title: Biomechanical study of expandable pedicle screw fixation in severe osteoporotic bone comparing with conventional and cement-augmented pedicle screws.
abstract: Pedicle screws are widely utilized to treat the unstable thoracolumbar spine. The superior biomechanical strength of pedicle screws could increase fusion rates and provide accurate corrections of complex deformities. However, osteoporosis and revision cases of pedicle screw substantially reduce screw holding strength and cause loosening. Pedicle screw fixation becomes a challenge for spine surgeons in those scenarios. The purpose of this study was to determine if an expandable pedicle screw design could be used to improve biomechanical fixation in osteoporotic bone. Axial mechanical pull-out test was performed on the expandable, conventional and augmented pedicle screws placed in a commercial synthetic bone block which mimicked a human bone with severe osteoporosis. Results revealed that the pull-out strength and failure energy of expandable pedicle screws were similar with conventional pedicle screws augmented with bone cement by 2 ml. The pull-out strength was 5-fold greater than conventional pedicle screws and the failure energy was about 2-fold greater. Besides, the pull-out strength of expandable screw was reinforced by the expandable mechanism without cement augmentation, indicated that the risks of cement leakage from vertebral body would potentially be avoided. Comparing with the biomechanical performances of conventional screw with or without cement augmentation, the expandable screws are recommended to be applied for the osteoporotic vertebrae.
authors.affiliation: Institute of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan; Department of Neurosurgery, Taipei City Hospital, Taipei, Taiwan.
authors.forename: Yi-Long
authors.initials: YL
authors.lastname: Chen
authors.affiliation: Orthopaedic Device Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Wen-Chuan
authors.initials: WC
authors.lastname: Chen
authors.affiliation: Department of Human Physiology, University of Oregon, OR, United States.
authors.forename: Chi-Wei
authors.initials: CW
authors.lastname: Chou
authors.affiliation: Orthopaedic Device Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Jou-Wen
authors.initials: JW
authors.lastname: Chen
authors.affiliation: Institute of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chia-Ming
authors.initials: CM
authors.lastname: Chang
authors.affiliation: Orthopaedic Device Research Center, National Yang-Ming University, Taipei, Taiwan. Electronic address: yslai@ym.edu.tw.
authors.forename: Yu-Shu
authors.initials: YS
authors.lastname: Lai
authors.affiliation: Institute of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan; Orthopaedic Device Research Center, National Yang-Ming University, Taipei, Taiwan. Electronic address: ckcheng@ym.edu.tw.
authors.forename: Cheng-Kung
authors.initials: CK
authors.lastname: Cheng
authors.affiliation: School of Medicine, National Yang-Ming University, Taipei, Taiwan. Electronic address: stwang@vghtpe.gov.tw.
authors.forename: Shih-Tien
authors.initials: ST
authors.lastname: Wang
mesh_terms: D001843:Bone Cements; D006801:Humans; D008422:Materials Testing; D055595:Mechanical Phenomena; D019637:Orthopedic Procedures; D010024:Osteoporosis / Q000601:surgery*; D065289:Pedicle Screws; D011475:Prosthesis Failure; D013131:Spine / Q000601:surgery*
chemical_list: D001843:Bone Cements
keywords: Cement augmentation; Expandable pedicle screw; Failure energy; Osteoporosis; Pedicle screw; Pull-out