In the most common type of distal amputation, a part of the sterile matrix is preserved. In these cases, efforts to preserve length and to provide sensitive, non-painful cover are the goal. Immediate wound coverage is the highest priority to prevent further tissue desiccation and length loss. In recent years, we witnessed considerable advances in flap design, owing to a better understanding of the blood supply to the thumb[7-9]. This has entailed that cross-finger flaps and many distant flaps are currently either reserved for extreme situations, or plainly discarded, and thus will not be discussed.
Smaller than 50% of the pulp surface
Semi-occlusive dressing
Healing by secondary intention by application of semi-occlusive dressing, as described by Mennen and Weiss, is a simple and inexpensive method for small defects without fracture or tendon exposure; it provides a consistent pulp with excellent contouring and a satisfactory return of sensation[10-13].
The stump is covered with a semi-occlusive transparent adhesive dressing after cleaning and debridement, which is changed weekly. The patient is allowed to use the thumb freely. The patient should be informed that a foul odor is normal and advised of the importance of keeping the dressing in place while healing occurs.
Volar advancement flap
Small soft tissue defects that require less than 5 mm of advancement can be covered readily by local advancement with palmar V-Y plasty, bilateral V-Y plasty, or modifications thereof[14-16]. The choice is based on the preference and experience of the surgeon, as all flaps are equally effective.
Moberg volar advancement flap
Moberg described a flap based on proper neurovascular bundles for coverage of palmar defects of the pulp[17] [Figure 2]. The flap permits covering moderate-size defects and provides sensitive skin simultaneously. If good coverage of the pulp requires more than 45º of interphalangeal (IP)-joint flexion, transforming the flap into a true island[18] or combining the advancement with a V-Y flap[19],or Z-plasty can provide some extra length[20].
Defects up to 2 cm (about half the pulp length) can be covered with this flap; however, this benefit comes at the price of causing a flexion contracture of the IP joint that can result in a painful thumb and a beaked nail deformity. Problems ensue when asking too much of the flap [Figure 3].
Larger than 50% of the pulp surface
Dorso-ulnar homodigital flap (Brunelli)
Brunelli et al. studied the arteries’ layout on the thumb’s dorsal surface[7,21]. The constant disposition and anastomoses permitted raising a distally-based flap safely from the dorso-ulnar region of the metacarpophalangeal joint[22,23].
This flap is based on the ulnar dorsal digital artery of the thumb, which (like its radial counterpart) has a peculiar anatomy [Figure 4]. During its short course, it has two constant anastomoses that allow this flap to rotate in two locations. The first pivot point is located at the neck of the proximal phalanx (2.5 cm proximal to the cuticle), reaching dorsal thumb defects; the second is located at the level of the nail fold arcade (0.9 to 1 cm proximal to the cuticle), providing the possibility to cover the nail and the pulp.
Several essential details should be considered. First, the flap may only be used if the area of cross anastomosis is intact. Second, venous congestion might occur if the skin over the pedicle is closed or tunneling is performed; therefore, skin grafting is recommended. Third, a first-web contracture might occur if the donor site is closed overly tight; therefore, skin grafting is recommended if large flaps are raised[24,25].
This flap does not provide sensitive skin, even when the dorsal branch of the radial nerve is connected to the ulnar digital nerve. For this reason, we only recommend it for more than 50% pulp loss in older adults, where sensory recovery is frequently poor, irrespective of the reconstructive option selected, or in patients that do not want a more complex reconstruction.
Dorso-radial advancement flap (Moschella and Cordova)
Moschella and Cordova described a similar flap based on the radial dorsal digital artery to treat radial and dorsal thumb defects[21,26] [Figure 4].
The rotation point of this flap is always the middle of the proximal phalanx. This is so because it has a different arterial communicating pattern than the ulnar counterpart, with a distal arcade only being present in about 20%. The flap can be quite large (up to 3 cm × 4 cm) while still achieving primary closure, as there is no risk of web contracture[26,27]. The flap is a rapid and safe solution for many lateral and dorsal defects of the thumb.
First dorsal metacarpal island flap (Kite flap/Foucher flap)
One of the most popular procedures for thumb defects is the first dorsal metacarpal artery flap, also known as the “kite flap”, initially described by Foucher and Braun in 1978[28] [Figure 5]. The flap was devised for dorsal defects and as a vein carrier for thumb replantation. However, the fact that it can include a sensory branch from the radial nerve has made it usable for covering palmar defects, particularly in older adults[29].
The arterial supply of the flap is based on the dorsal radial artery of the index. This branch originates from the first dorsal metacarpal artery, which takes off from the radial artery between the crossing of the extensor pollicis longus and its penetration into the apex of the first interosseus space. The dorsal radial artery of the index is constant[28].
We prefer to assess the vascularity of the flap only after it has been sutured onto its final position. Doing otherwise will not prevent later necrosis due to pedicle kinking by a fascial band or constriction in the tunnel.
The flap is particularly indicated for dorsal thumb defects. We do not consider this flap applicable for pulp defects, except in older adults[29]. The donor site can be a source of hypertrophic scarring and painful ulcerations. To prevent this, the flap should not trespass the metacarpophalangeal or proximal interphalangeal joint creases, and the peritenon should be left intact. Furthermore, the kite flap plays an indisputable starring role for dorsal thumb defects combined with venous outflow difficulties[30] [Figure 6].
Heterodigital island flap (Littler flap)
The Littler flap[31] is taken from the ulnar aspect of the middle finger and tunneled to the pulp of the thumb, based on its neurovascular bundle, providing sensation to the pulp [Figure 7].
During the elevation of the flap, the utmost care should be taken to preserve the sheath of the flexors and the peritendineum of the extensor; otherwise, the bed may not be graftable. To safely pass the flap to the thumb, the tunnel should be large, and the graft should be pushed rather than pulled into the recipient side.
The flap is safe and effective in many respects but has problems and limitations. The most significant drawback derives from the fact that this is a sensitive flap with innervation for the middle finger, and hoping for cortical reorientation often ends in disappointment[32-35]. Therefore, if there are nerves available, to avoid cortical disorientation, it is preferable to connect the recipient thumb ulnar nerve and the nerve of the flap[32,33].
Flexion contracture of the middle finger is a common complication that occurs more frequently when a large flap has been raised, when the skin graft has not taken well or when proper aftercare is neglected. We prevent contracture by night-splinting the proximal interphalangeal joint in extension. Venous problems might occur in large flaps and in case of pedicle skeletonizing and can be prevented by including a dorsal vein and connecting it in the recipient site. For the standard-sized flap, this is not necessary. If the pedicle is insufficiently dissected, the flap will reach the thumb with difficulties, causing a painful band in the palm.
In summary, this flap is used in patients with considerable bone exposure and who do not wish for more complex reconstruction.
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