Comparison of Changes in Scleral Exposure Following Modified Le Fort III Osteotomy versus Le Fort I Osteotomy With Maxillary Bone Grafting
Twenty-five patients (50 eyes) with midface hypoplasia treated by modified Le Fort III osteotomies (24 eyes) as described by Kufner or Le Fort I osteotomies with maxillary bone grafting (26 eyes) were randomly selected and enrolled in an IRB-approved study. Photographs were obtained in natural head position pre- and postoperatively (average 11.8 months). Photographs were sized and analyzed using Adobe Photoshop software and exposed scleral surface area (SSA) in each eye was determined by pixel count. The distance from the inferior eyelid margin to the center of the pupil (mid-pupil eyelid distance, MED) was measured in each eye both pre- and postoperatively. All measurements were obtained on three different occasions at one week intervals between measurements by one examiner and converted into ratios for standardization purposes. The average percent change in SSA and MED from preoperative baseline values was calculated for each eye. A decrease in percent change ≥ 5% was considered clinically important. Intra-class correlation coefficients (ICC) and repeated measure ANOVA p-value were computed for the SSA measurements on ten randomly selected eyes. A p-value of <0.05 was considered to be statistically significant.
Pre- and postoperative ICC values were both 0.99, demonstrating reliability and validity of the measurement method. Repeated measure ANOVA p-value were 0.71 and 0.18 for preoperative and postoperative measurements, respectively, indicating that there was no systematic difference between SSA measurements. The 25% to 75% interquartile range for average percent change in total SSA was calculated. For LFI eyes, ten of 26 eyes showed clinically important changes in scleral exposure with an interquartile range in reduction from -8.58% to -1.27% (median -3.79%). In comparison, 18 of 24 LFIII eyes demonstrated clinically important percent change in SSA (-13.38% to -5.6%, median -8.59%). The average percent change in MED ranged from -6.88% to -0.86% (median -3.51%) for LFI eyes whereas the range was -12.7% to -6.11% (median -9.33%) for LFIII eyes. Of these, ten LFI eyes and 22 LFIII eyes demonstrated clinically important percent reduction in scleral exposure from the inferior eyelid margin to the center of the pupil.
ICC values demonstrated that SSA can be reliably determined using the aforementioned method. Analysis of preoperative and postoperative SSA and MED measurements revealed the modified Le Fort III osteotomy decreases medial, lateral, and inferior scleral exposure more predictably, and to greater clinical importance, than a Le Fort I osteotomy with maxillary bone grafting. These preliminary results may assist clinicians in determining which operation to perform.