Assessment of biomechanical properties of paraspinal muscles in adolescent idiopathic scoliosis

Abstract

Objective: To assess the bio-mechanical properties of paraspinal muscles in adolescent idiopathic scoliosis (AIS). Methods: The MyotonPro® device and shear wave elasticity imaging(SWEI) technique were applied to detect the paraspinal muscle tone (F), stiffness (S), relaxation time (R), Deborah number (C) and elasticity (D) of paravertebral muscles on the concave side and convex side of scoliosis curvature at several points: apex of the curve (a), upper (b) and lower (c) limits of the curve in 23 cases of AIS treated from October to December 2017 in Beijing Chaoyang Hospital.Cobb angle of the main curve was measured on the standing anteroposterior whole spine radiograph.Pearson correlation analysis was applied to detect the relation between the bio-mechanical properties and Cobb angle of the main curve. Results: A total of 23 AIS patients [3 males and 20 females, mean age was (15±4) years] were assessed in this study.The mean Cobb angle was (66±33) degrees.The MyotonPro® data showed that the muscle tone on the concave side were all significantly greater than those on the convex side [a: (18.9±2.2) Hz vs (17.4±1.6) Hz, t=4.435, P<0.05; b: (18.2±2.0) Hz vs (16.7±1.7) Hz, t=4.183, P<0.05; c: (18.0±2.3) Hz vs (16.8±1.7) Hz, t=4.520, P<0.05]. The muscle stiffness on the concave side were all significantly greater than those on the convex side at the three points (t=1.974, 2.048, 1.749, all P<0.05). The relaxation time were all longer on the convex side (t=-3.422, -2.713, -2.380, all P<0.05). The Deborah number were greater on the convex side at a and b points (t=-2.939, -2.466, both P<0.05). No significant difference in elasticity was found between the muscles of the two sides.The SWEI results also indicated that the elasticity of the paraspinal muscles of the two sides were similar.The Pearson correlation analysis showed that stiffness on the concave side was moderate positively correlated with Cobb angle of the main curve (r=0.582, P<0.05). Deborah number on the two sides and relaxation time on the concave were moderate negatively correlated with Cobb angle of the main curve (r=-0.632, -0.432, -0.611, all P<0.05). Conclusions: The bio-mechanical properties of paraspinal muscles in AIS are different significantly between the concave and convex side and affected by the severity of scoliosis.