MSK Nerves of the lower limb Flashcards
Where is the lumbar plexus located?
In the lumbra region, within the psoas major and anterior to transverse process of lumbar vertebrae
What are the spinal nerves forming the lumbar plexus?
T12-L4
At each vertebral level paired spinal nerves leave the spinal chord via the intervertebral foramina. The nerves then divide into anterior and posterior - the lumbar plexus is the anterior fibres
List the major peripheral nerves of the lumbar plexus
Iliohypogastric nerve Ilioinguinal nerve Genitofemoral nerve Lateral cutaneous nerve of the thigh Obturator nerve Femoral nerve
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What is lumbosacral plexopathy?
Rare disorder affecting either lumbar or sacral plexus
The symptoms cannot be localised to a single nerve - may be numbness, weakness, muscle wastage
Main cause is diabetic amyotrophy - high blood sugar levels damage the nerves
Tumors can cause compression of the plexus
Describe the Iliohypogastric nerve
Runs along posterior abdo wall to the iliac crest.
Nerve roots are L1 with some contribution of T12
Motor functions: internal oblique and transversus abdominis
Sensory functions: posterolateral gluteal skin
Describe the Ilioinguinal nerve
Roots: L1
Motor functions: (same as iliohypogastric) internal oblique and transversus abdominas
Sensory functions: skin of upper middle thigh and genitalia
Describe the Genitofemoral nerve
Roots: L1 L2
Motor functions: genital branch innervates a muscle in the testis
Sensory functions: Genital branch innervates skin of genitals and femoral branch innervates skin of upper anterior thigh
Describe the Lateral cutaneous nerve of thigh
Purely sensory function
Enters thigh at lateral inguinal ligament
Roots: L2 and L3
Sensory functions: anterior and lateral thigh down to knee
Describe the Obturator nerve
Roots: L2 3 4
Motor functions: medial adductors of thigh (adductor longus brevis magnus, gracilis, pectineus and obturator externus)
Sensory functions: skin of medial thigh
Describe the Femoral nerve
Largest branch of lumbar plexus
Roots: L2 3 4
Motor functions: hip flexers (iliacus, pectineus, sartorius) all quads
Sensory functions: anterior thigh (anterior cutaneous branches) and medial leg (saphenous nerve)
What is the anatomical course of the femoral nerve?
Descends from lumbar plexus in the abdo through the psoas major muscle
The nerve travels through the pelvis to midpoint of inguinal ligament, goes behind ligament into the thigh and splits into anterior and posterior division
Passes through femoral triangle and gives off articular branches to knee and hip joints.
The terminal branch is the saphenous nerve which passes through adductor canal into leg
What are the signs of damage to the saphenous nerve?
Pain paraesthesia or complete loss of sensation of medial side of lower leg
What is the anatomical course of the obturator nerve?
Runs through psoas major along the pelvic wall to obturator foramen. Enters the thigh through the obturator canal and splits into anterior and posterior divisions.
Anterior division descends between adductor longus and brevis. It then pierces fascia lata to become the cutaneous branch of obturator nerve.
Posterior division descends through obturator externus then anteriorly to adductor magnus
Where is the sacral plexus located?
Posterior pelvic wall, anterior to piriformis
What are the spinal nerves that make up the sacral plexus?
S1-4
Receives contributions from L4-5 which combine to form the lumbosacral trunk
Name the branches of the sacral plexus
Superior + inferior gluteal nerve Sciatic nerve Posterior femoral cutaneous nerve Pudendal nerve Nerve to piriformis, obturator externus and quadrator femoris
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What are the 2 main destinations for the nerves of the sacral plexus?
Leave the pelvis via the great sciatic foramen and enter the gluteal region
Remain in the pelvis and innervate structures there
Describe the superior gluteal nerve
Accompanied by superior gluteal artery and vein for musch of its course
Roots: L4 5 S1
Motor functions: glut med min, tensor fascia lata
No sensory
Describe the inferior gluteal nerve
Accompanied by inferior gluteal artery and vein for much of its course
Roots: L5 S 1 2
Motor functions: glut max
No sensory
Describe the posterior femoral cutaneous nerve
Roots: S1 2 3
No motor
Sensory: posterior thigh and leg and perineum
Describe the pudendal nerve
Roots: S 2 3 4
Motor functions: perineal muscles, sphincter
Sensory functions: penis and clit
What are the roots of the sciatic nerve?
L4 5 S1 2 3
What are the 2 terminal branches of the sciatic nerve?
Tibial branch
Common fibular branch
Describe the tibial branch of the sciatic nerve
Motor functions: innervates all posterior thigh muscles except short head of biceps femoris, all posterior leg and all foot
Sensory functions: posterolateral and lateral foot and sole
- medial calcaneal branches innervate heel skin
- medial plantar nerve innervates lateral 3 1/2 digits and associated sole area
- lateral plantar nerve innervates lateral 1 2/2 digits and associated palm area
Describe the common fibular branch of the sciatic nerve
Motor functions: short head of biceps femoris, all anterior and lateral leg and extensor digitorum brevis
- superficial fibular innervates lateral leg muscles
- deep fibular nerve innervates anterior leg muscles and intrinsic muscles of foot
Sensory functions: anterolateral leg and dorsal of foot
- superficial fibular innervates anterolateral leg and dorsal of foot
- deep fibular nerve innervates skin between 1st and 2nd toes
What is the anatomical course of the sciatic nerve?
Enters glut region via the greater sciatic foramen and emerges inferiorly to piriformis
Enters posterior thigh by passing deep to long head of bicep femoris
When it reaches the apex of the popliteal fossa it terminates by bifurcating into the tibial and common fibular nerves
What are the motor functions of the sciatic nerve?
Posterior thigh and hamstring part of adductor magnus
What is the best site for intramuscular injections in the gluteal region and why?
Split bum into 4 quadrants?:
one line vertically from highest point of iliac crest
the other line passes horizontally midway between highest point of iliac crest and ischial tuberosity
Injection given in upper lateral quadrant to avoid the sciatic nerve
What is tarsal tunnel syndrome?
The tibial nerve is compressed in the tarsal tunnel by osteoarthritis pr rheumatoid arthritis or post trauma ankle deformities.
There is paraesthesia of ankle and sole of foot which gets is relieved by rest
Treatment includes anti-inflammatory drugs, footware or surgery to cut the flexor retinaculum to release pressure
What is the anatomical course of the tibial nerve?
Arises from sciatic nerve at apex of popliteal fossa
Descends down leg posterior to tibia
Passes through tarsal tunnel, posteriorly and inferiorly to the medial malleolus.
Gives off medial calcaneal branches to innervate heel
Gives off medial and plantar branches to innervate sole of foot
What is the anatomical course of the common fibular nerve?
Arises from sciatic nerve at the apex of the popliteal fossa
Follows medial border of biceps femoris and gives rise to 2 cutaneous branches.
To enter lateral leg it wraps around neck of fibula and terminates by dividing into superfical and deep fibular nerves
What is the cause and result of entrapment of the superficial fibular nerve?
Usually from ankle sprains and twisting which stretches the nerve or where the nerve exits the deep fascia and is compressed (needs surgery)
Pain and parasthesia in the lower leg and dorsum of foot
How is the superficial fibular nerve directly damaged?
Fracture of the fibula or a wound to lateral leg
