Evaluating Osteotomy Accuracy in Mandibular Reconstruction: A Preliminary Study Using Custom Cutting Guides and Virtual Reality

Abstract

Background: Mandibular reconstruction has evolved significantly since its inception in the early 1900s. Currently, the fibula free flap (FFF) is considered the gold standard for mandibular and maxillary reconstructions, particularly for extensive defects, and the introduction of Extended Reality (XR) and virtual surgical planning (VSP) is revolutionizing maxillofacial surgery.

Methods: This study focuses on evaluating the accuracy of using in-house cutting guides for mandibular reconstruction with FFF supported by virtual surgical planning (VSP). Planned and intraoperative osteotomies obtained from postoperative CT scans were compared in 17 patients who met the inclusion criteria. The proposed analysis included measurements of deviation angles, thickness at the centre of gravity, and the maximum thickness of the deviation volume. Additionally, a mandibular resection coding including 12 configurations was defined to classify and analyze the precision of mandibular osteotomies and investigate systematic errors. Preoperative, planned, and postoperative models have been inserted in an interactive VR environment, VieweR, to enhance surgical planning and outcome analysis.

Results: The results proved the efficiency of adopting customized cutting guides and highlighted the critical role of advanced technologies such as CAD/CAM and VR in modern maxillofacial surgery. A novel coding system including 12 possible configurations was developed to classify and analyze the precision of mandibular osteotomies. This system considers (1) the position of the cutting blade relative to the cutting plane of the mandibular guide; (2) the position of the intersection axis between the planned and intraoperative osteotomy relative to the mandible; (3) the direction of rotation of the intraoperative osteotomy plane around the intersection axis from the upper view of the model.

Conclusions: This study demonstrates the accuracy and reliability of in-house cutting guides for mandibular reconstruction using fibula free flaps (FFF) supported by virtual surgical planning (VSP). The comparison between planned and intraoperative osteotomies confirmed the precision of this approach, with minimal deviations observed. These findings highlight the critical role of CAD/CAM and XR technologies in modern maxillofacial surgery, offering improved surgical precision and optimizing patient outcomes.

Keywords: VR; VSP; fibula free flap; maxillofacial surgery; virtual reality; virtual surgical planning.

Figure 1

Points defined by the surgeon in four axial views of the postoperative CT scan for identifying the intraoperative resection plane.

Figure 2

Representative points of the intraoperative resection plans (body and ramus osteotomies) in two clinical cases and the related 3D models.

Figure 3

Details of the possible regions of intersection (internal, in the middle, and external) between the planned and the actual resection plane in the mandibular body (a) and mandibular ramus (b).

Figure 4

Intersections between the planned and the intraoperative osteotomy, represented by the yellow and the blue line, respectively, when the blade is to the left of the cutting guide.

Figure 5

Intersections between the planned and the intraoperative osteotomy, represented by the yellow and the blue line, respectively, when the blade is to the right of the cutting guide.

Figure 6

Regions of interest (ROIs) considered to align the planned and the postoperative models.

Figure 7

Definition of the deviation volume figure and analysis of thickness using the colorimetric map.

Figure 8

Overview of VieweR, an interactive VR environment for viewing surgical outcomes.

Figure 9

Boxplots of angle, thickness in the centre of gravity and maximum thickness of the deviation volume values, comparing body and ramus osteotomies.