Background: Aesthetic soft tissue filler injections for lip enhancement are highly popular and are performed throughout the world. When injecting lips with cannulas, as the cannula is advanced, resistance is perceived in consistent locations potentially indicating boundaries between intralabial compartments.
Objective: To investigate whether intra-labial compartments exist and (if so) to describe their volumes, location, boundaries, and dimensions.
Methods: This cadaveric study investigated a total of n = 20 (13 males, 7 females) human body donors with a mean age at death of 61.9 (23.9) years and a mean body mass index of 24.3 (3.7) kg/m 2. The investigated cohort included n = 11 Caucasian, n = 8 Asian, and n = 1 African American donors. Dye injections simulating minimally invasive lip treatments were conducted.
Results: Independent of gender or race, 6 anterior and 6 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 - 0.39 cc whereas the posterior compartment volume ranged from 0.44 - 0.52 cc. Centrally, the compartment volumes were larger and decreased gradually towards the oral commissure.
Conclusion: The volume and the size of each of the 24 compartments contribute to the overall appearance and shape of the lips. To achieve a natural and lip-shape preserving aesthetic outcome it may be preferable to administer the volumizing product using a compartment-respecting injection approach.
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