A generic detailed multibody model for simulating thoracic spine and ribcage kinematics

A reliable and comprehensive multibody musculoskeletal model of the thoracic spine and ribcage can offer valuable insight into the biomechanics of healthy and curved spines. In this study, we developed a generic rigid-body thoracic spine and ribcage model, which is kinematically determinate and controlled by spinal posture. A newly devised averaging constraint was implemented to model the kinematics of individual ribs and the sternum. Rib motion validation confirmed that the movement of adjacent ribs matched measured data across different tasks. We simulated 39 adolescent idiopathic scoliosis subjects aged 7–17 years, with an average (SD) Cobb angle of 15.9 (8.2) degrees. The average errors of multiple scoliosis metrics were less than 4 degrees for angle parameters, 5 mm for displacement parameters, and 3 percent for the ratio parameter. The model is straightforward and can simulate various daily activities (e.g., spinal articulation and breathing) while accurately capturing pathological deformities conforming to experimental data. It is available to the public on the open science platform Zenodo and will also be accessible through the AnyBody Managed Model Repository.