Remember, equine TMJ have an intra-articular disc....

Contrast arthrography of the equine temporomandibular joint

Clara S. Kim, Nathalie A. Reisbig, James L. Carmalt*

Background
Disorders of the equine temporomandibular joint (TMJ) are increasingly recognized, but imaging techniques to assess intra-articular structures remain limited and expensive, with modalities such as CT and MRI not widely accessible. This study aimed to develop and validate a technique for single- and double-contrast arthrography to evaluate the TMJ in equine cadavers and live animals.

Methods
A descriptive experimental study was conducted in two phases. In Phase I, 12 cadaveric equine heads were subjected to single- and double-contrast arthrography of both TMJ compartments using specific radiographic projections. In Phase II, the refined technique was applied to three live horses. Injections were performed into the joint compartments, followed by radiographic imaging to assess the filling of joint spaces and delineation of intra-articular structures. Joint manipulation and air injection were also evaluated for enhancing contrast delineation.

Results

-Cadaveric Study: Contrast arthrography delineated the dorsal and ventral surfaces of the intra-articular disc and highlighted joint margins. Double contrast was superior to single contrast for visualizing disc extremities and synovial pouches. Contrast extravasation was common, and iatrogenic disc perforation was noted in two cases.

-Live Animals: The procedure was well tolerated, with radiographic results comparable to those from cadavers. Needle placement for discomandibular joint injection was challenging, with multiple attempts required in 50% of cases. Contrast extravasation occurred but did not impact diagnostic outcomes.

Limitations
The small sample size of live animals limits the generalizability of findings. Challenges in needle placement and the potential for iatrogenic damage emphasize the need for further refinement and operator training. The study relied on cadaver models, which may not fully replicate in vivo conditions.

Conclusions
Contrast arthrography is a feasible technique for assessing the equine TMJ, providing clear delineation of joint and intra-articular disc margins. Double contrast is particularly beneficial for enhanced visualization. Caution is necessary to avoid iatrogenic complications, and further studies are needed to improve technical success rates and validate the procedure in larger populations.

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