Quantification of cervical and lumbar spine health in navy high-performance craft crewmen across the training and deployment cycle

Abstract Background Back pain is a leading cause of disability in military personnel. This burden is heightened in high-demand military occupations, such as Navy High-Performance Craft Crewmen (HPCC), who operate high-speed vessels under variable sea states. Biomechanical exposures differ across the training–deployment cycle. Thus, this study characterized injury accumulation, paraspinal muscle, and intervertebral disc (IVD) health across the training–deployment cycle in HPCC. Methods Thirty-two active-duty male HPCC operators underwent 3T MRI scanner using Dixon, T1-weighted, T2-mapping, and diffusion tensor imaging (DTI) sequences. Each participant underwent an MRI at baseline and at one or two additional timepoints: pre-deployment and/or post-deployment. Injuries reported between scans were documented through structured interviews and medical histories. Cervical and lumbar muscles were manually segmented to quantify volume, fat fraction, and diffusion tensor metrics. Cervical and lumbar IVD T2 relaxation times were quantified as measures related to IVD hydration. Results Twenty-three HPCCs (72%) reported at least one injury. Injuries recorded as traumatic brain injury (TBI) or concussion accounted for 47.5% of the 40 reported injuries. Of these injuries, 57.5% occurred during training, 20% during deployment, and 22.5% during unrelated activities. No significant time effects on T2 relaxation were detected at any lumbar or cervical IVD level. In the cervical spine, post-deployment changes included increased volumes of the Multifidus, Semispinalis, Spinalis Cervicis, Interspinalis, Rotatores (MC), and the Rectus Capitis Posterior Major and Minor (RCPM), along with greater RCPM fat fraction. Fractional anisotropy of the Longus Colli/Capitis (LC), Obliquus Capitis (OC), and RCPM decreased post-deployment. Conclusion The training–deployment cycle was associated with heterogeneous spinal muscle and disc adaptations, with evidence of concurrent hypertrophy, microstructural change, and localized fatty degeneration in select muscles. The high proportion of injuries recorded as TBI or concussion supports further research examining whether head-injury status is associated with cervical muscle measures, underscoring the value of integrated musculoskeletal–neurologic surveillance to support readiness in HPCC personnel.