MECHANICAL INJURY

ML Classification of Injury:

MEDICAL
1.Mechanical
A)DUE TO BLUNT FORCE

Abrasion
Contusion
Laceration
Fracturew and dislocation
B)DUE TO SHARP FORCE

a)Incised wound
b) Chop wound
c)Stab wound

C.FIREARM WOUNDS

a) Firearm wound
2.Thermal
DUE TO COLD-frost bite ,immersion foot
DUE TO HEAT-burns,scald
3.Chemical corrosive acid ,corrosive alkali
4.physical- electricity .lightning,Xray.
5.explosions


LEGAL

1.SIMPLE
2.GREVIOUS

MEDICOLEGAL

1.SUICIDE
2.HOMICIDE
3.ACCIDENT
4.FABRICATED
5.DEFENCE

Contusion:
  • Surface injury to the skin and sub-cutaneous which leads to an effusion of blood into tissues
  • usually caused by blunt trauma.
  • Appears 1-2 hours after injury.
  • may take the shape of weapon eg railway tract appearance.
  • Children, old, obese women bruise easily.
  • Mongolian spot shouldn’t be confused with bruise.
  • Contusion may be also in the internal organs
  • Gravity shifting of bruise may occur in late occuring bruises

Color changes in a bruise:
  • 1st day- red
  • 2nd day- 3rd day -bluish
  • 4th day- brown day(haemosiderin)
  • 5th-6th day- green(haematoidin)
  • 7th-12th day- yellow(bilirubin)
  • 13th-15th day ,2 weeks – normal
  • Subconjunctival Hage donot undrego colour change

ML aspect of contusion:
  • Patterned bruise-Identification of weapon,ligature,vehicle
  • Degree of violence from size
  • Time since injury
  • Purpose of injury
  • Homicidal, suicidal, accidental .position of assylant while arms are grasped


Difference between antemortem and postmortem bruise:

Antemortem contusion

  • Swelling present
  • Color changes present
  • Epithelium abraded
  • Clotted blood in tissue present


Postmortem contusion

  • Not present
  • Not present
  • Not present
  • Not present

Difference b/n artificial and true bruise
Artificial bruise

  • By juice of marking nut,calotropis or plumbago
  • At exposed accessible site
  • Dark brown colour
  • Shape irregular
  • Margins well defined and regular
  • Itching present
  • Positive chemical test

True bruise

  • Trauma
  • Anywhere
  • Typical colour changes
  • Usually rounded
  • Not well defined,diffuse,no vesicles
  • Absent
  • negative


Patterned intradermal bruise on the forehead due to a
fall onto ribbed ceramic tiles.


Bruising of the upper arm. The pattern of these bruises
is typical of forceful gripping. Small abrasions from fingernails are
also seen.


Typical ‘railway-line’ bruises caused by a wooden rod.
Note that the centre of the parallel contusions is unmarked.


Recent bruising of the abdominal wall and scrotum due
to kicking.

Abrasion:

  • destruction of only superficial layer of epidermis,thickness of skin is 1.6mm.
  • Bleed very slightly
  • Heal very rapidly
  • Leave no scar

Types of abrasions:
  • Scratch or linear abrasion-has length but no significant width.eg by pin, thorn, nail etc. very sharp objects
  • Graze(sliding,grinding abrasion)-longitudional parallel lines. by rough surface in contact with a broader surface of skin, eg. RTA
  • Patterned abrasion (pressure and impact abrasions)- thumb mark in strangulation, ligature mark in hanging, wheel mark of tyre,teethbite mark.

Age of abrasion by color change: exact age cant be determined
  • Red color- fresh
  • Red scab- 12-24 hours-by dryind of blood and lymph
  • Reddish brown scab- 2 to 4 days
  • Healing from periphery- 4 to 7 days,dark brown
  • Complete healing- 10 to 14 days
  • Seperation of scab- 10 to 14 days

ML importance:
  • Identification of object
  • Direction of injury
  • Time since injury
  • Possibility of internal injury
  • Somtime erosion by ants look like abrasion.d/d-ants produce abrasion that are brown,irregular margin,commonly at mucocutaneous junction about eyelids,nostril,mouth,axilla,by hand lens show multiple cresent shaped,sand like bite marks

Difference
Antemortem abrasion

  • has Moist surface
  • Bleeding present
  • On drying scab formation,scab slightly raised
  • Blurred margin
  • Inflammation present
  • Intravital reaction and congestion seen

Postmortem abrasion

  • Dry surface
  • No bleeding
  • No scab
  • Sharply defined margin
  • Inflammation absent
  • Not seen


Abrasions from scraping against a rough surface
during a fall.


Extensive abrasions caused by stumbling, drunk and
naked, against furniture. The dark leathery appearance is due to
post-mortem drying of the damaged areas of skin

Incised wound:(cut,slash,slice)
  • Clean cut through tissues ,usually skin and subcut. By sharp edged or cutting weapon, eg. knife, sword, glass.
  • Edges are smooth, clean cut and everted.
  • Broader than the edge of weapon
  • Length is greater than depth and breadth.
  • Bleed profusely
  • Superficial towards the end of wound k/a tailing
  • Edges may be inverted in case of underlying muscle attached to skin, eg. scrotum.

ML importance:to find homicidal,accidental or suicidal

  • Homicidal, anywhere in the body, deep
  • Suicidal- multiple, superficially, usually in the left hand
  • Accidental- anywhere
  • Edges of the wound indicate: antemortem or postmortem, sharp or blunt weapon.

Difference between incised wound
Antemortem

  • Bleed freely and profusely
  • Arterial spouting present
  • Blood is clotted
  • Edges gape
  • Inflammation present
  • Serum serotonin and histamine increased

Postmortem

  • Very slight or no hemorrhage
  • Not present
  • Not clotted
  • Edges closely
  • Not present
  • Not raised

Difference between suicidal and homicidal cut-throat wounds
Suicidal

  • Left side of neck,passing across the throat,usually in rt handed
  • Level above thyroid cartilage
  • Multiple no ,superficial,rarely single
  • Edges usually ragged,due to overlapping
  • Hesitation cuts present
  • Defence wound absent
  • Weapon usually present
  • Clothes not torn or damaged
  • Circumstancial evidence, quite place

Homicidal wounds

  • Usually on both sides
  • On or below thyroid cartilage
  • Multiple .cross each other at a deep level
  • Sharp and clean cut,bevelling may be seen


Incised wound to the flank; it is clearly longer than it
is deep


A complex stab wound where all three injuries are
caused by a single action. The first entry is in the right breast; there
is an exit wound in the middle and a re-entry wound over the centre
of the chest.

Stab or punctured wound:

  • Type of incised wound whose depth is greatest in dimension.
  • Eg. Knife wound, dagger

Types of stab wound:
  • Penetrating wound- has only wound of entry
  • Perforating wound- has both entry and exit wound

Features of stab wound:
  • Aperture is usually smaller than the weapon due to elasticity of the skin
  • Depth is greater than breadth and length.
  • Very little external hemorrhage but profuse internal hemorrhage

  • Shape- Wedge shaped with knife, elliptical with dagger, rounded with needle, slit-like opening with screw driver,
  • Margins of entry wound are clean and inverted,
  • Margins of exit wound are small and everted
  • Direction determined by line joining entry and exit wounds or X-ray after radio-opaque dyes.


ML(medical legal ) importance:
  • Nature of weapon
  • Direction of wound
  • to find Suicidal, homicidal or accidental

Lacerated wound:
  • Wound in which skin and underlying tissue is turned due to blunt force application

Classification:
  • Split laceration
  • Stretch laceration
  • Avulsion
  • Tears (caused by irregular sharp object)

1.Split laceration (incised looking wound)
  • Usually found overlying the bones
  • caused by blunt perpendicular impact
  • Skin splits between 2 hard objects and simulate an incised wound

2.Stretch laceration:
  • Overstretching of skin produces a flap
  • Caused by blunt tangential impact
  • Also by sudden deformity of bone after a fracture

3. Avulsion:
  • Caused by horizontal crushing impact
  • Commonly truck, bus wheel, muscles are crushed
  • Also known as degloving of skin


Multiple lacerations from a blunt steel bar. These were
initially mistaken by the police for axe wounds. The abraded or
crushed margins can be easily seen.


Laceration of an arm of a pedestrian struck by a car.
The impact has been oblique, causing a flap of skin to tear away
to the right.

Nature of injuries- simple, grievous, dangerous
1.Simple injury:
  • Neither serious nor extensive
  • Heals rapidly w/o leaving permanent deformity or disfigurement

2. Grievous injury:
  • Emasculation
  • Permanent loss of sight of either eye
  • Permanent loss of hearing of either ear
  • Destruction of joint or any member of body eg. Limb
  • Permanent disfigurement of head or face
  • Fracture or disfigurement of bone or tooth
  • Any hurt to be in hospital for 20 days

3. Dangerous injury:
  • Compound fracture of skull
  • Injury to vital organ eg. spleen, liver
  • A wound of large artery eg. radial femoral