Position of the major curve influences asymmetrical trunk kinematics during gait in adolescent idiopathic scoliosis

Background and purpose Adolescent idiopathic scoliosis (AIS) is a structural, lateral curvature with rotation of the spine that develops around puberty. The influence of this spinal deformity on three-dimensional trunk movements during gait has not yet been elucidated. The aim of this study was to determine the influence of spinal curve pattern (single thoracic curve vs. single lumbar curve) on trunk kinematics during gait. Methods Twenty-two patients with a single thoracic curve (Lenke type 1) and 17 patients with a single lumbar curve (Lenke type 5) were included in this study. Trunk symmetry in the sagittal, coronal, and transverse planes during gait was evaluated using an optoelectronic motion capture system. Results In the type 1 group, the trunk was significantly rotated towards the concave side in the transverse plane during gait (mean difference of transverse rotation angle between concave side load and the convex side load, 8.8 ± 0.6°, p < 0.01). In the type 5 group, the trunk was significantly rotated towards the convex side in the coronal plane throughout the stance phase of gait (mean difference of coronal inclination angle, 1.9 ± 0.3°, p < 0.05). Conclusions The AIS patients with a single thoracic curve showed asymmetrical trunk movement in the transverse plane, and patients with a single lumbar curve showed asymmetrical trunk movement in the coronal plane. These results indicate that the spinal curve pattern influenced trunk kinematics, and suggest that the global postural control strategy of patients with AIS differs according to the curve pattern.