Twisted Distal Lateral Arm Flap for Immediate Reconstruction of Thumb Avulsion Injury

INTRODUCTION

The gold standard approach to the thumb skin avulsion injuries is the immediate reconstruction using one of the available local skin flaps or using a distant inguinal flap^1–3. A valid alternative is to resort to a free flap. However, most of the free flaps are too thick for this purpose. Free dorsalis pedis flap is quite thin, but it has the drawback of rather big donor site morbidity. Similarly, the donor site defect after a free lateral arm flap harvested in a common fashion can hardly be closed without the use of a skin graft^4–5.

The authors describe a new technique of harvesting the distal lateral arm flap on a series of three patients. Our modification allows primary closure of the donor site defect with good aesthetic outcomes.

MATERIAL AND METHODS

Patients

Three patients underwent immediate thumb reconstructions using twisted lateral arm flap in our department from July 2004 to January 2014. All of the procedures were performed under general anaesthesia, within 8 hours after the injury. Intravenous antibiotics were administered. At first, the wounds were treated by thorough washout and careful debridement. The flap was harvested on the same extremity as the injured thumb.

Surgical technique

After a careful debridement of the wound, the recipient vessels are exposed on the dorsum of the hand. Usually we expose the branch of the cephalic vein with an appropriate calibre and the radial artery in the snuffbox. We use the dorsal branch of the radial nerve as the recipient nerve.

Furthermore, on the dorsolateral side of the ipsilateral forearm the long distally planned lateral arm flap is drawn along the course of the posterior antebrachial cutaneous nerve. The flap width, which can reach up to 5–6 cm, is measured so that it is possible to safely close the donor site with primary suture. The flap must be thin and long enough, i.e. 13–15 cm below the lateral epicondylus of the humerus.

The anatomic landmarks are summarized in Fig. 1.

The vascular anatomy of the pedicle is well known and defined.

The flap is designed ideally on the perforator, which is usually about 4–7 cm above the lateral epicondyle. The perforators reach the skin running into a septum between the Triceps brachii muscle and the Brachialis muscle (septum lateralisbrachii) (see Fig 1.). The pedicle of the lateral arm flap is dissected for the required length. The nervus cutaneus antebrachii posterior is harvested as a sensitive nerve of the flap.

Distally, the flap is wrapped around the thumb where it is not simply folded, as usual, but it is loosely coiled into a spiral running upwards towards the tip of the finger. The spin (helix) will be over 360 degrees. In this manner, the flap conveniently covered the defect of the thumb.

RESULTS

No infection, hematoma, partial or complete flap necrosis were observed after the procedure. All the flaps healed without complications. The handgrip was restored in all cases.

CASE SERIES

Case I

A 42-year-old patient sustained an avulsion injury of the dominant right hand thumb in a belt machine. The lesion had the typical appearance and the skin, including the nail and the distal half of the distal phalanx, was amputated at the dorsum of the hand. The remaining skeleton of the thumb was intact. Digital arteries were damaged in such an extent that replantation of the avulsed part was impossible (Fig 2). The lateral arm flap based on two distal perforators, with a maximum width of 6 cm and a length of 15 cm distally to the epicondyle, was used to reconstruct the defect and the flap was wrapped around the thumb in a spiral fashion (Fig. 3). The flap’s vessels were anastomosed in the “snuffbox”. Secondarily, the distal phalanx of the thumb was elongated using a graft from the iliac bone and subsequently the flap was reshaped on the dorsum of the hand by small liposuction. In this case the spin was of 720 degrees. The aesthetic outcome and the handgrip after the reconstruction were optimal (Fig. 4). Two sessions of complementary flap liposuction were performed to reduce thickness of its subcutaneous tissue

Case II

A 35 years old man sustained an occupational injury of his non-dominant left hand in a grinding machine. Avulsion injury included a loss of skin on the entire dorsal side of the thumb and the palmar region of half of its distal phalanx. Replantation was not possible due to the devastation of the vessels on the stump. Skin flap had dimensions of 5 x 16 cm and was transferred based on the most distal perforator. The vessels were anastomosed in the “snuffbox”. The spin was 630 degrees in this case. Small defect on the dorsum of the thumb was covered with a skin graft. After 12 months, a slight correction of the excess of the flap and the scars was performed.

Case III

A 62-year-old man sustained amputation of the right dominant thumb caused by a drilling machine. The skeleton of the thumb was avulsed at the level of the IP joint and skin avulsion reached up to the base of the first metacarpal bone. The amputated part was not available. The defect was covered using the lateral arm flap based on the two distal perforators. Rotation of the helix in this case was only 380 degrees. The distal part of the thumb was covered with a skin graft of the size of 3 x 5 cm. There was excess of the flap after it healed and therefore it was further reduced by secondary operations.

DISCUSSION

The ideal method of immediate reconstruction in avulsion injuries is replantation of avulsed skin. In cases where replantation is not possible, it is mandatory to maintain the function and to reconstruct the skeleton of the thumb. The optimal solution is immediate reconstruction of the thumb using great toe transfer, fillet free flap or wrap-around flap ^6–10.

Some patients, however, are not willing to accept the donor site morbidity on the foot and therefore we resorted to another option.

The local flaps come into consideration; especially reverse radial forearm flap or posterior interosseous flap. Concerning the distant flaps, the standard method is the reconstruction using the direct inguinal flap^11–12. The advantage of a free flap reconstruction is a one-stage procedure and the possibility of flap sensitivity. If flaps harvested from the leg (e.g. dorsalis pedis flap) are not considered, due to their donor site morbidity, thin perforator flaps come into consideration. These flaps, however, have less sensitivity due to the reduction of the subcutaneous tissue with resection of cutaneous nerve.

The size of the flap required to cover the defect of the thumb is at least 8 x 9 cm. Harvesting a flap of such size in the classical fashion imply the use of a skin graft to cover the donor site defect ^4–5. When the flap is set up in a spiral manner, the maximum width required is reduced to 4–6 cm provided that the flap length is extended. Ideally a flap for this kind of reconstruction should be thin, sensitive and longitudinally oriented. These requirements are best met in a variant of a distally planned lateral arm flap or lateral forearm flap^13–18. Both of these variants are based on the distal septocutaneous perforators of the posterior radial collateral artery. The advantage of both mentioned flaps is a long pedicle and a thin subcutaneous tissue.

The sensory nerve and the vessel, which provide sensory innervation and good blood circulation, pass through the central longitudinal axis of the flap.

CONCLUSION

Spiral placement of the distally planned lateral arm flap or the lateral forearm flap allows the reconstruction of the entire skin of the thumb, including a part of the hand dorsum. The flap has a potentially higher sensitivity than a groin flap and a single-stage microsurgical reconstruction is possible. Besides this, such reconstructive technique leads to low donor site morbidity, due to the possibility of direct closure.

Corresponding Author:

Libor Streit, M.D.

Department of Plastic and Aesthetic Surgery St. Anne University Hospital

Berkova 34, 612 00 Brno, Czech Republic

e-mail: liborstreit@gmail.com