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Abstract

Venous return native the foot is worthy of attention for both research and also clinical purposes. This testimonial summarizes the accessible knowledge the venous return from the foot with a special focus on research and also clinical implications. The anatomy and physiology the venous return are explained with focus on the differences in between standing and walking and the interplay between the venous equipment of both the foot and the calf. Selected problems of clinical interest are discussed and mechanistically interpreted, including the distinctive localization of leg ulcers, the corona phlebectatica, the possible independence of dilatation that the veins that the foot from refluxing varices, and the arteriovenous fistulae that the foot. Indigenous this perspective, the practice of using a postoperative lower-leg bandage is likewise discussed.

Little attention has actually been committed to the veins the the foot: surgeons begin the saphenectomy whereby the foot ends and echographists execute not extend their expedition distally to the malleolus. Even anatomists have actually been an ext interested in the arteries that the foot, fairly than the veins, as demonstrated through the an ext detailed summary of arteries in anatomical tables. Finally, experts in hemodynamics focus on the calf to describe the system of the limb pump, leaving the blood in the foot “undrained.” However, as presented in the existing bibliography, a couple of well-conducted classic studies have clarified the anatomical and functional qualities of venous circulation in the foot, back some areas of skepticism still exist.

The main ideas concerning the anatomy and physiology of venous return native the foot will certainly be revisited in this article, followed by observations of clinical interest and also hypotheses because that research and daily practice.

Anatomy

In 1968, Kuster et al listed the most complete description that the veins the the foot,1 describing 5 systems: (i) the superficial veins of the single (also known as Lejars’ venous plexus)2; (ii) the deep veins that the sole; (iii) the superficial dorsal plexus; (iv) the marginal veins and dorsal venous arch; and also (v) the perforating system.

i. T that superficial veins that the single (Lejars’ venous plexus), once considered the most crucial impulse because that venous return, is a network of small veins with restricted clinical interest (Figure 1).3
Figure 1. The superficial vein network the the sole is do by aplexus of tiny veins that room 1 come 2 mm in diameter.Image courtesy that J. F. Uhl.

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ii. The deep veins of the sole are the most interesting from a functional point of view.

o The deep plantar venous arch operation from the proximal end of the an initial interosseous an are to the base of the fifth metatarsal and accompanies the deep plantar arterial arch, i m sorry receives the deep metatarsal veins and also surrounding muscular veins (Figure 2).4 The deep plantar venous arch steps ≈9 centimeter (range, 5 come 14 cm) according to Binns and Pho5 and also ≈48 mm according to Corley,6 with an average exterior diameter that 5 mm.5 In 8 out of 10 foot dissections, 2 deep plantar venous arches were identified, i beg your pardon is frequently referred to together being doubled.6 A single, constant, and proximally oriented valve has actually been described.5

o The medial plantar vein is a thin and short vein (≈5 cm long according come Uhl et al,3 ≈12 cm according to Binns and Pho,5 and ≈38 mm follow to Corley6) the is normally doubled, with a couple of proximally oriented valves.5 that runs follow me the medial border the the sole from the medial end of the plantar arch to the medial malleolus to form the posterior tibial veins after the confluence v the lateral plantar vein. The medial plantar vein obtain blood from the adjacent muscles, ie, the abductor hallucis, the flexor digitorum brevis, and the plantar quadratus muscle.
Figure 2. Deep plantar veins projected end the foot bones.


o The lateral plantar vein (length between 80 mm5 and 84 mm6) is curved, constantly doubled, and large (2 mm) through fusiform dilatations (resembling the gastrocnemius sinuses),3 and also it is located in between the two muscle layers of the sole of the foot (ie, quadratus plantae and abductor allucis). Proximally directed valves are existing in the lateral plantar vein.5 The lateral plantar artery lies between the two components of this vein, which room interconnected an average of 3 times.3 The lateral plantar vein is in continuity through the lateral finish of the plantar venous arch and runs back across the single to join the medial vein in ~ the calcaneal confluent, creating the posterior tibial veins. The receives blood native the lateral marginal vein, the calcaneal veins, and the veins in the adjacent huge plantar muscles.

In the deep plantar system, double veins have actually been constantly observed through the matching arteries.6 The vessels room surrounded through connective tissue and this plan facilitates venous compression by the artery, serving together a localized pumping action.7 Furthermore, if performing cadaveric dissections, Corley uncovered a continuous presence of an evident second arch either situated deep in the quadratus plantae or as component of a more complicated network that deep interconnections.6 This can represent a potential blood reservoir explaining the interindividual distinctions in venous outflow recorded throughout muscular activity.8

iii. The superficial dorsal plexus might be clinically important since it is in continuity through the superficial veins that the leg and ankle and also may be involved in varicose dilatation the the superficial veins. These veins are very superficial (limited come the fat layer), fine visible (esthetically demanding), and also contiguous with the cutaneous nerves (easily encountered during foot phlebectomies).

iv. The marginal veins and also the dorsal arch are separated indigenous the superficial dorsal plexus by a relatively strong connective fascia (corresponding to the fascia spanning the an excellent saphenous vein and the little saphenous vein everywhere the limb); thus, the superficial network of the dorsum runs separately over this veins in a unique layer (Figure 3 and also 4).4,9 The dorsal arch lies over the proximal end of the metatarsal bones and also is the origin of the marginal veins, receiving the dorsal metatarsal veins and several perforating veins. The medial marginal vein occurs from the perforator the the an initial metatarsal interspace and is contiguous with the great saphenous vein. That receives several perforators native the plantar veins the are crucial from a functional allude of view. The lateral marginal vein end in the short saphenous vein, i m sorry receives necessary perforators indigenous the deep plantar veins.

v. The perforating mechanism is the many distinctive mechanism of the foot due to the fact that these veins space valveless or save on computer valves oriented indigenous deep come superficial veins. According to Uhl et al:3

o The perforator that the first metatarsal interspace generally has a large diameter there is no valves and connects the dorsal venous arch v the deep plantar system, and as a consequence, that is the true beginning point of all venous networks in the foot. The accompanies the dorsalis pedis artery.

o The medial marginal perforators, i m sorry open into the medial marginal vein, differentiate into plantar veins (ie, malleolar, navicular, and cuneiform veins) and dorsal veins (ie, anterior tibial vein).
Figure 3. Marginal veins and also their superficial network.The marginal veins, linked anteriorly through the anterior archvein (Panel A), room the beginning of the two saphenous veins, andare an in similar way situated under the superficial fascia. The superficialnetwork of the dorsum the the foot is in continuity with thesuperficial network of the anterior leg (Panel B).



o Consistently, the lateral marginal perforators—the calcaneal and also cuboidal veins—join the lateral marginal vein at the perimalleolar plexus. Venomuscular Pumps

The power needed for venous blood to get rid of the hydrostatic pressure, which is produced by the distance between the heart and the leg in standing subjects in a dynamic state, is developed by multiple myofascial compartments that are different yet integrated, act choose muscle pump units,10 and are recognized as the venomuscular pumps (VMP). The ingredient of VMPs contains the following11: (i) the venous foot pump; (ii) the distal and also proximal calf pumps; (iii) the thigh pump; and (iv) the abdominal muscle pump. The contraction and relaxation of the bones muscles neighboring the veins impress volume and pressure variations to the venous blood, if the flow direction is conditioned through the valvular arrangements.11

The position of each deep venous valvular street will recognize the pump output. A tract situated inside the muscle creates an extremely effective ejection systems (gastrocnemius, soleus).12 at the soleus and gastrocnemius sites, the veins room numerous and arranged in a spiral shape as result of the longitudinal excursion amplitude the the muscles in between contraction and also relaxation (volumetric pump). Extramuscular tracts are subjected come compression over hard surfaces, ie, bone or aponeuroses, by the close muscles; therefore, they have a lower, despite still satisfactory, effectiveness (distal calf pump or peristaltic pump). This is the situation for the posterior deep compartment veins (posterior tibial veins and peroneal veins) and the anterior external compartment veins (anterior tibial veins), which have a rectilinear organization, together the containing muscles lean versus the bones and have a minimal shortening throughout contraction.12

The superficial venous network is only indirectly affected by the VMPs v aspiration during muscle be sure or diastole; over there is an exception for the venous foot pump where the superficial veins may be directly filled, i m sorry is in contrast with the deep veins.

Proximal calf muscle pumpThe most active pump the the lower limb is the one due to the sural and gastrocnemius muscles: this muscles space rich in venous sinuses that space strongly squeezed during the impulse phase of the step, when pressure exceeds 200 mm Hg and also calf volume decreases by 80%.2

When the calf muscles contract, the pressure rises in all veins the the reduced limb, and also the boost is 3 times better in muscle than in superficial veins. Throughout muscle convulsion (systole), the solid pressure gradient in between the deep calf veins and the popliteal vein reasons a fast efflux that blood indigenous the calf come the thigh (Figure 5). Venous pressure exceeds the intramuscular pressure in calf compartments in many of the action phases, however competent venous valves avoid retrograde flow. On subsequent muscle be sure (diastole), venous pressure falls listed below the press at rest. The fall is higher in the deep veins, much less in the superficial veins, and also negligible in the popliteal vein. In this phase, perforator veins permit blood to flow from the superficial come the deep veins, while proficient valves avoid backflow indigenous the popliteal to the deep calf veins.3
Figure 5. Mechanism of action for the distal calf pump.Panel A. Muscle (M) are unsheathed by common fascia (F)and veins in ~ the exact same compartment. Contraction of the calfmuscles, together in plantar flexion the the fish eye joint during walking(bottom), expels blood into the proximal collecting vein. Duringrelaxation (top), the blood is drained indigenous the superficial veins(SV) right into the deep veins (DV) in addition to the arterial inflow;thereby, preparing for the succeeding ejection. V, venous valve.Panel B. Distal calf pump: ~ above dorsiflexion the the fish eye (passiveor active), the bulk of the calf muscle (M) descends within thefascial sheath (F) and also expels blood in the distal veins favor apiston. Dashboard C. The venous foot pump: upon load bearing,the tarso-metatarsal joints space extended and also the tarsal arch isflattened. Thus, the veins are stretched, bring about them to ejecttheir content of blood.Image courtesy that E. Stranden.


Distal calf “piston” pumpIn contrast with standard descriptions, there room two pumping equipment in the calf, a proximal (gastrocnemius/ soleus) and a distal system.4 The distal one is activated by dorsiflexion the the fishing eye (Figure 5), ie, as soon as the calf muscles space stretched and also their distal parts descend in ~ the fascial sheath. This activity acts like a piston, which expels venous blood in a proximal direction. The pump mechanism has been documented by ultrasound Doppler measurements of venous blood flow4 and also is supported by compartment press measurements.5

Venous foot pumpAccording to browse et al,13 the pressure required to conquer the press of the blood column within the venous mechanism of the lower legs over that created within the muscular compartments the the calf during motion. Because that Gardner and Fox,14 the plantar venous plexus can overcome this pressure. Located within the plantar surface ar of the foot, the plantar venous plexus is submitted to high-pressure compression during ambulation, possibly constituting a system for driving the venous outflow native the leg (Figure 6).15 throughout the gait process, the plantar plexus is may be to overcome the press of the blood column within the deep venous system of the calf.16 that squeezes a small volume (20 come 30 mL),17 but the pumping device is an extremely effective; it functions by voiding chambers distal to their axis and without a proximal valve, however closed distally in a cul-de-sac formation (C. Franceschi, unpublished data).

The venous foot pump, in fact, is activated by the compression led to by either body load or plantar muscle contractions during each step. According to the anatomical disposition, the website of the pump might be figured out in the lateral plantar veins, whose middle portion is dilated and acts together a reservoir v a volume the 20 to 30 mL (Figure 6).3,17 The ratio of the diameter that the lateral plantar veins when compared with the diameter that the posterior tibial veins is 1.91:1, which creates a bellows type effect to rapidly increase the velocity of circulation within the posterior tibial veins.15 The distal component of the pump is a sort of “suction pole” coming from the extremely vascularized toes and the large metatarsal perforator vein that drains the superficial network of the medial marginal vein.3 The posterior part, in ~ the calcaneal confluent, corresponds to one “ejection pole,” i m sorry empties directly into the posterior tibial veins.3

During a walking exercise, the foot is in contact with the floor 60% of the time and also remains turn off the floor 40% that the time.18 The foot style is draft so the weight bearing takes place almost entirely on the sphere of the foot, the heel, and also the lateral component of the plantar surface of the foot. The medial part remains press free; thus, the plantar veins, i beg your pardon are located here, are safeguarded from straight pressure, except in subjects with flat feet.18

The pumping mechanism has been explained as follows. The plantar veins are associated like a bowstring between the basic of the fourth metatarsal and also the medial malleolus. Upon load bearing, the tarso-metatarsal joints are extended and the tarsal arch is flattened. Thus, stretching provides the veins eject their contents of blood. Successively, upon heel strike, weight bearing top top the forefoot with dorsiflexion the the toes renders the muscle of the sole contract, resulting in compression the the pump in the musculotendinous airplane (Figure 7).19 over there is no difference between the venous volume elicited by weight bearing and by toe curls.8 it is still no clear why both of these mechanisms produce the same effect or which system is dominant; however, this two different venous foot pumps would be energetic at slightly various points in the step of the gait cycle and both space likely active during the stance phase.6 probably the muscle convulsion pump is a memory of the preplantigrade phase in ontogenesis (ie, suspended or immersed life) in the lack of plantar support. Finally, in the suspension phase, pump pour it until it is full is allowed.

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Figure 7. Anatomical structure of the foot pump.Abbreviations. 1, posterior tibial veins; 2, anterior tibial veins; 3, greatsaphenous vein; 4, short saphenous vein; 5, malleolar perforator vein; 6,navicular vein; 7, picture writing perforator vein; 8, perforator vein of the firstmetatarsal interspace; 9, dorsal perforator vein; 10, calcaneal perforatorvein; 11, dorsal vein that the hallux; 12, intermetatarsal vein; 13, medialmarginal vein; 14, lateral marginal vein; A, suction pole; R, human body of thepump or reservoir; C, ejection pole in ~ the calcaneal confluent.Image courtesy of C. Gillot.


During regular walking, the three vein-pumping solution (foot, proximal calf, and also distal calf pumps) space synchronized to type a complete network both in series and in parallel, which encourage venous return. Also moderate muscular motions of the legs, while in a sit position, might activate the pump mechanism, and significantly reduce mean distal vein pressure.20

Although synchronized through the calf pumps, the outflow indigenous the foot plexus is live independence of the proximal calf muscle contraction. This is feasible because the proximal calf pump and the venous foot pump work-related “in parallel,” ie, voiding your volumes individually into the main duct (popliteal vein) and not “in series,” ie, emptying in the same longitudinal duct in succession. This arrangement enables for one independent behavior of the two more powerful pumps.

Venous foot pump voidingConsidering the three key deep veins of the leg, (ie, anterior, posterior, and peroneal veins, which room all doubled, with frequent interduplication connections), during venous foot pump task (weight bearing and flexion the the first toe) the prevalent flow is directed into the posterior tibial veins.14,15 The posterior tibial vein is doubled v a depths vein the is parallel to a much more superficial vein. The an ext superficial vein originates native the medial plantar vein, vice versa, the deeper vein originates indigenous the lateral plantar vein.21

The peroneal vein is doubled and also drains the lateral facet of the foot surrounding the calcaneal confluent and the ankle, pass upward and posteriorly with the calf, and also passing posteriorly and also medially to the fibula.21 The peroneal veins might receive the soleus veins at midcalf, creating an elevation pump.

The anterior tibial vein is doubled and drains the blood indigenous the dorsum that the foot starting from the perforator the the first metatarsal interspace and running up the anterior compartment, lateral come the tibia, and also close come the interosseous membrane the connects the tibia and fibula. At the knee, the junction that the tibia and fibula, the vessels pass through the interosseous membrane and enter the posterior compartment of the leg. Just below the knee, the 4 anterior and also posterior tibial veins join with the two peroneal veins to become the large popliteal vein.21

Video phlebography investigations confirmed that the preferential outflow the the pump is the posterior tibial vein, i m sorry is in straight continuity through the venous foot pump.10 The peroneal and also anterior tibial veins re-publishing the same different outflow routes as the saphenous vein (through the malleolar perforators).

Mechanical compression the the plantar venous plexus created a typical peak velocity that 123±71 cm/sec in the posterior tibial veins, 29±26 cm/sec in the peroneal veins, and 24±14 cm/sec in the anterior tibial veins.15

Consequently, every volumetric pump is anatomically elevation (although through multiple connections) and connected in parallel through the last formation the the popliteal vein. However, the venous foot pump has actually a supplementary way of emptying through the saphenous vein, maybe by being fed from the medial marginal vein (ie, the dorsal perforator that communicates v the anterior tibial vein) and also the malleolar perforator vein, i m sorry is associated to the calcaneal confluent.3

This occasion is indirect demonstrated through the studies of Stranden et al the showed better ambulatory pressure reduction in the dorsal foot vein (behaving choose deep foot veins) 보다 in the saphenous vein of the calf (mean, 25 mm Hg) during exercise,22 saying that a part of the ejected volume walk via the good saphenous vein. In another more recent research by Neglén and also Raju, the drop in venous pressure in the dorsal foot is substantially more marked compared v both the popliteal vein and good saphenous vein at every levels (Figure 8).23 The recovery time is substantially increased in the lengthy saphenous vein compared with the deep vein, and also it is then further lengthy in the dorsal foot vein, proving that the 3 veins hydraulically law as different compartments. As the measurements are do distally to the calf pump, this suggests that the venous foot pump is the “engine” of the distal blood return. This may define why signs and symptoms the chronic venous insufficiency take place with regular ambulatory venous pressure in the dorsal foot. The channel through the reduced gradient will certainly be favored in any kind of occasion, depending on the muscular activity, temperature, position, overflow, and/or obstruction.

GaitAt the beginning of a step, the distal calf pump is activated. This procedure is initiated by dorsiflexion that the foot together the foot is lifted to take a step. The anterior compartment muscle contract, dorsiflect the foot, and also empty its veins (ie, the anterior tibial veins). Dorsiflexion passively follow me the Achilles tendon and also empties blood from the lower portions the the peroneal and also posterior tibial veins. Together the foot strikes the ground, weight bearing activates the 2nd phase: the above-described venous foot pumps. Plantar flexion initiates the third phase as the foot come up ~ above its toes: the muscle of the posterior compartments, an especially the gastrocnemius and also soleus muscles, contract, and then north the proximal venous reservoir. Plantar flexion likewise tenses and shortens the Achilles tendon, i m sorry maintains push on the distal section of the calf muscle pump.14