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Biomedical subjects

F Melsen

Publications and source records attributed to F Melsen.

178 records · Page 10Linked to original sources
PubMedDate not supplied

Three-dimensional morphology of trabecular bone osteons reconstructed from serial sections.

The anatomy of the remodeling sites in bone is only partly reflected by random histologic sections. This study is aimed at reconstructing the three-dimensional morphology of the osteons in human trabecular bone from serial sections of decalcified tissue. The osteons resembled broad bands, which were made up of parallel lamellae, bounded on one side by the marrow surface and on the other side by an irregular cement plane. The mean thickness was much less (less than 0.2) than the mean extent in the other dimensions. The plate may, therefore, be used as the morphologic model for stereologic studies. The plates were curved and irregular. One three-dimensional osteon can, therefore, give rise to a varying number of profiles in a single random section. The two-dimensional profiles, which are of unequal surface extent, are thus not appropriate sampling units for morphometric studies of, e.g., osteon thickness, osteoid thickness, or calcification rate in trabecular bone. When estimating thickness the number of measuring sites should be sampled proportional to the surface extent of the profiles.

Bone and Bones↗
PubMedDate not supplied

Thickness of bone formed at remodeling sites in normal human iliac trabecular bone: variations with age and sex.

The thickness of the bone walls formed at completed remodeling sites was estimated by morphometry in iliac trabecular bone from 85 normal individuals (48 women and 37 men) aged 18-90 years. The mean three-dimensional (3-D) wall thickness was 59.4 +/- 5.9 micron. No sex difference was observed. The wall thickness decreased with age: Thickness (micron) = 65.56 micron - 0.14 micron/yr X age (yr). This reduction may lead to a loss of bone with increasing age. The coefficient of variation in completed wall thickness between individuals of the same age was 7%. The factors controlling the thickness are largely unknown, but it was noted that the intraindividual distributions of linear 3-D wall thickness (proportional to the mass of the wall) were symmetric, while distributions of reciprocal 3-D thickness (proportional to the conductivity for oxygen and waste products) were markedly rightskewed. A subgroup comprising 42 individuals aged 18-56 years had been double labeled with tetracycline. The average 3-D calcification rate was 0.63 +/- 0.11 micron/day. No relationship to age or sex was demonstrated. Based on the estimates of completed wall thickness and calcification rate, the mean duration of calcification at remodeling sites was calculated to be approximately 100 days.

Adolescent↗
PubMedDate not supplied

Age- and sex-related changes in iliac cortical bone mass and remodeling.

Iliac crest bone biopsies were obtained from 64 normal individuals (41 women and 23 men) aged 19-90 (mean 48.2) years. Thirty-four were double-labeled with tetracycline before biopsy. The following variables were measured in all biopsies: biopsy core width (C.Wi), absolute (A.Ct.Wi) and fractional (F.Ct.Wi) cortical width, absolute (A.Cn.Wi) and fractional (F.Cn.Wi) cancellous width, cortical porosity (Ct.Po), osteon diameter (On.Dm), Haversian canal diameter (Ha.Ca.Dm), and wall thickness (W.Th). In the tetracycline-labeled biopsies the typical cortical remodeling cycle was reconstructed and the activation frequency was estimated. A negative cortical bone balance with aging was found in both sexes. In females F.Ct.Wi decreased (p < 0.02) with aging because of marrow expansion (p < 0.05). Furthermore, Ct.Po increased (p < 0.001) because of a decrease in W.Th (p < 0.01) and an increase in H.Ca.Dm (p < 0.001). In males the negative cortical bone balance with aging was exclusively caused by an increase in Ct.Po (p < 0.001) partially explained by an expanding H.Ca.Dm (p < 0.01). The On.Dm increased with aging (p < 0.01), but surprisingly, no fall in W.Th was observed. Reconstruction of the remodeling cycle did not reveal any significant difference between younger women and men. However, the activation frequency rose from 0.5 per year in premenopausal to 1.0 per year in postmenopausal women (p < 0.001), giving rise to a high turnover state, an increase in the remodeling space, and thereby the porosity in the cortical bone immediately after menopause. The present study has shown a reduction in cortical bone mass in elderly people, compared with younger, which may be explained by an age-related remodeling imbalance. This reduction is further increased in women in the postmenopausal state because of a postmenopausal accelerated bone turnover.

Adult↗
PubMedDate not supplied

Primary hyperparathyroidism: iliac crest cortical thickness, structure, and remodeling evaluated by histomorphometric methods.

Iliac crest bone biopsies from 62 patients (42 women, 20 men; median age 59 years; range 17-79 years) with primary hyperparathyroidism (PHP) were examined. Static and structural parameters were compared with 30 age- and sex-matched normal controls. Eighteen sex-matched younger controls were used for evaluation of the dynamic controls. On the endocortical surface increase in extension of eroded (p < 0.01) and formative (p < 0.01) surfaces was found in PHPs compared with normals. Endocortical bone formation rate was increased in PHPs (p < 0.05), but mineral appositional rate and adjusted appositional rate were normal. On the periosteal surface very little remodeling activity was found. Although bone formation rate was found increased in PHPs (p < 0.05), more than half of the labeled biopsies were without periosteal tetracycline in patients, and only 2 of 18 biopsies from normals contained periosteal tetracycline labels. No significant decreases in cortical width or relative cortical width were found in PHPs. In both patients and controls an age-related decrease in relative cortical width cortical width were found in PHPs. In both patients and controls an age-related decrease in relative cortical width was noted for women (PHPs: r = -0.52, p < 0.01; controls: r = -0.59, p < 0.001), but not for men. Cortical porosity was about 30% increased in PHPs (p < 0.02). Only normal women showed a positive age-related increase in porosity (r = 0.61, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Three-dimensional reconstruction of entire vertebral bodies.

This paper describes a technique for 3-D reconstruction of large cancellous bone regions. The output is a 3-D array describing the original cancellous bone region, and the output can be used for any kind of measurement of the bone architecture. The technique was developed as a tool for researchers conducting experimental and clinical studies related to cancellous bone architecture and, ultimately, to cancellous bone quality. A set of new and unbiased methods for quantification of cancellous bone has been a stimulus for the development of the technique, as the quantification methods rely on 3-D information. The technique is based on automated serial sectioning, and all steps from specimen preparation to image segmentation are described in detail. Examples of 3-D reconstructed vertebral bodies are given. By use of the described technique, between 300 and 600 sections can be made and registered per hour, which means that an average vertebral body can be reconstructed in about 2 h. Compared to previous implementations of the general principle of serial sectioning, this is a significant improvement both in resolution and in time efficiency.

Aged↗
PubMedDate not supplied

Marked changes in iliac crest bone structure in postmenopausal osteoporotic patients without any signs of disturbed bone remodeling or balance.

Successful iliac crest bone biopsies were obtained from 63 women with postmenopausal vertebral crush fracture osteoporosis. Structural and static histomorphometric parameters were compared with 25 age-matched normal females, who had suffered an unexpected and sudden death. The control group for dynamic parameters comprised 13 younger normal females. Marked structural changes were observed in the osteoporotic patients in cortical as well as cancellous bone. Cortical width, trabecular volume, trabecular bone surface density and trabecular number were all reduced, whereas trabecular separation and star volume were increased. On the other hand trabecular thickness was normal in the patients. These structural changes in cancellous bone indicate that extensive perforations of trabecular plates have occurred or that whole trabecular elements have been removed. The remodeling cycles of cancellous bone surface and the frequency by which they were repeated (activation frequency) did not differ significantly between osteoporotic patients and normal younger women. The bone balance per remodeling cycle in osteoporotic patients and controls was not significantly different. No subset of individuals in the group of osteoporotic patients could be identified regarding extent of resorptive and formative surfaces, bone formation rate or activation frequency. In the present osteoporotic patients nothing in the ongoing remodeling process could explain the marked changes in bone structure. The pathophysiological changes leading to osteoporosis may therefore occur earlier in life, maybe long before the manifestation of the disease.

Aged↗
PubMedDate not supplied

Histomorphometric analysis of iliac trabecular bone in otosclerosis.

With the aim of investigating whether patients with otosclerosis suffer from a generalized bone disorder, a histomorphometric analysis of trabecular bone from the iliac crest was performed. Iliac crest biopsies from 10 patients with otosclerosis and 20 normal controls were obtained after tetracycline double labelling and examined by histomorphometry. No significant differences were found in the estimates of density and remodeling of bone between patients and sex and age-matched normal controls. Qualitatively the bone specimens showed no signs of any generalized bone disorder.

Adult↗
PubMedDate not supplied

Relations of bone mineral content, ash weight and bone mass: implication for correction of bone mineral content for bone size.

Bone mineral content (BMC) was measured by photon absorptiometry in fresh bone specimens: 35 iliac crest and 39 forearms were used. BMC was related to ash weight, fat-free weight and the amount of bone determined by quantitative histologic methods. Ninety-five per cent of the variation in bone mineral concentration (BMC') in the iliac crest could be explained by variation in ash weight, and 88% of the variation in BMC in the forearm could be explained by variation in the amount of bone determined histologically. The total cross-sectional bone area of radius and ulna could be calculated from the width of the structures measured on the photon absorption curves. Using this parameter and the relation between BMC and ash weight, the actual in-vivo bone mineral content in the forearm could be expressed in terms of ash-weight in grams per cm3 of total bone.

Anthropometry↗
PubMedDate not supplied

Tissue reaction and material characteristics of four bone substitutes.

The aim of the present study was to qualitatively and quantitatively compare the tissue reactions around four different bone substitutes used in orthopedic and craniofacial surgery. Cylinders of two bovine bone substitutes (Endobon and Bio-Oss) and two coral-derived bone substitutes (Pro Osteon 500 and Interpore 500 HA/CC) were implanted into 5-mm bur holes in rabbit tibiae. There was no difference in the amount of newly formed bone around the four biomaterials. Interpore 500 HA/CC resorbed completely, whereas the other three biomaterials did not undergo any detectable biodegradation. Bio-Oss was osseointegrated to a higher degree than the other biomaterials. Material characteristics obtained by diffuse reflectance infrared Fourier transform spectrometry analysis and energy-dispersive spectrometry did not explain the differences in biologic behavior.

Animals↗