title: Monolithic superelastic rods with variable flexural stiffness for spinal fusion: modeling of the processing-properties relationship.
abstract: The concept of a monolithic Ti-Ni spinal rod with variable flexural stiffness is proposed to reduce the risks associated with spinal fusion. The variable stiffness is conferred to the rod using the Joule-heating local annealing technique. The annealing temperature and the mechanical properties' distributions resulted from this thermal treatment are numerically modeled and experimentally measured. To illustrate the possible applications of such a modeling approach, two case studies are presented: (a) optimization of the Joule-heating strategy to reduce annealing time, and (b) modulation of the rod's overall flexural stiffness using partial annealing. A numerical model of a human spine coupled with the model of the variable flexural stiffness spinal rod developed in this work can ultimately be used to maximize the stabilization capability of spinal instrumentation, while simultaneously decreasing the risks associated with spinal fusion.
authors.affiliation: École de technologie supérieure, 1100 Notre-Dame Street West, Montreal, QC, Canada H3C 1K3; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, boul. Gouin West, Montreal, QC, Canada H4J 1C5.
authors.forename: Yann
authors.initials: Y
authors.lastname: Facchinello
authors.affiliation: École de technologie supérieure, 1100 Notre-Dame Street West, Montreal, QC, Canada H3C 1K3; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, boul. Gouin West, Montreal, QC, Canada H4J 1C5. Electronic address: vladimir.brailovski@etsmtl.ca.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Brailovski
authors.affiliation: École de technologie supérieure, 1100 Notre-Dame Street West, Montreal, QC, Canada H3C 1K3; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, boul. Gouin West, Montreal, QC, Canada H4J 1C5.
authors.forename: Yvan
authors.initials: Y
authors.lastname: Petit
authors.affiliation: Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, boul. Gouin West, Montreal, QC, Canada H4J 1C5; Department of Surgery, Faculty of Medicine, University of Montreal, Pavillon Roger-Gaudry, S-749, C.P. 6128, succ. Centre-ville, Montreal, QC, Canada H3C 3J7.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Mac-Thiong
mesh_terms: D004548:Elasticity; D020342:Finite Element Analysis; D006358:Hot Temperature; D006801:Humans; D008962:Models, Theoretical; D009532:Nickel; D013123:Spinal Fusion; D013131:Spine / Q000601:surgery; D013314:Stress, Mechanical; D014025:Titanium
chemical_list: C040654:titanium nickelide; D009532:Nickel; D014025:Titanium
keywords: Finite element analysis; Instrumentation with variable flexural stiffness; Local Joule-heating annealing; Shape memory alloy; Spinal fusion