Biomechanical comparison of three different surgical methods in the surgical treatment of distal tibial metaphyseal fractures. An animal model study

BACKGROUND

The aim of this study is to investigate mechanical properties of minimally invasive plate osteosynthesis (MIPO), supracutaneousplating (SP), and unilateral external fixators (UEF) which can be performed for open tibial fractures.

METHODS

An unstable diaphysial tibia fracture was created in 60 fresh sheep tibia specimens by performing an osteotomy at the middle of bones. Specimens were divided into 3 groups. Specimens underwent fracture fixation with a standard MIPO technique, im-planting the plate 15 mm from the bone for SP group. Unilateral uniplanar external fixators were achieved for UEF group. First, thirty specimens (10 specimen for each group) were loaded vertically along the tibial axis to 1800 N. Second, other 30 preperated bones were used for cyclical loading to avoid metal fatigue. For dynamic tests, a 350 N force was applied for 10,000 cycles.

RESULTS

In compression testing (vertical loading up to 1800 N) of the three fixation instruments; construct stiffness was highest in MIPO group when compared with SP and UEF groups. While the stiffness of the MIPO group was similar to SP group, it was statistically higher than UEF group (P=0.08 and P=0.002, respectively). SP group was significantly stiffer than UEF group (P=0.0021). The mean peak load was highest in SP group and lowest in UEF group. The peak load in SP group was similar to the MIPO group, it was statistically higher than the UEF group (P=0.743 and P=0.002, respectively).

CONCLUSION

Based on the biomechanical properties from this in vitro animal model study, SP technique was biomechanically stronger than UEF and has similar biomechanical properties with MIPO in terms of axial loading.

Lifestyle and metabolic determinants of incident hypertension, with special reference to cigarette smoking: a longitudinal population-based study

BACKGROUND

Lifestyle and metabolic determinants of incident hypertension in a population with a high prevalence of metabolic syndrome (MetS) need to be further assessed.

METHODS

A representative sample of middle-aged and elderly Turkish adults was prospectively evaluated over a mean 7.4 years, after exclusion of prevalent hypertension and major renal dysfunction.

RESULTS

In 2,427 men and women, aged 45.8 +/- 11.7 years, Kaplan-Meier analysis showed in combined genders mean time to incident hypertension to be 7.23 years in never, 7.78 years in current smokers (P < 0.001). Age and female sex were major determinants of subsequent hypertension after adjustment for physical activity grade, family income bracket, smoking status, usage of alcohol and of hormone replacement or birth control pill. Relative risk (RR) for incident hypertension of current vs. never smoking was reduced in women (P = 0.058) and both genders combined (P = 0.054). Former smokers uniformly exhibited significantly higher risk for the development of hypertension than both never (P = 0.054) and current (P < 0.001) smokers, whereby abdominally obese individuals were at increased risk. In further multivariable models, circulating C-reactive protein (CRP) and fasting insulin emerged as modest independent determinants and waist girth, modulated by current smoking, as a major determinant of subsequent hypertension.

CONCLUSIONS

Age, female sex, and waist circumference are major and serum insulin and CRP modest determinants of incident hypertension in middle-aged Turkish adults in whom current cigarette smoking plays a protective role at borderline significance, largely by modulating waist girth. Former smokers with abdominal obesity are under higher risk of subsequent hypertension than current smokers.

Improvement of Dissolution Properties of Furosemide by Complexation with β-Cyclodextrin

The purpose of this study was to increase the solubility of furosemide (FR) with inclusion compound of beta-cyclodextrin (beta-CD). The interaction between FR and beta-CD in solution was studied by the solubility method. The phase solubility studies reveal a Bs-type diagram with an inclusion complex of 1:1 molar ratio and a stability constant of 823.5 M(-1). The solid complexes of FR with beta-CD were prepared by using freeze-drying, kneading, and co-precipitation methods. In addition, the physical mixture was prepared for comparison. Inclusion complexation was confirmed by the results from the studies of x-ray diffraction, differential scanning calorimetry, and infrared spectroscopy. The rates of release of the active material from the resulting complexes were determined from dissolution studies using the flow-through cell method. The dissolution rate of FR was significantly enhanced by inclusion of the beta-CD in the formulations. The rate of release of the active material was found to be dependent on the preparation method of the complexes, and the drug prepared by the kneading method was shown to have the fastest dissolution profile compared to the other methods used in this study.

Correlation of plasma B-type natriuretic peptide with shunt severity in patients with atrial or ventricular septal defect

The goal of this study was to test the utility of bedside plasma concentration of B-type natriuretic peptide (BNP) assay as a screen for large shunts in pediatric patients with atrial septal defects (ASDs) and ventricular septal defects (VSDs). Thirty-five children at a mean age of 70+/-129 weeks with ASD or VSD were included in the study. Nine patients had VSD and 26 had ASD. Plasma BNP values were compared with the Qp/Qs ratios derived from quantitative Doppler flow measurements. Mean BNP was 29+/-42 pg/ml, with a range between<5 pg/ml and 208 pg/ml. Sixteen patients had Qp/Qs values>1.5 and 19 had values<1.5. The difference of mean BNP in these patient groups was statistically significant (45+/-56 vs 14+/-17, p=0.03). BNP was positively correlated with shunt significance. Receiver operating characteristic curve analysis revealed a sensitivity of 69% and a specificity of 79% at a plasma BNP cut-off level of>or=20 pg/ml. Bedside measurement of BNP correlates with magnitude of ASD and VSD in children. BNP can provide information for the management of children with ASD or VSD. It can be used as part of the evaluation of a child with a preliminary diagnosis of a congenital defect.

Studies of floating dosage forms of furosemide: in vitro and in vivo evaluations of bilayer tablet formulations

For the purpose of enhancement the bioavailability of furosemide (FR), a floating dosage form with controlled release of FR was designed in this study. Because of the lower solubility of active material in the gastric medium, it was first enhanced by preparing an inclusion complex of FR with beta-cyclodextrin (beta-CD) in a 1:1 proportion using the kneading method. Following the design of dosage form, bilayer floating tablets were prepared. After dissolution rate studies were performed using the continuous flow-through cell method, the formulation that provided delivery of active material near the target profile was given to six healthy male volunteer subjects, and in vivo tests were performed. It was determined by radiographs that floating tablets prepared by adding BaSO4 stayed in the stomach for 6 hr. Further, values of the area under the plasma concentration-time curve (AUC) obtained with the floating dosage form were about 1.8 times those of the conventional FR tablet in blood analyses; maximum and minimum plasma concentrations were also found to be between the desired limits. In urine analyses, the peak diuretic effect seen in classical preparations was decreased and prolonged in floating dosage forms. Also, a considerably significant correlation was detected between in vivo results and in vitro data of the dissolution rate, and it was concluded that the modified continuous flow-through cell method is usable for in vitro dissolution rate tests of floating dosage forms.

Dissolution rate of furosemide from polyethylene glycol solid dispersions

In this study, by preparing the solid dispersions of furosemide, a substance that is poor-soluble in water, with polyethylene glycol 6000, 10,000 and 20,000, the enhancement of the dissolution rate of furosemide has been aimed. Solid dispersions were prepared by the fusion method in proportions of 1:4, 1:6 and 1:10 (active material/polymer). The formation of solid dispersion was tested by the techniques of X-ray diffraction, differential calorimetry (DSC) and infrared spectroscopy (IR). The release rate of active material from the solid dispersions prepared was examined by using the flow through cell method. Also, the effect of particle size of the complexes obtained, on the dissolution rate and the stabilities of these complexes were studied. It was determined that the dissolution rate of furosemide was markedly increased along with the formation of the complex and that a better dissolution profile was obtained even in the physical mixtures prepared for the purposes of comparison. It was found that the molecular weights of different kinds of polyethylene glycols and the various proportions of active material/polymer complexes as well as the particle sizes of the solid dispersions were not efficient in the release rate of active material. It was concluded that the increase of the dissolution rate was being a result of both wettability and solubility enhancing effects of polyethylene glycols.