Injury Severity

Injury severity refers to a quantitative measure of the extent and seriousness of injuries sustained by a patient, often used to predict outcomes such as mortality, morbidity, and hospital stay in trauma care. It is typically assessed using standardized scoring systems that classify injuries based on anatomical and physiological criteria.

The most widely used system is the Injury Severity Score (ISS), an anatomical scoring system that provides an overall score for patients with multiple injuries. The ISS is calculated by:

• Assigning each injury an Abbreviated Injury Scale (AIS) score, which ranks injury severity from 1 (minor) to 6 (virtually unsurvivable).
• Dividing the body into six regions: head/neck, face, chest, abdomen/pelvic contents, extremities/pelvic girdle, and external.
• Selecting the highest AIS score in each of the three most severely injured body regions.
• Squaring these three AIS scores and summing them to produce the ISS, which ranges from 0 to 75. An AIS of 6 automatically sets the ISS to 75, indicating unsurvivable injury.

For example, a patient with a fractured femur (AIS 3) and two rib fractures (AIS 2) might have an ISS of 14 based on this calculation method.

The ISS correlates with mortality and other outcomes but is not perfectly linear; it is often used categorically in research. Other scoring systems, such as ASCOT, combine physiological data (e.g., Glasgow Coma Scale, blood pressure) with anatomical scores to improve outcome prediction.

In summary, injury severity is a standardized, numerical representation of trauma extent, primarily measured by the Injury Severity Score, which helps clinicians assess prognosis and guide treatment decisions.