Three-dimensional quasi-static displacement of human middle-ear ossicles under static pressure loads: Measurement using a stereo camera system

ElsevierVolume 427, January 2023, 108651Hearing ResearchAuthor links open overlay panelHighlights•

Methods to measure 3D quasi-static displacements of the middle-ear ossicles under static pressure loads have been established using a stereo-camera system.

Rotation around the anterior-posterior axis is dominant for movement of the malleus-incus complex under static pressure loads.

Under positive ear-canal pressures, relative motion between the malleus and the incus at the IMJ reduces inward movements of the incus and stapes.

3D tracing of the middle-ear ossicular chain provides a better understanding of the protective function of the human middle ear under static pressure loads.

Abstract

The time delay and/or malfunctioning of the Eustachian tube may cause pressure differences across the tympanic membrane, resulting in quasi-static movements of the middle-ear ossicles. While quasi-static displacements of the human middle-ear ossicles have been measured one- or two-dimensionally in previous studies, this study presents an approach to trace three-dimensional movements of the human middle-ear ossicles under static pressure loads in the ear canal (EC). The three-dimensional quasi-static movements of the middle-ear ossicles were measured using a custom-made stereo camera system. Two cameras were assembled with a relative angle of 7° and then mounted onto a robot arm. Red fluorescent beads of a 106–125 µm diameter were placed on the middle-ear ossicles, and quasi-static position changes of the fluorescent beads under static pressure loads were traced by the stereo camera system. All the position changes of the ossicles were registered to the anatomical intrinsic frame based on the stapes footplate, which was obtained from µ-CT imaging. Under negative ear-canal pressures, a rotational movement around the anterior-posterior axis was dominant for the malleus-incus complex, with small relative movements between the two ossicles. The stapes showed translation toward the lateral direction and rotation around the long axis of the stapes footplate. Under positive EC pressures, relative motion between the malleus and the incus at the IMJ became larger, reducing movements of the incus and stapes considerably and thus performing a protection function for the inner-ear structures. Three-dimensional tracing of the middle-ear ossicular chain provides a better understanding of the protection function of the human middle ear under static pressured loads as immediate responses without time delay.

Keywords

Ambient pressure variation

Micro-computed tomography imaging

Middle-ear ossicles

Protection function

Quasi-static displacement

Static pressure

Static pressure loads

Stereo camera system

Three-dimensional displacement

AbbreviationsISJ

incudo-stapedial joint

SFC

µ-CT, micro-computed tomography

SFC

stapes footplate center

Data availability

The link for animation is indicated in the manuscript.

© 2022 The Authors. Published by Elsevier B.V.

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