Abrasions & Bruises (Contusion) — Features, Dating & Medico‑legal Importance

WOUNDS

Definition:

Wound: is disruption of the natural continuity of any tissue produced by external mechanical force.

Classification of wounds

I- Legal classification:

According to the duration of healing and whether or not the wound leads to permanent infirmity:

a- Simple wound: It is a wound that heals within 20 days.

b- Dangerous wound: It is a wound that heals in more than 20 days (may be associated with permanent infirmity).

c- Fatal wounds: It is a wound that leads to death.

Permanent infirmity: is loss of a functioning organ or loss (or impairment) of a function of an organ.

II-Medico-legal classification:

According to the causative instruments as follows:

1. Blunt force wounds due to:

   • Moving object striking the body as in a blow.

   • Moving body striking a fixed object or surface as in a fall. They may be abrasions, bruises, and contused wounds.

2. Sharp force wounds:

   • Caused by knife tip or edge, broken glass, or jagged metal.
   • The applied force is concentrated over a small area, so it requires little force to cut tissues.
   • They may be incised or stab wounds.

3. Firearm wounds:

   • Caused by small projectile with high velocity.

Types of skin wounds

1- ABRASIONS سحجات

Abrasion: is a superficial injury to the skin including the epidermis and may be the superficial layer of the dermis. It may only ooze serous fluid which may be blood-tinged when the superficial layer of the dermis is involved.

A scratch: is a linear abrasion produced by drawing a pointed instrument over the surface.

Causative instrument: Blunt instrument with a rough surface or pointed instrument.

Mechanism & types:

Types	Tangential abrasions	Imprint (Crush) abrasions
Mechanism	- Tangential impact → loss or scraping of epidermis/dermis by: a. Tangential friction on rough surface → grazing, sliding, or brush abrasion. b. Drawing a pointed instrument over the surface → scratch abrasion	- Direct vertical impact → crushing of epidermis - The causative object may stamp its shape or surface pattern on the skin → imprint or patterned abrasion as: - Ligature mark in hanging or strangulation. - Tire treads in road traffic accidents. - Bite mark - Fingernail abrasions on neck in throttling and around thighs & vulva in rape.
Medico-legal importance	- May reflect direction of impact	- May reflect pattern of causative surface

Medico-legal importance of abrasions:

1. They indicate violence.

2. Their shape gives an idea about the causative instrument as:

   • Fingernail abrasions
   • Teeth abrasions in bites.
   • Abrasions that take the shape of the radiator in car accidents.

3. Their site in the body may give an idea about the type of the crime as:

   • Fingernail abrasions on the neck suggest throttling
   • Fingernail abrasions on the inner sides of the thighs suggest rape.

4. The age of the abrasion gives an idea about the time of crime as:

   • In the first 2 days: it is covered with dry serum or a soft scab.
   • After 3 days: a dry brown scab is formed.

• After one week: the scab falls leaving a red colored area which disappears.

• After 2 weeks: it leaves no scar.

5- An abrasion may rarely cause death except if it is infected by tetanus or erysipelas.

6- Abrasions differentiate:

• Cut wounds from contused wounds in skin stretched over bone (e.g. skull & shin of tibia).
• Hypostasis from bruises.
• Homicidal from suicidal injuries.

7- It indicates direction of tangential impact: starting edge has beveled descent; a series of parallel furrows indicate direction of sliding motion; finishing edge has tags of heaped epidermis.

2- BRUISES (CONTUSION)

Definition:

Bruise: is leakage of blood from ruptured small vessels (veins or arterioles) into the surrounding tissues as a result of trauma. They may be seen in skin, muscle, or any internal organ.

N.B. Bruise is called when the lesion is visible through the skin.

Contusion can be anywhere in the body as muscles or internal organs.

Causative instrument:

Heavy blunt instrument.

Mechanism:

Bruises occur due to:

• A moving object strikes a stationary body (blow with fist or weapon).
• A moving body strikes a stationary object (fall).
• Pinching or squeezing.
• Skin has greater elastic limit than underlying fat and blood vessels so:
  • When the force applied exceeds the elasticity of subcutaneous blood vessels → rupture → bruising.
  • When the force applied exceeds the elasticity of the skin → contused wound

Types

I- According to the amount of extravasated blood:

A- Haematoma: large bruise
B- Ecchymosis: Small bruise.
C- Petechial haemorrhage: the size of a pin head (bruise less than 2mm).

II- According to its site:

A- External bruises:

Superficial bruise rapidly appears at the site of impact.

B- Internal bruises:

Deeper bruise in muscle or internal organs are not visible through overlying fat and skin e.g., neck in strangulation, fatal brain injuries, blows to chest & abdomen

Factors affecting the appearance of a bruise:

(1) Anatomical site:

• Areas over bony prominence (e.g., shin, cheeks), lax vascular tissue (e.g., eyelid, orbit), and fatty tissue (e.g., buttocks) will bruise easily.
• Resilient muscles of the anterior abdominal wall rarely bruise (although there may be severe underlying visceral injury).
• Dense tough tissue (e.g., palms, soles) rarely bruises

(2) Age:

• Infants have loose, delicate, fatty tissues which bruise easily.
• Elderly: atherosclerosis of blood vessels allows easy bruising

(3) Obesity & Sex:

• Obese individuals bruise more easily than lean due to a greater proportion of subcutaneous fat
• Females generally bruise more easily due to having a greater proportion of subcutanous fat than males

(4) Disorders of clotting:

• Hemophilia, leukemia, and platelet disorders
• Liver disease (including alcoholism).
• Vitamin C deficiency (scurvy).
• Medications e.g., salicylates.

(5) Skin color

• Black skin may mask bruising. Examination under UV light is needed to show up the bruises.

(6) Effect of gravity:

A bruise usually occurs at the site of violence, but sometimes extravasated blood tracks along natural/traumatic planes of least resistance, influenced by gravity and body movement (migrating bruises) as:

• Blow to the forehead $\to$ bruise on eyelid, giving a black eye (D.D)
• Blow to the calf gives $\to$ bruise on the heel.
• Blow on temple $\to$ bruise on cheek.
• Fractured jaw $\to$ bruising on neck.
• Fractured hip $\to$ bruise on thigh.
• Blow on the abdomen $\to$ bruise on scrotum or labia.

(7) Site of bruise:

Deep bruising may take up to 24 hours to appear at the surface (come out). So, re-examination of a body or live victim after a time must be done to reveal bruises not initially apparent. Ultraviolet light may disclose an otherwise unidentifiable bruise.

(8) Onset of death:

Rapid death will limit the extension of leaked blood and its appearance as a bruise usually occurs under circulatory blood pressure

e.g., blow to the pericardium may lead to sudden death without any apparent bruises. (An associated imprint abrasion is more useful in this case).

Medico-legal importance of bruises:

1. They indicate violence.

2. Their shape gives an idea about the instrument used as they take its shape as:

   • Longitudinal bruise is caused by a hard stick, having the same width.
   • 2 Parallel lines of bruises are caused by a rubber stick.
   • 2 Parallel lines of bruises going around body curvature are caused by a whip.
   • Tram-line bruises caused by rectangular or cylindrical objects.
   • 2 curved rows of bruises in case of human bite.
   • 2 Parallel lines of bruises in case of animal bite.
   • Clusters of small discoid bruises of about one cm in diameter are characteristic of finger tip pressure.

3. Their site in the body gives an idea about the type of the crime as:

   • discoid bruises of about 1cm in diameter around nose and mouth indicate smothering and those at the neck indicate throttling.

4. The Age of bruises gives an idea about the date of the crime as:

   • 1^(st) day: red in color (oxy Hb)
   • After 1-3 days: blue (reduced Hb).
   • After 4-5 days: green (biliverdin)
   • After 5-10 days: yellow (bilirubin)
   • Bruises fade away (heal) in 2-3 weeks.

N.B. Color changes occur gradually from the periphery to the center so; you can see two colors in the same day.

5. They usually occur at the same site of the blow but may gravitate downwards.
6. They may be dangerous if:

• They occur in a trigger zone.
• They are extensive.
• They become infected
• They hide a more serious injury: e.g., rupture organ.
• They cause an internal hemorrhage (if it occurs in mesentery).

7. They differentiate between:

• Cut from contused wounds in skin stretched over bone (e.g., skull)
• Homicidal from suicidal injuries.

8. Bruises must be differentiated from hypostasis.

D.D of black eye (periorbital haematoma):

1. Direct blow to orbit.
2. Tracking from forehead bruises (migrating).
3. Fractured anterior cranial fossa of the skull (gunshot)

Differences between hypostasis and bruises

	Hypostasis	Bruises
A.M or P.M	Post-mortem change	Ante-mortem wound
Skin	Intact	Associated with abrasions
Swelling	Absent	Present
Site	In the dependent parts	In any part of the body
Cellular infiltration	Absent	May be present
Color	No color changes	Color changes may be present
	Color disappears with applying pressure over it.	Color doesn’t disappear by pressure
Cutting over it	Small amount of blood (intravascular) oozing from the cut capillaries, Blood can be easily washed away.	Blood is extravascular in the surrounding tissues; It is not washable (fixed by tissue histocytes).
edges	Ill-defined edges	well-marked edges