Reliability and agreement of manual and automated morphological radiographic hip measurements

Objective: 

To determine the reliability and agreement of manual and automated morphological measurements, and agreement in morphological diagnoses. 

Methods: 

Thirty pelvic radiographs were randomly selected from the World COACH consortium. Manual and automated measurements of acetabular depth-width ratio (ADR), modified acetabular index (mAI), alpha angle (AA), Wiberg center edge angle (WCEA), lateral center edge angle (LCEA), extrusion index (EI), neck-shaft angle (NSA), and triangular index ratio (TIR) were performed. Bland-Altman plots and intraclass correlation coefficients (ICCs) were used to test reliability. Agreement in diagnosing acetabular dysplasia, pincer and cam morphology by manual and automated measurements was assessed using percentage agreement. Visualizations of all measurements were scored by a radiologist. 

Results: 

The Bland-Altman plots showed no to small mean differences between automated and manual measurements for all measurements except for ADR. Intraobserver ICCs of manual measurements ranged from 0.26 (95%-CI 0–0.57) for TIR to 0.95 (95%-CI 0.87–0.98) for LCEA. Interobserver ICCs of manual measurements ranged from 0.43 (95%-CI 0.10–0.68) for AA to 0.95 (95%-CI 0.86–0.98) for LCEA. Intermethod ICCs ranged from 0.46 (95%-CI 0.12–0.70) for AA to 0.89 (95%-CI 0.78–0.94) for LCEA. Radiographic diagnostic agreement ranged from 47% to 100% for the manual observers and 63%–96% for the automated method as assessed by the radiologist. 

Conclusion: 

The automated algorithm performed equally well compared to manual measurement by trained observers, attesting to its reliability and efficiency in rapidly computing morphological measurements. This validated method can aid clinical practice and accelerate hip osteoarthritis research.