Vibration analysis of the temporomandibular joints with meniscal displacement with and without reduction.

The vibrations of 102 joints demonstrating meniscal displacement with either early or late reduction (MDR-early/MDR-late) and 70 joints displaying meniscal displacement without reduction either incomplete or complete (MD-incomplete/MD-complete) were analyzed and compared to 83 arthrographically normal but symptomatic joints (NID) using electrovibratography (EVG). The total power density of the vibration [I(T)], peak power density [I(max)] and power density at each 50Hz range between O to 600 Hz [I(f)] showed the highest in the MDR-late group followed by the MDR-early group, suggesting that the level of vibration is related to the degree of disk displacement and reduction. The wave characteristic parameters such as the correlation coefficients between I(T) and each I(f) showed higher correlation at higher frequency ranges as the degree of disk displacement progressed, from MDR-early to MDR-late to MD-incomplete. The diagnostic sensitivity of EVG when using I(T) as a determining parameter was 96.6% for the MDR-early group, 91.8% for the MDR-late group, 77.8% for the MD-incomplete group and 57.4% for the MD-complete group with the specificity for the NID group at 75%.