Partial Toe Transfer
A partial toe transfer permits a one-stage reconstruction of complex losses of a digit, including distal defects and inter-positional defects, in an unprecedented way as compared with any nonmicrovascular method. The main drawback that limits its widespread usage is that it requires familiarity with vessel handling in the ultramicrosurgery (0.5 mm or less) range. In this article, the discussion is limited to pulp, neurocutaneous, and osteocutaneous flaps of the fingers and thumb. The reader should be warned, however, that depending on the defect, the components of the toe can be modified accordingly to an infinite number of variations.
Hemipulp toe flaps are indicated for major losses of the pulp of the radial part of the index, the ulnar part of the little finger, and the thumb.1
Neurocutaneous flaps from the tibial side of the second toe are specially indicated for restoring the sensibility in the index, little finger, and thumb when a compound neurocutaneous defect exists.2
This neurocutaneous flap can be used to treat painful digital neuromas in any digit when the bed is scarred due to multiple surgeries or initial trauma. The flap allows radical excision of the devascularized tissue and a tensionless nerve repair with a vascularized nerve.2
Flow-through flaps taken from the second toe are similar to the neurocutaneous flap but the nerve does not need to be included. The prime indication is to restore blood supply and cover to the finger even in chronic cases.3
A vascularized toe phalanx4 is ideal for reconstruction of complex osseous defects where vascularized bone is crucial, such as in infected beds or recalcitrant nonunions in phalanges. It also allows for single-stage complex reconstructions carrying specialized tissue, such as vascularized cartilage, with minimal donor-site morbidity ( Fig. 49.1a–c ).
Hemipulp or neurocutaneous flaps are not indicated in the central digits or in areas where sensibility is not crucial. For those defects, simpler methods are preferred.
Peripheral vascular disease is a relative contraindication.
Massive hand trauma and avulsion mechanisms increase the level of difficulty and may require the use of vein grafts.
In partial toe transfer, familiarity with surgery on very small vessels is a must. Anastomoses of arteries in the range of 0.5 mm (or even less) are the norm, if one wants to keep dissection in the foot to a minimum.
Planning is essential, more so the more structures the flap contains. Even in the simplest forms, such as a hemipulp or a neurocutaneous flap, dangerous crisscrossing between the vein, the artery, and the nerve will occur if the wrong toe side flap is harvested ( Fig. 49.2a,b ). In the case of the much more complex osteocutaneous or osteoneurocutaneous flaps, poor planning may make flap adaptation into the bed impossible.
At the time of locating a recipient artery, Doppler is often misleading, as the presence of a signal does not necessarily mean that the vessel is appropriate for anastomosis, either in the foot or in the hand. For the same reason, angiography is of no help.
Recipient arteries in the midst of scar tissue, even if patent, are inappropriate for anastomosis: they are very fragile, they break easily, and the intima delaminates into the lumen. At best, anastomosing scarred digital arteries will cause unremitting spasm despite a well-executed anastomosis.
Vein anastomoses are usually performed at the level of the web or base of the finger. The veins at those locations are of a size large enough for comfortable anastomosis and are surrounded by healthy fat.
When a toe phalanx is to be transferred, preoperative X-ray studies are mandatory, as considerable variation in the middle phalanx length exists ( Fig. 49.3 ). This was of more importance in the early days, when most toes were pedicled on the dorsal vessels and more specifically the dorsalis pedis artery. Such large pedicles are not used anymore. Partial toe transfers are usually based on a digital artery or at most in a short stump of a neighbor first plantar or dorsal metatarsal artery (whichever is the dominant vessel). This speeds up the dissection and limits the morbidity on the foot.
Distal dissection has, however, its own set of problems regarding the vessels. The artery does have anatomical variations, and it is not uncommon to have a dominant dorsal branch that curves palmar ( Fig. 49.4 ).
Drainage is in general via the dorsal veins. A dorsaltibial cutaneous flap is recommended when a phalanx is to be harvested, to protect the vessels and include the veins that drain the bone.
In some cases, particularly in the setting of hemipulp transfer of the second toe, the volar system of veins has to be relied upon. Veins at the distal toe level are very fragile in any case, but utmost care should be taken when dealing with the volar system ( Fig. 49.5 ).
The dorsal and plantar metatarsal arteries of the first web supply the hallux and the second toe competitively; that is, when the plantar metatarsal artery is large, the dorsal metatarsal is small, and vice versa.