Technique of Toe Transfer in Congenital Malformations

The current trend in the reconstruction of congenital malformations of the thumb and the digits is to operate early prior to completion of the first year of age. There are two major difficulties both at the hand and the foot level, the tedious dissection of the miniature anatomic structures into the rich subcutaneous fat and a constant risk of a spasm which is difficult to manage in the babies. Prevention of spasm goes through careful central monitoring of core body temperature and slight elevation of this temperature around 38° C during the operation with a warming blanket.

We favor a single team sequential approach to both recipient and donor sites, to ensure that the length of all anatomical structures is appropriate and matches for transfer without vein or nerve grafts. This has also been proven practical and time saving. Contrary to our technique in traumatic cases, in congenital malformations with hypoplasia, we begin with dissection on the recipient hand site due to frequent anatomical variations.

The surgical approach to the hand varies according to the type of malformation and the site of the transfer. In congenital band syndrome all structures are present and normal as with traumatic amputations; in hypoplastic hands, like symbrachydactyly, a number of anatomical variations may be present. The flexor tendons are usually found attached to the extensor at the distal part of the metac-arpal bones. Flexor tendons tend to form a mass, and it is necessary to dissect all the mass and cut their distal insertion to provide some course of motion. The median nerve is frequently absent and compensated by larger dorsal nerve branches (radial and ulnar); they are frequently used as recipient nerves but some palmar branches of the ulnar nerve could also be used. The ulnar or the radial artery are approached through a zig-zag incision to allow closure in a V-Y fashion to decrease vessel compression. This facilitates also the dissection of a dorsal vein. In cases where no veins are found near the artery, a transverse incision is performed dorsally at the wrist crease level to locate a dorsal vein. When the preparation of the hand has been completed, the length for each anatomical structure and most importantly that of the neurovascular bundle is marked and the tourniquet is deflated prior to moving to the donor foot level.

In a previous review of our patients11,16 we have found that there was no postoperative vascular crisis when more than one artery was nourishing the transferred toe. With this experience, we always try to dissect all available arteries of sufficient diameter. This is possible only through a unique dorsal approach to avoid a tedious dissection in the plantar fat.7 First the great saphenous vein is prepared, trying to save as many draining veins as possible. Then the dorsalis pedis artery is easily found, by lifting the extensor hallucis brevis. Proceeding distally the first dorsal metatarsal artery is dissected always running on the dorsum of the intermetatarsal ligament. When present it is immediately dissected from distal to proximal as it frequently passes through some part of the inter-osseous muscle.19 In the preparation of the second toe an early proximal osteotomy of the second metatarsal bone allows easy dissection of all anatomical plantar structures of the first and second space. This maneuver also facilitates foot closure at the end of the procedure. The plantar artery of the second space, an artery which has been overlooked in the literature, has proved to be constant in our experience and of good diameter.7 Frequently, the two arteries of the first space and the plantar artery of the second are dissected in continuity with

the dorsalis pedis, the proximal communicant artery and the plantar arch. A long segment of plantar nerves and flexor tendons could also be procured into the transfer.

When the toe is completely dissected and remains on its vessels, reperfusion is allowed for sufficient length of time prior to the transfer to avoid ischemic damage. This time is used to assess precisely the length of the different structures and to definitively select the exact recipient levels. If the metatarsophalangeal joint is incorporated into the transfer, a palmar tilt of more than 40° is mandatory to provide a functional range of motion ( in a joint working mainly in hyper-extension ); this is provided through an oblique cut of the metatarsal neck, protecting the growth plate. The order of repair is classical but could vary from case to case. After bone stabilization (usually with 0.6 K-wire) and periosteal suture, extensor and when possible intrinsic muscle repair is performed. The flexor tendon(s) are then sutured, usually by a "fish mouth" technique (trying to avoid repairing of the superficialis and profundus tendons a the same level). Nerve sutures are generally the next step, followed by distal skin suture to facilitate a good adjustment of the vessel length. The last step is the anastomosis of the artery and vein. Usually a "long" transplantation29 is performed using the radial artery for the thumb or the ulnar artery for long finger reconstruction. Sometimes the segment of dorsalis pedis in continuity with the plantar arch could be interposed in the recipient artery as a "T" graft, with two end-to-end sutures allowing to reconstruct the recipient vessel and maintain a physiological flow in the toe.8 The long saphenous vein is sutured to a recipient vein at the wrist level through a short dorsal transverse incision to decrease scarring on the dorsal aspect of the hand.

Then the tourniquet is released and during revascularization of the hand, the foot is closed with intermetatarsal ligament repair and skin suture.

The dressing has to be carefully performed to allow skin monitoring but to avoid slipping from the cast. In our practice no special postoperative regimen is used; a simple "Chinese" lamp (an ordinary light bulb) allows warming up the transplantation and enhances its capillary refilling. In case of an uneventful course the dressing is not disturbed until three to four weeks. Splinting to improve passive range of motion is begun at seven weeks. No formal program of rehabilitation is recommended, but exercises are encouraged sometimes with bandaging of the opposite nonoperated hand.

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