Intralabial Lip Compartments and Their Potential Clinical Relevance

Aesthetic soft-tissue filler injections for lip enhancement are popular and performed throughout the world. When injecting lips with a cannula, as the cannula is advanced, resistance is perceived in consistent locations, potentially indicating boundaries between intralabial compartments.

We aimed to investigate whether intralabial compartments exist and, if so, to describe their volumes, location, boundaries, and dimensions.

This cadaveric study investigated a total of 20 human body donors (13 male, seven female) with a mean (SD) age at death of 61.9 years (23.9) and body mass index of 24.3 kg/m 2 (3.7). The investigated cohort included 11 White donors, eight Asian donors, and one Black donor. Dye injections simulating minimally invasive lip treatments were conducted.

Independent of sex or race, six anterior and six posterior compartments in the upper and lower lip were identified, for a total of 24 lip compartments. Compartment boundaries were formed by vertically oriented septations that were found in consistent locations. The anterior compartments had volumes ranging from 0.30 to 0.39 cc; the posterior compartment volume ranged from 0.44 to 0.52 cc. The compartment volumes were larger centrally and decreased gradually toward the oral commissure.

The volume and size of each of 24 compartments contribute to the overall appearance and shape of the lips. To achieve a natural lip shape preserving aesthetic outcome it may be preferable to administer the volumizing product using a compartment-respecting injection approach.