nerves and vessels of lower limb Flashcards
what spinal levels supply which region *
c1-4 neck
c5-t1 upper limb
t2-l1 trunk
l2-s3 lower limb
s2-c1 perineum
what are teh 2 types of innervation *
segmental - dermatomes
peripheral - nerves to muscles and cutaneous nerves
where do peripheral nerves emerge from *
nerve plexuses
what is a nerve plexus *
it is formed when peripheral spinal nerve roots merge and split to produce a network of nerves from which new multi-segmental peripheral nerves emerge
multi-segmental means that fibres come from >1 spinal root
what are the 3 main nerves that supply the lower limb that come off the lumbosacral plexus *
femoral
obturator
sciatic
summarise the organisation of the lumbosacral plexus *
come of levels L2-S3
derived from the anterior rami of the spinal nerves
terminal branches have fibres off different roots
the lumbar plexus is derived from L1-L4, branches are:
- iliohypogastric and ilioinguinal nerves
- genitofemoral nerve
- lateral cutaneous nerve of thigh
- femoral nerve
- obturator nerve
- lumbosacral trunk
sacral plexus is derived from lumbosacral trunk and s1-4 anterior rami
- sciatic nerve
- nerve to piriformis
- posterior cutaneous nerve of the thigh
- pelvic splanchnic nerves - pns
- pudendal nerves
- nerve to obturator internus
- superior gluteal nerve
- inferior gluteal nerve
describe the anatomy of the gluteal region and the course of the sciatic nerve through it *
piriformis is one of the lateral rotator cuff muscles - important landmark
superior to piriformis have the superior gluteal nerve and vessels
inferior to the piriformis have the inferior gluteal nerve and vessels, and large nerves - the sciatic and posterior cutaneous nerve of thigh
sciatic then passes posterior in thigh and divides into tibial and common peroneal nerve
describe the femoral nerve *
L2-4
supplies - anterior compartment of the thigh and iliacus (hip flexor in pelvis - L1-4) [psoas and iliacus, pectineus, sartorius, rectus femoris, vastus medialis, vastus intermedius, vastus lateralis]
from lumbosacral plexus, passes under the inguinal canal, enters the femoral triangle and branches
it is a posterior division of the plexus but supplies anterior muscles because of the pronation that occurs in development
sensory to front of thigh and anteromedial knee
terminal branch is saphenous nerve - sensory to medial leg and foot
describe teh obturator nerve *
L2-4
supplies the medial - adductor compartment of thigh [obturator externus, adductor brevis and longus, part of adductor magnus, gracilis]
sensory to pelvis and upper medial aspect of thigh
comes off the lumbrosacral plexus and emerges on medial border of psoas muscle, runs inferiorly and anteriorly on pelvis and passes through the obturator foramen by piercing the fibrous membrane and muscle covering
is anterior division of the plexus
describe the sciatic nerve *
L4-S3
2 nerves that are stuck together - 1 anterior and 1 posterior division
passes through the greater sciatic foramen, behind the hip, then passes in posterior part of thigh
sciatic nerve proper supplies hamstring muscles in posterior part of thigh [biceps femoris, semimembranosus and semitendinosus, part of adductor magnus]
also has some sensory branches to back of thigh, lateral side of leg and foot, dorsal surface of foot
nerve divides just above the knee
branches are tibial and common peroneal branches
supply posterior thigh, anterior and posterior leg and foot ie all muscles in leg and foot
describe the tibial nerve *
l4-s3
branch of the sciatic nerve
stays posteriorly, runs on teh surface of the tibialis posterior and supplies posterior leg [gastrocnemius and soleus, plantaris, popliteus, tibialis posterior]
runs posterior to the medial malleolus, passes under the plantar aporneurosis where it divides into medial (L4 5)and lateral (S1 2) plantar nerves - supplies all muscles of the foot [flexor hallucis longus, flexor digitorum longus and brevis, abductor hallucis, fkexor hallucis brevis, interossei and lumbricles]
sensory to the back of teh leg and the sole of the foot and lateral side of foot
describe the common peroneal nerve *
L4-S2
branch of the sciatic nerve in posterior compartment of thigh/popliteal fossa
follows the medial margin of the biceps femoris tendon over the lateral head of the gastrocneumius to the fibular (here gives off sural nerve)
passes laterally round neck of fibular
give off deep (L5-S2) and superficial (L4-S1) peroneal nerves
superficial descends in lateral compartment, deep to fibularis longus and brevis
superficial supplies the lateral compartment of the leg ie the peroneus longus and brevis
a branch of superficial emerges just superior to the ankle joint where it divides into medial and lateral branches that supply cutaneous dorsum of foot - except for the web space between digits 1 and 2 (supplied by deep peroneal) and lateral side of little toe (supplied by tibial)
deep passes anteromedially from lateral part of leg through the intermuscular septum into the anterior compartment of the leg the passes deep to the extensor digitorum longus, reaches the nterosseous membrane where it meets and descends with the tibial artery
the deep supplies the anterior compartment of the leg [tibialis anterior, extensor hallucis longus, peroneus tertius, extensor digitorum longus], the goes to dorsal foot - innervates extensor digitorum brevis, contributes to innervation of the 1st two dorsal interossei muscles
deep supplies skin between teh 1st adn 2nd digits
where is the common peroneal nerve suseptible to damage *
round teh neck of the fibula
describe the saphenous nerve *
it is a branch of the femoral nerve
accompanies femoral artery through adductor canal but doesnt pass through adductor hiatus; instead it penetrates through connective tissue in canal - appears between sartorius and gracialis muscles on medial side of knee
here penetrates deep facia and continues down medial side of leg to foot
it a cutanous nerve of medial knee, leg and foot
what does the femoral nerve supply *
anterior compartment of thigh - motor
medial leg and foot - sensory via the saphenous nerve
describe the sural nerve *
formed from branches of the common peroneal nerve and tibial nerve
tibial part originate between heads of gastrocnemius, descends superficially to gastrocnemius, penetrates the deep fascia
here joined by sural communicating nerve from common peroneus
passes down leg and round the lateral malleolus and into the foot
it is a cutanous nerve of the lateral leg and foot and little toe
describe the superior gluteal nerve *
L4-S1
pass into gluteal region via the greater sciatic foramen superior to piriformis
supplies glut med and min and tensor fascia lata
describe inferior gluteal nerve *
L5-S2
pass into the gluteal region via greater sciatic foramen inferior to the piriformis
supplies glut max
summarise the segmental supply to the limbs *
groups of motor nerve cell bodies in teh spinal cord
plexi for each limb
anterior division/rami - flexor muscles which are posterior
posterior division/rami - extensor muscles which are anterior
muscles are supplied by 2 adjacent segments
if muscles have the same action on a joint - have same nerve supply
opposing muscles have supply from 1-2 segments above/below
the more distal the muscle, the more caudal in spine the segment
spinal segments that are involved in movementof the limbs *
hip - flex L2-3, extend L4 5
knee extend l3 4 flex l5 s1
ankle dorsiflex (extension) - l4 5, plantarflex s1-s2
what are dermatomes *
fields of the cutaneous surface whose sensation is supplied by a single spinal nerve
what is an axial line in reference to dermatomes *
boundary between lower and higher spinal roots
where the dermatomes are not linked at the spinal level eg s2 and l2 lie next to each other in posterior thigh
who is the peripheral nerve supply different to the dermatomes *
peripheral supply refers to peripheral nerves not the spinal roots
not all fibres from 1 spinal root go via 1 peripheral nerve
also, peripheral nerves contain fibres from >1 spinal roots
for example posterior cutaneous nerve comes from S1 2
what are autonomous sensory zones *
dermatomes overlap - so difficult to know what has been affected in spinal root damage
autonomous sensory zones are zones taht if you have abnormal sensation in them, it is indicative of spinal root damage for a particular dermatome
eg L3 region on thigh, L4 knee, S1 back of calf
obturator nerve enters medially and supplies muscle and skin of medial thigh - autonomous sensory zone
deep fibular nerve supplies cleft between 1st and 2nd digit - autonomous sensory zone
describe the cutanous innervation of foot *
saphenous nerve supply medial side of ankle and foot
deep and superficial peroneal nerves - become dorsal digital nerves
dorsal lateral cutaneous nerve - from sural nerve supplies lateral of foot
have common and proper plantar digital nerves and lateral and medial plantar nerve and medial calcaneal nerve on sole of foot
what do you assess in assessment of nerve function *
motor, sensory, reflex, autonomic and trophic
effect of prolapsed intervertebral disk at L5/S1 *
cause pressure on S1 nerve root - cause segmental loss
motor - loss of eversion and weakness elsewhere
sensory - loss of sensation on outer border of foot
reflex - loss of ankle jerk S1
autonomic - minimal - abnormalities in sweating in the S1 cutaneous nerve distribution
trophic - in long standing lesions there might be trophic changes in the lateral aspect of the foot
effect of lesion of common peroneal nerve at fibular neck *
peripheral nerve loss
motor - foot drop because of paralysis of anterior and lateral compartments of legs (cant raise toes so scuff front of shoes and have high stepping/swinging gait - can get springs to lift toes artificially iff long term)
sensory - dorsum of foot at least
reflex - none
autonomic - minimal - abnormalities of sweating in cutaneous distribution of the common preoneal nerve
trophic - in chronic cases may be damage to sole of foot due to pressure effects of foot drop
summarise the arterial anatomy *
aorta branches into common iliac arteries that branch into external and internal iliac arteries at pelvic brim - external is the main blood supply to lower limb (internal stays in pelvis exept for 1 branch is the obturator artery which passes through the obturator foramen into the thigh)
superior and inferior gluteal arteries are branches of the internal iliac
external pass under inguinal ligament at mid-inguinal point (halfway between syphysis pubis and ASIS) to become femoral which passes anteriorly in thigh
femoral has 4 branches below inguinal ligament - superficial circumflex iliac artery, superficial epigastric artery, superficial external pudendal artery, deep external pudendal artery
femoral gives off deep branch in the femoral triangle - the profunda femoris artery, this arises 4cm distal to the inguinal ligament - its branches are the perforating arteries and medial and lateral femoral circumflex arteries - they supply the distal head of the femer
femoral passes from anterior to posterior through the adductor hiatus to become the popliteal artery
popliteal artery gives off genicular (knee) branches
popliteal artery ‘‘trifurcates’’ - not true trifurcation
branches into anterior tibial artery and tibioperoneal artery
tibioperoneal then branches into peroneal and posterior tibial artery
anterior tibial pierces interosseous membrane then is deep in anterior compartment between bones running on the interosseous mem, becomes dorsalis pedis artery when it passes over the ankle, passing anteromediolaterally to turn laterally as the arcuate artery giving off the digital branches
perforating arteries communicate between the plantar arch adn arcuate artery
posterior tibial passes into posterior compartment of leg alongside the tibialis posterior around medial malleolus and branches into lateral and medial plantar arteries which form a plantar arterial arch, supplying sole of foot
what are the pulse points in the lower limb *
femoral artery
popliteal
posterior tuibial
dorsalis pedis
why are pulses important *
aging population
need to assess vascular health
lower limb is further away from heart so there are more issues
suseptible to PVD - need to know legs are being perfused
why is the femoral triangle important *
for access to the heart
femoral pulse important for cannulation
for cardiac arteriography access artery
for resuscitation - vein
describe the femoral artery and vein’s relation to adductor magnus *
they pass from anterior to posterior through teh adductor hiatus (of the adductor hiatus muscle)
the passing through the hiatus is a point where occlusion can occur
superficial short saphenous vein drains into the popliteal vein at the popliteal fossa
describe the arrangement of vessels in the popliteal fossa *
the artery is deeper than the vein