In the scoliosis screening program of the Student Health Service (SHS), Department of Health (DH), in Hong Kong, more than 50% of screened school children prescribed with x-ray examination basing on the screening protocol did not have Cobb angle greater than the referral threshold of 20°; ie they did not need specialist referral and thus were subjected to unnecessary x-ray exposure. Our primary objective is to determine whether a new radiation-free ultrasound system could identify subjects with Cobb angle greater than the referral threshold of 20° thus avoiding unnecessary x-rays in the referral workflow. The secondary objective is to evaluate if Angle of Trunk Rotation (ATR) can further increase the accuracy of ultrasound assessment.

This study is an extension of the registered project entitled "Using Radiation-free Ultrasound for Screening Scoliosis Among School Children in Hong Kong to Reduce Unnecessary X-ray Exposure", (ClinicalTrials.gov Identifier: NCT03135665), however focusing on validity of ultrasound measurement for immature female subjects aged around ten with year since menarche equal to or less than 9 months, who are prone to curve progression, and thus are among the most critical group in clinical management of scoliosis for regular monitoring, treatment decision, and brace indication.

Inclusion Criteria:

i. School children in Hong Kong attending School Screening Program provided by Student Health Service ii. Recommended for radiographic assessment in the scoliosis screening program iii. Female with year since menarche of equal to or less than 9 months

Exclusion Criteria:

i. Patients with standing height <1 m, or >2 m ii. Patients with body mass index (BMI) ≥25 kg/m2 iii. Subjects with skin diseases iv. Subjects with fracture or wound that affect ultrasound scanning v. Subjects with ferromagnetic implants vi. Subjects with surgery done for the spine vii. Subjects with winged scapula or other irregularity of back contour that affect ultrasound scanning viii. Subjects who cannot stand steadily during scanning ix. Subjects with allergy to ultrasound gel

Female with year since menarche (YSM) of equal to or less than 9 months