Vol. 2, No. 8, 2007

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ISSN: 1559-3959
Calculation of inertial properties of the malleus-incus complex from micro-CT imaging

Jae Hoon Sim, Sunil Puria and Charles R. Steele

Vol. 2 (2007), No. 8, 1515–1524
Abstract

The middle ear bones are the smallest bones in the human body and are among the most complicated functionally. These bones are located within the temporal bone making them difficult to access and study. We use the micro-CT imaging modality to obtain quantitative inertial properties of the MIC (malleus-incus complex), which is a subcomponent of the middle ear. The principal moment of inertia of the malleus along the superior-inferior axis (17.3 ± 2.3mg/mm3) is lower by about a factor of six in comparison to the anterior-posterior and lateral-medial axes. For the incus, the principal moment of inertia along the superior-inferior axis (35.3 ± 6.9mg/mm3) is lower by about a factor of two than for the other two axes. With the two bones combined (MIC), the minimum principal moment of inertia (132.5 ± 18.5mg/mm3) is still along the superior-inferior axis but is higher than for the individual bones. The superior-inferior axis inertia is lower by a factor of 1.3 than along the anterior-posterior axis and is lower by a factor 2 along the lateral-medial axis. Values for inertia of the MIC show significant individual differences in three human ears measured, suggesting that middle ear models should be based on individual anatomy. Imaging by micro-CT scanner is a nondestructive modality that provides three-dimensional volume information about middle ear bones at each stage of manipulation with resolution down to 10μm. In this work extraneous tissue is removed to obtain a sufficiently small specimen. However, advances in imaging hold promise that this capability will be available for in vivo measurements.

Keywords
inertial properties, principal axes, ossicles, malleus-incus complex (MIC), middle ear, computed tomography (CT)
Milestones
Received: 18 July 2006
Revised: 29 March 2007
Accepted: 20 April 2007
Published: 1 October 2007
Authors
Jae Hoon Sim
Mechanics and Computation Division
Department of Mechanical Engineering
Stanford University
496 Lomita Mall
Durand Building
Stanford, CA 94305-4035
United States
Palo Alto Veterans Administration
3801 Miranda Avenue
Palo Alto, CA 94304
United States
Sunil Puria
Mechanics and Computation Division
Department of Mechanical Engineering
Stanford University
496 Lomita Mall
Durand Building
Stanford, CA 94305-4035
United States
Department of Otolaryngology —Head and Neck Surgery
Stanford University
Stanford, CA 94305
United States
Palo Alto Veterans Administration
3801 Miranda Avenue
Palo Alto, CA 94304
United States
Charles R. Steele
Mechanics and Computation Division
Stanford University
496 Lomita Mall
Durand Building
Stanford, CA 94305-4035
United States