COSMETIC Subcutaneous Migration: A Dynamic Anatomical Study of Gluteal Fat Grafting Simeon Wall, Jr., M.D. Background: Recent anatomical studies have demonstrated that fat placed sub- Daniel Delvecchio, M.D. jacent to the fascia of the gluteus maximus muscle can migrate deep through Steven Teitelbaum, M.D. the muscle into the submuscular space, possibly causing tears in the gluteal Nathaniel L. Villanueva, veins, leading to fat embolisms. The purpose of this study was to define and M.D. to study subcutaneous migration and to determine whether fat placed in the Erez Dayan, M.D. subcutaneous space under a variety of pressures and fascial integrity scenarios Paul Durand, M.D. can indeed migrate into the deep submuscular space. Kyle Sanniec, M.D. Methods: Four hemibuttocks from two cadavers were used. Proxy fat was in- Rod J. Rohrich, M.D. serted using syringes with various fascia scenarios (1: fascia intact; 2: cannula Shreveport, La.; Boston, Mass.; Santa perforations; 3: 6mm fascia defects) or using expansion vibration lipofilling Monica, Calif.; and Dallas, Texas (4: fascia intact). Subcutaneous pressures were recorded. After injections, ana- tomical dissections were performed to evaluate the migration of the proxy fat for each of the scenarios. Results: Scenario 1: pressure reached approximately 125 to 150 mmHg and then plateaued and all the proxy fat remained in the subcutaneous space. Sce- nario 2: pressure reached a 199-mmHg plateau and no proxy fat spread deeper into the muscle or beneath it. Scenario 3: pressure gradually rose to 50 mmHg then fell again and the submuscular space contained a significant amount of proxy fat. Scenario 4: pressure rose to a maximum of 30 mmHg and all of the proxy fat remained in the subcutaneous space. Conclusions: The gluteus maximus fascia is a stout wall that sets up the danger- ous condition of deep intramuscular migration with subfascial injections and the protective condition of subcutaneous migration with suprafascial injec- tions. These persuasive findings are profound enough to propose a new stan- dard of care: no subfascial or intramuscular injection should be performed, and all injections should be performed exclusively into the subcutaneous tis- sue. (Plast. Reconstr. Surg. 143: 1343, 2019.) luteal fat grafting is a rapidly growing pro- defined this phenomenon as deep intramuscular cedure, having an annualized growth rate migration. Because of the fragile nature of the Gof 24 percent over the past 3 years.1 Despite gluteal veins, their short length, and their fixed this, its safety profile has been questioned, with increased awareness of fatal pulmonary fat embo- lism, heralded by the sentinel article by Cárdenas- Supplemental digital content is available for Camarena et al.2 this article. Direct URL citations appear in the Recent anatomical studies have demonstrated text; simply type the URL address into any Web that fat placed subjacent to the fascia of the glu- browser to access this content. Clickable links teus maximus muscle can migrate deep through to the material are provided in the HTML text the muscle into the submuscular space. We of this article on the Journal’s website (www. PRSJournal.com). SUPPLEMENTAL DIGITAL CONTENT IS AVAIL- From The Wall Center for Plastic Surgery; Back Bay Plastic ABLE IN THE TEXT. Surgery; private practice; the Department of Plastic Surgery, University of Texas Southwestern Medical Center; and the A “Hot Topic Video” by Editor-in-Chief Rod Dallas Plastic Surgery Institute. J. Rohrich, M.D., accompanies this article. Go Received for publication September 3, 2018; accepted Novem- to PRSJournal.com and click on “Plastic Sur- ber 8, 2018. gery Hot Topics” in the “Digital Media” tab to Copyright © 2019 by the American Society of Plastic Surgeons watch. DOI: 10.1097/PRS.0000000000005521 www.PRSJournal.com 1343 Copyright © 2019 American Society of Plastic Surgeons. Unauthorized reproduction of this article is prohibited. Plastic and Reconstructive Surgery • May 2019 bony egress from the iliac vein, a “nondirect hit” using expansion vibration lipofilling technique. theory for pulmonary fat embolism caused by sub- This consisted of in-line placement of fat through muscular fat stretching and tearing of these veins a 4-mm exploded caged cannula and slanted has been raised.3 Although the conclusion from canister (Black and Black, Atlanta, Ga.), silicone this prior study is that fat should be placed only tubing, a roller pump, and a power-assisted recip- in the subcutaneous space, some practitioners rocating cannula device (Microaire, Inc., Charlot- who perform gluteal fat grafting have questioned tesville, Va.) (Fig. 3). the potential for fat placed in the subcutane- After the acquisition of these data, the skin ous space to migrate into the deep submuscular and subcutaneous tissue of the posterior gluteal space. Furthermore, some suggest that occasional region were removed to examine the fascia of the unintended passes into the muscle can occur dur- gluteus maximus muscle and the submuscular ing fat grafting, which could cause perforations in space. After examination of the fascia, the gluteus the fascia, whereby fat could potentially enter and maximus muscle was incised medially along its ori- migrate into the deep submuscular space. The gin on the sacrum and reflected laterally toward purpose of the present study was to define and to the insertion on the greater trochanter to inspect study subcutaneous migration, and to determine the free submuscular space for the possible pres- whether fat placed in the subcutaneous space ence of fat. under a variety of pressures and fascial integrity scenarios can indeed migrate into the deep sub- RESULTS muscular space. Pressure-Volume Relationships MATERIALS AND METHODS The pressure-volume data for each hemibut- tock scenario are displayed in Table 1 and graphi- Four hemibuttocks from two human cadavers cally in Figure 4. (from the Dallas Plastic Surgery Institute) were used. Through a natal cleft incision, proxy fat Scenario 1: Syringe/Intact Fascia (applesauce mixed with blue food coloring) was In the intact fascia scenario, pressure increased inserted using 60-cc syringes (scenarios 1 through in spikes and dips until it reached a pressure of 3) or using expansion vibration lipofilling (sce- approximately 125 to 150 mmHg and then pla- nario 4). A Stryker manometer (Stryker, Inc., teaued. The pressure drops occurred following Kalamazoo, Mich.) was placed in the subcutane- visible spreading of the proxy fat, presumably as ous space to measure pressure at every 60 cc of pressure increased sufficiently to allow for move- grafting (Fig. 1). ment of the proxy fat into adjacent spaces in the Subcutaneous pressures were recorded after subcutaneous space by stretching and/or disrup- every 60 cc of injection. The reader, the recorder tion of the superficial fascial system. of the manometer, and the injector were separate individuals. The absence or presence of visual spreading of proxy fat in the subcutaneous tissues Disclosure: Dr. Wall a founder of SurgiStem Tech- away from the location of the cannula tip was also nologies, LLC, a medical device company involved assessed. in fat transplantation, and receives DVD royalties The hemibuttock scenarios differed as follows. from Quality Medical Publishing. No funding was In scenario 1, fat was inserted with a 60-cc syringe received for this article. Dr. Del Vecchio is a founder injection with fascia intact. In scenario 2, a ran- of Surgistem Technologies, LLC, a device company dom pattern of cannula perforations was made in involved in fat transplantation, receives royalties the gluteus maximus fascia at its point of maxi- from Microaire, and is a founding member of Penin- mum projection before fat insertion. In scenario sula Partners, LLC, a consulting firm in the plastic 3, 15 random defects in the gluteus maximus fas- surgery sector. Rod J. Rohrich, M.D., receives instru- cia were created with a 6-mm Baker punch biopsy ment royalties from Eriem Surgical, Inc., and book knife after 2-cm skin incisions were made to allow royalties from Thieme Medical Publishing; he is a for direct fascial visualization. These fenestra- Clinical and Research Study Expert for Allergan tions were made along the points of maximum Inc., Galderma, and MTF Biologics, and the owner projection of the gluteus maximus muscle. Inci- of Medical Seminars of Texas, LLC. No funding was sions were closed with a watertight running suture received for this article. No disclosures for the remain- and reinforced with staples (Fig. 2). In scenario 4, ing authors. proxy fat was inserted into the subcutaneous space 1344 Copyright © 2019 American Society of Plastic Surgeons. Unauthorized reproduction of this article is prohibited. Volume 143, Number 5 • Subcutaneous Migration of Fat Grafts Fig. 1. Stryker manometer. Fig. 2. In scenario 3, 15 random defects in the gluteus maximus fas- cia were created with a 6-mm Baker punch biopsy knife after 2-cm skin incisions were made to allow for direct fascial visualization. These fen- estrations were made along the points of maximum projection of the gluteus maximus muscle. Incisions were closed with a watertight run- ning suture and reinforced with staples. Fig. 3. Expansion vibration lipofilling setup. 1345 Copyright © 2019 American Society of Plastic Surgeons. Unauthorized reproduction of this article is prohibited. Plastic and Reconstructive Surgery • May 2019 Scenario 2: Syringe/Perforated Fascia lower than with the intact fascia of scenario 1 and In scenario 2, the spiking and eventual pla- the perforated fascia of scenario 2. Although a teau pattern of the pressure-volume curve was visible protrusion of the skin increased as fat was similar to scenario 1. The only difference was that injected in scenarios 1 and 2, in this scenario, but- the plateau pressure was higher than in scenario tock projection was not noticed to increase after 1. This might be explained by the fact that this the first several syringes were injected, with no was a different cadaver with different subcutane- visible subcutaneous migration observed in this ous capacities and different tissue tolerances.