Biomechanical Characterisation of the Human Auricular Cartilages; Implications for Tissue Engineering

Abstract

Currently, autologous cartilage provides the gold standard for auricular reconstruction. However, synthetic biomaterials offer a number of advantages for ear reconstruction including decreased donor site morbidity and earlier surgery. Critical to implant success is the material’s mechanical properties as this affects biocompatibility and extrusion. The aim of this study was to determine the biomechanical properties of human auricular cartilage. Auricular cartilage from fifteen cadavers was indented with displacement of 1 mm/s and load of 300 g to obtain a Young’s modulus in compression. Histological analysis of the auricle was conducted according to glycoprotein, collagen, and elastin content. The compression modulus was calculated for each part of the auricle with the tragus at 1.67 ± 0.61 MPa, antitragus 1.79 ± 0.56 MPa, concha 2.08 ± 0.70 MPa, antihelix 1.71 ± 0.63 MPa, and helix 1.41 ± 0.67 MPa. The concha showed to have a significantly greater Young’s Elastic Modulus than the helix in compression (p < 0.05). The histological analysis demonstrated that the auricle has a homogenous structure in terms of chondrocyte morphology, extracellular matrix and elastin content. This study provides new information on the compressive mechanical properties and histological analysis of the human auricular cartilage, allowing surgeons to have a better understanding of suitable replacements. This study has provided a reference, by which cartilage replacements should be developed for auricular reconstruction.Electronic supplementary materialThe online version of this article (doi:10.1007/s10439-016-1688-1) contains supplementary material, which is available to authorized users.

Applied Basic Science of the Auricular Cartilage

“…It is also characterized by ridges and depressions formed by the auricular cartilage; there are five regions caused by this molding such as helix, antihelix, tragus, antitragus and concha [1].…”

“…Also, similar mechanical properties to the surrounding tissue prevent stress at the interface [1]; mechanical mismatch can lead to micromovement between the skin and the implant when subcutaneously implanted [13], thus implant failure and extrusion.…”

Biomechanical Characterization of Human Soft Tissues Using Indentation and Tensile Testing

“…Cover the cartilage sample with phosphate-buffered saline (PBS) prior to and during compression testing to ensure that the sample is hydrated. NOTE: PBS does not exactly match the physiological environment, but it allows both the materials and the tissues to be compared equally 15,16 . 2.…”

“…This method captures both the viscoelastic and relaxation properties of the tissue within the same test, which can be applied directly to the synthetic material. We have used the indentation protocol to evaluate human soft tissues, including skin and cartilage [14][15][16] . Cartilage is assessed using indentation testing and skin is evaluated using tension testing [14][15][16] .…”

“…We have used the indentation protocol to evaluate human soft tissues, including skin and cartilage [14][15][16] . Cartilage is assessed using indentation testing and skin is evaluated using tension testing [14][15][16] . Researchers aiming to engineer materials with similar properties to human soft tissues could consider implementing these protocols.…”