This document discusses various types of mechanical injuries including abrasions, contusions, lacerations, incised wounds, stab wounds, fractures, and their classification. It provides details on the features, appearance, complications and medico-legal aspects of each type of injury. Blunt force injuries can cause abrasions, contusions and lacerations while sharp force injuries result in incised wounds and stab wounds. Fractures can occur from direct or indirect blunt force. The document emphasizes the importance of analyzing injuries for determining the weapon, force, direction and time since injury for medical or legal investigations.

2. INJURY
• Clinically its defined as solution or disruption
of the anatomical continuity of any tissues of
the body.
• Legally under section 44 IPC, its defined as any
harm whatever illegally caused to any person
in body,mind,reputation or property.

3. Wound
• Medico-legally include any lesion,external
or internal,caused by violence,with or
without breach of continuity of skin.

4. Mechanical Injuries
• Are those,which are caused by the physical
violence to the body,depending on the
manner and how they are caused.
• Examples:- Blunt force injury.
Sharp force injury.
Fire-arm injury.

5. Classification of Mechanical Injuries
Blunt Force Injuries/Trauma:
Abrasions.
Contusions,.
Lacerations.
Sharp Force Injuries/Trauma:
Incised wounds.
Stab wounds.
Chop wounds.
Fractures.
Fire arm injuries.

6. Abrasions
• Injuries involving superficial layers of the skin and
are caused by
-Impact of an object.
-Fall on rough surface.
-Pressure of finger nails,teeth,muzzle of
a gun or by rope.

7. Abrasion
Tangential Compression
(friction/sliding/scrape) (crushing/pressure)
Linear Brush Patterned Non-Patterned
(scratch) (graze)
Impact Contact

8. Age of abrasion
• Recent abrasion appears bright red scab 12-24
hrs.
• Reddish brown scab 2-4 days.
• Healing process starts 4-7 days.
• Epithelium grows and dried scab falls 8-10 days.
• Absence of infection.

11. Antemortem Abrasions
• Reddish brown colour.
• Margins are blurred due to vital reactions.
Postmortem Abrasions
• Yellowish in colour.
• Translucent area.
• Margins are sharply defined.
• Absence of vital reactions.

12. Artifacts in Abrasion
• By Ants.
• By Insects.
• By Animals.
• By Marine animals.

13. Medico-Legal Aspects
• Site of impact and possibility of internal
injury.
• Identification of object causing the injury.
• Cause of injury.
• Direction of injury.
• Time of injury.

14. Contusion/Bruise
• Contusion is an infiltration or extravasion of
blood into the tissue due to rupture of
vessels by the application of blunt force.
• Examples:-Stick,stone or fist.
• Its subcutaneous without discontinuity of
skin.

15. Features of contusion
• Varies in sizes-Haematoma.
• Superficial contusions are slightly raised over the
skin.
• May not be present at site of the impact.
• Superficial contusions appear soon with red
colour.
• Deeper contusion appear late,can be detected by
infra red photography.
• Contusions over bony prominences are less
visible externally.

16. Factors modifying the appearance of
contusion
• Site of injury.
• Vascularity of the part.
• Age.
• Sex.
• Colour of the skin.
• Nature of disease.
• Shifting of blood due to gravity.

17. Colour changes in the contusion
• Colour changes in the contusion is due to
disintegration and haemolysis of red blood cells.
• Haemosiderin-Iron pigments,dark brown colour to
blue colour. 2-4 days.
• Haematoidin-Iron free pigment. Green in colour. 5-
7 days.
• Bilirubin-Yellow colour.7-10 days.
• Normal colour of skin 15-20 days.
• Pigments are removed by phagocytes.

21. Age of the contusion
• Colour changes.
• Histologically.
• Healing process depends on:
-Size and situation of contusion.
-Age and physique of the person.
-Presence and absence of disease.

22. Antemortem contusion
• Sharp,well defined margins.
• Swelling of the tissues.
• Discoloration of the skin.
• Extravasation of blood into the true skin and
subcutaneous tissue.
• Doubtful cases-Microscopic examination.

23. Postmortem contusion
• Can be produced with in 1-2 hrs after
death.
• If body is decomposed it is difficult to
differentiate between antemortem and
postmortem contusions.

24. Self inflicted contusion
• Rare-can be inflicted by irritant substances
like Marking nut,root of plumbago zeyloxica
or rosea.
• Can be differentiated by chemical analysis.

25. Homicidal contusion
• Shape and size of contusion,indicates the
weapon used.
Accidental contusion
• Their position,arrangement,circumstances
and surroundings.

26. Medico-Legal Aspects
• Identification of the object.
• Degree of violence.
• Cause of injury.
• Time of injury.

27. Laceration wounds/Injuries
• These are the wounds caused by the blunt
force resulting torn of the skin and the
underlying tissue,with a minimal bleeding.

28. Features of the lacerated wounds
• Edges are ragged,irregular and contused.
• Margins are abraded due to impact of blunt
force.
• Deep tissues are crushed.
• Hair bulbs are crushed.
• Less bleeding due to crushing of underneath
vessels.
• Presence of foreign materials.
• Shape-Irregular.
• Size-May or may not correspond to the weapon.

29. • Margins-Irregular
• Floor-Tags of tissue seen across the floor.
• Damage to the tissue-Gross and extensive.
• Haemorrhage-Less because of crushing of
vessels.
• Foreign substances at the site of injury-
dust,mud,gravels etc.
• Healing-Process delayed due to gross damage
and infection.
• Scars-Due to damage to skin and tissue.

30. Types of lacerated wounds
Split laceration:
• Found in pats overlying bones-scalp,face,hands
and lower limbs.
• Due to perpendicular impact by blunt force.
• Due to crushing of skin between two hard
objects.
• It simulates the incised wound.

31. Stretch laceration:
• Due to over stretching of skin and produces
flap.
• Due to blunt tangential impact-when head
strikes on the wind screen of the vehicle.
• Due to sudden deformity of bones after
fractures.

32. Avulsion wound:
• Degloving of skin over the impacted area
due to compression and grinding of
underlying tissue.
• Commonly seen in road traffic accidents
and by machinery in heavy industries.

33. Tears laceration:
• Due to friction with irregular or pointed
end of a weapon or an object on the
surface of the body.
• Deeper at the string point than at the
terminal.

34. Cut laceration:
• This type of lacerated wound is produce by
“not so sharp” edge of heavy weapon.
• Seen in chop wounds.
• Margins are not clear cut.
• Abrasions or contusions are seen on the
margins.

41. Medico-Legal importance
• Homicidal-occurs in any part of the
body.produced by blows with hard and
blunt weapon.
• Suicidal-Very rare.
• Accidental-Road traffic accidents,
accidental fall from height.
• Foreign bodies-Mud,gravel,oil etc.

42. Incised wounds
• Its produced by sharp cutting instruments-
knife,razor,blade,swords,chopper,axe etc.
Features:
• Edges are regular,clear cut, retracted and
averted.
• Except in neck and scrotum-edges are inverted.
• Spindle shaped wound,maximum widening in the
central part.
• Length is greater than the breadth.
• Breadth is greater than the thickness of the

43. • Gaping is greater if underlying muscles are
divided across or cut obliquely.
• Haemorrhage is excessive due to the cleat
division of blood vessels.
• Half severed artery bleeds more as they can
neither retract nor contract.
• Edges of wound may be irregular when skin is
loose and if cutting edge is blunt.

44. • By nature of the incised wound,weapon used
can be identified.
• Light sharp cutting weapons-razor blades,knife
an produce incised wounds by striking,drawing
or by sawing.
• Drawing cuts-Deeper at start,gradually become
shallow and at the end only skin is cut with
scratch “Tailing of the wound”

45. • The position of the accused and victim can
be identified in homicidal cases,and suicidal
cases which hand has been used.
• Sawing cuts-Multiple at the beginning and
only one deep cut wound called “Tentative
or Hesitation cuts”
• Bevelling cuts-When weapon is used
oblique or tangential way over the body.

47. • Heavy sharp cutting weapons-like
swords,axes,choppers etc-wounds are greater
and severe. Usually homicidal in nature.
• Injuries caused by these weapons show signs
of bruising over the edges and extensive
damage to deeper structures and organs.

48. • Incised wounds made by curved weapons
like sickle, tangi etc will cause single wound
when hit over the convex portion of body.
• Weapons applied over the flat surface, it
will make two wounds with intact of skin
between these two wounds and they will
be in the same line.

49. Medico-Legal importance
• Homicidal-Any part of the body, commonly on the
neck, head and trunk, also be found on the inner
side of forearm or hand of victim while defending or
protecting. ‘Defence Wounds’.
• Suicidal-Found in the accessible parts by light
weapons on the throat (cut throat wounds). Tail end
of the wound indicates which hand has been used.
• Accidental-Any part of the body hands, fingers
during the handling of knife, razor blades etc.

50. Weapon
• Incised wound means use of sharp cutting
weapons.
• Bevelled cuts and chop wounds suggest use
of heavy or moderately heavy sharp cutting
weapons.

51. Manner of use of weapon
• Deep chop wounds and bevelling suggests
striking by the weapon.
• Tailing and hesitation cuts indicate drawing
of the weapon.
• Multiple superimposed or overlapping
injuries are indicated by saw like movement
of the weapon.

52. Direction of application of force
• From the tailing and bevelling, the direction
of application of force can be known.
• The relative position of the victim and the
assailant can also be known, by the
direction of application of force.

53. Age of the wound or time since injury
• In case of dead bodies-histological examination
of tissue from the margin of the wound, gives the
clue that the survival of time after injury.
• Time since injury can be studied by the healing
process.

54. • When fresh- Bleeding is still present or fresh soft
clot is adhered, margins are red, swollen and
tender.
• By 12 hrs- Blood clot and lymph dry up, margins are
red and swollen. Histologically there is infiltration of
leucocytes.
• By 24 hrs- Proliferation of connective tissue cells
and vascular endothelium for neo-vascularisation.
• By 36 hrs- Fibroblastic infiltration and capillary

55. • By 48hrs- Capillary network is completed.
Fibroblasts run across the new vessels.
• By 3-5days- Vessels are obliterated and thickened,
wound heals and scar formation starts and
advances.
• By 6th day- Scar formation is completed. Scab over
the wound falls off. After weeks and months, soft,
tender, reddish scar becomes tenderless, whitish
and firm.

56. Defence wounds
• Defence wounds result from the immediate and
instinctive reaction of the victim to save himself,
either by raising the arm to prevent the attack or by
grasping the weapon.
• If the weapon is blunt, bruises and abrasions
produced on the forearms or backs of the hand.
• If the weapon is sharp the injuries will depend upon
the type of attack, whether stabbing or slashing.
• If the weapon is single edged and grasped-single
wound. Double edged-double wound.

57. Fabricated & Self-inflicted wounds
• They are the wounds inflicted by a person on his
own body.
• Fabricated wounds-produced by a person on his
own body or others body with consent. (fictitious,
forged or invented)
• To charge an enemy with assault or attempted
murder.
• To aggravate a simple injury.

58. • By the assailant to pretend self defence.
• In theftsrobbery where servants of the
house are involved, to get absolved from
the crime.
• By woman to bring a charge of rape against
an enemy.

59. Stab woundPunctured wound
• These are the deep wounds produced by the
pointed end of a weapon or an object, entering the
body.
• These injuries generally caused by ‘sharp pointed
piercing stabbing weapons-knives, dagger,
bayonet, arrow, pick-axe, broken glass pieces.
• A stab wound caused by a sharp pointed and
cutting instrument has clean cut edges, have sharp
angles at the two extremities.
• The wound is wedge shaped if it is produced by
instrument with only one cutting edge.

60. • A sharp pointed and cylindrical or conical
instrument produces a wound having a circular or
slit like opening.
• When the edges of the weapon are sharp, the
wound produced is an ‘Incised penetrating
wound’.
• When the weapon edge is blunt, it produces a
‘Lacerated penetrating wound’.

61. • When a stab wound enters into a body
cavity-thoracic, abdominal, joint cavities
‘penetrating wound’.
• When the wound pierces the body through
and through it is known as ‘perforating
wound’.

62. Features of punctured wound
• Length of the external wound should correspond
with the breadth of the blade of the weapon.
• Entry wound length is little shorter than breadth
of the blade or body of the weapon.
• Exit wound also similar to entry wound.
• Breadth of the entry or exit wound should
correspond with the thickness of the part of the
blade of the weapon. But it depends on the
elasticity of the skin, direction of underlying
muscle fibres and their intactness.

63. • If the fibres are not cut, due to rigor mortis
reduces the breadth-fibres are cut
increases the breadth.
• Depth is the greatest dimension of a stab
wound produced by the length of the
weapon introduced and its length and
breadth by the breadth and thickness of
the weapon respectively.
• Sometimes wound may be greater than the
length of weapon in the yielding parts.

64. • Edges are retracted, clean or lacerated and
bruised according to the weapon used.
• Knives, daggers, bayonets and other sharp
cutting weapons cause surface injuries will
be an ‘Incised Wound’.
• Pick-axe or horn of animals which have
blunt edges-margins irregular, bruised and
lacerated.

65. • Shape of the wound of entrance in case of
stab wound depends on the shape of the
weapon and its edges.
• Hilt marks are common when the weapon
is pushed till the handle.
• Haemorrhage is more internally than
external wound.
• Injury to the vital organs are common in
stab wounds.

69. Concealed Punctured Wound
• These are punctured wounds produced by
needles, nails or pins.
• Concealed parts of the body-nostrils,
frontanella, fornix of the upper eyelids,
axilla, vagina, rectum and nape of the
neck.

70. Complications
• Marked internal haemorrhage.
• Infection to the wound due to foreign
materials.
• Air embolism.
• Pneumothorax.
• Asphyxia due to inhalation of blood.

71. Medico-Legal Importance
• Shape of wound indicates the type of weapon.
• The depth of the wound indicates the force of the
penetration.
• Direction and dimensions of the wound indicate the
positions of assailant and victim.
• Age of the injury can be determined.
• Position, number and direction of wounds can give
clue for manner of production-Suicidal, Accidental,
Homicidal.

72. Fracture
• Fracture of a bone is defined as
disintegration or breakage of bone due to
blunt force either directly or indirectly.
• Direct fracture.
• Indirect fracture.

73. Direct Fracture
Focal fractures
• Small force applied to a small area. Injury to
overlying soft tissue is minimal.
• Eg-forearm and leg, where two bones lie
adjacent to each other. While defending
blows during an attack. ‘Tapping Fracture’.

74. Crush fractures
• It results from application of a large force
over a large area and is typically
fragmented.
• Injury to the surrounding soft tissue is
usually extensive.
• If two bones lie adjacent to each other,
both are involved.
• Eg- fracture of tibia and fibula in RTA.

75. Penetrating fracture
• It results from applications of a large force
over a small area.
• Eg- Bullet injury to a bone. Both tissue
damage and the comminuted type of
fracture.

76. Indirect Fractures
Traction Fractures
• It results when a bone is pulled apart by
traction.
• Eg- Transverse patellar fracture due to
violent contraction, of this type of fracture
due to sudden contraction of quadriceps.

77. Angular fraction
• It occurs due to bending of bone. The
concave surface of the bend is compressed,
while the convex surface is put under
traction resulting in breakage.
Rotational fracture
• Fracture in spiral, when it is twisted.

78. Vertical compression fracture
• In this type fracture can be seen in long
bones with oblique fracture when hard
shaft of the bone is driven into the cellous
portion.
• In RTA there has been a collision and knee
has impacted violently against the
dashboard.

79. Angular-Compression fracture
• Here the fracture line is curved, with an
oblique component due to compression
and a transverse component due to
angulation.

80. Repair and healing of the fracture
• Healing of the fracture depends on the age and
nutritional status of a person. Usually cancellous
bone unites faster than cortical bone.
• Haemorrhage phase.
• Proliferation phase.
• Callus phase.
• Consolidation phase.
• Remodeling phase.

81. • In the Haemorrhagic phase, bleeding will be at
the site of fracture.
• In the Proliferation phase, a collar is formed
around the fractured ends by proliferation of
cells from periosteum and endosteum.
• In the Callus phase, cellular elements give rise
to osteoblasts and chondroblasts which
produce a matrix of collagen and
polysaccharide, impregnated with calcium.

82. • In the Consolidation phase the callus is
transformed into mature bone by 4-6weeks
in children and in adults by 12-14weeks.
• In the final, the Remodeling phase,
matured bone will take place.

83. Medico-Legal Importance
• Fracture of a bone constitutes grievous
injury according to law.
• The type of fracture can give the clue of
causative force, whether direct, indirect,
rotational or angular etc.
• The site of fracture may help to indicate the
cause of death.
• Eg- fracture of hyoid bone suggestive of
throttling.