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.ObjectiveTo compare and contrast two arthroscopic systems for assessing the equine temporomandibular joint compartments in cadavers and standing horses.Study designExperimental study.MethodsPhase 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.ResultsNeedle 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 LimitationsNot blinded—bias; learning curve.ConclusionsThe 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.

Contrast arthrography of the equine temporomandibular joint

“…In both cases, this occurred while attempting to enter the DMJ and the error resulted in contrast material being present in both joint compartments simultaneously. This diagnostic finding mimics that associated with pathological tears of the disc and could potentially lead to erroneous diagnoses or further, unnecessary, diagnostic tests such as arthroscopy ( 18–20 ). The condylar process of the mandible slopes medioventrally away from the skin with the intra-articular disc in close apposition.…”

Equine Models of Temporomandibular Joint Osteoarthritis: A Review of Feasibility, Biomarkers, and Molecular Signaling

“…Similar bone changes can be observed on CT images in both humans [ 51 , 63 ] and horses [ 6 , 7 , 41 , 59 ]. Cartilage defects can be visualized using arthroscopy, more often in horses [ 34 , 59 , 64 ] than in humans [ 65 ], and MRI, on the contrary, more often in humans [ 49 , 60 , 66 , 67 , 68 ] than in horses [ 62 , 69 ].…”

“…Recently, challenges such as the difficulty and expense of housing and managing horses [ 139 ], as well as the high cost, long research period, and slow disease progression [ 14 ], have been highlighted. While it is acknowledged that horses represent an expensive experimental model, the numerous studies referenced focusing on both equine athletes and experimental horses suggest that they are manageable subjects [ 5 , 6 , 7 , 8 , 25 , 34 , 36 , 37 , 38 , 39 , 40 , 41 , 59 , 61 , 62 , 64 , 137 ].…”

“…Therefore, improving animal TMJ OA models may be considered the primary means of testing potential therapeutic agents to determine their potential efficacy in this specific disease [ 14 , 16 ]. On the other hand, evaluating treatments in clinical equine practice [ 6 , 7 , 34 , 36 , 37 , 40 , 59 , 64 ] faces similar challenges to those in humans [ 35 ]. In both cases, high-quality randomized, controlled trials with well-validated outcome measures are needed to improve the investigation of the efficacy of TMJ OA treatment strategies.…”