Patterned abrasions and the sequence of abrasion healing
THE CONTEXT
Surface patterns can indicate the contact object, while gross and microscopic healing changes help assess the approximate age of an abrasion. Exact age cannot be determined.
Production and description of patterns
•
When a patterned surface has varying heights, its ridges abrade the epidermis. Skin compressed into the cavities may sustain capillary damage and an intradermal bruise, as when a motor tyre passes over it.
•
Examples include bicycle-chain imprints, coarse fabric weave, electric-wire spirals, ropes and serrated knives.
•
A multi-thonged whip produces a series of linear abrasions or superficial tears; the pattern and shape are usually non-specific.
•
Multiple minor abrasions in one region can be described together by stating the dimensions of the affected area and its anatomical location.
Gross healing changes
•
Abrasions heal from the periphery through new epithelial-cell growth.
•
Fresh abrasions are bright red. At 12 to 24 hours, lymph and blood dry to form a bright-red scab.
•
At 2 to 3 days, the scab is reddish-brown. At 4 to 7 days, it is dark brown to brownish-black, with epithelium covering the defect beneath it.
•
After 7 days, the scab dries, shrinks and falls off, leaving a depigmented area that gradually becomes pigmented.
Microscopic healing changes
•
Perivascular cellular infiltration is seen at 4 to 6 hours.
•
At 12 hours, there are three layers: superficial fibrin and red cells, a deeper zone of infiltrating polymorphs, and a deepest layer of abnormally staining collagen.
•
At 48 hours, the scab is well formed and epithelial regeneration is visible at its margins. Small abrasions are completely covered by epithelium by 4 to 5 days.
•
Subepithelial granulation tissue is prominent at 5 to 8 days. Reticulum fibres appear at 8 days and collagen fibres at 9 to 12 days.
•
Regression begins at about 12 days, with epithelial remodelling, thinning and possible atrophy.