Adolescent idiopathic scoliosis (AIS) is a progressive three-dimensional skeletal deformity that affects spinal mobility and trunk symmetry. It was previously believed that AIS was not accompanied with pain, but recent studies have shown that approximately 31.5% of the patients complain of low back pain, which may due to factors such as paravertebral muscle imbalance and fatigue.

To observe morphological changes of paravertebral multifidus muscles at the top of the main curvature after high energy laser therapy (HILT) combined with physiotherapy scoliosis specific exercise (PSSE) in AIS patients with low back pain by using musculoskeletal ultrasound. and evaluate the clinical effect of treatment on the correction of paravertebral muscle imbalance.

A total of 30 patients with AIS RigoE1 admitted to the Scoliosis Correction Center of the Fifth Hospital of Harbin from December 2020 to December 2021 were selected for a randomized single-blind controlled trial and divided into the experimental group (n=15) and control group (n=15) , the experimental group was treated with HILT combined with PSSE, and the control group was only treated with HILT. Musculoskeletal ultrasound, visual analogue scale (VAS) scores, range of motion of the patient's lumbar joints and Roland-Morris lumbar spine dysfunction questionnaire (RDQ) were performed before and 4 weeks after treatment in both groups. Pearson correlation analysis was used to investigate whether there was a correlation between the changes in the multifidus muscles after treatment and the treatment effect.

The cross-sectional area of the convex side of multifidus muscles, anterior flexion, left lateral flexion, left rotation and right rotation of the experimental group were higher than those of the control group after treatment (P<0.05) , the cross-sectional area and thickness of multifidus muscles on the concave side, the cross-sectional area and thickness ratios of multifidus muscles on the concave and convex sides, extension after treatment were higher than those before treatment in the experimental group (P<0.05) . VAS scores and RDQ scores after treatment were lower than those before treatment, and anterior flexion, left lateral flexion, right lateral flexion, left rotation and right rotation were higher than those before treatment (P<0.05) in both two groups. The extension after treatment was lower than that before treatment in the control group (P<0.05) . Pearson correlation analysis showed that the cross-sectional area ratio of multifidus muscles on the concave and convex sides was negatively related with right rotation of the lumbar spine after treatment in the experimental group (r=-0.660, P<0.01) , the thickness ratio of the concave and convex sides of multifidus muscles was negatively related with right flexion of the lumbar spine (r=-0.614, P<0.05) .

HILT combined with PSSE can change the morphology of the multifidus muscles on the concave side of the parietal vertebrae of scoliosis, reduce low back pain, increase lumbar spine mobility, reduce lumbar spine dysfunction and improve activities of daily living; the use of HILT alone can effectively relieve low back pain caused by scoliosis, although it has no significant effect on the morphological changes of the multifidus muscles. Balancing the morphology of the multifidus muscles on both sides of the spine has a positive effect on improving the lateral flexion and rotation of the lumbar spine.