<p xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" class="first" id="d1408026e123">Conductive
hearing loss, due to middle ear pathologies or traumas, affects more than
5% of the population worldwide. Passive prostheses to replace the ossicular chain
mainly rely on piston-like titanium and/or hydroxyapatite devices, which in the long
term suffer from extrusion. Although the basic shape of such devices always consists
of a base for contact with the eardrum and a stem to have mechanical connection with
the residual bony structures, a plethora of topologies have been proposed, mainly
to help surgical positioning. In this work, we optimize the topology of a total ossicular
replacement prosthesis, by maximizing the global stiffness and under the smallest
possible volume constraint that ensures material continuity. This investigation optimizes
the prosthesis topology in response to static displacement loads with amplitudes that
normally occur during sound stimulation in a frequency range between 100 Hz and 10 kHz.
Following earlier studies, we discuss how the presence and arrangement of holes on
the surface of the prosthesis plate in contact with the umbo affect the overall geometry.
Finally, we validate the designs through a finite-element model, in which we assess
the prosthesis performance upon dynamic sound pressure loads by considering four different
constitutive materials: titanium, cortical bone, silk, and collagen/hydroxyapatite.
The results show that the selected prostheses present, almost independently of their
constitutive material, a vibroacustic behavior close to that of the native ossicular
chain, with a slight almost constant positive shift that reaches a maximum of ≈5 dB
close to 1 kHz. This work represents a reference for the development of a new generation
of middle ear prostheses with non-conventional topologies for fabrication via additive
manufacturing technologies or ultraprecision machining in order to create patient-specific
devices to recover from conductive hearing loss.
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