Musculoskeletal modeling and simulations of scoliotic standing postures

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Adolescent idiopathic scoliosis (AIS) is not only characterized by a deformed spine and rib cage distortion but also by altered head, shoulders and pelvis orientation in all three planes. Spinal deformity, morphology and posture are reflected in the body segment inertial parameters (BSIP). Though there is literature-based evidence that BSIP affects standing posture and balance little is known about their interaction with muscle control. The overall research goal is to develop musculoskeletal models focusing on the scoliotic trunk to simulate the effects BSIP in different upright stance conditions and estimate muscle activations required to restore balance in AIS girls. The specific objectives are to develop a generic able-bodied (AB) and three generic spine modules for small, moderate and severe deformity in the musculoskeletal models of SIMM/Opensim; simulate changes in BSIP and muscle moments on standing balance in 10 able-bodied and 30 AIS girls for eight upright stance conditions and simulate trunk muscles activation patterns using subject-specific models to improve standing balance in AIS. To perform these simulations personalized 3D spine data will be obtained by the EOS system, an ultra low dose digital X-ray radiation technique, available at the clinic and in-vivo personalized BSIP using methods developed in my previous Discovery grant. Standing balance will be quantified by two force plate and posture by a 6 camera video-based system. The spine modules to be developed in SIMM will then be imported into OpenSim for the simulations. These softwares are currently available in the laboratory. If modifying muscle moment can improve standing balance in AIS then these simulations will test which muscles are the most effective. Though we are using similar approaches in our shoulder model and others in modeling the lower limbs during locomotion no one addressed standing balance, asymmetrical standing postures and muscle simulations in scoliosis. This research develops the foundations for a scoliotic spine musculoskeletal model toolkit and provides a unique and novel advance with potential clinical impact leading to better posture training programs and improve body brace and spinal instrumentation.