Bilateral Asymmetry in Kinematic Strategies for Obstacle-crossing in Adolescents with Severe Idiopathic Thoracic Scoliosis

Introduction: Adolescent idiopathic scoliosis (AIS) is the most common three-dimensional spinal deformity pathology during adolescence, often accompanied with sensory integration and proprioception problems, which may lead to abnormal postural control and altered end-point control during functional activities. This paper identifies the effects of AIS on the end-point control and on angular kinematics of the trunk and pelvis-leg apparatus during obstacle-crossing for both the concave- and convex-side limb leading.

Materials And Methods: Sixteen adolescents with severe Lenke 1 AIS (age: 14.9 ± 1.7 years, height: 154.7 ± 5.0 cm) and sixteen healthy controls (age: 14.8 ± 2.7 years, height: 154.9 ± 5.6 cm) each walked and crossed obstacles of 3 heights with either the concave- (AIS-A) or convex-side (AIS-V) limb leading. Angular motions of the trunk, pelvis and lower limbs, and toe-obstacle clearances were measured. Two-way analyses of variance were used to study between-subject (group) and within-subject (limb and height) effects on the variables. Whenever a height effect was found, a polynomial test was used to determine the linear trend. α = 0.05 was set for all tests.

Results: Patients with AIS significantly reduced pelvic downward list but increased dorsiflexion in both stance and swing ankles at leading limb crossing when compared to controls (p < 0.05). During AIS-A, additional kinematic modifications were observed, i.e., increased stance hip adduction (4.2 ± 0.8°, p = 0.005) and increased swing knee flexion (12.6 ± 1.4°, p = 0.106), with significantly decreased leading toe-clearance (AIS-A: 121.4 ± 6.7 mm, controls: 140.1 ± 5.6 mm, p = 0.031).

Conclusions: Patients with AIS adopted an altered kinematic strategy for successful obstacle-crossing. With the concave-side limb leading, more joint kinematic modifications with reduced toe-clearance were found when compared to those during the convex-side limb leading, suggesting an increased risk of tripping. Further studies on the kinematic strategies adopted by different types of AIS will be needed for a more complete picture of the functional adaptations in such patient group.