Low-cost Design and Manufacturing of Surgical Guides for Mandibular Reconstruction Using a Fibula

Abstract

Background: Surgical cutting guides are used in mandibular reconstruction involving osteotomy of the mandible and fibula. Cutting guides produced using computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies have been reported recently. These guides aim to increase the benefits to patients by improving the accuracy, shortening the operating time, and correcting occlusion. However, the availability of these advanced technologies is limited in some regions of the world. To test whether we could produce low-cost surgical cutting guides, we made surgical guides and investigated their accuracy.

Methods: Using free CAD software, we designed surgical cutting guides for the mandible and fibula and used these to perform virtual mandibular segmental osteotomies and fibula transplants in 12 model surgeries. The cutting guides were printed on a 3-dimensional (3D) printer. The model surgeries were performed using 3D mandibular models and cutting guides to check their accuracy. Deviations between the virtually simulated plan and the actual model surgery were investigated.

Results: CAD and CAM technologies were used to design and 3D print the cutting guides and models. The guided surgeries were performed. The deviations were about 1.3 mm for mandibular osteotomy, less than 1 mm for fibular osteotomy, and within 2.4 mm for reconstructions of the mandible.

Conclusions: Without using expensive software or products, we were able to design surgical cutting guides for the mandible and fibula and used these to perform virtual simulation of mandibular segmental osteotomy and fibular reconstruction. Model surgeries using 3D-printed surgical guides showed that the accuracy of reconstruction was within a 3-mm deviation. In circumstances where commercial CAD/CAM guides are not available, it may be possible to use CAD/CAM surgical guides in the clinic if doctors are willing to volunteer their time for the design and printing.

Fig. 1.

Defect areas are shown in black (n = 12).

Fig. 2.

Virtual mandibular osteotomy and fibula inset. A, Two osteotomy planes are set near the condyle and right mental tubercle. Between these 2 planes, another plane, which includes the gonion, is set for later use in the osteotomy with the gonion. B, Mandibular osteotomy is performed virtually. C, The fibula transplant is set to reproduce the ramus of the mandible. D, After cutting of the fibula to fit the ramus to the gonion, the remaining fibula is rotated to fit to the body of the mandible. E, Two osteotomized fibular segments are placed.

Fig. 3.

Designing the mandibular cutting guide. A, The osteotomy plane near the condyle is thickened to show the cutting plane. B, To make the guide fit to the mandible, the outer surface of the remaining ramus is thickened. C, The cutting plane solid and fitting surface solid are united. D, The cutting guides at both ends of the osteotomy are connected with pillars. This becomes the final cutting guide.

Fig. 4.

Designing the fibular cutting guide. A, The osteotomy planes are decided at the time the virtual fibula is inset into the mandible. B, The osteotomy planes are connected to make a solid. The box-shaped solid is made by subtracting the fibula solid. Each solid is connected with a pillar. C, Reverse view of the fibular guide.

Fig. 5.

Three-dimensional printing of the design. A and B, The virtual mandibular guide and actual printed guide. C and D, The virtual fibular guide is also printed.

Fig. 6.

Model surgery. A, The printed mandibular cutting guide is fitted to the mandibular model. B, The fibular guide is placed in the fibular model. C, The osteotomies are performed on the model fibula. D, The fibular bone parts are transplanted to the model after the mandibular osteotomy, and the titanium plates are fixed. E, After removal of the mandibular guide.

Fig. 7.

Measurements: the defect lengths (cranial and caudal, A), osteotomy lengths (mesial and distal, B), transplanted fibular lengths (cranial and caudal, C), and reference points, such as Cl-Cl, Cl-Go, and Go-T, are measured in both the virtual plan and model surgery (D).

Fig. 8.

Results of the osteotomies. The average deviations between the plan and model are shown. The average distance deviations were 1.33 mm for the bone defect gap (n = 22; 0.15–5.46 mm; SD = 1.43), 0.66 mm for osteotomy length (n = 16; 0.01–1.79 mm; SD = 0.55), and 0.92 mm for fibular length (n = 54; 0–6.18 mm; SD = 1.00). The average error for the complete procedure was about 1 mm.

Fig. 9.

Results for reconstructed reference point discrepancies. The average deviation in distance between the reference points for points not involved in the reconstruction was 1.02 mm (n = 38; 0–8.61 mm; SD = 1.52) except for Cl-Cl. The average deviation between points directly involved in the reconstruction was 1.59 mm (n = 44; 0.02–6.08 mm; SD = 1.23). The most deviated point was the Cl-Cl distance, which was not directly involved in the reconstruction. The average deviation was 2.34 mm (n = 12; 0.02–6.34 mm; SD = 2.30).