| dc.description.abstract | Epidemiological studies report a prevalence of neck pain among rotary-wing aircrew (RWA)
potentially associated with head-supported mass (HSM), frequent physiologic motions of head-neck,
aircraft vibration, and prolonged time in non-neutral head-neck positions. Experimental studies with
human volunteers and computational studies using head-neck models have suggested potential causal
pathways for neck pain in RWA, including increased activity in muscles and increased forces in the
spinal column. However, additional insight is required to understand the interactions of HSM, which
comprises a helmet with optional mounted devices, and non-neutral head-neck positions. The present
study aimed to simulate RWA non-neutral head-neck positions with the HSM using a detailed finite
element (FE) head-neck model to assess the tissue-level biomechanical response and potential sources
for neck pain in RWA.
A detailed FE head-neck model (NMM50) was extracted from a full human body model of a 50th
percentile male. The NMM50 model was enhanced, verified and validated starting sequentially from the
ligamentous upper cervical spine (UCS), full cervical spine, and full head-neck with active musculature
for physiologic loading conditions (NMM50-Hill-E). The NMM50-Hill-E model was simulated for non-neutral
head-neck positions (flexion and axial rotation) using a conventional boundary condition and a novel
active muscle repositioning approach, demonstrating the importance of active muscle repositioning on
tissue-level response. Finally, the NMM50-Hill-E model with active muscle repositioning was simulated
for non-neutral head and neck positions with HSM.
The present study demonstrated that the muscle-based method of repositioning the FE head-neck model
improved the head and neck kinematic response by capturing the in vivo flexion and axial rotation
positions better than the conventional boundary condition method. In the simulated RWA head-neck
positions, tissue-level investigations demonstrated an increase in the muscle force, intervertebral disc
(IVD) force, endplate stress and annulus fibrosus (AF) collagen fiber strain with an increase in the HSM
in flexion. Similarly, an increase in the magnitude of non-neutral position from flexion to a combined
position was shown to increase the ligament distraction along with an increase in muscle force, IVD
force, endplate stress and AF collagen fiber strain. The detailed FE head-neck model provided valuable
insight by predicting tissue-level biomechanical responses in the RWA neck while providing guidance
on factors that may contribute to neck pain risk in the RWA. | en |
