Purpose or Case Report: Radiographic bone age determination is part of the routine evaluation of suspected growth disorders. Simplicity and low cost are its major advantages but ionizing radiation should be taken into consideration. Conventional ultrasonography (US) has proven effective to identify ossification centers of the hand and wrist between 0 and 24 months of age. It may become an innocuous follow-up tool for patients with growth disorders. We aimed to asses the chronological US emergence of the ossification centers of the hand and wrist in healthy infants between 2 and 4 years of age.
Methods & Materials: Cross-sectional study of healthy patients aged between 24 and 44 months (n=96, girls n=47). After written parental consent, all patients underwent US evaluation of the left hand and wrist to identify and measure the different bone nuclei. For statistical analyses, patients were divided in 3 age ranges: 24-29 months, 30-35 and 36 or over.
Results: Size-for-age relation showed linear increase of the measured nuclei. Girls showed an earlier emergence of the evaluated nuclei and a trend to a greater size than age-range-matched boys, less significantly with age progression. Between 24-29m, all patients had their Hamate, Capitate and distal epiphysis of the radius nuclei present. The second metacarpophalangeal joint (index finger) followed in order of emergence, fully present in girls and in almost every boy (p=ns) between 24-29m. The proximal epiphysis of the first metacarpal bone (thumb) followed in order of appearance almost at the same time with the triquetrum, in accordance with the radiographic atlas. The nucleus of the Thumb was present significantly earlier in girls during the first age-range (OR 27.4, 95%CI: 3.28, 229.7 p<0.001). Between 30-36m of age, sign-test showed it should be present in girls (p=0.016) and not necessarily in boys (Sign-test p=0.69). After 36m of age it was present in all the patients. Girls showed a trend to earlier emergence of the Triquetrum, becoming more frequent with age progression but not fully present over 36months of age. Lunate nucleus was absent in both groups between 24-29m (Sign-Test p<0.001 for both). After 36m it could be either present or absent in girls, but most likely absent in boys (Sign test for boys p=0.02).
Conclusions: Conventional US allows proper identification of the ossification centers of the hand and wrist and may become an innocuous follow-up tool for patients with growth disorders.