Three-dimensional computer model of the human buttocks, in vivo.

In an effort to reduce the incidence of decubitus ulcers among wheelchair users, current work in cushion design concentrates on minimizing the pressure at the buttock-cushion interface. Finite element analysis can show the stress levels throughout the soft tissue between the cushion and the ischial tuberosity and give designers a better indication of the effects of a particular cushion. Finite element models were generated of the tissues around the ischial tuberosities of male and female subjects. Linear three-dimensional models were generated using a 386 computer and solved with infinitesimal deflection theory. The resulting minimal principal stresses were 17 kPa and 15 kPa at the buttock-cushion interface for seated male and female subjects, respectively. Computational results were verified experimentally with magnetic resonance imaging and interface pressure measurements.