Some anatomical factors of the upper compartment of the temporomandibular joint related to the disc position.

Temporomandibular joint (TMJ) arthrograms of 20 joints with superior disc position (SDP), 20 joints with anterior disc displacement with reduction (ADDWR), and 20 joints with anterior disc displacement without reduction (ADDWOR) were compared. The distance from the insertion of the posterior disc attachment of the upper joint compartment to the top of the mandibular fossa in joints with ADDWR was significantly longer than in joints with SDP and ADDWOR (p = 0.003). The distance from the top of the mandibular fossa to the top of the articular eminence in joints with ADDWR was significantly shorter than in joints with ADDWOR (p = 0.006). The entire distance of the upper joint compartment in joints with ADDWR was significantly longer than in joints with SDP and ADDWOR (p = 0.02).