Experts have found that by dividing the lips into separate zones, they may be able to further improve patients' satisfaction with the procedure.
Lip augmentation is a particularly popular non-surgical cosmetic procedure
among young women, as wider, fuller lips are deemed to be a mark of attractiveness.
Writing in the Archives of Facial Plastic Surgery, study authors note: "There has been a dramatic increase in cosmetic surgery in western culture in the past few decades, with an increasing focus on achieving aesthetic ideals and maintaining a youthful appearance."
A researcher at the New York Centre for Facial Plastic Surgery carried out 137 lip augmentation procedures on 66 patients using the injectable gel filler Restylane, which he injected into 15 distinct lip zones.
Dr Andrew Jacono claimed that the technique increased the ability "to better control lip shape and size in lip augmentation".
When patients were asked to rate their satisfaction with the procedure, the average score was 4.5, on a scale from nought to five.
Dr Jacono concluded: "This technique was met with high patient satisfaction and no adverse effects."