The accuracy of three-dimensional prediction planning for the surgical correction of facial deformities using Maxilim

The motivation for orthognathic surgery is to improve facial appearance and quality of life. This study aimed to validate a three-dimensional (3D) orthognathic planning programme (Maxilim) for predicting soft tissue changes following Le Fort I advancements. Cone beam computed tomography (CBCT) scans were taken before surgery (T-1) and at 6-12 months after surgery (T-2) for 13 patients. For each patient the 3D hard tissue changes between T-1 and T-2 were determined by CBCT superimposition on the cranial vault. Using Maxilim, each patient's skeletal movements were used to generate a 3D soft tissue prediction. The actual soft tissue mesh at T-2 was compared to the predicted mesh. The face was divided into areas: nose, right and left nares, right and left paranasal regions, upper and lower lip, and chin. The absolute distance between meshes for each region was calculated. A one-sample t-test showed the distances between the meshes for all of the areas were within 3 mm (P < 0.05), except for the upper lip which was greater than 3 mm (P = 0.577). Using Maxilim, 3D soft tissue predictions for Le Fort I advancements were clinically satisfactory in the regions assessed, but associated with marked errors around the region of the upper lip.