Asymmetry of paraspinal EMG-time characteristics in idiopathic scoliosis.

The purpose of this study was to investigate the activation pattern of the paraspinal muscles in scoliotic and normal subjects. Force-time and electromyography (EMG)-time curves of paraspinal muscles were recorded during maximal isometric trunk extensions in 15 girls with adolescent idiopathic scoliosis (AIS) and in 14 healthy girls with structurally normal spines. The isometric force-time curves as well as the maximal integrated electromyography (IEMG) activities that were recorded from both sides of the thoracic and lumbar spine did not show any significant differences between the two subject groups. However, in the subjects with AIS, the IEMG activities recorded at the onset and during the early (submaximal) phases of muscle contraction were significantly higher in the left lumbar muscles compared with the right side. The observed intensity-specific EMG asymmetry in the present scoliotic subjects may be attributed to the imbalanced neural input associated with AIS that may also have pathogenetic importance in the etiology of idiopathic scoliosis.