Can The Extensor Digitorum Brevis Muscle Flap Help Salvage A Diabetic Limb With Osteomyelitis?
Anatomical variations exist in which additional muscular branches stem from the dorsalis pedis artery to the extensor digitorum brevis muscle. In some individuals, the perforating branch of the peroneal artery supplies the extensor digitorum brevis muscle. Once the dorsalis pedis artery reaches the first intermetatarsal space, it branches off deeply plantar and continues on as the first dorsal metatarsal artery. The first dorsal metatarsal artery then courses distally towards the first web space where it passes over the deep transverse intermetatarsal ligament, branches into two dorsal digital arteries, and communicates with the plantar arterial network.
The extensor digitorum brevis muscle has a type 2 vascular pattern, which means its dominant vascular pedicle is near the muscle origin and has minor vascular pedicles. Typically, the lateral tarsal artery or the dorsalis pedis supplies the dominant vascular pedicle.
There are three ways to provide blood supply for a distally based flap: the medial tarsal artery; the connection between the first dorsal interosseous artery and the plantar system at the level of the metatarsal head; and the deep plantar branch with communication of the lateral plantar artery. The most reliable option is at the pivot point at the tarsometatarsal joint since it has the most reliable vasculature and venous return. The extended, distally-based extensor digitorum brevis muscle flap is based on the first dorsal metatarsal artery.
One should confirm the presence of retrograde flow using a Doppler and/or angiogram before committing to this procedure. If the dominant vascularity is based on the peroneal or dorsalis pedis artery as a single vessel runoff to the foot, then the surgeon should consider other options.
Keys To Surgical Planning
Perioperative planning involves deciding on the optimal incision approach. Reported incisions have included a single linear, parallel linear, lazy S shape and reverse J incision.6 Authors have described an approach consisting of two parallel longitudinal incisions for the reverse extensor digitorum brevis muscle flap procedure.8 The purpose of this modification is to expose the dorsalis pedis artery and the sinus tarsi branch of the lateral tarsal artery separately to avoid donor site morbidity.
Incisions vary in part due to local vascularity and location of the recipient site. A poorly placed incision where peroneal perforators are poor or nonexistent may place the dorsal skin at risk for necrosis. A medially based incision as opposed to a laterally based incision helps avoid insult to the peroneal artery. We use a straight incision over the dorsum of the foot as this approach minimizes subcutaneous undermining.
Performing The Flap Procedure
One would perform a dorsal linear incision extending from the first web space to the origin of the extensor digitorum brevis muscle and spare the branches of the superficial peroneal nerve. Identify the medial and lateral border of the extensor digitorum longus, and mobilize these borders as a single unit. Incise the extensor digitorum brevis to the great toe to permit visualization of the dorsalis pedis artery.