Flashcards in M: Neurovasculature of the lower limb Deck (69):
The superior and inferior gluteal arteries are branches of which artery?
The internal iliac arteries
How do the internal and external iliac arteries arise?
1) The abdominal aorta divides into 2 common iliacs
2) The common iliacs each divide into an internal and external iliac
The cruciate anastomosis around the hip is made up of which 5 arteries and where does each arise?
From the internal iliacs:
1) Superior gluteal artery
2) Inferior gluteal artery
From the profunda femoris artery:
3) The lateral circumflex femoral artery
4) The medial circumflex femoral artery
5) 1st perforating artery
Why is the cruciate anastomosis around the hip clinically important?
Allows blood to bypass a blockage of the internal iliac artery or proximal femoral artery
Which artery supplies the anterior compartment of the thigh and where does it arise?
Continuation of external iliac (boundary = inguinal ligament)
Which arteries supply the posterior compartment of the thigh, where do they aris?
4 perforating arteries
Arise from the profunda femoris artery
The profunda femoris artery is a branch of which artery?
The femoral artery
Which artery supplies the medial compartment of the thigh, where does it arise?
Branch of the internal iliac
From where does the popliteal artery arise?
Femoral artery passes from the anterior compartment to enter the popliteal fossa via the adductor hiatus
Once its entered the popliteal fossa, the femoral artery becomes the popliteal artery
In what position is the popliteal artery best palpated?
Knee in flexion
Where is the genicular anastomosis found?
Around the knee
What is the function of the genicular anastomosis?
Maintains blood supply to the leg during knee flexion which may impinge the popliteal artery
What 5 arteries is the genicular anastomosis comprised of, where do they arise from?
All arise from the popliteal artery, 5 genicular branches:
1) Superior lateral
2) Superior medial
4) Inferior lateral
5) Inferior medial
At the back of the leg, the popliteal artery divides to form what 2 terminal branches?
The anterior and posterior tibial arteries
Which artery supplies the anterior compartment of the leg, from where does it arise?
Anterior tibial artery
Terminal branch of the popliteal artery
Which artery supplies the posterior compartment of the leg, from where does it arise?
Posterior tibial artery
Terminal branch of the popliteal artery
Which artery supplies the lateral compartment of the leg, from where does it arise?
Branch of the posterior tibial artery
Which artery supplies the dorsal aspect of the foot, from where does it arise?
Dorsalis pedis artery
Continuation of the anterior tibial artery
Which 2 arteries supply the plantar aspect of the foot, from where do they arise?
Medial and lateral plantar arteries
Formed by bifurcation of posterior tibial artery
The deep plantar arch is what?
Anastamosis of deep plantar branch of dorsalis pedis artery with lateral plantar artery
In what percentage of the population is the superficial plantar arch present?
Which 4 pulses should be palpated in an examination of the lower limb, where are they located?
1) Femoral - superficial in the femoral triangle
2) Popliteal - popliteal fossa with knee flexed
3) Posterior tibial - behind medial malleolus
4) Dorsalis pedis - Dorsum of foot between 1st and 2nd metatarsals
What is the clinical importance of the femoral artery? 3
1) Superficial in the femoral triangle so vulnerable to laceration
2) Site to obtain ABG in emergencies in people with poor peripheral perfusion/pulses
3) Site to undertake minimally invasive procedures - eg. coronary stent placing
Why is the femoral artery an important access point?
A catheter can be placed in to the femoral artery which can then be advanced up the arterial tree to a target organ eg. heart or brain
The femoral artery provides minimally invasive access for which 3 common procedures?
1) Coronary angiogram - imaging of heart with die
2) Coronary angioplasty - PCI
3) Embolisation of berry aneurysms
Peripheral vascular disease is common in lower limb, what is the treatment for acute limb ischaemia?
Medical emergency requiring revascularisation
What are the 6P's of the presentation of an acute ischaemic leg?
3) Perishingly cold
Atherosclerotic changes in the lower limb commonly occur where?
Lower femoral artery
When atherosclerotic changes occur in the lower femoral artery, how does the body compensate?
Collateral circulation via anastomoses between branches of profundus femoris and popliteal arteries
What would be the treatment for an acute ischaemic limb caused by narrowing of the lower femoral artery?
A graft from the common femoral to popliteal to bypass the occluded vessel
What is the general treatment for an acute ischaemic limb?
Imaging shows the sight of occlusion
Revascularisation is required to prevent irreversible tissue loss
What is the 5 step course in chronic ischaemia of the lower limb?
1) Asymptomatic phase
2) Intermittent claudication - mild
3) Intermittent claudication - severe
4) Rest pain/ night pain
5) Tissue loss/ ulceration/ gangrene
What are the likely differences in presentation with acute limb ischaemia in someone with chronic ischaemia compared to someone without?
Symptoms of acute limb ischaemia will be less dramatic in someone who already has chronic ischeamia as they will already have colour changes, pain etc. and thus the acute limb ischaemia will be harder to spot
What is the main difference between superficial and deep veins of the lower limb?
Superficial are superficial to the deep fascia of the lower limb (lying within the subcutaneous tissue)
Deep are deep to the deep fascia of the lower limb
What are the 2 superficial veins of the lower limb?
Great and short saphenous veins
Where does the great saphenous vein run?
Comes of the medial aspect of dorsal venous arch up medial leg to join femoral vein in femoral triangle
Where does the short saphenous vein run?
Comes off the lateral end of dorsal venous arch and moves posteriorly to drain into the popliteal vein
What are the 6 main deep veins of the lower limb, where do they run?
Accompany the major arteries:
1) Femoral vein
2) Profunda femoris vein
3) Popliteal vein
4) Anterior tibial vein
5) Posterior tibial vein
6) Fibular vein
Which 3 of the main deep veins of the lower limb are actually venae commitantes?
1) Anterior tibial vein
2) Posterior tibial vein
3) Fibular vein
What are perforating veins?
Drain blood from the superficial veins to the deep veins - contain valves to prevent back flow (from deep veins to superficial veins)
What 2 mechanisms aid venous return from the deep veins into the central circulation?
1) Muscular contraction - muscle pump
2) Deep fascia - compression stocking
The femoral vein can be used for temporary IV access in which 3 situations, why should it only be temporary?
3) Otherwise very difficult access (shock, IVDU, thrombosed peripheral veins, obesity)
Should be as temporary as possible as high infection risk
Other than IV access what else could the femoral vein be used for in emergencies?
Why can the great saphenous vein be important clinically in emergencies?
Has a very constant position compared to the varying position of other veins - lies immediately infront of the medial malleolus, this site can be used in ermegencies to obtain IV access
What are varicose veins caused by?
Increased pressure in saphenous veins can be caused by proximal venous obstruction eg. pregnancy or pelvic tumour
The veins become dilated and incompetent with failing valves allowing backflow of blood
Blood then may stagnate in the skin leading to breakdown and ulceration
What are the 3 possible complications of varicose veins?
2) Superficial thrombophlebitis
3) Venous/varicose ulcers - medial side of ankle, dermatitis and skin thickening
What percentage of people with DVT have long term pain and swelling in the affected leg?
What percentage of untreated DVT lead to mortality from PE?
What are the 6 risk factors for DVT?
1) Previous VTE
3) Recent surgery
4) Malignancy - blood hypercoagulable
6) IV drug use (injecting into femoral vein)
The lumbar plexus is formed from what?
Anterior rami of L1-L4
The sacral plexus is formed from what?
Anterior rami of L4-S5
The lumbar plexus gives rise to what 2 important nerves (with nerve roots)?
1) Obturator nerve (L2-L4)
2) Femoral nerve (L2-L4)
The sacral plexus gives rise to what 3 important nerves (with nerve roots)?
1) Sciatic nerve (L4-S3)
2) Superior gluteal nerve (L4-S1)
3) Inferior gluteal nerve (L5-S2)
The femoral nerve supplies which compartment of the thigh?
The anterior compartment of the thigh
What route does the femoral nerve take to enter the thigh?
Passes under the inguinal ligament
What is the terminal branch of the femoral nerve and what does this supply?
Terminal branch is the saphenous nerve which passes through the adductor hiatus to supply the skin of medial leg
The obturator nerve supplies which compartment of the lower limb?
Medial compartment of the thigh
The obturator nerve divides into which 2 branches which lie where?
Divides into anterior and posterior branches which lie on either side of adductor brevis
The sciatic nerve supplies which part of the lower limb?
Posterior thigh and all of the leg and foot
The sciatic nerve is really composed of what 2 nerves?
1) Tibial nerve - anterior divisions of anterior rami
2) Common fibular nerve - posterior divisions of anterior rami
Where does the sciatic nerve usually bifurcate into the tibial and common fibular nerves?
Usually bifurcates in the distal thigh but is already separate as it leaves the pelvis in 12% of the population
In which 2 siutations is the sciatic nerve at risk of injury?
1) Iatrogenic injury during IM injections into gluteus maximus
2) Also at risk in hip injuries/ dislocations
Where must IM injections into gluteus maximus be performed to avoid injury to the sciatic nerve?
IM injections must be performed in superolateral quadrant
The common fibular nerve bifurcates into what 2 nerve what does each supply?
1) Superficial fibular nerve - supplying lateral compartment of leg
2) Deep fibular nerve - supplying anterior compartment of leg
Why is the common fibula nerve particularly vulnerable to injury?
It winds around the neck fibula
What would injury to the common fibular nerve lead to?
Paralysis of dorsiflexor muscles resulting in foot drop and altered gait
The tibial nerve supplies what part of the lower limb?
The posterior compartment of the leg
The tibial nerve divided where into what 2 branches?
Bifurcates deep to the flexor retinaculum into medial and lateral plantar nerves