Impact of postural variations on trunk rotation angle during the forward bending test in adolescents idiopathic scoliosis.

Purpose: To evaluate the impact of different positions of adolescent idiopathic scoliosis (AIS) patients and examiners on the angle of trunk rotation (ATR) measured during the forward bending test (FBT) with Scoliometer.

Methods: Adolescents who had come to the hospital for outpatient were recruited. Considering the location of the subject and the examiner, four postural combinations of ATR were measured. After measuring ATR, the subject underwent radiographic measurements for diagnosis of AIS. Mann-Whitney test was used for the inter-group reliability test in two examiners, and the Kruskal-Wallis test was used to measure intra-group differences in ATR for the four positions. The receiver operating characteristic curve and area under the curve were used to evaluate the diagnostic performance of ATR in AIS measured by different postures. Preplanned sensitivity analyses of the primary outcome were performed by subgroup.

Results: Of the 63 participants suspected of having AIS included, there was no statistically significant difference (P > 0.05) observed between ATR measurements taken in different postures. Only the measurements taken by the examiner from behind the subject demonstrated diagnostic capability for AIS (AUC = 0.73 for both feet together and apart, $P<0.05$ ). There was no statistically significant difference ( $P=0.989)$ in diagnostic ability between the subjects who stood with feet together or apart. The sensitivity analysis supports the robustness of the conclusions ( $P>0.05)$ .

Conclusion: When the examiner measured from behind the subject, AIS can be effectively diagnosed, regardless of whether the subject is standing on feet apart or feet together. There is no difference in diagnostic ability in ATR between the two forward bending positions.

Level of evidence: Level III.