Marginal Mandibulectomy Defect Reconstruction with Pectoralis Major Myocutaneous (PMMC) Flap in Cases of Carcinoma Buccal Mucosa: Experience from a Tertiary Cancer Institute

Abstract

Patients with carcinoma buccal mucosa requiring marginal mandibulectomy pose various key challenges with regard to reconstruction. To study the role and feasibility of the PMMC flap reconstruction in patients of carcinoma buccal mucosa with intact mandible. Study design: retrospective analysis of prospectively maintained data at a tertiary cancer institute in India. Inclusion criteria: all patients of carcinoma buccal mucosa undergoing marginal mandibulectomy at our institute from 1st Jan 2015 to 31st March 2018 with reconstruction done by the PMMC flap. The retrospective analysis showed 82 patients satisfied the inclusion criteria. Median age of the patients was 46 years. Seventy-seven (93.90%) patients were male while 5 (6.09%) patients were female. Median Ryle’s tube dependency was 13 days. Median follow-up period was 28 months. All the patients had acceptable cosmesis and mouth opening with minimal morbidity. PMMC flap reconstruction after marginal mandibulectomy in patients with carcinoma buccal mucosa is a robust, cosmetically, and functionally acceptable option.

Introduction

The mandible has paramount importance in maintaining the airway, the first phase of swallowing and articulation of speech [1]. Management of mandible in oral cancer has changed significantly with the increasing knowledge on patterns of mandibular invasion by the tumor [2–5].

In selected cases of oral cancer, wide local excision of the lesion with marginal mandibulectomy is preferred because maintaining the continuity of the mandible improves the quality of the life of the patient significantly. Its oncological safety is well established in the literature [6–10]. While microvascular reconstruction of the mandible with free bone flap is possible, marginal mandibulectomy continues to be relevant till date as a conservative procedure [11, 12].

Pectoralis major myocutaneous (PMMC) flap continues to be the workhorse flap for head and neck reconstruction as it is a reliable, simple, and cost-effective option [13]. PMMC is rarely utilized in marginal mandibulectomy defects due to concerns like pedicle compression, bulk of the flap, difficult inset, loss of gingivo-lingual sulcus, and dental rehabilitation problems.

We present our experience of PMMC flap reconstruction in marginal mandibulectomy defects in cases of carcinoma buccal mucosa. There are very few reports in the literature about this type of reconstruction. It is also the largest review available in literature till date to the best of our knowledge.

Patients and Methods

A retrospective study was designed to analyze prospectively maintained database from 1st Jan 2015 to 31st March 2018. Study was approved by Institutional Ethics committee.

Inclusion Criteria

patients with squamous cell carcinoma of buccal mucosa, lower gingivobuccal sulcus, and retromolar trigone abutting or superficially involving the cortical bone of the mandible were included.

Exclusion Criteria

Patients with gross paramandibular tumor invasion, involvement of the mandibular canal, gross bone erosion, previously irradiated and expected residual height of the bone less than 1 cm.

All patients underwent contrast-enhanced CT scan of oral cavity and neck as part of preoperative evaluation, followed by marginal mandibulectomy along with PMMC flap reconstruction (Fig. 1). PMMC flap harvest was done with “V”-shaped muscle over the pedicle avoiding excessive muscle bulk as illustrated in Fig. 2 [14]. All the flaps were given inset with pedicle over the mandible and in single layer without much tension.

Fig. 1.

Marginal mandibulectomy defect

Fig. 2.

PMMC Flap with mucle over pedicle in “V” shape

They were evaluated for post-operative wound and flap complications, Ryle’s tube dependency, and mouth opening.

Results

The retrospective analysis showed 82 patients satisfied the inclusion criteria. Median age of the patients was 46 years. Seventy-seven (93.90%) patients were male while 5 (6.09%) patients were female. Bipaddled PMMC flap was done in 26 (31.70%) patients for both inner lining and outer cover. Thirty-eight (46.34%) patients had oral submucous fibrosis (Fig. 3).

Fig. 3.

PMMC with marginal mandibulectomy for only mucosal defect

Median duration of the surgery was 210 min. All donor site defects were closed primarily. In the immediate postoperative period, all the patients were kept intubated, monitored overnight in surgical ICU, and extubated the next morning. No patient had airway compromise. Tracheostomy was not done in any case.

Median Ryle’s tube dependency was 13 days (range 7 to 26 days). Thirteen (15.85%) patients developed partial necrosis of flap, treated with debridement under local anesthesia (clavien dindo grade IIIa). No total flap loss was seen.

Adjuvant chemoradiotherapy was received by 24 (29.26%) patients and adjuvant radiotherapy alone was received by 32 (39.02%) patients. Twenty-six (31.70%) patients were not given adjuvant therapy based on the decision by Multidisciplinary Tumor Board. No patient had delay in starting adjuvant therapy (Table 1).

Table 1.

Results

No. of cases satisfying inclusion criteria	82
Male	77 (93.90%)
Female	5 (6.09%)
Oral submucous fibrosis present	38 (46.34%)
Bipaddled flap done in	26 (31.70%)
Adjuvant radiation	32 (39.02%)
Adjuvant chemoradiation	24 (29.27%)
Partial flap necrosis	13 (15.85%)
Median Ryle’s tube removal	13 days

Median follow-up period was 28 months. During follow-up, one patient developed osteoradionecrosis (ORN) and subsequent fracture of the mandible which was treated accordingly. The median mouth opening at 6-month follow-up visit was 3.2 cm (range 1.8 to 4.7 cm). None of the patients had reduced mouth opening during follow-up in comparison to preoperative state (Fig. 4).

Fig. 4.

Post-operative mouth opening

Discussion

The advantages of marginal mandibulectomy over segmental mandibulectomy are numerous and well described in literature. These include better cosmesis and functional outcomes and obviate the need for bony reconstruction [10, 15]. Oncological safety of marginal mandibulectomy in selected patients has been extensively studied and well established in literature [7, 8, 11, 16–18].

The reconstruction of the marginal mandibulectomy defect is a challenge to the reconstructive surgeon as the exposed surface of the mandible needs pliable vascularized tissue cover (Fig. 5).

Fig. 5.

For mucosa and skin defect, bipaddled PMMC with marginal mandibulectomy

Due to the unique habits of placement of smokeless tobacco and quid in the lower gingivobuccal sulcus, cancer in this area is very common in India (up to 72% of all oral cancers) [19]. In our study, we observed that most of the patients with carcinoma of buccal mucosa had large defects that required flaps to cover buccal mucosa defects with or without the outer skin defect.

Pectoralis major myocutaneous flap is a versatile, robust flap as far as survival is concerned. Harvest of the flap is technically easy, quick, and economical. It has good vascularity, adequate bulk, and can cover extensive defects.

Inadequate tissue coverage after marginal mandibulectomy is one of the high-risk factors for the development of osteoradionecrosis (ORN) [20]. According to literature, the rate of development of ORN following marginal mandibulectomy is 16% [1]. In our series, one patient (1.21%) developed ORN; it occurred 6 months after adjuvant radiotherapy.

Total loss of the PMMC flap is rare. Partial necrosis of the PMMC flap has been reported as 6.6–32% [13]. In our series, 15.85% patients had partial necrosis of the flap. This also alludes to the fact that there is no vascular compromise of PMMC flap in intact mandible.

Dental rehabilitation improves the quality of life but it is not always feasible. Gingivobuccal sulcus creation, post-operative radiation, and height of the residual bone determine the feasibility of dental rehabilitation [21, 22]. In our series, dental rehabilitation was not performed, but patients were able to use the opposite teeth for chewing.

Conclusion

Pedicled pectoralis major myocutaneous flap is a robust, reliable, and versatile reconstructive option. It can be used for reconstruction of extensive gingivobuccal complex defects with intact mandible (marginal mandibulectomy) with acceptable cosmesis and functional outcomes.