Arthroscopic anatomy of the equine temporomandibular joint.

This research discusses the development and testing of an arthroscopic technique for exploring the equine temporomandibular joint (TMJ), based on a cadaveric study initially and further tested on live horses.

Study Design

• The researchers started with a cadaveric study involving 10 equine heads, after which the technique developed was tested on 5 normal horses.
• Both the specimens and live horses were positioned in right lateral recumbency, i.e., turned onto their right sides. Post this, the researchers used fluid to distend the TMJ, thereby allowing expanded visibility and access.
• The team then created arthroscopic portals at the most prominent portion of the joint’s outpouching (a caudodorsal approach), as well as in rostral (toward the front) and intermediate locations. The joint was thoroughly explored and photographed for further study.
• Instrument portals were created as well to assess the feasibility of performing surgical arthroscopy.

Observations and Results

• The caudodorsal arthroscopic approach provided the best view of the dorsal compartment of the TMJ, with key observations made on the rostral and caudal synovial pouches and the lateral aspect of the joint, including the articular disc.
• The exploration of the medial aspect of the joint was restricted to the most rostral and caudal aspects, while access to the lateral aspect of the TMJ’s ventral compartment was not possible due to the position of the transverse facial artery and vein.
• In terms of potential damage, the cadaveric study recorded minimal iatrogenic (caused by medical examination or treatment) damage, chiefly limited to the articular fibrocartilage, articular disc, and penetration of the parotid salivary gland. No adverse effects were noticed when these occurrences were replicated in actual horses.
• Post-operation, mild fluid extravasation (leaking of bodily fluid into surrounding tissues) was observed which resolved within a day. All horses continued to eat as normal but exhibited periarticular swelling and mild pain at the TMJ site for two days post-surgery.

Conclusions

• The arthroscopic approach developed allowed a detailed view of the lateral aspect of the dorsal compartment of the joint, making it a potentially viable technique for equine TMJ examination.
• Access to the ventral compartment remained a challenge due to anatomical structures like the transverse facial artery and vein.
• The arthroscopic approach should allow visibility of conditions affecting the lateral and caudal aspects of the dorsal compartment of the TMJ making diagnosis easier.