Stress distribution in a physical buttock model: effect of simulated bone geometry

Area of Science:

• Biomechanics
• Biomedical Engineering
• Tissue Mechanics

Background:

• Mechanical stresses during prolonged sitting can lead to pressure ulcers (bedsores) in individuals with paralysis.
• Cushions are commonly used to redistribute pressure and prevent tissue damage.

Purpose of the Study:

• To investigate how different bone core geometries (round vs. flat base) affect stress distribution in buttock models.
• To determine if cushion responses to pressure are influenced by bone core shape and loading direction.

Main Methods:

• Developed two-dimensional physical models simulating the buttock, using PVC gel for soft tissue and a wooden core for bony prominences.
• Utilized models with distinct round-base and flat-base bone cores.
• Employed etched grids for strain measurement and subsequent stress calculations.

Main Results:

• The flat-base (sharp) bone core model exhibited extensive high shear stress regions under vertical and inclined loading.
• The round-base bone core model generated maximal compressive stress during vertical loading.
• Relative cushion performance varied based on bone core geometry and the direction of applied load.

Conclusions:

• Buttock tissue stress distribution is significantly influenced by the geometry of underlying bony prominences.
• Cushion effectiveness in mitigating pressure-related tissue damage is dependent on both the shape of the bony prominence and the direction of mechanical loading.