Mechanical Injuries

ROLL NO: 78-88

Classification
of injuries
Incised wounds

 An incised wound (cut, slice) is a clean cut

through the tissues, (usually the skin and
subcutaneous tissues, including blood vessels),
caused by sharp-edged instrument. The
wound is longer than it is deep.
Mechanism

 It is produced by the pressure and friction against the tissue, by

an object having a sharpcutting edge, such as knife, razor,
scalpel, scissors, sickle, cleaver, sword, etc. In this, the force is
delivered over a very narrow area, corresponding with the
cutting edge of the blade.
Causes

 Striking the body with the edge of sharp-cutting

weapon,
 by drawing the weapon, against the body
surface,
 by using the weapon like a saw in which case
there may be more than one cut in the skin at
the beginning of the wound which merge into
one at the end.
Characters

 Margins : The edges are cleancut, well-defined and usually everted. The edges may be inverted, if a
thin layer of muscle fibres is adherent to the skin as in the scrotum. The edges are free from
contusions and abrasions. A dull irregular- edged or nicked cutting edge may produce a wound with
irregular, contused, and/or abraded margins, as the wound is caused more by the pressure appljed by
the weapon than by the cutting edge. A serrated knife may produce a saw-toothed cut on the body, if
the blade passes obliquely or at shallow angle. The depth of the wound will not show any bridging
tissue.
 Width : The width is greater than the thickness of the edge of the weapon causing it, due to retraction
of the divided tissues. Shaking of the blade tends to make the wound wider than the weapon.
 Length : The length is greater than its width and depth, and has no relation to the cutting edge of the
weapon, for it may be drawn to any distance. When the skin becomes folded under the cutting edge of
the weapon, a single movement of the weapon may produce a series of incised wounds separated one
from another by bridges of normal skin. A curved weapon like a sickle, produces a stab from the
pointed end, and incised wound from the blade, sometimes with an intervening intact skin. Rarely,
there may be a superficial tail (a shallow scratch) at the termination known as tailing of wound which
indicates direction.
 Shape: It is usually spindle-shaped due to greater retraction of the
edges in the centre. Gaping is greater if the underlying muscle fibres
have been cut transversely or obliquely, and less when cut
longitudinally. Incised wounds crossing irregular surfaces may be
irregular in depth, but will be linear. The wound may take zig-zag course
if the skin isloosely attached as in axillary fold, because the skin is
pushed in front of the blade before it is cut. If the blade is curved, the
edges will be crescentic. If the surface is convex, such as the occipital
region or buttocks, the straight-bladed weapon may also produce a
crescentic wound.
 Haemorrhage:As the vessels are cut cleanly, the haemorrhage is
more. I f the artery is completely cut, the bleeding will be more due to
its inability to contract or retract. Spurting of blood occurs if an artery is
cut.
 Direction: Incised wounds are deeper at the beginning, because more
pressure is exerted on the knife at this point. This is known as the head
of the wound. Towards the end of the cut the wound becomes
increasingly shallow, till finally as the knife leaves the tissues the skin
alone is cut. This is known as the tailing of the wound, and indicates the
direction in which the cut was made.
 Bevelling cut : If the blade of weapon enters obliquely, the wound will
have a bevelled margin on one side with undermining (undercut) on the
other side so that subcutaneous tissue is visible, indicating the direction
from whick the blade entered. and if the blade is nearly horizontal, a
flap wound is caused. Bevelling can be produced by sharp weapon only.
Age of incised wound

 In an uncomplicated wound, healing occurs as follows:

 Fresh: Haematoma formation.
 12 hours: The edges are red, swollen and adherent with blood and
lymph; leucocytic infiltration.
 24 hours : A continuous layer of endothelial cells covers the smface;
overlying this a crust or scab of dried clot is seen.
 Histopathology

 Few minutes: Dilatation of capillaries and margination and emigration of neutrophils, reactive changes
in the tissue histiocytes and swelling of the vascular endothelium.
 12 hours: Reactive changes occur in the fibroblasts at the site of injury within few hours; monocytes
appear in the exudate. Leucocytic infiltration is appreciable.
 15 hours: Monocytes begin to undergo mitotic division.
 24 hours: Epithelium begins to grow at the edges. Vascular buds begin to form.
 72 hours: Neutrophils are largely replaced by macrophages. Vascularised granulation tissue is formed.
 4 to 5 days: New fibrils are formed. Epithelial cell proliferation continues, forming a thickened layer.
 One week: Soft, reddish scar formation in small wounds. The above changes are considerably
modified if infection of the wound occurs.
 In healing by second intention, inflammatory reaction is more intense and much larger amounts of
granulation tissue are formed resulting in greater mass of scar tissue.
Wound by glass
 Wounds produced by glass are
lacerated, but can resemble incised and
stab wounds. If a sharp-pointed piece of
glass enters by its point, the wound has
a stab-like appearance. Margins of the
wound will almost always show tiny side
cuts due to irregularities of the glass.
Particles of glass may be found in the
wound. Assault with broken glasses or
bottles show multiple irregular incised-
type wounds of variable depth and
severity.
Homicidal wounds

 They are usually multiple and can occur in any

region of the body. Wounds of the chest are
usually present over a wider area and are more
horizontal. They may be directed from below
upwards which is rarely seen in suicidal
wounds. Incised wounds situated on the back,
or in such a position as cannot be easily
reached by a suicide, are homicidal. Incised
wounds on nose, ears and genitals are usually
homicidal, and are inflicted on account of
jealousy or revenge in cases of adultery,
causing disfiguration. Cut-throat wounds cause
immediate death from haemorrhage,air
embolism, or inhalation of effused blood into
the respiratory tract.
 In a decomposed body, it is difficult to differentiate a laceration from an
incised wound. When a body with incised wounds, stab wounds, or
lacerations is immersed in water soon after infliction of injuries, the
blood in the wounds is lysed by water and passes into the water, and
whether the injuries are antemortem or postmortem cannot be made
out.
Medicolegal importance

 They indicate the nature of weapon (sharp-edged).

 The age of the injury can be determined.
 They give an idea about the direction of the force.
 Position and character of wounds may indicate mode of production, i.e.,
suicide, accident, homicide.
Chop wound

 They are deep gaping wounds caused by a blow with the sharp-cutting
edge of a fairly heavy weapon, like a hatchet, an axe, sword, broad
heavy knife, chopper, saber, or meat cleaver.
 Undermining occurs in the direction towards which the chop
is made. When the whole blade strikes the body at the same
time,the depth may be same throughout the wound. Usually
the lower end (heel) of the axe strikes the surface first, which
produces a deeper wound than the upper (toe) end. The
deeper end indicates the position of the assailant. In the
skull, the undermined edge of the fracture defect is the
direction in which the force is exerted, and the slanted edge
is the side from which the force was directed.
 In case of long bones, the bone fragments get loosened on
the opposite side of the force. With axe and heavy cutting
weapons, the initial impact slices cleanly through the bone
on one edge. The rebound removal of the weapon is at a
slightly different angle, either from deliberate intention or
from relative movements between bone and blade. This
cracks off an irregular fragment of bone of the opposite side
so that the defect has one smooth and one rough edge
particularly near the ends of the chop wound. If the
extremities are attacked, there may be complete or
incomplete amputation of the fingers or other bones, and the
joints may be separated or disarticulated. Wounds on the
head and trunk are usually associated with injuries to
important structures and are fatal. The cranium may be
depressed, but if the weapon strikes obliquely, a piece of the
skull may be removed. If the chopping blow is tangential, a
disk-shaped portion of bone or skin or soft tissue may be cut
away. The neck may be almost completely separated.
Medicolegal importance
Stab wound

 A stab wound is produced when force is

delivered along the long axis of a narrow or
pointed object, such as knife, dagger, sword,
chisel, scissors, nail, needle. spear, atTow,
screw driver, etc. into the depths of the body.
The wound is deeper than its length and width
on the surface of skin. This can occur by driving
the object into the body, or from the body's
pressing or falling against the object. The most
common stabbing instruments at·e kitchen
knives, sheath knives or pen- knives.
Types
Puncture wounds When soft tissues are involved.
penetrating wounds, when they enter a cavity of body or a
viscus. When the weapon enters the body on one side and comes
out from the other side.
perforating wounds or through-and-through puncture wounds
are produced. The wound of entry is larger with inverted edges,
and the wound of exit is smaller with everted edges, due to
tapering of blade. The victim of a fatal penetrating injury may not
show signs and symptoms of injury until many hours have passed.
Characters

 Margins: The edges of the wound are clean-cut and inverted. The margins can be everted when
the wound is situated over the fatty area, such as portuberant abdomen or gluteal region. There is
usually no abrasion or bruising of the margins, but in full penetration of the blade, abrasion and
bruising (hilt mark) may be produced by the hilt-guard (metal piece between the blade and handle)
striking the skin.
 Length : The length of the wound is slightly less than the width of the weapon up to which it has
been driven in, because of stretching of the skin. For measuring the length of stab wound, the
edges of the wound should be brought together. Deliberate lateral, forward, or backward
movement of the weapon during its withdrawal from the body tends to widen the wound, and the
length will be more than the maximum width of the blade.
 Width: By examining multiple stab wounds in the body, the length and width of the knife blade can
be determined approximately.
 Depth: The depth (length oftrack) is greater than the width and length of the external injury. It is
not safe to find out the depth of a stab wound by introducing a probe, because it may disturb a
loose clot and may lead to fatal haemorrhage, or cause serious damage and may produce multiple
false wound tracks.
The force required to inflict stab
wound:

 Condition of the knife

 The resistance offered by the tissues or organs
 Clothing
 The speed of thrust of the knife.
 Stretched skin is easier to penetrate than lax skin, e.g. chest wall.
 When the knife strikes the skin at right angle, it usually penetrates
more deeply than when it strikes from some acute angle.
 When the knife penetrates the skin rapidly
 Weapons causing stab wounds:

• If a single-edged weapon is used, the surface wound will be

triangular or wedge-shaped, and one angle of the wound will
be sharp, the other rounded, blunt or squared off. Blunt end of
the wound may have small splits in the skin at each end of the
corner, so- called "fishtailing", if the back edge of the blade is
stout.
• If a double- edged weapon is used, the wound will be elliptical
or slit-like and both angles will be sharp or pointed.
 A round object like the spear may produce a circular wound.
 A round blunt-pointed object, such as a pointed stick, or metal rod may produce a
circular surface wound with inverted ragged and bruised edges.
 A pointed square weapon may produce a cross-shaped injury, each of the 4 edges
tearing its way through the tissues.
 A fall on a pointed article, e.g., pieces of broken glass, will produce a wound with
irregular and bruised margins, and fragments of glass may be found embedded in
the soft tissues.
 Stab wounds inflicted with a broken bottle, appear as clusters of wounds of different
sizes, shapes, and depth, with irregular margins, and varying depth.
 Stabbing with a fork produces clusters of 2 or 3 wounds depending upon the
number of prongs on the
Medicolegal importance

 The shape of the wound may indicate the class and type of the weapon
which may have caused the injury.
 The depth of the wound wiII indicate the force of penetration.
 Direction and dimensions of the wound indicate the relative positions
of the assailant and the victim.
 The age of the injury can be determined.
 Position, number and direction of wounds may indicate manner of
production, i.e., suicide, accident, or homicide.
 If a broken fragment of weapon is found. it will identify the weapon or
will connect an accused person with the crime.
Defense
wound
 Defense wounds
result due to the
immediate and
instinctive reaction of
the victim to save
himself.
Types

 Active defense wounds are caused when the victim tries to grasp the
weapon.
 Passive defence wounds are caused when the victim raises the hands, arms
or legs.
 When attacked with blunt object, most persons will attempt to protect their
eyes, head and neck by raising their arms, flexing their elbows and covering
the head and neck, or try to grasp the weapon. As a result bruises and
abrasions are produced on the extensor or ulnar surfaces of the forearms,
wrists, backs of the hands, knuckles and lateral/posterior aspects of the upper
arms. Fractures of the carpal bones, metacarpals and digits may occur.
Defence wounds may be found rarely on the shins and feet if the victim was
lying on the ground usually face up, as he kicks at the assailant. The arms and
posterior aspects of lower limbs and back may be injured as the victim curls
into a ball with flexion of spine, knees and hips to protect the anterior part of
the body and genitals.
 Defence wounds are absent if the victim is unconscious, or is taken by
surprise, or attacked from the back, or under the influence of alcohol or drugs.
Fabricated
wounds
 Self-inflicted wounds
are those inflicted by
a person on his own
body. Fabricated
wounds (fictitious,
forged or invented
wounds) are those
which may be
produced by a person
on his own body (self-
inflicted), or by
another with his
consent.
Motives:

 They may be produced for the following reasons.

 (1) To charge an enemy with assault or attempted murder.
 (2) To make a simple injury appear serious.
 (3) By the assailant to pretend self-defence or to change the appearance of wounds,
which might connect him with the crime.
 (4) By policemen and watchmen acting in collusion with robbers to show that they
were defending the property.
 (5) In thefts by servants or messengers for the above reason.
 (6) By prisoners, to bring a charge of beating against officers.
 (7) By recruits to escape military service.
 (8) By women to bring a charge of rape against an enemy.
Types

 Fabricated wounds are mostly incised wounds, and sometimes contusions. stab wounds and
burns. Lacerated wounds are rarely fabricated. Incised wounds are usually superficial, multiple
and parallel, are of equal depth at origin and termination.
 They avoid vital and sensetive areas like the eyes, lips, nose and ears. The direction is from
behind forwards on the top of the head, from above downwards on the outer side of upper
arm, from below upwards on the front of forearms, variable on the legs and vertical on the
abdomen and chest.
 Some mentally disordered persons may inflict hundreds of small wounds upon themselves.
Paranoid schizophrenics with a strong religious flavour to their delusions may remove penis,
scrotum and testes.
 Stab wounds are usually multiple and superficial and seen about the left arm or shoulder and
sometimes on the chest. Burns are superficial and seen usually on the left upper arm.
 The clothes are not cut and if cuts are seen they are not compatible with the nature of the
wounds. The history of the assault is incompatible with the injuries.
Medicolegal importance

 It is important to identify which type of wound

for proper identification.
Thank you