Effect of body morphology on standing balance in adolescent idiopathic scoliosis

Objectives: The objective of this study was to determine the effect of body somatotype on standing balance in girls with adolescent idiopathic scoliosis (AIS) who are under observation but not wearing a body brace. Design: In all, 74 girls participated in this study to form the able-bodied (n = 36) and the AIS (n = 38) groups, having an average age of 13 yrs. Quiet standing balance was tested using a force platform. Afterward, subjects in each group were divided according to their dominant body somatotype, namely endomorphs (fatness), mesomorphs (muscular), or endomorphic ectomorphs (lean). Results: The center of pressure measured in the anteroposterior position was closer to the heels for the AIS ectomorphic group by approximately 14 mm (P = 0.00497). Only the AIS mesomorphic group displayed a statistically significant 12-mm shift to the right in their center of pressure (P = 0.01211) compared with the able-bodied girls of the same morphotype. In the endomorphic group, the sway area was statistically higher for the scoliotic subjects (P = 0.00839). The distances traveled by the AIS subjects were all statistically longer for all three body morphologic somatotypes. Conclusion: Different postural responses seem to be dependent on body somatotypes. The endomorphic AIS girls had a larger sway area than their able-bodied counterparts while maintaining a similar center of pressure position. The AIS ectomorphic girls had a tendency to lean further back than a comparable able-bodied group. This could be emphasizing a hypokyphotic trunk attitude and increasing the risk of spinal deformity progression. The AIS mesomorphic subjects characterized by a large muscular and bony structure had a tendency to position their center of mass more to their right, indicating less postural adaptability and a stiffer trunk.