Validation of the foot profile score.
McCahill J., Stebbins J., Lewis A., Prescott R., Harlaar J., Theologis T.
BACKGROUND: There are numerous static measures of foot posture but there is no published score of dynamic foot motion. Three-dimensional gait analysis can include a multi-segment foot model like the Oxford Foot Model (OFM) to comprehensively quantify foot kinematic deviations across the gait cycle but it lacks an overall score, like the Gait Profile score (GPS), used to summarize the quality of lower extremity motion. RESEARCH QUESTION: This paper introduces the Foot Profile Score (FPS), a single number, analogous to the GPS but based on kinematic data of the OFM. The aim of this study is to validate the FPS by studying its properties and design, and analyse it against a clinical assessment of foot deformity. METHODS: Concurrent validity was established for the FPS analysing the relationship with Clinical Foot Deformity Score (CFDS) in 60 subjects with a condition affecting the lower limbs globally Content validity was established for the six Foot Variable Scores (FVS) that make up the FPS using a multiple regression of the CFDS on the 6 FVS in the 60 subjects. Predictive validity was established analysing the relationship of the FPS and GPS comparing 60 global involvement subjects with 60 subjects with isolated foot deformity. RESULTS: Pearson correlation between the FPS and CFDS was significant at 0.62 (p < 0.001). Each element of FVS contributes positively to predicting the CFDS with R2 = 0.456 (p < 0.001). FPS contributed independently to the prediction of CFDS (t = 3.9, p < 0.001). The correlation between the GPS and FPS in the global involvement group was significant at r = 0.64 (p < 0.001), while there was no correlation found with r = 0.08 (p = 0.54) in the foot deformity group. SIGNIFICANCE: The FPS is the first validated score of dynamic foot motion.