A contusion, also known as a bruise is the extravasation or collection of blood due to the rupture of blood vessels caused by the application of mechanical force of blunt nature without loss of continuity of tissues. It is caused by a blunt force impact causing crushing or tearing of subcutaneous tissue or dermis without breaking the overlying skin. As the blood vessels rupture, the blood gets collected underneath the tissue. This causes swelling and pain.
Contusions may be present in the internal organs like the brain, lungs also. Contusions over the brainstem are often fatal. Contusions on the heart can disrupt the normal rhythm and can cause cardiac failure. Contusions when present on organs can rupture the cellular covering with resulting bleeding. If contusions are inflicted on vital parts like the heart, or neck then it may cause death. Multiple contusions can cause death due to shock, or hemorrhage.
There are different types of contusions namely intradermal bruise, subcutaneous bruise, deep bruise, tram-line contusion, patterned contusion, six-penny bruises, horseshoe-shaped contusion, shifting contusion, and contusions over organs. The size of the bruise may not correspond with the size of the offending weapon nor do they indicate the direction in which the force was applied.
When a large blood vessel is injured, a tumor-like mass called hematoma is formed. Petechial bruises are finely mottled or stippled. If the petechiae become larger and confluent, they are called ecchymoses. The greater the force of violence used, the more extensive the bruise will be. Postmortem and antemortem contusions can be distinguished as swellings, extravasation of blood, signs of inflammation, and hemorrhage are present only in antemortem contusions.
Factors Affecting Modification of Bruise
1. Condition of Tissue
In contusions when the collection of blood happens due to rupture of blood vessels, there should be space in the surrounding tissues to accommodate this extravasated blood. In lax tissues, more space is available and hence contusion can be seen more rapidly in such locations like the scrotum or eye socket and rare/slowly in areas like the sole or palm that have dense tissues.
Similarly, fat people produce bruises easily than thin people because of a greater volume of fat.
As women have more subcutaneous fat and delicate tissues than men, they bruise more easily than men.
Children bruise easily as they have more soft tissue composition and less volume of protecting tissues. Old persons too bruise easily owing to loss of flesh and accompanying cardiovascular change.
4. Color of Skin
Bruising appears more prominently in people with fair complexion than in people with a darker complexion.
5. Body Part
Resilient areas or yielding areas such as the buttock, thighs will bruise less than unyielding or rigid surfaces like heat, chest, or shin.
6. Situation of Bruise
Contusions that are present in the deeper tissues take time to appear to the surface or will be visible on dissection but contusions located in the dermis or subcutaneous tissue will appear more quickly.
7. Condition of Blood Vessels
The blood vessels are more fragile in older individuals and hence bruises easily and heavily even with trivial trauma.
8. Presense of Disease
People with diseases such as scurvy, liver disorder, bleeding diathesis, arteriosclerosis, leukemia, purpura, hemophilia, vitamin C and K deficiency, chronic alcoholics, or certain medications such as aspirin will bruise easily.
9. Optical Character of Skin
Bruises present towards the surface will appear reddish and those present in the deeper layer give more bluish color due to the scattering process in the dermis as the blue wavelengths of light are scattered to a greater extent than the red wavelengths.
Contusions have medicolegal importance because bruises like patterned bruising can indicate the offending weapon. The age of injury, character, and manner of the injury can be determined. The application of the degree of violence can also be estimated.
The bruises may be confused with postmortem lividity, congestion, artificial bruise, or purpura and hence it is important to know about the features of such injuries to avoid false findings.