While electronic cigarettes, or “vaping”, do not contain tobacco constituents, they still contain variable amounts of their primary constituent nicotine. Nicotine is known to cause vasoconstriction and inhibition of endothelial-dependent vasodilatation, and so skin flaps with a fragile blood supply may still be placed at risk in patients substituting electronic cigarettes for traditional cigarettes.62
Previous breast conserving surgery (wide local excision and radiotherapy) may increase the incidence of MSFN, presumably mediated in part by the effects of previous chest wall radiotherapy.63
Advancing age alone does not appear to be a risk factor for surgical complications following microvascular breast reconstruction (including MSFN) according to a retrospective series from Los Angeles.64 Moreover, it is specifically an increased number of medical comorbidities and a poorer American Society of Anesthesiologists (ASA) grade that are predictive of surgical complications. Therefore, the overall health status of the patient seems to be more predictive of surgical complications than age alone.
Diabetes mellitus is generally considered a risk factor for vascular complications, owing to a range of vascular abnormalities that can develop, including altered blood viscosity, abnormalities in intimal repair and abnormalities in endothelial cell, red cell and platelet function. A retrospective review from the MD Anderson Cancer Center reported 893 free transverse rectus abdominis myocutaneous (TRAM) flap reconstructions and found no difference in flap complications in diabetic patients, provided euglycemia was maintained.65 Specifically, there was no significant difference in terms of the MSFN rate in subgroups with insulin-dependent diabetes mellitus (IDDM; 9.8%) and non-insulin-dependent diabetes mellitus (NIDDM; 5.3%) and the nondiabetic group (7.7%). However, only patients with euglycemia were included in this series, which may limit the broader application of these interesting findings to every diabetic patient being considered for mastectomy.
A large retrospective review of 718 patients undergoing mastectomy and immediate breast reconstruction in British Columbia looked for factors associated with MSFN.42 The overall rate of MSFN was 12.9% in this series with a number of patient and surgical risk factors identified as predictors of MSFN. Body mass index (BMI) >30, smoking and preoperative radiation were independent predictors of MSFN. Surgical factors included a longer duration of surgery and a Wise pattern mastectomy incision. There was no difference in the MSFN rate between immediate autologous versus implant-based reconstruction methods in this series.
Mlodinow et al37 looked for factors predicting MSFN following immediate tissue expander breast reconstruction in their institution. In all, 1566 mastectomies were reviewed, with an MSFN rate of 8.6%. Regression analysis revealed smoking status, increased age, tumescent mastectomy technique and high intraoperative expander fill volumes (>66.67%) to be associated with an increased risk of MSFN.
A retrospective review from Harvard of all immediate microsurgical breast reconstructions at a single center investigated risk factors predictive of MSFN.66 The MSFN rate in this large series of 746 reconstructions was 13.4%. Univariate analysis revealed a significantly higher incidence of MSFN in patients with a higher mastectomy weight (p<0.001), higher autologous flap weight (p<0.001), higher BMI (p=0.002) and diabetes mellitus (p=0.021). Multivariate analysis showed significant associations between MSFN and both increasing mastectomy weight (odds ratio [OR] =1.348 per quartile increase, p=0.009) and diabetes (OR =2.356, p=0.011). Possible explanations for the increased MSFN rate with larger mastectomy weights could be the larger skin flap surface area with the larger breast volume or perhaps increased skin tension on the flaps following reconstruction. These predictors may be particularly helpful in preoperative counseling and procedure selection.
The majority of the literature investigating risk factors for MSFN is limited to retrospective series, with inconsistencies in the definition of MSFN and patient selection. However, Matsen et al10 have recently published a prospective study to address these limitations. This prospective study measured MSFN rates (scoring it mild, moderate or severe) and measured pre-, peri- and postoperative variables to look for associated factors, with 8 weeks of follow-up. A total of 606 consecutive mastectomies (SSM =84% and NSM =16%) with immediate reconstruction (implant or expander based =94% and autologous =6%) were performed. A total of 85 (14%) cases experienced some form of MSFN. In all, 46 (8%) MSFN were mild, 6 (1%) were moderate and 31 (5%) were severe. The median size of the necrotic tissue, reported as the largest single dimension, was 3 cm (range: 0–24 cm), 9 cm (range: 1.5–15 cm) and 8 cm (range: 0.5–26 cm), respectively. A total of 25 of the severe necrosis cases were not healed by 8 weeks following surgery. Nine breasts underwent debridement in theater, and four implants were lost. Univariate analysis for any MSFN showed smoking, history of breast augmentation, NSM and time from incision to specimen removal to be significant. In multivariate analysis, nipple sparing, time from incision to specimen removal, sharp dissection and previous breast reduction were significant for any necrosis. NSM was associated with higher rates of MSFN for every severity. In those with moderate or severe MSFN, univariate analysis showed BMI, diabetes, NSM, specimen size and expander size to be significant. Multivariate analysis showed NSM and specimen size to be significant. Interestingly, the majority of MSFN was mild in this prospective study (the degree of necrosis being difficult to measure and quantify in retrospective studies) and so did not delay adjuvant therapy. Moderate necrosis and severe necrosis were less common, and return to theater and implant loss rates were <2% in these groups. This may be due to their policy of full muscle coverage for expander-based reconstructions.
Surgical technique and skin flap viability
Surgical factors increasing the risk of MSFN include higher mastectomy weight;43,48 incision type,6,47,67–69 including the Wise pattern mastectomy incision;48 decreased mastectomy skin flap thickness;70 volume of tissue expander fill45 and perhaps the mastectomy technique itself, such as the use of tumescence.37,44,45,47
Lee et al11 performed a review of the rate of mastectomy flap complications for NSM and reconstruction at their institution. They found higher rates of mastectomy flap complications, including mastectomy flap necrosis and nipple loss, in implant-based rather than autologous techniques. This initially seems somewhat surprising, as one might have expected the autologous group to have more risk factors for MSFN, such as a longer operative time, and perhaps, this technique is selected more often in women with larger, more ptotic breasts, who may also tend to have a higher BMI. However, the patient- and procedure-related characteristics were reportedly similar between the groups in this review. Whatever may be the true explanation for the differences observed in mastectomy flap complications between the groups, this is an interesting finding in light of the trend toward increased numbers of implant-based reconstructions now being performed.
The determinants of optimum mastectomy flap thickness have previously been reviewed.70 A balance must be obtained during mastectomy between achieving clear resection margins, while not making the flaps so thin that they risk flap necrosis. This is achieved through careful adherence to the oncoplastic plane between the subcutaneous fat and the breast parenchyma. Subcutaneous tissue thickness can be extremely variable and does not correlate with BMI, patient age or the thickness in the other breast.71 The oncoplastic plane may be difficult to identify in some patients and a distinct superficial fascial layer may be absent in up to 44% of patients.72 However, once identified, close adherence to it is crucial to achieving both an oncologically sound SSM while preserving the blood supply to the skin. Along with meticulous surgical technique, a good knowledge of the blood supply to the skin and nipple of the breast may help to avoid MSFN in SSM and NSM.73
Neoadjuvant therapy may help downsize tumors that are close to the skin, or adjuvant chest wall radiotherapy may be utilized for close resection margins, which might help avoid the need for overly thin skin flaps. MSFN rates close to 17% have been reported with flaps 4–5 mm thick,74 whereas others have achieved rates of <5% with thicker 10 mm flaps,75,76 suggesting that thicker flaps may reduce rates of MSFN. However, these reports are only case series and not randomized controlled trial (RCT) evidence, and the measurement methods for thickness are not standardized and are therefore difficult to reproduce.
There are of course various operator technical factors that may reduce the chances of MSFN, such as careful tissue handling (especially while raising the mastectomy flaps), avoiding tension during closure (especially important with Wise pattern incisions) and respecting the oncoplastic plane of dissection for mastectomy flaps, so they are not fashioned overly thin.
While preservation of more breast skin during mastectomy (as in SSM or NSM) may improve the esthetic results of breast reconstruction, MSFN rates remain high with this technique.77 NSM is a significant predictor of MSFN, as well as nipple areolar necrosis, and has been associated with higher complication rates in several studies.6,10,53,78
Higher rates of MSFN have also been reported with the use of Wise pattern skin-reducing mastectomy techniques and immediate reconstruction for large breast volumes.79 In this retrospective series, mastectomy weight was significantly associated with skin complications requiring surgery (age-adjusted OR per 100 g=1.6, CI 1.1–2.3, p=0.02). This might be expected to some extent, as Wise pattern reduction techniques are inherently at risk of “T junction” necrosis, and larger breasted individuals requiring skin reduction may carry other contributory patient risk factors, such as an elevated BMI. As always, minimizing skin tension is crucial in avoiding MSFN in Wise pattern techniques.