I was very impressed with this study that have measured the three-dimensional (3D) accuracy of the orthognathic surgery using virtual surgical planning.

A1. When compared to Choi et al.’ study,¹ this study showed higher values of precision percentage {[number of patients with precise outcome/number of total patients] × 100 (%); Discrepancies less than 1 mm between virtual surgical simulation and post-surgery landmarks indicated a precise outcome} in maxillary setback (80.0% vs. 69.2%) and maxillary posterior impaction (75.0% vs. 69.0%), but lower precision percentage in maxillary advancement (33.3% vs. 87.5%) and maxillary anterior elongation (50.0% vs. 83.3%) (Table 3). In terms of the causes of difference in precision percentage between Choi et al’s study¹ and this study, I totally agree with questioner’s opinion. Several factors including the severity of skeletal discrepancy, the degree of difficulty in performing the planned surgical movement, and surgeon’s skill are important for obtaining the successful surgical outcome. Therefore, further studies are necessary to investigate the effects of surgeon on surgical accuracy with a larger sample size from diverse users for generalization.

A2. The precision analysis in this study could be used as an educational tool for surgeons. After they review data and refine surgical plane, they can provide better accurate surgical outcome in future surgery. However, the frequency of maxillary advancement and maxillary elongation in this study might be too low to draw a decisive conclusion. Therefore, it would be better to increase the sample size with multi-center study for validation of the results of this study in the future study.

A3. The purpose of this study was to investigate 3D surgical accuracy between virtually planned and actual surgical movements of the maxilla in two-jaw orthognathic surgery. The amounts of precision percentage (< 2.0 mm and < 1.0 mm) were as follows: 100% and 64.3% in anterior midline correction, 100% and 69.2% in posterior midline correction, 66.7% and 33.3% in maxillary advancement, 100% and 80% maxillary setback, 100% and 80% in maxillary total impaction, 83.3% and 50% in maxillary anterior elongation, and 91.7% and 75% in maxillary posterior impaction (Table 3). Therefore, there would be no specific surgical movement that can cause a significant problem in terms of accuracy except maxillary advancement and maxillary elongation. However, it is necessary to increase the sample size with multi-center study for interpreting the results with robust statistical significance.