Assessment of a novel musculoskeletal lumbar spine model: sensitivity analyses and validation

The physiological equilibrium of the spine depends on the interaction between musculoskeletal structures and gravitational forces. Understanding this equilibrium is crucial for analysing spine biomechanics in both healthy and pathological conditions. Computational models provide valuable insights by simulating complex conditions while avoiding invasive and costly experiments. This study proposes a Finite Element lumbar spine model that incorporates muscles. Details on modeling choices and their effects on the variables of interest are provided. Since muscle activations must be predefined, an iterative process adjusts muscle forces while minimizing a kinematic criterion. This enables sensitivity analysis of muscle effects on spinal motion. Global muscle forces are found to have the leading effect on kinematics, accounting for 52-91% of total variance in local ranges of motion. An established energy criterion and work exerted by muscles are also monitored to quantify variations in energy expenditure. By applying the kinematics and energy criteria, an optimal solution for standing is identified. Biomechanical variables of interest are extracted and agree well with in vivo and in silico data. The model also allows to visualize how different structures contribute to spine biomechanics by supporting different entities of compressive and shear forces and bending moments. This study provides a strong foundation for future research by identifying key variables and the model sensitivity. It also emphasizes the potential of this approach for accurately characterizing spine biomechanics. Such a tool holds promise for improving spine disorder prevention, diagnosis, and treatment.