Application of digital surgical guides in mandibular resection and reconstruction with fibula flaps

Abstract

Surgical guides have been used widely in maxillofacial surgery. Details of the types of digital surgical guide used in mandibular resection and reconstruction with fibula flaps at the authors’ institution are presented in this article. Three patients diagnosed with mandibular ameloblastoma underwent mandibular resection and reconstruction with fibula flaps using surgical guides for assistance. These digital surgical guides included a mandibular osteotomy guide, a fibular osteotomy guide, and a mandibular fixation guide. Surgical guides are helpful in improving the accuracy of operations and are appropriate for many types of mandibular resection and reconstruction.

Many studies have proved that digital surgical techniques, including image-guided navigation and surgical guides, are helpful in improving the accuracy of maxillofacial operations. Surgical guides are used widely in bone fracture reduction, bone resection, and related applications. For bone resections, surgical guides are used to determine the resection border, as planned virtually before the operation. In this manner, the surgeon can directly transfer their virtual surgical planning to the real-time operation, thereby improving the accuracy of the operation, saving surgical time, and enhancing postoperative outcomes.

Mandibular resection and reconstruction with autogenous bone is the most reliable treatment for mandibular tumours. In addition, surgeons generally prefer vascularized fibula flaps for the treatment of mandibular defects. However, it is very difficult to rehabilitate the structures and functions affected by mandibular defects relying only on surgeon experience, especially when the mandibular defects are extensive. With the employment of digital techniques, surgeons have greatly improved their success rates and accuracy. Several reports have discussed surgical guides used in mandibular resection and reconstruction, and the guides seem to have proved their value in transferring the virtual surgical plan to the actual surgeries. However, most of the digital approaches reported to date have been quite complicated in terms of design and fabrication.

In this article, a series of surgical guides, including a mandibular osteotomy guide and a fibular osteotomy guide, which are simple and were designed by the present authors, are discussed. The first reported mandibular fixation guide that has been applied in mandibular resection and primary reconstruction is also presented. Because of the moveable nature of the remaining mandible parts after resection, it is very difficult to fix them in their primary positions even with the help of a preformed reconstruction plate. However, the mandibular fixation guide can solve this problem. All of the surgical guides presented here have proved to be helpful in the types of mandibular tumour cases reported.

Technique

Three middle-aged male patients suffering long-term expansion of the lower jaw were accepted for treatment in the study clinic in Chengdu, China. All of the patients complained of facial asymmetry and had many loose teeth. The mandibles involved affected the patients’ facial appearance and their speaking, chewing, and swallowing functions extensively. None of the patients presented with facial paralysis or other nerve symptoms. Panoramic radiographs showed that at least 9 cm of the mandible body was affected; the region affected was in the centre in one patient and was unilateral in the other two. All had biopsy-proven mandibular ameloblastoma. The treatment plans were nearly identical, because all patients required a partial mandibular resection and primary reconstruction with a vascularized fibula flap. To improve the precision and success rates of the surgeries, it was decided by the surgeons to use digital surgical techniques following careful virtual surgical planning using a three-dimensional (3D) skull model and surgical guides. This study was approved by the institutional ethics committee of the hospital, and informed consent was obtained from the patients.

Before the operation, the virtual surgical planning, a 3D skull model, a preformed reconstruction plate, and surgical guides were prepared. First, spiral computed tomography (CT) equipment (Siemens Sensation 16; Siemens, Munich, Germany) was used to perform a head CT scan and a devoted fibula CT scan. The CT data were obtained in Digital Imaging and Communications in Medicine (DICOM) format, with 0.625-mm slice thickness, and were imported into Mimics software (Materialise NV, Leuven, Belgium) for medical image processing. In Mimics, each patient’s skull was used to construct a 3D virtual model.

A simulation of the mandible resection and reconstruction with the fibula flap was performed in the 3D model. The boundaries of the resected mandible were located 1 cm beyond the tumour area. Then, based on the length and the contour of the defect, a section of fibula was harvested and cut into three segments to fit the mandibular defect. Next, the surgical guides for the mandibular resection and fibular osteotomy were designed in Mimics ( Fig. 1 ); these included slots located according to the osteotomy lines. The fixation guide was designed alongside the remaining healthy mandible in Mimics ( Fig. 2 ). Following this, all of the surgical guides and the reconstructed mandibular model were saved in stereolithography (STL) format and were imported into a rapid prototyping machine (Wiiboox; JOC, Jiangsu, China) for 3D printing into real 1:1 models. The mandibular model was then used to preform the reconstruction plate. The fixation guide was fixed to the mandibular model with screws to ensure it was perfectly adapted to the defect ( Fig. 3 ). Finally, the surgical guides, skull model, and reconstruction plate and screws were sent to be sterilized.

Fig. 1
Virtual design of the surgical guides (yellow arrows: the right and left mandibular osteotomy guides; green arrow: the fibular osteotomy guide). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2
Virtual design of the surgical guides (red arrow: the mandibular fixation guide). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 3
3D printed models of the reconstructed mandible and surgical guides and the preformed reconstruction plate (yellow arrows: right and left mandibular osteotomy guides; green arrow: fibular osteotomy guide; red arrows: mandibular fixation guide; white arrow: preformed reconstruction plate; black arrow: screws (which were used to fix the fixation guide to the mandibular model). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

For the real-time operation, the surgeons were divided into two teams to concurrently carry out the mandibular resection and fibula flap harvesting. After one team had exposed the mandible, the mandibular osteotomy guide was fixed to the mandible and used to guide the mandibular resection as planned. Then the fixation guide was fixed to the remaining mandible with screws to make it whole, preserving the space left by the excised mandibular defect. The preformed reconstruction plate was then fixed to the mandible. Meanwhile, the other surgical team used the fibular osteotomy guide to cut the fibula ( Fig. 4 ). With the help of the surgical guides, the mandibular osteotomy and fibular osteotomy were carried out exactly according to the preoperative virtual plan. Therefore, the harvested fibula flap fitted the mandibular defect perfectly. Finally, the fibula was fixed to the mandible with the reconstruction plate to restore the normal contour of the mandible.

Dec 15, 2017 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Application of digital surgical guides in mandibular resection and reconstruction with fibula flaps
Premium Wordpress Themes by UFO Themes