Vessels of the Lower Limb Flashcards
What is the main arter of the lower limb?
The femoral artery
What is the femoral artery a continuation of?
The external iliac artery (terminal branch of the abdominal aorta).
When does the external iliac artery become the femoral artery?
when it crosses under the inguinal ligament and enters the femoral triangle
What branch arises from the femoral artery in the femoral triangle?
Profunda femoris (and perforating branches)
Where do the perforating branches of profunda femoris pass?
perforate the adductor magnus, contributing to the supply of the muscles in the medial and posterior thigh
The femoral artery also gives rise to the medial and lateral circumflex arteries. What do these suppy?
These anastamose around the femur and supply the neck and supply its head and neck.
How can a fracture of the femoral neck affect the blood supply?
In a fracture of the femoral neck the medial circumflex artery can easily be damaged, and avascular necrosis of the femur head can occur.
Where does the femoral triangle pass after exiting the femoral triangle?
Continues down the anterior aspect of the thigh. (During its descent, the artery supplies the anterior thigh muscles.) Then passes through the adductor hiatus and enters the posterior compartment of the thigh.
What is the adductor hiatus?
An opening in adductor magnus
After passing through the popliteal fossa, what does the femoral artery become?
Popliteal artery
Where does the obturator artery arise from?
The internal iliac artery in the pelvic region
How does the obturator artery enter the thigh?
It descends via the obturator canal to enter the medial thigh
Where do the superior and inferior gluteal arteries arise from?
The internal iliac artery
How do the superior and inferior gluteal arteries enter the gluteal region?
Via the greater sciatic foramen
Where does the superior gluteal artery leave the foramen in relation to piriformis? How about the inferior gluteal artery?
Superior - leaves the foramen above the piriformis muscle
Inferior - leaves the foramen below piriformis
What does the popliteal artery divide into?
- Anterior tibial artery
- Posterior tibial artery (continuation of popliteal artery)
Where does the anterior tibial artery then travel? What does it become when it reaches the foot?
Passes anteriorly through apertures in IOM (between tibia and fibula) and then moves inferiorly down the leg. It runs down the entire length of the leg, and into the foot, where it becomes the dorsalis pedis artery.
What branch does the posterior tibial artery give rise to?
Fibular artery
What does the fibular artery supply?
Muscles in the lateral compartment of the leg
Where does the posterior tibial artery travel? How does it enter the foot?
Continues inferiorly, along the surface of the deep posterior leg muscles (such as tibialis posterior). It enters the sole of the foot via the via the tarsal tunnel, accompanying the tibial nerve.
Where is dorsalis pedis palpable?
On the dorsum of the foot
How is arterial supply to the foot delivered?
Via 2 branches:
- Dorsalis pedis (a continuation of the anterior tibial artery)
- Posterior tibial
What branch does does dorsalis pedis give in the foot?
Deep plantar - travels deep into the foot.
The dorsalis pedis then moves inferiorly towards the sole of the foot
How does the posterior tibial artery enter the sole of the foot?
Via the tarsal tunnel
What does the posterior tibial artery then split into in the foot?
into the lateral and medial plantar arteries
What does the lateral plantar atery continue on to form?
The plantar arch
What does the plantar arch anastamose with?
The deep plantar artery (travelled down from dorsum of foot)
Why is the femoral artery easy to access?
The femoral artery is located superficially within the femoral triangle, and is thus easy to access. This makes it suitable for a range of clinical procedures.
When would the femoral artery need to be accessed?
- To obtain an arterial blood gas in emergencies if poor peripheral perfusion / pulses
- To undertake minimally invasive processes
- E.g. coronary angioplasty
What is the general procedure for accessing the femoral artery in minimally invasive procedures?
A catheter can be placed into the femoral artery which can then be advanced up the arterial tree to target organ
What is coronary angiography?
Here, the femoral artery is catheterised with a long, thin tube. This tube is navigated up through the external iliac artery, common iliac artery, aorta, and into the coronary vessels. A radio-opaque dye is then injected into the coronary vessels, and any wall thickening or blockages can be visualised via x-ray.
What is ischaemia?
When perfusion fails to meet the demands of tissues; tissue hypoxia and anaerobic metabolism result, leading to tissue damage (and death, if adequate perfusion is not restored)
What is lower limb ischaemia most commonly caused by?
Atherosclerotic disease
What is chronic ischaemia caused by?
A gradual process caused by atherosclerosis
What is acute ischaemia? What is it usually caused by?
A sudden loss of perfusion of the limb – usually the result of an occlusive thrombus or embolus in an artery, but can also occur secondary to trauma
What is atherosclerosis?
- Atherosclerosis = disease process - lipids deposited in arterial walls
- Plaques may remain stable but partially occlude the artery and cause symptoms
- Plaque may become unstable and rupture
What happens when an atherosclerotic plaque ruptures?
- The contents of the core exposed to blood
- The core is highly thrombogenic > platelet aggregation and activation of the coagulation cascade
What happens when a thrombus forms?
It either:
- stays where it is but occludes the vessel lumen
- breaks away from the vessel wall (now termed an embolus), travels downstream, eventually lodging in and occluding a vessel
The result is an acute ischaemic event
When a thrombus breaks away from the vessel wall, what is it now termed?
An embolus
Why does atherosclerosis happen?
- Atheroma formation occurs with age
- Certain risk factors greatly accelerate atherosclerosis: smoking, diet, hypertension, male, diabetes
Where does atherosclerosis happen?
- Affects large and medium sized conduit arteries
- Turbulence of blood flow at bifurcation points
- Commonly affects the coronary, carotid and lower limb arteries, plus the aorta itself
Image of an atherosclerotic plaque at bifurcation of the common carotid:
What is the Fontaine classification of chronic limb ischaemia?
- Asymptomatic
- Intermittent claudication
- Ischaemic rest pain
- Ulceration / gangrene ( = critical ischaemia)
What happens to circulation as plaques develop in chronic ischaemia?
Blood flow progressively obstructed – but time for collateral circulation to develop.
At first, when is occlusion in chronic lower limb ischaemia only noticeable?
When the patient is active; perfusion cannot meet O2 demand of the limb muscles > anaerobic metabolism in the muscle
This is ischaemia and causes pain: intermittent claudication; initially this pain is relieved with rest
What is ‘rest pain’ a sign of?
Critical ischaemia
What is ulceration and gagrene signs of?
Critical ischaemia
What are the signs of critical ischaemia?
- Foot pain at rest
- Ulceration
- Gangrene
What is ‘dry’ gangrene?
Tissue necrosis without infection. Toes are usually first – black, dry, shrunken
When does ‘dry’ gangrene often occur?
Often occurs in chronic ischaemia as there is minimal blood supply (hence limited oxygen and glucose) to drive bacterial infection.
What is ‘wet’ gangrene?
Tissue necrosis + infection with the affected part being black, soft and putrid. Can rapidly lead to sepsis and death.
Is acute lower limb ischaemia an emergency?
Yes this is a surgical emergency –> RAPID RECOGNITION AND ACTION IS REQUIRED TO SAVE THE LIMB
What must occur in order to save the limb during acute lower limb ischaemia?
The limb must be revascularised within a matter of hours to be saved
What is acute limb ischaemia most often caused by?
- Plaque rupture, resulting in complete occlusion of the artery by a thrombus in situ, or giving rise to an embolus that travels down the arterial tree until it becomes ‘stuck’ in a distal vessel and occludes it.
- Can also be caused by emboli from elsewhere E.g. the heart, in a patient with AF
- Patients who have undergone recent LL angioplasty or grafting of an occlusion may also present with acute limb ischaemia
Why does tissue perfusion suddenly cease in acute limb ischaemia?
the patient does not have a collateral circulation to maintain tissue perfusion
What are the signs and symptoms of acute limb ischaemia?
The 6 P’s:
- Painful
- Pulseless
- Perishingly cold
- Pallor (pale)
- Paraesthesia (reduced or abnormal sensation)
- Paralysis (difficulty moving the limb)
What should follow your referral of an acute limb ischaemia to the vascular surgeons?
- Investigations into the cause (if unknown) – bloods, ECG, Echo, etc.
- Searching for and treating vascular disease elsewhere E.g. coronary arteries, carotid doppler
- Initiating / optimising the treatment of risk factors – E.g. diabetes, hypertension, hyperlipidaemia
- Lifestyle modification and education – diet, smoking cessation
- Other aspects of further management will depend on the individual patient, the type of revascularisation procedure undertaken etc.
What is the main venous structure of the foot?
The dorsal venous arch, which mostly drains into the superficial veins.
What do the deep veins of the lower limb follow?
the deep veins accompany and share the name of the major arteries in the lower limb
What 2 major superficial veins does the dorsal venous arch give rise to?
- Great saphenous vein
- Small saphenous vein
Where is the small saphenous vein seen?
It moves up the posterior side of the leg, passing posteriorly to the lateral malleolus, empties into the popliteal fossa
Where is the great saphenous vein seen? What does it drain into?
It ascends up the medial side of the leg, passing anteriorly to the medial malleolus at the ankle, and posteriorly to the medial condyle at the knee.
Drains into the femoral vein.
When would the femoral vein need to be accessed?
In emergency situations:
- Trauma
- Burns
- Temporary accessed
What vein is preferred for central lines?
Internal jugular vein
Where can the great saphenous vein be accessed?
Anterior to the medial malleolus –> site can be used in emergencies to obtain IV access
Can you cannulate the dorsal veins of the foot?
Yes (not ideal though)
What are varicose veins?
- If valves in the veins become incompetent, blood can flow back into the superficial veins.
- This results in an increased intra-luminal pressure, which the veins cannot withstand, causing them to become dilated and tortuous.
What are the complications of varicose veins?
- Bleeding
- Superficial thrombophelbitis
- Venous/varicose ulcers - medial side of ankle, dermatitis and skin thickening
What is a DVT?
Thrombus (blood clot) in the deep veins of the pelvis or legs. Thrombus can break up / break away from vein wall and travel to the lungs > pulmonary embolus (PE).
Signs and symptoms of DVT?
- limb is swollen, red, warm and painful
- extent of swelling depends on location of DVT
- tender on examination
- always ask patient about any symptoms of chest pain and SOB, take O2 sats
- 50% of those with DVT have long term pain and swelling in the affected leg
What are the risk factors of DVT?
- Previous VTE
- Immobility (any cause)
- Recent LL surgery, recent LL fracture
- Malignancy (pro-thrombotic)
- Pregnancy
- IV drug use (injecting into femoral vein)
- Sepsis (patients with sepsis anticoagulated unless contraindicated (‘CI’)
N.B. young, fit healthy people with no risk factors can get DVTs too - always exclude DVT in patients with unexplained leg / calf pain
Investigation of DVT?
- ‘Well’s score’ (proformas in A&E, ‘checklist’ to follow and then add up the score)
- US scan of the LL veins
- If chest symptoms / signs > CTPA (gold standard for PE unless CI)
Anticoagulate patient while waiting for results if there is suspected DVT.
General areas innervated by major nerves of the lower limb
Motor and sensory function of femoral nerve?
Motor: anterior thigh muscles
Sensory: anteromedial thigh and the medial side of the leg and foot
Roots of femoral nerve?
L2-L4
Roots of obturator nerve?
L2-L4
Motor and sensory function of obturator nerve?
Motor: muscles of medial compartment
Sensory: skin of medial thigh
Roots of sciatic nerve?
L4-S3
Motor and sensory function of sciatic nerve?
Motor:
Tibial nerve – the muscles of the posterior leg (calf muscles), and some of the intrinsic muscles of the foot.
Common fibular nerve – the muscles of the anterior leg, lateral leg, and the remaining intrinsic foot muscles.
Sensory:
Tibial nerve – supplies the skin of the posterolateral leg, lateral foot and the sole of the foot.
Common fibular nerve – supplies the skin of the lateral leg and the dorsum of the foot.
What 2 maps are commonly used to show dermatomes of lower limb
- More closely related to embryology
- More closely related to clinical findings
What spinal nerves are responsible for hip flexion?
L1, L2
What spinal nerves are responsible for knee extension, (knee jerk tendon reflex if unconscious)?
L3, L4
What spinal nerves are responsible for knee flexion?
L5-S2
What spinal nerves are responsible for ankle plantarflexion (toes towards floor)?
S1, S2
What spinal nerves are responsible for adduction of toes?
S2, S3
What is intermittent claudication?
Leg pain that occurs on activity
