De novo topology optimization of total ossicular replacement prostheses

Abstract

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 resultsshow 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.

Mechanics of Mineralized Collagen Fibrils upon Transient Loads

“…However, although native bone presents a mineralization up to 70%, due to the extrafibrillar mineralization, 39,40 they used a collagenous material with 40%HA to avoid a possible embrittlement of the material that might cause a failure. 63…”

“…66,67 Moreover, since collagen and bone are at the base of the musculoskeletal system, a further understanding of the native tissue may help the development of replacement devices with different functions, from sound transmission or conduction to structural purposes. 62,68 Finally, although the main focus of this study is about the effect of the mineralization on the mechanical behavior of bone, our results are not limited to tissue engineering applications. The development of bioinspired/biomimetic materials may also benefit from our research: dedicated artificial intelligence approaches 69 may, indeed, exploit a tuned viscoelastic behavior in a new generation of materials/structures that, upon transient loads (e.g., impact, fatigue), may show superior toughness and strength than traditional solutions, preventing structural failures or body traumas.…”

Molecular origin of viscoelasticity in mineralized collagen fibrils

“…A deeper knowledge of healthy collagen-based structures can also pave the way to new bioinspired materials to replace and treat native tissues after traumas of pathologies 51,[63][64][65] . With the advent of additive manufacturing and Machine Learning, new generation of optimized prostheses and structures can take advantage of this study to mimic, and even improve, the behavior of native tissues to the eventual benefit of patients suffering different bone-related diseases (e.g., osteogenesis imperfecta, osteoporosis) or injuries [66][67][68][69] . In view of this, new research avenues could be pursued to develop novel inks for replacing load-bearing bone parts.…”

Trends in Managing Cardiac and Orthopaedic Device-Associated Infections by Using Therapeutic Biomaterials

“…Additive manufacturing of antimicrobial materials is a small but rapidly growing field [ 98 ]. In this regard, topological modifications by additive manufacturing have been observed in ossicular prostheses produced by Milazzo et al, a real niche application, demonstrating to improve hearing recovery while facilitating the implantation [ 99 , 100 , 101 , 102 ], and which could also be easily integrated for reaching antifouling features.…”