Lower limb

Femoral triangle

Boundaries:

• • Inguinal ligament
  • Medial border of sartorius
  • Medial border of adductor longus
  • Floor: iliopsoas, pectineus, adductor longus and brevis (from lateral to medial)
  • Roof: fascia lata, which attaches to the inguinal ligament
    • Breached by fossa ovalis - allows lymphatics and GSV to enter. In turn, the fossa ovalis is covered by cribriform fascia.
  • Apex: SFA, SFV, saphenous nerve exiting the triangle

Content, from lateral to medial:

• • Femoral nerve (divides into anterior and posterior divisions within the triangle)
  • Femoral sheath (see 'inguinal region')
  • Femoral artery - branches within the triangle
  • Femoral vein
  • Femoral canal (see 'inguinal region')

Obturator canal

• A small opening in the superior aspect of the obturator foramen which connects the pelvis to the medial compartment of the thigh
• Contents:
  • Obturator nerve, artery and vein

Adductor canal

• The adductor canal (of Hunter) or 'sub-sartorial canal' is a triangular aponeurotic tunnel in the thigh which transmits the femoral vessels from the thigh to the popliteal fossa/
• It extends from the apex of the femoral triangle to the underside of the opening in adductor magnus, which is also known as the adductor hiatus
• Boundaries
  • Posteriorly - adductor longus above and magnus below
  • Anterior - vastus medialis
  • Medially - sartorius
• Contents
  • Femoral artery
  • Femoral vein (crosses posteriorly to artery, to become lateral to it)
  • Saphenous nerve (anterior to artery)
  • Nerve to vastus medialis (from the femoral nerve, in the upper tunnel)

Popliteal fossa:

• Diamond-shaped space behind the knee, which is the distal continuation of the adductor canal
• Boundaries:
  • Laterally - biceps femoris and gastrocnemius
  • Medially - Semitendinosus and semimembranosus
  • Floor (from above down): popliteal surface of femur, capsule of knee joint, popliteus
  • Roof: fascia lata (pierced by SSV and posterior femoral cutaneous nerves)
  • Inferiorly: gastrocnemius
• Contents - from superficial to deep:
  • Nerves (from division of sciatic nerve)
    • Common peroneal nerve - leaves the fossa in the far lateral aspect
    • Tibial nerve - runs down vertically, lateral to vessels above and medial below
  • Popliteal vein
  • Popliteal artery - divides into anterior and posterior tibial arteries in distal aspect of fossa
  • Fat
  • Popliteal lymph nodes
  • Bursea

Fascia, muscle and compartments

• Thigh
  • Fascia lata - deep fascia
    • Thickest laterally, where it forms the iliotibial tract
  • Encloses soft tissue into three compartments, usually with separate innervation and lymphatic drainage:
    • Adductor (pretty much all supplied by obturator nerve)
      • Gracilis
        • Most superficial
        • Arises from lower part of pubic body/ramus and inserts into upper tibia
        • Hip flexor/adductor
      • Pectineus
        • Flat, quadrangular muscle
        • Arises from pecten pubis and inserts into femur between lesser trochanter and linea aspera
        • Supplied by femoral nerve
        • Adductor of the thigh
      • Adductor longus
        • Most anterior of the adductors
        • Fans out to insert to linea aspera
        • Floor of the adductor canal
      • Adductor brevis
      • Adductor magnus
        • Largest adductor
    • Sartorius
      • Arises ASIS, inserts upper medial tibia
      • Medial blood supply with multiple small arteries entering along medial side from SFA
      • Flexes hip and knee, externally rotates femur
      • Medial edge is aligned with a straight line from ASIS to medial femoral condyle
      • Supplied by anterior division of femoral nerve

• Quadriceps
  • Rectus femoris
    • Two tendons - one from AIIS and the other above acetabulum
    • Inserts via patellar tendon
  • Vastus lateralis
    • Largest of the vasti
  • Vastus medialis
  • Vastus intermedius
  • Patellar tendon inserts into the tibial tuberosity

• Posterior femoral/hamstrings
  • Biceps femoris
    • Long head from ischial tuberosity; short head from linea aspera
    • Attaches to head of fibula
  • Semitendinosus
    • Arises from ischial tuberosity and inserts to medial tibia
  • Semimembranosus
    • Arises from ischial tuberosity and mostly inserts to medial tibial condyle

• Leg
  • Superficial fascia encircles the leg and is continuous with fascia lata of the thigh. This is adherent to underlying structures around knee joint and ankle joint. Thickened bands condense into retinacula at the ankle: restraining extensor, flexor and evertor tendons.
  • Strong septa join the crural fascia to the fibula, and also partition the leg into anterior, posterior and lateral compartments.
  • Tough interosseous membrane divides the anterior from posterior spaces. There is also a secondary interosseous septum arching posteriorly, dividing the posterior spaces into superficial and deep compartments.
  • Only two of the compartments contain arteries:
    • ATA in anterior compartment
    • PTA and peroneal arteries in the deep posterior compartment, sending branches to superficial posterior and lateral compartments.
  • Each major compartment contains a nerve:
    • Deep posterior compartment - tibial nerve
    • Anterior - deep peroneal nerve
    • Lateral - superficial peroneal nerve

Muscles of leg

• Posterior compartment:
  • Superficial:
    • Gastrocnemius
    • Soleus
    • Plantaris
    • All insert into the calcaneal tendon
  • Deep: (flexors of the ankle joint)
    • Tibialis posterior - central
      • PTA and peroneal artery descend on this muscle proximally
    • FDL - medial
    • FHL - lateral
  • All muscles supplied by the tibial nerve, which runs in the deep compartment

• Anterior compartment:
  • Medial: tibialis anterior
  • Lateral column of muscles, from proximal to distal origin:
    • EDL
    • EHL
    • Peroneus tertius
  • In between the two columns of muscle are the anterior tibial vessels and deep peroneal nerve, which supplies all the muscles
  • All muscle tendons pass deep to extensor retinaculum at the ankle

• Lateral compartment:
  • Peroneus longus
  • Peroneus brevis
  • Both originate from lateral border of fibula, then tendons passing under the superior peroneal retinaculum, posterior to the lateral malleolus
  • Supplied by superficial peroneal nerve which is in this compartment. Evert the foot and aid in flexion.

Nerves

• Thigh:
  • Femoral nerve
    • Largest branch of the lumbar plexus - L2-4
    • Passes beneath the inguinal ligament to enter the femoral triangle, lateral to femoral sheath. Separated from femoral vessels by the iliopectineal arch.
    • Divides into anterior and posterior divisions about 4cm into the thigh
    • Branches
      • Early branches to pectineus, sartorius, quadriceps muscles
      • Cutaneous branches to intermediate and medial femoral cutaneous branches
      • Saphenous nerve arises as the continuation of posterior division, travelling through the adductor canal
• Leg:
  • Tibial part of sciatic nerve, becoming tibial nerve - supplies posterior compartment
    • Branches:
      • Medial half of sural nerve
      • Medial and lateral plantar nerves
  • Peroneal part of sciatic nerve, becoming peroneal nerve
    • Superficial peroneal nerve - peroneal muscles (longus and brevis)
    • Deep peroneal nerve - anterior compartment
  • Sural nerve - arises from the tibial nerve and common peroneal nerve, passes alongside SSV

Arterial supply:

• Common femoral artery
  • Path:
    • EIA becomes CFA at the inguinal ligament
    • Enters the thigh just medial to the mid-point of the inguinal ligament
    • Initially lying on psoas major tendon
    • Descends on pectineus towards the apex of the femoral triangle
  • Surface markings:
    • Two-thirds of the way along a line between mid-inguinal point towards the adductor tubercle
  • Branches:
    • Superficial
      • External pudendal
      • Circumflex iliac (commonly used to run a groin flap)
      • Epigastric
    • Deep external pudendal
    • Profunda femoris: arises from lateral side of CFA about 3-4cm distal to IL, then spiralling down deep to it, passing between pectineus and adductor longus (whose upper border separates SFA and DFA), towards medial aspect of femur. Continues down on adductor brevis and magnus and ends as the fourth perforating artery. Supplies the majority of blood to thigh muscles. Distal perforators anastomose with popliteal branches.
      • Branches
        • Four perforating arteries - pass backwards through adductor magnus.
        • Lateral circumflex femoral (within femoral triangle)
          • Arises from lateral side of PFA. Divides into three branches: ascending, transverse and descending. Supplies proximal quadriceps muscle.
        • Medial circumflex femoral
          • Arises from medial side of profunda. Supplies proximal adductor compartment.
      • Parts:
        • Within femoral triangle - approach anteriorly
        • Behind adductor longus - medial approach, which bluntly dissects the plane between sartorius and adductor muscles
        • Behind linea aspera - same medial approach
  • Approach:
    • Can be approached in the adductor canal with an incision on the medial aspect of the lower thigh, then retracting sartorius medially and dividing the fascial roof

• Superficial femoral artery
  • Path
    • Becomes superficial femoral artery at the point where the deep femoral artery branch comes off.
    • Enters adductor canal (Hunter's canal) deep to sartorius
  • Branches
    • Highest geniculate just proximal to adductor canal (important in adductor hiatus occlusions)
• Popliteal artery
  • Path:
    • Begins where it exits the adductor canal at the apex of the popliteal fossa
    • Extends to the lower border of popliteus muscle
    • Divides into ATA and TPT in the distal popliteal fossa
      • True trifurcation about 3%
      • Generally forms ATA and TPT, with the other two vessels coming off TPT 2-3cm distally
  • Branches
    • Five genicular arteries - superior and inferior medial, superior and inferior lateral, and middle
• Tibioperoneal trunk
  • Short trunk that bifurcates into two terminal branches - peroneal and posterior tibial

• Peroneal artery (lateral)
  • Initially descends on tibialis posterior in deep posterior compartment
  • Distal third runs within and behind the belly of FHL
  • Terminates in a variable branch perforating through the distal interosseous membrane and calcaneal branches
• Posterior tibial artery (medial)
  • Descends on tibialis posterior in deep posterior compartment
  • Passes down along with tibial nerve between FDL and FHL
• Anterior tibial artery
  • Passes into anterior compartment at the upper end of the interosseous membrane
  • Lies lateral to tibialis anterior and the medial to the other muscles in the anterior compartment (see above)
  • Emerges at the ankle with the deep peroneal nerve
  • Continues distally as DP

Venous system:

• Deep:
  • Located beneath deep fascia and accompany corresponding arteries
  • Anterior and posterior tibial -> popliteal -> femoral
  • Femoral vein
    • Tributaries - GSV and profunda femoris vein and circumflex femoral veins
  • Popliteal vein
    • Formed from the union of the two venae comitantes of the anterior and posterior tibial arteries
    • Receives SSV
• Superficial:
  • The superficial system collects blood from superficial tissues and skin and then routes it back to the deep system for return.
  • GSV, SSV and many communications
  • Great saphenous vein (GSV - also long saphenous vein)
    • Path:
      • Begins as the upward continuation of the medial marginal vein of the foot, and courses upward in front of the medial malleolus.
      • Runs behind the medial border of tibia to the knee (together with saphenous nerve)
      • Hand's breadth behind medial edge of patella
      • Posterior arch vein joins it at or below the knee joint. In the vast majority of cases, the GSV at calf level is anterior-dominant.
      • Spirals forward round the medial convexity of the thigh
      • The GSV passes between deep and superficial layers of fascia (see below diagram).
      • It ends (at the fossa ovalis) by passing through the cribriform fascia covering the saphenous opening (which lies about 3cm below and lateral to the pubic tubercle), where it joins the femoral vein into its anteromedial side, 1-3cm below the inguinal ligament (saphenofemoral junction).
      • External pudendal artery runs between GSV and CFV and is susceptible to injury
    • Structure:
      • It contains 7-20 valves, mostly below knee level.
      • Longest vein in the body
    • Tributaries
      • Up to four tribs join the GSV near the saphenofemoral junction:
      • Superficial circumflex iliac
      • Superficial (inferior) epigastric
      • Superficial external pudendal
      • Deep external pudendal
      • Can also see posteromedial and anterolateral accessory branches
    • Fascial envelope: 60% have type A, 30% type B, 10% type C (see below for diagram)
    • 8% have a lateral-dominant system instead
    • Variant anatomy
      • Duplication of GSV
      • Some tributaries draining directly into SFJ/CFV

• Small saphenous vein (SSV)
  • Path:
    • Forms from the confluence of the lateral aspect of the dorsal venous network of the foot (lateral marginal vein of the foot)
    • Originates inferior and posterior to the lateral malleolus, and ascends on the posterior aspect of the calf between the gastrocnemius heads to the popliteal fossa.
    • It generally joins with the popliteal vein within 5cm of the knee crease, however the confluence has a variable location, and can be above-knee popliteal in 33%.
    • Note that SSV is intimately associated with the sural nerve at the posterolateral aspect of the ankle.
    • The SSV also lies within its own fascial compartment and has 7-10 valves.
    • Lots of perforators
• Communicating veins
  • Cockett's perforators occur at 3, 6 and 9cm above the medial malleolus, usually terminating in posterior tibial veins
  • Gastrocnemius veins emerge from medial and lateral heads of gastrocnemius, and may join the popliteal vein directly or merge with the SSV to form a common trunk then enter popliteal.
  • Intersaphenous (Giacomini) vein courses up the posterior medial aspect of the thigh. It is often a tributary of SSV
  • Reticular veins are thin-walled blue venules lying within the superficial compartment, often connecting to telangiectasias
  • Telangiectasias are dilated venules, capillaries or arterioles 0.1 to 1.0mm in diameter. Arterial telangiectasias are flat and red, while venous telangiectasias are raised and blue.

Lymphatics:

• Superficial inguinal nodes - about 20 nodes, arranged in a T pattern in the subcutaneous fat of the femoral triangle, deep to Scarpa's but superficial to fascia lata
  • Distal group lies vertically along terminal great saphenous vein - the vertical part of the T
  • Proximal group just distal to inguinal ligament - the horizontal part of the T
    • Lateral nodes - buttock, flank, back below the waist - below the lateral part of inguinal ligament.
    • Medial - umbilicus, anterior abdominal wall below umbilicus, external genitalia (excluding testes, but including lower vagina), lower anal canal and perineum - below the medial part of the inguinal ligament, and possibly encroaching above it.
    • Vertical/distal - all the superficial lymphatics from the lower limb except those from the posterolateral calf. Lie lateral to termination of GSV.
  • Drain mainly to the external iliac nodes by efferent lymphatics which converge on the saphenous opening, passing through the cribriform fascia
• Deep inguinal nodes - lie deep to the fascia lata, medial to femoral vein. Receive deep lymphatics accompanying femoral vessels from popliteal fossa, glans penis and a few efferent lymphatics from the superficial inguinal nodes. But most of the deep inguinal nodes drain to the external iliac nodes through the femoral canal.