Relationship between secondary ankylosis of temporomandibular joint and childhood longitudinal fracture of mandibular condyle

Jun YAO; Jilin ZHOU; Min HU; Min HONG; Yanyi WANG

ABSTRACT

BACKGROUND:

Much attention has been focused on mandibular condyle fracture, which has long been considered as a severe injury to the temporomandibular joint(TMJ). Restricted by diagnostic methods, many studies have been conducted on transverse fracture whereas little attention has been paid to longitudinal fracture of the mandibular condyle. Even less is known about longitudinal fracture in young children.

OBJECTIVE:

To evaluate the effects of childhood longitudinal fracture of the mandibular condyle on secondary ankylosis of TMJ.

DESIGN:

A randomized controlled study.

SETTING:

Department of Stomatology, General Hospital of Chinese PLA.MATERIALS The experiment was completed in the Center for Experimental Animals, General Hospital of Chinese PLA. Twelve young Chinese experimental miniature pigs bred by the Institute of Experimental Animals, Beijing Agriculture University, aged 2 -3 months and weighing(5 -5.5) kg, were used and raised with mixed feed, and then divided into 3 groups randomly.

METHODS:

Food and water was forbidden for the miniature pigs 12 hours before operation. Under anesthesia with(5.0 - 15.0) mg/kg ketamine/xylazine abdominally injected, conventional disinfection was performed in the right lateral decubitus position and layer-by-layer preauricular incisions were made on the left side of the miniature pigs. The joint cyst was incised transversely and the lower cavity of TMJ was exposed and dragged downwards. The mandibular condyle was cleaved into two vertically along the inner 1/3 part of it with a 5.0 mm-wide bone chisel to cause inferior and posterior sagittal fractures. The miniature pigs were executed 3 months and 6 months after operation, and their condyles were cut for observation.MAIN OUTCOME

MEASURES:

①The morphological changes of mandibular condyle specimens in the three groups observed with the naked eyes.②The pathological changes of mandibular condyle specimens under light microscope.

RESULTS:

The articular disc was adhered to the mandibular condyle after 3months. Temporal fossa adhered to the articular disc and mandibular condyle could still be observed in one specimen. Bifid condylar deformity was found in two specimens and no disc perforation was found. The adhesions became more severe after 6 months and bifid condylar deformity was formed in all the 3 specimens, with distinctly thickened discs. Light microscope observationThree months after fracture, the adhesion between disc and condyle was obvious. There was no clear boundary between the surrounding tissues. The adhesion was composed of fibro-connective tissues, with a large number of chondrocytes in it. Fibro-connective tissues tightly adhered to the trabeculae were found in some adhesions. The fiber of disc became deranged and blood vessels and fatty cells were seen. Six months after fracture, blood vessels, a large number of fibroblasts and sparse chondrocytes were seen in the adhesions. The collagen fibers of the discs were arranged in whirlpool shape. There were a large number of fatty cells and blood vessels within it. The fiber-cartilage of the condylar surface was found thickened and the fiber deranged in the unadhered tissues. Proliferative changes were seen on disc surfaces.

CONCLUSION:

Childhood longitudinal fracture of the mandibular condyle causes severe secondary injury to TMJ, suggesting a close correlation between longitudinal fracture of the mandibular condyle and TMJ ankylosis.