Mechanobiological Models for Bone Tissue. Applications to Implant Design

García-Aznar, J.M.; Gómez‐Benito, María José; Pérez, M.Á.; Doblaré, M.

doi:10.1002/9783527632732.ch4

Cited by 3 publications

(3 citation statements)

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“…One of the main roadblocks for the exploitation of mechanotransduction in the structural design of bone scaffolds is that they are required to provide desirable biomechanical characteristics for complex in-vivo loading while deforming within the bone regenerative range of strain. Currently, except for bioinert metallic materials, other types of scaffolding materials, i.e., bioactive ceramics or hydrogels, are not mechanically strong to be used in load-bearing sites directly [18,43]. Bioceramics are typically bioactive and osteoconductive, however, they are brittle in nature and have a fairly low fracture toughness, and can be extremely weak at high porosity (>50 vol.%) [44].…”

Section: Discussionmentioning

confidence: 99%

A modular design strategy to integrate mechanotransduction concepts in scaffold-based bone tissue engineering

et al. 2020

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Section: Discussionmentioning

confidence: 99%

A modular design strategy to integrate mechanotransduction concepts in scaffold-based bone tissue engineering

et al. 2020

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“…Generally, bone adapts to mechanical stimulus by apposition under high loading and by resorption under disuse (or less than habitual loading [11]). It is likely that osteocytes respond to bone tissue strain by recruiting osteoclasts to sites where bone remodelling is required [12, 13], indeed, there are both theories (Wolff’s Law, Perren’s strain theory, Frost’s “mechanostat”) [14] and experiments that corroborate the effect of mechanical loads and strain on bone adaptation [15, 16]. Adaptation and remodelling is hypothesised to optimise the stiffness and strength of bones, while minimising the metabolic cost of maintenance and ensures that animal skeletons are continuously adjusted to control strain [15].…”

Section: Introductionmentioning

confidence: 99%

The design and in vivo testing of a locally stiffness-matched porous scaffold

Ghouse

Reznikov

Boughton

et al. 2019

Applied Materials Today

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An increasing volume of work supports utilising the mechanobiology of bone for bone ingrowth into a porous scaffold. However, typically during in vivo testing of implants, the mechanical properties of the bone being replaced are not quantified. Consequently there remains inconsistencies in the literature regarding ‘optimum’ pore size and porosity for bone ingrowth. It is also difficult to compare ingrowth results between studies and to translate in vivo animal testing to human subjects without understanding the mechanical environment. This study presents a clinically applicable approach to determining local bone mechanical properties and design of a scaffold with similar properties. The performance of the scaffold was investigated in vivo in an ovine model. The density, modulus and strength of trabecular bone from the medial femoral condyle from ovine bones was characterised and power-law relationships were established. A porous titanium scaffold, intended to maintain bone mechanical homeostasis, was additively manufactured and implanted into the medial femoral condyle of 6 ewes. The stiffness of the scaffold varied throughout the heterogeneous structure and matched the stiffness variation of bone at the surgical site. Bone ingrowth into the scaffold was 10.73±2.97% after 6 weeks. Fine woven bone, in the interior of the scaffold, and intense formations of more developed woven bone overlaid with lamellar bone at the implant periphery were observed. The workflow presented will allow future in vivo testing to test specific bone strains on bone ingrowth in response to a scaffold and allow for better translation from in vivo testing to commercial implants.

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“…Cortical bone is highly dense, leaving only 3-5% porosity for osteocytes, canaliculi, blood vessels, etc [143]. Furthermore, bone continuously adapts its structure to ensure optimal functionality with minimal metabolic cost [144,145,146]. The functional adaptation of bone is achieved by morphology variations that depend on the strain stimulus of the bone [145].…”

Section: Lattice Structures For Orthopedic Implantsmentioning

confidence: 99%

Design, modeling and characterization of lattice structures for orthopedic implant applications

Alaña¹

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Interest in lattice structures has soared in recent years thanks to the advances in the field of additive manufacturing, which has led to increasingly complex designs and the production of parts which was impossible up to not long ago. These advances enabled to create lattice structures that mimic the cellular solids of nature, which attracted broad attention due to its applicability in the aerospace and biomedical industries. These structures can be designed to have predefined stiffness and strength values, which enables the production of parts with engineered mechanical properties. One problem of traditional implants made of monolithic parts of Ti6Al4V, CoCr, pure Ti, etc., is the mismatch between the stiffness of the host bone and the metallic implant, which creates the so-called stress shielding. Stress shielding occurs when the bone adjacent to the implant does not have to withstand the main physiological loads because the much stiffer implant bears them in its place. Bone is a living tissue, which is created or resorbed (diluted in blood) depending on the loads to optimize its functionality. Thus, the stiffness mismatch between bone and the implant leads to the bone resorption due to the lack of mechanical stimuli on the host bone. The bone surrounding the implant loses density and weakens, which causes pain to the patient, affects implant stability, and may lead to the loosening of the implant. Lattice structures offer the possibility to create porous implants with tailored mechanical properties to match the stiffness of the surrounding bone, thus avoiding stress shielding and subsequent bone loss. Furthermore, lattice structures form porous parts with high surface to volume ratios, and this porosity enables the bone ingrowth within the implant, improving its fixation and long-term stability. This work is devoted to the development of tools to design lattice structures with controlled mechanical properties, as well as to deepen into the factors that affect such properties. Thus, the main purpose of this dissertation is to create lattice structures that mimic bone stiffness and could be implemented in orthopedic implants to avoid the stress shielding. In addition, orthopedic implants must withstand millions of load cycles throughout the lifetime of the patients, thus the fatigue behavior of the structures was also studied in this thesis. Finally, the small feature sizes required to implement such structures in orthopedic implants requires to reach the manufacturing limits of current additive manufacturing technologies, which induces important deviations from the actually designed geometry and in turn the mechanical properties. Another goal of this work is to understand the impact of such manufacturing deviations on the stiffness of the structures. The obtained results show that there are different possibilities to design structures with stiffness levels comparable to bone. The developed analytical or semi-analytical models predict and enable to design the mechanical properties of the structures for different topologies. These models can be used with personalized bone data to mimic the bone stiffness of each patient. Furthermore, the anisotropy of the structures can also be controlled to adapt it to the complex loads that arise in various anatomical sites. Regarding dynamic loads, fatigue life prediction tools in literature were compared and adapted to improve their applicability, and a fatigue failure surface was developed to easily predict the fatigue life of the structures. Moreover, it was concluded that hot isostatic pressing enhanced the fatigue strength of the structures. Finally, the manufacturing deviations were studied, developing a methodology to consider the proximity to the nodes in the analysis of the imperfection level, and to include such imperfections in a numerical model that predicts the change of anisotropy in the structure.

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Mechanobiological Models for Bone Tissue. Applications to Implant Design

Cited by 3 publications

References 98 publications

A modular design strategy to integrate mechanotransduction concepts in scaffold-based bone tissue engineering

A modular design strategy to integrate mechanotransduction concepts in scaffold-based bone tissue engineering

The design and in vivo testing of a locally stiffness-matched porous scaffold

Design, modeling and characterization of lattice structures for orthopedic implant applications

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