Examining the correlates of cigarette smoking, e-cigarette use and dual use among Canadian post-secondary students

Many Canadians use nicotine products such as cigarettes and e-cigarettes. A particular subpopulation of concern is post-secondary students given they have a higher prevalence of use. Many correlates of cigarette smoking and e-cigarette use have been identified. However, less focus has been on examining the correlates of cigarette smoking, e-cigarette use and dual use. This study explores the correlates of different nicotine modality use in post-secondary students. Using data from the Canadian Campus Wellbeing Survey (CCWS; n = 27,164), a multi-level nominal regression assessed the correlates of nicotine modality use. In comparison to individuals who were <20, individuals 20-24 (OR = .448, 95% CI .321, .625), 25-29 (OR = .140, 95% CI .093, .212), 30-34 (OR = .076, 95% CI .046, .125) and over 35 (OR = .041, 95% CI .024, .071) had lower odds of e-cigarette use compared to cigarette smoking. Identifying as a woman (OR = 1.553, 95% CI 1.202, 2.006), non-heterosexual (OR = .642, 95% CI = .485,0.851), current cannabis user (OR = 1.651, 95% CI 1.296, 2.104), and being an international student (OR = .350, 95% CI .251, .487) also impacted the odds of e-cigarette use vs only cigarette smoking. When considering dual use vs cigarette smoking, individuals aged 20-24 (OR = .491, 95% CI .337, .717), 25-29 (OR = .221, 95% CI .137, .357), 30-34 (OR = .163, 95% CI .091, .292) and over 35 (OR = .122, 95% CI .065, .230) had lower odds than individuals <20. Current cannabis use (OR = 1.680, 95% CI = 1.209, 2.138), binge drinking (OR = 1.885, 95% CI 1.384, 2.568), and international student status (OR = .689, 95% CI .476, .996) also impacted cigarette smoking vs dual-use. Overall, a minority of young adults (11.5%) at post-secondary institutions in our sample use nicotine products, and the higher prevalence of e-cigarette use warrants continued monitoring. Health promotion campaigns addressing e-cigarette use are required. Additionally, tailored intervention efforts could prioritize the treatment needs of international students studying in Canada.

Re-assessing the social climate of physical (in)activity in Canada

Social-ecological models suggest that a strategy for increasing population physical activity participation is to reconstruct the "social climate" through changing social norms and beliefs about physical activity (PA). In this study, we assessed whether the PA social climate in Canada has changed over a five-year period after controlling for sociodemographic factors and PA levels. Replicating a survey administered in 2018, a sample of adults in Canada (n = 2,507) completed an online survey assessing social climate dimensions, including but not limited to descriptive and injunctive norms. Descriptive statistics were calculated, and binary logistic regressions were conducted to assess the associations of sociodemographic factors and year of the survey with social climate dimensions. Results suggest some social climate constructs are trending in a positive direction between 2018 and 2023. Physical inactivity was considered a serious public health concern by 49% of respondents, second to unhealthy diets (52%). Compared to those who participated in the 2018 survey, participants in 2023 were less likely to see others walking or wheeling in their neighbourhood (OR = 1.58, 95% CI: 1.41, 1.78), but more likely to see people exercising (OR = 0.82, 95% CI: 0.73, 0.92) and kids playing in their neighbourhood (OR = 0.75, 95% CI: 0.66, 0.85). No changes were reported between 2018 and 2023 in individuals' perceptions of whether physical inactivity is due to individual versus external factors (OR = 0.99, 95% CI: 0.87, 1.13). The findings of this work indicate a modest positive shift in some measured components of the social climate surrounding PA although attributing causes for these changes remain speculative.

Lonely but not alone: Examining correlates of loneliness among Canadian post-secondary students

Objective: Loneliness is increasingly acknowledged as a public health concern due to its association with morbidity and mortality. The prevalence of loneliness is highest in the post-secondary population. Understanding the correlates of loneliness may assist in developing policy and program interventions. Participants and Methods: Post-secondary students (n = 28,975) from the Winter 2022 Canadian Campus Wellbeing Survey (CCWS) cycle. A multi-level logistic regression controlling for the institution was built to determine how demographic, health behaviors, mental health and institutional level factors are associated with loneliness. Results: The prevalence of loneliness was 31% in our sample. Demographic (e.g., gender, sexual orientation, social economic status), health behaviors (e.g., physical activity and substance use), mental health (e.g., mental distress and social support) and institutional factors (e.g., college or university institution) impacted the odds of reporting loneliness (p < 0.05). Conclusion: Our findings suggest loneliness might require greater attention by institutional staff and administrators.

Form-function relationships underlie rapid dietary changes in a lizard

Macroevolutionary changes such as variation in habitat use or diet are often associated with convergent, adaptive changes in morphology. However, it is still unclear how small-scale morphological variation at the population level can drive shifts in ecology such as observed at a macroevolutionary scale. Here, we address this question by investigating how variation in cranial form and feeding mechanics relate to rapid changes in diet in an insular lizard (Podarcis siculus) after experimental introduction into a new environment. We first quantified differences in the skull shape and jaw muscle architecture between the source and introduced population using three-dimensional geometric morphometrics and dissections. Next, we tested the impact of the observed variation in morphology on the mechanical performance of the masticatory system using computer-based biomechanical simulation techniques. Our results show that small differences in shape, combined with variation in muscle architecture, can result in significant differences in performance allowing access to novel trophic resources. The confrontation of these data with the already described macroevolutionary relationships between cranial form and function in these insular lizards provides insights into how selection can, over relatively short time scales, drive major changes in ecology through its impact on mechanical performance.

Physical activity and substance use among Canadian adolescents: Examining the moderating role of school connectedness

Physical activity may play a role in promoting or preventing substance use among youth. The purpose of this study was to examine the association between different types of physical activity [i.e., non-competitive school sport, competitive school sport, outside of school sport and minutes of moderate to vigorous physical activity (MVPA) per day] and substance use (i.e., current smoking, e-cigarette, cannabis, binge drinking) among Canadian youth. Interaction effects between physical activity and school connectedness were also examined. Using data from the COMPASS study (2018-19; n = 73,672), four multi-level logistic regression models were developed to investigate whether physical activity lessened or worsened the odds of (1) smoking; (2) e-cigarette use; (3) cannabis use; and (4) binge drinking. Models were stratified by gender to reflect the inherent differences between genders. Models were adjusted for demographic factors and other covariates. Sport participation was consistently associated with substance use, whereas less evidence was found for meeting MVPA guidelines. Non-competitive school sport lessened the odds of cannabis use for males and females. However, non-competitive school sport only lessened the odds of e-cigarette use for females but increased the odds of binge drinking for males. Participation in competitive school sport lessened the odds of cigarette smoking but increased the odds of e-cigarette use and binge drinking for males and females. Outside of school sport lessened the odds of cigarette smoking and cannabis use but increased the odds of e-cigarette use and binge drinking for males and females. A significant moderation effect was found for males participating in sport outside of school and meeting MVPA guidelines who were at a lower risk of e-cigarette use in the presence of high levels of school connectedness. Our study provides evidence for further consideration and provision of extracurricular activities, specifically non-competitive sport, in protecting against substance use. Caution is required in claiming that sport participation or physical activity, in general, is negatively associated with substance use among youth.

Strange Days: Adult Physical Activity and Mental Health in the First Two Months of the COVID-19 Pandemic

Background: In addition to its physical health benefits, physical activity is increasingly recognized as a means to support mental health. Regular moderate-to-vigorous physical activity (MVPA) is associated with improved mental well-being, reduced likelihood of developing mental illness, and improved symptom management. Despite these benefits, most people fail to achieve minimum recommended levels of MVPA. Population levels of physical activity have further declined since the onset of the COVID-19 pandemic and implementation of public health measures (e.g., shelter-in-place protocols). The potential impact of this decline on mental heath outcomes warrants ongoing investigation. Purpose: To investigate associations between changes in MVPA and mental health (depressive symptoms, anxiety symptoms, and life satisfaction) in adults impacted by the COVID-19 pandemic. Method: Research followed a cross-sectional design. English-speaking adults were invited to complete an online questionnaire. MVPA was assessed retrospectively (before COVID-19) and currently (during COVID-19) with the International Physical Activity Questionnaire. Mental health was assessed with the Patient Health Questionnaire, 9-Item (PHQ-9), the Generalized Anxiety Disorder, 7-Item (GAD-7), and the Satisfaction with Life Scale (SWLS). Regression was used to assess relationships between MVPA and mental health. ANOVA with follow-up tests examined whether participants who differed in mental health status (e.g., no symptoms vs. severe symptoms) differed in their change in MVPA. T-tests were used to examine differences in mental health symptomatology between participants who were sufficiently (i.e., achieving MVPA guidelines of ≥ 150 min/week) vs. insufficiently active. Results: Prior to COVID-19, 68.2% of participants were classified as being sufficiently active, vs. 60.6% during COVID-19. The majority of participants reported experiencing some level of depressive symptoms (62.0%) or anxiety symptoms (53.7%). After controlling for covariates, changes in MVPA accounted for significant variability in the PHQ-9 (7.7%), GAD-7 (2.5%), and SWLS (1.5 %). Participants with clinically significant mental health symptomatology reported greater declines in MVPA than those who reported no symptoms. Conversely, participants who were sufficiently active during COVID-19 reported significantly lower depression and anxiety, and higher life satisfaction. Conclusion: Participants who experienced the greatest declines in MVPA reported relatively greater psychological distress and lower life satisfaction. While preliminary, these findings suggest the importance of maintaining and promoting physical activity during a period of pandemic.

Coffee and cigarettes: Examining the association between caffeinated beverage consumption and smoking behaviour among youth in the COMPASS study

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Caffeinated beverage consumption is associated with smoking behaviours in youth.

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High energy drink consumption is most strongly associated with smoking behaviours.

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Caffeinated beverages and smoking behaviour demonstrate a dose–response association.

In adults, coffee, sugar-sweetened beverage (SSB) and high energy drink consumption have been related to increases in risky behaviour, including smoking. However, these associations are not well understood during adolescence. The purpose of this study was to examine the association between beverage consumption and smoking behaviour among Canadian adolescents. Using data from the COMPASS study (2016–2017; n = 46,957), four models were developed to investigate whether beverage consumption explained variability in smoking behaviour in adolescence (age = 15.7 ± 1.2 yrs); 1) smoking status; 2) e-cigarette use status; 3) days smoking cigarettes per month; and 4) days using an e-cigarette per month. Models were adjusted for demographic factors. Logistic (models 1 and 2) and ordinal logistic (models 3 and 4) were used for analysis. An association between the frequency of SSBs, coffee/tea or high energy drinks consumption and smoking behaviour was identified in all models. Greater beverage consumption was associated with being a current smoker (OR = 2.46 (2.02, 2.99)), former smoker, (OR = 2.50 (1.53, 4.08)), and currently using an e-cigarette (OR = 4.66 (3.40, 6.40)). Higher beverage consumption was also associated with more days smoking/using an e-cigarette per month (OR = 2.67 (1.92, 3.70) and 3.45 (2.32, 5.12), respectively). High energy drink consumption on 4 or 5 days of the school week was the best predictor of smoking behaviour in all models. Given the health consequences of smoking and e-cigarette use and their association with SSB, high energy drinks and coffee consumption, policy initiatives to prevent smoking initiation and limit access to these beverages needs ongoing attention and implementation.

Effects of Caffeine and Acute Aerobic Exercise on Working Memory and Caffeine Withdrawal

Studies show that a single bout of exercise confers cognitive benefits. However, many individuals use psychoactive substances such as caffeine to enhance cognitive performance. The effects of acute exercise in comparison to caffeine on cognition remain unknown. Furthermore, caffeine use is associated with withdrawal symptoms upon cessation. Whether acute exercise can reduce withdrawal symptoms also remains unknown. The objectives of this study were to compare the effects of acute moderate intensity aerobic exercise to caffeine on working memory (WM) and caffeine withdrawal symptoms (CWS). In Phase I, non-caffeine (n = 29) and caffeine consumers (n = 30) completed a WM assessment, followed by acute exercise and caffeine. In Phase II, caffeine consumers (n = 25) from Phase I underwent the WM assessment and reported CWS following a 12-hour deprivation period. Acute moderate intensity aerobic exercise and caffeine (1.2 mg/kg) significantly improved WM accuracy and reduced CWS comparably. WM performance was not reduced following caffeine deprivation.

A biomechanical analysis of prognathous and orthognathous insect head capsules: evidence for a many-to-one mapping of form to function

Insect head shapes are remarkably variable, but the influences of these changes on biomechanical performance are unclear. Among 'basal' winged insects, such as dragonflies, mayflies, earwigs and stoneflies, some of the most prominent anatomical changes are the general mouthpart orientation, eye size and the connection of the endoskeleton to the head. Here, we assess these variations as well as differing ridge and sclerite configurations using modern engineering methods including multibody dynamics modelling and finite element analysis in order to quantify and compare the influence of anatomical changes on strain in particular head regions and the whole head. We show that a range of peculiar structures such as the genal/subgenal, epistomal and circumocular areas are consistently highly loaded in all species, despite drastically differing morphologies in species with forward-projecting (prognathous) and downward-projecting (orthognathous) mouthparts. Sensitivity analyses show that the presence of eyes has a negligible influence on head capsule strain if a circumocular ridge is present. In contrast, the connection of the dorsal endoskeletal arms to the head capsule especially affects overall head loading in species with downward-projecting mouthparts. Analysis of the relative strains between species for each head region reveals that concerted changes in head substructures such as the subgenal area, the endoskeleton and the epistomal area lead to a consistent relative loading for the whole head capsule and vulnerable structures such as the eyes. It appears that biting-chewing loads are managed by a system of strengthening ridges on the head capsule irrespective of the general mouthpart and head orientation. Concerted changes in ridge and endoskeleton configuration might allow for more radical anatomical changes such as the general mouthpart orientation, which could be an explanation for the variability of this trait among insects. In an evolutionary context, many-to-one mapping of strain patterns onto a relatively similar overall head loading indeed could have fostered the dynamic diversification processes seen in insects.

New insights into the biomechanics of Legg-Calvé-Perthes' disease: The Role of Epiphyseal Skeletal Immaturity in Vascular Obstruction

Objectives

Legg–Calvé–Perthes’ disease (LCP) is an idiopathic osteonecrosis of the femoral head that is most common in children between four and eight years old. The factors that lead to the onset of LCP are still unclear; however, it is believed that interruption of the blood supply to the developing epiphysis is an important factor in the development of the condition.

Methods

Finite element analysis modelling of the blood supply to the juvenile epiphysis was investigated to understand under which circumstances the blood vessels supplying the femoral epiphysis could become obstructed. The identification of these conditions is likely to be important in understanding the biomechanics of LCP.

Results

The results support the hypothesis that vascular obstruction to the epiphysis may arise when there is delayed ossification and when articular cartilage has reduced stiffness under compression.

Conclusion

The findings support the theory of vascular occlusion as being important in the pathophysiology of Perthes disease.

Cite this article: M. Pinheiro, C. A. Dobson, D. Perry, M. J. Fagan. New insights into the biomechanics of Legg-Calvé-Perthes’ disease: The Role of Epiphyseal Skeletal Immaturity in Vascular Obstruction. Bone Joint Res 2018;7:148–156. DOI: 10.1302/2046-3758.72.BJR-2017-0191.R1.

Cranial sutures work collectively to distribute strain throughout the reptile skull

The skull is composed of many bones that come together at sutures. These sutures are important sites of growth, and as growth ceases some become fused while others remain patent. Their mechanical behaviour and how they interact with changing form and loadings to ensure balanced craniofacial development is still poorly understood. Early suture fusion often leads to disfiguring syndromes, thus is it imperative that we understand the function of sutures more clearly. By applying advanced engineering modelling techniques, we reveal for the first time that patent sutures generate a more widely distributed, high level of strain throughout the reptile skull. Without patent sutures, large regions of the skull are only subjected to infrequent low-level strains that could weaken the bone and result in abnormal development. Sutures are therefore not only sites of bone growth, but could also be essential for the modulation of strains necessary for normal growth and development in reptiles.

Masticatory loadings and cranial deformation in Macaca fascicularis: a finite element analysis sensitivity study

Biomechanical analyses are commonly conducted to investigate how craniofacial form relates to function, particularly in relation to dietary adaptations. However, in the absence of corresponding muscle activation patterns, incomplete muscle data recorded experimentally for different individuals during different feeding tasks are frequently substituted. This study uses finite element analysis (FEA) to examine the sensitivity of the mechanical response of a Macaca fascicularis cranium to varying muscle activation patterns predicted via multibody dynamic analysis. Relative to the effects of varying bite location, the consequences of simulated variations in muscle activation patterns and of the inclusion/exclusion of whole muscle groups were investigated. The resulting cranial deformations were compared using two approaches; strain maps and geometric morphometric analyses. The results indicate that, with bite force magnitude controlled, the variations among the mechanical responses of the cranium to bite location far outweigh those observed as a consequence of varying muscle activations. However, zygomatic deformation was an exception, with the activation levels of superficial masseter being most influential in this regard. The anterior portion of temporalis deforms the cranial vault, but the remaining muscles have less profound effects. This study for the first time systematically quantifies the sensitivity of an FEA model of a primate skull to widely varying masticatory muscle activations and finds that, with the exception of the zygomatic arch, reasonable variants of muscle loading for a second molar bite have considerably less effect on cranial deformation and the resulting strain map than does varying molar bite point. The implication is that FEA models of biting crania will generally produce acceptable estimates of deformation under load as long as muscle activations and forces are reasonably approximated. In any one FEA study, the biological significance of the error in applied muscle forces is best judged against the magnitude of the effect that is being investigated.

Intraluminal thrombus has a selective influence on matrix metalloproteinases and their inhibitors (tissue inhibitors of matrix metalloproteinases) in the wall of abdominal aortic aneurysms

BACKGROUND

The influence of intraluminal thrombus (ILT) on the proteolytic environment within the wall of an abdominal aortic aneurysm (AAA) is unknown. This is the first study to examine the correlation between ILT thickness and the levels of matrix metalloproteinases (MMPs) and their natural inhibitors (tissue inhibitors of matrix metalloproteinases [TIMPs]) within the adjacent AAA wall.

METHODS

Thirty-five patients undergoing elective repair of AAAs were studied. A single full-thickness infrarenal aortic sample was obtained uniformly from the arteriotomy site from each patient. All samples were snap frozen and analyzed for total and active MMP 2, 8, and 9 and TIMP 1 and 2. Thrombus thickness at the specimen site was measured on the preoperative contrast computed tomographic angiograms.

RESULTS

There was a statistically significant correlation between ILT thickness, concentration of TIMP 1, and active concentration of MMP 9. MMP 2 (active and total) and TIMP 2 demonstrated a positive correlation with ILT thickness, although not statistically significant.

CONCLUSION

In this novel study, we found a significant positive correlation of ILT thickness with active MMP 9 and TIMP 1 concentration in the adjacent AAA wall, and this may have implications for AAA expansion and eventual rupture.

Finite element modelling of squirrel, guinea pig and rat skulls: using geometric morphometrics to assess sensitivity

Rodents are defined by a uniquely specialized dentition and a highly complex arrangement of jaw-closing muscles. Finite element analysis (FEA) is an ideal technique to investigate the biomechanical implications of these specializations, but it is essential to understand fully the degree of influence of the different input parameters of the FE model to have confidence in the model's predictions. This study evaluates the sensitivity of FE models of rodent crania to elastic properties of the materials, loading direction, and the location and orientation of the models' constraints. Three FE models were constructed of squirrel, guinea pig and rat skulls. Each was loaded to simulate biting on the incisors, and the first and the third molars, with the angle of the incisal bite varied over a range of 45°. The Young's moduli of the bone and teeth components were varied between limits defined by findings from our own and previously published tests of material properties. Geometric morphometrics (GMM) was used to analyse the resulting skull deformations. Bone stiffness was found to have the strongest influence on the results in all three rodents, followed by bite position, and then bite angle and muscle orientation. Tooth material properties were shown to have little effect on the deformation of the skull. The effect of bite position varied between species, with the mesiodistal position of the biting tooth being most important in squirrels and guinea pigs, whereas bilateral vs. unilateral biting had the greatest influence in rats. A GMM analysis of isolated incisor deformations showed that, for all rodents, bite angle is the most important parameter, followed by elastic properties of the tooth. The results here elucidate which input parameters are most important when defining the FE models, but also provide interesting glimpses of the biomechanical differences between the three skulls, which will be fully explored in future publications.

Isolated word recognition of silent speech using magnetic implants and sensors

There are a number of situations where individuals wish to communicate verbally but are unable to use conventional means-so called 'silent speech'. These include speakers in noisy and covert situations as well as patients who have lost their voice as a result of a laryngectomy or similar procedure. This paper focuses on those who are unable to speak following a laryngectomy and assesses the possibility of speech recognition based on a magnetic implant/sensors system. Permanent magnets are placed on the tongue and lips and the changes in magnetic field resulting from movement during speech are monitored using a set of magnetic sensors. The sensor signals are compared to sets of pre-recorded templates using the dynamic time warping (DTW) method, and the best match is identified. Experimental trials are reported for subjects with intact larynx, typically using 500-1000 utterances used for speaker dependant training and testing. It is shown that recognition rates of over 90% are achievable for vocabularies of at least 57 isolated words: sufficient to drive command-and-control applications.

Validation of a Morphometric Reconstruction Technique Applied to a Juvenile Pelvis

Three-dimensional reconstructions of bone geometry from microCT (computed tomography) data are frequently used in biomechanical and finite element analyses. Digitization of bone models is usually a simple process for specimens with a complete geometry, but in instances of damage or disarticulation it can be very challenging. Subsequent to digitization, further imaging techniques are often required to estimate the geometry of missing bone or connecting cartilage. This paper presents an innovative approach to the reconstruction of incomplete scan data, to reproduce proper anatomical arrangements of bones, including absent connecting cartilaginous elements. Utilizing geometric morphometric tools, the reconstruction technique is validated through comparison of a reconstructed 9 year old pelvis, to the original CT data. A principal component analysis and an overlay of the two pelves provide a measure of the accuracy of the reconstructed model. Future work aims to investigate the biomechanical effects of any minor positional error on the bone's predicted structural properties through the use of finite element analysis.

Combined finite element and multibody dynamics analysis of biting in a Uromastyx hardwickii lizard skull

Lizard skulls vary greatly in shape and construction, and radical changes in skull form during evolution have made this an intriguing subject of research. The mechanics of feeding have surely been affected by this change in skull form, but whether this is the driving force behind the change is the underlying question that we are aiming to address in a programme of research. Here we have implemented a combined finite element analysis (FEA) and multibody dynamics analysis (MDA) to assess skull biomechanics during biting. A skull of Uromastyx hardwickii was assessed in the present study, where loading data (such as muscle force, bite force and joint reaction) for a biting cycle were obtained from an MDA and applied to load a finite element model. Fifty load steps corresponding to bilateral biting towards the front, middle and back of the dentition were implemented. Our results show the importance of performing MDA as a preliminary step to FEA, and provide an insight into the variation of stress during biting. Our findings show that higher stress occurs in regions where cranial sutures are located in functioning skulls, and as such support the hypothesis that sutures may play a pivotal role in relieving stress and producing a more uniform pattern of stress distribution across the skull. Additionally, we demonstrate how varying bite point affects stress distributions and relate stress distributions to the evolution of metakinesis in the amniote skull.

Rigid-body analysis of a lizard skull: modelling the skull of Uromastyx hardwickii

Lizard skulls vary greatly in their detailed morphology. Theoretical models and practical studies have posited a definite relationship between skull morphology and bite performance, but this can be difficult to demonstrate in vivo. Computer modelling provides an alternative approach, as long as hard and soft tissue components can be integrated and the model can be validated. An anatomically accurate three-dimensional computer model of an Uromastyx hardwickii skull was developed for rigid-body dynamic analysis. The Uromastyx jaw was first opened under motion control, and then muscle forces were applied to produce biting simulations where bite forces and joint forces were calculated. Bite forces comparable to those reported in the literature were predicted, and detailed muscular force information was produced along with additional information on the stabilizing role of temporal ligaments in late jaw closing.

Assessing mechanical function of the zygomatic region in macaques: validation and sensitivity testing of finite element models

Crucial to the interpretation of the results of any finite element analysis of a skeletal system is a test of the validity of the results and an assessment of the sensitivity of the model parameters. We have therefore developed finite element models of two crania of Macaca fascicularis and investigated their sensitivity to variations in bone material properties, the zygomatico-temporal suture and the loading regimen applied to the zygomatic arch. Maximum principal strains were validated against data derived from ex vivo strain gauge experiments using non-physiological loads applied to the macaque zygomatic arch. Elastic properties of the zygomatic arch bone and the zygomatico-temporal suture obtained by nanoindentation resulted in a high degree of congruence between experimental and simulated strains. The findings also indicated that the presence of a zygomatico-temporal suture in the model produced strains more similar to experimental values than a completely separated or fused arch. Strains were distinctly higher when the load was applied through the modelled superficial masseter compared with loading an array of nodes on the arch. This study demonstrates the importance of the accurate selection of the material properties involved in predicting strains in a finite element model. Furthermore, our findings strongly highlight the influence of the presence of craniofacial sutures on strains experienced in the face. This has implications when investigating craniofacial growth and masticatory function but should generally be taken into account in functional analyses of the craniofacial system of both extant and extinct species.

Three dimensional stereolithography models of cancellous bone structures from muCT data: testing and validation of finite element results

Stereolithography (STL) models of complex cancellous bone structures have been produced from three-dimensional micro-computed tomography data sets of human cancellous bone histological samples from four skeletal sites. The STL models have been mechanically tested and the derived stiffness compared with that predicted by finite element analysis. The results show a strong correlation (R2 = 0.941) between the predicted and calculated stiffnesses of the structures and show promise for the use of STL as an additional technique to complement the use of finite element models, for the assessment of the mechanical properties of complex cancellous bone structures.

A comparative study of aortic wall stress using finite element analysis for ruptured and non-ruptured abdominal aortic aneurysms

BACKGROUND

The decision to repair an asymptomatic abdominal aortic aneurysm (AAA) is currently based on diameter (> or =5.5 cm) alone. However, aneurysms less than 5.5 cm do rupture while some reach greater than 5.5 cm without rupturing. Hence the need to predict the risk of rupture on an individual patient basis is important. This study aims to calculate and compare wall stress in ruptured and non-ruptured AAA.

METHODS

The 3D geometries of AAA were derived from CT scans of 27 patients (12 ruptured and 15 non-ruptured). AAA geometry, systolic blood pressure and literature derived material properties, were utilised to calculate wall stress for individual AAA using finite element analysis.

RESULTS

Peak wall stress was significantly higher in the ruptured AAA (mean 1.02 MPa) than the non-ruptured AAA (mean 0.62 MPa). In patients with an identifiable site of rupture on CT scan, the area of peak wall stress correlated with rupture site.

CONCLUSIONS

Peak wall stress can be calculated from routinely performed CT scans and may be a better predictor of risk of rupture than AAA diameter on an individual patient basis.

Cutting or round-bodied needles for tendon repair

We carried out a biomechanical study comparing tensile strength after using round-bodied or cutting needles for tendon repair. Swine tendons were repaired in three groups: Group 1 core suture repair only; group 2 core and circumferential suture repair; and group 3 isolated circumferential suture repair. The tendons were tested at longitudinal stress to failure at 5mm/minute. No significant differences were found between the round-bodied and cutting needles in any group. Equal numbers in the core suture repair group failed by suture pullout when comparing cutting and round-bodied needles. We conclude that the choice of needle has no effect on the outcome of tendon repair if there is consistency of surgeon's skill and experience.

Stereo visualization of 3D trabecular bone structures produced by bone remodelling simulation

Adult human bone is constantly being renewed by a process known as remodelling. For cancellous bone this renewal process occurs at the interface between bone and marrow where bone is depleted by osteoclasts and rebuilt by osteoblasts. This remodelling process allows bone to repair itself. Software simulators for bone remodelling provide insight into the bone remodelling process; they allow investigation into bone form and structural properties, and they also allow the emulation of bone diseases and possible treatments for these diseases over long periods of time. BONESIM is a software that simulates bone remodelling in terms of Basic Multi-cellular Units (BMUs). 3D visualization of trabecular bone and its attributes is an essential tool in understanding this remodelling process for cancellous bone. It enables the bone researcher to quickly understand the dynamic behaviour of remodelling, the resulting geometry of the bone structure and it allows alternative remodelling scenarios to be compared. This paper presents the volume visualization technique that has been developed to provide this visualization tool.

Finite element analysis in spine research

Finite element analysis is a widely accepted tool used in many industries and research activities. It allows new designs to be thoroughly 'tested' before a prototype is even manufactured, components and systems which cannot readily be experimented upon to be examined, and 'diagnostic' investigations to be undertaken. Finite element models are already making an important contribution to our understanding of the spine and its components. Models are being used to reveal the biomechanical function of the spine and its behaviour when healthy, diseased or damaged. They are also providing support in the design and application of spinal instrumentation. The spine is a very complex structure, and many of the models are simplified and idealized because of the complexity and uncertainty in the geometry, material properties and boundary conditions of these problems. This type of modelling simplification is not peculiar to spinal modelling problems. Indeed, the idealization is often a strength when there is such uncertainty and variation between one individual and another, allowing cause-effect relationships to be isolated and fully explored, and the inherent variability of experimental tests to be eliminated. This paper reviews the development of finite element analysis in spinal modelling. It shows how modelling provides a wealth of information on our physiological performance, reduces our dependence on animal and cadaveric experiments and is an invaluable complement to clinical studies. It also leads to the conclusion that, as computing power and software capabilities increase, it is quite conceivable that in the future it will be possible to generate patient-specific models that could be used for patient assessment and even pre- and inter-operative planning.

Patient-specific spine models. Part 1: Finite element analysis of the lumbar intervertebral disc--a material sensitivity study

If patient-specific finite element models of the spine could be developed, they would offer enormous opportunities in the diagnosis and management of back problems. Several generic models have been developed in the past, but there has been very little detailed examination of the sensitivity of these models' characteristics to the input parameters. This relationship must be thoroughly understood if representative patient-specific models are to be realized and used with confidence. In particular, the performance of the intervertebral discs are central to any spine model and need detailed investigation first. A generic non-linear model of an intervertebral disc was developed and subjected to compressive, flexion and torsional loading regimes. The effects of both material and geometric non-linearities were investigated for the three loading schemes and the results compared with experimental data. The basic material properties of the fibres, annulus and nucleus were then varied and the effects on the stiffness, annulus bulge and annulus stresses analysed. The results showed that the non-linear geometry assumption had a significant effect on the compression characteristics, whereas the non-linear material option did not. In contrast, the material non-linearity was more important for the flexural and torsional loading schemes. Thus, the inclusion of non-linear material and geometry analysis options in finite element models of intervertebral discs is necessary to predict in vivo load-deflection characteristics accurately. When the influence of the material properties was examined in detail, it was found that the fibre properties did not have a significant effect on the compressive stiffness of the disc but did affect the flexural and torsional stiffnesses by up to +/-20 per cent. All loading modes were sensitive to the annulus properties with stiffnesses varying by up to +/-16 per cent. The model also revealed that for a particular compressive deformation or flexural or torsional rotation, the disc bulge was not sensitive to any of the material properties over the range of properties considered. The annulus stresses did differ significantly as the material properties were varied (up to 70 per cent under a compressive load and 60 per cent during disc flexion).

Stochastically simulated assessment of anabolic treatment following varying degrees of cancellous bone resorption

The aim of this study was to investigate the recovery in cancellous bone stiffness resulting from anabolic treatment following varying degrees of resorption, using a stochastic simulation applied to a simplistic structure consisting of five vertical and five horizontal trabeculae. The structure was initially resorbed, and "bone" elements were stochastically removed until nominal resorptions of 10%, 15%, 20%, 25%, and 30% were achieved. A stochastic simulation of anabolic treatment was then applied where bone elements were added, continuing until the original stiffness had been regained, for example, simulating treatment of a patient with an anabolic agent after a period of postmenopausal resorption. The resorption and anabolic simulations were repeated three times for each of the nominal resorptions. The stiffness of the bone structure decreased linearly with resorption, with a slope of approximately -2 and an R(2) of 97.0%; hence, the stiffness fell at approximately twice the rate of the reduction in density. When the various structures regained their original density, the resultant stiffness also had a linear relationship with the original resorption, with a slope of -1 and a lower R(2) of 86.1%. This implies that the reduction in stiffness, when original density was regained, fell proportionately with the degree of initial resorption and, therefore, after a resorption of 30%, when original density was regained, the stiffness of the resultant structure was approximately 30% less than that of the original structure. The density required for the original stiffness to be regained increased linearly with the degree of initial resorption, with a slope of approximately 0.5 and an R(2) of 65.2%, lower than that observed for the previous relationships. This indicates a greater spread of data and suggests greater variability in the formation phase beyond the point of regained original density. Because irreversible connectivity reduction is widely considered to be one of the earliest manifestations of estrogen loss, these findings, although obtained on a simulation of a simplistic cancellous bone structure, support the concept of early intervention to prevent potentially irreversible deterioration of trabecular architecture after menopause.

Use of an open-ended question to supplement a patient satisfaction questionnaire in a medical residents' clinic

OBJECTIVES

To determine (1) the proportion of responses to an open-ended question related to patient satisfaction that could be categorized into 1 or more of 9 previously developed domains of out-patient care and (2) whether any other important aspects of care could be identified by adding the open-ended question to a satisfaction questionnaire.

STUDY DESIGN

A 3-month observational study was done at the internal medicine clinic of an urban teaching hospital.

PATIENTS AND METHODS

As part of a patient satisfaction study, 511 visitors were asked after their visit, "What are the 1 or 2 things that are most important to you when you see a doctor?" The responses were categorized independently by 2 raters into 1 or more of the 9 domains. When these 2 raters disagreed, the responses were read to a third rater. When either all 3 raters disagreed, or at least 1 rater thought a new domain was mentioned, those responses were categorized by consensus. Interobserver reliability between raters 1 and 2 was calculated by using Cohen's kappa statistic.

RESULTS

The 355 responses were categorized as follows: 303 (85.4%) identified one or more domains that were part of the previously developed taxonomy, 9 (2.5%) identified a new domain, 11 (3.1%) identified both old and new domains, and 32 (9.0%) could not be categorized. Cohen's kappa was 0.57 (P < .001). Cultural sensitivity and physician honesty were the additional domains identified, by 1.1% and 4.5% of respondents, respectively.

CONCLUSIONS

The previously developed taxonomy of domains can be used in this setting to categorize the large majority of open-ended responses. Such responses can identify important aspects of care that were either previously unidentified or were already identified but given low ratings. This information then can help improve quality of care.

Enhanced emergency department referral improves primary care access

OBJECTIVE

People who use the emergency department (ED) as their main source of medical care cite access barriers to primary care as the reason. The purpose of this study was to test an intervention designed to refer regular ED users to primary care.

STUDY DESIGN

A prospective randomized clinical trial.

PATIENTS AND METHODS

Adults who stated the ED is their regular source of care and have no primary care (n = 189) were randomized to 2 groups: the intervention being studied or usual care. The study took place over 3 months at a northeastern urban hospital.

RESULTS

Subjects in the intervention group were more than twice as likely to keep the primary care appointment compared with the usual care group, and most also received some measure of preventive care. There was no significant difference in ED utilization by these patients in the 12-month period following study entry.

CONCLUSION

Making an appointment with detailed instructions during a visit to the ED markedly improves show rates at follow-up appointments with a primary care provider and allowed for opportunity to provide important preventive services.

Satisfaction with methods of Spanish interpretation in an ambulatory care clinic

OBJECTIVE

To describe the utilization of various methods of language interpretation by Spanish-speaking patients in an academic medical clinic and to determine patients' and physicians' satisfaction with these methods.

METHODS

Survey administered to medical residents and Spanish-speaking patients asking about their experience and satisfaction with various methods of language interpretation.

MAIN RESULTS

Both patients and residents had the highest level of satisfaction for professional interpreters (92.4% vs 96.1% reporting somewhat or very satisfactory, p =.17). In contrast, patients were significantly more satisfied than residents with using family members and friends (85.1% vs 60.8%, p <.01). Physicians and patients agreed that accuracy, accessibility, and respect for confidentiality were highly important characteristics of interpreters (>90% of both groups reporting somewhat or very important). However, patients were more concerned than residents about the ability of the interpreter to assist them after the physician visit (94% vs 45.1%, p < 0.01).

CONCLUSIONS

Using family members and friends as interpreters for Spanish-speaking patients should be more seriously considered; however, in order to optimize patient satisfaction, differences between patients and providers should be taken into account when using interpretation in medical settings.

Dynamic stochastic simulation of cancellous bone resorption

A stochastic simulation of cancellous bone resorption was developed and applied to a simple two-dimensional lattice structure representing the vertebral body. The simulation is based upon the concept of a basic multicellular unit (BMU) where net resorption (-deltaB.BMU) is considered at bone/marrow surfaces. The cancellous bone structure is defined as a binary matrix with the size of the pixels corresponding to a square element of approximately 20 microm dimension. The simulation considers both the probability that any surface pixel will be activated into a BMU and, if activated, the length of the resorption cavity. The relationship between relative stiffness and density for the simulation was predicted by finite element analysis. The stochastic simulation was iterated eight times with the mechanical properties assessed after each stage. Perforation of a single trabeculae was first observed at step 2, the structure completely lacking connectivity and mechanical integrity by step 8. The slope of the stiffness-porosity graph was greater than unity for the first five steps, but thereafter approached zero because the structure had lost connectivity and effectively collapsed. The eight-step simulation was repeated five times and demonstrated that, although the stiffness/density relationships were similar at the extremes of density, the dependence of stiffness upon density varied. This clearly demonstrates the stochastic nature of the simulation upon cancellous bone structure, and is probably indicative of a significant dependence of mechanical integrity upon perforation effects.

The effect of primary care training on patient satisfaction ratings

This study examines the association between type of internal medicine training and satisfaction ratings among 509 patients who visited the clinic of an urban teaching hospital over a 3-month period in 1994. When controlling for patient, health-system, and other resident factors, primary care training was significantly associated with higher satisfaction ratings (cumulative odds ratio 1.53; 95% confidence interval 1.04, 2.25; p = .031) than categorical training. Using satisfaction ratings to rank the residents without adjusting for patient and health-system factors would have correctly classified only 27% of the residents in the lowest quartile. These findings have implications for both the education and potential employment of internists.

Do internists and emergency physicians agree on the appropriateness of emergency department visits?

The purpose of this study was to determine the levels of agreement between three methods of assessing appropriateness of emergency department (ED) visits. In particular, we tested the agreement between internists and emergency physicians reviewing the ED nurses' triage notes, containing information that might be available by telephone to an internist. For 892 adult patient ED visits reviewed, we found only moderate agreement (kappa = 0.47) between these groups. In cases of disagreement, emergency physicians were 10.3 times more likely than internists to classify those with minor discharge diagnoses as appropriate for ED care. As managed care grows, the determination of ED appropriateness may depend on open discussions between physician groups, as well as on access to timely care in office settings.

Glucose metabolism in 'Sphingomonas elodea': pathway engineering via construction of a glucose-6-phosphate dehydrogenase insertion mutant

'Sphingomonas (formerly Pseudomonas) elodea' produces the industrially important polysaccharide gellan when grown in media containing glucose. Glucose catabolic enzymes and enzymes of central carbon metabolism were assayed in crude extracts of glucose-grown cultures of this bacterium. Based on these analyses it was concluded that glucose is converted to either gluconate or glucose 6-phosphate and that both of these products are converted to 6-phosphogluconate, a precursor for the Entner-Doudoroff (ED) and pentose phosphate pathways. Phosphoglucoisomerase (Pgi) activity was detected, but the lack of phosphofructokinase activity indicated that the Embden-Meyerhof glycolytic pathway is non-functional for glucose degradation. Thus, this bacterium utilizes glucose mainly via the ED and pentose phosphate pathways. Enzyme analyses suggested the involvement of glucose-6-phosphate dehydrogenase (Zwf) in glucose utilization and CO2 production. The zwf gene was cloned from 'S. elodea' and partially sequenced, and a null zwf mutant was constructed. This mutant exhibited no Zwf activity in in vitro assays, grew normally on glucose minimal medium and accumulated biomass (cells plus gellan) and produced CO2 at the same rates as the parental strain. Potential explanations for this finding are provided. Clones carrying the pgi gene were isolated fortuitously.

Pediatric asthma care in US emergency departments. Current practice in the context of the National Institutes of Health guidelines

OBJECTIVES

To determine whether US emergency department care for pediatric asthma conforms to the National Institutes of Health guidelines and whether the guidelines are likely to be adopted in clinical practice.

DESIGN

Mail survey conducted from January to April 1992, and stratified by hospital type (children's, public and community).

SETTINGS

Emergency departments of US hospitals.

PARTICIPANTS

Simple stratified random sample of emergency department directors from 376 sampled hospitals.

MEASUREMENTS

Self-reported data on emergency department pediatric asthma care, and knowledge and attitudes about the National Institutes of Health guidelines. Data are reported as mean (+/- SE).

RESULTS

Sixty-eight percent of the surveyed emergency department directors responded. During 1991, there were an estimated 1.6 million visits for pediatric asthma care. Asthma accounted for 16.9% (+/- 9.0%) of all pediatric emergency department visits. Only 2.1% (+/- 1.0%) reported the use of written protocols or guidelines, with significant variation by hospital type. Sixty-seven percent (+/- 3.0%) reported the use of pulse oximetry. Eighty percent reported the use of beta-agonists by inhalation as the initial treatment. Only 44.7% (+/- 2.9%) reported the use of steroids if there was a poor response to the initial treatment. An estimated 45.5% (+/- 3.9%) of respondents had heard of the guidelines at the time of this survey; approximately 24% reported that they had read the guidelines. Most respondents reported that the guidelines were credible, clear and concise, and likely to be adopted in their emergency department.

CONCLUSIONS

These data suggest that reported pediatric asthma care in US emergency departments differs substantially from the National Institutes of Health guidelines, with considerable variation by hospital type. The guidelines appear to provide an acceptable tool for emergency departments to use in assessing their pediatric asthma care. However, in light of the lack of evidence that the guidelines will improve outcomes, the impact of national guideline adoption remains unclear.

P-type ATPases of eukaryotes and bacteria: sequence analyses and construction of phylogenetic trees

The amino acid sequences of 47 P-type ATPases from several eukaryotic and bacterial kingdoms were divided into three structural segments based on individual hydropathy profiles. Each homologous segment was (1) multiply aligned and functionally evaluated, (2) statistically analyzed to determine the degrees of sequence similarity, and (3) used for the construction of parsimonious phylogenetic trees. The results show that all of the P-type ATPases analyzed comprise a single family with four major clusters correlating with their cation specificities and biological sources as follows: cluster 1: Ca(2+)-transporting ATPases; cluster 2: Na(+)- and gastric H(+)-ATPases; cluster 3: plasma membrane H(+)-translocating ATPases of plants, fungi, and lower eukaryotes; and cluster 4: all but one of the bacterial P-type ATPases (specific for K+, Cd2+, Cu2+ and an unknown cation). The one bacterial exception to this general pattern was the Mg(2+)-ATPase of Salmonella typhimurium, which clustered with the eukaryotic sequences. Although exceptions were noted, the similarities of the phylogenetic trees derived from the three segments analyzed led to the probability that the N-terminal segments 1 and the centrally localized segments 2 evolved from a single primordial ATPase which existed prior to the divergence of eukaryotes from prokaryotes. By contrast, the C-terminal segments 3 appear to be eukaryotic specific, are not found in similar form in any of the prokaryotic enzymes, and are not all demonstrably homologous among the eukaryotic enzymes. These C-terminal domains may therefore have either arisen after the divergence of eukaryotes from prokaryotes or exhibited more rapid sequence divergence than either segment 1 or 2, thus masking their common origin. The relative rates of evolutionary divergence for the three segments were determined to be segment 2 < segment 1 < segment 3. Correlative functional analyses of the most conserved regions of these ATPases, based on published site-specific mutagenesis data, provided preliminary evidence for their functional roles in the transport mechanism. Our studies define the structural and evolutionary relationships among the P-type ATPases. They should provide a guide for the design of future studies of structure-function relationships employing molecular genetic, biochemical, and biophysical techniques.

Relationship between nurses' assessments of perfusion and toe temperature in pediatric patients with cardiovascular disease

This descriptive study reports on 17 children who had undergone open-heart surgery. The children were assessed for 6 hours after surgery and once at 18 hours after operation to determine relationship between two scales assessing peripheral perfusion and the temperature of the great toe. There were 119 individual assessments. The scales used to assess the quality of peripheral pulses, extremity warmth, and capillary refill were (1) those representative of assessment scales used in common nursing practice and (2) more specific scales that attempt to "quantify" the qualitative assessment of peripheral perfusion. The more specific set of scales was used by "trained observers," with the bedside nurse using the nurses' scales. Results demonstrated that both sets of scales and observers were accurate in assessing peripheral perfusion as measured by the actual toe temperature. Analyses revealed which scales were better than others, and a method of assessing peripheral perfusion that includes the best components of all scales is suggested.

Role of the collar on the femoral stem of cemented total hip replacements

Three dimensional finite element models with realistic loading conditions were used to analyse the role of the collar of cemented total hip stems. Three types of implant were considered: large collared stems, small collared stems and totally collarless stems. A computer model of the natural femur provided an indication of the bone stresses before hip replacement, and thus aided the identification of possible mechanisms of bone resorption. In particular, resorption of the medial femoral neck was examined, and its effect on the stress distribution within the stem-cement-bone structure is discussed. The results indicate that loss of bone at the femoral neck is a serious symptom for any design of implant. The factors leading to the resorption are complex but it is clear that it is not a consequence of simple stress shielding of the bone. The most likely cause is the manner in which the stem moves within the femoral shaft, which is a function of whether the stem is collared or not.

Tropical pulmonary eosinophilia associated with pleural effusions

A 28-year-old Indian female presented with shortness of breath, white cell count of 27,400 with 39% eosinophils, and increased interstitial markings and bilateral pleural effusions on chest x-ray. Although the clinical presentation was consistent with tropical pulmonary eosinophilia (TPE), to our knowledge there has been only one previous report in the world's literature of pleural effusion associated with TPE. We suggest that pleural effusions are not incompatible with the diagnosis of TPE and that TPE be added to the list of conditions causing eosinophilic pleural effusions.