The Comparison of Validity and Reliability of a Novel Smartphone-based Tool with Foot Scanner for Hallux Valgus Angle Measurement

Abstract

Objective: This study aimed to assess the validity and reliability of a novel smartphone-based tool (NSBT) for measuring the hallux valgus angle (HVA) compared to a foot scanner.

Methods: Thirty-five feet with hallux valgus underwent two measurement sessions using both the NSBT (Hallux-Valgus-meter app) and a DSI foot scanner (Iranian Daneshsalar Company). Intra- and inter-rater reliability for each tool were assessed using Cronbach's alpha and ICC(2,K). Agreement between tools was evaluated using Pearson's correlation coefficient and Bland-Altman analysis. Statistical analyses were performed in SPSS v27 (α = 0.05).

Results: The NSBT demonstrated excellent inter-evaluator reliability (ICC = 0.952, Cronbach's alpha = 0.953) and intra-evaluator reliability (ICC = 0.943, Cronbach's alpha = 0.939) (all p < 0.001). The NSBT also showed strong agreement with the foot scanner (r = 0.93, p < 0.001). Bland-Altman analysis confirmed this agreement with a small mean difference (0.34 degrees) and minimal data scatter.

Conclusion: The NSBT offers a valid, reliable, and consistent method for HVA measurement. Compared to traditional methods, it presents advantages of portability, ease of use, reduced cost, and eliminates radiation exposure. This technology has the potential to improve accessibility and efficiency in hallux valgus assessment within physiotherapy practice.