Purpose: This study aimed to assess the effect of Boston brace on trunk muscles length as well as lower limbs and trunk range of motion in patients with idiopathic scoliosis.

Methods: Five patients with idiopathic scoliosis with C shape curve and mean (SD) age, height, and weight of respectively 12.61(1.16) years, 1.53(0.08) m, and 35.6(6.1) kg participated in this study. Spatiotemporal parameters, range of motion of lower limbs and trunk, and muscle fiber length of erector spinae, internal and external oblique are the variables of this study. Qualysis motion analysis system and Kistler force plate was used to obtain and record raw data. Also, we used QTM and OpenSIM software to extract data. Statistics analysis was done by SPSS ver. 22 at the significance of 0.05.

Results: Based on the results, trunk range of motion in sagittal plane decreased significantly (P=0.02), while pelvis range of motion in frontal plane increased significantly (P=0.006) during walking with brace. The changes in erector spinae and external oblique muscle fibers length were small and not significant (P>0.05).

Conclusion: Walking with brace decreases trunk range of motion in sagittal plane that can lead to change in erector spinae and external oblique muscles length. Thus, it is recommended that flexibility and rehabilitation of these muscles be considered. More studies are needed to assess these muscles weakness after a long time use of the brace.