"Review of Nerves and Vessels of the Lower Limb" Questions Flashcards
What can the nervous system of the body be divided into and what does each component contain?
Central nervous system - brain + spinal cord
Peripheral nervous system - cranial + spinal nerves
Other than central/peripheral, what other category can the nervous system of the body be divided into and what are the components of each?
Somatic nervous system
- somatic motor (efferent) to skeletal muscle
- somatic sensory (afferent) sensory information from skin + muscle
Autonomic nervous system
- autonomic motor
- autonomic sensory
- this is from/to cardiac and smooth muscle, glands, gut etc
How many pairs of spinal nerves are there, what are the divisions of these nerves and what are they formed from?
31 pairs
- 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
- each spinal nerve is formed from a union between an anterior root (motor) and dorsal root (sensory) and the roots merge at the intervertebral foramen to form a spinal nerve
Where do autonomic fibres pass, in terms of vertebral levels?
Between T1-L2 and S2-S4
Which of the anterior and posterior rami form the major plexi (plexuses) of the limbs?
Anterior rami
- of C4-T1 for upper limb
- of L2-S2/S3 for lower limb
What are the 5 main nerves innervating the muscles of the leg and which muscles/compartment do they innervate?
Femoral nerve (L2-L4, posterior fibres) - iliopsoas, anterior compartment of the thigh
Obturator nerve (L2-L4, anterior fibres) - medial compartment of the thigh
Sciatic nerve (L3-S3, anterior + posterior fibres) - posterior compartments of thigh and leg, foot
Superior gluteal nerve (L4-S1) - gluteus medius + minimus, tensor fascia lata
Inferior gluteal nerve (L5-S2) - gluteus maximus
What is the principle about muscles with the same action regarding their nervous supply?
If they have the same action on a particular joint, they will have a common nerve supply
What is the principle about muscles/muscle groups with opposing actions?
Opposing muscle have nerve supplies 1-2 segments above or below
What are the spinal nerve roots for hip flexion/extension, knee flexion/extension, and ankle dorsiflexion/plantarflexion?
Hip flexion - L2, L3 Hip extension - L4, L5 Knee flexion - L5, S1 Knee extension - L3, L4 Ankle dorsiflexion - L4, L5 Ankle plantarflexion - S1, S2
How are the spinal nerves divided amongst the areas of the body in terms of where they supply?
C1-C4 - neck C5-T1 - upper limbs T2-L1 - trunk L2-S2 - lower limbs S2-C1 - perineum
What is the peripheral innervation for the lower limb derived from and what is this structure derived from?
Derived from the lumbo-sacral plexus
- lumbo-sacral plexus is derived from the anterior rami of the lumbar and sacral spinal nerves
What are the 6 branches of the lumbar plexus and their spinal roots?
Iliohypogastric and ilio-inguinal (L1)
Genitofemoral (L1, L2)
Lateral cutaneous nerve of the thigh (L2, L3)
Femoral nerve (L2, L3, L4, posterior divisions)
Obturator nerve (L2, L3, L4, anterior divisions)
Lumbosacral plexus (L4, L5 - feeds sacral plexus)
What are the 8 branches of the sacral plexus and their spinal roots?
Sciatic nerve (L4, L5, S1, S2, S3) Nerve to piriformis (S1, S2) Posterior cutaneous (S1, S2, S3) Pelvic splanchnic (S2, S3, S4 - parasympathetic) Pudendal (S2, S3, S4) Nerve to obturator internus (L5, S1, S2) Superior gluteal (L4, L5, S1) Inferior gluteal (L5, S1, S2)
What motor and sensory innervations does the femoral nerve provide and what does it terminate as?
Motor - iliopsoas and anterior thigh muscles
Sensory - front of the thigh
Terminates as the saphenous nerve (sensory to medial aspect of the leg)
What motor and sensory innervations does the ubturator nerve provide?
Motor - supplies the adductor (medial compartment) muscles of the thigh
Sensory - medial aspect of the thigh (and parts of the pelvis)
What motor and sensory innervations does the sciatic nerve supply and how does it branch?
Sciatic nerve proper supplies the hamstring muscles and some sensory branches to the back of the thigh
- passes through greater sciatic foramen into the posterior compartment of the thigh and (just above the knee joint) branches into tibial and common peroneal nerves
What motor and sensory innervations does the common peroneal nerve provide and what does it terminate as?
Motor - anterior and lateral compartments of the leg
Sensory - anterior and lateral aspects of the leg and dorsum of the foot
Terminal branches are the superficial and deep peroneal nerves (motor), sural nerve (important sensory branch)
What motor and sensory innervations does the tibial nerve provide?
Motor - posterior compartment of the leg and most intrinsic muscles of the foot
Sensory - back of the leg and sole of the foot
Nerve function (and its impairment) can be assessed by 5 modalities, what are they?
Motor Sensory Reflex Autonomic (like sweat etc) Trophic (growth/cellular damage)
As an example, describe the nerve function after damage to the common peroneal nerve at the level of the fibular neck (very common place for it to be damaged).
Motor - foot drop, loss of muscle action in anterior and lateral compartments of the leg
Sensory - loss of sensation in the distribution of the common peroneal nerve i.e. the dorsum of the foot at least
Reflex - no loss of reflexes as ankle jerk reflex is innervated by the tibial nerve
Autonomic - abnormalities of sweating in the cutaneous distribution of the common peroneal nerve
Trophic - in chronic cases there may be damage to the sole of the foot due to the pressure effects of the foot drop
How likely is the femoral nerve to get injured and what can injure it?
Rarely damage except iatrogenically
- commonest injury is via traction injuries during hip replacements and laparoscopic repairs of inguinal hernias
- can be damaged during erroneous attempted cannulations of the femoral artery/vein
During surgery or poor cannulation of femoral artery/vein
How likely is the lateral cutaneous nerve of the thigh to get injured and what can injure it?
Fairly unlikely
Superficial nerve that passes 2cm medial to the ASIS at the level of the inguinal ligament
- can be compressed at this level causing Bernhardt-Roth syndrome
- BR syndrome is numbness/pain in the outer thigh caused by nerve injury rather than trauma to the thigh
How likely is the obturator nerve to get injured and what can injure it?
Rarely damaged
- pain in the distribution of the obturator nerve can be indicative of malignant pelvic disease
How likely is the superior gluteal nerve to get injured and what can injure it?
Fairly uncommon
- commonest injury is in hip replacement
- leads to Trendelenberg’s gait due to loss of gluteus medius/minimus muscles
How likely is the sciatic nerve to get injured and what can injure it?
Fairly uncommon
- commonest cause is after hip replacement
- common peroneal division is more at risk than the tibial division
- sciatic nerve can be damaged at the hip by erroneous IM injection (remember use safe quadrant)
- less common causes are hip dislocations/acetabular fractures (trauma), and pelvic disease
Where can the common peroneal nerve get injured and what can injure it?
Can be damaged at the level of the hip and highly vulnerable at the level of fibular neck (wraps around it)
- causes of damage include trauma, knee replacement and external pressure (e.g. during surgical procedure)
How likely is the tibial nerve to get injured?
Rarely damaged in isolation as it is very deep
- only really going to get damaged if sciatic nerve is damaged at the hip
How likely is the saphenous nerve to get injured and what can injure it?
Commonly injured
– can be damaged at the medial malleolus or at the level of the knee (e.g. ACL surgery)
What are nerve blocks and what are they used for?
Nerve blocks can be utilised by anaesthetists to aid or substitute general anaesthesia during surgery
What are some examples of nerve blocks in the lower limb?
Femoral nerve blocks
Sciatic nerve blocks
Ankle blocks
Blocks of the lateral cutaneous nerve of the thigh
How does the anaesthetist determine the best place to insert local anaesthetic?
Knowledge of peripheral anatomy
- allows to localise best place to put it and predict the level and extent required
Summarise the arterial supply of the thigh. (write it out on a piece of paper)
Aorta splits into the common iliac arteries at L4
Common iliac arteries bifurcate at the pelvic brim into the internal iliac artery (gives off obturator artery) and external iliac artery
External iliac artery becomes the femoral artery at the inguinal ligament
Femoral artery passes underneath the inguinal ligament at the mid-inguinal point
Just underneath the inguinal ligament it has four branches; superficial circumflex iliac artery, superficial epigastric artery, superficial external pudendal artery, deep external pudendal artery
The femoral artery continues downward and gives off the profunda femoris artery before itself becoming the superficial femoral artery
The femoral artery enters the adductor canal and becomes the popliteal artery
The popliteal artery bifurcates at the distal end of the popliteal fossa into the anterior and posterior tibial arteries
Summarise the arterial supply to the leg. (also write this down on a piece of paper then summarise the whole lower limb)
The anterior tibial artery passes into the anterior compartment of the leg, running on the interosseous membrane.
- at the level of the foot, the anterior tibial artery becomes the dorsalis pedis artery
The posterior tibial artery passes into the posterior compartment of the leg alongside tibialis posterior
- it passes behind the medial malleolus and enters the foot before dividing into the MEDIAL and LATERAL PLANTAR arteries
- the posterior tibial artery gives off a branch called the peroneal artery which supplies the lateral compartment of the leg
Briefly summarise the superficial veins of the lower limb.
Dorsal venous arch receives most of the blood from the foot
Long saphenous vein starts from the medial portion of the dorsal venous arch of the foot and runs up the medial aspect of the leg
Short saphenous vein starts from the lateral aspect of the dorsal venous arch of the foot
Both saphenous veins communicate until short saphenous vein ends by draining into popliteal vein (deep system)
The long saphenous vein eventually (at the sapheno-femoral junction) drains into the femoral vein (deep system)
There are a multitude of important veins that act as a passage for blood to move from the superficial veins to the deep veins - these are the PERFORATING veins
Junctions with these veins have valves to prevent back flow of blood from deep to superficial systems - faulty in varicose veins
Briefly summarise the deep veins of the lower limb.
The deep veins lie within the deep fascia and generally run alongside the arteries.
They have valves to prevent back flow of blood.
The venae comitantes of the anterior/posterior tibial arteries and the popliteal artery form the popliteal vein.
The deep veins are mainly within muscle, and the “muscle pump” contributes towards the venous return from the lower limb to the abdomen.
The popliteal vein receives the short saphenous vein at the popliteal fossa.
Popliteal vein eventually becomes the femoral vein
Just proximal to the inguinal ligament, the profunda femoris veins and then the long saphenous vein join the femoral vein.
Once the femoral vein has passed the inguinal ligament it comes the external iliac vein.
What is the anatomy of the femoral sheath and what structures lie where?
Femoral sheath encloses the femoral vessels distal to the inguinal ligament
- femoral artery is always lateral to the femoral vein
Where would you palpate the femoral artery pulse?
Mid-inguinal point
Where would you palpate the popliteal artery pulse?
Inferior part of the popliteal fossa, against the posterior surface of the tibia
Where would you palpate the posterior tibial artery pulse?
Behind medial malleolus
Where would you palpate the dorsalis pedis artery pulse?
Dorsum of foot, lateral to extensor hallucis longus tendon
