Types of Injury 31 Bruises

The terms contusion and ecchymosis have been used to differentiate between different types of injury that can more simplistically be called bruising. These terms have been used variously to describe different injury sizes but do not enhance understanding of either causation or mechanism of injury and should no longer be used. A hematoma is best used to refer to a collection of blood forming a fluctuant mass under the skin and may be associated with substantial trauma. The difference between that and a standard bruise is that a hematoma may be capable of being aspirated in the same way a collection of

Fig. 2. Production of bruising.

pus is aspirated. Bruising is caused when an impact damages blood vessels so that blood leaks into the perivascular tissues and is evident on the skin surface as discoloration. Such discoloration changes in color, shape, and location as the blood pigment is broken down and resorbed. In some cases, although blood vessels may be damaged, there may be no visible evidence on the skin. In certain cases, it may take hours or days for any bruise to become apparent because the blood diffuses through damaged tissue. The blunt force ruptures small blood vessels beneath the intact skin, and blood then escapes to infiltrate the surrounding subcutaneous tissues under the pumping action of the heart (see Fig. 2). Thus, theoretically at least, bruising is not produced after death. In fact, severe blows inflicted after death may cause some degree of bruising, although this is usually only slight. Bruises may be associated with other visible evidence of injury, such as abrasions and lacerations, and these lesions may obscure the underlying bruise.

Bruising may need to be differentiated from purpura, which develop spontaneously in those with a hemorrhagic tendency and in the elderly and tend to be rather blotchy, are less regular in outline, and are usually confined to the forearms and lower legs. Bruises vary in severity according to the site and nature of the tissue struck, even when the force of the impact is the same.

Fig. 3. Production of a black eye. (1) Direct blow to the orbit. (2) Injury to the front of the scalp. (3) Fracture of base of scull.

Where there is an underlying bony surface and the tissues are lax, as in the facial area, a relatively light blow may produce considerable puffy bruising. The orbit is the most vulnerable, giving rise to the common "black eye." However, remember that there are other mechanisms for the production of a black eye, such as an injury to the front of the scalp draining down over the supraorbital ridge or a fracture of the base of the skull allowing blood to escape through the roof of the orbit (see Fig. 3).

Bruises can enlarge over a variable period of time, which can be misleading regarding the actual site of injury. Because a bruise is a simple mechanical permeation of the tissues by blood, its extension may be affected by movement and gravity. Thus, bruising of the face can result from an injury to the scalp. Further difficulties arise if a bruise, as it extends, tracks along tissue planes from an invisible to a visible location. Bruising of this kind may not become apparent externally for some time and then some distance from the site of the original impact. This delay in the appearance of bruising is of considerable significance because absence of apparent injury at an initial examination is not necessarily inconsistent with bruising becoming apparent 24-48 hours later. Thus, in cases of serious assault, it is often advisable to conduct a further examination a day or so later.

Fig. 4. Tramline bruising caused by a blow from a rod-like implement.

Fig. 4. Tramline bruising caused by a blow from a rod-like implement.

Generally, bruises, unless superficial and intradermal, tend to be nonspecific injuries, and it is usually not possible to offer any detailed opinions on the agent responsible. However, some bruises may have a pattern (a patterned bruise), or because of their shape or size or location, may have particular significance. Common patterning types include petechial bruising reproducing the texture of clothing, the ridge pattern from the sole of a shoe or tire, or the streaky linear purple bruising seen on the neck, wrists, or ankles caused by the application of a ligature. Beating with a rod-like implement often leaves a patterned bruise consisting of an area of central pallor outlined by two narrow parallel bands of bruising, so-called tramline bruising (see Fig. 4).

Other bruises of particular medicolegal significance are the small circular or oval bruises, usually approx 1-2 cm in diameter, characteristic of fingertip pressure from either gripping or grasping with the hand, prodding with the fingers, or the firm impact of a knuckle. They may be seen on the limbs in cases of child abuse when the child is forcibly gripped by the arms or legs and shaken or on the abdomen when the victim is poked, prodded, or punched. However, such nonaccidental injuries must be differentiated from bruises seen on toddlers and children associated with normal activities, play, or sports. Bruises may be seen on the neck in cases of manual strangulation and are then usually associated with other signs of asphyxia.

When sexual assault is alleged, the presence of bruising on the victim may help support the victim's account and give an indication of the degree of violence that was used. For example, grip marks or "defense" injuries may be present on the upper arms and forearms, whereas bruising on the thighs and the inner sides of the knees may occur as the victim's legs are forcibly pulled apart. Bruising of the mouth and lips can be caused when an assailant places a hand over the face to keep the victim quiet. Love bites ("hickeys") may be present often in the form of discrete areas of ovoid petechial bruising on the neck and breasts. However, it is important to recognize that the latter may be the sequelae of consensual sexual encounters.

Fig. 5. Production of an abrasion.
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