The Development Of The Built-in Expandable Bio-coating Anterior Spinal Internal Fixation System

Objective Nano hydroxyapatite coatings were prepared on the surface of the built-in expandable anterior spinal screws by plasma spraying,and their physicochemical properties,biomechanics and biocompatibility were studied.Methods 1.Preparation of the nano hydroxyapatite coating and the physical and chemical properties of the built-in expandable bio-coating anterior spinal internal fixation system.Nano hydroxyapatite coating was prepared by plasma spraying on the surface of the built-in expandable anterior spinal screws,and its physicochemical properties were detected.2.Biomechanical testing of the built-in expandable bio-coating anterior spinal internal fixation system.24 porcine vertebral specimens were randomly divided into four groups(6 per group).Group A:uncoated and non expandable screw,group B:coated and non expandable screw,group C:expanded and uncoated screw,group D:coated and expanded screw.The four sets of screws were implanted in the specimens,and the maximum torque and pulling force were measured by the biomechanical performance measuring instrument.3.Biocompatibility test of the built-in expandable bio-coating anterior spinal internal fixation system.The in vitro cytotoxicity test:according to the tetrazolium colorimetric method,we used the L-929 mouse fibroblast cells as the research object,the relative growth rate calculated and graded cell morphology were observed.The maximum dose sensitization test:the guinea pigs were induced by intradermal induction,local induction and excitation,and the skin conditions and inflammation were observed.Muscle implantation test:SD rats were taken as the research subjects for 26 weeks,and the local tissue reaction of muscles was observed.Results 1.Nano hydroxyapatite coating was successfully prepared on the surface of the built-in expandable anterior spinal screws,and the physical and chemical properties of the built-in expandable bio-coating anterior spinal internal fixation system were in accordance with the standards provided by the enterprise.2.There was no significant difference of the maximum torques and pullout strength between group A and group B,and also between group C and group D.The maximum pullout force between group D and group B was significant,and there was no significant difference of the maximum torques group D and group B,Moreover,the maximum torques between group D and group A was significant.3.The in vitro cytotoxicity test:the cells of each experimental group was grade 0-1.The maximum dose sensitization test:there was no erythema or edema in the experimental group,and the Magnusson and Kligman levels were 0.In addition,the skin tissue showed no obvious inflammatory reaction,and the inflammation grade was I.Muscle implantation test:after first weeks,the degree of inflammatory cell reaction and the formation of the cyst wall in the experimental group were IV and 0,respectively,? and ? after fourth weeks,? and ? after twelfth weeks,? and ? after twenty-sixth weeks respectively.Conclusion 1.Nano hydroxyapatite coating was successfully prepared on the surface of the built-in expandable anterior spinal screws,and the physical and chemical properties of the built-in expandable bio-coating anterior spinal internal fixation system were in accordance with the standards provided by the enterprise.2.The maximum pullout strength and torques of the built-in expandable bio-coating anterior spinal internal fixation system before and after the Nano hydroxyapatite coating are almost the same.This means that this fixation system also has good biomechanical properties after hydroxyapatite coating.Moreover,the maximum torque of the coated and expanded screw is larger than that of the uncoated and non expandable screw.3.The built-in expandable bio-coating anterior spinal internal fixation system did not have cytotoxicity in vitro,and it did not cause sensitization.Furthermore,this internal fixation system has no stimulation on the surrounding tissues in muscle implantation test.