Christian M. Crowder

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 mm(2)) than non-human ribs (deer = 0.017 mm(2) , dog = 0.013 mm(2)). 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.

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.

The Utility of Forensic Anthropology in the Medical Examiner's Office

Over the past few decades, the field of forensic anthropology has seen major advancements and experienced a considerable growth of professionals in medical examiner/coroner offices. Despite this expansion, misconceptions regarding the role and utility of the anthropologist in the medicolegal setting still exist. This article brings together practitioners employed full-time in four medical examiners offices, with each practitioner providing a unique perspective and emphasis regarding their role as an anthropologist. Discussed is the history of the anthropology division in each office as well as the types of casework and ancillary duties completed by the anthropologists. Consistently, the anthropologists are involved in the search and recovery of human remains, managing long-term unidentified cases, facilitating disposition of unclaimed decedents, and developing mass disaster protocols for their respective agency. Also consistent across the four offices is the fact that the anthropologists receive far more consult requests for trauma evaluation of nonskeletonized cases than any other type of case.

Chapter 18 – Bone Histology as an Integrated Tool in the Process of Human Identification

Abstract The analysis of unknown skeletal material requires a multilevel, polymodal approach that can be strengthened by the application of microscopic methods. First, a basic discussion of bone biology, histomorphology, and histomorphometry is presented, providing background for the interpretation of bone structure and organization at the microscopic level. This is followed by a discussion of applicable methods for distinguishing human from nonhuman bone, as well as methods for estimating age-at-death, a common use of the histological approach in forensic anthropology. Lastly, this chapter offers a discussion of current research that uses bone histology to guide sampling procedures for nuclear DNA analyses, specifically addressing why certain sampling locations may be preferred and providing guidelines for sample selection.

Recent advancements in the analysis of bone microstructure: New dimensions in forensic anthropology

Abstract Bone is a mechanically active, three-dimensionally (3D) complex, and dynamic tissue that changes in structure over the human lifespan. Bone tissue exists and remodels in 3D and changes over time, introducing a fourth dimension. The products of the remodelling process, secondary and fragmentary osteons, have been studied substantially using traditional two-dimensional (2D) techniques. As a result, much has been learned regarding the biological information encrypted in the histomorphology of bone, yielding a wealth of information relating to skeletal structure and function. Three-dimensional imaging modalities, however, hold the potential to provide a much more comprehensive understanding of bone microarchitecture. The visualization and analysis of bone using high-resolution 3D imaging will improve current understandings of bone biology and have numerous applications in both biological anthropology and biomedicine. Through recent technological advancements, we can hone current anthropological applications of the analysis of bone microstructure and accelerate research into the third and fourth dimensional realms. This review will explore the methodological approaches used historically by anthropologists to assess cortical bone microstructure, spanning from histology to current ex vivo imaging modalities, discuss the growing capabilities of in vivo imaging, and conclude with an introduction of novel non-histological modalities for investigating bone quality.

Progress in the Accreditation of Anthropology Laboratories

While crime laboratories are commonly accredited under programs utilizing international standards, options for forensic anthropologists to do the same were limited, until recently. The American National Standards Institute-American Society for Quality (ANSI-ASQ) National Accreditation Board (ANAB) and the American Association for Laboratory Accreditation (A2LA) both offer accreditation programs for forensic anthropology services using either the International Organization for Standardization/International Electrotechnical Commission (ISO/IEC) 17025 or ISO/IEC 17020 standard. The significant efforts made to specifically include forensic anthropology, and also forensic pathology, in these national programs demonstrate the importance for all practitioners in the field of forensic science to develop and maintain quality assurance programs consistent with international standards. Among the requirements for quality assurance is validation of methods, a practice that was previously identified as needing improvement within the forensic anthropology community.