Abstract
Background: The Foot Posture Index (FPI-6) is a validated and rapid clinical method for evaluating standing foot posture through assessing six individual criteria. Although it has been widely used without radiographic examination, evidences for correlation of FPI-6 with radiographic parameters remain scanty. The objective of this study is to investigate the correlation of FPI-6 with radiographic measurements and to assess the feasibility of FPI-6 for clinical evaluation of standing foot postures. Methods: Sixty patients (M:F,33:27, mean age 62 ) of foot and ankle symptoms and 40 asymptomatic male volunteers (age, 20-28), were included in this study. FPI-6 scores were evaluated by 4 raters and inter-rater reliability of FPI-6 was assessed by intraclass correlation coefficient (ICC). Radiologic measurements including talo-first metatarsal angle (TMA), Meary’s angle (MA), talonavicular coverage angle (TNCA), talocalcaneal angle (TCA), calcaneal pitch angle (CPA), and hindfoot alignment angle (HAA) were measured. For the correlation analysis between FPI-6 and radiographic parameters, statistical analysis was performed using Pearson’s correlation test.Results: Inter-rater reliability was ‘high to excellent’ among raters. However, FPI-6 score was more repeatable in patients group and in more experienced raters. In total group, FPI-6 score was correlated with TNCA, TMA, lateral TCA, MA, and HAA. Especially, TNCA and HAA were more strongly correlated among them. When we analyzed the subdomains of FPI-6, the congruence of the medial longitudinal arch and the prominence in the region of the talonavicular joint were most strong indicators for TNCA and HAA, respectively. Conclusion: This study manifested that not only the feasibility of the FPI-6, but also its correlation to radiographic parameters, is significant for both the patients and the asymptomatic group. We assert that FPI-6 scoring system can be used as a first-line tool for foot posture assessment in clinics without radiographic evaluation if used carefully.