Abrasions (gravel rashes) is a destruction of the skin, which usually involves the superficial layers of the epidermis only. Thickness of skin is 1.6 mm. They are caused by friction against a rough surface or by compression, such as a lateral rubbing action by a blow, a fall on a rough surface, by being dragged in a vehicular accident, fingernails, thorns or teethbite. Some pressure and movement by agent on the surface of the skin is essential.
In its simplest form, the epidermal cells are flattened and their nuclei are elongated. If sufficient friction is applied, partial or complete removal of the epithelium may occur and the superficial layer of dermis is damaged.
Many abrasions have some deeper areas of subepidermal damage which may result in superficial scarring. Sometimes, full thickness of the skin may be damaged in places, but usually in an interrupted, irregular manner, and intact epidermis remains within the area of the abrasion.
The rougher the surface, and the more rapid the movement of the skin over it, the deeper is the injury. The exposed raw surface is covered by exudation of lymph and blood which produces a protective covering known as a scab or crust.
Abrasions vary in size, depending on the extent of the body surface exposed to the abrading force. They are simple injuries, bleed slightly, heal rapidly and scar is not formed. Large abrasions can cause severe pain and bleeding. The size, situation,pattern and number of abrasions should be noted.
Types : Abrasions are of four types.
Scratches
A scratch (linear abrasion) is an abrasion with length but no significant width, or a very superficial incision, depending on the agent. A scratch produced from the tip of the knife or razor can be called a point scratch.
They are caused by a sharp or pointed object, not sharp enough to incise, but pointed enough to gouge or scratch, i.e. remove a portion of the skins surface, passing across the skin, such as fingernails, pin or thorn. The surface layers of the skin are collected in front of the object, which leaves a clean area at the start and tags at the end.
When the skin is gripped in a static fashion, fingernail abrasions may be straight or curved, one to 2 mm breadth, often about half to one cm. long, wide at the start, narrow at the end. They may be parallel linear scratches if the fingers are dragged down the skin.
As the skin is put under lateral tension when it is indented by nails, it may distort, so that when the tension is released the elasticity of the skin causes it to return to its original position, carrying the nail mark with it.
The curve may then reverse to form either a straight line or a convexity, but this is always not true. Pointed nails are more likely than those with straight edges to give these paradoxical results.
Grazes (sliding, scraping or grinding abrasions)
They are the most common type. They occur when there is movement between the skin and some rough surface in contact with it. They show uneven, longitudinal parallel lines (grooves or furrows) with the epithelium heaped up at the ends of these lines, which indicate the direction in which the force was applied.
The furrow may be broad at one end, and narrow in the opposite direction. Usually, the skin is uniformly denuded at the start or may be serrated. The epidermis is scraped away, destroyed or detached.
A glancing kick with a boot also produces a graze. These abrasions are commonly seen in a road accident. Many abrasions extend into the dermis, because of the corrugations of the dermal papillae, and bleeding occurs.
Deep abrasions have a typical punctate or spotty appearance. An abrasion caused by violent lateral (tangential) rubbing against a surface as in dragging over the ground is called brush burn or gravel rash. It is a scraping injury over a large area.
“Friction burn” (scuff or brush abrasion) is an extensive, superficial, reddened excoriated area without serous ooze or bleeding and with little or no linear mark. It may occur due to tangential contact with a smooth surface or when the skin is covered by clothing.
Brush bums and friction burns are seen in motor cyclists, persons ejected from vehicles, pedestrians, cyclists thrown forward after the primary impact from a motor vehicle.
Pressure abrasions (crushing or friction abrasions)
They are caused by crushing of the superficial layers of the epidermis and are associated with a bruise of the surrounding area. If the movement of instrument is around 900 to the skin, a pressure type of abrasion occurs. In this type, the movement is slight and largely directed inwards. The ligature mark in cases of hanging and strangulation and the teethbite marks are the examples.
Impact abrasions (contact or imprint abrasions)
They are caused by impact with a rough object, when the force is applied at or near a right angle to the skin surface. The abrasion is slightly depressed below the surface, unless there is bulging due to underlying contusion or local oedema. If the impact is forcible, the dermis is damaged with an underlying bruise.
When a person is knocked down by a motor car, the pattern of the radiator grille, a headlamp rim or the tread of the tyre may be seen on the skin, which may contain road dirt, paint flakes, grease, etc.
Impact by a solid object may produce abrasions at the periphery where the skin is forced downwards. If aperson strikes a flat and relatively smooth surface, an abrasion can be produced which shows little or no linear markings, as in traffic accidents.
Impact abrasions and pressure abrasions reproduce the pattern of the object causing it and are called patterned abrasions. Patterned injury is any injury that suggests an inflicting instrument or unique means of its causation.
Patterned abrasions are produced when the force is applied at right angle to the surface of skin. If the skin is struck with a weapon having a patterned surface, the ridges of the object damage the epidermis, and the skin may be compressed into the cavities of the pattern, causing intradermal bruise.
Other examples of patterned abrasion are : imprint of bicycle chain, weave of coarse fabrics, the spiral of electric wires, ropes, serrated knife, etc. Multi-thonged whip, such as a cat-o-nine-tails, leaves a series of linear abrasions or superficial tears. Usually, the pattern and shape are non-specific.
If there are multiple minor abrasions on a particular area, they can be described together as present over an area of (giving dimensions) on the particular anatomic region.
Age of the abrasions
Abrasions heal from theperiphery by new growth of epithelial cells. The exact age cannot be determined. Fresh : Bright red.12 to 24 hours : Lymph and blood dries up leaving a bright red scab. 2 to 3 days : Reddish-browti scab. 4 to 7 days Dark brown to browinsh-black scab.
Epithelium grows and covers defect under the scab.Reticulum fibres are seen in about 6 to 8 days. After 7 days : Scab dries, shrinks and falls off, leaving depigmented area underneath, which gets gradually pigmented.
Histologically, perivascular cellular infiltration is seen at four to six hours. At 12 hours three layers are seen a surface zone of fibrin and red cells; a deeper zone of infiltrating polymorphs; and a deepest layer of abnormally staining collagen.
At 48 hours, scab is well-formed and epithelial regeneration is seen at the margins of the scab. By 4 to 5 days, small abrasionss are completely covered by epithelium. By 5 to 8 days, subepithelial formation of granulation tissue is prominent.
Reticulum fibres are seen at 8 days, and collagen fibres at 9 to 12 days. The last stage is regression which begins about 12 days. During this phase, the epithelium is remodelled and becomes thinner and even atrophic.
Antemortem and Postmortem abrasions:
Abrasions produced slightly before or after death cannot be differentiated even by microscopic examination. In superficial lesions or when decomposition is advanced, differentiation is difficult.
On drying, abrasions become dark-brown or even black. In a body recovered from water, abrasions may not be seen on first inspection, but they are easily seen after the skin dries. Abrasions may be produced after death when a body is dragged away from the scene of crime.
The distribution of such abrasions depends upon the position of the body while it is being dragged. Postmortem abrasions are typically found over the forehead, the prominent points of the face, anterior trunk, backs of hands and the fronts of the lower legs.
Facial injuries ooze blood, mimicking ante- mortem wounds. After death, the abraded epidermis becomes stiff, leathery and parchment-like, brown, more prominent and may be mistaken for bums.
Circumstances of Injuries : abrasions are usually seen in accidents and assaults. Suicidal abrasions are rare. Sometimes, hysterical women produce abrasions over accessible areas like the front of forearms or over the face to fabricate a false charge of assault.
Abrasions on the face or body of the assailant indicate a struggle. Persons collapsing due to heart attack tend to fall forward and receive abrasions to the eyebrow, nose and cheek, but there will be no injuries on the upper limbs.
A conscious person when falling puts out his hands to save himself, and abrasions may be produced on the palmar surfaces of the hands. The alcoholic tends to fall backwards and strikes his occiput on the ground.
Medicolegal Importance
(1) They give an idea about the site of impact and direction of the force.
(2) They may be the only external signs of a serious internal injury.
(3) Patterned abrasions are helpful in connecting the wound with the object which produced them.
(4) The age of the injury can be determined, which helps to corroborate with the alleged time of assault.
(5) In open wounds, dirt, dust, grease or sand are usually present, which may connect the injuries to the scene of crime.
(6) Character and manner of injury may be known from its distribution.
- In throttling, crescentic abrasions due to fingernails are found on the neck.
- In smothering, abrasions may be seen around the mouth and nose.
- In sexual assaults, abrasions may be found on the breasts, genitals, inside of the thighs and around the anus.
- Abrasions on the face of the assailant indicate a struggle.
- Abrasionss on the victim may show whether the fingernails of the assailant were long, irregular or even broken.
Differential Diagnosis
(1) Erosions of the Skin Produced by Ants: Ants produce brown erosions with minute irregular margins of the superficial layers of the skin. They are most commonly found at mucocutaneous junctions, about the eyelids, nostrils, mouth, ears, knuckles, axillae, groins, and genitalia. They are also seen in the moist folds of the skin. Sometimes they are localised, and may simulate antemortem abrasions. Examination by hand lens shows multiple crescent-shaped, sand- like bite marks. Each one is separated by normal skin. Vital reaction is not seen.
(2) Excoriations of the Skin by Excreta: In infants, slight inflammation with excoriation may be seen in the napkin area at the time of the death. After death, these areas become dry, depressed and parchment- like and the colour varies from pale- yellow to deep- copper.
(3) Pressure sores.
(4) Drying of the skin of the scrotum produces hardened, reddish-brown colouration resembling abrasions.
