Arterial Anastomoses of the Lower Extremity
Although the range of motion of the joints of the lower limb is less than those in the upper limb, the arterial supply surrounding them is still susceptible to damage. Consequently, arterial anastomoses are necessary to provide an alternative route for blood to flow should the primary arterial supply be occluded or severed. This article will address the arterial anastomoses found in the lower limb.
Pelvic & Gluteal Anastomoses
The divisions of the common iliac arteries are responsible for delivering oxygenated blood to the lower extremity. The common iliac artery bifurcates to form the external and internal iliac arteries about half way between the first and second anterior sacral foramina. Just lateral to the level of the second anterior sacral foramina, the internal iliac artery gives off the iliolumbar artery and the superior gluteal artery. The iliolumbar artery travels superiorly (posterior to the common iliac artery) before bifurcating into its lumbar and iliac branches at the level of the iliosacral joint. The iliac artery then courses along the inner margin of the iliac crest, after which it exits the false pelvis superior to the lateral portion of the inguinal ligament.
The iliac artery joins an anastomosis with four other arteries just inferior to the anterior superior iliac spine (ASIS). The superior gluteal artery leaves the pelvis via the greater sciatic foramen and courses posterior to the iliac bone. It gives a superficial and a deep branch; the latter of which travels deep to gluteus medius. Just lateral to the level of the posterior gluteal line, the deep superior gluteal artery divides to form superior and inferior divisions. The superior division joins the iliac artery in the ASIS anastomosis. The deep circumflex iliac artery (a branch of the external iliac artery) travels superolaterally, medial and deep to the inguinal ligament to join the anastomosis at the ASIS. Similarly, the superficial circumflex iliac artery (also a branch of the external iliac artery) takes a superolateral course (lateral and anterior to the inguinal ligament) to meet with the anastomosis at the ASIS. Finally, the ascending branch of the lateral circumflex femoral artery, a branch of profunda femoris, recurs anterior to the neck of the femur to join the ASIS anastomosis.
Trochanteric & Obturator Anastomoses
The neck of the femur is vascularized by anastomosing branches from the profunda femoris artery (a branch of the femoral artery). Profunda femoris gives off a lateral circumflex and a medial circumflex femoral artery. The lateral circumflex femoral artery trifurcates, giving rise to the ascending, descending and transverse branches. The ascending branch travels superiorly in the anterior aspect of the femoral neck, just medial to the greater trochanter. The ascending branch of the medial circumflex femoral artery also travels superiorly, but along the trochanteric line in the posterior aspect of the neck of the femur. They both meet with the inferior division of the deep superior gluteal artery in the trochanteric fossa. The inferior gluteal artery (a terminal branch of the internal iliac artery) also joins the trochanteric anastomosis along the neck of the femur.
The medial circumflex femoral artery also forms an anastomosis with the posterior branch of the obturator artery (a terminal branch of the internal iliac artery) as it courses along the inner margin of the ramus of the ischium (in the obturator foramen). The obturator artery also gives off anterior and acetabular branches as it enters the obturator foramen, posterior to the superior pubic ramus. The anterior branch of the obturator artery follows the inner margin of the inferior pubic ramus to anastomose with the posterior branch.
The cruciate anastomosis is formed at about the mid-point of the lesser trochanter. In the anterior compartment of the thigh, the transverse branch of the lateral circumflex femoral artery travels laterally and courses around the greater trochanter. In the posterior aspect of the thigh, the transverse branch of the medial circumflex femoral artery also travels laterally to meet with corresponding branch of the lateral circumflex femoral artery. The descending branch of the inferior gluteal artery joins the anastomosis from above, while the first perforating branch of profunda femoris recurs to join the anastomosis from below.
Popliteal & Patellar Anastomoses
The femoral artery travels through the anteromedial compartment of the thigh before changing its course to the posterior compartment through the hiatus of adductor magnus. Prior to diverging, the femoral artery gives off the descending genicular artery, which divides to give an articular branch and a saphenous branch. After passing through the adductor hiatus, the femoral artery is now referred to as the popliteal artery. At the level of the distal part of the medial supracondylar line, the popliteal artery gives off a superior medial genicular artery and a superior lateral genicular artery before continuing its descent in the popliteal fossa. The superior lateral genicular artery bifurcates at the distal part of the lateral supracondylar line. Its ascending branch meets with the descending branch of the lateral circumflex femoral artery in the substance of vastus lateralis.
The descending branch from the superior lateral genicular artery travels medially to join the patellar anastomosis. The superior medial genicular artery bifurcates at the adductor tubercle; giving one branch that courses laterally in the anterior compartment to join the patellar anastomosis, and another that travels inferomedially to communicate with the inferior medial genicular artery in the popliteal fossa. The inferior lateral genicular artery courses superomedially around the lateral condyle to join the patellar anastomosis as well. In the distal popliteal fossa, the popliteal artery bifurcates into the anterior and posterior tibial arteries. The anterior tibial artery gives off a posterior tibial recurrent artery (proximal to the peroneal bifurcation) that joins the inferior lateral genicular artery. In the interosseous foramen (at the proximal tibiofibular joint) the anterior tibial artery gives off a circumflex fibular branch and an anterior tibial recurrent artery. The former travels superiorly to join the inferior lateral genicular artery, while the latter travels superiorly to complete the patellar anastomosis.
Ankle & Foot Anastomoses
The posterior tibial artery communicates with its anterior counterpart as well as with the fibular (peroneal) artery. This communication can be observed in the posterior aspect of the leg (deep to the Achilles tendon), where a communicating branch of the peroneal artery travels medially towards the posterior tibial artery, and a perforating branch passes through the interosseous membrane (at the distal tibiofibular joint) then inferolaterally to join the anterior tibial artery. The medial calcaneal branch of the posterior tibial artery forms a calcaneal anastomosis with the lateral calcaneal branch of the peroneal artery on the calcaneus. The anterior tibial artery communicates with the posterior tibial artery via their respective anterior and posterior malleolar arteries. A similar malleolar anastomosis exists on the lateral malleolus. However, the branches form intercommunication between the peroneal artery and its perforating branch.
The anterior tibial artery continues down the dorsum of the foot and trifurcates just distal to the transverse tarsal joint, to give the medial tarsal, dorsalis pedis and lateral tarsal arteries. The dorsalis pedis artery then bifurcates above the medial and intermediate cuneiform bones to give the arcuate and deep plantar arteries. The arcuate artery courses laterally along the tarsometatarsal joint (TMJ), where it is joined by the lateral tarsal artery at the 5th TMJ. The posterior tibial artery divides to form a medial and a lateral plantar artery as it emerges from the lower border of the flexor retinaculum (between the tendons of flexor digitorum longus, medially, and tibialis posterior laterally). The lateral plantar artery then courses to the 5th TMJ, travels vertically to the middle of the 5th metatarsal, then takes an abrupt medial turn to form the deep plantar arch. It terminates by anastomosing with the deep plantar artery in the first intertarsal space. The arch gives off posterior perforating branches in the intertarsal spaces that anastomose with the arcuate artery.