MRI safety, imaging artefacts, and grid distortion evaluated for FFP3 respiratory masks worn throughout the COVID-19 pandemic.

AIM: To determine which filtering face piece (FFP3) respirators worn throughout the COVID-19 pandemic are safe for magnetic resonance imaging (MRI). MATERIALS AND METHODS: Three clinical MRI sequences were performed to assess imaging artefacts, grid distortion, and local heating for eight commercially available FFP3 respirators. All examinations were performed at Cardiff University Brain Research Imaging Centre using a 3 T Siemens Magnetom Prisma with a 64-channel head and neck coil. Each FFP3 mask was positioned on a custom-developed three-dimensional (3D) head phantom for testing. RESULTS: Five of the eight FFP3 masks contained ferromagnetic components and were regarded as "MRI unsafe". One mask was considered "MRI conditional" and only two masks were deemed "MRI safe" for both MRI staff and patients. Temperature strips positioned at the nasal bridge of the phantom did not exhibit local heating. A maximum grid distortion of 5 mm was seen in the anterior portion of the head of the ferromagnetic FFP3 masks. CONCLUSION: This study has demonstrated the importance of assessing respiratory FFP3 masks for use in and around MRI machines. Future research involving FFP3 masks can be conducted safely by following the procedures laid out in this study.

A comparison of floor surfaces for injury prevention in care settings: impact forces and horizontal pulling force required to move wheeled equipment.

Shock-absorbing flooring is one potential solution to prevent fall-related injuries. No standards exist to characterize shock-absorbing healthcare flooring. This study explores two mechanical tests for impact force reduction and horizontal force required to move wheeled objects. An appropriately designed rubber underlay can reduce peak impact by 25% compared with 1% with standard vinyl. INTRODUCTION: Severe falls often occur in hospitals and care homes. Shock-absorbing flooring is one potential solution to prevent fall-related injuries; however, no standards exist for characterizing flooring as an injury prevention measure. Shock-absorbing flooring use in high-risk settings may influence both patients (injury-saving potential) and staff (manoeuvring equipment). We aimed to explore two tests to characterize floors, to determine shock absorbency and horizontal pulling force required to move wheeled objects. METHODS: Mechanical testing was performed according to the Canadian Standards Association Z325 Hip Protectors document. This test was developed for hip protectors but is applicable to compliant surfaces that form part of the floor. Tests were performed on commercially available floor materials (suitable for care settings) to assess the force required to initiate movement of a wheeled object across the floor. We explored the relationships between horizontal force required to pull wheeled objects, impact force, floor thickness, and core material. RESULTS: Considerable differences were identified between floor samples in their ability to reduce the peak impact force (range 0.7-25%). A peak force reduction of up to 25% can be achieved with a specially designed rubber underlay. Horizontal pulling force increased with floor thickness but was lower for rubber floors. There was no direct relationship between impact attenuation and horizontal pulling force. Whilst thickness and core material explain some variations (66.5% for wheel movement; 82.3% for impact), other unmeasured factors clearly influence floor performance. CONCLUSIONS: These results can inform the development of flooring and the establishment of standards needed to underpin practice, research, and development in this field.

Biomechanical testing of hip protectors following the Canadian Standards Association express document.

A variety of hip protectors are available, but it is not clear which is the most effective and there is no standard test to evaluate their performance. This is the first study that uses a standard mechanical test on hip protectors. Some protectors perform well but others are almost ineffective, providing little to no protection to the wearer during a fall. INTRODUCTION: Each year, over 70,000 patients are admitted to hospital in the UK with hip fractures. There are a variety of commercial hip protectors currently available. However, it is not explicitly clear which is the most effective with regard to maximum force attenuation, whilst still being both comfortable for the user and providing reasonable force reduction if misplaced from the intended position. The numerous test methods reported in the literature have given conflicting results, making objective comparison difficult for users, researchers, and manufacturers alike. The Canadian Standards Association (CSA) has therefore published an express document (EXP-08-17) with a draft standard test method. This paper presents initial results for a range of hip protectors. METHODS: Eighteen commercially available hip protectors were tested according to EXP-08-17. Each hip protector was impacted five times in correct anatomical alignment over the greater trochanter and once at 50 mm displacements in the anterior, posterior, and lateral directions. RESULTS: Considerable differences were identified between individual hip protectors in their ability to reduce impact forces on the femur (between 3% and 36% reduction in peak force). The performance was reduced when misplaced in many cases (maximum reduction only 20%). CONCLUSIONS: This is the first study that uses a standard mechanical test on hip protectors. Previous studies have used a variety of methods, making it difficult to interpret results. We hope that these results using a standard test method will facilitate the effective comparison of results, as well as providing useful data for clinicians, users, and purchasers.

APOE e4 polymorphism in young adults is associated with improved attention and indexed by distinct neural signatures.

The APOE e4 allele, which confers an increased risk of developing dementia in older adulthood, has been associated with enhanced cognitive performance in younger adults. An objective of the current study was to compare task-related behavioural and neural signatures for e4 carriers (e4+) and non-e4 carriers (e4-) to help elucidate potential mechanisms behind such cognitive differences. On two measures of attention, we recorded clear behavioural advantages in young adult e4+ relative to e4-, suggesting that e4+ performed these tasks with a wider field of attention. Behavioural advantages were associated with increased task-related brain activations detected by fMRI (BOLD). In addition, behavioural measures correlated with structural measures derived from a former DTI analysis of white matter integrity in our cohort. These data provide clear support for an antagonistic pleiotropy hypothesis--that the e4 allele confers some cognitive advantage in early life despite adverse consequences in old age. The data implicate differences in both structural and functional signatures as complementary mediators of the behavioural advantage.

Rapid, non-invasive, in vivo measurement of tissue mechanical properties using gravitational loading and a nonlinear virtual fields method.

Measuring the mechanical properties of soft tissues in vivo is important in biomechanics and for diagnosis and staging of diseases, but challenging because it is difficult to control the boundary conditions. We present a novel, non-invasive method for measuring tissue properties using gravitational loading. MRI images of an organ in different positions are registered to measure tissue displacements due to gravitational forces in different positions. Considering equilibrium between stresses and gravity, we established a nonlinear virtual fields method to identify the tissue properties. The method was applied to the human brain as a proof of concept, using an Ogden model. Sensitivity analysis showed that the bulk modulus could be identified accurately while the shear modulus was identified with greater uncertainty; the strains were too small to identify the strain stiffening exponent. The measured properties agreed well with published in vitro data. The technique offers very promising perspectives, allowing the non-invasive measurement of otherwise inaccessible tissues and providing new information such as the bulk modulus under static loading, which has never previously been measured in vivo.

Review of decontamination protocols for shared non-critical objects in 35 policies of UK NHS acute care organizations.

BACKGROUND: Decontamination of non-critical objects shared by patients is key in reducing hospital-acquired infections (HAIs), but it is a complex process that needs precise guidance from UK National Health Service (NHS) acute care organizations (ACOs). AIM: To review the indications given by NHS ACOs' policies regarding the decontamination of shared non-critical devices. METHODS: Detailed lists of decontamination protocols for shared non-critical objects were retrieved from cleaning, disinfection and decontamination policies of 35 NHS ACOs. Three parameters were considered for each object: decontamination method, decontamination frequency, and person responsible for decontamination. FINDINGS: In total, 1279 decontamination protocols regarding 283 different shared non-critical objects were retrieved. Of these, 689 (54%) did not indicate the person responsible for decontamination, and only 425 (33%) were complete, giving indications for all three parameters analysed. Only 2.5% (32/1279) of decontamination protocols were complete and identical in two policies. In policies where cleaning represented the major decontamination method, chemical disinfection was rarely mentioned and vice versa. General agreement among policies was found for four main decontamination methods (detergent and water, detergent wipes, disinfectant wipes, and use of disposable items), two decontamination frequencies (between events and daily) and two responsible person designations (nurses and domestic staff). CONCLUSIONS: Decontamination protocol policies for shared non-critical objects had some similarities but did not concur on how each individual object should be decontaminated. The lack of clear indications regarding the person responsible for the decontamination process put at risk the ability of policies to serve as guidance.

Evening preference correlates with regional brain volumes in the anterior occipital lobe.

Chronotype or diurnal preference is a questionnaire-based measure influenced both by circadian period and by the sleep homeostat. In order to further characterize the biological determinants of these measures, we used a hypothesis-free approach to investigate the association between the score of the morningness-eveningness questionnaire (MEQ) and the Munich chronotype questionnaire (MCTQ), as continuous variables, and volumetric measures of brain regions acquired by magnetic resonance imaging (MRI). Data were collected from the Baependi Heart Study cohort, based in a rural town in South-Eastern Brazil. MEQ and anatomical 1.5-T MRI scan data were available from 410 individuals, and MCTQ scores were available from a subset of 198 of them. The average MEQ (62.2 ± 10.6) and MCTQ (average MSFsc 201 ± 85 min) scores were suggestive of a previously reported strong general tendency toward morningness in this community. Setting the significance threshold at P > .002 to account for multiple comparisons, we observed a significant association between lower MEQ score (eveningness) and greater volume of the left anterior occipital sulcus (ß = -0.163, p = .001) of the occipital lobe. No significant associations were observed for MCTQ. This may reflect the smaller dataset for MCTQ, and/or the fact that MEQ, which asks questions about preferred timings, is more trait-like than the MCTQ, which asks questions about actual timings. The association between MEQ and a brain region dedicated to visual information processing is suggestive of the increasingly recognized fluidity in the interaction between visual and nonvisual photoreception and the circadian system, and the possibility that chronotype includes an element of masking.

Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.

BACKGROUND: In the wake of the SARS-CoV-2 pandemic and unprecedented global demand, clinicians are struggling to source adequate access to personal protective equipment. Respirators can be in short supply, though are necessary to protect workers from SARS-CoV-2 exposure. Rapid decontamination and reuse of respirators may provide relief for the strained procurement situation. METHOD: In this study, we investigated the suitability of 70°C dry heat and microwave-generated steam (MGS) for reprocessing of FFP2/N95-type respirators, and Type-II surgical face masks. Staphylococcus aureus was used as a surrogate as it is less susceptible than enveloped viruses to chemical and physical processes. RESULTS: We observed >4 log10 reductions in the viability of dry S. aureus treated by dry heat for 90 min at 70°C and >6 log10 reductions by MGS for 90 s. After 3 reprocessing cycles, neither process was found to negatively impact the bacterial or NaCl filtration efficiency of the respirators that were tested. However, MGS was incompatible with Type-II surgical masks tested, as we confirmed that bacterial filtration capacity was completely lost following reprocessing. MGS was observed to be incompatible with some respirator types due to arcing observed around some types of metal nose clips and by loss of adhesion of clips to the mask. CONCLUSION: Considering the advantages and disadvantages of each approach, we propose a reprocessing personal protective equipment/face mask workflow for use in medical areas.

Hip protectors: recommendations for biomechanical testing--an international consensus statement (part I).

INTRODUCTION: Hip protectors represent a promising strategy for preventing fall-related hip fractures. However, clinical trials have yielded conflicting results due, in part, to lack of agreement on techniques for measuring and optimizing the biomechanical performance of hip protectors as a prerequisite to clinical trials. METHODS: In November 2007, the International Hip Protector Research Group met in Copenhagen to address barriers to the clinical effectiveness of hip protectors. This paper represents an evidence-based consensus statement from the group on recommended methods for evaluating the biomechanical performance of hip protectors. RESULTS AND CONCLUSIONS: The primary outcome of testing should be the percent reduction (compared with the unpadded condition) in peak value of the axial compressive force applied to the femoral neck during a simulated fall on the greater trochanter. To provide reasonable results, the test system should accurately simulate the pelvic anatomy, and the impact velocity (3.4 m/s), pelvic stiffness (acceptable range: 39-55 kN/m), and effective mass of the body (acceptable range: 22-33 kg) during impact. Given the current lack of clear evidence regarding the clinical efficacy of specific hip protectors, the primary value of biomechanical testing at present is to compare the protective value of different products, as opposed to rejecting or accepting specific devices for market use.

Cyclopentyl ketones: identification and function in Azteca ants.

The anal gland secretions of dolichoderine ants in the genus Azteca are fortified with cyclopentyl ketones. Since these compounds, 2-methylcyclopentanone, cis-1-acetyl-2-methylcyclopentane, and 2-acetyl-3-methylcyclopentene, release sustained alarm behavior in ant workers, they constitute a new chemical class of insect pheromones. The ketones probably also function as defensive compounds and thus are part of the ants' alarm-defense system.

On the implementation of a wrinkling, hyperelastic membrane model for skin and other materials.

A number of researchers have studied the mechanical properties of skin and developed constitutive models to describe its behaviour. Typically, many of these studies have concentrated on the uniaxial tensile behaviour of the skin, on the grounds that it will wrinkle under in-plane compression and have minimal stiffness. However, although there is a substantial body of literature on wrinkling models, the practical implementation of such a model of skin in a finite element setting has not been widely addressed. This paper presents computational details of a wrinkling, hyperelastic membrane model and aspects of its implementation and areas requiring further research are discussed. The model is based on an Ogden constitutive model, which provides accurate results at moderate strains, but it would be straightforward to implement other constitutive models such as the Fung or Arruda-Boyce models using a similar approach. Example results are presented which demonstrate that the model can provide a good approximation to experimental data. The model has many other possible applications, both for biological materials and for other thin hyperelastic membranes.

Comparing different data collection and analysis techniques for quantifying healthy knee joint function during stair ascent and descent.

There is currently no standard data collection or analysis method for the assessment of stair gait using motion analysis. This makes the comparison of results from different studies difficult. It is important to gain an appreciation of the discrepancies in kinematic and kinetic information generated by employing different computational approaches, as these differences may be critical in cases where methodologies were to change over a long-term study. This study explores the effect of using different methodologies for the assessment of non-pathological knee function of ten subjects during stair ascent and descent. Two methods of computing knee kinematics were compared: (a) using in-house software and a pointer method of anatomical calibration and (b) using commercial software, Visual3D (C-motion, Inc.) and skin-mounted markers. Significant differences were found between the two methods when calculating a frontal plane range of motion (p < 0.05). Three methods of computing knee moments were compared. Knee moments computed using the inverse dynamic analysis (IDA) approach of Visual3D (C-motion, Inc.) were significantly different (p < 0.05) to those calculated using in-house IDA software that ignores the foot and ankle and to those computed using a vector cross-product approach. This study highlights the implications of comparing data generated from different collection and analysis methods.

Dynamic tracking of the scapula using skin-mounted markers.

The shoulder complex is prone to numerous pathologies and instabilities due to its large range of motion. The extent of injury is assessed through a series of observations and physical examinations. It is hypothesized that objective kinematic analysis of the shoulder could yield useful functional insights to aid clinical practice. Non-invasive motion analysis techniques to monitor shoulder function have been developed using passive markers; however, accurate measurement of scapula kinematics is problematic because of overlying tissue. The scapula locator is the accepted standard by which alternative non-invasive techniques of scapula tracking are validated. In this study, the viability of using skin-mounted markers to measure dynamic scapula movement is determined. Complete kinematic descriptions of ten healthy shoulders were obtained. Elevations of the glenohumeral joint were similar with both techniques, indicating that the skin marker method is suitable for gathering functional glenohumeral data. The main differences of note are seen at the scapulothoracic articulation where the skin marker method underestimated lateral rotation by more than 50 degrees at maximum elevation. However, the correlation between the two approaches is greater than 0.7, suggesting that it may be possible to derive linear regression models to predict dynamic scapulothoracic lateral rotation accurately using skin-mounted scapula markers.

Medical engineering at Cardiff University. Part 1: Undergraduate programmes of study.

Cardiff University has offered a medical engineering undergraduate programme since 2001 and hence delivers one of the longest-running and most established medical engineering programmes within the UK. It currently offers BEng (Hons) and MEng (Hons) programmes that are both accredited by the Institution of Mechanical Engineers and include the option to undertake a year in industrial employment. The admissions policy ensures that the intake consists of a diverse range of students and is typically very successful in attracting female students. The programmes consist of six key academic threads which ensure that the content is both relevant and continuous, with all threads tailored to provide a patient-focused learning environment. Students initially learn core and fundamental principles in years 1 and 2, supported by a range of laboratories and practical experimentation. The latter years then encourage the students to corroborate and apply this knowledge, including involvement in a range of project-based learning exercises. The programme is delivered by a core of experienced academic medical engineers, with support from other engineering colleagues, as well as colleagues from the School of Biosciences, the School of Medicine, and the National Health Service. Thus, the programme delivers a wide range of modules which guarantee that graduating students have a thorough understanding of all possible career options. These two factors are significant in making it possible for students to follow their chosen career path upon graduation.

Medical engineering at Cardiff University. Part 2: Postgraduate programmes of study.

The Medical Engineering team within the School of Engineering, Cardiff University, delivers two postgraduate programmes of study. Established over 10 years ago, the part-time MSc programmes in Orthopaedic Engineering and Clinical Engineering offer the opportunity of further study while remaining within full-time employment. Both programmes deliver 120 taught credits over two academic years via a series of residential weekends, with successful completion enabling the student to undertake and then defend a 60-credit research dissertation. Fulfilling a specific role on the career pathway for both student cohorts, the strength of each programme is indicated by the consistent number of applicants.

Metabolic syndrome alters relationships between cardiometabolic variables, cognition and white matter hyperintensity load.

Cardiometabolic risk factors influence white matter hyperintensity (WMH) development: in metabolic syndrome (MetS), higher WMH load is often reported but the relationships between specific cardiometabolic variables, WMH load and cognitive performance are uncertain. We investigated these in a Brazilian sample (aged 50-85) with (N = 61) and without (N = 103) MetS. Stepwise regression models identified effects of cardiometabolic and demographic variables on WMH load (from FLAIR MRI) and verbal recall performance. WMH volume was greater in MetS, but verbal recall performance was not impaired. Age showed the strongest relationship with WMH load. Across all participants, systolic blood pressure (SBP) and fasting blood glucose were also contributors, and WMH volume was negatively associated with verbal recall performance. In non-MetS, higher HbA1c, SBP, and number of MetS components were linked to poorer recall performance while higher triglyceride levels appeared to be protective. In MetS only, these relationships were absent but education exerted a strongly protective effect on recall performance. Thus, results support MetS as a construct: the clustering of cardiometabolic variables in MetS alters their individual relationships with cognition; instead, MetS is characterised by a greater reliance on cognitive reserve mechanisms. In non-MetS, strategies to control HbA1c and SBP should be prioritised as these have the largest impact on cognition.

Metal-backed versus all-polyethylene unicompartmental knee arthroplasty: Proximal tibial strain in an experimentally validated finite element model.

OBJECTIVES: Up to 40% of unicompartmental knee arthroplasty (UKA) revisions are performed for unexplained pain which may be caused by elevated proximal tibial bone strain. This study investigates the effect of tibial component metal backing and polyethylene thickness on bone strain in a cemented fixed-bearing medial UKA using a finite element model (FEM) validated experimentally by digital image correlation (DIC) and acoustic emission (AE). MATERIALS AND METHODS: A total of ten composite tibias implanted with all-polyethylene (AP) and metal-backed (MB) tibial components were loaded to 2500 N. Cortical strain was measured using DIC and cancellous microdamage using AE. FEMs were created and validated and polyethylene thickness varied from 6 mm to 10 mm. The volume of cancellous bone exposed to < -3000 µÎµ (pathological loading) and < -7000 µÎµ (yield point) minimum principal (compressive) microstrain and > 3000 µÎµ and > 7000 µÎµ maximum principal (tensile) microstrain was computed. RESULTS: Experimental AE data and the FEM volume of cancellous bone with compressive strain < -3000 µÎµ correlated strongly: R = 0.947, R2 = 0.847, percentage error 12.5% (p < 0.001). DIC and FEM data correlated: R = 0.838, R2 = 0.702, percentage error 4.5% (p < 0.001). FEM strain patterns included MB lateral edge concentrations; AP concentrations at keel, peg and at the region of load application. Cancellous strains were higher in AP implants at all loads: 2.2- (10 mm) to 3.2-times (6 mm) the volume of cancellous bone compressively strained < -7000 µÎµ. CONCLUSION: AP tibial components display greater volumes of pathologically overstrained cancellous bone than MB implants of the same geometry. Increasing AP thickness does not overcome these pathological forces and comes at the cost of greater bone resection.Cite this article: C. E. H. Scott, M. J. Eaton, R. W. Nutton, F. A. Wade, S. L. Evans, P. Pankaj. Metal-backed versus all-polyethylene unicompartmental knee arthroplasty: Proximal tibial strain in an experimentally validated finite element model. Bone Joint Res 2017;6:22-30. DOI:10.1302/2046-3758.61.BJR-2016-0142.R1.

Effects of porosity on the fatigue performance of polymethyl methacrylate bone cement: an analytical investigation.

Porosity has been shown to affect the fatigue life of bone cements, but, although vacuum mixing is widely used to reduce porosity in the clinical setting, results have been mixed and the effects of porosity are not well understood. The aim of this study was to investigate the effects of porosity using stress analysis and fracture mechanics techniques. The stress concentrations arising at voids in test specimens were found using analytical solutions and boundary element methods. The fatigue life of specimens containing voids of various sizes was predicted using fracture mechanics techniques. For spherical voids that do not occupy a significant proportion of the cross-section, the resulting stress concentration is independent of void size and too small to account for the observed crack initiation. Cracks must therefore initiate at additional stress raisers such as radiopacifier particles or additional voids. For large voids, the stress increases as the remaining cross-section of the specimen decreases, and this may account for much of the observed reduction in fatigue strength in hand-mixed cement. Although crack initiation may be largely independent of void size, there is an effect on crack growth rate. Cracks are predicted to grow faster around larger voids, since they remain in the stress concentration around the void for longer. This effect may account for the relationship between porosity and fatigue life that has been observed in samples without large voids. Since porosity appears to affect crack growth more than initiation, it may be less damaging in high-cycle clinical fatigue, which may be predominantly initiation controlled, than in short laboratory tests.

Metallosis following implantation of magnetically controlled growing rods in the treatment of scoliosis: a case series.

AIMS: We present a case series of five patients who had revision surgery following magnetic controlled growing rods (MGCR) for early onset scoliosis. Metallosis was found during revision in four out of five patients and we postulated a mechanism for rod failure based on retrieval analysis. PATIENTS AND METHODS: Retrieval analysis was performed on the seven explanted rods. The mean duration of MCGR from implantation to revision was 35 months (17 to 46). The mean age at revision was 12 years (7 to 15; four boys, one girl). RESULTS: A total of six out of seven rods had tissue metallosis and pseudo-capsule surrounding the actuator. A total of four out of seven rods were pistoning. There were two rods which were broken. All rods had abrasive circumferential markings. A significant amount of metal debris was found when the actuators were carefully cut open. Analytical electron microscopy demonstrated metal fragments of predominantly titanium with a mean particle size of 3.36 microns (1.31 to 6.61). CONCLUSION: This study highlights concerns with tissue metallosis in MCGR. We recommend careful follow-up of patients who have received this implant. Cite this article: Bone Joint J 2016;98-B:1662-7.

Three-dimensional measurement of intervertebral kinematics in vitro using optical motion analysis.

Measurement of the stiffness of spinal motion segments is widely used for evaluating the stability of spinal implant constructs. A three-dimensional motion analysis technique has been developed that allows accurate measurement of the relative movement of the vertebral bodies about a well-defined anatomical axis system. The position of marker clusters on each vertebra is tracked using digital infrared cameras (Qualisys AB, Gothenburg). Landmarks are identified using a marked pointer, and an anatomical coordinate system is defined for each vertebra. The transformation relating the upper and lower vertebrae is calculated, using the joint coordinate system approach of Grood and Suntay to find the rotations and translations in each anatomical plane. The stiffness of vertebrectomy constructs was investigated using a Synex vertebral body replacement and an anterior rod with one or two screws in each vertebral body, with or without damage to the posterior longitudinal ligament (PLL). A moment of 2 N m was applied about each anatomical axis, and the range of motion about each axis was calculated. The range of motion in flexion-extension and lateral bending was significantly greater with only one screw. When the PLL was cut, there was no significant increase in the range of motion.