Streamlining the Fat: A Systematic Review of Active Closed Wash and Filtration in Autologous Fat Grafting After Breast Reconstruction

Abstract

 

Although fat grafting in breast reconstruction continues to grow in popularity, the optimal technique remains elusive and outcomes are varied. This systematic review of available controlled studies utilizing active closed wash and filtration (ACWF) systems sought to examine differences in fat processing efficiency, aesthetic outcomes, and revision rates. A literature search was performed from inception to February 2022 following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) in Ovid MEDLINE (Wolters Kluwer, Alphen aan den Rijn, the Netherlands), Ovid Embase (Wolters Kluwer), and Cochrane Library (Wiley, Hoboken, NJ). Two independent reviewers screened the studies for eligibility with Covidence software. Bibliographies and citing references from selected articles were screened from Scopus (Elsevier, Amsterdam, the Netherlands). The search identified 3476 citations, with 6 studies included. Three studies demonstrated a significantly higher volume of graftable fat harvested in a significantly lower mean grafting time with ACWF than with their respective controls. With respect to adverse events, 3 studies reported significantly lower incidences of nodule or cyst formation with ACWF with respect to control. Two studies reported a significantly lower incidence of fat necrosis with ACWF vs control, with this trend upheld in 2 additional studies. Three studies reported significantly lower revision rates with ACWF with respect to control. No study reported inferiority with ACWF for any outcome of interest. These data suggest that ACWF systems yield higher fat volumes in less time than other common techniques, with decreased rates of suboptimal outcomes and revisions, thereby supporting active filtration as a safe and efficacious means of fat processing that may reduce operative times. Further large-scale, randomized trials are needed to definitively demonstrate the above trends.

Level of Evidence: 4

See the Commentary on this article here.

Autologous fat grafting, first performed by Neubauer in 1893, has been regarded for more than a century as a useful tool to improve aesthetic outcomes in plastic surgery.^1,2 More recently, autologous fat transfer has been established as a successful means of improving outcomes following breast surgery. In fact, the American Society of Plastic Surgeons reported in 2013 that 62% of plastic surgeons employ fat grafting in breast reconstruction.³ From 2015 to 2021, the Aesthetic Plastic Surgery National Databank reported a 24% increase in the frequency of procedures involving fat transfer to the breast, with a total of 22,467 procedures performed in 2021.^4,5 The theoretical advantages to autologous grafts are numerous—such grafts are biocompatible, nonimmunogenic, and cost-effective, with several options available for donor site selection. Additionally, patients frequently find large-volume grafting appealing as it may offer an aesthetic benefit in reducing undesired adipose stores at donor sites.² In practice, however, outcomes remain highly varied, with postoperative graft retention rates historically ranging from 10% to 50%.⁶ Moreover, grafts are reliant on diffusion until sufficient neovascularization can be achieved; for this reason, larger grafts are frequently subject to central necrosis, resulting in the formation of palpable masses and cysts as well as microcalcification within the graft site.² Nevertheless, since the 1995 standardization and apparent optimization of autologous grafting by Coleman, the procedure has continued to steadily gain popularity in both aesthetic breast augmentation as well as reconstruction.^7,8

In the absence of clear, evidence-based guidelines, the specific means of fat processing remain largely a matter of physician preference. For example, a 2013 study among American Society of Plastic Surgeons members reported that 45% of members used a decantation technique, 34% utilized a filtration system, and 11% used gauze.³ Accumulating evidence suggests that active closed wash and filtration (ACWF) systems, defined by the immediate harvest of lipoaspirate into the device, serial sterile washes, and direct separation from tumescent fluid and debris via an internal filter basket (200-μm pores) under vacuum suction, yield superior results to their passive counterparts, as well as to other traditional fat grafting techniques. More specifically, such systems directly harvest lipoaspirate into a closed, central cannister using mechanical suction, perform serial washes via propeller with lactated Ringer's solution, and actively filter out lysed cellular debris 3 times before the resulting graftable tissue is loaded for injection directly from the cannister and injected into the patient.⁹ The integration of all components of lipoaspirate processing into a single device affords several advancements beyond simply reducing operative time. For example, ACWF systems are more reliably able to control contaminants by minimizing tissue handling, exposure to outside air, pH, and osmolarity. Additionally, ACWF systems are able to process up to 350 mL of lipoaspirate per run.⁹ Although our anecdotal experience with ACWF has suggested superior results, there remains no clear standard in the practice of fat grafting. As such, this systematic review of available controlled studies utilizing ACWF systems sought to examine differences in fat processing efficiency, aesthetic outcomes, and revision rates between ACWF and other common fat grafting techniques.

METHODS

This study was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, with the 2020 PRISMA checklist available in the Supplemental Figure.¹⁰

Search Strategy

A medical librarian (M.D.) performed comprehensive searches to identify studies that compared outcomes from use of ACWF with those from standard lipoaspirate processing techniques in adult females undergoing breast reconstruction with autologous fat grafting. The protocol was registered on Open Science Framework and has been made publicly available at https://osf.io/b5vnz/?view_only=57ce269951a24bfdbb72fc025fe1fe1f. Searches were run on January 7, 2021 and rerun on February 17, 2022 by M.D. in the following databases: Ovid MEDLINE (Wolters Kluwer, Alphen aan den Rijn, the Netherlands) (1946 to present), Ovid Embase (Wolters Kluwer) (1974 to present), and the Cochrane Library (Wiley, Hoboken, NJ). Searches included all appropriate subject headings and keywords for the concepts of “breast reconstruction,” “fat grafting,” and ACWF. The full search strategy for Ovid MEDLINE is available in the Appendix. Articles considered for inclusion: (1) utilized ACWF, (2) had >10 patients in their cohorts, (3) employed a comparison or control group, and (4) reported follow-up data from at least 1 clinic visit. Review articles, meeting abstracts, editorials, or commentaries were excluded. To limit publication bias, there were no language, publication date, or article type restrictions on the search strategy. For articles selected for inclusion in this study, reference lists and citing articles were pulled from Scopus (Elsevier, Amsterdam, the Netherlands) and also screened. Database searches and the included studies’ reference lists and citing articles retrieved 4737 results. After results were de-duplicated, 2 independent reviewers (N.A.V. and W.F.J.) screened a total of 3476 citations with Covidence systematic review software, with conflicts resolved by consensus. Full text was then pulled for 15 selected studies for a second round of eligibility screening. The full PRISMA flow diagram outlining the study selection process is shown in Figure 1.

Figure 1.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram outlining the process of study identification and selection.

RESULTS

The selected studies included 2 retrospective chart reviews (1042 patients), 2 retrospective cohort studies (382 patients), 1 prospective pilot study (40 patients), and 1 retrospective, propensity-matched analysis (38 breasts per group; 76 breasts total). A full summary of included studies is given in Table 1.

Table 1.

Summary of Studies Evaluating Success of Active Closed Wash and Filtration Systems in Autologous Fat Grafting

Author (year) and study type	Study period	Comparison and/or controls	Patients (n)/(age, years)/(BMI, kg/m2)	Follow-up	Treatment outcomes	Adverse effects	Limitations/risk of bias
Gabriel (2017) RCS	1/2012-1/2013	ACWF and centrifugation	ACWF: (98)/(51.89)/(27.38) Centrifugation: (96)/(50.06)/(27.06)	6 months	Significantly higher (P < .0001) lipoaspirate volume (506.0 mL vs 126.1 mL) and fat injected (117.3 mL vs 79.2 mL) in the ACWF group. Mean grafting time was significantly shorter (P < .0001) in the ACWF group (34.6 min vs 90.1 min)	ACWF group had a significantly smaller number of patients with nodule (10.2% vs 28.1%, P = .004) or cyst (7.1% vs 18.8%, P = .023) formation, as well as reintervention rates (37.8% vs 58.3%, P = .007). Fat necrosis was less frequent (3.1% vs 9.4%) in the ACWF group (P = .131)	Retrospective, single-center, single-surgeon study; study groups not concurrent; different volumes of fat harvested and injected between groups; no randomization
Chiu (2019) RCR	1/2008-10/2017	ACWF and decantation	ACWF: 504 fat grafting procedures on 301 breasts/(48.7)/(26.9) Decantation: 654 fat grafting procedures on 474 breasts/(49.5)/(25.2)	Mean follow-up = 10.6 months	Significantly higher (P < .01) lipoaspirate volume transferred with ACWF (105 mL) vs decantation (50.6 mL)	Significantly higher (P = .01) fat necrosis incidence in decantation (3.2%) vs ACWF (1.0%). Decantation was an independent risk factor for fat necrosis (5.90, 95% CI, 1.94-18.0). No significant difference in nodule/cyst formation, biopsy, or ultrasound performed. Cancer recurrence rate of 5/6 in the decantation group (1.05%), association was not significant (P = .19). Decantation resulted in significantly higher (P < .01) number of revision procedures (1.56) vs ACWF (1.38)	Retrospective, single-site, single surgeon study; absence of formal volume retention via imaging; no randomization
Hanson (2019) prospective, observational PS	11/2013-5/2014	ACWF and passive filtration	ACWF: (20)/(52.3)/(27.2) Passive filtration: (20)/(50.5)/(27.5)	Mean follow-up = 3 years	Rate of fat grafting was significantly higher (P ≤ .001) with ACWF (19.8 mL/min) vs passive filtration (5.3 mL/min), with resulting percentage of graftable fat comparable between groups (41% ACWF vs 42% passive filtration; P = .83)	No difference in postoperative complications between groups. There was 1 incidence of palpable fat necrosis per group, and no reported fat emboli. Revision procedures performed for 20% of patients (n = 4) per group	single-site, consecutive study; self-reported “learning curve” potential given more surgeon experience with passive filtration; no randomization
Ruan (2019) RCR	2012-2016	ACWF, Telfa rolling, and centrifugation	ACWF: (55)/(51.44)/(27.93) Telfa rolling: (44)/(51.93)/(28.60) Centrifugation: (168)/(54.77)/(26.19)	Varied; minimum of 1 follow-up visit	Significantly higher (P < .0001) lipoaspirate volume transferred with ACWF (160 mL) vs centrifugation (120 mL) or Telfa (70 mL)	Oil cyst formation was significantly higher (P = .034) in centrifugation (12.5%) vs ACWF (7.3%) and centrifugation (0%). Combined variable of all complications was significantly higher (P = .001) with centrifugation (25.6%) vs ACWF (10.9%) and Telfa (4.5%). Reintervention was significantly higher (P = .029) with centrifugation (19.6%) vs ACWF (5.5%) and Telfa (11.4%)	Retrospective, single-center, multisurgeon study; variable follow-up time; no randomization
Valmadrid (2020) RCS	1/2013-9/2017	ACWF and Telfa rolling	ACWF: (110)/(51.3)/(27.4) Telfa rolling:(76)/(53.1)/(28.4)	Minimum of 180-day follow-up	No significant differences in total lipoaspirate, volume of fat grafted. For second autologous graft procedures performed often after second-stage reconstruction, operative time was significantly longer (P = .03) for Telfa rolling patients (100 min) vs ACWF (79 min)	Telfa rolling breasts had significantly more (P = .01) palpable masses requiring imaging (26%) vs ACWF (14.4%) and a significantly higher (P < .01) incidence of fat necrosis (20.6%) vs ACWF (8%). There was no difference in fat necrosis excision or cancer recurrence rates between groups	Retrospective, single-surgeon, single-site study; nonblinded; no randomization
Assad (2021) RPMA	3/2016—1/2019	ACWF and passive filtration	ACWF (38 breasts/52/28) Passive filtration (38 breasts/52/28)	minimum of 1-year follow-up	Mean total volume of graftable fat was comparable between groups (ACWF = 130 mL; passive filtration = 159 mL; P = .23)	No significant difference between overall complication rates between the ACWF (18%) and passive filtration (26%) systems; although passive filtration patients had a higher incidence of fat necrosis (18%) with respect to ACWF (11%), this difference failed to achieve significance; multiple conditional logistic regression indicated that device choice was not associated with higher odds of overall complications	Retrospective, single-site study; small sample size and event rate

ACWF, active closed wash and filtration; PS, pilot study; RCR, retrospective chart review; RCS, retrospective cohort study; RPMA, retrospective propensity-matched analysis.

In 2017, Gabriel et al conducted a retrospective cohort study comparing fat grafting time, volume efficiency, reoperations, and complication rates between ACWF and centrifugation in 194 patients undergoing breast reconstruction (98 in the ACWF arm; 96 in the centrifugation arm).¹¹ Mean volumes of lipoaspirate (506.0 mL vs 126.1 mL) and fat injected (177.3 mL vs 79.2 mL) were significantly higher (P < .0001) in the ACWF vs centrifugation group. Mean time to complete fat grafting was significantly shorter in the ACWF vs centrifugation group (34.6 minutes vs 90.1 minutes, respectively; P < .0001). Proportions of patients with nodule and cyst formation and/or who received reoperations within 6 months were significantly smaller in the ACWF vs centrifugation group. Interestingly, all reoperations were performed to add more soft tissue to the breast. Based on these outcomes and an assumed per minute operating room cost, an average per patient cost savings of US$2870.08 was estimated with ACWF with respect to centrifugation. The authors concluded that, when compared to centrifugation, ACWF allowed for the processing of a larger lipoaspirate volume and decreased operative time, potentially leading to cost savings. It should be noted that the authors utilized visual observation and skin testing to assess the level of graft retention and acknowledged that without quantitative volume measures, it was not possible to precisely compare long-term retention rates.

In 2019, Chiu et al published a retrospective chart review of a single surgeon's experience comparing outcomes between ACWF and decantation in 1158 patients (504 ACWF vs 654 decantation performed on 775 breasts).¹² The study period was 9 years (January 2008-October 2017). Primary outcome measures were postoperative complications or events (nodule/cyst, ultrasound, fat necrosis, biopsy, cancer recurrency) and efficacy (measured by fat graft volume and number of revision procedures) with a mean follow-up time of 10.6 months. The authors reported a significantly higher rate of necrosis in the decantation group vs the ACWF group (3.2% vs 1.0%, P = .01). No significant differences were noted for nodule/cyst, biopsy, or ultrasounds performed. Although 5 of the 6 local cancer recurrences occurred in the decantation group (1.05%), this association was not significant (P = .19). On average, 75.7 [54.3] mL fat was injected into the breast per procedure. There was a lower volume in the decantation group than in the ACWF group (50.6 mL vs 105.0 mL, P < .01), with the decantation group requiring more revisions. More specifically, patients in the decantation group required a higher number of second procedures (39.9% vs 29.6%, P < .01). Although this trend was upheld through 2 years postoperatively, there was no significant difference observed in the percent of patients requiring further revisions (26.6% for decantation vs 22.9% for ACWF, P = .27 after 1-year follow-up; 33.5% for decantation vs 29.2% for ACWF, P = .24 after 2-year follow-up). This study demonstrates that although decantation and ACWF yield similar complication profiles, use of the ACWF enabled the successful harvesting of a larger graft volume, which the authors postulate may have accounted for decreased revision procedures in the ACWF group.

Also in 2019, Hanson et al published a prospective pilot study comparing the rate of graft processing between ACWF and the Puregraft passive filtration system in 40 patients (20 patients per arm) with a mean follow-up time of 3 years.¹³ There was 1 incidence of palpable fat necrosis per group (5%). For all patients, this was the first fat grafting procedure; 20% of patients (n = 4 per group) had additional fat grafting. Overall, the rate of adipose tissue preparation was significantly higher with ACWF compared with passive filtration (19.8 mL/min vs 5.3 mL/min, P ≤ .001). The resulting percentage of graftable fat was comparable between treatment groups (ACWF, 41% vs passive filtration, 42%; P = .83). Revision procedures with additional fat grafting were required by 20% of patients in each group (n = 4 per group). This prospective time-and-motion study suggests that ACWF is significantly more efficient than passive filtration.

That same year, Ruan et al conducted a single-center, retrospective chart review of adverse events in patients who had undergone autologous fat transfer in breast reconstruction from 2012 through 2016.¹⁴ A total of 267 patients were divided into 3 treatment arms (55 ACWF, 44 Telfa rolling, and 168 centrifugation). The use of centrifugation was associated with the greatest incidence of oil cysts (12.5%; P = .034), postoperative adverse events warranting a clinic visit (13.7%; P = .002), reintervention (19.6%; P = .029), and total overall complications (2.3%; P = .001). It is noteworthy that use of ACWF resulted in a significantly lower revision rate when compared with centrifugation (5.45%; P = .011). The authors concluded that although ACWF and Telfa rolling exhibited similar safety profiles, there was a significantly increased rate of complication with the use of centrifugation with respect to either ACWF or Telfa rolling.

Valmadrid et al published a 2020 retrospective chart review of 186 women undergoing 319 fat grafting procedures using either ACWF or Telfa rolling between January 2013 and September 2017.¹⁵ Telfa rolling had a longer operative time for second fat grafting procedures (100 minutes vs 79 minutes; P = .03) than ACWF. With regards to postoperative complications, Telfa rolling results in a significantly higher incidence of palpable masses requiring imaging (26% vs 14.4%; P = .01) as well as fat necrosis (20.6% vs 8.0%; P < .01) than ACWF. Importantly, the authors report no significant difference in fat necrosis excision, number of revision procedures, or cancer recurrence between groups.

Most recently, Assad et al published a 2021 retrospective, propensity-matched analysis in which outcomes following fat grafting in 38 breasts utilizing ACWF were compared to those in 38 matched breasts utilizing the Puregraft passive filtration system.¹⁶ The authors report a comparable mean total volume of graftable fat between groups (ACWF, 130 mL; passive filtration, 159 mL; P = .23). Additionally, this study did not report any significant difference between overall complication rates between the ACWF (18%) and passive filtration (26%) systems. Although patients who had received fat processed through the passive filtration system had a higher incidence of fat necrosis (18%) with respect to ACWF (11%), this difference failed to achieve significance; multiple conditional logistic regression indicated that device choice was not associated with higher odds of overall complications.

DISCUSSION

Given the rapid expansion of autologous fat grafting as a mainstay tool in the plastic surgeon's armamentarium, it is somewhat surprising that work up to this point has failed to establish a clear best-practice guideline. As the number of such procedures continues to increase, there is rapidly growing value in determining means by which surgeons can optimize fat grafting to maximize efficiency, reduce adverse effects, and improve patient satisfaction. Closed wash and filtration systems such as ACWF and passive Puregraft systems were intended to streamline the grafting process and increase the purity of lipoaspirate to improve retention rates and reduce nodule or cyst formation; that is, to increase the ratio of viable fat containing both adipocytes and adipocyte-derived stem cells to extracellular lipid and cellular debris in an effort to promote nourishment and neovascularization and avoid an inflammatory response. Previous work in both animal models and ex vivo lipoaspirate analyses has demonstrated that such filtration systems yield lipoaspirate with significantly reduced erythrocyte and free lipid content compared with more conventional methodologies such as Coleman centrifugation or standard decantation. Importantly, such composition of the fat to be grafted corresponds to significantly greater graft take and retention rates in these studies.^17,18 Additionally, although still somewhat controversial, accumulating literature has suggested that downregulation of local inflammatory mediators can improve graft retention and decrease the incidence of cyst formation. In fact, recent in vivo studies have demonstrated a potential role for anti-inflammatory adjunct pharmacotherapy in nonvascularized fat grafting, namely with melatonin and indomethacin, both of which have been shown to improve cell viability and enhance graft retention.^19,20

It should be noted that there are surgeons who believe the presence of autologous blood and matrix proteins is not inherently undesirable. For example, anecdotal evidence has suggested a role for platelet-rich plasma (PRP) as a useful tool to enhance graft take and neovascularization. Proponents of PRP treatment attribute its success to the effects of key growth factors degranulated by platelets, namely isomers of platelet-derived growth factor and transforming growth factor-β, vascular endothelial growth factor, and epithelial growth factor, as well as extracellular mediators of adhesion such as fibronectin, vitronectin, fibrinogen, osteocalcin, and osteonectin.^21,22 Although the presence of such cytokines should theoretically aid angiogenesis and increase the proliferation of adipocyte-derived stem cells, the clinical data, however, suggest that the benefits are questionable.²³ Yet, despite conflicting reports of its efficacy, the use of PRP as a complementary treatment in cosmetic fat grafting remains somewhat popular. Its use in breast reconstruction, however, remains extremely limited; based upon this review, it appears that reducing cellular debris and extracellular components may be associated with reduced incidences of fat necroses and further revision procedures and should therefore be prioritized whenever possible in breast reconstruction.^12,14,15

There are several distinct features of ACWF that might contribute to its success. First, the device contains an internal filter that immediately contacts the fat after liposuction and removes unwanted tumescent fluid even before washing. The immediate reduction of erythrocytes, leukocytes, platelets, and accompanying cellular debris and free lipids likely reduces the likelihood of inducing an inflammatory response upon grafting, as has been described above. Second, the use of lactated Ringer's as a wash closely approximates physiologic conditions and might serve to optimize cell viability and minimize microcellular disruption. Additionally, the use of a mechanical force during washing via internal paddles allows for the thorough removal of unwanted extracellular matrix proteins.

To the best of our knowledge, this study is the first to systematically review and assess differential outcomes resulting from the use of ACWF with respect to several other commonly employed lipoaspirate processing techniques. We believe that the value of this study lies in its ability to elucidate trends, albeit preliminarily, that support the superiority of ACWF in terms of operative efficiency and, often, perioperative complications. Interestingly, the included studies do not provide overwhelming evidence that the use of ACWF improves graft retention. However, graft retention itself is a complicated and indirect measure of graft method efficacy, as retention is dependent upon a myriad of factors related to the reconstruction technique as a whole, rather than the grafting process, specifically. Rather, several of the above studies have supported ACWF as a uniquely efficient means of fat processing, with reduced operative times, cost per mL of fat transferred, patient exposure to anesthesia, and time during which the lipoaspirate is outside of the body, which might also serve to improve viability.^11,13,15,24 These unique advantages of ACWF have been consistently demonstrated in the included studies and are a more direct measure of variables related to the grafting process; therefore, these findings may be helpful in establishing best-practice guidelines for autologous fat grafting.

Limitations

Our study has several limitations. First, the number of included studies is notably small. Additionally, the retrospective nature of many of the studies introduces inherent and unavoidable heterogeneity, including but not limited to patient demographics, method of reconstruction, quantity of prophylactic vs index cancer cases, volume of fat lipoaspirated and injected, presence or absence of radiation and chemotherapy, and intersurgeon and interinstitutional variability, among others. Such differences, coupled with the relatively small sample sizes of the included studies, did not allow for data synthesis and meta-analysis. Similarly, the retrospective nature of several studies precluded controls with regards to the standardization of active screening for fat necrosis or nodule formation, which limits their generalizability to only those patients whose adverse outcomes were dramatic enough to warrant exam, documentation, imaging, or reintervention. Moreover, many of the studies were nonblinded, with surgeons choosing their personal preferred technique and results subsequently analyzed. Additionally, without formal volume assessment via imaging with standardized follow-up intervals, it is not possible to make a definitive assessment with regards to differences in long-term retention rates between lipoaspirate processing methods. Finally, there was also large heterogeneity with regards to the follow-up periods of each included study, which prevented us from directly comparing longitudinal outcomes between studies.

CONCLUSIONS

This is the first study to systematically aggregate and present data comparing ACWF systems to more traditional methods of autologous fat grafting in breast surgery and reports findings consistent with previous findings indicating reduced cost and operative times, larger harvested lipoaspirate volumes, and reduced adverse events with regards to more traditional fat grafting techniques. The simple design of ACWF systems allows for their use in virtually any hospital or outpatient clinic, and further expansion of their use might allow for increased access to fat grafting for community-based plastic surgeons. None of the studies included in this study is a randomized, controlled, blinded trial; further large-scale, randomized, controlled trials are therefore needed to definitively demonstrate the above trends.

Supplemental Material

This article contains supplemental material located online at www.aestheticsurgeryjournal.com.

Disclosures

The authors declared no potential conflicts of interest with respect to the research, authorship, and publication of this article.

Funding

This work was supported by the National Institutes of Health (Bethesda, MD) #TL1-TR-002386.