Distribution Pattern of Cervical Disc Degeneration Is Associated With Slippage Direction in Degenerative Cervical Spondylolisthesis: An Age- and Sex-Matched Analysis.

Abstract

Retrospective comparative study. To identify intrinsic factors associated with slippage direction in degenerative cervical spondylolisthesis (DCS) using an age- and sex-matched analytical framework. DCS occurs as either anterior cervical spondylolisthesis (AS) or posterior cervical spondylolisthesis (PS), yet the determinants of slippage direction remain poorly understood. Prior studies suggest associations with cervical alignment parameters; however, demographic differences between AS and PS populations may confound these findings. We retrospectively reviewed 472 consecutive patients who underwent cervical spine surgery for cervical myelopathy at a single institution between 2013 and 2025. Among them, 111 patients with radiographic cervical spondylolisthesis were identified and categorized into AS (n=34) and PS (n=77) groups. Propensity score matching for age and sex generated 24 matched pairs. Cervical sagittal alignment parameters, muscle cross-sectional areas (CSA), facet joint orientation asymmetry, and intervertebral disc degeneration, assessed using the Pfirrmann classification, were compared between groups. AS and PS demonstrated contrasting patterns of disc degeneration and sagittal alignment. AS was associated with significantly more advanced lower cervical disc degeneration, particularly at C5/6 and C6/7, but relatively mild degeneration at the spondylolisthetic level. In contrast, PS was associated with more advanced disc degeneration at the spondylolisthetic level but relatively preserved lower cervical discs. AS showed a smaller C2-C7 angle and greater C2-C7 sagittal vertical axis, indicating relative sagittal imbalance, whereas PS showed a more lordotic sagittal profile. In contrast, cervical muscle CSA, flexor-extensor balance ratios, and facet joint orientation asymmetry did not differ between groups. Slippage direction was associated with the distribution of cervical disc degeneration and sagittal alignment, rather than cervical muscle morphology or facet orientation asymmetry. These findings suggest that disc degeneration patterns and sagittal compensatory capacity may contribute to the directional characteristics of DCS.