Virtual Surgical Planning: The Pearls and Pitfalls

Abstract

Objective: Over the past few years, virtual surgical planning (VSP) has evolved into a useful tool for the craniofacial surgeon. Virtual planning and computer-aided design and manufacturing (CAD/CAM) may assist in orthognathic, cranio-orbital, traumatic, and microsurgery of the craniofacial skeleton. Despite its increasing popularity, little emphasis has been placed on the learning curve.

Methods: A retrospective analysis of consecutive virtual surgeries was done from July 2012 to October 2016 at the University of Montreal Teaching Hospitals. Orthognathic surgeries and free vascularized bone flap surgeries were included in the analysis.

Results: Fifty-four virtual surgeries were done in the time period analyzed. Forty-six orthognathic surgeries and 8 free bone transfers were done. An analysis of errors was done. Eighty-five percentage of the orthognathic virtual plans were adhered to completely, 4% of the plans were abandoned, and 11% were partially adhered to. Seventy-five percentage of the virtual surgeries for free tissue transfers were adhered to, whereas 25% were partially adhered to. The reasons for abandoning the plans were (1) poor communication between surgeon and engineer, (2) poor appreciation for condyle placement on preoperative scans, (3) soft-tissue impedance to bony movement, (4) rapid tumor progression, (5) poor preoperative assessment of anatomy.

Conclusion: Virtual surgical planning is a useful tool for craniofacial surgery but has inherent issues that the surgeon must be aware of. With time and experience, these surgical plans can be used as powerful adjuvants to good clinical judgement.

Fig. 1.

Algorithmic approach to virtual surgical planning. A, Step-by-step approach for the planning of orthognathic cases. B, Approach to free osseous flaps performed with virtual surgery planning.

Fig. 2.

Representation of adherence to initial virtual surgical plans, divided as complete, partial, or abandoned.

Fig. 3.

List of reasons explaining incomplete adherence or abandonment of initial virtual surgical plans.

Fig. 4.

Checklist to aid in minimizing communication errors between the surgeon and the engineer during virtual online planning. DICOM, Digital Imaging and Communications in Medicine.

Fig. 5.

3D planning for genioplasty. Positioning of spacer guide with temporary fixation for genioplasty (A). Osteotomies and bone to be resected for Lefort I in red (B). Bone graft from right genioplasty and Lefort 1 (C).

Fig. 6.

Preoperative photography of patient from Figure 4 with hemifacial microsomia (A). Postoperative results at 1 month (B) and at 6 months (C) after virtual surgical planning. Symmetric facial morphology and a natural smile.

Fig. 7.

Patient with hemifacial microsomia smiling (A). Virtual surgical planning illustrates bony segments’ positions after Lefort I osteotomies, bilateral sagittal split osteotomies, and genioplasty (B). Results at 4-month follow-up demonstrates an improved symmetry and smile (C).

Fig. 8.

Patient with squamous cell carcinoma of the oral cavity invading into the right mandible (A). Virtual surgical planning for mandible resection guides with slot widths of 1 mm and 2.2 mm holes for temporary fixation (B). Significant tumor growth between the initial scan on which virtual planning was performed and the time of surgery, rendering the preconceived mandible cutting guides unusable (C). Results at 6 months of follow-up (D).

Fig. 9.

Solution to problem encountered in Figure 7. Preoperative planning on virtual models of different cutting slots depending on tumor growth and resection margins (A). Intraoperative tumor resection with selection of the appropriate slot on the mandibular cutting guide (B). Example of fibular cutting guide with incremental slots to accommodate for tumor resection margins (C).