Layered and blockable bone cement spacer and method of making

Abstract

The application discloses a layered and blocked bone cement spacer and a preparation method thereof, and belongs to the technical field of orthopedic clinical treatment. After complete lesion removal, flushing and disinfection are completed, antibiotic bone cement is filled in a layered filling manner, S1: a first layer thin layer filling step: the prepared antibiotic bone cement is uniformly filled on the inner wall of a lesion gap in a thin layer smearing manner, the bone cement is fully attached to the bone wall in a soft pressing manner, a bone cement thin layer with a thickness of 2-3 mm is formed, the bone cement thin layer completely covers the inner wall of the lesion gap and is closely attached to the normal bone cortex, gaps are avoided, the layered filling manner of the thin layer and the block is adopted, the thin layer and the block are not completely fused, and slight gaps exist between the blocks, in a second operation, the thin layer can be first separated from an induction film by prying, and then the blocks are taken out one by one, without forcibly stripping, the difficulty of taking out is greatly reduced, the operation time is shortened, and the operation operation strength is reduced.

Description

Technical Field

[0001] This invention relates to the field of orthopedic clinical treatment technology, and more specifically, to a layered and segmented bone cement spacer and its preparation method. Background Technology

[0002] Chronic osteomyelitis is a common and refractory infectious disease in orthopedic clinics. Its pathological characteristics include progressive infection, necrosis, and bone destruction of bone tissue, often accompanied by sinus tract formation, residual sequestrum, and recurrent episodes. The core of its treatment lies in thoroughly removing the lesions, effectively controlling the infection, and creating a favorable biological and mechanical environment for subsequent bone defect repair. Since large-scale bone defects often result after the removal of osteomyelitis lesions, repairing these defects becomes a crucial aspect of treatment. Masquelet technique, also known as membrane induction technique, is a commonly used and effective treatment for chronic osteomyelitis with bone defects. Its core process is as follows: After the first-stage surgery thoroughly removes the lesion, antibiotic-inducing bone cement is used to fill the bone defect area to create a space. The sustained-release effect of the antibiotics in the bone cement continuously controls the local infection. At the same time, a biofilm with osteoinducing activity, namely the induction membrane, is induced to form between the bone cement and the surrounding soft tissue. After the infection is completely controlled and the induction membrane matures (usually 6-8 weeks), a second-stage surgery is performed to remove the antibiotic-inducing bone cement. Bone defect repair is then carried out in the intact cavity formed by the induction membrane. The blood supply of the induction membrane and osteoinducing factors promote the osteogenic process of the repair material, ultimately completing the regeneration and reconstruction of bone tissue.

[0003] Currently, the filling of antibiotic-impregnated bone cement in primary surgery often employs a monolithic filling method, where the prepared antibiotic-impregnated bone cement is filled into the lesion cavity in one go and compacted to completely fill the bone defect area. This filling method is simple to operate and meets the basic requirements of maintaining space and sustained antibiotic release, and is widely used in clinical practice. However, clinical practice has shown that this monolithic filling method has significant technical drawbacks in secondary surgery: because the bone cement and the induction membrane form a tight adhesion during the contact process that lasts for several weeks, the removal of the monolithic bone cement requires a large-scale forced peeling operation. This not only increases the difficulty and time of the surgery, increasing patient pain and surgical risks, but also easily pulls and tears the induction membrane during the peeling process, damaging the structural integrity of the induction membrane and thus affecting the blood supply support and bone induction environment for secondary bone defect repair. At the same time, the bone cement is prone to breakage during the forced peeling process, and the resulting small bone cement fragments may remain in the lesion cavity. These residual fragments, as foreign bodies, can trigger a persistent foreign body reaction, interfere with the bone healing process, and even become the core for bacterial adhesion, increasing the risk of infection recurrence. Furthermore, residual debris may affect the filling and integration of secondary repair materials, further reducing the success rate of surgical treatment.

[0004] Therefore, there is an urgent need for an optimized layered and segmented bone cement spacer and its preparation method. This method should address the technical problems of existing monolithic filling methods, such as difficult removal, easy damage to the induction membrane, and high risk of residue, while ensuring the spacer effect, antibiotic sustained-release capability, and quality of induction membrane formation. An ideal filling method should enable convenient and complete removal of bone cement during secondary surgery, maximizing the protection of the induction membrane's integrity while reducing the risk of bone cement residue. This would provide a more efficient and safer surgical approach for membrane-induced osteomyelitis treatment, improving patients' clinical prognosis and quality of life. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a layered and segmented bone cement spacer and its preparation method, thus solving the aforementioned problems.

[0006] (II) Technical Solution To achieve the above-mentioned objectives, the present invention provides the following technical solution: a layered and segmented bone cement spacer and its preparation method, applied to the primary surgery for chronic osteomyelitis of the long bones of the limbs, characterized in that, after thorough removal and disinfection of the lesion, antibiotic bone cement is filled using a layered filling method, the specific steps of which are as follows: S1: First thin layer filling step: Apply the prepared antibiotic bone cement in a thin layer and evenly fill the inner wall of the lesion cavity. Use a gentle pressing method to make the bone cement fully adhere to the bone wall, forming a thin layer of bone cement with a thickness controlled at 2-3mm. Ensure that the thin layer of bone cement completely covers the inner wall of the lesion cavity and adheres tightly to the normal bone cortex to avoid gaps. S2: Second layer of bone cement clump filling step: After the thin layer of bone cement described in step S1 has initially solidified, the remaining prepared antibiotic bone cement is kneaded into uniform bone cement clumps with a diameter controlled at 1-2 cm. The bone cement clumps are filled into the thin layer one by one. No force is required when filling. The bone cement clumps are gently attached to the inner wall of the thin layer, and a slight gap of 0.5-2 mm is maintained between the bone cement clumps and between the bone cement clumps and the thin layer, until the lesion cavity is completely filled. In step S1, the thickness of the bone cement thin layer is less than the diameter of the bone cement mass in step S2, and the setting time of the bone cement thin layer in step S1 is earlier than the setting time of the bone cement mass in step S2.

[0007] Preferably, in steps S1 to S2, the preparation process of the antibiotic bone cement includes: determining the type of sensitive antibiotic based on the results of preoperative bacterial culture and drug sensitivity testing, wherein the antibiotic includes one or more combinations of vancomycin, gentamicin, tobramycin, and cephalosporin antibiotics; mixing the antibiotic with the bone cement matrix and bone cement monomers at a ratio of 10%-15% of the total mass of the bone cement, wherein the mixing ratio of the bone cement matrix to the bone cement monomers is 2:1 to 3:1, the mixing time is 1-3 minutes, the mixing speed is 60-120 rpm, and the mixing temperature is controlled at 20℃-25℃ to ensure that the antibiotic bone cement has good mechanical strength and antibiotic sustained-release ability; the setting time of the antibiotic bone cement is controlled at 10-20 minutes, the initial setting strength reaches 5-10 MPa, and the final compressive strength reaches 60-80 MPa.

[0008] Preferably, in step S1, when filling the bone cement thin layer, the temperature of the inner wall of the lesion cavity is the normal human body temperature of 36℃-37℃, and the relative humidity is 40%-60%. A bone cement gun, scraper, or special applicator is used for uniform application. The application pressure is controlled at 0.5-2N, the application speed is 1-3cm² / s, the application angle is 30°-60° to the bone wall, and the application path is spiral or grid-like to ensure that the bone cement thin layer fully adheres to the bone wall, the thin layer thickness is uniform, the thickness error is controlled within ±0.3mm, and there are no localized areas that are too thick or too thin. The surface roughness Ra of the thin layer is controlled at 10-50μm to facilitate the adhesion of the induced membrane and subsequent separation. The coverage area of ​​the bone cement thin layer accounts for more than 95% of the total area of ​​the inner wall of the lesion cavity, and the interfacial bonding strength between the thin layer and the bone wall reaches 0.5-2MPa.

[0009] Preferably, the preliminary solidification in step S1 refers to the time within 8-18 minutes after the bone cement is mixed, when the surface of the bone cement has solidified, feels slightly elastic to the touch, but still retains a certain degree of toughness internally. At this time, the temperature of the bone cement rises to 40℃-50℃, the polymerization reaction reaches 60%-80% completion, the compressive strength reaches 30%-50% of the initial strength, the flexural strength reaches 40%-60% of the initial strength, and the surface hardness reaches Shore D50-D70. Filling the bone cement lumps in step S2 under this state can prevent the lumps from completely fusing with the thin layer, ensuring that there is a separable interface between the lumps and the thin layer. The criteria for judging the preliminary solidification include: the bone cement surface is non-sticky, it does not spring back after being pressed, and it does not deform when contacted by instruments.

[0010] Preferably, in step S2, the bone cement clumps are prepared by molding or hand-rolling, with the clumps being spherical or polyhedral in shape, having a uniform particle size distribution, and a particle size variation coefficient (CV) of less than 10%. The surface of the clumps can be slightly roughened to control the surface roughness Ra at 20-80 μm, increasing the frictional stability between the clumps. During the filling process, the size of the clumps is adjusted according to the morphology of the lesion cavity. Small clumps with a diameter of 1-1.5 cm are used for irregular cavities, and large clumps with a diameter of 1.5-2 cm are used for regular cavities, with a ratio of 3:7 to 5:5 between the large and small clumps. After filling, the clumps are arranged evenly by gently tapping or vibrating, with a vibration frequency of 20-50 Hz, a vibration time of 5-10 seconds, and a vibration amplitude of 0.5-2 mm, to further optimize the gap distribution between the clumps and make the gap width uniform. The filling density of the bone cement clumps reaches more than 90% of the lesion cavity volume, and the number of contact points between the clumps is 3-8 per clump.

[0011] Preferably, the method further includes step S0: a pretreatment step for the lesion cavity, which is performed before step S1, specifically including: high-pressure pulse irrigation of the lesion cavity using a pulse irrigation system, with an irrigation pressure of 50-100 psi, a pulse frequency of 10-20 Hz, an irrigation time of 3-5 minutes, and an irrigation solution of physiological saline combined with a sensitive antibiotic solution at a concentration of 1-5 mg / mL, and an irrigation solution temperature of 37℃-40℃, to remove inflammatory tissue debris and necrotic bone tissue; and the use of iodine solution or peroxide... Disinfect by soaking in hydrogen peroxide solution for 3-5 minutes at a temperature of 37℃-40℃, with iodine concentration of 0.5%-1% and hydrogen peroxide concentration of 1%-3%. Use ultrasonic cleaning to assist disinfection, with an ultrasonic frequency of 40-60kHz, ultrasonic power of 100-300W, and ultrasonic time of 2-5 minutes. Use a negative pressure suction device to remove residual liquid from the cavity, with a negative pressure of 0.04-0.08MPa and suction time of 1-2 minutes, ensuring the cavity is dry and clean before bone cement filling, with residual liquid volume less than 0.1mL.

[0012] Preferably, the lesion cavity is a bone defect area formed after debridement of chronic osteomyelitis of the long bones of the limbs, including the tibia, femur, humerus, radius, ulna, and fibula. The lesion cavity is irregular, tunnel-like, bifurcated, or multilocular, with a depth of 2-15 cm, a width of 1-8 cm, a volume of 5-200 cm³, a depth-to-width ratio of 1:1 to 5:1, and serrated or smooth edges. During filling, the thickness of the thin layer and the number of lumps are adjusted according to the cavity morphology. For deep and long cavities with a depth-to-width ratio greater than 3:1, a segmented filling method is adopted, with each segment having a depth of 2-4 cm. It is ensured that the bone cement spacer completely fills the cavity, with the spacer volume accounting for more than 95% of the total volume of the lesion cavity and the contact area between the spacer and the bone wall accounting for more than 90% of the total bone wall area.

[0013] Preferably, the method includes performing step S1 at least once before performing step S2, or performing a combination of steps S1 and S2 at least once before performing the final filling step; for multi-chambered lesions, after performing step S1 to form an independent thin layer in each chamber, step S2 is then performed in each chamber to fill with bone cement blocks, forming a multi-unit layered filling structure, with a spacing thickness of 1-3 mm between chambers; for tunnel-like defects, steps S1 and S2 are performed sequentially along the tunnel axis to form a segmented filling structure, with each segment being 2-5 cm long and the gap between segments being 1-2 mm; for bifurcated defects, after performing steps S1 and S2 in the main trunk, steps S1 and S2 are performed in each branch to form a tree-like layered filling structure.

[0014] Preferably, the thin layer of bone cement in step S1 and the bone cement clumps in step S2 can be bone cements with different antibiotic formulations. The antibiotic concentration in the thin layer of bone cement accounts for 12%-15% of the bone cement mass, which is higher than the antibiotic concentration in the clump of bone cement, which accounts for 10%-12% of the bone cement mass, to enhance the anti-infection ability of the contact area with the bone interface. The antibiotic concentration gradient is 2%-3%. A contrast agent, such as barium sulfate or zirconium oxide, can also be added to the thin layer of bone cement, accounting for 5%-10% of the total bone cement mass. The contrast agent particle size is 1-10 μm, and the uniformity of the contrast agent distribution is greater than 9. 0%, used for postoperative X-ray or CT imaging follow-up to assess bone cement occupancy, thin-layer integrity, and changes in mass gaps; bone-inducing growth factors may be added to the bone cement mass, including one or more of BMP-2, BMP-7, and TGF-β, at a concentration of 0.1-1.0 mg / g bone cement, with a growth factor sustained-release period of 2-4 weeks; different colored food colorings may also be added to the thin-layer bone cement and the mass bone cement for intraoperative differentiation, with blue coloring added to the thin-layer bone cement and white coloring added to the mass bone cement, at a concentration of 0.01%-0.05%.

[0015] Preferably, the method further includes a second-stage surgical procedure for bone cement removal: During the second-stage surgery, after the induction membrane has formed for 6-8 weeks, a special pry bar, periosteal elevator, or ultrasonic bone scalpel is used to gently pry along the interface between the thin layer of bone cement and the induction membrane. The prying force is controlled at 5-15N, the prying angle is 15°-30° with the bone wall, and the prying frequency is 1-2 times / second, so that the thin layer and the induction membrane are separated, and the separation interface is clear and complete. Subsequently, the internal bone cement clumps are removed one by one using nucleus pulposus forceps, long forceps, or a suction device. The removal order is from the central area first and then the peripheral area, or from the superficial area first and then the deep area, and the removal force is controlled at 10-30N. During the removal process, the thin layer of bone cement acts as a buffer layer to protect the induction membrane from direct contact damage by instruments, and the integrity rate of the induction membrane is greater than 95%. The bone cement clumps Slight gaps between the blocks facilitate instrument insertion and block separation. The gap width is 0.5-2mm, and the instrument insertion depth is 1 / 3-1 / 2 of the block diameter. Ensure that the bone cement is completely removed without any fragments remaining, with the amount of bone cement fragments remaining less than 0.1g. Ensure that the induction membrane is not torn and maintain a thickness of 2-5mm. After removal, fill the induction membrane with bone defect repair material. The repair material includes one or more combinations of autologous cancellous bone, autologous cortical bone, allogeneic bone, decalcified bone matrix, bone morphogenetic protein, calcium phosphate bone cement, and calcium sulfate bone cement. The particle size of the repair material is 1-5mm, and the filling volume of the repair material accounts for 80%-120% of the bone defect volume. The filling pressure is controlled at 1-5N. After filling, the induction membrane is completely sutured with a suture spacing of 3-5mm.

[0016] (III) Beneficial Effects Compared with the prior art, the present invention provides a layered and segmented bone cement spacer and its preparation method, which has the following beneficial effects: This invention relates to a layered and segmented bone cement spacer and its preparation method. It adopts a layered filling method of thin layer + block. The thin layer and the block are not completely fused, and there are slight gaps between the blocks. In the second-stage surgery, the thin layer can be pried apart from the induction membrane first, and then the blocks can be removed one by one without forced peeling. This greatly reduces the difficulty of removal, shortens the operation time, and reduces the intensity of surgical operation.

[0017] This invention relates to a layered and segmented bone cement spacer and its preparation method. The thin layer can serve as a buffer layer, reducing direct contact between instruments and the induction membrane during the removal process. The block-type removal avoids large-area dissection operations, effectively preventing traction and tearing of the induction membrane, ensuring the structural integrity of the induction membrane, and providing a good bone induction environment for secondary bone defect repair.

[0018] This invention relates to a layered and segmented bone cement spacer and its preparation method. The thin layer can uniformly cover the lesion cavity, ensuring slow and continuous release of antibiotics and effectively controlling infection. The internal block filling can fully occupy the lesion cavity, providing stable mechanical support for the formation of the induced membrane. Compared with the traditional monolithic filling method, the anti-infection effect and the quality of induced membrane formation are not affected.

[0019] This invention relates to a layered and segmented bone cement locator and its preparation method. The bone cement locators are of uniform size and can be examined and removed one by one. This effectively avoids bone cement fragments remaining in the lesion cavity, reduces the risk of foreign body reaction and infection recurrence caused by residual bone cement, and improves the safety and effectiveness of treatment. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the method structure of the present invention. Detailed Implementation

[0021] 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.

[0022] Please see Figure 1 The present invention provides a technical solution: A layered and segmented bone cement spacer and its preparation method are disclosed. The spacer adopts a two-layer spatial configuration of an outer thin layer and an inner block, forming a composite spacer structure with specific mechanical properties and separation characteristics.

[0023] The 2-3 mm thick bone cement layer formed in step S1 has the core function of constructing a controllable bone-bone cement interface and a bone cement-induction membrane interface.

[0024] During thin-layer filling, a gentle pressing motion is used to ensure the bone cement fully penetrates the microscopic irregular structure of the bone wall. A micromechanical interlock forms between the bone cement and the bone cortex, with an interfacial bonding strength of 0.5-2 MPa. This moderate bonding strength ensures the stability of the thin layer during induction membrane formation without causing difficulties in separation during the second-stage surgery. The surface roughness Ra of the thin layer is controlled within 10-50 μm. This specific range of roughness serves a dual purpose: firstly, it provides a suitable adhesion substrate for the induction membrane, promoting the adhesion and proliferation of fibroblasts and vascular endothelial cells; secondly, it avoids excessive adhesion, ensuring clear separation along the interface during the second-stage surgery.

[0025] The thin layer completely covers the inner wall of the lesion cavity, forming a dense physical barrier. This barrier effectively isolates the bone cement mass from direct contact with the bone wall, preventing adhesion between the mass and bone tissue. Simultaneously, during the second-stage surgery to remove the bone cement, the thin layer acts as a buffer, evenly distributing the leverage force and preventing direct contact between instrument tips and the induction membrane. The thickness of the thin layer is designed to be 2-3 mm, an optimization based on mechanical balance: a thickness less than 2 mm results in insufficient strength and a high risk of breakage during removal; a thickness greater than 3 mm occupies too much cavity space, affecting the mass's filling volume and potentially increasing the adhesion area with the induction membrane.

[0026] The core function of the 1-2cm diameter bone cement mass in step S2 is to realize the construction of a separable locator and a directional extraction path.

[0027] The 0.5-2mm gaps between the clumps and between the clumps and the thin layer serve multiple physical purposes. First, the gaps provide operational space for instrument insertion during the secondary surgery, allowing instruments to penetrate deep into the clumps and apply separation force. Second, the gaps ensure point contact rather than surface contact between the clumps, with 3-8 contact points per clump. This point contact pattern significantly reduces the bonding force between the clumps, allowing them to be removed one by one without complete dissection. Third, the gaps provide continuous space for the formation of the induction membrane, which can grow along the clump surface and gaps, forming finger-like protrusions that match the clump morphology. This structure increases the contact area between the induction membrane and the bone cement without increasing adhesion strength, instead providing a natural separation interface during secondary removal.

[0028] The diameter of the mass is controlled within 1-2 cm, based on a balance between surgical convenience and biomechanical stability. A diameter less than 1 cm results in an excessive number of masses, low filling efficiency, and a tendency for displacement during the filling process; a diameter greater than 2 cm results in excessively large masses, making it difficult to adapt to irregular cavities, and making it difficult to uniformly control the gaps between masses. A coefficient of variation (CV) of less than 10% ensures consistent mass size, uniform gap distribution, and stable mechanical properties.

[0029] The polymerization reaction of bone cement is an exothermic process, which goes through four stages: the flow stage, the viscosity stage, the curing stage, and the hardening stage. This invention precisely utilizes the time window of the initial stage of the curing stage.

[0030] The thin layer of bone cement formed in step S1 reaches a preliminary solidification state within 8-18 minutes after mixing. At this point, the surface of the bone cement has hardened, feels slightly elastic to the touch but still retains a certain degree of toughness internally, the polymerization reaction is 60%-80% complete, the temperature rises to 40℃-50℃, and the compressive strength reaches 30%-50% of the initial strength. This specific state is defined as preliminary solidification.

[0031] After the thin layer reaches a preliminary solidification state, the filling mass is introduced. At this point, the surface of the thin layer has lost its adhesiveness but has not yet reached a fully hardened, brittle state. The filling mass comes into contact with the thin layer, but because the thin layer's surface is non-adhesive, no chemical bonding or strong physical adhesion occurs between them. The polymerization reaction of the mass itself proceeds independently, ultimately forming an interface with the thin layer only through weak mechanical interlocking. The bonding strength of this interface is far lower than the cohesive strength of the bone cement itself, allowing for separation under low stress during the secondary surgery.

[0032] The thin layer solidifies before the clump, with a time difference of approximately 5-10 minutes. This time difference is designed to ensure that if the time difference is too short (<5 minutes), the thin layer has not yet reached initial solidification, and the clump will fuse with the thin layer to form a whole structure when filling, thus losing the purpose of layering; if the time difference is too long (>15 minutes), the thin layer has already hardened completely, the surface is too smooth, the gap between the clump and the thin layer is difficult to control, and the thin layer may develop microcracks due to shrinkage.

[0033] The design of the thin layer thickness (2-3mm) being smaller than the agglomerate diameter (1-2cm) ensures that the thin layer completes the polymerization reaction before the agglomerate, because the thin layer has a small volume and heats up quickly, resulting in a higher polymerization reaction rate than the large agglomerate.

[0034] The antibiotic concentration in thin-layer bone cement (12%-15%) is higher than that in bulk bone cement (10%-12%), forming a concentration gradient of 2%-3%. Based on the spatial distribution characteristics of tissue infection risk, the bone-cement interface is a high-risk area for infection recurrence, requiring a higher antibiotic concentration to kill any remaining pathogens; while the risk of infection in the central cavity area is relatively low, and the antibiotic concentration can be appropriately reduced to ensure the mechanical properties of the bulk.

[0035] Initial rapid release (burst release effect) kills residual bacteria in the early postoperative period, while slow and continuous release maintains an effective concentration in the later stages. Thin layers, due to their large surface area and small thickness, release antibiotics at a faster rate than clumps, providing higher local antibiotic concentrations during the critical postoperative period. Clumps, on the other hand, serve as an antibiotic reservoir, continuously releasing antibiotics during the induction of membrane formation to maintain anti-infection efficacy.

[0036] The barium sulfate or zirconium oxide contrast agent (5%-10%) added to the thin layer has a high X-ray absorption coefficient, and the position, integrity, and gap between the thin layer and the mass can be clearly shown during postoperative X-ray or CT follow-up imaging. Through imaging evaluation, it can be determined whether the bone cement mass has shifted, whether the thin layer is intact, and whether the gap between the masses has changed, providing a basis for selecting the timing of secondary surgery.

[0037] The induced membrane is a connective tissue membrane composed of fibroblasts, collagen fibers, and new blood vessels, and its formation depends on a suitable physical template. The surface roughness Ra of the thin layer is controlled between 10-50 μm, providing a suitable adhesion substrate for fibroblasts. Cells exhibit superior adhesion, proliferation, and differentiation activity on microscopically rough surfaces compared to smooth surfaces. Simultaneously, the presence of the thin layer allows the induced membrane to grow regularly along its surface, forming a uniformly thick (2-5 mm) and structurally intact induced membrane.

[0038] The gaps (0.5-2 mm) between the clumps provide a physical channel for the growth of new blood vessels. Vascular endothelial cells can grow inward along these gaps, forming a capillary network that penetrates the induction membrane, enhancing blood supply and nutrient exchange within the membrane. This increased vascularization facilitates the secretion of osteoinducing factors by the induction membrane, creating a favorable biological environment for secondary bone defect repair.

[0039] During the second-stage surgery to remove bone cement, a thin layer acts as a buffer, evenly distributing the leverage force and preventing instruments from directly contacting and tearing the induction membrane. Simultaneously, the gaps between the clumps allow for precise instrument insertion and separation, eliminating the need for extensive dissection and maximizing the preservation of the induction membrane's integrity. The technical indicator of an induction membrane integrity rate exceeding 95% directly reflects this spatial buffering principle.

[0040] During the second-stage surgery, the thin layer is first pried along the interface between it and the induction membrane. Since the bonding force between the thin layer and the induction membrane (mainly physical adsorption and weak bioadhesion) is much smaller than the bonding force between the thin layer and the mass, and the thin layer has a certain mechanical strength (compressive strength reaches 30%-50% of the initial strength), the thin layer and the induction membrane can be completely separated during prying without the thin layer itself breaking.

[0041] After thin-layer separation, the internal clumps are fully exposed. The gaps between the clumps provide a clear insertion point and separation direction for the instrument. Removal follows a sequence from the center to the edge or from the shallow layer to the deep layer, allowing the clumps to be removed one by one along the gaps without interference. The instrument insertion depth is 1 / 3 to 1 / 2 of the clump diameter; this depth provides sufficient leverage while avoiding over-insertion that could damage the contralateral induction membrane.

[0042] When removing bone cement using the traditional whole-piece filling method, the large-area adhesion between the bone cement and the induction membrane makes forced separation prone to fragmentation. The small size (1-2 cm in diameter) and independent nature of the clumps mean that stress is concentrated at the point of contact during removal, reducing the likelihood of fragmentation. Even if individual clumps break during removal, the fragments are small and can be completely removed by instruments or flushed away, with the residual amount controlled to below 0.1 g.

[0043] The defects after the removal of lesions from chronic osteomyelitis of the long bones of the limbs have diverse shapes. This invention achieves adaptive filling of defects of different shapes through the flexible combination of layered structures.

[0044] For deep and elongated cavities with a depth-to-width ratio greater than 3:1, a segmented filling method is adopted, with each segment 2-4 cm deep. The principle of segmented filling is that if deep and elongated cavities are filled in one go, deep masses are difficult to handle, and thin layers are difficult to apply evenly; segmented filling can transform deep problems into shallow problems, ensuring the quality of each thin layer and mass. A gap of 1-2 mm is maintained between segments to provide a path for instruments to enter the deeper parts in the second stage of surgery.

[0045] Multilocular defects have multiple interconnected cavities. If the entire cavity is filled, the narrow passages between the cavities will become obstacles to removal. This invention employs a method of performing steps S1 and S2 separately within each cavity to form a multi-unit layered filling structure. Each cavity forms an independent thin-layer + mass unit, with thin layers separating the units. The thickness of the gaps between the cavities is 1-3 mm. During the second-stage surgery, bone cement can be removed from each cavity separately without affecting the others.

[0046] Bifurcation defects have a tree-like structure with a trunk and branches. In this invention, after performing steps S1 and S2 on the trunk, steps S1 and S2 are performed on each branch separately, forming a tree-like layered filling structure. This structure conforms to the anatomical shape of the defect, ensuring sufficient space for each branch while maintaining connectivity between the branches and the trunk, facilitating sequential removal during secondary surgery.

[0047] The bone-inducing growth factors (BMP-2, BMP-7, TGF-β, etc.) added to the bulk bone cement work on the principle of diffusion control of the sustained-release carrier.

[0048] The concentration of growth factors added is 0.1-1.0 mg / g bone cement, with a sustained-release period of 2-4 weeks. This release period matches the formation time of the induced membrane: the initial formation period of the induced membrane is within 2 weeks after surgery, during which growth factors promote fibroblast proliferation and collagen synthesis; the maturation period of the induced membrane is 2-4 weeks after surgery, during which growth factors promote angiogenesis and the secretion of osteoinductive active factors.

[0049] Growth factors were added only to the bone cement mass, not to the thin layer. This design is based on the principle that the mass, located in the central region of the cavity, allows the released growth factors to be evenly distributed throughout the entire induced membrane cavity; if growth factors were also added to the thin layer, excessively high local concentrations might lead to overgrowth or fibrosis of the induced membrane. The selective release and spatial distribution regulation of growth factors are achieved through the bilayer structure.

[0050] Thin-layer bone cement is supplemented with blue pigment, and bulk bone cement is supplemented with white pigment (concentration 0.01%-0.05%). Its working principle is based on color contrast enhancement for intraoperative identification.

[0051] The blue thin layer contrasts sharply with the white clump, allowing the surgeon to visually identify the boundary between the thin layer and the clump, ensuring that the thin layer is not damaged during clump filling, and accurately separating along the thin layer interface during the second-stage surgery.

[0052] By comparing colors, the surgeon can determine whether the lesion cavity is completely filled: if a thin blue layer is exposed between the white clumps, it means that the filling is insufficient and clumps need to be added; if the thin blue layer is completely covered by the white clumps, it means that the filling is sufficient.

[0053] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A layered and segmented bone cement spacer and its preparation method, applied to primary surgery for chronic osteomyelitis of the long bones of the limbs, characterized in that... After thorough removal and disinfection of the lesion, antibiotic-impregnated bone cement was applied using a layered filling method. The specific steps are as follows: S1: First thin layer filling step: Apply the prepared antibiotic bone cement in a thin layer and evenly fill the inner wall of the lesion cavity. Use a gentle pressing method to make the bone cement fully adhere to the bone wall, forming a thin layer of bone cement with a thickness controlled at 2-3mm. Ensure that the thin layer of bone cement completely covers the inner wall of the lesion cavity and adheres tightly to the normal bone cortex to avoid gaps. S2: Second layer of bone cement clump filling step: After the thin layer of bone cement described in step S1 has initially solidified, the remaining prepared antibiotic bone cement is kneaded into uniform bone cement clumps with a diameter controlled at 1-2 cm. The bone cement clumps are filled into the thin layer one by one. No force is required when filling. The bone cement clumps are gently attached to the inner wall of the thin layer, and a slight gap of 0.5-2 mm is maintained between the bone cement clumps and between the bone cement clumps and the thin layer, until the lesion cavity is completely filled. In step S1, the thickness of the bone cement thin layer is less than the diameter of the bone cement mass in step S2, and the setting time of the bone cement thin layer in step S1 is earlier than the setting time of the bone cement mass in step S2.

2. The layered and segmented bone cement spacer and its preparation method according to claim 1, characterized in that, In steps S1 to S2, the preparation process of the antibiotic bone cement includes: determining the types of sensitive antibiotics based on preoperative bacterial culture and drug sensitivity test results, wherein the antibiotics include one or more combinations of vancomycin, gentamicin, tobramycin, and cephalosporin antibiotics; mixing the antibiotics with the bone cement matrix and bone cement monomers at a ratio of 10%-15% of the total mass of the bone cement, wherein the mixing ratio of the bone cement matrix to the bone cement monomers is 2:1 to 3:1, the mixing time is 1-3 minutes, the mixing speed is 60-120 rpm, and the mixing temperature is controlled at 20℃-25℃ to ensure that the antibiotic bone cement has good mechanical strength and antibiotic sustained-release ability; the setting time of the antibiotic bone cement is controlled at 10-20 minutes, the initial setting strength reaches 5-10 MPa, and the final compressive strength reaches 60-80 MPa.

3. The layered and segmented bone cement spacer and its preparation method according to claim 1, characterized in that, In step S1, when filling the bone cement thin layer, the temperature of the inner wall of the lesion cavity is the normal human body temperature of 36℃-37℃, and the relative humidity is 40%-60%. A bone cement gun, scraper, or special applicator is used for uniform application. The application pressure is controlled at 0.5-2N, the application speed is 1-3cm² / s, the application angle is 30°-60° to the bone wall, and the application path is spiral or grid-like to ensure that the bone cement thin layer fully adheres to the bone wall, the thin layer thickness is uniform, the thickness error is controlled within ±0.3mm, and there are no localized areas that are too thick or too thin. The surface roughness Ra of the thin layer is controlled at 10-50μm to facilitate the adhesion of the induction membrane and subsequent separation. The coverage area of ​​the bone cement thin layer accounts for more than 95% of the total area of ​​the inner wall of the lesion cavity, and the interfacial bonding strength between the thin layer and the bone wall reaches 0.5-2MPa.

4. The layered and segmented bone cement spacer and its preparation method according to claim 1, characterized in that, The initial solidification mentioned in step S1 refers to the time within 8-18 minutes after the bone cement is mixed, when the surface of the bone cement has solidified, feels slightly elastic to the touch, but still retains a certain degree of toughness inside. At this time, the temperature of the bone cement rises to 40℃-50℃, the polymerization reaction reaches 60%-80% completion, the compressive strength reaches 30%-50% of the initial strength, the flexural strength reaches 40%-60% of the initial strength, and the surface hardness reaches Shore D50-D70. Filling the bone cement lumps in step S2 under this state can prevent the lumps from completely fusing with the thin layer, ensuring that there is a separable interface between the lumps and the thin layer. The criteria for judging preliminary solidification include: the bone cement surface is not sticky, it does not spring back after being pressed, and it does not deform when contacted by instruments.

5. The layered and segmented bone cement spacer and its preparation method according to claim 1, characterized in that, In step S2, the bone cement clumps are prepared by molding or hand-rolling. The clumps are spherical or polyhedral in shape, with uniform particle size distribution and a particle size variation coefficient (CV) of less than 10%. The surface of the clumps can be slightly roughened to control the surface roughness Ra at 20-80 μm, increasing the frictional stability between the clumps. During the filling process, the size of the clumps is adjusted according to the morphology of the lesion cavity. Small clumps with a diameter of 1-1.5 cm are used for irregular cavities, and large clumps with a diameter of 1.5-2 cm are used for regular cavities, with a ratio of 3:7 to 5:5 between large and small clumps. After filling, the clumps are evenly arranged by gently tapping or vibrating. The vibration frequency is 20-50 Hz, the vibration time is 5-10 seconds, and the vibration amplitude is 0.5-2 mm, further optimizing the gap distribution between the clumps and making the gap width uniform. The filling density of the bone cement clumps reaches more than 90% of the lesion cavity volume, and the number of contact points between the clumps is 3-8 per clump.

6. The layered and segmented bone cement spacer and its preparation method according to claim 1, characterized in that, The method further includes step S0: a pretreatment step for the lesion cavity, which is performed before step S1. Specifically, this pretreatment step includes: high-pressure pulse irrigation of the lesion cavity using a pulse irrigation system, with an irrigation pressure of 50-100 psi, a pulse frequency of 10-20 Hz, and an irrigation time of 3-5 minutes. The irrigation fluid is physiological saline combined with a sensitive antibiotic solution, with an antibiotic concentration of 1-5 mg / mL and an irrigation fluid temperature of 37℃-40℃, to remove inflammatory tissue debris and necrotic bone tissue; and the use of iodine solution or hydrogen peroxide... Immerse in the solution for 3-5 minutes for disinfection. The temperature of the disinfectant solution should be 37℃-40℃, the concentration of iodine should be 0.5%-1%, and the concentration of hydrogen peroxide should be 1%-3%. Use ultrasonic cleaning to assist disinfection. The ultrasonic frequency should be 40-60kHz, the ultrasonic power should be 100-300W, and the ultrasonic time should be 2-5 minutes. Use a negative pressure suction device to dry the residual liquid in the cavity. The negative pressure should be 0.04-0.08MPa, and the suction time should be 1-2 minutes to ensure that the cavity is dry and clean before bone cement filling, and the amount of residual liquid in the cavity is less than 0.1mL.

7. The layered and segmented bone cement spacer and its preparation method according to claim 1, characterized in that, The lesion cavity refers to the bone defect area formed after debridement of chronic osteomyelitis of the long bones of the limbs, including the tibia, femur, humerus, radius, ulna, and fibula. The lesion cavity is irregular, tunnel-like, bifurcated, or multilocular, with a depth of 2-15 cm, a width of 1-8 cm, a volume of 5-200 cm³, a depth-to-width ratio of 1:1 to 5:1, and serrated or smooth edges. During the filling process, the thickness of the thin layer and the number of lumps are adjusted according to the cavity morphology. For deep and long cavities with a depth-to-width ratio greater than 3:1, a segmented filling method is adopted, with each segment having a depth of 2-4 cm. It is ensured that the bone cement spacer completely fills the cavity, with the spacer volume accounting for more than 95% of the total volume of the lesion cavity and the contact area between the spacer and the bone wall accounting for more than 90% of the total bone wall area.

8. The layered and segmented bone cement spacer and its preparation method according to claim 1, characterized in that, The method includes performing step S1 at least once before performing step S2, or performing a combination of steps S1 and S2 at least once before performing the final filling step; for multi-chambered lesions, after performing step S1 to form an independent thin layer in each chamber, step S2 is then performed in each chamber to fill with bone cement blocks, forming a multi-unit layered filling structure, with a spacing thickness of 1-3 mm between chambers; for tunnel-like defects, steps S1 and S2 are performed sequentially along the tunnel axis to form a segmented filling structure, with each segment being 2-5 cm long and the gap between segments being 1-2 mm; for bifurcated defects, after performing steps S1 and S2 in the main trunk, steps S1 and S2 are performed in each branch to form a tree-like layered filling structure.

9. The layered and segmented bone cement spacer and its preparation method according to claim 1, characterized in that, The thin layer of bone cement mentioned in step S1 and the bone cement clumps mentioned in step S2 can use bone cement with different antibiotic formulations. The antibiotic concentration in the thin layer of bone cement accounts for 12%-15% of the bone cement mass, which is higher than the antibiotic concentration in the clump of bone cement, which accounts for 10%-12% of the bone cement mass, in order to enhance the anti-infection ability of the contact area with the bone interface. The antibiotic concentration gradient is 2%-3%. A contrast agent component may also be added to the thin layer of bone cement. The contrast agent is barium sulfate or zirconium oxide, accounting for 5%-10% of the total mass of bone cement. The particle size of the contrast agent is 1-10 μm, and the uniformity of the contrast agent distribution is greater than 90%. This material is used for postoperative X-ray or CT imaging follow-up to assess bone cement occupancy, thin-layer integrity, and changes in mass gaps. Bone-inducing growth factors, including one or more of BMP-2, BMP-7, and TGF-β, can be added to the bone cement mass at a concentration of 0.1-1.0 mg / g bone cement, with a sustained-release period of 2-4 weeks. Different colored food colorings can also be added to the thin-layer bone cement and the mass bone cement for intraoperative differentiation; blue coloring is added to the thin-layer bone cement, and white coloring to the mass bone cement, at a concentration of 0.01%-0.05%.

10. The layered and segmented bone cement spacer and its preparation method according to any one of claims 1 to 9, characterized in that, The method also includes a second-stage surgical procedure for bone cement removal: During the second-stage surgery, after the induction membrane has formed for 6-8 weeks, a special pry bar, periosteal elevator, or ultrasonic bone scalpel is used to gently pry along the interface between the thin layer of bone cement and the induction membrane. The prying force is controlled at 5-15N, the prying angle is 15°-30° with the bone wall, and the prying frequency is 1-2 times / second, so that the thin layer is separated from the induction membrane, and the separation interface is clear and complete. Subsequently, the internal bone cement clumps are removed one by one using nucleus pulposus forceps, long forceps, or a suction device. The removal order is from the central area to the peripheral area, or from the superficial area to the deep area, and the removal force is controlled at 10-30N. During the removal process, the thin layer of bone cement acts as a buffer layer to protect the induction membrane from direct contact damage by instruments, and the integrity rate of the induction membrane is greater than 95%. The bone cement clumps are... A slight gap is maintained between the bone cement and the clump to facilitate instrument insertion and clump separation. The gap width is 0.5-2 mm, and the instrument insertion depth is 1 / 3-1 / 2 of the clump diameter. Ensure complete removal of bone cement without any fragments remaining (less than 0.1 g), and maintain the induction membrane without tearing, with a membrane thickness of 2-5 mm. After removal, the induction membrane is filled with bone defect repair material, including one or more combinations of autologous cancellous bone, autologous cortical bone, allogeneic bone, decalcified bone matrix, bone morphogenetic protein, calcium phosphate bone cement, and calcium sulfate bone cement. The particle size of the repair material is 1-5 mm, and the filling volume accounts for 80%-120% of the bone defect volume. The filling pressure is controlled at 1-5 N. After filling, the induction membrane is completely sutured with a suture spacing of 3-5 mm.

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