Biomedical subjects

E-M Lochmüller

Publications and source records attributed to E-M Lochmüller.

7 recordsLinked to original sources

PubMed2006

Structural analysis of trabecular bone of the proximal femur using multislice computed tomography: a comparison with dual X-ray absorptiometry for predicting biomechanical strength in vitro.

We investigated whether trabecular microstructural parameters determined in multislice spiral computed tomographic (MSCT) images of proximal femur specimens differed in male and female donors and improved the prediction of biomechanical strength of the femur compared to bone mineral density (BMD) and content (BMC) determined with dual X-ray absorptiometry (DXA) as the standard diagnostic technique. Proximal femur specimens (n = 119) were harvested from formalin-fixed human cadavers (mean age 80 +/- 10 years). BMD was determined using DXA. Trabecular microstructural parameters (bone volume fraction, fractal dimension, and trabecular thickness, spacing, and number) were calculated in MSCT-derived images of the proximal femur. Failure load (FL) was measured using a biomechanical side-impact test. An age-, height-, and weight-matched subgroup (n = 54) was chosen to compare male and female donors. BMC, BMD, and structural parameters correlated significantly with FL, with r up to 0.75, 0.71, and 0.71, respectively. In a multiple regression model, an increase up to r = 0.82 was obtained when combining trabecular structural parameters and BMC. BMD differed between males and females only at the trochanter. BMC showed significant gender differences in all regions. This experimental study showed that a combination of BMC and microstructural parameters could improve the prediction of FL, suggesting that bone mass and trabecular structure carry overlapping but complementary information and that a combination of the two provides the best prediction of bone strength. Male donors had larger femora even after adjustment for body size and height, but no differences in trabecular structure were found between males and females.

Absorptiometry, Photon↗

PubMed2004

Technical considerations for microstructural analysis of human trabecular bone from specimens excised from various skeletal sites.

The purpose of this study was to test the effect of repositioning, systematic displacements of the region of interest (ROI), and acquisition parameters (scan mode and integration time) on quantitative analysis of human trabecular bone microstructure at various skeletal sites, using microcomputed tomographic (microCT) technology. We investigated 28 cylindrical specimens of human trabecular bone (length 14 mm, diameter 8 mm) from four skeletal sites (femoral neck, greater trochanter, second lumbar vertebra, and distal radius). These specimens were selected from over 200 microCT measurements, in order to cover a large range of bone volume fraction (BV/TV) observed at each site. Cylindrical ROIs (length 6 mm, diameter 6 mm) were examined twice at an isotropic resolution of 26 microm, 8 weeks apart. In addition, comparative analyses were performed for displacements of the volumes of interest (VOIs) by 1, 2, 3, and 4 mm (83.4%, 66.6%, 50%, and 33.3% overlap), respectively. Eventually, comparative measurements were obtained at different resolution scan modes and integration times. The results show that microCT measurements are highly reproducible (range of the root mean square coefficient variation % (RMS CV%) = 0.64% to 1.29% for BV/TV at different sites). Displacements of the VOI of up to 4 mm generally led to non significant systematic differences in mean values of < 10%. When comparing various combinations of resolution scan modes and integration times, the use of an integration time of 100 ms was found to be preferable for determining microstructural parameters from human samples with this microCT scanner.

Aged↗

PubMed2004

[Juvenile gigantomastia. Case report and literature survey].

A juvenile gigantomastia with wet tender ulceration in a 13-year-old premenarchal girl (155 cm, 51 kg) developed in only 6 months. Treatment consisted of a bilateral reduction mammoplasty with free transplantation of the areolae and nipples and the removal of 4.2 kg of breast tissue. Macroscopically the resections consisted of "white and solid" tissue. Histologically a fibrous-cystic mastopathia was confirmed. It is thus suggested that the etiology of this disease might be related to a local hypersensitivity to estrogen. Mediactions (Tamoxifen) are mostly ineffective. The treatment consisted of reduction plasty.

Adolescent↗

PubMed2004

Image-based micro-finite-element modeling for improved distal radius strength diagnosis: moving from bench to bedside.

Although osteoporosis is characterized by quantitative (mass) and qualitative (structural) changes, standard clinical techniques (dual-energy X-ray absorptiometry, DXA) only measure the former. Three-dimensional micro-finite-element (micro-FE) models based on high-resolution images can account for structural aspects as well, and it has recently been shown that an improved prediction of distal radius strength is possible with micro-FE analysis. A clinical application of this technique, however, is limited by its high imaging and computational demands. The objective of this study is to investigate if an improved prediction of bone strength can be obtained as well when only a small part of the radius is used for micro-FE modeling. Images of a 1-cm region of the metaphysis of the distal radius of 54 cadaver arms (mean age: 82 +/- 9 SD) made with a three-dimensional peripheral quantitative computed tomography (pQCT) device at 165- micro m resolution formed the basis for micro-FE models that were used to predict the bone failure load. Following imaging, specimens were experimentally compressed to failure to produce a Colles'-type fracture. Failure loads predicted from micro-FE analyses agreed well with those measured experimentally (R2 = 0.66, p < 0.001). Lower correlations were observed with bone mass (R2 = 0.48, p < 0.001) and microstructural parameters (R2 = 0.47, p < 0.001). Hence, even when only a small region is modeled, micro-FE analysis provides an improved prediction of radius strength.

Absorptiometry, Photon↗

PubMed2002

Estimation of distal radius failure load with micro-finite element analysis models based on three-dimensional peripheral quantitative computed tomography images.

There is increasing evidence that, in addition to bone mass, bone microarchitecture and its mechanical load distribution are important factors for the determination of bone strength. Recently, it has been shown that new high-resolution imaging techniques in combination with new modeling algorithms based on the finite element (FE) method can account for these additional factors. Such models thus could provide more relevant information for the estimation of bone failure load. The purpose of the present study was to determine whether results of whole-bone micro-FE (microFE) analyses with models based on three-dimensional peripheral quantitative computer tomography (3D-pQCT) images (isotropic voxel resolution of 165 microm) could predict the failure load of the human radius more accurately than results with dual-energy X-ray absorptiometry (DXA) or bone morphology measurements. For this purpose, microFE models were created using 54 embalmed cadaver arms. It was assumed that bone failure would be initiated if a certain percentage of the bone tissue (varied from 1% to 7%) would be strained beyond the tissue yield strain. The external force that produced this tissue strain was calculated from the FE analyses. These predictions were correlated with results of real compression testing on the same cadaver arms. The results of these compression tests were also correlated with results of DXA and structural measurements of these arms. The compression tests produced Colles-type fractures in the distal 4 cm of the radius. The predicted failure loads calculated from the FE analysis agreed well with those measured in the experiments (R(2) = 0.75 p < 0.001). Lower correlations were found with bone mass (R(2) = 0.48, p < 0.001) and bone structural parameters (R(2) = 0.57 p < 0.001). We conclude that application of the techniques investigated here can lead to a better prediction of the bone failure load for bone in vivo than is possible from DXA measurements, structural parameters, or a combination thereof.

Aged↗

PubMed2002

Mechanical strength of the thoracolumbar spine in the elderly: prediction from in situ dual-energy X-ray absorptiometry, quantitative computed tomography (QCT), upper and lower limb peripheral QCT, and quantitative ultrasound.

The objective of this study was to compare the ability of clinically available densitometric measurement techniques for evaluating vertebral strength in elderly individuals. Measurements were related to experimentally determined failure strength in the thoracic and lumbar spine. In 127 specimens (82 women and 45 men, age 80 +/- 10 years), dual-energy X-ray absorptiometry (DXA) was performed at the lumbar spine, femur, radius, and total body, and peripheral-quantitative computed tomography (pQCT) at the distal radius, tibia, and femur under in situ conditions with intact soft tissues. Spinal QCT and calcaneal ultrasound parameters were performed ex situ in degassed specimens. Mechanical failure loads of thoracic vertebrae 6 and 10 (T-6 and -10), and lumbar vertebra 3 (L-3) were determined in axial compression on functional three-segment units. In situ anteroposterior DXA and QCT of the lumbar spine explained approximately 65% of the variability of thoracolumbar failure. A combination of cortical and trabecular density (QCT) provided the best prediction in the lumbar spine. However, this was not the case in the thoracic spine, for which lumbar cortical density (QCT) and DXA provided significantly better estimates than trabecular density (QCT). pQCT was significantly less correlated with the strength of lumbar and thoracic vertebrae (r(2) = 40%), but was equivalent to femoral or radial DXA. pQCT measurements in the lower limb showed no advantage over those at the distal radius. Ultrasound explained approximately 25% of the variability of vertebral failure strength and added independent information to spinal QCT, but not to spinal DXA. These experimental results advocate site-specific assessment of vertebral strength by either spinal DXA or QCT.

Absorptiometry, Photon↗

PubMed2002

Body composition, bone mass and microstructural analysis in GH-transgenic mice reveals that skeletal changes are specific to bone compartment and gender.

Experimental and clinical studies suggest that high serum levels of growth hormone (GH) increase cortical but not trabecular bone. We studied body composition and bone structure in transgenic mice (MT-bGH) with systemic overexpression of GH. Body composition was examined with dual-energy X-ray absorptiometry (DXA), ashing, and chemical analysis, and the femora with DXA and micro computerized tomography. The absolute fat and bone tissue contents were significantly higher in GH transgenic mice vs controls (P < or = 0.05), but no significant difference was noted when normalizing the values to body weight. Male transgenics displayed no change in apparent (volumetric) femoral bone density, relative cortical area and trabecular bone volume fraction. Female transgenic mice demonstrated an increase in apparent femoral density and in trabecular bone volume fraction (+130%; P < or = 0.01). The mineralized tissue matrix density was decreased in male and female transgenic mice (P < or = 0.05). The results show that chronic GH excess affects trabecular bone in a gender-specific manner and that bone changes depend on the compartment investigated.

Animals↗