The inferiorly based gastrocnemius muscle flap: anatomic aspects

The arterial communication between the gastrocnemius muscle heads through their lowest anastomotic arteriole bundle alone was examined in specimens from 14 fresh cadavers. In 3 specimens, the larger vessels in close vicinity to the lowest vessels were preserved as well. Distinct communication between the arterial networks of the heads was demonstrated in all cases after injecting dyes through both sural arteries or into the lateral sural artery and the lowest anastomotic arteriole in 11 and 3 specimens, respectively. Therefore, it seems that one head can be adequately supplied from the contralateral one through their lowest anastomotic arteriole(s); nevertheless, the location of this vessel varies significantly and cannot be detected preoperatively. Measurements demonstrated that although this vessel is not found at a constant level, it is invariably detected in the lower third of the medial gastrocnemius head's length and, in 93 percent of cases, in the lower fourth. Thus, rough preoperative planning becomes feasible. Given that the venous communication between the heads has been documented as well, the authors think that an inferiorly based flap of the medial gastrocnemius head for defects of the middle third of the tibia might be both reliable and applicable; however, for reasons of safety, the muscle heads should remain attached along their lower third.     

Orbital venous anatomy of the rat

Ten rats were embalmed, the veins of the head latex-injected, and the heads were dissected. Five rats were used to prepare corrosion casts of the venous structures of the head. It was found that the rat has an orbital venous plexus rather than an orbital venous sinus as seen in the mouse and hamster. The orbital venous plexus was formed by the external dorsal ophthalmic vein, the external ventral ophthalmic vein and numerous anastomoses between these veins. Of major interest was a large anastomotic vein located in the caudaldorsal area of the orbit. The anastomotic vein joined the orbital venous plexus and the superficial temporal vein.     

The arterial communication between the gastrocnemius muscle heads: a fresh cadaveric study and clinical implications

The purpose of this investigation was to describe the anatomy of the communicating (anastomotic) vessels between the gastrocnemius muscle heads and to record the extent of their supply potential. Ensuing clinical implications are discussed. Fourteen fresh cadaveric gastrocnemius muscles were examined. Detailed dissections of the communicating vessels were facilitated after injections of methylene blue or cadaveric blood solutions through the medial, lateral, or both sural arteries. The extent of the arterial cross-supply between the muscles' heads through these vessels was determined in-eight specimens after methylene blue perfusions through the lateral sural arteries, while one specimen was examined after injection of methylene blue and yellow ink through the lateral and medial sural arteries, respectively. Communicating vessels were detected in all 14 specimens. A mean number of 5.8 vascular bundles and single vessels was found. The bundles consisted of arterioles and, as all indications suggested, of concomitant venules as well. Regarding arterial cross-supply, it was clearly evident that each head could be vascularized solely from the contralateral one, mostly through these bundles. However, even if only a part of the bundles was preserved intact, vasculature was not affected.     

Anatomic study of the venous drainage architecture of the forearm skin and subcutaneous tissue

The venous anatomy of the forearm skin was examined radiographically in 15 fresh cadavers that had been injected systemically with a lead oxide-gelatin mixture. In 10 specimens, the forearm skin was divided into the skin and superficial adipofascial layer and the deep adipofascial layer. Five specimens were radiographed stereoscopically. Despite the thinness of the skin and subcutaneous tissue of the forearm, the cutaneous vein was seen three-dimensionally. Judging from the architecture and direction of the venous valves, most of the venous blood that had perfused the dermis was believed to: (1) pool in a venous network located in the superficial zone of the skin and subcutaneous tissue, (2) flow chiefly in the accessory cephalic and median antebrachial veins, and (3) enter the cephalic and basilic veins near the antecubital fossa. Venae comitantes of the septocutaneous and musculocutaneous perforators of the radial or ulnar arteries were thought to be only bypasses to the deep vein.     

A new flap design: neural-island flap

This report introduces the "neural-island flap" concept, which represents a consistent and reliable skin flap design supplied only by the intrinsic vasculature of a cutaneous nerve. In this study, the lateral femoral cutaneous nerve was selected as the pedicle of the neural-island flap, and a standard skin flap, which is the territory of the accompanying vessels (i.e., iliac branches of the iliolumbar artery and vein), was elevated on the lower dorsal region of the rats. In a total of 92 Wistar rats, three experiments were performed. In part I (n = 24), the vascular anatomy of the lateral femoral cutaneous nerve was established by the methods of dissection, microangiography, nerve mapping, perfusion with colored latex and India ink, and histologic analysis. In part II (n = 46), the role of the cutaneous nerve in supporting an acutely elevated skin flap was explored by creating five flap groups as follows: group 1, conventional flap (artery, vein, and nerve intact); group 2, neural island flap (only the nerve intact); group 3, neurocutaneous flap (vein and nerve intact); group 4, denervated flap (artery and vein intact); and group 5, skin graft. In part III (n = 22), the role of a preliminary surgical delay procedure to augment the survival of the neural island flap was investigated. Results of the anatomic studies indicated a consistent perineural vasculature by the accompanying iliolumbar artery. Skin flaps survived totally in groups where the artery and vein were intact, whereas mean survival rates for the neural island flap and the neurocutaneous flap were 38.2 +/- 3.1 percent and 44.5 +/- 3.8 percent, respectively (p > 0.05). Results of part III of the experiment demonstrated a significantly higher survival for the delayed neural island flap (94.5 +/- 5.5 percent) compared with the acutely elevated neural island flap (p < 0.05). The perineural and intraneural vessels were found to be greatly dilated after a delay procedure, demonstrated by direct observation, microangiography, histologic analysis, dye injection study, and scanning electron microscopy. On the basis of this promising series of experiments, a clinical technique was developed using the sural neural-island flap. The flap was used to reconstruct lower extremity defects in four cases. A delay procedure was accomplished in the first stage by elevating a fasciocutaneous flap from the midcalf region based on a posterior skin bridge and the sural nerve. After a 2-week delay period, a sural neural-island flap was created based on the nerve and transposed to the defect. Flap survival was complete in all cases, with a satisfactory result. The authors conclude that this report proves for the first time that a robust and reliable skin flap can be created pedicled only by the intrinsic vasculature of a cutaneous nerve, after a proper surgical delay. The so-created neural-island flap design offers two novel advantages: (1) a very narrow pedicle and (2) a pedicle without any restriction to a specific pivot point, in addition to the previously described unique advantages of preservation of a major artery and avoidance of microvascular anastomoses.     

The medial sural artery perforator free flap.

The medial sural artery supplies the medial gastrocnemius muscle and sends perforating branches to the skin. The possible use of these musculocutaneous perforators as the source of a perforator-based free flap was investigated in cadavers. Ten legs were dissected, and the topography of significant perforating musculocutaneous vessels on both the medial and the lateral gastrocnemius muscles was recorded. A mean of 2.2 perforators (range, 1 to 4) was noted over the medial gastrocnemius muscle, whereas in only 20 percent of the specimens was a perforator of moderate size noted over the lateral gastrocnemius muscle. The perforating vessels from the medial sural artery clustered about 9 to 18 cm from the popliteal crease. When two perforators were present (the most frequent case), the perforators were located at a mean of 11.8 cm (range, 8.5 to 15 cm) and 17 cm (range, 15 to 19 cm) from the popliteal crease. A series of six successful clinical cases is reported, including five free flaps and one pedicled flap for ipsilateral lower-leg and foot reconstruction. The dissection is somewhat tedious, but the vascular pedicle can be considerably long and of suitable caliber. Donor-site morbidity was minimal because the muscle was not included in the flap. Although the present series is short, it seems that the medial sural artery perforator flap can be a useful flap for free and pedicled transfer in lower-limb reconstruction.     

Two new cutaneous free flaps: the medial and lateral thigh flaps

Two new cutaneous free-flap donor areas are described on the medial and lateral sides of the thigh. The medial thigh flap is supplied by an unnamed artery from the superficial femoral artery and is drained by the accompanying venae comitantes. Its nerve supply is from the medial femoral cutaneous nerve. The lateral thigh flap has its vascular pedicle from the third perforating artery of the profunda femoral artery and its accompanying vein. The lateral femoral cutaneous nerve provides sensation over the area. These flaps provide a large surface area of both skin and subcutaneous tissue without the usual bulk of subcutaneous fat and muscle. Their desirable features include long vascular pedicles with large vessel diameters and potential of being neurovascular flaps with specific sensory nerve supply and predictable anatomy. The principal disadvantage is that the donor site may leave a slight contour defect with primary closure or require grafting when a large flap is taken. We predict that these flaps will become important donor sites for reconstructive problems requiring resurfacing of cutaneous defects in various anatomic areas.     

Venous return in the trunk of the Port Jackson shark, Heterodontus portusjacksoni

The longitudinal veins of the trunk of the Port Jackson shark exhibit low venous pressures and blood flow is facilitated by four subsidiary mechanisms. The sucking action of the heart is augmented by the presence of single flap valves at the central ends of certain longitudinal veins. The flexion of the trunk in swimming transfers blood from the dorsal aorta to the caudal vein; both the segmental arteries and the segmental veins are valved at their origins from the main vessels. Movement of the median dorsal fins and of the tail pumps blood from cutaneous veins to the caudal vein by the compression and dilation of valved venous reservoirs located close to radial muscles. Movement of the rectum generates negative pressures in certain cutaneous veins. A division of the trunk venous system, into abdominal and postpelvic regions is suggested on functional and anatomical grounds.     

Shear stress and pressure modulate saphenous vein remodeling ex vivo

Vein graft failure remains an important clinical challenge, but factors contributing to vein graft failure have not clearly been defined. We investigated the role of the mechanical environment in vein remodeling in an ex vivo perfusion system. Porcine saphenous veins were subjected to five different ex vivo hemodynamic environments, including one mimicking an arterial bypass graft, for one week in order to independently assess the effects of shear stress and pressure on vein remodeling. The extent of intimal hyperplasia decreased with culture under increasing shear stress, with veins cultured under the lowest levels of shear stress exhibiting the greatest ratio of intimal/medial area, 0.15+/-0.03, which was greater than that of fresh veins (0.06+/-0.01, p<0.05). All perfused veins displayed characteristics of both medial hypertrophy and eutrophic remodeling, with those veins cultured under elevated pressures showing greater increases in mass and area than those cultured under venous pressures. Medial area correlated with the average pressure under which veins were cultured (R2=0.95, p<0.001), with veins cultured under bypass graft conditions, which were exposed to the greatest pressure during the one week culture, exhibiting the largest medial area (1.69+/-0.15 mm2), which was significantly greater than that of fresh veins (1.08+/-0.05 mm2, p<0.05). However, pulsatility was not a necessary stimulus for medial growth, as increases in medial area were observed in culture conditions in which steady flow and pressure were present. Our results suggest that pressure and shear stress act independently to regulate vein remodeling, influencing changes in vessel size as well as the nature of the remodeling.     

Spatial interaction between tissue pressure and skeletal muscle perfusion during contraction

The vascular waterfall theory attributes decreased muscle perfusion during contraction to increased intramuscular pressure (P(IM)) and concomitant increase in venous resistance. Although P(IM) is distributed during contractions, this theory does not account for heterogeneity. This study hypothesises that pressure heterogeneity could affect the interaction between P(IM) rise and perfusion. Regional tissue perfusion during submaximum (100kPa) tetanic contraction is studied, using a finite element model of perfused contracting skeletal muscle. Capillary flow in muscles with one proximal artery and vein (SIM(1)) and with an additional distal artery and vein (SIM(2)) is compared. Blood flow and pressures at rest and P(IM) during contraction ( approximately 25kPa maximally) are similar between simulations, but capillary flow and venous pressure differ. In SIM(2), venous pressure and capillary flow correspond to P(IM) distribution, whereas capillary flow in SIM(1) is less than 10% of flow in SIM(2), in the muscle half without draining vein. This difference is caused by a high central P(IM), followed by central venous pressure rise, in agreement with the waterfall theory. The high central pressure (SIM(1)), obstructs outflow from the distal veins. Distal venous pressure rises until central blood pressure is reached, although local P(IM) is low. Adding a distal vein (SIM(2)) restores the perfusion. It is concluded that regional effects contribute to the interaction between P(IM) and perfusion during contraction. Unlike stated by the vascular waterfall theory, venous pressure may locally exceed P(IM). Although this can be explained by the principles of this theory, the theory does not include this phenomenon as such.     

Some aspects concerning the peculiarities of the pterygoid venous plexus in man related to age

The pterygoid venous plexus (pt.v.pl.) was studied in 54 human heads (adults, children, fetuses) halved in the middle sagital plan, using microdissections and injections with PVC, coloured gelatin and roentgenopaque masses. In adults, the pt.v.pl. was closely related to the external pterygoid muscle. The superficial variant (more frequent) maintained connections with the facial vein through a venous network named by us "plexus pterygo-temporo-buccalis". The deep variant (less frequent) could be included in the system of venous plexuses placed at the basis cranii. Its tributaries, accompanying the lingual nerve, established connections with the veins of the sublingual compartment (a fact not yet mentioned in the literature). In children and old humans the pt.v.pl. was formed only by some large veins giving a radiate structure ("starfish-shaped" plexus) corresponding to the first and second portion of the maxillary artery. These results revealed that the pt.v.pl. is a unique formation which could be more developed laterally or medially in comparison with the external pterygoid muscle, in relation with the superficial or deep position of the maxillary artery. The practical importance of the pt.v.pl. is emphasized.     

Absence of venous valves in mice lacking Connexin37

Venous valves play a crucial role in blood circulation, promoting the one-way movement of blood from superficial and deep veins towards the heart. By preventing retrograde flow, venous valves spare capillaries and venules from being subjected to damaging elevations in pressure, especially during skeletal muscle contraction. Pathologically, valvular incompetence or absence of valves are common features of venous disorders such as chronic venous insufficiency and varicose veins. The underlying causes of these conditions are not well understood, but congenital venous valve aplasia or agenesis may play a role in some cases. Despite progress in the study of cardiac and lymphatic valve morphogenesis, the molecular mechanisms controlling the development and maintenance of venous valves remain poorly understood. Here, we show that in valved veins of the mouse, three gap junction proteins (Connexins, Cxs), Cx37, Cx43, and Cx47, are expressed exclusively in the valves in a highly polarized fashion, with Cx43 on the upstream side of the valve leaflet and Cx37 on the downstream side. Surprisingly, Cx43 expression is strongly induced in the non-valve venous endothelium in superficial veins following wounding of the overlying skin. Moreover, we show that in Cx37-deficient mice, venous valves are entirely absent. Thus, Cx37, a protein involved in cell–cell communication, is one of only a few proteins identified so far as critical for the development or maintenance of venous valves. Because Cxs are necessary for the development of valves in lymphatic vessels as well, our results support the notion of common molecular pathways controlling valve development in veins and lymphatic vessels.     

Venous valves in the large branches of superior vena cava

In 97 human cadavers the valves of the following blood vessels were investigated with regard to their cusps and their sizes and positions: the internal jugular veins, the subclavian veins, the brachiocephalic veins, and the superior vena cava. The cusps of each of the valves, which consist of two or three parts, are neither always of equal size nor obligatorily sufficient. Unipartite valves may be sufficient as well as insufficient. Internal jugular veins: The inferior bulb of the internal jugular vein is provided with valves which in 6% of the cases consist of three parts, in 66% of two parts, and in 15% of only one cusp. The concave margins of most of them go down as far as the venous angle. The convex edges attached to the wall of the vein extend to a higher level on the right side than on the left. In 13% there do not exist any valves. Varieties are described separately in this paper. Subclavian veins: Valves are found along the length of the vessel. Only few of them reach the venous angle. In rare cases there exist two valves: one at the beginning, the other at the end of the subclavian vein. In 4% of the cases the valves consist of three, in 75% of two cusps. In 12% they are unipartite. In 9% there are no valves to be found. The right side is more often without valves than the left. Brachiocephalic veins: Only a minority of these vessels is provided with valves. Most of these consist of one cusp, are insufficient, and are situated in the left innominate vein.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reversed forearm island flap supplied by the septocutaneous perforator of the radial artery: anatomical basis and clinical applications

The cutaneous perforators of the radial artery adjacent to the superficial branch of the radial nerve and the lateral antebrachial cutaneous nerve were investigated, and the vascular anatomical features of the reversed forearm island flap supplied by those accompanying perforators were documented. Ten fresh cadavers were systemically injected with lead oxide, gelatin, and water. Twenty forearms were then dissected, and an overall map of the cutaneous vasculature and source vessels was constructed. The accompanying arteries were observed to lie along the lateral antebrachial cutaneous nerve and the superficial branch of the radial nerve and to nourish the skin through cutaneous branches. Vascular communication among these cutaneous vessels was evaluated, to determine the cutaneous vascular territory of the radial forearm flap. This anatomical information facilitates flap design in the forearm region. Clinical experience regarding the usefulness of the reversed forearm island flap for hand reconstruction for a series of five patients is presented.     

The venous territories (venosomes) of the human body: experimental study and clinical implications

The venous architecture of the integument and the underlying deep tissues was studied in six total-body human fresh cadavers and a series of isolated regional studies of the limbs and torso. A radiopaque lead oxide mixture was injected, and the integument and deep tissues were dissected and radiographed. The sites of the venous perforators were plotted and traced to their underlying parent veins that accompany the source (segmental) arteries. A series of cross-sectional studies were made in one subject to illustrate the course of the perforators between the integument and the deep tissues. The veins were dissected under magnification to identify the site and orientation of the valves. Results revealed a large number of valveless (oscillating) veins within the integument and deep tissues that link adjacent valved venous territories and allow equilibration of flow and pressure throughout the tissue. Where choke arteries define the arterial territories, they are matched by boundaries of oscillating veins in the venous studies. The venous architecture is a continuous network of arcades that follow the connective-tissue framework of the body. The veins converge from mobile to fixed areas, and they "hitchhike" with nerves. The venous drainage mirrors the arterial supply in the deep tissues and in most areas of the integument in the head, neck, and torso. In the limbs, the stellate pattern of the venous perforators is modified by longitudinal channels in the subdermal network. However, when an island flap is raised, these longitudinal channels are disconnected, and once again the arterial and venous patterns match. Our venous studies add strength to the angiosome concept. Where source arteries supply a composite block of tissue, we have demonstrated radiologically and by microdissection that the branches of these arteries are accompanied by veins that drain in the opposite direction and return to the same locus. Hence each angiosome consists of matching arteriosomes and venosomes. The clinical implications of these results are discussed with particular reference to the design of flaps, the delay phenomenon, venous free flaps, the pathogenesis of flap necrosis, the "muscle pump," varicose veins, and venous ulceration.     

Alternative venous drainage of heart ventricles in rabbits

The objective of this study was to describe the uncommon connections between cardiac veins, alternative pathways within cardiac venous circulation and complex variability of the venous system in the heart ventricles. The study was carried out on 30 adult New Zealand White rabbits. The arrangement of the cardiac veins was studied by using the corrosion casts prepared with the Spofacryl® and by perfusion of coloured latex. The presence and organization of principal veins of the heart ventricles was relatively constant with a great variability in the mode of opening and forming a common trunk. The highest variations were observed in the region of the paraconal interventricular vein, the left and right marginal vein and the left distal ventricular vein. The left proximal ventricular vein was an inconstant tributary of the left circumflex vein and was seen in 17% of cases. The left distal ventricular vein was visible as one (13% of cases) or two veins (87% of cases). Angular vein was observed in 20% of cases. Numerous anastomosis were found among cardiac veins.     

A morphological study of the vertebral venous plexus and its connections in the Cape dune mole‐rat,Bathyergus suillus (Bathyergidae)

Bathyergus suillus are subterranean rodents found in the Western Cape of South Africa, where they inhabit sandy, humid burrows. Vertebral venous plexuses around the vertebral column have been implicated in aiding the maintenance of a constant central nervous system temperature via its connections with muscles and interscapular brown adipose tissue. The morphology of the vertebral venous plexuses and its connections in B.suillus were investigated. Frozen (n = 10) animals were defrosted; the venous system injected with latex and the vertebral venous plexuses, azygos‐ and intercostal veins dissected along the dorsal and ventral aspects of the vertebral column. Specimens (n = 4) were used for histological serial cross sections of the thoracic vertebrae. Veins drained from the interscapular brown adipose tissue to the external vertebral venous plexus, via a dorsal vein at the spinous process of T2 which might represent the “vein of Sulzer” described in rats. The intercostal veins cranial to the level of T8 drained directly into the ventral external vertebral venous plexus instead of into the azygos vein as seen in rats. The azygos vein was situated ventrally on the thoracic vertebral bodies in the median plane as opposed to most rodents that have a left sided azygos vein. The internal vertebral venous plexus consisted of two ventrolateraly placed longitudinal veins in the spinal epidural space. Veins from the forelimbs entered the internal vertebral venous plexus directly at the levels of C7 and T1 and have not been described in other rodents. Serial histological sections, revealed no regulatory valves in vessels leading toward the internal vertebral venous plexus, allowing blood to presumably move in both directions within the vertebral venous plexus. The vertebral venous plexus of B. suillus shows similarities to that of the rat but the vessels from the forelimbs draining directly into to the internal vertebral venous plexus and the position of the azygos vein and the intercostal veins draining into the external vertebral venous plexus are notable exceptions. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.     

Phenotype of distinct primary sensory afferent subpopulations and caspase-3 expression following axotomy

Specific sensory neuronal subpopulations show contrasting responses to peripheral nerve injury, as shown by the axotomy-induced death of many cutaneous sensory neurons whilst muscular sensory afferents survive an identical insult. We used a novel combination of retrograde neuronal tracing with immunohistochemistry and laser microdissection techniques, in order to describe the neurochemistry of medial gastrocnemius (muscular sensory afferents) and sural (cutaneous sensory afferents) branches of the rat sciatic nerve and relate this to the pro-apoptotic caspase-3 gene expression following nerve transection. Our results demonstrated distinctions in medial gastrocnemius and sural neuron populations with the most striking difference in the respective proportions of isolectin B4 (IB4) staining neurons (3.7 V 32.8%). The mean neuronal area of the medial gastrocnemius (MG) neurons was larger than that of the sural (SUR) neurons (1,070.8 V 646.2 μm2) and each phenotypic group was significantly smaller in sural neurons than in MG neurons. At 1 week post-axotomy, MG neurons markedly downregulated caspase-3, whilst SUR neurons upregulated caspase-3 gene expression; this may be attributable to the differing IB4-positive composition of the subpopulations. These findings provide further clarification in the understanding of two distinct neuronal populations used increasingly in nerve injury models.     

Prostacycin production by arterialized autogenous venous grafts in dogs

Arteries are capable of producing significantly larger quantities of protacyclin than are veins. To test the hypothesis, whether prostacyclin production by the vessel wall is related to blood pressure and flow, we measured the amounts of PGI₂ released and synthesized by venous segments transplanted for 6 weeks into the arterial circulation. These results were compared with the production of prostacyclin by normal veins and arteries. In 20 dogs a segment of jugular vein was interposed into the carotid system; a sham dissection was done on the opposite side. “Arterialized” vein grafts showed prominent intima lined by endothelium, medial smooth muscle cell proliferation and fibrotic proliferation in adventitia. Spontaneous and arachidonic acid- stimulated prostacyclin production (measured by radioimmunoassay for 6-keto-PGF_1α) was not significantly different between arterialized venous autografts and jugular veins. Significantly larger amounts of prostacyclin were synthesized by the carotid artery. Thus, histologic changes and rheologic effects occurring in vein grafts transposed to the arterial site do not affect prostacyclin production.     

Differential activity of leukotrienes upon human pulmonary vein and artery

Responses to leukotrienes B4, C4, D4 and E4 were examined in human pulmonary artery and pulmonary vein preparations from surgical specimens. Leukotrienes C4 (LTC) and D4 (LTD) were potent contractants of pulmonary vein over the dose range of 10(-10) M to 10(-6) M, whereas they produced minimal contractions of human pulmonary artery only at concentrations of 10(-8) M or greater. Leukotriene E4 was less potent than LTC or LTD, and leukotriene B4 (LTB) at concentrations up to 10(-6) M had no effect upon either pulmonary veins or pulmonary arteries. Contractions of pulmonary vein by LTD were inhibited in a competitive manner by FPL 55712. Dose response characteristics of LTD and inhibition by FPL 55712 were similar for pulmonary venous and bronchial smooth muscle. We conclude that pulmonary vein smooth muscle has leukotriene receptors comparable to those of bronchial smooth muscle whereas pulmonary artery does not.