A systematic review and meta-analysis of sagittal cervical spine parameters: Normative values, correlation with quality of life, and biomechanical modeling

Quantitative evidence shows that cervical alignment is prognostically decisive rather than merely descriptive. Across several clinical cohorts, a C2-7 sagittal vertical axis > 40 mm or a T1-slope minus cervical-lordosis mismatch > 15-20° consistently predicted clinically meaningful disability as measured by NDI, EQ-5D and SRS-22. These thresholds, supported by biomechanical modelling, define actionable targets for surgical planning, rehabilitation and long-term follow-up. Standardized measurement protocols and patient-specific reference ranges are now the critical next steps to transform these radiographic markers into personalized care pathways and prospective interventional trials.