Differences in neuromusculoskeletal injury and disability rates between US Navy aircraft carrier and amphibious assault ships.

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, limited duty (LIMDU), and long-term disability episode counts of all Sailors assigned to US Navy Aircraft Carriers (CVNs) and Amphibious Assault Ships (LHA/LHD) from November 2016 to February 2023 were extracted from the Musculoskeletal Naval Epidemiological Surveillance Tool. A negative binomial regression and general additive (gaussian) models evaluated the association of ship platform, deployment status, days underway, and sex on MSKI rates and the proportion of cases that resulted in LIMDU, returned-to-duty following LIMDU, or progressed to long-term disability. Results: Sailors attached to CVNs contributed a mean 17893.8±23280.6 person-months, with those attached to LHA/LHDs contributing an average 5981.8±8432.7 person-months. Aboard CVNs, MSKI occurred at a rate of 0.30±0.16/1000 person-months while deployed and 0.64±0.31/1000 person-months in homeport. Aboard LHA/LHDs, Sailors incurred MSKI at a rate of 0.59±0.58/1000 person-months while on deployment and 1.24±0.68/1000 person-months in homeport. Among Sailors aboard CVNs, LIMDU 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 LIMDU while deployed and 4.95±5.27% while in homeport. In the multivariable assessment of LIMDU, 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 PT 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.