STUDY AIMS

At the end of your study, you should be able to:

•	Describe the arterial supply of the lower limb, distinguishing the arteries supplying each of the compartments of the thigh and leg
•	Know the surface markings to locate the femoral artery and palpate the pulses of the popliteal, posterior tibial, and dorsalis pedis arteries
•	Describe the venous drainage of the lower limb
•	Describe the lymphatic drainage of the lower limb
•	Know the nervous innervation to the compartments of the thigh and leg and recognize the course of the major nerves of the lower limb
•	Understand the dermatome and myotome maps of the lower limb

GUIDE

7-6: Lower Limb: Neurovasculature

Vascular Supply: Arteries ( Fig. 7-6-1) (Fig. 7-6-6) Femoral artery Continuation of the external iliac artery Main artery of lower limb Palpable inferior to the midinguinal point, not at the midpoint of the inguinal ligament Descends in femoral triangle on iliopsoas and pectineus, lateral to femoral vein Enters adductor canal deep to sartorius and exits at adductor hiatus Profunda femoris (deep artery of thigh) Main artery to the thigh Largest branch of femoral Arises from lateral aspect of femoral in femoral triangle Supplies anterior and medial (adductor) compartments of the thigh Supplies posterior compartment by perforating arteries Gives off medial and lateral circumflex femoral arteries that supply the head of the femur and muscles of lateral thigh Obturator artery Branch of the internal iliac artery (or may arise from the inferior epigastric) Enters thigh through obturator foramen Divides into anterior and posterior branches Supplies adductor compartment of the thigh along with profunda femoris Popliteal artery Continuation of the femoral artery (at adductor hiatus) Palpable in the popliteal fossa (best felt when knee is flexed) Gives off five genicular branches supplying articular capsule and ligaments of knee joint Medial and lateral superior genicular Middle genicular Medial and lateral inferior genicular Form anastomosis around knee joint Bifurcates into anterior and posterior tibial arteries Anterior tibial artery Smaller of two terminal branches of popliteal Passes through gap in interosseous membrane Supplies muscles of anterior compartment of the leg Descends on interosseous membrane and becomes dorsalis pedis artery Posterior tibial artery Larger of two terminal branches of popliteal Supplies muscles of posterior compartment Gives off fibular artery Descends deep to soleus Provides main blood supply to foot, after passing inferior to medial malleolus Palpable behind the medial malleolus Gives off nutrient artery to the tibia Circumflex fibular artery Arises from origin of anterior or posterior tibial Passes over neck of fibula to anastomosis around knee Fibular artery Largest branch of posterior tibial Supplies muscles of lateral compartment of the leg Begins below tendinous arch of soleus Gives off nutrient artery to the fibula Pierces interosseous membrane to reach dorsum of foot Dorsalis pedis Continuation of the anterior tibial artery Palpable between the first and second metatarsal heads Divides into plantar and arcuate arteries Supplies muscles on dorsum of foot Pierces first dorsal interosseous muscle as deep plantar artery of foot (plantar arterial arch) Medial plantar artery Smaller of two terminal branches of posterior tibial artery Supplies muscles of great toe, skin on medial side of sole Gives off plantar digital arteries Lateral plantar artery Larger than medial Accompanies lateral plantar nerve Arches medially across foot, beginning at base of fifth metatarsal as deep plantar arch Gives off four plantar metatarsal arteries Joins branches of medial plantar to form plantar digital arteries to toes

Vascular Supply: Veins (Fig. 7-6-2) Lower limb has superficial and deep venous systems with perforating veins communicating between them Veins have valves Veins of foot Superficial Metatarsal veins merge to form dorsal venous arch Communicates with plantar arch Both drain medially to great saphenous vein and laterally to small saphenous vein Deep Begin as dorsal digital and plantar digital veins Merge to deep veins accompanying arteries in leg and thigh Superficial veins of leg and thigh Great saphenous vein Courses along medial side of dorsum of the foot Passes in front of medial malleolus (location for venous cut down for emergency IV access here) Anastomoses freely with small saphenous vein Ascends medial side of leg, then posterior to the knee Ascends along medial thigh to saphenous hiatus in fascia lata Traverses hiatus to empty into femoral vein Has many valves Small saphenous vein Runs behind the lateral malleolus Ascends along lateral border of calcaneal tendon Pierces the deep fascia Ascends between heads of gastrocnemius Empties into popliteal vein Accompanied by the sural nerve Deep veins of leg and thigh Accompany all major arteries (venae comitantes) Are usually paired Are variable and anastomose freely Unite to form the popliteal vein and ascend as femoral vein Perforating veins Penetrate deep fascia Connect superficial and deep veins Have valves

Lymphatics (Plate 546) (Fig. 7-6-3) Superficial lymphatics follow the superficial veins Lymphatics following the great saphenous drain into superficial inguinal nodes Lymphatics following the small saphenous vein drain into popliteal nodes Deep lymphatics Follow vasculature in the muscle compartments Drain to deep inguinal nodes Popliteal nodes drain into the deep inguinal nodes

Nerves Cutaneous nerves (Fig. 7-6-4) Subcostal nerve (T12) to skin anterior to greater trochanter Iliohypogastric nerve (L1) to superior lateral buttock Ilioinguinal (L1) to proximal and medial thigh Genitofemoral nerve (L2–L3) to immediately inferior to middle inguinal ligament Lateral femoral cutaneous ((L2–L3) to lateral and anterior thigh Femoral nerve (L2–L4) Via anterior femoral cutaneous branches to anterior and medial thigh Via saphenous nerve to medial side of leg and foot Obturator nerve—branch to anterior, medial and posterior proximal thigh Posterior femoral cutaneous nerve—to posterior thigh and popliteal region Sciatic nerve: Supplies foot and most of leg Via sural, common, superficial, and deep fibular nerves Cluneal nerves (superior middle and inferior)—buttock Nerves to muscles of lower limb from lumbosacral plexus ( Plate 497) (Fig. 7-6-5) Nerves in the gluteal region: Superior gluteal nerve (L4–S1) Emerges superior to piriformis Supplies gluteus medius, gluteus minimus and tensor fasciae latae Inferior gluteal nerve (L5–S2) Inferior to piriformis Supplies gluteus maximus Nerve to quadratus femoris (L4–S1): also supplies inferior gemellus Pudendal nerve (S2–S4): supplies the perineum (not structures in the gluteal region) Nerve to obturator internus (L5–S2) Nerves to anterior and lateral thigh Femoral nerve (L2–L4) (Plate 538) Enters thigh lateral and deep to femoral artery Supplies the anterior compartment of the thigh Obturator nerve (L2–L4) (Plate 539) Enters thigh through obturator foramen and divides into anterior and posterior branches Supplies medial (adductor) compartment of thigh Nerves of posterior thigh Sciatic nerve (L5–S2) ( Plate 540) Enters gluteal region from pelvis through greater sciatic foramen Emerges inferior to the piriformis muscle Supplies no structures in the gluteal region Supplies posterior thigh muscles Bifurcates in lower third of thigh into tibial and common fibular nerves Via tibial and common fibular nerves, supplies all leg and foot muscles Nerves of leg Tibial nerve (Plate 541) Supplies the posterior compartment of leg Ends by dividing into medial and lateral planter nerves Common fibular nerve (Plate 542) Wraps around fibular head Divides into deep and superficial peroneal nerves Deep fibular nerve supplies anterior compartment of leg Superficial fibular nerve supplies lateral compartment of leg Nerves of foot Medial plantar to 3½ muscles of plantar foot Lateral plantar to remaining muscle of plantar foot

Dermatomes (Plate 543)

Myotomes (Plate 543) (Table 7-6-1) A group of muscles supplied by fibers from a single spinal nerve or a discrete group of spinal nerves is called a myotome

FIGURES

Plate 497: Lower Limb—Hip and Thigh—Lumbosacral and Coccygeal Plexuses (see Section 7-2: Lower Limb: Hip and Thigh)

Plate 540: Lower Limb—Neurovasculature—Sciatic Nerve and Posterior Femoral Cutaneous Nerve of Thigh

Fig. 7-6-1: Principal arteries of the lower limb (From Gosling JA, Harris PF, Whitmore I, et al. Human Anatomy, 4th Edition. Mosby, 2005. P. 228, Fig. 6.5)

Fig. 7-6-2: Veins of the lower limb (From Gosling JA, Harris PF, Whitmore I, et al. Human Anatomy, 4th Edition. Mosby, 2005. P. 228, Fig. 6.6)

Fig. 7-6-3: Lymphatic drainage of the lower limb (From Gosling JA, Harris PF, Whitmore I, et al. Human Anatomy, 4th Edition. Mosby, 2005. P. 229, Fig. 6.7)

Fig. 7-6-4: Areas of distribution of cutaneous nerves in the lower limb (From Gosling JA, Harris PF, Whitmore I, et al. Human Anatomy, 4th Edition. Mosby, 2005. P. 230, Fig. 6.9)

Fig. 7-6-5: Principal nerves of the lower limb (From Gosling JA, Harris PF, Whitmore I, et al. Human Anatomy, 4th Edition. Mosby, 2005. P. 229, Fig. 6.8)

Fig. 7-6-6: Computed Tomography (CT) Angiogram of the pelvic region and lower limbs showing vascular supply. (Image courtesy of Stephen W. Carmichael, Ph.D., D.Sc., Professor and Chair Emeritus, Department of Anatomy, Mayo Clinic, Rochester MN US)

TABLES

Table 7-6-1: Myotomes of the lower limb

		L2	L3	L4	L5	S1	S2
Hip	Flexion
	Extension
Knee	Extension
	Flexion
Ankle	Dorsiflexion
	Plantarflexion
Foot	Inversion
	Eversion
	Intrinsic

FACTS & HINTS

PART A: HIGH-YIELD FACTS

Box 7-6-1: Clinical Points

Chronic Arterial Occlusive Disease Caused by atherosclerosis In the lower limb, most commonly affects femoral artery as it passes through adductor canal Symptoms of intermittent claudication (pain in a muscle group because of poor blood supply) brought on by exertion in the early phase; may progress to pain at rest Ischemic ulcers can also develop Patients with advanced disease require vascular surgical intervention with bypass or endarterectomy

Box 7-6-2: Clinical Points

Foot Drop Injury to the common fibular nerve can result in loss of eversion and dorsiflexion of the foot Foot drops and toes drag on the ground when walking unless high-stepping gait is employed Variable amount of sensation also lost on the anterolateral aspect of the leg and dorsum of foot Nerve is vulnerable owing to superficial course as it wraps around fibular neck Nerve may be severed during fracture of fibula or dislocation of knee joint

Box 7-6-3: Clinical Points

Meralgia Paresthetica (Gunslinger's Neuralgia) Compression of the lateral cutaneous nerve of the thigh against the anterior superior iliac spine Causes a stinging or burning sensation in the anterolateral thigh Was caused by low-riding gun belt in the Old West

PART B: MNEMONICS

Box 7-6-4: Memory Aids

Nerves of the leg and their functions:

FED (Fibular nerve Everts and Dorsiflexes the foot) TIP (Tibial nerve Inverts and Plantarflexes the foot)