title: Biomechanical analysis of proximal junctional failure following adult spinal instrumentation using a comprehensive hybrid modeling approach.
abstract: Proximal junctional failure is a severe proximal junctional complication following adult spinal instrumentation and involving acute proximal junctional kyphotic deformity, mechanical failure at the upper instrumented vertebra or just above, and/or proximal junctional osseoligamentous disruption. Clinical studies have identified potential risk factors, but knowledge on their biomechanics is still lacking for addressing the proximal junctional failure issues. The objective of this study was to develop comprehensive computational modeling and simulation techniques to investigate proximal junctional failure.
  
  
  
  A 3D multibody biomechanical model based on a 47year old lumbar scoliosis surgical case that subsequently had traumatic proximal junctional failure was first developed to simulate patient-specific spinal instrumentation (from T11 to S1), compute the postoperative geometry of the instrumented spine, simulate different physiological loads and movements. Then, a highly detailed finite element model of the proximal junctional spinal segment was created using as input the geometry and displacements from the multibody model. It enabled to perform detailed stress and failure analysis across the anatomical structures.
  
  
  
  The simulated postoperative correction and traumatic failure (wedge fracture at upper instrumented vertebra) agreed well with the clinical report (within 2° difference). Simulated stresses around the screw threads (up to 4.7MPa) generated during the instrumentation and the buckling effect of post-operative functional loads on the proximal junctional spinal segment, were identified as potential mechanical proximal junctional failure risk factors.
  
  
  
  Overall, we demonstrated the feasibility of the developed hybrid modeling technique, which realistically allowed the simulation of the spinal instrumentation and postoperative loads, which constitutes an effective tool to further investigate proximal junctional failure pathomechanisms.
authors.affiliation: Polytechnique Montréal, Department of Mechanical Engineering, P.O. Box 6079, Downtown Station, Montreal, Quebec H3C 3A7, Canada; Sainte-Justine University Hospital Center, 3175, Cote Sainte-Catherine Road, Montreal, Quebec H3T 1C5, Canada; iLab-Spine (International Laboratory - Spine Imaging and Biomechanics), Montreal, Canada and Marseille, France.
authors.forename: Leo
authors.initials: L
authors.lastname: Fradet
authors.affiliation: Polytechnique Montréal, Department of Mechanical Engineering, P.O. Box 6079, Downtown Station, Montreal, Quebec H3C 3A7, Canada; Sainte-Justine University Hospital Center, 3175, Cote Sainte-Catherine Road, Montreal, Quebec H3T 1C5, Canada.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Wang
authors.affiliation: The Spine Hospital, New York-Presbyterian/Allen Hospital, 5141 Broadway, 3 Field West, New York, NY 10034, USA.
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Lenke
authors.affiliation: Polytechnique Montréal, Department of Mechanical Engineering, P.O. Box 6079, Downtown Station, Montreal, Quebec H3C 3A7, Canada; Sainte-Justine University Hospital Center, 3175, Cote Sainte-Catherine Road, Montreal, Quebec H3T 1C5, Canada; iLab-Spine (International Laboratory - Spine Imaging and Biomechanics), Montreal, Canada and Marseille, France. Electronic address: carl-eric.aubin@polymtl.ca.
authors.forename: Carl-Eric
authors.initials: CE
authors.lastname: Aubin
mesh_terms: D001863:Bone Screws; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D012600:Scoliosis / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods
keywords: Finite element model; Multibody model; Pathomechanisms; Proximal junctional failure; Spine