VCOM Research Day Program Book 2023

Medical Student Research Biomedical

14 Mallear Articular Surface Morphology – A Pilot Study

Robleh Omar; Ajmal Baray; Grace Greene; Michael Reymundi Pabon; Jonathan Millard Corresponding author: romar@vt.vcom.edu

Edward Via College of Osteopathic Medicine-Virginia Campus

The development of three articulating auditory ossicles in the middle ear cavity for transmission of air-based vibrations represents an important mammalian exaptation to increase hearing acuity. Pressure waves reaching the tympanic membrane conduct first through the malleus, incus, and stapes, respectively, before entering the cochlear apparatus. Clinical audiometric measures often identify sensorineural hearing loss; however, many patients may experience conduction hearing loss/ ossicular chain discontinuity or deficits from an indeterminant cause. Recent evidence suggests that dysfunction of the incudomallear joint may play a role in conduction hearing loss. The primary aim of this pilot study is to utilize statistical shape analysis to explore variation in the mallear articular surface and evaluate demographic differences. Left mallei from 15 whole-body formalin-fixed donors were collected with typical dissection techniques (mean age 86 yrs.). The bones were scanned with a Bruker SkyScan-1278 microCT scanner (100 µm). Volumes were segmented with 3DSlicer v5.2.1 and imported

into MeshLab v2022.02 for mesh production. Meshes were landmarked using Landmark Editor (IDAV) v3.0. The limit of the articular mallear surface was noted beginning at a distinct indention of the medioinferior limit of the joint boundary, and an 8×8 semilandmark patch was placed along its perimeter for a total of 64 semilandmarks. Raw landmark coordinates were imported into MorphoJ v1.07a for Procrustes superimposition and subsequent geometric analyses. Principal component analysis was used to explore variability in articular surface shape. Independent samples t-tests were used to evaluate differences between male and female PC scores. The principal component analysis revealed 14 total components, with the first six components capturing 84.714% of the overall variation in the shape. Male and female conformation separate along the first principal component axis (PC1) ( t (14)= 2.036, p =0.06), which is characterized by variable convexity of the articular surface, exaggeration of the articular rim, and generalized mallear head elongation. No

appreciable patterns were detected which would suggest a relationship between mallear shape and age. The result of these preliminary findings suggest that there is substantial difference in normal mallear articular morphology. Differences between sexes in morphology are interesting but should be interpreted with caution until the sample size is increased. Similarly, geometric morphometric techniques are excellent to assess subtle age-related changes in the bones, which may affect effective conduction. Future directions will include increasing the sample size to further explore these outcomes.

69

2 0 2 3 R e s e a r c h R e c o g n i t i o n D a y