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Impact of Skin Tone on Skin Tolerance to Shear in the Context of Pressure Injuries: Theory and Computer Modeling
1Tomer Katz, BSc, is Graduate Student, Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, Israel. Amit Gefen, PhD, is Professor of Biomedical Engineering and Herbert J. Berman Chair in Vascular Bioengineering, Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University; Researcher, Skin Integrity Research Group (SKINT), University Centre for Nursing and Midwifery, Department of Public Health and Primary Care, Ghent University, Ghent, Belgium; and Researcher, Department of Mathematics and Statistics and the Data Science Institute, Faculty of Sciences, Hasselt University, Hasselt, Belgium. Acknowledgments: This work was partially supported by the Israeli Ministry of Science & Technology (Medical Devices Program grant 3-17421, awarded to Prof Amit Gefen in 2020). The authors have disclosed no other financial relationships related to this article. Submitted August 22, 2023; accepted in revised form April 16, 2024.
Objective:
To investigate the impact of darker skin tones on skin tolerance to shear forces in the context of pressure injuries (PIs) and explore the mechanobiological hypothesis that people with darker skin may be at an increased PI risk due to altered biomechanical skin properties resulting from a lower water content (WC) as some literature suggests.
Methods:
The authors developed a computational modeling framework simulating skin with varying Poisson ratios to represent different WC levels in the stratum corneum (SC), focusing on the effects of ethnicity and WC on mechanical stresses in superficial skin during weightbearing postures. Mechanical properties of the tissues were based on literature values. Pure compression and compression with shear were applied to the skin model.
Results:
A lower Poisson ratio in the SC, indicating lower WC, is associated with higher tissue stresses and more intense stress concentrations, especially under combined compression and shear loading. The initial reduction in the Poisson ratio had the most significant impact on increased tissue loading. These results support the hypothesis that the lower WC in darker skin, associated with increased transepidermal water loss, may lead to altered biomechanical behavior and increased PI risk.
Conclusions:
The modeling suggests that reduced WC and increased transepidermal water loss, notably present in darker skin tones, lead to higher stress concentrations within the SC, thus elevating the PI risk. Comprehensive clinical and biomechanical data across various skin tones are needed to improve the practice of PI prevention in individuals with darker skin.
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