Plate fixation of premaxillomaxillary suture and compensatory midfacial growth changes in the rabbit

It has been suggested that rigid fixation of the developing craniofacial skeleton may lead to altered craniofacial growth. However, recent experimental studies have shown that microplate fixation of slow-growing calvarial sutures resulted in regional growth disturbances but had little effect on overall craniofacial growth. The present study was designed to assess the effects of microplate fixation of the more rapidly growing facial sutures on compensatory midfacial growth in the rabbit. Twenty-two 1.5-week-old rabbits were randomly divided into 2 groups: sham controls (n = 11) and animals with bilateral premaxillomaxillary suture fixation (n = 11). Fixation was accomplished using an intraoral approach, a 6-mm straight Luhr microplate, and two 2-mm long self-tapping screws across each suture. Serial lateral head radiographs were collected at 1.5, 3.5, 6, 12, and 18 weeks of age. Results revealed that by 3.5 weeks, animals with rigid fixation showed significantly shortened premaxillary lengths (p < 0.05), class III occlusal relationships, decreased midfacial heights, and abnormal palatocranial base angles compared with sham control animals. By 12 weeks of age, "catch-up" growth was evident in most dimensions in animals with fixation compared with shams. Gross examination of the cleaned and dried skulls revealed bony bridging across the premaxillomaxillary suture and osseous fracture lines extending superiorly from the site of screw fixation. Results demonstrated that rigid fixation of a rapidly growing facial suture did not impair long-term midfacial growth in the rabbit model and suggest that compensatory changes may have occurred at fracture lines from the self-tapping screws in these animals.