Disorders of the temporomandibular joint: value of gradient-echo T1 sequences to evaluate bony changes

Purpose. To identify and classify the different types of bony changes of th e condyles in patients with disorders of the temporomandibular joint (TMJ). Materials and methods. Since 1993, we have imaged over 600 patients with 0. 5T MR unit by using gradient-echo T1-weighted sequences in the sagittal and coronal planes. Results. We will first describe the appearance. of the normal TMJ. Then, we will introduce the concept of "Condylo-diskal disunion" using a three grad e classification system. We will then describe three patterns of condylar c hanges: adaptive remodeling, either anterior or more frequently posterier, degenerative lesions with subchondral sclerosis, erosive lesions due to synovial hyperplasia. Conclusion. Using a 0.5T MR unit, a GRE T1 sequence is useful to identify l esions of the disk and detect bony changes. In addition, the tissues poster ior to the disk can also be assessed on postcontrast images.