CN114767945A - Ribbon for fixing comminuted fracture block and preparation method thereof - Google Patents
Ribbon for fixing comminuted fracture block and preparation method thereof Download PDFInfo
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- CN114767945A CN114767945A CN202210246410.9A CN202210246410A CN114767945A CN 114767945 A CN114767945 A CN 114767945A CN 202210246410 A CN202210246410 A CN 202210246410A CN 114767945 A CN114767945 A CN 114767945A
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- comminuted fracture
- fixing
- fracture fixation
- fracture
- lock catch
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L31/00—Materials for other surgical articles, e.g. stents, stent-grafts, shunts, surgical drapes, guide wires, materials for adhesion prevention, occluding devices, surgical gloves, tissue fixation devices
- A61L31/14—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
- A61L31/16—Biologically active materials, e.g. therapeutic substances
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B17/00—Surgical instruments, devices or methods
- A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
- A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws or setting implements
- A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
- A61B17/82—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin for bone cerclage
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L31/00—Materials for other surgical articles, e.g. stents, stent-grafts, shunts, surgical drapes, guide wires, materials for adhesion prevention, occluding devices, surgical gloves, tissue fixation devices
- A61L31/04—Macromolecular materials
- A61L31/041—Mixtures of macromolecular compounds
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L31/00—Materials for other surgical articles, e.g. stents, stent-grafts, shunts, surgical drapes, guide wires, materials for adhesion prevention, occluding devices, surgical gloves, tissue fixation devices
- A61L31/14—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
- A61L31/148—Materials at least partially resorbable by the body
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B17/00—Surgical instruments, devices or methods
- A61B2017/00004—(bio)absorbable, (bio)resorbable or resorptive
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- General Health & Medical Sciences (AREA)
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- Heart & Thoracic Surgery (AREA)
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- Orthopedic Medicine & Surgery (AREA)
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Abstract
The invention relates to the technical field of medical instruments, in particular to a bandage for fixing comminuted fracture blocks, which is prepared from polycaprolactone and levorotatory polylactic acid, wherein the weight ratio of the polycaprolactone to the levorotatory polylactic acid is (70-80): (20-30). The invention also provides a preparation method and application of the cable tie for fixing the comminuted fracture. The in vitro experiment and the preliminary animal experiment of the prepared bandage for fixing the fracture block show that the bandage has the self-reinforcing locking function and good mechanical property, physical property and biological property; the shape of the implant can still keep a complete shape after being implanted into a human body for three months, the implant can play a good role in fixing in the early stage, the implant can be gradually degraded in the human body after three months and absorbed by the human body, the degradation is completed in about 2 years, the implant does not need to be taken out by a secondary operation, the post-operation CT and MRI examination are not influenced, and the pain of a patient is reduced.
Description
Technical Field
The invention relates to the technical field of medical instruments, in particular to a degradable binding belt for fixing comminuted fracture blocks and a preparation method thereof.
Background
In the clinical treatment of fracture, the nondegradable metal implant has good mechanical properties and can realize the fixation of early fracture, but because the elastic modulus of the metal implant is far greater than that of human bone, the metal implant can generate stress shielding while playing the role of fracture fixation, so that osteoporosis and osteolysis of a fracture fixation section are caused, and secondary fracture is possibly generated due to stress concentration of bones close to the far ends and the near ends of internal fixation. In addition, in the process of taking out the implant through the secondary operation, important tissues such as peripheral blood vessels, nerves and the like can be accidentally injured due to the formation of local scar tissues, so that the risk of surgical complications is increased. In addition, the secondary operation also increases physical pain and economic burden of the patient.
To avoid these problems, degradable orthopedic implants have been used clinically over the last two decades, and these implants have good biocompatibility and biodegradability and are increasingly accepted by clinicians and patients. For example, the inherent initial strength of the internal fixation bone nail made of the bio-absorbable material can play the role of a fracture fixation device made of traditional metal at certain non-bearing parts, and the biodegradable bone nail is gradually absorbed by human tissues and does not accumulate in the body and has almost no toxic effect after the fracture is healed along with the lapse of time; the original space can be replaced by bone tissue, and the patient does not need to suffer from the pain of secondary operation. The bone nail made of the absorbable material does not affect the examination of CT or MRI and the like of a patient at any time after the operation due to the non-metallic characteristic. Therefore, absorbable materials are theoretically the most desirable orthopedic materials.
Disclosure of Invention
The invention aims to provide an absorbable bandage for fixing comminuted fracture blocks and a preparation method thereof, which are based on the blending modification of PCL and PLLA with high degradation rate and good mechanical property and have the advantages of safety, reliability, easy use, degradability and no need of taking out.
Comminuted fracture belongs to complete fracture, indicates that the fracture splits into more than three, because the fracture piece number is more, the gimmick effect is not good enough, stability after reseing is poor, improper treatment can cause serious sequelae, mainly adopt metal steel wire, titanium wire to fix at present clinically, easily lead to adverse reactions such as periosteum damage, pressure shielding, metal point are separated, inflammation, need the secondary operation to take out. Some experts and scholars also adopt absorbable sutures to tie fracture blocks, but have the problems of loose tying, easy slipping and breaking and the like. Clinically, a fixing device which can play a role in fixing metal steel wires and titanium wires and overcome adverse reactions of the metal steel wires and the titanium wires is urgently needed, and the research and development of the PCL-PLLA blending modified absorbable fracture block fixing bandage successfully provides the best choice for clinicians to treat comminuted fractures.
Chinese patent document CN204542334U discloses a fracture fixation device, which includes a pressurizing chuck, and a lock catch and a binding band connected with each other, wherein the lock catch is provided with an opening in a horizontal direction in a penetrating manner, and the top surface of the lock catch is provided with a clamping groove which is communicated with the opening; after the free end of the binding belt penetrates through the opening in the horizontal direction of the lock catch, the pressurizing chuck is clamped in the clamping groove and is abutted against the binding belt, so that the binding belt forms an annular structure. The beneficial effects of the utility model are that, the free end that will tie the area runs through behind the opening of hasp horizontal direction and adjusts to suitable position after, adopt and directly strike the pressurized mode and go into the hasp with the pressurization dop card in, make the sawtooth of pressurization dop side surface and the sawtooth tooth's socket of draw-in groove side match complementally, tie the pawl of area and the pawl tooth's socket of draw-in groove bottom surface match complementally, so that tie the further meshing of area and hasp, fixing device's stability has been improved, make and tie the difficult deviating from of area, be favorable to patient's early function exercise. However, the fracture fixation device of the utility model is made of self-reinforced polylactic acid (SR-PLA), which is brittle and cannot meet the mechanical requirements of fracture fixation, so that the fracture fixation device has no clinical application value. According to the invention, polylactic acid (PLLA) and flexible copolymer Polycaprolactone (PCL) are blended and modified to toughen the polylactic acid, so that the fracture fixation material not only meets the mechanical requirements of fracture fixation, but also has good biocompatibility, degradability and thermal stability, and can meet clinical requirements.
The bone elastic modulus of an adult is 3-20 GPa, and in order to avoid stress shielding, the technical problem to be solved by the invention is that the elastic modulus of the fracture fixing bandage is generally lower than that of a normal bone, the fracture end can be mechanically fixed (the elastic modulus is 100MPa), more than 80% of the initial mechanical property of the material can still be maintained within 12 weeks after the fracture fixing bandage is implanted into a body, and the maximum breaking force is not less than 100N. The degradation is finished after the plant is implanted into a human body for about 2 years.
In order to achieve the purpose, the invention adopts the following technical scheme:
based on the commercial feasibility of the degradable high polymer material at present, the invention selects a mode of utilizing melt blending modification to design different modified composite materials, namely PLLA enhanced PCL, PLGA enhanced PCL and PLLA enhanced PLCL; the evaluation of the physical and chemical properties and the biological properties of the series of polyester modified materials is carried out in sequence, and more possibilities are provided for the selection of the internal fixation mechanical material. The specific contents are as follows:
(1) a modified material standard sample bar is prepared by using a melt blending mode and a miniature double-screw extruder, and the sample bar uniformity and the degradation performance of the modified material standard sample bar are evaluated. Selecting levorotatory polylactic acid (Poly (L-lactide), PLLA), Polycaprolactone (PCL), polylactic acid-glycolic acid (Poly (lactic-co-glycolic acid)), PLGA and Poly (L-lactide-caprolactone) (PLCL) as experimental raw materials, wherein PCL is used as a main substrate material, and modification research is carried out through different blending components and proportions. The related blending components comprise PCL/PLGA, PCL/PLLA and PLCL/PLLA. The blending formula comprises the following components in percentage by mass: (a) PCL PLGA three groups are 80:20(CG82), 70:30(CG73) and 60:40(CG 64); (b) two groups of PCL and PLLA are 80:20(CA82) and 70:30(CA 73); (c) PLCL and PLLA are 80:20(73A82) and 70:30(73A 73).
(2) By nuclear magnetic hydrogen spectroscopy (H)1NMR), scanning electron microscope image (SEM), PH value and mechanical property test in the in-vitro degradation process, the performance of the blending modified composite material standard sample bar is represented, and the optimal formula is screened out.
In a first aspect of the invention, the invention provides a bandage for fixing comminuted fracture fragments, which is made of Polycaprolactone (PCL) and poly-L-lactic acid (PLLA), wherein the weight ratio of the polycaprolactone to the poly-L-lactic acid is (70-80): (20-30). Preferably, the weight ratio of polycaprolactone to poly (L-lactic acid) is 80: 20.
Furthermore, the binding belt for fixing the comminuted fracture comprises a pressurizing chuck, and a lock catch and a binding belt which are connected with each other, wherein an opening is arranged in the horizontal direction in a penetrating manner of the lock catch, and a clamping groove is formed in the top surface of the lock catch and communicated with the opening; after the free end of the binding belt penetrates through the opening in the horizontal direction of the lock catch, the pressurizing chuck is clamped in the clamping groove and is abutted against the binding belt, so that the binding belt forms an annular structure.
Furthermore, the side surface of the pressurizing chuck is provided with at least one row of saw teeth; and sawtooth tooth grooves matched with the sawteeth are formed in the side faces of the clamping grooves.
Furthermore, the surface of the binding belt is provided with at least one row of inverted teeth; the bottom surface of the clamping groove is provided with a tooth chamfering tooth groove matched with the tooth chamfering. The inverted teeth of the binding belt and the inverted tooth sockets on the bottom surface of the clamping groove are matched and complemented so that the free end of the binding belt is inserted into the opening of the lock catch and is tightened to a certain degree to be meshed with each other, and the binding belt is connected with the lock catch.
Further, the junction of hasp and binding area be equipped with the arc angle, the angle of this arc angle is 90 ~ 150. The arc-shaped angle is convenient for bending and binding the binding belt along the curvature of the fracture part.
Further, the compression chuck includes a cap section and a body section, and the serrations are transversely provided on opposite sides of the body section.
Furthermore, the number of the rows of the inverted teeth on the bottom surface of the clamping groove is 4-6.
In a second aspect of the present invention, there is provided a method for preparing a cable tie for fixing comminuted fracture, which uses injection molding, and the injection molding process parameters are as follows:
multi-stage temperature of the barrel: 165-180 ℃; 175 ℃ and 195 ℃; 170-195 ℃; 165-185 ℃ of reaction;
injection pressure: 50-60 bar;
injection speed: 140-160 mm/s;
pressure maintaining: 700-850 bar;
pressure maintaining time: 6-8 s;
cooling time: 9-12 s;
temperature of the die: 14.5-16 ℃.
In injection molding, the quality of injection molding products is related to a plurality of factors, and after raw materials, the model of an injection molding machine and the structure of a mold are determined, injection molding process parameters are the most critical factors influencing the molding quality. The temperature of the charging barrel determines the fluidity of the material, and has important influence on the molten state and the forming effect, the fluidity is poor when the temperature is too low, and the material is degraded too fast when the temperature is too high. And if the injection pressure, the pressure maintaining pressure and the pressure maintaining time are too low, the mold is not full, and if the injection pressure, the pressure maintaining pressure and the pressure maintaining time are too high, the defects of flash and the like are caused.
Further preferably, the injection molding processing parameters are as follows:
multi-stage temperature of the barrel: 170 ℃; 185 ℃; 185 ℃; 175 deg.C
Injection pressure: 55bar
Injection speed: 150mm/s
Pressure maintaining: 800bar
Pressure maintaining time: 7s
Cooling time: 10s
Temperature of the die: at 15 deg.C.
Further, the preparation method of the bandage for fixing the comminuted fracture comprises the following steps: successively putting the vacuum-dried raw materials of polycaprolactone and levorotatory polylactic acid into a high-efficiency mixer, and adjusting the rotating speed: 20r/min, mixing time 30 minutes, and then transferring the mixed mixture into a charging barrel of an injection molding machine immediately for injection molding processing.
In a third aspect of the invention, there is provided a use of a cable tie for comminuted fracture fixation as described above in the manufacture of an orderly absorbable fracture fixation device. The sequential absorption means that the bandage can keep complete shape within three months after being implanted into a human body, the maximum breaking force is not less than 100N, the degradation is accelerated after six months, and the bandage can be completely degraded in about two years.
The invention has the advantages that:
1. the invention adopts the biomedical materials approved by FDA to improve the mechanical property and the degradability of the product by adopting a melt blending modification mode on the premise of good biocompatibility; the pure polylactic acid bandage has the characteristics of hardness and brittleness, the application of the pure polylactic acid bandage in the field of fracture internal fixation is limited, and blending modification of polylactic acid and flexible polymers is one of the most economical and effective methods for toughening polylactic acid. Polycaprolactone not only shows high flexibility at normal temperature, but also has good biocompatibility, degradability and thermal stability, and is widely applied to biomedical material tissue engineering;
2. the in vitro experiment and the preliminary animal experiment of the prepared bandage for fixing the fracture block show that the bandage has the self-reinforcing locking function and good mechanical property, physical property and biological property;
3. the bandage for fixing the fracture block, which is prepared by the invention, has the elastic modulus similar to that of human bone tissues, and can promote fracture healing; the tensile elastic modulus of the modified polycarbonate is 924.56/748.39/496.04/398.43/340.99MPa measured at 0/2/4/6/8 th cycle of degradation, and the modified polycarbonate is relatively better than that of other formulas;
4. the bandage for fixing the fracture block, which is prepared by the invention, is mainly used for fixing the fragments of the long diaphysis fracture, fixing the large and small trochanter fracture of the osteoporosis patient and binding and fixing the bone around the long handle in the hip joint replacement operation clinically, and can realize the accurate treatment of the comminuted fracture. At present, no similar fixing device is applied to clinic at home and abroad;
5. after the invention is put into clinical use, the invention can provide the best choice for the clinician to treat comminuted fracture, reduce the overall medical insurance cost for hospitals and countries while reducing the pain and the treatment cost for patients, and obtain good social benefit;
6. the staged research result can be used as a bioabsorbable material to supplement the orthopedic internal fixation product, provides a methodological basis for the next research on the orthopedic internal fixation product, and indicates research directions for more researchers;
7. the ribbon for fixing the fracture block, which is designed by the invention, does not generate waste water and waste gas and has no environmental pollution in the processing and production process.
8. The bandage for fixing the fracture block is implanted into a human body for three months, the appearance of the bandage is still kept in a complete shape, the maximum breaking force is not less than 100N, the bandage has a good fixing effect in the early stage, the bandage is gradually degraded in the human body after three months and absorbed by the human body, the bandage is degraded and completed in about 2 years, the bandage is not required to be taken out through a secondary operation, the postoperative CT and MRI examination is not influenced, and the pain of a patient is reduced.
Drawings
FIG. 1 is an optical photograph of a dumbbell-shaped standard sample bar obtained by injection molding.
FIGS. 2A-D Nuclear magnetic resonance Hydrogen Spectroscopy (H) for control and modified materials of different formulations1-NMR) chart
Wherein, FIG. 2A shows (a) PCL, (b) PLLA, (c) PLGA and (d) PLCL material H1-NMR spectrum; FIG. 2B is H for PCL/PLGA blends (a) CG82, (B) CG73 and (c) CG641-NMR spectrum; FIG. 2C is H for PCL/PLLA blends (a) CA82 and (b) CA731-NMR spectrum; FIG. 2D is H for PLCL/PLLA blends (a)73A82 and (b)73A731-NMR spectrum.
FIG. 3 is a SEM cross-sectional view of standard parts made of different formulation-modified materials (a) CG82, (b) CG73, (c) CG64, (d) CA82, (e) CA73, (f)73A82 and (g)73A 73.
FIG. 4 is a graph showing the change of the tensile elastic modulus of modified materials with different formulations along with the degradation time.
FIG. 5 is a graph showing the change of pH of the in vitro degradation soaking solution of the modified materials with different formulations along with time.
Fig. 6 is a schematic structural view of the tie of the present invention.
Fig. 7 shows a schematic view of a compression clamp in a cable tie according to the invention.
Fig. 8 is a cross-sectional view of a locking portion of a cable tie of the present invention.
Fig. 9 is a schematic view of the mode of use of the cable tie of the present invention for humeral fracture fixation.
Fig. 10 optical photograph of one month post-surgery band implantation biger dogs with different formulations.
Fig. 11 optical photograph of three months after implantation of different formulation bands into beagle dogs.
Wherein:
1-lock catch 2-binding belt 3-pressurizing chuck
31-cap body section 32-body section 4-card slot
5-saw tooth 6-saw tooth groove 7-inverted tooth
8-inverted tooth socket 9-arc angle
Detailed Description
The following examples are provided to illustrate specific embodiments of the present invention.
Example 1:
1. experimental part
1.1 Experimental materials, reagents and devices
TABLE 1 Experimental materials and reagent table
TABLE 2 Experimental Instrument
1.2 preparation of specimens
The dumbbell-type standard specimens were prepared using a mini-twin-screw extruder and a mini-injection molding machine. The used material is taken out of a refrigerator with the refrigerating temperature of 2-8 ℃, placed in a laboratory for more than 2 hours and restored to the room temperature so as to prevent the material from absorbing water.
TABLE 3 injection molding test parameter table for different formulations
Then weighing quantitative materials according to different proportions, roughly mixing the two materials in a beaker, and placing the beaker in a constant temperature air blast drying oven at 40 ℃ for drying. The drying time is determined by using a drying constant weight method, and the specific drying time difference of different formulas is small, so that the drying time is uniformly set to be 4 h. After drying, the beaker mouth was sealed with a sealing film and quickly transferred to a closed container with desiccant to bring the material back to room temperature and prevent moisture in the air from being absorbed.
And (3) opening the double-screw extruder and the injection molding machine, preheating for 15min according to injection molding parameters, and then performing injection molding according to injection molding conditions of different formulas to prepare the dumbbell-type standard sample strips. And marking the injection-molded standard sample strips according to the injection molding sequence for subsequent tests. The specific injection molding test parameter settings are shown in table 3. And after the injection molding operation is finished, raising the temperature of the machine by 30-50 ℃, and wiping off the residual molten blend in the machine by using non-woven fabrics for next use.
2. Material characterization and testing
2.1 nuclear magnetic resonance hydrogen Spectroscopy (H)1-NMR) analysis
The nuclear magnetic resonance spectroscopy is an analysis method for researching the structure and composition of an organic compound by using an absorption electromagnetic spectrum generated by nuclear spin energy level transition of a spin nucleus under the action of an external magnetic field. The nuclear magnetic spectrum can be used for qualitatively and quantitatively analyzing the types and the contents of different polymers in the prepared dumbbell-type standard sample bars. And the different sample strips with the same formula are cut into small blocks, and then three test samples are randomly taken for testing, so that whether the polymers of all components in the prepared dumbbell type standard sample strip are uniformly mixed can be detected.
Weighing a sample in a glass bottle, weighing 20-50 mg of the sample, adding 1000 mu L of deuterated chloroform, heating to about 60 ℃, after the sample is fully dissolved, sampling into a nuclear magnetic tube by using a pipette, and testing by using a nuclear magnetic resonance spectrometer (400MHz type, BRUKER). And (3) testing conditions are as follows: the temperature is 23 ℃, the solvent is deuterated trichloromethane, the sampling time is 4s, the spectrum peak width is 8012.820Hz, the pulse sequence is ZG30, the scanning times are 16 times, and the relaxation time is 1 s.
2.2 Scanning Electron Microscope (SEM)
The field emission Scanning Electron Microscope (SEM) detects information such as surface morphology and composition of a sample to be measured by using interaction between electrons and a material. An electron gun emits an electron beam, the electron beam is focused and impacted on the microscopic surface of a tested sample under the action of an accelerating voltage, so that physical signals such as secondary electrons, back scattering electrons, transmission electrons and the like are excited, and the secondary electrons and the back scattering electrons are captured by a detector and converted into an SEM image.
And observing the cross section appearance of the cross section of the dumbbell-type standard sample strip after the dumbbell-type standard sample strip is brittle through a scanning electron microscope image. And soaking the prepared standard dumbbell-shaped sample strip in liquid nitrogen for 10-15 min, taking out, wearing gloves, and rapidly quenching the sample strip along the direction vertical to the melt flow. Selecting one section, cutting the section into sheets by using scissors, then adhering the sheets on a sample table by using a conductive adhesive, carrying out vacuum gold spraying treatment on the quenched section of the sample, and observing the morphological structure of the quenched section of the sample by using a scanning electron microscope (Q45-XFlash 6-30 type, FEI-Bruker), wherein the acceleration voltage is 10 kV.
2.3 testing of PH value and mechanical Properties in vitro degradation Process
Firstly, preparing a soaking solution PBS for an in-vitro degradation test, putting 10 PBS instant tablets in a beaker, adding 200mL double distilled water, fully stirring to dissolve the PBS instant tablets, then transferring the dissolved PBS instant tablets into a 1L volumetric flask, taking a small amount of double distilled water to wash the beaker and a glass rod for a plurality of times, finally fixing the volume of the solution to 1L, heating the solution to 37 ℃, measuring the pH value of the solution by using a pH meter (S210 type, Mettler Toledo), and adjusting the pH value to about 7.40 by using HCl or NaOH.
The degradation performance is mainly tested through an in-vitro degradation experiment, an injection molded dumbbell-shaped standard sample bar is placed in a reagent bottle with a cover, soaking solution PBS is added according to the proportion that the volume of the soaking solution is not less than 30 to the mass of a material, the soaking solution needs to completely immerse the soaking material, and then the sample bar is taken out for 2 weeks, 4 weeks, 6 weeks and 8 weeks respectively for testing.
The main characterization is divided into two parts: the change of the tensile elastic modulus of different composite material standard sample bars and the change of the pH value of the sample bar soaking solution. The material was taken out of the vial, left at room temperature for 30min, and then subjected to a tensile test at room temperature using a universal tester (E42.503 type, MTS), using a 1kN sensor, the tensile parameter set being tested with reference to the GB/T1040.1-2006 standard: the original gauge length of the sample was set to 10mm, the large deformation extensometer gauge length was 10mm, the drawing speed was 20mm/min, the preload force was 5N, the temperature was 23 ℃ and the indoor relative humidity was 52%. The tensile elastic modulus of the sample was calculated using the tensile strain at the deformation of 0.05% and 0.25%, and averaged after testing at least 3 splines per set. Taking out the materials in the soaking solution at a fixed time point, then putting the reagent bottles filled with the soaking solution back into the constant-temperature drying oven for constant temperature for 30min, quickly measuring by using a pH meter after taking out, measuring for 3 times by using each reagent bottle, and taking an average value.
3. Results and discussion
3.1 optical photograph of Standard sample strip
As shown in FIG. 1, the injection-molded standard bars were dumbbell-shaped, having a total length of 30mm, a middle gauge length of about 18mm, a width of 2.2mm, and a thickness of 2 mm.
3.2 Nuclear magnetic resonance Hydrogen Spectroscopy (H)1-NMR)
As shown in FIGS. 2A-2D, they are the NMR spectra (H) of the control and the modified materials of different formulations1-NMR) profile.
3.3SEM characterization
As shown in FIG. 3, (a) to (c) are scanning electron microscope photographs of the quenched cross section of a standard sample prepared from the PCL and PLGA blend modified material. In the PCL matrix in (a), PLGA in the PCL matrix is in micron-sized globules with uniform size, and is uniformly distributed in the whole PCL matrix. This indicates that PCL and PLGA are difficult to be fully compatibilized to form a homogeneous phase of the modified material, but the microspheres are well dispersed throughout the matrix, which also laterally indicates the homogeneous mixing state of the two copolymers in the standard bars. With the increase of the content of PLGA in PCL, the relationship between PCL and PLGA gradually transits from a 'sea-island structure' to a 'sea-sea structure', and careful observation of the section shows that the section of CG64 is smoother than that of CG82, which may be because PLGA is a brittle material, and the blending modified material is more prone to brittle fracture with the increase of the PLGA content. (d) And (e) is a scanning electron microscope photograph of the quenched cross section of a standard sample bar prepared by blending PCL and PLLA modified materials. (f) And (g) is a scanning electron micrograph of the PLLA and PLCL blend. It can be seen from the figure that there is a distinct interface in the PCL and PLLA blended modified material, indicating that the two materials are not completely compatible with each other. Careful observation revealed that the cross-section of CA82 was flatter than that of CA73, with no significant difference in the degree of uniformity of PLLA distribution.
3.4 degradation Properties
TABLE 4 statistical table of the variation of tensile elastic modulus with degradation time for modified materials of different formulations
FIG. 4 is a graph of the change in tensile modulus with respect to degradation time for standard specimens prepared from modified materials of different formulations, and Table 4 is a statistical table of the change in tensile modulus with respect to degradation time for standard specimens prepared from modified materials of different formulations. In comparison with the tensile elastic modulus, the addition of PLGA material and PLLA material with PCL as the matrix can indeed enhance the tensile elastic modulus of PCL. The tensile modulus of elasticity is higher in the CG group than in the CA group when PLGA and PLLA are added in the same ratio. The tensile elastic modulus of the PCL can be greatly improved by 20% of PLLA, and the tensile elastic modulus of the composite material gradually increases along with the increase of the content of the PLLA. The standard sample bar prepared by the PLGA and PLLA modified PCL composite material is white and opaque, and has no obvious change in appearance in the degradation process.
The tensile elastic modulus test result shows that the tensile elastic modulus of the PCL is effectively improved by adding 20% of PLGA and PLLA, and the tensile elastic modulus is respectively improved from 586.18MPa to 1258.91MPa and 924.56 MPa; the degradation rate of pure PCL is slowest, and the tensile elastic modulus of 8 weeks is reduced by about 40% of the initial tensile elastic modulus.
FIG. 5 is a graph showing the change of pH value of the in vitro degradation soaking solution with time for different formulations of modified materials. Table 5 is a statistical table of the change of the pH values of the in vitro degradation liquids of the modified materials with different formulas along with time. As can be seen from the graph, the pH was unchanged for the first two weeks because PBS had some buffering capacity. In the fourth week, except for the pure PCL material, the pH of the in-vitro degradation soak solution of other various composite materials is reduced to different degrees. By the eighth week the pH of the in vitro degradation soak of PCL only decreased to 7.38. From another perspective, the pH of the in vitro degradation soak dropped more rapidly over the period of weeks 6 to 8, which reflects an increase in the rate of material degradation, since the acidic environment can promote the degradation of these several materials.
TABLE 5 statistical table of pH of degradation soak solutions of each formulation at different time points over time
According to the analysis of the time-varying data of the tensile elastic modulus and the PH of the degradation soak solution of samples with different formulas, PCL, CG82, CA82 and CA73 with the degradation speed as slow as possible are selected.
Example 2:
the bandage for fixing the fracture block as shown in fig. 6 to 8 comprises a pressurizing chuck 3, a lock catch 1 and a binding belt 2 which are connected with each other, wherein an opening is arranged in the lock catch 1 in a penetrating manner in the horizontal direction, and a clamping groove 4 is formed in the top surface of the lock catch;
after the free end of the binding belt 2 penetrates through the opening of the lock catch 1 in the horizontal direction along the direction A, the pressurizing chuck 3 is clamped in the clamping groove 4 and is abutted against the binding belt 2, so that the binding belt 2 forms an annular structure.
The side surface of the pressurizing chuck 3 is provided with at least one row of saw teeth 5;
and sawtooth tooth grooves 6 matched with the sawteeth 5 are transversely arranged on the side surfaces of the clamping grooves 4.
The surface of the binding belt 2 is provided with at least one row of inverted teeth 7;
the bottom surface of the clamping groove 4 is provided with a tooth chamfering tooth groove 8 matched with the tooth chamfering 7. The inverted tooth 7 of the binding band 2 and the inverted tooth socket 8 on the bottom surface of the clamping groove 4 are matched and complementary, so that after the free end of the binding band 2 is inserted into the opening of the lock catch 1 and tightened to a certain degree, the free end of the binding band 2 and the lock catch 1 are meshed with each other, and the binding band 2 and the lock catch 1 are connected.
The connecting part of the lock catch 1 and the binding belt 2 is provided with an arc angle 9, the angle of the arc angle is 90-150 degrees, and the arc angle 9 is convenient for the binding belt to be bent and bound along the curvature of the fracture part.
The length of the lock catch 1 is 5-10 mm, the width is 5-8 mm, and the height is 5-10 mm;
the length of an opening in the lock catch 1 is 5-10 mm, the width is 3-5 mm, and the height is 3-5 mm;
the length of the clamping groove 4 is 3-5 mm, the width is 3-5 mm, and the height is 3-5 mm;
the pressurizing chuck 3 comprises a cap body section 31 and a body section 32, the saw teeth 5 are transversely arranged on the opposite side surfaces of the body section 32, the length of the cap body section 31 is 1-1.5 mm, and the length of the body section 32 is 3-5.5 mm.
The binding band 2 has a length of 150 to 200mm, a width of 3 to 10mm and a thickness of 1.5 to 2 mm.
Different specification models can be made as required to the ribbon, to the simple oblique line fracture of humerus, need 2 ~ 3 absorbable fracture piece fixing ribbon of the same or different models usually, to comminuted fracture, then according to the size of fracture piece and how many can choose for use the absorbable fracture piece fixing ribbon of many the same or different models fixed.
Fig. 9 is a schematic view of the mode of use of the cable tie of the present invention for humeral fracture fixation.
Example 3: injection molding experiment part
1. Experimental materials
Produced by Yingchuang (Evonik) industrial group
Series of polycaprolactone (PCL, model C212, viscosity of 1.13-1.38dl/g) and polylactide (PLLA, model L206S, viscosity of 0.8-1.2 dl/g).
2. Main instrument equipment
35-55CX type injection molding machine, Claus Ma Fei GmbH, Germany;
BLD-01A model air-cooled box-type water chiller, shenzhen, baylend refrigeration technology ltd;
DZF series vacuum drying ovens, Shanghai sperm macro laboratory facilities, Inc.;
VH series high-efficiency mixer (shanghai tianhe mechanical equipment);
a vacuum sealing machine.
3. Preparation of the Material
3.1 drying of the Material
And taking out the polycaprolactone hermetically stored in a refrigerator with the refrigerating temperature of 2-8 ℃ to restore to room temperature, weighing the PCL and the PLLA according to the proportion, respectively placing the PCL and the PLLA in a wide-mouth glass ware, and placing the two materials in a vacuum drying oven to remove the moisture of the materials. Drying conditions are as follows: the temperature is 40 ℃, the vacuum degree is-0.095 MPa, and the drying time is 4 hours.
3.2 premixing of materials
The 2 raw materials after vacuum drying were placed in a VH series high efficiency mixer (shanghai switching mechanical equipment company) in sequence, and the rotational speed was adjusted: 20r/min for 30 minutes, and then the 2 blends mixed immediately transferred to the barrel of an injection molding machine for processing.
3.3 injection Molding
Preheating the oil temperature to 35 ℃, starting the engine, operating the injection molding machine, and checking whether the equipment has no abnormal problems. The barrel was pre-washed with industrial plastic polypropylene to ensure the interior of the tunnel was clean. And in order to ensure the normal operation of the machine and the stable process setting, the sample strips of the first 5 guns are abandoned, and the sample strips in the 6 th to 30 th guns are taken as test samples.
3.3.1 injection Molding Process Conditioning
3.3.1.1CA82
Firstly, setting basic injection molding process parameters:
multi-stage temperature of the barrel: 165 ℃; 170 ℃; 175 ℃; 180 deg.C
Injection pressure: 70bar
Injection speed: 40mm/s
Pressure maintaining: 50bar
Pressure maintaining time: 20s
Cooling time: 10s
Temperature of the die: 15 deg.C
Gun 1-5, the material filled the mould, but there was serious flashing phenomenon, so consider the reason of the pressure excess, so reduce injection pressure and pressurize pressure, 50bar, 30bar respectively. 4 th to 5 th guns, the flash phenomenon is improved, but the material does not fill the mould, so the injection pressure and the holding pressure are properly adjusted to be 55bar and 35bar respectively. And 6, filling the mold with the material, and effectively adjusting. However, the 7 th to 10 th guns did not release smoothly, and the cooling time was increased to 20 s. No improvement was seen in the 8 th to 10 th gun release problems. Then the temperature of the mould is reduced to 10 ℃, and the upper part of the mould is not smooth after being demoulded by a gun 11-15. The dwell time was adjusted to 10 s. Gun 16-20, gate demolding is not smooth. And the dwell time is adjusted to 15s, the dwell pressure is adjusted to 25bar, and the 21 st to 25 th guns are adopted, so that the problem is not obviously improved. The dwell pressure was then adjusted to 35bar and the cooling time was 10 s. Guns 26-30, demold successfully, and no flashing occurred.
After injection molding process parameters are adjusted for multiple times, according to the appearance and the appearance of the material and the demoulding difficulty, the ratio of PCL to PLLA is 8: the optimal process parameters for preparing the sample strips by blending in the proportion of 2 are as follows:
multi-stage temperature of the barrel: 170 ℃; 185 ℃; 185 ℃; 175 deg.C
Injection pressure: 55bar
Injection speed: 150mm/s
Pressure maintaining: 800bar
Pressure maintaining time: 7s
Cooling time: 10s
Temperature of the die: at 15 deg.C.
3.4 preservation of samples
And labeling the prepared samples according to the sequence, and then sealing and storing the samples through a vacuum sealing machine for different testing requirements.
4. Mechanical testing
TABLE 6 initial time point mechanical testing of bands made of modified materials of different formulations
5. Animal experiments
The bandages made of the modified materials with different formulas are respectively sterilized by ethylene oxide and then implanted into the femoral bone defect of the beagle dog. Respectively taking materials in the first month and the third month, analyzing, and screening out the optimal material formula by comparing the degradation conditions in the animal body.
TABLE 7 one month post-operation bandage mechanical test (37 ℃, 5mm/min)
TABLE 8 binding tape mechanics test three months after operation (37 deg.C, 5mm/min)
6. Conclusion of the experiment
According to the standard sample bar test analysis prepared by the previous miniature twin-screw extruder and the mechanical test of the animal test of the cable ties made of modified materials with different formulas, the formula of the cable tie is finally determined to be CA82 (PCL: PLLA ═ 8: 2). The tensile modulus of elasticity of the standard sample bars of the formulation was 924.56/748.39/496.04/398.43/340.99MPa measured at 0/2/4/6/8 th week of degradation, respectively, and was relatively better than the modulus of elasticity of the other formulations. And the shape of the beagle dog after three months of implantation in vivo is kept intact by material selection and observation, and the maximum breaking force is the best in all formulas: 127N (fig. 10 and 11).
Example 4:
a bandage for fixing fracture block is prepared from Polycaprolactone (PCL) and levorotatory polylactic acid (PLLA), wherein the weight ratio of the PCL to the PLLA is 80: 20. The structure of the ribbon is the same as that of the embodiment 2, wherein the length of the lock catch 1 is 10mm, the width is 8mm, and the height is 8 mm;
the length of an opening in the lock catch 1 is 10mm, the width is 5mm, and the height is 5 mm;
the length of the clamping groove 4 is 4mm, the width of the clamping groove is 3mm, and the height of the clamping groove is 2 mm;
the length of the cap section 31 of the pressurizing chuck 3 is 1.3mm, and the length of the body section 32 of the pressurizing chuck 3 is 5.2 mm;
the length of the binding belt 2 is 200mm, the width is 5mm, and the thickness is 1.5 mm;
the angle of the arc angle 9 arranged at the joint of the lock catch 1 and the binding belt 2 is 135 degrees.
The preparation method of the cable tie comprises the following steps: successively putting the vacuum-dried raw materials of polycaprolactone and levorotatory polylactic acid into a high-efficiency mixer, and adjusting the rotating speed: 20r/min, mixing for 30 minutes, and immediately transferring the mixed blend into a charging barrel of an injection molding machine for injection molding; the process parameters are as follows:
multi-stage temperature of the barrel: 165-180 ℃; 175 ℃ and 195 ℃; 170-195 ℃; 165-185 ℃;
injection pressure: 50-60 bar;
injection speed: 140-160 mm/s;
pressure maintaining pressure: 700-850 bar;
pressure maintaining time: 6-8 s;
cooling time: 9-12 s;
temperature of the die: 14.5-16 ℃.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. The utility model provides a ribbon for comminuted fracture piece is fixed which characterized in that, the ribbon make by polycaprolactone and levorotatory polylactic acid, wherein polycaprolactone and levorotatory polylactic acid's weight ratio is (70-80): (20-30).
2. A strap for comminuted fracture fixation as recited in claim 1, wherein the strap comprises a pressurizing chuck, a lock catch and a binding band, the lock catch and the binding band are connected with each other, the lock catch has an opening extending through it in the horizontal direction, and the top surface of the lock catch has a slot, the slot is connected with the opening; after the free end of the binding belt penetrates through the opening in the horizontal direction of the lock catch, the pressurizing chuck is clamped in the clamping groove and is abutted against the binding belt, so that the binding belt forms an annular structure.
3. A cable tie for comminuted fracture fixation as recited in claim 2, wherein a side surface of said compression clamp is provided with at least one row of serrations; and sawtooth tooth grooves matched with the sawteeth are formed in the side faces of the clamping grooves.
4. A tie for comminuted fracture fixation as recited in claim 2, wherein the surface of said tie is provided with at least one row of inverted teeth; the bottom surface of the clamping groove is provided with a tooth chamfering tooth groove matched with the tooth chamfering.
5. The strap for comminuted fracture fixation of claim 2 wherein the junction of the locking device and the strap has an arcuate angle of 90 to 150 °.
6. A cable tie for comminuted fracture fixation as recited in claim 2, wherein the compression clamp includes a cap section and a body section, the serrations being disposed laterally on opposite sides of the body section.
7. A method for preparing a bandage for comminuted fracture fixation according to any one of claims 1 to 6, characterised in that an injection moulding process is used, said injection moulding process having the parameters:
multi-stage temperature of the barrel: 165-180 ℃; 175 ℃ and 195 ℃; 170-195 ℃; 165-185 ℃;
injection pressure: 50-60 bar;
injection speed: 140-160 mm/s;
pressure maintaining: 700-850 bar;
pressure maintaining time: 6-8 s;
cooling time: 9-12 s;
temperature of the die: 14.5-16 ℃.
8. The method of preparing a cable tie for comminuted fracture fixation of claim 7 including the steps of: successively putting the vacuum-dried raw materials of polycaprolactone and levorotatory polylactic acid into a high-efficiency mixer, and adjusting the rotating speed: 20r/min, mixing time 30 minutes, and then immediately transferring the mixed mixture into a charging barrel of an injection molding machine for injection molding processing.
9. Use of a cable tie for comminuted fracture fixation according to any one of claims 1 to 6 in the manufacture of an orderly absorbable fracture fixation device.
10. The use of claim 9, wherein said ordered absorption is achieved by implantation in the human body for three months with the band remaining intact, and after six months the degradation is accelerated and over about two years.
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