Functional anatomy of the equine temporomandibular joint: Histological characteristics of the articular surfaces and underlining tissues.

This study examined the histological characteristics of healthy temporomandibular joints (TMJ) in horses. The purpose was to better understand how these joints are affected by dental conditions and whether they can adapt to different loading conditions. The research found that the articular surfaces of the TMJ exhibited a zoning pattern and were made up of three tissue layers. Furthermore, differences in glycosaminoglycans, indicative of pressure, suggest varying biomechanical demands in different parts of the equine TMJ.

Objective of the Study

• The main purpose of the study was to investigate the histological attributes of healthy equine TMJs. This was intended to delve into how these joints adapt to diverse loading conditions and the impact of dental conditions on the joints, since dental disorders in horses are hypothesized to cause TMJ disorders due to biomechanical overload or aberrant loading.

Method of Research

• The research utilized ten TMJs extracted from horses that didn’t have a history of dental or TMJ disorders.
• Through analysis, the researchers observe the zoning pattern and tissue components of the TMJ’s articular surfaces.
• The tissue components comprised of three layers: a superficial layer rich in cells composed of dense connective tissue, an intermediate layer of fibrocartilage, and a hyaline-like cartilage layer at the core.
• The researchers also investigated the composition and structure of the articular disc and mandibular fossa

Key Findings

• The study revealed that the articular surfaces were made up of uniform zoning patterns. They also noted that apart from the mandibular fossa, the osseous facets of the TMJ adhered to this zoning pattern.
• The articular disc was found to have an inner core composition of fibrocartilage and hyaline-like cartilage meshwork. It was covered with a layer of cell-rich dense connective tissues and fibrocartilage on its dorsal and ventral aspects. On the contrary, the mandibular fossa only had a cover of dense connective tissue.
• The presence of glycosaminoglycans was predominantly noted within the rostral part of the articular tubercle, the retroarticular process, the dorsal part of the articular disc, and across the mandibular head. This indicates areas subjected to high compressive loads. They were absent within the mandibular fossa, suggesting lower biomechanical stress.
• The research concluded that the equine TMJ may face different biomechanical demands in its dorsal and ventral compartments. This discovery could have noteworthy implications for understanding the impact of dental issues on the overall health and functionality of the TMJ in horses.