Equine temporomandibular joint diseases: A systematic review.

Background: The temporomandibular joint (TMJ) is a unique joint that enables mandibular movement. Temporomandibular diseases (TMDs) impair joint function, leading to more or less specific clinical signs.

Objectives: To compile and disseminate clinical data and research findings from existing publications on equine TMD.

Study design: Systematic review.

Methods: Following PRISMA 2020 guidelines, literature searches were conducted in PUBMED, Scopus, and Web of Knowledge. The inclusion criteria covered case reports and research articles on equine TMDs. The selected records were grouped considering septic TMJ arthritis, primary TMJ osteoarthritis (OA), and non-arthritic TMDs. A risk of bias assessment was performed for the research articles.

Results: Equine TMD has been described in 51 publications to date, with septic TMJ arthritis accounting for 41.2% of TMD cases, fractures/luxations for 29.4%, and primary TMJ OA for 21.6%. Trauma was confirmed or suspected in 54.9% of TMD cases. The severity of clinical signs was mild to moderate in primary TMJ OA and mild to severe in septic TMJ arthritis and non-arthritic TMDs. Clinical signs were related to the underlying cause, particularly in terms of TMJ swelling, pain, and masticatory problems. Among diagnostic imaging modalities, CT was utilised in 92.2% of horses, radiography in 84.4%, and ultrasonography in 21.6%.

Main limitations: The lack of clinical data in some reports. A risk of bias due to missing data.

Conclusions: TMDs are infrequently described, with trauma being the most common TMD cause. TMDs are associated with TMJ dysfunction; however, the diagnostic protocol is varied. Regardless of the TMD type, a detailed diagnostic protocol should include a thorough history, detailed TMJ examination, and radiography as the first imaging choice in field practice, with CT as the 'gold standard' in clinical settings. For septic TMJ arthritis, a bacterial culture is recommended, while for primary TMJ OA, functional tests and local analgesia.