Magnitude of thoracic spine deformity affecting morphologial characteristics of paraspinal muscles in patients with severe idiopathic scoliosis

Abstract

Introduction Morphological, biochemical and histopathological characteristics of paraspinal muscles have been well described in patients with idiopathic scoliosis. However, there is a paucity of literature on morphological picture of paraspinal muscles in patients with severe idiopathic scoliosis. Objective To explore how the magnitude of thoracic spine deformity affects morphological characteristics of paraspinal muscles in patients with severe idiopathic scoliosis. Material and methods A total 21 patients with idiopathic scoliosis were reviewed. The patients were assigned to two groups depending on magnitude of preoperative thoracic spine deformity. A major group consisted of patients with scoliosis of ≥ 60º (n = 11) and control group included patients with a curve < 60º (n=10). Biopsy samples were taken from muscle fragments (multifidus muscle) at the apex of the curve (major arc) at the Th6-Th10 level on the convex side while approaching to the posterior spinal structures during surgical correction of kyphoscoliosis using light microscope. The specimens were examined histologically with light microscope. Results Patients with severe idiopathic scoliosis (≥ 60º) showed evident muscle fiber atrophy and dystrophy of different extent. There were nucleus free areas and homogenized muscle fragments observed with connective tissue layers being swollen and frayed with multiple fibroblasts seen in nearly all the samples. Arterial walls were normally fibrotized. Structural changes ranged from minimal with a curve of 60º to degrading muscles with the fibers replaced by fat and connective tissues with a curve angle of 145º. Conclusion Morphological characteristics of paraspinal muscles have been shown to be severely affected by the magnitude of thoracic spine deformity in patients with severe idiopathic scoliosis. The findings should be considered in surgical correction of kyphoscoliosis with special focus on postoperative vascular and neurotropic therapy to allow wound healing and lower complication rate.