Comparison of sheep and human middle-ear ossicles: anatomy and inertial properties

Abstract

The sheep middle ear has been used in training to prepare physicians to perform surgeries and to test new ways of surgical access. This study aimed to (1) collect anatomical data and inertial properties of the sheep middle-ear ossicles and (2) explore effects of these features on sound transmission, in comparison to those of the human. Characteristic dimensions and inertial properties of the middle-ear ossicles of White-Alpine sheep (n = 11) were measured from high-resolution micro-CT data, and were assessed in comparison with the corresponding values of the human middle ear. The sheep middle-ear ossicles differed from those of human in several ways: anteroinferior orientation of the malleus handle, relatively small size of the incus with a relatively short distance to the lenticular process, a large area of the articular surfaces at the incudostapedial joint, and a relatively small moment of inertia along the anterior-posterior axis. Analysis in this study suggests that structure and orientation of the middle-ear ossicles in the sheep are conducive to an increase in the hinge-like ossicular-lever-action around the anterior-posterior axis. Considering the substantial anatomical differences, outcomes of middle-ear surgeries would presumably be difficult to assess from experiments using the sheep middle ear. Keywords Hinge-like rotational motion • Middle-ear ossicles • Moment of inertia • Principal moment of inertia • Sheep Abbreviations 3D Three dimensional C.O.M Center of mass CT Computed tomography FT Stapes footplate IMJ Incudomalleal joint ISJ Incudostapedial joint MI Malleus-incus complex consisting of the malleus and incus MIS Intact middle-ear ossicular chain consisting of the malleus, incus, and stapes PMOI Principal moments of inertia STL Standard tessellation language

Optical coherence tomographic measurements of the sound-induced motion of the ossicular chain in chinchillas: Additional modes of ossicular motion enhance the mechanical response of the chinchilla middle ear at higher frequencies

“…Our results also point out that kinematic analyses of ossicular motion that ignore the effects of supporting ligaments and other ossicular supports and constraints (e.g. Puria and Steele 2010;Péus et al 2020) can lead to inaccurate predictions of modes of ossicular motion. Six 'B-scans' of the TM and ossicles of the right ear of CH2 taken at different y (superiorinferior) positions.…”

Anatomical and morphometric study of goat middle ear ossicles (Capra aegagrus hircus)

“…The goat incus was similar to the sheep incus with regard to process length as the long process was almost three times larger than the short process and due to the presence of the lenticular process (Péus et al, 2020). The manubrium was thinner and longer in goats than in adult rats; the lenticular process of the incus was not bent toward the short process; the stapes had a triangular shape, and their rostral and caudal crura were longer.…”

“…The lack of scientific studies describing the macroscopic anatomy and morphometry of goat middle ear ossicles restricted this subject to comparisons with other domestic and wild species and with humans. There were morphological similarities with sheep and bovines (Getty, 1986;Péus et al, 2020), guinea pigs and adult rats (Albuquerque et al, 2009), paca (Martins et al, 2015), and humans (Costa, 2008;Sobotta, 2018).…”

“…In general, these studies use guinea pigs, rats, mice, hamsters (Schanaider and Silva, 2004;Albuquerque et al, 2009;Reis et al, 2017), chinchillas, cats, dogs, and monkeys, among others (Reis et al, 2017), due to their ease of handling and similarity with the human ear. Although all mammals have these three ossicles, differences in the middle ear shape and size can interfere with some results (Péus et al, 2020), motivating the search for an experimental model that gathers all desirable features. The significant expression of goat farming in Northeastern Brazil, which concentrates 90% of the national goat herd (Pesquisa…, 2017), in addition to the important social and economic role that it performs to the rural population and the regional economic structure (Nogueira Filho and Kasprzykowski, 2006;Costa et al, 2008), and the fact that the use of goat ossicles for research and human surgery training has not yet been proposed justify the study of their applicability as an experimental model.…”

Feasibility study of the Vitom 3D exoscope in ENT surgery using an animal model: relevance to coronavirus disease 2019

“…Sheep heads were chosen as substitutes for this research project given the poor accessibility to human temporal bones during the pandemic. Although there are similarities between sheep and human temporal bone anatomy, as per a comparison by Péus et al ., 22 the substantial differences in middle-ear anatomy may potentially have been a factor in the poor visualisation of ossicles at high magnification. Moreover, the study did not involve a direct comparison between the Vitom 3D exoscope and the microscope; the results may therefore be subject to recall bias.…”