Developing a 3D Multi-Body Model of the Scoliotic Spine with Lateral Bending Motion for Comparison of Ribcage Flexibility

In this paper, a fully discretized bio-fidelity simulation model for bio-mechanical (kinematic) analysis of scoliosis for various patients was developed to analyze forces on vertebrae, loads acting on the intervertebral disc, corresponding angles between vertebrae, and tension in the spine muscles during lateral bending. It was further developed to study the movement limitation and muscle activation of a scoliotic subject. This system was built by using the commercial software LifeMOD. The whole spine (pre-defined by the software) was discretized into individual vertebra segments with rotational joints representing intervertebral discs. In this study, two female subjects (with 40±1.0 kg weight and 154±3 cm height), one with normal spine and the other one with scoliotic spine, were asked to do lateral bending and bend as far as they can. Motion capture data of these two subjects was obtained. Next, motion capture data was assigned to the model using a motion agent set and the inverse dynamics simulation was performed to simulate the complicated multi-body motion of lateral bending. The mobility of the ribcage, activity of muscles which are important in the lateral motion of body, as well as joint angles were analyzed using the developed simulation model. According to the obtained results, the mobility of the ribcage in scoliosis model was less than that of the normal model with the same anthropometric data. This finding is in direct agreement with the qualitative experimental results done by other researchers.