ABSTRACT
<p><b>OBJECTIVE</b>To reconstruct a finite element model of human middle ear and measure characteristic dimensions of this model and calculate the mass properties of the ossicles.</p><p><b>METHODS</b>The proposed method starts with the histologic section preparation of human temporal bone. Through tracing outlines of the middle ear components on the sections in AutoCAD2005, a set of exterior contours of the components is obtained. The three-dimensional solid model of middle ear, including tympanic membrane, ossicular bones, middle ear suspensory ligaments/muscles, are reconstructed using these contours in Unigraphics (UG). To prepare for finite element analysis (FEA) of the middle ear, all surfaces of the solid model are translated into ADINA, a commercial FE model package. Based on these surfaces, FE meshes of the middle ear are created, and material properties and boundaries are set up. The characteristic dimensions of this model are measured and the mass properties of the ossicles are calculated to confirm the accuracy of the geometric model constructed following the proposed method.</p><p><b>RESULTS</b>The three-dimensional finite element model of the human middle ear that included tympanic membrane, ossicular bones and middle ear suspensory ligaments/muscles was reconstructed. The accuracy of this geometric model was confirmed with the outcome of the characteristic dimensions of this model and the mass properties of the ossicles.</p><p><b>CONCLUSIONS</b>The proposed method not only provides an effective, convenient, economic, accurate way to reconstruct the three dimensional finite element model of human middle, but also provides a detailed knowledge of middle ear geometry that is required for finite element analysis.</p>
Subject(s)
Humans , Ear, Middle , Finite Element Analysis , Models, AnatomicABSTRACT
<p><b>OBJECTIVE</b>To design a tool for evaluating the sound transmission function of ossicular prosthesis and explore the impacts of ossicular prosthesis bead area and the effects of the mass of ossicular prosthesis on the sound transmission function in mechanical middle ear model.</p><p><b>METHODS</b>Two latex membranes were used to represent the tympanic membrane and oval window membrane. The ossicular prosthesis was fitted between the artificial tympanic membrane and oval window membrane during the test. Pure tune signals were used to stimulate the vibration of tympanic membrane. The vibration of oval window membrane was recorded by a laser Doppler vibrometer. The ossicular transmission function was evaluated by comparing the vibration velocities of oval window membrane. Two groups of titanium ossicular prosthesis with different head area and mass respectively were fitted into a mechanical middle ear model to evaluate their sound transmission functions.</p><p><b>RESULTS</b>The feeling threshold curve of mechanical middle ear model (MMEM) was similar to the hearing threshold curve of normal person. The transmission function of the prosthesis with small head area was better than that of prostheses with large head area at frequencies 1500-4000 Hz. The small-massed prostheses functioned better at higher frequencies and the large-massed prostheses functioned better at lower frequencies. But small-massed prostheses functioned better as a whole.</p><p><b>CONCLUSIONS</b>The MMEM was an idea tool to evaluate the transmission functions of different ossicular prostheses. Both the head area and prosthesis mass had an influence on the transmission function of ossicular prosthesis. So while designing the ossicular prosthesis or performing ossiculoplasty, both the head area and prosthesis mass should he taken into consideration.</p>