Intra- and inter-observer reliabilities of cervical sagittal radiographic measurements among evaluators with different levels of training.

OBJECTIVE: To assess the intra- and inter-observer reliabilities of cervical sagittal radiographic measurements performed by evaluators with varying levels of clinical experience. METHODS: This study analyzed lateral cervical radiographs from 14 patients who had undergone single-level anterior cervical discectomy and fusion. Four evaluators, a spine surgeon, radiologist, spine surgery resident, and medical student, measured five sagittal alignment parameters (C2-C7 Cobb angle, T1 slope, cervical sagittal vertical axis, cervical sagittal vertical axis via C-shape, and T1- C2-C7 Cobb angle). Intra-observer variability was calculated as the deviation from the median measurements. Inter-observer reliability was assessed using intra-class correlation coefficients. RESULTS: Intra-observer variability was lowest among experienced evaluators (13% for both the spine surgeon and radiologist) and highest for the medical student (19.4%). The intra-class correlation coefficients ranged from 0.54 to 0.96, indicating moderate to excellent agreement. When only the two most experienced evaluators were included in the analysis, intra-class correlation coefficients exceeded 0.88 for all parameters. CONCLUSION: Observer experience significantly influences the reliability of sagittal cervical radiographic measurements. Although less experienced evaluators demonstrate higher variability, their performance remains within acceptable limits. Standardized training protocols may help improve consistency across different levels of expertise.