Geometric determinants to cement line debonding and osteonal lamellae failure in osteon pushout tests

Cement lines are the boundaries between secondary osteons and the surrounding interstitial bone matrix in cortical bone. The interfacial properties of cement lines have been determined by osteon pushout tests. However, distinctively different material properties were obtained when osteon pushout tests were performed under different test geometries. In the present study, an axisymmetric two-dimensional finite element model was used to simulate an osteon pushout test using the test geometry of actual experiments. The results indicated that shear failure within the osteonal lamellae would occur when the osteon pushout test was performed under the condition of a thick specimen and large supporting hole. On the other hand, cement line debonding occurred when the osteon pushout test was performed using a thin specimen and small supporting hole. The finite element results were consistent with previous experiments of osteon pushout tests under different test geometries. Furthermore, the finite-element results suggest that a smoothly curved punch would most likely cause debonding at the cement line instead of osteonal lamellae.     

Histologic estimation of age at death using the anterior cortex of the femur

This report describes a new histologic method for determination of age at death, the latest in a series of studies that began with Kerley's pioneer presentation in 1965. The study population was collected from 328 documented individuals from an anatomy dissecting room in the United States, from two modern cemeteries in the Dominican Republic, and from autopsies performed in a Chilean hospital. Undecalcified thin sections 1.0 cm wide were made from specimens taken from the femoral midshaft directly opposite the linea aspera. Five 0.886 mm2 fields were located at the periosteal edge and photographed, mainly for purposes of defining the fields and providing a permanent record. Secondary osteons, type II osteons, osteon fragments, resorption spaces, and non-Haversian canals were recorded as number/mm2, and a 100-space grid was used to measure average percent of unremodeled, osteonal, and fragmental bone. Stepwise regression analysis of the measurements produced a series of regression equations for age estimation for females, males, and sexes combined. Most equations have a standard error of estimate of about 10 years, but the coefficients of determination (r2) range from 0.48 to 0.72. In practice, sex-specific equations gave better results than opposite-sex or nonspecific equations, mainly because males and females differed in the pattern of relations between osteons and osteon fragments with advancing age.     

Effects of field size when using Kerley's histological method for determination of age at death

The field size at which a bone is read affects the results obtained when using Kerley's histological method for age estimation, even after applying the recommended correction factor. Whereas there is no tendency for any one of three field sizes tested to consistently underestimate or overestimate age, a field size closest to that used by Kerley in his original study had significantly lower variances for its age estimates, and thus provides greater reliability. This particular field size yields more precise estimates because it is sampling a pattern and number of structures more similar to that of Kerley. Correction factors cannot equalize the counts of osteons and osteon fragments because of spatial variations in the distributions of these histological structures. A field size similar to that used by Kerley in gathering the data from which he developed his regression equations must be used to assure that the same pattern and number of structures is being sampled. For this reason, we suggest a field size as close to 2.06 mm² as possible be used when employing Kerley's method.     

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.     

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).     

Estimation of age at death from second metacarpals.

This study examined the estimation of age at death from the second metacarpal in 227 individuals aged 30-98 years. Variables ascertained from each bone were: cortical thickness and microdensitometric cortical bone density measured on radiographs of the bone and total osteon count and density recorded on microradiographs of the complete cross section at its midshaft. Based on the latter two variables, two age groups were formed; a middle age group representing those individuals aged 30-65 years, and an older group aged 65+. Stepwise regression analysis of the four variables produced a series of regression equations for age estimation for the middle, old and combined age groups for each sex and sexes combined. Sex-specific equations provided better results than nonspecific ones, especially in females. Total osteon density and combined cortical thickness were found to be the most useful estimators in the middle and the old age group, respectively. The standard error of estimate was 6.71 and 6.90 years in each age group for the sexes combined. In the combined age group, age could be estimated accurately from total osteon count, cortical thickness and MD cortical bone density with the standard error of estimate of 11.10 years. The relative error of estimate ranged within +/- 30% in almost all individuals aged above 60 years.     

Micromechanics fracture in osteonal cortical bone: a study of the interactions between microcrack propagation, microstructure and the material properties

A two-dimensional micromechanical fibre reinforced composite materials model for osteonal cortical bone is presented. The interstitial bone is modelled as a matrix, the osteons are modelled as fibres, and the cement line is presented as interface tissue. The interaction between osteons and microcracks is evaluated by linear elastic fracture mechanics theory, followed by a determination of the stress intensity factor at the vicinity of the microcrack tips. The results indicate that bone microstructural heterogeneity greatly influences fracture parameters. Furthermore, microstructural morphology and loading conditions affect growth trajectories, the microcrack propagation trajectory deviates from the osteon under tensile loading, and osteon penetration is observed under compressive loads.     

The effect of hydration on mechanical anisotropy,topography and fibril organization of the osteonal lamellae

The effect of hydration on the mechanical properties of osteonal bone, in directions parallel and perpendicular to the bone axis, was studied on three length scales: (i) the mineralized fibril level (~100 nm), (ii) the lamellar level (~6 µm); and (iii) the osteon level (up to ~30 µm).We used a number of techniques, namely atomic force microscopy (AFM), nanoindentation and microindentation. The mechanical properties (stiffness, modulus and/or hardness) have been studied under dry and wet conditions. On all three length scales the mechanical properties under dry conditions were found to be higher by 30–50% compared to wet conditions. Also the mechanical anisotropy, represented by the ratio between the properties in directions parallel and perpendicular to the osteon axis (anisotropy ratio, designated here by AnR), surprisingly decreased somewhat upon hydration. AFM imaging of osteonal lamellae revealed a disappearance of the distinctive lamellar structure under wet conditions. Altogether, these results suggest that a change in mineralized fibril orientation takes place upon hydration.     

Methods for improving the efficiency of estimating total osteon density in the human anterior mid-diaphyseal femur

In order to preserve whole bone integrity and minimize destruction, paleohistologists often rely on histomorphometric data obtained from small areas (1.5–50 mm²) sampled within the anterior mid-diaphyseal femur. Because bone exhibits significant histological variation, the validity of results based on such sampling is questionable. The accuracy of various subareas (columns, rows, squares approximating dimensions and locations assessed by paleohistologists) in predicting total osteon density in the anterior mid-diaphyseal femur is assessed in the present study. Thirty-five specimens (12.7 mm wide, 100 μm thick, average area 56.7 mm²) were chosen at random from a skeletal population of 94 Inuits and Pueblo agriculturists. The specimens were photographed and enlarged; an acetate grid (12 columns, 10 rows, 120 squares, square = 1 mm² of bone surface) was superimposed over the photograph; and secondary osteons and fragments were identified. Alternate columns (50% total area, T.Ar) predicted over 98% of entire section total osteon density. Two column combinations (15% T.Ar), separated by at least one column, predicted 91 to 95% of total osteon density. Individual column (8% T.Ar) predictability ranged from 48 to 86%. Two row combination (32 to 40% T.Ar) predictability values ranged from 86 to 95%. Individual rows (<1 to 20% T.Ar) predicted from 45 to 92% of total variation. Combinations of squares approximating areas and locations assessed by other paleohistologists ranged in predictability values from 80 to 94%. The results demonstrate that subareas of as little as 15% predict 95% of variation in total osteon density in the entire anterior mid-diaphyseal femoral section. A minimization of histological area evaluated without the loss of accuracy allows for a minimization of time invested in data collection and the utilization of partially damaged specimens. Am J Phys Anthropol 107:13–24, 1998. © 1998 Wiley-Liss, Inc.     

Free fibula long bone reconstruction in orthopedic oncology: a surgical algorithm for reconstructive options

The fibula free flap became popular in orthopedic oncology for limb-sparing long bone tumor resection. It is particularly suitable for intercalary or resection arthrodesis options. In the present series, a surgical reconstruction algorithm was used, enabling each patient to receive a personalized technique. During the years 1998 to 2002, 30 patients underwent limb-sparing surgery for long bone sarcoma. There were 18 males and 12 females. Their mean age was 23 years (range, 9 to 70 years). The diagnoses were Ewing's sarcoma (11 patients), osteogenic sarcoma (eight patients), chondrosarcoma (five patients), giant cell tumor of bone (three patients), high-grade soft-tissue sarcoma (two patients), and leiomyosarcoma of bone (one patient). The majority of tumors where located in the lower extremity (23 patients), mostly in the femur (15 patients with four tumors in the proximal femoral shaft, five tumors in the distal femoral shaft, five tumors in the whole femoral shaft, and one tumor in the proximal femoral head). In seven patients, the upper extremity was involved; in six patients, the radius was involved; and in one patient, the humerus was involved. The free fibula flap was used in three types of approaches: vascularized fibula as an osseous flap only (18 patients), a combination of a vascularized fibula flap in conjunction with an allograft (Capanna's technique; 10 patients), and a free double-barreled fibula (two patients). All flaps survived. Postoperatively, all patients were monitored clinically, radiologically, and by radioisotope bone scan studies. Callus formation and union were shown 2.6 to 8 months postoperatively. Patients who underwent lower extremity reconstruction were nonweightbearing for 3 to 9 months, with a transition period in which they used a brace and gradually increased weightbearing until full weightbearing was achieved. Eight patients had 11 recipient-site complications. Two patients (6.7 percent) had hematomas, and three patients (10 percent) had infection and dehiscence of the surgical wound with bone exposure in one patient; all complications resolved with conservative treatment only. Failure of the hardware fixation system occurred in two patients, mandating surgical correction. No fibula donor-site complications were recorded. In intercalary resections, the use of the vascularized fibula flap as an isolated osseous flap might be insufficient. Different body sites have different stress loads to carry, depending on the age of the patient and on his individual physical status. To achieve initial strength in the early period, the authors combined the free fibula flap with an allograft (Capanna's method) or augmented it as a double-barreled fibula. They propose a surgical algorithm to assist the surgeon with the preferred method for reconstruction of various long bone defects in different body locations at childhood or adulthood. Long bone reconstruction using a vascularized fibula flap, alone or in combination with an allograft, autogenous bone graft, or double-barreled fibula for limb-sparing surgery, is a safe and reliable method with a predictable bony union, good functional outcome, and a low complication rate.     

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.     

Mechanical properties of river otter limb bones

The determination of the bone strengths of wild animals has many potential advantages, which include the ability to estimate age of animals; monitor strengths of bones as influenced by contaminants, particularly lead; provide appropriate data for design of capture, handling, and holding equipment to minimize the possibility for bone fracture in captured animals; and measure effects of nutrition on bone strength. The objectives of of this study were to provide data on the mechanical properties of limb bones of river otters and to consider effects of age and sex on the properties. Three-point bending and shear tests were conducted on the radius, ulna, tibia, and fibula. The three-point bending tests were first conducted on the bones loaded within their elastic limit. These tests were used to evaluate the modulii of elasticity of the bones. The data on the modulii indicated that age and sex did not have significant effects on the values. The four different bones tested had approximately the same modulus of elasticity, with an average value of 14. 1 gigapascal (GPa). The shear tests were conducted on the limb bones to failure in order to determine the maximum breaking force and strength of the bones. The shear force of the radius tended to increase with age and there was a significant (P < .001) age effect. The shear force of the ulna for males was significantly (P < .002) higher than that of the females. A similar trend was observed for the fibula (P < .03). The shear strength of the radius increased with age and there was a significant (P < .005) age effect. There was also a significant (P < .001) effect of sex on shear strength of the radius; values for females were higher. There were no significant effects of sex or age found on shear strengths of the ulnae, tibia, and fibulae.     

Reconstruction of the mandible with osseous free flaps: a 10-year experience with 150 consecutive patients.

Osseous free flaps have become the preferred method for reconstructing segmental mandibular defects. Of 457 head and neck free flaps, 150 osseous mandible reconstructions were performed over a 10-year period. This experience was retrospectively reviewed to establish an approach to osseous free flap mandible reconstruction. There were 94 male and 56 female patients (mean age, 50 years; range 3 to 79 years); 43 percent had hemimandibular defects, and the rest had central, lateral, or a combination defect. Donor sites included the fibula (90 percent), radius (4 percent), scapula (4 percent), and ilium (2 percent). Rigid fixation (up to five osteotomy sites) was used in 98 percent of patients. Aesthetic and functional results were evaluated a minimum of 6 months postoperatively. The free flap success rate was 100 percent, and bony union was achieved in 97 percent of the osteotomy sites. Osseointegrated dental implants were placed in 20 patients. A return to an unrestricted diet was achieved in 45 percent of patients; 45 percent returned to a soft diet, and 5 percent were on a liquid diet. Five percent of patients required enteral feeding to maintain weight. Speech was assessed as normal (36 percent), near normal (27 percent), intelligible (28 percent), or unintelligible (9 percent). Aesthetic outcome was judged as excellent (32 percent), good (27 percent), fair (27 percent), or poor (14 percent). This study demonstrates a very high success rate, with good-to-excellent functional and aesthetic results using osseous free flaps for primary mandible reconstruction. The fibula donor site should be the first choice for most cases, particularly those with anterior or large bony defects requiring multiple osteotomies. Use of alternative donor sites (i.e., radius and scapula) is best reserved for cases with large soft-tissue and minimal bone requirements. The ilium is recommended only when other options are unavailable. Thoughtful flap selection and design should supplant the need for multiple, simultaneous free flaps and vein grafting in most cases.     

Evaluation of bone height in osseous free flap mandible reconstruction: an indirect measure of bone mass

Osseous free flaps have become the preferred method of mandibular reconstruction after oncologic surgical ablation. To elucidate the long-term effects of free flap mandibular reconstruction on bone mass, maintenance or reduction in bone height over time was used as an indirect measure of preservation or loss in bone mass. Factors potentially influencing bone mass preservation were evaluated; these included site of reconstruction (central, body, ramus), patient age, length of follow-up, adjuvant radiotherapy, and the delayed placement of osseointegrated dental implants. A retrospective analysis of patients undergoing osseous free flap mandible reconstruction for oncologic surgical defects between 1987 and 1995 was performed. Postoperative Panorex examinations were used to evaluate bone height and bony union after osteotomy. Fixation hardware was used as a reference to eliminate magnification as a possible source of error in measurement. There were 48 patients who qualified for this study by having at least 24 months of follow-up. There were 27 male and 21 female patients, with a mean age of 45 years (range, 5 to 75 years). Mandibular defects were anterior (24) and lateral (24). Osseous donor sites included the fibula (35), radius (6), scapula (4), and ilium (3). There were between zero and four segmental osteotomies per patient (excluding the ends of the graft). Nineteen percent of all patients had delayed placement of osseointegrated dental implants. Initial Panorex examinations were taken between 1 and 9 months postoperatively (mean, 2 months). Follow-up Panorex examinations were taken 24 to 104 months postoperatively (mean, 47 months). The bony union rate after osteotomy was 97 percent. Bone height measurements were compared by site and type of reconstruction. The mean loss in fibula height by site of reconstruction was 2 percent in central segments, 7 percent in body segments, and 5 percent in ramus segments. The mean loss in bone height after radial free flap mandible reconstruction was 33 percent in central segments and 37 percent in body segments; ramus segments did not lose height. The central and body segments reconstructed with scapular free flaps did not lose height, but one ramus segment lost 20 percent of height. There was no loss in bone height in mandibular body reconstruction with the ilium free flap. Fibula free flaps did not significantly lose bone height when evaluated with respect to age, follow-up, radiation therapy, or dental implant placement. The retention in bone height demonstrated in this study suggests that bone mass is preserved after osseous free flap mandible reconstruction. The greatest amount of bone loss was seen after multiply osteotomized radial free flaps were used for central mandibular reconstruction. The ability of the fibula free flap to maintain mass over time, coupled with its known advantages, further supports its use as the "work horse" donor site for mandible reconstruction.     

Age, sex, and grip strength determine architectural bone parameters assessed by peripheral quantitative computed tomography (pQCT) at the human radius

The purpose of this study was to estimate the relation of some noninvasively derived mechanical characteristics of radial bone including architectural parameters for bone strength to grip strength and muscle cross-section. Sixty-three males between 21 and 78yr of age and 101 females between 18 and 80yr of age were measured at the nondominant forearm using peripheral quantitative computed tomography (pQCT). We assessed the integral bone mineral density (BMD(I)) and content (BMC(I)) by pQCT at the distal and at the mid-shaft radius. Integral bone area (Area(I)), cortical thickness (C-th), and a newly proposed index for bone strength; the stress-strain index (SSI) were also calculated. The dynamometrically measured maximum grip strength was taken as a mechanical loading parameter and muscle cross-section as a substitute for it. Sex, grip strength, BMC(I) and BMD(I) (distal radius) were identified in a multiple regression analysis to significantly predict bone strength as expressed by SSI, after adjusting for all other independent variables, including age and sex (p<0.0001). Grip strength was closest related to age, sex, BMD(I) and SSI(p) of the distal radius. The cross-sectional area of muscle was not significantly determining the grip strength within the analysis model. In conclusion, our results suggested that architectural parameters at the distal radius were better related to grip strength than to cross-sectional muscle area in both males and females. Maximum muscle strength as estimated by grip strength might be a stronger determinant of mechanical characteristics of bones as compared with cross-sectional muscle area.     

Scaling of Haversian canal surface area to secondary osteon bone volume in ribs and limb bones

Studies of secondary osteons in ribs have provided a great deal of what is known about remodeling dynamics. Compared with limb bones, ribs are metabolically more active and sensitive to hormonal changes, and receive frequent low‐strain loading. Optimization for calcium exchange in rib osteons might be achieved without incurring a significant reduction in safety factor by disproportionally increasing central canal size with increased osteon size (positive allometry). By contrast, greater mechanical loads on limb bones might favor reducing deleterious consequences of intracortical porosity by decreasing osteon canal size with increased osteon size (negative allometry). Evidence of this metabolic/mechanical dichotomy between ribs and limb bones was sought by examining relationships between Haversian canal surface area (BS, osteon Haversian canal perimeter, HC.Pm) and bone volume (BV, osteonal wall area, B.Ar) in a broad size range of mature (quiescent) osteons from adult human limb bones and ribs (modern and medieval) and various adult and subadult non‐human limb bones and ribs. Reduced major axis (RMA) and least‐squares (LS) regressions of HC.Pm/B.Ar data show that rib and limb osteons cannot be distinguished by dimensional allometry of these parameters. Although four of the five rib groups showed positive allometry in terms of the RMA slopes, nearly 50% of the adult limb bone groups also showed positive allometry when negative allometry was expected. Consequently, our results fail to provide clear evidence that BS/BV scaling reflects a rib versus limb bone dichotomy whereby calcium exchange might be preferentially enhanced in rib osteons. Am J Phys Anthropol 151:230–244, 2013. © 2013 Wiley Periodicals, Inc.     

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.     

用显微镜确定骨龄的初步研究

作者对在广西地区收集的年龄从5岁至86岁的35副完整骨骼的右股骨中点横断磨片的骨单位数、骨间板数、非哈弗氏管数及外环骨板平均相对厚度进行了观测和计算。这些指标与年龄之间均存在非常显著的相关,并建立了相应的回归方程。这些回归方程的估计年龄与实际年龄的误差在±5岁以内的,达80％左右;在±10岁以内的,达90％左右。与用Kerley法所作的对比检验表明,本文方法较适用于国人材料。     

Collagen orientation patterns in human secondary osteons, quantified in the radial direction by confocal microscopy

The composite structure of secondary osteon lamellae, key micro-mechanical components of human bone, has intrigued researchers for the last 300 years. Scanning confocal microscopy here for the first time systematically quantifies collagen orientations by location within the lamellar thickness. Fully calcified lamellar specimens, extinct or bright in cross-section under circularly polarized light, were gently flattened, and then examined along their thickness direction, the radial direction in the previously embedding osteon. Collagen orientation was measured from confocal image stacks. So-called extinct lamellae and so-called bright lamellae are found to display distinct, characteristic patterns of collagen orientation distribution. Orientations longitudinal to the osteon axis in extinct lamellae, transverse to the osteon axis in bright lamellae, and oblique to the osteon axis in both lamellar types, show parabolic distribution through specimen thickness. Longitudinal collagen in extinct lamellae, and transverse collagen in bright lamellae, peaks at middle third of lamellar thickness, while oblique collagen peaks at outer thirds of both types. Throughout the thickness, longitudinal collagen orientations characterize extinct lamellar specimens, while orientations oblique to the original osteon axis characterize bright lamellar specimens. Measured patterns complement previous indirect results by different methods and reinforce previously hypothesized differences in lamellar mechanical functions.     

Variation in cortical bone histology within the human femur and its impact on estimating age at death

Histological methods for the estimation of age at death using cortical bone are based on the evaluation of microstructural changes over time. Since histological analysis is a destructive method, most techniques attempt to limit the amount of cortical bone needed for analysis. Sample location, however, can have a significant effect on the accuracy of these methods. Furthermore, research demonstrates that both intersection and intrasection variation is present at the midshaft of the femur, which is the primary location for estimating age at death in humans. This research determines the extent of regional variation within the adult human femur and its effect on age estimation. Secondary osteon lamellae and Haversian canal ratio and cortical thickness were quantified. Thompson's All Males Left Femur regression equation was used to estimate age. Results show that significant regional variation occurs in the estimated ages derived from the posterior aspect of the femoral shaft and significant intrasection variation occurs in age estimates from the mid and mid-distal cross-sections. Thus, the inter and intrasection variation that occurs in bone remodeling within the femoral cortex has the potential to produce significant differences amongst age estimates taken from various femoral diaphyseal locations compared to the age estimated from the standard location used in Thompson's core method (1978). The results indicate that the use of this histological method is dependant on the ability to correctly identify the four anatomical locations, but the extracted core used for age estimation is not necessarily confined to the anterior midshaft.