Posterior Leg Anatomy PDF

Posterior Leg Paul Fletcher  Outline for today Lecture: posterior leg Revision Quiz: up until today’s content Review lecture: nerves and vessels of the lower extremity Posterior Leg  Posterior compartment Divided into 2 sub-compartments: superficial and deep Supe...

Posterior Leg Paul Fletcher  Outline for today Lecture: posterior leg Revision Quiz: up until today’s content Review lecture: nerves and vessels of the lower extremity Posterior Leg  Posterior compartment Divided into 2 sub-compartments: superficial and deep Superficial compartment: gastrocnemius, soleus, plantaris Gastrocnemius (two heads) + soleus = triceps surae Deep compartment: popliteus, flexor hallucis longus (FHL), flexor digitorum longus (FDL), tibialis posterior (TP)  Gastrocnemius Origin: two heads: above the medial and lateral femoral condyles (ie. Above the knee joint) … join at the mid-leg… Insertion: tendo achilles (tendo calcaneus) Innervation: tibial nerve Action: foot plantarflexion, knee flexion  Question How many joints does gastrocnemius cross? – supinates a supinated STJ, pronates a pronated STJ  Soleus Lies deep to gastrocnemius Origin: head and upper 1/3rd of fibula, soleal line Insertion: joins with gastrocnemius into tendo achilles Innervation: tibial nerve Action: Foot (AJ) plantarflexor Action: triceps surae: active during gait from forefoot loading to toe off Triceps surae pathology: contracture (muscular equinus) Stretching?  Plantaris Small muscle of little functional importance Origin: lateral supra condylar line (ie. Above knee joint) Insertion: achilles tendon Action: very weak KJ flexor and AJ plantarflexor  Deep posterior compartment Muscles: popliteus, flexor hallucis longus (FHL), flexor digitorum longus (FDL), tibialis posterior (TP) Popliteus: forms the ‘floor’ of the popliteal fossa – Origin/insertion: lateral condyle of the femur/lateral meniscus --> soleal line of posterior tibia – Innervation: tibial nerve – Action: medial/lateral rotation of the knee joint  Flexor hallucis longus Origin/insertion: lower 2/3rds fibula/IoM & intermuscular septa --> wraps around the medial malleolus, passes between the sesamoids (under the 1st MTPJ) --> insert into the distal hallux phalanx Innervation: tibial nerve Action: 1st MTPJ/IPJ flexion, AJ flexion  Flexor digitorum longus Origin/insertion: posterior tibia --> wraps around medial malleolus under flexor retinaculum --> passes laterally into plantar foot - divides into 4 tendons - insert into distal phalanx of lesser 4 toes Innervation: tibial nerve Action: plantarflex the lesser 4 phalanges and foot plantarflexor, stabilises toes on ground during gait  Tibialis Posterior Origin/insertion: IoM and tibia/fibula --> flexor retinaculum --> navicular tuberosity and all tarsal bones except talus Nerve supply: tibial nerve Action: Foot inversion and AJ plantarflexion Pathology: weakness/rupture --> progressively pronated foot  Structures under flexor retinaculum ‘Tom, Dick and very naughty Harry’ – TP – FDL – Artery – Vein – Nerve – FHL (Anterior to posterior)  Nerve supply Tibial nerve – Larger terminal branch of the sciatic nerve – Popliteal fossa --> passes deep to triceps surae (tibialis posterior, tibia) --> wraps behind medial malleolus (between FDL and FHL, under flexor retinaculum) --> medial and lateral plantar nerves – Muscular branches (soleus, FDL, FHL, TP) – Cutaneous branch (medial calcaneal branch) – Articular branch (AJ)  Nerve supply: leg Cutaneous nerves of leg – Posterior cutaneous nerve of the thigh (branch of sacral plexus) – Lateral cutaneous nerve of the calf (branch of common peroneal) – Sural nerve (branch of tibial nerve) – Saphenous nerve (branch of femoral nerve)  Review of nerves and vessels of the lower extremity  Blood supply to the lower limb External iliac (under inguinal ligt in femoral sheath) --> femoral artery (thru femoral triangle) --> branches into profunda femoris (medial & lateral circumflex and perforating a.) --> (adductor canal & adductor hiatus) (popliteal fossa) --> popliteal a. --> anterior and posterior tibial a. --> ant tibial (above IoM) --> medial/lateral malleolar branches --> (AJ) dorsalis pedis … --> post tibial --> medial and lateral plantar arteries (metatarsal branches, plantar arterial arch)  Blood supply to the lower limb Abdominal aorta --> common iliac a. External iliac a. --> superior and inferior gluteal a.  Anastomoses between arteries supplying the lower limb Trochanteric fossa: branches of the gluteal a. anastomose with branches of the medial and lateral femoral circumflex a. Circumflex a. with gluteal a and upper perforating branch of profunda femoris a. = ‘cruciate’ anastomosis Perforating a.’s and genicular vessels Therefore, a chain of anastomoses is created such that the leg can derive arterial supply if the femoral trunk is blocked at different sites  Venous drainage of the lower limb Superficial veins = drain the skin and superficial fascia Deep veins = travel in pairs with smaller arteries = ‘venae comitantes’ Connecting these 2 sets (separated by fascia lata) = communicating veins  Venous drainage of the lower limb Superficial drainage: dorsal venous arch – --> laterally drained by short saphenous vein (runs behind lat. malleolus and up posterior leg to popliteal fossa and drains into popliteal vein) – --> medially drained by long saphenous veing (passes in front of med. Malleolus -- > ascends superficially in leg and thigh on medial side) --> femoral vein --> external iliac vein --> inferior vena cava  Venous drainage of the lower limb Deep drainage: two venae comitantes accompany each of the smaller arteries in the leg and eventually join to form the popliteal vein --> adductor hiatus --> femoral vein Varicose veins are common: valves within veins become incompetent – Tortuous, engorged veins – Superficial veins usually as deep veins utilise muscle pump to work – If blood remains pooled in the extremities long enough --> interstitial spaces - oedema - haemosiderin - ulceration  Lymphatic drainage of the lower limb The lymphatic drainage follows the general pattern of the superficial and deep venous drainage – Little communication between superficial and deep lymphatics – Superficial lymph glands: near inguinal ligament and popliteal fossa ‘The big 3’ Sciatic Femoral Obturator Nerve supply: Sciatic nerve Sciatic nerve (L4/5, S1-3): divides into tibial and common peroneal nerves Tibial nerve: passes down posterior leg superficial to TP and deep to triceps surae --> medial malleolus --> divides into medial and lateral plantar nerves – Articular, muscular and cutaneous branches (sural, medial calcaneal branch)  Common peroneal Common peroneal nerve – Popliteal fossa --> wraps around lateral neck of the fibula – Supplies the knee joint (articular) and skin on posterior and postero-lateral aspects of the leg – Divides into superficial and deep peroneal nerves – Superficial peroneal n.: lateral compartment of leg (supplies skin: lower lateral leg, anterior ankle, dorsum of foot [except 1st webspace] – Deep peroneal n.: enters anterior compartment, moves under extensor retinaculae (supplies skin: 1st webspace)  Sural nerve Formed by branches of both tibial and common peroneal nerves – Runs down posterior calf with the short saphenous vein – Supplies skin on posterior calf, heel and lateral foot  Femoral & Obturator nerves Femoral nerve: inguinal ligament/sartorius/adductor canal After passing underneath the inguinal ligt., the femoral n. breaks up into its terminal branches Motor branches: anterior compartment muscles Sensory branches: supply skin over anterior and medial thigh; saphenous nerve (supplies strip of skin running medially down the limb to the 1st MTPJ Note: lateral cutaneous nerve of the thigh arises separately from the lumbar plexus --> supplies lateral aspect of the thigh  Femoral & Obturator nerves Passed through obturator foramen – Anterior and posterior branches – Supplies muscles in thigh adductor compartment, overlying skin and HJ & KJ  Summary Now that you’ve learnt about most of the lower extremity - importance of ‘putting it together’ Practice surface anatomy on family members/friends to appreciate anatomical variation Questions?