FE Model Solution: Solved by ABAQUS/STANDARD
FE Model Validation: Displacement on the skin (30 regions of interests) and MRI Images vs. FE Analysis Results:
A: The largest displacements were immediately underneath IT. Substantial displacements were mostly seen in the central and the medial ROIs of the buttock closed to IT. The displacement in the more medial region of the buttock was generally larger than that of the more lateral region.
B: The distribution pattern of the displacement in the posterior-anterior direction was in favorable consistency with that measured from MRI images, however, with smaller values. 
Internal pressure distribution for the entire buttock-thigh predicted by FE model. High pressure is identified on the regions (circle in figure) immediately underneath IT in the fat and muscle. For the skin, the pressure distribution is in well accordance with that measured from pressure mapping of sitting posture.  
In skin: the maximum compressive pressure was seen in the medial central region of buttock (45~60kPa). This pattern was in general comparable with the actual pressure mapping data measured seated individuals. In fat: the maximum compressive pressure was found in the region closer to bony prominences bore (50~60kPa). In muscle: the maximum compressive pressure was also seen in the region close to bony prominences (55~65kPa) and spread out toward the exterior of the muscle. Distribution of von Mises stress for the entire buttock-thigh (upper) and the muscle group 1 (lower). von Mises stress is higher on the regions (circle in figure) immediately underneath IT in the fat and muscle compared with that of other regions.  
Conclusions: FE model can be a powerful tool to investigate the soft tissue response to sitting load, if properly developed
Clinical implications from FE simulation: Soft tissue necrosis may start from deep muscle, which bears the highest stress. Spinal cord injury individuals may be at higher risk of tissue breakdown, because their gradually loss of muscle bulk and muscle tone. | 
