Cannula characteristics and mortality risk in Gluteal Lipofilling: does diameter and tip design matter? A narrative review

Gluteal fat grafting, or Brazilian butt lift, is a rapidly growing aesthetic procedure but remains associated with the highest mortality among cosmetic operations, primarily because of fatal pulmonary fat embolism after injury to the deep gluteal veins. Although safety discussions have focused mainly on injection plane, cannula diameter, tip design, rigidity and port configuration are modifiable technical factors that may influence vascular penetration and intravascular fat delivery. This narrative review synthesised English-language evidence from PubMed/MEDLINE, Embase and the Cochrane Library, supplemented by society advisories, cadaveric studies, biomechanical data, clinical series and forensic reports. Survey and autopsy data link fatal embolism to deep intramuscular injection, downward cannula angulation and cannulas smaller than 4 mm. Cadaveric studies show that subcutaneous vessels are approximately 1 mm in diameter, whereas the superior and inferior gluteal veins measure about 7.6 mm and 13.7 mm, respectively, supporting the rationale for large-bore blunt cannulas only when maintained in the subcutaneous plane. Dynamic studies demonstrate that subfascial or intramuscular fat can migrate into deep compartments and enter injured veins, whereas subcutaneous fat does not. Current consensus recommendations therefore support subcutaneous-only injection using a large-bore (≥4 mm), blunt, rigid cannula with continuous motion, low-pressure delivery and real-time ultrasound confirmation. However, evidence remains indirect, with no controlled studies isolating cannula geometry as an independent determinant of mortality. Standardised reporting and prospective registries are needed.