Feasibility of Ultrasound in Infant Wrist and Thumb Imaging.

OBJECTIVES: To determine the feasibility of ultrasound (US) in infant lateral carpal and base-of-the-thumb imaging. We hypothesized that US would be a practical modality for visualizing the unossified structures.

METHODS: Institutional review board approval was obtained for this single-center pilot study. Healthy infants aged 12 months or younger were enrolled. Ultrasound examinations of the distal radial epiphysis through the first metacarpal were performed with a high-frequency transducer.

RESULTS: Ultrasound evaluations of the base of the thumb were performed in 18 healthy infants (mean age ± SD, 13.8 ± 9.1 weeks; 44% female). Assuming an elliptical shape, the mean areas of the scaphoid and first metacarpal epiphysis measured 0.85 ± 0.19 and 0.44 ± 0.087 cm2 , respectively. The mean areas of the trapezium and ossified first metacarpal as approximate rectangular shapes measured 0.23 ± 0.069 and 0.49 ± 0.16 cm2 . A perimeter tracing was also used as an alternative area calculation. The mean trapezium area-to-scaphoid area ratio (0.28 ± 0.10) showed less variability compared to the first metacarpal epiphysis area-to-scaphoid area ratio (0.55 ± 0.20) or first metacarpal area-to-scaphoid area ratio (0.64 ± 0.31).

CONCLUSIONS: Our data suggest that US is well suited for the evaluation of the lateral carpus and base of the thumb in young infants. These data serve as a reference to which wrist and thumb abnormalities can be compared.