The combination of endoscopy and distraction osteogenesis in the development of a canine midface advancement model

The requirements for reconstruction in patients with midface hypoplasia can be formidable: a bicoronal scalp incision, Le Fort III or monobloc skeletal advancement, harvesting and insertion of bone grafts, application of rigid (and occasionally intermaxillary) fixation, blood transfusions, and prolonged operative time and hospitalization. The introduction of the endoscope offers the possibility of minimally invasive surgery with improved visualization of the osteotomy sites. The development of distraction osteogenesis as a surgical technique allows controlled and gradual advancement of the osteotomized skeletal segment and associated soft tissue. The purpose of this study was to develop a canine model of an endoscopically assisted Le Fort III osteotomy with attendant midface distraction. Four mongrels (20 kg in weight) were study subjects. Three 2-cm skin incisions were made (two perpendicular to the zygomaticomaxillary suture and one perpendicular to the nasofrontal suture). The soft tissue and periosteum were evaluated bluntly. Retractors specially designed for the project created a space for endoscopic visualization. Bilateral zygomatic, nasofrontal, and medial orbital wall osteotomies, corticotomies, or both were performed under endoscopic visualization using a reciprocating saw; the medial orbital wall sectioning was specifically not completed (i.e., corticotomy) to avoid laceration of the mucosa and attendant bleeding. The pterygomaxillary osteotomy was completed with an osteotome and mallet. Finally, the nasal septum was only partially divided with an osteotome to avoid excessive blood loss. Four distraction devices were placed across the above-noted osteotomies (two across the nasofrontal osteotomy and one across each lateral osteotomy). The animals were distracted 1 mm per day for 16 to 40 days after surgery (16-40 mm of linear distraction). Cephalograms and computed tomography scans were obtained before and after distraction. The animals were killed after remaining in fixation for 4 to 6 weeks after distraction. All soft tissue was removed and the skull was examined. Photos were obtained throughout the experiment for documentation. The study demonstrated that Le Fort III osteotomies can be performed successfully via small incisions with endoscopic assistance in canine subjects with excellent visualization and minimal bleeding. The advancement of the midface segment can be achieved by activation of an external distraction device.