Innovative 3D Model of the Human Middle Ear in High Resolution with a Histological Microgrinding Method: A Feasibility Study and Comparison with μCT.

Susanne Bradel,Thomas Lenarz,Gudrun Brandes,Nils Prenzler,Franziska Lexow,Laura Doniga-Crivat,Michael Fehr,Silke Besdo

doi:10.1155/2017/6753604

Abstract

Conclusion. The development of a histological 3D model of the tympanic cavity visualizes the exact microanatomy of the sound conduction organ and is therefore essential for finite elements simulations and surgical training. Objectives. So far, no accurate histological 3D model of the sound conduction system existed in literature. For 3D reconstruction of the very fine structures inside and outside the auditory ossicles, a method based on histological slices allows a more differential analysis of both hard and soft tissues and could thus be superior to μCT. Method. A complete temporal bone was embedded in epoxy resin and microground in distances of about 34 μm. After photodocumentation of every plane, a 3D reconstruction was performed by using the Computer Aided Design (CAD) program Rhinoceros 5®. For comparison, a μCT of the same specimen resulted in a 3D model of the calcified structures in the middle ear. Results. The histological 3D model gives an excellent overview to all anatomical soft and bony tissues of the human auditory ossicles. Specifically the fine blood vessel system and the exact dimension of cartilage areas inside the ossicles can be illustrated much more precisely than with μCT data. The present technique also allows the evaluation of the fine connecting ligaments inside the tympanic cavity.

Highlights

The middle ear can be affected by a number of pathologies which may lead to hearing loss
In this study an embedded specimen of a left adult human temporal bone was examined by the microgrinding method with removal of circa 35 μm per grinding run in the region of the auditory ossicles. This fine working and the high resolution of the 20996 histological images taken in total during the microgrinding process allow a very detailed histological examination of the images, and an anatomically correct and highly accurate 3D reconstruction of the structures inside the tympanic cavity
The histological images of the microgrinding surface as well the deeper transparent zones of the embedded middle ear show that the tympanic cavity and the ossicular chains are covered by a thin layer of mucosa

Summary

Introduction

The middle ear can be affected by a number of pathologies which may lead to hearing loss. In understanding the physiological conditions of the blood supply inside the tympanic cavity, complications in the middle ear surgery, for example, the necrosis of the long process of the incus after stapes prosthesis surgery, can be explained. In the middle of the 16th century, the anatomists Andreas Vesalius (1514–1564) and Giovanni Filippo Ingrassia (1510–1580) discovered the auditory ossicles in the tympanic cavity of the human petrous portion. The malleus is fixed with its manubrium to the ear drum and the stapes with its footplate to the oval window. They bridge the gap between the external and internal ear, acting as sound conduction organ

Methods

Results

Conclusion