Bruises are discoloration of skin surface caused by leakage of blood into underlying tissues from dam- aged blood vessels.
Two events must occur before a bruise can form:
damage to a blood vessel (usually small-calibre blood vessels such as veins and arterioles) from which blood leaks, and the leakage of that blood into surrounding tissues. Bruising is most com- monly seen in the skin, but it can also occur in the deeper tissues, including muscle and internal organs. The extent of damage to the blood ves- sels is generally proportionate to the force applied:
the greater the force, the more blood vessels are damaged, the greater the leakage of blood and the bigger the bruise.
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Figure 8.4 (a) Variable depth abrasions (grazes) caused by impact against concrete surface. (b) Linear abrasions caused by fi ngernail scratching on torso.
Figure 8.6 Hand with abrasions, swelling, reddening and underlying fracture of 5th metacarpal caused by repeated punching of cell door.
Figure 8.5 Laceration, with irregular edges, maceration and skin bridging caused by direct impact to forehead with wooden pole.
8 Asse ss ment, class ification and do cumentation of injury
Once outside the confines of the blood vessel, blood is broken down, resulting in the various colour changes seen. Eventually, all of the blood is removed and the overlying skin returns to its normal colour.
Bruises are one of the areas where a number of terms have been used in the past, which complicate the understanding of their nature. The term ‘ecchy- mosis’ has been used for specific types of bruise but should not now be used as it does not assist in understanding the type or mechanism of injury.
Bruising is best used to describe visible external marks caused by leakage of blood into skin and subcutaneous tissues, while contusion can be used
for leakage of blood into tissues in body cavities.
The term ‘haematoma’ can be used to refer to a pal- pable collection of blood under the skin (and one which, if a needle aspiration were to be undertaken, would show liquid blood in a cavity). ‘Petechiae’ are small bruises, often described as ‘pin-point haem- orrhages’, that have been said to be < 2 mm in size. However, that is an arbitrary figure and, like all bruises, petechiae can develop and evolve and coalesce, and the use of a rigid size measurement is inappropriate (Figure 8.7).
Direct blunt force, in addition to unambiguous impacts such as strikes with fists, kicks or weap- ons, also includes mechanisms such as poking, squeezing and gripping. Indirect blunt force may be represented by suction (as in ‘love bites’;
Figure 8.8) or following compression. Compression may produce petechiae at the level of or above the compressing force (e.g. in ligature strangulation).
Bruises evolve and can ‘migrate’. Gravity and tis- sue planes are two of the factors that may deter- mine how the appearance of a bruise might change (Figure 8.9). Thus the presence of a bruise at a par- ticular site does not necessarily imply that the blunt impact was applied at that site. Some very super- ficial bruises (often called intradermal bruises), caused by leakage of blood confined to the epider- mis and the upper strata of the dermis, can remain in the position in which the impact occurred, and
‘patterned’ bruises, which reproduce the nature of the object that caused them, often have such an
‘intradermal’ element. Intradermal bruises are often
Figure 8.7 (a) Close-up of face after manual strangulation 2 hours after compression with multiple petechial bruising over facial skin. (b) Scleral blood, caused by coalescence of multiple petechiae, 36 hours after manual strangulation.
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Figure 8.8 Classical love or ‘hickey’ bite – bruising to neck caused by suction.
Types of injur y
Figure 8.9 Extensive bruising following tissue planes and contours, one week after multiple blunt force impacts to (a) head and (b) face (neck was spared impacts).
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associated with diffuse compression forces such as pressure from a car tyre or from a shoe during a stamp or a kick (Figure 8.10).
Certain types of blunt injury commonly cause evi- dentially useful patterns. Single patterned bruises may indicate the nature of the impacting object.
‘Tramline’ bruises (Figure 8.11) are those caused by impacts from longitudinal, generally cylindrical
Figure 8.10 (a) Patterned bruise – intradermal bruising caused by stamping on back with textured clothing intervening.
(b) Patterned bruise caused by impact of dog chain.
(c) Patterned bruise (bruise obliquely towards midline) caused by impact of 2 × 2 length of wood.
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8 Asse ss ment, class ification and do cumentation of injury
or rod-like, objects (where blood is forced laterally from the point of impact, rupturing blood vessels either side of the impacting object) and footprint imprint bruises may be seen from stamp injuries (Figure 8.12).
Patterns of a number of bruises may also help corroborate the nature of the causative force. For example a row of four 1–2 cm oval or round bruises may be caused by the impact of knuckles in a punch; groups of small oval or round bruises are also indicative of fingertip pressure, as in gripping, and there is sometimes a single, larger, thumb bruise on the opposite side of the limb (Figure 8.13). Fingertip bruises on the neck or along the jaw line are com- monly seen in manual strangulation.
Examination of injuries must be undertaken in good light and, in the case of bruises, such is required in order to ensure that small or subtle skin colour changes are not missed. Even with darker skin tones, a proper examination will be able to identify areas of bruising.
Age estimation based on the colour of bruising is not now considered appropriate, with one excep- tion – a yellow-coloured bruise may be more than 18 hours old. The colouring must not be taken from
Figure 8.12 Shoeprint bruise following stamping injury to face.
Figure 8.13 Grip marks from fi ngers on assailant bruises from grip and abrasions from fi ngernails seen on upper inner arm.
Figure 8.11 Tramline bruise caused by impact from cylindrical fi rm object (in this case, a police baton).
Types of injur y
photographic images where colour reproduction may be inaccurate and it must also be understood that the perception of yellow colour may be influenced by the visual capability of the viewer, interobserver vari- ation and underlying skin tone. Studies in children suggest that estimation of ageing of bruising cannot be achieved by colour interpretation, and this princi- ple generally applies to adults also.
Bruising can occur after death: blood vessels are just as easily damaged by the application of
force and, provided that there is blood with some pressure within those vessels, bruising can occur.
Such pressure may exist at the lowermost vessels because of the static weight of the column of blood.
Post-mortem bruises are generally small and lie on the dependent parts of the body. Bruising may also be found in areas of post-mortem dissection and care must be taken in interpreting ‘new’ bruises when an autopsy has been performed.