The Frequency of Communication Between the Synovial Compartments of the Equine Temporomandibular Joint: A Contrast-Enhanced Computed Tomographic Assessment

Abstract

Background: There is conflicting evidence regarding communication between the two compartments of the equine temporomandibular joint (TMJ). Understanding the inter-relationship between TMJ compartments is critical for diagnostic and clinical management purposes.Objective: To determine the frequency of communication between the discotemporal joint (DTJ) and the discomandibular joint (DMJ) of the equine TMJ in horses free of overt disease.Study Design: A randomized, blinded, controlled cadaveric study.Methods: Equine cadaver heads (n = 20), with no reported history of potential TMJ disease, were collected and stored frozen until use. Horses were randomized to the treatment group, such that Group A horses (n = 10) underwent arthrocentesis of the left DTJ and the right DMJ compartments, while Group B (n = 10) underwent arthrocentesis of the left DMJ and the right DTJ compartments of the TMJ, for a total of 40 joints. Computed tomography (CT) imaging was performed before, and after, intra-articular injection of contrast media in each head. Two observers, blinded to the treatment group, independently interpreted CT images.Results: Communication between synovial compartments occurred in the left TMJ of two horses. Arthroscopic evaluation revealed that both horses had a perforation of the intra-articular disc in the region of the caudomedial fibrous expansion. Mild anterior displacement of the abnormal disc in the joint of one horse was demonstrated using magnetic resonance imaging (MRI).Main Limitations: Sample size, the use of owner provided animals' history, and frozen specimens.Conclusions: No physiological communication was present between the DTJ and the DMJ in the equine TMJ of the cases studied, regardless of which compartment underwent arthrocentesis. Two joints had pathological communications. These results suggest that diagnostic, and medical, treatment of intra-articular disease may be most effective when both joint compartments are injected. Furthermore, this study illustrates the value of contrast enhancement while imaging the equine TMJ.

Long-Term Outcome of Horses Undergoing Unilateral Mandibular Condylectomy and Meniscectomy for Temporomandibular Joint Disease

“…Post-operative complications included serous or serosanguinous drainage from the incision (5 horses), swelling at the incision ( 5 ), formation of a sequestrum and draining tract at the incision ( 2 ), formation of an abscess ventral to the incision ( 1 ), signs of colic ( 2 ), and hyporexia ( 2 ) ( Table 3 ).…”

“…The temporomandibular joint (TMJ) of the horse is an incongruous joint formed ventrally by the mandibular condyle and dorsally by the zygomatic process of the temporal bone ( 1 ). The joint is divided into two compartments, which are separated by the fibrocartilagenous intra-articular disc and communicate only when one or both are diseased ( 2 , 3 ). The discotemporal compartment is dorsal to the disc, and larger than the ventral discomandibular compartment.…”

Contrast arthrography of the equine temporomandibular joint

“…Relative to the bone margins of the joint, the intra-articular disc is radiolucent (soft tissue radiodensity), unless there is dystrophic mineralization associated with the structure. Contrast CT has been used to assess the integrity of the joint compartments and the intra-articular disc, but this modality is not readily accessible to a significant portion of the horse-owning population ( 16 ). Single- and double-contrast arthrography has been used to examine the joints of the appendicular skeleton and may be beneficial in the investigation of the equine TMJ.…”

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

“…Similar to the human anatomy, the equine TMJ is comprised of two independent synovial compartments ( 2 ), the larger dorsal discotemporal joint (DTJ) and the smaller discomandibular joint (DMJ), separated by a biconcave intra-articular disc. The arthroscopic approach and anatomy of the equine joint compartments have been well-described ( 3 – 7 ).…”

“…Equine TMJ-OA has also been associated with colic ( 18 ), poor performance ( 19 ), and behavioral abnormalities under saddle ( 20 ). Specialized radiographic projections have been described to evaluate this joint ( 21 , 22 ); however advanced imaging, including contrast-enhanced computed tomography (CT), has been shown to be useful in the assessment of this joint ( 2 ). When access to these advanced modalities is limited, or when surgical treatment is required, arthroscopic techniques offer the ability to thoroughly assess the articular cartilage and intra-articular disc ( 3 , 19 , 23 ).…”