Investigating the Geometry and Mechanical Properties of Human Round Window Membranes Using Micro-Fringe Projection.

Hypothesis: The geometry and the mechanical property of the round window membrane (RWM) have a fundamental impact on the function of cochlea.

Background: Understanding the mechanical behavior of RWM is important for cochlear surgery and design for the cochlear implant. Although the anatomy of RWM has been widely studied and described in the literature, argument remains regarding the true shape of RWM. The mechanical properties of RWM are also scarcely reported due to the difficulty of the measurement of the small size RWM.

Methods: In this paper, micro-fringe projection was used to reconstruct the 3-dimensional geometries of 14 RWMs. Mechanical properties of the RWMs were subsequently measured using finite element (FE) model and an inverse method. The three-dimensional surface topographies and the curvatures of the two major directions reconstructed from the micro-fringe projection both demonstrated wide variations among samples.

Results: The diameters of the RWMs vary from 1.65 to 2.2 mm and the curvatures vary from -0.97 to 3.76 mm-1. The nonlinear elasticity parameters in the Ogden model for each sample was measured and the average effective Young's modulus is approximately 1.98 MPa.

Conclusion: The geometries and mechanical properties of the human RWM measured in the work could potentially be applied to surgery design and on modeling analysis for the cochlea.