A comparison of ultrasonography measurement on the abdominal muscle thickness between adolescent idiopathic scoliosis and healthy subjects.

Background: Many studies have shown asymmetric behavior of the surface and deep layers of spine muscles in scoliosis patients, compared to normal individuals. However, there is a lack of research on the transversus abdominal (TA) muscle, which plays an important role in trunk stabilization.

Objective: To assess symmetry in subjects with adolescent idiopathic scoliosis (AIS) by measuring the thickness of abdominal muscles, and to investigate characteristic features through a comparative analysis of the data with healthy aged-matched group.

Methods: Subjects consisted of 33 AIS and 32 healthy subjects of similar ages between 11-28 years old. We measured TA, internal abdominal oblique (IO), and external abdominal oblique (EO) muscles were measured using ultrasonography imaging. Three repeat measurements of the thickness of each muscle were performed during rest and contraction.

Results: For the healthy subjects, the intra-class correlation coefficients (ICCs) for the muscle thickness measures ranged from 0.70 to 0.99, standard error of measurement (SEM) was 0.38 cm, and minimal detectable change (MDC) was 1.07 cm. The ICCs for the muscle thickness measures in the AIS group ranged from 0.90 to 0.98, SEM was 0.45 cm, and MDC was 1.24 cm. The symmetry of the two groups was compared, and showed significant difference only in TA in AIS patient group (P< 0.01).

Conclusions: In conclusion, treatment should be focused on exercises that emphasize symmetry, to induce normal action of the TA and structural changes in the spine because AIS induces asymmetry in TA, which plays an important role in trunk stability.