Ultrasound Measurements of the Lateral Abdominal Muscle Thicknesses in Girls With Adolescent Idiopathic Scoliosis

Background It has been suggested that weakness and asymmetry of core stabilizing muscles have an important role in the development of scoliosis and its complications, especially low back pain. However there is insufficient data comparing symmetry and function of these muscles in scoliotic patients with the normal population. Also there are only a few studies assessing the relationship between the degree of spinal deviation and asymmetry of core stabilizing muscles. This study evaluates the thickness, symmetry, and activation of the external oblique (EO), the internal oblique (IO) and the transversus abdominis (TrA) muscles of patients with AIS and compares these data with a group of normal adolescents. Objectives The objective of this observational study was to know the asymmetry pattern of lateral abdominal muscles at rest and during the abdominal drawing-in maneuver (ADiM) in adolescents with idiopathic scoliosis and to compare it with a group of healthy adolescents. Methods Twenty healthy adolescents and twenty patients with AIS, aged 10 to 18 years, were included. The thickness of lateral abdominal muscles was measured, using ultrasound, at the end of normal exhalation at rest and during the abdominal drawing-in maneuver (ADiM). Muscular activity was represented as absolute difference and percentage change in the muscle thickness during the ADiM compared with rest. Results There was no side to side asymmetry in muscle thickness at rest and also during ADiM in two groups. Thickness of right EO [0.39 (0.09) in the AIS group compared to 0.51 (0.12) in the normal group] and left EO [0.38(0.10) in the AIS group compared to 0.50 (0.11) in the normal group] at rest was higher in the normal group (P < 0.05). The activity of right and left EO was higher in AIS group (P < 0.05). There was a positive correlation between the lumbar Cobb’s angle with the right and the right-to-left difference of TrA thickness during the ADiM (P < 0.05). In other words, the more the lumbar Cobb’s angle to the right, the thicker the right TrA relative to the left TrA during the ADiM. Conclusions The EO muscle was thinner and had higher activity during ADiM in the AIS group. Analysis of our data showed that in the AIS group the higher the lumbar spinal curve to the right, the thicker the right TrA compared to the left TrA.