Abstract: BACKGROUND: Previous studies have confirmed that neck muscle strength and intervertebral stress can influence the progression of cervical spine degeneration. However, no quantitative analysis has been conducted to examine the interaction between the biomechanical changes in cervical spondylotic myelopathy and cervical vertebral stress and paravertebral muscles.
OBJECTIVE: To explore the cervical spine movement patterns of patients with cervical spondylotic myelopathy based on biomechanical principles, quantify the synergistic imbalance effects between paraspinal muscle strength and intervertebral stress in these patients, and discuss and reveal the dialectical relationship between the traditional Chinese medicine theory of “musculoskeletal imbalance” and the modern biomechanical concept of “dynamic and static imbalance” in cervical spondylotic myelopathy.
METHODS: Twenty cervical spondylotic myelopathy patients who visited the orthopedic outpatient and inpatient departments of the First Affiliated Hospital of Guangxi University of Chinese Medicine were analyzed as the cervical spondylotic myelopathy group. Ten healthy individuals from health check-up centers and "prevention of disease" centers were included as the healthy group. The age and gender of all subjects were recorded. The six-degree-of-freedom motion data of the neck were collected through motion capture and Opensim virtual simulation models, with repeated measurements taken three times. After optimizing and sorting out the data, the range of motion, peak changes in motion angle, distribution of the center of pressure on the vertebral body, average muscle strength of each muscle, average maximum joint pressure, and average maximum joint shear force of the two groups were quantified using the Forward Dynamics tool algorithm.
RESULTS AND CONCLUSION: (1) There were no significant differences in gender and age between the two groups from a statistical perspective. (2) In the left rotation, right rotation, and extension directions, the peak changes in movement angles were significantly smaller in the cervical spondylotic myelopathy group compared with the healthy group. In the lateral flexion, rotation, and extension directions, the range of motion was significantly greater in the cervical spondylotic myelopathy group compared with the healthy group. (3) Comparisons of pressure centers at C4 and C5 vertebrae indicated that the joint pressure centers in cervical spondylotic myelopathy patients were more dispersed. (4) The average muscle strength of cervical spondylotic myelopathy patients was significantly lower than that of the healthy population. (5) The maximum joint pressure on the C4 to C6 vertebrae during extension movements in cervical spondylotic myelopathy patients was significantly greater than that in the healthy population, while the maximum joint pressure on the C3 to C7 vertebrae during flexion, lateral flexion, and rotation movements was lower than that in the healthy group; the average maximum joint shear force on the C4 to C7 vertebrae during extension, lateral flexion, and rotation movements in the healthy population was greater than that in the cervical spondylotic myelopathy group. (6) It is indicated that during cervical movements, cervical spondylotic myelopathy patients exhibit reduced cervical muscle strength, baseline vertebral stress imbalance, altered stress distribution and pressure center distribution in the vertebral facet joints, accelerated degenerative changes in cervical vertebral bone structure and muscle, and impaired cervical stability. The biomechanical alteration mechanisms of “musculoskeletal imbalance” and “dynamic-static imbalance” in cervical spondylotic myelopathy are correlated.

Key words: dynamic and static equilibrium, traditional Chinese medicine theory of tendons and bones, musculoskeletal model, biomechanics, motion capture, personalized medicine