Comparison of Various Radiological Measures for Diagnosing Flatfoot: A Diagnostic Accuracy Study

Research Objectives: - To identify the best radiographic measures to diagnose flatfoot.
- To determine the cutoff values for the five radiographic measures, including calcaneal pitch (CP), talar-first metatarsal angle (TFM), lateral talar angle (LTA), talar inclination angle (TIA), and navicular index (NI).
- To explore the relationships among different sets of radiographic measures by maintaining the arch angle as the reference value.

Design: cross-sectional

Setting: The study was conducted in the Department of Physical Therapy, King Abdulaziz University.

Participants: Foot Posture Index (FPI ≥ +6) was used to screen the flatfoot. Subjects who scored ≥+6 for one or both feet were included in the study. Subjects with any history of surgery or restricted foot and ankle range of motion were excluded. A total of 32 healthy young females were recruited.

Interventions: Foot X-rays were taken for all eligible subjects from a lateral weight-bearing view. The five angles and one index were measured on the radiographs to measure flatfoot.

Main Outcome Measures: To predict flatfoot, the receiver-operating characteristic (ROC) test was conducted for the five radiographic measures, compared to the arch angle. Matthews correlation coefficient (MCC) was performed to determine the cutoff values for all radiographic measurements.

Results: The strongest relationship was found between the arch and CP angles [r = −0.91, p ≤ 0.0001, 95% confidence interval (CI) (from −0.94 to −0.84)]. Also, other significant relationships existed between arch angle and NI [r = 0.62, p ≤ 0.0001, 95% CI (0.42 to 0.76)], and TFM [r = 0.50, p ≤ 0.0001, 95% CI (from 0.266 to 0.68)]. CP angle with a cutoff value of 12.40 demonstrated the highest accuracy level with a value of 100% sensitivity and specificity followed by NI which showed 82% sensitivity and 89% specificity.

Conclusions: CP angle and NI are simple and accurate determinants of the flatfoot which can be easily applied in clinical contexts. However, the findings of this study generate reference values for various radiographic measurements which can be used to indicate the flatfoot.

Author(s) Disclosures: No conflict of interest for this study.