Free moment contribution to quiet standing in able-bodied and scoliotic girls

Adolescent idiopathic scoliosis girls are known to display standing imbalance. In addition to a motor deficit problem, the axial torsion of the spine and trunk torsion could reflect an imbalance around the vertical axis. Unlike the excursion of the center of pressure (COP), the forces and moments were rarely addressed to characterize the quiet standing balance. Nonetheless, one dynamical parameter, called free moment (TV), representing the vertical torque on the feet can reflect the oscillation around the vertical axis associated to the standing imbalance. The objectives of this study were to test if the free moment variability can be utilized to characterize standing balance in a group of able-bodied and non-treated scoliotic girls and to determine if it was associated with that of the COP among each group of subjects tested. Forty-six adolescent girls with half of them presenting an adolescent idiopathic scoliosis were tested during quiet standing balance. Standing balance was assessed with the subjects standing upright and bare feet on a force plate. RMS and range of COP excursions and free moment were calculated.The scoliotic group displayed higher variability in COP excursion by about 24% than the able-bodied girls. Similarly, the TV RMS (P = 0.00136) and range (P = 0.00197) were statistically higher by about 42% in the scoliotic group. The variability of TV was associated with that of the COP in both groups. In the medio-lateral direction, the significant correlations between the RMS and range of the free moment and those of the COP were about 0.7 for the able-bodied group and 0.5 for the medio-lateral COP range for the scoliotic group girls. Along the antero-posterior axis, the only statistically significant correlations were observed for the scoliotic group. The free moment variability about the COP measured during quiet standing can be suggestive of an asymmetry control of the trunk around the vertical axis during standing balance. Its variability was more pronounced in scoliotic girls and was associated with the antero-posterior COP variability reflecting both biomechanical and motor control deficits. Free moment calculation could be a supplement insight into the standing balance of scoliotic subjects

Abnormal activation of the motor cortical network in idiopathic scoliosis demonstrated by functional MRI

The aetiology of idiopathic scoliosis (IS) remains unknown, but there is growing support for the possibility of an underlying neurological disorder. Functional magnetic resonance imaging (fMRI) can characterize the abnormal activation of the sensorimotor brain network in movement disorders and could provide further insights into the neuropathogenesis of IS. Twenty subjects were included in the study; 10 adolescents with IS (mean age of 15.2, 8 girls and 2 boys) and 10 age-matched healthy controls. The average Cobb angle of the primary curve in the IS patients was 35° (range 27°–55°). All participants underwent a block-design fMRI experiment in a 1.5-Tesla MRI scanner to explore cortical activation following a simple motor task. Rest periods alternated with activation periods during which participants were required to open and close their hand at an internally paced rate of approximately 1 Hz. Data were analyzed with Statistical Parametric Mapping (SPM5) including age, sex and laterality as nuisance variables to minimise the presence of bias in the results. Compared to controls, IS patients showed significant increases in blood oxygenation level dependent (BOLD) activity in contralateral supplementary motor area when performing the motor task with either hand. No significant differences were observed when testing between groups in the functional activation in the primary motor cortex, premotor cortex and somatosensory cortex. Additionally, the IS group showed a greater interhemispheric asymmetry index than the control group (0.30 vs. 0.13, p < 0.001). This study demonstrates an abnormal pattern of brain activation in secondary motor areas during movement execution in patients with IS. These findings support the hypothesis that a sensorimotor integration disorder underlies the pathogenesis of IS