The use of ultrasound imaging to measure midfoot plantar fat pad thickness in children

STUDY DESIGN: Descriptive and reliability study. OBJECTIVES: To design a reliable imaging method to quantify the thickness of the medial midfoot plantar fat pad in the feet of young children and to determine any between-foot (right versus left) differences in thickness. BACKGROUND: Before we can establish whether persistent fat padding in the medial midfoot or a structural collapse of the longitudinal arch is the mechanism of flatter footprints displayed by obese children, a reliable method to quantify midfoot plantar fat pad thickness in children is required. METHODS AND MEASURES: A portable ultrasound imaging system was used to quantify medial midfoot plantar fat pad thickness for the right and left foot of 14 healthy children (mean ± SD: 3.8 ± 0.8 years) using 3 different measurement techniques. Intraclass correlation coefficients (ICC) and standard error of the measurement (SEM) were calculated to assess intrarater reliability of these measurement techniques. RESULTS: Medial midfoot plantar fat pad thickness (method 1, right foot) ranged from 3.1 to 4.9 mm. Similar values were observed for methods 2 and 3. The ICC values (0.82-0.94) and SEM values (0.12-0.23 mm) suggested that all 3 methods provided good reliability. Based on an ANOVA model, there was no significant interaction and no significant main effect for side, method, or day between the measurement techniques. CONCLUSIONS: We found ultrasonography to be a reliable field tool to quantify medial midfoot plantar fat pad thickness in children. Although there was no difference in reliability across the 3 measurement techniques, the technique in which the transducer was placed directly beneath the dorsal-navicular landmark was the most time-efficient procedure to measure the thickness of the midfoot plantar fat pad in young children.