| Project Detail |
It has been recently shown that the human stapedial annular ligament (SAL) has a structure of two membrane-like thin fiber layers and a thick fiber-free core layer and thereby offers relatively low stiffness against acoustic vibrations but high stiffness against large static displacements. This unique structure makes the human SAL a critical component of the middle ear that significantly contributes to and defines its overall functionality. However, this functionality has not been sufficiently explained. Further, alteration of the SAL functionality in pathological and surgically reconstructed conditions has not been systematically investigated. This project aims to reveal i) functionality of the SAL in correlation with other middle-ear (ME) anatomy, ii) effects of the pathological changes on structures and functionality of the SAL, and iii) modified functionality of the human SAL in the surgically reconstructed MEs, in dynamic and static aspects.The functionality of the SAL in normal conditions is explored by comparative studies between different types of the SAL, i.e., a) two separate membrane-like fibrous layers, b) uni-layer, and c) synovial capsule. Species representing the three types of the SAL (human, sheep, and guinea pig, respectively) are chosen, and dynamic and static behaviors of the SAL in reaction with other ME anatomy are analyzed through measurements of mechanical properties of the SAL and 3D motion of the ME ossicles under acoustic and quasi-static stimuli using cadaveric temporal bones (TBs) and numerical simulation of the corresponding mathematical models.Structural changes, caused by pathological causes such as otosclerosis and chronic otitis media, are investigated through literature review and examination of histological sections. Then, the altered functionality of the SAL is analyzed using the corresponding mathematical models. In the models, precise anatomical features of the SAL such as three-layer structures and varying inclination of the fiber layers, are described, and pathological effects on the detailed structures are simulated.Investigation on the surgically reconstructed MEs include modified dynamic and static functionalities of the SAL and long-term postoperative changes of the SAL such as relaxation of preloads and formation of membranous tissue as a substitute of the SAL, in ME implants of ossiculoplasty and stapes surgeries. This investigation is performed through examination of histological sections, postoperative follow-up of patients with audiometric tests, middle-ear absorbance measurements using wide-band tympanometry (WBT), imaging of prostheses using an optical coherence tomography (OCT) system, and simulation of the mathematical models.The results of this project are expected to add a new aspect to our understanding of ME mechanics, i.e., dynamic and static functional roles of the SAL in reaction with other ME anatomy and thus functionality of the human SAL with its unique anatomy. From the clinical point of view, the proposed project will explain pathological changes of the SAL functionality with alterations of the SAL substructures, which most existing models do not describe. The investigation on ME reconstructions is expected to provide knowledge for optimal prosthesis design for both efficient transmission of acoustic stimuli and prevention of transmission of large static displacements. The proposed study also includes investigations on long-term postoperative changes of the SAL such as relaxation of preloads in ossiculoplasty and formation of membranous tissue as a substitute of the SAL in stapes surgery, which are crucial to determine optimal surgical conditions but have not been examined systematically. |
