A New 3D Tool for Assessing the Accuracy of Bimaxillary Surgery: The OrthoGnathicAnalyser

Abstract

AimThe purpose of this study was to present and validate an innovative semi-automatic approach to quantify the accuracy of the surgical outcome in relation to 3D virtual orthognathic planning among patients who underwent bimaxillary surgery.Material and MethodFor the validation of this new semi-automatic approach, CBCT scans of ten patients who underwent bimaxillary surgery were acquired pre-operatively. Individualized 3D virtual operation plans were made for all patients prior to surgery. During surgery, the maxillary and mandibular segments were positioned as planned by using 3D milled interocclusal wafers. Consequently, post-operative CBCT scan were acquired. The 3D rendered pre- and postoperative virtual head models were aligned by voxel-based registration upon the anterior cranial base. To calculate the discrepancies between the 3D planning and the actual surgical outcome, the 3D planned maxillary and mandibular segments were segmented and superimposed upon the postoperative maxillary and mandibular segments. The translation matrices obtained from this registration process were translated into translational and rotational discrepancies between the 3D planning and the surgical outcome, by using the newly developed tool, the OrthoGnathicAnalyser. To evaluate the reproducibility of this method, the process was performed by two independent observers multiple times.ResultsLow intra-observer and inter-observer variations in measurement error (mean error < 0.25 mm) and high intraclass correlation coefficients (> 0.97) were found, supportive of the observer independent character of the OrthoGnathicAnalyser. The pitch of the maxilla and mandible showed the highest discrepancy between the 3D planning and the postoperative results, 2.72° and 2.75° respectively.ConclusionThis novel method provides a reproducible tool for the evaluation of bimaxillary surgery, making it possible to compare larger patient groups in an objective and time-efficient manner in order to optimize the current workflow in orthognathic surgery.

Virtual setup in orthodontics: planning and evaluation

“…Preparation of orthognathic surgery is currently completely performed digitally with the use of CBCT and special software simulating treatment to predict the final outcome [4]. Post-operatively, it is also possible to analyze whether the surgery has been performed according to the virtual 3D planning [26]. For orthodontic treatment, these 3D treatment simulations and post-treatment analyses are not commonly used [9].…”

Achievability of 3D planned bimaxillary osteotomies: maxilla-first versus mandible-first surgery

“…The strength of the present study is not only the use of 3D CBCT data to carry out the preoperative 3D planning and postoperative evaluation, but also the application of the newly designed and validated tool, the OGA 8 . In contrast to all conventional 2D and 3D cephalometric analyses, the OGA eliminates the necessity of identifying anatomical landmarks multiple times.…”

“…Step 2: Virtual triangles were constructed on the maxilla and distal mandibular segment by using previously validated cephalometric landmarks (Table 1 ) 8 , 20 .…”

“…The coordinates of the landmarks (virtual triangle) in the postoperative position were imported into the OGA. The translation and rotation differences of the maxilla and distal mandibular segment between the 3D planning and actual postoperative results were calculated 8 .…”

“…Compared to conventional cephalometry, OGA is able to quantify the concordance of the postoperative maxillary and mandibular positions with the 3D surgical planning without the need to identify anatomical landmarks multiple times, thereby minimizing the observer variability. With OGA, the accuracy of 3D planning and surgical outcome of bimaxillary surgery with different sequencing protocols can be analysed in an objective, reproducible and systematic way 8 .…”