Lucien Diotalevi1, Nicolas Bailly1, Éric Wagnac2, Jean-Marc Mac-Thiong3, Julien Goulet4, Yvan Petit5. 1. Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Street West, Montréal, Québec H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; International Laboratory on Spine Imaging and Biomechanics (iLab-Spine), Canada. 2. Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Street West, Montréal, Québec H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; International Laboratory on Spine Imaging and Biomechanics (iLab-Spine), Canada. Electronic address: eric.wagnac@etsmtl.ca. 3. Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; Department of Orthopaedic Surgery, Université de Montréal, P.O. box 6128, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada. 4. Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; Department of Orthopaedic Surgery, Université de Montréal, P.O. box 6128, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada. Electronic address: julien.goulet@umontreal.ca. 5. Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Street West, Montréal, Québec H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400 Gouin blvd, Montréal H4J 1C5, Québec, Canada; International Laboratory on Spine Imaging and Biomechanics (iLab-Spine), Canada. Electronic address: yvan.petit@etsmtl.ca.
Abstract
BACKGROUND: In thoracolumbar burst fractures, spinal cord primary injury involves a direct impact and energy transfer from bone fragments to the spinal cord. Unfortunately, imaging studies performed after the injury only depict the residual bone fragments position and pattern of spinal cord compression, with little insight on the dynamics involved during traumas. Knowledge of underlying mechanisms could be helpful in determining the severity of the primary injury, hence the extent of spinal cord damage and associated potential for recovery. Finite element models are often used to study dynamic processes, but have never been used specifically to simulate different severities of thoracolumbar burst fractures. METHODS: Previously developed thoracolumbar spine and spinal cord finite element models were used and further validated, and representative vertebral fragments were modelled. A full factorial design was used to investigate the effects of comminution of the superior fragment, presence of an inferior fragment, fragments rotation and velocity, on maximum Von Mises stress and strain, maximum major strain, and pressure in the spinal cord. FINDINGS: Fragment velocity clearly was the most influential factor. Fragments rotation and presence of an inferior fragment increased pressure, but rotation decreased both strains outputs. Although significant for both strains outputs, comminution of the superior fragment isn't estimated to influence outputs. INTERPRETATION: This study is the first, to the authors' knowledge, to examine a detailed spinal cord model impacted in situ by fragments from burst fractures. This numeric model could be used in the future to comprehensively link traumatic events or imaging study characteristics to known spinal cord injuries severity and potential for recovery.
BACKGROUND: In thoracolumbar burst fractures, spinal cord primary injury involves a direct impact and energy transfer from bone fragments to the spinal cord. Unfortunately, imaging studies performed after the injury only depict the residual bone fragments position and pattern of spinal cord compression, with little insight on the dynamics involved during traumas. Knowledge of underlying mechanisms could be helpful in determining the severity of the primary injury, hence the extent of spinal cord damage and associated potential for recovery. Finite element models are often used to study dynamic processes, but have never been used specifically to simulate different severities of thoracolumbar burst fractures. METHODS: Previously developed thoracolumbar spine and spinal cord finite element models were used and further validated, and representative vertebral fragments were modelled. A full factorial design was used to investigate the effects of comminution of the superior fragment, presence of an inferior fragment, fragments rotation and velocity, on maximum Von Mises stress and strain, maximum major strain, and pressure in the spinal cord. FINDINGS: Fragment velocity clearly was the most influential factor. Fragments rotation and presence of an inferior fragment increased pressure, but rotation decreased both strains outputs. Although significant for both strains outputs, comminution of the superior fragment isn't estimated to influence outputs. INTERPRETATION: This study is the first, to the authors' knowledge, to examine a detailed spinal cord model impacted in situ by fragments from burst fractures. This numeric model could be used in the future to comprehensively link traumatic events or imaging study characteristics to known spinal cord injuries severity and potential for recovery.