Radiological evaluation of posterior cervical misalignment by ligamentum flavum angle in patients with degenerative cervical myelopathy.

PURPOSE: Posterior cervical misalignment is commonly observed in patients with degenerative cervical myelopathy (DCM), yet its clinical significance remains unclear. This study takes aim to investigate the radiological value of ligamentum flavum angle (LFA) to evaluate the implications of posterior cervical misalignment in DCM.

METHODS

Baseline LFA was determined in 76 adults with normal cervical alignment. LFA was then analyzed in 155 DCM patients and categorized into enlarging (eLFA), normal (nLFA), and decreasing LFA (dLFA) groups. Cervical spine parameters and MRI findings were compared, and multiple linear regression identified factors associated with LFA changes. Static LFA on MRI and dynamic LFA (ΔLFA) on X-ray were evaluated for detecting cervical instability.

RESULTS

The mean LFA in normal subjects (C2/3 to C6/7) was 76.3 ± 7.2°, varying by segment and age. The LFA was significantly reduced in DCM patients (70.7 ± 11.6°). The spinal cord diameter of the adjacent vertebrae and the increased signal intensity were significant difference among eLFA, nLFA and dLFA groups. LFA correlated with vertebral body movement (β = - 3.361, P < 0.001) and cervical disc angle (β = - 0.774, P < 0.001). The static LFA cutoff for posterior slippage was 67.6°, and △LFA for instability was 12.3°.

CONCLUSIONS

Posterior cervical spine misalignment in DCM is closely linked to both horizontal and angular vertebral displacements, potentially exacerbating spinal cord injury. Static and dynamic LFA measurements provide valuable supplementary parameters for the accurate assessment of cervical instability.