title: Optimizing bone screw pullout force.
abstract: Stability of internal fixation by plate and screw depends on the interface of bone and screw threads. Bone-screw thread design was tested in a synthetic bone model to determine maximum bone-screw pullout force. The model was confirmed to provide reproducible results in a clinically relevant range. Consistent material properties were reflected in the relatively small standard deviations in pullout force, which were less than 10% of mean values. As expected, major diameter was an important determinant of pullout force in a roughly linear manner. Pitch was important with a finer thread giving greater purchase. Minor diameter and the ratio of major to minor diameter had a small but significant effect on pullout force. This study was significant for establishing a good bone-screw testing model and suggesting important thread parameters in selecting or manufacturing a bone screw to optimize its holding power.
authors.affiliation: Department of Orthopaedics and Rehabilitation, University of New Mexico School of Medicine, Albuquerque 87131.
authors.forename: T A
authors.initials: TA
authors.lastname: DeCoster
authors.forename: D B
authors.initials: DB
authors.lastname: Heetderks
authors.forename: D J
authors.initials: DJ
authors.lastname: Downey
authors.forename: J S
authors.initials: JS
authors.lastname: Ferries
authors.forename: W
authors.initials: W
authors.lastname: Jones
mesh_terms: D001696:Biomechanical Phenomena; D001863:Bone Screws; D004867:Equipment Design; D004868:Equipment Failure; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans