SN7 SHORT NOTE 5M

Describe the healing of wounds and the determination of the age of an injury.

Forensic Medicine · 2nd Professional — Para-Clinical

Wound Healing and its Stages

0 to 12 hours — haemorrhage and clot
margins swollen and red
neutrophil infiltration begins at about 4 hours and becomes a continuous layer by about 12 hours
fibrin exudate → 12 to 24 hours — a continuous zone of leucocytes
a scab forms
the basal epithelium begins to proliferate → 24 to 72 hours — macrophages appear and clear the debris
fibroblasts and new capillaries begin to invade
epithelium bridges the surface by about 48 hours in a clean incised wound → 3 to 5 days — granulation tissue is established
collagen fibres first appear at about day 4 to 5 → 1 to 2 weeks — collagen accumulates
the wound is filled
the scar is red and vascular
sutures are removed → 2 to 4 weeks — the scar begins to contract and pale as vessels regress → Months — the scar becomes white, avascular and glistening, and continues to contract
after about 6 months it can no longer be dated
Histology dates a wound far more reliably than its appearance, and should be used wherever the timing matters — the sequence of neutrophils, macrophages, fibroblasts, capillaries and collagen is reasonably consistent, whereas surface appearances vary greatly
Histochemistry and immunohistochemistry extend the range downward, demonstrating enzyme changes and markers such as fibronectin and cytokines within minutes of injury — which is how a wound inflicted just before death is distinguished from one inflicted just after

Dating the Individual Injury Types

Injury	Findings by age
Abrasion	Fresh: red, moist, oozing. 12–24 h: bright red scab. 2–3 days: reddish-brown scab. 4–7 days: dark brown to black, the scab loosening at the periphery first. Over 7 days: scab shed, leaving a depigmented area that slowly returns to normal colour
Contusion	Red → blue → green (biliverdin, 4–5 days) → yellow (bilirubin, 7–10 days) → normal (14–15 days), the change proceeding from periphery to centre. Dating from colour is unreliable; the only defensible statement is that a yellow bruise is more than about 18 hours old
Incised wound	Follows the healing sequence above; heals rapidly with a linear scar
Laceration	Slower, with more infection and granulation tissue; heals with an irregular scar
Fracture	Haematoma immediately; soft callus at 1 to 2 weeks; callus visible on radiograph at 2 to 3 weeks; consolidation over 2 to 3 months; remodelling over months to years. A radiograph therefore dates a fracture better than clinical examination
Burn	Redness and blistering at once; slough separating at about 1 week; granulation from 2 weeks; healing with contracture and keloid over months
Scar	Red and vascular for weeks to months; pale and white after about 6 months; thereafter undateable, and it contracts with time so it is smaller than the original wound

CLINICAL PEARL

Dating injuries is where confident opinions are destroyed, and the honest answer is a wide range. Controlled studies have shown experienced examiners dating bruises wrongly from colour, and the same is true of abrasions. The defensible positions are narrow: a yellow bruise is over about 18 hours
callus on a radiograph means over two weeks
histology gives a reasonable sequence. Anything stated more precisely than that will not survive a competent cross-examination.

Factors Affecting Healing and Applied Aspects

Factors delaying healing — infection (the commonest); a foreign body or dead tissue in the wound; poor blood supply; movement of the part; old age; malnutrition, particularly protein and vitamin C deficiency; diabetes; anaemia; corticosteroids and cytotoxic drugs; irradiation; and immunosuppression
Factors accelerating it — youth, good nutrition, a clean apposed wound, rest, and a good blood supply — which is why wounds of the face and scalp heal fast and those of the shin heal slowly
These factors must be considered before giving any age; a diabetic elderly patient with an infected wound will show findings appropriate to a far shorter interval than has actually elapsed, and the estimate will be badly wrong if this is ignored
Give a range, and state the factors that widen it; an opinion that accounts for the person's age, nutrition, disease and the site of the wound is far more persuasive than a bare figure
Take histology where the age matters, and record that it was taken; the microscopic sequence is the only reasonably reliable method available
Injuries of different ages in one person are themselves a finding — in a child they suggest repeated abuse, in an adult they may indicate a pattern of domestic violence, and in either case the differing ages must be recorded individually rather than described together
Do not date an old scar beyond saying it is more than about six months old; and remember it has contracted, so the original wound was larger
Callus on a radiograph means at least two weeks, which is among the few firm dating statements available and is easily obtained
Neutrophils at four hours, macrophages at twelve to twenty-four, collagen at four to five days — the histological sequence is the reliable timetable, and the surface appearance is not
Scalp and face heal fast, the shin slowly; the site alone shifts the estimate substantially and must be stated with the opinion
Immunohistochemistry dates a wound to within minutes, which is how a perimortem injury is separated from a postmortem one when the gross appearance cannot do it

All questions in Mechanical Injuries

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