Influence of structural pelvic disorders during standing and walking in adolescents with idiopathic scoliosis.

BACKGROUND CONTEXT: In adolescents with idiopathic scoliosis (AIS), several studies have shown that the pelvis is structurally changed by the spinal disorder. In fact, a significant correlation has been observed between the three-dimensional changes in the lumbar curve and the reduction in pelvic displacement in the three spatial planes during gait. However, the impact of this pelvic disorder on the walking mechanism has not been established. PURPOSE: To quantitatively evaluate the influence of scoliosis on the three-dimensional (3D) pelvic position during bipedal standing, on the 3D pelvic displacement during gait, and on the walking mechanics in adolescents with idiopathic lumbar and thoraco-lumbar scoliosis. STUDY DESIGN/SETTING: Paired sample matched for age and gender. PATIENT SAMPLE: Twenty-four subjects, 12 healthy adolescents matched for age and gender with 12 adolescents with lumbar or thoraco-lumbar idiopathic scoliosis. OUTCOME MEASURES: A test battery including clinical examination, radiological assessment, static 3D pelvic examination in bipedal position, and instrumented gait analysis. The statistical analysis was performed by a paired t test to evaluate the differences on nominally recorded data between control subjects and patients and a signed rank test for ordinal data. METHODS: The spine and pelvis were assessed by X-ray, clinical examination, and 3D analysis with the Elite system V5, in the standing position. The gait was assessed by instrumented analysis, including synchronous kinematic, dynamic, and electromyographic (EMG) recordings. RESULTS: Our results showed that radiological measurements of the pelvis were significantly different between patients and control subjects. However, 3D pelvic kinematics were not significantly different between AIS patients and normal subjects during standing and walking. We observed an increase in the muscular external work, a reduction in the efficiency of the locomotor mechanism, and a prolonged duration of activation of the lumbar muscles, ie, erector spinae and quadratum lumborum, in AIS patients. CONCLUSIONS: The scoliosis affected the structural bones of the pelvis with no effect on the 3D pelvis position during standing. During walking, normal 3D pelvic displacements could be explained by the prolonged duration of activation of the erector spinae and quadratum lumborum muscles bilaterally allowing the equilibrium of the pelvis to be maintained. This excessive muscular activity caused a failure of the locomotor mechanism as shown by an increase in the muscular external work