Biomechanical modeling to prevent ischial pressure ulcers

Area of Science:

• Biomechanics
• Biomedical Engineering
• Materials Science

Background:

• Ischial pressure ulcers affect 300,000 paraplegic individuals in France, posing a significant public health challenge.
• Current prevention methods using surface pressure sensors are inadequate as internal tissue strains, not just surface pressure, cause ulcers.
• Understanding the biomechanical properties of buttocks soft tissues is crucial for developing effective prevention strategies.

Purpose of the Study:

• To perform a stiffness sensitivity analysis of buttocks soft tissues using a finite element model.
• To determine the influence of different tissue layer stiffnesses (skin, fat, muscle) on internal strain.
• To investigate how variations in sitting posture and muscle thickness affect internal strains.

Main Methods:

• A finite element model was developed simulating buttocks soft tissues with distinct Neo-Hookean material layers.
• Young's moduli were assigned to skin [100-500 kPa], fat [25-35 kPa], and muscle [80-140 kPa] layers.
• Sensitivity analysis was conducted by varying material properties, sitting postures, and muscle thickness.

Main Results:

• Maximum internal strains reached realistic values of 50-60% under the tested conditions.
• Fat and muscle stiffness significantly influenced internal strain variations.
• Skin stiffness had a lesser impact on strain compared to fat and muscle stiffness.

Conclusions:

• Accurate modeling of soft tissue biomechanics, particularly fat and muscle stiffness, is essential for predicting internal strains.
• Finite element analysis provides a valuable tool for understanding the mechanical factors contributing to pressure ulcer development.
• Further research should incorporate these findings into improved prevention strategies for ischial pressure ulcers.