The purposes of this study were as follows: 1) to compare locomotion parameters (kinematic, EMG, mechanical work and energy cost changes during walking in able-bodied subjects and AIS patients,2) to evaluate the effects of the frontal curve's severity of the AIS and 3) the effects of the treatment (orthosis or surgery)on these gait parameters.

Introduction X-ray studies and three-dimensional analysis in standing showed that this Adolescent Idiopathic Scoliosis was characterised by stiffness of the affected vertebral levels [3, 7, 10] with decreased segmental mobilities. The impact of this stiffness was studied during functional activity such as walking to quantify the functional dynamic consequences. During gait, thoracic AIS provided an asymmetrical trunk rotation with a lack of rotation on the convex side [8] and an excessive paravertebral muscular bilateral activity [11]. These studies included only moderate scoliosis. There were no studies approaching the effects of the severity of the scoliosis curves on gait parameters.

We hypothesize first that, the spinal deformations in AIS, producing a stiffness of the trunk, pelvic and hip motions, will deteriorate the gait by reducing the segmental mobilities, increasing the mechanical work and the energy cost and second that the severity of the frontal curves will be more damaging on this parameters. To this end, we hope to gain valuable insight as to the functional effects of the scoliosis aggravation from a more dynamic perspective.

Material Fifty-four female adolescents will be included in the study. This sample consists in two groups: healthy girls and girls with adolescent idiopathic scoliosis (divided in 3 subgroups according to the Cobb angle range) [9].

A standard full spine XRay assessment will be performed to measure the Cobb angle curve, the frontal body balance, the apical vertebral rotation [13].

Gait will be assessed by a three-dimensional analysis, including synchronous kinematic [4], electromyographic (EMG) [14], mechanic [5, 6, 15] and energetic measurements [1, 2, 12].

The sessions begins with a rest period, in which the subjects stand barefoot on the motor driven treadmill for the static calibration of kinematic and energetic variables. Thereafter, the subjects will be asked to walk at a constant speed of 4 km h-1 for a few minutes until a steady state will be reached and maintained for at least two minutes. Then, energetic variables will be computed for two minutes. Other variables will simultaneously be recorded for twenty seconds and averaged for ten successive strides. The mean of each value will be used for statistical analysis. Scoliosis patients will be assessed at T0 i.e. before any treatment and at T1 i.e. one year after the starting of the orthosis wearing (scoliosis subgroup 2) or the surgery (scoliosis subgroup 3)

Inclusion Criteria:

• healthy subjects : no scoliosis diagnosed
• Scoliosis subjects : scoliosis diagnosed by X-Ray assessment

Exclusion Criteria:

• Patients with leg length discrepancies higher than 1 cm, any locomotor disorders, low back pain, neurological abnormalities observed on clinical examination or with any previous treatment for their scoliosis

Healthy subjects girls were recruited in the town and adolescent idiopathic scoliosis attended our outpatient clinic