3.Mechanical Injury

INJURIES

By Dr. Naveen

Injuries

-hurt or harm -Usually applied to damage inflicted to the

body by an external force.

Brief Review: INJURY CLASSIFICATIONSA: According to causative factors

• Mechanical injuries (or physical injuries)• Thermal injuries• Chemical injuries• Miscellaneous injuries ( i.e., electrical injuries etc.)

B: According to severity of the injuries Simple Grievous (deadly or not)

C: Medicolegal classification Suicidal Homicidal Accidental

D: According to time inflicted: Antemortem wounds Postmortem wounds

Types of bodily injuries

CLASSIFICATION OF WOUND

A.Classification of Injuries according causative factors

1. Mechanical or Physical injuries ____produced by application of mechanical force.

1) Abrasion 2) Bruise or contusion 3) Laceration 4) Incised wound 5) Punctured wound 6) Fracture or dislocation of a bone,tooth or joint 7) Firearm wound

Handcuffsimprints

2. Thermal injuries (due to application of heat or cold)

3.Chemical injuries (I.e. acids or alkalies etc.)

4. Miscellaneous injuries ( I.e. Electrical injuries etc.)

B. Classification according to severity of the Injuries

1. Simple

2.Grievous which may or may not be dangerous to life

C. Medicolegal classification of Injuries

1) Self-inflicted or suicidal 2) Injuries inflicted by others or

Homicidal 3) Accidental injuries 4) Defence wound

D. Classification in relation to moment of Death

1) Antemortem wounds

2) Postmortem wounds

Mechanical injuries

ABRASION Definition: In an abrasion there is

damage or destruction of the superficial epithelial covering of skin (epidermis) or mucus membrane ,due to impact with hard ,blunt and rough object or weapon.

There may be loss of continuity of the epidermis (denudation of cuticle) or the mucus membrane.

Causative agent or Weapon

Hard blunt or hard blunt and rough ,or pointed end of an object or weapon. Example:stone, stick, needle or any other weapon ,or rough surface of any other material.

Mode of production

Abrasions are produced by the impact of the above materials,when friction is caused between the object and the epidermis due to the impact.

The direction of force causing the friction may be horizontal (as in scratches or grazes)or tangential or it may be more or less perpendicular (as in pressure or imprint abrasion).

Features of Abrasions Abrasions are superficial

injuries. But often there is accompanying injury to the subcutaneous or still deeper tissues. At the site of abrasion, there may be oozing of lymph and sometime very slight oozing of blood.

The lymph or blood which oozes out, and the denuded epithelial debris,dry up within a few hours to form a scab. Abrasions heal without formation of permanent scars.

Types of Abrasions

SCRATCHES or LINEAR Abrasions

• SCRATCHES or LINEAR Abrasions

A scratch or linear abrasion, caused by horizontal or tangential movement of the pointed end of an object will be wider at the starting point than at the ending point. In this type, the denuded cuticle heaps up at the terminal point.

• SCRATCHES or LINEAR Abrasions

From a scratch, the type of weapon and the direction of application of force or the relative position of the victim and the assailant can be known. The direction of the force is from the wider side to the narrower side of the scratch. The position of the assailant is at the wider side of the scratch i.e.,opposite the side of heaping up of the denuded cuticle.

• GRAZES or SLIDING Abrasions

These occur due to horizontal or tangential friction between the epidermis and wider part of the rough surface of an object, weapon or ground.

These abrasions are more commonly seen in road traffic accident cases, where the victim after being knocked down by a vehicle, falls on the ground with motion ,resulting in horizontal friction of the skin against the ground.

• GRAZES or SLIDING Abrasions

In this type of abrasion also, the starting part is wider and deeper with narrowing and thinning at the terminal part.

From grazes also, the direction of application of force can be asserted.

• PRESSURE Abrasions These are the result of more or less

perpendicular application of force on the body surface. The extent of friction is less and is directed towards the depth of the body.

The size and shape of the abrasion depends on the part of the weapon or object coming in contact with the body. Abrasions on the ligature marks around the neck in case of hanging are the examples of pressure abrasions.

From pressure abrasions, the type of the weapon used, can be said.

•IMPRINT or PATTEREND Abrasions

In case of pressure abrasion,the design of the weapon with its shape may be left imprinted on the abrasion. These are imprint abrasions.

From the design imprinted on the abraded area,the weapon of offence can be guessed. Example- abrasion caused by tyre of a wheel.

Medicolegal importance of abrasions

1. From abrasion, the type of the weapon used, can be said.

2. From linear or graze abrasion, the direction of application of force and the relative position of the victim and the assailant can be known.

3.From abrasions,time of assault can be roughly assessed. When fresh, an abrasion is red with evidence of

oozing of serum and a little blood. By 8-24 hours, there is a reddish scab formation. By

6th day, it is blackish and it starts falling off from the margins.

4. Abrasions sometime give indication about the specific type of offences committed.

Nail scratches in the neck of a dead body may be indicative of manual strangulation or throttling may be indicative of killing by smothering.

5. Abrasions may be produced on the vulnerable sites of the dead body during shifting of the body to the mortuary. These postmortem abrasions may be mistaken as antemortem abrasions.

These abrasions are present mostly against the vulnerable bony prominences.

These are yellowish,parchmentised and slightly translucent when dried, do not have oozing, scab formation or color change, as are seen in antemortem abrasions.

BRUISE OR CONTUSION

Definition: In bruise or contusion there is ecchymoses or effusion of blood in the subcutaneous or submucus tissue due to extravasation of blood, due to rupture of capillaries, caused by application of hard blunt force.

In bruise, there is no solution or breach of continuity of the covering skin but the epidermis may occasionally be abraded.

Features of bruise When fresh a bruise is reddish in color, slightly r

aised above the surrounding area, is painful and tender and may or may not have denudation of the covering cuticle.

Gradually, it changes in color and subsides by two weeks.

It is usually roundish or takes the shape of the striking part of the weapon.

Along with rupture of the capillaries. There is damage in the soft tissue. But the skin is usually spared because skin tissue is quite tough.

Type of weapon Impact with hard blunt

weapon produces bruise. Example- stone, stick. Impact by a stick or rod will cause two parallel linear bruises along the two margins of the impact, with a pale gap intervening, the breadth of which corresponds with the diameter of the stick

From this kind of bruise, the type of the weapon used, can be known.

Factors which influence the formation and appearance of a bruise

1. Quantity of force used- A greater force is more likely to cause a bruise.

2. Quality of force- A hard blunt force will cause a bruise, but a soft blunt force may not.Thus, striking with a stone will produce a bruise, but covering the part of the body with a rug before hitting with a stick may not produce a visible bruise. No bruise may be apparent externally, because the impact being soft,there may not be any rupture of capillaries underneath the skin.

But it may cause deep bruise or haematoma adjacent to the bone because, the applied force causes the soft tissue to strike the hard bone, resulting in the rupture of the capillaries and venules there.

3. Site of application of force

A greater force may even not produce any bruise on the anterior wall of the abdomen due to toughness and yielding force absorption capacity of the tissue there.

But bruises are easily produced against a bony prominence, say malar prominence because the capillaries in the subcutaneous tissue rupture easily in between the bone underneath and the hard blunt force applied on the surface.

4. Sex Females bruise easily due to delicacy of tissu

e in them including the vessels, and also due to more subcutaneous fat in them. Vessels present in the fatty tissue are more likely to be ruptured on application of force than the vessels present in the tough fibromuscular tissue.

5. Age Infants, young children and very old persons b

ruise more easily than young adults. In infants and young children, it is due to delicacy of tissue including vessels and more amount of subcutaneous fat.

6. Certain pathological conditions

Persons suffering from some disease (example- leukaemia vitamin ”K” deficiency ), bruise easily without application of much force. These persons may even develop haemorrhagic spots without application of any force.

7. Complexion of the person

A bruise appears more prominent in a fair complexioned person. In dark-skinned persons, it may not be well appreciated.

8. Shifting of bruise or appearance of a bruise at a site away from the site of impact.

When extravasation occurs at a site where the tissue is so tough and tissue space is less that, the extravasated blood cannot be accommodated there, the blood settles down to a lower level where tissue is loose.Gravity helps such shifting of extravasated blood. Example – When ecchymosis occurs in the subcutaneous tissue on the forehead due to impact over there, the blood cannot accumulate there due to lack of loose tissue at the subcutaneous level there. Gravity shifts the extravasated blood from the forehead to the loose tissue of the eyelid, giving rise to bruise on the eyelid or “black eye”, as this is otherwise known .

PATTERNED bruise The design on the surface of the weapon may

be imprinted on the bruise. Such a bruise is called a patterned bruise.

Example – bruises caused by a cycle chain or motor vehicle grill. A bruise caused by the roundish end of a weapon is circular in shape. When caused by the margin of the circular end of the weapon, it is crescent shaped. If caused by the body of a rod or stick then two parallel lines of bruises appear with a gap in between, which is roughly equal to the breadth of the weapon.

Medicolegal importances of Bruise

1. Bruises are generally considered as simple injuries. But multiple extensive bruises, distributed all around the body can be the cause of death .

2. Patterned bruises tell about the type of weapon used.

3. From bruise, time of assault can be ascertained.

A fresh bruise is slightly above the surface of the surrounding area; it is slightly warm. When fresh, a bruise is reddish in color.

Within a few hours it becomes bluish and remains bluish for about up to three days.

By 4th /5th day, it appears brownish due to persence of haemosiderin pigments at the site of extravasation. By 5th /6th day, the bruise appears greenish due to presence of haematoidin pigments.

After this period,it becomes yellowish due to the presence of bilirubin and it continues to be yellowish which gradually fades away and clears out by the end of the second week.

4. False bruise or bruise like lesion may be produced by application of some chemical or plant juice like, that of semicarpus anacardium, to bring false charge of assault against somebody. However they can be differentiated easily.

Differences between bruises and lesions produced by chemicals or plant juices

Features Bruise False bruise or bruise like lesionsShape regular irregular Swelling slight no swellingAbrasion over the area may be present not presentCause mechanical force chemicals or plant juice

Extravasation of blood present in the subcutaneous tissue not presentChemical test of skin scrapping detects nothing

detects the chemical or the plantjuice used

5. Like abrasions, bruises at some particular parts of the body may be indicative of some particular type of offences , e.g., bruises near the private parts of a woman may be indicative of sexual offence having been committed on her, forcefully.

LACERATIONS

Definition: In laceration there is breach of

continuity of tissue involving depth more than the covering epithelium of skin or that of an organ.

Lacerations are caused due to impact by hard blunt and rough weapons or objects.

Features Shape – Usually irregular.

Margin – Irregular.

Floor – Tags of tissue may be seen passing across the floor .

Dimensions – length or length and breadth both are more than the depth of the injury .

Foreign substances at the site of laceration – Many of these injuries being sustained on roads or due to fall etc., often the lacerations gave dust or such materials adhered to their floors . These foreign materials may sometime help to find out the place of occurrence of the injury or assault.

Medicolegal importance of the lacerated wounds

1. From a laceration some idea about the causative agent may be formed.

Sometimes the shape and the design of the weapon may be known from the wound . If the circular of spherical surface of a weapon strikes the body perpendicularly then a circular wound will be produced. If the margin of a circular surface strikes , a crescentic laceration will be there.

If the length of a cylindrical weapon strikes the body then a linear laceration will be produced. If the end part of such a cylindrical weapon is used then a “Y” shaped wound will be caused. The design of a tyre may get imprinted on the avulsion laceration when a person is run over by a vehicle.

2. Foreign substance like dust, sand, gravel etc. present on the wound will speak about the site or place where the injury was sustained.

INCISED WOUNDS

Incised wounds are cuts or slashes produced by the sharp edge of a weapon like, knife, razor, sword etc.

Mode of infliction

By drawing or sawlike movement of the weapon on the body surface when the weapon is rather light like, a knife or razor,

by striking the sharp edge on the body when the weapon is heavy or moderately heavy like, axe,sword etc.

Features of incised wounds

1. Shape – The shape of an incised wound is elliptical or it is spindle shaped. It may be oval if the wound gaps much. .

The shape of the incised wound may change in its curvature due to elasticity, creases and cleavages of the skin and the direction of the underlying muscle.

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2. Length of the wound - Length of an incised wound is greater than breadth and depth.

Length of the wound does not correspond with the length of the blade of the weapon when the incised wound is caused by drawing or sawing. It may correspond when the wound is caused by striking.

3. Breadth – Breadth of an incised wound primarily depends on the thickness of the effective part of the blade i.e., the thickness of the blade at that level upto which the edge of the weapon has gone in the tissue.

But the breadth depends much on the elasticity of the skin of the area and direction of the fibres of the muscle underneath the skin,in relation with the length of the wound.

If the underlying muscle fibres are cut across their length then, contraction or shortening of the cut muscle fibres on both sides of the incised wound will cause widening of the gap (bread) of the wound.

This does not happen if the muscle fibres not cut across or if the fibres run along the length of the incised wound.

4. Angles - The angles at both ends of the incised wound is sharply defined.

5. Margin – Margins of an incised wound are well defined, cleanly cut and sharp.

6. Floor – Floor of the wound is also sharply cut and divided.

7. Haemorrhage – As the vessels are also sharply cut,there is excessive external haemorrhage.

If the haemorrhage is from a vein then bleeding occurs in drops, which is stellate in appearance.

If it is from the arterial source, then there is spurting effect and the bleeding occurs in jets .

8. Hesitation cuts – These are also termed “tentative cuts”.

These are multiple superficial cuts placed around the beginning part of the main wound, in cases of suicide.

These superficial tentative or hesitation cuts indicate hesitation or indecisive state of mind of the suicide, before he finally inflicts the deep fatal wound on his own body.

9. Defence wounds : These are in most occasions , incised wounds t

hough abrasions; bruises, lacerations or punctured wounds also may be sustained in defence for self protection.

Defence cuts may be persent on the palmar aspects of the hand if, when attacked with a sharp cutting weapon, the victim holds the blade of the weapon to escape the assault.

In such a case there may be incised wounds on the palmar aspects of more than one finger, but all of them are expected to be in one line, if the blade of the weapon is single edged.

Medicolegal aspects of incised wound

1. Incised wounds are usually suicidal, then homicidal and only occasionally accidental.

Suicidal incised wounds are usually placed in front and sides of the neck or sometimes in front of the wrists, to cut the radial artery to bleed to die.

2. Direction of application of force – From the tailing and bevelling, the direction of application of force can be known.

3. Cause of death – In case of incised wound there is excessive external bleeding. Death therefore in many cases occur due to haemorrhage and shock. In case of cut-throat injury, death, in addition, may occur due to axphyxia due to choking of the respiratory passage by blood.

CHOP WOUNDS Chop wounds are incised wounds pr

oduced by striking with sharp cutting, heavy or moderately heavy weapons, like axe, sword etc.

These wounds are comparatively deeper and broader than the incised wounds produced by drawing or saw like movement of light sharp cutting weapons.

Abrasions or contusions may be produced at the margins due to friction with the surface of the thick and heavy blade. These wounds usually have bevelling also.

Bevelling – When a sharp cutting heavy or moderatily heavy weapon is used (striking) tangentially or at an angle to the body, then there is flapping at one margin of the wound at the cost of the other margin. This is bevelling.

Medicolegal importance of the chop wounds

1. Chop wounds are mostly homicidal in nature.

2. Sometimes the length of the weapon used can be said.

PUNCTURED OR STAB WOUND

Definition: Punctured or stab wounds are

deep wounds produced by the pointed end of a weapon or an object, entering the body.

Depth is the greatest dimension of punctured wound.

Causative Weapon : Punctured wounds may be caused by the

tip of a knife, arrow, needle. Punctured wounds may also be caused by

an object or weapon having no pointed end, e.g., blunt end of an iron rod.

The pointed weapon may or may not have sharp edge. Example: spear (have pointed end but may or may not have sharp edge), needles (have pointed end but no sharp edge), end of an iron rod (not pointed or sharp edged).

Varieties of punctured wounds 1. Perforated wound. Here part of the weapon passes through the

whole thickness of any part of the body, e.g. when the tip of a weapon enters the body through anterior surface of the chest and exits out through the posterior surface of the chest.

In a perforated wound there will be two outer or external wounds with a single strike, (a) wound of entrance, the wound through which the weapon enters the body and (b)wound of exit, through which the tip of the weapon comes out of the body.

2. Penetrated wound. Here the wound terminates inside a

body cavity or viscus, e.g.peneterating wound ending inside the abdominal or chest or cranial cavity.

3. Punctured or stab wound without causing penetration to a body cavity or without perforating the whole thickness of the body.

Here the tip of the weapon terminates inside the body except in a body cavity.

Features of punctured wounds

1.Shape

The shape of the wound of entrance in case of stab wound depends mostly on the shape of the weapon or shape of the edge of a weapon.

When a double edged pointed weapon is used, the external wound is elliptical, spindle shaped or slit-like in appearance.

In spindle shaped or elliptical wounds produced by double edged weapon, both the margins and angles will be sharp, clean and well-defined.

When a single-edged pointed weapon is used, the external wound will be triangular or wedge-shaped.

In wedge-shaped wounds produced by single-edged pointed weapons two margins and one angle will be sharply defined.

2. Margin When stabbed with double-edged sharp

cutting pointed weapon, both the margins of the elliptical external wound will be clean cut, regular, sharp and well defined.

When caused by a single-edged sharp cutting pointed weapon, the wedge shaped external wound will have two long, clean cut, regular, well defined margins with one short irregular margin.

When caused by pointed or blunt ended weapon without any sharp edge, then the margin will be irregular, uneven with abrasion, contusion and even tears.

3. Depth Depth is the greatest dimension of a p

unctured wound. The depth of the wound usually depends on the length of the weapon or the blade of the weapon upto which it enters in the body.

If the whole length of the blade of the weapon enters the body, then surrounding the wound of entrance there will be a contusion or abrasion due to friction or pressure by the hilt or blade-guard of the weapon.

If the whole length of the weapon does not e

nter the body then, there will not be any hilt mark in the form of abrasion or bruise. In such cases, the depth of the wound will not correspond with the length of the blade of the weapon.

Similarly, in case of a perforated wound, when a part of the weapon comes out through the wound of exit, the depth of the wound will not give the length of the blade of the weapon even though, hilt mark may be present around the wound of entrance indicating that, whole length of the blade has passed through the tissue.

4. Hilt mark

Most of the sharp cutting pointed weapons have a hilt or hand guard in between the butt and the blade, so that,during use the hand will not slip down over the blade of the weapon and get injured.

When in a stab wound, the whole length of the blade is pushed inside the body then the hilt strikes against the skin around the wound of entrance and keeps its mark over there in the form of abrasion or occasionally in the form of bruise.

Thus, hilt mark has two importances. If there is abrasion due to hilt around the wound, we can say that, that wound is the wound of entrance and that the whole length of the blade of the weapon was pushed inside the body and the weapon has a hilt.

5. Haemorrhage In case of stab wound internal hae

morrhage is more than the external haemorrhage due to injury to internal vessels.

The extent of internal haemorrhage may not be guessed untill the body is dissected open.

6. Injury to the internal organs

In stab wounds, injury to the vital internal organs is more common and is the real danger. Stab wounds over the head, neck, chest or abdomen are obviously more dangerous due to possible injury to the vital organs.

7. Examination of punctured wounds require extra vigil, because, these wounds have greater depth which cannot be examined from outside and because, punctured wounds are expected to cause injury to the vital organs of the body and extensive internal haemorrhage.

The depth and direction of the track of the wound should not be attempted from outside with the help of a probe. Such an attempt may cause further extension of the depth or extension in a new direction during probing.

If the victim is living, then the depth and direction of the wound should be examined on the operation table, so that, danger of further damage or additional haemorrhage will not be there. If the person is dead, then depth and direction of the track should be examined during dissection of the body.

As a doctor, it is very important to a victim who is living to examine and treat with all the haemorrhagic tissues and organs around the track of the punctured wound, or the victim may die of the haemorrhage.

Medicolegal importances of stab wounds

1. About the nature of the injury

Generally speaking, stab wounds are most commonly homicidal, next in occurrence suicidal and lastly accidental.

有刃

刺器种类

有刃

无刃

Homicidal stab wounds are usually more than one in number, all are quite deep, may be located anywhere on the body, including self unapproachable parts. In homicidal cases, the covering clothes usually bear corresponding cutmarks or tears. Defence wounds and marks of resistance may be present on the body. Foreign materials like foreign scalp hair or shirt-button etc. may be found in the tight grip of the hand of the victim in a state of cadaveric spasm. The weapon of offence may not be available on the spot.

Suicidal stab wounds are located on the approachable parts of the body, more commonly over the left side front of chest, neck and lower abdomen. The main wound may be only one. The covering clothes may not bear corresponding cut marks as that may be partly removed from the area while doing the act. The weapon may be held in the hand in a state of cadaveric spasm, or it may be present near the dead body.

No defence wounds or marks of resistance will be present on the body, but some self-inflicted incised wounds may be present on the other approachable parts of the body. The place of occurrence will not be disturbed and it may be a secluded place, not approachable to others. Sometimes a suicidal note may be left behind by the suicide. In some cases the suicide might have tried some other method before stabbing himself to death. Evidence in support of this may be present on the body.

2. From the shape and size of the external wound and the depth, the type of the blade of the weapon used can be said.

3. Differences between Incised, Punctured and Lacerated wounds

Points Incised wounds Punctured wounds Lacerated wounds 1.Weapon responsible Sharp edge. Pointed or elongated. Hard,blunt and rough2. Site Suicide often is on the neck,front of wrist, head; homicide is

anywhere. Suicidal often is on the chest (cardiac area) and abdomen. Anywhere, but fatal ones are on chest,abdomen and head

3. Mode of production By drawing, sawing or striking By pushing the pointed end By fricton,stretching

or compression4. Different dimensoins Length is the greatest Depth is the greatest

Length and breadth are greater than depth 5. Margin Cleanly cut, smooth, sharp and well defined Usually clea

n cut and well defined but may be irregular Irregular, uneven,ragged

6. Floor or depth of the wound Cleanly cut . Tapering, cleanly cut or ragged. Ragged with loose tags of tissue

7. Haemorrhage More and is external . Internal haemorrhage is more . Haemorrhage is less

4. Differences between Suicidal, Homicidal and Accidental wounds

Points Suicidal Homicidal Accidental

1. Type Mostly incised sometimes stab

Mostly stabs, and lacerations Mostly lacerated

2. Site Accessible parts of body. Anywhere on the body. Anywhere

3. Number Usually only a few Multiple May be of any number

4. Severity One or two severe All may be severe Nothing specific

5. Hesitation wound Present Absent Absent

6. Defence wound Absent Present Absent

7. Clothes Usually spared Bears corresponding tear or cut

Will have corresponding tears

8. Weapon Usually present Usually absent Usually present

9. Suicidal note Present Absent Absent

10. Sign of struggle Absent May be present Absent

11. Motive or cause Present Present Absent