Clinical Overview
The Injury Severity Score (ISS) is the gold standard anatomical scoring system used universally in trauma centers and registries. Developed to assess patients with multiple traumatic injuries, it correlates directly with morbidity, mortality, and hospital length of stay.
Pathophysiology & Evidence
The ISS is based on the Abbreviated Injury Scale (AIS), which grades injuries in six different body regions (Head/Neck, Face, Chest, Abdomen, Extremities, External) on a scale from 1 (minor) to 6 (unsurvivable). The ISS specifically addresses the cumulative physiological burden of polytrauma by taking the sum of the squares of the highest AIS grades in the three most severely injured body regions.
Formula Breakdown
Because the maximum AIS score is 6, the maximum possible ISS is 75 (6² + 6² + 5² is theoretically 97, but by definition, any single injury with an AIS of 6 automatically assigns a total ISS of 75, indicating an unsurvivable injury).