Otosclerosis is a bone disease of the middle ear that often causes conductive hearing loss. This type of hearing loss can be treated by implanting a prosthesis, which replaces the stapes bone and attaches to the adjacent bone: the incus. Current stapes prostheses produce excellent hearing results, however the procedure is difficult to perform and success is not assured. With current prostheses, safe clamping forces cannot be accurately controlled, despite being crucial to the surgery’s long-term success. Inappropriate clamping force may cause slipping of the prosthesis or necrosis of the incus.
The objective of this study was to first create an overview of current prostheses and subsequently examine their pitfalls, and to design a new stapes prosthesis that addresses these pitfalls. Throughout the literature review a classification and evaluation system was developed to catalogue existing and future prostheses based on, for example, air bone gap difference, force controllability and ease of implantation. From this study we found the category of prostheses that utilise elastic material behaviour to securely clasp around the incus to have the most potential in a new prosthesis design.
Presented in this thesis is a novel prosthesis which features a bistable, fully compliant, two-dimensional mechanism, designed to be simpler to insert and with a more predictable clamping force compared with existing prostheses. For any incus diameter within the recorded range, the force around the incus is sure to be safe by design. The new prosthesis can be placed around the bone without causing unwanted stresses in the ossicles and joints, and is easily clicked shut.