The relative importance of the deep and superficial vascular systems for delay of the transverse rectus abdominis musculocutaneous flap as demonstrated in a rat model

Blood Supply to the Integument of the Abdomen of the Rat: A Surgical Perspective

BACKGROUND

Many fundamental questions regarding the blood supply to the integument of the rat remain to be clarified, namely the degree of homology between rat and humans. The aim of this work was to characterize in detail the macro and microvascular blood supply to the integument covering the ventrolateral aspect of the abdominal wall of the rat.

METHODS

Two hundred five Wistar male rats weighing 250-350 g were used. They were submitted to gross anatomical dissection after intravascular colored latex injection (n = 30); conversion in modified Spalteholz cleared specimens (n=10); intravascular injection of a Perspex solution, and then corroded, in order to produce vascular corrosion casts of the vessels in the region (n = 5); histological studies (n = 20); scanning electron microscopy of vascular corrosion casts (n = 10); surgical dissection of the superficial caudal epigastric vessels (n = 100); and to thermographic evaluation (n = 30).

RESULTS

The ventrolateral abdominal wall presented a dominant superficial vascular system, which was composed mainly of branches from the superficial caudal epigastric artery and vein in the caudal half. The cranial half still received significant arterial contributions from the lateral thoracic artery in all cases and from large perforators coming from the intercostal arteries and from the deep cranial epigastric artery.

CONCLUSIONS

These data show that rats and humans present a great deal of homology regarding the blood supply to the ventrolateral aspect of the abdominal integument. However, there are also significant differences that must be taken into consideration when performing and interpreting experimental procedures in rats.

The Technique and Benefits of Angiographic Embolization of Inferior Epigastric Arteries Prior to Pedicled TRAM Flap Breast Reconstruction: Results from a Single Center

PURPOSE

To report a single center's experience with selective arterial embolization of the deep inferior epigastric arteries (DIEA) prior to pedicled TRAM flap breast reconstruction including techniques and outcomes.

MATERIALS AND METHODS

Retrospective chart review was performed for 15 patients who underwent pedicled TRAM flap breast reconstruction after selective embolization of bilateral DIEA. Data were analyzed to display the spectrum of postoperative outcomes following the TRAM flap procedure status post-selective angiographic embolization of the bilateral DIEA to improve vascularity of the TRAM flaps by rendering the tissue partially ischemic to undergo neovascularization. We then compared our results to historical controls of those delayed by ligating the DIEA via traditional surgical means to see if the outcomes are similar. We also compared our results to historical non-delayed TRAM flap reconstruction.

RESULTS

One patient had a small area of partial flap skin necrosis, and no patients had total flap loss. 13.3% of patients had clinically significant TRAM flap fat necrosis. Outcomes of TRAM flaps delayed by selective arterial embolization are comparable to historical controls of those delayed by traditional surgical means and better than non-delayed flaps.

CONCLUSION

Angiographic delayed TRAM flap reconstruction procedure is a reasonable safe alternative to the surgical delayed TRAM flap reconstruction procedure with less morbidity and is better than non-delayed TRAM flap procedures.

Angiographic delay: a viable alternative to surgical delay

BACKGROUND

Selective embolization of the inferior epigastric arteries can serve as a method for transverse rectus abdominis musculocutaneous (TRAM) flap delay. The purpose of this study was to determine whether delay by selective arterial embolization is comparable to traditionally surgically delayed TRAM flaps as reported in the literature, in terms of skin and fat necrosis, and to examine whether certain risk factors play a role in TRAM flap fat necrosis despite angiographic delay.

METHODS

Retrospective chart review was performed for 88 consecutive patients who underwent unilateral TRAM flap breast reconstruction after selective embolization of bilateral inferior epigastric arteries.

RESULTS

Between 1997 and 2009, 88 pedicled TRAM flaps were performed for breast reconstruction in women with a mean age of 49.7 years. No patients had flap skin necrosis or total flap loss. In all, 13.6% patients had TRAM flap fat necrosis. Two patients in the TRAM fat necrosis group (16.7%) had a positive history of smoking, which was a statistically significant risk factor for necrosis (P = 0.048).

CONCLUSIONS

Outcomes of pedicled TRAM flaps delayed by selective arterial embolization are comparable to historical controls of those delayed by traditional surgical means (ligation of artery and vein) and better than nondelayed flaps. Smoking remains a significant risk factor for TRAM flap fat necrosis despite the benefit of delay.

Nicotine on rat TRAM flap

PURPOSE

The transverse rectus abdominis myocutaneous (TRAM) flap is one of the preferential techniques used in breast reconstruction following mastectomy. Nicotine has a detrimental effect on cutaneous flap survival; although there are no experimental studies proving this effect on musculocutaneous flaps. The aim of this study is to verify the effect of nicotine on the rat TRAM flap.

METHODS

30 Wistar EPM-1 rats were randomly distributed in two groups: control and experimental. The animals of the control group received saline solution injected subcutaneously, in a volume of 0.2 ml, twice a day, during 28 days in the preoperative period. The animals of the experimental group were treated with nicotine, injected subcutaneously, in a dose of 2 mg/kg twice a day, during 28 days in the preoperative period. All the animals were submitted to the caudally based, right unipedicled TRAM flap. 48 hours after the procedure, a study of the viable area of the flap was done through photographic documentation. Statistical analysis was performed with nonparametric Mann-Whitney's test.

RESULTS

The experimental group had significantly greater area of necrosis when compared with the control group (p<0.001).

CONCLUSION

Nicotine increased the area of necrosis of the TRAM flap, in rats.

Comparison of two different vascular delay methods in a rat cranial epigastric perforator flap model

The effectiveness of vascular delay in transverse rectus abdominis muscle flaps has been demonstrated in many studies. In deep inferior epigastric perforator flaps, however, the effectiveness of ligation of deep versus superficial epigastric vessels in producing delay is unclear. Using a rat model, we compared ligation of deep and superficial vessels with each other and with a (nondelayed) control group (n = 10). One vascular delay group (n = 10) had ligation of the contralateral cranial epigastric vessels (homolog to the human deep inferior epigastric vessels); the other (n = 10) had ligation of contralateral superficial inferior epigastric vessels. One week later, cranial epigastric perforator flap elevation was performed. Both vascular techniques were effective in producing delay, and there was no statistically significant difference between the 2 groups. Ligation of superficial inferior epigastric vessels, deep inferior epigastric vessels, or both, at least 1 week prior to the deep inferior epigastric perforator flap elevation may increase the usable skin paddle area in humans.

Effect of Hydrostatic Dilation on Flap Viability of the Transverse Rectus Abdominis Musculocutaneous Flap Model in Rats

BACKGROUND

The technique of intraoperative vessel hydrostatic dilation is sometimes used to facilitate microvascular anastomosis and prevent vasospasm. Currently, delay procedures remain a reliable method of maximizing flap survival. The authors aimed to increase rat transverse rectus abdominis musculocutaneous (TRAM) flap viability by imitating the physical effect of a surgical delay procedure with hydrostatic dilation.

METHODS

Forty-five male Sprague-Dawley rats were randomly assigned to one of three TRAM flap groups (15 rats in each group): the control group, the delay group, and the hydrostatic dilation group. The surgical delay procedure was performed by division of right-sided cranial epigastric vessels and contralateral superficial inferior epigastric vessels. While elevating the flap, hydrostatic dilation was performed to the cranial epigastric artery and vein with a mean pressure of 250 mm Hg. The groups were compared by means of microangiography and survival ratio of TRAM flaps and mean artery lumen area, mean vein lumen area, and mean artery wall area of the flap pedicle 48 hours after elevation.

RESULTS

There was a significant difference between the control and hydrostatic dilation groups in favor of surface area viability and angiographic assessment (p < 0.01). Surgical delay has traditionally been accepted as the most reliable method of enhancing flap viability. No significant difference was revealed between the surgical delay and hydrostatic dilation groups (p > 0.05). In the hydrostatic dilation group, compared with the control group, an increase in vein diameter, a thinning of the artery wall, and an increase in lumen diameter were observed.

CONCLUSIONS

The physical effect of blood flow is achieved acutely with hydrostatic dilation. This simple, dependable, one-stage hydrostatic dilation procedure can be used in clinical applications.

Vascular Delay Revisited

The technique of vascular delay has been used by plastic surgeons for nearly 500 years and has proven useful for reliably transferring tissue and allowing for a greater volume of tissue to be reliably harvested. Delay procedures are an essential plastic surgical tool for a variety of aesthetic and reconstructive procedures. Despite the widespread use of vascular delay procedures, the mechanism by which this phenomenon occurs remains unclear. A number of groups have exhaustively examined microvascular changes that occur during vascular delay. Theories have been proposed ranging from the dilation of choke vessels to changes in metabolism and new blood vessel formation. Inherent in these theories is the concept that ischemia is able to act as the primary stimulus for vascular changes. The purpose of this review is to revisit the theories proposed to underlie the delay phenomenon in light of recent advances in vascular biology. In particular, the participation of bone marrow-derived endothelial progenitor cells in the delay phenomenon is explored. Greater understanding of the role these cells play in new blood vessel formation will be of considerable clinical benefit to high-risk patients in future applications of delay procedures.

Cutaneous Viability in a Rat Pedicled TRAM Flap Model

BACKGROUND

The transverse rectus abdominis musculocutaneous (TRAM) flap is widely used in breast reconstruction. However, morbidity with its pedicled form has resulted in a high incidence of complications. The authors conducted a study of the pedicled TRAM flap procedure in 35 female Wistar rats based on the left deep inferior epigastric vessel, which was nondominant.

METHODS

In all the rats, the flap was divided into four areas: area 1, the skin on the left rectus abdominis muscle pedicle; area 2, the skin contralateral to the midline, opposite of the left rectus abdominis muscle pedicle; and areas 3 and 4, the skin lateral to areas 1 and 2, respectively. The occurrence, percentage, and distribution of necrosis on the TRAM flap surface were determined.

RESULTS

Necrosis was observed at four statistically distinct and significant levels, distributed in the four different areas as follows: area 1, 9 percent; area 2, 37 percent; area 3, 74 percent; and area 4, 100 percent (p < 0.001). The median proportion of necrosed flap surface was 15 percent (range, 2 to 42 percent).

CONCLUSIONS

The determination of necrosis allowed us to identify three distinct levels of necrosis: area 4 with the highest scores, area 3 with intermediate scores, and areas 1 and 2 with the lowest scores (p < 0.001). Areas 1 and 2 of the TRAM flap surface had less incidence of necrosis, contrary to the lateral areas 3 and 4, in which cutaneous necrosis was found to be more significant.

Is it Possible to Increase the Survival of the Transverse Rectus Abdominis Musculocutaneous Flap following previous Abdominoplasty Using a Delay Procedure? An Experimental Study in the Rat

BACKGROUND

Although, because of the disruption of perforators, abdominoplasty has been suggested as a major contraindication for patients undergoing autologous breast reconstruction with the transverse rectus abdominis musculocutaneous (TRAM) flap, many researchers encourage the search for a means of improving the survival of the skin paddle of the flap in patients who have undergone previous abdominoplasty. In this study, the effect of the surgical delay phenomenon on the survival of the TRAM flap following abdominoplasty was investigated.

METHODS

Thirty adult Wistar rats were used: the control group (n = 6), the short-term group (n = 12), and the long-term group (n = 12). In the control group, a standard superior pedicled TRAM flap was harvested with no abdominoplasty procedure, and the flap was replaced in situ. In all other animals, an abdominoplasty procedure was performed initially. The short-term and long-term groups were divided into two subgroups: the abdominoplasty plus TRAM-only subgroup (n = 6), and the abdominoplasty plus delay plus TRAM subgroup (n = 6). In the short-term group, the experiment was performed 1 month after abdominoplasty, whereas the same surgical procedures were applied 6 months after abdominoplasty in the long-term group.

RESULTS

The short-term abdominoplasty plus TRAM subgroup, the long-term abdominoplasty plus TRAM subgroup, the short-term abdominoplasty plus delay plus TRAM subgroup, the long-term abdominoplasty plus delay plus TRAM subgroup, and the conventional superior pedicled TRAM flap group showed 2.33 +/- 3.01 percent, 13.33 +/- 8.76 percent, 24.17 +/- 13.57 percent, 60 +/- 8.94 percent, and 70.83 +/- 9.70 percent survival rates for the skin paddle, respectively.

CONCLUSION

The data demonstrate that surgical delay after long-term abdominoplasty can enhance the survival rate of the skin paddle of the TRAM flap.