Contrast arthrography of the equine temporomandibular joint

Abstract

Background: Disorders of the equine temporomandibular joint (TMJ) cause clinical problems and detailed investigations of this joint are becoming more common. Specialist radiographic projections have the potential to highlight osseous abnormalities; however, the ability to assess the intra-articular soft tissue structures is currently limited to computed tomography (with, or without contrast enhancement) or magnetic resonance imaging. Both modalities are expensive and not readily accessible.

Objective: To develop a technique of contrast arthrography of both compartments of the equine TMJ in cadavers and then perform the refined technique in three living horses as a proof-of-principle.

Study design: A descriptive, experimental, study.

Methods: Contrast arthrography of the discomandibular and discotemporal joint compartments of both TMJs was performed in 12 cadaveric equine heads using needles placed in the caudal pouches of the respective joint compartments. Radiographs were taken using previously published techniques, repeated with the mouth open and after air had been injected into the joints, to perform a double-contrast study. The TMJs of three healthy horses were subsequently examined to determine the validity of the procedure in live animals.

Results: Single and double-contrast arthrography allowed delineation of the dorsal and ventral surfaces of the intra-articular disc in addition to filling the rostral and caudal joint pouches of the independent joint compartments. Contrast extravasation was common, and in two instances iatrogenic disc penetration resulted in the false diagnosis of pathologic disc perforation. The techniques were well tolerated in all three live horses.

Main limitations: Low number of horses.

Conclusion: Contrast arthrography allows interpretation of intra-articular soft tissue structures, but caution is advised in diagnosing intra-articular disc perforation. Even with experience, accessing the discomandibular joint can be challenging.

Keywords: TMJ; horse; imaging; intra-articular disc; radiography.

Figure 1

The radiographic image obtained using the R45°V30°L-CdDLO projection. The intra-articular disc is not delineated but is present between the temporal bone and mandibular condyle.

Figure 2

The generator and image capture device position while taking a radiograph of the TMJ using the R45°V30°L-CdDLO projection in a live horse. Beam angle is denoted by the arrow.

Figure 3

Double—contrast injection of the DMJ pools in the rostral pouch (*) and delineates the ventral border of the intra-articular disc (arrows). Note the contrast extravasation lateral to the joint.

Figure 4

Double -contrast injection of both joints in a different horse delineates the dorsal and ventral margins of the intra-articular disc (arrows).

Figure 5

Double contrast lateral oblique radiographic projection of the left TMJ delineating joint margins (*), rostral (r) and caudal (c) disc, and contrast pooling (†).