title: Hydroxyapatite composite resin cement augmentation of pedicle screw fixation.
abstract: Pedicle screw stability is poor in osteopenic vertebrae attributable, in part, to low screw-bone interface strength. The current authors examined cement augmentation using a low curing temperature hydroxyapatite and bis-phenol-A glycidol methacrylate-based composite resin. This cement may stiffen the screw-bone interface and reduce the harmful effects associated with polymethylmethacrylate regarding temperature and toxic monomer. Thirty-five lumbar vertebrae from human cadavers were instrumented with pedicle screws, with one pedicle previously injected with cement and the other as the control. Caudocephalad toggling of +/- 1 mm for 1600 cycles was applied to the pedicle screws, and the resulting forces supported by the implant-bone interface were captured by a load cell. A curve was constructed from the peak caudal load for each cycle and three mechanical measures parameterized this curve: (1) initial load; (2) rate of load decay during the first 400 cycles; and (3) final load. The initial load increased by 16% as a result of cement augmentation, the final load increased by 65%, and the rate of load decay decreased by 59%. Cement augmentation of pedicle screws increased the stiffness and stability of the screw-bone interface.
authors.affiliation: Orthopaedic Research Laboratories, Division of Surgery, The University of New South Wales, Prince of Wales Hospital, Sydney, NSW, Australia.
authors.forename: Alexander W L
authors.initials: AW
authors.lastname: Turner
authors.forename: R Mark
authors.initials: RM
authors.lastname: Gillies
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Svehla
authors.forename: Masanobu
authors.initials: M
authors.lastname: Saito
authors.forename: William R
authors.initials: WR
authors.lastname: Walsh
mesh_terms: D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D001843:Bone Cements; D015519:Bone Density; D001863:Bone Screws; D002102:Cadaver; D017886:Durapatite; D004867:Equipment Design; D006801:Humans; D016014:Linear Models; D008159:Lumbar Vertebrae / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation*; D013314:Stress, Mechanical
chemical_list: D001843:Bone Cements; D017886:Durapatite