Degenerative characteristics of the subaxial cervical spine in patients with degenerative lateral atlantoaxial osteoarthritis: A propensity score-matched study based on computed tomography imaging

Study Design: The study design was an observational study. Objective: To investigate degenerative characteristics of the subaxial cervical spine in patients with degenerative lateral atlantoaxial osteoarthritis (AAOA). Methods: Patients with Grade 3 atlantoaxial degeneration were included in the AAOA group. Propensity score matching (PSM) was employed for cohort matching to minimize the impact of age and sex. AAOA patients were matched with non-AAOA patients at a 1:4 ratio. Cervical sagittal parameters, classifications of subaxial cervical degeneration, and the three-dimensional volume of the suboccipital muscles were all measured on computed tomography. The receiver operating characteristic curve was calculated to estimate the diagnostic ability of the logistic regression model based on risk factors of the subaxial cervical spine. Results: Fifty-six patients (23 males and 33 females) with Grade 3 atlantoaxial degeneration were identified. The severity of atlantoaxial degeneration exhibited a significantly positive correlation with increasing age. After PSM, 272 patients (55 patients in the AAOA group and 217 patients in the non-AAOA group) were ultimately enrolled. Compared to the non-AAOA group, AAOA patients exhibited significantly more severe C2/3 to C3/4 cervical facet joint degeneration (CFD) and multifidus fatty degeneration (MFD) ( P < 0.05) and C2/3 to C6/7 intervertebral disc degeneration (IVDD) ( P < 0.001). Significant atrophy of the rectus capitis posterior major was observed in AAOA group ( P < 0.001). Multivariate regression identified two independent risk factors: Severe C2/3 CFD (Odds ratio [OR], 1.55; P = 0.029) and severe C3/4 IVDD (OR, 1.61; P = 0.004). Based on C2/3 CFD and C3/4 IVDD, a logistic regression model was constructed. Moreover, the area under the curve of the model to predict AAOA was 0.807. Conclusions: Advanced age was identified as a critical risk factor for degenerative AAOA. This study also demonstrated that degenerative AAOA was not only associated with the CFD, MFD, and IVDD in C2/3–C3/4 segments but also IVDD in C4/5–C6/7 segments. These insights enhance the understanding of the impact of atlantoaxial dysfunction on the degeneration of the subaxial cervical spine and may improve AAOA detection in clinical practice.