Osteology and skeletal radiology

DEFINITION: Subdiscipline of physical anthropology specializing in the scientific study of bone and bony anatomy.

SIGNIFICANCE: When remains are discovered that are decomposed, skeletonized, or otherwise unrecognizable, osteology and radiology are used to determine whether the remains are human and how many individuals are represented. Osteological examination may further enable identification of the person or persons and the possible manner of death.

Bone is connective tissue that comprises both organic (living bone cells) and inorganic (mineral) components. Bones provide support for the body’s locomotion and other movement, protection of the vital organs, and regulation of bodily substances (such as calcium). Osteologists study the growth, development, morphology, and functions of bone, as well as the pathologies that affect it, in order to understand the human skeletal system.

Origins of the Field

In 1897, George A. Dorsey became the first anthropologist to apply his knowledge of osteology to expert testimony in a criminal trial—the infamous Luetgert sausage factory trial in Chicago. Dorsey testified that he had identified four small fragments of human bone (believed to be the bones of the wife of factory owner Adolph Luetgert) found in a sausage vat in Luetgert’s factory. Luetgert was convicted of the murder of his wife and sentenced to prison, where he died shortly thereafter.

Forensic anthropologist Wilton Marion Krogman illustrated the importance of osteology to law enforcement in his seminal 1939 work, “A Guide to the Identification of Human Skeletal Material,” which appeared in the FBI Law Enforcement Bulletin. World War II, the Korean War, and the Vietnam War saw the regular application of osteology toward the identification and repatriation of the remains of US soldiers. In the twenty-first century, forensic anthropologists routinely use osteology and radiology in the identification of decomposed or unrecognizable human remains and the interpretation of the events preceding, surrounding, and postdating deaths in situations involving both individual and multiple fatalities.

Identifying Human Bones

The first question in a forensic investigation of decomposed, skeletonized, or otherwise unrecognizable animal remains is whether the remains are human. Osteologists answer this question by applying their detailed knowledge of human bony fragments. Such an assessment can often be made visually through comparison of the remains with known human ones in terms of size, shape, density, and significant bony features. Radiographic and microscopic comparisons may be needed, focusing on bone density, trabecular (spongy) bone patterns, and microscopic structures of human versus animal bone.

After remains are confirmed as human, osteologists assess the number of individuals represented by the remains. This can be accomplished through a variety of methods, one of which is the principle known as the minimum number of individuals (MNI), a conservative estimate of the smallest number of people the remains could represent. MNI is assessed through the documentation of duplication of bony elements (for example, the presence of two right femurs, or thighbones, equals the presence of at least two individuals) as well as differences in age, sex, ancestry, stature, size, shape, coloration, and overall morphology of the bony fragments.

Individuating Remains

The primary applications of osteology and skeletal radiology to forensic science are toward the individuation of human remains and reconstruction of perimortem events—that is, the events around the time of death. Individuation is accomplished in a variety of ways, the most basic of which is the determination of a biological profile for the remains. Such a profile, which is derived from detailed analysis of the recovered remains, comprises the individual’s age at death, sex, ancestry, and stature. For example, age at death for a child may be determined through analysis of the growth of long bones and dental eruption, whereas for an adult, the osteologist may consider dental wear and degeneration of significant bony regions (such as pubic symphysis) and joints (osteoarthritis). Sex of the remains is established through consideration of the morphology and metrics of major long bones, pelvis, and cranium, if present, and stature is mathematically derived from the maximum length of a long bone. Ancestry is suggested by the morphological and metric features of the mid and lower face.

Tentative identification may be based on a comparison of the biological profile of a set of remains with the biological profile of a missing individual or potential victim. A more confident (in some cases, positive) identification can be derived from a comparison of unique antemortem (before death) anomalies and pathologies observed on the remains to those from a suspected identity. These might include prior healed fractures, unique anomalies, or identifying pathological conditions.

The discovery of such anomalies and pathologies is often accelerated through the use of forensic radiology—that is, the application of radiological imaging to a legal context. This can involve traditional radiology (X-rays), computed tomography (CT or CAT scans), or magnetic resonance imaging (MRI). One of the most common methods of obtaining positive identifications of remains involves antemortem and postmortem comparisons of radiographic images of teeth; forensic odontologists focus on patterns of missing and filled teeth as well as unique dental traits in applying this method.

In the absence of dental comparisons, frontal sinus patterns can be used. Frontal sinus patterns are believed to be similar to human fingerprints in that each person’s sinus “print” is unique. Radiographic comparisons of antemortem and postmortem frontal sinus morphology—including area size, bilateral symmetry, and superior margin outline—have been admissible in court cases to confirm identification. Comparisons of other sinuses (of the maxilla, ethmoid, sphenoid, and mastoid process) have also been used.

Remains may also be identified based on the exact placement of orthopedic and other surgical devices (such as surgical plates, screws, rods); in addition, such devices sometimes carry identifying serial numbers. The presence of pathological (disease) states (such as osteoporosis or osteoarthritis) can be helpful for identification in terms of their level of severity and location within the body, if medically documented. The morphology of trabecular bone patterns within the postcranium has also been used in identification. Trabecular bone is found at the ends of long bones and is characterized by a complex crisscross pattern that may be unique for every individual. Finally, comparisons of multiple and unique concordant bony anomalies (such as an extra rib) may offer supportive evidence for a positive identification.

Interpreting Trauma at Time of Death

A second important application of forensic osteology and skeletal radiology is the interpretation of perimortem trauma. Evidence for blunt force, sharp force, and gunshot wound trauma is often (but not always) visible in characteristic signatures on bone. Such signatures include gunshot entrance and exit defects, impact fractures, radiating and concentric fractures, and cut marks. Osteologists can assess the number of traumatic events (such as gunshot, blunt force, or sharp force wounds), the directionality and trajectories of the events, and sometimes the sequence of impacts (if multiple), often with the help of forensic radiology. These interpretations can be applied toward an assessment of the individual’s manner of death.

Osteologists must be cautious when interpreting and comparing antemortem and postmortem radiographs to avoid possible sources of error. For example, the body positions of postmortem radiographs must match those from antemortem sources. Other technical difficulties may arise from the level of detail captured in the radiographs as well as the level of skill of the technician in reading them. Bone remodeling over many years may eliminate many potentially concordant details (for example, evidence of healed fractures may fade over several decades and may not be visible on radiographs). Finally, locating antemortem radiographs may be difficult—without comparative antemortem radiographs of appropriate bony regions, a positive identification based on forensic osteology and radiology may not be possible.

Bibliography

Bass, William M. HumanOsteology: ALaboratory and FieldManual. 5th ed. Columbia: Missouri Archaeological Society, 2005.

Brogdon, B. G., ed. Forensic Radiology. Boca Raton, Fla.: CRC Press, 1998.

Campanacho, Vanessa, et al. "Documented Skeletal Collections and Their Importance in Forensic Anthropology in the United States." Forensic Sciences, vol. 1, no. 3, 15 Dec. 2021, doi.org/10.3390/forensicsci1030021. Accessed 16 Aug. 2024.

Klepinger, Linda L. Fundamentals of Forensic Anthropology. Hoboken, N.J.: John Wiley & Sons, 2006.

Komar, Debra A., and Jane E. Buikstra. Forensic Anthropology: Contemporary Theory and Practice. New York: Oxford University Press, 2008.

Matshes, Evan, et al. Human Osteology and Skeletal Radiology: An Atlas and Guide. Boca Raton, Fla.: CRC Press, 2005.

Schwartz, Jeffrey H. Skeleton Keys: An Introduction to Human Skeletal Morphology, Development, and Analysis. 2d ed. New York: Oxford University Press, 2007.

White, Tim D., and Pieter A. Folkens. The Human Bone Manual. Burlington, Mass.: Elsevier Academic Press, 2005.

‗‗‗‗‗‗‗. Human Osteology. 2d ed. San Diego, Calif.: Academic Press, 2000.

Zhang, Min. "Forensic Imaging: A Powerful Tool in Modern Forensic Investigation." Forensic Sciences Research, vol. 7, no. 3, Sept. 2022, doi.org/10.1080/20961790.2021.2008705. Accessed 16 Aug. 2024.