Developing a 3D multi-body model of a scoliotic spine during lateral bending for comparison of ribcage flexibility and lumbar joint loading to the normal model

Knowledge of the movements of the whole spine and lumbosacral joint is important for evaluating clinical pathologic conditions that may potentially produce unstable situations in human body movements. At present there are few studies that report systematic three-dimensional (3D) movement and force analysis of the whole spine. In this paper, a fully discretized bio-fidelity 3D musculoskeletal simulation model for biomechanical (kinematic) analysis of scoliosis for a patient with right thoracolumbar scoliosis is presented. It is important to note that this method can be used for modeling various types of scoliosis. It should be noted that this is the first time that such a detailed model of this kind has been constructed according to known literature. The combined loading conditions acting on the intervertebral joints and corresponding angles between vertebrae were analyzed during lateral bending through the motion capturing and musculoskeletal modeling of two female subjects, one with normal spine and the other with scoliosis. The scoliosis subject who participated in this study has thoracolumbar scoliosis with convexity to the right. Since lateral bending is one of the typical tasks used by clinicians to determine the severity of scoliosis condition, the motion data of the subjects in lateral bending while standing was captured. These motion data were assigned to train the musculoskeletal multi-body models for the inverse and forward dynamics simulations. The mobility of the ribcage, joint angle, as well as joint force were analyzed using the developed simulation model. According to the results obtained the combined loadings at the lumbar joints in the scoliosis model are considerably higher than the loads of the normal model in this exercise. This research has investigated the effect of thoracolumbar scoliosis on spinal angles and joint forces in lateral bending by the application of motion data capturing and virtual musculoskeletal modeling. The results of this study contribute to a better understanding of human spine biomechanics and help future investigations on scoliosis to understand its development as well as improved treatment processes.