Comparison of radiological measures for diagnosing flatfoot

BackgroundIn the Taiwanese military, flatfoot is indicated by a calcaneal-fifth metatarsal angle (arch angle) ≥165°. However, the arch angle is not always easily defined.PurposeTo assess correlations between the arch angle and other radiographic measures and thus identify an alternative radiographic measure for diagnosing flatfoot.Material and MethodsEighty-seven male Taiwanese military recruits were studied (median age 22 years, interquartile range 20–23 years). Lateral, weight-bearing radiographs were taken. Five radiographic measurements, including the calcaneal-fifth metatarsal angle (arch angle), medial arch angle (MAA), calcaneal pitch angle (CP), talus angle (TA), and talar-first metatarsal angle (TFM) were made. Correlations between the arch angle and all other measures were determined. A cut-off value for predicting flatfoot (arch angle ≥165°) was determined for each measure using the Youden index and receiver-operating characteristic (ROC) curves were generated for each measure to assess diagnos...