Digitally Guided Intraoral Segmental Mandibulectomy and Fibula Flap Reconstruction for Locally Invasive Odontogenic Tumors

Summary

This protocol demonstrates a reproducible digitally guided workflow for intraoral segmental mandibulectomy and mandibular reconstruction using a free vascularized fibula flap. The method integrates virtual surgical planning with patient-specific guides to achieve precise tumor resection and scar-free reconstruction.

Abstract

Radical treatment of ameloblastoma and other benign locally invasive odontogenic tumors frequently requires mandibular segmentectomy followed by functional reconstruction. Conventional reconstruction is typically performed through an extraoral approach to obtain sufficient exposure; however, this technique often results in visible facial scarring, extensive soft-tissue dissection, and potential injury to the marginal mandibular branch of the facial nerve. This protocol describes a reproducible digitally guided workflow for mandibular segmental resection and reconstruction using a free vascularized fibula flap performed entirely through an intraoral approach. Preoperative imaging data are imported into virtual surgical planning software to construct three-dimensional models of the mandible and fibula. Resection margins and fibular osteotomies are simulated digitally, enabling the fabrication of patient-specific osteotomy guides and pre-shaped reconstruction plates. During surgery, the mandibular tumor is exposed and resected via a strictly intraoral incision with the assistance of the customized cutting guide. Simultaneously, a second surgical team harvests and shapes the fibula flap according to the digital plan. The fibular segments are then transferred to the mandibular defect, and microvascular anastomosis is performed through a minimally invasive buccal window, restoring vascular supply and mandibular continuity without external incisions. This technique is particularly suitable for patients with benign or locally aggressive mandibular tumors who prioritize scar-free reconstruction. However, it is not recommended for cases with severe trismus, extensive soft-tissue invasion, or those requiring cervical lymph node dissection. Overall, the protocol provides a reproducible framework for integrating digital surgical planning with minimally invasive intraoral mandibular reconstruction.

Introduction

Benign odontogenic tumors with local invasions usually require mandibular segmentectomy for radical resection^1,2. Successful postoperative reconstruction is crucial for restoring mandibular continuity, facial symmetry, occlusal and chewing functions, and speech functions³. The vascularized free fibular flap is regarded as the "gold standard" for mandibular reconstruction due to its reliable blood supply, sufficient bone mass, and few donor-site complications⁴.

Traditional mandibular reconstruction primarily uses an extraoral approach to fully expose the surgical field, facilitating osteotomy and flap fixation. However, this method inevitably leaves visible facial scars and, due to the need for extensive soft-tissue separation, increases the risk of injury to the mandibular marginal branch of the facial nerve and other complications⁵. The advent of virtual surgical planning (VSP) and computer-aided design/computer-aided manufacturing (CAD/CAM) has revolutionized the mandibular reconstruction process⁶. These technologies enable preoperative simulation of the resection and reconstruction, allowing for the fabrication of patient-specific osteotomy guides and pre-shaped reconstruction plates, which significantly improve accuracy and reduce operative time compared to freehand surgery^7,8.

Consequently, a pure intraoral approach has been introduced as a scarless, aesthetically pleasing surgical alternative for selected benign mandibular lesions⁹. However, due to the narrow operating space and restricted surgical field of this approach, precise osteotomy and control of incision margins pose technical challenges, limiting its wide application. Without intraoperative navigation or the assistance of rigid guides, it is often difficult to guarantee reconstruction accuracy, particularly with respect to condylar localization and the restoration of occlusal relationships¹⁰.

This protocol proposes a reconstruction scheme that integrates the aesthetic advantages of pure intraoral approaches with the geometric accuracy of virtual surgical planning. By precisely transferring the digital surgical plan to the surgical area, surgeons can achieve precise tumor resection and three-dimensional shaping of the fibular flap within the limited oral space, while ensuring oncological safety. In addition, completing microvascular anastomosis through the buccal minimally invasive window can protect the blood supply to soft tissues while avoiding external scars. This digitally guided workflow is considered a reliable, high-precision option for minimally invasive mandibular reconstruction. It is particularly valuable for patients with benign tumors requiring segmental resection who prioritize a scar-free outcome. However, success relies heavily on strict case selection and the surgeon's microvascular experience.

Protocol

This research is approved by the institutional Ethics Board of West China Hospital of Stomatology (protocol approval number: WCHSIRB-D-2022-343). Written informed consent was obtained from the patient. All the materials, softwares or tools used for this study are listed in the Table of Materials.

1. Virtual surgical planning (VSP) and guide design

1. Obtain high-resolution maxillofacial computed tomography (CT) scans with a slice thickness of ≤ 1 mm to evaluate tumor extent and mandibular anatomy accurately.
2. Acquire CT Angiography (CTA) of the lower extremities to assess fibular vascular anatomy and confirm donor-site suitability.
3. Perform virtual surgical planning (Figure 1A).
   1. Import the CT dataset into the virtual surgical planning (VSP) software (e.g., Materialise Mimics 27.0) by clicking File > Import DICOM.
   2. Generate the three-dimensional mandibular model by selecting Segmentation > Bone.
   3. Utilize the segmentation tool again and set the manual threshold range to 50–150 Hounsfield Units (HU) to generate the 3D tumor model.
4. Define the resection boundaries on the virtual mandible with predefined oncologic safety margins (Figure 1B).
   1. Identify the tumor margins on the three-dimensional mandibular model using the CT dataset.
   2. Select the Cutting Plane tool in the planning software. Place osteotomy planes on both sides of the lesion, establishing the margins 5 mm beyond the anterior and posterior radiographic borders of the tumor.
   3. Adjust the orientation and position of the planes to ensure adequate clearance from the tumor.
   4. Apply the virtual cutting function to simulate the segmental mandibular osteotomy.
5. Design fibular osteotomies to allow multi-segment reconstruction of the mandibular arch (Figure 1C).
   1. Import the virtual fibula model into the planning workspace.
   2. Align the fibula with the mandibular defect according to the planned reconstruction.
   3. Select the Cutting Plane tool and position osteotomy planes along the fibula to create the required number of segments.
   4. Adjust the orientation and spacing of the segments to reproduce the curvature of the mandibular arch.
6. Design patient-specific mandibular and fibular osteotomy guides according to the virtual plan and fabricate them using three-dimensional printing technology.
7. Virtually position and pre-shape the reconstruction plate to assemble the segmented fibula.
8. Simulate the final mandibular contour and occlusal relationship (Figure 1D).
   1. Reposition the fibular segments within the mandibular defect in the planning workspace.
   2. Use the Transform tool to adjust the translation and rotation of each segment.
   3. Arrange the segments sequentially to reproduce the curvature of the mandibular arch.
   4. Evaluate the occlusal relationship by aligning the reconstructed mandible with the maxillary dentition in the virtual model.
      ​NOTE: Ensure that the mandibular cutting guide incorporates stable reference points (e.g., dental surfaces, inferior border of the mandible) to allow passive and reproducible intraoral seating.

2. Patient preparation

1. Perform nasotracheal intubation to maximize intraoral surgical access and position the patient supine with a shoulder roll to extend the neck.
2. Prepare and drape the face, oral cavity, neck, and the selected lower leg donor site in a sterile manner to allow a simultaneous two-team approach.
3. Administer prophylactic antibiotics and ensure the availability of hypotensive anesthesia to minimize intraoperative bleeding.

3. Intraoral mandibular exposure and tumor resection

1. Perform a mucosal incision along the mandibular vestibule to expose the tumor-bearing segment while preserving surrounding soft tissues.
2. Elevate the mucoperiosteum carefully to expose the buccal surface of the mandible and ramus within the limits required for guide placement.
3. Position and secure the patient-specific mandibular osteotomy guide onto the exposed bone and confirm stable, passive seating using anatomical landmarks.
4. Fix the guide with temporary monocortical screws through the predesigned fixation holes to prevent intraoperative displacement (Figure 2A).
5. Perform the segmental osteotomies using a reciprocating saw through the guide under continuous saline irrigation to prevent thermal injury (Figure 2B).
6. Dissect the lingual soft tissue attachments and remove the tumor-bearing mandibular segment as a single intact specimen without fragmentation (Figure 2C–D).
7. Orient the resected specimen and mark the anatomical margins (e.g., anterior, posterior, superior, inferior) using specific suture ties.
8. Send the peripheral soft tissue and osseous margins for immediate intraoperative frozen section analysis. Confirm tumor clearance prior to proceeding with the reconstructive phase.
   NOTE: If the guide does not seat passively, inspect for residual soft tissue or bony irregularities. Do not force the guide.

4. Fibula flap harvest and shaping

1. Expose the fibula through a standard lateral approach. Mark the planned osteotomy lines directly on the fibular surface and verify guide positioning prior to bone division (Figure 3A).
2. Harvest the vascularized fibula flap while preserving the peroneal vessels and adequate pedicle length (Figure 3B).
   1. Perform a lateral incision over the fibula.
   2. Expose the fibula by dissecting between the peroneus and soleus muscles.
   3. Identify the peroneal vessels along the posteromedial aspect of the fibula.
   4. Elevate the flap while preserving the vascular pedicle and maintaining adequate pedicle length.
3. Apply the patient-specific fibular osteotomy guide to the harvested fibula and perform segmental osteotomies according to the virtual surgical plan (Figure 3C).

5. Mandibular reconstruction and fixation

1. Transfer the contoured fibular segments to the mandibular defect through the intraoral incision and align them with the native mandibular stumps.
   CAUTION: Ensure that the vascular pedicle is not twisted or excessively stretched during flap transfer, as this may compromise blood flow and lead to flap ischemia.
2. Access the facial artery and vein through a minimally invasive buccal window. Remove excess adventitia to prepare the recipient vessels and fibular pedicle (Figure 4A).
   CAUTION: Avoid sharp angulation or compression of the vascular pedicle when positioning it within the surgical field.
3. Perform end-to-end microvascular anastomoses of the artery and vein using 8-0 nylon sutures and a microvascular anastomosis device under an operating microscope (Figure 4B).
4. Confirm vessel patency by observing the bleeding from the bone edges or skin paddle to verify flap perfusion.
5. Secure the fibular segments to the native mandible using titanium screws and reconstruction plates according to the preoperative plan (Figure 4C–D).
6. Confirm proper mandibular alignment, contour, and occlusal relationship.
   NOTE: Evaluate the reconstructed mandible by visually assessing the continuity and symmetry of the mandibular arch. Verify occlusion by bringing the maxillary and mandibular dentition into contact and confirming stable intercuspation.
7. Achieve watertight closure of the intraoral mucosa over the reconstruction plate and bone graft using absorbable sutures to minimize the risk of salivary leakage.
   NOTE: Ensure a tension-free pedicle course within the submucosal tunnel or buccal window to prevent kinking or compression.

6. Postoperative management

1. Monitor free flap perfusion closely during the first 24 h using clinical assessment and Doppler ultrasound.
2. Administer antibiotics and anticoagulation therapy according to institutional protocols. Provide analgesics and edema-control medications as needed.
3. Maintain enteral nutrition via a nasogastric tube during the early postoperative period. Gradually transition to oral liquid intake after confirming mucosal healing and absence of salivary fistula.
4. Schedule follow-up evaluations at 1, 3, 6, and 12 months postoperatively. Perform CT imaging to assess mandibular alignment, graft integration, and bone healing.

Results

The digitally guided intraoral workflow described in this protocol has been successfully performed in 5 patients. While this sample size precludes statistical analysis of long-term outcomes, it is strictly sufficient to demonstrate the technical feasibility and reproducibility of this surgical protocol. The representative case presented herein highlights the standard execution of this procedure. The digitally guided intraoral segmental mandibulectomy and free fibula flap reconstruction were completed without intraoperati...

Discussion

This protocol outlines a digitally guided workflow for the entire mandibular segmentectomy and free fibular flap reconstruction via a strictly intraoral approach. By integrating virtual surgical planning (VSP) with patient-specific osteotomy guides, this method enables precise tumor resection and functional mandibular reconstruction within the constraints of the intraoral surgical field, while avoiding facial incisions.

Several technical steps are critical for the success of this procedure. Ac...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
3-0 antibaterial vicryl absorbable suture	Johnson (Suzhou) Medical Devices Co., Ltd.	VCP1772D	For tissue suturing
8-0 Polypropylene Non-Absorbable Suture	Ethicon,LLC	W2777	For microvascular anastomosis
DSRobot 4K-Station	Digital Vision	-	Surgery video recording
High-Frequency Electrosurgical Unit	Guangdong Baisheng Medical Equipment Co., Ltd.	OBS-350A	Precise tissue cutting and coagulation
Matrix Mandible Reconstruction Plate	Synthes GmbH	04.503.732	Secure the fibular
Matrix Mandible Screw	Synthes GmbH	04.503.440.01C	Secure the fibular
Microvascular Anastomosis Device	Huarong Kechuang Biotechnology Co., Ltd.	KC3500	For microvascular anastomosis
Materialise Mimics software	Materialise	-	For virtual surgical planning
Operating microscope	Zumax	OMS3200Pro	For microvascular anastomosis
Powered Maxillofacial Surgery System	Crown Eagle	DSQ-3L ZD3	For osteotomy
Ultrasonic cutting and hemostasis system	Tianjin Ruiqi Surgical Instrument Company	CSUS6000	For cutting and hemostasis