What Is the Accuracy of Bimaxillary Orthognathic Surgery Using Occlusally-Based Guides and Patient-Specific Fixation in Both Jaws? A Cohort Study and Discussion of Surgical Techniques

Abstract

The development of advanced digital orthognathic surgical protocols requires investigation to determine the accuracy of surgical outcomes. This report's purpose is to quantify 3-dimensional linear discrepancies between simulated and actual results for double-jaw orthognathic surgery utilizing occlusally-based guides in conjunction with patient-specific fixation in both jaws. This retrospective cohort study assessed the accuracy of double-jaw orthognathic surgery, in all cases performed by 1 surgeon between May 2019 and January 2021, utilizing occlusally-based guides and patient-specific fixation plates in both maxillary and mandibular surgeries. The primary outcome was absolute linear discrepancy between virtually-planned and surgically-achieved maxillary and mandibular position in 3 dimensions. Secondary outcomes were relative (directional) discrepancy, to assess if protocols erred in 1 direction of each surgical axis. Sequencing of bimaxillary surgery, age, and sex were covariates. Absolute and relative linear differences at A-point, B-point, and pogonion were evaluated using t tests. Descriptive statistics were amassed, and results were analyzed to determine if discrepancies differed from a null hypothesis of 2-mm error. Forty-nine patients were enrolled, consisting of 25 males and 24 females with a mean age of 24.8years. Thirty-five single-piece and 14 multipiece LeFort I osteotomies, 49 bilateral sagittal splits, and 35 genioplasties were studied; there were 22 maxilla-first and 27 mandible-first surgeries. Mean A-point absolute discrepancies of 0.57 (95% confidence interval: 0.41-0.73), 0.37 (0.24-0.50), and 0.45 (0.33-0.57) mm were observed in horizontal, transverse, and vertical planes, respectively. B-point discrepancies were 1.15 (0.79-1.52), 0.62 (0.47-0.78), and 1.14 (0.91-1.38) mm. Pogonion discrepancies were 1.29 (0.86-1.73), 0.85 (0.64-1.06), and 1.24 (1.00-1.49) mm. All P values were <.001. Sequencing of bimaxillary surgery did not alter absolute differences (P=.2 to>.9) with A-point discrepancies consistently smaller than B-point and pogonion discrepancies regardless of sequencing. Mandible-first surgery was associated with posterior directional error; both sequences were associated with superior directional error at B-point and pogonion. Bimaxillary orthognathic surgery utilizing a patient-specific protocol in both jaws produces results highly reproducible to planned simulated surgery and accurate below a 2-mm hypothesis, with maxillary discrepancies approaching 0.5mm and mandibular discrepancies approaching 1mm.