Abstract: BACKGROUND: Static imaging parameters in adolescents with Lenke type 5 adolescent idiopathic scoliosis suggest that lumbar deformity may alter relative pelvic alignment. However, quantitative evidence on segmental kinematics of the trunk–pelvis–lower limb complex during walking and on compensatory control by core musculature remains limited.
OBJECTIVE: To evaluate the kinematic characteristics during walking in patients with Lenke type 5 adolescent idiopathic scoliosis.
METHODS: Twenty patients with Lenke type 5 adolescent idiopathic scoliosis (Cobb angle 20°-36°, age 10-15 years) and 20 age-matched healthy adolescents were enrolled. Spatiotemporal gait parameters, kinematic parameters, and electromyographic differences during walking at a constant speed were simultaneously collected and analyzed between the two groups. 
RESULTS AND CONCLUSION: (1) Gait parameters: Step width, the percentage of convex-side double-support phase, and percentage of concave-side swing phase over the gait cycle were significantly greater in the Lenke type 5 adolescent idiopathic scoliosis group compared with the healthy control group (P < 0.05). The percentages of convex-side stance phase and double-support phase were significantly greater than those on the concave side (P < 0.05), while convex-side step length and swing phase percentage were significantly smaller than those on the concave side (P < 0.05). (2) Kinematic parameters: The range of motion in the coronal plane for the lumbar spine and spine-pelvis relative movement was significantly greater in the Lenke type 5 adolescent idiopathic scoliosis group than the healthy control group (P < 0.05). Convex-side peak hip flexion angle and peak ankle plantarflexion angle were significantly smaller than those in the healthy control group, and these angles were greater on the concave side than on the convex side (P < 0.05). (3) Surface electromyography results: Electromyographic signals of the bilateral erector spinae, bilateral gluteus medius, convex-side external oblique, and convex-side gluteus maximus were significantly greater in the Lenke type 5 adolescent idiopathic scoliosis group compared with the healthy control group (P < 0.05). Signals from the convex-side erector spinae and external oblique were significantly greater than those on the concave side, while convex-side gluteus medius signals were significantly smaller than those on the concave side (P < 0.05). (4) Overall, these findings suggest that during walking, in patients with Lenke type 5 adolescent idiopathic scoliosis, the convex-side lower limb serves as the primary support. The concave-side lower limb compensates during the swing phase by increasing range of motion at the hip and ankle joints. Increased coronal-plane trunk mobility helps maintain gait stability. Convex-side erector spinae–external oblique co-activation and concave-side gluteus medius recruitment indicate side-specific neuromuscular compensation to maintain balance. This indicates that adolescents with Lenke Type 5 idiopathic scoliosis maintain body balance and stability through bilateral imbalanced muscle control strategies based on joint mobility.

Key words: adolescent idiopathic scoliosis, Lenke type 5, gait analysis, kinematics, surface electromyography, spine, pelvis, lumbar spine