DEPARTMENT OF ANATOMICAL SCIENCES
AN321 - FORENSIC OSTEOLOGY
W. B. Wood
The University of Queensland
Stewart (1979 p76) defines the role of the forensic anthropologist relative to skeletal trauma as being "to describe any evidence of bone damage, point out its location in relation to vital centers, explain the possibility of its having been sustained at the time of death or otherwise, and discuss the likely types of objects that produced the damage."
Careful examination is therefore made by the forensic anthropologist of every recovered bone or bone fragment both macroscopically and under x10 magnification to try to identify the presence of bone injuries.
If any skeletal injury is found then it must be fully described and recorded and analysed in terms of whether it was sustained antemortem, perimortem or postmortem. In particular, if an injury is determined to be perimortem, then one must try to ascertain whether it may have caused or contributed to the death of the person. Such determinations are not always easy.
Injuries may be of many different types and include fractures; joint subluxations and dislocations; surface nicks or cuts, scratches, abrasions, erosions, gouges, punctures, and chip or splinter injuries.
Specific types of injury are associated with specific causes e.g. gunshot wound, stab wounds, blunt trauma, saw cuts, gnawing etc, and such injuries must be recognised for what they are. In some cases bony reconstruction and even examination of cut or broken surfaces with a scanning electron microscope may be required before the true nature and cause of the underlying bone injury can be recognised.
An excellent review of bone trauma and the role of the forensic anthropologist/osteologist is provided in Maples (1986). Kerley (1976) discusses the diagnosis of the battered child from skeletal evidence. A good clinical reference text is that of Crawford Adams (1978)
ANTEMORTEM V POSTMORTEM INJURIES
Bone injuries may be the result of accidents or they may be intentionally inflicted.
Accidental - motor vehicle accidents, occupational injuries, falls, injuries from
flying/falling objects etc
Intentional - aggressive assault by man or animal
- surgical operations, autopsies etc
Antemortem injuries can only be diagnosed when there are visible signs of bone reaction in the form of bone resorption around the fracture margins, bone healing (callus formation) or infection. Such signs may take up to a week or more to become apparent (Maples 1986 pp220-221).
Antemortem bone injuries that are more than a week old will show evidence of bone reaction and repair processes. Periosteal and endosteal callus (new bone) formation results in surface bone deposition and bone swelling that may persist with little change for many years. Ancient (remote antemortem) injuries may leave little evidence in the bones especially if sustained while the skeleton was still immature. In these cases bone remodelling may have completely erased all such evidence.
Injuries received immediately postmortem may be difficult to separate from perimortem and recent antemortem (<1 week) injuries.
Alterations in bone elasticity due to water and collagen loss gradually develop during the 2-3 weeks immediately after death and result in increasing brittleness and altered fracture patterns of bones which can be recognised by the experienced forensic anthropologist.
Like antemortem injuries, postmortem injuries may be recent or remote, accidental or deliberate. Contextual evidence may be inportant in making these determinations.
Examples of culturally related postmortem trauma still practised in society today are autopsies & mortuary inquisition. In ancient contexts postmortem trauma was associated with postmortem disarticulation of dead bodies for ceremonial purposes, use of bones for making bone tools and other utensils, cannibalism, scalping and skull trophy collection and display.
The study of the history of bones from the time of death and deposition to the time of recovery is called TAPHONOMY.
AETIOLOGY OF BONE INJURIES
Mechanical compression (crushing, piercing)
Heat low - surface browning, no weight loss
moderate - charring, moderate moisture and weight loss,
severe - calcination, grey/white coloration, lightweight, brittle
loss of all moisture and bone protein.
Weathering sunlight (UV light) produces bleaching
alternate heating & cooling produces surface
cracking & flaking of cortical bone
alternate wet/dry conditions may produce bone cracking &
acids or alkalis
causes bone (& tooth) demineralisation & softening
surface etching or erosion
NOTE: effects of crocodile digestion on consumed bones & teeth
animal - rodents
- sharks & crocodiles
- marine predators
root or fungus penetration of bony foramina etc.
Types of fracture - sudden injury, stress, pathological,
a) Sudden injury: direct violence (mechanical force)
b) Stress fracture: due to oft-repeated stress
similar to metal fatigue
mainly in lower limb bones
c) Pathological: in bones weakened by disease
congenital - (fragilitas ossium)
tumours (benign & malignant, primary & secondary)
miscellaneous: Paget's disease
Simple (closed), compound (open)
Terminology Commonly Associated with Fractures & Fracture Patterns:
transverse oblique spiral
comminuted compression (crush) greenstick
impacted fissure depressed
bone sequestrum - this is an isolated fragment of dead bone.
malalignment angulation shortening
HEALING OF FRACTURES (BONE REPAIR).
The rate and type of healing process may be affected by:
rigidity of fixation
closeness of apposition of bone ends (any intervening soft tissue?)
whether in compact tubular bone or cancellous bone
Repair in Tubular Bones. This is described as occurring in 4 Stages:
Stage of Inflammatory Reaction:
. lasts about 4 days.
. includes both haematoma formation and cellular proliferation
. haematoma formation is associated with oedema and pain.
. osteoclasts and macrophages remove necrotic bone & tissue debris.
. subperiosteal & endosteal proliferation of reparative cells - fibroblasts,
osteoblasts and endothelial cells.
Stage of Soft Callus Formation:
. begins within 2 days (overlapping the above) and lasts about 3-4 weeks.
. contains proliferating osteoblasts, fibroblasts, and chondroblasts embedded
in a matrix rich in glycoproteins and collagen into which new blood
vessels grow and calcium is deposited.
. both periosteal and endosteal callus formation (called woven bone).
Stage of Hard Callus Formation (Consolidation)
. commences 3-4 weeks after injury and lasts 2-3 months.
. involves the conversion of soft callus to lamellar bone.
Stage of Remodelling:
. may last for several years.
. reshaping (moulding) of the lamellar bone in conformity with the forces
acting upon the bone.
Repair in Cancellous Bones
The spongy nature of cancellous bone with no medullary cavity means that a much
broader area of contact exists between the bone fragments and that penetration by
bone-forming tissue is much easier. Direct union occurs without formation of
external and internal callus. The sequence is: haematoma formation; osteogenic
proliferation and penetration until fusion with opposite fragment occurs; woven
SPECIFIC TYPES OF BONE INJURY
BULLET (& other projectile) WOUNDS
Terminology: small/large calibre, low/high velocity
CUT & STAB WOUNDS - knives, swords, hatchets, machetees
lances, spears, arrows, daggers, javelins
scratch, abrasions, gouges
Dislocation or subluxation injuries
often secondary to another disease process eg destructive or neuropathic arthritis, or to a structural deficiency (patellar dislocation) or previous bone
By far the most common cause.
HEAT EFFECTS ON BONE (CREMATION)
The effects of heat on bone vary with the time and intensity of the exposure and also with the presence or absence of flesh on the bones.
With increasing heat and length of exposure, bones are first scorched, then charred, and finally calcined. Limbs tend to be burnt off a cremated body and the skull tends to expand and disintegrate into numerous smaller pieces.
There is progressive loss of water and organic matrix from the exposed bones resulting in shrinkage and weight loss, increasing brittleness, fracturing, distortion and colour changes (brown, black, blue-grey and white).
A skeleton cannot be completely consumed by an ordinary household or building fire and the characteristic features that identify them as human bones usually survive provided the remains are not subjected to further crushing and grinding (Bass 1984 p159).
Age, sex, race and stature are still usually possible to ascertain. The forensic anthropologist must be aware that due to the moisture loss and shrinkage the sexual characteristics of some cremated bones may be so altered that a female origin may erroneously be inferred.
Distinctive patterns of surface fracturing distinguish cremations in which flesh is still present on the bones from those involving already skeletonised remains (Stewart 1979 p62-63, Ubelaker 1989 pp35-38). Notwithstanding the heat related injuries to bone, the identification of precremation injuries may still be possible by careful examination and analysis of the remains.
CAUSE OF DEATH?
It is up to the Coroner to determine the specific cause of death after considering the evidence and expressed opinions of the various experts that examined the remains and were asked to given evidence or present reports (pathologists, forensic osteologists etc.)
Bass WM 1984 "Is It Possible to Consume a Body Completely in a Fire?" in Human Identification: Case studies in forensic anthropology. Rathbun T.A. & J.E. Buikstra (Eds.), Charles C Thomas
Crawford Adams J 1978 Outline of Fractures 7th Edition, Churchill Livingstone
Kerley ER 1976 "Forensic Anthropology and Crimes Involving Children." J For Science 333-339
Maples WR 1986 "Trauma Analysis by the Forensic Anthropologist." In Forensic Osteology. KJ Reichs (Ed), C.C. Thomas, 218-228
Stewart TD 1979 Essentials of Forensic Anthropology. C.C. Thomas Publishers pp76-81
Ubelaker DH 1989 Human Skeletal Remains. 2nd. edn., Taraxacum Publisher pp35-38