Trunk rotational strength asymmetry in adolescents with idiopathic scoliosis: an observational study

Kevin L McIntire, Marc A Asher, Douglas C Burton & Wen Liu

Recent reports have suggested a rotational strength weakness in rotations to the concave side in patients with idiopathic scoliosis. There have been no studies presenting normative values of female adolescent trunk rotational strength to which a comparison of female adolescents with idiopathic scoliosis could be made. The purpose of this study was to determine trunk rotational strength asymmetry in a group of female adolescents with AIS and a comparison group of healthy female adolescents without scoliosis.

Twenty-six healthy adolescent females served as the healthy group (HG) (average age 14 years) and fourteen otherwise healthy adolescent females with idiopathic scoliosis served as the idiopathic scoliosis group (ISG). Participant's isometric trunk rotational strength was measured in five randomly ordered trunk positions: neutral, 18 degrees and 36 degrees of right and left pre-rotation. Rotational strength asymmetry was then compared within each group and between the two groups.

The HG showed strength asymmetry in the 36 degrees pre-rotated trunk positions when rotating towards the midline (p<0.05). The ISG showed strength asymmetry when rotating towards the concavity of their primary curve from the neutral position (p<0.05) and when rotating towards the concavity from the 18 degrees (p<0.05) and 36 degrees (p<0.05) concave pre-rotated positions. The ISG is significantly weaker than the HG when rotating away from the midline toward the concave (ISG)-left (HG) side from the concave/left pre-rotated 18 degrees (p<0.05) and 36 degrees (p<0.05) positions.

In conclusion, the AIS females were found to be significantly weaker when contracting toward their main curve concavity in the neutral and concave pre-rotated positions compared to contractions toward the convexity. These weaknesses were also demonstrated when compared to the group of healthy female adolescent controls. Possible mechanisms for the strength asymmetry in ISG are discussed.

Scoliosis 2007, 2:9

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