The Equine Temporomandibular Joint: Comparisons Between Standard and Needle Arthroscopic Examination of Cadaver Specimens and Standing Horses

Abstract

Background: Definitive diagnosis of equine temporomandibular joint osteoarthritis (TMJ-OA) may require advanced diagnostic imaging. Arthroscopy is a modern, minimally invasive, diagnostic, and treatment modality. Standing arthroscopic treatment of joint disease is a relatively recent advance in equine surgery, despite which there are few published comparisons between the available arthroscopic systems.

Objective: To compare and contrast two arthroscopic systems for assessing the equine temporomandibular joint compartments in cadavers and standing horses.

Study design: Experimental study.

Methods: Phase I involved the assessment of the discotemporal joint (DTJ) and discomandibular (DMJ) joint compartments of both temporomandibular joints (TMJ) of 14 cadaveric equine heads using a caudally placed arthroscopy portal. Joints were initially examined using the needle arthroscope and the results compared to the findings of examination using a 2.5 mm 30° arthroscope system (standard). Three healthy horses were subsequently examined to determine the validity of the procedure in live animals in Phase II.

Results: Needle and standard arthroscopy, in combination with mandibular manipulation, allowed evaluation of the caudal aspects of both joint compartments of the TMJ in Phase I. However, the extreme margins of the joint were more commonly visualized using standard arthroscopy. Live horses in phase II were restrained in stocks and both the rostral and caudal aspects of the DTJ and DMJ compartments of both TMJs were examined successfully understanding sedation and local analgesia. The use of a modified Guenther speculum allowed the mandible to be manipulated and offset, which facilitated a complete examination of the joint compartments. Despite adverse behavior encountered during the procedure in one horse, no surgical complications ensued.

Main limitations: Not blinded-bias; learning curve.

Conclusions: The needle arthroscope system is a relatively inexpensive diagnostic tool, which can be used to evaluate the TMJ in the absence of advanced diagnostic imaging such as computed tomography or magnetic resonance imaging. However, if arthroscopic treatment is required after advanced imaging and pre-operative diagnosis, superior image quality and ease of manipulation may favor the use of the standard equipment.

Keywords: arthroscopy; fiberoptic; needle arthroscopy; temporomandibular joint; video arthroscopy.

Figure 1

Still arthroscopic image of the medial aspect of the discotemporal joint (DTJ) using the needle (NAS) (A) and standard (STAN) (B) arthroscopic systems. 1, the articular eminence of the temporal bone; 2, intra-articular disc.

Figure 2

Still arthroscopic image of the caudolateral aspect of the discotemporal joint (DTJ) using the NAS (A) and the STAN (B). 1, intra-articular disc; 2, caudal aspect of the joint.

Figure 3

Still arthroscopic image showing the caudal aspect of the condylar process of the mandible (1) with synovial plical insertion (2) within the discomandibular joint (DMJ) using the NAS (A) and STAN (B).

Figure 4

Still arthroscopic image of the caudomedial aspect of the DTJ using the NAS (A) and the STAN (B). A perforation (black arrow) in the intra-articular disc was identified at the caudomedial fibrous expansion (cfe) with both modalities. 1, intra-articular disc; 2, articular eminence of the temporal bone.

Figure 5

Still arthroscopic image of the DMJ using the STAN illustrating two abnormalities identified with this system which were not identified during joint exploration using the NAS. (A) View of an abnormal discoloration on the ventral aspect of the intra-articular disc from a distance. (B) Advancing the arthroscope highlights the dark pigmentation (blue arrow) present on the ventral aspect of the intra-articular disc. (C) Caudal aspect of the condylar process of the mandible with a defect on the articular surface. (D) Advancing the arthroscope confirms the presence of a cloaca associated with a mandibular cyst (black arrow). 1, Intra-articular disc; 2, condylar process of the mandible.