External cause coding of injury encounters in the Military Health System among active component U.S. service members, 2016-2019.

Knowledge of injury causes is essential for prevention. To investigate cause coding in service members' electronic medical records, injury encounters from 2016 to 2019 containing at least 1 external cause code were analyzed. Approximately 10% of incident injury encounters contained at least 1 cause code describing the mechanism, activity, or place of occurrence. Less than 2% of overuse injury encounters had a cause code each year, compared to 36.4-44.0% of acute injuries occurring from 2016 to 2019. Cause coding occurred more frequently in records from military facilities compared to outsourced care (p<0.001). Inpatient records were more likely to be cause-coded than outpatient records (p<0.001). More injury encounters in emergency clinics were cause coded (>50%), compared to approximately 7% of primary care and 2% of specialist encounters. In 2019, the leading mechanism was overexertion (19.9%), followed by falls, slips, or trips (18.7%). The primary activity associated with injuries was running (21.1%). Military training ground was the leading place of occurrence (13.0%). Improvements to the quality and quantity of external cause coding in the medical records would provide critical details to inform military injury prevention. From 2016 through 2019, approximately 10% of 1.5 million annual U.S. service member incident injury medical encounters contained external cause codes. Acute injuries were approximately 20 times more likely to receive a cause code than overuse injuries. Causes were less likely to be recorded in outpatient care records and at non-military health care facilities.