Le Fort III Distraction With Internal vs External Distractors: A Cephalometric Analysis.

OBJECTIVE: This study compares the change in midface position following Le Fort III advancement using either rigid external distraction (group 1) or internal distraction (group 2). We hypothesized that, with reference to right-facing cephalometry, internal distraction would result in increased clockwise rotation and inferior displacement of the midface. DESIGN: Le Fort III osteotomies and standardized distraction protocols were performed on 10 cadaveric specimens per group. Right-facing lateral cephalograms were traced and compared across time points to determine change in position at points orbitale, anterior nasal spine (ANS), A-point, and angle ANB. SETTING: Institutional. PATIENTS, PARTICIPANTS: Twenty cadaveric head specimens. INTERVENTIONS: Standard subcranial Le Fort III osteotomies were performed from a coronal approach and adequately mobilized. The specified distraction mechanism was applied and advanced by 15 mm. MAIN OUTCOME MEASURE(S): Changes of position were calculated at various skeletal landmarks: orbitale, ANS, A-point, and ANB. RESULTS: Group 1 demonstrated relatively uniform x-axis advancement with minimal inferior repositioning at the A-point, ANS, and orbitale. Group 2 demonstrated marked variation in x-axis advancement among the 3 points, along with a significant inferior repositioning and clockwise rotation of the midface ( P < .0001). CONCLUSION: External distraction resulted in more uniform advancement of the midface, whereas internal distraction resulted in greater clockwise rotation and inferior displacement. External distraction appears to provide increased vector control of the midface, which is important in creating a customized distraction plan based on the patient's individual occlusal and skeletal needs.