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Mental fatigue (MF) is likely to occur in the industrial working population. However, the link between MF and industrial work performance has not been investigated, nor how this interacts with a passive lower back exoskeleton used during industrial work. Therefore, to elucidate its potential effect(s), this study investigated the accuracy of work performance and movement duration through a dual task paradigm and compared results between mentally fatigued volunteers and controls, with and without the exoskeleton. No main effects of MF and the exoskeleton were found. However, when mentally fatigued and wearing the exoskeleton, movement duration significantly increased compared to the baseline condition (βMF:Exo = 0.17, p = .02, ω2 = .03), suggesting an important interaction between the exoskeleton and one's psychobiological state. Importantly, presented data indicate a negative effect on production efficiency through increased performance time. Further research into the cognitive aspects of industrial work performance and human-exoskeleton interaction is therefore warranted.

The aim of this study was to determine the effect of Thiel embalming on the biomechanical properties of nerve tissue, to validate the use of Thiel embalmed bodies as a reliable model system for obtaining biomechanical data to supplement neurodynamic models, for anesthesiological and neurosurgical training and for future preclinical test set-ups involving nerve tissue. Upon the arrival of a body at the anatomy department, a fresh median nerve was harvested, the harvest site was sutured and following the Thiel embalming procedure the Thiel embalmed median nerve of the opposing wrist was harvested. Micro CT was performed to establish the cross-sectional area and biomechanical tensile testing was performed to compare the Young's modulus/elasticity of fresh frozen and Thiel embalmed nerves. Thiel embalming did not cause a significant difference in elasticity when comparing Thiel embalmed and fresh frozen specimens. A correlation was found between the cross-sectional area of Thiel embalmed nerve specimens and their Young's modulus. Thiel embalming does not significantly alter the elasticity of nerve tissue compared to fresh frozen nerve tissue. Similar shapes were observed when comparing the stress/strain curves of both specimen types. This indicates that Thiel embalmed nerve tissue is a viable alternative for using fresh frozen specimens when investigating biomechanical principles/mechanisms. Some specimens showed a reversed trend in Young's modulus that could be related to slight differences in embalming outcome, so caution is advised when Thiel embalmed specimens are used to obtain raw numerical data for direct application in the clinic.

Background Percutaneous left atrial appendage (LAA) closure can be optimised through diligent preprocedural planning. Cardiac computational tomography (CCT) is increasingly recognised as a valuable tool in this process. A CCT-based computational model (FEops HEARTguide™, Belgium) has been developed to simulate the deployment of the two most commonly used LAA closure devices into patient-specific LAA anatomies. Objective The aim of this study was to validate this computational model based on real-life percutaneous LAA closure procedures and post-procedural CCT imaging. Methods Thirty patients having undergone LAA closure (Amulet™ n = 15, Watchman™ n = 15) and having a pre- and post-procedural CCT-scan were selected for this validation study. Virtually implanted devices were directly compared to actual implants for device frame deformation and LAA wall apposition. Results The coefficient of determination (R2) and the difference in measurements between model and actual device (area, perimeter, minimum diameter, maximum diameter) were ≥0.91 and ≤ 5%, respectively. For both device types, the correlation coefficient between predicted and observed measurements was higher than 0.90. Furthermore, predicted device apposition correlated well with observed leaks based on post-procedural CCT. Conclusion Computational modelling accurately predicts LAA closure device deformation and apposition and may therefore potentiate more accurate LAA closure device sizing and better preprocedural planning.

BACKGROUND: Despite the potential of occupational passive shoulder exoskeletons (PSEs) to relieve overhead work, limited insights in overhead work precision performance impedes large-scale adoption in industry. OBJECTIVE: To investigate the effect of PSE support on the reduction in task performance caused by physical fatigue. METHODS: This experiment consisted of a randomized, counterbalanced cross-over design comparing Exo4Work PSE support and no support, in a physically fatigued state and a control condition. Precision performance was determined using execution speed and drilling errors. Muscle activity and shoulder joint kinematics were recorded. RESULTS: Fatigue altered task performance, shoulder joint kinematics, muscle activity and subjective experience during overhead work. The PSE support mitigated the fatigue-induced changes in shoulder kinematics. Additionally, a part of the fatigue-induced co-activation of shoulder stabilizing muscles was avoided when working with the PSE. The PSE support also reduced the activity of the anterior and medial deltoid. CONCLUSION: Physical fatigue provokes compensatory movements and increased co-contraction of muscles when executing overhead work. These fatigue-induced alterations are generally believed to increase the overall musculoskeletal load. The support provided by the PSE reduced muscle activity of muscles working to elevate the arm, but also partially mitigated those fatigue-induced effects. SIGNIFICANCE: This study shows that the effect of PSE support on precision performance is limited, and suggested that, apart from the known effects of PSE support during overhead work, wearing the exoskeleton in a physically fatigued state may provide additional advantages. ispartof: APPLIED ERGONOMICS vol:106 ispartof: location:England status: published

Exoskeleton technologies have the potential to reduce the prevalence of work-related musculoskeletal disorders. Despite the fast-growing industrial exoskeleton market, several bottlenecks have prevented their wide application, namely the lack of wearability, the amount of assistance they deliver and their usefulness in various working scenarios, outside of those they were specifically designed to perform. In this work we present the design, realization and evaluation of a new wearable shoulder exoskeleton that is kinematically compatible with the glenohumeral joint and features a new passive remote actuation system (pRAS). The latter has a twofold function: it delivers assistance only when needed and allows for a more convenient repositioning of the exoskeleton components, reducing the exoskeleton’s footprint and limiting the weight on the user’s arm. A test bench has been designed to validate the mechanical performance of the shoulder exoskeleton and experiments have been conducted to investigate its effect on users while executing overhead working tasks. Based on the muscle activity monitored in six subjects, we conclude that our exoskeleton reduces anterior deltoid activity by 22% during the execution of overhead work. This preliminary study suggests that our device can successfully provide relief at the level of the shoulder without hindering the subject.

This study proposes a new framework to optimize the design of a transcatheter aortic valve through patient-specific finite element and fluid dynamics simulation. Two geometrical parameters of the frame, the diameter at ventricular inflow and the height of the first row of cells, were examined using the central composite design. The effect of those parameters on postoperative complications was investigated by response surface methodology, and a Nonlinear Programming by Quadratic Lagrangian algorithm was used in the optimization. Optimal and initial devices were then compared in 12 patients. The comparison was made in terms of device performance [i.e., reduced contact pressure on the atrioventricular conduction system and paravalvular aortic regurgitation (AR)]. Results suggest that large diameters and high cells favor higher anchoring of the device within the aortic root reducing the contact pressure and favor a better apposition of the device to the aortic root preventing AR. Compared to the initial device, the optimal device resulted in almost threefold lower predicted contact pressure and limited AR in all patients. In conclusion, patient-specific modelling and simulation could help to evaluate device performance prior to the actual first-in-human clinical study and, combined with device optimization, could help to develop better devices in a shorter period.

Shoulder exoskeletons potentially reduce overuse injuries in industrial settings including overhead work or lifting tasks. Previous studies evaluated these devices primarily in laboratory setting, but evidence of their effectiveness outside the lab is lacking. The present study aimed to evaluate the effectiveness of two passive shoulder exoskeletons and explore the transfer of laboratory-based results to the field. Four industrial workers performed controlled and in-field evaluations without and with two exoskeletons, ShoulderX and Skelex in a randomized order. The exoskeletons decreased upper trapezius activity (up to 46%) and heart rate in isolated tasks. In the field, the effects of both exoskeletons were less prominent (up to 26% upper trapezius activity reduction) while lifting windscreens weighing 13.1 and 17.0 kg. ShoulderX received high discomfort scores in the shoulder region and usability of both exoskeletons was moderate. Overall, both exoskeletons positively affected the isolated tasks, but in the field the support of both exoskeletons was limited. Skelex, which performed worse in the isolated tasks compared to ShoulderX, seemed to provide the most support during the in-field situations. Exoskeleton interface improvements are required to improve comfort and usability. Laboratory-based evaluations of exoskeletons should be interpreted with caution, since the effect of an exoskeleton is task specific and not all in-field situations with high-level lifting will equally benefit from the use of an exoskeleton. Before considering passive exoskeleton implementation, we recommend analyzing joint angles in the field, because the support is inherently dependent on these angles, and to perform in-field pilot tests. This paper is the first thorough evaluation of two shoulder exoskeletons in a controlled and in-field situation.

BACKGROUND Performing daily activities is challenging for individuals with a transfemoral amputation. Technological advancements in prosthetic prototypes aim at improving functional independence. A state-of-the-art active device, the CYBERLEGs-gamma (CLs-ɣ) prosthesis, consisting of powered ankle and knee joints, has been designed and constructed. The control system combines pressure-sensitive insoles and inertial motor units to synchronize both joints to work together. To date, the novel device has not een clinically evaluated. Therefore, the objective of this study was to investigate the efficacy of the CLs-ɣ prosthesis during daily activities compared to current passive and quasi-passive devices . METHODS Participants performed a familiarization trial, an experimental trial with the current prosthesis, three adaptation trials and an experimental trial with the CLs-ɣ prosthesis. Participants completed a stair climbing test, a timed-up & go test, a sit to stand test, a two-minute dual task (i.e. the psychomotor vigilance task during treadmill walking) and a six-minute treadmill walk test at normal speed. Nonparametric Wilcoxon-signed rank tests were conducted with critical alpha set at 0.05. RESULTS Eight individuals with a transfemoral amputation (age: 55 ± 15 years, K-level 3) were included. Stride length significantly increased during walking with the CLs-ɣ prosthesis (p=0.012) because of a greater step length of the amputated leg (p=0.035). Normal walking speed was significantly slower (p=0.018), the net metabolic cost of transport was significantly higher (p=0.028) and reaction time significantly worsened (p=0.012) when walking with the CLs-ɣ compared to the current prosthesis. When participants took stairs, they adopted a step-over-step strategy with the CLs-ɣ prosthesis in contrast to step-by-step wearing the current prosthesis. CONCLUSION S A higher physical effort and cognitive demand were required during activities wearing the novel motorized prosthesis. Although performance outcome measures did not improve, participants had a greater stride length and better simulated able-bodied stair ambulation.

Introduction Evaluating the efficacy of a lower-limb prosthetic device (LLPD) is a crucial step in the iterative process of redesigning and product development of new generation prostheses. To date, no standardized experimental methodology for the evaluation of LLPDs is available which complicates the comparison of results. Objective This systematic review provides an overview of study designs, tests and outcome measures to evaluate a LLPD. Ultimately, guidelines and recommendations are formulated. Methods Two databases were screened on studies evaluating a LLPD, published between 2009 and 2019. Results 109 articles were eventually included. We identified 43 outcome measures in four main categories: 53% were biomechanical, 26% physiological, 14% physical performance and 7% psychological. Mainly walking tests were included (78%), of which 31% were performed on a slope, followed by stair climbing (15%) and other functional tasks (15%). Conclusion An overview of currently used study designs and experimental protocols is presented, which led to guidelines and recommendations for the evaluation of a LLPD. The main recommendation is to include daily activities in a case-report and in a later stage in a randomized controlled study design. Biomechanical, physiological, physical performance and psychological outcome measures are key for the evaluation of a LLPD.

Purpose Carotid artery stenting (CAS) is an alternative procedure for the treatment of severely stenosed carotid artery lesions in high-risk patients. Appropriate patient selection and stent design are paramount to achieve a low stroke and death rate in these complex high-risk procedures. This study introduces and evaluates a novel virtual, patient-specific, pre-operative environment to quantify scaffolding parameters based on routine imaging techniques. Methods Two patients who underwent CAS with two different sizes of the Acculink stent (Abbott Vascular, Santa Clara, CA, USA) were studied. Pre-operative data were used to build the numerical models for the virtual procedure. Numerical results were validated with post-operative angiography. Using novel virtual geometrical tools, incomplete stent apposition, free cell area and largest fitting sphere in the stent cell were evaluated in situ as quantitative measures of successful stent placement and to assess potential risk factors for CAS complications. Results A quantitative validation of the numerical outcome with post-operative images noted differences in lumen diameter of 5.31 ± 8.05% and 4.12 ± 9.84%, demonstrating the reliability of the proposed methodology. The quantitative measurements of the scaffolding parameters on the virtually deployed stent geometry highlight the variability of the device behavior in relation to the target lesion. The free cell area depends on the target diameter and oversizing, while the largest fitting spheres and apposition values are influenced by the local concavity and convexity of the vessel. Conclusions The proposed virtual environment may be an additional tool for endovascular specialists especially in complex anatomical cases where stent design and positioning may have a higher impact on procedural success and outcome.

Clinical studies have demonstrated the efficacy of stent supported coiling for intra-cranial aneurysm treatment. Despite encouraging outcomes, some matters are yet to be addressed. In particular closed stent designs are influenced by the delivery technique and may suffer from under-expansion, with the typical effect of "hugging" the inner curvature of the vessel which seems related to adverse events. In this study we propose a novel finite element (FE) environment to study potential failure able to reproduce the microcatheter "pull-back" delivery technique. We first verified our procedure with published in vitro data and then replicated the intervention on one patient treated with a 4.5 × 22 mm Enterprise microstent (Codman Neurovascular; Raynham MA, USA). Results showed good agreement with the in vitro test, catching both size and location of the malapposed area. A simulation of a 28 mm stent in the same geometry highlighted the impact of the delivery technique, which leads to larger area of malapposition. The patient specific simulation matched the global stent configuration and zones prone to malapposition shown on the clinical images with difference in tortuosity between actual and virtual treatment around 2.3%. We conclude that the presented FE strategy provides an accurate description of the stent mechanics and, after further in vivo validation and optimization, will be a tool to aid clinicians to anticipate the acute procedural outcome avoiding poor initial results.

Supersonic shear wave imaging (SSI) has recently emerged as a reliable technique for soft tissue characterization in bulk tissues (e.g. in the context of breast and liver cancer diagnostics). Another promising application of SSI is arterial stiffness assessment, though challenged by complex shear wave (SW) propagation phenomena in this thin-walled setting such as guided waves, dispersion, reflection and refraction on the arterial walls. Therefore, we investigated the sensitivity of SSI to (i) stretch-induced stiffening and (ii) the arterial fiber organization in a simpler ex-vivo arterial setup based on equine aortic tissue, where the SW propagation is deprived of dispersion and guided-wave effects. For this purpose, we conducted simultaneous dynamic mechanical testing of the tissue along with SSI measurements. The probe was rotated around its axis relative to the tissue to investigate whether SSI is able to determine the dominant collagen fiber direction in the tissue. The cyclic behavior of the SW velocities as a response to the dynamic mechanical testing demonstrated the ability of SSI to detect stretch-induced stiffening, though mainly in the circumferential direction. Furthermore, SW velocities were lower when the probe was positioned away from the circumferential direction of the tissue, which could be explained due to the uni-axial testing, the arterial anisotropy and the progressive recruitment of collagen fibers in the circumferential direction. The elasticity modulus assessed from the SSI measurements and the mechanical testing demonstrated the feasibility of SSI to detect the increase in E-modulus as expected from the measured stress-strain curve (factor 2.1 versus 2.3 increase for SSI and mechanical testing respectively). Future work will include performing histology on the investigated tissue to confirm these findings and clarify the link between SSI measurements and the actual fiber orientation.