Virtual Surgery Planning in Mandibular Surgery: Variation Between Planned and Performed Position of Cutting Guides as Measured by Intraoperative Cone Beam Ct

Objectives: In mandibular tumor surgery, the position of the resection planes affects both radical tumor resection and accurate reconstruction. Therefore, the exact positions of the resection planes are virtually planned, preoperatively. To translate the planned resection planes to the operating room, patient-specific cutting guides are used. However, differences between the planned resection and the postoperative outcome exist. In the current study, we evaluated whether cutting guides are positioned according to the virtual plan and in what extent this affects the position of the resection planes.

Methods: The positions of resection planes were planned on a preoperative CT scan. Based on this, a patient-specific cutting guide was designed and printed. After surgical placement of the cutting guide, a cone beam CT (CBCT) was acquired. The cutting guide was manually segmented from the CBCT. The translation between the planned and performed position of the cutting guide was calculated and applied to the planned resection planes. Distances between planned and performed resection planes were measured on the most cranial and caudal ends of the resection planes.

Results: The planned and performed position of the patient-specific cutting guides were evaluated in eight patients. Deviations of the cutting guide placement from the virtual plan resulted in a shift between planned and performed resection planes, in such a way that resection margins increased in eight resection planes (+2.1 ± 1.5 mm) and reduced in seven resection planes (-1.7 ± 1.6. mm).

Conclusion: Patient-specific cutting guides fit the mandible with a few millimeters accuracy, resulting in a shift of ~2 mm between planned and performed resection planes. This study shows the need for intra-operative guidance on the positioning of cutting guides.