The Sealed Osteons of Cortical Diaphyseal Bone. Early Observations Revisited With Scanning Electron Microscopy

Congiu, Terenzio; Pazzaglia, U. E.

doi:10.1002/ar.21309

Cited by 12 publications

(29 citation statements)

References 15 publications

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“…Another way for an osteon to discontinue transpires within the mid‐cortex itself through relatively rare occurrences called ‘blind’ or sealed osteons (Koltze, ; Cohen & Harris, ; Congiu & Pazzaglia, ). In three dimensions, blind osteons gradually become narrower before they end.…”

Section: Discussionmentioning

confidence: 99%

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Three‐dimensional reconstruction of Haversian systems in human cortical bone using synchrotron radiation‐based micro‐CT: morphology and quantification of branching and transverse connections across age

Maggiano

Clement

et al. 2016

Journal of Anatomy

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This study uses synchrotron radiation-based micro-computed tomography (CT) scans to reconstruct three-dimensional networks of Haversian systems in human cortical bone in order to observe and analyse interconnectivity of Haversian systems and the development of total Haversian networks across different ages. A better knowledge of how Haversian systems interact with each other is essential to improve understanding of remodeling mechanisms and bone maintenance; however, previous methodological approaches (e.g. serial sections) did not reveal enough detail to follow the specific morphology of Haversian branching, for example. Accordingly, the aim of the present study was to identify the morphological diversity of branching patterns and transverse connections, and to understand how they change with age. Two types of branching morphologies were identified: lateral branching, resulting in small osteon branches bifurcating off of larger Haversian canals; and dichotomous branching, the formation of two new osteonal branches from one. The reconstructions in this study also suggest that Haversian systems frequently target previously existing systems as a path for their course, resulting in a cross-sectional morphology frequently referred to as 'type II osteons'. Transverse connections were diverse in their course from linear to oblique to curvy. Quantitative assessment of age-related trends indicates that while in younger human individuals transverse connections were most common, in older individuals more evidence of connections resulting from Haversian systems growing inside previously existing systems was found. Despite these changes in morphological characteristics, a relatively constant degree of overall interconnectivity is maintained throughout life. Altogether, the present study reveals important details about Haversian systems and their relation to each other that can be used towards a better understanding of cortical bone remodeling as well as a more accurate interpretation of morphological variants of osteons in cross-sectional microscopy. Permitting visibility of reversal lines, synchrotron radiation-based micro-CT is a valuable tool for the reconstruction of Haversian systems, and future analyses have the potential to further improve understanding of various important aspects of bone growth, maintenance and health.

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Section: Discussionmentioning

confidence: 99%

“…). Studies suggest diverse reasons for the occurrence of blind osteons, as for example a relationship to necrotic vessels making them evidence for the dynamic requirements of intracortical blood flow (Schumacher, ; Koltze, ; Cohen & Harris, ; Congiu & Pazzaglia, ) and/or trauma (Henrie et al. ).…”

Section: Discussionmentioning

confidence: 99%

Three‐dimensional reconstruction of Haversian systems in human cortical bone using synchrotron radiation‐based micro‐CT: morphology and quantification of branching and transverse connections across age

Maggiano

Clement

et al. 2016

Journal of Anatomy

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“…Sealed + partially sealed osteons were much less frequent in the non‐human bones (< 0.1 vs. 1.8% in human femora, n = 30) despite comparatively equivalent and often higher OPD compared with the human bones we examined. Congiu & Pazzaglia () reported that the percentage of sealed and partially sealed osteons from amputated tibiae from three patients (ages 25, 28, and 52 years) was 4.2 and 1.7%, respectively. However, in a later study of tibial and femoral mid‐diaphyses from four healthy young males (ages 25, 28, 30, and 32) who underwent amputations because of traumatic limb injuries, they found that only 2.2% of the total osteons were sealed (Pazzaglia et al.…”

Section: Discussionmentioning

confidence: 99%

“…It is suggested that increases in the prevalence of sealed osteons might reflect reduced bone quality which can accompany ischemia that presumably accompanies progressive remodeling seen with age in humans (Congiu & Pazzaglia, ; Pazzaglia et al. ).…”

Section: Introductionmentioning

confidence: 99%

“…), understanding how and why sealed osteons form can shed light on the mechanisms that regulate normal bone remodeling and how this process can be perturbed with aging and some diseases. In their study of the cortices of tibiae from three human males (amputated legs, ages 25, 28, 52 years), Congiu & Pazzaglia () showed that, as a percentage of all secondary osteons examined, 4–5% were sealed. They theorized that sealed osteons occur because

‘changes in flow dynamics in the system may cause some branches to become excluded from blood flow, with subsequent collapse and degeneration of the capillary vessel.…”

Section: Introductionmentioning

confidence: 99%

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Sealed osteons in animals and humans: low prevalence and lack of relationship with age

et al. 2018

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Sealed osteons are unusual variants of secondary osteons that have received little attention, especially in non-human bones. Sealed osteons are characterized by central canals that are plugged with bone tissue. As with other variants of secondary osteons (e.g. drifting, dumbbell, multi-canal), understanding how and why sealed osteons form can shed light on the mechanisms that regulate normal bone remodeling and how this process can be perturbed with aging and some diseases. In a recent microscopic evaluation of human tibiae obtained after traumatic amputations, 4-5% of the osteons were sealed. It is suggested that this high prevalence reflects occasional localized microscopic ischemia from normal osteonal remodeling; hence sealed osteons are implicated in human skeletal fragility. Therefore, osteon prevalence would be expected to correlate with the bone remodeling seen with aging; for example, showing positive relationships between sealed osteons and the population density of typical secondary osteons (OPD). We evaluated the prevalence of partially sealed (80-99% sealed) and fully sealed osteons with respect to age and variations in OPD in 10 adult human femora (34-71 years) and in various non-human appendicular bones of mature animals that were not of advanced age, including deer calcanei, equine radii and equine third metacarpals. An additional sample of 10 bilateral human femora with unilateral non-cemented total hip replacements (F,+HR) and non-implanted contralateral femora (F,-HR) were evaluated (10 patients; 52-94 years). In non-human bones, sealed + partially sealed osteons were rare (~0.1%) even when having relatively high OPD. When considering sealed + partially sealed osteons in femora from patients without any HR, results showed that 1.6% of the osteons were sealed or partially sealed, which was much lower than anticipated, but this is 10- to 20-fold more than in any of the non-human bones. Additionally, in all bones, sealed + partially sealed osteons were significantly smaller than typical secondary osteons (mean diameters: 125 vs. 272 μm; P < 0.005). In the patients with HR, the percentage of sealed + partially sealed osteons: (i) did not correlate with age, (ii) showed no significant difference between F,-HR and F,+HR (1.9 vs. 2.1%; P = 0.2), and (iii) was positively correlated with OPD (r = 0.67, P = 0.001), which differs from the very weak or lack of correlations in the non-human bones and the other human femur sample. The lack of an age-related relationship, in addition to the very low prevalence of sealed + partially sealed osteons are inconsistent with the idea that they contribute to reduced bone quality seen in aging humans. The small size of sealed and partially sealed osteons, regardless of species affiliation, suggests that they represent closing cones at the termini of some osteons. Available evidence suggests that osteons of primates might have a greater capacity for branching that is associated with closing cones, which might explain the 10-20 times higher prevalence of sealed + partia...

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Morphometry and Patterns of Lamellar Bone in Human Haversian Systems

Pazzaglia

Congiu

Marchese

et al. 2012

The Anatomical Record

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The lamellar architecture of secondary osteons (Haversian systems) has been studied with scanning electron microscopy (SEM) in transverse sections of human cortical bone. Na 3 PO 4 etching was used to improve the resolution of the interface between neighboring lamellae and the precision of measurements. These technical improvements permitted testing of earlier morphometry assumptions concerning lamellar thickness while revealing the existence of different lamellar patterns. The mean lamellar thickness was 9.0 6 2.13 lm, thicker and with a wider range of variation with respect to earlier measurements. The number of lamellae showed a direct correlation with the lamellar bone area, and their thickness had a random distribution for osteonal size classes. The circular, concentrical pattern was the more frequently observed, but spiral and crescent-moonshaped lamellae were also documented. Selected osteons were examined by either SEM or SEM combined with polarized light microscopy allowing comparisons of corresponding sectors of the osteon. The bright bands observed with polarized light corresponded to the grooves observed in etched sections by SEM. The dark bands corresponded to the lamellar surface with the cut fibrils oriented approximately longitudinally along the central canal axis. However, lamellae with large and blurred bright bands could be observed, which did not correspond to a groove observed by SEM. These findings are in contrast with the assumption that all the fibril layers within a lamella are oriented along a constant and unchangeable angle. The different lamellar patterns may be explained by the synchronous or staggered recruitment and activation of osteoblasts committed to the osteon's completion. Anat Rec, 295:1421Rec, 295: -1429Rec, 295: , 2012. V C 2012 Wiley Periodicals, Inc.Key words: human; cortical bone; lamellae; scanning electron microscopyThe concentric laminar structures found in secondary bone were first recognized by Havers in 1691 (thus, ''Haversian'' systems and canals). A mature Haversian system structure in bone is also called an ''osteon.'' The structure of Haversian systems was subsequently confirmed and extended by many subsequent studies. However, these lead to two contrasting models on how the collagen fibrils were arranged within the individual

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The Sealed Osteons of Cortical Diaphyseal Bone. Early Observations Revisited With Scanning Electron Microscopy

Cited by 12 publications

References 15 publications

Three‐dimensional reconstruction of Haversian systems in human cortical bone using synchrotron radiation‐based micro‐CT: morphology and quantification of branching and transverse connections across age

Three‐dimensional reconstruction of Haversian systems in human cortical bone using synchrotron radiation‐based micro‐CT: morphology and quantification of branching and transverse connections across age

Sealed osteons in animals and humans: low prevalence and lack of relationship with age

Morphometry and Patterns of Lamellar Bone in Human Haversian Systems

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