Nearthrosis in true long-standing temporomandibular joint dislocation; a report on pathogenesis and clinical features with review of literature.

The behavior and function of the condyle are not the same in every type of temporomandibular joint (TMJ) dislocation. Acute displacement or dislocation of the condyle is not a rare incident, and the treatment modalities have been well known by physicians for a long time. Chronic dislocation of the condyle is considered a relatively common entity for which treatment may indispensably be surgical intervention. Type of dislocation, duration and the number of episodes are taken into account while constructing the treatment plan. Chronic dislocation that has been left untreated for a long time is a relatively less often encountered type exhibiting difficult clinical conditions for treatment. This type of dislocation is usually seen in elderly patients with poor general health conditions and can be classified as "long-standing dislocation." In this clinical condition, after having some chronic dislocation episodes, the condyle leaves the original fossa, sits in the anterior part of the eminence permanently, creates a new fossa and never gets back to the original place again. Duration is the most important criterion in classifying long-standing dislocations and has a great effect on decisions regarding the type of management. The relevant literature includes few reports, most of which speculate upon "duration," which varies on a large scale ranging from 5 weeks to 33 years. There has been neither an agreement on time span within which long-standing dislocation develops, nor a universally accepted definition for what "long-standing" is indeed meant to be. On the other hand, in some cases, the condition has been named "true long-standing dislocation" due to some permanent pathological changes that the TMJ undergoes, such as pseudoarticulation/nearthrosis/false joint/neo-joint. In this paper, management of true long-standing/permanent dislocation in two patients, whose conditions lasted more than 1 year and resulted in permanent changes in TMJ anatomy, is presented. Due to the poor general health condition of the two elderly patients, they were treated in the most conservative way possible. In one of the patients, eminectomy and head-gear application were used to attain gradual relocation of the condyles. Rehabilitation of masticatory function of the other patient was improved prosthetically.