Herniated nucleus pulposus: rates and outcomes among U.S. Army aviators.

The incidence and age-specific rates, and aeromedical dispositions of herniated nucleus pulposus (HNP) are unknown among U.S. Army aviators. The U.S. Army Aviation Epidemiology Data Register (AEDR) was queried for Army aviators with the finding of HNP for the period 1987 to 1992. This study tabulated the incidence, age-specific annual rates of HNP, and the distribution of aeromedical dispositions for aircrew with HNP. The U.S. Army aviation medicine community can expect an annual incidence rate about 1 case of HNP per 1,000 aviator-years. However, the annual incidence rate per 1,000 aviator-years increased significantly by fivefold from 0.49 in 1987 to 2.60 in 1992 (p < 0.001). Aviators who were 40-44 years old were at the greatest risk, with an annual rate of 1.6 cases per 1,000 aviator-years. Among 132 aviators, 25.8% had cervical HNPs, 74.2% had lumbar HNPs, and none had thoracic HNPs. Operative management was required in 66.6% of cases. Those with cervical HNPs were not at increased risk for operative management compared to those with lumbar HNPs (RR = 0.961, CI0.95 = 0.723, 1.28). About 7.4% of the aviators with HNP were permanently removed from Army flying duties due to HNP complications.