Identify the Abbreviated Injury Scale (AIS) scores for each body region to calculate the composite anatomic index for major trauma.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Anatomical scoring of polytrauma severity.
Defining "Major Trauma"—universally defined as ISS > 15.
Correlating synergistic organ injuries with overall mortality.
Benchmarking trauma centre performance and outcomes.
Section 2
Formula & Logic
Calculation Formula
ISS = (AIS₁)² + (AIS₂)² + (AIS₃)²
The Rule of Maxima
Identify the highest Abbreviated Injury Scale (AIS) score from six body regions (Head/Neck, Face, Chest, Abdomen, Extremities, External).
Take the highest AIS from the three most severely injured regions.
Any single AIS 6 (Unsurvivable) automatically results in a total ISS of 75.
Section 3
Pearls/Pitfalls
The ISS 3 Head Penalty
In neurosurgery, a "Serious" head injury (AIS 3, e.g., a small subdural or multiple contusions) already contributes 9 points to the score. If combined with a fractured femur (AIS 3), the score jumps to 18, officially categorizing the patient as Major Trauma.
Section 4
Evidence Appraisal
Primary Reference
The injury severity score: a method for describing patients with multiple injuries and evaluating emergency care
