Evaluating intraoperative C2 slope as a radiographic guide for cervical deformity correction

Abstract

Achieving and maintaining optimal sagittal alignment is a key goal in cervical deformity correction, yet reliable intraoperative tools to guide alignment remain limited. The C2 slope (C2S) is a simple parameter that reflects the relationship between the upper thoracic and cervical spine and has been associated with health-related quality of life. However, its role as an intraoperative guide for alignment correction has not been fully explored. This study analyzed 45 patients with cervical deformity who underwent correction with at least 2-year follow-up. Intraoperative lateral radiographs were obtained before final construct assembly, and C2S was actively measured and used to guide correction through surgical adjustments. Radiographic parameters-including C2S, C2-7 lordosis, T1 slope, T1 slope minus cervical lordosis (T1S-CL), and sagittal vertical axis-were evaluated preoperatively, intraoperatively, and during follow-up. Clinical outcomes included visual analog scale for neck and arm pain, Neck Disability Index, Japanese Orthopedic Association score, and EQ-5D. Both C2S and T1S-CL demonstrated significant correction which remained stable during follow-up. Final C2S and T1S-CL also showed significant correlations with clinical outcomes. These findings suggest that intraoperative C2 slope may serve as a practical reference for guiding alignment correction and could contribute to favorable radiographic and clinical outcomes.