title: Pullout strength and load to failure properties of self-tapping cortical screws in synthetic and cadaveric environments representative of healthy and osteoporotic bone.
abstract: BACKGROUND
  The parameters of self-tapping screw (STS) performance in normal and osteoporotic bone have been defined in representative environments, but the question remains as to the clinical application of such findings. The goal of this study was to analyze the biomechanical performance of STSs in cadaveric and synthetic environments representative of healthy and osteoporotic bone.
  
  
  METHODS
  Ninety-six Synthes STSs were inserted into cadaveric and synthetic models representative of osteoporotic and healthy bone. Screws were inserted to depths of 1 mm short of the far cortex, flush and 1 mm and 2 mm beyond the far cortex. Screws were tested with an Instron 8511 material testing system utilizing axial pullout forces. A SAS procedure was used to conduct analysis of variance for unbalanced datasets.
  
  
  RESULTS
  Substantial differences were appreciated with respect to screw performance between osteoporotic and healthy bone specimens. Although a similar pattern of increased pullout strength and loading energy with increasing depth of insertion was demonstrated, absolute values were lower in osteoporotic specimens. Although performance trends were similar in cadaveric and synthetic testing models for both osteoporotic and healthy bone, values obtained during testing were different. Incomplete insertion of STSs resulted in a 21.5% and 37% reduction of biomechanical properties in osteoporotic and normal bone, respectively.
  
  
  CONCLUSIONS
  These results indicate that previously published findings on the performance of STSs in synthetic models cannot reasonably be applied to the clinical realm. Although trends may be similar, screw performance in synthetic, as compared with cadaveric, models is markedly different.
authors.affiliation: Department of Orthopaedic Surgery, Northeastern Ohio Universities College of Medicine, Akron, Ohio, USA. ajschoen@neoucom.edu
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Schoenfeld
authors.forename: Suneel
authors.initials: S
authors.lastname: Battula
authors.forename: Vivek
authors.initials: V
authors.lastname: Sahai
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Vrabec
authors.forename: Steven
authors.initials: S
authors.lastname: Corman
authors.forename: Lyndsey
authors.initials: L
authors.lastname: Burton
authors.forename: Glen O
authors.initials: GO
authors.lastname: Njus
mesh_terms: D001696:Biomechanical Phenomena; D001863:Bone Screws; D018786:Bone Substitutes; D002102:Cadaver; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing / Q000379:methods*; D008954:Models, Biological; D010024:Osteoporosis; D033081:Shear Strength; D013314:Stress, Mechanical
chemical_list: D018786:Bone Substitutes