The use of pseudo-dynamic magnetic resonance imaging for evaluating the relationship between temporomandibular joint anterior disc displacement and joint pain

Abstract

The relationship between temporomandibular joint (TMJ) pain and the magnetic resonance imaging (MRI) finding of articular disc displacement is debated. The purpose of this study is to investigate the correlation between TMJ pain and anterior disc displacement (ADD) using pseudo-dynamic MRI. A retrospective review of MRI studies was carried out on 130 TMJs in 65 patients presenting unilateral TMJ pain. The contralateral asymptomatic joints served as the control group. Bilateral oblique sagittal and coronal MRIs as well as pseudo-dynamic studies in the oblique sagittal plane were obtained. The disc–condyle relationship was divided into three subtypes (normal disc position, ADD with reduction, and ADD without reduction), based on the pseudo-dynamic MRI findings. Fisher’s exact test was used to determine whether the TMJ pain was linked to ADD. The results showed that TMJ pain was significantly related to ADD (with and without reduction) compared to the group with a normal disc position ( P = .0001). A significant correlation was found between TMJ pain and the ADD subtype without reduction, as compared to the ADD subtype with reduction ( P = .0156). These data suggest that a displaced disc, particularly in the subtype without reduction, is an important source of pain.

Pain is a symptom that frequently arises in patients with TMJ dysfunction. The disc location is of prime importance for the TMJ because a displaced disc is a critical sign of joint dysfunction. Many other conditions, including joint effusion, osteoarthritic changes, and bone marrow oedema in the mandibular condyle may serve as indirect signs of TMJ dysfunction. The prevalence of TMJ disc displacement among asymptomatic volunteers was previously reported to be up to 22–35%, and the prevalence of normal articular discs in symptomatic TMJs was reported to be 16–46%. MRI is currently the standard imaging modality for evaluating TMJ pathology, due to its high-resolution, non-invasive, and non-radiating nature. The aim of this study was to determine whether any significant relationship exists between TMJ pain and ADD, based on pseudo-dynamic MRI findings.

Materials and methods

The authors retrospectively evaluated the clinical records of MRI studies performed on the TMJs between March 2008 and June 2009. 65 patients who exhibited unilateral TMJ pain were included in this study. The contralateral pain-free TMJs were used as the control group. The patients comprised 17 men and 48 women, ranging in age from 11 to 66 years, with a mean age of 30.1 years. There were 40 patients with right TMJ pain and 25 patients with left TMJ pain. All patients underwent MRI for bilateral TMJs (a total of 130 TMJs). The authors excluded patients with bilateral TMJ pain. Patients with TMJ pain due to muscular disorders based on the Research Diagnostic Criteria for the Temporomandibular Disorders (RDC/TMD) criteria were also excluded.

The MRI examinations were performed using a 1.5-T imager (Gyroscan; Philips Medical System, The Netherlands) with a dual surface coil. An axial scout image of both condyles was first obtained to visualize the long axes of the bilateral condyles. The imaging protocols consisted of spin echo T1-weighted imaging (T1WI) (repetition time/echo time: 448/20) and fast field echo (gradient echo) T2-weighted imaging (T2WI) (repetition time/echo time: 458/23; flip angle 20–30°) with 3 mm slice thickness in the oblique coronal plane parallel to the horizontal long axis of the mandibular condyle and in the oblique sagittal plane perpendicular to the horizontal long axis of the mandibular condyle. The data were collected on a 256 × 256 matrix with a field of view of 140 mm in the oblique sagittal plane and 120 mm in the oblique coronal plane. Pseudo-dynamic studies were performed on T2WI in the oblique sagittal plane with patients in the closed-mouth, 1/4 open-mouth, 1/2 open-mouth, 3/4 open-mouth and maximum open-mouth positions. Patients were educated and they practiced prior to the examinations. No intravenous contrast medium was administered.

MRI studies were interpreted by two experienced neuroradiologists who were blinded to the clinical information (i.e. which joint was painful) and the decision was made by consensus. The definition for the normal disc position was to visualize the end of the posterior band at the 12 o’clock position relative to the condyle on closed-mouth position in static MRI, and normal disc–condyle relationship in pseudo-dynamic studies ( Fig. 1 ). Any forward displacement of the disc on closed-mouth position was regarded as ADD. The joints with ADD were further divided into two subtypes, with and without reduction, based on pseudo-dynamic MRI findings. If the displaced disc restored the normal disc–condyle relationship in the open-mouth position, it was classified as ADD with reduction ( Fig. 2 ). If the displaced disc remained in an anterior position relative to the condyle in the maximum open-mouth position, it was classified as ADD without reduction ( Fig. 3 ).