Majority of the head and neck cancers arise in oral cavity and about 90% of them are squamous cell carcinomas [1]. In our population, about 75% of them present in an advanced stage, of which gingivobuccal sulcus (GBS) cancers predominate in view of the habit of chewing tobacco [2]. The primary treatment modality adopted for GBS cancers is surgery and the close anatomical relation to the mandible warrants the need to appropriately address it, for superior oncological outcomes. The extent of resection of mandible, i.e., marginal versus segmental mandibulectomy, is dependent on the extent of involvement and the possible routes of entry of tumor into it, which is often at the junction of the reflected and attached mucosa [3].
The patients with radiological cortical or marrow involvement or GBS tumors with significant para-mandibular spread necessitate segmental mandibulectomy [4]. This results in a complex bony defect requiring multiple osteotomy of the fibula to create a neo-mandible (Fig. 1).
Fig. 1.
Defect following resection
The planning of osteotomies depends on basic understanding of the anatomy of the mandible which is a horseshoe-shaped bone with complex angulation. The osteotomies are based on the principle that the mandible has four corners: two vertical corners that make the angles of the mandible, and two horizontal corners that are centered at the canine teeth on each side in the dentate mandible, and are roughly 7 mm anterior from the mental foramen in the edentulous jaw. These corners show the points of change in the form of the mandible and the increasing need to shape a graft with osteotomies [5].
We propose a technique by modifying the placement of posterior osteotomy below the sigmoid region of the mandible.
Prior to performing the osteotomies, the soft tissue attachment on the mandible is released and the periosteum is stripped off the mandible using Molts periosteal elevator at the planned osteotomy site. The identification of the anti-lingula serves as an important landmark in planning the osteotomy. It is a bony tubercle or prominence on the lateral surface of the ramus of the mandible and corresponds to the mandibular foramen on the medial surface of the ramus of the mandible. Identification of the anti-lingula is important in cases where the medial surface of the ramus is not visualized and the osteotomy can be placed posterior and superior to the anti-lingula, thereby including the IAN and vessels. Anterior osteotomy is placed distal to the canine or in between central incisors depending on the extent of the tumor with adequate surgical margins of 1 cm. Anterior osteotomy is performed before posterior osteotomy as it improves the visibility and accessibility to the posterior region which has complex vascular anatomy. Posterior osteotomy is placed by identifying the anti-lingula and staying 1 cm below the neck of the condyle starting from the sigmoid notch passing in anteroposterior direction obliquely up to the angle region of the mandible; and the planning of this posterior osteotomy cut is crucial. The osteotomies are always bicortical, performed using an oscillating saw and includes the inferior alveolar vessels and nerve (Fig. 2).
Fig. 2.
Specimen including inferior alveolar vessels
The 2 main advantages of sigmoid osteotomy technique are obtaining good oncological clearance by including the inferior alveolar nerve in the resection and the other advantage being preserving a wide strut of posterior mandible which gives more space for the placement of reconstruction plates and screws (Fig. 3), thereby improving functional outcome, and by understanding the patterns of bone invasion and the reconstruction principles, this technique of osteotomy helps us to achieve standardization of oncological resection and reconstruction principles with superior outcomes.
Fig. 3.
Reconstruction with free fibula flap
Declarations
Conflict of Interest
The authors declare no competing interests.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
References
- 1.Vigneswaran N, Williams MD. Epidemiologic trends in head and neck cancer and aids in diagnosis. Oral Maxillofac Surg Clin. 2014;26(2):123–141. doi: 10.1016/j.coms.2014.01.001. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Misra S, Chaturvedi A, Misra NC. Management of gingivobuccal complex cancer. Ann Royal Coll Surg Engl. 2008;90(7):546–553. doi: 10.1308/003588408X301136. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Shaw RJ, Brown JS, Woolgar JA, Lowe D, Rogers SN, Vaughan ED. The influence of the pattern of mandibular invasion on recurrence and survival in oral squamous cell carcinoma. Head Neck: J Sci Spec Head Neck. 2004;26(10):861–869. doi: 10.1002/hed.20036. [DOI] [PubMed] [Google Scholar]
- 4.Gou L, Yang W, Qiao X, Ye L, Yan K, Li L, Li C. Marginal or segmental mandibulectomy: treatment modality selection for oral cancer: a systematic review and meta-analysis. Int J Oral Maxillofac Surg. 2018;47(1):1. doi: 10.1016/j.ijom.2017.07.019. [DOI] [PubMed] [Google Scholar]
- 5.Brown JS, Barry C, Ho M, Shaw R. A new classification for mandibular defects after oncological resection. Lancet Oncol. 2016;17(1):e23–30. doi: 10.1016/S1470-2045(15)00310-1. [DOI] [PubMed] [Google Scholar]