The present study suggest a new way of expressing the anterior disc displacement through the angle formed by the most concave portion of the glenoid fossa, the center of the mandibular condyle and the junction of the posterior band and
retrodiscal
tissue. The new method was tested on MRI findings of 40 symptom-free joints. The angle was 0* on 14 joints, and 82.5% of the joints were within -5*~5* range, with one joint having more than 10* displacement. The mean angle was -120+3.79, and this
results shows that there are little disc displacemrents in asymptomatic joints. The result suggest that the new method may be used as a meaningful way of expressing the anterior displacement. In this method, the center of the condyle head is
esaily
recognized regardless of its shape, and no matter where the condyle head is located relative to the fossa, the reference line connccting the center of the condyle head and the concavity of the fossa can be easily obtained. The reference line
includes
all of the anatomical and functional structures of the joint, can compensate for the anatomical variations in the condyle shape, and can easily be applied with high reproducibility. Instead of using confusing references as '12 o' clock direction
'
or
'immediately superior to the condylar head' this method uses anatomical reference points thereby accounting for the individual variations.
|