MORPHOLOGICAL FEATURES OF THE MUSCULUS MASSETER IN PATIENTS WITH POST-IMMOBILIZATION EXTRA-ARTICULAR CONTRACTURES OF THE MANDIBLE

Aim. To determine the morphological features of the musculus masseter in patients with extra-articular post-immobilization contractures of the mandible. Materials and methods. The research material was fragments of the musculus masseter, which were divided into three groups. Group 1 included musculus masseter fragments from 8 people, whose autopsy did not reveal any pathology of the head and neck. Group 2 included fragments of the macroscopically altered musculus masseter from 6 people who underwent immobilization of the lower jaw using a double-jaw splinting during the first hospitalization, and metal-osteosynthesis during the second hospitalization. Group 3 included fragments of the macroscopically altered musculus masseter from 6 people who underwent immobilization of the lower jaw using a parieto-chin sling bandage during the first hospitalization, and metal-osteosynthesis during the second hospitalization. In patients of groups 2 and 3, an average of 37.6 days passed between the use of conservative immobilization methods and metal-osteosynthesis. Microslides stained with hematoxylin and eosin, picrofuchsin according to van Gieson were subjected to morphometric examination. Results. In patients with post-immobilization extra-articular contractures of the mandible, changes in the morphofunctional state of the parenchymal and stromal components of the musculus masseter were recorded. In the parenchymal component, wave-like deformation, ischemic-dystrophic and atrophic changes in muscle fibers were noted. The stromal component was characterized by the presence of focal-diffuse polymorphic cellular infiltration; excessive content of connective tissue fibers with the presence of adipocytes between them; a decrease in the number of vessels with the presence of dystrophic-necrotic and desquamative changes in endothelial cells, sclerotic changes in all layers of the vascular wall; dystrophic-sclerotic changes in nerve fibers. Conclusions. The structural changes in the musculus masseter identified by the authors, which are more pronounced in cases of using a parieto-chin sling bandage and less pronounced in cases of using a double-jaw splinting, may underlie the development of post-immobilization extra-articular contractures of the mandible.