Structure and fibro-angio-architectonics of the temporomandibular joint ligament set in patients with systemic connective tissue dysplasia

Aim of study. The study aimed at investigating the role played by congenital connective tissue failure in the temporomandibular joint (TMJ) dysfunctional disorders, while relying on the data obtained through histological and morphometric analysis of the intracapsular ligament set.
Material and methods. The respective pathomorphological studies (visual examination, histomorphometry) were performed on 26 bodies of certified persons (aged 18–45) killed in accidents, with preserved dentition. The objects of the study were intracapsular ligaments isolated from 52 TMJ sets. The sectional material was divided into 2 groups, namely, Group 1 (n=11) – individuals featuring no phenotypic markers of undifferentiated connective tissue dysplasia (UCTD); Group 2 (n=15) – individuals with phenotypic manifestations of UCTD. When identifying collagen fibers on micro-preparations of TMJ intracapsular ligaments, the Masson trichrome staining method (Goldner modification with light green) was employed. Computer morphometric examination (ImageJ and ACDSee Photo Studio Ultimate 2021 software) involving micro-preparations was used to study the quantitative indicators of collagen fibers (specific surface area, thickness, staining intensity, degree of spatial ordering) as well as the vascular system (share obliterated vessels VS. the total number of vessels).
Results. The specific features of the collagen fibers microstructure of TMJ ligament set in patients with UCTD markers, unlike in Group 1, included bundle (strand) branching into separate thinned threads; spiral-like twist of fibers; reduced uniformity of the contact spot and density between the fiber fibrils; expanded inter-fiber spaces; increased number of tendinocyte nuclei, and a smaller vascular network along with an increase in the number of vessels bearing signs of endotheliosis. Changing quantitative factors of collagen fibers of the TMJ intracapsular ligaments in Group 2 (if matched against data obtained from cases with no collagenopathy) can be described (by Me) with an insignificant (p≥0.05) decrease in specific surface area (1.10 times); thickness (1.19 times), staining intensity (1.06 times). Moreover, the decrease in the level of spatial arrangement of fibers (2.63 times) against the background of an increase in the proportion of obliterated vessels in the entire volume of the vascular bed (3.38 times) turned out to be statistically significant (p<0.05).
Conclusion. Changes in the structure and fibro-angio-architectonics of the TMJ intracapsular ligaments in individuals with signs of UCTD result in a disturbance affecting the correct position of intraarticular disc relative to the lower jaw condylar process head. The dysplastic changes in the linear, volumetric and spatial parameters of collagen fibers, manifested through enhanced extension (compliance), lack of stability, and lower elasticity of the capsule-ligament  joint set, promote dislocations of intraarticular structures along with internal TMJ issues, as well as they are behind a rapid progression of destructive processes in the joint tissues.
Keywords: connective tissue dysplasia, temporomandibular joint, intracapsular ligaments, collagen fibers, histological examination, computer morphometry
Conflict of interest. The author have no conflicts of interest to declare.
Funding. There was no funding for this study.