Non-modifiable Risk Factors Associated with Avascular Necrosis in the US Military

Often referred to as aseptic or osteonecrosis, avascular necrosis (AVN) typically affects people between 30 and 50 years of age. Given the substantial morbidity associated with AVN as well as overlapping age groups of both the military and average age at diagnosis for AVN, the military represents an ideal cohort for a large database study to elicit the incidence and epidemiology of AVN. The purpose of this study was to identify demographic risk factors in the United States military.

First-time occurrences for ICD-9-CM codes for all types of AVN (head of humerus, head and neck of femur, medial femoral condyle, talus, and other bone) between 2004 and 2014 were queried in the Defense Medical Epidemiology Database. Multivariate data analysis was performed to obtain adjusted rate (adjusted for age, sex, race, rank, and branch of service).

Between 2005 and 2014, 2,671 cases of AVN occurred among an at-risk population of 13,820,906 servicemembers for an unadjusted IR of 0.19 per 1,000 person-years. The most common location was located at the proximal femur, responsible for 41.7% of all cases. With an adjusted rate ratio of 18.7, the over 40 age-group accounted for 53.3% of cases. Servicemembers of black race, Senior rank, and the Army branch of service were more at risk for AVN.

The overall incidence of AVN was 0.19 per 1,000 person-years. Whilte increasing age had the greatest influence on the development of symptomatic AVN, other statistically significant risk factors were found to be increasing age, black race, senior enlisted rank, and Army branch of service.