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Open AccessArticle

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

1
Department of Anatomy, University of Otago, Dunedin 9016, New Zealand
2
Institute of Materials Science and Engineering, Chemnitz University of Technology, 09125 Chemnitz, Germany
3
Department of Macroscopic and Clinical Anatomy, Medical University of Graz, 8010 Graz, Austria
4
Institute of Legal Medicine, University Medical Center Hamburg-Eppendorf, 22529 Hamburg, Germany
5
Department of Orthopaedic and Trauma Surgery, University of Leipzig, 04103 Leipzig, Germany
6
Fraunhofer IWU, 01187 Dresden, Germany
*
Authors to whom correspondence should be addressed.
Medicina 2020, 56(10), 520; https://doi.org/10.3390/medicina56100520
Received: 24 August 2020 / Revised: 27 September 2020 / Accepted: 28 September 2020 / Published: 5 October 2020
(This article belongs to the Special Issue Variational Anatomy and Developmental Anomalies in Clinical Practice)
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. View Full-Text
Keywords: biomechanical parameters; elastic modulus; mechanical variation; ultimate tensile strength; tensile testing biomechanical parameters; elastic modulus; mechanical variation; ultimate tensile strength; tensile testing
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MDPI and ACS Style

Zwirner, J.; Scholze, M.; Ondruschka, B.; Hammer, N. 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. Medicina 2020, 56, 520. https://doi.org/10.3390/medicina56100520

AMA Style

Zwirner J, Scholze M, Ondruschka B, Hammer N. 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. Medicina. 2020; 56(10):520. https://doi.org/10.3390/medicina56100520

Chicago/Turabian Style

Zwirner, Johann; Scholze, Mario; Ondruschka, Benjamin; Hammer, Niels. 2020. "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" Medicina 56, no. 10: 520. https://doi.org/10.3390/medicina56100520

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