Review of Lower Limb Nerves and Vessels Flashcards
What do the spinal nerves supply?
C1-4: neck C5-T1: upper limb T2-L1: trunk L2-S3: lower limb S2-C1: perineum
What supplies the anterior compartment of the thigh?
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.
What does the obturator nerve supply?
medial (adductor) compartment of thigh (so it has mainly anterior division fibres)
- It passes through the obturator foramen
What does the sciatic nerve supply?
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
Where does the piriformis attach? What’s the significance of this?
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)
What supplies the gluteal muscles?
The inferior gluteal nerve ONLY supplies gluteus maximus
The superior gluteal nerve supplies gluteus medius and minimus
- It ALSO supplies the tensor fascia lata
What is the safe area?
(upper, lateral quadrate)
emphasised for intramuscular injection (into gluteus medius muscle to avoid superior gluteal nerve and sciatic nerve)
What does the sciatic nerve branch into?
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
Where do the common peroneal and tibial nerve run?
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)
What is the sural nerve? What does it supply?
common peroneal nerve and tibial nerve give off branches to form the sural cutaneous nerve
The sural nerve supplies some regions in the foot
What does the tibial nerve supply?
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
What does the peroneal nerve supply?
The deep peroneal nerve supplies the lateral compartment
What is the segmental motor supply to the limbs?
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
What does the posterior cutaneous nerve supply?
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.
What are autonomous sensory zones?
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
Which branch of the femoral nerve supplies the foot?
saphenous nerve
What are the consequences of a prolapsed intervertebral disc at L5/S1?
- 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
What are the effects of a lesion of the common peroneal nerve at the fibular neck?
- 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
How do the arteries divide in the lower limb?
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
What to the iliac arteries supply?
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)
Where does the femoral artery run?
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)
Which vessels can be found in the popliteal fossa?
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
Where do the tibial arteries run?
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
What are the arteries in the foot?
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.
What are the superficial veins of the lower limbs?
- 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
What are the deep veins of the lower limbs?
- 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
What is saphenous cut down?
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
What is compartment syndrome?
- 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)
What do you do when someone has acute compartment syndrome?
emergency fasciotomy to prevent death of muscles in affected compartment - deep fascia opened up
What are varicose veins?
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
What is the calf pump?
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
What can cause DVT?
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
What can venous graphs be used for?
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)
What are the causes of DVT?
- idiopathic
- immobility
- trauma
- surgery within abdomen, pelvis or limb
- obesity
- malignancy
- pregnancy
- oral contraceptive pill
What are the consequences of DVT?
- 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.
