The evaluation of lateral pterygoid muscle pathologic changes and insertion patterns in temporomandibular joints with or without disc displacement using magnetic resonance imaging.

Temporomandibular joint (TMJ) disc displacement is a common disorder in patients with internal derangement. Certain anatomic features of TMJ may make the patient prone to this condition, namely lateral pterygoid muscle (LPM) insertion variations. The aim of this study was to investigate LPM attachments and their relationships with disc displacement and subsequent pathologic changes. A total of 26 patients with clinical temporomandibular disorders (TMDs) and a control group of 14 unaffected individuals were studied. Magnetic resonance images (MRIs) were taken to evaluate LPM insertion patterns, superior LPM head pathologic changes, and relative disc to condyle position. Data registration and analysis were done using SPSS v. 16.0. The most common variation (type I) was shown to be the superior head with two bundles, one attached to the disc and another to the condyle. No significant relationship between LPM insertion type and disc displacement or pathologic changes of the muscle was found. However, a link between disc displacement and muscle pathologic changes was established (P=0.001).