CASE                               48                               

The patient is a 47-year-old male who sustained a tablesaw injury to the volar aspect of his nondominant left thumb (Fig. 4–24). He has no other injuries and the remainder of his hand and fingers is uninjured. On examination, there is a 3 × 2 cm soft tissue defect on the volar aspect of his thumb distal to the IP joint, with preservation of the dorsal skin and nailbed of his thumb. The FPL tendon is intact but exposed at the base of the wound with a 30% laceration. The distal dorsal aspect of the thumb is perfused.

Figure 4–24

Which of the following is the best reconstructive option for this patient?

1. Full thickness skin graft from the hypothenar eminence

2. Allow to heal by secondary intention with dressing changes alone

3. Thenar flap

4. First dorsal metacarpal artery flap (“Kite” flap)

5. Moberg advancement flap

Discussion

The correct answer is (D). This patient has a volar thumb soft tissue defect which

measures 3 × 2 cm in area. Given the exposed FPL tendon at the base of the wound, soft tissue coverage with a flap is the most appropriate reconstructive option. Allowing the thumb to heal by secondary intention would likely result in a paucity of coverage and/or a flexion contracture. A thenar flap is not possible for the thumb and is a better option for middle finger volar pulp defects. The Moberg advancement flap is a good option for volar thumb defects but is generally limited to defects 1.5 cm2 in area.

If the defects of the distal volar thumb were smaller, 1 cm2, but had exposed FPL tendon at the base, what would be another acceptable option for reconstruction unique to the thumb?

1. Full thickness skin graft from the hypothenar eminence

2. Healing by secondary intention with dressing changes

3. Thenar flap

4. Cross-finger flap

5. Moberg advancement flap

Discussion

The correct answer is (E). As mentioned above, the Moberg flap is a good reconstructive option for volar thumb defects less than 1.5 cm2. This reconstruction is unique to the thumb because of the robust dorsal circulation, allowing perfusion to be maintained when the volar advancement flap is raised. A cross-finger flap is another acceptable reconstruction in this situation but is not unique to the thumb.

Why is the Moberg flap possible for thumb reconstruction but is not typically possible for similar reconstruction in other digits?

1. The thumb is shorter in length than other digits

2. The thumb has a greater width than other fingers

3. The thumb has sufficient dorsal perfusion that allows for this reconstruction

4. The thumb has less sensory requirement than other digits

5. The thumb is more expendable than other digits

Discussion

The correct answer is (C). The blood supply to the thumb predominantly arises from the princeps pollicis artery, which emerges from the radial artery. The princeps pollicis artery runs between the first dorsal interosseous artery and the adductor pollicis, and branches into the radial and ulnar digital arteries to the thumb.

There are axial dorsal arterial branches that supply the dorsum of the thumb, which are reliable and can provide sufficient inflow to maintain perfusion to the thumb tip.

Objectives: Did you learn...?

Describe the indications of a Kite Flap?

Describe the indications for a Moberg advancement flap? Identify the anatomy of the thumb?