The role of paraspinal muscle degeneration in cervical spondylosis.

Purpose: To explore the relationship between paraspinal muscle degeneration and cervical spondylosis through cervical spine MRI and lateral X-ray.

Methods: A retrospective study included 83 cervical spondylosis patients as the experimental group, consisting of 28 axial joint pain (Group A), 29 cervical radiculopathy (Group B), and 26 myelopathy (Group C), as well as 29 healthy individuals as the control group (Group D). The cross-sectional area (CSA) of paraspinal muscles at the C3-4, C4-5, and C5-6 segments was measured, including the deep extensor area (DEA), deep flexor area (DFA), and superficial extensor area (SEA). Additionally, fatty infiltration (FI) ratio was calculated, namely the deep extensor fatty infiltration ratio (DEFIR), deep flexor fatty infiltration ratio (DFFIR), and superficial extensor fatty infiltration ratio (SEFIR). Correlations of CSA and FI ratio with age, body mass index, Pfirrmann grading, and Cobb angle were analyzed.

Results: (1) Pfirrmann grading in groups A, B, and C was significantly higher than that in group D (P < 0.001), with group C higher than groups A and B (P < 0.05), but the difference between groups A and B was not statistically significant (P > 0.05). (2) There was no significant difference in the CSA among groups (P > 0.05). For DEFIR and DFFIR, group C > group B > group A > group D, with significant differences (P < 0.05). For SEFIR, groups A, B, and C were significantly higher than group D (P < 0.001), with no significant differences between the other pairs (P > 0.05). (3) The CSA of males was significantly greater than females (P < 0.001), while the difference in FI ratio was not significant (P > 0.05). (4) In the control group, DEFIR and DFFIR were positively correlated with age (r = 0.538, P = 0.003; r = 0.829, P < 0.001) and negatively correlated with Cobb angle (r=-0.523, P = 0.004; r=-0.535, P = 0.003). In the experimental group, DEFIR and DFFIR were positively correlated with age (r = 0.731, P < 0.001; r = 0.741, P < 0.001) and Pfirrmann grading (r = 0.778, P < 0.001; r = 0.812, P < 0.001), and negatively correlated with Cobb angle (r=-0.507, P < 0.001; r=-0.539, P < 0.001). There were no correlations between the other parameters.

Conclusion: In cervical spondylosis patients, the FI ratio of the deep cervical muscle is linked to both worsening disc degeneration and changes in cervical spine alignment. Among the different subtypes, cervical myelopathy shows the highest FI ratio of the deep cervical muscle and disc degeneration, indicating its significant impact on spinal structure and muscular integrity.