Anatomy and blood supply

The radial forearm flap is a fasciocutaneous flap that is supplied by multiple, vertically directed septocutaneous perforating vessels arising along the entire course of the radial artery, which run within the radial intermuscular septum. Proximally the radial artery courses between the supinator muscle and the fibrous origin of the flexor digitorum super-ficialis muscle. In the medial third of the forearm, the artery runs between the pronator teres and brachioradialis muscles, and further distally anterior to the flexor pollicis longus muscle. At the wrist, the artery may be palpated between the radius and the tendon of the flexor carpi radialis muscle. From there, the superficial palmar branch passes anteriorly or through the thenar muscles to join the superficial branch of the ulnar artery forming the superficial palmar arch. At the snuff box, the first dorsal metacarpal artery gives off the princeps pollicis artery to the thumb and terminates in the deep palmar arch. The venous drainage is provided by the basilic and cephalic vein, respectively (superficial system), and by paired concomitant veins (deep venous system) that travel with the arteries and terminate in the cubital vein.

Indication and landmarks

For tissue defects of the upper extremity, the radial forearm flap having a long, wide and reliable pedicle is a very good option. It may be used in different compositions of tissues including fascia, tendons, nerve, and bone. It may also be used as a flow-through flap (eg, defect coverage proximally and revascularization of the fingers distally) or a sensitive flap, including the antebrachial cutaneous nerve [37]. The distally based pedicled radial forearm flap with retrograde flow is versatile and suitable for reconstructions of the hand, the fingers and the forearm. With a proximally based pedicle and antegrade blood flow the radial forearm flap is usually used for reconstructions around the elbow ( Fig 10.5-1a–b ). It has been challenged by pedicled perforator flaps (chapter 10.4), other fasciocutaneous or free muscle flaps. When planning a radial forearm flap, the patency of the ulnar artery with sufficient blood supply to all fingers must be assessed by the Allen test. This test is used to check the collateral circulation of the hand by alternating evaluation of the patency of the radial and ulnar arteries. It involves the following:

1. 
   

   The patient is asked to make a fist for ~ 30 seconds with the hand elevated.

   
   
2. 
   

   Pressure is applied in order to temporarily occlude both the radial land ulnar arteries.

   
   
3. 
   

   The elevated hand is opened and should appear blanched (pallor can be observed at the fingernails).

   
   
4. 
   

   Pressure is released, and the color should return within ~ 7 seconds, demonstrating adequate recapillarization due to a patent radial/ulnar artery.

In doubtful cases (eg, after direct trauma to the arm or in elderly patients), Duplex sonography or angiography may be indicated in order to demonstrate an adequate perfusion of the palmar arches. The size and position of the skin island for the flap are chosen so that they will fit the defect. The flap usually measures 5–8 cm in width and 8–10 cm in length. Its widest extension may reach from ~ 3 cm proximal to the cubital fossa to the distal crease of the wrist (ie, 10–12 cm in width and 20–30 cm in length) ( Fig 10.5-1c ). The landmarks consist of the cubital fossa, the palmaris longus muscle and the flexor carpi radialis muscle as well as the snuff box and, if visible or palpable, the cephalic vein.

Surgical technique

Distally based pedicled flap with retrograde blood flow

After outlining the island flap on the skin, the dissection begins proximally on the ulnar margin ( Fig 10.5-1d ). The deep fascia of the forearm is included and temporarily fixed to the skin ( Fig 10.5-1e ). The incision is continued distally, identifying and exposing the radial artery and its associated veins. Dissection continues from ulnar to radial beneath the deep fascia preserving the paratenon of the flexor carpi radialis muscle as far as the ulnar aspect of the intermuscular septum. Next, the skin is incised on the radial side, again including the deep fascia, but taking care not to injure the superficial branch of the radial nerve. The brachioradialis muscle is retracted exposing the radial artery and its accompanying veins within the intermuscular septum radially ( Fig 10.5-1f ). The vascular pedicle can now be isolated as far distally as defined by the pivot point. All small periosteal and muscle branches are coagulated or clipped and transected. Proximal clamping of the vascular pedicle and releasing the tourniquet allows observing whether distal reperfusion and capillary filling of the flap′s septum and skin island and the fingers is adequate. If this is the case, the pedicle is divided proximally and the flap may now be elevated completely and transposed into the defect needing to be covered ( Fig 10.5-1g–h ). The donor site is usually covered with a split-thickness skin graft, possibly supplemented by dermal substitutes (eg, Matriderm^® or Integra^®) (chapter 10.2). If small-sized flaps are used, donor-site closure may be achieved by primary intention, possibly supplemented by a local advancement and/or a rotation flap, pedicled on the ulnar artery. The following modifications of the flap are useful:

Outcome

Most complications develop at the donor site including delayed wound healing and/or skin-graft loss with reduced function of the hand as well as hypo- or hyperesthesia along the dorsal aspect of the thumb and index (superficial branch of the radial nerve) (chapter 12.12).

Pearls and pitfalls

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  The flap is versatile in its use and one of the best flaps for the hand.

  
  
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  The flap has a wide, safe, and reliable pedicle.

  
  
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  Venous drainage may be provided by the superficial and/or deep venous system.

  
  
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  Gentle dissection of the skin island is advised in order to preserve the paratenon of the flexor tendons and thus ensure skin-graft take.

  
  
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  Careful flap elevation is recommended in order to preserve septal branches for vascularization of the skin island.

  
  
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  In situ preservation of the superficial branch of the radial nerve is advised.

  
  
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  Poor donor-site appearance may result if large skin islands are raised and the donor site is covered with a split-thickness skin graft.

Anatomy and blood supply

The distally based sural flap is a fasciocutaneous flap with retrograde blood flow based on a dense arterial network surrounding the sural nerve, which arises from the superficial sural artery and the fibular artery. The former originates either from the popliteal artery or from the sural artery [40]. After perforating the fascia that separates the two heads of the gastrocnemius muscles, the superficial sural artery follows the lesser saphenous vein and sural nerve distally to the lateral malleolus. This artery is connected to a consistent network of musculocutaneous perforators from the fibular artery. The most distal one, which may be localized about 4 cm proximal to the lateral malleolus with a handheld Doppler device, is also the most distal pivot point for the flap.

Indication and landmarks

The distally based sural flap has a wide arc of rotation that easily reaches:

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  the distal third of the lower leg (chapter 12.13) [41]

  
  
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  both malleoli

  
  
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  the posterior aspect and the weight-bearing area of the heel [42]

  
  
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  the dorsum of the foot ( Fig 10.5-2a–c ).

The skin island may be elevated anywhere along the oblique course of the sural nerve and artery within the distal two thirds of the lower leg and it is designed to fit the defect. As a rule of thumb, the size of the skin island should not exceed the muscle bellies of the gastrocnemius muscle laterally, respectively medially, and it should be centered onto the pedicle ( Fig 10.5-2d ). Landmarks are the popliteal fossa, the crease between both heads of the gastrocnemius muscle and the posterior aspect of the lateral malleolus. Sometimes the lesser saphenous vein is visible.

Surgical technique

Outcome

While the functional outcome is often good, the reported morbidity may be considerable with rates of partial flap failure of up to 27%, which mostly depends on the patency of the fibular artery. In case of peripheral artery occlusive disease, the sural artery network may be unreliable, possibly contributing to ischemic complications [43]. Fasciocutaneous flaps are more reliable than adipofascial flaps. Cosmetic outcome depends on the need of a skin graft at the donor site. Accordingly, the use of large fasciocutaneous flaps should be thoroughly discussed, especially in case of female patients.

Pearls and pitfalls

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  It is a straightforward one-stage operation without microsurgery and few technical pitfalls.

  
  
• 
  

  No major limb vessel is sacrificed.

  
  
• 
  

  Identification of the most distal musculocutaneous perforators (ie, pivot point) and the course of the pedicle is necessary using a handheld Doppler device.

  
  
• 
  

  It has a large arc of rotation.

  
  
• 
  

  A tear-drop shape of the skin island can reduce tension over the pedicle.

  
  
• 
  

  Primary closure of the donor site is required if the skin island is < 4–6 cm.

  
  
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  It is less reliable than muscle flaps of the leg.