Evaluation of a new sitting concept designed for prevention of pressure ulcer on the buttock using finite element analysis

In the United States, many of the 1.4 million people who rely on wheelchairs for mobility develop serious tissue breakdown (Pressure Ulcer) at pressure areas such as the ischium and sacrum from prolonged sitting. Our previous studies have introduced a new sitting concept, Intelligent Automated Pressure Relief Seat (IAPRS), for wheelchair users in the attempt to reduce sitting pressure under the ischia and sacrum. The objective of this investigation was to evaluate the newly designed sitting concept using Finite Element (FE) analysis. A FE model was created for a specific subject based on 3D reconstruction of the buttock-thigh structure obtained in sitting posture. The actual interface pressure (IP), which measured by a pressure mapping mat for normal and an special ischial-released sitting configuration (WO-BPS posture) provided by IAPRS system, were applied to the developed 3D FE model. The displacement, deformation, internal pressure and von Mises stresses on the skin, fat and muscle were estimated and analyzed for both sitting configurations. Compared to that in normal configuration, the high IP region was seen under the thighs rather than under the buttocks in WO-BPS configuration. FE model analysis shows that the largest soft tissue displacement was underneath the ischial tuberosities (IT) (14.2mm) in normal configuration, while in WO-BPS configuration, it was on posterior side of the thighs (5.5mm) with a reduction of magnitude. The deformation pattern change on the muscle induced by WO-BPS sitting configuration was in general comparable with that of the displacement for the entire buttock-thigh structure. The current study confirms our hypothesis that the interface pressure relief effect of the IAPRS may have substantial benefits in terms of mechanical responses within the deep tissues. It can be concluded that incorporating our IAPRS system into a rehabilitation and treatment program for individuals who have sitting-related PU wounds may prove beneficial and promote the healing process while maintaining their mobility.