Biomechanical study of rod stress after pedicle subtraction osteotomy versus anterior column reconstruction: A finite element study

BACKGROUND

In an effort to minimize rod fractures and nonunion in pedicle subtraction osteotomy (PSO) constructs, surgeons have adopted multirod constructs and interbody cages. Anterior column realignment (ACR) with posterior column osteotomies is a minimally invasive alternative to PSO in sagittal balance correction, however, there is a paucity of evidence with respect to rod survival.

METHODS

Three-dimensional (3D) finite-element-model of a T12-sacrum spine segment was used to compare a 25° PSO at L3 and an ACR with a posterior column osteotomy and 30° hyperlordotic interbody cage at L3-4. The amount of overall T12-S1 lordosis correction was the same for each condition. Each simulation included cobalt chromium alloy primary rods with: (1) PSO; (2) PSO with an interbody cage (IB) at L2-3 (PSO+IB); (3) PSO with accessory (A) rods and IB at L2-3 (PSO+IB+A); (4) PSO with satellite (S) rods and IB at L2-3 (PSO+IB+2S); (5) ACR; 6) ACR with satellite rods (ACR + 2S). A 400 N follower preload was simulated for each condition.

RESULTS

PSO condition had the largest rod stress of 286 MPa in flexion. Adding interbody support reduced the rod stress by 15%. The 4-rod constructs further reduced rod stress, with the satellite rod condition facilitating the largest reduction. The rod stress in the ACR+2S was equivalent to the PSO+2S, with 50% reduction in rod stress.

CONCLUSION

The rod stress with an ACR was comparable to a PSO coupled with interbody support. These results suggest an ACR is a viable MIS alternative to a PSO without the need for a large posterior osteotomy.

Lower incidence of myocardial infarction after smoke-free legislation enforcement in Chile

Objective

To evaluate the impact of a complete smoking ban in enclosed spaces on the incidence of acute myocardial infarction in Chile.

Methods

The population-based study involved residents of urban areas, where 80% of the Chilean population live, aged 20 years or older who had a myocardial infarction. Monthly myocardial infarction incidence and mortality rates at health-care facilities between January 2011 and December 2014 were derived from admission and mortality databases. Regression discontinuity methods were used to estimate the near-immediate impact on disease incidence of enforcing smoke-free legislation in March 2013. The same analysis was performed for ischaemic stroke, degenerative disc disease and colon cancer. Data on the concentration of fine respirable particulates were included in an additional analysis of myocardial infarction incidence in the Santiago metropolitan area.

Results

The enforcement of smoke-free legislation was associated with an abrupt, near-immediate decline of 0.639 cases of myocardial infarction per 100 000 adults per month (95% confidence interval, CI: 0.242 to 1.036; relative decline: 7.8%). Similar declines were observed in men and women and in people aged over and under 70 years. However, enforcement of the legislation was not associated with a significant change in the rate of ischaemic stroke, degenerative disc disease or colon cancer. The abrupt decline in myocardial infarction incidence was also observed when data on fine respirable particulates were included in an analysis for Santiago.

Conclusion

The enforcement of extensive smoke-free legislation in Chile was associated with an abrupt, near-immediate decline in the incidence of myocardial infarction.

Allocation of Residency Training Positions in Spain: Contextual Effects on Specialty Preferences

In Spain's 'MIR' system, medical school graduates are ranked by their performance on a national exam and then sequentially choose from the available residency training positions. We took advantage of a unique survey of participants in the 2012 annual MIR cycle to analyze preferences under two different choice scenarios: the residency program actually chosen by each participant when it came her turn (the 'real') and the program that she would have chosen if all residency training programs had been available (the 'counterfactual'). Utilizing conditional logit models with random coefficients, we found significant differences in medical graduates' preferences between the two scenarios, particularly with respect to three specialty attributes: work hours/lifestyle, prestige among colleagues, and annual remuneration. In the counterfactual world, these attributes were valued preferentially by those nearer to the top, while in the real world, they were valued preferentially by graduates nearer to the bottom of the national ranking. Medical graduates' specialty preferences, which we conclude, are not intrinsically stable but depend critically on the 'rules of the game'. The MIR assignment system, by restricting choice, effectively creates an externality in which those at the bottom, who have fewer choices, want what those at the top already have. Copyright © 2016 John Wiley & Sons, Ltd.

Level of agreement of occupational titles between persons with traumatic brain injury and their informants

BACKGROUND

Returning to work is one of the most important goals cited by individuals with traumatic brain injury (TBI). However, they may have difficulty evoking past work history. The ability to recall work history is integral to the rehabilitation process of return to work.

OBJECTIVE

The aim of this study was to determine 1) the level of agreement on the reporting of occupations and 2) if agreement is affected when specific occupational details are required in recall between adults with traumatic brain injury and their informants.

METHODS

This is a retrospective cohort study of 259 individuals, with moderate to severe traumatic brain injury, and their selected informants (e.g. spouse, parent). Interviews were conducted separately for the individual and respective informant to gather information on type of occupation at time of injury and at time of interview. Reported occupations were coded using a standard classification system. Level of agreement was analyzed by interclass correlation coefficients and percent agreement, and the significance of bias was calculated.

RESULTS

Participants were a mean age of 44.5 at time of study with 40% employed compared to 77% at time of injury. Agreement between participants and their informants for occupational title was high for both time periods though more so at the time of injury compared to current status. Level of agreement for specificity was moderate to high however, decreased as need for specificity of detail increased.

CONCLUSION

While participant-informant responses appear to be reliable for occupational classification, when detailed information is required corroborating information is likely needed.

The effect of posterior polyester tethers on the biomechanics of proximal junctional kyphosis: a finite element analysis

OBJECTIVE

Proximal junctional kyphosis (PJK) remains problematic following multilevel instrumented spine surgery. Previous biomechanical studies indicate that providing less rigid fixation at the cranial aspect of a long posterior instrumented construct, via transition rods or hooks at the upper instrumented vertebra (UIV), may provide a gradual transition to normal motion and prevent PJK. The purpose of this study was to evaluate the ability of posterior anchored polyethylene tethers to distribute proximal motion segment stiffness in long instrumented spine constructs.

METHODS

A finite element model of a T7–L5 spine segment was created to evaluate range of motion (ROM), intradiscal pressure, pedicle screw loads, and forces in the posterior ligament complex within and adjacent to the proximal terminus of an instrumented spine construct. Six models were tested: 1) intact spine; 2) bilateral, segmental pedicle screws (PS) at all levels from T-11 through L-5; 3) bilateral pedicle screws from T-12 to L-5 and transverse process hooks (TPH) at T-11 (the UIV); 4) pedicle screws from T-11 to L5 and 1-level tethers from T-10 to T-11 (TE-UIV+1); 5) pedicle screws from T-11 to L-5 and 2-level tethers from T-9 to T-11 (TE-UIV+2); and 6) pedicle screws and 3-level tethers from T-8 to T-11 (TE-UIV+3).

RESULTS

Proximal-segment range of motion (ROM) for the PS construct increased from 16% at UIV−1 to 91% at UIV. Proximal-segment ROM for the TPH construct increased from 27% at UIV−1 to 92% at UIV. Posterior tether constructs distributed ROM at the UIV and cranial adjacent segments most effectively; ROM for TE-UIV+1 was 14% of the intact model at UIV−1, 76% at UIV, and 98% at UIV+1. ROM for TE-UIV+2 was 10% at UIV−1, 51% at UIV, 69% at UIV+1, and 97% at UIV+2. ROM for TE-UIV+3 was 7% at UIV−1, 33% at UIV, 45% at UIV+1, and 64% at UIV+2. Proximal segment intradiscal pressures, pedicle screw loads, and ligament forces in the posterior ligament complex were progressively reduced with increasing number of posterior tethers used.

CONCLUSIONS

Finite element analysis of long instrumented spine constructs demonstrated that posterior tethers created a more gradual transition in ROM and adjacent-segment stress from the instrumented to the noninstrumented spine compared with all PS and TPH constructs. Posterior tethers may limit the biomechanical risk factor for PJK; however, further clinical research is needed to evaluate clinical efficacy.

Tobacco control campaign in Uruguay: Impact on smoking cessation during pregnancy and birth weight

We analyzed a nationwide registry of all pregnancies in Uruguay during 2007-2013 to assess the impact of three types of tobacco control policies: (1) provider-level interventions aimed at the treatment of nicotine dependence, (2) national-level increases in cigarette taxes, and (3) national-level non-price regulation of cigarette packaging and marketing. We estimated models of smoking cessation during pregnancy at the individual, provider and national levels. The rate of smoking cessation during pregnancy increased from 15.4% in 2007 to 42.7% in 2013. National-level non-price policies had the largest estimated impact on cessation. The price response of the tobacco industry attenuated the effects of tax increases. While provider-level interventions had a significant effect, they were adopted by relatively few health centers. Quitting during pregnancy increased birth weight by an estimated 188 g. Tobacco control measures had no effect on the birth weight of newborns of non-smoking women.

Utilization of motor imagery in upper limb rehabilitation: a systematic scoping review

Objective:

To determine how motor imagery is being delivered in upper limb rehabilitation to guide practice and research.

Data source:

MEDLINE, PubMed, CINAHL, EMBASE, PsychINFO databases were searched from 1987 to November 2014

Study selection:

English, adults, any clinical population or diagnosis, intervention for upper limb with an outcome measure used. All types of studies were included. Two authors independently selected studies for review using consensus.

Data extraction:

Seven motor imagery elements were extracted using a model implemented in sport research: PETTLEP model (Physical, Environment, Task, Timing, Learning, Emotion, and Perspective).

Results:

The search yielded 1107 articles with 1059 excluded leaving 48 articles for full review. A total of 38 articles involved individuals with stroke, five articles involved individuals with complex regional pain syndrome, and five articles for other conditions. Motor imagery elements most commonly described were physical, environment, task, and perspective. Elements less commonly described were timing, learning, and emotional aspects. There were significant differences between study populations (e.g. stroke and complex regional pain syndrome) and within populations on how motor imagery was delivered.

Conclusion:

Many of the imagery elements reviewed are not being considered or reported on in the selected studies. How motor imagery is being delivered within and between populations is inconsistent, which may lead to difficulties in determining key elements of effectiveness.

COL1A1 C-propeptide cleavage site mutation causes high bone mass, bone fragility and jaw lesions: a new cause of gnathodiaphyseal dysplasia?

Gnathodiaphyseal dysplasia (GDD) is a rare autosomal dominant condition characterized by bone fragility, irregular bone mineral density (BMD) and fibro-osseous lesions in the skull and jaw. Mutations in Anoctamin-5 (ANO5) have been identified in some cases. We aimed to identify the causative mutation in a family with features of GDD but no mutation in ANO5, using whole exome capture and massive parallel sequencing (WES). WES of two affected individuals (a mother and son) and the mother's unaffected parents identified a mutation in the C-propeptide cleavage site of COL1A1. Similar mutations have been reported in individuals with osteogenesis imperfecta (OI) and paradoxically increased BMD. C-propeptide cleavage site mutations in COL1A1 may not only cause 'high bone mass OI', but also the clinical features of GDD, specifically irregular sclerotic BMD and fibro-osseous lesions in the skull and jaw. GDD patients negative for ANO5 mutations should be assessed for mutations in type I collagen C-propeptide cleavage sites.

[Important differences between faculties of medicine. Implications for family and community medicine]

OBJECTIVE

To determine if there are significant differences between universities in the proclivity to choose Family and Community Medicine (FCM), given the constraints imposed by the number of choice. To test the hypothesis that the Schools of Medicine that have the FCM as a compulsory subject in the degree (3 of 27) had the highest preference for this specialty.

DESIGN

Observational study on the data file of all the individuals taking the MIR examination between 2003 and 2011.

LOCATION

Spain.

PARTICIPANTS

All those who sat the examinations called by MIR 2003-2011.

MAIN MEASUREMENTS

Position in the ranking of each candidate, elected position (specialty and center), post code of residence, sex, nationality and university in which they studied, and post code location for the residence chosen.

RESULTS

The percentage electing FCM is highly correlated with the position in the ranking: 8% of graduates for the 'best' college, 46% for the worst. Very noticeable and consistent differences in the preparation for the MIR among the 27 medical schools. Ranking in the exam, female and foreigner, help predict the choice of FCM. The FCM compulsory curriculum from three universities does not seem to exert any influence.

CONCLUSIONS

The convenient yardstick competition between the schools of medicine, FCM in their curriculum and the emphasis on the most attractive attributes of the specialty can contribute to the necessary renewal of FCM.

Specialty choice in times of economic crisis: a cross-sectional survey of Spanish medical students

OBJECTIVE

To investigate the determinants of specialty choice among graduating medical students in Spain, a country that entered into a severe, ongoing economic crisis in 2008.

SETTING

Since 2008, the percentage of Spanish medical school graduates electing Family and Community Medicine (FCM) has experienced a reversal after more than a decade of decline.

DESIGN

A nationwide cross-sectional survey conducted online in April 2011.

PARTICIPANTS

We invited all students in their final year before graduation from each of Spain's 27 public and private medical schools to participate.

MAIN OUTCOME MEASURES

Respondents' preferred specialty in relation to their perceptions of: (1) the probability of obtaining employment; (2) lifestyle and work hours; (3) recognition by patients; (4) prestige among colleagues; (5) opportunity for professional development; (6) annual remuneration and (7) the proportion of the physician's compensation from private practice.

RESULTS

978 medical students (25% of the nationwide population of students in their final year) participated. Perceived job availability had the largest impact on specialty preference. Each 10% increment in the probability of obtaining employment increased the odds of preferring a specialty by 33.7% (95% CI 27.2% to 40.5%). Job availability was four times as important as compensation from private practice in determining specialty choice (95% CI 1.7 to 6.8). We observed considerable heterogeneity in the influence of lifestyle and work hours, with students who preferred such specialties as Cardiovascular Surgery and Obstetrics and Gynaecology valuing longer rather than shorter workdays.

CONCLUSIONS

In the midst of an ongoing economic crisis, job availability has assumed critical importance as a determinant of specialty preference among Spanish medical students. In view of the shortage of practitioners of FCM, public policies that take advantage of the enhanced perceived job availability of FCM may help steer medical school graduates into this specialty.

Tobacco control campaign in Uruguay: a population-based trend analysis

BACKGROUND

In 2005, Uruguay initiated a series of comprehensive anti-smoking measures. We aimed to assess the effect of Uruguay's anti-tobacco campaign.

METHODS

We did a population-based trend analysis, using neighbouring Argentina, which has not instituted such extensive anti-tobacco measures, as a control. We assessed three key endpoints in both countries: per-person consumption of cigarettes, as measured by tax records; the prevalence of tobacco use in adolescents, as measured by school-based surveys; and the prevalence of tobacco use in adults, as measured by nationwide household-based surveys.

FINDINGS

During 2005-11, per-person consumption of cigarettes in Uruguay decreased by 4·3% per year (95% CI 2·4 to 6·2), whereas per-person consumption in Argentina increased by 0·6% per year (-1·2 to 2·5; p=0·002 for difference in trends). During 2003-09, the 30-day prevalence of tobacco use in Uruguayan students aged 13 years, 15 years, and 17 years decreased by an estimated 8·0% per year (4·5 to 11·6), compared with a decrease of 2·5% annually (0·5 to 4·5) in Argentinian students during 2001-09 (p=0·02 for difference in trends). From 2005 to 2011, the prevalence of current tobacco use in Uruguay decreased annually by an estimated 3·3% (2·4 to 4·1), compared with an annual decrease in Argentina of 1·7% (0·8 to 2·6; p=0·02 for difference in trends).

INTERPRETATION

Uruguay's comprehensive tobacco-control campaign has been associated with a substantial, unprecedented decrease in tobacco use. Decreases in tobacco use in other low-income and middle-income countries of the magnitude seen in Uruguay would have a substantial effect on the future global burden of tobacco-related diseases.

FUNDING

J William Fulbright Foreign Scholarship Board and the US Department of State.

Publishing nutrition research: a review of multivariate techniques--part 2: analysis of variance

This article is the eighth in a series exploring the importance of research design, statistical analysis, and epidemiology in nutrition and dietetics research, and the second in a series focused on multivariate statistical analytical techniques. The purpose of this review is to examine the statistical technique, analysis of variance (ANOVA), from its simplest to multivariate applications. Many dietetics practitioners are familiar with basic ANOVA, but less informed of the multivariate applications such as multiway ANOVA, repeated-measures ANOVA, analysis of covariance, multiple ANOVA, and multiple analysis of covariance. The article addresses all these applications and includes hypothetical and real examples from the field of dietetics.

Why we don't have an HIV vaccine, and how we can develop one

Confronted with the recent high-profile failures of several clinical trials of promising candidate vaccines against HIV, many scientists have all but given up hope of producing a human-ready vaccine within the next decade. In this review I contend that although the scientific obstacles remain formidable, the economic challenges are just as real. The groundwork will be laid for a major scientific breakthrough in vaccine development only when there are new contractual structures that enhance private incentives for vaccine development; when we have clearly specified the rights to the profitable North American market; when we have established a system of liability protection for vaccine side effects; and when our clinical trials also test the behavioral consequences of vaccination.

Review of enteric outbreaks in prisons: effective infection control interventions

OBJECTIVES

To identify documented outbreaks, worldwide, of enteric illness in correctional facilities over the last 10 years to understand the epidemiology of the outbreaks and explicitly identify effective infection control measures.

STUDY DESIGN

Review of literature and outbreak investigation reports.

METHODS

Computer-aided searches of literature databases and systematic searches of government websites were completed to identify relevant outbreak reports. Reference lists were hand-searched to validate the electronic search methodology. Reports identified through personal communications with public health officials were also included.

RESULTS

Of the 72 outbreaks meeting the inclusion criteria, 76% and 21% were associated with bacterial agents and viral agents, respectively. The majority of outbreaks were associated with Salmonella (n=20), Clostridium perfringens (n=14), norovirus (n=14), pathogenic Escherichia coli (n=10) and Campylobacter spp. (n=5). Transmission was primarily foodborne (67%). During an outbreak, the most common control measures included limiting movements of ill inmates and staff, and their exclusion from kitchen duty. The most common retrospectively reported preventative recommendations included monitoring food temperatures and effective infection control procedures.

CONCLUSIONS

It is essential to monitor food temperatures to prevent enteric outbreaks in prisons. Training in safe food handling should be offered to inmates who work in the kitchen. Enteric outbreaks are best controlled by effective infection control practices, while active surveillance and early diagnosis may prevent further spread of illness.

Isolation and characterization of a novel thermophilic, freshwater methanogen

A novel thermophilic, coccoid methanogen isolated from nonthermal freshwater sediments is described. Hydrogen plus carbon dioxide and formate were substrates for methanogenesis, and methane production was stimulated by yeast extract, Casamino Acids, and tryptose. Growth also occurred autotrophically. Elevated levels of sodium chloride were not required for maximum growth and were inhibitory above 2%. The minimum doubling time occurred at 57 degrees C, and the upper and lower limits for methane production were 62 and 26 degrees C, respectively. The optimum pH for growth was between 7.0 and 7.5. Inhibitory antibiotics included metronidazole, anisomycin, chloramphenicol, and lasalocid. Colonies were circular, dark yellow, shiny, and convex with entire edges. Cells were 1 to 2.5 mum in diameter, nonmotile, occurring singly or in pairs, and fimbriated. Cells were lysed by pronase or trypsin digestion, glass-distilled water, and 1% sodium dodecyl sulfate. Electron micrographs of thin sections showed a monolayered cell wall ca. 20 nm thick. The DNA base ratio was 49.2 mol% guanine plus cytosine. The whole cell protein pattern differed from that of other named coccoid methanogens.

Spontaneous Disaggregation of Methanosarcina mazei S-6 and Its Use in the Development of Genetic Techniques for Methanosarcina spp

When monomethylamine was the growth substrate, spontaneous disaggregation of Methanosarcina mazei S-6 commenced at the mid-exponential phase and resulted in the formation of a suspension containing 10 to 10 free cells per ml. Free cells were osmotically fragile and amenable to extraction of DNA. Hypertonic media for the manipulation and regeneration of free cells into aggregates were developed, and plating efficiencies of 100% were achieved for M. mazei S-6 and LYC. Free cells of strain S-6 required MgCl(2) (10 mM) for growth, whereas aggregates did not. Specific growth rates of strains S-6 and LYC were increased by MgCl(2). Treatment with pronase caused sphere formation and removal of the protein wall of cells of strain S-6, but protoplasts could not be regenerated. The disaggregating enzyme produced by strain S-6 facilitated the preparation of suspensions of free cells of some strains of Methanosarcina barkeri. Although this provided a means of extracting high-molecular-weight DNA from M. barkeri, less than 0.1% of free cells were viable.

Heterogeneous impact of the "Seguro Popular" program on the utilization of obstetrical services in Mexico, 2001-2006: a multinomial probit model with a discrete endogenous variable

OBJECTIVE

We evaluated the impact of Seguro Popular (SP), a program introduced in 2001 in Mexico primarily to finance health care for the poor. We focused on the effect of household enrollment in SP on pregnant women's access to obstetrical services, an important outcome measure of both maternal and infant health.

DATA

We relied upon data from the cross-sectional 2006 National Health and Nutrition Survey (ENSANUT) in Mexico. We analyzed the responses of 3890 women who delivered babies during 2001-2006 and whose households lacked employer-based health care coverage.

METHODS

We formulated a multinomial probit model that distinguished between three mutually exclusive sites for delivering a baby: a health unit specifically accredited by SP; a non-SP-accredited clinic run by the Department of Health (Secretaría de Salud, or SSA); and private obstetrical care. Our model accounted for the endogeneity of the household's binary decision to enroll in the SP program.

RESULTS

Women in households that participated in the SP program had a much stronger preference for having a baby in a SP-sponsored unit rather than paying out of pocket for a private delivery. At the same time, participation in SP was associated with a stronger preference for delivering in the private sector rather than at a state-run SSA clinic. On balance, the Seguro Popular program reduced pregnant women's attendance at an SSA clinic much more than it reduced the probability of delivering a baby in the private sector. The quantitative impact of the SP program varied with the woman's education and health, as well as the assets and location (rural vs. urban) of the household.

CONCLUSIONS

The SP program had a robust, significantly positive impact on access to obstetrical services. Our finding that women enrolled in SP switched from non-SP state-run facilities, rather than from out-of-pocket private services, is important for public policy and requires further exploration.

Publishing nutrition research: a review of nonparametric methods, part 3

This is the third article in a periodic five-part series on publishing nutrition research. These monographs are designed to assist in the interpretation of the Journal of the American Dietetic Association author guidelines and provide guidance in publishing and interpreting nutrition-related research articles. This installment focuses on the use of nonparametric statistical methods. The rationale for their use, their advantages and disadvantages, nonparametric alternatives to parametric tests, nonparametric statistical analysis, examples of their use, and helpful resources for further study are topics and issues addressed in this article.

Optimizing resource allocation for HIV/AIDS prevention programmes: an analytical framework

INTRODUCTION

Although investment in HIV/AIDS prevention has increased worldwide, it remains uncertain how the additional resources can be most efficiently allocated to maximize the number of infections averted, especially at the country, regional and local levels.

METHODS

Data from developing countries in Africa, Asia and Latin America were reviewed on the allocation of HIV/AIDS prevention funds in relation to the prevalence of infection, as well as budgetary allocations for specific population groups at high risk of infection, such as sex workers, intravenous drug users and men who have sex with men. The variation in unit costs of voluntary counselling and testing in five countries was also examined.

RESULTS

Evidence was found of three distinct sources of inefficiency in the allocation of HIV/AIDS prevention resources: inefficiency in the mix of interventions selected; inefficient targeting of key populations; and technical inefficiency in the production of HIV prevention services.

CONCLUSION

A general conceptual framework for evaluating the efficiency of HIV/AIDS prevention programmes at the country, regional and local levels is proposed. This framework stresses three equally important components of programme efficiency: cost-effectiveness (the choice of the mix of interventions); targeting (the choice of the mix of target populations); and technical efficiency (the delivery of prevention services at least cost).

Asymmetric peer effects in the analysis of cigarette smoking among young people in the United States, 1992-1999

We extend the recent literature on peer effects to test the possible role of asymmetric social influences in the determination of youth smoking. We analyzed cigarette smoking among people aged 15-24 in approximately 90,000 households in the 1992-1999 U.S. Current Population Surveys. The presence of additional smoking sibling in a household, we estimated, raised a young person's probability of smoking by 7.6%, while each non-smoking sibling lowered the probability by an estimated 3.5%. Moreover, the overall deterrent effect of an increase in cigarette price on the probability of smoking was approximately 60% greater than the estimated effect when peer influences were held constant. The concept of asymmetric social influence may have applications in other fields, including labor economics, education, crime prevention, and group dynamics.