Moberg Modification using the First Web Space: Thumb Reconstruction Following Distal Amputation

Abstract

The Moberg neurovascular advancement flap, first described in 1964, has proven to be ideal for soft tissue defects of the thumb pulp measuring ≤1.5 cm in size [8]. For such small defects, this technique provides sufficient skin coverage allowing preservation of length and most importantly good restoration of sensation and function [2, 5]. Modifications to the Moberg flap have allowed coverage of deficits >1.5 cm but have been hampered by the residual defect located at the donor site. In 1968, O’Brien proposed the use of a split thickness skin graft to cover the donor deficit [9]. The disadvantages of a skin graft such as immobilization, risk of graft failure, and contracture render this technique less attractive. Others have avoided grafting with V–Y modifications to the Moberg flap [1, 3, 4, 10]. However, tension at the donor site often occurs and may result in incomplete closure or in skin necrosis. In these instances, splinting in the flexed position to decrease tension or dressing changes to encourage epithelialization when complete primary closure is not feasible is required [4, 7]. As a consequence, scar hypertrophy, contractures, joint stiffness, and delayed mobilization may prolong return to function. Dellon demonstrated that defects of up to 3 cm could be resurfaced using an extended palmar flap with dissection into the thenar eminence [3]. Two rotational flaps are used to close the donor deficit. Although providing good closure, this technique requires extensive dissection and is technically difficult. We present a new modification of the Moberg–O’Brien technique that utilizes the skin of the first web space to fill the proximal defect caused by the mobilization of the flap. This simple technique provides tension-free closure and avoids the need for immobilization or dressing changes. Excellent esthetics and function is achieved by deepening the first web space with a Z-plasty and hence increasing the relative length of the thumb. Operative Technique After drawing the incisions, we proceed with the elevation of the Moberg flap along a single plane superficial to the flexor pollicus longus tendon sheath (Fig. 1). A transverse incision at the base of the thumb metacarpophalangeal (MCP) joint is made in order to elevate the flap on its neurovascular bundles. Hence the incision is made on the volar side of the MCP; care is taken to leave the base of the transposition flap intact (located at the base of the thumb on the dorso–ulnar side). Once the flap is advanced and fixed with 4-0 nylon, the proximal deficit is covered using the transposition flap of the first web space (Fig. 2) with a 3:1 ratio and removal of the triangular point for a final rectangular shape. This transposition flap is raised in a plane superficial to the first dorsal interosseous and thumb adductor muscles. It is rotated 150° to cover the proximal deficit and is sutured loosely with 4-0 nylon in a manner as to not compromise the neurovascular pedicle of the Moberg flap (Fig. 2). In order to deepen the first web space and to prevent the formation of scar contracture, a Z-plasty is then performed in the first web space (Fig. 3). A loose dressing is positioned without immobilization. Patients were satisfied with esthetic and functional outcomes (interview and at follow-up visit). For the purpose of this paper, we present the readers with three cases. Open in a separate window Fig. 1 Case 1—operative technique: Moberg–O’Brien flap. Two mid-axial incisions dorsal to the neurovascular bundle and one transverse incision at the base of the first metacarpal are drawn according to the Moberg–O’Brien flap. The transverse incision must not cross the base of the transposition flap, which is based on the dorso–ulnar aspect of the side of the thumb and extending across the first web space. The tracings for the Z-plasty of the first web space are completed. The flap is elevated along a single plane superficial to the flexor pollicis longus tendon sheath