Comprehensive Approach to Segmental Mandibulectomy Reconstruction: From Nonvascularized Bone Grafting to Vascularized Free Flaps and Emerging Technologies

Thomas Lee MD, Cheryl Yu MD, Daniel Hawkins DDS, Chris Kandl MD

Abstract: 

Segmental mandibulectomy defects present a significant reconstructive challenge for the head and neck surgeon. The treatment approach must be tailored to each patient’s unique defect characteristics and medical history for optimal outcomes. In this comprehensive review, we present our current treatment algorithm for managing these complex defects, drawing from over 12 years of experience and more than a thousand trauma and cancer reconstructive cases.

For patients with intact mucosa, skin, and no history of radiation, nonvascularized bone grafting with bone morphogenetic protein and a custom cage plate can provide reliable reconstruction, even for longer segmental defects. However, for patients with significant mucosal or skin defects, a history of radiation, or those requiring postoperative radiation therapy, vascularized free flaps, such as the fibula and scapula flaps, remain the primary reconstructive options.

We also discuss recent advancements in hardware technology, including patient-specific TMJ prostheses, which are changing the approach to select condylectomy defects. Additionally, we explore the evolving landscape of dental rehabilitation, from traditional implants to the novel KLS IPS preprosthetic system, aimed at overcoming the challenges associated with failed conventional dental implants in free flap patients.

Through a series of illustrative case examples, this article provides a comprehensive, evidence-based approach to managing segmental mandibulectomy defects, highlighting the key factors that guide surgical decision-making and the application of emerging techniques to optimize both functional and aesthetic outcomes.

Introduction:

Segmental mandibulectomy defects, whether resulting from trauma, cancer, or congenital conditions, present a significant reconstructive challenge for the head and neck surgeon. The surgical approach must be carefully tailored to each patient’s unique defect characteristics and medical history to achieve reliable functional and aesthetic outcomes.

Over the past 12 years, we have accumulated extensive experience in managing these complex defects, having performed over a thousand trauma and cancer reconstructive cases. During this time, we have refined our treatment algorithm, incorporating the latest advancements in hardware and tissue engineering to optimize patient outcomes.

In this comprehensive review, we present our current approach to segmental mandibulectomy reconstruction, discussing the key factors that guide surgical decision-making, the application of both conventional and emerging techniques, and the management of dental rehabilitation in free flap patients.

Patient Evaluation and Surgical Decision-Making:

When evaluating a patient requiring segmental mandibulectomy, several key factors must be considered to determine the optimal reconstructive approach.

Radiation Therapy:
Patients with a history of radiation therapy or those requiring postoperative radiation are at a significantly higher risk of complications such as osteoradionecrosis and hardware extrusion through compromised soft tissue. In these patients, placing nonvascularized bone grafts typically results in graft failure, likely from poor vascular ingrowth. Similarly, postoperative radiation therapy usually leads to nonvascularized bone graft failure. In these patients with radiation therapy, we typically consider vascularized free flap reconstruction.

Mucosal & Skin Defects:
It is imperative for bone grafts and hardware to remain buried. This means that any intraoral leaks must be addressed with watertight closure, as intraoral contamination can lead to a significant risk of total bone graft and hardware failure. Therefore, if there is a significant intraoral mucosal defect or external skin defect, the clinician must determine if locoregional flap options are reliable when deciding between nonvascularized and vascularized free flap reconstruction. In situations where reliable locoregional options are not available, a vascularized free flap is preferred to minimize intraoral or external skin breakdown, which can lead to total bone graft or hardware failure.

Mandibular Subsite and Defect Size:
Anterior mandible defects located between the first premolars are associated with a higher risk of hardware and bone extrusion compared to posterior defects. Along the anterior mandible arch, a reconstruction plate placed without adequate bone graft will consistently lead to hardware extrusion either intraorally or externally. As such, anterior segmental defects require bone reconstruction if hardware needs to be placed to maintain mandibular continuity. Historically, the size of the bony defect was a significant factor in determining the need for vascularized versus nonvascularized bone grafting. However, recent studies by Melville et al. have challenged this notion, suggesting that for non-irradiated patients with good soft tissue coverage, even longer segmental defects may be managed successfully with nonvascularized bone grafting techniques.

Medical Comorbidities:

For patients who are considered too high-risk for general anesthesia or have extremely poor wound healing, it may be best to consider deferring bone reconstruction altogether and opting for soft tissue-only reconstruction. In such situations, the benefit of performing bony reconstruction to restore mandibular continuity must be weighed against the surgical risks. Placement of bone graft and hardware will increase the risk of hardware or bone graft failure, whereas soft tissue-only reconstruction will have a lower infection risk.

The anesthetic risk will be higher for free flap reconstruction compared to nonvascularized bone grafting techniques due to differences in surgery duration and the postoperative wound healing required.

For patients with posterior mandibular defects, combined with relatively poor medical comorbidities or poor wound healing potential, one could consider soft tissue-only reconstruction with a reconstruction plate to restore mandibular continuity and address mucosal defects in the first stage of surgery to prevent ongoing infection from salivary leaks. One can consider second-stage bone grafting once the mucosal reconstruction has been completed. However, if there is an unacceptably high risk of poor wound healing or infection, it may be better to defer reconstruction plate placement and provide soft tissue-only reconstruction with a staged approach for restoring mandibular continuity once the infection and mucosal defect have been addressed.

Unfortunately, for anterior mandibular defects, placement of a reconstruction plate without bone reconstruction will universally lead to hardware extrusion. In such cases, it is safer to consider soft tissue-only reconstruction without hardware, with the understanding that there will be a “gump” deformity resulting in notable cosmetic deformity from a recessed menton due to the lack of bony support, and oral incompetence from the lack of lower lip support.

Reconstruction Strategies:

Nonvascularized Bone Graft Reconstruction

Patients with Intact Mucosa and Skin & No Radiation Therapy:
For patients with intact mucosa or reliable watertight primary mucosal closure, intact skin, and no history of radiation, a combination of nonvascularized iliac bone grafting, bone morphogenetic protein-2 (BMP), bone marrow aspirate concentrate (BMAC), cellular bone allograft (Vivigen), and a custom cage plate with postoperative maxillomandibular fixation for at least 3 weeks, can be utilized with good clinical success. This approach uses tissue engineering concepts by providing three key components: cells, scaffolds, and signaling molecules.

In a case series from Dr. Hawkins, successful reconstruction of both posterior and anterior segmental mandibular defects was demonstrated using this approach, with patients achieving reliable bone growth and even dental rehabilitation using dental implants in the newly grafted bone. Similarly, Melville et al. reported their clinical success in segmental mandibulectomy reconstruction in 27 out of 30 patients using a combination of BMP, BMAC. Allogenic bone graft.  Interestingly, a case report from Alfi et al. took it one step further by describe the use of Vivigen alone, without autogenous bone grafting, to reconstruct a segmental defect in a pediatric patient, highlighting the potential of these novel biomaterials.

These findings suggest that for the right patient population, nonvascularized bone grafting may be a viable option, even for longer segmental defects, provided that soft tissue coverage is adequate and there is no history of radiation and no need for postoperative radiation therapy.  In cases of treatment failure, vascularized free flap can be used as a back up option.

Vascularized Bone Graft Reconstruction

Patients with Mucosal and/or Skin Defects & Radiation Therapy: 

For patients with significant mucosal or skin defects where watertight closure with primary or locoregional flaps is not possible, or for those with a history of previous radiation therapy or requiring postoperative radiation therapy, vascularized free flaps remain the cornerstone of our reconstructive approach. Our preferred choice is the fibula free flap, which provides a reliable source of both bone and soft tissue for reconstruction. In cases where the fibula is not a suitable option, such as in patients with inadequate leg blood supply (less than three-vessel runoff) or requiring reconstruction of a large soft tissue defect, we turn to the scapula free flap.

Careful flap monitoring is crucial to the success of free flap reconstruction. In our practice, we have found that venous Doppler monitoring, combined with a high index of suspicion for vascular compromise, has been instrumental in maintaining our consistently high free flap success rate of over 99%.

Unique Clinical Situations:

Massive Intraoral Mucosal & External Skin Defect:

The scapula free flap can be utilized in cases of massive soft tissue defects that involve both intraoral and external skin defects. Since the scapula flap can provide a much larger skin flap for reconstruction from the latissimus flap harvest, it can be used to reconstruct both intraoral and external skin defects. However, a major disadvantage of the scapula flap is that it offers a shorter bone length (10-14cm) for reconstruction. Fibula bone can provide up to 25cm of bone for reconstruction.  As such, if there is a need for a long bone reconstruction with a massive soft tissue defect, we typically perform a combination of a fibula flap and a pectoralis flap. The fibula flap with a skin paddle will be used for intraoral reconstruction, and the pectoralis flap is used for external skin reconstruction.

Management of Gunshot Injuries and High-Energy Trauma: 

Patients presenting with high-energy gunshot injuries or other forms of high-speed projectile trauma require a distinct management approach compared to those with low-energy blunt trauma. In these cases, our primary goal is to aggressively debride all devitalized tissues and eliminate the risk of salivary leaks, which can lead to devastating complications such as necrotizing neck fasciitis.

In patients with severely comminuted mandible bones and disrupted intraoral mucosa or external skin where primary closure is not possible, we employ a two-stage approach. The first stage focuses on addressing the mucosal and skin defects, often using a pectoralis major flap to eliminate dead space, reconstruct composite mucosal or skin defects, and minimize soft tissue scar contracture. Minimal hardware is placed in the mandible during this stage. In the second stage, osseous reconstruction is performed, typically using a fibula free flap.

This staged approach has significantly reduced the risk of hardware failure and infection, which were previously major challenges in managing these complex trauma cases. In cases of gunshot mandible trauma that do not exhibit significant comminution or mucosal/skin defects, we can consider mandible bone debridement until healthy bleeding bone is encoutnered followed by hardware placement, similar to the management of blunt trauma cases.

Condylectomy Defects and Emerging Hardware Technologies:

The reconstruction of segmental condylectomy defects presents unique challenges, particularly for patients who have undergone prior radiation therapy or require postoperative radiation. In these cases, we generally prefer vascularized fibula free flap reconstruction, as it provides a reliable source of both bone and soft tissue. The distal fibula serves as the new condylar head segment, while the proximal segment becomes the angle and posterior body. The fibula flap vessels emerge anteriorly, facilitating vessel anastomosis. Any intraoral or skin defects are reconstructed using the skin flap from the fibula.

However, for traumatic patients without a significant history of radiation, we have begun exploring the use of permanent TMJ prostheses, such as the Stryker TMJ Concepts system. This technology allows for TMJ reconstruction without the need for a fibula free flap in select patients, potentially reducing donor site morbidity and simplifying the reconstructive process. We present a case of gunshot trauma to the condyle and posterior mandible with relatively intact mucosa. In this case, we performed aggressive mandibular debridement followed by placement of a reconstruction plate with a temporary TMJ prosthesis. Three months later, we placed an extended TMJ prosthesis to reconstruct the posterior body-to-condyle defect. This approach relies on the presence of reliable mucosal and external skin coverage overlying the hardware and a segmental defect that does not involve the anterior arch.

Dental Rehabilitation in Free Flap Patients: 

Dental rehabilitation is a critical component of segmental mandibulectomy reconstruction, as it directly impacts the patient’s ability to eat solid food as well as the cosmetic outcomes of having full dentition. Traditional dental implants placed into free flap bone have generally provided reliable outcomes, with reported success rates of up to 94%.

However, complications such as mucositis around dental implants and recurrent infections can lead to hardware failure, necessitating the removal of implants. To address this challenge, we have explored the use of the KLS IPS preprosthetic system, a novel implant design for dental rehabilitation.

The KLS IPS system features custom-fabricated piers that are secured directly to the reconstruction hardware. As such, mucositis that is commonly seen around the dental implants is less of a concern, as the reconstruction plate is secured well away from where the piers are located. Contrastingly, traditional implants are osseointegrated directly to the fibula, and mucositis around the dental implants can lead to fibula bone infection. Due to this unique difference in hardware design, we have successfully utilized this technology in patients who have previously failed traditional implants placed in the fibula.

Conclusion: 

Managing segmental mandibulectomy defects requires a patient-specific approach, tailored to factors such as mucosal and skin integrity, radiation history, and the location and size of the bony defect. While nonvascularized bone grafting remains a viable option for patients with good soft tissue coverage and no history of radiation, vascularized free flaps remain the gold standard for patients requiring postoperative radiation or presenting with significant soft tissue defects. The application of emerging technologies, such as patient-specific TMJ prostheses and the KLS IPS preprosthetic system, is beginning to revolutionize dental rehabilitation in these patients, providing new avenues for improving both functional and aesthetic outcomes.

References:

Melville J, Tran H, Bhatti A, Manon V, Young S, Wong M. Is reconstruction of large mandibular defects using bioengeering materials effective? J Oral Maxillofac Surg. 2020;78:661.e1-661.e29.

Alfi DM, Hassan A, East SM, Gianulis EC. Immediate Mandibular Reconstruction Using a Cellular Bone Allograft Following Tumor Resection in a Pediatric Patient. FACE. 2021;2(4):490-495. doi:10.1177/27325016211057287

Kumar BP, Venkatesh V, Kumar KA, Yadav BY, Mohan SR. Mandibular Reconstruction: Overview. J Maxillofac Oral Surg. 2016 Dec;15(4):425-441. doi: 10.1007/s12663-015-0766-5. Epub 2015 Apr 19. PMID: 27833334; PMCID: PMC5083680.