title: Reply to the letter to the editor entitled: response to "comparative analysis of international standards for the fatigue testing of posterior spinal fixation systems".
authors.affiliation: Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza L. da Vinci 32, 20133, Milano, Italy; IRCCS Istituto Ortopedico Galeazzi, Via R. Galeazzi, 4, 20161, Milano, Italy.
authors.forename: Tomaso
authors.initials: T
authors.lastname: Villa
authors.affiliation: Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza L. da Vinci 32, 20133, Milano, Italy; IRCCS Istituto Ortopedico Galeazzi, Via R. Galeazzi, 4, 20161, Milano, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: La Barbera
authors.affiliation: IRCCS Istituto Ortopedico Galeazzi, Via R. Galeazzi, 4, 20161, Milano, Italy; Institute of Orthopaedic Research and Biomechanics, Center of Musculoskeletal Research Ulm, University of Ulm, Helmholtzstr. 14, 89081 Ulm, Germany.
authors.forename: Fabio
authors.initials: F
authors.lastname: Galbusera
mesh_terms: D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008422:Materials Testing / Q000592:standards*; D013123:Spinal Fusion / Q000295:instrumentation*; D013314:Stress, Mechanical