We have read the paper by D uan and Z hang with interest, and would like to discuss an important finding.
The most interesting and important finding of this study population is the presence of concomitant mandibular fracture in all the patients of the ankylosis group with type III sagittal fracture of the mandibular condyle (SFMC) . The finding was over looked by the authors. In the study, the authors categorized SFMC into three types . In type I and type II, the lateral pole of the condyle remains within the confines of the articular fossa . In type III there is juxtaarticular positioning of the lateral pole (i.e. over the outer rim of glenoid fossa ) due to superolateral displacement of fractured lateral condyle and ramus complex. The juxta-articular adhesion of TMJ was noted in all the type III cases and the authors held the disc displacement as a primary responsible factor for the ossifying pathology . However, we consider disc displacement as a secondary factor for development of TMJ ankylosis in cases of type III SMFC. Insight into the mechanism of type III SMFC related TMJ ankylosis, an intact lateral condylar pole which provides vertical and horizontal support the mandible demands a release (fracture) from the body or symphysis region to displace superolaterally over the juxta-articular region (resulting in widening of mandibular arch or increased inter-condylar width ). Without the release, it is usually not possible from an intact lateral pole of a condyle to leave the confines of the articular fossa. This displacement disrupts the periarticular anatomical boundaries which cause extensive haemorrhage spreading to the extracapsular sites bypassing any impediment the articular disc may produce . At this instance, it is mandatory to reduce the concomitant fracture adequately to achieve original inter-condylar distance/mandibular arch width and to place the intact lateral pole of the condyle within the confines of the articular fossa under the cover of the meniscus. No or inadequate reduction of concomitant fractures leaves the fractured lateral condylar pole in contact with the lateral rim of glenoid fossa . Ossification occurs whenever the extra-capsular haematoma is populated by endoosseous vessels culminating in juxta-articular type of TMJ adhesion in the absence of adequate fracture reduction . Against this back ground, one could put forth the hypothesis that the common cause for type III SFMC is the presence of a concomitant fracture and no or inadequate reduction of associated mandibular fracture is a predisposing factor for juxta articular type of TMJ ankylosis. Unfortunately, in the study of D uan and Z hang , there is no mention of quality of reduction of concomitant fractures and the postoperative position of the lateral condylar pole.
The above observation also provides evidence that it is the displacement of the lateral condyle rather the meniscus (which is relatively similar to type II) is a high risk factor in developing lateral adhesion of TMJ in cases of types II and III SFMC. In cases if type I SFMC, we believe the amount of damage to the meniscus is a risk factor for obliteration of TMJ joint.
For type III SFMC, we follow a protocol (‘Arakeri’s protocol’ developed by author GA) to prevent/treat trans-articular adhesion and we found less incidence and reduced recurrence of TMJ ankylosis ( Fig. 1 ).