PubMed Health⌕ Search

Biomedical subjects

M A Dambacher

Publications and source records attributed to M A Dambacher.

At least 19 recordsLinked to original sources
PubMed2000

Is the amount of trabecular bone-loss dependent on bone mineral Density? A study performed by three centres of osteoporosis using high resolution peripheral quantitative computed tomography.

For the risk getting osteoporosis as well as for diagnosis of osteoporosis 3 facts are highly important: bone-mass, the amount of bone-loss and bone-structures (microarchitecture of bone). All three parameters can be validated today with high precision but the amount of bone-loss seems to be the most important one, even for the decision of either antiresorptive or bone-stimulating therapy. But to calculate the amount of bone-loss until now at least two measurements of bone mineral density (BMD) are necessary which have to be performed within a certain period of time, depending on the reproducibility of the method to be used. If on the other hand the amount of bone-loss would be dependent on actual base-line bone-mass the right therapy could be started already after only one measurement of BMD. The aim of this study was therefore to investigate if there is any relation between the amount of bone-loss and base-line volumetric BMD. For this we separately measured trabecular and cortical bone densities of 135 women in three independent centres of osteoporosis in Zurich and Munich using the method of high resolution quantitative computed tomography - pQCT - with the Densiscan 1000, Scanco Medical, Zurich. We did this at least twice and then compared absolute volumetric BMD in the first step before we calculated trabecular and cortical bone loss per year for each woman. We could not only confirm again that bone loss in trabecular bone was significantly higher than in cortical bone and that the non-weight-bearing trabecular bone as could be found in the distal radius seems to be the skeletal site of maximum bone-loss, but moreover - and this is the more important finding - we could show that the amount of relative bone-loss was the higher the lower trabecular base-line volumetric BMD was. According to this the rate of fast-loser (more than 3.5% per year) increased the lower trabecular base-line volumetric BMD was. These results may lead to a new screening-test for the assessment of the individual risk of osteoporosis and for the individual risk of fast bone-loss which now can be evaluated with only one single measurement of BMD, to treat the so classified patients not only earlier but even more rational, dependent if either antiresorptive therapy or stimulation of bone-formation seems to be more important.

Adult↗
PubMed2000

Peripheral volumetric bone mineral density in pre- and postmenopausal Chinese women in Hong Kong.

The aim of this cross-sectional study was to use a newly available precise and multislice pQCT (Densiscan 2000) for establishing reference data of volumetric bone mineral density (vBMD) of the distal radius. vBMD of the nondominant wrist was measured in 118 healthy Hong Kong Chinese women aged 41-60. Anthropometric parameters, menstrual status, and handgrip strength were also measured. Results showed that there was a significant age-related decline in trabecular BMD (tBMD), integral BMD (iBMD), and cortical BMD (cBMD), with correlation coefficients ranging from -0.401 to -0.547 (P < 0.001). The annual decline of vBMD was 2.22%, 1.79%, and 0.88% in tBMD, iBMD, and cBMD, respectively. When subjects were divided into premenopausal and postmenopausal groups, we found an age-related decline in tBMD and iBMD, but not in cBMD in both groups. The vBMD values interpreted in mg/cm3 in premenopausal women were 238.4 +/- 57.2 in tBMD, 604.6 +/- 82.9 in iBMD, 1415.5 +/- 129.9 in cBMD, and declined significantly (all P < 0.001) to 193.7 +/-54.7 in tBMD, 500.0 +/- 90.3 in iBMD, and 1306.7 +/- 153.5 in cBMD in the postmenopausal women. On average, 16.7% of the subjects showed their vBMDs to be below-1 SD and only 1.7% of them lower than -2 SD. Linear regression showed that the annual decline of vBMD was faster in postmenopausal women with 2.42% in tBMD, 1.90% in iBMD, and 0.88% in cBMD compared with 1.91% in tBMD, 0.98% in iBMD, and 0.55% in cBMD in the premenopausal women. After adjustment for age, only the iBMD with dominant trabecular elements showed a significantly accelerated decrease after the onset of menopause (P = 0.008). Weak or no association was found among vBMDs with anthropometric parameters, years since menopause, or handgrip strength. In conclusion, we found a significant age-related decline of vBMDs in Hong Kong Chinese women aged 41-60 years, characterized by the early reduction of metabolically active trabecular bone after entering the fourth decade of life, with an accelerated decline after the onset of menopause.

Adult↗
PubMed2000

Bone mineral density in upper and lower extremities during 12 months after spinal cord injury measured by peripheral quantitative computed tomography.

OBJECTIVE: To evaluate the loss of trabecular and cortical bone mineral density in radius, ulna and tibia of spinal cord injured persons with different levels of neurologic lesion after 6, 12 and 24 months of spinal cord injury (SCI). DESIGN: Prospective study in a Paraplegic Centre of the University Hospital Balgrist, Zurich. SUBJECTS AND METHODS: Twenty-nine patients (27 males, two females) were examined by the highly precise peripheral quantitative computed tomography (pQCT) soon after injury and subsequently at 6, 12 and in some cases 24 months after SCI. Using analysis of the bone mineral density (BMD), various degrees of trabecular and cortical bone loss were recognised. A rehabilitation program was started as soon as possible (1-4 weeks) after SCI. The influence of the level of neurological lesion was determined by analysis of variance (ANOVA). Spasticity was assessed by the Ashworth Scale. RESULTS: The trabecular bone mineral density of radius and ulna was significantly reduced in subjects with tetraplegia 6 months (radius 19% less, P<0.01; ulna 6% less, P>0.05) and 12 months after SCI (radius 28% less, P<0.01; ulna 15% less, P<0.05). The cortical bone density was significantly reduced 12 months after SCI (radius 3% less, P<0.05; ulna 4% less, P<0.05). No changes in BMD of trabecular or cortical bone of radius and ulna were detected in subjects with paraplegia. The trabecular BMD of tibia was significantly reduced 6 months (5% less, P<0.05) and 12 months after SCI (15% less, P<0.05) in all subjects with SCI. The cortical bone density of the tibia only was decreased after a year following SCI (7% less, P<0.05). No significant difference between both groups, subjects with paraplegia and subjects with tetraplegia was found for tibia cortical or trabecular BMD. There was no significant influence for the physical activity level or the degree of spasticity on bone mineral density in all subjects with SCI. CONCLUSIONS: Twelve months after SCI a significant decrease of BMD was found in trabecular bone in radius and in tibia of subjects with tetraplegia. In subjects paraplegia, a decrease only in tibia BMD occurred. Intensity of physical activity did not significantly influence the loss of BMD in all subjects with para- and tetraplegia. However, in some subjects regular intensive loading exercise activity in early rehabilitation (tilt table, standing) can possibly attenuate the decrease of BMD of tibia. No influence was found for the degree of spasticity on the bone loss in all subjects with SCI.

Adult↗
PubMed2000

Longitudinal changes in bone in men with spinal cord injury.

INTRODUCTION: Quantitative bone assessment today is primarily based on the analysis of bone mineral density (BMD). The geometric and structural properties of bone, which are important parameters for skeletal strength, are generally not considered in the routine clinical assessment of spinal cord injury-related osteopenia. OBJECTIVE: To study changes in structural and geometric properties of tibia bone longitudinally by means of peripheral quantitative computerized tomography and a biomechanical test method (bone stiffness measurement device Swing) in 12 subjects with spinal cord injury. DESIGN: Measurements were conducted in the 5th week and around the 104th week after the spinal cord injury in a university hospital. RESULTS: Paired Student's t-tests showed a significant decrease in trabecular (p < 0.05) and cortical bone (p < 0.05), as well as a significant decrease in geometric properties of tibia bone (p < 0.05) within two years after the spinal cord injury. Phase velocity propagation changed in three subjects within two years following the spinal cord injury. CONCLUSIONS: This study indicates that beside changes in tissue composition, changes in bone geometric indices and in structural properties occur in the lower extremity after a spinal cord injury. In the tibia, consideration of geometric and biomechanical parameters of bone combined with bone mineral density measurements could result in an improved screening for spinal cord injury-related osteopenia and the prediction of fracture risk in spinal cord injury.

Adult↗
PubMed1999

Changes of tibia bone properties after spinal cord injury: effects of early intervention.

OBJECTIVE: To evaluate the effectiveness of an early intervention program for attenuating bone mineral density loss after acute spinal cord injury (SCI) and to estimate the usefulness of a multimodality approach in diagnosing osteoporosis in SCI. DESIGN: A single-case, experimental, multiple-baseline design. SETTING: An SCI center in a university hospital. METHODS: Early loading intervention with weight-bearing by standing and treadmill walking. PATIENTS: Nineteen patients with acute SCI. OUTCOME MEASURES: (1) Bone density by peripheral computed tomography and (2) flexural wave propagation velocity with a biomechanical testing method. RESULTS: Analysis of the bone density data revealed a marked decrease of trabecular bone in the nonintervention subjects, whereas early mobilized subjects showed no or insignificant loss of trabecular bone. A significant change was observed in 3 of 10 subjects for maximal and minimal area moment of inertia. Measurements in 19 subjects 5 weeks postinjury revealed a significant correlation between the calculated bending stiffness of the tibia and the maximal and minimal area moment of inertia, respectively. CONCLUSION: A controlled, single-case, experimental design can contribute to an efficient tracing of the natural history of bone mineral density and can provide relevant information concerning the efficacy of early loading intervention in SCI. The combination of bone density and structural analysis could, in the long term, provide improved fracture risk prediction in patients with SCI and a refined understanding of the bone remodeling processes during initial immobilization after injury.

Adult↗
PubMed1998

Highly precise peripheral quantitative computed tomography for the evaluation of bone density, loss of bone density and structures. Consequences for prophylaxis and treatment.

The importance of serial examinations over time with peripheral quantitative computed tomography (pQCT) is that they enable the detection of patients at high risk of osteoporosis, and the individualisation of prophylaxis and treatment. We have shown that postmenopausal patients with high bone turnover evaluated by biochemical markers are identical to fast bone losers as determined by pQCT. As a consequence, we use agents that inhibit bone resorption in patients who are fast bone losers and agents that stimulate bone formation in patients who are slow bone losers. To visualise bone microarchitecture, and to evaluate bone density and the rate of bone loss, we used a highly sensitive pQCT system (DENSISCAN 1000, reproducibility of 0.3% in a mixed population of normal individuals and patients with osteopenia or osteoporosis). This system enabled us to separately assess trabecular and cortical bone density in the radius and tibia, and to differentiate between fast and slow bone losers within a few months (threshold: 3% loss of trabecular bone density in the radius per year). We have shown that the lower the trabecular bone density in the distal radius, the higher the relative bone loss. To classify patients as slow and fast losers in the future, we may need only one measurement. With this highly precise measurement method, we have shown that calcitonin and etidronate are more effective in fast than in slow bone losers, and that vitamin D metabolites (calcitriol or 1 alpha-calcidol) and estrogens can halt fast bone loss. In conclusion, highly sensitive pQCT enables us to adapt the treatment to different forms of osteoporosis and bone turnover, resulting in an increase in the number of patients successfully treated and also in patient compliance. Because our treatment is based on precise, objective measurements, treatment modifications--especially in those who change from a slow to a fast bone-loser state--can be easily justified.

Adult↗
PubMed1998

[Prevention of osteoporosis].

The European Parliament presented June 10th in Brussels the 'Osteoporosis Report in EU--Means for Prevention'. It was emphasized that in the EU more than 3500 million Ecu have to be spent for hospitalization and that more than 500,000 hospitals beds are being used by osteoporotic patients. According to some calculations this number will double within the next 50 years. The EU has set up eight steps to be considered, e.g. have densitometric measurements available for persons with high risk and have these measurement paid by the insurances to further finance and support research for the very important areas of prevention and treatment. One distinguishes between primary, secondary and tertiary prevention of osteoporosis. Primary prevention aims at reaching at adolescent age a peak bone mass as high as possible. Secondary prevention aims at reducing bone loss peri- and postmenopausal. The tertiary prevention with manifest osteoporosis aims at preventing fractures. Emphasis of the primary prevention is, besides a sufficient calcium intake, to omit risk factors; with secondary prevention the use of medical treatments such as estrogens/gestagens, bisphosphonates, and recently also SERMs is applied. The tertiary prevention tries mostly to reduce the femur fractures. In addition to drugs such as vitamin D/calcium, vitamin D metabolites and bisphosphonates it is very important to create 'a fall-proof home'. Also very useful are hip protectors.

Adolescent↗
PubMed1997

Can the fast bone loss in osteoporotic and osteopenic patients be stopped with active vitamin D metabolites?

The aim of this study was to evaluate whether fast trabecular bone loss in osteoporotic and osteopenic patients can effectively be treated with active vitamin D metabolites. Thirty-one osteoporotic and osteopenic patients were monitored between 4 and 22 months before and between 8 and 18 months during the treatment. Fast bone losers were designated as osteoporotic or osteopenic patients with a loss of trabecular bone density in the radius of 3% or more calculated for 1 year. For this differentiation, the high precise peripheral quantitative computed tomography system (DENSISCAN 1000) was used (reproducibility 0.3% in mixed collectives). The pretreatment loss and the "gain" under treatment with active vitamin D metabolites was calculated for 1 year. The treatment consisted of either 0.5 micro;g calcitriol daily or 1 micro;g of alfacalcidol daily. Before treatment, the trabecular bone loss in the radius/year was -6.6 +/- 0.5% (mean +/- SEM). After treatment with vitamin D metabolites, the trabecular bone gain in the radius/year was 0.01 +/- 0.6% (mean +/- SEM). The difference was highly significant (P < 0.001). In contrast to this, the loss of cortical bone density before treatment was -1.8 +/- 0.3% (mean +/- SEM) and the reduced loss after treatment -0.2 +/- 0.4% (mean +/- SEM), both values calculated for 1 year. This difference was less significant (P < 0. 05). This study shows that the treatment with active vitamin D metabolites is very effective in slowing fast trabecular bone loss in osteoporotic and osteopenic patients.

Aged↗
PubMed1995

Comparison of the treatment effects of ossein-hydroxyapatite compound and calcium carbonate in osteoporotic females.

The aim of the study was to evaluate whether ossein-hydroxyapatite (OHC) is more effective than calcium carbonate (CC) in preventing further bone loss in postmenopausal osteoporosis. Forty osteoporotic patients were monitored for 20 months. The patients were randomly assigned to one of two groups and treated in a double-masked manner with 1400 mg calcium per day, in the form of either OHC or CC. OHC consists of hydroxyapatite, collagens and non-collagenous proteins/peptides containing insulin-like growth factor I (IGF-I; 1341 ng), insulin-like growth factor II (IGF-II; 670 ng), transforming growth factor beta (TGF-beta; 166 ng) and osteocalcin (47 micrograms). The bone densities were evaluated at intervals of 4 months with high-precision peripheral quantitative computed tomography. After 20 months of treatment the loss of trabecular bone was 0.8 +/- 0.5% in the OHC group and 1.8 +/- 0.7% in the CC group. The difference between the OHC and CC groups was statistically significant. This study shows that OHC is more effective than CC in slowing peripheral trabecular bone loss in patients with manifest osteoporosis.

Aged↗
PubMed1994

[Problems with bone densitometry].

Today, bone density can be measured by different technical methods which show variations in terms of reproducibility, accuracy and sensibility. A crucial parameter is the reproducibility, which differs considerably from method to method. With densitometric methods it is possible not only to evaluate patients at risk getting an osteoporosis but also to establish an individual prophylaxis and therapy by means of highly precise quantitative methods, based on the parameters 'bone density' and 'loss of bone density'. A high bone turnover leads to fast bone loss and, vice versa, fast bone loss, measured by densitometry, is correlated with high bone turnover in postmenopausal women. This allows to establish an individual therapy with antiresorption resp. bone-stimulating agents and the knowledge about a tailored, individual treatment increases patients' compliance and reduces the rate of 'non-responders'.

Aged↗
PubMed1994

[Osteoporosis therapy, current status].

Treatment of osteoporosis includes various possibilities with drugs. Furthermore, approaches with physiotherapy and adequate diet are also important. As to drugs substances like calcium, estrogens, bisphosphonates, calcitonin, fluoride and vitamin D have to be mentioned. Anabolic steroids have some beneficial effects on bone, but there are problems with side effects. Strontium and ibriflavone show interesting potentials, but they need to be studied in more detail.

Aged↗
PubMed1994

[Bone density measurements and their indications].

Today the following two methods of measuring the bone mineral density (BMD) are widely used: dual-photon absorptiometry with X-rays (DEXA) and quantitative computed tomography (qCT). DEXA measures the BMD of the vertebral column, the femur and the whole skeleton, qCT the vertebral column and the radius and tibia. The qCT method permits a distinction to be made between trabecular and cortical bone, which offers an advantage in terms of the choice of treatment because cortical and trabecular bone do not change in parallel. For example, fluorides are contraindicated when cortical bone is diminished. There are important differences among the methods of densitometry concerning reproducibility. The highly sensitive method of peripheral qCT (Densiscan) has an overall reproducibility of 0.3% (mixed population), allowing a change in BMD of less than 1% to be detected. This enables us to adapt quickly the treatment according to the stage and progression of the disease. In the perimenopausal patient, bone mineral densitometry is indicated to detect high-risk patients; in the postmenopause patient, densitometry should be performed in order to "tailor" the treatment of osteoporosis. Patients with a "slow loser" osteoporosis are preferably treated with bone-simulating substances (e.g., fluorides, ossein-hydroxyapatite compound), patients with a "fast loser" osteoporosis (trabecular bone loss, measured at the distal radius, of more than 3.5% per year) with anti-resorption agents such as estrogens, bisphosphonates, calcitonin and anabolic steroids. This tailored treatment reduces not only the number of non-responders, but improves patient compliance because it allows the choice, duration or change of the treatment to be substantiated by means of hard data.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1992

[Loss of bone mass in patients with anorexia on tube feeding and its prevention with biphosphonates].

Women with long-lasting anorexia nervosa often display osteopenia. Furthermore, we have observed additional marked loss of bone mass under tube feeding in underweight anorexia patients. Such loss of bone substances can lead to spontaneous fractures. Therefore, we investigated in this study whether this undesirable effect of tube-feeding might be prevented by administration of bisphosphonates (Didronel), a substance that inhibits the activity of osteoclasts. Bone density was assessed by a high-precision, low dose, quantitative computed tomography of the distal radius and the distal tibia. A group of 6 anorexia patients (tube feeding with an initial underweight of 74.9 +/- 10.3% of ideal weight, mean +/- SD) treated with bisphosphonates showed only slight loss of trabecular bone (0.8 +/- 0.2%, mean +/- SEM) after 2 months of observation, whereas in 2 control groups a marked diminution of trabecular bone was observed (4.4 +/- 0.7% and 7.6 +/- 1.1% respectively, p less than 0.001 for each comparison). Cortical bone was unchanged throughout. Treatment with bisphosphonates provides effective prevention of bone loss observed in tube-feeding.

Adult↗
PubMed1991

Formation of neutralizing antibodies during intranasal synthetic salmon calcitonin treatment of postmenopausal osteoporosis.

Nineteen patients with postmenopausal osteoporosis were treated with 200 u (15 nmol) synthetic salmon calcitonin (sCT) intranasally per day for 15 months. Six months after the start of the nasal administration of sCT, antibodies were recognized in 7, and after 15 months in 10 of the 19 patients studied. The half-maximal dilution of serum binding to 60 pmol/l [125I]sCT (dilution-50) ranged from 2 to 490, and half-maximal inhibition of [125I]sCT binding (60 pmol/l) from 91 to 221 pmol/l sCT. In a cultured breast cancer cell line (T47D) cAMP production was stimulated by sCT (EC50 70 pmol/l). Stimulated cAMP production by sCT (50 pmol/l) was reduced to between 4% and 23% in the presence of serum from patients with antibody dilution-50 of [125I]sCT binding exceeding 32. In patients with lower titer antibodies cAMP production was only marginally suppressed. The values of patients with postmenopausal osteoporosis were in the range of those of earlier studied patients with Paget's disease and clinical resistance to sCT. There was a linear relation between the antibody dilution-50 and the serum dilution required for half-maximal inhibition of cAMP production (P less than 0.01). In conclusion, neutralizing antibodies to sCT may contribute to the decreased responsiveness of bone mineral loss during prolonged treatment with sCT.

Administration, Intranasal↗
PubMed1991

Localization of regional forearm bone loss from high resolution computed tomographic images.

The precise site of bone loss was evaluated in early postmenopausal women using high resolution computed tomographic (CT) images of forearm measurements. A procedure was devised to quantitate trabecular and subcortical bone density of the distal radius, cortical bone density of the diaphyseal radius, and cortical wall thickness at both measuring sites. Twenty women (mean age 52 years, time since menopause 1 to 4 years) were examined twice at one-year intervals to determine the yearly change of the above mentioned bone parameters. Trabecular bone and subcortical bone showed the same density reduction of 7 mg/cm3 per year. Cortical bone density remains unchanged and no increase in porosity can be seen. For early postmenopausal women the reduction of bone mass (BMC) in the diaphysis of the radius is, therefore, due to a thinning of the cortical wall. This is in accordance with the observed average loss of wall thickness of 0.04 mm per year. The non-invasive determination of the precise localization of bone changes in individual patients should be of value in the assessment of the severity of osteoporosis. Furthermore it has potential in the evaluation of the efficacy of therapeutic procedures in the various disease states.

Absorptiometry, Photon↗
PubMed1991

Differential effects of aging and disease on trabecular and compact bone density of the radius.

We constructed a special purpose CT system to get a spatial resolution of 0.2 mm and developed a procedure for the precise determination of trabecular and compact bone density (TBD and CBD) in the radius. Seven groups of healthy females and patients were measured to explore differential effects on compact and trabecular bone. In healthy females CBD remains constant within 0.2% from age 20 to 70. TBD measured in the same individuals is reduced by 50%. The scatter of the individual CBD values is 1.5% only, that of TBD 20%. Longitudinal examinations of corticosteroid treated asthmatics during one year showed a loss of TBD of 4.8%. During the same period CBD remained completely stable. In other diseases such as hyperparathyroidism CBD is reduced as well. This study showed the feasibility of a noninvasive determination of the density of compact bone and demonstrated that density loss of compact and trabecular bone is considerably different.

Adrenal Cortex Hormones↗