The objective of this study is to translate, cross-culturally adapt, and validate the Spanish version of the Foot Posture Index (FPI-6). This clinical tool is widely used to evaluate standing foot posture through six visual criteria. The study aims to provide Spanish-speaking clinicians and researchers with a reliable and valid instrument to assess foot posture in the Spanish population, ensuring that the psychometric properties of the original scale are preserved
This study follows a prospective, observational design and will be carried out in two phases: Phase 1: Translation and Cross-Cultural Adaptation. Following international standards (forward-backward translation method), the original English FPI-6 will be translated into Spanish by two independent translators. A synthesis version will be created, followed by a back-translation into English to ensure conceptual equivalence. A pilot test will be conducted to ensure the clarity of the items. Phase 2: Validation and Psychometric Evaluation. The Spanish version of the FPI-6 will be administered to a sample of participants. To evaluate reliability, intra-rater and inter-rater reliability will be calculated using the Intraclass Correlation Coefficient (ICC). Internal consistency will be assessed using Cronbach's alpha. Construct validity will be analyzed by comparing FPI-6 scores with other validated clinical measures of foot posture
Study Type
OBSERVATIONAL
Enrollment
100
The assessment consists of the clinical application of the Spanish version of the Foot Posture Index (FPI-6). This is a non-invasive observational method where the investigator evaluates six specific criteria of the foot while the participant stands in a relaxed position. The six criteria include: talar head palpation, supra and infra-malleolar curvature, calcaneal frontal plane position, prominence in the region of the talonavicular joint, congruence of the internal longitudinal arch, and abduction/adduction of the forefoot on the rearfoot. Each item is scored between -2 and +2, providing a total score between -12 and +12
Clinical assessment of standing foot posture using the Spanish translation of the Foot Posture Index (FPI-6). This tool evaluates six criteria: talar head palpation, supra and infra-malleolar curvature, calcaneal frontal plane position, prominence in the region of the talonavicular joint, congruence of the internal longitudinal arch, and abduction/adduction of the forefoot on the rearfoot. Each item is scored on a scale from -2 to +2. The tool will be applied to a sample of children (from 5 years old) and adults to evaluate its psychometric properties, including reliability and internal consistency
Intra-rater and Inter-rater Reliability of the Spanish FPI-6
Consistency of the Foot Posture Index (FPI-6) scores evaluated through the Intraclass Correlation Coefficient (ICC). Intra-rater reliability will be assessed by one examiner repeating the test after 1-2 weeks. Inter-rater reliability will be assessed by two examiners evaluating each subject with a one-hour interval.
Time frame: Baseline and 7-14 days later
Internal Consistency of the Spanish FPI-6
Measured using Cronbach's alpha to ensure that all six items of the FPI-6 contribute coherently to the total score. A value \> 0.70 is expected.
Time frame: At Baseline (Day 1)
Criterion Validity
Correlation of the Spanish FPI-6 total score with the Foot Function Index (FFI) and the American Orthopaedic Foot and Ankle Society (AOFAS) scale using Spearman's correlation
Time frame: At Baseline (Day 1)
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