Purpose: To investigate the threshold of the curve difference on ultrasound measurement relative to the previous radiographic measurements to detect curves progression in children who have idiopathic scoliosis (IS).
Methods: Two hundred children with IS (F:170, M:30; mean age: 14.6 ± 1.9) were recruited from a single center. A retrospective study on comparing the current ultrasound measurements with the previous radiographic measurements with threshold values from 3° to 8° to detect curve progression was conducted. The receiver operating characteristic (ROC) analysis, accuracy (ACC), and odd ratio (OR) were calculated to determine the optimal threshold value of the curve differences between ultrasound and previous radiographic measurement.
Results: Both thresholds of 4° and 5° for curve difference from ultrasound scans presented the sensitivities ≥ 0.90 and specificities ≥ 0.85, and can reduce by 73 and 79% of radiographs on the studied subjects, respectively. Especially, for 4° threshold, the negative likelihood ratio (LR-) was only 0.08, which indicated that there is only 8% probability that the subject has progressed if the US measurement detected non-progression.
Conclusions: The ultrasound imaging method can be applied to identify curve progression in children with IS. Four degree is the preferred threshold value to detect the curve which had progressed, since it also had the lower rate of undetected progressed cases (false negatives).
Keywords: Curve progression; Idiopathic scoliosis; Sensitivity and specificity; Threshold of curve progression; Ultrasonic imaging method.