Preliminary study on ultrasound-based quantitative assessment of epiphyseal ossification angle for bone age...

Bone age (BA) assessment is crucial for evaluating pediatric growth, yet the standard radiographic method involves ionizing radiation. This study aimed to investigate the feasibility of a novel, quantitative ultrasound parameter-the epiphyseal ossification angle (OA)-as a non-invasive alternative for BA evaluation, and to examine its correlation with radiographically determined BA.

In this prospective study, 201 Chinese Han girls aged 5-14 years (mean age: 9.24±2.15 years) underwent both left wrist radiography and ultrasonography of the distal radius, distal ulna, and medial femoral condyle within a 1-week interval. The OA and the established ossification ratio (OR) were measured at each site. Composite indices-the total ossification angle (TOA, sum of OAs) and skeletal maturity score (SMS, sum of ORs)-were calculated. Radiographic BA was determined by the Tanner-Whitehouse 3 (TW3) method as the reference standard. Reproducibility was assessed using intraclass correlation coefficients (ICC), and correlations were analyzed with Pearson's method.

Both OA and OR measurements demonstrated excellent intra- and inter-observer reproducibility, with ICCs ranging from 0.81 to 0.92 and 0.78 to 0.89, respectively (all P<0.001). OA at all individual sites showed significant negative correlations with TW3 BA (radius: r=-0.686; ulna: r=-0.650; femur: r=-0.721; all P<0.001). The composite TOA demonstrated a strong inverse correlation with BA (r=-0.808, P<0.001). Similarly, OR was positively correlated with BA at all sites (radius: r=0.807; ulna: r=0.632; femur: r=0.708; all P<0.001), with SMS showing the strongest positive correlation (r=0.813, P<0.001). A linear regression model based on TOA explained 65.3% of the variance in BA (R²=0.653, P<0.001).

The ultrasound-derived OA demonstrates a strong inverse correlation with radiographic BA. The composite TOA shows particular promise as a novel, non-invasive marker for pediatric BA assessment. These findings support the feasibility of the OA as a quantitative ultrasound parameter and warrant further investigation to develop and validate clinical prediction models.