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Disc mobility and arthroscopic condition of the temporomandibular joint associated with long-term mandibular discontinuity.

PURPOSE
The present study aimed to explore disc mobility and arthroscopically diagnosed morphologic changes in the temporomandibular joint (TMJ) associated with long-term mandibular discontinuity.


PATIENTS AND METHODS
Twelve patients (24 TMJs) who had undergone mandibulectomy including the unilateral condyle or segmental mandibulectomy without mandibular reconstruction, more than 8 months before this study were examined. The 24 TMJs were classified into 3 groups as follows: group 1, TMJs with a major mandibular fragment including the mandibular body (n = 11); group 2, TMJs with a mandibular ramus including the coronoid process (n = 5); and group 3, TMJs with only a condylar process, a mandibular ramus not including the coronoid process, or without a condyle (n = 8). Disc mobility was evaluated by magnetic resonance imaging, and arthroscopic observation of the superior joint compartment (SJC) was performed in all TMJs. The relationship between disc mobility and the arthroscopic findings was also studied.


RESULTS
The frequency of immobile discs differed significantly among groups 1 (0%), 2 (40.0%), and 3 (100%). Arthroscopic findings were normal in all SJCs of group 1. Various types of fibrous adhesions were observed in 40.0% of group 2 and in 75.0% of group 3. The development of fibrous adhesions in the SJC was significantly related to the presence of an immobile disc.


CONCLUSIONS
Long-term immobilization of the TMJ in a nonfunctional state seems to promote the development of fibrous adhesions in the SJC. Preservation of the mandibular fragment including the coronoid process, during mandibulectomy appears to contribute to postoperative TMJ mobility. To ensure recovery of a physiologic TMJ after mandibulectomy, it seems important to re-establish TMJ mobility by establishing mandibular continuity as soon as possible.