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In Vivo Degradation and Biomechanical Analysis of Centrum-vertebra-fracture-repairing Absorbable Supporting Plugger

Author: YinJin
Tutor: TangXun
School: Kunming Medical College
Course: Surgery
Keywords: Poly -D L- lactic acid ( PDLLA ) Calcium beta - tricalcium phosphate ( beta - TCP ) The absorbent composite material Can absorb the vertebral body support ( CASP ) Animal experiments In vivo degradation Biocompatibility Biomechanics
CLC: R318.08
Type: Master's thesis
Year: 2008
Downloads: 26
Quote: 0
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The purpose of using a poly-D, L-lactic acid (poly-D, L-lactic acid, PDLLA) and the beta-phosphate tribasic calcium (the beta-TricalciumPhosphate, beta-TCP) in different proportions composite made 6% β-TCP/PDLLA a 12% β-TCP/PDLLA and pure PDLLA can absorb the vertebral body support (Centrum-vertebra-fracturerepairingabsorbable supporting plugger, CASP) and 4mm, 5mm in length of columnar material specimens were implanted into New Zealand white rabbits gluteus maximus and femur The condylar within. To study the in vivo degradation process the appearance of the material, morphological changes, the compatibility of the material with the surrounding tissue, the material mass loss rate, the loss of mechanical strength of materials in the process and speed, and many other parameters for the three materials. The purpose of the evaluation of different composite materials CASP after the implantation of the material and degradation products safety, degradation rate, biomechanical properties. And to filter out material more suitable for clinical application. The method can be absorbed in vivo degradation of the vertebral support observational studies: CASP and columnar material electronic weighing scales, recorded as the original quality. 120 New Zealand white rabbits (male and female), weight 2.5 ± 0.3kg, were randomly divided into three groups, namely 6% β-TCP/PDLLA group, 12% β-TCP/PDLLA group PDLLA group, n = 40 . CASP and columnar material specimen were implanted into New Zealand white rabbits gluteus maximus and the femoral condyle, the experimental animals after general observation and experimental animals were sacrificed at 4, 8, 12, 16 weeks, six months, observing the muscles around the material organizations and whether the femoral condyle morphological changes, and compared with the contralateral normal tissue. Remove intramuscular specimen, excised attached organizations, to observe the appearance of the material, and morphological changes. Cleaning material, after drying weighed again to calculate the mass loss rate (n = 8). Evaluation of different material difference deadline to six months early and mid degradation process security and degradation products, degradation processes and rates. And filter out all aspects of performance is more suitable for clinical application materials. Can absorb the vertebral body support degradation in vivo experimental study of biomechanics: Shimadzu AG-1 universal material testing machine is made of three different materials the CASP and columnar material destructive testing compression, record load - displacement curve calculated and plotted the stress - strain curve and calculate the initial compressive strength (n = 8). After 4, 8, 12, 16 weeks, half of the experimental animals were sacrificed remove intramuscular specimen, removed from the attached tissue, cleaning, drying again in the universal testing machine mechanical experiments, to calculate the compressive strength and compressive modulus (n = 8). Observed in the degradation process change and the rate of loss of compressive strength, compressive modulus, combined with the mass loss rate of change in the degradation process, the evaluation of three different materials up to six months early, mid-degradation process biomechanical properties and filter out material more suitable for a certain period of time to provide effective support for the role of the vertebral. Results of three composite cylindrical body and after CASP implanted animals generally in good condition, the day of the postoperative animal awake, start drinking water, eating the next day, healing postoperative wound I / A, no purulent infection, subcutaneous effusion is formed. Within a maximum period of 6 months of observation time, visible bone tissue close, the distal femur swelling, necrosis, osteoporosis; muscle tissue tightly packed the CASP and columnar material around the part of the specimen mild muscle fibers , no infection, purulent tissue liquefaction phenomenon. 2 4 weeks after surgery, the 6% β-TCP/PDLLA, group material appearance, quality loss is not obvious the material surface 12% β-TCP/PDLLA group slightly rough, mild softening, loss of quality is not obvious; pure PDLLA group degradation of performance between the two materials; 4-8 weeks, three materials are gradually softening the surface becomes rough change, and with varying degrees of weight loss, 6% β-TCP/PDLLA group degradation process slightly slower than the other two materials. 8-12 weeks, 6% β-TCP/PDLLA degradation process has stabilized, the shape did not change significantly; 12% β-TCP/PDLLA the increased rate of degradation, formed on the surface of a large number of visible varying shades of cracks, edge blunting intensified material curved shape, a serious loss of quality; the pure PDLLA material degradation process is slightly slower than the former, surface roughness, blunt edge, inside the material becomes cloudy, accelerated loss of quality; 12-16 weeks, 6% β-TCP/PDLLA group of materials degradation process remains stable, an increase in surface cracks, curved shape, the upper and lower side walls of the tines blunt; 12% β-TCP/PDLLA to degrade more rapidly, material distortion, severe deformation of, Casp double side wall cavity compression, the upper, the lower wall surface of the tines significant blunting; abnormal fragile material, means that the force will be able to be broken; turbid the pure PDLLA materials interior, the edge becomes blunt, curved shape is obvious, material softening, to shorten the length of the columnar materials, Volume narrow at both ends degradation into a circular shape. Half of the 16 Monday, 6% β-TCP/PDLLA material accelerated degradation of the material appearance further bending, deformation, significant blunting sharp teeth, an increase in surface cracks, darker, increased mass loss. 12% β-TCP/PDLLA in complete loss of strength of the material, severe softening of muscle tissue is tightly wrapped in compression deformation of the support can not be completely removed, until late in the muscle tissue of an absorbable material fragmentation as an amorphous particulate matter, has been unable to removed intact; pure PDLLA materials soften significantly further narrow shape, CASP distortion serious, columnar material looks like spherical. The 3.6% β-TCP/PDLLA, 12% β-TCP/PDLLA the pure PDLLA materials CASP the initial state can withstand compressive load of 6551 ± 316N, 6433 ± 251N, 6865 ± 244N, much larger than the lumbar day-to-day activities of the axial suffered loads. Implanted 12 weeks, the compressive strength still reached 3128.9 ± 147N/cm ~ 2,1287.1 ± 107N/cm ~ 2,3209.9 ± 176N/cm ~ 2, is still higher than the lumbar ultimate compressive strength. The initial compressive strength of the three columnar materials were 106.121 ± 7.651MPa 104.240 ± 10.407MPa, 109.803 ± 12.089MPa, much larger than the cancellous bone compressive strength (1-17MPa); compressive strength decreased after 12 weeks of implantation, 90.601 ± 16.626MPa, 39.401 ± 4.720MPa, 81.529 ± 6.662MPa, 12% TCP / PDLLA group showing a the intense downward trend, but the strength is still higher than the cancellous bone; implanted in six months, 6% TCP / PDLLA and pure the PDLLA compressive strength decreased to 37.248 ± 4.771MPa, 19.735 ± 2.328MPa, still slightly higher than the compressive strength of cancellous bone. The compressive modulus, the initial modulus of the three materials were 12.311 ± 0.888GPa, 12.093 ± 1.207GPa, 12.738 ± 1.402GPa, much higher than the the human vertebral elastic modulus (2GPa); after 12 weeks, respectively, dropped to 10.511 ± 1.929GPa, 4.571 ± 0.548GPa, 9.458 ± 0.773GPa, still higher than the vertebral cancellous bone compressive modulus; Six months later, 12% TCP / the PDLLA group of materials compression modulus can not be measured, but 6% TCP / the material compressive modulus of PDLLA and pure PDLLA Group group 4.321 ± 0.553GPa, 2.289 ± 0.270GPa, still slightly higher than the vertebral compression modulus. Conclusion 1. Initial report of research and absorbing polymer composite materials with inorganic bio-ceramic materials made for thoracolumbar burst fractures of the vertebral body reconstruction can absorb the vertebral body support. 2 three materials have good biocompatibility, implanted in the body can be the body absorption and degradation, degradation of the early and mid-material itself and its degradation products will not have adverse effects in experimental animals, materials implanted in the surrounding muscle tissue and bone tissue abnormalities. 3 accompanied by a loss of quality of materials, three materials appear different rate of degradation processes, but have the ability to absorb body degradation. 4 three materials of their initial compressive strength and elastic modulus higher than the human vertebral cancellous bone, but compared to the metal implant, the compressive modulus is closer to the normal vertebral cancellous bone, and with the body degradation process further decline. Can absorb the vertebral body support fully meet the support requirements within the vertebral body to avoid the occurrence of stress shielding. 5 No matter what kind of material, their respective mass loss rate and the rate of decrease of compressive strength of apparent inconsistencies, the decrease in strength was significantly faster than the loss of quality. Loss of quality and strength decreased the degradation process of the of 6.6% β-TCP/PDLLA material than 12% β-TCP/PDLLA pure PDLLA smooth, it might be more ideal vertebral reconstruction absorbing composite materials.

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