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WIREs Forensic Sci

Current and emerging histomorphometric and imaging techniques for assessing age‐at‐death and cortical bone quality

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Abstract Bones are dynamic living organs that undergo continual change throughout life. An internal process of tissue renewal, called remodeling, removes mature microscopic packets of bone, and replaces them with new bone in a highly coordinated manner. To date, it remains difficult to directly observe and track individual remodeling events in cortical bone due to the small size of the structures involved. High‐resolution imaging techniques hold the potential to provide novel three‐dimensional information pertaining to changes in bone's microarchitecture, cortical porosity, and the remodeling process. This review critically explores the methodological approaches used historically by researchers to assess the products of remodeling within cortical bone and relate it to age‐at‐death estimation, extending from histology to modern ex vivo imaging modalities, and discusses the growing potential of in vivo imaging. We further provide an introduction to various histological indicators of bone quality and fragility, their forensic relevance, and examples of novel imaging modalities employed for their investigation. The review concludes with an introduction to cutting‐edge in vivo four‐dimensional imaging techniques that include the use of animal models to shed new light on the dynamic nature of bone, and the processes of bone aging and disease. Data gleaned from these new insights will ultimately lead to the development of future histologic age‐estimation methods in forensic anthropology. This article is categorized under: Forensic Anthropology > Age Assessment Forensic Chemistry and Trace Evidence > Emerging Technologies and Methods Forensic Medicine > Imaging Modalities
Haversian system morphometry varies depending on where the cross‐sectional plane intersects the BMU. Serial sections of a human midshaft sixth rib demonstrate Haversian system progress from a completed secondary osteon after the closing cone (100 μm depth) to a resorption bay at the cutting cone (300 μm depth). Scale bar = 100 μm. (Photo Credit: Mary Cole)
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Synchrotron radiation‐based micro‐computed tomography 3D renders of a core from the anterior midshaft femur visualize cortical porosity (red) and osteocyte lacunae (yellow). Age‐associated increases in cortical porosity are seen between a 21‐year‐old female (left) and a 88‐year‐old female (right). Scale bar = 300 μm. (Photo Credit: Janna Andronowski)
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Laboratory micro‐computed tomography provides 3D visualization of the midshaft of a sixth rib from a 26‐year‐old male. Image processing of the original 3D reconstruction of the cortex (upper left) can extract trabecular architecture (upper right), cortical pore networks colored by local thickness (lower left) and maps of pore separation (lower right). Scale bar = 1,000 μm. (Photo Credit: Mary Cole)
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Micro‐computed tomography 3D renders of the human femoral neck reveal age‐associated trabecular bone loss. Females (aged 39 and 70, top row) tend to decrease in trabecular number and connectivity and increase in trabecular spacing. Males (aged 34 and 77, bottom row) tend to lose trabecular bone through the thinning of individual struts. Scale =1,000 μm. (Photo Credit: Mary Cole)
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Confocal laser scanning microscopy can generate 3D isosurfaces of the osteocyte lacunar‐canalicular network, as seen in this comparison of osteocyte lacunar network volume in a 21‐year‐old female (left) and 101‐year‐old female (right). Scale bar = 5 μm. (Photo Credit: Janna Andronowski)
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A 2D image slice generated with confocal laser scanning microscopy demonstrates age‐associated reduction in the osteocyte lacunar‐canalicular network in females (aged 21 and 90, top row) and males (aged 20 and 94, bottom row). Scale bar = 5 μm. (Photo Credit: Janna Andronowski)
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The progress of remodeling at the cross‐sectional level of the cutting cone determines pore size, shape, and classification, as seen in a cryosection of a human midshaft sixth rib. When remodeling is complete, a small Haversian canal is surrounded by a secondary osteon with circumferential lamellae and a cement line at its periphery. Larger, irregular resorption bays with few or no lamellae indicate incomplete remodeling. Marrow‐adjacent pores become trabecularized when they coalesce with neighboring pores or merge with the endosteum. Scale bar = 100 μm. (Photo Credit: Mary Cole)
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Transverse drift of osteons is observable between two cross‐sections, spaced 240 μm apart. Sections were taken from the rib of a 33‐year‐old male and stained with a silver nitrate stain. More recently formed bone is less mineralized and absorbs more stain. Each drifting osteon has a trailing, darkly stained “tail” of hemicyclic lamellae. Drift in diverse directions (white arrows) within the plane of cross‐section may reflect steering toward local microdamage for targeted remodeling. Scale bar = 500 μm. Samples were originally prepared by Dr. Neil Tappen (1977) and donated to Dr. Sam D. Stout. (Photo Credit: Mary Cole)
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Forensic Medicine > Imaging Modalities
Forensic Chemistry and Trace Evidence > Emerging Technologies and Methods
Forensic Anthropology > Age Assessment

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