Dorsoradial forearm flap with silicone bone spacer in reconstruction of A combined THUMB injury – case report

INTRODUCTION

Osseous reconstruction of the thumb following traumatic bone loss can be performed using a range of techniques. Immediate reconstruction using composite grafts with bone as a free or pedicled flap^1-3 have been described as well as delayed primary bone grafting. The use of early bone grafting may be associated with a relatively higher risk of infection⁴. Silicone block interposition^4,5 or antibiotic-impregnated cement spacer⁶ and secondary bone grafting are advantageous therapeutic options. In case of combined injuries, simultaneous immediate reconstruction of missing soft tissues over the spacer by well-vascularised skin cover is essential.

Various techniques in the reconstruction of soft tissue defects of the thumb have been reported. Immediate reconstruction using one of the available local flaps is the gold standard. Distally or proximally based pedicled island flaps (e.g. posterior interosseous flap^7,8 or Foucher’s kite flap⁹) are among the most effective. The use of emergency free flap is another valid and advanced surgical approach^10,11,12. Finally, an immediate distant inguinal flap is still included among the standard techniques of soft tissue reconstruction¹³. However, some of these flaps appear to be too thick, especially for limited defects of the thumb.

The dorsoradial forearm flap, as described by Bakhach et al. ^14,15, is a distally based cutaneous flap, harvested over the distal dorsal border of the forearm. Its blood supply is provided in antegrade fashion by the dorsoradial artery, a constant branch of the radial artery, which arises at the apex of the first webspace. After a 3 to 5 cm proximal course parallel to the tendon of the extensor pollicis longus, the artery enters the subcutaneous tissues and supplies the skin of the distal dorsal radial quarter of the forearm. The pivot point of the pedicle allows a wide arc of rotation that covers the dorsal aspect of the hand and metacarpophalangeal joints of the fingers, the dorsal aspect of the thumb and the first web space; it can also reach to the palmar aspect of the wrist.

A case of a 52-year-old patient with a combined injury of the thumb reconstructed 1) primarily with emergency dorsoradial forearm flap together with the implementation of a silicone spacer to a bone defect and 2) secondarily by bone grafting is reported together with a brief literature review.

Case report

52-year-old male patient was transferred to our department after he sustained a severe combined thumb injury on the left non-dominant hand at home by a milling cutter (Fig. 1). There was a skin defect on the dorsal side of the thumb at the level of the proximal phalanx (3 x 4.5 cm) together with distal two thirds of the proximal phalanx. The extensor pollicis longus tendon was pulled out from its insertion to the distal phalanx. All volar structures remained intact as well as the distal phalanx.

Surgical technique

The procedure was performed under general anaesthesia and intravenous antibiotics were administrated.

After a careful debridement of the wound, the bone defect was filled with silicone spacer. The spacer was made from two pieces of silicone tendon spacer (8 mm in diameter, 2 cm long) fixed together in a double barrel fashion by 3-0 nylon monofilament suture. Appropriate position of the spacer was fixed to the preserved skeleton with axial K-wire of 1.2 mm in diameter. The extensor pollicis longus tendon was fixed to the distal phalanx base by adaptive suture using single 4-0 monofilament nylon suture.

For the simultaneous reconstruction of the missing soft tissues, the flap paddle was designed over the distal dorsal radial quarter of the forearm (Fig. 2). Longitudinal axis of the skin paddle was oriented parallel to the extensor pollicis longus tendon. The flap pedicle was exposed using S-shaped skin incision with preservation of the superficial venous network. The flap was then raised from proximal to distal preserving extensor retinaculum. The pedicle was dissected with the surrounding subcutaneous tissue in order to avoid injury to the vessels. From the intersection of the EPL tendon over the ECRL tendon, the dissection continued parallel to the EPL tendon to the origin of the dorsoradial vessels from the radial artery, obtaining a pedicle length of 4.5 cm. Tourniquet was released just after completing flap dissection to check reperfusion of the skin paddle before transferring to the recipient area. The flap was then rotated 180° and transposed through subcutaneous tunnel to the recipient site to cover the tissue loss. The donor site was closed primarily without the need of a skin graft.

Postoperatively, the patient was taking antibiotics every 8 hours (amoxicillin clavulanate 1.2g intravenously for the first 48 hours and then 625 mg orally until the 10^th postoperative day (Augmentin, Biopharma, Roma, Italy)), low-molecular-weight heparin – 3800 IU antiXa every 12 hours for 7 days (Fraxiparine, Aspen, Notre Dame de Bondeville, France) and pentoxifylline every 12 hours for 2 weeks (Agapurin SR 400, Zentiva a.s., Bratislava, Slovak Republic). The perfusion of the flap was closely monitored by observation of skin turgor and its colour. A palmar resting splint was applied to the operated thumb and wrist for four weeks to enhance wound healing.

Osseous reconstruction was performed in second stage 5 months after primary surgery removing the silicone spacer through the initial radial scar and transferring iliac bone graft to proximal phalanx of the thumb (Fig. 3). The bone graft was fixed to the residual bone of the proximal phalanx with K-wires (1 mm in diameter) and with a wire loop (0.3 mm in diameter). Distally, the bone graft was attached to the distal phalanx without any internal fixation. The thumb was immobilized using a palmar resting splint for 5 weeks. Physiotherapy of the thumb started on the 3rd week after surgery. Osteosynthetic material was removed completely 10 months after secondary bone grafting.

Clinical follow-up

Clinical follow-up was one year (Fig. 4). There was no infectious complication. Opposition of the thumb remained intact as well as its length and sensitivity. Active range of motion in MPJ was 35° compared with 50° on the contralateral side. IPJ was stabilized in 5° semiflexion compared with active range of motion of 70° on the contralateral side. The patient is very satisfied with the reconstruction and he uses his thumb normally during common daily activities and also at work.

Discussion

An extensive traumatic soft tissue defect combined with significant bone loss of proximal phalanx of the thumb requires adequate surgical treatment with bridging the bone defect when the immediate reconstruction of missing soft tissues seems to be an optimal solution.

Except of primarily contaminated wounds, osseous reconstruction may be performed also primarily after adequate debridement. However, in cases with inadequate skin coverage, primary bone grafting is not recommended⁴. Composite tissue transfers including well-vascularized bone segment as pedicled or free flap have been described^1-3. However, the use of early bone transfer may be associated with a relatively higher risk of infection⁴. We believe that the risk of infectious complications in recipient site with a potential need of bone fragment removal should be considered in relation with the donor site morbidity. From this point of view, removal of the prefabricated spacers has therefore smaller consequences for the patient, because its use is not associated with any donor site morbidity. Silicone spacer creates a space surrounded by a capsule for the introduction of the bone graft. Appropriate position of the spacer within the remaining skeleton was secured by intramedullar K-wire fixation.

The dorsoradial forearm flap is an axial island flap based on the dorsoradial artery, a constant branch of the radial artery. The main advantage of a dorsoradial flap is that it is thin and the dissection is relatively simple. Moreover, the donor site is closed primarily if the width does not exceed 3 cm¹⁵.

In this case report, Foucher’s kite flap⁹ was also considered as the surgical alternative to the dorsoradial flap as the kite flap is performed more commonly in similar defects at our department. We chose dorsoradial flap as it is not associated with the donor site morbidity in the index finger and thus with the need of skin grafting.

The other possible reconstructive alternatives were considered less appropriate compared with the use of the dorsoradial flap. The use of distant inguinal flap does not allow appropriate immobilization of the thumb after the bridging of the bone defect. Moreover, its use would be associated with unpleasant immobilisation of the entire upper extremity and a higher risk of infection and with the need of secondary surgery – disconnection of the pedicle. The use of distally pedicled posterior interosseous flap would be associated with higher donor site morbidity as the pivot point is situated proximally and medially to the pivot point of the dorsoradial flap. The number of thin free flaps that would be appropriate for the reconstruction of a relatively small dorsal skin defect of the proximal phalanx of the thumb is limited. Possible use of a venous free flap that could be relatively suitable is technically more demanding but it is associated with possible microsurgical complications, while the morbidity is about the same.

CONCLUSION

This early experience with dorsoradial flap in reconstruction of traumatic dorsal defect of the thumb is very promising. The use of the silicone spacer with secondary bone grafting allowed us to preserve the length of the thumb with satisfied functional result.

Corresponding Author:

Libor Streit, M.D.

Department of Plastic and Aesthetic SurgerySt. Anne University Hospital

Berkova 34

612 00 Brno

Czech Republic

E-mail: liborstreit@gmail.com