Anatomy and circulation of the canine skin

The skin of the dog has several anatomic differences from human skin. Skin thickness, hair growth, and circulation vary regionally in the dog and between breeds to some degree. Direct cutaneous arteries supply the canine skin. The deep or subdermal layer is closely associated with the panniculus muscle (where present) and should be elevated with the overlying skin during routine flap elevation or undermining procedures. Flaps in the dog elevated without inclusion of a direct cutaneous artery and vein have been termed subdermal plexus flaps to avoid confusing them with random flaps in the human based on musculocutaneous vessels. Axial pattern flaps developed for veterinary clinical use are discussed, several of which have potential for free flap transfer in cutaneous reconstructive surgery.     

Studies on the nature of the flap/bed interaction in rodents--Part I: Flap survival under varying conditions

A flap needs close contact with its bed for optimal flap survival. Using a rat dorsal flap model, flap/bed contact times were varied by use of a sterile polyethylene film. In addition, the flap was modified either by removing the panniculus carnosus or by converting the distal flap into a skin graft. Finally, the effect of using a dressing was assessed. Several observations were made: (1) The initial 6 to 12 hours of a flap's interaction with its bed is critical for optimal survival; (2) fluorescein accurately predicted flap survival upon polyethylene removal; (3) removing the panniculus carnosus increased flap and skin graft survival; (4) dressing allowed flaps and skin grafts to better withstand bed deprivation; and (5) distal flaps and skin grafts under various conditions responded differently to bed deprivation.     

Distribution of glucose in the pedicle skin flaps of guinea pigs

Consistency of necrosis was determined in skin flaps created on the back of guinea pigs. The average amount of skin necrosis ranged from 20 to 45% of the flaps. Glucose distribution within the skin flaps was quantitated in the epidermis, hair follicles, dermis, and panniculus carnosus at various distances from the pedicle. The distal end of the flaps exhibited a drastic decrease in glucose content in all strata of skin, excluding the panniculus carnosus, while the proximal half of the flaps displayed no significant alteration in tissue glucose content during 7 days following flap elevation. The epithelium and dermis exhibited a similar degree of magnitude for the decrease in glucose level in association with skin necrosis.     

Resistance of rapidly expanded random skin flaps to bacterial invasion

This study tested the hypothesis that rapidly expanded random pattern skin flaps demonstrate enhanced resistance to bacterial invasion from intradermal injection of Staphylococcus aureus in a porcine model. Sites for a 6 X 12 cm expanded, a 6 X 9 cm sham-expanded, and a 6 X 6 cm acute random pattern skin flap were outlined, but not elevated, on the backs of 14 white pigs. A 450-cc tissue expander inserted beneath the panniculus carnosus at the site for expansion was sequentially filled to the limits of skin viability each day for 5 days. At the sham site a tissue expander was similarly inserted but left unexpanded; the acute flap site was left undisturbed. On day 8, flaps were elevated, immediately sutured in place, and 0.1 ml of saline solution containing 10(7) Staphylococcus aureus inoculated intradermally at four corresponding sites in each flap and at three sites in normal skin. In seven animals these sites were at the proximal base of the flaps; in seven others the sites were distal. The resulting areas of erythema and skin ulceration were measured on each of the next 3 days and the measurements compared. At corresponding proximal sites, the mean area of erythema and ulceration measured over the next 3 days in expanded flaps (31.2 mm2) and in sham-expanded flaps (33.8 mm2) was significantly less than in acute flaps and control skin (47.5 mm2, 43.4 mm2, p less than 0.05). Measurements in the rapidly expanded flaps were not significantly different than those in the sham-operated expanded flaps.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reconstruction of Scalp Defects Using Simple Designed Bilobed Flap

We have devised a novel rational method to design a bilobed flap. In our method, two triangle flaps are designed; the angle of the first flap is three-fourths the angle of a rhombus at the defect site, and the angle of the second flap is also three-fourths that of the first flap. We have successfully performed reconstruction of scalp defects as large as 50 × 45 mm using simple designed bilobed flaps. The location of the defect was the parietal region in 10 cases, the frontal region in 6 cases, the temporal region in 3 cases, and the occipital region in one case. The advantages of this method for use in reconstruction of scalp defects are as follows: (1) the dispersion tension on the flap provides stable circulation and prevents expansion of scar formation; (2) since the suture line is zigzag, alopecia at the suture line can be hidden under the hair; (3) since this flap is a random pattern flap using galea aponeurotica with blood flow to the skin, flap design is possible for any part of the scalp; and (4) design and elevation of this flap are easy and do not take much time.     

Effects of clopidogrel on survival of rat skin flaps.

Clopidogrel is a thienopyridine derivative that is chemically related to ticlopidine, which irreversibly inhibits platelet aggregation by selectively binding to adenylate cyclase-coupled adenosine diphosphate receptors on the platelet's surface. In animal models, clopidogrel has been shown to reduce the incidence of both arterial and venous thrombi. In the present study the effects of clopidogrel on the survival of rat epigastric island flaps was researched. Epigastric island flaps of 7x7cm were raised from symphisis pubis to arcus costa with the panniculus carnosus. The experimental group received seven doses of 25mg/kg clopidogrel postoperatively, the first dose given immediately after the suturing of the flaps. The rats were anaesthetised on postoperative day 7 to assess the survival of flaps. The difference between the clopidogrel and the control group was significant (P<0.005). The full-thickness skin samples obtained after the calculation of survival percentages revealed thinning of the epidermis layer and active chronic inflammation in both groups. However, diffuse dilated vessels, extravasated eritrocytes were seen in the clopidogrel group flaps. The results indicated a significant increase in flap survival in rats given clopidogrel. Further research is needed to assess the critical doses of clopidogrel to create optimal flap survival improvement.     

The superficial inferior epigastric artery fascia flap in the rabbit

In reconstructive surgery, fascial flaps provide thin, pliable tissue for mucosal closure or serve as a highly vascularized support for skin grafts. Their angiogenic potential is used for experimental neovascularization of avascular tissue grafts. However, most fascial flaps in animal surgery have random pattern design with short reach. As a pilot study for a femur revascularization project in rabbits, a new axial fascial flap is described based on the superficial inferior epigastric (SIE) vessels. They were used in this species previously only as ligated bundles or in fasciocutaneous flaps. The topographical anatomy of the SIE-vessels, lower abdominal fascia, and panniculus carnosus are outlined. The angiogenic capabilities are demonstrated microangiographically by abundant vessel formation in a femur allograft. Used in a pedicled fashion, this flap is an alternative to femoral and saphenous vessels for prefabrication or revascularization procedures in the lower abdomen, genital area, and thigh. Distant recipient sites seem possible with microsurgical transfer.     

皮瓣血管交通支的定量研究方法

目的采用血管造影量化相邻血管交通吻合程度,为皮瓣血管研究提供理论依据。方法健康小型猪5头,体长100～115cm,体重25～35kg。一侧腹壁于旋髂深动脉与腹壁上动脉穿支交界区域肉膜下埋植300ml扩张器1枚,每周1次扩张注水,每次30～40ml,扩张2个月(扩张组);另一侧腹壁不作任何处理(非扩张组)。于双侧腹壁设计以旋髂深血管为蒂、20cm×20cm轴型皮瓣10个,并分别携带双侧腹直肌及腹壁上动、静脉。将动物颈总动脉放血处死,颈动脉灌注明胶-氧化铅混悬液后,动物尸体冻存24h,断蒂取下皮瓣,摄皮瓣动脉X线影像。在该图像上于旋髂深动脉和腹壁上动脉大致的交通部位设计等距的3条平行线垂直于2条血管的长轴方向,总宽度以能覆盖所有交通支为佳,计数平行线和这一区域内血管支的切割次数,并进行统计分析。结果扩张组平行线与交界区动脉切割次数为81.20±10.33,非扩张组为22.40±5.41,组间比较差异有统计学意义(P<0.01)。结论设计测量血管交通支的方法简便易行,能真实反映血管交通支的改变,并可用于其他相关实验和临床研究。     

Preconditioning of the distal portion of a rat random-pattern skin flap.

It has been shown that preconditioning either by proximal pedicle clamping or by pedicle intravascular drug administration, for example with adenosine, can improve flap survival. These methods, however, are not well suited to random-pattern flap transfer in the clinical setting. The aim of this study was to evaluate clinically applicable preconditioning methods for random-pattern flaps. Eighteen male Sprague-Dawley rats were used. Bipedicled dorsal skin flaps (2 x 8cm) containing panniculus carnosus were elevated. In the ischaemic preconditioning group the cranial pedicle was clamped for 20min, followed by 40min reperfusion before the cranial pedicle was cut, producing a caudally based random-pattern flap. In the pharmacologic preconditioning group adenosine was locally injected in the cranial half of the flap before the cranial pedicle was cut. In the control group saline was locally injected instead of adenosine and the pedicle was cut in the same manner. Flap survival area was evaluated at day 7. Flap survival area in both preconditioning groups was significantly higher than in the control group (P<0.05). Both preconditioning methods can improve random-pattern flap survival in rats. These methods may prove useful in the clinical setting.     

掌背皮神经营养血管蒂岛状皮瓣修复手指深度烧伤

目的　总结分析用掌背皮神经营养血管蒂逆行岛状皮瓣修复手指深度烧伤的疗效。方法　应用掌背皮神经营养血管蒂逆行岛状皮瓣治疗手指深度烧伤 15例。结果　全部皮瓣成活良好 ,皮瓣最大面积 5cm× 3cm ,最小面积 3cm× 2cm ,经随访外观功能感觉均满意。结论　该皮瓣血供可靠 ,不损伤知名血管 ,能满足指端修复需要 ,供区损伤小 ,操作简单 ,易推广应用     

小腿筋膜皮瓣及小腿内侧逆行轴形皮瓣在下肢创伤修复时的选择及评估

目的:探讨两种小腿皮瓣(小腿筋膜皮瓣及小腿内侧逆行轴形皮瓣)在下肢创伤后皮肤软组织缺损修复时的选择及评估。方法:①在小腿设计局部随意筋膜皮瓣,皮瓣大小范围4cm×6cm～7cm×15cm,转移修复同侧或对侧小腿皮肤软组织缺损并骨外露;②以胫后动脉内踝上发出的皮动脉穿支为轴,在小腿内侧设计逆行轴形皮瓣,皮瓣大小范围4cm×12cm～6cm×15cm,转移修复同侧或对侧足底、踝部、小腿皮肤软组织缺损并肌腱或骨外露。结果:临床共选用11个皮瓣,其中6例为筋膜皮瓣,5例为小腿内侧逆行轴形皮瓣,修复同侧或对侧下肢皮肤软组织缺损并肌腱或骨外露。11例皮瓣术后均成活良好,创面修复效果良好,随访6～12个月,伤肢外形及功能恢复满意。结论:小腿筋膜皮瓣,设计灵活,切取便利,不损伤主要血管,血供丰富,尤其在局部主要血管受损时是修复下肢严重创伤的有效方法之一。小腿内侧逆行轴形皮瓣可切取皮瓣距离长,面积大,血供恒定可靠,成活率高,是修复足底、踝部、小腿严重创伤的最佳选择。此两种皮瓣的应用应针对小腿创面的部位、面积及其创伤特点进行合适的选择,可达到满意的修复效果。     

Evolution of ischemic tissue injury in a random pattern flap: a new mouse model using intravital microscopy

BACKGROUND: Dissection of random pattern flaps may cause microcirculatory dysfunction and ischemia, which jeopardize wound healing due to impaired tissue viability. The aim of this study was to develop an in vivo model that enables continuous monitoring of the interplay between microcirculatory dysfunction, ischemia, and tissue injury by intravital microscopy. MATERIALS AND METHODS: A laterally based random pattern skin flap (15 x 11 mm) including the panniculus carnosus was raised in the back of mice and fixed into a dorsal skinfold chamber (n = 10). Arteriolar blood flow, functional capillary density, number of apoptotic cells, and area of tissue necrosis were analyzed by intravital fluorescence microscopy in the proximal, middle, and distal part of the flap at day 1, 3, 5, and 7 after surgery. Chamber preparations without flap harvesting served as controls (n = 6). RESULTS: At day 1, the distal part of the flap showed a decreased arteriolar blood flow (266 +/- 124 pl/s versus controls: 1418 +/- 351 pl/s; P < 0.05), which resulted in severe alteration of functional capillary density (43 +/- 11 cm/cm2 versus 270 +/- 7 cm/cm2; P < 0.001). The impaired microcirculation was associated with apoptotic cell death (277 +/- 50 cells/mm2 versus 50 +/- 5 cells/mm2; P < 0.05). Microcirculatory dysfunction persisted over 7 days, and, finally, resulted in 49 +/- 3% flap necrosis. CONCLUSIONS: This new model enables repetitive and simultaneous in vivo microscopic evaluation of microvascular hypoperfusion, apoptosis, and tissue necrosis in a random pattern flap. By the use of gene-targeted mice, it bears great potential to analyze distinct mechanisms of flap failure. It further represents an ideal tool to study novel protective strategies, including induction of angiogenesis, heat shock proteins, and HIF-1alpha.     

股上部直接皮动脉皮瓣在肢体组织缺损中的应用

目的探讨股上部直接皮动脉皮瓣修复肢体组织缺损的临床疗效。方法应用Doppler血流探测仪在腹股沟中点以下约4cm处确定股上部直接皮动脉血管发出点，该点向髂-髌连线中点外上方探测血流声最响处，为动脉穿出点。动脉发出点与穿出点连线为皮瓣轴线，切取皮瓣面积4cm×6cm-11cm×18cm，共修复46例皮肤软组织缺损。结果本组46例股上部直接皮动脉皮瓣，除3例皮瓣边缘部分坏死外，其余皮瓣全部成活，术后随访2-21个月，平均14．1月。皮瓣外形满意，质地柔软，感觉恢复良好。结论该皮瓣不携带肌肉，切取容易，可携带股前外侧皮神经，同时修复缺损部位感觉，是肢体组织缺损修复较为理想的选择。     

Effects of Retinoic and Glycolic Acids on Neoangiogenesis and Necrosis of Axial Dorsal Skin Flaps in Rats

Retinoic acid (RA) and glycolic acid (GA) are frequently used in the treatment of acne and skin aging, as well as improving skin healing after dermabrasion and in photoaged skin. Examples of histologic alterations caused by these substances are vascularization increase and interference with inflammatory as well as regenerative skin processes. The objective of this study was to evaluate the possible decrease of skin flap necrosis areas in rats, by applying both substances to the skin 14 and 30 days before surgery, and analyzing histopathologic skin alterations after treatment. Fifty Wistar rats were divided into five groups of 10 animals each. They received daily retinoic acid application for 14 and 30 days, daily glycolic acid application for 14 and 30 days, and vehicle application (control group) for 14 days. After treatment, each rat was submitted to random dorsal skin flap (10 × 3 cm) elevation; flaps were sutured back in place over isolating plastic strips. The rats were sacrificed after 7 days and flap necrosis areas were measured through transparency and then analyzed using computer scanning. Statistical analysis was carried out using monocaudal nonpaired t tests and histopathologic examination was performed in all cases. Compared with the control group, treatment with both acids did not decrease average flap necrosis areas. Though groups RA 30 days and GA 14 days presented larger necrosis area averages (p < 0.05), groups RA 14 days and GA 30 days showed no statistically significant difference (p > 0.05) when compared to the control group. Both substances caused spongiosis, stratum corneum thickening, and vascularization increase, with GA inducing greater granulomatous reaction and RA more spongiosis and queratinization. Group RA 30 days showed the most significant dermo-epithelial (including vascular) regenerative and proliferative effects. Retinoic and glycolic acid treatment led to significatuve and well-known skin alterations, with group RA 30 days showing most notable dermo-epithelial proliferative effects. In our experimental model, preoperatory RA and GA application did not decrease rat dorsal skin flap necrosis area when compared to the control group.     

Accelerated delay of random flaps in a rat model

Random flaps have been supplanted by more immediate and reliable reconstructive methods because the former require two or more procedures and a period of delay. This study was designed to test the hypothesis that a random flap can be elevated, delayed, and safely divided within 4 days. Ninety-two Sprague–Dawley rats were operated by elevating an 8 cm × 4 cm cranially based dorsal flap with its underlying panniculus carnosus muscle. The rats were divided into four groups, one control and three experimental, with 23 rats in each. In the control group, the flap was elevated and its caudal end divided at the same time without delay. In the experimental groups, we tested three delay procedures and all flaps had their caudal end divided 4 days after elevation. The number of flaps showing total viability compared to the flaps showing any amount of necrosis was as follows: control group 1:22, mini delay group 18:5, progressive craniocaudal elevation group 19:4, and the accelerated delay group 22:1. The extent of necrosis, expressed as mean percentage area of necrosis in each group, was as follows: control group 45.9%, in the mini delay group 2.3%, progressive craniocaudal elevation group 2.5%, and the accelerated delay group 0.1%. Delay of this random flap can be accomplished safely in 4 days. In terms of total flap survival and mean percentage necrosis, all three experimental delay procedures were effective in improving total viability and reducing the extent of necrosis significantly. We believe the observed difference in total viability and mean percentage necrosis in the accelerated delay group to be clinically significant.     

The viability of skin flaps.

The historical development of skin flaps is outlined, and in particular their division into two types: random, which are supplied by small musculocutaneous vessels; and axial flaps, which are supplied by named cutaneous vessels running within the flap. Experiments are described into the viability of random skin flaps, using the pig as an experimental model. These experiments confirm that random flaps should not be designed longer than their base and probably should not exceed 12.5 cm (5 in) in length.     

带皮穿支血管的皮神经营养血管皮瓣的临床应用

目的探讨带皮穿支血管与皮神经营养血管相结合的皮瓣手术方法及临床应用效果。方法以深部知名血管发出的皮肤穿支为皮瓣转轴点,切取皮神经营养血管带蒂皮瓣或岛状皮瓣,转位修复肢体远端皮肤软组织缺损创面。结果临床已应用43例,其中腓动脉穿支腓肠神经营养血管皮瓣13例,面积30 cm×12 cm~16 cm×8 cm;胫后血管穿支隐神经营养血管皮瓣9例,面积17 cm×9 cm~5 cm×4 cm;以骨间前血管腕背穿支前臂背侧皮神经营养血管皮瓣8例,面积16 cm×6 cm~10 cm×4 cm;以掌指动脉指蹼穿支手背皮神经营养血管逆行皮瓣13例,皮瓣面积6.0 cm×3.5 cm~2.5 cm×1.5 cm;皮瓣完全成活42例,1例因静脉回流障碍远端1/4坏死。随访6~24个月,皮瓣质地优良,外形与功能恢复满意。结论该术式结合了穿支蒂皮瓣与皮神经营养血管皮瓣的优点,扩大了皮瓣切取面积与修复范围,皮瓣设计灵活,切取方便,血供可靠,是修复肢体皮肤软组织缺损的一种可取的方法。     

Vascular endothelial growth factor gene therapy with intramuscular injections of plasmid DNA enhances the survival of random pattern flaps in a rat model.

The objective of this study was to determine the effects of the naked plasmid DNA encoding vascular endothelial growth factor (VEGF) on the survival of random flaps on rats. Thirty Sprague-Dawley rats whose random flaps were elevated on the back were randomised into three groups of 10 animals each. In the experimental group, the naked plasmid DNA encoding VEGF was injected directly into the panniculus carnosus of the flap. In the two control groups, either control plasmid DNA or physiologic saline was injected. After 7 days, the flaps were evaluated with the following devices: RT-PCR for the expression of VEGF gene, immunohistochemistry for the expression of VEGF protein, histology for vascular density, single photon emission computerised tomography for RBC in the flap, and image analysis for flap survival area. Notably increased expressions of VEGF mRNA and VEGF protein were found in the treatment group. Vascular density was markedly more increased in the treatment group than those in the two control groups (P < 0.01). Compared with the two control groups, the flap treated with VEGF plasmid DNA showed a more significantly enhanced tissue viability: 87 +/- 5 versus 47 +/- 6% for the control plasmid DNA group and 46 +/- 5% for the saline group (P < 0.01). Our results indicated that the VEGF gene therapy was able to enhance the survival of random pattern flaps by inducing angiogenesis.     

腓动脉皮支逆行岛状皮瓣的解剖与应用改进

目的探讨腓动脉皮支逆行岛状皮瓣的解剖学基础及临床应用效果。方法采用新鲜及防腐尸体下肢共25肢,对腓动脉皮支进行解剖学观测。于2003年9月~2005年6月收治足跖趾关节处软组织缺损患者10例,男8例,女2例。年龄21~55岁。其中背侧6例,跖侧4例,缺损范围10cm×6cm~15cm×10cm。应用带有外踝上11.0±1.7cm腓动脉固定皮支的腓动脉皮支逆行岛状皮瓣修复,皮瓣范围11.0cm×6.5cm~16.0cm×11.0cm。供区6例直接减张缝合,4例行自体游离皮片覆盖。结果解剖学观测外踝上11.0±1.7cm自腓动脉发出一固定皮支,起始点直径1.45±0.12mm,入深筋膜点距腓肠神经营养血管皮瓣轴线15.70±1.20mm。10例患者术后皮瓣均成活,血运良好,无静脉回流障碍;供区愈合良好。术后获随访6~12个月,皮瓣外形良好,质地、色泽与周边相似,足功能恢复良好,两点辨别觉11~18mm。结论腓动脉皮支逆行岛状皮瓣经改进后血运好,逆转距离长,修复范围大,操作简便,为临床修复足中远端软组织缺损提供了一种新方法。     

A free microsurgical transfer of a radial (Chinese) flap in reconstructing the lower limb

The microsurgical transplantation of the radial flap to the hind limb has as main advantages to offer a good quality and sensitive skin cover, the possibility to use the flap's radial artery as a vascular bypass and to raise composite flaps with tendon or bone in case of complex reconstruction. MATERIAL AND METHODS: The authors present 9 free radial flap transfers to the foot. Patients' ages ranged from 22 to 50 years. Flap dimensions varied between 7 x 5 cm and 12 x 9 cm. Two flaps contained the flexor carpi radialis tendon to reconstruct the Achilles' tendon and one flap included a bone graft from the radial shaft to resolve a bone defect in the second metatarsal. All flaps were reinnervated by suturing the antebrachial cutaneous nerve of the flap to a cutaneous nerve in the recipient site. RESULTS: There was only one failure in an extensive crush injury. We recommend the radial flap in reconstructing complex defects for it's versatility and for the fact that it can include all types of tissue that may be necessary.