Technical procedures for template-guided surgery for mandibular reconstruction based on digital design and manufacturing

Abstract

Background: The occurrence of mandibular defects caused by tumors has been continuously increasing in China in recent years. Conversely, results of the repair of mandibular defects affect the recovery of oral function and patient appearance, and the requirements for accuracy and high surgical quality must be more stringent. Digital techniques--including model reconstruction based on medical images, computer-aided design, and additive manufacturing--have been widely used in modern medicine to improve the accuracy and quality of diagnosis and surgery. However, some special software platforms and services from international companies are not always available for most of researchers and surgeons because they are expensive and time-consuming.

Methods: Here, a new technical solution for guided surgery for the repair of mandibular defects is proposed, based on general popular tools in medical image processing, 3D (3 dimension) model reconstruction, digital design, and fabrication via 3D printing. First, CT (computerized tomography) images are processed to reconstruct the 3D model of the mandible and fibular bone. The defect area is then replaced by healthy contralateral bone to create the repair model. With the repair model as reference, the graft shape and cutline are designed on fibular bone, as is the guide for cutting and shaping. The physical model, fabricated via 3D printing, including surgical guide, the original model, and the repair model, can be used to preform a titanium locking plate, as well as to design and verify the surgical plan and guide. In clinics, surgeons can operate with the help of the surgical guide and preformed plate to realize the predesigned surgical plan.

Results: With sufficient communication between engineers and surgeons, an optimal surgical plan can be designed via some common software platforms but needs to be translated to the clinic. Based on customized models and tools, including three surgical guides, preformed titanium plate for fixation, and physical models of the mandible, grafts for defect repair can be cut from fibular bone, shaped with high accuracy during surgery, and fixed with a well-fitting preformed locking plate, so that the predesigned plan can be performed in the clinic and the oral function and appearance of the patient are recovered. This method requires 20% less operating time compared with conventional surgery, and the advantages in cost and convenience are significant compared with those of existing commercial services in China.

Conclusions: This comparison between two groups of cases illustrates that, with the proposed method, the accuracy of mandibular defect repair surgery is increased significantly and is less time-consuming, and patients are satisfied with both the recovery of oral function and their appearance. Until now, more than 15 cases have been treated with the proposed methods, so their feasibility and validity have been verified.

Figure 1

Outline of technical procedure. Three modules: image processing, defect resection, and graft osteotomy, are included.

Figure 2

Reconstructed mandibular and fibular models. (a) Reconstructed maxilla and mandible. (b) Separated mandible shows the defect. (c) Reconstructed shank bones and separated fibular bone.

Figure 3

Design of resection template and repaired model. (a) CT image with marked defect. (b) Resection curves of defect. (c) Remain mandible after defect resection. (d) Resecting template based on bone surface. (e) Resection template. (f) Mirrored model and original model of mandible. (g) Repaired model after two parts merging.

Figure 4

Design of template for fibular graft osteotomy and harvesting. (a) Virtual plan for mandibular reconstruction with three barrels of fibular graft. (b) Resection template for fibular osteotomy.

Figure 5

Design of template for fibular graft shaping. (a) Shaping template is positioned on mandible. (b) Shaping template.

Figure 6

Fibular graft resection and harvesting. (a) The template for defect resection is fixed on mandible. (b) The resected tumor. (c) Surgical routine is drawn on the skin with the help of fibular osteotomy template. (d) The fibular osteotomy template is placed on the fibular bone. (e) Shaped fibular graft. (f) The graft is placed and fixed in the defect area.

Figure 7

Comparison of preoperative view and postoperative view. (a) Preoperative 3D view of maxillofacial bone. (b) Postoperative 3D view of maxillofacial bone. (c) Photo before surgery. (d) Photo of one month after surgery.