Biomechanical evaluation of human and porcine auricular cartilage

Objectives/hypothesis: The mechanical properties of normal auricular cartilage provide a benchmark against which to characterize changes in auricular structure/function due to genetic defects creating phenotypic abnormalities in collagen subtypes. Such properties also provide inputs/targets for auricular reconstruction scaffold design. Several studies report the biomechanical properties for septal, costal, and articular cartilage. However, analogous data for auricular cartilage are lacking. Therefore, our aim in this study was to characterize both whole-ear and auricular cartilage mechanics by mechanically testing specimens and fitting the results to nonlinear constitutive models.

Study design: Mechanical testing of whole ears and auricular cartilage punch biopsies.

Methods: Whole human cadaveric ear and auricular cartilage punch biopsies from both porcine and human cartilage were subjected to whole-ear helix-down compression and quasistatic unconfined compression tests. Common hyperelastic constitutive laws (widely used to characterize soft tissue mechanics) were evaluated for their ability to represent the stress-strain behavior of auricular cartilage.

Results: Load displacement curves for whole ear testing exhibited compliant linear behavior until after significant displacement where nonlinear stiffening occurred. All five commonly used two-term hyperelastic soft tissue constitutive models successfully fit both human and porcine nonlinear elastic behavior (mean R(2) fit >0.95).

Conclusions: Auricular cartilage exhibits nonlinear strain-stiffening elastic behavior that is similar to other soft tissues in the body. The whole ear exhibits compliant behavior with strain stiffening at high displacement. The constants from the hyperelastic model fits provide quantitative baselines for both human and porcine (a commonly used animal model for auricular tissue engineering) auricular mechanics.

Level of evidence: NA