A retrospective characterization of pediatric facemasks marketed in the United States and implications for future designs.

BACKGROUND: Device manufacturers who seek to market their pediatric facemasks in the United States (U.S.), as part of anthropometric data requirement, need to demonstrate their mask designs are expected to fit the intended user population. However, currently there are no well accepted test methodologies for pediatric facemasks. In addition, unlike N95 respirators, the expected maximum flow rate, and the pressure drop at that expected maximum flow rate for pediatric facemasks have not been established. METHOD: The objective of this article is three-fold; use a literature survey to determine the worst-case flow rate, and an acceptable breathing resistance; and come up with a bench-test based protocol for assessing fit of pediatric facemasks. RESULTS & DISCUSSION: The worst-case breathing flow rate for mask testing in the pediatric population is 45-60 Liters/minute (LPM), and the acceptable pressure drop at the worst-case flow rate is 2.0 mmH2O. A retrospective assessment of all the four brands of legally marketed facemasks in the U.S. that could be purchased, revealed that majority of the brands have high filtration efficiency (>95%) at low flow rate 5 LPM which reduces to ~ 80% at 45 LPM. At 5 LPM, the pressure drop ranges from 0.3-0.6 mmH2O, remaining below the 2.0 mmH2O. However, at higher flow rates, (representing strenuous activities, or older children (> 12 years)), most masks exhibited a pressure drop within the range of 2.9 to 6.0 mmH2O. Furthermore, opening the pleats of the facemasks completely results in a notable reduction in pressure drop (a 6.6-fold decrease, p = 0.03). To assess fit of these same brands of facemasks, we then updated our previous validated adult manikin fit-test method and used it in manikins in the age group of 2 to 14 years. Either poor nose-clip adherence to the manikin, low filtration efficiency of the pediatric facemasks, or off-label use (i.e. when donned on manikins representing 2 years to 14 years) contributed to low fit. CONCLUSIONS: A new bench-top tool to evaluate quantitative fit of pediatric facemasks was developed. In addition, based on the research reported here, we provide practical implications for the members of the community: users, academia and medical device manufacturers.

Evidence-based clinical practice guidelines for the management of acute ankle injuries according to: a PRISMA systematic review and quality appraisal with AGREE II.

BACKGROUND: Acute ankle injuries are commonly seen in emergency rooms, with significant social impact and potentially devastating consequences. While several clinical practice guidelines (CPGs) related to ankle injuries have been developed by various organizations, there is a lack of critical appraisal of them. The purpose of this systematic review is to identify and critically appraise evidence-based clinical practice guidelines (EB-CPGs) related to acute ankle injuries in adults. METHOD: We conducted searches in the Cochrane Library, MEDLINE, EMBASE databases, WHO, and reviewed 98 worldwide orthopedic association websites up until early 2023. Two authors independently applied the inclusion and exclusion criteria, and each evidence-based clinical practice guideline (EB-CPG) underwent independent critical appraisal of its content by all four authors using the Appraisal of Guidelines for REsearch and Evaluation (AGREE II) instrument. AGREE II scores for each domain were then calculated. RESULTS: This review included five evidence-based clinical practice guidelines. The mean scores for all six domains were as follows: Scope and Purpose (87.8%), Stakeholder Involvement (69.2%), Rigour of Development (72.5%), Clarity of Presentation (86.9%), Applicability (45.6%), and Editorial Independence (53.3%). CONCLUSION: The number of EB-CPGs related to ankle injuries are limited and the overall quality of the existing evidence-based clinical practice guidelines (EB-CPGs) for ankle injuries is not strong, with three of them being outdated. However, valuable guidance related to Ottawa rules, manual therapy, cryotherapy, functional supports, early ambulation, and rehabilitation has been highlighted. Challenges remain in areas such as monitoring and/or auditing criteria, consideration of the target population's views and preferences, and ensuring editorial independence. Future guidelines should prioritize improvements in these domains to enhance the quality and relevance of ankle injury management. SYSTEMATIC REVIEW: Systematic review.

English Translation of the Breastfeeding Knowledge Survey for Pediatricians.

Pediatricians need to be knowledgeable to adequately carry out their role in the support of breastfeeding, so assessing their knowledge of breastfeeding is vitally important. There are not English language validated questionnaires for pediatricians in the literature; however, in Spanish and Portuguese, there is the Breastfeeding Knowledge Survey (ECoLa, derived from Encuesta de Conocimientos en Lactancia). Our goal is to translate the ECoLa into English. The original survey consisted of true/false questions, including one with an image of a breastfeeding baby, multiple-choice questions featuring clinical cases, and two open-ended short questions. We used a translation approach that incorporated both forward and backward translations and a multidisciplinary committee to evaluate the translation process. During translation, four Spanish versions and seven English versions were considered prior to consensus approval of the final survey. The intraclass correlation coefficient between the English questionnaire and the original Spanish version was 0.85 (95% CI [0.60, 0.95]). A sample of 51 participants completed the survey, resulting in a Cronbach's alpha of 0.78 for the English version (95% CI [0.70, 0.86]). The Breastfeeding Knowledge Survey is now accessible under a Creative Commons license, permitting its free re-use.

A Critical Appraisal of the Congress of Neurological Surgeons Evidence-Based Guidelines on the Evaluation and Treatment of Patients With Thoracolumbar Spine Trauma.

Background and objective Thoracolumbar spine trauma (TST) is frequently associated with spinal cord injury and other soft tissue and bony injuries. The management of such injuries requires an evidence-based approach. This study used the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument to assess the methodological quality of clinical guidelines for the management of TST published by the Congress of Neurological Surgeons (CNS). Methods All clinical guidelines on TST published by CNS until 2020 were assessed. Five appraisers from three international centers evaluated the quality of eligible clinical guidelines by using AGREE II. Mean AGREE II scores for each domain were determined. In higher-quality domains, the scores for individual items were analyzed. Results A total of 12 guidelines published by CNS on TST were assessed. Mean scores for all six domains were as follows: Scope and Purpose (75.2%), Stakeholder Involvement (45.4%), Rigor of Development (57.0%), Clarity of Presentation (58.7%), Applicability (16.9%), and Editorial Independence (64.1%). The mean score for the overall quality of all CNS guidelines was 52.9% [95% confidence interval (CI): 52.2-53.5%]. The overall agreement among appraisers was excellent [intra-class correlation coefficients (ICCs) for each guideline ranged from 0.903 to 0.963]. Conclusions CNS guidelines for the management of TST demonstrated acceptable quality across most domains; however, the domains of Applicability and Stakeholder Involvement could be further improved in future guideline updates. The assessors concluded that all guidelines could still be recommended for clinical practice with or without modifications.

Additive manufacturing inert gas flow path strategies for multi-laser powder bed fusion systems and their impact on lattice structure mechanical responses.

Multi-laser Additive Manufacturing systems hold great potential to increase productivity. However, adding multiple energy sources to a powder bed fusion system requires careful selection of a laser scan and inert gas flow strategy to optimize component performance. In this work, we explore four different laser scan and argon flow strategies on the quasi-static compressive mechanical response of Body Centered Cubic lattices. Three strategies employ a swim lane method where laser pathing tends to progress parallel to argon flow. Method one only uses a single laser while method two uses four, both with the laser path working against the argon flow. The third method uses four lasers, each operating in their own lane like the second method, but the laser pathing progresses with the argon flow. The fourth method has all four lasers operating in quadrants and the laser pathing trends against the argon flow.The single-laser strategy generally had the lowest mechanical responses compared to the other three strategies. A quadrant strategy generally had the highest quasi-static mechanical responses and was at least 25% greater in stiffness, yield force, ultimate force, and energy absorption when compared to the single laser strategy. However, the four-laser swim strategy where the laser pathing tends against the argon flow was found to be statistically similar to the quadrant strategy. It is hypothesized that spatter introduced onto the powder layer from the melt pool and particle entrainment may be worse for laser pathing which trends with the argon flow direction. Additionally, the additional energy added to the build volume helps to mitigate inter-layer cool time which reduces temperature gradients. This shows that multi-laser AM systems have an impact on part performance and potentially shows lattices built with multi-laser AM systems may have certain advantages over single-laser AM systems.

Three-dimensional domain identification in a single hexagonal manganite nanocrystal.

The three-dimensional domain structure of ferroelectric materials significantly influences their properties. The ferroelectric domain structure of improper multiferroics, such as YMnO3, is driven by a non-ferroelectric order parameter, leading to unique hexagonal vortex patterns and topologically protected domain walls. Characterizing the three-dimensional structure of these domains and domain walls has been elusive, however, due to a lack of suitable imaging techniques. Here, we present a multi-peak Bragg coherent x-ray diffraction imaging determination of the domain structure in single YMnO3 nanocrystals. We resolve two ferroelectric domains separated by a domain wall and confirm that the primary atomic displacements occur along the crystallographic c-axis. Correlation with atomistic simulations confirms the Mexican hat symmetry model of domain formation, identifying two domains with opposite ferroelectric polarization and adjacent trimerization, manifesting in a clockwise arrangement around the hat's brim.

Build parameter influence on strut thickness and mechanical performance in additively manufactured titanium lattice structures.

Additively manufactured lattices have been adopted in applications ranging from medical implants to aerospace components. For solid AM components, the effect of build parameters has been well studied but comparably little attention has been paid to the influence of build parameters on lattice performance. For this project, the main aim was to evaluate static compressive mechanical performance of regular and stochastic lattices as a function of build parameters. The second aim was to compare strut dimensions of the metal lattice structures as build parameters were changed. Both regular and stochastic lattices were fabricated with a designed strut diameter of either 200 µm or 300 µm on a laser powder bed fusion machine. A range of laser power (140-180 W), scan speed (1700-2100 mm/s), and laser offset (0-45 µm) were used in fabricating each lattice. Compression tests were performed following the ISO 13314 (2011) standard to measure modulus, yield strength, and ultimate compressive strength values. Laser power adjustments produced the most significant effect on lattice performance. A change of 50 W resulted in roughly a 2X increase in maximum load and modulus for both regular and stochastic lattice structures. Regular lattice structures had a higher mechanical response during the mechanical evaluation. Internal strut diameters varied between build parameters as well, with laser offset adjustments producing the most noticeable change in strut geometry between lattice samples. These findings suggest that build parameter optimization, in lieu of using OEM parameters developed for solid structures, is necessary to ensure the optimum mechanical performance of AM lattice structures.

Work Patterns and Intensity of Chinese Surgical Residents- A Multicenter Time-and-Motion Study.

OBJECTIVE: This study aimed to record and analyze surgical resident trainee time allocation among junior doctors in China in order to understand the training environment and optimize realistic training and patient care objectives. DESIGN: Multicenter observational time and motion study. SETTING: Multicenter, carried out in 5 tier 3 public hospitals in 5 provinces across China. PARTICIPANTS: Surgical resident trainees at various stages of training were eligible to enter the study, total n = 44. Registered nurses were eligible to be observers, n = 4 from each hospital.  An expert team comprising 4 chief surgeons and 10 surgical residents participated in establishing the clinical activity list. RESULTS: Participants were observed during working hours (08.00-17.00) for 10 consecutive working days and time spent on different activities were recorded. Work patterns between hospitals were often dissimilar. Most time was spent on direct patient care (34.1%; 95% CI, 28.0%-40.1%) followed by indirect patient care (24.4%; 95% CI, 15.5%-33.2%), scholarly activity (21.1%; 95% CI, 13.7%-28.5%) and other (20.4%; 95% CI, 14.1%-26.8%). Subcategory analysis showed that the amount of time spent each day performing certain tasks was 137 minutes for operating theatre tasks, 103 minutes for medical record-keeping, 25 minutes for direct patient contact, 20 minutes being taught, 12 minutes teaching others, 12 minutes hand-over time, and 0 minutes of outpatient clinic attendance. Inter-observer reliability of 96.5% was obtained prior to recordings. CONCLUSIONS: Chinese surgical resident work patterns fall within the range found in other international studies albeit with some exceptions. The training environment appears broadly suitable for competence-based surgical training in China. Inadequate outpatient activity has led to changes in trainee work rosters and trainer requirements. Both strengths and deficiencies were confirmed and addressed. Further audit is required.

Changes in Lipid biomarker related to trauma severity in intertrochanteric fracture patients.

This study aimed to identify whether there are elevations or declines in specific plasma lipids in intertrochanteric fracture (ITF) patients which might serve as potential biomarkers for assessing the severity of trauma, or therapeutic targets for controlling post-traumatic responses. Ten metal work removal patients were enrolled. Their preoperative blood samples served as the control group (C group). Their 24-hour postoperative blood samples served as the moderate trauma group (M group). The ITF group was composed of 12 intertrochanteric fracture patients. A total of 707 lipid species were identified from 32 plasma samples (10 controls, 10 moderate trauma and 12 ITF samples). We first identified 31 lipids that were elevated and 6 lipids that were decreased in the more severe trauma group in aged patients, with an especially strong relationship among 14 lipids that are candidates as markers for trauma severity evaluation. Fourteen lipids were identified as potential markers of bone trauma. The definition of important lipids in trauma may not only provide guidance for the formulation of optimum ITF operation time, but may also have importance in other traumatic models, and in further understanding the components of the systemic inflammatory response for new drug targets.

Influence of topology optimization parameters on the mechanical response of an additively manufactured test structure.

Topology Optimization (TO) determines a material distribution within a domain under given conditions and design constraints, and generally generates complex geometries as a result. Complementary to TO, Additive Manufacturing (AM) offers the ability to fabricate complex geometries which may be difficult to manufacture using traditional techniques such as milling. AM has been used in multiple industries including the medical devices area. Hence, TO may be used to create patient-matched devices where the mechanical response is catered to a particular patient. However, during a medical device regulatory 510(k) pathway, demonstrating that worst-cases are known and tested is critical to the review process. Using TO and AM to predict worst-case designs for subsequent performance testing may be challenging and does not appear to have been thoroughly explored. Investigating the effects of TO input parameters when AM is employed may be the first step in determining the feasibility of predicting these worst-cases. In this paper, the effect of selected TO parameters on the resulting mechanical response and geometries of an AM pipe flange structure are investigated. Four different input parameters were chosen in the TO formulation: (1) penalty factor, (2) volume fraction, (3) element size, and (4) density threshold. Topology optimized designs were fabricated using PA2200 polyamide and the mechanical responses (reaction force, stress, and strain) were observed through experiments (universal testing machine and 3D Digital Image Correlation) and in silico environments (finite element analysis). In addition, 3D scanning and mass measurement were performed to inspect the geometric fidelity of the AM structures. A sensitivity analysis is performed to examine the effect of each TO parameters. The sensitivity analysis revealed mechanical responses can have non-monotonic and non-linear relationships between each tested parameter.

Benchtop assessment of sealing efficacy and breathability of additively manufactured (AM) face masks.

The onset of the 2019 novel coronavirus disease (COVID-19) led to a shortage of personal protective equipment (PPE), medical devices, and other medical supplies causing many stakeholders and the general public alike to turn to additive manufacturing (AM) as a stopgap when normally accessible devices were not available. However, without a method to test these AM constructs, there continued to be a disconnect between AM suppliers and the community's needs. The objective of this study was to characterize the pressure drop and leakage of four different publicly available AM face mask models with two filter material combinations, as well as to investigate the impact of frame modification techniques including the use of foam strips and hot-water face forming to improve fit when the masks are donned on manikin head forms. AM face mask frame designs were downloaded from public repositories during the early stages of the COVID-19 pandemic. AM face masks were fabricated and tested on manikin head forms within a custom chamber containing dry aerosolized NaCl. Pressure drops, particle penetration, and leakage were evaluated for various flow rates and NaCl concentrations. Results indicated that filter material combination and frame modification played a major role in the overall performance of the AM face masks studied. Filter material combinations showed improved performance when high filtration fabric was used, and the cross-sectional area of the fabric was increased. AM frame modifications appeared to improve AM face mask leakage performance by as much as 69.6%.

In Silico Fit Evaluation of Additively Manufactured Face Coverings.

In response to the respiratory protection device shortage during the COVID-19 pandemic, the additive manufacturing (AM) community designed and disseminated numerous AM face masks. Questions regarding the effectiveness of AM masks arose because these masks were often designed with limited (if any) functional performance evaluation. In this study, we present a fit evaluation methodology in which AM face masks are virtually donned on a standard digital headform using finite element-based numerical simulations. We then extract contour plots to visualize the contact patches and gaps and quantify the leakage surface area for each mask frame. We also use the methodology to evaluate the effects of adding a foam gasket and variable face mask sizing, and finally propose a series of best practices. Herein, the methodology is focused only on characterizing the fit of AM mask frames and does not considering filter material or overall performance. We found that AM face masks may provide a sufficiently good fit if the sizing is appropriate and if a sealing gasket material is present to fill the gaps between the mask and face. Without these precautions, the rigid nature of AM materials combined with the wide variation in facial morphology likely results in large gaps and insufficient adaptability to varying user conditions which may render the AM face masks ineffective.

Modifying NIOSH's Manikin Fit Evaluation Method to Match Fit Testing with Human Subjects.

A manikin fit test method developed by the Center for Disease Control and Prevention's (CDC) National Institute of Occupational Safety and Health (NIOSH) has been proposed as an alternative to fit testing with human subjects. The advantages of a manikin fit test method over actual fit testing are that it does not require human subjects which can be resource intensive, and hence easier to implement. At the beginning of coronavirus 2019 (COVID-19) pandemic, although early studies showed that manikin fit can be maintained after several decontamination cycles, real world evidence obtained using human subjects revealed that the N95 respirators failed only after a few decontamination cycles. The goal of this article was to make modifications to the NIOSH's manikin fit-test method so it can mimic real world performance of N95 respirators better. After making modifications to this method, we then investigated the effect of long-term wear after donning of the respirators, repeated donning and doffing, as well as decontamination methods (i.e. autoclaving and microwave generated steam) on the fit factor. Averaging the overall manikin fit factor across all scenarios, our modified method overpredicted overall fit factor by only 7 % and 14 % compared to adult human subjects using a breathing routine that included simulated heavy breathing rates of 85, and 70 Liters/minute, respectively. In addition, a constant flow produced similar results as cyclic flow using a breathing simulator. The modified test method also offered the following additional insights into reuse of respirators during future pandemics - when reused within a single work shift, more than 5 donnings should be avoided; and microwave generated steam may be a more viable option for decontaminating N95 respirators compared to autoclaving for a single decontamination cycle.

The wellbeing pandemic: Outline of a contested terrain and a proposed research agenda.

Wellbeing has emerged as a central, if not defining, feature of contemporary social life. Yet, despite its global significance spanning the political, social and economic spectrum, there is a remarkable lack of agreement regarding the conceptualization, definition or operationalisation of wellbeing nor any clear evidence of its success as an instrument of policy. This essay explores the contested terrain of wellbeing by examining the concept in relation to emerging politics, complexities and contradictions. More specifically, the essay: (1) briefly describes the historical origins and development of wellbeing; (2) discusses how it has been reconceptualised within the context of neoliberalism; and, (3) outlines a research agenda offering three ways to investigate wellbeing including: (a) as a wicked problem; (b) as part of the process of "wellbeing washing" within state and other institutional structures and policies; and, (c) in relation to alternative futures, which might encourage us to reimagine or jettison the term altogether.

Chinese cross-culturally adapted patient-reported outcome measures (PROMs) for knee disorders: a systematic review and assessment using the Evaluating the Measurement of Patient-Reported Outcomes (EMPRO) instrument.

BACKGROUND: Knee patient-reported outcome measures (PROMs) are widely used in research in China, but there is limited evidence on the quality of cross-culturally adapted and original Chinese PROMs. We investigated Chinese language knee PROMs to provide evidence for clinicians on their quality and to guide PROM choices. METHOD: A systematic literature search of databases: PUBMED, CINAHL, EMBASE, and CNKI, using adequate search strings and a three-step screen process identified relevant studies. An independent standardized assessment of the selected studies based on the Evaluating the Measurement of Patient-Reported Outcomes (EMPRO) tool was performed. Inter-rater reliability was assessed using intraclass coefficients (ICC). RESULTS: Thirty-three articles corresponding to 23 knee PROMs were evaluated with EMPRO global scores (100) ranging from 11.11 to 55.42. The attributes 'reliability,' 'validity,' and 'cultural and language adaptation' were significantly better evaluated compared to the attributes 'responsiveness,' 'interpretability,' and 'burden' (for all comparisons p < 0.0001). Moderate-to-excellent inter-rater agreement was observed with ICC values ranging from 0.538 to 0.934. CONCLUSION: We identified six PROMs with a minimum acceptable threshold (> 50/100). The osteoarthritis of knee and hip quality of life, the lower extremity function scale, and the Western Ontario Meniscal Evaluation tool ranked highest. Nevertheless, no single PROM had evidence encompassing all EMPRO attributes, necessitating further studies, especially on responsiveness, interpretability, and burden. We identified duplication of effort as shown by repeated translations of the same PROM; this inefficiency could be ameliorated by rapid approval of Chinese language PROMs documented on original PROM developers' platforms.

An anatomical feasibility study using CTA reconstruction for modified percutaneous lumbar vertebroplasty.

BACKGROUND: Lumbar vertebroplasty via several different types of extrapedicular approach has been reported with acceptable clinical results yet the anatomical basis for its safety is not fully explored. Injury to the lumbar arteries (LAs) is one of the most important potential complications. However, anatomical research on the course and variability of this structure is lacking. To investigate the anatomical feasibility of percutaneous vertebroplasty for lumbar osteoporotic vertebral compression fractures via a unilateral Extrapedicular approach. METHODS: A total of 300 LAs of 30 patients with non-spinal disorders were retrospectively analyzed by computed tomographic angiography (CTA). The lateral aspect of the vertebral body was divided into 9 zones of approximately equal area. The anatomy and orientation of LAs were analyzed in detail. RESULTS: LAs were most commonly found in the middle third of the body (zones 4, 5, and 6); the upper 1/3 of the vertebral body had LAs distributed only anteriorly and laterally (zones 1 and 2). No arteries were observed in the postero-superior segment (zone 3). From L1 to L3 an arched pattern predominated. At L4 an inferior oblique pattern (antero-superior to postero-inferior) predominated. Limited CTA visualization at L4 and particularly L5 as well as greater anatomical variation means that there is more uncertainty at these levels. CONCLUSION: From L1 to L3, the posterior superior segment (zone 1) of the vertebral body appears to be a safe area with low risk of arterial injury. This has relevance for design of a safe lumbar vertebral extrapedicular approach.

Dimensional variability characterization of additively manufactured lattice coupons.

BACKGROUND: Additive manufacturing (AM), commonly called 3D Printing (3DP), for medical devices is growing in popularity due to the technology's ability to create complex geometries and patient-matched products. However, due to the process variabilities which can exist between 3DP systems, manufacturer workflows, and digital conversions, there may be variabilities among 3DP parts or between design files and final manufactured products. The overall goal of this project is to determine the dimensional variability of commercially obtained 3DP titanium lattice-containing test coupons and compare it to the original design files. METHODS: This manuscript outlines the procedure used to measure dimensional variability of 3D Printed lattice coupons and analyze the differences in external dimensions and pore area when using laser and electron beam fabricated samples. The key dimensions measured were the bulk length, width, and depth using calipers. Strut thickness and pore area were assessed for the lattice components using optical imaging and µCT. RESULTS: Results show a difference in dimensional measurement between printed parts and the computer-designed files for all groups analyzed including the internal lattice dimensions. Measurements of laser manufactured coupons varied from the nominal by less than 0.2 mm and results show averages greater than the nominal value for length, width, and depth dimensions. Measurements of Electron Beam Melting coupons varied between 0.4 mm-0.7 mm from the nominal value and showed average lengths below the nominal dimension while the width and depths were greater than the nominal values. The length dimensions of Laser Powder Bed Fusion samples appeared to be impacted by hot isostatic press more than the width and depth dimension. When lattice relative density was varied, there appeared to be little impact on the external dimensional variability for the as-printed state. CONCLUSIONS: Based on these results, we can conclude that there are relevant variations between designed files and printed parts. However, we cannot currently state if these results are clinically relevant and further testing needs to be conducted to apply these results to real-world situations.

Cryo-cooled silicon crystal monochromators: a study of power load, temperature and deformation.

Crystal monochromators are often the primary optics in hard X-ray synchrotron beamlines. Management of power load is central to their design. Strict requirements on stability and deformation are to be met, as new-generation synchrotron sources deliver brighter beams of X-rays. This article sets out to illustrate an overall picture of the deformation caused by heat load in a cryo-cooled Si crystal monochromator using first principles. A theoretical model has been developed to predict the temperature distribution and surface deformation by applying intrinsic properties of Si material and the cooling system parameters. The model explains the universal behaviour of crystal slope error versus absorbed power; it has been benchmarked against experimental data and used to interpret finite-element analysis of cryogenically cooled crystals.

Nylon lattice design parameter effects on additively manufactured structural performance.

Lattice structures are used in a multitude of applications from medical to aerospace, and their adoption in these applications has been further enabled by additive manufacturing. Lattice performance is governed by a multitude of variables and estimating this performance may be needed during various phases of the design and validation process. Numerical modeling and constitutive relationships are common methodologies to assess performance, address risks, lower costs, and accelerate time to market for innovative and potentially life altering products. These methods are usually accompanied by engineering rationales to justify the methods appropriateness. However, engineering analyses and numerical models should be validated using experimental data when possible to quantify the accuracy of their predictions under conditions relevant to their planned use. In this work, a set of lattice design parameters are evaluated using numerical modeling and experimental methods under quasi-static tensile, compressive, and shear modalities. Regular body centered cubic (BCC) and stochastic Voronoi Tessellation Method (VTM) lattices are constructed with three different cell lengths (2.5 mm, 4.0 mm, 5.0 mm) and various strut diameter thicknesses (ranging from 0.536 mm-1.3506 mm) while maintaining the lattice's relative density (0.2 and 0.3). Some strut diameters were selected to challenge the AM process limits. Specimens were fabricated in nylon 12 on a laser powder bed fusion system. Optical microscopy showed up to a 28.6% difference between as-designed and fabricated strut diameters. Simulated reaction loads revealed up to a 4.6% difference in BCC lattices within a constant relative density at a 1.4 mm displacement boundary condition while the VTM samples had up to a 19.5% difference. Errors between the experimental and simulated lattice reaction loads were as high as 97.0%. This error magnitude appears to strongly correlate with lattice strut diameter. These results showcase that a computational estimation, even one with reasonable assumptions, may erroneously characterize the performance of these lattice structures, and that these assumptions should be challenged by experimentally evaluating and validating critical quantities of interest.

Critical Appraisal of Paralyzed Veterans of America Guidelines in Spinal Cord Injury: An International Collaborative Study Using the Appraisal of Guidelines for Research and Evaluation II Instrument (AGREE II).

INTRODUCTION: Spinal cord injuries (SCI) in military personnel, veterans, and others require an evidence-based, multidisciplinary approach to their care. This appraisal used the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument to evaluate the methodological quality of clinical guidelines for the management of SCI published by the Paralyzed Veterans of America (PVA) organization. MATERIALS AND METHODS: We searched clinical guidelines on SCI published by PVA until December 2019. Four appraisers across three international centers independently evaluated the quality of eligible clinical guidelines using AGREE II. Mean AGREE II scores for each domain were calculated. In higher quality domains, scores for individual items were analyzed. RESULTS: A total of 12 guidelines published by PVA on SCI were assessed. Mean scores for all six domains were as follows: Scope and Purpose (78.8%), Stakeholder Involvement (63.7%), Rigor of Development (68.4%), Clarity of Presentation (80.1%), Applicability (53.0%), and Editorial Independence (28.5%). The mean score for the overall quality of all PVA guidelines was 71.9% (95% CI: 69.7-74.1). No guideline was assessed as "not recommended" by any appraiser. Overall quality was significantly associated with year of publication (rs = 0.754, P = 0.0046). Overall agreement among appraisers was excellent (intraclass correlation coefficients for each guideline ranged from 0.96 to 0.99). CONCLUSIONS: PVA guidelines for the management of SCI demonstrated acceptable or good quality across most domains. We recommend the use of PVA guidelines for the assessment and treatment of SCI and related disorders. The quality of PVA guidelines for the management of SCI have improved over time.