Laser flap delay: comparison of Erbium:YAG and CO2 lasers

The delay phenomenon has long been recognized as a powerful tool in reconstructive surgery. This phenomenon involves creating alterations in skin flap blood supply or microcirculation to increase the size of the surviving flap. In the past many reconstructive surgeons depended on surgical delay as an integral part of their surgical planning. Today surgical delay remains a reliable method for maximizing flap survival. Although surgical delay remains the gold standard many have searched for methods to create the same effect with less morbidity and reduced cost. The purpose of this study was to determine whether near-scarless delay can be performed with either the Erbium:YAG or CO2 laser using a standard McFarlane skin flap model. Four groups were identified. Surgical delay, Erbium laser delay, and CO2 laser delay groups were each compared with a nondelayed control. Each group consisted of ten Sprague-Dawley rats. On Day 0 all delay procedures were performed on the lateral periphery of the outlined dorsal skin flaps. Interruption of this lateral blood supply was accomplished by two parallel 10-cm incisions in the surgical delay group. Likewise blood supply and microcirculatory alterations were accomplished in the laser delay groups by two parallel 10-cm laser treatments. On Day 7 a 10 x 4-cm cranially based dorsal skin flap was elevated. On Day 14 flap survival was analyzed by calculating percentage flap survival. The Erbium:YAG laser delay of the McFarlane flaps resulted in an average of 32 per cent less flap loss compared with controls (P = 0.0001). The CO2 laser resulted in an average of 36 per cent less flap loss compared with controls (P = 0.0002), whereas the surgical delay group had a 23 per cent smaller flap loss (P = 0.009). There was no significant difference between any of the delay groups. These results indicated that CO2 and Erbium:YAG lasers are as effective as surgery for delay of skin flaps in the rat model. They may provide an effective and inexpensive method for near-scarless skin flap delay in humans.     

Effects of microneedle length and duration of preconditioning on random pattern skin flaps in rats

To date, the surgical delay of skin flaps is the most common and reliable method that increases skin flap survival. In this study, we aimed to increase skin flap viability using preconditioning by microneedling. Seventy-two Sprague Dawley rats were randomly divided into control, surgical flap delay (SFD), and four microneedling groups (7 or 14 days of preconditioning with 0.5 mm or 1 mm needles). Modified McFarlane flaps were raised on the back of rats. In Group I, a caudal pedicled skin flap was raised and the flap survival rate was assessed on postoperative day 14. In the SFD group, a bipedicled flap was created and after 14 days of surgical delay, all skin flaps were raised. In the microneedling groups, 0.5 mm or 1 mm needles were used for 7 or 14 days. The flap survival rates of all microneedling and SFD groups were significantly higher than the control group. The plasma levels of vascular endothelial growth factor (VEGF) did not significantly differ between groups, but the VEGF level of skin samples in the SFD group was higher than the control group. The vessel counts of all microneedling and SFD groups were statistically higher than the control group in all skin samples taken before raising the flaps, but skin samples taken 14 days after raising the skin flap did not show any difference between groups. We showed that preconditioning by microneedling can be used to improve the viability of critical ischemic skin flaps at a level similar to surgical delay.     

Effects of low-power diode lasers on flap survival

We investigated the effect of low-power laser irradiation on the survival of experimental skin flaps in rats. A gallium-aluminum-arsenide diode laser that was developed by the Japan Medical Laser Laboratory was used. The laser power was 15 mW and the wavelength 830 nm. Irradiation was carried out, either before or after flap elevation, in two groups of 20 Wistar strain rats. A third group of 20 rats served as controls. A caudally based skin flap, 3 X 9 cm, was designed on the back of each rat. Laser irradiation therapy was performed for 5 consecutive days for 6 minutes per flap per day, preoperatively in one group and postoperatively in the other. Seven days postoperatively, the survival areas of the flaps were measured and compared. The survival area was increased significantly in both groups receiving laser therapy, probably due to the observed proliferation of blood vessels around the irradiated points and an increase in blood flow.     

The effects of tumescent solutions containing lidocaine and epinephrine on skin flap survival in rats

The effects of tumescent solutions consisting of lidocaine and epinephrine on skin flap survival in rats were studied. Dorsal skin flaps of rats were infiltrated using lidocaine (1%) with epinephrine in concentrations of 1:100,000, 1:200,000, 1:400,000, and 1:800,000 prior to elevating flaps of the different experimental groups. The solutions were applied intradermally or subcutaneously, and the flaps were raised "immediately" or "delayed" after injection in the different groups. Control flaps were infiltrated by lidocaine (1%) only. The survival of the flaps was assessed on the seventh day after the operation. As a result, the flaps showed higher necrosis rates in the groups injected by lidocaine with epinephrine in concentration of 1:100,000 and 1:200,000 than of the other experimental or all control groups (P < 0.01). In conclusion, lidocaine with epinephrine in concentrations of 1:400,000 and 1:800,000 was found safe on skin flap survival for tumescent technique in rats.     

重组人生长激素对大鼠随意皮瓣成活的影响

目的探讨重组人生长激素(rhGH)对大鼠随意皮瓣成活的影响。方法将24只健康的Wistar大鼠随机分为两组,每组12只。在其背部制作随意皮瓣后,分别在皮瓣的皮下注射0.25ml(0.1IU/kg)的rhGH(实验组)和0.25ml的生理盐水(对照组),观察两组皮瓣的成活面积及成活率,并行免疫组化检查。结果实验组的皮瓣成活率及皮瓣的中段、远段的血管密度和VEGF的表达均较对照组高,实验组皮瓣血管的再生明显多于对照组。结论rhGH能直接或间接地促进皮瓣血管的生成,提高随意皮瓣成活的面积。     

Delay in neurovenous flaps: experimental and clinical experience

The objective of this study was to examine the effects of the standard surgical delay in the flaps based on the cutaneous branches of the vascular axis around a superficial sensory nerve. The delay procedure was experimentally tested in rats and subsequently used in patients.In the experimental study, the survival of a delayed inferior epigastric neurovenous flap was compared with that of a nondelayed inferior epigastric neurovenous flap. One type of clinically applicable delay pattern (standard bipedicled technique) was employed. A 3 x 3 cm flap was raised in 20 female Wistar rats assigned randomly to 2 groups. Each group consisted of 20 flaps. The standard bipedicled delay pattern increased the percentage survival of the delayed inferior epigastric neurovenous flap. The survival percentage of the delayed flaps was 59.8 +/- 185.0 (P < 0.5). The histologic findings of the skin revealed that our delay procedure enhanced the perfusion of the flap by dilating the arterial network.Stimulated by our experimental findings, we used the island bipedicled surgical flap delay or combined strategic-standard delay in the distally pedicled sural flap successfully on 9 cases.     

The Effects of Tadalafil on Axial-Pattern Skin Flap Survival in Rats

BACKGROUND Pharmacologic augmentation to mimic the delay phenomenon that increases skin flap survival has been studied extensively. Tadalafil is a phosphodiesterase V inhibitor that is used for treatment of erectile dysfunction by enhancing vascular smooth muscle relaxation.
OBJECTIVE The aim of this study was to investigate the effects of local injection of tadalafil in enhancing axial-pattern skin flap survival in rats.
MATERIALS AND METHODS Twenty Sprague-Dawley rats were used and a McFarlane-type caudally based axial-pattern skin flap was designed on the dorsum of the rat (2 × 9 cm). Rats were divided into two groups: the treatment group and the control group. Tadalafil 10 mg/kg/day was injected to the distal flap area of the treatment group for 3 days, and normal saline was injected for the control group. On Postoperative Day 7, necrotic flap area was measured and compared, and angiograms of the skin flaps were obtained in the two groups.
RESULTS In the treatment group, the mean necrotic area was 21.9±6.4%, and in the control group, 37.7±5.9%. There was a statistically significant increase of skin flap survival in the treatment group ( p =.001). Angiography also showed vasodilation of the choke vessels between adjacent angiosomes to form true anastomosis in the treatment group.
CONCLUSION The results demonstrate that the use of local injection of tadalafil to failing skin flaps increases the survival of axial-pattern flaps in rats.     

Increased flap survival after sensory denervation with capsaicin accompanied by delay

The effect of capsaicin, combined with delayed surgical procedures, was studied in adult rats. After denervation of the experimental subjects' cutaneous nerves with capsaicin, the time required for the flaps to become completely necrotic was prolonged; when accompanied by delayed flap raising for a period of up to eight weeks, the flap survival rate was increased. Although there were no significant differences in flap survival between the control and the capsaicin animals undergoing flap raising with no delay, increased vascularity and flap survival were confirmed in capsaicin animals in whom procedures had been delayed. Maximum flap survival was found in capsaicin animals undergoing a six-week delay in the procedures. These results suggest that sensory nerves play an important role in flap survival, perhaps in the areas of flap vascular supply and tension control of the A-V shunt in the microcirculation of a flap.     

血管内皮生长因子促进跨区供血反流轴型皮瓣成活的实验研究

目的研究血管内皮生长因子（vascular endothelial growth factor，VEGF）的局部皮下注射对大鼠背部跨区供血反流轴型皮瓣成活的影响及效果。方法取20只SD大鼠，制备8cm×2cm大鼠背部跨区供血反流轴型皮瓣模型，随机分成两组，每组10只。实验组：于皮瓣远端7．5cm及6．5cm处共选择4个对称位点，分别予100ng／100μlVEGF溶液50μl；对照组：每一位点予生理盐水50μl。术后1～7d行皮瓣大体观察，并于7d处死大鼠，切取皮瓣，行皮瓣成活率测定、组织学观察及血管密度检测。结果大体观察，实验组皮瓣成活面积明显大于对照组，实验组皮瓣成活面积15．55±0．27cm^2，对照组13．42±0．57cm^2，差异有统计学意义（P〈0.01）。组织学观察，实验组皮瓣血管密度34．40±3．75个／10倍光镜下视野，对照组21．00±3．16个／10倍光镜下视野，差异有统计学意义（P〈0.01）。镜下见实验组有大量新生肉芽组织形成，胶原纤维排列规则，成纤维细胞较多，炎性细胞浸润程度轻；对照组新生肉芽组织少，胶原纤维凝集成块，成纤维细胞少，炎性细胞浸润程度重。结论VEGF在皮瓣成活早期，通过促进缺血皮瓣新生血管形成，增加血管数量，改善缺血组织的血液供应，促进皮瓣成活；在皮瓣形成时局部、单次、足量应用VEGF是促进跨区供血反流轴型皮瓣远端成活的有效方法。     

水蛭素对大鼠随意型皮瓣存活的影响

目的 研究水蛭素对大鼠背部超长随意型皮瓣存活的影响.方法 采用改良大鼠"McFarlane flap"模型,将实验动物随机分为水蛭素实验组(水蛭素组)和生理盐水对照组(生理盐水组),水蛭素组局部注射3 ml(30 ATU)水蛭素,生理盐水组则注射3 ml生理盐水,连续注射7 d后分别检测两组皮瓣的存活面积百分比,并取皮瓣近、中、远段(即Ⅰ、Ⅱ、Ⅲ区)组织做光镜观察,免疫组化法检测血管内皮生长因子(VEGF)和碱性成纤维细胞因子(bFGF)的表达.结果 术后7 d,水蛭素组皮瓣的存活面积百分比为(69.52±3.23)%,生理盐水组为(50.36±2.37)%,水蛭素组显著高于生理盐水组,差异有统计学意义(P＜0.01);水蛭素组皮瓣坏死与存活并存的Ⅱ区,组织水肿、炎性细胞浸润情况明显比生理盐水组轻.水蛭素和生理盐水组皮瓣Ⅱ区的新生血管计数分别为(28.24±4.23)个/mm2和(17.45±5.43)个/mm2,两组比较差异有统计学意义(P＜0.05).通过计算累积吸光度A值(IA),得到水蛭素和生理盐水组VEGF阳性量分别为9262.23±896.99和4938.05±1623.67,bFGF阳性量分别为5122.83±1176.12和2779.45±472.00,水蛭组VEGF及bFGF的表达均高于生理盐水组,差异均有统计学意义(P＜0.01).结论 水蛭素可能通过体内一系列复杂的调控通路,最终增加VEGF、bFGF表达,促进皮瓣新生血管增生,改善皮瓣血供,减轻炎性反应,降低缺血皮瓣的坏死率,从而提高大鼠随意型皮瓣的存活.

Abstract：

Objective To investigate the effect of Hirudin on random skin flap survival in rats.Methods 24 SD rats were randomly divided into control group and experimental group. The "McFarlane flap(3 cm ×9 cm)" rat models were established on the rat dorsum. 3 ml Hirudin (30 ATU) was injected into the flap in the experimental group, while 3 ml saline in the control group. The injection was performed for 7 days. The flap survival area in the two groups was measured. The tissue samples were taken from proximal( Ⅰ ), middle( Ⅱ ) and distal( Ⅲ ) portions of flaps for histologic study. The VEGF and bFGF expression was also detected with immunohistochemistry method. Results 7 days after operation, the flap survival rate was ( 69.52 + 3.23 )% in the experimental group, while ( 50.36 ± 2.37 )% in control group,showing a significant difference between the two groups ( P ＜ 0.01 ). In the middle portion, tissue edema and infiltration of neutrophils in experimental group was markedly slighter than that in control group. The VEGF and bFGF expression and neovascularization was enhanced markedly in experimental group.Conclusions Hirudin can increase the survival of random pattern skin flaps. It may increase the VEGF,bFGF expression through a series of complex regulatory pathway. Then flap neovascularization is promoted and the flap blood supply is increased.     

Accelerated flap prefabrication with vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) is a potent promoter of angiogenesis that has been shown to enhance revascularization of ischemic tissues, including skin flaps. This study was designed to investigate the value of a single topical application of recombinant human VEGF to accelerate flap viability in a rat model of a non-ischemic prefabricated flap. Prefabricated flaps were created in 48 Sprague-Dawley rats. An autologous tail artery loop was anastomosed to the femoral artery and vein, and implanted subcutaneously in the lower abdomen. Flaps were divided into two groups of 24 each. At the time of loop implantation the control group received 0.9 percent NaCl or a 16 percent vol/wet polyvinyl alcohol (PVA) solution: the treatment group received VEGF in 0.9 percent NaCl or VEGF in PVA. The PVA gel was used to facilitate topical application In each group, 3- x 4-cm flaps nurtured by the tail artery pedicle were elevated and resutured into place after 3, 4, and 5 weeks. The percentage of surviving skin of each flap was determined by planimetry 7 days after flap elevation. Mean skin survival areas at 3, 4, and 5 weeks were control group 0 percent. 8 percent and 17.5 percent; and VEGIF-treated group, 6 percent, 40 percent, and 66.7 percent respectively VEGF significantly improved flap survival by 5 weeks (p = 0.02). These results suggest that VEGF can accelerate maturation of prefabricated flaps. This approach could expand the application of flap prefabrication as a resource for reconstructive surgery.     

Comparison of contraction rates of epigastric and extended dorsal island skin flaps in rats

Flap surgery is a wide field in plastic and reconstructive surgery practice and experimental research is needed to improve surgical success. These research is often performed on rats. Rat is a loose-skinned animal and contraction of skin flaps on rats is an underestimated condition. Besides this variable contraction of survived and necrotic tissues may mislead calculations and results. In this study, contraction patterns of epigastric and dorsal island skin flaps were investigated to identify this phenomenon. Forty-two male Sprague-Dawley rats were divided into four groups. Eleven epigastric flaps with unilateral pedicles, 11 epigastric flaps with bilateral pedicles, 10 extended dorsal island skin flaps with unilateral pedicles, and 10 extended dorsal island skin flaps with bilateral pedicles were prepared. Total, necrotic and viable flap areas were calculated from standardized photographs which were taken daily. The animals were placed on marked papers and image processing software was used the calculate flap areas from the photographs. Respect to these daily flap areas, the contraction rates in epigastric flaps were highly significant. The area loss in necrotic tissues were faster than the viable areas. Compared to the epigastric flaps, the contraction was not significant in extended dorsal island skin flaps flap groups. In conclusion, the rat extended dorsal island skin flap is a more reliable model for experimental flap research, which is resistant to contraction, when compared to the epigastric skin flap model.     

Effects of natural and recombinant hirudin on superoxide dismutase, malondialdehyde and endothelin levels in a random pattern skin flap model

We have assessed the anti-inflammatory, anti-oxidative and anti-coagulant effects of locally applied natural and recombinant hirudin in a random skin flap rat model. Thirty Wistar rats with venous congested skin flaps were randomly divided into two treatment groups and a control group to receive subcutaneous injections of natural hirudin (6 U), recombinant hirudin (6 U) or physiological saline, respectively. Superoxide dismutase, malondialdehyde and endothelin levels as well as flap survival rates of the skin flaps were measured after surgery. Compared to the control group, the treatment groups had significant higher superoxide dismutase levels and lower malondialdehyde and endothelin levels in the skin flaps. The surviving areas of the flaps were larger in the treatment groups than the control group. Our results demonstrated that hirudin could improve skin flap survival through its anti-inflammatory, anti-oxidative and anti-coagulant activities.     

Comparison of flash lamp pulsed-dye laser (585 nm) and conventional surgery in the delay of random dorsal rat flaps.

BACKGROUND AND OBJECTIVE: Delay is a basic surgical technique used by flap surgeons to improve the blood supply to the distal parts of a random skin flap. The aim of this study was to determine whether a scarless delay can be done by the use of the flash lamp pulsed-dye laser operating at a wavelength of 585 nm. STUDY DESIGN/MATERIALS AND METHODS: The pilot study showed that 6 J/cm(2) had a selective photothermolysis effect and therefore was chosen for testing the delay procedure on 15 rats. The percentage of flap necrosis of this group was compared to the results of 15 rats that underwent delay by surgery and 15 rats that were not treated prior to flap surgery (control group). RESULTS: Laser delay of McFarlane flaps resulted in an average of 15.5% smaller necrotic area compared to the control group (52.7% +/- 14.4% and 68.2% +/- 9.6%, respectively, P < 0.01) and was as effective as surgical delay (53.3% +/- 13.6%). CONCLUSIONS: The results indicate that the flash lamp pulsed-dye laser operating at 585 nm is effective for delaying cutaneous flaps in the rat model.     

Effect of allopurinol,superoxide-dismutase,and hyperbaric oxygen on flap survival

The effect of allopurinol, superoxide-dismutase, and hyperbaric oxygen was compared on axial pattern skin flap survival. An abdominal flap based on the inferior epigastric pedicle was raised in rats for this purpose. Three experimental groups were studied. In the first group, adult male Wistar rats received 50 mg/kg I.P. of allopurinol. The second received 20,000 I.U./kg of superoxide-dismutase. The third group was submitted to hyperbaric oxygen therapy. The flaps were exposed to 8-h warm ischemia. Flap survival was evaluated on postoperative day 7. All flaps survived, and the mean survival areas were 63.53%, 83.03%, and 55.98%, respectively, in the allopurinol, superoxide-dismutase, and hyperbaric groups. The percentage of flap necrosis was significantly smaller in all experimental groups when compared to controls (P < 0.05). It was clear that the superoxide-dismutase group had better results on axial pattern ischemic skin flap survival, under the tested conditions. The tested methods improved flap survival to ischemic injury, and the flap designed is a reliable model for further investigations.     

撕脱皮瓣修剪成真皮下血管网皮瓣后对成活面积影响的研究

目的研究撕脱皮瓣修剪制成真皮下血管网薄皮瓣后对皮瓣成活面积的影响.方法采用3～4月龄白色约克夏小猪7头,麻醉后在自行研制的皮肤撕脱伤模型机中复制撕脱伤模型,将一侧的撕脱皮瓣制成真皮下血管网薄皮瓣,另一侧为撕脱皮瓣,原位缝合;7天后,对两侧皮瓣的成活和坏死面积进行测量和计算分析.结果修剪制成真皮下血管网薄皮瓣后的成活面积为(60.90±15.26)%,而撕脱皮瓣组的成活面积为(40.41±9.23)%,统计学处理两组有显著差异(P＜0.05).结论皮肤撕脱伤撕脱皮瓣修剪制成真皮下血管网薄皮瓣后增加了成活面积.     

Effect of the delay phenomenon in the rat single-perforator-based abdominal skin flap model

During the last decade, innovations in reconstructive surgery have presented a new type of flap called the "perforator-based flap." Perforator-based flaps became useful alternatives for solving difficult problems. In the authors' previous study, they created a single musculocutaneous perforator-based abdominal skin flap. In their current study they evaluate the effect of various surgical delay procedures on this model. They divided 32 Sprague-Dawley rats equally into four groups (one control group and three delay groups). Three different delay procedures were employed in the delay groups. In one group, only the flap boundaries were incised (delay group 1). In the other delay groups, flap boundaries were incised and the contralateral (opposite side of the pedicle, delay group 2) or ipsilateral (pedicle side, pedicle left intact; delay group 3) musculocutaneous perforators were ligated. The period of delay was 1 week in all groups. After 1 week, a single-perforator-based abdominal skin flap was elevated as in the control group. One week after the final procedure, surviving skin areas were calculated and microangiograms were acquired. The mean surviving skin area was 75% +/- 3% (standard deviation) in the control group, 97% +/- 3% in delay group 1, 81% +/- 6% in delay group 2, and 96% +/- 3% in delay group 3. Delay group 2 showed substantial necrosis 1 week after the delay procedure and was thus excluded from the study. Results were analyzed using one-way analysis of variance, and post hoc analyses were performed using Tukey's multiple comparison test. The authors observed the advantages of the delay phenomenon in the two delay groups (p < 0.05). Microangiograms were examined grossly, and a marked difference between the two delay groups and the control group was observed. Many dilated choke vessels were seen in delay groups 1 and 3. Incising the flap boundaries with or without ligating the ipsilateral perforators (keeping the pedicle intact) 1 week before harvesting single-perforator-based abdominal skin flaps in the rat results in a delay effect. Conversely, incising the flap boundaries and ligating the contralateral perforators have no delay effect in this model.     

Effect of tissue ultrafiltration on skin flap survival.

OBJECTIVE: Tissue ultrafiltration (TUF) is a method of reducing tissue edema by removal of interstitial fluid. Considering the deleterious effects of edema on microcirculation and tissue viability, the effect of TUF on skin flap survival was tested. STUDY DESIGN AND SETTING: Survival of modified McFarlane skin flaps was determined in 40 Sprague-Dawley rats. In 20 treated animals, four 5-cm ultrafiltration catheters were placed in the subdermal plane of the distal flap 24 hours after flap elevation and connected to a down-regulated vacuum manifold for 8 hours. No catheters were placed in the control group. RESULTS: Skin flap survival was improved in the experimental group (87.2 +/- 1.6) over the control group (76.7 +/- 2.2). DISCUSSION: TUF effectively improved skin flap survival. These results provide evidence of the causal effect of edema on tissue viability. The relative ease of use of TUF would allow cost-effective clinical application of this technique.     

Experimental studies of skin flaps with subcutaneous veins

The authors have previously reported that skin flaps with subcutaneous veins nourished by arterial or venous inflow survived, despite being sited on recipient beds with poor circulation. In these previous studies, experimental models were based on axial pattern flaps of rabbit ears. However, for clinical application, there are problems in the use of axial pattern flaps with central vessels. This report classifies skin flaps with subcutaneous veins and produces experimental models that are suitable for clinical application and investigation of survival rates. Thirty-seven rabbits (74 ears) were used in this study. A 3.0-cm x 4.5-cm skin flap with only a "passing" vein (one that traveled through the tissue without major branches to that tissue) was raised at the level of the perichondrium on the dorsum of the auricular cartilage. The flaps were divided into three groups: Group A--composite flaps (n = 10); Group B--totally venous perfused flaps (n = 30); and Group C--afferent arterialized venous perfused flaps (n = 34). More than 80 percent of the flaps became necrotic in Group A. In Group B, 18 of 20 survived with partial superficial necrosis and two became more necrotic. In Group C, 18 of 21 flaps survived with superficial necrosis and three became more necrotic. Microangiographically, as concerns the "passing" veins in Groups B and C flaps, all of the flaps survived with only superficial necrosis. The skin flaps with subcutaneous veins survived as total venous perfusion flaps (TVPF) and as arterialized afferent venous perfusion flaps (AAVPF) even though the artery was not included in the flap. The experimental model is suitable for the investigation of the clinically unconventional flap.