The injury severity score (ISS) is an anatomical scoring system that provides an overall score for patients with multiple injuries. Each injury is assigned an abbreviated injury scale (AIS) score and is allocated to one of six body regions. The highest AIS score in each body region is used.

Is an established medical score to assess trauma severity.

It correlates with mortality, morbidity and hospitalization time after trauma. It is used to define the term major trauma.

A major trauma (or polytrauma) is defined as the Injury Severity Score being greater than 15.

ISS Definition

The ISS is based upon the Abbreviated Injury Scale (AIS).

To calculate an ISS for an injured person, the body is divided into six ISS body regions.

These body regions are:

Head or neck - including cervical spine

Face - including the facial skeleton, nose, mouth, eyes and ears

Chest - thoracic spine and diaphragm

Abdomen or pelvic contents - abdominal organs and lumbar spine

Extremities or pelvic girdle - pelvic skeleton


To calculate an ISS, take the highest AIS severity code in each of the three most severely injured ISS body regions, square each AIS code and add the three squared numbers for an ISS (ISS = A2 + B2 + C2 where A, B, C are the AIS scores of the three most injured ISS body regions). The ISS scores ranges from 1 to 75 (i.e. AIS scores of 5 for each category). If any of the three scores is a 6, the score is automatically set at 75. Since a score of 6 (“unsurvivable”) indicates the futility of further medical care in preserving life, this may mean a cessation of further care in triage for a patient with a score of 6 in any category.

  • injury_severity_score.txt
  • Last modified: 2021/12/27 12:35
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