Ossicular replacement prostheses from banked bone with ergonomic and functional geometry

Abstract

This study shows the fabrication of innovative ossicular replacement prostheses (ORPs) based on banked cortical bone using computer numerically controlled ultraprecision micromilling, as a substantial improvement of "second generation" ORPs. Our aim is to combine optimal middle ear compatibility and surgical manageability in a single device, by releasing off-the-shelf homograft ORPs provided with the appealing features of synthetic ORPs, such as lightness, safety, measurement accuracy, surface decoration, and geometric plasticity. The new total ORP prototype was 13.1 ± 0.1 mg, leading to 81% weight reduction with respect to the previous model. Surface motifs of the head plate were applied to prevent slipping and migration after surgery, as shown by finite element modeling analysis. In addition, bone ORPs were provided with holed head plates to facilitate their surgical positioning while reducing their mass. A comparative measurement of acoustic responses of bone against synthetic partial ORPs in the 250-8000 Hz frequency range demonstrated their superior behavior. This study showed that banked compact bone can be optimally manufactured, eventually enabling the fabrication of light, standardized, and highly performant ORPs. The new bone ORPs may represent the ideal combination of biocompatibility and technology which can ultimately accomplish unmet otosurgical needs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2495-2506, 2017.

De novo topology optimization of total ossicular replacement prostheses

“…3A shows the geometry of a prosthesis before and after filtering and smoothing the raw outcomes from SIMULIA-Tosca via MeshLab. The shapes obtained in this study resemble the well-known piston-like geometry of commercial devices and earlier studies, with the shaft asymmetrically positioned with respect to the umbo plate to compensate the anatomic distance between the axes of the two contact interfaces (i.e., umbo and oval window) [7,8]. The 5-mm devices present a simple piston-like geometry that does not significantly change with the presence of the holes.…”

“…By choosing cortical bone as a constitutive material, the preferred approach is a fabrication with auto-/heterologous tissues from the bank, which requires the use of ultraprecision milling. However, the tiny dimensions of the devices and their features might be hard to achieve, also due to the brittleness of the bone itself [6,8]. Silk, on the other hand, is a natural protein fiber that can be easily used as an ink for Direct Ink Writing or, once solidified, shaped via ultraprecision milling.…”

“…The otocompatibility of the non-bioresorbable synthetic prostheses is therefore limited, with extrusion rates of at best ≈ 20% after 5 years even when interposing a slice of cartilage [30], eventually enhancing unwanted device migration. To improve prosthesis durability by controlling the phenomena at the prosthesis/biological interfaces, researchers have pursued two main approaches: developing prostheses made of (1) bulk synthetic materials with antimicrobial additives (e.g., silver nanoparticles [7,31,32]) or (2) engineered biological materials [8,33,34]. These studies have mainly focused on solving the otocompatibility problem, or developing new methodologies to fabricate miniature prostheses with specific features.…”

“…These studies have mainly focused on solving the otocompatibility problem, or developing new methodologies to fabricate miniature prostheses with specific features. For instance, Milazzo et al did a preliminary study on how holes and carved motifs on the prosthesis umbo plate not only reduce the weight, but also allow a better positioning of the prosthesis during surgery, limiting the migration effect [8].…”

Additive Manufacturing Approaches for Hydroxyapatite‐Reinforced Composites

“…AM, as largely demonstrated, has allowed scaffolds to be tailored in terms of specific features such as shape, micro/macroporosity, and pore interconnectivity ratio, while, at the same time, the fabrication time has significantly reduced . Since then, AM has spread into a wide family of techniques to fabricate customized and complex 3D constructs, being a much more versatile alternative to other traditional approaches where complex topologies are difficult to achieve (e.g., electrospinning, machining, screw extrusion, solvent casting/particulate leaching, freeze drying, gas foaming, replica molding, and masking) . Although the conventional fabrication techniques cited here represent important milestones for the production of HA‐reinforced composites for TE, they achieve a controlled internal/external architecture of the scaffolds (i.e., dimensions, pore morphology, pore size, pore interconnectivity) only in a limited manner.…”