抄録
Locally sustained forces are the main cause for the onset of pressure ulcers. Therefore, it is important to reduce and redistribute these forces using antidecubitus cushions. In this study, we constructed a three-dimensional buttock model incorporating two bones (ischial tuberosity, a site prone to the development of pressure ulcers, and femur) covered by soft tissue. Using the model, we evaluated cushions that can effectively distribute seat-interface pressure (SIP) and von Mises stress in subcutaneous tissue (SiST). To examine the differences of force distribution capability in four materials (soft and hard gels/foams) and three thicknesses (10, 30 and 50 mm), we simulated sitting single-layer cushions. The results showed that SIP and SiST decreased as the thickness of the cushion increased. In addition, to determine whether a two-layer cushion can distribute force more effectively than a single-layer cushion, we combined two of the materials (thickness of each material: 25 mm) to form a 50-mm-thick two-layer cushion. The results showed that when foam was placed under the gel, the SIP and SiST values were smaller than those for a single-layer cushion. Results of previous studies have indicated a three-material two-layer cushion, in which the softest material of the three materials is placed under the ischial tuberosity region—where high contact forces develop—and is surrounded by the hardest material to support the remainder of the pelvic structure, has the best force distribution efficiency. Therefore, we made a three-material two-layer cushion, placing the softest material under the ischial tuberosity region. The results indicated that SIP was similar to that of the two-layer cushion, but SiST was the smallest in this simulation. From these results, we conclude that forces can be distributed efficiently in a three-material cushion by placing the softest material under the ischial tuberosity region.
