title: Biomechanical comparison of pullout strengths of five cortical screw types: An innovative measurement method.
abstract: OBJECTIVE
  This study aims to assess five different cortical screw types using artificial femurs, under equated testing conditions.
  
  
  METHODS
  We investigated the maximum force needed to cause deformation at screw-bone interface using fourth generation composite femurs by conducting separate pullout tests for each screw type. We normalized obtained results with traditional methods and cross-comparison. To conduct pullout tests dependent on screw dimensions, we eliminated the effect of bicortical bone thickness by equalizing the conditions of screw insertion.
  
  
  RESULTS
  Non-locking screws with larger diameter and pitch depth required larger pullout forces to be extracted, showing statistically superior performance compared to locking screws with smaller dimensions. However, the statistical differences between the absolute pullout forces decreased after the traditional normalization of the results. We proposed a new normalization method based on solid geometric reasoning.
  
  
  CONCLUSIONS
  This novel approach showed that a screw type that appeared to show average performance, in fact, did not have statistically significantly different results than the top performers. Surgeons are not required to prefer larger dimension screws in small dimension host bones.
authors.affiliation: Department of Orthopedics and Traumatology, Medical Faculty of Dokuz Eylul University, 35340, Balçova, İzmir, Turkey.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Karakaşlı
authors.forename: Nihat
authors.initials: N
authors.lastname: Acar
authors.forename: Mehmet Hilal
authors.initials: MH
authors.lastname: Özcanhan
authors.forename: Fatih
authors.initials: F
authors.lastname: Ertem
mesh_terms: D001696:Biomechanical Phenomena; D001863:Bone Screws; D000071538:Cortical Bone / Q000601:surgery*; D004867:Equipment Design; D005269:Femur / Q000601:surgery; D006801:Humans; D008422:Materials Testing; D013718:Tensile Strength