Lumbar Disc Herniation in Military Helicopter Pilots vs. Matched Controls

Lumbar disc herniation (LDH) is a common injury among active duty service members resulting in missed duty hours and limited duty status. Little is known about the current burden of disease and risk factors for LDH among military rotary wing aviators.

A query was made using the Defense Medical Epidemiology Database (DMED), including patient encounters for the U.S. Military from 2006-2015 using the ICD-9 code for LDH. Incidence rates were calculated for patients with the occupation of helicopter pilot and stratified by age, gender, and branch of service, then compared to matched controls using a Poisson regression analysis. Then, data from a 17-yr period were examined for long term trends.

We identified 1218 cases of LDH among 141,383 person-years among helicopter pilots, yielding a 1.22-fold higher incidence rate compared to controls. Significant risk factors identified after Poisson regression analysis were age greater than 30 yr old and Army service branch affiliation. Male gender was not found to be a significant risk factor. Long term data revealed a 2.6-fold increased incidence of LDH among helicopter pilots since 1997.

We identified significant increased risk of LDH in rotary wing pilots as compared to their nonpilot peers. Among rotary wing pilots, the incidence of this condition has increased, with both increasing pilot age and Army branch affiliation identified as risk factors. This information will allow targeted prevention strategies and further investigation to potential aircraft-specific causes of increased risk in Army pilots.Knox JB, Deal JB Jr, Knox JA. Lumbar disc herniation in military helicopter pilots vs. matched controls. Aerosp Med Hum Perform. 2018; 89(5):442-445.