title: A Biomechanical Comparison of Expansive Pedicle Screws for Severe Osteoporosis: The Effects of Screw Design and Cement Augmentation.
abstract: Expansive pedicle screws significantly improve fixation strength in osteoporotic spines. However, the previous literature does not adequately address the effects of the number of lengthwise slits and the extent of screw expansion on the strength of the bone/screw interface when expansive screws are used with or without cement augmentation. Herein, four designs for expansive pedicle screws with different numbers of lengthwise slits and different screw expansion levels were evaluated. Synthetic bones simulating severe osteoporosis were used to provide a comparative platform for each screw design. The prepared specimens were then tested for axial pullout failure. Regardless of screw design, screws with cement augmentation demonstrated significantly higher pullout strength than pedicle screws without cement augmentation (p < 0.001). For screws without cement augmentation, solid screws exhibited the lowest pullout strength compared to the four expansive groups (p < 0.01). No significant differences in pullout strength were observed between the expansive screws with different designs (p > 0.05). Taken together, our results show that pedicle screws combined with cement augmentation may greatly increase screw fixation regardless of screws with or without expansion. An increase in both the number of slits and the extent of screw expansion had little impact on the screw-anchoring strength. Cement augmentation is the most influential factor for improving screw pullout strength.
authors.affiliation: Graduate Institute of Medical Mechatronics, Department of Mechanical Engineering, Chang Gung University, Kweishan, Taoyuan, Taiwan.
authors.forename: Ching-Lung
authors.initials: CL
authors.lastname: Tai
authors.affiliation: Department of Orthopedic Surgery, Bone and Joint Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Kweishan, Taoyuan, Taiwan.
authors.forename: Tsung-Ting
authors.initials: TT
authors.lastname: Tsai
authors.affiliation: Department of Orthopedic Surgery, Bone and Joint Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Kweishan, Taoyuan, Taiwan.
authors.forename: Po-Liang
authors.initials: PL
authors.lastname: Lai
authors.affiliation: Graduate Institute of Medical Mechatronics, Department of Mechanical Engineering, Chang Gung University, Kweishan, Taoyuan, Taiwan.
authors.forename: Yi-Lu
authors.initials: YL
authors.lastname: Chen
authors.affiliation: Graduate Institute of Medical Mechatronics, Department of Mechanical Engineering, Chang Gung University, Kweishan, Taoyuan, Taiwan.
authors.forename: Mu-Yi
authors.initials: MY
authors.lastname: Liu
authors.affiliation: Department of Orthopedic Surgery, Bone and Joint Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Kweishan, Taoyuan, Taiwan.
authors.forename: Lih-Huei
authors.initials: LH
authors.lastname: Chen
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology*; D001843:Bone Cements / Q000627:therapeutic use*; D001842:Bone and Bones / Q000601:surgery; D004867:Equipment Design / Q000295:instrumentation*; D006801:Humans; D008422:Materials Testing; D010024:Osteoporosis / Q000601:surgery / Q000628:therapy*; D065289:Pedicle Screws
chemical_list: D001843:Bone Cements