DEPARTMENT
OF ANATOMICAL SCIENCES
AN321
- FORENSIC OSTEOLOGY
BONE
INJURIES
W.
B. Wood
Senior
Lecturer
The
University of Queensland
INTRODUCTION
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
PHYSICAL FORCES
Mechanical compression
(crushing, piercing)
distraction
(tension)
bending
twisting
shearing
(cutting)
Heat low
- surface browning, no
weight loss
moderate
- charring, moderate moisture and
weight loss,
fracturing
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 &
bending
(warping)
CHEMICAL INJURIES
acids
or alkalis
causes
bone (& tooth) demineralisation & softening
surface
etching or erosion
NOTE:
effects of crocodile digestion on consumed bones & teeth
BIOLOGICAL INJURIES
animal - rodents
-
carnivours
-
sharks & crocodiles
-
marine predators
termites
(white-ants)
root
or fungus penetration of bony foramina etc.
BONE FRACTURES
Classification:
Types of fracture - sudden injury, stress,
pathological,
a) Sudden injury: direct violence
(mechanical force)
indirect
violence
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)
infections
tumours
(benign & malignant, primary & secondary)
miscellaneous:
Paget's disease
osteoporosis
rickets
Sub-classification
Simple (closed),
compound (open)
Terminology Commonly Associated with Fractures & Fracture Patterns:
Fracture Types:
transverse oblique spiral
comminuted compression (crush) greenstick
impacted fissure depressed
Other Terms:
bone sequestrum - this is an isolated fragment of
dead bone.
malalignment angulation shortening
deformity, pseudoarthrosis
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
bone formation.
SPECIFIC TYPES OF BONE INJURY
BULLET (& other
projectile) WOUNDS
entry wound
exit wound
associated
fractures
Terminology:
small/large calibre, low/high velocity
shotgun
CUT & STAB WOUNDS - knives, swords, hatchets, machetees
lances,
spears, arrows, daggers, javelins
teeth,
saws
sharp blunt
BLUNT WOUNDS
crush
injuries
depressed
fractures
scratch,
abrasions, gouges
JOINT INJURIES
Dislocation or
subluxation injuries
Aetiology:
Congenital eg
club foot
dislocated
hip
Spontaneous
often
secondary to another disease process eg destructive or neuropathic arthritis, or to a
structural deficiency (patellar dislocation) or previous bone
injury
Traumatic
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.)
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REFERENCES
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