Reliability and validity of Foot Posture Index (FPI-6) for evaluating foot posture in participants with low back pain

Abstract

Previous studies have demonstrated that Foot Posture Index (FPI-6) is a valid and moderately reliable tool to evaluate foot posture. However, data about reliability and validity of FPI-6 in the assessment of foot posture in people with low back pain (LBP) is lacking. To investigate reliability and validity of FPI-6 in the assessment of foot posture in people with LBP. Thirty volunteers with LBP, aged 20–64 years, were recruited for the research and assessed by two raters. The data measured by different raters on the same day were used to calculate the inter-rater reliability. The data measured by the same rater on different dates were used to calculate the test–retest reliability. The reliability of FPI-6 was tested with intraclass correlation coefficient (ICC), and absolute reliability with standard error of measurement (SEM), minimal detectable change (MDC) and Bland–Altman analysis. The validity of FPI-6 was tested with Exploratory Factor Analysis (EFA) and Spearman's correlation coefficients. The FPI-6 indicated excellent inter-rater and test–retest reliability in the evaluation of foot posture in people with LBP (ICC = 0.97 and 0.95). The agreement for inter-rater and test–retest was excellent based on the SEM (SEM = 0.12) and MDC value (MDC = 0.33). Bland–Altman plots showed that there was no significant systematic bias for the agreement on the ground of low mean difference (< 1). The EFA suggested that the fit indices were considered acceptable according to the Kaiser–Meyer–Olkin (KMO) value (KMO = 0.620) and Bartlett's sphericity test (P < 0.01). There was a statistically significant positive correlation between each item and total score of FPI-6 because the Spearman’s correlation coefficient of six items were all > 0.3 (P < 0.01). The inter-rater and test–retest reliability and validity of FPI-6 on people with LBP were proved reliable. It might be considered a reliable and valid adjunctive tool to detect possible changes of foot posture after interventions in patients with LBP.

Translation, Cross-Cultural Adaptation, and Validation of the Foot Posture Index (FPI-6)—Italian Version

“…The population sample of previous validations available in the literature was highly variable in terms of the subjects' number and age [14,28,[30][31][32][33][34].…”

A Short-Term Evaluation of Foot Pronation Tendency in Healthy Recreational Runners

“…The FPI consists of six criteria, and to evaluate, the participant must be in a comfortable standing position where they support their feet as they usually do naturally. The evaluation lasted approximately two minutes, the maximum for each of the feet, and afterwards, an independent total value is obtained for each subject that indicates a prone, supinated, or normal posture that goes from −12 to + 12 values [19,[27][28][29][30]. The six items are as follows: palpation of the talus, inframalleolar and supramalleolar curvature, position of the calcaneus in the frontal plane, prominence of the talo-scaphoid region, congruence of the medial longitudinal arch, and adduction or abduction of the forefoot (Figure 1).…”

Immediate effect of anti-pronation foot taping on myoelectric activity of knee muscles in patellofemoral pain syndrome: a randomised controlled trial

“…A score from −12 (highly supinated) to +12 (highly pronated) was obtained with scores from 0 to 5 indicating normal foot posture, + 6 to + 9 pronated, 10+ highly pronated, −1 to −4 supinated and −5 to −12 highly supinated. The Foot Posture index has moderate to good reliability and its content, construct, criterion, and predictive validity are acceptable as a simple-to-use, cost-effective, clinical measurement tool that can be used for screening, diagnosis and prognosis for most disorders of the foot and ankle [28].…”