Biofabrication of Electrospun Scaffolds for the Regeneration of Tendons and Ligaments

Tendon and ligament tissue regeneration and replacement are complex since scaffolds need to guarantee an adequate hierarchical structured morphology, and non-linear mechanical properties. Moreover, to guide the cells\u2019 proliferation and tissue re-growth, scaffolds must provide a fibrous texture mimicking the typical of the arrangement of the collagen in the extracellular matrix of these tissues. Among the different techniques to produce scaffolds, electrospinning is one of the most promising, thanks to its ability to produce fibers of nanometric size. This manuscript aims to provide an overview to researchers approaching the field of repair and regeneration of tendons and ligaments. To clarify the general requirements of electrospun scaffolds, the first part of this manuscript presents a general overview concerning tendons\u2019 and ligaments\u2019 structure and mechanical properties. The different types of polymers, blends and particles most frequently used for tendon and ligament tissue engineering are summarized. Furthermore, the focus of the review is on describing the different possible electrospinning setups and processes to obtain different nanofibrous structures, such as mats, bundles, yarns and more complex hierarchical assemblies. Finally, an overview concerning how these technologies are exploited to produce electrospun scaffolds for tendon and ligament tissue applications is reported together with the main findings and outcomes

The use of digital image correlation in the biomechanical area: a review

This paper offers an overview of the potentialities and limitations of digital image correlation (DIC) as a technique for measuring displacements and strain in biomechanical applications. This review is mainly intended for biomechanists who are not yet familiar with DIC. This review includes over 150 papers and covers different dimensional scales, from the microscopic level (tissue level) up to macroscopic one (organ level). As DIC involves a high degree of computation, and of operator- dependent decisions, reliability of displacement and strain measurements by means of DIC cannot be taken for granted. Methodological problems and existing solutions are summarized and compared, whilst open issues are addressed. Topics addressed include: preparation methods for the speckle pattern on different tissues; software settings; systematic and random error associated with DIC measurement. Applications to hard and soft tissues at different dimensional scales are described and analyzed in terms of strengths and limitations. The potentialities and limitations of DIC are highlighted, also in comparison with other experimental techniques (strain gauges, other optical techniques, digital volume correlation) and numerical methods (finite element analysis), where synergies and complementarities are discussed. In order to provide an overview accessible to different scientists working in the field of biomechanics, this paper intentionally does not report details of the algorithms and codes used in the different studies

In vitro and in silico methods for the biomechanical assessment of osseointegrated transfemoral prostheses: a systematic review

The amputee population according to the World-Health-Organization is about 40 million. However, there is a high abandon rate of socket prostheses for the lower limb (25%–57%). The direct connection between the external prosthesis and the patient’s bone makes osseointegrated prostheses for transfemoral amputees advantageous (e.g., improvement of the motor control) compared to socket prostheses, which are currently the gold standard. However, similarly to other uncemented prostheses, the osseointegrated ones are at risk of aseptic loosening and adverse bone remodelling caused by stress-shielding. The preclinical assessment of these prostheses has already been evaluated using different methods which did not provide unanimous and comparable evidence. To compare data from different investigations, a clear and detailed overview of the methods used to assess the performance is necessary. In this review 17 studies investigating the primary stability, stress shielding and stress concentration of osseointegrated transfemoral prostheses are examined. Primary stability consists in the biomechanical stability upon implant insertion. Primary stability is assessed measuring extraction force (either with a pull-out or a push-out test) and micromotion at the interface between the implant and the host bone with LVDT (in vitro test) or numerical models. Stress-shielding causes adaptive changes in the bone density around metal implants, and thus in the bone strength and stiffness. Stress-shielding is assessed with strain gauges or numerical models measuring the load transfer and the strain distribution on the surface of the femur, and between the implant and the bone respectively. Stress concentration can lead to the formation of cracks inside the bone, resulting in fractures. The stress concentration is assessed measuring the load transfer and the strain energy density at the interface between the implant and the bone, using numerical models. As a result, a global view and consensus about the methods are missing from all these tests. Indeed, different setup and loading scenario were used in the in vitro test, while different model parameters (e.g., bone properties) were used in the numerical models. Once the preclinical assessment method is established, it would be important to define thresholds and acceptance criteria for each of the possible failure scenarios investigated

Computational modelling of the scoliotic spine: A literature review

open4siScoliosis is a deformity of the spine that in severe cases requires surgical treatment. There is still disagreement among clinicians as to what the aim of such treatment is as well as the optimal surgical technique. Numerical models can aid clinical decision-making by estimating the outcome of a given surgical intervention. This paper provided some background information on the modelling of the healthy spine and a review of the literature on scoliotic spine models, their validation, and their application. An overview of the methods and techniques used to construct scoliotic finite element and multibody models was given as well as the boundary conditions used in the simulations. The current limitations of the models were discussed as well as how such limitations are addressed in non-scoliotic spine models. Finally, future directions for the numerical modelling of scoliosis were addressed.Marco Viceconti and Giorgio Davico were supported by the EU funded project Mobilise-D. The charity Reuse-WithLove is gratefully acknowledged for the financial support to this research.openGould, Samuele L; Cristofolini, Luca; Davico, Giorgio; Viceconti, MarcoGould, Samuele L; Cristofolini, Luca; Davico, Giorgio; Viceconti, Marc

Computational modelling of the scoliotic spine: A literature review

Scoliosis is a deformity of the spine that in severe cases requires surgical treatment. There is still disagreement among clinicians as to what the aim of such treatment is as well as the optimal surgical technique. Numerical models can aid clinical decision-making by estimating the outcome of a given surgical intervention. This paper provided some background information on the modelling of the healthy spine and a review of the literature on scoliotic spine models, their validation, and their application. An overview of the methods and techniques used to construct scoliotic finite element and multibody models was given as well as the boundary conditions used in the simulations. The current limitations of the models were discussed as well as how such limitations are addressed in non-scoliotic spine models. Finally, future directions for the numerical modelling of scoliosis were addressed

Full-field strain distribution in multi-vertebra spine segments: An in vitro application of digital image correlation

The biomechanics of the spine is experimentally assessed in terms of range of motion and overall stiffness. Quantification of the surface strain distribution is currently limited either to the vertebrae or the discs, whereas a full-field approach to measure the strain distribution in a multi-vertebra segment is currently missing. The aim of this work was to explore the feasibility of using Digital Image Correlation (DIC) to measure the strain distribution simultaneously on the vertebral bodies and the intervertebral discs of spine segments in different loading configurations. Three porcine spine segments were tested. A white-on-black speckle pattern was prepared which covered the hard and soft tissues. Two different loading configurations (flexion and lateral bending) were reproduced, while two sides of the spine were analyzed with DIC. Measurements were successfully performed on the entire region of interest of all specimens, in both configurations. The DIC analysis highlighted the strain gradients present on the spine segments including tension and compression associated with bending, the direction of principal strains in the different regions, as well as bulging of the discs under compression. Strains of tens of thousands microstrain were measured in the discs, and below 2000 microstrain in the bone. This work showed the feasibility of applying DIC on spine segments including hard and soft tissues. It also highlights the need for a full-field investigation, because of the strain inhomogeneity in the vertebrae and discs. (C) 2017 IPEM. Published by Elsevier Ltd. All rights reserved

Stereophotogrammetric approaches to multi-segmental kinematics of the thoracolumbar spine: a systematic review

Spine disorders are becoming more prevalent in today's ageing society. Motion abnormalities have been linked to the prevalence and recurrence of these disorders. Various protocols exist to measure thoracolumbar spine motion, but a standard multi-segmental approach is still missing. This study aims to systematically evaluate the literature on stereophotogrammetric motion analysis approaches to quantify thoracolumbar spine kinematics in terms of measurement reliability, suitability of protocols for clinical application and clinical significance of the resulting functional assessment

A NEW PARADIGM FOR THE IN VITRO SIMULATION OF SIDEWAYS FALL LOADING OF THE PROXIMAL HUMAN FEMUR

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Editorial: Electrospinning of Bioinspired Materials and Structures for Bioengineering and Advanced Biomedical Applications

The Research Topic “Electrospinning of Bioinspired Materials and Structures for Bioengineering and Advanced Biomedical Applications” includes submissions that relate to the “Biomaterials” and “Bionics and Biomimetics” sections of Frontiers in Bioengineering and Biotechnology. The collection aims to provide an overview of how electrospinning, inspired by nature, can reproduce the hierarchical structure and biomechanical properties of biological tissues, ranging from the nanoscale to the macroscale. The development of such innovative nanofibrous structures requires the improvement of both functionalization and biofabrication strategies, to enhance the scaffold bioactivity and to drive cells in the regeneration of the extracellular matrix (ECM) of the target tissues of interest. Recent technological advances have given rise to the availability of intelligent and smart biomaterials for the regeneration of innovative procedures for manufacturing nanometric structures, and methods for assembling multiscale hierarchical structures. Furthermore, imaging has improved considerably in the last few years, allowing multimodal imaging with nanometric resolution

Assessment of foraminal decompression following discoplasty using a combination of ex vivo testing and numerical tools

: Percutaneous Cement Discoplasty (PCD) is a minimally invasive surgical technique to treat degenerated intervertebral discs. When the disc is severely degenerated, the vacuum observed in place of the nucleus pulposus can be filled with bone cement to restore the disc height, open the foramen space, and relieve pain. This study aimed to evaluate the foramen geometry change due to PCD, in the loaded spine. Cadaveric spines (n = 25) were tested in flexion and extension while Digital Image Correlation (DIC) measured displacements and deformations. Tests were performed on simulated pre-operative condition (nucleotomy) and after PCD. Registering DIC images and the 3D specimen geometry from CT scans, a 3D model of the specimens aligned in the experimental pose was obtained for nucleotomy and PCD. Foramen space volume was geometrically measured for both conditions. The volume of cement injected was measured to explore correlation with the change of foramen space. PCD induced a significant overall foraminal decompression in both flexion (foramen space increased by 835 ± 1289 mm3, p = 0.001) and extension (1205 ± 1106 mm3, p < 0.001), confirming that the expected improvements of PCD show also during spine motion. Furthermore, in extension when the foramen is the most challenged, the impact of PCD on the foramen correlated with the injected cement volume