The aim of this project is to provide detailed and well-validated musculoskeletal models of the thoracolumbar spine and rib cage, particularly for investigators with an interest studying musculoskeletal loading in the trunk.
The model includes a fully articulated thoracolumbar spine (T1 through L5), with 3 rotational degrees-of-freedom at each inter-vertebral joint, and ribcage (24 individual ribs and a sternum). It also includes a lumped head and neck body, and upper extremities. Major lumbar spine and abdominal muscle groups were incorporated from the previously developed OpenSim lumbar spine model (https://simtk.org/projects/lumbarspine), and muscles attaching to the upper and mid-thorax were adapted from the neck musculoskeletal model (https://simtk.org/projects/neck_mechanics) and upper extremity model (https://simtk.org/projects/up-ext-model). Additional muscle groups were added, including the external and internal inter-costals, the thoracic multifidus, the lower portion of the trapezius, the serratus anterior, and the transversus abdominis. Muscle measurements from in vivo computed tomography scans of the trunk were used to adjust the cross-sectional area (CSA) and position of the trunk muscles in the model to match a community-based sample of 51 men (generic male model) or 49 women (generic female model). In total the model has 93 degrees-of-freedom, and 552 musculotendon actuators. It may be used in Static Optimization analyses, but not yet in Computed Muscle Control.
The model is validated for estimations of spinal loading and trunk muscle tension against previously collected in-vivo measurement of intradiscal pressure, vertebral compression from telemeterized implants and trunk muscle EMG. For more information, see our paper describing model development and validation: https://www.ncbi.nlm.nih.gov/pubmed/25901907
Also see our webinar: http://opensim.stanford.edu/support/event_details.html?id=143
We are currently using this model to study variations in spine loading in the population, including effects of spine curvature, as well as how this relates to the risk of vertebral fractures in older adults. See our publications list for recent papers.