The role of the venous system in the abdominal flap of the rat

The abdominal flap of the rat has become a popular model with investigators. Recently, researchers have been reporting survival of skin flaps with varying blood supplies. We studied the viability of skin flaps on a consistent model with varied blood supply. An 8 x 9 cm flap was raised in 40 male Sprague-Dawley rats. The viability of the flaps could be studied in 25 rats. The survival of a pedicled flap based on the left inferior epigastric artery and vein was compared with that of a pedicled flap with enhanced venous drainage. The survival of a venous flap based on the paired inferior epigastric veins and the paired long thoracic veins was compared with that of an arterialized venous flap. A composite graft was used as a control for all groups. A qualitatively improved survival was found in the pedicled venous-enhanced group (66 percent) compared with the pedicled flaps (56 percent) (p > 0.05). An improved survival was found in the arterialized venous flap (57 percent) compared with the venous flap (40 percent) (p < 0.05). All flaps had improved survival compared with the composite graft (0.6 percent) (p < 0.05).     

Recipient bed vascularity and the survival of ischaemic flaps

The purpose of this study was to identify the length of the ischaemic period required to induce the 'no-reflow' phenomenon in a rat epigastric flap on an avascular recipient site. The vascularity of the recipient bed may affect flap survival in the early postischaemic stage after flap transfer. Initially, we designed epigastric flaps in 300-350 g Sprague-Dawley rats and separated the rats into four groups of 5 rats each (total 20 rats). In groups 1, 2, 3, the flaps were made ischaemic for 1 hour, 6 hours and 10 hours, respectively, by temporarily clipping the epigastric artery and vein. In group 4, the epigastric artery and vein were divided to create permanent ischaemia. In groups 1, 2 and 3, ischaemia was ended by removing the clips. After the ischaemic flaps were reperfused, their viability was studied by measuring the flap survival rate at postoperative day 7. Flap survival was studied by direct observations, laser Doppler flowmeter measurement of flap blood flow, histopathology, and carbon particle perfusion of the flap vasculature. Ischaemic flaps of groups 1 and 2 recovered almost completely after reperfusion due to the short period of ischaema. In a second series of experiments, in order to evaluate the contribution to flap survival of the recipient vascularised bed, another four groups of epigastric flaps (of 5 animals each, using the same time periods as above) were raised and a piece of Biobrane was interposed between the flap and the recipient bed before the flap wound was closed, to eliminate all nutrient supply from the recipient bed. THe results showed that the combined effect of the reperfused flap vasculature plus the metabolic contribution of the recipient bed significantly (P < 0.01) increased the extent of flap survival of the 6- and 10-hour ischaemic flaps as well as the divided pedicle flaps, which were never reperfused. An absolute 'no-reflow' rat model flap for further flap salvage studies was also developed.     

How to fashion a TRAM flap in the presence of a lower midline laparotomy scar. An experimental study in rats

The transverse rectus abdominis musculocutaneous (TRAM) flap cannot be used successfully in a patient with a pre-existing midline abdominal scar because the area distal to the scar undergoes circulatory failure leading to necrosis. To investigate the usefulness of various procedures to improve the circulation in such a flap, we studied the percentage area survival of experimental abdominal island flaps in five groups of rats with pre-existing midline scar treated by different procedures which depended on the source of blood used to supply the flap (control, arterial, venous, arteriovenous shunt, and delayed, n = 5 in each group). All flaps in the arterial group survived completely. The mean (SEM) percentages of the flaps that survived in the control (17(2)%) and venous (17(1)%) groups were significantly lower than those in the delayed (31(2)%) and arteriovenous shunt (67(6)%) groups (all, p < 0.01). These results indicate that preservation of arterial inflow by arterial anastomosis or arteriovenous shunt on the opposite side is important if the flap is to survive across the midline scar. Preservation of the vein in the opposite flap is not essential, because venous outflow is supposed to drain through the midline scar into the epigastric vein of the pedicle without any signs of congestion.     

Two-stage arterialized flow-through venous flap transfer for third-degree burn defects on the dorsum of the hand

A modified, two-stage arteriovenous flow-through venous flap was designed to repair skin defects due to third-degree burns on the dorsum of the hand in four patients. Two weeks after plasty of an arteriovenous (A-V) shunt between the greater saphenous vein and dorsalis pedis artery, the arterialized flow-through venous flap was transferred using the greater saphenous vein as the pedicle. The size of the flaps utilized ranged from 7 x 13 cm to 9 x 13 cm. In three patients the entire flap survived without complication. In one patient whose flap had only one drainage vein, the flap survived with superficial necrosis of about 10 percent of the flap at the borders. During the 2 weeks after A-V shunt creation, the authors believe that microcirculation around the arterialized vein probably develops, contributing to better irrigation and thereby to flap survival. Using this two-stage procedure, it might be feasible to obtain larger grafts and to attain a higher flap survival rate.     

Comparison of two different delay procedures in a rat skin flap model

The overall objective of this study was to investigate how a strategic delay procedure could generate large flaps survival. On the basis of the vascular anatomy in 10 rats, a long three-territory skin flap spanning the length of the rat dorsum was designed. This flap was distally based on the deep circumflex iliac artery. The adjacent territories consisted of a large perforator of the posterior intercostal artery and the lateral thoracic artery in sequence. Two different vascular delay procedures were used and compared in nine animals. One dorsal midline incision was used to perform the two different delay procedures. The limited delay technique was performed by ligating a large cutaneous perforator of the posterior intercostal artery on one side of the rat. The extensive delay procedure was completed by ligating the cutaneous perforators of the posterior intercostal artery and the lateral thoracic artery on the other side of the rat. After a delay period of 10 days, the paired flaps were elevated, respectively, and sutured back in place. Seven days later, the area of viable skin flap was measured by the paper template technique. The animals were then killed, and the dorsal skin arteriograms were obtained by injecting a lead oxide mixture. Vascular changes of the paired flaps were assessed. In the extensive delay group, 100-percent survival was seen in four animals and distal partial necrosis was observed in five animals. The average survival area in the extensive delay group was 85.5 +/- 14.2 percent (mean +/- SD), whereas the flaps in limited delay group showed 100-percent survival in all animals (p < 0.05). In flaps that survived completely, the choke vessels among three vascular territories anastomosed throughout the flap. In the partially necrotic flaps, some choke and true anastomoses existed between the deep circumflex iliac and the posterior intercostal artery territories and the flap necrosis occurred in the third territory. This study suggests that the limited delay technique (ligation of one artery in the territory adjacent to the base of the flap) was the more effective delay procedure in the rat dorsal skin flap model.     

MRI of the intracerebral lesions at 0.5 Tesla: comparison of fast spin-echo and conventional spin-echo sequences

The purpose of this study was to identify the angiosome of the medial saphenous artery and vein and to evaluate the use of this cutaneous angiosome as a free skin flap in the dog. In phase 1 of this study, selective angiography of the medial saphenous artery performed in six canine cadavers showed that the skin covering the entire medial femorotibial area, the distal half of the caudal head of the sartorius muscle, and the gracilis muscle were perfused by the medial saphenous artery. In phase 2, a medial saphenous fasciocutaneous island flap was raised and sutured back to the skin edges of the donor wound in three dogs. One hundred percent survival of all of the flaps occurred. In phase 3, a medial saphenous fasciocutaneous microvascular free flap was transferred to a wound that was created over the dorsal metacarpal (n = 3) or metatarsal region (n = 3). The mean length +/- SD of the medial saphenous vascular pedicle was 80 +/- 13 mm (n = 5); the mean diameter +/- SD of the medial saphenous artery was 2.8 +/- 0.2 mm (n = 5) and the mean diameter +/- SD of the medial saphenous vein was 4.2 +/- 0.2 mm (n = 5). One hundred percent of all flaps survived (n = 6). Selective angiography or the distal cranial tibial artery (metatarsal wounds, n = 3) and the median artery (metacarpal wound, n = 3) was performed 3 weeks after surgery. All of the vascular anastomoses were patent and neovascularization of the wound beds was present. This free flap was found to be acceptable for cosmetic reconstruction of wounds located on the distal extremity.     

Superiority of the microvascularly augmented flap: analysis of 50 transverse rectus abdominis myocutaneous flaps for breast reconstruction

Our experience with 50 transverse rectus abdominis myocutaneous (TRAM) flap transfers was evaluated as to the types of TRAM flaps, indications for breast reconstruction with a TRAM flap, and complications. The TRAM flap was transferred as a free flap in 7 patients, a unipedicled flap in 14 patients, and a microvascularly augmented flap in 29 patients. Microvascular augmentation was performed through the contralateral inferior epigastric vascular system to the superiorly pedicled muscle in 10 patients who had undergone radical mastectomy and the ipsilateral inferior epigastric vascular system in 19 patients who had undergone modified radical mastectomy. In this series, the incidence of flap-site complications, including total flap loss, partial flap loss, and fat necrosis, was lowest in the microvascularly augmented flap group. Particularly, incidence of partial flap loss in the microvascularly augmented flap group was significantly lower than in the unipedicled flap group (p < 0.01). These outcomes demonstrated the superiority of the microvascularly augmented TRAM flap for breast reconstruction.     

Rat strain differences in flap tolerance to ischemia

The rat epigastric island flap model is commonly used to explore ischemia-related phenomena. We sought to evaluate strain differences in tolerance to ischemia using two commonly used rat strains: Sprague-Dawley and Lewis. Epigastric flaps (3 x 6 cm) based on the superficial epigastric artery and vein were raised bilaterally in each rat (2 flaps/rat). Ischemia was induced for 10,12,14, or 16 hours by placing temporary occlusion clamps on each vessel of the vascular pedicle. Surviving flap areas were assessed planimetrically after 7 days. The average area of surviving flap tissue was greater in the Lewis rats for all ischemia times; this achieved significance for 12 hours and 14 hours of ischemia (P < 0.005). These findings indicate that comparisons among studies on rat flap ischemia must take into account the particular strain used. Furthermore, these findings suggest an inherent capacity of Lewis rat tissue to withstand ischemia better than tissue of the Sprague-Dawley rat strain.     

Internal mammary artery and vein supercharge in TRAM flap breast reconstruction

To improve the blood supply of the pedicled flap we have performed an additional microvascular augmentation to this type of breast reconstruction procedure since 1991. The ipsilateral deep inferior epigastric pedicle is anastomosed to the internal mammary artery and vein (IMAV supercharge). In 19 of 20 patients this technique proved to be feasible. For the venous anastomoses the 3M microvascular anastomosis system facilitated the procedure. In one patient the venous anastomosis failed due to the small calibre of two internal mammary veins. In a majority of the cases rapid improvement of flap perfusion could be observed as the direct result of the supercharging. The IMAV supercharged flap is quite comparable with the free flap as regards to the operative procedure. Disadvantages are a slightly more extensive dissection and less freedom in positioning the flap due to the presence of the superior muscular pedicle. The main advantage is that the supercharge procedure minimises the risk of total flap loss. Further technical improvement may be obtained by the use of a contralateral vascular pedicle dissected with muscle-sparing techniques.     

Experimental prevention of free flap thrombosis. I: A model of free flap failure

A model to evaluate the efficacy of therapies aimed at reducing the failure rate of microvascular free flaps was developed in the rat, inspired by earlier work on the rabbit ear by Ozbek et al. (Ann Plast Surg 32:474-477, 1994). It consisted in raising an epigastric groin flap on the femoral pedicle, while cutting the femoral artery, twisting it around the femoral vein, and resuturing it. Immediate patency was always seen, but 19 of 20 such anastomoses presented with thrombosis after 24 hours (15 venous and 4 mixed thromboses). Ten similar anastomoses performed without twisting did not result in thrombosis (P = 0.000000366). This model appears to be adequate for simulating free flap failure.     

Superior gluteal artery perforator free flap for breast reconstruction

The purpose of this paper is to present a new method of breast reconstruction utilizing skin and fat from the buttock without muscle sacrifice. Cadaver dissections were done to study the musculocutaneous perforators of the superior gluteal artery and vein. Eleven breasts were reconstructed successfully with skin/fat flaps based on the superior gluteal artery with its proximal perforators. Long flap vascular pedicles allow the internal mammary or thoracodorsal vessels to be used as recipient vessels. This new technique has several advantages over the previously described gluteus maximus myocutaneous flaps, including long vascular pedicle and no muscle sacrifice.     

Stimulation of angiogenesis to improve the viability of prefabricated flaps

The cutaneous area in a prefabricated myocutaneous flap surviving after elevation is dependent on the rate and amount of vascular ingrowth that occurs from the underlying muscle. Two modalities, basic fibroblast growth factor and hyperbaric oxygen, were used separately and together in a prefabricated myocutaneous flap animal model to improve flap survival. The semimembranous muscle, based on the saphenous vessels of 40 female Wistar rats weighing between 250 and 325 grams, was tunneled under the ipsilateral abdominal skin and sutured in place. A 3 x 5-cm silicone sheet was placed beneath the muscle flap, and the ipsilateral epigastric vessels were ligated. Four groups of 10 animals each received one of the following treatment regimes: a 1-ml normal saline infusion into the saphenous arterial pedicle, a 1-ml infusion of basic fibroblast growth factor (1.0 microg/gm of muscle), a 1-ml normal saline infusion and 14 hyperbaric oxygen treatments, or a 1-ml basic fibroblast growth factor infusion and 14 hyperbaric oxygen treatments. After 1 week, the muscle, still based on the saphenous vessels, was elevated with a 3 x 5-cm abdominal skin paddle. The flap was sutured back in place, leaving the silicone sheet intact. The surviving area of each flap was measured 1 week later after it had demarcated into viable and necrotic regions. Laser Doppler skin perfusion measurements were taken before and after flap elevation and before animal euthanasia. Sixteen flaps, 4 in each group, were examined histologically for vascularity by means of hematoxylin and eosin staining. There was a statistically significant increase in flap survival area when either basic fibroblast growth factor or hyperbaric oxygen was used alone. Further improvement was noted with combination therapy. Histology confirmed improved vascularity in the basic fibroblast growth factor and hyperbaric oxygen-treated flaps. This study shows a significant and reliable increase in the area of prefabricated myocutaneous flap survival using either basic fibroblast growth factor or hyperbaric oxygen. There is a further complementary effect when these two modalities are combined, leading to near complete flap survival through improved vascularity.     

Total knee arthroplasty covered with pedicle peroneal flap

Three cases of total knee arthroplasty (TKA) covered with pedicle peroneal flaps are reported. One peroneal flap was performed after TKA to correct post-TKA skin necrosis. Two peroneal flaps were performed before TKA to replace previous traumatic scar formed around the knee. All three TKAs were successful after the procedure. The thickness, elasticity, appearance, and durability of the peroneal flaps were more suitable for the skin around the knee than the gastrocnemius muscle flap or the local fasciocutaneous flap. As the peroneal flap was elevated as a pedicle flap, freedom of transfer was good, microanastomosis was not necessary, and no donor sites were needed from the contralateral limb. Scar tissue around the knee can be effectively replaced by the pedicle peroneal flap before TKA.     

Secondary ischemic tolerance improved by administration of L-NAME in rat flaps

Nitric oxide (NO) under basal conditions is an important regulator of vascular tone. Under ischemic conditions, however, NO can combine with superoxide anion to produce the damaging hydroxyl free radical. The current project observes the effect of inhibiting NO production (L-Nitro-amino-methyl-arginine, L-NAME) on flaps rendered ischemic by secondary (2 degrees) venous obstruction. Eighty rats had 3 x 6 cm skin flaps based on the epigastric vessels. Primary (1 degree) ischemia was produced by arteriovenous occlusion for 2 hours; (2 degrees) venous ischemia was induced by clamping the vein, alone for either 3 or 5 hours. Thirty minutes prior to 2 degrees ischemia, rats received either L-NAME (30 mg/kg) or saline buffer. Flap survival was assessed 7 days later and Chi-square analysis was used. At 3 hours of ischemia, treatment improved survival from 55% to 85% (P < 0.05). Treatment also improved survival at 5 hours of ischemia from 5% to 35% (P < 0.04). Although under resting conditions, NO is a potent vasodilator, during 2 degrees venous obstruction it may contribute to flap necrosis.     

Effect of parenteral pentoxifylline and topical nitroglycerin on skin flap survival

Flap necrosis is still a significant complication in all types of flap surgery. The effect of parenteral pentoxifylline and nitroglycerin in improving survival of ischemic skin flaps was tested in Wistar rats. In the control group (n = 15) the mean viable length of the flaps was calculated to be 6.160 +/- 0.936, and nonnecrotic flap area was found to be 1859.1 +/- 269.3. In the group treated with pentoxifylline and nitroglycerin (n = 15), the mean viable length of the flap was calculated to be 6.907 +/- 0.617, and the mean nonnecrotic flap area was found to be 2078.5 +/- 172.7. In this study results showed that the use of parenteral pentoxifylline and topical nitroglycerin is effective on skin flap survival.     

The distally based forearm island flap in hand reconstruction

The distally based forearm island flap is vascularized by the perforators of the distal radial artery. The skin flap is along the axis of the radial artery, and the pivot point of its subcutaneous pedicle is about 2 to 4 cm above the radial styloid process. We have treated 12 patients with 12 flaps for soft-tissue defects of the hand. Of these recipient sites, seven were in dorsal hands, two were in thumbs, two were in forearms, and one was in the palmar area. The donor-tissue variants included eight skin flaps, two adipofascial flaps, and two sensate flaps. The sizes of the flaps ranged from 6 x 4 cm to 14 x 6 cm. The donor site wound could be closed primarily in five patients. Two sensate flaps, innervated by the lateral antebrachial cutaneous nerve, could provide sensation for thumb reconstruction. The advantage of this flap is its constant and reliable blood supply without sacrifice of the main radial artery. The elevation of the flap is simple and rapid. There is the potential that this flap can be used as an innervated flap, and there is no need of microsurgical technique.     

The influence of skin flap ischemia on serum nitric oxide concentrations

Nitric oxide (NO), identified as a mediator of endothelium-dependent relaxation of vascular smooth muscle, is known to cause a number of inflammatory diseases, especially ischemia-reperfusion injury. This experimental study, using a rabbit epigastric island flap, was designed to investigate whether skin flap ischemia followed by reperfusion influences serum NO concentrations. In addition, the author investigated the effects of NO synthase inhibitors and heparin on skin flap ischemia. Serum NO concentrations after 15, 30, 45, and 60 minutes of ischemia followed by reperfusion were significantly increased compared with non-ischemic controls and elevated flaps. On the other hand, serum NO concentrations were suppressed in nitro-amino-methyl-L-arginine- and aminoguanidine-treated animals. Furthermore, administration of heparin increased serum NO concentrations in controls and animals with elevated flaps, but decreased serum NO concentrations in ischemic flaps with subsequent reperfusion. These results suggest that NO is one of the factors responsible for ischemia-reperfusion injury and that NO synthase inhibitors and heparin may protect against such injury.     

Fate of the TRAM flap after abdominoplasty in a rat model

During a classical abdominoplasty, all musculocutaneous perforators from the deep inferior epigastric vessels are normally divided. Even if somehow neovascularization could relink the abdominal skin and rectus abdominis muscles, reestablishing these same discrete perforators would be unlikely because of the barrier effect of the abdominal wall fascia. Therefore, a lower transverse rectus abdominis musculocutaneous (TRAM) flap intuitively should not regain sufficient vascularity for viability after a prior abdominoplasty, and a history of the latter should be expected to be a major contraindication for this procedure. Nevertheless, anecdotal observations of successful lower TRAM flaps following abdominoplasty seem to contradict our basic principles, which may need better further elucidation. Consequently, this two-stage study in Sprague-Dawley rats was undertaken, initially performing an abdominoplasty in all rats. This was followed 1 or 10 months later by the creation of an unipedicled superiorly based TRAM flap that incorporated virtually all of the abdominal skin. From our identical historical TRAM flap control (n = 5) except without prior abdominoplasty, 72.8 +/- 12.83 percent of this area survived. TRAM flaps raised 1 month after the abdominoplasty (n = 6) had 2.2 +/- 3.4 percent or essentially no viability. Unexpectedly, the long-term group (n = 7) demonstrated 13.7 +/- 10.0 percent viability, ranging from 0 to 30 percent. Both groups of TRAM flaps after abdominoplasty had a flap survival area significantly less than that of the control by two-tailed group t test (p < 0.001), and that of the long-term group area was significantly greater than that of the short-term (p = 0.022). Lead oxide studies 10 months after abdominoplasty revealed no irrefutable evidence of the reestablishment of rectus abdominis perforators to the integument, although obviously some reconnections had formed at the microcirculatory level to partially revascularize some flaps. The range of viability of the long-term rat TRAM flaps documented that for the majority, surviving surface area was minuscule even following a delay equivalent to a human decade after abdominoplasty (1 rat month - 1.1 human years), yet rarely sufficient revascularization did indeed occur, which could explain the prior unusual clinical successes. However, the basic principle that a TRAM flap raised following a classical abdominoplasty at any time would be a risky maneuver seems to still be a valid concept.     

The effect of vascular endothelial cell growth factor on survival of skin flap in rats

In order to study the effect of vascular endothelial cell growth factor (VEGF) on the survival of skin flap 30 SD rats were used. A randomized flap measuring 7.5 cm x 3.0 cm was created on the back of each SD rat. The treatment group (n = 10) received VEGF 40 ng/flap by subcutaneous injection with microinjector during and 24 hours after operation. The control groups received heparin 16 U/flap (n = 10) or normal saline 800 microliters/flap (n = 10). After operation, on the 3rd and 11th day, the survival rate of the skin flaps and the dermovascular density of each flap were investigated by histological and histo-morphometrical examination. The results showed that there was no significant difference in the survival rate between the treatment group and the controls on the 3rd day after operation, while on the 11th day, there was a significant difference between them, and the survival rate was much higher in the treatment group. Besides, dermovascular density was much more increased in the treatment group than that in the controls, especially in the distal 1/3 of the flap (P < 0.02). The conclusion was that VEGF could accelerate the vascularization of the flap and enhance the survival rate of the flap.     

One-stage total penile reconstruction with a free sensate osteocutaneous fibula flap

This is the first series of total penile reconstructions with the free sensate osteocutaneous fibula flap. The main advantages of this flap lie in its intrinsic rigidity, its superior donor-site location, and its long vascular pedicle. The fibula flap provides better bone volume than does the radial forearm flap, which commonly results in a floppy phallus in the absence of bone. Penile prostheses in other flaps have enjoyed limited success. Forearm donor-site complications can be avoided. The donor site in the lower extremity can be readily covered with a sock. The vascular pedicle of the fibula flap is of sufficient length to allow end-to-side anastomosis of the flap to the femoral artery. Interpositional vein grafts are unnecessary, and dissection of the inferior epigastric artery system to serve as a donor artery may be avoided. The appearance of the neophallus is excellent. We present only the first four continuous cases of the six we have performed because sufficient follow-up data are available only for these four. The advantages and disadvantages of fibula and forearm donor sites, the long-term fate of the bony component, the importance of sensation, and the vascularized urethral reconstruction are discussed. High patient satisfaction and the advantages of the technique convince us that the fibula osteocutaneous flap is superior for total penile reconstruction.