What is the difference between the inferior labial artery and the horizontal labiomental artery?

The inferior labial artery (ILA) and horizontal labiomental artery (HLA) can be regarded as the main arteries used in the lower lip pedicle for the perioral reconstruction. However, the courses of the ILA and HLA are described in diverse ways, and there is no obvious standard for distinguishing between them. The aim of this study was to elucidate the distribution patterns of the ILA and HLA, and the significance of the HLA in the vascularization of the lower lip. Sixty-three hemifaces from 18 Korean and 19 Thai cadavers were used in this study. The distribution patterns of the arteries of the lower lip area were classified based on the assumption that the HLA travels in the middle of the lower lip area, while the ILA runs along the lower lip border. The arterial distribution pattern of the HLA was classified into three types (I-III): type I, where the HLA ran horizontally in the lower lip area; type II, where the HLA curved upward to the vermilion border of the lower lip; and type III, where the HLA bifurcated into two branches. The ILA was also classified into three types (A-C): type A, where the ILA was not observed; type B, ILA was ramified from facial artery at the level of mouth corner; and type C, ILA arose from the superior labial artery (SLA) and supplied the lower lip vermillion border. Types I, II, and III were observed in 52.4 % (33/63), 39.7 % (25/63), and 7.9 % (5/63) of cases, respectively; and types A, B, and C were observed in 52.4 % (33/63), 36.5 % (23/63), and 11.1 % (7/63) of cases. Consideration of the two artery classifications together revealed seven types: type IA (14.3 %, 9/63), type IB (28.6 %, 18/63), type IC (9.5 %, 6/63), type IIA (30.2 %, 19/63), type IIB (7.9 %, 5/63), type IIC (1.6 %, 1/63), and type III (7.9 %, 5/63). The distance between the HLA and the midpoint between the mouth corner and the inferior mandibular margin was 0.4 +/- A 3.1 mm (mean +/- A SD) inferior to this point. The ILA and HLA should be differentiated according to the location of their origin rather than their terminating areas. The HLA could be considered as the main artery supplying the lower lip mucosa.