Abstract: BACKGROUND: Modern research suggests that the “muscle-bone imbalance” in cervical spondylotic radiculopathy is associated with changes in the performance of cervical muscles due to biomechanical alterations of the head and neck. However, most studies have focused on static analysis of the cervical spine, lacking dynamic quantitative data on neck muscle strength and activation.
OBJECTIVE: To investigate the differences in muscle strength and muscle activation during cervical spine movement between patients with cervical spondylotic radiculopathy and healthy individuals from a biomechanical perspective.
METHODS: From October 1, 2023 to March 1, 2024, 10 volunteers were recruited from the orthopedic outpatient clinic, inpatient ward, and health check-up center of the First Affiliated Hospital of Guangxi University of Chinese Medicine. These included five patients with cervical spondylotic radiculopathy (cervical spondylotic radiculopathy group) and five healthy individuals (healthy control group). Inertial motion capture sensors were used to collect movement data of the neck in six degrees of freedom: cervical flexion, cervical extension, left lateralization, right lateralization, left rotation, and right rotation. Data were measured three times per participant, yielding 18 sets of data. Based on muscle parameters obtained from magnetic resonance imaging scans, OpenSim head and neck musculoskeletal models were established for patients and healthy individuals separately. After preprocessing, the collected cervical motion data were imported into the OpenSim simulation models to calculate and compare neck muscle strength and muscle activation between the two groups.
RESULTS AND CONCLUSION: The healthy control group showed orderly synergistic activation of muscle groups, while the cervical spondylotic radiculopathy group exhibited disordered synergistic activation patterns, characterized by insufficient activation of affected-side muscles, excessive compensation on the unaffected side, and significantly reduced synergy of core muscles including the sternocleidomastoid, middle and upper trapezius, and longus colli. Muscle strength in the cervical spondylotic radiculopathy group was lower than that in the healthy control group (P < 0.05) as follows: during cervical extension (sternocleidomastoid, middle trapezius, longus capitis, upper trapezius); during cervical flexion (sternocleidomastoid, longus capitis, longus colli, levator scapulae, multifidus, splenius cervicis, splenius capitis, middle/upper trapezius); during left lateralization (sternocleidomastoid, longus capitis, longus colli, scalenus, levator scapulae, multifidus, splenius cervicis, splenius capitis, middle/upper trapezius); during right lateralization (longus colli, upper trapezius); during left rotation (levator scapulae); and during right rotation (longus colli). Overall, these findings indicate that patients with cervical spondylotic radiculopathy exhibit cervical muscle synergy imbalance during all cervical movements. This imbalance is characterized by degeneration of affected-side muscles and nerves with reduced muscle strength and coordination, while unaffected-side muscles and nerves overcompensate for the functional deficiency of the affected side. Among the muscle groups involved in cervical motion, degeneration of the sternocleidomastoid and the middle/upper trapezius is most significant, which is an important feature of cervical spondylotic radiculopathy.

Key words: cervical spondylotic radiculopathy, cervical muscle biomechanics, inertial motion capture, digital orthopedic model, muscle synergy imbalance, dynamic muscle strength assessment