Pattern of asymmetry of paraspinal muscle size in adolescent idiopathic scoliosis examined by real-time ultrasound imaging : a preliminary study

The symmetry of lumbar multifidus size was examined in 20 patients with adolescent idiopathic scoliosis, aged 12-19 years. With the subject prone, bilateral real-time ultrasound images were obtained at the level of the 4th lumbar vertebra. Cross-sectional area and linear (horizontal and vertical) measurements were made using on-screen calipers. A pattern of asymmetry of lumbar multifidus cross-sectional area was shown to exist for the different curve types. The cross-sectional area was smaller (P < 0.0001) on the opposite side to the convexity of a primary thoracic curve, and on the convex side of a lumbar or thoracolumbar curve. The combined linear measurements (multiplied) correlated with cross-sectional area (r = 0.95) and could therefore be used for rapid clinical assessment of multifidus size. These preliminary findings provide a basis for further investigation of the role of the musculature in the pathogenesis of adolescent idiopathic scoliosis.