Lower Limb: Nerves Flashcards
What are the 2 plexi associated with the LL?
Lumbar and sacral plexus
What spinal nerves make up the lumbar plexus & where is it formed?
ventral (anterior) rami of L1 - L4 combine WITHIN psoas major to form lumbar plexus
Peripheral nerves emerge from psoas
What forms the sacral plexus and where is it formed?
The remaining part of ventral rami of L4 + ventral rami of L5 combine to form the lumbosacral trunk.
Lumbosacral trunk + ventral rami of S1-S3 and a bit of S4 combine to form the sacral plexus
Formation is ON piriformis, on the posterior wall of the pelvis
What is the main nerves of the gluteal region?
Superior + inferior gluteal nerve (SP)
What is the main nerve of the anterior compartment of thigh?
Femoral nerve (LP)
What is the main nerve of the medial compartment of thigh?
Obturator nerve (LP)
What is the main nerve of the posterior compartment of thigh?
Sciatic (SP)
What is the main nerve of the anterior compartment of Leg?
Deep fibular (terminal of sciatic)
What is the main nerve of the lateral compartment of Leg?
Superficial fibular (terminal of sciatic)
What is the main nerve of the posterior compartment of Leg?
Tibial nerve (terminal of sciatic)
What peripheral nerves emerge from the lateral border of psoas major?
L) L I I F
Ilioinguinal & iliohypogastric
Lateral cutanenous nerve of thigh
Femoral nerve
What peripheral nerves emerge from the anterior and medial borders of psoas major?
Anterior - genitofemoral
Medial - obturator
‘Get Amongst My Ovaries’
What is the course, spinal contribution and supply of the iliohypogastric & ilioinguinal nerves?
L1
Arise from the lateral border of psoas major onto QUADRATUS LOMBORUM
Motor - muscles of Ant abdo wall
Damage in old appendectomy could lead to inability to close inguinal canal - indirect hernia
Cutaneous - anteromedial part of upper thigh
What is the course, spinal contribution and supply of the genitofemoral nerve?
L1, L2
Arise from anterior border of psoas major
Motor (genital branch) - spermatic cord
Cutaeneous (femoral branch) - skin immediately beneath inguinal ligament
What is the course, spinal contribution and supply of the lateral cutaneous nerve?
L2, L3
Emerges from lateral border of psoas onto ILIACUS
Goes underneath the inguinal canal and drops into the anterior compartment of the thigh
Cutaneous - Skin of lateral thigh
Pregnancy & obesity - can get compressed against ASIS causing pins & needles
What is the course, spinal contribution and supply of the femoral nerve?
Posterior fibres of L2 - L4
Emerges from lateral border of psoas and goes beneath the inguinal ligament, passing through femoral triangle (adjacent to femoral sheath)
Divides into anterior & posterior terminal branches 2.5cm below inguinal ligament
Nerve of anterior compartment of thigh (except iliopsoas as it gets rami fibres)
Motor - sartorius & quadriceps
Sensory - anteromedial part of thigh (anterior cutaneous nerve) and medial part of knee, leg & ankle (saphenous nerve) + articular branches to hip & knee joints
What is the course, spinal contribution and supply of the obturator nerve?
Anterior fibres of L2 - L4
Nerve of medial compartment of thigh
Emerges from medial aspect of psoas and drops onto lateral wall of the pelvis, passing through the obturator canal and into medial compartment of thigh
Motor - 3 Adductors (- hamstring part of AM), pectineus, gracilis
Anterior & posterior divisions emerge between the 3 named adductors
Sensory - inferomedial skin of thigh + skin overlying hip joint
What are the peripheral branches of the sacral plexus?
A bit of L4, L5 + S1 - S3
Superior + inferior gluteal nerves
Posterior cutaneous nerve of the thigh
Sciatic nerve
What does the superior gluteal nerve innervate & what are its spinal routes?
Gluteus minimus + medius
L4 - S1
Emerges above piriformis
What does the inferior gluteal nerve innervate & what are its spinal routes?
Gluteus maximus
L5 - S2
Arises below piriformis
What does the posterior cutaneous nerve of the thigh innervate & what are its spinal routes?
S1 - S3
Skin over posterior aspect of thigh
What is the course of the sciatic nerve?
Formed from L4-S3 in the sacral plexus in the pelvis
Exits the pelvis from the greater sciatic foramen, emerging beneath piriformis in the gluteal region
Descends posterior to the hip through the thigh, underneath biceps femoris
Divides into terminal branches - tibial and common fibular nerves at the apex of the popliteal fossa
What does the sciatic nerve supply?
Only supplies the hamstrings (except short head of biceps femoris) via the tibial component
Remaining supply through terminal branches
What endangers the sciatic nerve?
Posterior dislocation of the hip joint
Intramuscular injections not given in the upper outer quadrant
Now give IM injections in the lateral thigh as variations in branching can occur that the fibular component may be affected by injection to upper outer quadrant
What are the terminal branches of the sciatic nerve?
Tibial nerve –> sural nerve, medial+lateral plantar nerves
Common fibular nerve –> superficial + deep fibular nerves, lateral cutanenous aural nerve
What is the course of the tibial nerve?
Continues verticle course of sciatic nerve through popliteal fosa, slips beneath fibrous arch of soleus and descends on tibialis posterior, between the superficial & deep muscles
Travels posterior to the medial malleolus (underneath flexor retinaculum) and onto the plantar surface of the foot (with deep posterior leg tendons)
Branches into the medial and lateral plantar nerves
What spinal routes does the tibial nerve arise and what does it supply?
Anterior division L4 - S3
Motor - Muscles of posterior leg (superficial & deep) + muscles of sole of foot
Sensory - sural nerve = posterolateral part of leg, lateral foot
- med + lat plantar nerves = plantar surface of foot
What is the course of the common fibular nerve & what spinal routes does it arise from?
Posterior division L4 - S2
Heads laterally, medial to biceps femurs and superficial to lateral head of gastrocnemius, winding round the neck of the fibula (lateral compartment) to sink into the substance of fibularis longus, where it divides into terminal branches
Terminal branches of common fibular nerve?
Superifical fibular + Deep fibular
Lateral cutaneous sural
What does the common fibular nerve supply?
Motor from terminal branches
Upper lateral cutaneous sural nerve supplies upper lateral leg and gives communications to the sural nerve
What is the course of the DEEP fibular nerve & what does it supply?
Beings in fibularis longus and descends deep to EDL and anterior to IO membrane
Passes beneath the extensor retinaculum with tendons of the anterior compartment of the leg and onto the dorsum of the foot
Motor - muscles of anterior compartment of the leg (EDL, EHL, Tibialis anterior, fibularis tertius)
Sensory - 1st toe cleft, articular branches to ankle and foot
What is the course of the SUPERFICIAL fibular nerve and what does it supply?
Descends in the lateral compartment of the leg
Motor - muscles of lateral compartment of leg (fibularis longus + brevis)
Sensory - lower lateral leg (common fibular does upper lateral part) and dorsum of foot (tibial nerve does plantar)
What causes a ‘foot drop’?
fracture/laceration to the neck of the fibula can damage the common fibular nerve
Affects motor supply to the muscles of the anterior and lateral compartments of leg
Anterior muscles - dorsiflex and extend toe + eversion (FT)
Lateral muscles - eversion of foot
Therefore can’t dorsiflex, evert foot or extend toes = foot drop
