Why is lip augmentation with autologous fat injection less effective in the vermilion border?

Lip augmentation is a well tolerated procedure leading to a more youthful appearance. Augmentation of lips is most frequently performed with autologous tissue, biomaterials, or alloplastic materials. Autologous fat grafting is a simple procedure because of the ease of harvesting and subsequent injection into selected sites. Fat injection is suitable for the bulk of the red lips, but is less effective for the vermilion border. This study was performed to determine why fat injection is less effective for the vermilion border.