The Effects of Unilateral Discectomy and Condylectomy on the Contralateral Intact Rabbit Craniomandibular Joint

Purpose

The purpose of this study is to determine the effects of unilateral discectomy and condylectomy on the contralateral intact rabbit craniomandibular joint at the histological level.

Materials and Methods

Fifteen New Zealand white rabbits were used and divided into 3 groups. Three rabbits were used as controls (group A) whereby a sham operation was undertaken without breaching the joint space of the left craniomandibular joint (CMJ). In 6 rabbits (group B), the articular disc of the left CMJ was excised. The remaining 6 rabbits (group C) underwent surgical resection of the left condylar head at the level of the condylar neck. The resultant surgical defects were left to heal without any grafting and the incisions were closed with resorbable sutures. The rabbits were sacrificed at 4, 12, and 20 weeks after surgery and both the left and right CMJs were histologically prepared and examined under light microscopy.

Results

In the 4-week group, unilateral discectomy and condylectomy resulted in remodeling of the unoperated right CMJ with histological evidence of flattening of the condylar head which was more pronounced in the condylectomy group. In the 12-week group, the remodeling process in the unoperated right CMJ was less pronounced with most of the activity concentrated in the medial pole, especially in the condylectomy group. The 20-week group showed no obvious signs of remodeling in the unoperated right CMJs in both the discectomy and condylectomy groups. Evidence of condylar regeneration was seen in all groups in the left CMJ which had undergone condylectomy. No evidence of disc regeneration in the operated left CMJ was seen in any of the discectomy groups.

Conclusions

Unilateral discectomy and condylectomy have an early adverse effect on the structural integrity of the contralateral unoperated CMJ which appears to be short lived. The early remodeling effects on the unoperated right CMJ appear to be reversible as the operated left CMJ heals.