Some surgeons inject saline into the subcutaneous plane (often with local anesthetic and/or adrenaline), to perhaps “hydrodissect” the breast off the skin flap if performed under pressure or at least to make the fascial plane thicker and easier to adhere to, while also purportedly minimizing blood loss and the use of diathermy. It is argued that the liquid finds the plane of least resistance between the subcutaneous fat and the fat of the glandular breast tissue below. Anecdotally, this approach seems quite popular and effective across different units. However, the literature reports contrasting experiences with tumescence. Two retrospective case series urge caution, reporting this as a risk factor for the development of postoperative skin flap necrosis, while two more recent studies (one prospective) did not find tumescence to be a significant factor for MSFN. Chun et al44 reported tumescent mastectomy technique as a significant risk factor for MSFN after mastectomy and immediate reconstruction in a retrospective series of 380 consecutive cases (OR =3.98, p<0.001). Other risk factors in this series included previous irradiation, age and BMI. Mlodinow et al37 also reported tumescent mastectomy technique to be associated with MSFN in their large series of 1566 immediate tissue expander reconstructions. However, these retrospective series do not prove causality. However two very recent publications indicate that tumescence is not a significant risk factor for MSFN.10,80 These contrasting findings suggest that other factors may be involved.
It has also been suggested that the use of diathermy rather than scalpel dissection may increase the MSFN rate, presumably via coagulation injury to the adjacent subdermal plexus. However, in a retrospective study of 151 SSMs, there was no significant difference between diathermy and scalpel dissection.48
Carlson et al81 have looked at predisposing factors for nipple ischemia after NSM in a prospective series of 71 NSMs. In all, 40 mastectomies were for cancer and 31 were risk reducing (n=45 patients). The majority were expander or implant reconstructions, with only three flap-based reconstructions. Partial nipple necrosis occurred in 28.2% of cases, and the majority healed uneventfully, with only one case requiring secondary nipple reconstruction. Higher rates of nipple necrosis occurred with periareolar incisions (OR =9.69, CI: 1.57–59.77, p=0.014) or excision of the ducts from the undersurface of the nipple (OR =10.54, CI: 1.88–59.04, p=0.007).
A number of methods and devices have been used to assess tissue perfusion intraoperatively in order to try and avoid mastectomy flap necrosis, but none have achieved universal acceptance. Intraoperative devices are often not readily available in all hospitals and can be expensive or time consuming when compared to traditional methods of clinical evaluation of skin flap perfusion. Therefore, in resource-limited environments, their use may be best reserved for operations at a higher risk of MSFN. The various different methods of evaluation have been reviewed and helpfully summarized in a tabulated form, along with supporting references, by Gurtner et al.82 The ideal system would allow accurate identification of the supplying vessels (and their corresponding perfusion zones), accurate assessment of tissue perfusion and delineation of vulnerable tissue at risk of necrosing. For breast reconstruction, particularly implant based, the earlier the MSFN is detected, the better it is. Ideally, areas of nonviable skin or areas of dubious viability would be detected intraoperatively, permitting excision during the mastectomy, before necrosis ensues. For implant-based reconstructions, it may also provide an opportunity to consider choosing a smaller implant or perhaps choosing an expander in such cases, according to the surgeon’s judgment and preference.
If ischemic areas are not identified intraoperatively, early postoperative detection may still allow excision and resuturing and may save an underlying implant from potential infection and extrusion.83
Clinical evaluation of flap perfusion has been the traditional and most widely used method to assess the adequacy of the remaining blood supply, once the underlying breast has been removed.84Traditional methods of skin flap viability assessment include assessment of skin color, capillary refill, skin temperature and dermal bleeding. However, clinical evaluation alone has its limitations,85,86leading to the development of several technologies that can be used intraoperatively, including handheld Doppler,87 laser Doppler flowmetry,88,89 fluorescein angiography56,90,91 and indocyanine green angiography.92
Doppler ultrasound is somewhat limited by being inherently operator dependent, while laser Doppler flowmetry may underestimate flap survival and the equipment is large. Fluorescein dye testing has been used to evaluate skin flaps in plastic surgery for many years and may play a role in the evaluation of equivocal mastectomy flap viability, allowing excision of areas with poor perfusion unlikely to survive. The fluorescein dye is injected intravenously, and a wood’s lamp is used to evaluate flap fluorescence. Losken et al56 studied this in the periareolar skin of 50 SSM flaps. Flaps with areas of nonfluorescence >4 cm2 tended not to survive, while areas <4 cm2 typically would survive, except in the irradiated breast. However, fluorescein techniques are limited by the long half-life of the contrast medium, preventing reevaluation during the intraoperative period and risking false positives.
Indocyanine green contrast agent has shown some encouraging results in the intraoperative assessment of mastectomy flap perfusion and prediction of subsequent flap necrosis. A large case series from Emory University has looked specifically at indocyanine green angiography in predicting MSFN in a prospective cohort of 118 patients undergoing SSM and breast reconstruction.77 In all, 14 patients experienced postoperative skin flap necrosis. Skin with ≤25% perfusion was not viable 90% of the time, while areas with ≥45% perfusion survived 98% of the time. This may be a useful adjunct to the prediction and avoidance of MSFN. Intraoperative indocyanine laser perfusion assessment tools, such as the SPY system (LifeCell Corp., Branchburg, NJ, USA), have been used to identify mastectomy skin flaps at risk of subsequent ischemia and necrosis.93 Indocyanine green was used to evaluate mastectomy flap perfusion in 39 patients undergoing mastectomy and immediate breast reconstruction with a prosthesis, and this was compared to 52 patients in the pre-SPY era. The postoperative complication rate in this retrospective study was reported as twofold higher in the pre-SPY group, but this did not reach statistical significance (p=0.06). However, the number of repeat visits to theater was significantly higher in the pre-SPY era. Five of the seven patients with complications in the post-SPY group were identified by SPY as having poor flap perfusion, but none were identified with clinical judgment alone. The main limitations of this study were its small size and retrospective nonrandomized design, but it still suggests that the SPY system may be able to contribute perioperatively to the identification of tissue at risk of ischemia and necrosis. Indocyanine green has also been used to describe specific NAC perfusion patterns and may be a helpful adjunct in evaluating higher risk perfusion patterns in NSM to try and avoid ischemic complications.94
Indocyanine green angiography has the advantage of a short half-life and good safety profile. It is also cleared rapidly from tissues, facilitating repeat evaluations of tissue perfusion during the same procedure. It may have advantages over clinical evaluation or fluorescein techniques in predicting MSFN.43 However, although this method may aid in predicting necrosis, it only appears cost-effective if used selectively for high-risk cases.95 A prospective trial has compared two intraoperative vascular imaging techniques with clinical assessment to assess mastectomy skin flap perfusion to predict areas of necrosis.43 Laser-assisted indocyanine green dye angiography, fluorescein dye angiography and clinical assessment were all compared to evaluate the skin flaps of 51 tissue expander–implant reconstructions (n=32 patients). In all, 21 cases (41.2%) underwent “all-inclusive necrosis”, of which 6 cases were full thickness; 5 (9.8%) of these cases required intervention. Unsurprisingly, statistically significant risk factors for necrosis included smoking, obesity and a breast weight of >1 kg. However, laser-assisted indocyanine green dye angiography and fluorescein dye angiography overpredicted areas of necrosis by 72% and 88%, respectively (p=0.002). The laser-assisted indocyanine green dye angiography was a better predictor of MSFN and more specific than fluorescein dye or clinical assessment, but would overpredict MSFN without quantitative analysis.
The intraoperative oxygen tension of mastectomy skin flaps can be measured, as reported in a pilot study by Rao et al.96 In this small series of 10 patients undergoing simple mastectomy or SSM, only one patient developed flap necrosis and the authors identified a reduction in skin flap oxygen saturation and flap length as predictors of this. This noninvasive technique requires further evaluation before any recommendations can be made regarding its use in MSFN prediction.
Unfortunately, many patient risk factors are not modifiable in the time scale between diagnosis and surgery. Where patients are assessed as having a high risk of MSFN, performing a simple mastectomy with a delayed reconstruction may permit not only the timely administration of any adjuvant therapy but also more time for modification of any adjustable risk factors prior to reconstruction.
Very large tumors may benefit from downsizing with neoadjuvant therapies prior to surgery in selected suitable patients, which may avoid the need to fashion ever-thinner mastectomy skin flaps to achieve tumor clearance and thus reduce the chances of MSFN. Consideration ought to be given within the multidisciplinary team (MDT) as to which patients might benefit from neoadjuvant chemotherapy97 or neoadjuvant endocrine therapy.98,99
Khavanin et al45 performed a retrospective review of 966 consecutive patients undergoing SSM or NSM and expander-based reconstruction at a single institution in Chicago between 2004 and 2012. They were looking for risk factors for MSFN requiring surgical excision and found that necrosis rates were higher in the high fill cohort than in the low fill cohort (10.4% vs 7.1%, p=0.027). However, multivariate logistic regression did not identify high expander fill volumes as an independent risk factor for MSFN. Interestingly, four risk factors were identified that acted synergistically with high fill volume to increase the risk of MSFN, namely, tumescence (synergy index [SI] =25.3), followed by hypertension (SI =2.39), obesity (SI =2.28) and age >50 (SI =1.17). Acellular dermal matrix (ADM) use was not associated with MSFN in this study. The authors suggest that the epinephrine in the tumescent solution may reduce dermal blood flow sufficient to put the flap at risk of necrosis, while the small vessel disease associated with the other three risk factors may also decrease mastectomy skin flap perfusion, which then go on to manifest as full-thickness necrosis in the setting of high intraoperative fill volumes. This study has significant limitations of course, not least the retrospective nature, being from a single center and only addressing those variables documented in the records, when other factors may be at play. However, despite these limitations, using smaller intraoperative inflation volumes for expanders in higher risk cases may reduce the incidence of significant MSFN.