Sequential Ring Opening/In Situ SO2-Capture/Alkynylation of Cyclopropanols with Alkynyl Triflones Initiated by Energy Transfer.

A visible-light-triggered ring opening/in situ SO2-capture/alkynylation sequence of cyclopropyl alcohols with alkynyl triflones using 4CzIPN as a triplet energy transfer photocatalyst is herein described. This metal-free protocol provides a straightforward and atom-economical approach to alkynyl-substituted γ-keto sulfones with a broad scope of substituents. In this transformation, alkynyl triflones could be used as both radical acceptors and SO2 donors. Preliminary experimental mechanistic studies and synthetic utility are also demonstrated.

Urban Fine Particulate Matter and Elements Associated with Subclinical Atherosclerosis in Adolescents and Young Adults.

The relationships between the elemental constituents of PM2.5 and atherosclerosis remain limited, especially in young populations. This study included 755 subjects aged 12-30 years in the Taipei metropolis. A land use regression model was used to estimate residential annual mean concentrations of PM2.5 and eight elemental constituents. We evaluated the percent differences in carotid intima-media thickness (CIMT) with PM2.5 and elemental constituent exposures by linear regressions. Interquartile range increments for PM2.5 (4.5 µg/m3), sulfur (108.6 ng/m3), manganese (2.0 ng/m3), iron (34.5 ng/m3), copper (3.6 ng/m3), and zinc (20.7 ng/m3) were found to associate with 0.92% (95% confidence interval (CI): 0.17-1.66), 0.51% (0.02-1.00), 0.36% (0.05-0.67), 0.98% (0.15-1.82), 0.74% (0.01-1.48), and 1.20% (0.33-2.08) higher CIMTs, respectively. Factor analysis identified four air pollution source-related factors, and the factors interpreted as traffic and industry sources were associated with higher CIMTs. Stratified analyses showed the estimates were more evident in subjects who were ≥18 years old, females, or who had lower household income. Our study results provide new insight into the impacts of source-specific air pollution, and future research on source-specific air pollution effects in young populations, especially in vulnerable subpopulations, is warranted.

Neuropathology changed by 3- and 6-months low-level PM2.5 inhalation exposure in spontaneously hypertensive rats.

BACKGROUND: Epidemiological evidence has linked fine particulate matter (PM2.5) to neurodegenerative diseases; however, the toxicological evidence remains unclear. The objective of this study was to investigate the effects of PM2.5 on neuropathophysiology in a hypertensive animal model. We examined behavioral alterations (Morris water maze), lipid peroxidation (malondialdehyde (MDA)), tau and autophagy expressions, neuron death, and caspase-3 levels after 3 and 6 months of whole-body exposure to urban PM2.5 in spontaneously hypertensive (SH) rats. RESULTS: SH rats were exposed to S-, K-, Si-, and Fe-dominated PM2.5 at 8.6 ± 2.5 and 10.8 ± 3.8 µg/m3 for 3 and 6 months, respectively. We observed no significant alterations in the escape latency, distance moved, mean area crossing, mean time spent, or mean swimming velocity after PM2.5 exposure. Notably, levels of MDA had significantly increased in the olfactory bulb, hippocampus, and cortex after 6 months of PM2.5 exposure (p < 0.05). We observed that 3 months of exposure to PM2.5 caused significantly higher expressions of t-tau and p-tau in the olfactory bulb (p < 0.05) but not in other brain regions. Beclin 1 was overexpressed in the hippocampus with 3 months of PM2.5 exposure, but significantly decreased in the cortex with 6 months exposure to PM2.5. Neuron numbers had decreased with caspase-3 activation in the cerebellum, hippocampus, and cortex after 6 months of PM2.5 exposure. CONCLUSIONS: Chronic exposure to low-level PM2.5 could accelerate the development of neurodegenerative pathologies in subjects with hypertension.

A Computational Study on Deformed Bioprosthetic Valve Geometries: Clinically Relevant Valve Performance Metrics.

Transcatheter aortic valves (TAV) are symmetrically designed, but they are often not deployed inside cylindrical conduits with circular cross-sectional areas. Many TAV patients have heavily calcified aortic valves, which often result in deformed prosthesis geometries after deployment. We investigated the effects of deformed valve annulus configurations on a surgical bioprosthetic valve as a model for TAV. We studied valve leaflet motions, stresses and strains, and analog hydrodynamic measures (using geometric methods), via finite element (FE) modeling. Two categories of annular deformations were created to approximate clinical observations: (1) noncircular annulus with valve area conserved, and (2) under-expansion (reduced area) compared to circular annulus. We found that under-expansion had more impact on increasing stenosis (with geometric orifice area metrics) than noncircularity, and that noncircularity had more impact on increasing regurgitation (with regurgitation orifice area metrics) than under-expansion. We found durability predictors (stress/strain) to be the highest in the commissure regions of noncircular configurations such as EllipMajor (noncircular and under-expansion areas). Other clinically relevant performance aspects such as leaflet kinematics and coaptation were also investigated with the noncircular configurations. This study provides a framework for choosing the most challenging TAV deformations for acute and long-term valve performance in the design and testing phase of device development.

Trajectory-Assisted Source Apportionment of Winter-Time Aerosol Using Semi-continuous Measurements.

Receptor models, e.g., positive matrix factorization (PMF), are beneficial in designing effective control strategies to improve air quality. Additionally, integrating the trajectory analysis data into receptor modeling facilitates identifying the contributions from long-range transported aerosols. This study was conducted in Taipei City of Taiwan, a representative urban area with high population density, heavy traffic, and residential-commercial complexes. Hourly measurements were applied into an integrated trajectory-source apportionment approach. PMF was used to identify seven potential sources, including ammonium sulfate related, oil combustion, firework/firecracker, dust, vehicle, coal/marine, and industry/vehicle. Ammonium sulfate related source (33%) was characterized as the largest contributor, followed by coal/marine (18%) and industry/vehicle (16%). Through this integrated method, contribution estimates of the ammonium sulfate related factor from distant potential source regions were differentiated. Additionally, detailed distributions of source contributions to PM2.5 event periods were revealed by applying these highly time-resolved measurements.

[Relationship between long non-coding RNA MALAT1 and prostate cancer].

Prostate cancer (PCa), as a malignant tumor originating in the prostate glandular epithelium, has become a global "killer" that threatens the health of elderly men. PCa-related studies have been focusing on the progression mechanisms and treatment strategies of the malignancy, particularly on the role of long non-coding RNA (lncRNA) in recent years. The lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) plays a key role in the progression and treatment of PCa, as well as in its metastasis and invasion and cell proliferation. lncRNA MALAT1 not only influences the biological characteristics of PCa, but also has a regulatory effect on the medicinal treatment of the disease, its action mechanisms involving ceRNA and AR signaling pathways. This review focuses on the relationship between lncRNA MALAT1 and PCa, aiming to provide a new research direction for the diagnosis and treatment of the malignancy.

Accurate placement of cervical pedicle screws using 3D-printed navigational templates : An improved technique with continuous image registration.

OBJECTIVE: Accurate placement of cervical pedicle screws remains a surgical challenge. This study aimed to test the feasibility of using a novel three-dimensional (3D-)printed navigational template to overcome this challenge. METHODS: Cervical spines were scanned using computed tomography (CT). A 3D model of the cervical spines was created. The screw trajectory was designed to pass through the central axis of the pedicle. Thereafter, a navigational template was designed by removing the soft tissue from the bony surface in the 3D model. A 3D printer was used to print the navigational template. The screws were then placed in the cadavers following CT scanning. The 3D model of the designed trajectory and the placed screws were registered. The coordinates of the entry and exit points of the designed trajectory and the actual trajectory were recorded. The numbers of qualified points that met the different degrees of accuracy were compared using a χ2 test. RESULTS: A total of 158 screws were placed. Five screws breached the pedicle cortex with a distance <2 mm. There was no significant difference between the pre- and postoperative entry points with a degree of accuracy ≥1.7 mm (P = 0.131). Meanwhile, there was no significant difference between the pre- and postoperative exit points with degrees of accuracy ≥6.4 mm (P = 0.071). CONCLUSION: A navigational template can be designed by removing the soft tissue from the bony surface in a CT-generated 3D model. This guiding tool may effectively prevent intraoperative drifting and accurately places cervical pedicle screws.

A Novel Anterior Transpedicular Screw Artificial Vertebral Body System for Lower Cervical Spine Fixation: A Finite Element Study.

A finite element model was used to compare the biomechanical properties of a novel anterior transpedicular screw artificial vertebral body system (AVBS) with a conventional anterior screw plate system (ASPS) for fixation in the lower cervical spine. A model of the intact cervical spine (C3-C7) was established. AVBS or ASPS constructs were implanted between C4 and C6. The models were loaded in three-dimensional (3D) motion. The Von Mises stress distribution in the internal fixators was evaluated, as well as the range of motion (ROM) and facet joint force. The models were generated and analyzed by mimics, geomagic studio, and ansys software. The intact model of the lower cervical spine consisted of 286,382 elements. The model was validated against previously reported cadaveric experimental data. In the ASPS model, stress was concentrated at the connection between the screw and plate and the connection between the titanium mesh and adjacent vertebral body. In the AVBS model, stress was evenly distributed. Compared to the intact cervical spine model, the ROM of the whole specimen after fixation with both constructs is decreased by approximately 3 deg. ROM of adjacent segments is increased by approximately 5 deg. Facet joint force of the ASPS and AVBS models was higher than those of the intact cervical spine model, especially in extension and lateral bending. AVBS fixation represents a novel reconstruction approach for the lower cervical spine. AVBS provides better stability and lower risk for internal fixator failure compared with traditional ASPS fixation.

Application of a novel 3D drill template for cervical pedicle screw tunnel design: a cadaveric study.

PURPOSE: To develop and validate the efficacy and accuracy of a three-dimensional (3D) computed tomography (CT) reconstructive rapid prototyping drill template for cervical pedicle screw placement. METHODS: CT thin-layer scans were obtained from 12 adult cadaveric cervical specimens and reconstructed. The ideal screw channels were chosen by analyzing the cross sections of the reconstructed 3D images. The navigation templates were designed and printed based on the optimal screw channels. The pedicle screws were placed on the cadaver specimens under template guidance, and the cadaver specimens were scanned and reconstructed. The pre- and post-operative models were compared. Entry point and exit point data of these two models were collected and compared using the Chi-square test. RESULTS: A total of 164 cervical pedicle screws were placed; among them, six punctured the cortical bone of the vertebral pedicle reaching an accuracy of 96.3%. Among the outside screws, all of the deviation distances were <2 mm. The Chi-square test results showed that when a deviation of 1.2 mm was used as a standard for the entry point, there was no difference between the two groups (χ 2 = 1.346, p = 0.248); when a deviation of 2.2 mm was used as a standard for the exit point, there was no difference between the two groups (χ 2 = 3.250, p = 0.061). CONCLUSION: The 3D CT reconstructive rapid prototyping drill template combined with the screw tunnel design based on 3D cutting technique can help facilitate accurate cervical pedicle screw insertion.

Mortality risk attributable to high and low ambient temperature: a multicountry observational study.

BACKGROUND: Although studies have provided estimates of premature deaths attributable to either heat or cold in selected countries, none has so far offered a systematic assessment across the whole temperature range in populations exposed to different climates. We aimed to quantify the total mortality burden attributable to non-optimum ambient temperature, and the relative contributions from heat and cold and from moderate and extreme temperatures. METHODS: We collected data for 384 locations in Australia, Brazil, Canada, China, Italy, Japan, South Korea, Spain, Sweden, Taiwan, Thailand, UK, and USA. We fitted a standard time-series Poisson model for each location, controlling for trends and day of the week. We estimated temperature-mortality associations with a distributed lag non-linear model with 21 days of lag, and then pooled them in a multivariate metaregression that included country indicators and temperature average and range. We calculated attributable deaths for heat and cold, defined as temperatures above and below the optimum temperature, which corresponded to the point of minimum mortality, and for moderate and extreme temperatures, defined using cutoffs at the 2·5th and 97·5th temperature percentiles. FINDINGS: We analysed 74,225,200 deaths in various periods between 1985 and 2012. In total, 7·71% (95% empirical CI 7·43-7·91) of mortality was attributable to non-optimum temperature in the selected countries within the study period, with substantial differences between countries, ranging from 3·37% (3·06 to 3·63) in Thailand to 11·00% (9·29 to 12·47) in China. The temperature percentile of minimum mortality varied from roughly the 60th percentile in tropical areas to about the 80-90th percentile in temperate regions. More temperature-attributable deaths were caused by cold (7·29%, 7·02-7·49) than by heat (0·42%, 0·39-0·44). Extreme cold and hot temperatures were responsible for 0·86% (0·84-0·87) of total mortality. INTERPRETATION: Most of the temperature-related mortality burden was attributable to the contribution of cold. The effect of days of extreme temperature was substantially less than that attributable to milder but non-optimum weather. This evidence has important implications for the planning of public-health interventions to minimise the health consequences of adverse temperatures, and for predictions of future effect in climate-change scenarios. FUNDING: UK Medical Research Council.

Ambient air pollution and risk of tuberculosis: a cohort study.

OBJECTIVES: Several respirable hazards, including smoking and indoor air pollution from biomass, were suggested to increase the risk of tuberculosis. Few studies have been conducted on ambient air pollution and tuberculosis. We investigated the association between exposure to ambient air pollution and incidence of active tuberculosis. METHODS: We conducted a cohort study using 106,678 participants of a community-based screening service in Taiwan, 2005-2012. We estimated individual exposure to air pollution using data from the nearest air quality monitoring station and the road intensity within a 500 m buffer zone. The incidence of tuberculosis was ascertained from the national tuberculosis registry. RESULTS: After a median follow-up of 6.7 years, 418 cases of tuberculosis occurred. Exposure to fine particulate matter (PM2.5) was associated with increased risk of active tuberculosis (adjusted HR: 1.39/10 µg/m3 (95% CI 0.95 to 2.03)). In addition, traffic-related air pollution including nitrogen dioxide (adjusted HR: 1.33/10 ppb; 95% CI 1.04 to 1.70), nitrogen oxides (adjusted HR: 1.21/10 ppb; 95% CI 1.04 to 1.41) and carbon monoxide (adjusted HR: 1.89/ppm; 95% CI 0.78 to 4.58) was associated with tuberculosis risk. There was a non-significant trend between the length of major roads in the neighbourhood and culture-confirmed tuberculosis (adjusted HR: 1.04/km; 95% CI 0.995 to 1.09). CONCLUSIONS: Our study revealed a possible link between ambient air pollution and risk of active tuberculosis. Since people from developing countries continue to be exposed to high levels of ambient air pollution and to experience high rates of tuberculosis, the impact of worsening air pollution on global tuberculosis control warrants further investigation.

Age of asthma onset and vulnerability to ambient air pollution: an observational population-based study of adults from Southern Taiwan.

BACKGROUND: Late-onset asthma (onset > 12 years) is pathologically distinct from early-onset asthma. The mechanism of air pollution is not a classic allergic inflammation and could have differential effect on late-onset and early-onset asthma. However, there is little known about the association of onset-age phenotype and air pollution. In this population-based study, we aimed to determine the association of asthma severity outcomes and air pollution regarding age at onset of asthma. METHODS: In 2004, we conducted a cross-sectional questionnaire survey about respiratory health among schoolchildren's parents randomly selected from 94 of 816 elementary and middle schools in southern Taiwan. Participants ever having typical asthma symptoms were enrolled. We used kriging method to estimate individual exposure to ambient air pollution in the preceding year before the year of asthma severity survey. Ordered logistic regression was used to determine the association of exposure and asthma severity scores. Age at asthma onset of 12 years was used as a cut-off to define early- or late-onset asthma. RESULTS: The study surveyed 35,682 participants. Data from 23,551 participants remained satisfactory with a response rate of 66 %. Among 20,508 participants aged 26-50 years, 703 questionnaire-determined asthmatics were identified and included for analysis. Using the median of PM10 (66 µg/m(3)) as a cut-off, those exposed to higher PM10 were more likely to have higher severity scores (OR = 1.74; 95 % CI, 1.13 - 2.70) only for asthmatics with asthma onset at > 12 years. CONCLUSIONS: In adulthood, exposure to PM10 has a greater effect on late-onset asthma than early-onset asthma and deserves greater attention among ambient air pollutants.

[Digital design of internal fixation for distal femoral fractures via 3D printing and standard parts database].

OBJECTIVE: To study the method of internal fixation by the navigation embedded plate from standard parts database for the distal femoral fractures based on digital design by Mimics software with 3D printing technology, and to explore its feasibility and accuracy. METHODS: A total of 21 cases with distal femoral fractures admitted into the Department of Orthopedics, Affiliated Hospital of Putian University were included in this study. Dicom format data of lamellar CT scanning was imported into Mimics software for 3D anatomical modeling and virtual fracture reduction. The steel plates was chose from standard parts database for virtual internal fixation, and to design the navigation module with screw. 3D printing skeleton, steel plates, navigation module, internal fixation implants were simulated based on the printed bones model. Locations of steel plates and screws were determined by the navigation module. Then the sticking effects of navigation module, screws position and postoperative appearance were observed. After second CT scan and 3D reconstruction, 3D registration was performed to obtain the data of the three-dimensional coordinate values of screws entrance points and piercing points to analyze the results. RESULTS: A total of 21 plates and 180 screws were placed with the assistance of navigation module. CT scanning and 3D reconstruction was performed in twenty-one cases of postoperative bone model. The position of plates was in high accordance with the digital design by Mimics software. There were no significant differences between spatial location of screw entrance points and piercing points. The real operation was quite consistent with preoperative design. Navigation module and the corresponding distal femur bony structure jointed closely. The sticking effects and stability of navigation module were good, which was able to guide placement of steel plates and screws. CONCLUSION: These methods can enhance the accuracy of internal fixation of the standard parts database steel plate in distal femur fractures, with the assistance of navigation module.

A land use regression model for estimating the NO2 concentration in Shanghai, China.

Limited by data accessibility, few exposure assessment studies of air pollutants have been conducted in China. There is an urgent need to develop models for assessing the intra-urban concentration of key air pollutants in Chinese cities. In this study, a land use regression (LUR) model was established to estimate NO2 during 2008-2011 in Shanghai. Four predictor variables were left in the final LUR model: the length of major road within the 2-km buffer around monitoring sites, the number of industrial sources (excluding power plants) within a 10-km buffer, the agricultural land area within a 5-km buffer, and the population counts. The model R(2) and the leave-one-out-cross-validation (LOOCV) R(2) of the NO2 LUR models were 0.82 and 0.75, respectively. The prediction surface of the NO2 concentration based on the LUR model was of high spatial resolution. The 1-year predicted concentration based on the ratio and the difference methods fitted well with the measured NO2 concentration. The LUR model of NO2 outperformed the kriging and inverse distance weighed (IDW) interpolation methods in Shanghai. Our findings suggest that the LUR model may provide a cost-effective method of air pollution exposure assessment in a developing country.

Different Severity and Severity Predictors in Early-Onset and Late-Onset Asthma: A Taiwanese Population-Based Study.

BACKGROUND: Late-onset asthma has been shown to be more severe than early-onset asthma in clinic-based studies. However, population-based studies are scarce, and the predictors of severity have been less studied. OBJECTIVES: To determine asthma severity and severity predictors regarding age at onset. METHODS: A cross-sectional questionnaire survey was conducted among parents of children from 94 schools in Taiwan in 2004. Asthma severity was defined as short-acting ß2-agonist (SABA), inhaled corticosteroid (ICS) and health care use in the last year. Information on age at onset, demographics, heredity and home exposure was collected. Ordered logistic or logistic regression was used for determining the associations between risk factors and severity. RESULTS: Participants aged 26-50 years were included, resulting in 21,057 (67.8%) participants. Among them, 449 reported ever having had physician-diagnosed asthma, and 381 of those subjects answered the question on age at asthma onset. The risks of rescue SABA, ICS and health care use were generally higher among late-onset (13-50 years) than early-onset (0-12 years) asthmatics. Use of SABA and health care increased from childhood-onset, adolescent- or young adult-onset to adult-onset asthma. Allergic rhinitis was positively associated with SABA use (OR, 9.08; 95% CI, 1.06-77.99) and ICS use (OR, 5.08; 95% CI, 1.47-17.52) in early-onset asthma. Dehumidifier use was negatively associated with SABA use (OR, 0.50; 95% CI, 0.29-0.87) and ICS use (OR, 0.38; 95% CI, 0.19-0.78) in late-onset asthma. CONCLUSIONS: In adults, late-onset asthma was more severe than early-onset asthma. Severity, as indicated by SABA and ICS use, was positively associated with allergic rhinitis in early-onset asthma and negatively associated with dehumidifier use in late-onset asthma.

Global variation in the effects of ambient temperature on mortality: a systematic evaluation.

BACKGROUND: Studies have examined the effects of temperature on mortality in a single city, country, or region. However, less evidence is available on the variation in the associations between temperature and mortality in multiple countries, analyzed simultaneously. METHODS: We obtained daily data on temperature and mortality in 306 communities from 12 countries/regions (Australia, Brazil, Thailand, China, Taiwan, Korea, Japan, Italy, Spain, United Kingdom, United States, and Canada). Two-stage analyses were used to assess the nonlinear and delayed relation between temperature and mortality. In the first stage, a Poisson regression allowing overdispersion with distributed lag nonlinear model was used to estimate the community-specific temperature-mortality relation. In the second stage, a multivariate meta-analysis was used to pool the nonlinear and delayed effects of ambient temperature at the national level, in each country. RESULTS: The temperatures associated with the lowest mortality were around the 75th percentile of temperature in all the countries/regions, ranging from 66th (Taiwan) to 80th (UK) percentiles. The estimated effects of cold and hot temperatures on mortality varied by community and country. Meta-analysis results show that both cold and hot temperatures increased the risk of mortality in all the countries/regions. Cold effects were delayed and lasted for many days, whereas heat effects appeared quickly and did not last long. CONCLUSIONS: People have some ability to adapt to their local climate type, but both cold and hot temperatures are still associated with increased risk of mortality. Public health strategies to alleviate the impact of ambient temperatures are important, in particular in the context of climate change.

Asthma incidence, remission, relapse and persistence: a population-based study in southern Taiwan.

BACKGROUND: In western countries, late-onset asthmatics are more severe than early-onset asthmatics in clinic-based studies. However, whether asthma occurrence rates were higher in late ages than in younger ages was inconclusive. This information is essentially lacking in Asian population. METHODS: The participants were schoolchildren's parents recruited from 94 elementary and middle schools in 2004. A cross-sectional self-administered questionnaire was sent through the children to their parents to survey their respiratory health. We investigated typical asthma symptoms occurring at different ages and subsequent remission or relapse after the first asthma event. Person-years of the participants from birth to the time of survey were used as the denominator. RESULTS: Among the 25,377 participants consisting of 949,807 total person-years, 860 reported ever having asthma. Highest incidences occurred at ages 0-12 and 36-40 years. The incidence of asthma was higher in males before puberty, and higher in females after puberty, with overall incidences 1.00 and 0.77 per 1000 person-years for females and males, respectively. Participants with late-onset asthma (onset age >12 years) comprised a large portion of adult current asthmatics. More than 52% of persistence or relapse was observed in early-onset asthma (onset age ≤12 years). The younger birth cohort had a more prominent later peak of asthma incidence than the older one. CONCLUSIONS: In Asian population, asthma occurrence showed a U-shape age distribution with a prominent second peak in the thirties. A high proportion of early-onset asthma relapsed and most of late-onset asthma persisted or relapsed in adulthood.

Modeling horizontal and vertical variation in intraurban exposure to PM2.5 concentrations and compositions.

Land use regression (LUR) models are increasingly used to evaluate intraurban variability in population exposure to fine particulate matter (PM2.5). However, most of these models lack information on PM2.5 elemental compositions and vertically distributed samples. The purpose of this study was to evaluate intraurban exposure to PM2.5 concentrations and compositions for populations in an Asian city using LUR models, with special emphasis on examining the effects of having measurements on different building stories. PM2.5 samples were collected at 20 sampling sites below the third story (low-level sites). Additional vertically stratified sampling sites were set up on the fourth to sixth (mid-level sites, n=5) and seventh to ninth (high-level sites, n=5) stories. LUR models were built for PM2.5, copper (Cu), iron (Fe), potassium (K), manganese (Mn), nickel (Ni), sulfur (S), silicon (Si), and zinc (Zn). The explained concentration variance (R(2)) of the PM2.5 model was 65%. R(2) values were >69% in the Cu, Fe, Mn, Ni, Si, and Zn models and <44% in the K and S models. Sampling height from ground level was a significant predictor in the PM2.5 and Si models. This finding stresses the importance of collecting vertically stratified information on PM2.5 mass concentrations to reduce potential exposure misclassification in future health studies. In addition to traffic variables, some models identified gravel-plant, industrial, and port variables with large buffer zones as important predictors, indicating that PM from these sources had significant effects at distant places.

A biomechanical study to evaluate the effect of PMMA augmentation and restoration of the strength of cervical vertebral screws inserted in an osteoporotic vertebral body.

STUDY DESIGN: An experimental study. OBJECTIVE: To compare the peak pull-out force (PPF) of vertebral screws fixed in osteoporotic vertebrae versus polymethylmethacrylate (PMMA) used for augmentation or restoration, before and after fatigue. SUMMARY OF BACKGROUND DATA: Failure of screw fixation in anterior cervical interbody fusion remains a significant clinical problem. However, little is known of the biomechanical characteristics of cervical vertebral screws before and after restoration or augmentation, especially after fatigue. METHODS: Fifty fresh cervical vertebrae, of which 40 were randomly selected, from 12 adult cadavers were used. The vertebrae were divided into healthy controls, osteoporotic controls, a PMMA restoration group, and a PMMA augmentation group. In each of the control groups, 2 pilot holes on each side of 20 vertebral bodies were implanted with vertebral screws (4 mm in diameter). Each side randomly received either acute PPF or PPF beyond fatigue that was ensured using cyclic loading (2 Hz; 20,000 times). In the PMMA groups, pilot holes were drilled parallel to the sagittal plane and injected with 0.6-1.0 mL PMMA before the vertebral screw was inserted. Each side of each vertebral body randomly received either PPF or PPF beyond fatigue that was ensured using cyclic loading (2 Hz; 20,000 times). A Bose3510-AT fatigue testing machine measured the PPF of vertebral screws with or without PMMA for all specimens before and after fatigue. RESULTS: In all groups, the prefatigue PPF was significantly higher than the postfatigue PPF. Compared with the prefatigue PPF, postfatigue PPF was reduced by 37.40%, 43.10%, 32.08%, and 31.85% in the healthy controls, osteoporotic controls, PMMA restoration, and PMMA augmentation groups, respectively. The acute and postfatigue PPFs of the healthy controls were significantly higher from that of the osteoporotic controls. The acute and postfatigue PPFs of both control groups were significantly lower from that of both PMMA groups. There was no difference in acute and postfatigue PPFs between the PMMA restoration and augmentation groups. CONCLUSIONS: The results indicated that both PMMA augmentation and PMMA restoration could significantly increase cervical screw pull-out strength and antifatigue capability. The results provide a biomechanical justification for spine surgeons to use PMMA for augmentation or restoration in cases of surgeries with poor bone quality or osteoporotic vertebral bodies.