Ultrasonographic evaluation of masseter, trapezius, and sternocleidomastoid muscles in patients with internal derangement in the temporomandibular joint.

OBJECTIVES: This study aimed to evaluate the thickness, echogenicity, and fractal dimensions (FD) of the masseter, trapezius, and sternocleidomastoid (SCM) muscles on ultrasonography (US) images of patients with internal derangement in the temporomandibular joint (TMJ) and compare them with healthy individuals. METHODS: The study included 60 individuals who underwent US and magnetic resonance imaging (MRI) of the TMJ region for various reasons. The thickness, echogenicity, and FD of the masseter, trapezius, and SCM muscles were evaluated bilaterally in three groups as disc displacement with reduction (DDwR) (n:21), disc displacement without reduction (DDwoR) (n:18), and healthy controls (n:21), on US images and compared. RESULTS: Muscle thickness was higher in the control group than the patient group for all evaluated muscles and a statistically significant difference was observed for masseter muscles (p = 0.001). When the internal structure of the muscles was examined, Type I echogenicity was more common in the control group, and Type II echogenicity, was more common in the patient group. In the control group, FDs were higher for all muscles and statistical significance was found for masseter muscles (p = 0.019). CONCLUSION: Patients with internal derangement of the TMJ had decreased muscle thickness and deterioration in echogenicity compared to the healthy group.