Dermal microvasculature and tissue selective thinning techniques (ultrasound and water-jet) of short-time expanded skin in dogs

Certain reconstructive procedures, like auricular reconstructions, require thin and well-vascularized skin. The aims of this study were to analyze if the increased survival of expanded skin flaps was due to morphologic changes of the dermis, if thinning of short-time expanded skin was possible without harm to the microcirculation and if tissue selective cutting methods could be used to resect subcutaneous fat without damaging its vessels. Eighty-two 200-ml expanders were implanted into the trunk regions of 26 beagles and filled immediately with sterile saline. In the first series of experiments, the expansion was terminated after intervals of 0.5-5 weeks and dermal vessels were analyzed morphometrically. In the second series the expanded flaps were raised after 2 weeks and thinned solely surgically or with the additional use of an ultrasonic knife or with cutting by water jet. In contrast to sham flaps, the expanded skin showed only very few areas of necrosis and these were located superficially in most cases. The relative volume of the dermal vessels and their quantity showed a significant increase after the expansion. Additionally, the subcutaneous tissue could be thinned down to 0.4 mm with the water-jet-cutter. Findings demonstrated that the method used could create a well-vascularized skin flap of minimal thickness that could be very helpful for special reconstructive procedures.     

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.     

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.     

Arteriovenous cross-flow flap in rats: a novel skin flap

Angiosomes are blocks of tissues, composed of the integument and underlying deep structures, supplied and drained by a named artery and its accompanying vein. The purpose of the current study is to describe a new principle, which allows extension of the territory of an angiosome into the adjacent angiosome, thus enabling the creation of a large skin flap (arteriovenous cross-flow flap). Epigastric skin flaps, measuring 8 x 8 cm, were raised in 30 Sprague-Dawley male rats. In group A (single-pedicle flap), the flaps were based on the epigastric artery and vein on the ipsilateral side, and the contralateral pedicle was divided. In group B (cross-flow flap), the epigastric vein on the ipsilateral side and the epigastric artery on the contralateral side of the flap were divided. In group C (skin graft), the vascular pedicles were divided bilaterally. A definitive assessment was made on the seventh day. Digital images of the flaps were analyzed using an imaging software and the areas of skin survival and necrosis were determined. Lead oxide microangiogram was performed in another set of flaps both acutely and 1 week after flap elevation. The percent survival flap area in group A was 69.94, in group B was 89.07, and in group C was 13.00. All the groups are statistically different, with a p value < 0.001. The microangiograms showed striking differences in the vascular pattern in the cross-flow and the single-pedicle flaps. It is clearly demonstrated that the arteriovenous cross-flow flaps have increased survival of skin when compared with the conventional axial-pattern flaps.     

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.     

Flap prefabrication: effectiveness of different vascular carriers

A new experimental model of a vascular carrier to prefabricate a "secondary" island flap, the popliteal musculovascular pedicle, was developed in the rat. Using quantitative skin-surface fluorometry 30 minutes after sodium fluorescein injection and a flap survival area in the prefabricated 8 x 2.5-cm abdominal composite island flap, we compared the revascularization ability of our muscular carrier to nonrevascularized controls: the skeletonized arteriovenous pedicle and the fasciovascular pedicle. The free composite graft with no vascular carrier exhibited near-total necrosis. The skeletonized vascular pedicle demonstrated 15.2% +/- 7.8% perfusion of normal skin on dye fluorescence index measurements and 50% flap survival. The fasciovascular pedicle exhibited better revascularization, with a dye fluorescence index of 36.2 +/- 15.5 (p < 0.01) and 90% +/- 10% flap survival (p < 0.001). India ink injection study and histological examination of our model provided visual evidence of revascularization from the musculovascular pedicle, along with preservation of the carrier's muscular architecture. The musculovascular pedicle is a reliable carrier for making new, vascularized composite flaps.     

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.     

Comparative pathogenesis of human WA1 and Babesia microti isolates in a Syrian hamster model

The medial thigh flap is a perforator-based flap nourished with septocutaneous or muscle perforators originating from the femoral vessels. To date, 8 patients have been repaired with this flap and extended or connected flaps including this flap: 4 patients with lower leg defects and 4 patients with intraoral and neck defects. The advantages of this flap are (1) several pedicle perforators exist for this flap, which makes possible duplicated vascular anastomoses to establish reliable circulation of the transferred flap; (2) the flap can be extended or connected to other neighboring flaps in the anterior thigh, so that extensively wide defects can be closed in one stage; (3) the great saphenous vein can be simultaneously used as a vein graft or for venous drainage for the flap; (4) the anterior branch of the femoral nerve can be used for sensory potential; and (5) there is minimum morbidity of the donor defect and a large dominant vessel for the leg can be preserved. The suitable indications for this flap are defects after removal of skin cancer in the foot or lower leg and wide defects after resection of head and neck cancer, which can be reconstructed with the flap connected to neighboring skin flaps. The disadvantages of this flap are that it has a small, short vascular pedicle and the bulkiness of the flap's fatty tissue often requires thinning.     

Study of relapsing remitting experimental allergic encephalomyelitis SJL mouse model using MION-46L enhanced in vivo MRI: early histopathological correlation

Constitutive expression of VEGF after implantation of genetically engineered myoblasts into non-ischemic muscle led to an increase in vascular structures. Previously, effects of VEGF delivery to adult muscle have only been reported in ischemic tissues. The resulting vascular structures were reminiscent of those formed during embryonic vasculogenesis, rather than angiogenesis, sprouting from preexisting vessels. Initially, VEGF caused an accumulation of endothelial cells and macrophages, followed by networks of vascular channels and hemangiomas with locally high serum VEGF levels. No effects were evident in adjacent tissue or contralateral legs, where low serum VEGF was detected. These data suggest that the induction by VEGF of angiogenesis or vasculogenesis may be dose-dependent. Furthermore, VEGF expression must be carefully modulated, as overexpression is deleterious.     

Eruption of the permanent upper canine: a radiologic study

Fibroblast-seeded collagen scaffolds or ligament analogs are potentially useful for reconstruction of the anterior cruciate ligament of the knee. To provide lasting benefits, the seeded cells must survive implantation within the harsh synovial environment of the knee joint. Our objective was to determine the in vivo fate of autogenous fibroblast-seeded ligament analogs as a function of fibroblast source (anterior cruciate ligament or skin), implantation site (knee joint or subcutaneous space), and time after implantation (1, 2, 4, 6, or 8 weeks). Before implantation, fibroblasts were labeled with PKH26-GL, a fluorescent membrane dye. Immediately after retrieval of the implant, the viability of the labeled seeded cells was assessed under a fluorescent microscope. Viable seeded fibroblasts remained attached to the collagen fibers within the ligament analogs for at least 4 weeks (skin fibroblasts) or 6 weeks (anterior cruciate ligament fibroblasts) after implantation. A larger number of viable seeded cells were consistently observed in the subcutaneous space than in the knee joint. Scaffold resorption prevented observation at the 8-week time period. Fibroblast-seeded ligament analogs remained viable for prolonged periods in the knee joint and therefore have the potential to influence the formation and remodeling of neoligament tissue after reconstruction of the anterior cruciate ligament.     

Requirement of vascular integrin alpha v beta 3 for angiogenesis

Angiogenesis depends on the adhesive interactions of vascular cells. The adhesion receptor integrin alpha v beta 3 was identified as a marker of angiogenic vascular tissue. Integrin alpha v beta 3 was expressed on blood vessels in human wound granulation tissue but not in normal skin, and it showed a fourfold increase in expression during angiogenesis on the chick chorioallantoic membrane. In the latter assay, a monoclonal antibody to alpha v beta 3 blocked angiogenesis induced by basic fibroblast growth factor, tumor necrosis factor-alpha, and human melanoma fragments but had no effect on preexisting vessels. These findings suggest that alpha v beta 3 may be a useful therapeutic target for diseases characterized by neovascularization.     

Elective stent implantation after optimal debulking for complex coronary lesions: acute and mid-term results

OBJECTIVE: To determine the vascular and collagen effects of supplemental basic fibroblast growth factor (bFGF) in irradiated porcine skin flaps. INTERVENTION: Animals were subjected to 2 fractions of 650 cGy orthovoltage radiation. Following this, the skin flaps were administered bFGF intracuticularly for 6 days before and after surgery. The animals were sacrificed 3 weeks after the start of bFGF administration. Tissues were analyzed for vascularity, collagen content, wound-breaking strength, and histopathological analysis. RESULTS: The bFGF-treated flaps showed a 62% increase in vascularity compared with controls (10.4%+/-2.4% vs 6.43%+/-2.27%; P<.05). The bFGF flaps had a significantly lower collagen concentration compared with control flaps when measured by hydroxyproline content (0.0619+/-0.0211 nm/microg vs 0.0784+/-0.0150 nm/microg). Wound-breaking strength was not significantly different, although the bFGF flaps had a trend toward lower breaking strength. Histologically, the bFGF-treated flaps showed increased cellularity, fibroblasts, and extracellular mucopolysaccharides compared with controls. CONCLUSIONS: This study provides evidence that supplemental bFGF can increase vascularity to skin flaps in previously irradiated porcine skin tissue. Histologically, radiation did not prevent the angiogenic effect of bFGF.     

Experimental substantiation of a two-staged method of microsurgical transplantation of the complex composite flaps

The authors have proposed two-staged flap transplantation, consisting of flap mobilization on vascular pedicle with subsequent its transplantation in several days. In experiment on muscular flaps, obtained from regio epigastrica of 30 rabbits, it was established that optimal time for the second stage of operation conduction may be end of the second--beginning of the third day after the transplant mobilization.     

Effect of sciatic nerve transection or TTX application on enzyme activity in rat spinal cord

BACKGROUND/PURPOSE: Treatment of several congenital anomalies is frequently hindered by lack of enough tissue for surgical reconstruction in the neonatal period. The purposes of this study were (1) introduction of a novel concept in perinatal surgery, involving minimally invasive harvest of fetal tissue, which is then processed through tissue engineering techniques in vitro while pregnancy is allowed to continue, so that, at delivery, the newborn can benefit from having autologous, expanded tissue promptly available for surgical implantation at birth; (2) analysis of the progress of an engineered fetal skin graft with time, after implantation in the neonate; and (3) study of the effects of current tissue engineering techniques on fetal keratinocytes and fetal dermal fibroblasts. METHODS: Ten 90- to 95-day-gestation fetal lambs underwent surgical creation of two large paramedian excisional skin defects on the posterior body wall. Subsequently, fetal skin specimens no larger than 1.5 x 1.5 cm were videofetoscopically harvested. Fetal keratinocytes and dermal fibroblasts were then separately cultivated and expanded in vitro for 45 to 50 days, resulting in a total of approximately 250 to 300 million cells. Seven to 10 days before fetal delivery, all cells were seeded in two layers on a 16 to 20-cm2, 3-mm thick biodegradable polyglycolic acid polymer matrix. One to 4 days after delivery, the autologous engineered skin was implanted over one of two previously created skin defects. The second skin defect region received an absorbable polymer scaffold without cells as a control. If necessary, the original skin wounds were further amplified before implantation. Each animal provided at least one time-point for histological analysis of both types of repair through excisional biopsies performed at weekly intervals, up to 8 weeks postimplantation. Normal skin specimens were also used as controls. RESULTS: Fetal and neonatal survival rates were 100%. Based on previous postnatal skin engineering studies, fetal dermal fibroblasts multiplied significantly faster in vitro (approximately fivefold) than expected. Fetal keratinocytes multiplied at expected postnatal rates. The engineered grafts induced faster epithelization of the wound (partial at 1 week and complete between 2 and 3 weeks postoperatively) than did the acellular ones (partial at 3 weeks and complete between 3 and 4 weeks postoperatively). Analysis of skin architecture showed a higher level of epidermal organization and less dermal scarring in the wounds that received the engineered, cell-implanted polymer scaffold. CONCLUSIONS: (1) Videofetoscopically assisted fetal tissue engineering is a viable method for obtaining expanded autologous tissue for prompt surgical reconstruction at birth. (2) Fetal skin can be expanded and engineered in vitro at faster rates than expected postnatally, with current tissue engineering techniques. (3) Engineered autologous fetal skin induces a faster and more organized healing of neonatal skin defects than that observed with second intention. This concept may prove useful for the treatment of certain human neonatal conditions such as giant neoplasias, ectopia cordis, and other body wall defects.     

Prefabrication of mucosa-lined flaps: a preliminary study in the pig model

There is a need in reconstructive surgery for flaps lined by nonkeratizing stratified squamous epithelium or mucous membrane. Applications could be found in nasal, oral, genital, and esophageal reconstruction and even in reconstruction of hollow intra-abdominal tubes. Prefabrication of lined flaps has so far been limited to a pretransfer grafting of split-thickness skin. However, in certain situations this does not satisfy the primary requirement of replacing "like with like." Also, the availability of donor sites for harvesting mucosa is limited. The present study involves prefabrication of mucosa-lined flaps without causing donor site morbidity. The study was carried out on six mini-Hartford pigs. Buccal mucosa was harvested from the cheeks; the sheet was divided into several smaller graft pieces of 1 to 2 cm2 area. These graft pieces were then applied to the deep fascia at a distance of 5 to 15 mm from one another, also to galea, and to the undersurface of skin flaps. The grafted area was isolated from the opposing surface with a silicone sheet or Marlex mesh. The grafts were allowed to take and, it was hoped, merge together to form a sheet graft of dimensions greater than those of the original. Two to 7 weeks after the initial grafting, the skin flap was elevated; the mucosal grafts were observed macroscopically for take and surface area and microscopically to confirm that the lining was indeed mucosa. The mucosa took well on both the fascia and galea and also on the undersurface of the skin; it enlarged in size, and the small pieces became confluent to form a single sheet. The increase in surface area varied from 33 percent at 11 days postgrafting to a maximum of 238 percent after 7 weeks. All pigs had positive cultures from the mucosa before implantation but only one developed gross infection leading to partial graft loss.     

Skin fold advancement flaps for closing large sternal and inguinal wounds in cats and dogs

Skin fold advancement flaps can be created from the elbow and flank folds to close large wounds in the pectoral and inguinal regions of cats and dogs, respectively. The attachments of the laterally facing (outer) and medially facing (inner) layers of the skin fold to the adjacent limb are divided to produce a U-shaped pedicle graft attached to the trunk. This mobilizes skin that can be advanced over large wounds involving the ventral chest or abdomen, or both. The use of skin fold advancement flaps enables direct closure of large skin defects without undue tension and without compromising the mobility of the adjacent limb.     

Clinical application of thoraco-umbilical skin flap

Since 1987 we have successfully used thoraco-umbilical skin flaps as free transplants to repair 8 cases of severe burn scar deformities of jaw-neck and hand regions, thoraco-umbilical insular skin flaps to each case of congenital vaginal atresia, severe vulval scar due to sulfuric acid burn and large penal tissue defect accompanied with severe urethral leakage. This flap has the following advantages: namely definite anatomical position, larger vascular diameter, fight large skin flap area, and similar skin completion as that of the jaw-neck region. Therefore they are the ideal substitute for the repair of soft tissue defects of jaw-neck region as well as extremities. The flap has long vascular pedicle, abundant vascularization, easy transportation and it is suitable to be a retrograde insular flap for repairing of vulval tissue defect, reformed penal vaginoplasty.     

Magnetic resonance tomography in diagnosis of cardiac space-occupying lesions]

The ability to assess viability of tissues by monitoring changes in oxygenation and perfusion during harvesting and following transfer of free and pedicled flaps is potentially important in reconstructive surgery. Rapid detection of a critical change in tissue oxygenation could enable earlier and more successful surgical intervention when such problems arise. In this study near infra-red spectroscopy (NIRS) was used to assess changes in tissue oxygenation, haemoglobin oxygenation and blood volume in a porcine prefabricated myocutaneous flap model in response to pedicle manipulations. As far as we are aware this is the first usage of a NIRS instrument to assess changes in oxygenation in a flap model which closely simulates the clinical situation. A myocutaneous flap was raised (n = 9 pigs), tubed and the flap circulation allowed to readjust for periods between 7 and 9 days. The pedicle vessels were then subjected to arterial (n = 9), venous (n = 12) and total occlusion (n = 6). Repeatable and reproducible patterns of change were measured in each case. Comparison of mean values indicated that the differences between arterial and venous, and venous and total occlusions were significant for all NIRS parameters. The monitor was easily able to detect two additional features: (i) the presence of venous congestion indicated by raised levels of deoxygenated haemoglobin and an increase in blood volume; and (ii) the presence and magnitude of reactive hyperaemia. In two flaps release of arterial or total occlusion did not result in the expected reactive hyperaemia associated with an increase in blood volume (oxygenated haemoglobin) suggestive of possible damage to the vascular bed. NIRS proved able to detect and distinguish between microcirculatory changes occurring as a result of arterial, venous or total vascular occlusion. We believe that NIRS provides a sensitive and reliable postoperative monitor of tissue viability following transfer of free and pedicled flaps. It can accurately identify different types of problems with the pedicle vessels. In addition its predictive capabilities would allow assessment of flaps buried deep to the skin. This monitor is excellent for surgical and intensive care unit monitoring since it is unaffected by light, portable and is extremely easy to use.     

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.     

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.