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.