Variability in osteon size in recent human populations

The possibility of smaller osteons in the cortical bone of Late Pleistocene human populations begs the question of how these histological features vary within individual skeletons among and between populations. The distributional characteristics of total osteon area (On.Ar) and Haversian canal area (H.Ar) are explored using data from three samples of historically known individuals: ribs and femora from eighteenth-century Huguenots in England (Spitalfields, n = 20), ribs and femora from nineteenth-century British settlers in Canada (St. Thomas, n = 21), and ribs from twentieth-century South African cadavers (University of Cape Town; following curatorial classifications, n = 10 white, 10 black, 10 colored). Neither histological variable is normally distributed. About 96% of the random variation is within the individual bone sample. There are no significant differences between sexes for either variable in any sample, and age has no effect in most instances. Femoral osteons are significantly larger than rib osteons within individuals and across samples. Haversian canal area is more variable than On.Ar, especially in the twentieth-century sample, where within-sample coefficients of variation are frequently >100%. Using modern centiles developed here, some Late Pleistocene long bone samples have On.Ar values below the range of modern variation. Because of ribs' smaller cross-sectional areas and less broadly ranging values for On.Ar, ribs would provide a preferable site for future comparative studies. Am J Phys Anthropol 106:219–227, 1998. © 1998 Wiley-Liss, Inc.     

Secondary osteon and Haversian canal dimensions as behavioral indicators

Variation in the size of structures within mature cortical bone is relevant to our understanding of apparent differences between human samples, and it is relevant to the development of histologically based age-estimation methods. It was proposed that variation may reflect effects of physical activity, through biomechanical and/or metabolic mechanisms. If these factors are local, femoral osteon area (On.Ar) should be more histologically variable than On.Ar in ribs. Ribs should show a higher variation in Haversian canal area (H.Ar) if they are sites of more remodeling activity and hence of arrested refilling of secondary osteons at time of death. This study compares On.Ar and H.Ar of secondary osteons from femora (15) and ribs (29) from 44 Holocene (Later Stone Age) foragers from South Africa (M = 19, F = 25) to values from paired femora and ribs from historic samples (Spitalfields and St. Thomas, 20 pairs from each). Fixed-effects analysis of variance demonstrates rib On.Ar to be significantly smaller than femur, but with no sex or age effects. The femur-to-rib On.Ar ratio is lower for the Holocene foragers than for the two modern samples because of relatively large rib On.Ar. Femora and ribs from the same skeleton normally show femoral On.Ar larger than rib On.Ar (37/44 pairs). Mean femoral values of On.Ar are more diverse than rib On.Ar values, but within-sample coefficients of variation are similar. Values for H.Ar are highly variable and do not reflect anatomical site, age, sex, or population effects. The patterning of osteon size does not appear to be linked to physical activity or to different rates of metabolic activity within the skeleton, at least not in a straightforward way.     

Rib remodeling dynamics in a skeletal population from Kulubnarti, Nubia

Bone remodeling variables in the rib were analyzed for a skeletal population of medieval antiquity (ca. A.D. 550-1450) from Kulubnarti, in Sudanese Nubia. The skeletal remains are naturally mummified and in an excellent state of preservation. The study sample consists of thin sections from the ribs of 80 individuals, ranging in age from 15-50+ years. Ribs were examined using a standard microscope and image analysis software. Numbers of intact osteons, fragmentary osteons, forming osteons, and resorption spaces were counted, osteon and Haversian canal areas were measured, and several variables were calculated to assess morphometric and remodeling status in the rib. Variables calculated included mean annual activation frequency, mean bone formation rate, and net osteonal remodeling. Results indicate that age changes are consistent with those observed for other archaeological and modern samples. High numbers of resorption spaces in young males may reflect slower skeletal development in boys compared to girls. Comparisons of rib data with results of a previous study on patterns of femoral bone remodeling in the same population indicate that ribs have more osteons and higher bone formation rates compared to the femur. Also, sexual differences in osteon size observed in the femur were not observed in the rib. Activation frequency and bone formation rate are low in the Kulubnarti population compared to previously published data for a modern sample, a finding consistent with reported results from other archaeological samples. Genetic factors influencing the minimum effective strain setpoint and duration of skeletal maturation, in addition to repetitive high strains at Kulubnarti, may contribute to observed differences.     

Osteon remodeling dynamics in the Cayo Santiago Macaca mulatta: The effect of matriline

At the microstructural level, bones remodel throughout life. This process is recorded in bone cortex as osteons. A more comprehensive understanding of the interaction between genetic regulation and environmental factors in osteon remodeling will increase the value of this skeletal record and enable more accurate reconstruction of individual life histories. The purpose of this study was to examine the contribution of maternal lineage to normal age and sex variation in osteon remodeling dynamics in Macaca mulatta. Femoral cross sections from 57 Cayo Santiago-derived rhesus macaques representing five matrilines were examined to evaluate the effect of genetic relatedness on osteon remodeling dynamics. Analysis of variance revealed an effect of maternal lineage on osteon area and Haversian canal area. The other variables did not differ significantly among matrilines. Analysis of covariance revealed no significant interactions among age, sex, and matriline for any of the microstructural variables.     

The utility of osteon shape and circularity for differentiating human and non-human Haversian bone

Distinguishing human from non‐human bone fragments is usually accomplished by observation of gross morphology. When macroscopic analysis is insufficient, histological approaches can be applied. Microscopic features, like plexiform bone or osteon banding, are characteristic of non‐humans. In the absence of such features, distinguishing Haversian bone as either human or non‐human proves problematic. This study proposes a histomorphometric approach for classifying species from Haversian bone. Two variables, osteon area (On.Ar.) and circularity (On.Cr.), are examined. Measurements were collected from three species (deer, dog, human) represented by various skeletal elements; only ribs were available for humans (ribs: deer n = 6, dog n = 6, human n = 26; humeri: deer n = 6, dog n = 6; femora: deer n = 6, dog n = 6). Qualitative analysis comparing human to non‐human On.Ar. demonstrated that human ribs have larger mean On.Ar. (0.036 mm²) than non‐human ribs (deer = 0.017 mm², dog = 0.013 mm²). On.Cr. in the ribs showed minor differences between species (deer = 0.877; dog = 0.885; human = 0.898). Results demonstrated no significant difference across long bone quadrants in long bones. Discriminant analyses run on the means for each sample demonstrated overlap in deer and dog samples, clustering the non‐human and human groups apart from each other. Mean On.Cr. proved a poor criterion (ribs only: 76.3%, pooled elements: 66.1%), while mean On.Ar. proved useful in identifying human from non‐human samples (ribs only: 92.1%, pooled elements: 93.5%). When variables were combined, accuracy increased to 100% correct classification for rib data and 98.4% when considering data from all elements. These results indicate that On.Ar. and On.Cr. are valuable histomorphometric tools for distinguishing human from non‐human Haversian bone. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.     

The system of bony canals as the basis for the angioarchitectonics of bones]

The spatial interrelationships of osteon canals were studied in corrosion preparations with the help of rastral electron microscopy. The structure of microvessels, their belonging to a definite link of the microcirculatory bed, the interaction of vessels and their position with respect to the osseous matrix were studied in bone sections impregnated with silver nitrate after V. V. Kuprijanov. Haversian canals in the compact substance of the bone are longitudinally oriented, can duplicate and form a single system of canals. The neighbouring canals of osteons might be bound by means of Volkmann's canals. The investigation of the Haversian canals in serial sections has shown that the diameter of the same canals of osteons can change at different levels, the diameter of the osteons themselves remaining unchanged. This seems to speak of uneven development of osteons in their different parts. In the Haversian canal there are one-two or occasionally three vessels having all three links of the morphocirculatory bed. The course and ramification of the vessel are identical to the shape of the osteon canal which includes them. The vessels are closely connected with the bony matrix by means of connective tissue bundles directed from the canal wall to the vessel wall. These bundles appear to serve as a peculiar anchor or amortizing apparatus and its elasticity might be a factor of a change of the shape and direction of the canal vessels in the bone development process.     

Patterns of femoral bone remodeling dynamics in a medieval Nubian population

The relationship between age, sex and histomorphometry in femoral cortical bone was examined in a skeletal population of late Medieval antiquity (AD 1250–1450) from Kulubnarti, in Sudanese Nubia. These skeletal remains are naturally mummified and in an excellent state of preservation. The study sample consisted of femoral cross sections from 24 females and 19 males ranging in age from 20 to 50+ years. Femoral cross sections were examined using an image analysis system. Numbers of secondary osteons and osteon fragments were counted, osteon area and Haversian canal area were measured, and several variables were calculated to assess differences between sexes and among age groups in bone remodeling variables. The results indicate significant differences between the sexes in osteon number and size. Males had significantly more intact osteons than females, whereas females had significantly larger osteons than males. Haversian canal dimensions were not statistically significant between the sexes. Sex differences in activity patterns in which males were involved in more physically strenuous tasks may have contributed to differences in remodeling variables. Interpopulational comparisons suggest that mechanical strain affects the microstructural features examined in this study. In particular, small Haversian canals in some archaeological skeletal populations are associated with higher bone volume, which may result from high levels of mechanical strain. Am J Phys Anthropol 104:133–146, 1997. © 1997 Wiley-Liss, Inc.     

Three-dimensional reconstruction of Haversian systems in ovine compact bone

Haversian systems or secondary osteons are an integral component of compact bone. However, as their exact shape is debatable, this study describes a technique to view their morphology in three dimensions. Bone remodeling in adult ovine long bones was labelled at intervals using a series of chelating fluorochromes. A series of longitudinal sections were cut at 25 microm intervals through blocks of the distal radius embedded in methylmethacrylate using a sledge macrotome. The chelating agents were used as markers of bone formation in the study of bone growth and osteon morphology. The two-dimensional image of each section was examined using an epifluorescence microscope. Images were transferred to a PC via a CCD low light colour video camera. Surface reference points were noted on each of the sections and, using computer software, a three-dimensional image of a refilling labelled osteon was reconstructed and its dimensions measured. Haversian systems may have a gentle spiral course along the longitudinal axis of the bone. They intertwine with adjacent osteons and give multiple branches along their course producing a complex pattern of organization. The mean labelled length and diameter of the osteons was 1.4 + 1 mm and 145 + 0.42 microm [Mean + S.D], respectively.     

Quantitative histology of changes with age in rat bone cortex

Changes with age in bone cortex of the rat were investigated by establishing histological parameters which could be quantitated to estimate age at death. Decalcified cross sections of mandible, femur and tibia were prepared from rats two to 120 days old, and measurements were made of: (1) number of osteons, (2) average number of lamellae per osteon, (3) average Haversian canal diameter, and (4) number of non-Haversian (primary) canals. Multiple regression techniques were used to estimate age at death from several combinations of these variables. With age, the number of osteons per unit area of bone and the number of lamellae per osteon increased, but Haversian canal diameter and the number of primary canals decreased. Multiple regression analyses indicated that age at death could be estimated to ± 3 days of the true value in 95% of the cases. Nomographs based on histological measurements of each bone were prepared which can provide accurate estimates of age between two and 120 days in the Sprague-Dawley female rat. It was concluded that microstructure of bone cortex can not only be quantitated to provide accurate estimates of age but it may also constitute a sensitive measure of the metabolic state of the organism. The techniques utilized should prove useful in anthropology as well in studies of bone aging.     

Osteon interfacial strength and histomorphometry of equine cortical bone

The interfacial strength of secondary osteons from the diaphysis of the Thoroughbred equine third metacarpal was evaluated using the fiber pushout test. The pushout was performed on 300-500 microm sections of 4x4x15 mm bone blocks machined from four anatomic regions of the cortex. Pushout strength was evaluated from proximal to distal location within the diaphysis on four osteon types classified under polarized light on adjacent histologic sections from each block. The shear strength of the interfaces were estimated from shear lag theory. Differences were found in the interfacial strength of osteons based on appearance under polarized light with bright field having the highest interfacial strength (40.3 MPa). The lowest strength was found in the dark field osteons (22.8 MPa). The dorsal region had the highest shear strength and toughness compared to all other regions. The cement line and interlamellar interfaces are similar in strength, but exhibit regional dependence--specifically, the palmar region strength is less (17.5 MPa) than the osteon interlamellar interfaces (30.4 MPa) and osteon type dependent (alternating significantly weaker than other types). Histomorphometry revealed significant regional differences (p<0.0001) in osteon area fraction among the four osteon types as well as differences in the osteon diameter (p=0.01), with dorsal regions having larger osteons (170 microm) than the palmar region (151 microm). Fatigue life and fracture toughness of Haversian bone are reported in the literature to be regionally dependent and are known to be associated with osteon pullout--an osteon interfacial phenomenon. Therefore, the results presented in this study are important to further the understanding of the mechanisms of fragility and damage accumulation in cortical bone.     

Residual stress distribution in rabbit limb bones

The presence of the residual stresses in bone tissue has been noted and the authors have reported that there are residual stresses in bone tissue. The aim of our study is to measure the residual stress distribution in the cortical bone of the extremities of vertebrates and to describe the relationships with the osteon population density. The study used the rabbit limb bones (femur, tibia/fibula, humerus, and radius/ulna) and measured the residual stresses in the bone axial direction at anterior and posterior positions on the cortical surface. The osteons at the sections at the measurement positions were observed by microscopy. As a result, the average stresses at the hindlimb bones and the forelimb bones were 210 and 149 MPa, respectively. In the femur, humerus, and radius/ulna, the residual stresses at the anterior position were larger than those at the posterior position, while in the tibia, the stress at the posterior position was larger than that at the anterior position. Further, in the femur and humerus, the osteon population densities in the anterior positions were larger than those in the posterior positions. In the tibia, the osteon population density in the posterior position was larger than that in the anterior position. Therefore, tensile residual stresses were observed at every measurement position in the rabbit limb bones and the value of residual stress correlated with the osteon population density (r=0.55, P<0.01).     

Microstructural mechanical study of a transverse osteon under compressive loading: The role of fiber reinforcement and explanation of some geometrical and mechanical microscopic properties

This Finite Element study aims at understanding the transverse osteon as a composite microstructure, and at differentiating the actions of each of its main components and their interactions. Three components of the osteon have been distinguished: the lamellae mineral-collagen matrix, the lamellae mineral-collagen reinforcement fibers and the Haversian canal content made of intracortical fluid and soft tissues. Numerical compression experiments have been performed, varying the microstructure properties. Our results show that fiber reinforcement of transverse osteons is only efficient at resisting dynamic compressive loadings, but that the improvement of the static compressive properties is very poor. Furthermore, the modeled stress distribution within the matrix and reinforcement fibers may explain why transverse osteons are often limited to a small number of lamellae (<8) and why internal lamellae could be stiffer than external ones.     

Microanatomical diversity of amniote ribs: an exploratory quantitative study

Bone microanatomical diversity in extant and extinct tetrapods has been studied extensively, using increasingly sophisticated quantitative methods to assess its ecological, biomechanical and phylogenetic significance. Most studies have been conducted on the appendicular skeleton, and a strong relationship was found between limb bone microanatomy and habitat preferences. Few comparative studies have focused on the microanatomy of the axial skeleton and its ecological signal. In the present study, we propose the first exploratory study of the microanatomical diversity of amniote ribs. Our comparative sample comprises 155 species of extant amniotes and encompasses the taxonomic, ecological, and body size diversity of this group. We standardized our sampling location to the midshaft of mid‐dorsal ribs. Transverse sections were obtained from classical petrographic methods, as well as by X‐ray microtomography. Most of the microanatomical and size characters of the ribs display a phylogenetic signal, which is an expected result and is also observed in amniote limb bones and vertebrae. We found a significant relationship between rib cortical thickness, global compactness, and lifestyle. As for the vertebrae, the development of the spongiosa in the medullary region appears to be strongly correlated with size. Even though an ecological signal was found in the inner structure of the ribs, additional work is needed to document the intra‐individual variability of the rib microanatomy along the rib cage and within a single element.     

Secondary osteon size and collagen/lamellar organization (“osteon morphotypes”) are not coupled,but potentially adapt independently for local strain mode or magnitude

In bone, matrix slippage that occurs at cement lines of secondary osteons during loading is an important toughening mechanism. Toughness can also be enhanced by modifications in osteon cross-sectional size (diameter) for specific load environments; for example, smaller osteons in more highly strained “compression” regions vs. larger osteons in less strained “tension” regions. Additional osteon characteristics that enhance toughness are distinctive variations in collagen/lamellar organization (i.e., “osteon morphotypes”). Interactions might exist between osteon diameter and morphotype that represent adaptations for resisting deleterious shear stresses that occur at the cement line. This may be why osteons often have a peripheral ring (or “hoop”) of highly oblique/transverse collagen. We hypothesized that well developed/distinct “hoops” are compensatory adaptations in cases where increased osteon diameter is mechanically advantageous (e.g., larger osteons in “tension” regions would have well developed/distinct “hoops” in order to resist deleterious consequences of co-existing localized shear stresses). We tested this hypothesis by determining if there are correlations between osteon diameters and strongly hooped morphotypes in “tension”, “compression”, and “neutral axis” regions of femora (chimpanzees, humans), radii (horse, sheep) and calcanei (horse, deer). The results reject the hypothesis—larger osteons are not associated with well developed/distinct “hoops”, even in “tension regions” where the effect was expected to be obvious. Although osteon diameter and morphotype are not coupled, osteon diameters seem to be associated with increased strain magnitudes in some cases, but this is inconsistent. By contrast, osteon morphotypes are more strongly correlated with the distribution of tension and compression.     

Brief communication: Reevaluating osteoporosis in human ribs: the role of intracortical porosity

Osteoporosis is a major health concern in modern society and is continually being evaluated in past populations by quantifying bone loss. Cortical area measures are commonly used in anthropological analyses to assess bone loss in the ribs, but these values are typically based on endosteal expansion and do not account for intracortical bone loss. The objective of this study is to evaluate the effectiveness of using absolute cortical area, compared to traditional cortical area measures to describe global bone loss in elderly ribs. Transverse sections were prepared from sixth ribs of ten elderly subjects, and bone area measurements were made from 100× magnification composites of each rib for calculation of cortical area (Ct.Ar) and percent cortical area (% C/T). In addition, all areas of intracortical porosity were measured and percent porosity area (% Po.Ar) calculated. Absolute cortical area (Ct.Ar(A)) was calculated by subtracting porosity area from cortical area, and a percent absolute cortical area (% C(A)/T) calculated. ANOVA results reveal significant interindividual variation in percent porosity area (% Po.Ar). Percent cortical area and percent absolute cortical area values were compared and results show a mean difference of 4.08% exists across all subjects, with a range of 1.19-11.73%. This suggests that intracortical porosity is variable and does play a role in age-associated bone loss in the rib. All future investigations of osteoporosis should account for intracortical porosity in bone loss.     

Mechanical hysteresis loops from single osteons: technical devices and preliminary results

The purpose of this paper is to describe an original apparatus for recording hysteresis loops from single osteons and a special microgrinding lathe for preparing osteonic samples for testing. The results obtained by testing isolated osteons, and composite bone samples ground to the same size as an osteon sample justify one to draw the following main conclusions: at an equal degree of calcification, longitudinal osteons show larger hysteresis loops under compression and alternate osteons show larger hysteresis loops under tension; there seems to be little chance of acquiring detailed information on the mechanical effects of osteon calcification recording hysteresis loops; collagen orientation in lamellae is the main factor determining the kind of hysteresis loops displayed by a composite bone sample.     

Effects of the basic multicellular unit and lamellar thickness on osteonal fatigue life

A remodeling cycle sets the size of the osteon and associated lamellae in the basic multicellular unit. Treatments and aging affect these micro-structural features. We previously demonstrated decreased fatigue life with an unexplained mechanism and decreased osteon size in cortical bone treated with high-dose bisphosphonate. Here, three finite element models were examined: type-1: a single osteon, as a homogeneous unit and with heterogeneous lamellae and interlamellae, type-2: a control, interstitial-only tissue and type-3: the osteon with cement line, set within the interstitial tissue. Models were loaded in simulated, sinusoidal bending fatigue. As osteon size was decreased, lamellar number and lamellar thickness were incrementally adjusted for each model. As hypothesized, lamellae within the larger type-1 models attained greater cycles to failure and the addition of an osteon to type-2 models (generating a type-3 model set) yielded increased fatigue life. However, as the osteon size was decreased, the potential for compressive damage nucleation was increased within the lamellae of the osteons versus the interstitium. Also, osteons with fewer, thicker lamellae displayed increased fatigue life. Osteonal microstructure plays a role in damage initiation location, especially when BMU size is smaller. Previous findings by us and others could partially be explained by this further understanding of increased probability for damage nucleation in smaller osteons.     

生物衍生松质骨支架材料的Micro—CT量化分析

目的：在骨组织工程中,如何制备出理想的支架材料一直是研究重点;目前主要的有天然生物支架材料、人工合成有机材料和无机材料等;生物衍生骨即天然生物支架材料的一种,由于其与天然骨在形态结构上较为相似,是近年来研究较多的支架材料之一;既往形态学研究局限于在二维层面,对于其三维结构参数分析较少。故本实验主要运用Micro-CT对生物衍生松质骨的三维结构参数进行分析,量化评价其作为骨组织工程支架材料的结构参数。方法：截取新鲜猪松质骨,经脱脂脱蛋白部分脱钙及去抗原处理后,制作成生物衍生骨支架;应用Micro．CT扫描,重建三维图并量化分析其结构参数,统计软件SPSS分析各参数间的相关性。结果：经Micro．CT扫描,得到二维CT图和三维重建图。各三维结构参数的值分别为：BV／TV（20．48±5．14）％;BS／BV（41．66±5．39）1／ram;Porosity（79．52±5．14）％;Tb．Th（0．10±0．01）mm;Tb．N（1．99±0．47）l／mm;Tb．Sp（0．32±0．05）mm;Tb．Pf（2．03±4．70）1／mm;SMI（1．28±0．35）;DA（1．60±0．23）;Corm．Dn（158．53±106．09）I／mm3。各参数间相关系数具有统计学意义的为：（1）Porosity与BS／BV、Tb．Th;（2）BV／TV与BS／BV、Tb．Th;（3）BS／BV与Coma．Dn、Porosity、BV/TV、;（4）Tb．Th与Porosity、BV厂IV、Conn．Dn;（5）DA与Corm．Dn;（6）Conn．Dn与Bs／BV、Tb．Th、DA。结论：Micro-CT扫描、量化分析是评价支架材料结构参数的理想方法;也证明生物衍生骨支架符合骨组织工程对支架材料的三维结构要求,尤其在孔径大小、孔隙率、表面积体积比等三维结构参数,此外,也可为其他支架材料的制备在三维结构上的要求提供参考依据。     

Prediction of cortical bone elastic constants by a two-level micromechanical model using a generalized self-consistent method

A two-level micromechanical model of cortical bone based on a generalized self-consistent method was developed to take into consideration the transversely isotropic elasticity of many microstructural features in cortical bone, including Haversian canals, resorption cavities, and osteonal and interstitial lamellae. In the first level, a single osteon was modeled as a two-phase composite such that Haversian canals were represented by elongated pores while the surrounding osteonal lamellae were considered as matrix. In the second level, osteons and resorption cavities were modeled as multiple inclusions while interstitial lamellae were regarded as matrix. The predictions of cortical bone elasticity from this two-level micromechanical model were mostly in agreement with experimental data for the dependence of transversely isotropic elasticity of human femoral cortical bone on porosity. However, variation in cortical bone elastic constants was greater in experimental data than in model predictions. This could be attributed to variations in the elastic properties of microstructural features in cortical bone. The present micromechanical model of cortical bone will be useful in understanding the contribution of cortical bone porosity to femoral neck fractures.     

Brief communication: histological age estimation using rib and clavicle.

Histological methods for estimating age at death using osteon population densities for the rib, clavicle, and rib and clavicle combined are presented. Predicting formulas were generated from a sample of 40 individuals of known age, sex, and race. Independent samples of 12 ribs and 7 clavicles were used to test the formulas. Mean differences between known and predicted ages were 1.1 years, 2.6 years, and 3.4 years for the clavicle, rib and clavicle combined, and rib formulas respectively. An analysis of variance found no significant differences among the means for predicted and known ages. Since the formula based upon rib and clavicle combined has the higher standard error and r2, and includes data from different bones, it should provide better overall accuracy and reliability, and is recommended whenever both bones are available.