Analysis of Associating Radiologic Parameters With Clinical Outcomes After Posterior C1-2 Fusion.

Objective: To evaluate which radiologic parameters affect clinical outcomes in patients underwent posterior C1-2 fusion for atlantoaxial dislocation.

Methods: From January 2014 to December 2017, among 98 patients underwent C1-2 posterior fusion, patients with previous cervical surgery or extending to subaxial spine or basilar invagination were excluded. Finally, 38 patients were included. O-C2, C1-2, C1-C7, C2-C7 cobb angle (CA), T1 slope, C1-7, C2-7 sagittal vertical axis (SVA), and posterior atlantodental interval (PADI) were measured at preoperative and postoperative 1 year. The difference between postoperative and preoperative values for each parameter was designated as Δvalue. Postoperative subaxial kyphosis (PSK) was defined to decrease ≥ 10° at subaxial spine. Visual analogue scale (VAS), Japanese Orthopedic Association (JOA) score, Neck Disability Index (NDI) were used to evaluate clinical outcomes.

Results: Mean age was 54.4 ± 15.9. Male to female was 14 to 24. Of radiologic parameters, C1-7 SVA and PADI were significantly changed from 26.4 ± 12.9 mm, 17.1 ± 3.3 mm to 22.6 ± 13.0 mm, 21.6 ± 3.4 mm. ΔC1-2 CA was correlated with ΔC1-7 CA and ΔC2-7 SVA. ΔPADI correlates with ΔO-C2 CA. VAS correlates with ΔC1-7 CA (p = 0.03). JOA score also correlates with ΔC2-7 SVA (p = 0.02). NDI was associated with ΔPADI (p < 0.01). The incidence of PSK was 23.7%, and not significant with clinical outcomes.

Conclusion: ΔC1-2 CA was correlated with ΔC1C7 CA, ΔC2-7 SVA. ΔC1-7 CA, ΔC2-7 SVA, and ΔPADI were the key radiologic parameters to influence clinical outcomes. Postoperative C1-2 angle should be carefully determined as a factor affecting clinical outcomes and cervical sagittal alignment.