the bone-attaching area.

5. The bone-filled mesh bag according to claim 1, characterized in that, The inner mesh bag is made of one or more of PET, PEEK, or polyurethane materials.

6. The bone-filled mesh bag according to claim 1, characterized in that, The outer mesh bag is made of one or a mixture of several of polylactic acid, polycaprolactone, polylactic acid-glycolic acid copolymer, and polyglycolic acid.

7. The bone-filled mesh bag according to claim 1, characterized in that, The artificial bone material is one or a mixture of several of the following: calcium sulfate, calcium phosphate, β-tricalcium phosphate, and hydroxyapatite.

8. The bone-filled mesh bag according to claim 1, characterized in that, The connecting tubes are distributed along the circumference and / or axial direction of the inner mesh bag. The connecting tubes are hollow tube structures with open ends. The cross-sectional shape of the connecting tubes is circular, elliptical, or polygonal.

9. The bone-filled mesh bag according to claim 8, characterized in that, The cross-sectional shape of the connecting pipe is hexagonal.

10. The bone-filled mesh bag according to claim 1, characterized in that, The connecting tube is integrally formed with the inner mesh bag, or it is fixedly connected by hot melting, bonding, welding, weaving or sleeve connection.

11. The bone-filled mesh bag according to claim 1, characterized in that, The radial design distance between the outer surface of the inner mesh bag and the inner surface of the outer mesh bag is 1 to 4 mm.

12. An application of the bone-filled mesh bag according to any one of claims 1 to 11 in vertebral body reinforcement, characterized in that, include: First, artificial bone material is injected into the second filling cavity through the first injection channel, so that the artificial bone material fills the second filling cavity and seeps into the surrounding cancellous bone through the pores of the outer mesh bag; Then, polymethyl methacrylate (PMMA) bone cement is injected into the first filling cavity through the second injection channel. After filling the first filling cavity, the PMMA bone cement enters the second filling cavity along the connecting tube and fills the gaps in the artificial bone material. Finally, it forms a stable interface with the cancellous bone through the pores of the outer mesh bag.

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