Submental island flap - should we be worried about lymph node transfer? An anatomical and histological study.

The submental island flap has been increasing in popularity for both oncological and non-oncological reconstruction of the head and neck. However, the original description of this flap left it with the unfortunate designation as a lymph node flap. There has thus been significant debate on the oncological safety of the flap. In this cadaveric study the perforator system suppling the skin island is delineated and the lymph node yield of the skeletonised flap is analysed histologically. A safe and consistent approach to raising the perforator flap modification is described and the pertinent anatomy, and an oncological discussion with regards to the submental island perforator flap histological lymph node yield discussed. Ethical approval was received from Hull York Medical School for the anatomical dissection of 15 sides of cadavers. 6 x 4cm submental island flaps were raised following a vascular infusion of a 50/50 mix of acrylic paint. The flap size mimics the T1/T2 tumour defects these flaps would usually be used to reconstruct.The submental vascular anatomy, including length, diameter, venous drainage patterns, and the skin perforator system was documented. The dissected submental flaps were then histologically examined for the presence of lymph nodes by a head and neck pathologist at Hull University Hospitals Trust department of histology. The total length of the submental island arterial system, the distance from where the facial artery branches off from the carotid to the submental artery perforator entering the anterior belly of digastric or skin, averaged 91.1mm with anaverage facial artery length of 33.1mm and submental artery of 58mm. Vessel diameter for microvascular reconstruction was 1.63mm for the submental artery and 3mm for the facial artery. The most common venous anatomy drainage pattern was the submental island venaecomitantes draining to the retromandibular system then to the internal jugular vein. Almost half the specimens had a dominant superficial submental perforator allowing the ability to raise this as a skin only system. There were generally 2-4 perforators passing through the anterior belly of digastric to supply the skin paddle.73.3% (11/15) of the skeletonised flaps contained no lymph nodes on histological examination. The perforator version of the submental island flap can be safely and consistently raised with inclusion of the anterior belly of digastric. In approximately half the cases a dominant superficial branch allows for a skin only paddle. Due to the vessel diameter, free tissue transfer is predictable.Venous anatomy is variable and care needs to be taken when raising this flap. The skeletonised version of the perforator flap is largely devoid of nodal yield and on oncological review a 16.3% recurrence rate is equivalent to current standard treatment.