RESUMO
BACKGROUND: Soft-tissue filler injections for the treatment of facial aging can result in different skin surface effects depending on the targeted facial fat compartment and fascial plane. This work investigates the tissue response of defined amounts of soft-tissue filler material injected into superficial and deep facial fat compartments by means of the calculation of the surface-volume coefficient. METHODS: Four fresh frozen cephalic specimens obtained from human donors (three female and one male; mean age, 74.96 ± 22.6 years; mean body mass index, 21.82 ± 6.3 kg/m) were studied. The superficial and deep lateral forehead compartments, deep temporal fat pad, sub-orbicularis oculi fat compartment, and deep medial cheek fat compartment were injected with aliquots of 0.1 cc of contrast-enhanced material and scanned using three-dimensional surface imaging, resulting in a total of 226 injection and scanning procedures. RESULTS: The sub-orbicularis oculi fat compartment revealed the highest correlation coefficient (rp = 0.992; p < 0.001) and the highest surface-volume coefficient (0.94). The compartment with the lowest tissue response was the deep medial cheek fat compartment (rp = 0.745; p < 0.001; surface-volume coefficient = 0.29), followed by the deep lateral forehead compartment (rp = 0.814; p < 0.001; surface-volume coefficient = 0.68), superficial lateral forehead compartment (rp = 0.824; p < 0.001; surface-volume coefficient = 0.74), and deep temporal fat pad (rp = 0.947; p < 0.001; overall surface-volume coefficient = 0.64). CONCLUSIONS: These results, confirmatory in their nature to current injection strategies, provide evidence for the validity and reliability of the surface-volume coefficient. Injection procedures should be targeted in terms of facial fat compartments and fascial planes for a desired aesthetic outcome, as each fat compartment and fascial plane has unique tissue responses to injected soft-tissue fillers.