Temporomandibular joint and 3.0 T pseudodynamic magnetic resonance imaging. Part 1: evaluation of condylar and disc dysfunction

Abstract

Objectives: This study describes an improved method for examining and diagnosing temporomandibular joint (TMJ) dynamics by 3.0 T pseudodynamic MRI.

Methods: Clinical observation and conventional static MRI of volunteers (one without and eight with TMJ arthrosis) were followed by 3.0 T pseudodynamic MRI in positions ranging from the mouth closed to mouth fully opened. Condylar head (Cd), articular disc anterior border (Da) and articular disc posterior border (Dp) were digitized on sagittal images to determine trajectory and velocity patterns.

Results: Patients were divided into three groups based on the presence or absence of dysfunction: Group 1, no dysfunction on the right or left side of the TMJ; Group 2, dysfunction on the right or left side of the TMJ; and Group 3, dysfunction on both the right and left sides of the TMJs. In 75% of patients (12 of 16 joints), pseudodynamic TMJ analysis was useful for determining a functional abnormality. Using a points system based on three trajectory and seven velocity patterns, discs with adhesion and perforation had significantly fewer points than discs with anterior displacement (with and without reduction) and discs with no abnormality (P = 0.019 < 0.05).

Conclusions: Trajectory and velocity patterns based on 3.0 T pseudodynamic MRI identified the affected side and determined the extent of morbidity in the Cd as well as the Da and Dp. The typical abnormal movement pattern of discs with anterior displacement (with and without reduction) and pathological structural changes of the articular disc (such as adhesion and perforation) could be identified.

Figure 1

Co-ordinate points for pseudodynamic measurement. Em, lowest articular eminence; Cd, highest protrusion of the condylar head, where the perpendicular line from the posterior mandibular ramus meets the condylar head; Da, articular disc anterior border, where the posterior border of the anterior attachment showing low signal intensity is separated from the surrounding area in the anterior band of the articular disc; Dp, articular disc posterior border, where a bow tie configuration is derived from a temporal part of posterior attachment and a condylar part of posterior attachment

Figure 2

Normal (a) trajectory and (b) velocity patterns (Case 1, left temporomandibular joint)

Figure 3

Trajectory patterns I-a, I-b, II and III; Cd, condylar head; Dp, posterior border of the articular disc; Type I, relatively curved; subtype I-a, downward trajectory at flap 0 to 1; subtype I-b, upward trajectory at flap 0 to 1; Type II, relatively short and straight; Type III, zigzag

Figure 4

Velocity patterns 1A/2A/3A, 1B/2B/3B, 4A/5A/6A/7 and 4B/5B/6B/7. Type 1, chevron shape with one peak; Type 2, U-shape with one trough; Type 3, convexo-concave shape with one peak and one trough; Type 4, convexo-concave shape with a total of three asperities of velocity; Type 5, without peak or trough in velocity and move or stop gradually; Type 6, without peak or trough in velocity and becomes temporally stable; Type 7, without peak or trough in velocity and stable; 0–1 flap, initial step; 1–2 flaps, early steps; 2–3 flaps, intermediate steps; 3–4 flaps, late steps; 4–5 flaps, final steps

Figure 5

Anterior disc displacement with reduction (ADDwR) (Case 4): (a) trajectory pattern and (b) velocity pattern

Figure 6

Anterior disc displacement without reduction (ADDwR) (Case 6): (a) trajectory pattern and (b) velocity paltern

Figure 7

Disc adhesion (Case 9): (a) trajectory pattern and (b) velocity pattern

Figure 8

Disc perforation (Case 8): (a) trajectory pattern and (b) velocity pattern