Functional and clinical anatomy of the posterior insertion of the human vocal ligament.

The suggested methods of the formation of intubation granuloma as well as carcinoma invasion in the area of posterior vocal ligament insertion have been controversial. One reason for divergent opinions is possibly based on different judgements of morphology in this region. The present study analyzed structures of the vocal ligament and vocalis muscle insertion at the vocal process by means of histological, immunohistochemical and electron microscopic methods. Investigations were performed in three planes on the vocal cords of 22 men and 19 women (aged 21-97 years). Inside the insertion zone of the vocal ligament at the vocal process three structures could be distinguished: hyaline cartilage at the base of arytenoid cartilage, elastic cartilage at its apex and the posterior elastic nodule in front of them. No perichondrium could be seen around the elastic nodule. In elastic nodules type I and type III collagen fibrils as well as elastic fibers formed a scissor-like meshwork around large fibroblasts. The vocalis muscle inserted at the perichondrium in the lateral part of the arytenoid skeleton by short tendons. At the insertion zone blood vessels of the vocalis muscle penetrated the perichondrium and reached the cartilaginous matrix. At the beginning of osteogenesis, the blood vessels connected with intraosseous blood vessels of the arytenoid. Connective tissue cells of the insertion zone and extracellular matrix components formed by these cells fulfilled a biomechanical function by equalizing the different elastic moduli of tendon, cartilage or bone. The lack of perichondrium around the lengthened posterior elastic nodule made formation of intubation granulomas caused by perichondritis in this area impossible. Loosened perichondrium or periosteum in the area of the insertion of the vocalis muscle at the vocal process, ossification and associated vascularization of the arytenoid skeleton permitted invasion of carcinomas into the arytenoid.