MIDFACE DISTRACTION ADVANCEMENT IN THE CANINE WITHOUT OSTEOTOMIES

Midface hypoplasia, often associated with exorbitism and malocclusion, has been traditionally corrected by using Le Fort advancement osteoto mies through wide surgical exposure, These procedures suffer the disad vantages of hemorrhage, unpredictable bone graft resorption, the need for retained hardware, and bone graft donor-site morbidity. We present an investigation of midface distraction in the canine without osteoto mies, Five canines were the subjects of this study and were divided in to two groups, At the time of placement of the lengthening devices, Gr oup 1 animals were 10 weeks of age and Group 2 animals were 5 years of age, Under general anesthesia, four modified Hoffman bone distracters were mounted on 2-mm half pins placed individually across the nasofro ntal and the zygomaticotemporal sutures an each side of the craniofaci al skeleton, Distraction of all devices was begun on postoperative day 1 at the rate of 0.5 mm/day for 4 days and then 1.0 mm/day for 28 day s, after which interval the devices were removed, Phe dogs were serial ly monitored and examined for 3 months, one dog in the first group ser ved as a sham control, The results were assessed by standardized cepha lograms, and craniofacial computed tomographic scans with three-dimens ional reconstruction performed before device placement as well as afte r removal of the device, In one Group 1 animal, computed tomographic s canning was performed every 2 to 4 weeks far 3 months, Gross examinati on of the Group 1 animals demonstrated the development of enophthalmos , dolichocephaly, and a class II malocclusion-overbite. No evidence of distraction or advancement of the midface was observed in the Group 2 dogs. Midface distraction is feasible in the immature animal. If mini aturized devices could be developed, the clinical implications for you ng patients with midface hypoplasia may be significant.