Young’s moduli of subcutaneous tissues and muscles under different loads at the gluteal region calculated using ultrasonography

Abstract

Young's modulus distributions for subcutaneous and muscle tissues in a large sample of healthy individuals, based on ultrasonography and compression testing, remains uninvestigated till date. This study aimed to separately estimate the hardness of subcutaneous tissues and muscles in the human gluteal region under a range of loads in terms of mean Young's moduli and associated distributions. [Participants and Methods] Data of 21 males aged 20-22 years were acquired using synchronous compression testing and ultrasonography. Stress-strain curves comprised the loads applied (stress) were plotted against ultrasonographic changes in subcutaneous/muscle tissue thickness (strain). Young's moduli were calculated as slopes of approximation curves fitted to highly linear regions of the stress-strain curves. [Results] Young's moduli (mean ± standard deviation) for gluteal subcutaneous and muscle tissues were estimated as: 26.1 ± 19.0 kPa, 1-N load; 2,199.1 ± 1,354.8 kPa, and 62.2 ± 10.3 kPa, 440.4 ± 80.0 kPa, respectively. No correlation between any pair of these measures reached statistical significance. [Conclusion] Young's moduli were successfully measured for subcutaneous and muscle tissues in a large participant sample using ultrasonography and compression testing. Our results may serve as reference data when assessing tissue hardness by palpation.

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“…The stress-strain characteristics of the subcutaneous tissue layer, muscle layer, and muscle-nodule-palpation simulator do not deviate significantly from those measured on corresponding examples from living subjects (Fig. 2) 17) . A transparent plastic sheet was attached over the bottom of the muscle-nodule-palpation simulator to maintain the transparency of its bottom surface.…”

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“…Through comparison of their Young's moduli (440 kPa compared to 16 GPa), the flesh is more than 10 4 times weaker than the tibia's cortical bone, or the bone analogs used in this experiment 9 . This justifies the choice to ignore the muscles and tendons surrounding the tibia in our payload, as they do not have a significant effect on the strength of the sample.…”

“…To simulate the mechanical strength of bone most accurately, the team prioritised a close match on Young's modulus and cortical thickness. Human cortical bone has a Young's modulus of around 16 GPa 9 . Common animal bones have both a larger cortical thickness and a lower Young's modulus compared to humans 10 .…”