Relationship between photographic head–neck posture measurements and radiographic cervical sagittal alignment in asymptomatic adults

Background Photographic assessment provides a non-invasive, radiation-free evaluation of head–neck posture. From this perspective, it is significant for clinicians. Its relationship with radiographic cervical sagittal alignment has not been comprehensively investigated. Objective This study aimed to evaluate the relationship between photographic head–neck posture measurements and radiographic cervical sagittal alignment parameters in asymptomatic adults and to assess the inter-observer reliability of both approaches. Methods Ninety asymptomatic adults aged 20–40 years were included. Radiographic parameters included Cobb C2–C7 angle, Cobb C0–C2 angle, cervical sagittal vertical axis (cSVA), T1 slope, and C2 slope. Photographic parameters included craniovertebral angle (CVA), cranial rotation angle (CRA), chin-brow vertical angle (CBVA), and head tilt angle (HTA). Measurements were performed independently by two experienced clinicians. Pearson correlation and intraclass correlation coefficient (ICC) analyses were performed . Results After correction for multiple cross-domain comparisons, weak-to-moderate correlations were detected between some radiographic and photographic parameters. The strongest cross-domain correlation was observed between cSVA and CBVA (r = 0.477, 95% CI: 0.299 to 0.623, FDR-adjusted p < 0.001). Radiographic measurements demonstrated excellent inter-observer reliability (ICC: 0.927–0.963), whereas photographic measurements demonstrated good inter-observer reliability (ICC: 0.853–0.898). Conclusion Photographic and radiographic measurements assess related but distinct anatomical constructs. Photographic methods may provide reproducible, non-invasive and radiation-free information about external head–neck posture; however, they should not be considered substitutes for radiographic evaluation when precise assessment of internal cervical sagittal alignment is required.