The posterior interosseous artery island flap is capable of transporting the skin of the distal two-thirds of the forearm. The flap’s pedicle length determines its coverage possibilities.

It is particularly useful for covering extensive defects on the back of the hand as far distally as the dorsal aspect of the proximal phalanges of the fingers and for obtaining a complete coverage of the first web after the release of severe adduction contractures of the thumb. Buchler et al (2) noted that the flap could reach the dorsum of the proximal interphalangeal joints. It can be indicated in different
types of pathologies such as burn sequelae, wounds on the dorsum of the hand, tumors, and congenital deformities.

Contraindications for flap use include any injury to the posterior interosseous artery or deep laceration or crush wounds to the posterior forearm in the area of the flap pedicle. The flap is not recommended in patients with diabetes, in whom small vessels may be diseased. The flap has been used successfully in smokers, but smoking certainly carries a higher risk of flap complications.

Successful flap harvest is predicated on a thorough knowledge of the flap anatomy. Normally the anterior and posterior interosseous arteries in their course through the forearm are united through two main anastomoses, one proximal, at the level of the distal border of the supinator muscle, and one distal at the most distal part of the interosseous space (2 cm proximally of the distal radioulnar joint) (Fig. 16-1). The island posterior interosseous island flap is supplied by the reverse arterial blood flow through the distal anastomosis once the proximal anastomosis has been ligated. Venous drainage is produced by the venae comitantes of the posterior interosseous artery.

The angiosomal territory of the posterior interosseous artery was studied in a series of 80 cadaveric forearms in 1993 (1). Ink injections performed through catheter placed in the distal part of the anterior interosseous artery stained the distal two-thirds of the posterior forearm skin through the reverse flow through the distal anastomosis. The proximal third of the forearm skin remained unstained even when larger amounts of ink were injected (see Fig. 16-5). Ink injections through the catheter placed in the proximal part of the posterior interosseous artery stained the proximal two-thirds of the posterior forearm through the direct flow through the proximal cutaneous branch (1).

Other anatomic conclusions from this study can be summarized as follows: the posterior interosseous artery usually branches from the common interosseous artery in the proximal third of the forearm in 90% of cases, it can however be a direct branch of the ulnar artery in 10% of cases (1). It pierces the interosseous membrane about 6 cm distal to the lateral epicondyle of the humerus (14,15,16,17,18) forming its origin or proximal anastomosis between the anterior and posterior interosseous arteries. It enters into the posterior compartment of the forearm below the distal edge of the supinator muscle, located at the union of the proximal with the distal two-thirds of the dorsal aspect of the forearm (60 mm distal to the lateral epicondyle). At its entrance into the posterior compartment of the forearm, the posterior interosseous artery gives off branches to the recurrent interosseous artery that anastomoses at the elbow with a descending branch from the superior profunda, with the posterior ulnar recurrent and the anastomotica magna. In its ascending course the artery runs between the lateral condyle and the olecranon (Figs. 16-1 and 16-2).