title: Strain rate dependent behavior of the porcine spinal cord under transverse dynamic compression.
abstract: The accurate description of the mechanical properties of spinal cord tissue benefits to clinical evaluation of spinal cord injuries and is a required input for analysis tools such as finite element models. Unfortunately, available data in the literature generally relate mechanical properties of the spinal cord under quasi-static loading conditions, which is not adapted to the study of traumatic behavior, as neurological tissue adopts a viscoelastic behavior. Thus, the objective of this study is to describe mechanical properties of the spinal cord up to mechanical damage, under dynamic loading conditions. A total of 192 porcine cervical to lumbar spinal cord samples were compressed in a transverse direction. Loading conditions included ramp tests at 0.5, 5 or 50 s-1and cyclic loading at 1, 10 or 20 Hz. Results showed that spinal cord behavior was significantly influenced by strain rate. Mechanical damage occurred at 0.64, 0.68 and 0.73 strains for 0.5, 5 or 50 s-1loadings, respectively. Variations of behavior between the tested strain rates were explained by cyclic loading results, which revealed behavior more or less viscous depending on strain rate. Also, a parameter (stress multiplication factor) was introduced to allow transcription of a stress-strain behavior curve to different strain rates. This factor was described and was significantly different for cervical, thoracic and lumbar vertebral heights, and for the strain rates evaluated in this study.
authors.affiliation: 1 Département de Génie Mécanique, École Polytechnique de Montréal, Montréal, QC, Canada.|2 iLab-Spine (International Laboratory - Spine Imaging and Biomechanics), Montreal, Canada and Marseille, France.
authors.forename: Léo
authors.initials: L
authors.lastname: Fradet
authors.affiliation: 2 iLab-Spine (International Laboratory - Spine Imaging and Biomechanics), Montreal, Canada and Marseille, France.|3 Département de Génie Mécanique, École de technologie supérieure, Montréal, QC, Canada.|4 Research Center, Hôpital du Sacré-Coeur de Montréal, Montréal, QC, Canada.
authors.forename: Francis
authors.initials: F
authors.lastname: Cliche
authors.affiliation: 2 iLab-Spine (International Laboratory - Spine Imaging and Biomechanics), Montreal, Canada and Marseille, France.|3 Département de Génie Mécanique, École de technologie supérieure, Montréal, QC, Canada.|4 Research Center, Hôpital du Sacré-Coeur de Montréal, Montréal, QC, Canada.|5 Laboratoire de Biomécanique Appliquée, UMRT24 IFSTTAR, Université de la Méditerranée Aix-Marseille II, Marseille, France.
authors.forename: Yvan
authors.initials: Y
authors.lastname: Petit
authors.affiliation: 2 iLab-Spine (International Laboratory - Spine Imaging and Biomechanics), Montreal, Canada and Marseille, France.|4 Research Center, Hôpital du Sacré-Coeur de Montréal, Montréal, QC, Canada.|6 Department of Surgery, Université de Montréal, Montréal, QC, Canada.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Mac-Thiong
authors.affiliation: 2 iLab-Spine (International Laboratory - Spine Imaging and Biomechanics), Montreal, Canada and Marseille, France.|5 Laboratoire de Biomécanique Appliquée, UMRT24 IFSTTAR, Université de la Méditerranée Aix-Marseille II, Marseille, France.
authors.forename: Pierre-Jean
authors.initials: PJ
authors.lastname: Arnoux
keywords: Spinal cord; experimental tests; material properties; strain rate dependency