Fat Necrosis in Autologous Abdomen Based Breast.3

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BREAST

Fat Necrosis in Autologous Abdomen-BasedBreast Reconstruction: A Systematic Review

Ibrahim Khansa, M.D.Adeyiza O. Momoh, M.D.

Priti P. Patel, M.D.John T. Nguyen, M.D.Michael J. Miller, M.D.Bernard T. Lee, M.D.,

M.B.A.

Columbus, Ohio; Ann Arbor, Mich.;

and Boston, Mass.

Background: Fat necrosis is a common and potentially exasperating complica-tion of autologous breast reconstruction. The authors performed a systematicreview of the English literature on autologous breast reconstruction to deter-mine significant patient and surgical factors that are predictors of postoperativefat necrosis.Methods: A PubMed search using the terms fat necrosis and breast recon-struction was conducted. Articles were screened using predetermined inclusionand exclusion criteria. Data collected included patient characteristics, recon-structive techniques used, and the specific postoperative morbidity of interest.Patient cohorts were pooled, and the incidence of fat necrosis was calculated inthe presence and absence of each risk factor. Chi-square analysis was applied,and p 0.05 was considered statistically significant.

Results: Of 172 articles found, 70 met the inclusion criteria. The mean rate offat necrosis was 11.3 percent. Deep inferior epigastric artery perforator flaps hadthe highest rate of fat necrosis (14.4 percent), followed by pedicled transverserectus abdominis musculocutaneous (12.3 percent), superficial inferior epigas-tric artery (8.1 percent), and free transverse rectus abdominis musculocutane-ous flaps (6.9 percent). Significant predictors of fat necrosis included obesity(p 0.035), prereconstruction irradiation (p 0.022), postreconstructionirradiation (p 0.001), active smoking (p 0.001), and abdominal scars (p0.05). Protective factors included supercharging (p0.001) and bilateral re-construction (p 0.01).Conclusions: Although there is little agreement in the literature regarding riskfactors for fat necrosis, the authors were able to demonstrate several significantpredictors by systematically analyzing 70 articles. Improved knowledge of the risk

factors for fat necrosis can help surgeons provide improved preoperative coun-seling and take measures to minimize the risk of this complication. (Plast.Reconstr. Surg. 131: 443, 2013.)

Fat necrosis is a common complication in au-tologous breast reconstruction. It presents asa nodule or mass that can be palpated after

reconstruction.1 It is caused by ischemia of thesubcutaneous adipose tissue, leading to adiposecell necrosis, scarring, and sometimes calcifica-tion. Although fat necrosis is not inherently dan-gerous, it can mimic breast cancer recurrence

both clinically and radiographically. Clinically, itmay feel benign when it consists of a smoothround nodule, but it can be an irregular, fixedmass with skin retraction.1 On mammography, itcan appear as an irregular density, spiculatedmass, or microcalcifications.2When it mimics can-cer recurrence, fat necrosis can lead to patientanxiety and additional biopsies.3 Fat necrosis canalso negatively affect cosmetic outcome by causingdistortion of the reconstructed breast.

There is no uniform definition of fat necrosisin the literature. The most commonly used defi-

From the Department of Plastic Surgery, The Ohio StateUniversity Wexner Medical Center; the Department of Sur-gery, Division of Plastic and Reconstructive Surgery, Uni-versity of Michigan Medical Center; and the Department of Surgery, Division of Plastic and Reconstructive Surgery, BethIsrael Deaconess Medical Center, Harvard Medical School.Received for publication July 18, 2012; accepted September12, 2012.Copyright 2013 by the American Society of Plastic Surgeons

DOI: 10.1097/PRS.0b013e31827c6dc2

Disclosure: The authors have no financial inter-ests in this research project or in any of the tech-niques or equipment used in this study. The authorshave no conflicts of interest to disclose.

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nition is that of a palpable subcutaneous firmnessnot due to cancer.4 Other authors define fat ne-crosis based on size, with some using firmnessmeasuring 1 cm in diameter3 and others placingthe size threshold at 2 cm.5A less commonly useddefinition of fat necrosis is radiologic, and definesit as an ultrasound-detectable lesion greater than5 mm.6

Reported rates of fat necrosis vary widely, from3.04 to 37.9 percent.7 Although some risk factorsfor fat necrosis are consistent in the literature,others such as obesity, irradiation, and abdominalscars are the subject of debate.

Two studies have systematically examined fatnecrosis in autologous breast reconstruction. Manet al. conducted a meta-analysis of 36 studies,8 andSailon et al. conducted a systematic review of eightstudies.9 Both reviews included only free trans-

verse rectus abdominis musculocutaneous(TRAM) and deep inferior epigastric artery per-forator (DIEP) flaps, and did not specifically ex-amine risk factors for fat necrosis. The only riskfactor analyzed was flap type, with both studiesconcluding that the rate of fat necrosis was higherin DIEP flaps than in free TRAM flaps.

In this systematic review, our objectives were(1) to calculate the overall rate of fat necrosis inabdomen-based autologous breast reconstruction,including pedicled TRAM, free TRAM, DIEP, andsuperficial inferior epigastric artery (SIEA) flaps;

and (2) to identify potential predictors of fat ne-crosis, including flap type, obesity, irradiation,smoking, abdominal scars, recipient vessel selec-tion, surgical delay, supercharging, and lateralityof reconstruction.

MATERIALS AND METHODS

Literature Search

A PubMed database search was conducted inMarch of 2011 using the terms fat necrosis andbreast reconstruction as key words to identify

studies in the English language published between1982 and 2011. The articles were examined, andreferences were screened for further relevant ar-ticles. The search yielded a total of 172 citations.Inclusion criteria were English-language publica-tion, human subjects, autologous breast recon-struction, extractable outcomes on fat necrosis,and full-text availability. Exclusion criteria weresystematic reviews and meta-analyses, case reportsand case series with fewer than 15 patients, non-consecutive cases, reconstructions that includedexpanders or implants, and reconstructions that

included fat grafting. One hundred two studies

were excluded, yielding 70 articles suitable foranalysis (Fig. 1).

Data ExtractionFor each article, we extracted the data listed in

Table 1. Not all data were available in every article.The fat necrosis risk factors analyzed were flaptype, obesity, irradiation (prereconstruction orpostreconstruction), smoking (former or cur-rent), abdominal scars, recipient vessel, surgicaldelay, supercharging, and laterality.

The flap types included were pedicled TRAM,free TRAM, DIEP, and SIEA flaps. We excludedless commonly used flaps (e.g., superior glutealartery perforator flaps) because of a scarcity ofdata. Latissimus dorsi flaps were excluded, as fewarticles measured fat necrosis rates.

Data Analysis and StatisticsWhen two or more articles from the same in-

stitution had overlapping data collection dates,they were assumed to be from the same cohort.When computing the overall rate of fat necrosis,the article with the largest number of patients wasincluded, and redundant articles were excluded.However, some of the redundant articles analyzeddistinct predictors of fat necrosis, and those wereincluded in the analysis of individual fat necrosispredictors.

All articles that contained extractable data re-lated to potential risk factors were used. The datawere pooled, and the number of flaps with fatnecrosis was computed in the presence and ab-sence of that risk factor. A chi-square test wasapplied, with values ofp 0.05 signifying statis-tical significance.

RESULTSOverall Rate of Fat Necrosis

Forty-one articles3,5,6,1047 describeddistinct pa-tient cohorts and were included in computation of

the overall rate of fat necrosis. Those representeda total of 10,764 flaps in 8970 patients; 1212 flapshad fat necrosis, for an overall rate of 11.3 percent.

Flap TypeThirty-three articles3,6,7,2049 representing 7233

flaps in 6394 patients analyzed the rate of fat ne-crosis by flap type (Table 2). The overall rate of fatnecrosis was 11.1 percent.

DIEP flaps had a significantly higher rate of fatnecrosis (14.4 percent) than free TRAM (6.9 per-cent, p 0.001), pedicled TRAM (12.3 percent,

p

0.04), and SIEA flaps (8.1 percent, p

0.02).

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Free TRAM flaps had the lowest rate of fat necrosis(6.9 percent), which was significant in comparisonwith pedicled TRAM (p 0.001) and DIEP flaps(p 0.001).

ObesityFive articles4547,50,51 representing 1741 flaps in

1592 patients analyzed the rate of fat necrosis de-pending on body mass index (Table 3). The rateof fat necrosis in obese patients (body mass index

30) was 12.6 percent, significantly higher thannormal weight (body mass index25, 7.8 percent;p 0.009) and nonobese patients (body massindex 30, 8.7 percent; p 0.035). Fat necrosiswas also nonsignificantly higher in obese patientsthan in overweight patients (body mass index25and 30, 12.6 percent versus 8.7 percent; nonsig-nificant). Fat necrosis was more common in obesepatients than in normal weight patients receivinga pedicled TRAM flap (15.4 percent versus 9 per-cent,p 0.02) but not in free TRAM (7.8 percentversus 6.1 percent) or DIEP flaps (9.9 percent

versus 11.4 percent).

Radiation TherapyTwelve articles3,6,18,19,23,24,45,5256 representing 5059

flaps in 4587 patients analyzed the effect of radia-tion therapy on fat necrosis (Table 4). The rate offat necrosis among patients with no history of ir-radiation was 8.7 percent, significantly lower thanin patients who had prereconstruction (11 per-cent, p 0.022) and postreconstruction irradia-tion (22.3 percent,p 0.001). In pedicled TRAMflaps, those with prereconstruction irradiationhad a higher rate of fat necrosis than patients with

no history of irradiation (13.4 percent versus 9.3percent,p 0.028).

Smoking

Seven articles3,6,22,44,45,51,57 representing 2347flaps in 2187 patients analyzed the rate of fat ne-crosis in relation to smoking (Table 5). The rateof fat necrosis among current smokers was 15.6percent, which was significantly higher comparedwith patients who had never smoked (7.1 percent,p 0.001), former smokers (8.7 percent, p

0.03), and non current smokers (9.7 percent,p

Fig. 1. Study attrition diagram.

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0.001). The difference between current smokersand noncurrent smokers was significant in pedi-cled TRAM flaps (18.7 percent versus 9.5 percent,p 0.004), but not in free TRAM (11.1 percentversus 7.7 percent,p 0.22) or DIEP flaps (14.5percent versus12.8 percent,p 0.68). Fat necrosisin former smokers was no higher than in neversmokers (8.7 percent versus 7.1 percent,p 0.47).

Abdominal ScarsThree articles22,45,58 representing 874 flaps in

824 patients analyzed the effect of abdominal scars

on fat necrosis (Table 6). Fat necrosis among pa-

tients with abdominal scars was significantlyhigher than in those without abdominal scars(14.9 percent versus 10.4 percent,p 0.05). Thisdifference was also present in pedicled TRAMflaps (16.8 percent versus 8.5 percent,p 0.005)but not any other flap type.

One of the three articles58 specified what typeof abdominal scar each patient had and found thatpatients with Pfannenstiel, laparoscopic, midline,and right lower quadrant scars did not have anincreased rate of fat necrosis, whereas patientswith paramedian (50 percent versus 15 percent,p 0.17) and subcostal scars (20 percent versus 15percent,p 0.75) had a nonsignificant increasein fat necrosis.

Recipient Vessels

Five articles3,56,5961 representing 2064 flaps in1621 patients analyzed the effect of recipient ves-sel choice on fat necrosis (Table 6). The rate of fatnecrosis was no different when internal mam-mary vessels were used compared with thora-codorsal vessels (6.2 percent versus 7.6 percent,p 0.22). Among free TRAM flaps, the rate offat necrosis was significantly lower when internalmammary vessels were used compared with tho-racodorsal vessels (24.2 percent versus 14 per-cent, p 0.026).

Delay of Pedicled TRAM FlapsTwo articles62,63 representing 250 flaps in 181

patients analyzed the effect of surgical delay on fatnecrosis in pedicled TRAM flap reconstruction(Table 7). The rate of fat necrosis tended to belower when surgical delay was performed, but thedifference was not statistically significant (5.7 per-cent versus 11.8 percent, p 0.097).

Supercharge of Pedicled TRAM FlapsThree articles3133 representing 104 flaps in

104 patients analyzed the effect of microsurgical

supercharging of pedicled TRAM flaps on fat ne-crosis (Table 7). Supercharged flaps were found tohave a significantly lower rate of fat necrosis thannonsupercharged pedicled TRAM flaps (12.3 per-cent versus 41 percent, p 0.001).

Unilateral versus Bilateral ReconstructionNine articles6,20,21,43,51,6467 representing 1838

flaps in 1209 patients analyzed the effect of later-ality on fat necrosis (Table 6). Bilateral recon-structions had a significantly lower rate of fat ne-crosis than unilateral reconstructions (10.7

percent versus 14.8 percent,p

0.01). The same

Table 1. Data Extracted from the Articles

Study characteristicsInstitutionDates of data collection

Patients and flapsNo. of patientsNo. of flapsFlap type

pTRAMfTRAMDIEPSIEA

Patient characteristicsBMI

Normal weight (25)Overweight (25 and 30)Nonobese (30)*Obese (30)

IrradiationNo irradiationPrereconstruction irradiationPostreconstruction irradiation

Smoking

Never smokedFormer smokerNoncurrent smokerCurrent smoker

Abdominal scarsNo scar(s)Scar(s)

Other surgical detailsRecipient vessel used

Internal mammaryThoracodorsal

Surgical delay of pTRAM flappTRAM without delaypTRAM with delay

Supercharge of TRAM flapTRAM without supercharge

TRAM with superchargeLateralityUnilateral reconstructionBilateral reconstruction

Fat necrosisDefinitionOverall ratePredictors

pTRAM,pedicled TRAM; fTRAM,free TRAM; BMI, body massindex.*Obtained by combining the patients in the normal weight andoverweight categories.Obtained by combining the patientsin the never smoker and formersmoker categories.


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was true among free TRAM flaps (1 percent versus11.1 percent, p 0.003). There was also a notstatistically significant tendency toward lower ratesof fat necrosis in bilateral DIEP (12.6 percent ver-sus 16.7 percent,p 0.076) and pedicled TRAMflaps (10.3 percent versus 12.6 percent,p 0.48)

compared with unilateral reconstructions.

DISCUSSIONThe studies analyzed cite a fat necrosis rate in

autologous breast reconstruction ranging from3.04 to 37.9 percent.7 The overall rate of fat ne-crosis was 11.3 percent across all types of breastreconstruction in aggregate. In articles that dif-

ferentiated by type of reconstruction, the overall

Table 2. Fat Necrosis Rates in the Systematic Review of the Literature and Crude Pooled Analysis

Flap Type No. of Flaps Fat Necrosis (%) Range (%) p

pTRAM 2208 272 (12.3) 6.8376033 fTRAM 2423 168 (6.9) 2.14028.632 0.001 (vs. pTRAM)DIEP 2429 350 (14.4) 3.34242.920 0.04 (vs. pTRAM); 0.001 (vs. fTRAM)SIEA 173 14 (8.1) 5.73813.511 NS (vs. pTRAM); NS (vs. fTRAM); 0.02 (vs. DIEP)

Total 7233 804 (11.1) 2.140

6033

pTRAM, pedicled TRAM; fTRAM, free TRAM.

Table 3. Obesity as a Predictor of Fat Necrosis

No. of Flaps Fat Necrosis (%) p

Normal weight (BMI 25) 965 75 (7.8) pTRAM 488 44 (9) fTRAM 442 27 (6.1) DIEP 35 4 (11.4)

Overweight (BMI 25, 30) 242 21 (8.7) pTRAM fTRAM 212 19 (9) DIEP 30 2 (6.7)

Nonobese (BMI 30) 1431* 125 (8.7)*

pTRAM 488 44 (9) fTRAM 654 46 (7) DIEP 289 35 (12.1)

Obese (BMI 30) 310 39 (12.6) 0.009 (vs. normal weight); NS (vs. overweight);0.035 (vs. nonobese)

pTRAM 175 27 (15.4) 0.02 (vs. normal weight); 0.02 (vs. nonobese)fTRAM 64 5 (7.8) NS (vs. normal weight, overweight and nonobese)DIEP 71 7 (9.9) NS (vs. normal weight, overweight and nonobese)

BMI, body mass index; pTRAM, pedicled TRAM; fTRAM, free TRAM; NS, nonsignificant.*The numbers for nonobese patients may be larger than the sum of the numbers for normal weight and overweight patients, because somearticles report results as obese versus nonobese rather than obese versus overweight versus normal weight. No extractable data on obesity

were available for SIEA flaps.

Table 4. Radiation Therapy as a Predictor of Fat Necrosis

No. of Flaps Fat Necrosis (%) pPrereconstruction XRT 1051* 116 (11)*

pTRAM 343 46 (13.4) fTRAM 170 22 (12.9) DIEP 77 12 (15.6)

Postreconstruction XRT 188* 42 (22.3)* pTRAM 19 3 (15.8) fTRAM 32 14 (43.8) DIEP 55 14 (25.5)

No XRT 3820* 334 (8.7)* 0.022 (vs. prereconstruction XRT);0.001 (vs. postreconstruction XRT)

pTRAM 1169 109 (9.3) 0.028 (vs. prereconstruction XRT);NS (vs. postreconstruction XRT)

fTRAM DIEP 233 39 (16.7) NS (vs. prereconstruction and

postreconstruction XRT)

XRT, radiation therapy; pTRAM, pedicled TRAM; fTRAM, free TRAM; NS, nonsignificant.*The numbers for each category may be larger than the sum of the subcategories by flap type, because some articles that were included donot break their results down by flap type. No extractable data on irradiation were available for free TRAM and SIEA flaps.


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rate of fat necrosis was 11.1 percent. The mostimportant predictor of fat necrosis was flap type,with free TRAM flaps having the lowest rate of fatnecrosis (6.9 percent), followed by SIEA (8.1 per-cent), pedicled TRAM (12.3 percent), and DIEP

flaps (14.4 percent).

The lower rate of fat necrosis in free TRAMcompared with DIEP flaps has been demonstratedin the past. In their meta-analysis, Man et al. foundthat DIEP flaps were twice as likely as free TRAMflaps to have fat necrosis.8 Sailon et al.9 and Scheeret al.20 had similar findings. The free TRAM flapuses the dominant pedicle to the lower abdominal

tissue, the deep inferior epigastric vessels, takingadvantage of all perforators that course throughthe rectus muscle to the overlying adipose tissueand skin.68 In contrast, the DIEP flap selects onlythe largest perforators, potentially leading to areaswith suboptimal perfusion. A recent advance inDIEP flap reconstruction has been preoperativeperforator mapping using computed tomo-graphic angiography or magnetic resonance an-giography, which allows identification of a domi-nant perforator preoperatively and likely shortensoperative times.69 More studies are needed to show

whether this translates into lower rates of fat ne-

Table 5. Smoking as a Predictor of Fat Necrosis

No. of Flaps Fat Necrosis (%) p

Never smoked 680 48 (7.1) pTRAM 162 13 (8) fTRAM 518 35 (6.8) DIEP

Former smoker 173 15 (8.7) pTRAM 21 2 (9.5) fTRAM 152 13 (8.6) DIEP

Noncurrent smoker* 2026* 197 (9.7)* pTRAM 665 63 (9.5) fTRAM 757 58 (7.7) DIEP 399 51 (12.8)

Current smoker 321 50 (15.6) 0.001 (vs. never smoked); 0.03 (vs. former smoker);0.001 (vs. noncurrent smoker)

pTRAM 107 20 (18.7) 0.009 (vs. never smoked); NS (vs. former smoker);0.004 (vs. noncurrent smoker)

fTRAM 108 12 (11.1) NS (vs. never smoked, former smoker andnoncurrent smoker)

DIEP 83 12 (14.5) NS (vs. noncurrent smoker)

pTRAM, pedicled TRAM; fTRAM, free TRAM.

*The numbers for noncurrent smokers may be larger than the sum of the numbers for never smoked and former smokers, because somearticlesreport results as current smoker vs. noncurrent smoker rather thancurrentsmoker vs. former smoker vs. never smoker. Extractabledata on smoking were not available for SIEA flaps.

Table 6. Recipient Vessel, Laterality, and AbdominalScars as Predictors of Fat Necrosis in MicrosurgicalBreast Reconstruction*

No. ofFlaps

FatNecrosis (%) p

Recipient vesselInternal mammary 776 48 (6.2)

fTRAM 143 20 (14) Thoracodorsal 1288 98 (7.6) NS

fTRAM 153 37 (24.2) 0.026LateralityUnilateral reconstruction 580 86 (14.8)

pTRAM 127 16 (12.6) fTRAM 99 11 (11.1) DIEP 354 59 (16.7)

Bilateral reconstruction 1258 135 (10.7) 0.01pTRAM 526 54 (10.3) NSfTRAM 96 1 (1) 0.003DIEP 636 80 (12.6) NS

Abdominal scarsNo abdominal scars 566 59 (10.4)

pTRAM 413 35 (8.5) fTRAM 39 7 (17.9) DIEP 114 17 (14.9)

Abdominal scars 308 46 (14.9) 0.05

pTRAM 143 24 (16.8) 0.005fTRAM 61 7 (11.5) NSDIEP 104 15 (14.4) NS

pTRAM, pedicled TRAM; fTRAM, free TRAM; NS, nonsignificant.*No extractable data on recipient vessel selection were available forDIEP and SIEA flaps. No extractable data on laterality or abdominalscars were available for SIEA flaps.

Table 7. Surgical Delay and Supercharging asPredictors of Fat Necrosis in Pedicled TRAM FlapReconstruction

No. ofFlaps

FatNecrosis (%) p

Surgical delayDelay 106 6 (5.7)No delay 144 17 (11.8) NS

Supercharging

pTRAM 39 16 (41)Supercharged pTRAM 65 8 (12.3) 0.001

NS, not significant; pTRAM, pedicled TRAM.


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crosis. Another potential explanation for differ-ences between free TRAM and DIEP flaps may bethat articles analyzing DIEP flaps were publishedby surgeons early in the learning curve.35

Obesity is considered a risk factor for fatnecrosis in autologous breast reconstruction,with some studies demonstrating a significantrelationship,3,20,22,24,41,45,67,70,71 and othersnot.6,11,15,46,47,50 In our systematic analysis, obesepatients had a significantly higher rate of fat ne-crosis than nonobese patients. This relationshipwas true across all reconstruction types combinedand for pedicled TRAM flaps alone. This is likelyrelated to the larger size flap required in obesepatients. In the past, zone IV has been included toincrease the size of the reconstruction; however,current practices avoid use of zone IV, as perfusionis less reliable. Using ex vivo angiograms, Ohjimi

et al. demonstrated much lower perfusion in zoneIV.72 Vega et al. lowered rates of fat necrosis byroutinely excising zone IV in all patients.4 Krolllowered fat necrosis rates in DIEP flaps from 62.5percent to 17.4 percent by limiting the use of theDIEP flap to 70 percent of the flap, supporting thediscarding of zone IV.73

The literature on prereconstruction irradiationand fat necrosis is inconclusive. In our analysis, pa-tients with a history of prereconstruction irradiationwere at increased risk of fat necrosis compared withno irradiation. One study demonstrated increased

rates of fatnecrosis after prereconstruction radiationtherapy with pedicled TRAM flaps.70 Many studies,however, have not demonstrated an increased rateof fat necrosis.3,6,23,65 Fosnot et al. found that prere-construction irradiation made the dissection andmicrovascular anastomosis more difficult.18

In our analysis, patients with postreconstruc-tion irradiation had more than twice the rate of fatnecrosis compared with no irradiation. Irradiationis known to affect the microcirculation, and irra-diating a flap can compromise the blood supply tothe adipose tissue, leading to fat necrosis. Multiple

studies have found a correlation between postre-construction irradiation and fat necrosis.29,52,53,74

Some studies investigating the relationship be-tween smoking and fat necrosis have demon-strated a relationship,3,4,29,44,75whereas others havenot.6,11,45,57 In a review of 1195 breast reconstruc-tions, Mehrara et al. found that smokers were at noincreased risk of fat necrosis.15 In our analysis, activesmokers had a significantlyhigher rate of fatnecrosiscompared with past smokers and never smokers.Former smokers were at no increased risk of fatnecrosis compared with never smokers, demonstrat-

ing that patients who quit smoking can safely un-

dergo autologous breast reconstruction. Smoking isknown to adversely affect both microvasculature andmacrovasculature by several mechanisms, includingnicotine-mediated vasospasm.

The literature is ambivalent on abdominalscars as a risk factor for fat necrosis. Some studieshave demonstrated a relationship between scarsand fat necrosis,15,45 whereas others have not.22,58

In our analysis, patients with abdominal scars hadsignificantly higher rates of fat necrosis. Parrett etal. found that women with a Pfannenstiel scar wereat no increased risk of fat necrosis, provided thatthe scar was included at the border and notundermined.58 Midline scars were not a risk factorfor fat necrosis, provided that the contralateralpart of the flap was discarded in unilateral recon-structions. The highest rates of fat necrosis werefound in paramedian and subcostal scars, as these

have the highest potential to interrupt perforatorsto the abdominal wall. Interestingly, Mahajan et al.found that patients with a Pfannenstiel scar hadlarger perforators and concluded that the scareffectively led to surgical delay by ligation of thesuperficial inferior epigastric vessels.76 Xu et al.have advocated the use of bipedicle flaps for uni-lateral breast reconstruction in patients with ab-dominal scars.14

On review of the literature, free flaps anasto-mosed to the internal mammary and thoracodor-sal vessels had the same rate of fat necrosis. Tem-

ple et al.56 and Saint-Cyr et al.60 reached a similarconclusion. The choice of recipient vessel is oftenmade on a case-by-case basis. The thoracodorsalvessels are exposed and readily available in caseswhere axillary dissection is performed. However,with the rise of sentinel lymph node biopsy, theneed for axillary dissection has decreased, and useof the internal mammary vessels has become morecommon.59

Surgical delay has been used to improve vas-cularity of axial flaps. In pedicled TRAM flaps,ligation of the superficial and deep inferior epi-

gastric vessels is performed 2 to 3 weeks before theplanned reconstruction. On review of studies an-alyzing pedicled TRAM flaps in high-risk patients,we found a nonsignificant decrease in fat necrosisin patients who had undergone surgical delay.Codner et al. found a nonsignificant trend towardlower rates of fat necrosis when surgical delay wasperformed (3.3 percent versus 12 percent, p 0.14).62

Supercharging is another method of improv-ing blood flow in pedicled TRAM flaps. It consistsof anastomosing the deep inferior epigastric ves-

sels to recipient vessels in the chest in addition to


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the primary vascular supply of the superior epi-gastric pedicle. We found that supercharged pedi-cled TRAM flaps have a significantly lower rate offat necrosis. Most studies examining the effect ofsupercharging found that it does improve out-comes, namely, fat necrosis. Lee et al. demon-strated a significant increase in the venous oxygenconcentration in the flap, and lower rates of fatnecrosis.33 Because most fat necrosis tends to oc-cur in zone IV of the flap, supercharging a uni-pedicled TRAM flap through the contralateral in-ferior epigastric vessels may provide improvedblood flow into zone IV, as shown by Yamamotoet al.32 Hamdi et al. achieved a low rate of fatnecrosis by performing bipedicled perforatorfree flaps with two microvascular anastomosesfor unilateral reconstruction.77 This is an inno-

vative form of supercharging specific to perfo-rator flaps, and further studies are warranted tomeasure its effectiveness.

We found that bilateral reconstructions hadsignificantly lower rates of fat necrosis than uni-lateral reconstructions. Kroll demonstrated a sim-ilar result in DIEP flaps.73 Paige et al. found anonsignificant tendency toward lower rates of fatnecrosis in bilateral pedicled TRAM flaps.67 Theeffect of laterality relates to the size and reliabilityof the zones that are harvested. As bilateral flaps,by definition, cannot use any tissue across the mid-

line, these flaps are smaller and the blood supplyis more reliable.

Although our systematic review has severalstrengths, including a large number of patientsand flaps, and analysis of multiple risk factors forfat necrosis across four different types of autolo-gous breast reconstruction, it does have some lim-itations. The majority of studies in our review areretrospective and observational, with confoundersand biases beyond our control. Ideally, a meta-analysis would be performed from randomizedcontrol studies, but these were not found in ourreview and would be difficult to perform. Oursystematic review can be considered a form ofpooled analysis or meta-analysis from publisheddata. Finally, fat necrosis does not have a consis-tent definition across studies, as discussed in theIntroduction. This affects our ability to truly com-pare studies. As a result of the heterogeneity of thedefinition of fat necrosis, and different levels ofexperience among surgeons, the results shown inthis article may not reflect each surgeons indi-vidual experience, but are designed to identify risk

factors for fat necrosis in general.

CONCLUSIONSThere is significant variability in the literature

regarding risk factors for fat necrosis in autolo-gous breast reconstruction. By providing a com-prehensive review of risk factors for fat necrosis,

this study can help plastic surgeons adequatelycounsel patients preoperatively and take measuresto minimize the incidence of this complication.

Bernard T. Lee, M.D., M.B.A.Department of Surgery

Division of Plastic and Reconstructive SurgeryBeth Israel Deaconess Medical Center

Harvard Medical School110 Francis Street, Suite 5A

Boston, Mass. [email protected]

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