title: Quantitative validation of a computer-aided maxillofacial planning system, focusing on soft tissue deformations.
abstract: OBJECTIVE
  The aim of this study was to evaluate the accuracy of 3D soft tissue predictions generated by a computer-aided maxillofacial planning system in patients undergoing orthognathic surgery.
  
  
  METHODS
  Twenty patients with dentofacial dysmorphosis were treated with orthognathic surgery after a preoperative orthodontic treatment. Fourteen patients had an Angle Class II malocclusion; three patients had an Angle class III malocclusion, and three patients had an Angle Class I malocclusion. Skeletal asymmetry was observed in six patient. The surgeries were planned using the Maxilim software. Computer assisted surgical planning was transferred to the patient by digitally generated splints. The validation procedures were performed in the following steps: (1) Standardized registration of the pre- and postoperative Cone Beam CT volumes; (2) Automated adjustment of the bone-related planning to the actual operative bony displacement; (3) Simulation of soft tissue changes; (4) Calculation of the soft tissue differences between the predicted and the postoperative results by distance mapping.
  
  
  RESULTS
  Eighty four percent of the mapped distances between the predicted and actual postoperative results measured between -2 mm and +2 mm. The mean absolute linear measurements between the predicted and actual postoperative surface was 1.18. Our study shows the overall prediction was dependent on neither the surgical procedures nor the dentofacial deformity type.
  
  
  CONCLUSIONS
  Despite some shortcomings in the prediction of the final position of the lower lip and cheek area, this software promises a clinically acceptable soft tissue prediction for orthognathic surgical procedures.
authors.affiliation: Department of Cranio-Maxillofacial Surgery, AZ MONICA, Harmoniestraat 68, B-2018 Antwerp, Belgium University Hospital Antwerp, Belgium.
authors.forename: Nasser
authors.initials: N
authors.lastname: Nadjmi
authors.affiliation: Department of Cranio-Maxillofacial Surgery, AZ MONICA, Harmoniestraat 68, B-2018 Antwerp, Belgium University Hospital Antwerp, Belgium.
authors.forename: Ellen
authors.initials: E
authors.lastname: Defrancq
authors.affiliation: Medical Image Computing (Radiology - ESAT/PSI), Faculties of Medicine and Engineering University Hospital Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
authors.forename: Wouter
authors.initials: W
authors.lastname: Mollemans
authors.affiliation: Department of Cranio-Maxillofacial Surgery, AZ MONICA, Harmoniestraat 68, B-2018 Antwerp, Belgium University Hospital Antwerp, Belgium.
authors.forename: Geert Van
authors.initials: GV
authors.lastname: Hemelen
authors.affiliation: Department of Oral and Maxillofacial Surgery, Radboud University Nijmegen, Medical Centre, Nijmegen, The Netherlands.
authors.forename: Stefaan
authors.initials: S
authors.lastname: Bergé
keywords: 3D planning; orthognathic surgery; soft tissue prediction; virtual surgery