The free vascularised extensor retinaculum composite flap - an anatomical basis for a new means in reconstruction of complex extensor tendon injuries and its sequele

INTRODUCTION: Complex digital extensor tendon injuries are frequently associated with long-term reduction in hand function. Such injuries may result in deposition of dense scar tissue throughout anatomical tissue planes, adhesion formation between injured structures and contracture of the extensor mechanism. While reconstruction of individual anatomical components is feasible, re-establishing a gliding plane for tendon excursion remains a challenge. The present study aimed to demonstrate the microvascular supply to a composite flap comprising skin, subcutaneous tissue and extensor retinaculum including the intervening areolar gliding planes as a single unit for reconstruction of compound extensor injuries to the hand.

METHODS: An anatomical study was performed comprising the upper limbs (n=18) of fresh frozen cadavers. The anterior interosseous artery (n=9) or posterior interosseous artery (n=9) was selectively cannulated at the origin and injected with coloured dye for microvascular dissection of the proposed flap tissue at the extensor retinaculum. The vessels were then injected with a radiopaque medium for time-rendered digital subtraction angiography and cone-beam computed tomography angiography with multiplanar reconstructions to visualise the patterns of microvascular perfusion of the extensor retinaculum and overlying integument.

RESULTS: Both the anterior and posterior interosseous arteries contributed vascular supply to the extensor retinaculum, demonstrating a dense network of vessels associated with this structure. The anterior interosseous artery was consistently the dominant vessel, perfusing large perforator vessels through the septum between the second and third as well as the fourth and fifth extensor compartments. The posterior interosseous artery supplied perforator vessels to the fourth and fifth extensor compartment and overlying skin, in addition to the well described proximal forearm angiosome territory. Both posterior and anterior interosseous arteries supplied vessels located between fourth and fifth extensor compartments.