Idiopathic scoliosis and balance organisation in seated position on a seesaw

Abstract

The aim was to determine the biomechanical processes involved in postural regulation when self-imposed disturbances occur in the seated position in the antero-posterior direction. Twelve female adolescents with right thoracic scoliosis (SG) (Cobb = 30.4 degrees +/- 9.7) and 15 control adolescents (CG) were included in this study. The ground reaction forces (GRF) were studied whilst the subjects maintained their balance in the sitting position on a seesaw. Six conditions were tested: eyes open and closed; with an additional load placed on the subject's right or left shoulder; and with an additional load on the subject's right or left pelvis. The SG showed significantly higher force amplitudes and variability and fewer oscillations than the CG in all the conditions. In the SG, the time analysis showed that the duration of the GRF was significantly higher in forward and left directions. Whatever the condition tested, the intra-group differences were not significant. The scoliotic patients in seated position were characterised by larger changes of the GRF, especially with a postural control in the forward and left directions, corresponding to that on the concave side of their spinal curvature. No significant differences were found to exist between the various conditions (load and unload, eyes open and eyes closed). Clinical tests and rehabilitation methods should include assessments of seated patients' spatio-temporal adaptation to GRF.

Fig. 1

The experimental setup and data analysis. The top panel shows the experimental setup, consisting of a force platform, a seesaw and a destabilising device. The bottom panel shows the changes with time (ms) in the ground reaction forces recorded in response to antero-posterior (Fx) and medio-lateral (Fy) perturbations. The performance index (PI) is the area under the curve (black dotted line); the frequency is given by the number of oscillations (circles) divided by the duration of the movement (ms), the delta value is the maximum value of the force displacement minus the minimum value (arrows), and the time spent on the right or left is given by the respective parts of the curve on both sides of the mean line

Fig. 2

Mean number of falls per subject in the control group and the scoliotic group. Significant differences (p < 0.05) are indicated by a black horizontal line

Fig. 3

Antero-posterior destabilisation. Time spent on the right and left (as percentages) in the following conditions: eyes open or closed (EO and EC), right or left shoulder loaded (RS and LS) and right or left pelvis loaded (RP and LP). Results obtained with the control group (C) and the scoliotic group (S). Significant differences (p < 0.01) are indicated by three asterisks