title: Enhancement of pedicle screw stability using calcium phosphate cement in osteoporotic vertebrae: in vivo biomechanical study.
abstract: We conducted an experimental study using female beagles with and without ovariectomy-induced osteoporosis to determine the effect of calcium phosphate cement (CPC) on the mechanical stability of inserted pedicle screws. A drill hole was created from the base of the transverse process to the vertebral body; CPC was injected into the hole, and then a screw was inserted into the same hole. In the presence of osteoporosis evidenced by dual X-ray absorptiometry, the stability of the inserted screw augmented by CPC against pull-out and cephalocaudal forces were significantly greater by 28% and 54% at 1 week after operation, 48% and 71% at 2 weeks, and 56% and 68% at 4 weeks compared with those without CPC. The pull-out strength increased progressively with time after surgery, probably reflecting new-bone growth from the surrounding cancellous bone, which was in direct contact with the CPC, as shown in the histologic study. At each time point the cephalocaudal rigidity was similar and the pull-out strength greater than that for the screws inserted without CPC in nonporotic dogs. These findings suggest that CPC augments the stability of the inserted pedicle screws and increases the stiffness of fixed osteoporotic motion segments using instrumentation.
authors.affiliation: Department of Orthopaedic Surgery, Kochi Medical School, Kohasu, Oko-cho, Nankoku 783-8505, Japan.
authors.forename: Yoshimichi
authors.initials: Y
authors.lastname: Taniwaki
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Takemasa
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Tani
authors.forename: Hiroo
authors.initials: H
authors.lastname: Mizobuchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002130:Calcium Phosphates / Q000494:pharmacology / Q000627:therapeutic use*; D004285:Dogs; D005260:Female; D010024:Osteoporosis / Q000601:surgery*; D013131:Spine
chemical_list: D002130:Calcium Phosphates; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous