Juan Henao1, Hubert Labelle2, Pierre-Jean Arnoux3, Carl-Éric Aubin4. 1. Department of Mechanical Engineering, Polytechnique Montréal, P.O. Box 6079, Downtown Station, Montreal, Quebec, H3C 3A7, Canada; Research Center, Sainte-Justine University Hospital Center, 3175 Côte Sainte-Catherine Rd, Montreal, Quebec, H3T 1C5, Canada; iLab-Spine (International Laboratory - Spine Imaging and Biomechanics). 2. Research Center, Sainte-Justine University Hospital Center, 3175 Côte Sainte-Catherine Rd, Montreal, Quebec, H3T 1C5, Canada. 3. iLab-Spine (International Laboratory - Spine Imaging and Biomechanics); Laboratoire de Biomécanique Appliquée, UMRT24 IFFSTAR/ Aix-Marseille University, Bd. P. Dramard, Faculté de Medecine secteur-Nord, France 13916 Marseille cedex 20. 4. Department of Mechanical Engineering, Polytechnique Montréal, P.O. Box 6079, Downtown Station, Montreal, Quebec, H3C 3A7, Canada; Research Center, Sainte-Justine University Hospital Center, 3175 Côte Sainte-Catherine Rd, Montreal, Quebec, H3T 1C5, Canada; iLab-Spine (International Laboratory - Spine Imaging and Biomechanics). Electronic address: carl-eric.aubin@polymtl.ca.
Abstract
STUDY DESIGN: Biomechanical analysis of the spinal cord and nerves during scoliosis correction maneuvers through numerical simulations. OBJECTIVE: To assess the biomechanical effects of scoliosis correction maneuvers and stresses generated on the spinal nervous structures. BACKGROUND DATA: Important forces are applied during scoliosis correction surgery, which could potentially lead to neurologic complications due to stresses exerted on the nervous structures. The biomechanical impact of the different types of stresses applied on the nervous structures during correction maneuvers is not well understood. METHODS: Three correction techniques were simulated using a hybrid computer modeling approach, personalized to a right thoracic adolescent idiopathic scoliotic case (Cobb angle: 63°): (1) Harrington-type distraction; (2) segmental translation technique; and a (3) segmental rotation-based procedure. A multibody model was used to simulate the kinematics of the instrumentation maneuvers; a second comprehensive finite element model was used to analyze the local stresses and strains on the spinal cord and nerves. Average values of the internal medullar pressure (IMP), shear stresses, nerve compression, and strain were computed over three regions and compared between techniques. RESULTS: Harrington distraction maneuver generated high stresses and strains over the thoracolumbar region. In the main thoracic region, the segmental translation maneuver technique induced 15% more shear stress, 25% more strain, and 62% lower nerve compression than Harrington distraction maneuver. The segmental rotation-based procedure induced 25% lower shear stresses and 18% more strain, respectively, at the apical level, as well as 72%, 57%, and 7% lower IMP, nerve compression, and strain in the upper thoracic region, compared with Harrington distraction maneuver. CONCLUSION: This study quantified the relative stress induced on the spinal cord and spinal nerves for different correction maneuvers using a novel hybrid patient-specific model. Of the three maneuvers studied, the Harrington distraction maneuver induced the most important stresses over the thoracolumbar region.
STUDY DESIGN: Biomechanical analysis of the spinal cord and nerves during scoliosis correction maneuvers through numerical simulations. OBJECTIVE: To assess the biomechanical effects of scoliosis correction maneuvers and stresses generated on the spinal nervous structures. BACKGROUND DATA: Important forces are applied during scoliosis correction surgery, which could potentially lead to neurologic complications due to stresses exerted on the nervous structures. The biomechanical impact of the different types of stresses applied on the nervous structures during correction maneuvers is not well understood. METHODS: Three correction techniques were simulated using a hybrid computer modeling approach, personalized to a right thoracic adolescent idiopathic scoliotic case (Cobb angle: 63°): (1) Harrington-type distraction; (2) segmental translation technique; and a (3) segmental rotation-based procedure. A multibody model was used to simulate the kinematics of the instrumentation maneuvers; a second comprehensive finite element model was used to analyze the local stresses and strains on the spinal cord and nerves. Average values of the internal medullar pressure (IMP), shear stresses, nerve compression, and strain were computed over three regions and compared between techniques. RESULTS: Harrington distraction maneuver generated high stresses and strains over the thoracolumbar region. In the main thoracic region, the segmental translation maneuver technique induced 15% more shear stress, 25% more strain, and 62% lower nerve compression than Harrington distraction maneuver. The segmental rotation-based procedure induced 25% lower shear stresses and 18% more strain, respectively, at the apical level, as well as 72%, 57%, and 7% lower IMP, nerve compression, and strain in the upper thoracic region, compared with Harrington distraction maneuver. CONCLUSION: This study quantified the relative stress induced on the spinal cord and spinal nerves for different correction maneuvers using a novel hybrid patient-specific model. Of the three maneuvers studied, the Harrington distraction maneuver induced the most important stresses over the thoracolumbar region.