Radiographic Assessment and Measurement Reliability in Defining Flat-Top Talus in Ponseti-Treated Clubfeet

Flat-top talus (FTT) deformity in clubfoot may lead to ankle impingement and early degenerative changes. Several quantitative radiographic parameters have been proposed to define FTT, but their reliability in children remains unclear. We aimed to compare quantitative radiographic measures and evaluate their inter- and intrarater reliability relative to qualitative assessment of talar dome morphology.

This retrospective dual-center cohort included Ponseti-treated clubfeet (2005 to 2023) with at least one adequate lateral radiograph. Two independent raters per site measured talar height (H), length (L), radius (R), the R/L and H/L ratios, the anterior talar motion segment (ATMS), the anterior distal tibial angle (ADTA), and the Meary angle. Qualitative talar dome morphology (flat vs. round) served as the reference standard. Discrimination was assessed using correlation and receiver operating characteristic (ROC) analyses. Reliability was evaluated using intraclass correlation coefficients (ICC) and Cohen Kappa (κ).

In a selectively imaged cohort, 152 clubfeet were analyzed, of which 104 (68%) were classified as FTT. FTT feet demonstrated greater talar radius, length, and R/L ratio, and smaller H/L ratio and ATMS (all P <0.05). Radius (AUC=0.88), R/L ratio (AUC=0.85), and ATMS (AUC=0.79) demonstrated the best discrimination. However, inter-rater reliability was poor for radius (ICC=0.40) and R/L ratio (ICC=0.13). In contrast, qualitative assessment demonstrated substantial agreement (κ=0.80), with near-perfect agreement in children <6 years (κ=1.0). R/L ratio-based classification showed only fair agreement (κ=0.29).

Although several quantitative parameters discriminate FTT, curvature-based measures demonstrate limited reproducibility in children. Qualitative assessment of talar dome morphology showed superior reliability and appears to be the most practical method for defining FTT in pediatric clubfoot. Quantitative measures may aid research but require pediatric-specific validation.

Level III-retrospective multicenter reliability study.