Evaluation of Thoracic Paraspinal Muscles Imbalance in Adolescent Idiopathic Scoliosis with Main Thoracic Curve Based on Magnetic Resonance Imaging

Abstract

Objective: While the etiology of adolescent idiopathic scoliosis remains unclear, it is assumed that paraspinal muscle imbalance contributes to curve progression. Previous studies have found the paraspinal muscles imbalance, but no study comprehensively analyzed the roles of different paraspinal muscle layers. Our study distinguished the thoracic paraspinal muscle into superficial, intermediate, and deep layers, and analyzed the imbalance of the 3 layers.

Methods: We retrospectively included adolescent idiopathic scoliosis patients with thoracic curve. The paraspinal muscle parameters including relative muscle cross-sectional area (rmCSA) and fatty infiltration in upper end vertebra, apical vertebra, and lower end vertebra regions and in superficial, intermediate, and deep layers were calculated. The parameters between convex and concave sides were compared by paired t-test. The correlation between paraspinal muscle parameters and radiographic parameters was tested by Spearman correlation analysis.

Results: A total of 46 patients were included. In apical vertebra region, the rmCSA in superficial (P = 0.038), intermediate (P = 0.001), and deep (P = 0.001) layers on convex side was greater than that on concave side, while the fatty infiltration in intermediate (P = 0.023) and deep layers (P = 0.000) on concave side was greater than that on convex side. Radiographic parameters were associated with both intermediate ΔrmCSA (P = 0.002) and deep ΔrmCSA (P = 0.000).

Conclusions: Our research indicates that the severity of paraspinal muscle imbalance is different in three layers, with the deep layer most severe, followed by the intermediate layer, and the superficial layer least severe. The imbalance of deep muscle correlates strongly with radiographic parameters, suggesting its role as a compensatory adaptation to curve magnitude.

Keywords: Adolescent idiopathic scoliosis; Fatty infiltration; Paraspinal muscle imbalance; Relative muscle cross-sectional area; Three muscle layers.