Two-year cost comparison of vertebroplasty and kyphoplasty for the treatment of vertebral compression fractures: are initial surgical costs misleading?

The costs for treating kypho- and vertebroplasty patients were evaluated at up to 2 years postsurgery. There were no significant differences in adjusted costs in the first 9 months postsurgery, but kyphoplasty patients were associated with significantly lower adjusted treatment costs by 6.8-7.9% in the remaining periods through 2 years postsurgery.

INTRODUCTION

Vertebral augmentation has been shown to be safe and effective for treating vertebral compression fractures. Comparative cost studies of initial treatment costs for kypho- and vertebroplasty have been mixed. The purpose of our study was to compare the costs for treating kypho- and vertebroplasty patients at up to 2 years postsurgery.

METHODS

Vertebroplasty and kyphoplasty patients diagnosed with pathologic or closed lumbar/thoracic vertebral fractures were identified from the 5% sample of the Medicare dataset (2006-2009). The final study cohort with at least 2 years follow-up comprised of 1,609 vertebroplasty and 2,878 kyphoplasty patients. The cumulative treatment costs (adjusted to June 2011 US$) were determined from the payer perspective. Differences in costs and length of stay were assessed by generalized linear mixed model regression, adjusting for covariates.

RESULTS

The average adjusted costs for vertebroplasty patients within the first quarter and the first 2 years postsurgery were $14,585 [95% confidence interval (CI), $14,109-15,078] and $44,496 (95% CI, $42,763-46,299), respectively. The corresponding average adjusted costs for kyphoplasty patients were $15,117 (95% CI, $14,752-15,491) and $41,339 (95% CI, $40,154-42,560). There were no significant differences in adjusted costs in the first 9 months postsurgery, but kyphoplasty patients were associated with significantly lower adjusted treatment costs by 6.8-7.9% in the remaining periods through 2 years postsurgery.

CONCLUSION

Our present study addresses some of the limitations in previous comparative cost studies of vertebroplasty and kyphoplasty. The higher adjusted costs for vertebroplasty patients than kyphoplasty patients by 1 year following the surgery reflect greater utilization of medical resources.

Life expectancy following diagnosis of a vertebral compression fracture

SUMMARY

The life expectancy of vertebral compression fracture (VCF) patients was evaluated as a function of their treatment. Compared to non-operated patients, the kyphoplasty and vertebroplasty patient cohort had 115% and 44% greater adjusted life expectancy, respectively. Kyphoplasty patients had a 34% greater adjusted life expectancy than vertebroplasty patients.

INTRODUCTION

Balloon kyphoplasty and vertebroplasty are minimally invasive procedures for the treatment of painful VCFs. This comparative effectiveness study characterized the life expectancy of VCF patients as a function of their treatment.

METHODS

Life expectancy of VCF patients in the 100% U.S. Medicare dataset (2005-2008) was estimated using a parametric Weibull survival model (adjusted for comorbidities), and compared between operated and non-operated patients as well as between kyphoplasty and vertebroplasty patients. A total of 858,978 patients with a newly diagnosed VCF were identified, including 119,253 kyphoplasty patients (13.9%) and 63,693 vertebroplasty patients (7.4%).

RESULTS

Adjusted life expectancy was 85% greater for operated than non-operated patients (p < 0.001; 95% confidence interval: 82-89%). Compared to non-operated patients, the kyphoplasty and vertebroplasty patient cohort had 115% (p < 0.001; 95% confidence interval: 111-119%) and 44% (p < 0.001; 95% confidence interval: 42-47%) greater adjusted life expectancy, respectively. Kyphoplasty patients had a 34% greater adjusted life expectancy than vertebroplasty patients (p < 0.001; 95% confidence interval: 31-36%). Across all gender-age groups, the median life expectancy predicted by the parametric Weibull model was 2.2-7.3 years greater for operated than non-operated patients.

CONCLUSIONS

Statistically significant and substantial differences in life expectancy were observed between the treated and non-treated cohorts in the Medicare population. Among the treated cohorts, patients in the vertebroplasty group experienced less of a survival benefit than those who received kyphoplasty. The results will be a useful basis for future cost effectiveness studies of VCF treatments for the Medicare population.

First Report of Leaf Spot of Sesame Caused by Xanthomonas sp. In the United States

In July 2010 in Texas, extensive leaf spots (10 to 30% leaf area affected) occurred on a commercial planting of sesame (Sesamum indicum L.) in Hidalgo County and to a lesser extent (1 to 5% leaf area) on leaves of several varieties in experimental trials in Colorado and Victoria Counties. The leaf spots were light to dark brown, somewhat circular, and 1 to 3 mm in diameter. A symptomatic leaf from each of three to five plants per county was sampled for isolations. Leaves were sprayed with 70% ethanol and immediately blotted dry with a paper towel. The margins of spots (2 mm²) were excised with a scalpel and placed in a drop of sterile water for 5 min. Drops were streaked on nutrient agar (NA) and incubated at 30°C. The 12 isolations consistently yielded gram-negative, rod-shaped bacteria with yellow, translucent colonies that were visible after 2 days of incubation. The DNA of 11 isolates was extracted with the Norgen (Thorold, ON) Bacterial genomic DNA isolation kit (Cat. #17900) and the ITS region was amplified by 16S uni 1330 and 23S uni 322 anti primers (1). PCR products were treated with the ZymoResearch (Irvine, CA) DNA clean & concentrator kit (Cat. #D4003) and sequenced. With the NCBI database, a BLAST search of the 1,100 bp amplicons showed 93 to 99% identity with pathovars of either Xanthomonas oryzae or X. axonopodis (GenBank Accession Nos. CP003057.1 and CP002914.1, respectively). Amplicon sequences of the sesame isolates were deposited in GenBank as Accession Nos. JQ975037 through JQ975047. The reported species on sesame is X. campestris pv. sesami (2). To fulfill Koch's postulates, potted sesame plants (var. Sesaco 25), 15 to 20 cm tall, were sprayed until runoff with a suspension of bacteria (10⁶ to 10⁷ CFU/ml) from a 2-day-old NA culture. All 12 isolates were evaluated, with five to seven plants per isolate. Plants were maintained in a mist chamber in a greenhouse at 27 to 30°C and 100% relative humidity. The pathogenicity trial was repeated once. Leaf spots were first seen 7 days after inoculation and were prevalent 14 days after inoculation. All 12 isolates were pathogenic. There were no symptoms on leaves sprayed with sterile water. Bacteria that produced colonies consistent with Xanthomonas were reisolated on NA from symptomatic leaves but not from controls. The identities of three isolates were reconfirmed with PCR analysis and sequencing. In 2007, more than 2,000 ha of sesame were grown in the continental United States, with 80% of that in Texas. Currently, acreage of shatter-free varieties of sesame is increasing in arid areas of Texas, Oklahoma, and Kansas. In such areas, the yield impact of this disease is likely to be minimal, except in years with above-average rainfall. To our knowledge, this is the first report of this disease in the United States. References: (1) E. R. Gonçalves and Y. B. Rosato. Int. J. Syst. Evol. Microbiol. 52:355, 2002. (2) J. M. Young et al., New Zealand J. Agric. Res. 21:153, 1978.

Plasma concentration of pigment epithelium-derived factor is closely associated with blood pressure and predicts incident hypertension in Chinese: a 10-year prospective study

OBJECTIVES

Pigment epithelium-derived factor (PEDF) is secreted from the adipose tissue. It circulates at high concentrations, and was reported to play a causal role in obesity-induced insulin resistance and metabolic dysfunctions in mice. Previous cross-sectional studies also demonstrated plasma PEDF concentration correlated positively with systolic blood pressure (BP) and pulse pressure, and inversely with small artery elasticity. Here we investigated the relationship of plasma PEDF concentration with BP and incident hypertension in a 10-year prospective study.

METHODS

Baseline plasma PEDF concentrations were measured by ELISA in 520 Chinese subjects, aged 51 ± 12 years, followed up long-term from the population-based Hong Kong Cardiovascular Risk Factor Prevalence Study. The association between plasma PEDF concentration and BP was investigated in both cross-sectional and prospective studies, using multiple linear regression and path analyses. Cox proportional hazards analysis was used to determine whether baseline PEDF concentration was independently related to the subsequent development of hypertension over 10 years.

RESULTS

Baseline plasma concentrations of PEDF were higher in men (P < 0·001), and were directly related to systolic BP at 2 and 5 years, and to diastolic BP at 2 years, after adjustment for covariates. Of the 386 normotensive subjects at baseline, high baseline PEDF concentration was predictive of incident hypertension, independent of the effects of age, sex, baseline BP and obesity parameters (hazard ratio: 1·135; 95% CI: 1·039-1·241; P = 0·005).

CONCLUSION

Our data suggest that plasma PEDF concentration is significantly associated with BP, and incident hypertension. PEDF may be involved in the pathogenesis of hypertension in humans.

Prevalence of BRCA1 mutations in women with triple-negative breast cancer: A systematic review

181

Background: We have reported a strong association between “triple-negative” breast cancer (TNBC) [estrogen receptor (ER) and progesterone receptor (PR) negative, HER2 negative] and the risk of having BRCA1 mutations in a meta-analysis. We hereby present a systematic review of a larger pool of specific data investigating the overall prevalence of BRCA1 mutations in women with TNBC.

Methods: A Medline search combining the MeSH terms “BRCA” and “triple” and “negative” yielded 37 articles. A similar search in ASCO abstracts yielded 18 relevant articles. Prevalence in each study population as well as the overall prevalence was calculated.

Results: 13 eligible studies (from year 2006 to 2011) including 1075 women with TNBC were identified. Out of 13, 1 study each was carried out on Ashkenazi Jewish and Hong Kong Chinese women respectively. Overall prevalence of BRCA1 mutations in women with TNBC is 20.93% (225 out of 1075) (range = 4.8%–43%). Ashkenazi Jewish women with TNBC have a higher-than-average prevalence of BRCA1 mutations (29.2%) although it is lower than the prevalence rates of some study populations. A remarkably low prevalence rate of BRCA1 mutations (4.8%) is found in Chinese women with TNBC.

Conclusions: In view of the overall high prevalence rate of BRCA1 mutations (20.93%) in women with TNBC, genetic testing should be discussed with patients with TNBC. Further studies are suggested to evaluate the molecular basis of interestingly low BRCA1 prevalence (4.8%) in Chinese patients with TNBC.

Risk of having BRCA mutations in women with triple-negative breast cancer: A systematic review and meta-analysis

160

Background: Increased prevalence of BRCA1 mutations (BRCA1) has been associated with the occurrence of triple-negative breast cancer (TNBC) (estrogen receptor [ER]- and progesterone receptor [PR]-negative, HER2-negative) in independent clinical studies. However, BRCA2 mutation (BRCA2) has not been found to overrepresent in women with TNBC. We have performed a meta-analysis of these studies to provide further statistical evidence of the association between BRCA positivity and TNBC.

Methods: A Medline search of the MeSH terms “BRCA”, “triple”, and “negative” yielded 37 articles. A search of ASCO abstracts yielded 18 relevant articles. Random effects model was used for analysis due to heterogeneity among the proportions of included studies (Cochran’s Q = 18.52 and 15.18, tau2 = 0.61 and 1.29, I2 = 73% and 80% for BRCA1 and BRCA2 respectively). Mantel-Haenszel method was applied to calculate the pooled event-based odds ratio (OR) with 95% confidence interval (CI).

Results: 6 studies including 1,602 BC patients were eligible for analysis of BRCA1 and 4 studies including 1297 BC patients for BRCA2. 172 patients with BRCA1 mutations and 79 patients with BRCA2 mutations were analyzed. Among these 6 studies, 1 included Ashkenazi Jewish women exclusively and 1 included only women of Chinese descent. The overall prevalence of BRCA1 was 10.05% (172 out of 1,602), and for TNBC patients 21.94% (95 out of 433) with an odds ratio of 5.90 (CI: 2.75, 12.66, p < 0.00001). TNBC was not a risk for BRCA2 (OR = 0.67, CI: 0.19, 2.39, p = 0.53). Chinese women with TNBC did not have an elevated risk of BRCA1 (OR = 0.94, CI: 0.24, 3.66) in contrast to Jewish women with TNBC who had the highest risk of BRCA1 among the populations studied (OR = 21.79, CI: 9.03, 52.55).

Conclusions: Women with TNBC carry a significantly high risk of having BRCA1 but not BRCA2 mutations. We recommend genetic testing for BRCA1 mutations in women with TNBC especially in Ashkenazi Jewish population. Further studies on Chinese population are needed to further establish the relationship between TNBC and BRCA1 mutations in this cohort.

Child health, developmental plasticity, and epigenetic programming

Plasticity in developmental programming has evolved in order to provide the best chances of survival and reproductive success to the organism under changing environments. Environmental conditions that are experienced in early life can profoundly influence human biology and long-term health. Developmental origins of health and disease and life-history transitions are purported to use placental, nutritional, and endocrine cues for setting long-term biological, mental, and behavioral strategies in response to local ecological and/or social conditions. The window of developmental plasticity extends from preconception to early childhood and involves epigenetic responses to environmental changes, which exert their effects during life-history phase transitions. These epigenetic responses influence development, cell- and tissue-specific gene expression, and sexual dimorphism, and, in exceptional cases, could be transmitted transgenerationally. Translational epigenetic research in child health is a reiterative process that ranges from research in the basic sciences, preclinical research, and pediatric clinical research. Identifying the epigenetic consequences of fetal programming creates potential applications in clinical practice: the development of epigenetic biomarkers for early diagnosis of disease, the ability to identify susceptible individuals at risk for adult diseases, and the development of novel preventive and curative measures that are based on diet and/or novel epigenetic drugs.

Genetic variants associated with persistent central obesity and the metabolic syndrome in a 12-year longitudinal study

OBJECTIVE

Central obesity predisposes to various cardiometabolic diseases and is a key component of the metabolic syndrome (MetS). We have previously demonstrated that three obesity-susceptible single nucleotide polymorphisms (SNPs), rs10938397 (GNPDA2), rs8050136 (FTO) and rs17782313 (MC4R), were associated with obesity and waist circumference in cross-sectional studies in the Chinese population. In this study, we investigate whether these SNPs could also predict the persistence of central obesity and MetS in subjects from the Hong Kong Cardiovascular Risk Factors Prevalence Study (CRISPS) cohort.

DESIGN AND METHODS

We genotyped these SNPs in i) 354 subjects with and 994 subjects without central obesity at both baseline and a 12-year follow-up, ii) 2214 subjects (816 cases and 1398 controls) in an MetS cross-sectional case-control study and iii) 225 subjects with and 1221 subjects without MetS at both baseline and the 12-year follow-up.

RESULTS

Both FTO rs8050136 (P(age, sex-adjusted)=0.019; odds ratio (OR) (95% confidence intervals (CI)): 1.35 (1.05, 1.73)) and GNPDA2 rs10938397 (P(age, sex-adjusted)=3 × 10(-3); OR (95% CI): 1.34 (1.11, 1.63)) were significantly associated with persistent central obesity. GNPDA2 rs10938397 was also significantly associated with MetS (P(age, sex-adjusted)=0.011, OR (95% CI): 1.20 (1.04, 1.38)) in the case-control study. However, none of these SNPs showed an individual association with persistent MetS. In the combined genetic risk analyses for persistent central obesity and persistent MetS, the combined genetic risk score of the three SNPs showed an OR of 1.25 (95% CI: 1.10, 1.42; P(age, sex-adjusted)=4.92 × 10(-3)) and 1.19 (95% CI: 1.03, 1.38; P(age, sex-adjusted)=0.019) for each additional risk allele respectively.

CONCLUSION

This study demonstrated that FTO and GNPDA2 variants predicted persistent central obesity in the Chinese population, further supporting their importance as obesity-susceptible genes.

First Report of Stemphylium botryosum on Spinach in Texas

During the 2009 to 2010 growing season, symptoms of an unknown leaf spot were observed on spinach (Spinacia oleracea L.) in production fields in southwest Texas. Approximately 500 ha were affected, especially cvs. Rakaia and Viceroy. Disease incidence was 30 and 2% for Rakaia and Viceroy, respectively. Diseased plants exhibited small (1 to 3 mm in diameter), tan, necrotic lesions with a circular to oval shape and were void of any signs of a pathogen. Symptomatic leaves were surface sterilized in 1.5% NaOCl for 1 min, rinsed with sterile water, and air dried. Leaf sections (~1 cm²) were cut and placed on acidified potato dextrose agar (APDA), or APDA supplemented with streptomycin (SAPDA). Fungal mycelia growing from the edges of infected leaf sections were transferred to PDA and incubated at 25°C with a 12-h/12-h light/dark cycle. After 14 days of incubation, dark brown mycelia giving rise to unbranched conidiophores bearing brown, deeply septate, ovoid conidia were observed. Conidia measured 16.8 to 27.3 × 13.1 to 19.6 μm. On the basis of these morphological characteristics, the fungus was identified as Stemphylium botryosum (3). Cultures were transferred to clarified V8 juice agar to obtain inoculum for pathogenicity tests. Eight-week-old plants (n = 20) of spinach cvs. Hybrid 310, Wintergreen, Ashley, and Rakaia were sprayed until runoff with a suspension containing 0.001% Tween 80 and 1 × 10⁴ conidia/ml. Noninoculated plants served as a control treatment. Plants were placed in a growth chamber and incubated in the dark at 25°C and 95% relative humidity. Following 36 h of incubation, plants were transferred to a plastic enclosure and maintained at 23 ± 4°C. After 7 to 10 days, tan, oval-shaped lesions were observed on all inoculated spinach plants. All control plants, with the exception of Rakaia, failed to develop symptoms. Isolates of S. botryosum were recovered on SAPDA from symptomatic leaves, confirming Koch's postulates. Previous reports have shown that S. botryosum can be transmitted from infected seed (1), thus, additional plants of each cultivar (n = 36) were grown in the greenhouse to determine the potential for seedborne contamination. After 8 weeks, leaf spot symptoms identical to those observed on the original plants developed on 75% of the Rakaia plants, while symptom development on the other cultivars was negligible. Isolates of S. botryosum were only recovered from symptomatic Rakaia leaves. Similar field observations were made during the 2001 to 2002 growing season; however, attempts to isolate S. botryosum in that season were unsuccessful. Recent outbreaks of Stemphylium leaf spot have been reported in Arizona (4), California (3), Delaware and Maryland (2), and Washington (1). To our knowledge, this is the first report of S. botryosum on spinach in Texas. While the origin of inoculum causing the disease in Texas is unknown, S. botryosum may have been seedborne (2). The implementation within the past few years of very high density plantings of spinach (1.9 to 3.7 million seeds/ha) may lead to an increase in incidence and severity of this disease in Texas. References: (1) L. J. du Toit and M. L. Derie. Plant Dis. 85:920, 2001. (2) K. L. Everts and D. K. Armentrout. Plant Dis. 85:1209, 2001. (3) S. T. Koike et al. Plant Dis. 85:126, 2001. (4) S. T. Koike et al. Plant Dis. 89:1359, 2005.

Plasma level of pigment epithelium-derived factor is independently associated with the development of the metabolic syndrome in Chinese men: a 10-year prospective study

OBJECTIVE

Pigment epithelium-derived factor (PEDF), a serine protease inhibitor, is secreted from the adipose tissue and circulates at high concentrations. A recent study found that PEDF played a causal role in obesity-induced insulin resistance and metabolic dysfunctions in mice. Here we investigated whether circulating PEDF levels predicted the development of the metabolic syndrome (MetS) in a 10-yr prospective study.

RESEARCH DESIGN AND METHODS

Baseline plasma PEDF levels were measured with an ELISA in 520 nondiabetic subjects, recruited from the Hong Kong Cardiovascular Risk Factor Prevalence Study cohort. Multiple logistic regression was used to analyze whether PEDF was an independent factor related to the MetS at baseline. The role of PEDF in predicting the development of the MetS over 10 yr was analyzed using Cox regression analysis.

RESULTS

Plasma levels of PEDF were significantly higher in men than women. At baseline, sex-adjusted PEDF levels were significantly higher in subjects with MetS (P < 0.001), and the association remained significant (odds ratio: 1.17, P = 0.015), even after adjustment for covariates. Among the components of the MetS, PEDF was independently associated with hypertriglyceridemia (P = 0.026) and hypertension (P = 0.005). Of the 396 subjects without the MetS at baseline, a total of 80 had developed the MetS over 10 yr. High baseline sex-adjusted PEDF was an independent predictor of the development of the MetS in men (hazard ratio: 1.25, P = 0.034) but not in women.

CONCLUSION

Plasma PEDF was significantly associated with the presence of the MetS and predicted the development of the MetS in Chinese men.

An unusual case of knee locking

Knee locking is an incapacitating condition that requires urgent orthopaedic intervention. The most common cause is meniscal injury, followed by torn anterior cruciate ligament, osteochondral loose bodies and foreign bodies in the joint space. This report describes a patient who had an unusual case of left knee locking. After clinical examination and radiological investigations, the provisional diagnosis was a lateral meniscal tear, which was not visible on magnetic resonance imaging. Diagnostic arthroscopy of the left knee revealed a 1-cm yellowish lump on the medial meniscus, and the histology revealed pigmented villonodular synovitis. The menisci and cruciate ligaments were intact.

Obesity susceptibility genetic variants identified from recent genome-wide association studies: implications in a chinese population

CONTEXT

Recent large-scale genome-wide association studies identified novel genetic variants associated with obesity and body mass index (BMI) in addition to the well-described FTO and MC4R genetic variants.

OBJECTIVE

This study aimed to examine 13 previously reported obesity and/or BMI-associated loci for associations with obesity in Chinese.

DESIGN AND STUDY PARTICIPANTS

This was a cross-sectional case-control study in 470 obese cases (BMI > or =27.5 kg/m(2)) and 700 normal-weight controls (18.5 < or = BMI < or = 23.0 kg/m(2)).

RESULTS

A significant association with obesity could be replicated (one tailed P < 0.05) in seven of the 13 single-nucleotide polymorphisms (SNPs) in the case-control study. These included GNPDA2 rs10938397 (P = 7.3 x 10(-4)); FTO rs8050136 (P = 8 x 10(-4)); MC4R rs17782313 (P = 1.2 x 10(-3)); KCTD15 rs29941 (P = 8 x 10(-3)); SFRS10-ETV5-DGKG rs7647305 (P = 0.023); SEC16B-RASAL2 rs10913469 (P = 0.041); and NEGR1 rs3101336 (P = 0.046). Combined genetic risk scores were calculated, and we observed ORs ranging from 1.17 to 1.23 for each unit increase in the genetic risk scores. Associations with obesity-related quantitative traits were analyzed separately for cases and controls. KCTD15 SNP rs29941 (P = 1 x 10(-3)) was significantly associated with fasting glucose in the control group, whereas only the FTO SNP rs8050136 was associated with BMI (P = 3.5 x 10(-3)) in the obese group. However, in an extension study of 1938 subjects from the population-based Hong Kong Cardiovascular Risk Factors Prevalence Study, rs8050136, rs10938397, and rs17782313 showed significant associations with BMI.

CONCLUSION

We have succeeded in replicating, in a Chinese population, the associations with obesity in seven SNPs reported in recent genome-wide association studies. Further functional and fine-mapping studies to elucidate the roles of these putative obesity-related genes and genetic variants are warranted.

Metabolism, nitrogen excretion, and heat shock proteins in the central mudminnow (Umbra limi), a facultative air-breathing fish living in a variable environment

The central mudminnow ( Umbra limi (Kirtland, 1841)) is a continuous, facultative air-breathing freshwater fish found in swamps of central Canada and northeastern USA. The first goal of this field and laboratory-based study was to characterize the physicochemical conditions of mudminnow habitat during the summer. Our second goal was to determine the metabolic, stress response, and nitrogen excretion strategies of this fish following variations in water temperature, dissolved oxygen, external ammonia, and short-term periods of air exposure. We report profound diurnal fluctuations in water temperature (13–31 °C), dissolved oxygen (2%–159% air saturation), and ammonia levels (10–240 μmol·L−1) in habitat of central mudminnow measured on three dates at six different sites over 24 h. The central mudminnow does not induce urea synthesis as a mechanism of ammonia detoxification, either in response to emersion (6 or 20 h) or elevated external ammonia (10 mmol·L–1). Acute exposure to high temperature (~31 °C), aquatic hypoxia, or air resulted in significant increases in blood glucose and liver heat shock protein (Hsp) 70 and hypoxia also caused an increased reliance on anaerobic metabolism. This is the first description of the heat shock response in a facultative air-breathing fish following either hypoxia or air exposure. These metabolic and molecular responses are part of a strategy that allows the mudminnow to thrive in extremely variable freshwater environments.

Application of Magnetoelastic Thick Films for Wireless, In Vivo Monitoring of Pressure at Abdominal Aortic Aneurysm

According to the National Center for Health Statistics, cardiovascular diseases remain the number one killer in the United States. Among the various types of cardiovascular diseases, the aortic aneurysm is ranked number nine. The abdominal aortic aneurysm (AAA), in particular, is an abnormal, localized dilation of the abdominal aorta wall caused by weakened or diseased aorta walls. One of the treatments for this disease is using an endovascular surgery at which an endovascular graft is delivered to the aneurysm site through the femoral arteries. The deployment of the endovascular graft will exclude blood flow to the aneurysm, thus preventing further expansion of the aneurysm sac. Although this technique is preferred over open surgeries due to its minimal invasiveness, an event known as the endoleak, where the endovascular graft fails to retain the blood and leads to leakage to the aneurysm sac, may occur. Here, we are developing a novel pressure monitoring system to remotely and continuously measure the pressure in the aneurysm sac. The main component of the system is a pressure-sensitive material, made of a magnetoelastic, magnetically soft film attached or coated on the endovascular graft. When under an AC magnetic field (excitation field), the magnetoelastic film generates a secondary magnetic field. Due to its magnetoelastic property, the amplitude of the secondary field varies with applied stresses, allowing remote pressure monitoring. To eliminate noises from the excitation field, the generated secondary field is measured at twice the excitation frequency to obtain the 2nd-order harmonic field, which is used for tracking the pressure variations. A scaled-up prototype of the pressure monitoring system was constructed and examined to demonstrate the feasibility of this technology. A commercial magnetoelastic thick film, Metglas 2826MB from Metglas, Inc., was attached on a polycarbonate substrate and covered by a thin polycarbonate protective layer. The substrate was then embedded in a plastic tube with flowing liquid to represent the condition of an aorta. Liquid pressure in the tube was altered during the experiment by restricting or relaxing the flow channel. In this study, a 10mm×40mm file (Film A) and a 5mm×40mm film (Film B) were fabricated and tested. The amplitude of the 2nd-order harmonic field produced by the films was inversely proportional to the fluid pressure. It was also shown that films with different sizes exhibited different signal sensitivity with the smaller film (Film B) exhibited greater sensitivity. This experiment indicates that feasibility of the pressure monitoring technology.

Bioactive Magnetoelastic Materials as Coatings for Implantable Biomaterials

Enhanced fibroblast activity at the soft tissue-implant interface can dramatically decrease the stability, function, and lifespan of biomedical implants such as bone anchored prostheses. Although bone anchoring systems dramatically improve prosthetic limb mechanical stability, uncontrolled fibrosis at the soft tissue-mounting post interface is a significant problem. The aberrant cell growth leads to irregular skin folds that prevent proper sealing to the bone anchoring post and also serves as a site for opportunistic infection and failure of the prosthetic system. We are developing a bioactive vibrational coating to control fibrous tissue overgrowth. The coating is based on a magnetoelastic (ME) material that can be set to vibrate at a predetermined amplitude and frequency using a controlled magnetic field. We hypothesize that small local vibrations can be used to selectively control cell adhesion and gene expression to promote and maintain functional stability at the implant-tissue interface. For bone anchored prostheses, the ME coating would be applied around the mounting post at the soft tissue interface. The specific aims of this work were to (1) modify the coating for use in contact with a biologic environment and (2) determine if local vibrational strain can efficiently control cell attachment to the coating without significantly influencing viability. First, two common biocompatible polymers, polyurethane and chitosan, were deposited as thin films on the ME coating to allow for its use in tissue culture. An indirect cytotoxicity test was used to determine fibroblast (L929) viability in media conditioned for 24 and 48 hours with uncoated, chitosan coated, and polyurethane coated ME materials. Results demonstrated that both polymer coatings returned cell survival to levels statistically indistinguishable from controls (cells cultured on tissue cultured polystyrene, TCP) with cell viability over 96% under all coating conditions. Second, the affect of local vibrations on cell adhesion was tested in vitro. A cell viability assay (Calcein-AM) followed by fluorescent imaging was used to quantify attachment and viability of fibroblasts cultured directly on the bioactive ME material. Results clearly indicated that controlled local vibrations can induce complete cell detachment from the ME material compared with non-vibrated controls at up to 72 hours post-seeding. Further, cells detached via applied vibrations showed no significant decrease in viability compared to adherent controls. These results suggest the potential for this novel coating to effectively control fibrous tissue overgrowth using the mild application of tunable local vibrations, a significant and cost-effective approach that could improve the stability, function, and lifespan of biomedical implants and reduce the need for surgical revision.

Real-Time, In Vivo Measurement of Contact Pressures at a Knee Arthroplasty

There is a need to measure contact pressures at the femoral component and tibia plate of a knee arthroplasty implant to determine the wear and tear of the polyethylene (PE) insert of the implant. Today, most pressure monitoring systems for knee arthroplasty implants are either limited to in vitro or intraoperative use, or cannot measure contact pressures at the polyethylene surface. Here, we are developing a wireless passive sensor system for measuring the contact pressure at the knee arthroplasty in vivo. The sensor system is made of a pressure-sensitive magnetic layer embedded under the top surface of a PE insert used for mapping the contact pressures with the femoral components. The pressure-sensing layer consists of a grid of pressure and stress sensitive magnetoelastic thin strips that alter their magnetic properties with applied force. Measurements are taken at pressure points located at the crossings of the grid. The magnetization of each sensing strip is remotely measured by using an AC magnetic field to excite the material to generate higher-frequency fields, which are then detected through external detection coils. The responses of these sensing strips are fed into an algorithm to determine the pressure loadings at all pressure points, which allows for real-time, in vivo determination of pressure profiles on the PE insert. By using an array of magnetoelastic sensing strips, we have demonstrated the remote detection of pressure across a surface. The 2nd order harmonic amplitude of a 30 mm×1.5mm magnetoelastic strip decreased linearly with increasing pressure. For this sensing strip, the rate of decrease was about 0.1 (normalized to unstressed signal level) per 200 kPa. An algorithm was also developed to determine the pressures at all pressure points from the responses of the sensing strips. Experimental results have shown that the algorithm can accurately map the pressure profile of a 3×3 sensing strip array. Further works include developing a fabrication process for safely embedding the sensing strips into a PE insert, and modifying the algorithm for a larger sensing strip array.

A Wireless, Passive pH Sensor Based on Magnetic Higher-Order Harmonic Fields

A wireless, passive sensor was fabricated for remote monitoring of chemical analytes in the human body. The sensor was made of a magnetically soft film (sensing element) and a permanent magnetic film (biasing element) sandwiching a reversibly swelling hydrogel. When subjected to a low frequency magnetic AC field, the sensing element generated higher-order harmonic magnetic fields that were detected with a remotely located detection coil. In the presence of a DC magnetic field (biasing field), such as that generated from the biasing element, the pattern of the higher-order harmonic magnetic fields varied, and the magnitude of change (referred to as the harmonic field shift) was proportional to the strength of the biasing field. The hydrogel, which acted as a transducer that converted variations in the chemical concentration into changes in dimensions, physically varied the separation distance between the sensing and the biasing elements. This causes a change in the magnitude of biasing field experienced by the sensing element, thus changing its higher-order harmonic field shift allowing remote measurement of chemical concentrations. The novelty of this sensor was its wireless and passive nature, which allows it to be used inside a human body for long term chemical monitoring. A scaled-up prototype was fabricated and tested to demonstrate the pH monitoring capability of the sensor. The main structure of the prototype sensor was a polycarbonate substrate containing a larger rectangular well of 36mm×8mm×4mm on top of a smaller well of 30mm×5mm×2mm (see Fig. 1). The smaller well was filled with hydrogel made of (poly)vinyl alcohol and (poly)acrylic acid. A commercial magnetoelastic thick film, Metglas 2826MB from Metglas Inc., was attached to the step at the bottom of the larger well and allowed to rest on the hydrogel. The DC magnetic field was provided by an Arnokrome III film (Arnold Magnetic Technologies) of 30mm×6mm attached at the bottom of the sensor structure. The sensor was placed on the detection coil, and its response was measured with a spectrum analyzer while exposed to test solutions of varying pH. The sensor's harmonic field shift, when cycled between pH 7 and pH 3, was measured and plotted in Fig. 2. As shown in the figure, the hydrogel swelled when the sensor was exposed to pH 3, decreasing the harmonic field shift. The response and recovery times of the hydrogel were below 2 minutes. This experiment proves the feasibility of the technology for real-time, remote monitoring of pH. Further work includes improving the response time and sensitivity of the hydrogel, as well as miniaturization of the sensor.

Elevated blood pressure in overweight and obese Irish children

BACKGROUND

The Irish childhood obesity epidemic, one of the highest ranking internationally, represents a major threat to public health. We sought to perform a retrospective observational study of a clinic based cohort of obese Irish children.

METHODS

Clinical data relating to gender, age, height, weight, body mass index and blood pressure were analysed, from 206 children referred to a paediatric endocrine referral centre over a 15-year period for assessment of obesity.

RESULTS

Younger patients tended to have a higher standardised body mass index at initial presentation; 92% of boys and 96% of girls referred were obese (age-related BMI >/= 95th percentile). Boys (51%) and girls (49%) had initial blood pressure measurements in the hypertensive range. There was a correlation between the degree of obesity and systolic blood pressure, particularly in boys.

CONCLUSIONS

Obese Irish children present with significant long-term health risks, including hypertension at baseline.