A study was conducted on adolescents studying at a sports school in Jining from March to June 2023. Age, height and other information were recorded. Bone age assessment by X ray were performed within 1 week with an endocrinologist interpreted the bone age using the Greulich-Pyle atlas. Two sonographers scanned a total of 7 sites in the hand, wrist and knee joint of the non-dominant side (including the dorsal side of the third metacarpal head, the ulnar styloid process, the radial styloid process, the medial and the lateral femoral epicondyle, dorsal tibia, and medial tibial condyle). The ultrasonic epiphyseal cartilage thickness (UECT) was measured and its correlation with bone age was analyzed. Intraclass correlation coefficient (ICC) was used to evaluate the reliability and repeatability of UECT measurement.

A total of 141 adolescents were included, with 80 males and 61 females. The average age was 13 (12-14) years old. The average bone age was 15(13-17) years in males and 16 (14-17) years in females. The proportion of the males and females whose bone age was 1 year older than chronological age was 60% and 67%, respectively, and the height of the males was significantly higher than that of the females(P < 0.001). The UECT of 7 sites in the males and females decreased with the increase of bone age, and there was a significant negative correlation between UECT and bone age. In males, UECT was highly and negatively correlated with bone age (|r|≥0.80), while in females, it was moderately and negatively correlated (0.65≤|r|≤0.75). The correlation between the sum of UECT at seven sites and bone age reached high levels in both sexes(|r|=0.93, |r|=0.80).When 3 sites of hand and wrist or 4 sites of knee joint were selected separately, the UECT of the females was highly negatively correlated with bone age (|r| ≥0.76), while that of the males showed a very high correlation (|r| ≥0.90). The measurement consistency of UECT in all seven sites was good (ICC≥0.75).

Ultrasound can observe and describe the developmental change of long bone, and UECT has potential value in quantitative evaluation of bone maturity.

The study selected healthy adolescents from a middle school in Shandong Province in June 2023. Ultrasonic images were collected from five anatomical sites (the styloid process of the ulna, the styloid process of the radius, the lateral epicondyle of the femur, the medial condyle of the tibia, and the posterior median sagittal plane of the tibia). The second ossification center and epiphyseal area on these 2D ultrasound images were delineated to calculate AOR. This ratio was then compared with radiographic bone age measured by Greulich-Pyle (GP) atlas. Inter- and intra-observer consistency was evaluated using intraclass correlation coefficient (ICC) and the Bland-Altman method.

A total of 179 healthy adolescents (109 males and 70 females) were included. For both genders, AOR of each site exhibited a significant to high correlation with radiological bone age (r=0.60~0.91). The sum of the AORs of the five sites showed a high correlation with radiological bone age (males: r=0.95, females: r=0.87). Measurements of AOR by different doctors and the same doctor at different times demonstrated high repeatability (inter-observer: ICC=0.926, P < 0.001, intra-observer: ICC=0.954, P < 0.001).

The sum of AORs in adolescents is highly correlated with radiographic bone age, and the measurement method shows high repeatability. The AOR is a reliable parameter for the ultrasonic quantitative assessment of bone age in adolescents.

This cross-sectional study used stratified sampling to select adolescents aged 11-15 years from a sports school and some ordinary middle schools in Shandong Province in June 2023. The participants were divided into two groups: competitive sports group (high exercise intensity), and general sports group (moderate exercise intensity), based on their exercise intensity. Ultrasound images of long bones from nine body regions (including 3 upper limb bones and 6 lower limb bones) were collected for both groups. Two sonographers interpreted the images and calculated the ultrasound OR values (the ratio of ossification center length to epiphyseal length on the standard ultrasound section). The intraclass correlation coefficient (ICC) was used to assess the consistency of image interpretation between the observers. Differences in ultrasound OR values between the two groups were compared, and multivariate Logistic regression analysis was performed to assess the correlation between ultrasound OR values and exercise intensity.

A total of 252 adolescents who met the inclusion and exclusion criteria were included, with 154 in the competitive sports group (97 males and 57 females) and 98 in the general sports group (52 males and 46 females). The median height and average daily exercise duration were significantly higher in the competitive sports group than in the general sports group (all P < 0.001). The overall ICC for the interpretation of ultrasound OR values of long bones at 9 sites in 50 adolescents by the two sonographers was 0.930 (range: 0.853-0.964), indicating excellent inter-observer consistency. The medial femoral ultrasound OR values were higher in the competitive sports group than in the general sports group for both males and females (males: 0.87±0.07 vs. 0.84±0.04, P=0.025; females: 0.90±0.06 vs.0.85±0.14, P=0.027). Additionally, the differences in ultrasound OR values between the groups were observed in the lateral femoral and fibular bones in males and the radial bone in females (all P < 0.05). Multivariate Logistic regression analysis showed that the reciprocal of the medial femoral ultrasound OR value was correlated with exercise intensity (OR=0.046, 95% CI: 0.012-0.145, P=0.043), indicating that a decrease of 0.1 in the reciprocal of the medial femoral ultrasound OR value (equivalent to an increase of approximately 0.05-0.10 in the ultrasound OR value) was associated with a 2.17-fold increase in the likelihood of high-intensity exercise.

The medial femoral ultrasound OR value was correlated with exercise intensity among adolescents. This indicator may serve as an objective imaging parameter for assessing whether adolescent exercise meets recommended standards.