Development and validation of a subject-specific integrated finite element musculoskeletal model of human trunk with ergonomic and clinical applications

Abstract

Background and Objectives: Biomechanical modeling of the human trunk is crucial for understanding spinal mechanics and its role in ergonomics and clinical interventions. Traditional models have been limited by only considering the passive structures of the spine in finite element (FE) models or incorporating active muscular components in multi-body musculoskeletal (MS) models with an oversimplified spine. This study aimed to develop and validate a subject-specific coupled FE-MS model of the trunk that integrates detailed representation of both the passive and active components for biomechanical simulations. Methods: We constructed a parametric FE model of the trunk, incorporating a realistic muscle architecture, personalized through imaging datasets and statistical shape models. To validate the model, we compared tissue-level responses with in vitro experiments, and muscle activities and intradiscal pressures versus in vivo measurements during various physical activities. We further demonstrated the versatility of the proposed personalized integrated framework through additional applications in ergonomics (i.e., wearing an exoskeleton) and surgical interventions (e.g., nucleotomy and spinal fusion). Results: The model demonstrated satisfactory agreement with experimental data, showcasing its validity to predict tissue- and disc-level responses accurately, as well as muscle activity and intradiscal pressures. When simulating ergonomics scenarios, the exoskeleton-wearing condition resulted in lower intradiscal pressures (1.9 MPa vs. 2.2 MPa at L4-L5) and peak von Mises stresses in the annulus fibrosus (2.2 MPa vs. 2.9 MPa) during forward flexion. In the context of surgical interventions, spinal fusion at L4-L5 led to increased intradiscal pressure in the adjacent upper disc (1.72 MPa vs. 1.58 MPa), whereas nucleotomy minimally influenced intact disc pressures but significantly altered facet joint loads and annulus fibrosus radial strains. Conclusions: The integrated FE-MS model of the trunk represents a significant advancement in biomechanical simulations, providing insights into the intricate interplay between active and passive spinal components. Its predictive capability extends beyond that of conventional models, enabling detailed risk analysis and the simulation of varied surgical outcomes. This comprehensive tool has potential implications for the design of ergonomic interventions and the optimization of surgical techniques to minimize detrimental effects on spinal mechanics.