Craniovertebral Angle Measurement with MicroDicom and Digital Photography Method, A Reliability Testing

Abstract

Background: The craniovertebral angle (CVA) is a practical photogrammetric metric for quantifying forward head posture (FHP) in clinical populations, yet reliability data for measurements analyzed with MicroDicom in symptomatic cohorts are limited. Objective: To determine the intra- and inter-rater reliability of CVA measured from standardized digital photographs analyzed with MicroDicom in patients with myofascial pain syndrome (MPS). Methods: In a GRRAS-informed reliability study, 40 adults with MPS were photographed in a standardized seated posture across three consecutive days. Three raters (A–C) independently acquired images (three per day) and measured CVA in MicroDicom 2023.3. For intra-rater reliability, each rater’s three day means per participant were analyzed using ICC(3,1) and ICC(3,3). For inter-rater reliability, each rater’s grand mean across days was used to estimate ICC(2,1) and ICC(2,3). Absolute error indices (SEM, MDC9595 CV) and Bland–Altman agreement (bias, 95% limits of agreement [LoA]) were reported. Day effects (within rater) and mean differences between raters were tested with Friedman’s test (k=3, df=2). Results: Mean CVA values were similar across raters (A 42.83°, B 42.49°, C 42.68°). Intra-rater reliability was good to excellent (ICC(3,1)=0.865–0.889; ICC(3,3)=0.952–0.960). Inter-rater reliability was excellent (ICC(2,1)=0.960, 95% CI 0.930–0.978; ICC(2,3)=0.986). Absolute error was small (SEM 0.833–0.919°) with MDC9595 2.31–2.55° (intra-rater) and 2.40° (inter-rater); CV ≈5%. Bland–Altman analyses showed minimal bias (A vs B +0.34°, B vs C −0.19°, A vs C +0.15°) with 95% LoA within ±2.4° and no proportional bias (slopes <0.1). No significant day effects were observed for raters B and C; rater A showed a small, non-significant trend (p=.060). A small between-rater mean difference was statistically detectable (χ²(2)=6.752, p=.034) but clinically trivial given the high ICCs and narrow LoA. Conclusion: Standardized smartphone photogrammetry analyzed with MicroDicom yields highly reproducible CVA measurements in MPS, with SEM <1° and MDC9595 ≈2.3–2.6°. The protocol is suitable for routine assessment and longitudinal monitoring of FHP in clinical settings, particularly where low-cost, radiation-free methods are preferred. Future work should isolate pure rating agreement using shared images and validate against radiographic or 3D motion-capture references.