A reference line on temporomandibular joint MRI

Area of Science:

• Dentistry
• Radiology
• Orthodontics

Background:

• Accurate assessment of temporomandibular joint (TMJ) disk position is crucial for diagnosing early degenerative changes.
• Current methods for establishing reference points on MRI can be complex, limiting clinical application.

Purpose of the Study:

• To establish a reproducible reference line (RL) and 12 o'clock position on sagittal temporomandibular joint (TMJ) MRI images.
• To enable precise observation of early TMJ disk position changes.

Main Methods:

• Utilized MRI and limited cone-beam computed tomography (LCBCT) images from 53 patients (106 joints).
• Superimposed LCBCT-derived true horizontal line (THL) onto MRI images.
• Developed a clinically applicable reference line (RL) connecting the articular eminence and auditory canal center, assessing its correlation with THL.

Main Results:

• The mean angle between the true horizontal line (THL) and the reference line (RL) on MRI was 2.2°.
• A high positive correlation (r = 0.84) was found between THL and RL angulations, validating the RL's accuracy.

Conclusions:

• The established reference line (RL) and angle can be used to directly determine the true horizontal line (THL) on MRI in patients without advanced bony changes.
• The deepest point of the glenoid fossa intersecting the THL serves as the 12 o'clock position for evaluating incipient TMJ disk displacement.