MULTIDIMENSIONAL DISTRACTION OSTEOGENESIS - THE CANINE ZYGOMA

The principle of distraction osteogenesis, well-established in the enc hondral bones of the axial skeleton, has recently been applied to the membranous bones (mandible, cranium) of the craniofacial skeleton in t he experimental animal and in the human. In the craniofacial skeleton, however, the technique has been used only to lengthen bone in a direc tion along its major axis, i.e., unidimensional distraction. A canine model is presented to demonstrate the feasibility of distracting membr anous bone away from its dominant axis, i.e., multidimensional distrac tion. Four mongrel dogs, 5 months of age, were the subjects of this st udy. Two osteotomies were made in the zygomatic arch, and the bone-len gthening device was fixed to the zygoma. After 7 days of external fixa tion, the osteotomized segment was lengthened 1 mm/day away from the l ong axis of the bone for 15 days. External fixation was then maintaine d for a minimum of 4 weeks, after which the dogs were sacrificed. Cran iofacial CT with three-dimensional reconstruction documented multidime nsional bone lengthening, and histologic analysis of the specimen conf irmed the presence of new cortical bone in the expanded areas. Refinem ent in technique and miniaturization and internalization of the bone-l engthening device may allow for more precise changes in the amount and direction of lengthening, thus making distraction osteogenesis more w idely applicable for use in the human craniofacial skeleton.