Brazilian butt lifts are safe only if the injections remain in the subcutaneous tissue, suggests a new study in the May issue of Plastic and Reconstructive Surgery.

“These persuasive findings are profound enough to propose a new standard of care: no subfascial or intramuscular injection should be performed, and all injections should be done exclusively into the subcutaneous tissue," the researchers conclude.

More than 24,000 buttock augmentation with fat grafting procedures were performed in 2018 – an increase of 19 percent over the previous year, according to statistics from the American Society of Plastic Surgeons (ASPS). However, there is growing concern about serious complications resulting from this procedure.  A 2015 paper in Plastic and Reconstructive Surgery reported a series of 22 deaths in patients undergoing gluteal fat injection in Colombia and Mexico. The deaths were caused by pulmonary embolisms: collections of fat blocking the arteries in the lungs.

In 2018, the ASPS joined with other plastic surgery specialty societies in issuing an urgent warning regarding the "alarming" number of deaths related to gluteal fat augmentation. An advisory issued to plastic surgeons outlined steps to ensure that fat is injected only under the skin – never into the muscle.

To build the evidence base for this recommendation, the study authors performed a cadaver study to evaluate patterns of fat spread in the gluteal area after injection. Four approaches were evaluated, simulating injection techniques that might be used by plastic surgeons performing gluteal fat grafting. In three of the four injection techniques, the spread of the simulated fat was mainly limited to the subcutaneous area, immediately beneath the skin. Even when small perforations were made in the fascia, there was little or no spread of the simulated fat into the muscle itself.

Even with multiple perforations and high injection pressures, the muscle fascia prevented the simulated fat from crossing into the muscle. The researchers discuss the process of "subcutaneous migration" that keeps injected fat from spreading into or under the gluteal muscle, if injected into the subcutaneous "safe zone."

The findings were different in the fourth scenario, where multiple punctures were made in the gluteal muscle. In this situation, large amounts of proxy fat were found under the muscle – demonstrating that "deep intramuscular migration" had occurred. Once fat has migrated into the submuscular space, damage to the veins in that area could allow fat cells to enter the circulation, with a potential risk of pulmonary embolism.

"The study confirms that gluteal fat grafting is safe, only if the injections remain in the subcutaneous tissue," according to Daniel Del Vecchio, MD, a Boston plastic surgeon who developed the protocol. Moreover, a video commentary by coauthor Rod J. Rohrich, MD, of Dallas Plastic Surgery Institute strongly emphasizes the need to avoid any fat injection into the gluteal muscle itself in order to prevent serious complications.

Speaking as part of a panel on gluteal fat grafting at the annual Aesthetic Society meeting in New Orleans, Héctor Durán, MD, a plastic surgeon in Mexico stresses that surgeons who perform Brazilian butt lifts must know the anatomy and be prepared in the event that things don’t go as planned. “I am very comfortable with the safety of this procedure,” he says.