# 3D Soft-Tissue Prediction Methodologies for Orthognathic Surgery--A Literature Review
## 3 Results
### Prediction Methodologies
#### 3.2.3 Works Based on Other 3D Software
Average root mean square distances and average percentage of points less than 2 mm between real post-operative images and predictions were computed (Table 3); statistically significant differences resulted from the Friedman test. In particular, the post hoc Wilcoxon signed-rank test proved that RMS for PFEM and RMS for ProPlan had statistically significant lower values with respect to RMS for Dolphin 3D (\(p\) = 0.016). On the opposite, the differences between ProPlan and PFEM could not be considered statistically significant (\(p\) = 0.219). The conclusions of the authors was that ProPlan CMF and PFEM gave soft-tissue predictions with significant accuracies, particularly when using the correct post-operative maxillary position; because of the limitations introduced by a landmark-based algorithm and a sparse architecture, Dolphin 3D resulted to be inaccurate when surgery involved large maxillary advancements, particularly on lateral points. [PERSON] et al. [36] tried to assess if a 3D virtual surgery could accurately predict the soft tissue outcome of 29 patients who underwent bimaxillary orthognatic surgery (LFI, BSSO and genioplasty) performed by the same surgeon. The predicted outcome was generated using the Simplant Pro program. All simulations were performed by the same operator. The produced simulation of the soft tissue result was superimposed on the post-operative of the patients, and 10 landmarks were designed and positioned on the two models; the simulation error was determined by measuring distances (x, y, z) between the same landmarks on predicted and real images. From this analysis, an accuracy of 52.8% resulted, disagreeing with previous study reporting accuracies around 80%. Most of the errors were found for landmarks of lower lips, mouth corner and chin area (pogonion and menton), with a general larger error in points located on the mandible. Authors suggested as a possible cause of this trend the complexity of the surgery, involving more movements in the mandible rather than in the maxilla; it could determine lower errors in the maxilla but higher inaccuracy in the mandible. Inaccuracies reported for 18 of the 30 soft-tissue landmarks were considered statistically significant (\(p\) < 0.05), with errors concentrated at mouth corners. Possible explanations addressed by the authors were the ethnic differences between the data used for developing the software (Caucasian population) and the data used in this study (Asian population); moreover, it was not negligible that errors up to 2 mm could be due to the positioning of soft tissue landmarks. In conclusion, authors stated that 3D software in soft tissue prediction could have great potential, but the accuracy must be improved. Even if it is out of the scope of the present work, it is important to state that not only the surgical planning plays a crucial role in the optimal process of care of the patients. It is not negligible that maxillofacial surgery, as well as other branches of surgeries, could lead to medical complications such as venous thromboembolism, which can have fatal consequences when moving to the lung (DVT/PE) [37]. Moreover, surgeons must manage patients with rare disorders of hemostasis, which need particular care in the perioperative phase. The works by [PERSON] et al. [38; 39], and [PERSON] et al. [40] have been referred to in order to deepen understanding of this topic.