Prevalence and distribution of cervical facet joint degeneration in patients with cervical spondylotic myelopathy without/with instability and ossification of the posterior longitudinal ligament-a comparative study.

Objectives: To compare the prevalence and distribution characteristics of the grade of cervical facet joint degeneration (FJD) among patients with cervical spondylotic myelopathy without/with instability (CSM/CSMI), and ossification of the posterior longitudinal ligament (OPLL). Furthermore, to compare the differences in sagittal parameters and preoperative clinical symptoms between patients with mild and severe FJD.

Methods: The study enrolled 253 patients who underwent surgical treatment at our institution (90 CSM, 79 CSMI, 84 OPLL). A 5-grade computed tomography classification was used to assess bilateral cervical facet joint degeneration from C2/3 to C6/7, with higher grades indicating more severe degeneration. Patients in CSM, CSMI, and OPLL groups were divided into two subgroups separately according to the sum of bilateral FJD grades from C2/3 to C6/7: mild group and severe group. The sagittal parameters of the cervical spine on X-ray, as well as the preoperative Japanese Orthopaedic Association (JOA) score and visual analogue scale (VAS) for neck pain, were compared between the subgroups.

Results: The prevalence of grade 1 to 5 FJD in CSM, CSMI, and OPLL patients was: 77.5%, 17.8%, 3.6%, 1.1%, and 0% for CSM; 62.0%, 25.2%, 7.7%, 3.0%, and 2.1% for CSMI; and 72.4%, 24.4%, 2.2%, 0.3%, and 0.7% for OPLL. The grade of FJD at C2-6 was significantly higher in the CSMI group than the CSM and OPLL groups (P < 0.05). The grade of FJD was highest at C4-C5 in CSM and CSMI groups, while it gradually increased from C3-C4 to C6-C7 in the OPLL group. Patients in severe subgroup exhibited pronounced cervical lordosis, T1 slope, cervical sagittal vertical axis (cSVA), and neck pain (P < 0.05).

Conclusions: The grade of FJD is more severe in patients with CSMI than others. The grade of FJD in CSM and CSMI patients was most severe at C4-C5 level, while OPLL patients had increasingly severe FJD from C3-C7 levels, with maximal degeneration observed at C6-C7. Patients with severe cervical FJD in CSM, CSMI and OPLL groups exhibited pronounced cervical lordosis, increased T1 slope, elevated cSVA, and heightened neck pain.