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TECHNICAL BRIEFS

Mechanical Properties of Stapedial Tendon in Human Middle Ear

[+] Author and Article Information
Tao Cheng

Bioengineering Center, School of Aerospace & Mechanical Engineering, University of Oklahoma, Norman, OK 73019tcheng@ou.edu

Rong Z. Gan

Bioengineering Center, School of Aerospace & Mechanical Engineering, University of Oklahoma, Norman, OK 73019rgan@ou.edu

J Biomech Eng 129(6), 913-918 (Apr 19, 2007) (6 pages) doi:10.1115/1.2800837 History: Received April 21, 2006; Revised April 19, 2007

Abstract

Measurement on mechanical properties of the stapedial tendon in human middle ear has not been reported in the literature. In this paper, we used the material testing system to conduct uniaxial tensile, stress relaxation, and failure tests on stapedial tendon specimens harvested from human temporal bones. The digital image correlation method was employed to assess the boundary effect on experimental data. The stress-strain relationship of the tendon obtained from experiments was analyzed using the hyperelastic Ogden model. The results presented include (1) the constitutive equation of the tendon for stretch ratio of 1–1.4 or stress range of $0–1.45MPa$, (2) the mean ultimate stress and stretch ratio of the tendon at $4.04MPa$ and 1.65, respectively, and (3) the hysteresis and normalized stress relaxation function of the tendon. The data reported in this paper contribute to ear mechanics, especially for theoretical analysis of human ear function.

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Figures

Figure 1

Medial view of a left human middle ear model with the ST

Figure 2

(a) The ST harvested from a human temporal bone with the stapes and pyramidal eminence connected. (b) The ST specimen fixed at the mounting fixture along the longitudinal direction in a MTS. A ruler was attached to the metal holder at the load cell side as a reference for dimension measurement.

Figure 3

Illustration of the DIC method for calculating the strain distribution of the ST specimen under the loading process. The image of the specimen at time t=0 was a reference image, and three images of the specimen selected for illustration purpose at t=5s, 10s and 20s were deformed images. A grid (6×6) of 36 nodes was generated at the middle portion of each image. Two horizontal lines were identified along the top and bottom grids in the reference image, and six vertical lines, which connect corresponding grid nodes on the horizontal lines were identified as well. The length of each vertical line, in the reference image was used as the original length (L0) of the specimen, and the length of the corresponding vertical lines traced in deformed images was measured as the deformed length (L) of the specimen.

Figure 4

(a) Transverse strain distribution across the tendon specimen calculated from DIC analysis at four time steps. The number of nodes represents six locations (from left to right) across the specimen in the middle part of the grid shown in Fig. 3. The time interval for each step is 5s. (b) Comparison of stress-stretch loading curves of a ST specimen obtained from MTS experiment (solid line) and DIC analysis (broken line).

Figure 5

Stress-stretch curves of a ST specimen obtained from the uniaxial tensile test. The wavelike lines were the original stress-stretch curve recorded in MTS. The smooth lines were obtained after the Ogden model fitting process. A hysteresis loop was observed for the ST.

Figure 6

(a) Stress-stretch curves of 12 ST specimens under uniaxial loading processes. The maximum stretch ratio λ was around 1.4 and the displacement rate was 0.01mm∕s. (b) The mean curve of stress-stretch relationships obtained from 12 ST specimens with SD bars.

Figure 7

(a) Normalized stress relaxation function G(t) obtained from 9 ST specimens in stress relaxation tests. (b) The mean curve of G(t) of 9 tendon specimens with SD bars.

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