MECHANICAL INJURIES

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MECHANICAL INJURIES Definition: Injuries caused by application of

physical violence to the body are known as Mechanical injuries.

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Classification of Mechanical Injuries

Blunt Force Injuries/Trauma: Abrasions. Bruises(Contusions) Lacerations.

Sharp Force Injuries/Trauma: Incised wounds. Stab wounds. Chop wounds. Fractures. Fire arm injuries.

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MANNER OF CAUSATION

Self – Inflicted (suicidal) Assaults by others (Homicidal) Accidental

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ABRASIONDEFINITION: 1. It is a superficial injury

involving only the superficial layers of skin. (epidermis).

2. The outer layers of skin are scratched or removed leaving a bare area with little or no bleeding.

3. These heal rapidly in few days and leave no scar.

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MECHANISM OF CAUSATION CAUSED BY

a) RUBBING.b) SCRAPING.

CAUSATIVE AGENTS. SHARP OBJECTS= FINGER NAILS, PIN,

THORN SHARP POINTED OBJECTS. ROUGH SURFACE= GROUND, ROAD,

FLOOR.BLUNT OBJECTS= KICK WITH BOOT,

ROPES, STICKS, WHIP, TEETH.

OF SKIN WITH AN OBJECT

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CLASSIFICATION OF ABRASIONS 1. Scratches. 2. Grazes. Moving abrasion. 3. Imprint abrasion. 4. Friction abrasion.

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CLASSIFICATION: a) SCRATCHES: It is a linear injury caused by a

sharp pointed object such as pin or finger nail running across the skin.

CHARACTERISTICS: The direction of scratch is

indicated by sharp edge initially and heaped up epithelium/ epidermis at the end.

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CLASSIFICATION OF ABRASION

b) GRAZES / SLIDING/ FRICTIONAL BURNS / GRAVEL RASH :-

It is produced when broad surface of skin slides against a rough surface.

like ground, road also called as brush burns.

Example seen in: o Road traffic accidents

(RTA).o Dragging of body on a

ground.o Glancing kick with a boot 10

MEDICO-LEGAL SIGNIFICANCE:

Direction of force: shown by situation of “tags”.

Identification of scene of incidence: presence of foreign body (dirt or grit) in the graze. Compared with the scene.

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c) FRICTION ABRASION: Are caused by rubbing the skin surface with cords or ropes.

Example:

Ligature marks in cases of hanging, strangulation.

Blows with lash. Friction between skin & edges of

garments.

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CLASSIFICATION OF ABRASION d) IMPRINT/ STAMPED/

PRESSURE/ CONTACT/PATTERNED/ CRUSHED ABRASION:

It is produced as a result of direct impact or pressure without relative movement.

Example: Tire mark. teeth marks. ligature pattern. muzzle imprint. 13

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MEDICO-LEGAL SIGNIFICANCE: Identification of offending object.

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MEDICOLEGAL ASPECTS It provides valuable information about

1. Site of impact and possibility of internal injury These indicate that some force has been applied to the body.

2. Identification of Object causing injury For example as in case of Patterned or imprint

abrasions, Ligature in hanging, tire marks in RTA.

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MEDICOLEGAL ASPECTS 3. Cause of injury

The site of abrasion helps to determine cause of injury, For example; On Neck in Throttling. On Nose and mouth in smothering On thighs and genitalia in sexual assault.

4. Direction of Injury Sharp margins initial and heaped up epithelium

on it, terminate serrated borders initially and heaped up epithelium at the end.

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DATING AN ABRASION (AGE)OBSERVATION TIMEBRIGHT RED FRESHRED SCAB

DRIED BLOOD/SERUM

12-24 HOURS.

REDDISH BROWN SCAB

2-3 DAYS.

HEALING FROM PERIPHERY

4-7 DAYS.

COMPLETE HEALING

10-14 DAYS. 18

DIFFERENCE B / W ANTE MORTEM & POST MORTEM ABRASIONS.

INDICATOR A.M. P.M.

1. COLOR BROWNISH ON DRYING

YELLOW ON DRYING

2. MARGINS. BLURRED (DUE TO VASOCONSTRICTION)

SHARP

3. VITAL REACTION

PRESENT ABSENT

4. SIGNS OF REPAIR

PRESENT ABSENT

5. BLEEDING PRESENT ABSENT19

BRUISE (CONTUSION)DEFINITION: It is a hemorrhage into the tissues, due to

rupture of vessels by the application of blunt force, without breach of covering tissue (skin or capsule).

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DIAGNOSTIC FEATURES:

= Shape may correspond the shape of causative object.

= Reddened area when fresh. = Pain. = Swelling. = Size varies from pinhead to an extensive

haematoma.

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CAUSES: 1. SPONTANEOUS (DUE TO DISEASE): Disease of

blood, vessels, scurvy, leukaemia.

2. TRAUMATIC: Blows with club, fist, kicks, stone & bricks. Firm griping of weak persons, RTA.

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CLASSIFICATION OF BRUISE DEPENDING UPON DEPTH OF THE TISSUE

INVOLVED: Intra dermal bruise. Subcutaneous bruise. Deep/delayed bruise /visceral bruise. DEEP BRUISE MAY BECOME EVIDENT AFTER SOME

TIME (2-3 DAYS).

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ECTOPIC BRUISE: A bruise may not be present necessarily at the

site of impact. The extravasated blood may move along tissue planes

under gravity influence and gets collected at a distant place (gravity shifting).

EXAMPLE: - BLOW ON FOREHEAD OR FALL ON VERTEX BLACK

EYE. - FACTURE HEAD OF FEMUR LATERAL ASPECT OF

LOWER THIGH.- BLOW ON OUTER PART OF THIGH BRUISE AROUND

KNEE. 24

SPECTACLE HEMATOMA, BLACK EYE OR PERIORBITAL HEMATOMA OR RACCOON SIGN. A bruise round the tissues of the eyes &

eyelids may result called as Spectacle Hematoma,

It occurs due to A blow to the orbitFractured orbital roofA blow to the foreheadA fall on the vertex.

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BATTLE’S SIGN A bruise behind the ear called

Battle’s Sign may result from fall on the vertex or fracture of the base of the skull rather than a direct blow behind the ear.

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FACTORS MODIFYING APPEARANCE OF BRUISE Site of Injury Vascularity of area Age Sex Color of skin Nature of disease Gravity shifting of blood

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1. SITE OF INJURY IMPORTANT SITES 1 Areas covering bones 2 Loose tissue Bruising more marked in area covering the

bones without any intervening fibrous tissue e.g. over tibia.

No bony support for abdominal walls. Bruising is rare after physical impacts on

abdomen. Absence of bruising is no proof of undamaged

underlying tissue/viscera

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Bruising appears easily around lax tissue of eyes, face, genitals e.g. Black eye – with a small blow.

Bruise formation on scalp is uncommon except in birth trauma in a new born.

Rare bruising on palm/soles

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3) AGE: Children (due to loosening of skin) & old (due to loss

of flesh & changes in blood vessels) bruise easily. 4) SEX: Females (obese) bruise easily.5) VASCULARITY OF PART: Bruising is directly

proportional to vascularity of affected part.

6) COMPLEXION: Visibility better and clear in fair skinned people.

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7) PRESENCE OF DISEASE. Coagulation factor deficiency. Disease of blood vessels. Diminished platelets (thrombocytopenia). Persons with nutritional deficiency. Blood disorders (leukemia) Arteriosclerosis Varicose veins. Obese Alcoholics

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MEDICO-LEGAL SIGNIFICANCE Indicates offending object (blunt). Gives idea about degree of violence. Time of injury. Motive/purpose of injury. In throttling, pressure of pads of finger

homicide. Bruise on back of fingers, hand & forearms

( Defensive act). Multiple small bruise on arms just below

shoulders (Force full grasping during struggle) 33

MEDICO-LEGAL SIGNIFICANCE

Adults: alcoholics, drug dependent. In children: battered baby syndrome.

Tram track bruise: results from blow with rod, stick or whip & any flexible object. (Torture). Central depressed pale area with margins showing blood & swelling.

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MEDICO-LEGAL SIGNIFICANCE Suction petechie: bruising on

the cheeks & breast. (Sexual intercourse),(love bites)

Bruise on the medical aspect of thigh, vulva & around anus indicate forceful sexual intercourse.

Bruising of cervix shows dilatation cervix.

Bruising of buttocks indicate torture

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MEDICO-LEGAL SIGNIFICANCE Due to sudden compression of subcutaneous

tissues, fat may be displaced and enters into injured vessels lead into fat embolism.

Accidental: common occurrence. Suicidal: not common. Homicidal: common

Self inflicted: artificial bruised area produced by rubbing marking nut juice or Calotropis, or root of plumbago over skin.

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DIFFERENTIATE BETWEEN ARTIFICIAL BRUISE & TRUE BRUISE

Findings Artificial Bruise True Bruise

Cause Juice of Plant Blunt force

Situation On accessible parts Any part

Colour Dark brown Changes of colour

Margins Well defined Less defined

Shape Irregular Shape of weapon

Swelling, Redness, & echymosis Not present Present with slight swelling

Contents Serum Blood

Itching Present Absent

Chemical Tests Positive Negative

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DATING A BRUISE (AGE OF BRUISE) DONE BY:

- Macroscopic examination (color changes).- Microscopic examination (blood pigments).

Mechanism: Blood, due to disintegration of RBC by haemolysis,

releases haemoglobin that breaks down into haemosidrin, haemotoidin & bilirubin by the action of histiocytes & tissue enzymes.

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DATING A BRUISE (AGE OF BRUISE)CHANGES ARE SEEN FROM PERIPHERY TO CENTER.

COLOUR TIME OF INJURY PIGMENT

Fresh (Red) Fresh Hemoglobin

Red to blue One day Deoxygenated Hemoglobin

Bluish black to brown 2-4 Days Hemosiderin

Green 5-7 Days Haemotidin

Yellow 7-10 Days Billirubbin

Completely disappears 14 Days/ 2weeks Normal

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MICROSCOPIC CHANGES:

Hemosidirin within macrophages: not less than 24-48 hours.

Hemotoidin within Macrophages: not less than 3 days.

Bilirubin extra cellular: not less than 7 days.

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