DEVELOPMENT OF A NEW CLIP-PISTON PROSTHESIS FOR THE STAPES

275 inserted Clip-Pistons type “AWengen” within three years revealed difficulties in 14.5% of the cases. In those cases it was necessary to make adjustments to the clip shape (plastic deformation) before insertion due to the individual dimension of the long incudal process. During 100 middle ear surgeries the cross sections of the long incudal processes where the clip is attached was measured. This resulted in data hitherto unknown. By virtue of a Finite Element Model (FEM) these data were used for optimizing the clip shape. Design criteria were a minimal variation of the contact force for different cross-sections and to minimize the force necessary to slide the clip over the incudal process. The new clip has a lower stiffness and can therefore be applied onto different incus diameters. The lower contact force reduces the risk of arrosion. Due to its optimized shape, the maximal stress in the clip is lowered preventing plastic deformation during the application procedure. The application force was decreased by up to 45% depending on the application points. This leads to easy and safe application reducing the risk of damaging the ossicular chain.