Chr. Reiners

Bone Quality Parameters of the Distal Radius as Assessed by pQCT in Normal and Fractured Women

Abstract. The aim of this study was to test the ability of some indicators of different aspects of bone quality (assessed by peripheral quantitative computed tomography in the distal radius) to discriminate between fractured and nonfractured individuals. The study compared 214 women aged 45–85 years, free of any bone-affecting treatment, of whom 107 had suffered a Colles” fracture in the previous 6 months and 107 did not. The determinations included bone tissue or mineral “mass” indicators (trabecular, cortical and total volumetric mineral content, cortical bone area); bone “density” estimates (trabecular, cortical and total volumetric mineral density), and the Cartesian (rectangular) and polar moments of inertia as influences of cross-sectional architecture on resistance to bending and torsional loads, respectively. The influences of body height, weight and age on the tomographic indicators were minimized by adjusting the data according to the partial coefficients of multiple stepwise regressions. The adjusted values of all the indicators were lower in fractured than in nonfractured groups. The prevalence of fractures was directly related to the actual values of the indicators, rather than the age or body habitus of the individuals. The significance of these differences between the assessed indicators decreased in the following order: trabecular “mass” > trabecular “density” > cortical or total “mass” > cortical architecture > total or cortical “density” indicators. Within the same type of bone, the tissue or mineral “mass” indicators performed better than the “density” indicators. The cortical bone density did not give useful information, probably because of technical difficulties. Odds-ratios and receiver-operating characteristic (ROC) analyses confirmed those features. The selected “cut-off” values of the indicators as determined by the ROC curves (very close to those determined by the inflexion points of the logistic reression curves) may indicate reference limits to detect persons at risk of fracture according to the type of information provided by each variable. These results show that these tomographic indicators discriminate well between fractured and nonfractured individuals, and should be suitable to assess how total, cortical and trabecular bone strength in the distal radius could affect different kinds of strength regardless of the age or body habitus of the individual. Their ability to estimate fracture risk from different biomechanical points of view should be assessed by adequately designed, prospective studies.

Clinical evaluation of a high-resolution new peripheral quantitative computerized tomography (pQCT) scanner for the bone densitometry at the lower limbs

Precision, long-term stability, linearity and accuracy of the x-ray peripheral quantitative computerized tomographic (pQCT) bone scanner XCT 3000 (Norland-Stratec Medical Sys.) were evaluated using the European Forearm Phantom (EFP). In vivo measurements were assessed using a standardized procedure at the distal femur and the distal tibia. In the patient-scan mode, the spatial resolution of the system was 1.04 +/- 0.05 lp/mm as measured at the 10% level of the modulation transfer function (MTF). The contrast-detail diagram (CDD) yielded a minimal difference in attenuation coefficient (AC) of 0.07 cm(-1) at an object size of 0.5 mm. The effective dose for humans was calculated to be less than 1.5 microSv per scan. Short-term precision in vivo was expressed as root mean square standard deviation of paired measurements of 20 healthy volunteers (RMSSD = 0.5%). At the distal femur total volumetric density (ToD) and total cross-sectional area (ToA) were found to be less sensitive to positioning errors than at the distal tibia. Structural parameters like the polar cross-sectional moment of inertia (CSMIp) or the polar cross-sectional moment of resistance (CSMRp) showed a good short-term precision at the distal femur (RMSSD = 1.2 and 1.4%). The relation between the two skeletal sites with respect to CSMIp or CSMRp showed a high coefficient of determination (r2 = 0.77 and 0.74).

The use of recombinant human TSH in a patient with metastatic follicular carcinoma and insufficient endogenous TSH production

We present a case of a patient suffering from metastatic differentiated thyroid carcinoma (DTC) and insufficient endogenous TSH production suspicious of secondary hypothyroidism. The use of recombinant human TSH (rhTSH) enabled us to administer a therapeutic activity of radioactive iodine (RAI) under maximal TSH-stimulation, achieving a marked decrease in thyroglobulin accompanied by a clinical improvement.

Comparison of total and regional body composition in adolescent patients with anorexia nervosa and pair-matched controls

Body composition in 31 adolescent girls suffering from anorexia nervosa (AN was measured at the time of hospitalization in order to assess the muscle/bone relationship as a potential source of the development of osteopenia. Differences in lean tissue, fat and bone mass in total body, weight bearing and non weight bearing limbs were estimated in AN and pair-matched controls aged 14.2±1.8 years (range: 9–17 years). Further, it was investigat ed if bone mineral density (BMD) better reflects the muscle/bone relationship than bone min eral content (BMC). At the distal radius parameters measured by peripheral quantitative com puted tomography (pQCT) were used to estimate the association of volumetric bone density to bone strength and lean body mass. The correspondence to the same and different body regions was assessed. Total lean mass in the controls was closely related to total body bone mineral content (TBBMC), as was lean tissue and bone mass of the limb subregions (r=0.82 to 0.93). In contrast, the correlation was significantly lower in AN (r=0.33 to 0.77). In the con trols, the pQCT-derived bone strength was correlated with muscle mass of the forearm (r=0.78, p<0.001), but only moderately in AN (r=0.47, n.s.). Regional lean tissue was 11–20% and fat mass was 56–66% lower in AN (p<0.01). After adjustment for height, TBBMC was dif ferent at p=0.01. Within the limbs subregions, BMC (but not BMD) was different in both groups only in the upper arm and the thigh. BMC reflected the bone/muscle relationship bet ter than BMD. Intra- and between group regressions gave no significant differences between weight bearing and non weight bearing limbs. In conclusion, the assessment of muscu loskeletal factors may be a useful tool to develop individual preventive measures for therapy after recovery of our patients.

Serum Inorganic Iodide Determined by Paired-Ion Reversed-Phase Hplc with Electrochemical Detection

Abstract We propose an automated method for the analysis of serum inorganic iodide (SII), using paired-ion reversed phase HPLC with electrochemical detection and a silver working electrode. Assay conditions include a flow rate of 1.0 mL/min and an operating potential of 0.10 V. The retention time for iodide is 5.3 min. Sample preparation consists in protein removal by ultrafiltration and concentration of the ultrafiltrate, because of the very low levels of SII, especially in iodine deficient areas. Ultrafiltration separation is achieved by pouring 2mL of a serum sample into a filter cup (membrane cutoff: 5kD) and then using a centrifugal force of 14000G over 90 min. A 1200μL aliquot of the ultrafiltrate is concentrated by a factor of 10 to a volume of 120μL in a centrifugal vacuum concentrator (Speed-Vac). A 100μL aliquot of the concentrate is injected into the HPLC. Due to concentration the detection threshold (signal-to-noise ratio of 3) could be lowered to 0.004μmol/L. The recovery of iodide during con...

Changes in biomechanical properties of rat femora induced by ovariectomy as analyzed by pQCT

THE RELATIVE CONTRIBUTIONS OF AGE AND MENOPAUSE TO SPINAL DEMINERALIZATION R. Menkhaus, M. D~ren, H.P.G. Schneider Department of Obstetrics & Gynecology, University of MOnster Various regression models with logarithmic transformation of variables and breakpoint regressions (SPSS) were tested to quantify the contributions of age and menopause to bone loss in 9 cross-sectional sample of 300 pre-, 472 postmenopausal and 88 bilateral oophorectomized women. We determined bone mineral content (BMC) by quantitative computed tomography (QCT). In postmenop 9 women, bone loss due to age is explained by a linear regression with 9 loss of 1.08%/year beginning in the mid-forties and lasting for the whole lifetime. The event of menopause accounts for a 17.3% loss of BMC within the first 5 postmenopausal years following an exponential regression. 27.9% of the BMC variance is explained by age and menopause together. Bone loss starts around the age of 43 in premenopausal women. Hysterectomy did not influence BMC. In bilateral oophorectomized women demineralization does not have an exponential component. Nevertheless their mean BMC does not differ from the postmenopausal one. Weight and body mass index did not effect BMC in any of the examined patients. The menopausal influence on bone loss is limited to the first 5 postmenopaus 9 years and its impact might have been overestimated (I) compared to the influence of chronological age. Longitudinal studies are essential to substantiate our observation of premenopausal spinal bone loss. l.Nordin et al. J Clin Endocrinol Metab 1990;70:83-8