Histopathological Study of Extraocular Musele followinr Posterior Fixation Suture in Rabbits: Pathogenesis of Musele Fibrosis

ABSTRACT

The authors observed the histological and ultrastructural findings in a study of the fibrosis of the extraocular muscles following a posterior fixation suture in rabbits. the early findings demonstrated hyalinosis, clumping of the nuclei of muscle cells and collagenization of the muscle tissue. However, there was no evidence of collagen tissue in the degenerated muscle fiber, reserving cell membrane and basement membrane ultrastructurally. The late findings showed splitting and irregular stain of the muscle fibers, many nuclei of presumed muscle cell and filamentous structure at the collagen tissue in the extracellular space. Electron microscopic study showed atrophy and angulation with distortion of the myofibrillar matrix, along with other cytoplasmic degenerative phe nomena in the muscle fibers. Clumps of the well-arranged microfibrils(Mf) and irregularly arranged Mf with fine granular materials(FGM) were adjacent to the immature collagen fibrils. Many of the Mf and FGM were closely associated, and the number of the Mf and FGM decreased with the degree of maturity of the collagen fibrils. The anatomical structure of the myofibrill was identified as that of the Mf. From these findings, it would appear that formation of collagen fiber occurs in the extracellular space and that Mf and FGM are primarily responsible for the formation of the collagen fibils.