Kinematic limitations during obstacle-crossing in adolescent idiopathic scoliosis

Abstract

Scoliosis is a 3D spinal deformity that is known to affect patient’s alignment on static radiographs [1] and their movement during walking or other daily life activities [2]. Crossing obstacles is a common activity that can challenge patients’ stability. However, kinematics of the obstacle-crossing movement is still unknown in adolescent idiopathic scoliosis (AIS). Are kinematics affected in patients with AIS during obstacle-crossing? 18 AIS patients with major right convexity thoracic scoliosis (Cobb: 38° [25-55°]) and 15 controls (age and sex matched: 16 years, 85% F) underwent biplanar X-rays in standing position with the calculation of 3D radiographic spinopelvic parameters. 3D movement analysis was performed during obstacle-crossing, obstacle being fixed at 30% of lower limb length, and executed once with each leg leading the movement. Kinematic parameters of the head, trunk, pelvis, lower limbs and spinal segments were calculated [3,4]. Parameters were compared between the 2 groups and the relationship between kinematic and radiographic variables was investigated. During obstacle-crossing, AIS patients showed an increased thorax extension compared to controls (-19 vs 6°, p<0.05), especially in the main thoracic segment (T3T6-T6T9= 9 vs 14°, p<0.05). Conversely, AIS patients showed a decreased lumbar lordosis when compared to controls (T12L3-L3L5=-14 vs -20°, p<0.05). Moreover, AIS patients showed an anterior rotation (-2 vs 2°) and elevation (6 vs 0°, both p<0.05) of the right shoulder. Patients also showed a decreased hip abduction of the leading leg when compared to controls (-5 vs -9°, p<0.05). The main thoracic extension was correlated to the Cobb angle (r=-0.50) and the shoulder axial rotation to the apical vertebral rotation (r=0.75, both p<0.05; Fig. 1). AIS patients are known to have back flattening with a loss of lumbar lordosis due to their spinal deformity. This spinal malalignment was shown to persist dynamically during obstacle-crossing, associated with a forward shift and elevation of the convexity-side shoulder. The backward movement of the trunk and the shoulder rotation attitude, along with the decreased hip abduction, might hinder stability during obstacle-crossing. These kinematic alterations were shown to increase with the spinal deformity (increased Cobb and apical vertebral rotation). Future studies will investigate kinematic changes in AIS patients following spinal fusion. Fig. 1 Correlations between kinematic limitations and scoliosis severity in adolescent idiopathic scoliosis during obstacle-crossing movement.Download : Download high-res image (100KB)Download : Download full-size image