Venous Flaps

Abstract

Venous flaps—cutaneous free flaps raised on a venous plexus alone—are a unique subset of free flaps, which have specific characteristics ideally suiting them to reconstruction of the upper limb and, in particular, the hand and digits.

1 Introduction

Venous flaps—cutaneous free flaps raised on a venous plexus alone—are a unique subset of free flaps, which have specific characteristics ideally suiting them to reconstruction of the upper limb and, in particular, the hand and digits.

The technique was originally described in animal models by Nakayama [1] and subsequently translated into clinical practice for reconstruction of skin defects in digital replantation [2, 3]. The early flaps in humans were based solely on venous inflow, through the venous flap, with blood then returned to the venous system as a true “flow-through” flap. Anastomosis of an artery to the inflow of the venous flap has been used to enhance oxygen delivery to the transposed tissue, to increase the size and versatility of these flaps [4]. As such, venous flaps can be classified according to both their recipient inflow and outflow:

• V-V-V (vein-to-vein-to-vein). Venous inflow passes through the veins of the flap into an outflow vein as a true flow-through flap. This is most commonly useful on the dorsum of the hand where recipient veins are readily accessible and metabolic demands are relatively low.

• A-V-A (artery-to-vein-to-artery). As another flow-through flap, arterial inflow passes into the flap and is drained back into a distal artery. This technique is particularly useful in reconstructing a segmental arterial defect, thus perfusing both flap and tissue beyond, in addition to providing soft tissue cover, as may be required in complex digital revascularization.

• A-V-V (artery-to-vein-to-vein). Arterialized venous flaps are more similar to conventional free flaps, where the flap is designed in such a way as to restore vascular anatomy approximating a normal artery-to-venous system through a capillary bed. They are a useful option where reconstruction of the artery in continuity is not required for distal digital reperfusion, such as at the fingertip or elsewhere on the hand. The authors recommend the use of arterialized, as opposed to flow-through, flaps wherever possible, given the flap survival benefits of restoring a capillary bed.

2 Anatomy

Venous flaps are not defined by an anatomical donor site, but rather are united by the absence of an anatomical arterial-capillary-venous flow pattern. The flap can be raised on any subcutaneous venous network where an inflow and outflow vein can be selected and where the network is closely associated with the overlying skin; this is most commonly the dorsum of the foot, the volar forearm, and the medial leg.

The physiological mechanism for survival of these flaps is debated. It is certainly true that non-arterialized venous flaps will be required to survive on a lower PaO₂ than is normal and that for such flaps in particular, neovascularization is likely to be key to their long-term survival. The low PaO₂ may indeed be a significant driver in neovascularization. Even in the case of arterialized venous flaps, flow studies have shown that where blood flow passes through the flap in a straightforward anterograde manner (i.e., in the natural direction of flow-through venous valves), the peripheral flap is largely bypassed. A solution to this problem of shunting has been to divert the flow around the flap in a retrograde manner [5], so that resistance provided by the valves pushes blood out to the peripheries. More recently, this has been superseded by in-flap ligation of vessels, known as shunt restriction, to encourage one vessel to act as an afferent “artery” and one as an efferent “vein,” rather than relying on one vein to do both and thus forcing blood into the peripheries of the flap [6]. This technique drives blood through a capillary system between the main afferent and efferent vessels and significantly improves the survival of these flaps.

3 Preoperative Investigation

The venous flap donor site is usually planned to be readily expendable, and as such no specific preoperative investigation is required beyond standard preoperative planning for any microsurgical procedure. As these flaps are usually very thin, the superficial venous plexus can be easily assessed clinically, and indeed this is the most appropriate way to design the flap accurately. Handheld vein visualization devices may have a role when superficial veins are hard to see.

4 Flap Design and Markings

• 1. The venous networks of the volar forearm and dorsal foot make excellent donors for venous flaps (Fig. 30.1).

• 2. Numerous tributaries to the basilic and cephalic veins of the forearm are readily identified under the pliable skin of the volar forearm; compression of the forearm or upper arm may improve their visibility (Fig. 30.2).

• 3. The defect can be templated and superimposed over visible veins, with a note made of the position of the recipient artery and veins (Fig. 30.3).

• 4. The inflow vessel needs to be positioned in the flap to allow for anastomosis to the recipient vessel.

• 5. For an arterialized flow-through flap (A-V-A), a suitable vein should be selected to act as the inflow to the flap, paying attention to ensure an anterograde direction of flow. The vessel should run through the flap and then anastomosed to a distal artery in the defect.

• 6. For an arterialized venous flap (A-V-V), the inflow artery should enter the flap, ideally centrally, and run only for a short distance in the flap before being terminated by ligation or distally anastomosed to an outflow artery if an arterial defect needs to be bridged. The authors suggest that approximately one quarter to one third, but certainly less than half, of the surface of the flap overlies the arterialized vein, with the rest of the flap dedicated to outflow vein(s) (Fig. 30.4).

• 7. Outflow veins must also be selected in an appropriate position for anastomosis to the outflow recipient vessels (Fig. 30.5).

• 8. In arterialized venous flaps, in-flap ligations should be planned to be prevent all large connections between inflow and outflow vessels; this shunt restriction recreates a capillary bed and reduces the problem of direct shunt between the inflow and outflow systems.

• 9. The flap design can be adjusted to fit a wide range of defects. Design features such as concatenation of two skin paddles (to resurface adjacent digits), or the inclusion of additional structures such as the tendon of the palmaris longus, allow reconstruction of complex defects (Fig. 30.6).

• 10. The donor venous plexus must fit with the recipient vessels, and if it does not, then a different donor site must be explored.

Fig. 30.1

The venous plexus comprising tributaries to the cephalic and basilic veins of the forearm

Fig. 30.2

Manual compression of the forearm distends the veins and makes them easily visible for flap planning

Fig. 30.3

The defect can be templated and superimposed over the venous network for flap design

Fig. 30.4

(a, b) The arterialized inflow to the flap should be ideally positioned centrally, and terminated by ligation after running for a short distance within the flap (marked in red)

Fig. 30.5

(a, b) The outflow veins (marked in blue) are positioned to match the position of recipient veins. [Alternative Figure—The outflow venous network (highlighted) is positioned to match the position of the recipient veins.]

Fig. 30.6

Tendon (highlighted), such as palmaris longus, can be included within the flap for reconstruction of composite defects

5 Flap Raise/Elevation: A Step-by-Step Guide

• 1. Design

  In venous flaps, design is a critical phase. The inflow and outflow vessels must be carefully selected to match up to the intended recipient vessels (Fig. 30.7).

• 2. Tourniquet inflation

  Inflate an upper arm tourniquet.

• 3. Ulnar skin incision

  Begin on the ulnar border of the flap, closest to the operating surgeon. Incise carefully just through the dermis as the veins are very superficial and can easily be damaged. Once the veins are identified, they can be followed away from the flap to obtain an adequate pedicle length, usually up to 2 cm, and then ligated and divided (Fig. 30.8).

• 4. Radial skin incision

  Repeat the process for the radial border of the flap, again taking care not to injure the superficial venous network. Preserve some length even on veins that have not been identified for anastomosis as backup vessels (Fig. 30.9).

• 5. Complete sub-flap dissection

  Once the vessels have been dissected and ligated circumferentially around the flap, the flap can be raised relatively easily, by simply freeing it from the underlying forearm fascia with sharp dissection (Fig. 30.10).

• 6. Raise completed

  The flap is ready for inset after performing in-flap ligation on the underside using microvascular ligation clips or suture ties. Here the flap has been raised with paratenon and tendon for vascularized tendon reconstruction (Fig. 30.11).

• 7. Donor site closure

  The donor site can usually be primarily closed if the width of the flap is less than 2.5 centimeters using an absorbable monofilament suture. If a larger flap is raised or the skin closure is very tight, a full-thickness skin graft from the medial upper arm or a split-thickness skin graft is required (Fig. 30.12).

Fig. 30.7

The flap design completed, prior to raising

Fig. 30.8

The veins are very superficial and easily injured

Fig. 30.9

Circumferential incision is completed with all veins having been identified

Fig. 30.10

Sharp dissection is used to raise the flap from the underlying forearm fascia

Fig. 30.11

The flap is raised, here including a vascularized section of tendon

Fig. 30.12

The donor site is closed primarily using an absorbable monofilament suture

6 Core Surgical Techniques in Flap Dissection

• 1. Tourniquet

  An upper arm tourniquet is inflated to 250 mmHg, and exsanguination is by arm elevation and gentle manual compression only, so that the veins remain partly filled.

• 2. Vessel Dissection

  Sharp dissection using a 15 blade is preferred, with dissection along the vessels using the blade, fine tenotomy scissors, or microsurgery scissors. The first incision should be only just through the dermis until the veins are identified as the vessels may be immediately subdermal.

• 3. Sub-Flap Dissection

  Dissection just above the fascia of the forearm is a clear and safe plane, in which the flap can be readily raised. If required, tendon can be raised within its paratenon, in continuity with the skin component of the flap, for reconstruction of segmental tendon defects (see Case 1).

• 4. In-Flap Ligation

  Shunt restriction substantially improves the intra-flap blood flow. Ligation of shunting vessels using microvascular ligation clips or suture ties is strongly advised in arterialized venous flaps. This is performed on the underside of the flap after it has been raised, according to pre-planned design of the intended vascular pattern.

• 5. Hemostasis

  All free ends of the venous plexus must either be anastomosed to recipient vessels or ligated, and this should be checked before final inset as otherwise a hematoma may result once the vasospasm settles fully after inset is completed.

7 Clinical Scenario: Surgeon Jamil Moledina

A 45-year-old man presented to the emergency department following an injury with an electric router while working. Assessment revealed a complex, grossly contaminated wound to the dorsum of the left thumb, spanning from the head of the first metacarpal to the base of the distal phalanx. The dorsal cortex of the proximal phalanx and EPL from Zones 1 to 3 was lost with the overlying skin. The IPJ and MCPJ were exposed with loss of their ulnar collateral ligaments. The wound was thoroughly debrided surgically, and a venous flap from the contralateral forearm raised with a section of flexor tendon to simultaneously reconstruct tendon and skin (Figs. 30.13, 30.14, 30.15, 30.16, 30.17, 30.18, and 30.19).

Fig. 30.13

The complex wound to the thumb, caused by an electric router

Fig. 30.14

The surgically debrided wound with open interphalangeal- and metacarpophalangeal joints, ulnar collateral ligaments, unicortical injuries to the metacarpal and proximal phalanx, and loss of skin and extensor pollicis longus

Fig. 30.15

The flap during inset; the microvascular anastomoses have been completed and the flap is perfused

Fig. 30.16

The flap during inset; the vascularized tendon has been interposed

Fig. 30.17

The flap immediately postoperatively

Fig. 30.18

The flap result at 3 months

Fig. 30.19

Demonstration of thumb opposition

8 Pearls and Pitfalls

Pearls

• Use multiple outflow veins (at least two), ideally each with separate flow pathways.

• Ensure no more than a quarter to a third of the flap area is directly supplied by the arterialized vessel.

• Plan all flow anterograde to avoid potential complications with venous valves.

• Perform shunt-restricting ligations before reperfusing flap.

• Perform all anastomoses before releasing clamps and allowing inflow to the flap.

Pitfalls

• Hematoma. Ensure all open or reserved vessels are anastomosed or ligated before inset to reduce the risk of postoperative bleeding.

• Damage to vessels. Veins are thin walled and very superficial, so take extreme care when incising the skin.

• Redundancy of arterialized vein. The donor vessel will expand substantially after anastomosis when the pressure increases. Trim the vessel to an appropriate length or allow a gentle curve without kinking.

• Incorrect pedicle length. Plan the position of the recipient and donor veins carefully before raising the flap, to ensure the pedicles are appropriately placed.

• Incorrect skin paddle size. Allow for substantial postoperative swelling of flap by taking this into account in skin paddle design.

9 Selected Readings

• Nakayama Y, Soeda S, Kasai Y. Flaps nourished by arterial inflow through the venous system: an experimental investigation. Plast Reconstr Surg. 1981;67 (3):328–334.

  This paper is an early description of the arterialized venous flap, in rat models, to prove the concept of arteriovenous anastomosis in free flap survival. Comparison between types of flaps, initially pedicled with supporting microvascular anastomoses and later islanded on just microvascular anastomoses, demonstrated good flap survival, compared to composite grafts which predictably fully necrosed.

• Lin, YT, Henry SL, Lin CH, Lee HY, Lin WN, Lin CH, Wei FC. The Shunt-Restricted Arterialized Venous Flap for Hand/Digit Reconstruction: Enhanced Perfusion, Decreased Congestion, and Improved Reliability. The Journal of Trauma: Injury, Infection, and Critical Care 2010;69 (2), 399–404.

  This work provides a comprehensive description of a core principle in venous flaps – shunt restriction. The techniques of restriction are described in terms of four vascular arrangements, and the subsequent improvement in peripheral perfusion of the flaps, as well as reduced venous congestion, as demonstrated by laser Doppler flowmetry.

• Inoue G, Maeda N, Suzuki K. Resurfacing of skin defects of the hand using the arterialised venous flap. Br J Plast Surg 1990;43: 135–139.

  Inoue provides a good description of indications for the use of the venous flap in the hand in a case series of 22 patients. Of these, 12 were reconstructed in an A-V-A manner, and 10 in an A-V-V manner. Many flaps covered bone or tendon and as such provided good evidence of their vascularized nature. They report an overall survival of 95%.

• Woo SH, Kim KC, Lee GJ, Ha SH, Kim KH, Dhawan V, Lee KS. A retrospective analysis of 154 arterialised venous flaps for hand reconstruction: an 11 year experience. PRS 2007;119 (6):1823–1838.

  This paper showcases a wide range of applications of venous free flaps in a large retrospective case series. Interesting modifications are also presented, including simultaneous cover of adjacent digits, the use of vascularized tendon, and innervated flaps. They report flaps as large as 14x9cm in the hand, with complete survival.

• Brooks D, Buntic RF, Taylor C. Use of the venous free flap for salvage of difficult ring avulsion injuries. Microsurgery 2008;28:397–402.

  A typical indication for A-V-A venous flaps is in ring avulsion injuries, where the venous flap is used to both reconstruct segmental arterial injury and soft tissue. Here Brooks presents eight cases, reporting good, supple skin quality and good range of movement in the reconstructed digits.