Novel degradable cervical fusion cage and preparation method thereof

Abstract

The invention discloses a novel degradable cervical fusion cage and a preparation method thereof. The fusion cage is made of carboxylated silk protein, and barium titanate is added into the carboxylated silk protein. The cervical fusion cage is obtained by injecting a raw material solution into a porous mold, standing, curing with methanol, replacing methanol and machining. The prepared novel cervical fusion cage has the advantages of being good in biological tissue compatibility, similar to human cancellous bone in elasticity modulus and compression strength and the like, also has the effects of being biodegradable, promoting osteogenic activity through the piezoelectric effect, facilitating fusion of cervical vertebra and hooked vertebra joints and the like, and has wide clinical application prospects.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of intervertebral fusion and internal fixation, and particularly relates to a novel degradable cervical vertebra fusion device and a preparation method thereof. BACKGROUND

[0002] Intervertebral fusion devices mainly include metal fusion devices and non-metal fusion devices. The non-metal fusion devices can be divided into bio-inabsorbable fusion devices and bio-absorbable fusion devices. The non-absorbable non-metal fusion devices represented by carbon fibers and polyether ether ketone have good X-ray transparency, elastic modulus and biomechanical properties, but still cannot solve the problems of foreign body retention, sterile inflammation and lack of biological activity. The absorbable non-metal fusion devices represented by polylactic acid have the characteristics of degradable absorption and good biocompatibility, but the fusion with tissues and the mechanical properties are limited, which restricts the clinical application of the fusion devices. SUMMARY

[0003] In view of the defects or deficiencies of the prior art, the present application provides a novel degradable cervical vertebra fusion device.

[0004] The material of the novel degradable cervical vertebra fusion device provided by the present application is carboxylated silk fibroin, and barium titanate is added to the carboxylated silk fibroin.

[0005] Optionally, the cervical vertebra fusion device body is an elliptical sheet, and a cervical vertebra hook-vertebra joint fusion hole is formed at each end of the long axis of the elliptical sheet, and the axial direction of the cervical vertebra hook-vertebra joint fusion hole is perpendicular to the axial direction of the long axis of the elliptical sheet. Meanwhile, the long axis of the elliptical sheet is outwardly protruded along the axial direction of the long axis to form a lug structure at each end of the long axis. A vertebral body fusion hole is formed between the two cervical vertebra hook-vertebra joint fusion holes, and the axial direction of the vertebral body fusion hole is parallel to the axial direction of the cervical vertebra hook-vertebra joint fusion hole. The diameter of the vertebral body fusion hole is larger than the diameter of the cervical vertebra hook-vertebra joint fusion hole.

[0006] Optionally, the cervical vertebra hook-vertebra joint fusion hole and the vertebral body fusion hole are both circular.

[0007] Optionally, an image marker material mounting hole is further formed in the body of the cervical vertebra fusion device.

[0008] Alternatively, the cervical vertebra fusion device body is a rounded rectangular cross section and a trapezoidal longitudinal section, two vertebral fusion holes are formed on the cervical vertebra fusion device body, the vertebral fusion holes are longitudinally formed, and the two vertebral fusion holes are distributed along the length direction of the rounded rectangular shape, and a connecting body is arranged between the two vertebral fusion holes, hook-vertebral joint fusion holes are formed on the side walls of the two vertebral fusion holes, and the two hook-vertebral joint fusion holes are distributed along the length direction of the rounded rectangular shape of the cervical vertebra fusion device body and are far away from each other. Further, a process hole is formed on the connecting body. The vertebral fusion hole is a rounded rectangular shape, and the cross section of the hook-vertebral joint fusion hole is a rectangular shape.

[0009] The application also provides a preparation method of the cervical vertebra fusion device, and the method comprises the following steps:

[0010] 1) Dissolve the carboxylated silk protein freeze-dried powder in the barium titanate hexafluoroisopropanol suspension solution to obtain a carboxylated silk protein barium titanate hexafluoroisopropanol suspension solution;

[0011] 2) Inject the suspension solution into a porous mold, place the porous mold in methanol for solidification after releasing the bubbles to obtain a barium titanate carboxylated silk protein solid; the porous mold comprises a mold body, and a cavity is arranged in the mold body, and a plurality of micropores are formed on the side wall and the bottom surface of the cavity;

[0012] 3) Then remove the mold and sequentially place the barium titanate carboxylated silk protein solid in methanol aqueous solution and water with gradually decreasing concentrations, and obtain a carboxylated silk protein bulk material after replacing the methanol;

[0013] 4) Use a mechanical processing method to process the above silk protein bulk material into a cervical vertebra fusion device.

[0014] Further, in step 1), the mass-volume ratio of the barium titanate and the hexafluoroisopropanol is 1g:(1-100)ml; and the mass-volume ratio of the carboxylated silk protein freeze-dried powder and the barium titanate hexafluoroisopropanol solution is 1g:(1-10)ml.

[0015] Optionally, the mold comprises a cylindrical vessel and a top cover, the cylindrical vessel is internally provided with a cylindrical cavity, the top of the cavity is open, a plurality of micro-holes are arranged on the side wall of the cavity, the micro-holes in each circle are distributed at equal intervals in the circumferential direction, the micro-holes in different circles are distributed at intervals in the circumferential direction, and the micro-holes in different circles are distributed at intervals in the circumferential direction, and the micro-holes in different circles are distributed at intervals in the circumferential direction. The bottom plate of the cavity is provided with a plurality of micro-holes, and the micro-holes in each circle are distributed at equal intervals around the center of the bottom plate. The micro-holes in each circle are distributed at equal intervals, and the micro-holes in different circles are distributed at intervals in the circumferential direction. Further, the diameter of the micro-hole is 0.5mm. The standing temperature is 0-10℃, the standing time is 1min-50h, and the curing time is 6-10 days. In step 3), the initial concentration of the methanol solution is 80%(W / V), and the concentration of the methanol solution used thereafter decreases by 20% each time. The concentration of the methanol solution is changed to the next concentration every 4 times, the solution replacement period is 48h, and the methanol solution is replaced 16 times. After the methanol solution is replaced, water is used for replacement, and the number of water replacement is more than 24 times.

[0016] The novel degradable intervertebral fusion cage with piezoelectric function based on silk fibroin can meet good biocompatibility, biological activity, elastic modulus and compression strength, and can realize biodegradation, piezoelectric effect, promote bone formation and facilitate cervical fusion, and has wide clinical application prospect.

[0017] The left and right of the fusion cage are designed as convex, which can better contact with the uncinate joint, stimulate the piezoelectric effect through the movement of the uncinate joint, and facilitate the fusion of the uncinate joint.

[0018] The structure of the other fusion cage of the application is designed to be wide at the top and narrow at the bottom, which is more consistent with the anatomical structure of the uncinate joint, and better promotes the bone formation activity at the uncinate joint by piezoelectric effect, and facilitates the fusion of the uncinate joint. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The microstructure comparison chart of the block material prepared in the examples and comparative examples of the application; (a) is the block material prepared in example 1, and (b) is the block material prepared in the comparative example.

[0020] Figure 2 The structure diagram of the novel fusion cage (1) of the application, unit: mm; (a) is a top view, (b) is a left view of (a).

[0021] Figure 3Fig. 1 is a schematic diagram of the new fusion cage (2) of the present application, with units in mm; (a) is a top view, (b) is a left view of (a), and (c) is a front view.

[0022] Figure 4 Fig. 2 is a photograph of a traditional fusion cage; (a) and (b) are different perspective views of the fusion cage.

[0023] Figure 5 Fig. 3 is a pie chart of the piezoelectric effect detection results of the present application in Example 3; (a-1) is a butterfly curve of a pure carboxylated silk protein film, (a-2) is a hysteresis curve of the pure carboxylated silk protein film, (b-1) is a butterfly curve of a carboxylated silk protein film containing barium titanate, and (b-2) is a hysteresis curve of the carboxylated silk protein film containing barium titanate.

[0024] Figure 6 Fig. 4 is an intraoperative installation situation of the present application implanted in an animal body in Example 4; (a) is an intraoperative implantation photograph, and (b) is an immediate postoperative X-ray film.

[0025] Figure 7 Fig. 5 is a 3-month postoperative X-ray film of the present application implanted in an animal body in Example 4 (n = 6 sheep / group); (a) is a traditional structure cervical spine fusion cage, (b) is a new structure cervical spine fusion cage (1), and (c) is a fusion rate statistical chart.

[0026] Figure 8 Fig. 6 is a 3-month postoperative tissue section staining of the present application implanted in an animal body in Example 4 (collagen fibers (red, stained with eosin), muscle fibers (yellow, stained with picric acid), n = 6 sheep / group; (a) is a traditional structure cervical spine fusion cage, (b) is a new structure cervical spine fusion cage (1), and (c) is a bone percentage. **p < 0.01). Specific implementation method

[0027] Unless otherwise specified, the scientific and technical terms in this document are understood according to the knowledge of the relevant persons skilled in the art.

[0028] In order to enable the persons skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the persons skilled in the art without making creative efforts should belong to the scope of protection of the present application.

[0029] The following embodiments are not specified for specific conditions, and the experimental methods are selected according to conventional methods and conditions, or according to the instructions of the goods.

[0030] The carboxylated silk protein lyophilized powder used in the present application can be commercially available or self-made. The carboxylated silk protein lyophilized powder used in the following examples is self-made, and the specific preparation method is as follows:

[0031] The pupated cocoon is cut into pieces, and the pupated cocoon is heated and boiled in a 0.02 mol / L sodium carbonate solution at a ratio of 20:1 g / L for 30 min. 6.25 g of 1-butyl-3-methyl imidazole chloride is melted at a temperature of 100℃, and the reaction is carried out under normal pressure for 4 h. 1 g of degummed silk is added until the silk is completely melted. 15 ml of dimethylformamide is added, and the reaction is continued for 1 h. 2 g of succinic anhydride is added, and the reaction is continued for 1 h to obtain an initial carboxylated silk protein solution. The initial carboxylated silk protein solution is dialyzed using a dialysis bag with a specification of 3500 MWCO. The stirring speed of the magnetic stirrer is 200 r / min. The initial concentration of the urea solution during dialysis is 8 mol / L. The concentration of the urea solution is gradually reduced to ultrapure water at a concentration gradient of 2 mol / L. The dialysis time for each concentration gradient is 3 h. The solution in the dialysis bag is centrifuged at a speed of 12000 r / min for 20 min at a temperature of 4℃, and the precipitate is retained. The precipitate is mixed with a lithium bromide solution at a ratio of 1:4 g / mL. The concentration of the lithium bromide is 9.3 mol / L. The mixed solution is placed in a dialysis bag with a specification of 3500 MWCO and dialyzed in ultrapure water. The stirring speed of the magnetic stirrer is 200 r / min. The dialysis time is 72 h to obtain a purified carboxylated silk protein solution.

[0032] The purified carboxylated silk protein solution is poured into a 10 cm cell culture dish, and the solution height is 1 cm. The cell culture dish containing the solution is first frozen in an environment of-80℃ for 24 h, and then treated in a freeze dryer with a vacuum pressure of 0.5 kPa for 72 h. The freeze-drying temperature adopts a gradient heating freeze-drying method, and each temperature gradient differs by 10℃. The freeze-dried carboxylated silk protein sponge is obtained. The freeze-dried carboxylated silk protein sponge is crushed with a high-speed crusher to obtain carboxylated silk protein lyophilized powder.

[0033] Example 1:

[0034] Step 1, according to the ratio of 1 g:2 ml, the barium titanate is mixed with hexafluoroisopropanol to obtain a barium titanate hexafluoroisopropanol suspension. Then, under the condition of about 20℃, according to the ratio of 1 g:5 ml, the carboxylated silk protein lyophilized powder is dissolved in the barium titanate hexafluoroisopropanol solution, and after 6 h of dissolution, a carboxylated silk protein barium titanate hexafluoroisopropanol suspension is obtained.

[0035] Step 2, the suspension obtained in step 1 is injected into a porous mold and placed at 4℃. The mold structure used is as shown in Figure 1As shown, it comprises a cylindrical vessel and a top cover, the cylindrical vessel is a cylindrical cavity, the top of the cavity is open, the side wall and the bottom are provided with a plurality of micropores with a diameter of 0.5 mm, the material of the cylindrical vessel is polytetrafluoroethylene, the wall thickness is 2 mm, the inner diameter of the cavity is 50 mm, the internal axial height is 30 mm, the side wall of the cavity is distributed with 5 circles of micropores at equal intervals from top to bottom, each circle is distributed with 16 micropores at equal intervals, and the uppermost circle of micropores is 5 mm away from the top edge; the bottom is provided with 41 micropores, and the center of the bottom is provided with a micropore, and the micropore around the center is distributed with 4 circles of micropores, the micropores in each circle of the side wall and the bottom plate are distributed at equal intervals, and the micropores in the adjacent circles on the bottom plate or the side wall are distributed at equal intervals, and the micropores in different circles are distributed at equal intervals in the circumferential direction, the diameter and distribution of the micropores need to avoid the seepage of the suspension, and at the same time, it is convenient for methanol to slowly immerse into the mold, promote the coagulation of the carboxylated silk fibroin barium titanate hexafluoroisopropanol solution, and the top cover is covered on the open part after the suspension is filled), the standing time is 24 h, and the bubbles in the solution are completely released as much as possible;

[0036] Then the mold is placed in 100% (W / V) methanol for 1 week, the operation should be gentle and slow, and the mold should not be moved randomly during the process to prevent bubbles from being generated during the solidification process. After the crystallization solidification by methanol treatment, the porous mold is removed, and the carboxylated silk fibroin barium titanate solid is obtained;

[0037] Step 3, the carboxylated silk fibroin barium titanate solid is soaked in a gradient decreasing concentration of methanol water solution to remove methanol in the block material. The initial replacement is 80% (W / V) methanol water solution, and then the concentration of methanol used is decreased by 20% gradient. The solution replacement time interval is 48 h, and the concentration of methanol water solution is adjusted to the next concentration every 4 times. After 16 times of solution replacement, water is used for replacement, and the number of water replacement is more than 24 times, and the replacement period is 48 h. After the methanol is replaced, the block material is placed in a ventilated environment to volatilize the water in the carboxylated silk fibroin barium titanate solid, and finally the block material is obtained. The above ventilated environment temperature is 25℃, and the time length is 30 days.

[0038] The content of methanol in the block material is dynamically detected during the above step 3 process until the methanol is completely replaced after a total of 40 times of solution replacement, and finally the carboxylated silk fibroin block product micromorphology is shown in 1 (left). The detection method of the content of methanol is as follows: part of the solid material at the corresponding link is crushed into powder, 5 g of the powder is taken and placed in a conical flask, a polar solvent ethyl acetate is added, and after sealing, ultrasonic extraction is performed for 60 minutes. The extraction liquid is separated by filter paper or centrifugation, and the supernatant is detected by HPLC to detect the concentration of methanol.

[0039] Comparative Example 1:

[0040] The difference between this comparative example and Example 1 is that step 3 uses hot-pressing curing, and the specific curing process is as follows: the carboxylated silk fibroin freeze-dried powder is added to the cavity of the hot-pressing mold, the press head is placed, then transferred to the tablet press and fixed, and then hot-pressed at 145°C and a pressure of 632 MPa for 30 min. After natural cooling, the hot-pressed block material is obtained. The block material is cut longitudinally and observed by scanning electron microscopy, and the micro-morphology is as shown in Figure 1 (Left) and (Right) respectively, and it can be seen that there are a large number of cracks in the interior of the block material.

[0041] Example 2:

[0042] In this example, the carboxylated silk fibroin block material obtained in Example 1 is machined into two new types of cervical fusion cage structures (see Figure 2 and Figure 3 ) and a traditional cervical fusion cage structure (see Figure 4 ).

[0043] Figure 2 The body 1 of the cervical fusion cage (new cervical fusion cage 1) shown in the figure is an elliptical sheet (the thickness of the sheet in this example is 4 mm; the long axis of the elliptical body of the fusion cage is 12 mm, and the short axis is 11 mm, and the long axis is 1 mm outwardly protruding), and the long axis of the elliptical sheet is provided with a cervical facet joint fusion hole 13 at each end for bone grafting and facilitating fusion of the adjacent cervical facet joints. The axial direction of the cervical facet joint fusion hole is perpendicular to the axial direction of the long axis of the elliptical sheet, and the long axis of the elliptical sheet is outwardly protruding along the long axis axial direction to form a lug structure 14 which is helpful to exert the piezoelectric properties of the material. A vertebral fusion hole 11 is provided between the two cervical facet joint fusion holes for bone grafting and facilitating fusion of adjacent vertebral bodies, and the axial direction of the vertebral fusion hole is parallel to the axial direction of the cervical facet joint fusion hole. The hole diameter of the vertebral fusion hole is larger than that of the cervical facet joint fusion hole; in this example, the cervical facet joint fusion hole and the vertebral fusion hole are both circular, the hole diameter of the cervical facet joint fusion hole is 2 mm, and the hole diameter of the vertebral fusion hole is 6 mm. At the same time, the body of the cervical fusion cage of this example is also provided with an image marker material mounting hole 12, specifically three (two in front and one in back) circular mounting holes with a diameter of about 0.5 mm on the body of the fusion cage, which can place image marker materials such as tantalum wire.

[0044] Figure 3The cervical vertebra fusion cage (new cervical vertebra fusion cage 2) body 2 is a rounded rectangular cross section and a trapezoidal longitudinal section, two vertebral fusion holes 21 for bone grafting and promoting intervertebral fusion are arranged on the cervical vertebra fusion cage body, the vertebral fusion holes are longitudinally arranged, and the two vertebral fusion holes are distributed along the length direction of the rounded rectangle, and a connecting body 22 is arranged between the two vertebral fusion holes; hook vertebra joint fusion holes 23 for bone grafting, bone transverse growth and promoting bilateral hook vertebra joint fusion are arranged on the side walls of the two vertebral fusion holes, and the two hook vertebra joint fusion holes are distributed along the length direction of the rounded rectangle of the cervical vertebra fusion cage body and are far away from each other. The connecting body of the embodiment is provided with a process hole. The vertebral fusion hole in the embodiment is a rounded rectangle (that is, the corners of the rectangle are rounded), the size is 4mm*7mm, the hook vertebra joint fusion hole 23 is arranged along the length direction of the rounded rectangle, and the cross section of the hook vertebra joint fusion hole 23 is a rectangle, the size is 6mm*2mm. Figure 3 b shown).

[0045] The sizes of the key structures or parts of the fusion cage are not limited to the above-mentioned embodiments, and can be determined according to the anatomical parameters of the patient in actual application.

[0046] Further, the torsional performance of the cervical vertebra fusion cages with the traditional structure and the two new structures prepared in the above-mentioned embodiments is detected by using a torsional fatigue testing machine, and the compression mechanical properties of the three are detected by using an electronic universal testing machine. The results show that:

[0047] (1) Torsional performance: as shown in Table 1, when the three fusion cages are subjected to 100N physiological compression preloading and the test loading speed is 30deg / min:

[0048] The torsional stiffness of the traditional fusion cage is 0.22±0.08N·m / deg, the torsional stiffness of the new fusion cage (1) Figure 2 shown) is 0.30±0.05N·m / deg, and the torsional stiffness of the new fusion cage (2) Figure 3 shown) is 0.29±0.02N·m / deg;

[0049] The torsional yield torque of the traditional fusion cage is 8.61±0.19N·m, the torsional yield torque of the new fusion cage (1) is 13.43±0.61N·m / deg, and the torsional yield torque of the new fusion cage (2) is 12.89±0.49N·m / deg;

[0050] The angular displacement corresponding to the residual displacement of the traditional fusion cage is 1.22±0.37deg; the angular displacement corresponding to the residual displacement of the new fusion cage (1) is 1.40±0.22deg, and the angular displacement corresponding to the residual displacement of the new fusion cage (2) is 1.37±0.50deg;

[0051] The torsional limit torque of the conventional fusion cage is 1.52±0.26 N·m, the torsional limit torque of the new fusion cage (1) is 1.75±0.16 N·m, and the torsional limit torque of the new fusion cage (2) is 1.72±0.21 N·m;

[0052] The torsional limit angular displacement of the conventional fusion cage is 16.17±0.39 deg; the torsional limit angular displacement of the new fusion cage (1) is 17.29±0.41 deg, and the torsional limit angular displacement of the new fusion cage (2) is 17.11±0.45 deg.

[0053] (2) Compression mechanical properties: As shown in Table 2, the limit load of the conventional fusion cage is 30192±1008 N, the limit load of the new fusion cage (1) is 32796±1799 N, and the limit load of the new fusion cage (2) is 32080±1895 N; the limit displacement of the conventional fusion cage is 2.15±0.28 mm, the limit displacement of the new fusion cage (1) is 2.27±0.31 mm, and the limit displacement of the new fusion cage (2) is 2.22±0.27 mm; the stiffness of the conventional fusion cage is 21668.0±4405.5 N / mm, while the stiffness of the new fusion cage (1) is 22593.8±2317.7 N / mm, and the stiffness of the new fusion cage (2) is 22009.1±1906.2 N / mm.

[0054] Table 1 Comparison of torsional properties of new structure and conventional structure cervical spine fusion cages

[0055]

[0056] Table 2 Comparison of compression mechanical properties of new structure and conventional structure cervical spine fusion cages

[0057]

[0058] The above results show that the new structure cervical spine fusion cage has significant differences in torsional yield torque, angular displacement corresponding to residual displacement, torsional limit torque, compression limit displacement, and fusion cage compression stiffness (p<0.05), indicating that the two new structure silk fibroin-based cervical spine fusion cages have stronger anti-torsional performance than the conventional structure, and also have higher mechanical strength, and are closer to the elastic modulus of natural cervical spine, thereby effectively avoiding the stress shielding effect.

[0059] The following is the subsequent in vivo verification of the new cervical spine fusion cage (1) with better mechanical properties.

[0060] Example 3:

[0061] Fusioner piezoelectric performance test: pure carboxylated silk protein film and carboxylated silk protein piezoelectric film mixed with barium titanate were prepared, and piezoelectric response force microscope (PFM) was used for piezoelectric performance test. Specifically, the carboxylated silk protein solution used in Example 1 and the carboxylated silk protein barium titanate hexafluoroisopropanol solution suspension were spin-coated by using a homogenizer, and then dried to form a pure carboxylated silk protein film and a carboxylated silk protein piezoelectric film with uniform texture, which were tested by PFM.

[0062] The PFM test results are shown in Figure 5 The prepared carboxylated silk protein piezoelectric film showed typical butterfly curve and hysteresis curve compared with the pure carboxylated silk protein film, indicating that the combination of barium titanate and carboxylated silk protein endows it with piezoelectric properties, while the pure carboxylated silk protein film has no piezoelectric properties. After the change of current direction, the phase of material vibration changes accordingly, which is consistent with the anti-piezoelectric effect (intrinsic property of piezoelectric material), proving that the material has piezoelectric performance.

[0063] Example 4:

[0064] The traditional structure cervical fusion cage and the new type structure cervical fusion cage (1) prepared in Example 1 were subjected to animal in vivo test, and all animal experiment operations were approved by the Animal Protection and Use Committee of Air Force Military Medical University.

[0065] Before surgery, both the new and traditional cervical fusion cages were sterilized by soaking them in 75% ethanol for 24 hours. Before implantation, they were thoroughly rinsed three times with sterile distilled water to remove residual ethanol. The sheep were fasted for 24 hours before surgery and weighed. Atropine sulfate was injected intramuscularly before anesthesia to reduce salivation during surgery and prevent aspiration, choking, and suffocation. Suminxin II (xylazine hydrochloride injection) at 0.1 ml / kg was injected intramuscularly to achieve good anesthesia. The anesthetized sheep were placed supine. The sheep was fixed in a supine position on a surgical support table. The neck was shaved and disinfected with iodine tincture, then deiodinated with 70% ethanol. A 7-cm parallel longitudinal incision was made 3 cm to the right of the anterior midline of the neck. The skin and fascia were cut, the sternomastoid muscle and the jugular vein were separated, and the carotid artery and esophagus were exposed. The esophagus and trachea were pulled to the left side of the sheep and protected with wet gauze. The carotid artery was carefully pushed to the right and protected with wet gauze. Then, the longus colli muscle was cut from the middle with an electric knife and peeled off to the bone surface to expose the cervical vertebrae C3 / C4. On the ventral side, the bone ridge at the anterior edge of the vertebral body was removed with a rongeur, and the nucleus pulposus was gradually cleaned with a nucleus pulposus forceps. Soft tissue was removed, and the upper and lower surfaces were cut to the bone surface with an oscillating saw. The intervertebral space was gradually polished to accommodate the insertion of a cervical fusion device. The bone blocks removed and cut during the operation were trimmed into bone particles, and the two fusion device bone implant holes were filled and implanted into the C3 / C4 intervertebral space. When implanting the new cervical fusion device, care should be taken to place the binaural structure close to the anterior edge of the vertebral body and the single tantalum wire mounting hole below close to the posterior edge of the vertebral body. At the same time, the fusion holes of the left and right uncovertebral joints should be kept in contact with the uncovertebral joints. After ensuring that the fusion device is properly placed and that the upper and lower surfaces are tightly attached to the bone surface, it is fixed with an anterior cervical titanium plate and screws. The cervical vertebra is rinsed with hydrogen peroxide and briefly soaked, then rinsed with normal saline. After observing that there is no obvious active bleeding, a gelatin sponge is placed close to the anterior cervical titanium plate, the longus colli muscle is sutured, and the fascia and skin are sutured layer by layer. After the incision is sutured, the wound is bandaged to prevent infection. Infection prevention and analgesia are provided during the perioperative period.

[0066] Lateral X-ray examination was performed 3 months after surgery, and an imaging scoring system was used to evaluate the degree of spinal fusion: Grade 1: no fusion, with obvious X-ray translucent area in the intervertebral space; Grade 2: partial fusion, with partial bone ingrowth visible, and the middle part is divided by the X-ray translucent area; Grade 3: complete fusion, with bony connection between the upper and lower vertebrae, and no X-ray translucent area in the middle.

[0067] Three months after surgery, samples were collected for histological section staining and analysis. The cervical spine specimens with implanted fusion devices were fixed with formalin solution for one week, dehydrated with ethanol solutions of increasing concentrations, embedded and fixed with methyl methacrylate, and reserved for tissue section staining (picrofuchsin and methylene blue staining).

[0068] The fusion cage installation during surgery Figure 6 As shown, it shows that the fusion cage is well installed and fixed reliably; the lateral X-ray on the day after surgery shows that the fusion cage has no displacement, and both cervical fusion cages are marked with tantalum wire.

[0069] Lateral X-ray examination Figure 7 As shown in the figure, 3 months after implantation of the two structures of cervical fusion devices, partial bone growth was observed in the intervertebral space, which was divided by an X-ray transparent area in the middle, achieving partial fusion. This indicates that the present invention can achieve immediate mechanical stability of the cervical spine after implantation in animals. At the same time, in the short-term effect evaluation, the two structures of cervical fusion devices have good fusion efficiency. Further analysis found that the fusion rate of the new structure of cervical fusion device (1) can reach 83.33%, which is better than the traditional structure (66.67%), as shown in Table 3.

[0070] Table 3 Comparison of fusion after implantation of new and traditional cervical fusion cages in sheep cervical spine

[0071]

[0072] The tissue sections were stained with VG (picric acid and Ponceau red) and the results were as follows: Figure 8 As shown in the figure, with the help of autologous bone, both structures of cervical fusion cages can form bony connection 3 months after implantation. According to statistical analysis, the bone tissue filling ratio of the new structure cervical fusion cage (1) can reach 53.87±4.93%, while the bone tissue filling ratio of the traditional structure cervical fusion cage is only 32.50±3.85%, indicating that the new structure cervical fusion cage has better bone regeneration and fusion effects.

[0073] The above results indicate that the novel biodegradable silk protein-based cervical fusion device with piezoelectric effect presented in the present invention can effectively promote fusion of the cervical uncovertebral joint and has broad clinical application prospects.

Claims

1. A novel degradable cervical fusion cage, characterized in that, The material of the fusion device is carboxylated silk protein, and barium titanate is added in the carboxylated silk protein.

2. The novel degradable cervical fusion cage according to claim 1, wherein, The cervical vertebra fusion device body is an elliptical sheet, and a cervical vertebra uncinate joint fusion hole is formed at each end of the long axis of the elliptical sheet, and the axial direction of the cervical vertebra uncinate joint fusion hole is perpendicular to the axial direction of the long axis of the elliptical sheet; meanwhile, the two ends of the long axis of the elliptical sheet are respectively outwardly protruded along the axial direction of the long axis to form a lug structure; a vertebral body fusion hole is formed between the two cervical vertebra uncinate joint fusion holes, and the axial direction of the vertebral body fusion hole is parallel to the axial direction of the cervical vertebra uncinate joint fusion hole; the diameter of the vertebral body fusion hole is larger than the diameter of the cervical vertebra uncinate joint fusion hole.

3. The novel degradable cervical fusion cage according to claim 2, wherein, The cervical vertebra uncinate joint fusion hole and the vertebral body fusion hole are both circular.

4. The novel degradable cervical fusion cage according to claim 2, wherein, An image marker material mounting hole is further formed in the body of the cervical vertebra fusion device.

5. The novel degradable cervical fusion cage according to claim 1, wherein, The cross section of the cervical vertebra fusion device body is a rounded rectangle, and the longitudinal section is a trapezoid; two vertebral body fusion holes are formed in the cervical vertebra fusion device body, the vertebral body fusion holes are formed along the longitudinal direction, and the two vertebral body fusion holes are distributed along the length direction of the rounded rectangle; a connecting body is arranged between the two vertebral body fusion holes; a hook vertebra joint fusion hole is formed in the side wall of each vertebral body fusion hole, and the two hook vertebra joint fusion holes are distributed along the length direction of the rounded rectangle of the cervical vertebra fusion device body and are far away from each other.

6. The novel degradable cervical fusion cage according to claim 5, wherein, A process hole is formed in the connecting body.

7. The novel degradable cervical fusion cage according to claim 5, wherein, The vertebral body fusion hole is a rounded rectangle, and the cross section of the hook vertebra joint fusion hole is a rectangle.

8. The method of making the cervical fusion device of claim 1, wherein, The method comprises the following steps: 1) Dissolve the carboxylated silk protein freeze-dried powder in the barium titanate hexafluoroisopropanol suspension solution to obtain a carboxylated silk protein barium titanate hexafluoroisopropanol suspension solution; 2) Inject the suspension solution into a porous mold, place the porous mold in methanol after the bubbles are released to solidify to obtain a barium titanate carboxylated silk protein solid; the porous mold comprises a mold body, and a cavity is arranged in the mold body, and a plurality of micropores are formed in the side wall and the bottom surface of the cavity; 3) Then remove the mold, and sequentially place the barium titanate carboxylated silk protein solid in methanol aqueous solution and water with gradually decreasing concentrations to replace the methanol to obtain a carboxylated silk protein block; 4) Use a mechanical processing method to process the carboxylated silk protein block into a cervical vertebra fusion device.

9. The cervical fusion cage preparation method of claim 8, wherein, In step 1), the mass-volume ratio of the barium titanate to the hexafluoroisopropanol is 1g:(1-100)ml; and the mass-volume ratio of the carboxylated silk protein freeze-dried powder to the barium titanate hexafluoroisopropanol solution is 1g:(1-10)ml.

10. The cervical fusion cage preparation method of claim 8, wherein, The mold comprises a cylindrical vessel and a top cover, a cylindrical cavity is arranged in the cylindrical vessel, the top of the cavity is open, and a plurality of micropores are formed in the side wall of the cavity; the plurality of micropores in each circle are distributed at equal intervals in the circumferential direction, and the plurality of micropores in different circles are distributed at intervals in the circumferential direction; a plurality of micropores are formed in the bottom plate of the cavity, and the plurality of micropores in each circle are distributed at equal intervals around the center of the bottom plate; the plurality of micropores in different circles are distributed at intervals in the circumferential direction; and the plurality of micropores in each circle are distributed at equal intervals, and the plurality of micropores in different circles are distributed at intervals in the circumferential direction.

11. The cervical fusion cage preparation method of claim 10, wherein, The diameter of the micropore is 0.5mm.

12. The cervical fusion cage preparation method of claim 8, wherein, The standing temperature is 0-10℃, and the standing time is 1min-50h; and the solidification time is 6-10 days.

13. The cervical fusion cage preparation method of claim 8, wherein, The initial concentration of methanol aqueous solution in step 3) is 80% (W / V), and the concentration of methanol aqueous solution used thereafter is decreased by 20% each time; the concentration of methanol aqueous solution is changed to the next concentration every 4 times, the solution changing period is 48 h, and methanol aqueous solution is replaced for 16 times, and then water is used for replacement, and the number of water replacement is more than 24 times.

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