Analysis of In Vivo Skin Anisotropy Using Elastic Wave Measurements and Bayesian Modelling

Area of Science:

• Biomechanics
• Dermatology
• Medical Engineering

Background:

• In vivo skin exhibits complex mechanical properties like viscoelasticity, hyper-elasticity, and anisotropy due to collagen fiber reinforcement.
• Existing data on human skin anisotropy in vivo is limited in population scope and angular resolution.
• Understanding skin mechanics is crucial for pharmaceuticals, cosmetics, and surgical applications.

Purpose of the Study:

• To comprehensively characterize the anisotropy and stiffness of human skin in vivo across a wide age range.
• To investigate the influence of age, gender, and skin tension on skin mechanical properties.
• To introduce a novel, robust measurement for skin anisotropy.

Main Methods:

• Utilized elastic wave speed measurements on 78 volunteers (ages 3-93).
• Employed a Bayesian statistical framework to analyze data.
• Proposed and validated a new anisotropy measurement based on angular data eccentricity.

Main Results:

• Skin anisotropy increases logarithmically with age.
• Skin stiffness increases linearly along Langer Lines with age.
• Gender does not significantly impact anisotropy but affects stiffness (males stiffer).
• Skin tension significantly influences both anisotropy and stiffness measurements.

Conclusions:

• Elastic wave measurements show promise for determining in vivo skin tension.
• Age is a significant factor in skin anisotropy and stiffness.
• Findings have implications for surgical planning and cosmetic procedures, questioning universal practices for different age groups.