The Effect of Rigid Internal Fixation on Growth of the Mandibulofacial Bone in Growing Rabbits.

Yang, Sung Yurl; Lee, Kwang Choul; Kang, Nak Heon; Wee, Sung Shin; Lee, Chong Kun

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Original Article

Journal of the Korean Society of Plastic and Reconstructive Surgeons 1999;26(1):118-132.
Published online January 1, 1999.

The Effect of Rigid Internal Fixation on Growth of the Mandibulofacial Bone in Growing Rabbits.

Sung Yurl Yang, Kwang Choul Lee, Nak Heon Kang, Sung Shin Wee, Chong Kun Lee

Department of Plastic and Reconstructive Surgery, The Catholic University of Korea, Seoul, Korea.

Abstract

Craniofacial reconstructive procedures are frequently peformed with rigid fixation of the bone. During the period of active bone growth such manipulation may influence bone development. The purpose of this study was to determine the effects of metal plating of the mandible on the growth and morphology of the mandibulofacial skeleton. New Zealand white rabbits, 6 to7 weeks of age, were divided into 5 groups. They were designated as group I(nonoperated control, n=10), group II (rigid fixation of mandibular body after vertical osteotomy, n=10), group III(rigid fixation without osteotomy, n=10), group IV (interosseous wire fixation after osteotomy, n=10), and group V(rigid fixation and removal of plates and screws 4 weeks after osteotomy, n=7). Rabbits were sacrificed 12 weeks after operation and dry skull preparations were grossly measured and analyzed by direct measurement and by dorsoventral skull x-rays. Measurements taken were length, thickness, angle, and area of the mandibulofacial skeleton. Three-dimensional CT was used for volumetric measurement of the mandible. The data wee compared between the operated and nonoperated sides and significant differences between groups were evaluated using the paired t-test, the ANOVA test, and Dunn's test. The following results were obtained: 1. The length of the whole mandible and the anterior mandibular segment was decreased in groups II and III, compared with group I(p>0.05). These results show growth restriction of the plated mandible regardless of osteotomy. 2. The maxillary alveolus of the operated side was more anteriorly placed in groups II and III, compared with group I (p>0.05). 3. The thickness of the operated mandibular body showed a significant increase in groups II and III, compared with group I(p>0.05). 4. The length of the zygomatic arch of the operated side in all the experimental groups showed a significant decrease, compared with group I(p>0.05). The angular divergence of the mandibular ramus from the sagittal midline of the skull was increased in the operated side of groups II and III, compared with the nonoperated side (p>0.05). 5. Volume measurements of the mandible in groups II and III showed a significant reduction of the volume on the operated sides in the anterior mandibular segment, compared with group I(p>0.05). The volume of the operated mandibular body showed a significant increase in groups II and III, compared with group I(p>0.05). All gruops showed no significant difference in total hemiman dibular volume of the operated side compared with the nonoperated side. These results show that rigid fixation of mandibular fractures during the growth period causes a more severe growth restriction than either osteotomy or interosseous wiring.

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