Human stapedial annular ligament mechanical and geometrical property analysis using a bi-layer tapered beam model

Abstract

Stapedial annular ligament (SAL) is a ring-shaped bundle of elastic fibers which connects the base of the stapes to the margin of the oval window. Histological images and morphometric data from micro-CT imaging showed that a SAL has a sandwich structure with fibers concentrated near the medial and lateral surfaces and sparse fibers in the intervening space. A bi-layer computational model has been developed to obtain mechanical properties of SAL, including the shear and tensile stiffness with the principal moments of inertia. Each layer was divided into 200 sub-elements, which were analyzed as tapered and clamped-guided Timoshenko beam models in a linear system. The inertial properties of the stapes and the overall shape of SAL were calculated from 3-D reconstructions obtained from micro-CT imaging. A stiffness matrix of SAL that fully couples the effects of force and moment components was estimated from the physiologically based SAL model. The SAL stiffness was calculated by considering the principal axes of the stapes, and the mean stiffness values corresponding to the principal z direction of the stapes were found to be 0.21 N/m and 1.56 N/m, with respective Young’s moduli of 65 kN/m2 and 490 kN/m2.