A tangential radiographic projection for investigation of the equine temporomandibular joint.

Abstract

OBJECTIVE: To (1) describe a tangential radiographic projection of the equine temporomandibular joint (TMJ) and (2) optimize the radiographic angle and determine its use in standing sedated horses. STUDY DESIGN: Descriptive study. ANIMALS: Cadaveric equine skulls (n=11); 8 horses with a history of quidding or headshaking. METHODS: Tangential radiographic projections were taken of a TMJ of a cadaveric skull before and after intra-articular injection of radiographic contrast. Additional tangential radiographic projections were taken after TMJ dissection and placement of a wire along the articular surface of the mandibular condyle. Subsequently, 3 tangential radiographs were taken of both TMJs of 10 skulls at 75 degrees , 70 degrees , and 65 degrees to the dorsal plane (Rt/Le15Cd70D-Le/RtRVO). Each of the 3 images for each TMJ was ranked by 4 observers who were unaware of the projection angle. Interobserver variation was calculated using a Friedman analysis of variance and significance of the most prevalent angle with a 1-sample repeated measures test. Tangential radiographic projections of both TMJs were then taken of 8 standing sedated horses. RESULTS: Tangential radiographic projections allowed the lateral half of the TMJ to be viewed without superimposition of other structures and the anatomic orientation was determined. A 70 degrees projection to the dorsal plane was ranked as significantly better than other views (P<.001). There was no significant interobserver variation and the technique was safely performed in standing sedated horses with excellent image quality obtained. CLINICAL RELEVANCE: Tangential radiography of the TMJ may complement and add to information obtained from clinical examination and ultrasonography before referral for more advanced imaging techniques.