Wearable-device geometry and tissue mechanical variability determine sacral soft-tissue loading and pressure injury...

Area of Science:

• Biomechanics
• Biomedical Engineering
• Tissue Mechanics

Background:

• Wearable sensors are common in healthcare, often placed on bony areas like the sacrum.
• Sustained pressure from devices can cause tissue damage, with mechanical deformation being a key factor.
• The impact of device geometry on stress and strain in underlying tissues is not well understood.

Purpose of the Study:

• To investigate how different wearable device geometries influence stress and strain distribution in sacral tissues.
• To quantify the mechanical risk associated with various device shapes and pressure levels.
• To understand the role of tissue stiffness variability in pressure-induced tissue damage.

Main Methods:

• Developed a 3D finite element model of the sacral region including skin, fat, muscle, and bone.
• Simulated two device geometries: a circular sensor and an elongated cable segment.
• Applied static pressures (2-10 kPa) and varied tissue stiffness (±10%, ±20%) to assess mechanical exposure.

Main Results:

• Circular sensors concentrated stress superficially in the skin.
• Cable geometries redistributed mechanical load to deeper tissues (adipose and muscle).
• At high pressure, cable loading led to maximal strain-based risk in deeper tissues, while stress remained highest superficially.

Conclusions:

• Device geometry is a critical determinant of tissue-level mechanical exposure and potential damage.
• Circular devices pose a superficial stress risk, whereas cable designs create deeper tissue strain risk.
• Geometry-aware, deformation-based risk assessment is essential for wearable devices in pressure-vulnerable areas.