Effects of Neutral Postures on Mechanical Properties of Cervical Spine Under Different Gravitational Environments: A Musculoskeletal Model Study.

This study used the Anybody musculoskeletal model to investigate the effects of different neutral postures on the cervical spine and its associated muscle mechanical properties in various gravitational environments. A full-body musculoskeletal model (male, height: 1.74 m, mass: 74 kg) from the AMMR database, developed using the Anybody Modeling System, was employed to perform a quantitative analysis of three postures, including the neutral body posture in microgravity (NBP 0G), the neutral body posture in normal gravity (NBP 1G), and the relaxed standing posture in microgravity (SM 0G). The results showed that, compared to the NBP 1G posture in a gravitational environment, adopting the NBP 0G posture in microgravity resulted in an average reduction of 76.6% in the compressive force of the intervertebral discs, with shear forces in the same direction decreasing by 7.97 to 12.57 N. The shear force direction at the C6-C7 and C7-T1 segments changed, the intervertebral disc height increased by 1.6-4.8%, the disc cross-sectional area expanded by 3.2-6.9%, and the disc volume expanded by 4.8-9.4%. In addition, the total muscle force at the cervical region decreased while the ligament force increased. These changes in mechanical properties may significantly increase the risk of cervical disc herniation and degenerative disc diseases, as well as the risk of muscle atrophy in the neck.