Biomechanical analyses of stress distribution within the seated buttock and cushion

The elderly wheelchair users frequently encountered the prevalence of pressure sore, also known as decubitus, since they have to be seated in the wheelchair for daily activities. The major cause induced the formation of pressure sore was that the soft tissues were over-stressed. The purpose of this study was to provide the information about internal stresses of soft tissues and establish a simplified finite element model to simulate the behavior of the interface between human buttock and cushion. Computational stresses were verified by comparing the buttock-cushion interface pressures, which was measured with Q.A. pressure pads. The displacement of the cushion was also validated with the experimental results of buttock measuring system. Two cushion geometries, flat and contoured, were adopted in this study to explore the effects on stress distributions. The results showed that the simplified finite element model was consistent with the experimental data. Contoured cushions had better stress distribution and lower interface stress.