Development, validation, and psychometric analysis of Foot and Ankle Flexibility Index (FAFI)

Abstract

Objective To develop a new diagnostic tool for joint hypermobility of the paediatric foot and ankle, based on a dichotomous scoring system, the validated Lower Limb Assessment Score (LLAS). With separation of the foot and ankle items, we obtained a new diagnostic tool for joint hypermobility of the foot and ankle, specifically, based on a dichotomous scoring system. Methods A total of 205 children between 5 and 10 years of age participated in the present cross-sectional study. The new tool Foot and Ankle Flexibility Index (FAFI) was the choice of the last 7 items of LLAS, which are specific to assess the foot and ankle. The internal consistency was measured with Cronbach’s test. Kappa statistics with 95% CI were calculated to verify the level of inter-rater and intra-rater agreement for the FAFI test. Results Cronbach's alpha returned 0.82. The correlations between items returned a mean of 0.59 (range: 0.43–0.74). The discrimination score on the ROC curve (4 points) showed that the model can be used to identify children with joint hypermobility of the foot and ankle. Conclusions This study identified high reliability between evaluators, and high sensitivity and specificity, for a new reliable and valid tool for the diagnosis of foot and ankle joint hypermobility.