Abrasion is also known as gravel rash is a type of mechanical injury that causes destruction of the skin, and is characterized by the loss of superficial skin or mucous membrane due to the application of mechanical force. The general thickness of the skin is 1.6 mm. Pure abrasions do not ordinarily bleed, but because of the corrugated nature of the dermal papillae, quite often the dermis layer also gets injured. This results in bleeding. This bleeding is rarely serious as only small blood vessels are involved. Generally, abrasion does not leave any scar on healing.
Abrasions can be produced due to sliding force or compression force. It is caused by friction against any rough surface or by compression. It can happen either due to falling on a rough surface, lateral rubbing action by a blow, vehicle accident, fingernails, thorns, or teeth bite. When sufficient friction is applied, complete or partial removal of the epithelium occurs. The depth of the injury depends on the degree of roughness of the surface and the rapidness of the movement of skin over it. When it starts healing a protective covering known as scab or thrust forms.
Abrasions vary in size, depending on the extent of the body surface exposed to the abrading force. Large abrasions can cause severe pain and bleeding. The size, situation, pattern, and number of abrasions should be noted. Tangential forces cause linear or graze abrasions and compression forces cause patterned impressions or non-patterned abrasions. The patterned impression can be impact abrasion or contact abrasion.
Types of Abrasion
1. Linear Abrasion
They are otherwise known as scratch abrasions and are caused due to the sliding movement of any sharp, narrow object such as pin thorn, pointed weapon, etc. These are generally wider at the starting point and narrower towards the end with the accumulation of epithelium. This healing of the epithelium indicates the direction of movement of weapon or the object used.
2. Graze Abrasions
These are also known as gliding, sliding, brush or scrape abrasions. They are caused due to the horizontal or tangential friction between the wider surface and the skin or broader area of the skin and pointed weapon. These types of abrasions can be mostly seen in traffic accident cases where a pedestrian has been knocked down and is dragged over a distance on the ground.
They are uneven, longitudinal, parallel lines with the end area having a heap of epithelium and may frequently be associated with underlying bruising. If the friction force is more then it might look like a burn injury and are called Brush burns.
3. Imprint Abrasions
They are known as patterned or impact abrasion and are caused when force is applied in a perpendicular direction. Such forces will stamp the object into the skin. The skin depresses and compresses and reproduces the pattern of the object.
4. Pressure Abrasions
It is also known as crushing abrasion. When the impact is vertical to the skin surface, the epidermis gets crushed and pressure type of abrasions result, and the imprint of the impacting object may be produced. These may be seen in manual strangulation (abrasions produced by fingernails) and in hanging, where the weave of the ligature material may be reproduced. Such abrasions when dried up resemble parchment-like and appear brown to black.
5. Nappy Abrasion
These are seen in infants due to excoriation of skin at the nappy area caused by fecal matter or excreta.
Age of Abrasion
|Fresh||Reddish due to oozing out of serum and little blood|
|12-24 hours||Dries up to form a reddish scab|
|2-3 days||The scab is reddish-brown|
|4-5 days||The scab turns dark brown|
|5-7 days||The scab appears to be brownish-black and starts falling From the margins.|
|7-10 days||The scab shrinks and falls off, leaving some unpigmented area underneath.|
Antemortem and Postmortem Abrasion
|Features||Antemortem Abrasion||Postmortem Abrasion|
|Color||Bright red||Pale, dry and parchment-like|
|covering||Covered with scab composed of coagulation of blood and lymph||No scab formation|
|Inflammation||Signs of inflammation can be seen||No inflammation|
|Site||Can be seen anywhere on the body||Can be seen over bony prominences|
|Microscopy||Presence of congestion and vital reaction||No|
Postmortem abrasions are caused due to dragging of the body or it can be a fabricated abrasion. Ant bite marks in the postmortem state also resemble an abrasion.
The medicolegal importance lies in the fact that they are produced at the point of impact of the blunt force. They may exhibit a pattern thereby providing information regarding the nature of force. Their sites and distribution over the body may yield some clue towards the nature of the crime.
Scratches over the neck, face or inguinal region of a female may be produced by the fingernails of the assailant during the sexual assault. The presence of some foreign materials like mud, dust, sand, etc. in and around the abraded area will suggest the nature of the surface or agent responsible for its causation.
These are also helpful in determining the approximate period of infliction of the injury. Careful examination should be done to not confuse an abrasion with ant bite marks, pressure sore/bedsore, excoriation of the skin by excreta, and postmortem abrasion.