title: Improving fixation strength of pedicle screw by microarc oxidation treatment: an experimental study of osteoporotic spine in sheep.
abstract: Failure of fixation caused by loosening of pedicle screws in osteoporosis is a problem in spinal surgery. We compared the in vivo fixation strength between pedicle screws treated with microarc oxidation (MAO) and untreated screws in an osteoporotic model of ovariectomized sheep. The MAO treated and untreated screws were placed in lumbar vertebral bodies. After 3 months of implantation, biomechanical tests, micro-CT analysis, and histological observations were conducted to examine the performance of the two groups. At time 0, no significant difference was found between the two groups in biomechanical tests (p > 0.05); 3 months later, higher pull-out strength and load with less displacement were detected in the MAO-treated group (p < 0.05). Micro-CT analysis showed that the tissue mineral density, bone volume fraction, trabecular thickness, and trabecular number in the MAO-treated group were all higher than those in untreated group (p < 0.05), and trabecular spacing was smaller (p < 0.05). Histologically, the bone-implant interface in the MAO-treated group was better than that in untreated group (p < 0.05). In conclusion, pedicle screws with a bioactive surface treated by MAO can improve screw fixation strength in osteoporotic spines in sheep.
authors.affiliation: Department of Orthopedics, Xijing Hospital, Fourth Military Medical University, Xi'an, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
authors.forename: Ling
authors.initials: L
authors.lastname: Wang
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Zheng
authors.initials: Z
authors.lastname: Guo
authors.forename: Zi-xiang
authors.initials: ZX
authors.lastname: Wu
authors.forename: Da
authors.initials: D
authors.lastname: Liu
authors.forename: Ming-xuan
authors.initials: MX
authors.lastname: Gao
authors.forename: Huan
authors.initials: H
authors.lastname: Chen
authors.forename: Suo-chao
authors.initials: SC
authors.lastname: Fu
authors.forename: Wei
authors.initials: W
authors.lastname: Lei
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws; D005260:Female; D016268:Internal Fixators / Q000592:standards; D008159:Lumbar Vertebrae / Q000601:surgery; D016348:Osseointegration; D010024:Osteoporosis / Q000000981:diagnostic imaging / Q000601:surgery*; D010084:Oxidation-Reduction; D034561:Sheep, Domestic; D013131:Spine / Q000000981:diagnostic imaging; D013499:Surface Properties; D055114:X-Ray Microtomography