Foot plantar pressure characteristics during standing and gait in adolescents with moderate double-curve adolescent idiopathic scoliosis (Lenke type 3 and type 6): a case-control study

OBJECTIVE: Adolescent Idiopathic Scoliosis (AIS) is an idiopathic three-dimensional spinal deformity that predominantly affects adolescents during their peak growth period. This study aimed to understand the foot plantar pressure characteristics of individuals with Lenke 3 and 6 type AIS during standing and walking. METHOD: This case-control study enrolled 84 adolescent females aged 10 to 18 years. Based on the coronal plane imaging findings of standing full-spine radiographs, the individuals were classified into three groups according to the Lenke classification system: the Lenke 3 AIS group (n = 28, right thoracic-left lumbar double curves, primary thoracic), the Lenke 6 AIS group (n = 28, left thoracic-right lumbar double curves, primary thoracolumbar), and the control group (n = 28, healthy adolescents free from AIS). The MatScan™ pressure mat was employed to collect the plantar pressure and center of pressure (COP) characteristics of the subjects during bipedal standing, as well as the temporal characteristics of ground reaction forces and foot impulse characteristics during walking. Subsequently, we analyzed the inter - group differences in plantar pressure parameters across the three cohorts. RESULTS: The Lenke 3 AIS group showed a significant decrease in forefoot pressure compared to the control group. In contrast, rearfoot pressure, peak pressure, and average pressure in the left foot increased significantly. Additionally, the COP characteristic exhibits significant differences (P < 0.05). The Lenke 6 AIS group showed significant differences compared to the control group in the rear foot pressure, peak pressure, and average pressure of the left and right feet (P < 0.05). Compared with the Lenke 3 AIS group, the Lenke 6 AIS group exhibited significantly increased pressure in the right foot and forefoot. During gait, the Lenke 6 AIS group heel impulse decreased significantly while the midfoot impulse increased significantly (P < 0.05). CONCLUSION: The Lenke 6 group exhibited more complex changes in plantar pressure. Both groups showed a decline in balance ability, but the Lenke 6 group showed a more severe decline, likely attributable to the larger lumbar curvature angle. Furthermore, both groups exhibited significant alterations in key biomechanical parameters, including energy absorption efficiency during ground contact and propulsive efficiency during push-off.