An alternative method for reconstructing anterior segmental mandibulectomy defects with a plate and pectoral major muscle flap

Abstract

Background: 

Reconstruction of anterior segmental mandibulectomy still remains a challenge. Osteocutaneous free flap remains the ideal choice of reconstruction because it restores cosmesis and function. The use of other locoregional flaps compromises cosmesis and function. Here, we have introduced a unique technique of reconstruction with lingual cortex mandibular plate as an alternate choice for free flap.

Method: 

Six patients aged 12–62 years underwent oncological resection for oral cancer which involved the anterior segment of the mandible. Following resection, they underwent lingual cortex mandibular plating with pectoralis major myocutaneous flap reconstruction. Adjuvant radiotherapy was delivered to all patients.

Results: 

The mean bony defect was 9.2 cm. There were no significant perioperative events related to the surgery. None required tracheostomy and all were safely extubated with no post-surgical complications. The cosmetic and functional outcomes were acceptable. Following the completion of radiotherapy with a median follow-up of 11 months, Plate exposure occurred in one patient.

Conclusion: 

The technique is cheap, quick and simple, and can be effectively applied in resource-constrained and demanding situations. It is possible to consider this as an alternative treatment strategy for osteocutaneous free flap in anterior segmental defects.

Introduction

Oral cancer is the most common cancer among men in India, especially in the elderly and those from low socioeconomic strata.[¹] Among the surgeries for oral cancer, the most challenging procedure is the reconstruction following resection of any tumor resulting in anterior segmental mandibulectomy defect.[²] Reconstruction aims at restoring cosmesis with good functional outcome. Cosmetic morbidity includes the well-known Andy Gump deformity and pulls of the lower lip. Functional morbidity may be related to speech, swallowing, drooling, mastication and the dangerous tongue fall causing obstruction of the airway.

Previously, such defects were repaired using wires or plating techniques with or without vascularized tissue covers, but these subsequently lost favor because they nearly always extruded following radiotherapy. Eventually, the problem was overcome by the introduction of free bone grafts, where the free fibula flap was deemed the ideal flap.[^2,3]

If resources, cost and time are limited, or when facing a scenario like COVID-19, performing a free flap is challenging. With metal plating out of the picture and free flap being the only option left, we tried modifying the plating technique to provide a good functional and cosmetic outcome.

Usually, when considered, plating is done on the outer cortex of the mandible and the pectoralis major myocutaneous (PMMC) flap is tunneled medial to the plate. However, the technique was discontinued in most cancer centers because of plate-related complications observed in as much as 46% of the cases.[⁴]

We report a unique reconstruction technique that could yield a good cosmetic and functional outcome without plate exposure, even following radiotherapy.

Methodology

We reviewed six patients who underwent surgical resection of the anterior segment of the mandible in the department of head and neck surgery, between November 2019 and August 2020, most during the early COVID era. The resulting defect was bridged using the lingual cortex mandibular plating (LCMP) technique and covered with a PMMC flap. Data regarding patient demography, surgical details, pathological details and others were collected. In the case of patients who were unable to visit the hospital due to the COVID-19 pandemic, the functional status was reviewed at least nine months after surgery.

Technique [Figures 1 and 2]

Figure 1: (a-d) Images showing the planning and procedure (case 3). Image (a) show preoperative planning and contouring of plate based on standard adult mandible. Image (b) shows lingual cortex mandibular plating following tumor excision. Image (c) shows covering of the plate with remanent muscles after suturing of genioglossus and geniohyoid. Image (d) shows PMMC muscle bulk covering the plate after flap inset

Figure 2: (a-d) Technical aspect of reconstruction. Image (a) shows there was no outer skin defect in the primary site; distal skin paddle was sutured towards the ipsilateral posterior aspect of oral cavity defect and proximal skin paddle covers the contralateral side oral cavity defect (case 2). Images (b) show that in patient with outer skin defect in primary site, bipaddled PMMC flap was used; proximal aspect of the skin paddle was sutured to ipsilateral oral defect and the distal end covers the skin defect (case 5). Images (c) show the shape of the PMMC flap harvested (case 2). Image (d) shows plating completed before placing the mandible cuts (case 4)

Patients were examined preoperatively by the head and neck surgical team and maxillofacial team, and surgical planning was done.

Preoperatively, the lower border of the mandible was traced on a paper. We measured two areas - the intercanine and the junction of the horizontal ramus and the body of the mandible, which were 4 cm and 7.5 cm, respectively, in our cases. Based on the outline and region of resection, the load bearing recon plate was pre-bent to the shape of an inverted U [Figure 1a]. Excess angulation toward the tip and curves were avoided. The plate was targeted to be fixed posterior to the first molar, and this helped us to bury the plate inside the soft tissue of the oral cavity. Contouring the plate preoperatively helped us to avoid time-lapse and also provided a better occlusion for the patient. None of the plating required a significant modification during the course of the surgical procedure.

The plate was sterilized before the actual procedure. Oncological resection of the lesion and neck dissection was performed. LCMP was done with three locking screws fixed on either side [Figure 1b].

For lesions extending to the molar region, mandibulectomy cut was placed through the sigmoid notch. Excessive or unnecessary stripping of periosteum was avoided to prevent late necrosis of the mandible. Three screws were placed along the lingual cortex of the mandible: below the level of mylohyoid and on either side. Occlusion was checked and stability was ensured by movement.

Genioglossus and hyoglossus were sutured onto the plate using 2-0 prolene sutures, thus preventing tongue fall. Remanent muscles and soft tissues were sutured around the plates using 3-0 vicryl sutures, taking care that tongue movement was not restricted [Figure 1c]. Reconstruction of defect with PMMC flap was based on the type of defect as mentioned below:

1. Excision involving anterior segmental mandibulectomy without skin defect:
A horizontal skin-crease neck incision was used. After resection, LCMP was done, and PMMC flap was tunneled [Figures 1d and 2a]. The bulk of the muscle was placed along the outer aspect of the plate to rest over the plate entirely and cover the same. The proximal aspect of the skin paddle of the PMMC flap covered the contralateral side of the oral cavity defect and the distal aspect of the flap was sutured towards the ipsilateral posterior aspect of oral cavity defect.

2. Excision involving anterior segmental mandibulectomy with skin defect:
The Skin incision was marked with an adequate oncological margin. The incision was dropped as a reverse S-shaped curve toward the side of ipsilateral clavicle, 2 cm short of it. Horizontal skin-crease neck incision was preferred when the skin defect was small. The flap was tunneled through the neck and the bulk of the muscle was taken along the outer aspect of the plate to rest over the plate entirely and cover the same. The proximal aspect of the skin paddle of PMMC was sutured to ipsilateral oral defect and the distal end covered the skin defect [Figure 2b].
A boomerang-shaped PMMC flap was used for this technique [Figure 2c] with focus on the region medial to and below the nipple so as to avoid excess random area in the flap.
When possible, plating and screw fixation can also be done prior to placing the mandibulectomy cut [Figure 2d]. This was done only when the area around the lingual surface of the mandible was completely free of the tumor and the mandible did not show any signs of erosion. The advantage of doing this technique is the excellent occlusion achieved.
Hyoid hitching was performed only in the first two cases. A Stay suture was taken at the junction of the anterior and posterior junction of the tongue for safety in case of emergency tackling for tongue fall. This was removed after 48 hours. The patient was managed with head end 30° elevation inward during the initial phase of recovery following surgery.

Results

Among the six patients, four patients underwent surgery during the COVID-19 pandemic when free flap reconstruction was not considered. After a multidisciplinary tumor board discussion, radiotherapy was recommended for all patients. However, one patient (case 6) failed to comply with the treatment due to financial constraints and presented for RT after three months. All patients included in the study had stage IV squamous cell carcinoma with skin and bone involvement, except case 3 who was diagnosed with Ewing’s sarcoma. All patients had a follow-up period of at least nine months post surgery.

Demography, surgery and pathology-related events are mentioned in Table 1. Mean length of resected mandible was 9.2 cm. None of the patients required tracheostomy and all were safely extubated immediately following surgery. No significant intraoperative or perioperative events were encountered. No flap-related complications were noted in any of our patients. Case 6 developed Clavien–Dindo grade 1 wound complication on post-op day 5 which was managed conservatively. Case 3 had a suture site infection which was managed with antibiotics. None of these events lead to a delay in receiving radiotherapy.

Table 1: Patient Characteristics

Protrusion of the tongue was limited compared to the preoperative status in all patients. But other tongue movements were not impaired. Table 1 shows outcome of patients on follow-up, at least nine months post the surgery (mean: 12.5 months). All had legible speech understandable to the outsiders. All patients were able to mix and initiate swallowing with no significant subjective compromise. None had drooling of saliva or lip incompetence. Tooth occlusion and cosmetic appearance were satisfactory [Figure 3].

Figure 3: (a-e) Images showing outcomes of reconstruction. Images (a) show ortholatomogram(OPG) showing plate and screw in position with proper tooth occlusion (case 3). Image (b) shows CT scan, taken three months post radiotherapy, showing the depth of plate from skin (pointed arrow). Images (c-e) shows follow-up of patient (case 3) with good occlusion, facial symmetry and a healthy flap

One patient developed plate exposure in the anterior aspect near the chin 9 months after surgery which was removed under general anesthesia.

Discussion

Free flaps remain the first choice for reconstruction of any type of defects following oral cancer resections. It has the advantage of multiple donor site availability and reliability. Yet the procedure is intricate and time-consuming, and requires advanced training and resources; hence, it cannot be considered in all settings. Alternate reconstructive techniques with local and pedicled flaps have been adopted to reach the ultimate goal in most high volume cancer centers.[⁵]

Byar et al.,[³] in 1943, introduced Metallo-alloplastic material for internal fixation of the mandible, but there was a significant issue with the extrusion of the implant, of up to 80%. The use of the Arbeitsgemeinschaft für Osteosynthesefragen(AO) plate was introduced by Schmoker in 1983. But it was soon realized that the use of plate alone resulted in extrusion. So vascularized flap was used to give an adequate cover.

C. Bowe et al.,[⁶] in their study on 30 consecutive patients who underwent lateral segmental mandibulectomy with bridging reconstruction plate and anterolateral thigh flap, used chimeric flap with muscle flap, obliterating dead space between the skin and plate. By doing so, they noted extrusion of plate in only two patients (6.7%).

Taking these facts into consideration, we made modifications to prevent plate exposure, on its two surfaces. To avoid plate contact with skin, plate fixation was done on the inner surface of the mandible; the plate was covered with remanent muscles of oral cavity, when possible, and the area was further reinforced with a bulky PMMC flap. Regarding the inner aspect, three layers of reinforcement were used: first was the remanent muscle and sublingual gland, followed by the PMMC muscle or fascia, and then the cutaneous paddle of the flap.

LCMP differs from other traditional mandibles outer cortex plating techniques because:

• LCMP plate is deep from the surface [Figure 3b] so plate exposure-related issues can be prevented.
• PMMC flap will not be tunneled medial to the plate, unlike outer plating, thereby avoiding flap compromise due to compression between the oral cavity structures and plate. This will also reduce flap bulk inside the oral cavity, preventing the tongue from being pushed posteriorly.
• Suturing of geniohyoid and genioglossus to metal plate was possible, thereby preventing tongue fall.
• In conclusion, this approach reduces the risk of airway compromise. This allowed us to avoid tracheostomy in all patients and allow tongue mobility to be near optimal.

Free fibula flap remains the ideal option, in terms of reconstructing an anterior segmental mandibulectomy defect. Its disadvantages include the length of the surgery, low soft tissue volume, and insufficient skin paddle for very large defects.[^4,6] Compared with free flap surgery, which takes over 9 hours, the mean duration of surgery in our technique was 5 hours 45 minutes. The current reconstruction also has the advantage of shorter hospital stays, quicker recovery times, and low donor site morbidity.[⁷] Therefore, this flap can be reserved in case of need as an alternative.

Fanzio et al.[⁸] noted in their study that the average time for plate exposure among patients who underwent plating with anterio-lateral thigh free flap in mandibulectomy defect was 9.1 months. In the study, 49 out of 130 patients (37.7%) had plate exposure. When we relooked at our patients with plate exposure, which was one of the initial cases to start with, we noticed that the plate did not have a smooth bend. We used only two screws in fixing the lateral aspect of the plate. Other contributory factors might be radiotherapy-induced change on mandible due to plating or patient factors like anemia, age and tobacco intake.

The functional outcome was good [Table 1]. PMMC flap with LCMP can be preferred when we operate in situations where the duration of surgery should be minimized or in resource-constrained settings. In addition to cosmesis and function, the traditional thought complication of plate extrusion can be overcome by using this method. The drawbacks in the study were the need for long-term follow-up to know the effect of plating on radiated bone surface, and unlike free flap, osteointegration of tooth will not be possible.

Conclusion

Free fibular flap remains the ideal treatment of choice for reconstruction of anterior segmental mandibulectomy defect. PMMC flap with LCMP may be kept as an option, especially when surgery duration is a limiting factor. A prospective study can further strengthen our initial result. The result of our study with follow-up indicates cosmetic and function outcome being on par with free flap.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.