Incidence of primary blast injury in US military overseas contingency operations: a retrospective study.

OBJECTIVES The present retrospective study was performed to determine the incidence and outcome of primary blast injury and to identify possible changes over the course of the conflicts between 2003 and 2006. SUMMARY BACKGROUND DATA Combat physicians treating patients injured in overseas contingency operations observed an increase in the severity of explosion injuries occurring during this period. METHODS This retrospective study included service members injured in explosions between March 2003 and October 2006. The Joint Theater Trauma Registry provided demographic information, injury severity score, and International Classification of Diseases 9 codes used to diagnose primary blast injury. Autopsy reports of the last 497 combat-related deaths of 2006 were also reviewed. RESULTS Of 9693 admissions, of which 6687 were injured in combat, 4765 (49%) were injured by explosions: 2588 in 2003-2004 and 1935 in 2005-2006. Dates of injury were unavailable for 242 casualties. Injury severity score (9 +/- 10 vs. 11 +/- 10, P < 0.0001) and incidence of primary blast injury (12% vs. 15%, P < 0.01) increased. The return-to-duty rate decreased (40% vs. 18%, P < 0.001), but mortality remained low (1.4% vs. 1.5%, P = NS). There was no significant difference in incidence of primary blast injury between personnel who were killed in action and those who died of wounds at a medical facility. CONCLUSIONS Injury severity and incidence of primary blast injury increased during the 4-year period, whereas return-to-duty rates decreased. Despite increasingly devastating injuries, the mortality rate due to explosion injuries remained low and unchanged.