Correction of rabbit model with mandibular ramus shortening by distraction osteogenesis at condylar neck.

PURPOSE: The rabbit model has been established to mimic the effect of temporomandibular joint (TMJ) arthroplasty of ankylosis, and distraction at the level of the condylar neck is used to elongate the ascending ramus. The histomorphologic changes of TMJ and distraction gap were investigated.

MATERIALS AND

METHODS

The unilateral condyles and articular discs were extirpated, and the experimental mandibular rami were shortened by 5 mm. An embedded distracter was used to restore the height of the mandibular ramus by unilateral condylar neck distraction (0.8 mm daily for 7 days). A total of 12 adult white rabbits were used, 8 in the experimental group and 4 in the control group. Of the 8 rabbits in the experimental group, 4 each were killed at 4 and 8 weeks after completion of distraction. The TMJ and distracted calluses were harvested and processed for radiographic and histologic examination.

RESULTS

An open bite was seen in all rabbits postoperatively that had diminished at the end of distraction. The newly formed condyles radiologically showed remodeling, flattening, and sclerosis. The bony transport disc had gradually remodeled to a new condyle that was similar to the original condyle in appearance and structure. The surface of the transport disc was covered with a fibrous tissue. Moreover, the bony regeneration was perfect in the distraction gap.

CONCLUSION

These results suggest that distraction osteogenesis at the condylar neck using the traditional preauricular approach of TMJ surgery, without the additional incision, can be performed concurrently with arthroplasty of TMJ ankylosis at the same region.