The blood supply to the foot and ankle is mainly supplied by the anterior tibial and dorsalis pedis arteries and its anastomosis with the posterior tibial artery and terminal branches, the medial and lateral plantar arteries, forming together the pedal arch. Both the anterior and posterior tibial arteries also receive communicating branches from the peroneal artery and supply the heel with the lateral calcaneal artery (Fig. 37.1).

The dorsalis pedis and the plantar arteries arise as the terminal branches of the anterior and posterior tibial arteries. The anterior tibial artery continues as the dorsalis pedis when it crosses the ankle joint and is often the main blood supplier to the forefoot. After passing to the first interosseous space, the dorsalis pedis artery splits into the first metatarsal artery and the perforating deep plantar artery. By passing deeply between the heads of the first interosseous muscle, the deep plantar artery enters the sole of the foot where it unites with the lateral plantar artery to give rise to the deep plantar arch. Proximally, the lateral tarsal artery branches off the dorsalis pedis artery and runs beneath the extensor digitorum brevis muscle to join the arcuate artery, forming a dorsal arterial loop. The arcuate artery splits from the dorsalis pedis artery and runs to the lateral aspect of the forefoot under the extensor tendons. By running across the bases of the lateral four metatarsals, the arcuate artery supplies the second, third and fourth dorsal metatarsal arteries. Perforating branches connect these vessels that run distally to the toes, to the plantar metatarsal arteries and to the plantar arch. Each dorsal metatarsal artery supplies the dorsal aspect of two adjoining toes by dividing into two dorsal digital arteries. The dorsal arteries generally do not reach the end of the digits and this area is supplied by dorsal branches of the plantar digital arteries.

The posterior circulation of the foot derives its blood supply from the posterior tibial artery. At its terminal division under the flexor retinaculum, the tibial artery continues as the medial and lateral plantar arteries. The medial plantar artery gives rise to deep and superficial branches. As the smaller branch of the posterior tibial artery, the deep branches of the medial plantar artery supply the first toe, whereas its superficial branch supplies the skin of the sole on the medial side and has digital branches. Anatomic variations exist whereby the superficial branch anastomoses with the deep plantar arch or lateral plantar artery forming a superficial plantar arch. The lateral plantar artery, being the largest branch of the posterior tibial artery, runs laterally and anteriorly. The deep plantar arch is formed by the lateral plantar artery crossing the foot and arching medially and connecting with the deep plantar artery. Along its course, it branches into four plantar metatarsal arteries, three perforating branches and several branches supplying the muscles, fascia and skin of the sole. Near the base of the proximal phalanges, the plantar metatarsal arteries divide to form the plantar digital arteries that supply adjacent toes. The plantar digital arteries are the main blood supply to the distal toes and the nail bed which they reach via perforating and dorsal branches.

The pedal arch, as an essential anastomosis between the anterior and posterior tibial arteries in the foot, occurs in several anatomical variations and has been the subject of study in several pioneering studies [2, 3]. The circulation in the foot has been divided into superficial and deep plantar arches. The plantar arch is formed when the deep plantar artery joins the deep branch of the lateral plantar artery. The contribution of each artery differs among individuals. Based on a study by Ozer et al., the pedal arch has been divided into three anatomical categories [4]:

Several other studies have investigated the different anatomical variations of the arterial supply to the foot. Also, these studies have shown that the dorsalis pedis is most often the predominant artery in 40–82 % of cases [3, 5]. In most cases, the dorsalis pedis artery is a continuation of the anterior tibial artery. Less often, the dorsalis pedis can also arise from the anterior communicating branch of the peroneal artery (6.7 %). However, the dorsalis pedis is not always present and several studies have reported on a small or even absent dorsalis pedis in 1.9–14.2 % of the cases [2, 5–8]. Papon et al., in a dissection of 20 specimens, found the deep plantar artery present in only 16 cases. This artery was found to be easily accessible via the dorsal route, making it a possible anatomic site for the performance of a distal bypass [9].

Likewise, anatomical variations exist with an absent arcuate artery. When the arcuate artery is present, it most often branches from the dorsalis pedis directly (90 %) and less often from the lateral tarsal artery (10 %) [5]. The posterior tibial artery is more consistent in terms of location and presence and found to be absent in 0.18–2 % of cases only [2, 6].

The deep plantar arch gives off four plantar metatarsal arteries, four perforating branches and numerous branches to joints, muscles, etc. By penetrating through the first, second, third and fourth interosseous space, the perforating branches anastomose with the dorsal metatarsal arteries. A superficial plantar arch is formed when superficial branches from the lateral plantar artery and the medial plantar artery form and give off the first to the fifth common plantar digital arteries. This configuration, however, is only found in 2–8 % of the studies and was more often absent [3, 4].

In 1987, Taylor and Palmer published an elaborated study covering the anatomy of the whole human body describing their angiosome theory [10]. They defined the angiosome as a ‘three-dimensional jigsaw made up of composite blocks of tissue supplied by named source arteries. The arteries supplying these blocks of tissue are responsible for the supply of the skin and the underlying structures’. They identified five distinctive angiosomes in the leg and foot territory which are supplied by the anterior tibial (and dorsalis pedis), peroneal and posterior tibial arteries (with its terminal branches, the medial and lateral plantar arteries). However, Taylor and Palmer also described well-established anastomoses that exist between the angiosomes territorial distribution of different arteries. They also described finer arterial connections existing between the different angiosomes describing them as ‘choke vessels’. These ‘choke vessels’ link neighbouring angiosomes but also demarcate the border of each angiosome.

This angiosome concept has generated great interest in peripheral vascular disease, with several studies extrapolating this model on the treatment of patients with CLI and tissue loss.

In 2006, Attinger et al. published their first study looking into the angiosomal distribution in the ankle and foot region in cadavers concluding the presence of six angiosomes supplied by the anterior tibial/dorsalis pedis (one angiosome), the posterior tibial (three angiosomes) and the peroneal (two angiosomes) arteries [11].

However, Attinger et al. also stated that the blood flow to the foot and ankle is redundant because the three major arteries feeding the foot have multiple arterial–arterial connections. The ‘choke vessels ’ described by Taylor and Palmer illustrate a type of connection between different angiosomes, as well as the true anastomoses where no change in arterial calibre occurs. The anastomosis between the dorsalis pedis and the posterior tibial arteries perfectly demonstrate this type of connection.

Neville et al. published their study about the clinical implications of foot and ankle angiosomes on revascularization and limb salvage in CLI patients undergoing distal bypass surgery [12]. In the direct revascularization group, there was 91 % complete healing with only 9 % major amputation rate. While in the indirect revascularization group, only 62 % healed with a 38 % major amputation rate (p = 0.03). However, the total time to healing was not significantly faster in patients undergoing direct revascularization. The authors concluded that direct revascularization of the angiosome specific to the anatomy of the wound leads to a higher rate of healing and limb salvage, recommending that consideration should be given to revascularization of the artery directly feeding the ischemic angiosome. This is in line with a recent meta-analysis of 1290 limb revascularizations showing that direct revascularization leads to improved wound healing and limb salvage when compared to indirect revascularization [13].

Similar studies exploring this same angiosome concept in revascularization in CLI patients undergoing both infrapopliteal bypass surgery and angioplasty were published. These studies, however, reached different conclusions about the importance of this concept in healing tissue loss and limb salvage in patients with CLI . Most of these studies did not include data regarding the pedal arch quality in relation to the angiosome revascularized. The authors believe that there is a strong correlation between the angiosome concept and the quality of the foot arch in influencing the healing process of tissue loss in patients with CLI following revascularization. This could explain the contradicting results previously published using the concept of angiosomes in CLI.

In clinical practice, healing of tissue loss can be achieved significantly fast in spite of the severe disease of the angiosome artery supplying the area of tissue loss. This is well demonstrated by this diabetic patient presenting with severe plantar foot sepsis requiring emergency debridement of the medial aspect of the foot sole, heal and hallux (Fig. 37.2).

The patient was noted to have very good perfusion at the time of surgery. A duplex scan performed post-operatively demonstrated complete occlusion of the posterior tibial artery and severe stenosis of the peroneal artery with triphasic flow in the dorsalis pedis artery. The patient was managed with intravenous antibiotics, regular bedside debridement and negative pressure wound therapy. Within 2 weeks, the patient developed healthy granulation tissue (Fig. 37.3) that was easily covered by a split-thickness skin graft (Fig. 37.4).