Lumbar spine coordination during axial trunk rotation in adolescents with and without right thoracic idiopathic scoliosis.

Abstract

Adolescent idiopathic scoliosis (AIS) is a complex deformity that often leads to loss of coordination and dynamic posture. However, there is a lack of understanding on inter-segmental coordination in AIS. The purpose of this study was to compare spinal range of motion (ROM), as well as the relations to coupling angles (CA) in the spinal region during trunk rotation, between AIS and control subjects. There were 14 subjects with right thoracic AIS and 18 control subjects who participated in the study. All subjects were asked to perform five repeated axial trunk rotations in standing while holding a bar. The outcome measures included ROM at the first thoracic spinous process (T1), the seventh thoracic spinous process (T7), the twelfth thoracic spinous process (T12), and the first sacrum spinous tubercle (S1) by the motion capture system. The CA in each spinal region (trunk, lumbar spine, and lower and upper thoraces) were analyzed while considering age and body mass index (BMI). The Cobb angle demonstrated positive moderate relationships with ROM at T7 (r=0.62, p=0.04) and the CA in the upper thorax (r=0.69, p=0.02) in the AIS group. There was no CA difference at the spinous processes between groups; however, the lumbar spine ROM significantly decreased in the AIS group (t=2.40, p=0.02). The BMI demonstrated moderate relationships on the lumbar spine (r=-0.67, p=0.02) in the AIS group and the lower thorax (r=0.59, p=0.01) in the control group. The lumbar spine was significantly dissociated in the AIS group during trunk rotation, although the Cobb angle demonstrated positive relationships with ROM at T7. Collectively, the inter-segmental CA indicated that the AIS group compensated more independently to the right thoracic convexity. MINI ABSTRACT: The coordinated trunk rotations in the adolescent idiopathic scoliosis (AIS) group were compared with the control subjects. The lumbar spine motion was dissociated with the thorax in the AIS group and was negatively correlated with body mass index. Clinicians need to consider thorax convexity and dissociated lumbar motion for compensatory and rehabilitation strategies.