Differences in Musculoskeletal Injury and Disability Rates in U.S. Navy Sailors Aboard Aircraft Carrier and Amphibious Assault Ships

Abstract

ABSTRACT Introduction Musculoskeletal injuries (MSKI) are the most common clinical condition in the military that affect medical readiness. Evaluation of MSKI burden and the effects of these injuries on readiness in large deck Navy ships is warranted. Materials and Methods A retrospective cohort study assessing population-level MSKI rates, short-term disability (restricted duty), and long-term disability episode counts of all Sailors assigned to U.S. Navy Aircraft Carriers (CVNs) and Amphibious Assault Ships (LHA/LHD) from November 2016 to February 2023 was extracted from the Musculoskeletal Naval Epidemiological Surveillance Tool. A negative binomial regression and general additive (Gaussian) models evaluate the association of ship platform, deployment status, days underway, and sex with MSKI rates and the proportion of cases that resulted in short-term disability, returned-to-duty following restricted duty, or progressed to long-term disability. Results Sailors attached to CVNs contributed a mean 17,893.8 ± 23,280.6 person-months, with those attached to LHA/LHDs contributing an average 5,981.8 ± 8,432.7 person-months. Aboard CVNs, MSKI occurred at a rate of 0.30 ± 0.16/1,000 person-months while deployed and 0.64 ± 0.31/1,000 person-months in homeport. Aboard LHA/LHDs, Sailors incurred MSKI at a rate of 0.59 ± 0.58/1,000 person-months while on deployment and 1.24 ± 0.68/1,000 person-months in homeport. Among Sailors aboard CVNs, short-term disability occurred in 7.95 ± 7.75% of MSKI cases while deployed and 5.13 ± 5.26% while in homeport. Aboard LHA/LHDs, 8.57 ± 13.42% of MSKI cases were placed on short-term disability while deployed and 4.95 ± 5.27% while in homeport. In the multivariable assessment of short-term disability, being deployed underway was a significant factor (B = 3.62 P = .03, variance explained = 3.86%). Sailors that were female and served aboard LHA/LHDs returned to full duty at a significantly greater frequency compared to their male counterparts and Sailors serving aboard CVNs. None of the independent variables evaluated were associated with long-term disability. Conclusion The findings in the current study demonstrate the substantial burden of MSKI aboard large deck ships, both in homeport and while deployed. Inclusion of a physical therapist aboard LHA/LHDs, like the CVN, may help to prevent and mitigate the effects of MSKI through early access to specialized care and integral injury prevention and performance optimization methods.