MRI evaluation of multifidus muscles in adolescent idiopathic scoliosis

Background. The role of the multifidus muscles in the initiation and progre ssion of curve in adolescent idiopathic scoliosis is not fully understood a nd controversy exists as to the side of the abnormality. Objective. To evaluate on MRI the multifidus muscles at the apex of the maj or curve in adolescent idiopathic scoliosis to ascertain if the multifidus muscles on the convex or concave side are abnormal and the relationship to curve severity. Materials and methods. Forty-six patients with adolescent i diopathic scoliosis, separated into two groups, were studied using a 1.5-T MR scanner with the synergy spine coil, employing a modified STIR (short ta u inversion recovery) axial sequence obtained at the apex of the major scol iotic curve. Results. No hyperintense signal change was demonstrated in the convex side multifidus muscles in any patient. In group I, 16 of 18 patients with sever e or rapidly progressive curve showed increase in signal intensity in the m ultifidus muscle on the concave side of the apex of the curve. In group II, of the 15 patients with mild curve (Cobb angle 10-30 degrees), 4 had incre ased signal intensity in the multifidus muscle on the concave side; of the 13 with more severe curve (Cobb angle greater than 30 degrees), 10 had incr ease in multifidus signal intensity on the concave side. Conclusions. The concave-side multifidus muscle at the apex of a scoliotic curve was morphologically abnormal. A significant association between abnor mal signal change and curve severity was also established.