Manon Sterba1,2,3,4,5, Pierre-Jean Arnoux2,4, Hubert Labelle5, William C Warner6, Carl-Éric Aubin7,8,9. 1. Department of Mechanical Engineering, Polytechnique Montreal, Montreal, QC, Canada. 2. Laboratoire de Biomécanique Appliquée, Aix-Marseille Université, IFSTTAR, LBA UMR T24, Marseille, France. 3. iLab-Spine (International Laboratory - Spine Imaging and Biomechanics), Montreal, Canada. 4. iLab-Spine (International Laboratory - Spine Imaging and Biomechanics), Marseille, France. 5. Sainte-Justine University Hospital Center, Montreal, QC, Canada. 6. Campbell Clinic Orthopaedics, Germantown, TN, USA. 7. Department of Mechanical Engineering, Polytechnique Montreal, Montreal, QC, Canada. carl-eric.aubin@polymtl.ca. 8. iLab-Spine (International Laboratory - Spine Imaging and Biomechanics), Montreal, Canada. carl-eric.aubin@polymtl.ca. 9. Sainte-Justine University Hospital Center, Montreal, QC, Canada. carl-eric.aubin@polymtl.ca.
Abstract
PURPOSE: To study the risks of spondylolysis due to extrinsic loading conditions related to sports activities and intrinsic spino-pelvic postural parameters [pelvic incidence (PI) and sacral slope (SS)]. METHODS: A comprehensive osseo-disco-ligamentous L4-S1 finite element model was built for three cases with spondylolysis representing three different spino-pelvic angular configurations (SS = 32°, 47°, 59° and PI = 49°, 58°, 72°, respectively). After simulating the standing posture, 16 dynamic loading conditions were computationally tested for each configuration by combining four sport-related loads (compression, sagittal and lateral bending and axial torque). For each simulation, the Von Mises stress, L5-S1 facet contact force and resultant internal loads at the sacral endplate were computed. Significant effects were determined with an ANOVA. RESULTS: The maximal stress and volume of cancellous bone in the pars with stress higher than 75% of the ultimate stress were higher with 900 N simulated compression (2.2 MPa and 145 mm3) compared to only the body weight (1.36 MPa and 20.9 mm3) (p < 0.001). Combined compression with 10 Nm of flexion and an axial torque of 6 Nm generated the highest stress conditions (up to 2.7 MPa), and L5-S1 facet contact force (up to 430 N). The maximal stress was on average 17% higher for the case with the highest SS compared to the one with lowest SS for the 16 tested conditions (p = 0.0028). CONCLUSIONS: Combined flexion and axial rotation with compression generated the highest stress conditions related to risks of spondylolysis. The stress conditions intensify in patients with higher PI and SS. These slides can be retrieved under Electronic Supplementary Material.
PURPOSE: To study the risks of spondylolysis due to extrinsic loading conditions related to sports activities and intrinsic spino-pelvic postural parameters [pelvic incidence (PI) and sacral slope (SS)]. METHODS: A comprehensive osseo-disco-ligamentous L4-S1 finite element model was built for three cases with spondylolysis representing three different spino-pelvic angular configurations (SS = 32°, 47°, 59° and PI = 49°, 58°, 72°, respectively). After simulating the standing posture, 16 dynamic loading conditions were computationally tested for each configuration by combining four sport-related loads (compression, sagittal and lateral bending and axial torque). For each simulation, the Von Mises stress, L5-S1 facet contact force and resultant internal loads at the sacral endplate were computed. Significant effects were determined with an ANOVA. RESULTS: The maximal stress and volume of cancellous bone in the pars with stress higher than 75% of the ultimate stress were higher with 900 N simulated compression (2.2 MPa and 145 mm3) compared to only the body weight (1.36 MPa and 20.9 mm3) (p < 0.001). Combined compression with 10 Nm of flexion and an axial torque of 6 Nm generated the highest stress conditions (up to 2.7 MPa), and L5-S1 facet contact force (up to 430 N). The maximal stress was on average 17% higher for the case with the highest SS compared to the one with lowest SS for the 16 tested conditions (p = 0.0028). CONCLUSIONS: Combined flexion and axial rotation with compression generated the highest stress conditions related to risks of spondylolysis. The stress conditions intensify in patients with higher PI and SS. These slides can be retrieved under Electronic Supplementary Material.
Entities:
Keywords:
Biomechanics; Finite element model; Lumbar spine; Pars interarticularis; Spino-pelvic angles; Spondylolysis
Authors: Katie Beadon; James D Johnston; Kevin Siggers; Eyal Itshayek; Peter A Cripton Journal: Spine (Phila Pa 1976) Date: 2008-10-15 Impact factor: 3.468