Review of Lower Limb Nerves and Vessels

Question 1

What do the spinal nerves supply?

Answer 1

C1-4: neck
C5-T1: upper limb
T2-L1: trunk
L2-S3: lower limb
S2-C1: perineum

Question 2

What supplies the anterior compartment of the thigh?

Answer 2

femoral nerve

the femoral nerve is supplying anterior muscles (extensors, due to torsion during development below the hip joint) so is made of posterior divisions.

Question 3

What does the obturator nerve supply?

Answer 3

medial (adductor) compartment of thigh (so it has mainly anterior division fibres)

• It passes through the obturator foramen

Question 4

What does the sciatic nerve supply?

Answer 4

the remaining compartments (i.e. posterior thigh, anterior and posterior leg and foot). The sciatic nerve is made up of BOTH anterior AND posterior fibres

Question 5

Where does the piriformis attach? What’s the significance of this?

Answer 5

comes from the sacral region, and inserts into the intertrochanteric region of the proximal femur

• involved in lateral rotation of the hip, and stabilisation

Superior gluteal nerves and vessels emerge SUPERIORLY to the piriformis muscle. Inferior gluteal nerves and vessels emerge INFERIORLY to it. Both of these nerves pass through the GREATER SCIATIC FORAMEN. Some structures enter through the lesser sciatic foramen (e.g. branch of pudendal nerve)

Question 6

What supplies the gluteal muscles?

Answer 6

The inferior gluteal nerve ONLY supplies gluteus maximus

The superior gluteal nerve supplies gluteus medius and minimus

• It ALSO supplies the tensor fascia lata

Question 7

What is the safe area?

Answer 7

(upper, lateral quadrate)

emphasised for intramuscular injection (into gluteus medius muscle to avoid superior gluteal nerve and sciatic nerve)

Question 8

What does the sciatic nerve branch into?

Answer 8

The sciatic nerve gives off a big branch: the posterior cutaneous nerve of the thigh - supplies much of the posterior thigh

The sciatic nerve passes relatively deep in the posterior thigh, and supplies the posterior thigh muscles

branches into common peroneal and tibial

Question 9

Where do the common peroneal and tibial nerve run?

Answer 9

The tibial nerve continues in the leg

The common peroneal nerve leaves the popliteal fossa, goes laterally and inferiorly, and wraps around the head of the fibula (readily damaged because its superficial)

Question 10

What is the sural nerve? What does it supply?

Answer 10

common peroneal nerve and tibial nerve give off branches to form the sural cutaneous nerve

The sural nerve supplies some regions in the foot

Question 11

What does the tibial nerve supply?

Answer 11

posterior and a small part of the lateral compartment

It supplies superficial and deep calf muscles.

Then, it divides at the ankle (behind the medial malleolus) into the medial and lateral plantar nerves (supply the muscles and sensation of the foot

Question 12

What does the peroneal nerve supply?

Answer 12

The deep peroneal nerve supplies the lateral compartment

Question 13

What is the segmental motor supply to the limbs?

Answer 13

C5-T1 = upper limb

L2-S3 = lower limb

HIP:

• Flex: L2, L3
• Extend: L4, L5

KNEE:

• Extend: L3, L4
• Flex: L5, S1

ANKLE:

• Dorsiflex (extend): L4, L5
• Plantarflex (flex): S1, S2

Question 14

What does the posterior cutaneous nerve supply?

Answer 14

a large region of the lower part of the buttock, the majority of the posterior thigh and a portion of the knee region

fibres of the posterior cutaneous nerve originate in S1 and S2.

• However, other nerves (e.g. sural nerve) are made up of S1 and S2. The fibres from S1 and S2 are not exclusive.

Question 15

What are autonomous sensory zones?

Answer 15

There is a lot of overlap in the dermatomes (never clear cut). However, there are SOME areas where there are effects of sensation that are EXCLUSIVE. This is an emphasised sensation deficit in specific zones of the large dermatomes when nerves are damaged.

The lateral border of the foot is one that is commonly affected. The obturator nerve supplies a region on the medial thigh – this is an autonomous sensory zone

Question 16

Which branch of the femoral nerve supplies the foot?

Answer 16

saphenous nerve

Question 17

What are the consequences of a prolapsed intervertebral disc at L5/S1?

Answer 17

• Motor – loss of eversion, weakness in calf muscles
• Sensory – loss of sensation outer border of foot
• Reflex – loss of ankle jerk (S1) – tapping the calcaneal tendon
• Autonomic – minimal

Question 18

What are the effects of a lesion of the common peroneal nerve at the fibular neck?

Answer 18

• Motor – foot drop (this nerve supplies the anterior and lateral muscles of the leg)
• Sensory – dorsum of foot at least (possibly some other areas)
• Reflex – none
• Autonomic – minimal

Question 19

How do the arteries divide in the lower limb?

Answer 19

aorta -> common iliac artery -> internal/external iliac artery -> femoral artery -> profunda femoris artery -> circumflex femoral artery

femoral artery -> popliteal artery -> trifurcation -> anterior tibial artery (-> dorsalis pedis artery) + posterior tibial artery + peroneal artery

Question 20

What to the iliac arteries supply?

Answer 20

Internal iliac artery (supplies structures in the pelvis and gives supply via the obturator artery to the medial thigh)

External iliac artery (passes under the inguinal ligament to change its name to the femoral artery)

Question 21

Where does the femoral artery run?

Answer 21

The femoral artery continues anteriorly in the thigh in the adductor canal, and passes into the posterior of the thigh via the adductor magnus hiatus -> popliteal artery (vein also goes through here)

Question 22

Which vessels can be found in the popliteal fossa?

Answer 22

the tibial vein and tibial artery. They divide into the anterior and posterior tibial arteries

The posterior tibial artery also gives rise to the peroneal artery, which supplies the lateral structures of the leg

*The anterior tibial artery pierces the interosseous membrane to supply anterior structures in the leg

Question 23

Where do the tibial arteries run?

Answer 23

The posterior tibial artery goes BEHIND the medial malleolus (inside of the ankle region).

The anterior tibial artery crosses over, approximately in the middle of the ankle joint region to the dorsum of the foot, to form dorsalis pedis artery

Question 24

What are the arteries in the foot?

Answer 24

The posterior tibial artery gives medial and lateral plantar arteries, which themselves give off arteries to both the BULK of the foot, and the digits.

In the dorsum of the foot, the dorsalis pedis artery gives off arches and digital arteries.

There are LOTS of anastomoses between the plantar and dorsal vessels.

Question 25

What are the superficial veins of the lower limbs?

Answer 25

• Dorsal venous arch
  > gives the long saphenous vein medially
• Long saphenous vein
  > crosses the ankle joint anteriorly to the medial malleolus. It goes up the medial leg, skips slightly behind the knee (but stays medial), before becoming more anterior to drain into the femoral vein in the femoral triangle (pierces the saphenous opening)
• Short saphenous vein
  > goes posteriorly to the lateral malleolus, up the posterior of the calf and pierces the fascia of the popliteal fossa, to drain into the popliteal vein
• Perforating veins
• Sapheno-femoral junction

Question 26

What are the deep veins of the lower limbs?

Answer 26

• MIRROR IMAGE OF THE ARTERIES
• Venae comitantes
• Anterior and posterior tibial veins
• Popliteal vein (receives SSV)
• Profunda femoris vein
• Femoral vein (receives LSV)
• External iliac vein

Question 27

What is saphenous cut down?

Answer 27

Where the long saphenous vein crosses the ankle has been used previously in emergencies to administer fluids into a shocked patient

2cm lateral and proximal to medial malleolus

Question 28

What is compartment syndrome?

Answer 28

• The neuromuscular compartments of the limbs are enclosed in fibrous sheaths, which confine them. The muscle compartments are enclosed and separated.
• Ischaemia caused by trauma-induced increased pressure in a confined limb compartment
• Commonly the anterior, posterior and lateral leg compartments
• Normal pressure = 25mmHg - you only need 50-60mmHg to collapse vessels, so pulse still present
• can be acute (trauma associated) or chronic ( exercise induced)

Question 29

What do you do when someone has acute compartment syndrome?

Answer 29

emergency fasciotomy to prevent death of muscles in affected compartment - deep fascia opened up

Question 30

What are varicose veins?

Answer 30

Perforating veins connecting superficial and deep veins contain a valve that will allow flow only from superficial to deep. If such a valve is compromised, blood is pushed from deep to superficial veins leading to varicose veins

• Sapheno-femoral junction valve most important

Question 31

What is the calf pump?

Answer 31

Valves in the veins allow flow only up towards the heart

In the leg, the deep vessels are sandwiched between layers of calf muscles

During walking and running, contractions of these muscles squeeze the thin-walled veins -this pushes blood up the vein

Question 32

What can cause DVT?

Answer 32

immobility (e.g. a long plane journey) means less efficient venous return from the foot and leg - sluggish deep venous return can lead to Deep Vein Thrombosis (DVT)

• Elastic surgical socks compress the superficial veins promoting more vigorous deep venous return

Question 33

What can venous graphs be used for?

Answer 33

Veins are a source of graft material for bypass surgery.

• Coronary artery bypass graft
• Arterial by-pass surgery
• Valves! (Only allow flow in one direction, so graft must be oriented in the correct direction)

Question 34

What are the causes of DVT?

Answer 34

• idiopathic
• immobility
• trauma
• surgery within abdomen, pelvis or limb
• obesity
• malignancy
• pregnancy
• oral contraceptive pill

Question 35

What are the consequences of DVT?

Answer 35

• the clot may propagate into the pulmonary circulation, causing a pulmonary embolus (PE). A PE may be fatal and for this reason DVT’s are usually treated by anticoagulation to prevent this complication occurring.
• The clot in the deep veins may cause increased back pressure in the deep veins, causing venous insufficiency and leg ulcers (the post-phlebitic syndrome)
• The superficial veins may also clot or become inflamed/infected. This causes superficial thrombophlebitis. This is not so dangerous as DVT but can be very painful. The treatment is usually symptomatic (analgesia, rest, ice etc.) rather than with anticoagulation.