Area four technique: An effective injection approach to the posterior facial frame aesthetic treatment with injectable hyaluronic acid fillers.

Background: Defined as a contour line from the hairline, the zygomatic arch, to the ramus and gonial angle area of the mandible, posterior facial frame (PFF) is an important aesthetic units of the face. With the development of hyaluronic acid fillers and the improvement of injection techniques, minimally invasive injection has become one of the first options to improve PFF. However, effective and systematic injection methods to improve PFF are rarely reported in the literature.