Journal de la colonne vertébrale

Morphological and Morphometric Analysis of Paraspinal and Intercostal Musculature on Adolescent Idiopathic Scoliosis

Abstract

Aloysio Campos da Paz, Isabel CS Brandao, Eni Braga da Silveira and Cícero Ricardo Gomes

Background: Muscles of the human paraspinal region have been the focus of attention in patients with Adolescent Idiopathic Scoliosis (AIS). Despite the description of differences in muscle histology on the two sides of the scoliotic curve, there is no consensus on the significance of such findings. The purpose of this study was to assess changes in the thoracic wall muscles, including the paraspinal and the intercostal muscles (not previously described in the literature) in patients with AIS, and examine their relationship to the curvature.

Methods: The paraspinal and external intercostal muscles on both sides of the scoliotic curve were biopsied in 29 patients with AIS. Tissues were studied under light microscopy and submitted to morphometric examination.

Results: Both muscles on the concave side of the curve were characterized by a greater percentage of type 2 (fast twitch) fibers and a smaller mean fiber diameter than the contralateral muscles. Fiber diameter in the concavity, for both muscles, showed an inverse relationship to the Cobb angle.

Conclusion: Patients with AIS present variations in the microstructure of both paraspinal and intercostals muscles, with similar changes. This suggests that the process of AIS is broadly based; it affects more than one muscle group in the thoracic wall, and is not confined to the paraspinal region. The new findings on the intercostal muscles may be related to the rotation component of the scoliotic curve. Results suggest the possibility that an imbalance between muscle and vertebral growth may lead to the deformity through a bowstring phenomenon.