Introduction: Adolescent Idiopathic Scoliosis (AIS) can be biomechanically described as a three dimensional deformity of the spine, with deviations from the sagittal and frontal planes, usually combined with intervertebral rotation. Although, most previous studies on AIS patients focused on the trunk biomechanics in dynamic postures, there is a little information about Paraspinal muscles and lower limb function during static posture. The aim of this study was to investigate the electromyography activity of Paraspinal muscles and lower limb in Adolescent Idiopathic Scoliosis patients during static Sorensen test.
Methodology: A total of ten Adolescent Idiopathic Scoliosis patients with single right thoracic curve and ten control subject underwent an isometric extension Sorensen test. The AIS had a Cobb angle of 15-30° and their mean age, height and weight were 15.3±0.84, 161.8±7.6 cm, 50.5±11.2 kg respectively while it was 14.8±0.47, 158.6±4.5 cm, 48.1±7.7 kg, for the control group. Surface EMG activity was recorded bilaterally from the paraspinal muscles at T6, T10, L3 and BF. The EMG signal was processed in the time domain by calculating (RMS). The data were analyzed by means of repeated measures and one-way analysis of variance to investigate the differences between two groups. The significance level was adopted (P<0.05) level.
Results: In general, During Static Sorenson test, bioelectrical activity of Paraspinal muscles was symmetrical in both groups. Muscle activity ratio of two sides of spine was different in various regions (P=0.005). There was also no difference in bioelectrical activity of different regions.
Discussion: In conclusion, There is no significant differences in EMG activity of various parts of spine during an isometric extension Sorensen test. It seems that in AIS patients the more EMG muscle activity of L3 can affect lumbar muscle function during trunk extension in Sorensen test.