title: Effect of screw diameter, insertion technique, and bone cement augmentation of pedicular screw fixation strength.
abstract: This study investigated (1) the effect of screw diameter and insertion technique in lumbar vertebrae, and insertion site in the sacrum, on the axial pullout force and transverse bending stiffness of pedicle screws, and (2) the effect of bone cement augmentation using polymethylmethacrylate (PMMA) and the biodegradable composite, poly(propylene glycol-fumarate) on axial pullout force and transverse bending stiffness of pedicle screws inserted into lumbar vertebrae. The axial pullout force and transverse bending stiffness of a 6.25-mm Steffee screw and a 6-mm Kluger screw did not differ significantly in vertebral bodies of similar equivalent bone mineral density. The axial pullout force of Schanz screws was significantly increased with a 1-mm increase in screw diameter. However, there was no significant increase in transverse bending stiffness. In the sacrum, an approach through the S1 facet produced significantly higher axial pullout forces and transverse bending stiffness than the approach described by Harrington and Dickson. PMMA and a biodegradable composite bone cement poly(propylene glycol-fumarate) both increased the axial pullout force. PMMA also increased the transverse bending stiffness.
authors.affiliation: Department of Orthopaedic Surgery, Charles A. Dana Research Institute, Beth Israel Hospital, MA 02215.
authors.forename: R H
authors.initials: RH
authors.lastname: Wittenberg
authors.forename: K S
authors.initials: KS
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Shea
authors.forename: A A
authors.initials: AA
authors.lastname: White
authors.forename: W C
authors.initials: WC
authors.lastname: Hayes
mesh_terms: D001696:Biomechanical Phenomena; D015519:Bone Density; D001863:Bone Screws; D006801:Humans; D008159:Lumbar Vertebrae; D008768:Methylmethacrylates; D011108:Polymers; D011409:Propylene Glycols; D012447:Sacrum; D013718:Tensile Strength
chemical_list: D008768:Methylmethacrylates; D011108:Polymers; D011409:Propylene Glycols; C012504:polypropylene glycol