Mechanical properties of the human scalp in tension

Falland-Cheung, Lisa; Scholze, Mario; Lozano, Pamela F.; Ondruschka, Benjamin; Tong, D. M.; Brunton, Paul; Waddell, John Neil; Hammer, Niels

doi:10.1016/j.jmbbm.2018.05.024

Cited by 29 publications

(17 citation statements)

References 31 publications

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“…Jacquemound et al [22] performed dynamic tensile tests on forehead skin showing that, at high speed, the ultimate stress (4.6 MPa) is similar to the value of quasi-static tests, but that the ultimate tensile strain is half of the value reported for quasi-static tests. Recently, Falland-Cheung et al [23] performed tensile tests at 0.042 s -1 of strain rate on human scalp tissue with the aim of providing data for application in the impact biomechanics area. They tested specimens from different scalp locations: left temporal, fronto-parietal, right temporal and occipital.…”

Section: Introductionmentioning

confidence: 99%

Mechanical characterisation of human and porcine scalp tissue at dynamic strain rates

Trotta

Annaidh

2019

Journal of the Mechanical Behavior of Biomedical Materials

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Several biomedical applications require knowledge of the behaviour of the scalp, including skin grafting, skin expansion and head impact biomechanics. Scalp tissue exhibits a non-linear stress-strain relationship, anisotropy and its mechanical properties depend on strain rate. When modelling the behaviour of the scalp, all these factors should be considered in order to perform realistic simulations. Here, tensile tests at strain rates between 0.005-100 s-1 have been conducted on porcine and human scalp in order to investigate the non-linearity, anisotropy, and strain rate dependence of the scalp mechanical properties. The effect of the orientation of the sample with respect to the Skin Tension Lines (STLs) was considered during the test. The results showed that anisotropy is evident in the hyperelastic response at low strain rates (0.005 s-1) but not at higher strain rates (15-100 s-1). The mechanical properties of porcine scalp differ from human scalp. In particular, the elastic modulus and the Ultimate Tensile Strength (UTS) of the porcine scalp were found to be almost twice the values of the human scalp, whereas the stretch at failure was not found to be significantly different. An anisotropic hyperelastic model (Gasser-Ogden-Holzapfel) was used to model the quasi-static behaviour of the tissue, whereas three different isotropic hyperelastic models (Fung, Gent and Ogden) were used to model the behaviour of scalp tissue at higher strain rates. The experimental results outlined here have important implications for those wishing to model the mechanical behaviour of scalp tissue both under quasi-static and dynamic loading conditions.

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Section: Introductionmentioning

confidence: 99%

Mechanical characterisation of human and porcine scalp tissue at dynamic strain rates

Trotta

Annaidh

2019

Journal of the Mechanical Behavior of Biomedical Materials

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“…Mechanical parameters obtained from human tissues are fundamental to accurately simulate the load deformation behavior of these tissues in computer simulations [ 1 , 2 ] and physical replicas [ 3 , 4 ]. Further to this, direct comparison of characteristic mechanical properties allows to compare for age [ 5 ], sex [ 6 ] or site-dependent differences [ 7 ] of biological tissues when loaded. The elastic modulus (E mod ) is a mechanical parameter describing the ratio of stress and strain under small deformation assuming a linear elastic behavior of the respective tissue [ 8 ], and consequently the rigidity of a tissue when elastically deformed; it is one of the key parameters to mechanically simulate human tissues in computer models [ 1 , 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

“…Strain at maximum force (SF max ) describes the elongation of a tissue at the point of the maximum applicable load in relation to the tissues initial unloaded length; this seems useful to understand the contribution of individual components such as cells to the overall mechanical behavior of the respective tissue [ 11 , 12 ]. Generally, baseline datasets to obtain the aforementioned mechanical parameters in tensile tests reveal widespread variation throughout the body [ 5 , 6 , 7 , 13 ]—an accepted “expectable” condition for human tissues. However, several factors such as the clamping quality [ 14 , 15 ], strain rate [ 16 ] and the mechanical and bio-physico-chemical tissue structure [ 5 , 17 , 18 ] impact the mechanical parameters to a varying extent ( Figure 1 ).…”

Section: Introductionmentioning

confidence: 99%

What Is Considered a Variation of Biomechanical Parameters in Tensile Tests of Collagen-Rich Human Soft Tissues?—Critical Considerations Using the Human Cranial Dura Mater as a Representative Morpho-Mechanic Model

et al. 2020

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Background and Objectives: Profound knowledge on the load-dependent behavior of human soft tissues is required for the development of suitable replacements as well as for realistic computer simulations. Regarding the former, e.g., the anisotropy of a particular biological tissue has to be represented with site- and direction-dependent particular mechanical values. Contrary to this concept of consistent mechanical properties of a defined soft tissue, mechanical parameters of soft tissues scatter considerably when being determined in tensile tests. In spite of numerous measures taken to standardize the mechanical testing of soft tissues, several setup- and tissue-related factors remain to influence the mechanical parameters of human soft tissues to a yet unknown extent. It is to date unclear if measurement extremes should be considered a variation or whether these data have to be deemed incorrect measurement outliers. This given study aimed to determine mechanical parameters of the human cranial dura mater as a model for human soft tissues using a highly standardized protocol and based on this, critically evaluate the definition for the term mechanical “variation” of human soft tissue. Materials and Methods: A total of 124 human dura mater samples with an age range of 3 weeks to 94 years were uniformly retrieved, osmotically adapted and mechanically tested using customized 3D-printed equipment in a quasi-static tensile testing setup. Scanning electron microscopy of 14 samples was conducted to relate the mechanical parameters to morphological features of the dura mater. Results: The here obtained mechanical parameters were scattered (elastic modulus = 46.06 MPa, interquartile range = 33.78 MPa; ultimate tensile strength = 5.56 MPa, interquartile range = 4.09 MPa; strain at maximum force = 16.58%, interquartile range = 4.81%). Scanning electron microscopy revealed a multi-layered nature of the dura mater with varying fiber directions between its outer and inner surface. Conclusions: It is concluded that mechanical parameters of soft tissues such as human dura mater are highly variable even if a highly standardized testing setup is involved. The tissue structure and composition appeared to be the main contributor to the scatter of the mechanical parameters. In consequence, mechanical variation of soft tissues can be defined as the extremes of a biomechanical parameter due to an uncontrollable change in tissue structure and/or the respective testing setup.

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“…However, there is no information regarding the strength of the material. A recent experimental study by Falland-Cheung et al [89] reports an average tensile elastic modulus of 22.74 MPa and tensile strengths in the range of 2.75-3.61 MPa depending of the head region. Nonetheless, other recent studies (Pittar et al ([90]) point to the hypothesis that in impact simulation the hardness of the scalp is the main relevant parameter rather than its tensile properties.…”

Section: Scalpmentioning

confidence: 98%

“…Mechanical tests on human (Melvin et al [87]) and monkey scalp (Galford and McElhaney [30]) were performed in the 1970s, but little information about this tissue can be found in the recent literature. It has been addressed in some studies, focusing on its behaviour under tension (Raposio and Nordström (1997) [88], Falland-Cheung et al (2018) [89]) most of them obtaining a four-to-five times greater stiffness than regular skin [90].…”

Section: Scalpmentioning

confidence: 99%

Assessment of head injury risk caused by impact using finite element models

Toledano¹

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Impact loading is the primary source of head injuries and can result in a range of trauma from mild to severe. Because of the multiple environments in which impact-related injuries can take place (automotive accidents, sports, accidental falls, violence), they can potentially affect the entire population regardless of their health conditions. Despite the increasing research effort on the understanding of head impact biomechanics, accurate prediction and prevention of traumatic injuries has not been completely achieved.

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Mechanical properties of the human scalp in tension

Cited by 29 publications

References 31 publications

Mechanical characterisation of human and porcine scalp tissue at dynamic strain rates

Mechanical characterisation of human and porcine scalp tissue at dynamic strain rates

What Is Considered a Variation of Biomechanical Parameters in Tensile Tests of Collagen-Rich Human Soft Tissues?—Critical Considerations Using the Human Cranial Dura Mater as a Representative Morpho-Mechanic Model

Assessment of head injury risk caused by impact using finite element models

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