Dynamic identification of human trunk behavior as a diagnosis tool for pathologic problems

For certain trunk pathologies, such as some low back pain cases or functional abnormality, it is difficult to identify with precision the origin of the functional problem which reduces the effectiveness of the chosen treatment. Testing and modeling the trunk behavior under dynamic loads can be used as a mean to help to overcome diagnosis difficulties. In this work, a 3D biomechanical human trunk model was developed taking into account the spine, the rib cage and the unilateral behavior of 174 muscles. The masses of all the human upper body organs were considered with respect to their anatomical positions. The model is used to determine the trunk dynamic equilibrium under external loading and to calculate its flexural stiffness. The transient response calculated by the proposed model is compared with published experimental data for different horizontal directions. The main purpose of the dynamic identification approach is to explain, the relationship between the muscles' properties and the organs mass distributions on one hand, and the global trunk properties and dynamic behavior on the other hand. Therefore, certain trunk pathologies can be simulated to address their dynamic signature in terms of the transient response of the modeled trunk. The followed methodology is based on transient analysis of the trunk motion to non-periodic random excitations in order to detect the passive response of the constituent muscles.