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F Eckstein

Publications and source records attributed to F Eckstein.

At least 19 recordsLinked to original sources
PubMed2002

Knee cartilage of spinal cord-injured patients displays progressive thinning in the absence of normal joint loading and movement.

OBJECTIVE: Alterations in the morphologic, biochemical, and mechanical properties of cartilage occur after unloading and immobilization in animals. However, the findings have been inconsistent and it is unclear whether such changes also take place in humans. This study tested the hypothesis that progressive thinning of knee joint cartilage is observed after spinal cord injury. METHODS: In this in vivo study, knee cartilage was assessed in patients with complete, traumatic spinal cord injury at 6 (n = 9), 12 (n = 11), and 24 months (n = 6) after injury. Morphologic parameters of the knee cartilage (mean and maximum thickness as well as surface area) were computed from magnetic resonance imaging (MRI) data, and results were compared with those in young, healthy volunteers (n = 9). RESULTS: After 6 months of injury, the mean articular-cartilage thickness was significantly less in the patella and medial tibia (decrease of 10% and 16%, respectively; P < 0.05), but not in the lateral tibia (decrease of 10%), compared with the MRI findings in healthy volunteers. After 12 and 24 months of injury, the differences amounted to a reduction of 21% and 23%, respectively, in the patella, 24% and 25%, respectively, in the medial tibia, and 16% and 19%, respectively, in the lateral tibia. The changes were significant in all 3 surfaces of the spinal cord-injured joint cartilage (P < 0.05-0.01). CONCLUSION: Our data show, for the first time, that progressive thinning (atrophy) of human cartilage occurs in the absence of normal joint loading and movement. This may have important implications for patient management, in particular for spinal cord-injured patients and patients who are immobilized after surgery.

Adult↗
PubMed2002

[Quantitative cartilage analysis with magnetic resonance tomography (qMRI)--a new era in arthrosis diagnosis?].

Magnetic resonance imaging (MRI) is a new and very powerful method for the diagnostics and monitoring of osteoarthritis. Its advantage is that all articular tissues can be visualized directly and are accessible for three-dimensional analysis. This article reviews qualitative, semi-quantitative, and quantitative studies on articular cartilage with MRI. In particular we discuss pulse sequences and three-dimensional postprocessing methods for quantitative analysis of cartilage volume and thickness, along with their accuracy and precision in healthy volunteers and patients with osteoarthritis. It addition, we present approaches for quantitative analyses of structural/biochemical parameters and for the deformational behavior of cartilage in vivo.

Cartilage, Articular↗
PubMed2002

Mechanical strength of the proximal femur as predicted from geometric and densitometric bone properties at the lower limb versus the distal radius.

This experimental study compares geometric and densitometric properties of cortical and trabecular bone at the lower limb and the distal radius with those at the femoral neck, and evaluates their ability to predict mechanical failure loads of the proximal femur. One hundred five cadavers were examined with peripheral quantitative computed tomography (LpQCT), with measurements being performed in situ at the distal radius (4%, 20%, 33%), at the distal and proximal tibia, at the tibial and femoral shaft, and at the distal femur. Ex situ measurements were obtained at the femoral neck and at the proximal femoral shaft. Pairs of femora were mechanically tested in a vertical loading and a side impact (fall) configuration. The total (cross-sectional) bone mineral content and trabecular density, but not the cortical properties, displayed a higher association between the femoral neck and the peripheral lower limb than between the neck and the distal radius. Approximately 50%-60% of the variability of femoral failure loads (and >80% of trochanteric side impact fractures) were predicted by in vitro measurements at the neck. Geometric cortical parameters and density contributed independently and significantly to femoral strength. Measurements at the peripheral skeleton explained, however, only 30%-45% of the variability of femoral failure, with no significant difference between the lower limb and the distal radius. At peripheral sites, a combination of geometric and densitometric variables was slightly superior to bone mineral content alone in predicting failure in vertical loading, but this was less evident for cervical side impact fractures. The results show that a stronger association of total bone mineral content and trabecular density between the femoral neck and the lower limb does not translate into improved prediction of femoral strength from measurements at the lower limb vs. those at the distal radius.

Aged↗
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

Functional adaptation of human joints to mechanical stimuli.

OBJECTIVE: This study tests the hypothesis that functional adaptation occurs in human joints, and that substantial differences in joint 'loading history' explain the phenotypic variability observed in human cartilage morphology. METHOD: We examined 18 triathletes (nine men and nine women) who had been physically active throughout life (training for >10 h per week for the last 3 years), and 18 volunteers that had never been physically active on a regular basis. The right knee joints were imaged with a previously validated fat-suppressed gradient-echo MR sequence. Cartilage volume, thickness, joint surface areas, and normalized cartilage signal intensity were determined with post-processing software, specifically designed for these applications. RESULTS: The knee joint cartilage thickness, and signal intensity were not significantly different between athletes and inactive volunteers, but male athletes displayed significantly larger knee joint surfaces (P< 0.01; +8.8%). Female athletes displayed a significantly larger medial tibia (P< 0.05; +18.9%), the difference in the total knee surface area reaching borderline significance (P=0.08; +7.0%). CONCLUSIONS: The results suggest that joint size can be modulated during growth, but that (opposite to muscle and bone) the thickness of the cartilage does not adapt to mechanical stimulation. This finding may reveal a general principle in the development and functional adaptation of diarthrodial joints, elucidating an important mechanism for reducing mechanical stress in biphasic cartilage layers.

Adaptation, Physiological↗
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↗
PubMed2001

Magnetic resonance imaging-based assessment of cartilage loss in severe osteoarthritis: accuracy, precision, and diagnostic value.

OBJECTIVE: To examine the in vivo accuracy and precision of magnetic resonance imaging (MRI)-based assessment of cartilage loss in patients with severe osteoarthritis (OA) of the knee. METHODS: High-resolution MRI images of the tibial cartilage were obtained in 8 patients prior to total knee arthroplasty, using a water-excitation gradient-echo MRI sequence (acquisition time 6 minutes 19 seconds; spatial resolution 1.2 x 0.31 x 0.31 mm3). The MRI measurements were repeated after joint repositioning. The precision of the cartilage volume and thickness computations was determined after 3-dimensional reconstruction. During surgery, the tibial plateaus were resected, and the MRI data were compared with water displacement of surgically retrieved cartilage. RESULTS: The standard deviation (coefficient of variation) of repeated tibial cartilage volume measurements was 56 mm3 (5.5%) medially and 59 mm3 (3.8%) laterally. The deviation from surgically removed tissue was -13%, on average, with a high linear correlation between both methods (r = 0.98). In patients with varus OA, the tissue loss was estimated to be 1,290 mm3 in the medial tibia and 1,150 mm3 in the lateral tibia, compared with the data in healthy volunteers. CONCLUSION: Noninvasive quantitative MRI-based analysis of cartilage morphometry in severe OA is accurate, precise, and displays high potential diagnostic value.

Aged↗
PubMed2001

Age-related changes in the morphology and deformational behavior of knee joint cartilage.

OBJECTIVE: Alterations of cartilage morphology and mechanical properties occur in osteoarthritis, but it is unclear whether similar changes also take place physiologically during aging, in the absence of disease. In this in vivo study, we tested the hypothesis that thinning of knee joint cartilage occurs with aging and that elderly subjects display a different amount of cartilage deformation than do young subjects. METHODS: We evaluated 30 asymptomatic subjects ages 50-78 years. Morphologic parameters for the knee cartilage (mean and maximum thickness, surface area) were computed from magnetic resonance imaging data. Results were compared with those in 95 young asymptomatic subjects ages 20-30 years. Deformation of the patellar cartilage was determined after the subjects performed 30 knee bends. RESULTS: There was a significant reduction of patellar cartilage thickness in elderly women (-12%; P < 0.05), but not in elderly men (-6%). Femoral cartilage was significantly thinner in both sexes (-21% in women, -13% in men; P < 0.01), whereas tibial cartilage thickness displayed only nonsignificant trends (-10% in women, -7% in men). Patellar cartilage deformation was -2.6% in elderly women and -2.2% in elderly men. These values were significantly lower (P < 0.05) than those in young subjects. CONCLUSION: We confirmed the hypothesis that knee cartilage becomes thinner during aging, in the absence of cartilage disease, but that the amount of reduction differs between sexes and between compartments of the knee joint. We show that under in vivo loading conditions, elderly subjects display a lower level of cartilage deformation than do healthy young subjects.

Adult↗
PubMed2001

[Effect of muscle activity on the 3-dimensional movement pattern of the shoulder. Study with open MRI].

The objective of this study was to analyze the influence of shoulder muscle activity on the three-dimensional motion pattern of the shoulder girdle in the living. 14 healthy volunteers were investigated with an open MRI system at 60-120 degrees abduction--with and without activity of the shoulder abductors. The 3D motion pattern of the humerus, scapula, clavicle and M. supraspinatus were computed. Under muscle activity, the glenoid demonstrated a slightly reduced elevation at 60 degrees of abduction (20.5 degrees +/- 8.2 degrees vs. 23.1 degrees +/- 6.3 degrees; not significant), and at 120 degrees a significantly higher degree of rotation under muscle activity (43.3 degrees +/- 8.6 degrees vs. 36.1 degrees +/- 5.2 degrees; p < 0.01), whereas at 90 degrees no difference was observed. This caused a significant reduction of the scapulo-humeral rhythm at 120 degrees (2.6 vs. 1.5; p < 0.01), a significant increase of the supraspinatus angle (123.3 degrees +/- 6.7 degrees vs. 117.3 degrees +/- 6.5 degrees; p < 0.05) as well as a reduction of the supraspinato-humeral relationship (1.0 vs. 0.97). The study demonstrates that muscle activity leads to an alteration of shoulder girlde motion patterns at higher degrees of abduction, with increased rotation of the scapula, an altered spatial relationship between the supraspinatus and humerus.

Adult↗
PubMed2001

Effect of fixation, soft-tissues, and scan projection on bone mineral measurements with dual energy X-ray absorptiometry (DXA).

The objective of this study was to determine the effect of fixation, soft tissues, and scan projection on bone mineral measurements with dual energy X-ray absorptiometry (DXA). In seven fresh cadavers, DXA scans were obtained within 48 hours of death and after 10 months of fixation with 5% formalin/95% ethanol. The measurements showed a high linear relationship (r2 > 0.97; SEE% < 10%), with no significant deviation after fixation (except for total body BMD: -3.1%). In 14 specimens, the precision of femoral and spinal analyses was determined under in situ and ex situ conditions. There was no significant difference between ex situ and in situ reproducibility, the coefficient of variation being < 3% for the BMC and < 2% for the BMD (except at the greater trochanter). The effect of the soft tissues and scan projection was assessed in 83 cadavers aged 80.4 +/- 10.3 years. The soft tissues had only a small effect on analyses of the total femur (r2 > 0.90; SEE% < 9%), but led to more substantial deviations in regional femoral analyses and in the spine (r2 = 0.78-0.90; SEE% = 8-22%). Comparing lateral with anterior-posterior (AP) spinal scans, the vertebral bodies were found to occupy 40.2 +/- 7.2% of the BMC, and 62.0 +/- 11.2% of the BMD, the ranges being 26-58%, and 38-91%, respectively. There were large deviations from linearity between in situ AP and ex situ lateral spinal scans with r2 values of 0.63 and 0.73 for BMD and BMC (SEE% = 52% and 27% relative to the vertebral body), respectively.

Absorptiometry, Photon↗
PubMed2001

Gender differences in knee joint cartilage thickness, volume and articular surface areas: assessment with quantitative three-dimensional MR imaging.

OBJECTIVE: To compare the cartilage thickness, volume, and articular surface areas of the knee joint between young healthy, non-athletic female and male individuals. SUBJECTS AND DESIGN: MR imaging was performed in 18 healthy subjects without local or systemic joint disease (9 female, age 22.3 +/- 2.4 years, and 9 male, age 22.2 +/- 1.9 years.), using a fat-suppressed FLASH 3D pulse sequence (TR = 41 ms, TE = 11 ms, FA = 30 degrees) with sagittal orientation and a spatial resolution of 2 x 0.31 x 0.31 mm3. After three-dimensional reconstruction and triangulation of the knee joint cartilage plates, the cartilage thickness (mean and maximal), volume, and size of the articular surface area were quantified, independent of the original section orientation. RESULTS AND CONCLUSIONS: Women displayed smaller cartilage volumes than men, the percentage difference ranging from 19.9% in the patella, to 46.6% in the medial tibia. The gender differences of the cartilage thickness were smaller, ranging from 2.0% in the femoral trochlea to 13.3% in the medial tibia for the mean thickness, and from 4.3% in the medial femoral condyle to 18.3% in the medial tibia for the maximal cartilage thickness. The differences between the cartilage surface areas were similar to those of the volumes, with values ranging from 21.0% in the femur to 33.4% in the lateral tibia. Gender differences could be reduced for cartilage volume and surface area when normalized to body weight and body weight x body height. The study demonstrates significant gender differences in cartilage volume and surface area of men and women, which need to be taken into account when retrospectively estimating articular cartilage loss in patients with symptoms of degenerative joint disease. Differences in cartilage volume are primarily due to differences in joint surface areas (epiphyseal bone size), not to differences in cartilage thickness.

Adult↗
PubMed2001

In vivo morphometry and functional analysis of human articular cartilage with quantitative magnetic resonance imaging--from image to data, from data to theory.

Analyses of form-function relationships and disease processes in human articular cartilage necessitate in vivo assessment of cartilage morphology and deformational behavior. MR imaging and advanced digital post-processing techniques have opened novel possibilities for quantitative analysis of cartilage morphology, structure, and function in health and disease. This article reviews work on three-dimensional post-processing of MR image data of articular cartilage, summarizing studies on the accuracy and precision of quantitative analyses in human joints. It presents normative values on cartilage volume, thickness, and joint surface areas in the human knee, and describes the correlation between different joints and joint surfaces as well as their association with gender, body dimensions, and age. The article summarizes ongoing work on functional adaptation of articular cartilage to mechanical loading, analyses of in situ cartilage deformation in intact joints in vivo and in vitro, and the quantitative evaluation of cartilage tissue loss in osteoarthritis. We describe evolving techniques for assessment of the structural/biochemical composition of articular cartilage, and discuss future perspectives of quantitative cartilage imaging in the context of joint mechanics, mechano-adaptation, epidemiology, and osteoarthritis research. Specifically, we show that fat-suppressed gradient echo sequences permit valid analysis of cartilage morphology, both in healthy and severely osteoarthritic joints, as well as highly reproducible measurements (CV%=1 to 3% in the knee, and 2 to 10% in the ankle). Relatively small differences in cartilage morphology exist between both limbs of the same person (approximately 5%), but large differences between individuals (CV% approximately 20%). Men display only slightly thicker cartilage then women (approximately 10%), but significantly larger joint surface areas (approximately 25%), even when accounting for differences in body weight and height. Weight and height represent relatively poor predictors of cartilage thickness (r2 <15%), but muscle cross section areas display more promising correlations (r2 >40%). The level of physical exercise (sportive activity) does not account for interindividual differences in cartilage thickness. The thickness appears to decrease slightly in the elderly--in particular in women, even in the absence of osteoarthritic cartilage lesions. Strenuous physical exercises (e.g., knee bends) cause a 6% patellar cartilage deformation in young individuals, but significantly less deformation in elderly men and women (<3%). The time required for full recovery after exercise (fluid flow back into the matrix) is relatively long (approximately 90 min). Static in situ compression of femoropatellar cartilage with 150% body weight produces large deformations after 4 h (approximately 30% volume change), but only very little deformation during the first minutes of loading. Quantitative analyses of magnetization transfer and proton density hold promise for biochemical evaluation of articular cartilage, and are shown to be related to the deformational behavior of the cartilage. Application of these techniques to larger cohorts of patients in epidemiological and clinical studies will establish the role of quantitative cartilage imaging not only in basic research on form-function relationships of articular cartilage, but also in clinical research and management of osteoarthritis.

Cartilage, Articular↗
PubMed2001

Correlation of thoracic and lumbar vertebral failure loads with in situ vs. ex situ dual energy X-ray absorptiometry.

In this study we explore the hypothesis that estimates of failure loads in the thoracic spine by lumbar dual energy X-ray absorptiometry (DXA) are compromised of skeletal heterogeneity throughout the spine and artifacts of spinal DXA. We studied the correlation between mechanical failure loads of thoracic and lumbar vertebrae, and that of in situ vs. ex situ lumbar DXA with thoracic and lumbar fracture loads, respectively. One hundred and nineteen subjects (76 female, age 82+/-9yr; 43 male, age 77+/-11yr) were examined under in situ conditions (anterior-posterior direction), the scans being repeated ex situ (lateral projection) in 68 cases. The failure loads of thoracic vertebrae (T) 6 and 10, and lumbar vertebra (L) 3 were determined in axial compression, using a functional 3-segment unit. The correlation between thoracic failure loads (T6 vs. T10) was significantly (p<0.01) higher (r=0.85) than those between thoracic and lumbar vertebrae (r=0.68 and 0.61, respectively). Lateral ex situ DXA displayed a significantly higher correlation (p<0.05) with lumbar vertebral fracture loads than in situ anterior-posterior DXA (r=0.85 vs. 0.71), but the correlation of thoracic failure loads with lateral ex situ lumbar DXA was similar to that obtained in situ in anterior-posterior direction (r=0.69 vs. 0.69 for T10, and r=0.61 vs. 0.65 for T6). The correlation between fracture loads of different spinal segments, and between DXA and failure loads was not significantly different between men and women. The results demonstrate a substantial heterogeneity of mechanical competence throughout the spine in elderly individuals. Because of the high incidence of fractures in the thoracic spine, these findings suggest that, clinically, lateral DXA involves no relevant advantage over anterior-posterior measurements of the lumbar spine.

Absorptiometry, Photon↗
PubMed2001

An in vivo technique for determining 3D muscular moment arms in different joint positions and during muscular activation - application to the supraspinatus.

OBJECTIVE: To develop a 3D in vivo technique for determining the moment arm and insertion angle of muscles in different joint positions and under muscular activity. DESIGN: An open magnetic resonance imaging system and 3D processing techniques were used for determining the moment arm and insertion angle of the supraspinatus in healthy volunteers. BACKGROUND: Muscular moment arms are important parameters for the computation of joint forces, however, so far in vivo measurements have not considered the influence of muscle activity and were restricted to two dimensions. METHODS: 10 healthy shoulders were investigated in 30-150 degrees abduction with and without abducting muscular activity, using an open magnetic resonance imaging. The minimal distance between the midpoint of the humeral head and the line of action of the supraspinatus was determined in 3D. The insertion angle was derived by calculating the angle between the humerus and the supraspinatus. RESULTS: During elevation a significant (P < 0.001) increase of the supraspinatus moment arm was observed (19.9 mm (SD, 2.3 mm) at 30 degrees; 23.3 mm (SD, 2.5 mm) at 150 degrees ), being significantly larger at 90 degrees and 120 degrees under muscle activity. The insertion angle also increased significantly during elevation (P < 0.001), the values becoming larger under muscle activity at 60 degrees (P < 0.01) and at 90 degrees (P < 0.05). CONCLUSIONS: This 3D technique permits to determine the moment arm and insertion angle of muscles in vivo not only in various joint positions but also under in vivo muscle activity. For the supraspinatus, we observed a constant increase of both parameters during arm abduction. RELEVANCE: The technique and these data can be used for improved computation of joint forces in biomechanical model, and for precise diagnostics in patients with altered scapulohumeral motion patterns.

Adult↗