Independent Correlation Of The C1-2 Cobb Angle With Patient-Reported Outcomes After Correcting Chronic Atlantoaxial Instability

Objective: To investigate three-planar radiographic results and patient-reported outcomes (PROs) after correcting chronic atlantoaxial instability (AAI) by translaminar screw (TLS) and pedicle screw (PS) fixation, and to explore the potential association of atlantoaxial realignment with PRO improvements.Methods: Twenty-three patients who underwent Cl lateral mass screw (LMS)-C2 Us and 29 who underwent Cl LMS-C2 PS with >= 2 years of follow-up were retrospectively analyzed. Three-planar (sagittal, coronal, and axial) radiographic parameters were measured. PROs including the Neck Disability Index (NDI), Japanese Orthopaedic Association (JOA) score and the Short Form 36 Physical Component Summary (SF-36 PCS) were documented. Factors potentially associated with PROs were identified.Results: The radiographic parameters significantly changed postoperatively except the C1-2 midlines' intersection angle in the TLS group (p = 0.073) and posterior atlanto-dens interval in both groups (p = 0.283, p = 0.271, respectively). The difference in bilateral odontoid lateral mass interspaces at last follow-up was better corrected in the TLS group than in the PS group (p = 0.010). Postoperative PROs had significantly improved in both groups (all p < 0.05). Thereinto, NDI at last follow-up was significantly lower in the TLS group compared with PS group (p = 0.013). In addition, blood loss and operative time were obviously lesser in TLS group compared with PS group (p = 0.010, p = 0.004, respectively). Multivariable regression analysis revealed that a change in C1-2 Cobb angle was independently correlated to PROs improvement (NDI: beta = -0.435, p = 0.003; JOA score: beta = 0.111, p = 0.033; SF-36 PCS: beta = 1.013, p = 0.024, respectively), also age <= 40 years was independently associated with NDI (beta = 5.40, p = 0.002).Conclusion: Three-planar AAI should be reconstructed by Cl I.MS-C2 PS fixation, while sagittal or coronal AAI could be corrected by Cl LMS-C2 TLS fixation. PROs may improve after atlantoaxial reconstruction in patients with chronic AM. The C1-2 Cobb angle is an independent predictor of PROs after correcting chronic AAI, as is age <= 40 years for postoperative NDI.