The Design and Rapid Prototyping of Surgical Guides and Bone Plates to Support Iliac Free Flaps for Mandible Reconstruction

Abstract

Sir:FigureThis report describes a novel protocol for the construction of surgical cutting guides and reconstructive titanium bone plates to guide osteotomies according to the preoperative plan and to position and fix an osseous free flap in mandibular reconstruction after cancer removal. Computed tomographic data of a mandible affected by an ameloblastoma were elaborated to produce a virtual surgical plan that included the osteotomy cuts, area of bone resection, and reconstruction. STLfiles were elaborated for use with direct metal laser sintering, and a cutting guide and custom-made bone fixation plate were rapidly prototyped. The operating time was reduced in both the demolition and reconstruction phases. The patient's usual appearance and functionality were restored immediately. The new protocol for mandibular reconstruction is a viable way of reproducing the patient's anatomical contour while giving the surgeon better procedural control and reducing operating time. The innovative technique presented here involves three steps: (1) surgery planning, (2) computer-aided design/computer-aided manufacture and rapid prototyping, and (3) the surgery. High-resolution computed tomographic images of the patient's craniofacial skeleton and soft tissues were acquired using a multidetector computed tomography scanner (HiSpeed CT scanning station; General Electric Company, Fairfield, Conn.). The Digital Imaging and Communications in Medicine–format data were processed by the surgeons using CMF 6.0 software (Materialise, Leuven, Belgium). Three projections of the bone cuts were made in the three spatial axes and imported in Rhino 4.0 software (Robert McNeel & Associates, Seattle, Wash.) to allow the perfect transfer of the surgical plan. The computer-aided design of the surgical device was obtained using Rhino 4.0 software. The first component was a customized cutting guide for use in mandibular resection and to maintain free space after tumor ablation (Fig. 1, above). The second component was a customized reconstructive bone plate to support the iliac free flap (Fig. 1, below). The plate was designed by thickening the outer surface of the mirrored healthy side of the mandible to obtain an ideal mandibular contour and to avoid bone deformities on the side affected by the tumor. Reference notches were also added to delimit the part that would support the free flap. The two components (cutting guide and bone plate) were projected so that the same holes for the screws to fix the guide were used to secure the bone plate that supported the free flap.Fig. 1: The resin model used to train the surgeon with the surgical guide (above) and bone plate (below) in position.The cutting guide and bone plate were manufactured directly using the EOSINT M270 system (Electro Optical Systems, Munich, Germany). EOS CobaltChrome MP1 (Electro Optical Systems) was used to produce the cutting guide. The bone plate was produced with EOS Titanium Ti64 (Electro Optical Systems). A man with an ameloblastoma of the left mandibular body underwent mandibular resection and reconstruction using an iliac free flap. The mandibular cutting guide was fixed to the mandible to reproduce the demolition plan (Fig. 2, above). After mandibular resection, the cutting guide was removed and the reconstructive plate was introduced and fixed using the same holes as for the cutting guide. The reconstructive bone plate supported the iliac free flap in the correct position to restore the patient's original mandibulofacial contour exactly (Fig. 2, below).Fig. 2: Positioning of the surgical guide immediately before making the bone cuts (above) and the bone plate in the final position after connecting the iliac free flap (below).The protocol presented here offers several benefits. First, the virtual environment permitted optimal preoperative planning for tumor ablation: the resection boundaries were chosen accurately in safe tissues. No operating time was consumed by modeling a plate to the native mandible.1–5 Second, the morphology of the opposite hemimandible was mirrored and the reconstruction bone plate was designed using the external healthy cortical bone as a template, reproducing the patient's ideal mandibular contour and avoiding potential bone deformities. Consequently, a good facial soft-tissue contour was attained. Third, no complication occurred postoperatively. The reconstruction plate provided an appropriate bone-plate relationship and maintained the correct occlusal arrangement to avoid condylar distortion and a poor functional outcome. Good masticatory performance was attained 3 weeks postoperatively. Leonardo Ciocca, D.M.D., Ph.D. Section of Prosthodontics, Department of Oral Science Simona Mazzoni Faculty of Medicine Massimiliano Fantini Virtual Reality and Simulation Laboratory, Second Engineering Faculty Claudio Marchetti Faculty of Medicine Roberto Scotti Section of Prosthodontics, Department of Oral Science, Alma Mater Studiorum University of Bologna, Bologna, Italy DISCLOSURE The authors have no financial interest to declare in relation to the content of this article.