The Influence of Muscle Forces on the Stress Distribution in the LumbarSpine

摘要

Introduction: Previous studies of bone stresses in the human lumbar spine have relied on simplified modelswhen modeling the spinal musculature, even though muscle forces are likely major contributors to the stresses in thevertebral bones. Detailed musculoskeletal spine models have recently become available and show good correlation withexperimental findings. A combined inverse dynamics and finite element analysis study was conducted in the lumbar spineto investigate the effects of muscle forces on a detailed musculoskeletal finite element model of the 4th lumbar vertebralbody.Materials and Methodology: The muscle forces were computed with a detailed and validated inverse dynamicsmusculoskeletal spine model in a lifting situation, and were then applied to an orthotropic finite element model of the 4thlumbar vertebra. The results were compared with those from a simplified load case without muscles.Results: In general the von Mises stress was larger by 30 %, and even higher when looking at the von Mises stressdistribution in the superio-anterior and central part of the vertebral body and in the pedicles.Conclusion: The application of spine muscles to a finite element model showed markedly larger von Mises stressresponses in the central and anterior part of the vertebral body, which can be tolerated in the young and healthy spine, butit would increase the risk of compression fractures in the elderly, osteoporotic spine.