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
what bone do you press the femoral artery against for pulse *
pubic ramus
at mid-inguinal point it lies on the psoas tendon so can be palpated easily
what bone do you press dorsalis pedis artery against for pulse *
tarsal bones and maybe metatarsal
where do you feel the posterior tibial artery *
behind the medial malleolus
describe the path of the superficial veins *
lie in the subcutaneous tissue, have valves to prevent the backflow of blood
great and short saphenous emerge from the dorsal venous arch
great emerges from medial portion of arch and passes 2cm anterior and posterior to medial malleolus - travels up medial of leg, skirts behind medial femoral condyle of knee, pass up medial thigh going more anteriorly - through the saphenous opening (the cribiform fascia) 3cm below and lateral to the pubic tubercle to join the femoral vein. a number of venous tributaries join the vein here
short saphenous drains the lateral part of arch, goes behind the lateral malleolus, up posterior of leg with the sural vein, pierces fascia over the popliteal fossa and drains into the popliteal vein
short and long vein communicate at many levels
the popliteal vein lays in fossa between popliteal artery and tibial nerve
the femoral vein passes behind the femoral artery and lies medial to it at inguinal ligament
just before the long saphenous joins femoral, profunda femoris vein joins the femoral
when femoral goes under the inguinal ligament it becomes the external iliac vein
describe the depp veins of the lower limb *
they run alongside the arteries as venae comitantes
describe venae comitantes *
they are accompanying veins
multiple veins form a network of smaller veins with arteries which they accompany
there are connections between the venae comitantes
this allows heat exchange - cooled blood in veins from peripheries is warmed by blood from the arteries
artery pulses promote venous return
what is cut down of the long saphenous vein *
when patient in shock and all vessels have collapsed but you need to give them fluid
cut long saphenous vein 2cm lateral and proximal to the medial malleolus and get fluid in this way - small canular is inserted into vein
not used as much today - flouid given byu interosseous administration - a needle inserted into the bone marrow of anterior tibia
in well equipt fascilities US can be used tp find a patent vein
describe arterial embolism *
caused by sudden occlusion of an atherosclerotic vessle or by a thrombus formed by afib
if a vessel is suddenly occluded with no time for a collateral circulation to develop = acute ischaemia
intermittent claudication is where there is gradula occlusion of arteries, usually atherosclerotic - the muscles distal to occlusion become deprived of blood on exercise muscle pain, commonly in calf during activity
describe compartment syndrome *
the neuromuscular compartments of the limbs are enclosed in fibrous sheaths which confine them
compartment syndrome is where ischemia is caused by trauma induced increased in pressure in a confined limb compartment - commonly anterior, posterior and lateral compartments of the leg
normal pressure is 25mmHg - if rise to 50-60mmHg = collapse of small vessels, but BP is 120/80mmHg - so you can still feel pulse even though tissues are not being perfused
acute compartment syndrome is trauma associated eg fractures or muscle damage/inflammation
chronic - exercise induced - muscles get pumped up with increased pressure if built muscle mass quickly and the fascia hasnt had any time to adjust - exercise induced discomfort
treatment of acute compartment syndrome *
emergancy fasciotomy to prevent the death of muscle
descrive varicose veins *
perforating veins connect superficial and deep veins, they have a valve so blood only flows from superficial to deep - spheno-femoral junction is most important
if valve is comprimised - blood pushed into superficial = swelling of superficial veins - leading to varicose veins
valve may be comprimised if FH, lifestyle or multiple pregnancy
can get ulcers/pain
ulcers are important to consider in people with dm, older people and people who are less mobile
can get lipodermatosclerosis - skin thickening because of the increased pressure in the superficial circulation - possible chronic inflammatory cause
treatment involves tying off sapheno-femoral junction
describe DVT *
clot in deep veins
mainly in lower limb
risk factors - inactivity, long haul flights, surgery in abdo, pelvis or limbs, the pill
often silent but can present with pain and swelling in calf or proximal thigh
DVT can be dislodged - travel in veins and cause PE = sudden death
a distal dvt occurs in calf, distal occurs in thigh/pelvis - prox is dangerous because high risk of PE
dvts treated with anti-coag to avoid this
can cause increased back pressure in the deep veins = venous insufficiency and leg ulcers - this is post-phlebitic syndrome
superficial veins may also clot or be infected causing superficial thrombophlebitis - painful, the treatment is rest, ice, analgesic - less dangerous than dvt
describe muscle pump of deep veins *
valves mean blood only flows up leg
deep veins are sandwiched between layers of calf muscles
during movement - contraction of muscle squeeze veins and push blood up - they contract distal valve and open prox
immobility means less efficient venous return from foot/leg - sluggish return = dvt
elastic surgical socks compress superficial veins so more blood is pushed into deep system = more vigorous deep flow - redeuced chance of DVT
describe venous grafts *
coronary artery bypass graft
this is arterial bypass surgery around an occlusion
have to put the valves the right way round so that blood flows in right dirn
because of the anastomoses in the leg, there is rarely a problem in removing a superficial vein
what is included in the peripheral NS
cranial and spinal nerves
what is a spinal nerve *
formed from the union between an anterior (motor) and a dorsal (sensory) root
the roots merge at the intervertabral foramen to form a spinal nerve
where do autonomic fibres run
between t1-l2 and s2-4`
describe path of spinal nerves *
as soon as pass through intervertebral foramen splits into anterior and posterior ramus
the anterior rami merge to form the major plexi of the limbs
the posterior rami are less significant and are mainly cutaneous nerves
dermatomes of lower limb *
l3 front of thigh
l4 front of leg
l5 dorsum of great toe
s1 lateral aspect of foot
s2-s4 perineum and perianal region
describe the sequence for the knee jerk reflex *
tap
stretch the patella tendon
stimulation of afferent (1a) fibres in quadriceps
passes to spinal cord through posterior root
synapse with a motor neuron in anterior horn of the spinal cord
efferent signal to quadriceps
quadriceps extend the knee joint
reflexes in the lower limb*
stretch reflexes/deep tendon reflexes and are monosynaptic
knee jerk - L3
ankle jerk - S1
what is the sympathetic outflow to the lower limb
t11-l2
when can the femoral nerve be damaged *
iatrogenic - traction injuries via hip replacements and laproscopic repair of inguinal hernias
or in erroneus attempted cannulations of the femoral a or n
how can the lateral cutaneous nerve of the thigh be damaged *
passes 2cm medial to the ASIS at level of inguinal ligament
can be comprimised causing meralgia parasthesia - burning pain, numbness, and tingling sensation in the outer thigh.
describe damage to the obturator nerve *
rarely damaged
pain in the distribution of teh obturator nerve could be indicative of malignant disease in pelvis
describe injury to the superior gluteal nerve *
results in Tredelenburg gait - pelvis lurches during gait
commonest injury is during hip replacement
nerve lies 5cm proximal to tip of greater trochanteur and approaches the hip joint - should not extend >5cm from tip of greater trochanteur
describe injury to the sciatic nerve *
after hip replacement
trauma eg hip dislocations or acetbular fractures
pelvic disease
common peroneal division more vulnerable than tibial
how do you prevent damaging the sciatic nerve*
give an intramuscular injection in upper lateral quadrant of buttock - nerve most likely situated in lower inner qudrant
describe injury to the common peroneal nerve *
at level of hip and round fibular neck
from trauma, knee replacement, and external pressure - from plasters or during surgical procedures
describe damage to the tibial nerve *
very deep so rarely damaged in isolation
describe damage to the saphenous nerve *
common
at medial malleolus after varicose vein surgery or at knee after ACL surgery
describe anaesthetic nerve blocks
aid or substitute GA in surgery
eg femoral, sciatic, ankle, lateral cut nerve blocks
what is the location of the femoral canal *
medial to femoral vein at inguinla ligament - within the canal is a lymph node
palpate the femoral artery *
in midinguinal point
palpate the popliteal artery *
in inferior of popliteal fossa against posterior surface of tibia
palpate posterior tibial artery *
behind medial malleolus
palpate dorsalis pedis artery *
dorsum of foot
lateral to the extensor hallucis longus tendon
what structures are at risk during venepuncture of femoral vein *
femoral n
femoral a
femoral canal
palpate the popliteal lymph nodes *
only when enlarged
around popliteal fossa along small saphenous vein
palpate superficial inguinal lymph nodes *
near the termination of long saphenous vein
(deep inguinal nodes are along the proximal part of the femoral vein)
only palpable when enlarged
what are the levels of the dermatomes in the lower limb *
l1 - inguinal region
l2- thigh-upper lateral
l3 - thigh- lower lateral
l4 - leg and great toe medial
l5 - leg anterolateral and foot and toes 2-4 dorsal
s1 - sole lateral margin and heel
s3-s4 buttock medial, intergluteal cleft and peineum
how do you test the integrity of dermatomes *
touch in them with crude and light touch
describe the principle of deep tendon reflexes *
when tendon is tapped and so stretched, there is involuntary contraction of that muscle
test the patella tendon reflex - knee jerk *
ask subject to sit comfortably with legs dangling on edge of couch
examiner strike patella tendon with knee hammer
should see brisk extension of knee joint
palpate the contraction of the quadriceps
compare to opposite sife
test the calcaneal tendon reflex *
ask pt to sit comfortably with legs dangling on edge of couch - examiner should strike calcaneal tendon with a knee hammer while holding foot slightly dorsiflexed with other hand
plantar flexion of ankle joint will occur
might be absent of S1 sopinal nerve root is affected or tibial nerve damage
how would you test integrity of femoral nerve *
extension of the knee - test the quadriceps
sensation on anterior of thigh and medial side of leg and foot
how would you test for integrity of the obturator nerve *
check adduction - medial compartment of thigh
sensation on medial compartment of thigh
what is sciatica *
pain in the area of distribution of the sciatic nerve
l4 to s3 - over the buttock and in the posterolateral aspect of the leg
what is the significance of anastomoses *
the femoral circumflex arteries, inferior and superior gluteal and obturator arteries, with branches from the internal pudnendal branches anastomose in gluteal and upper thigh region- these anastomoses can provide collateral circulation if one of the vessels becomes occluded
genicular branches from the femoral, popliteal and lateral circumflex arteries in thigh and the circumflex fibular artery and recurrent branches from the anterior tibial artery in leg form an anastomotic network around the knee joint
describe the contents of the femoral triangle with regard to arterial sampling and catheter placement *
contents are: femoral nerve, artery, vein, lymph nodes (which are in femoral canal) from laterally to medially
radiological approaches involve catheterisation of fem a or v to get access to contralateral limb, ipsilateral limb, the vessels of the thorax and abdomen and the cerebral vessels
use the fem a to place catheters in vessels around the arch of the aorta and into coronary arteries to perform coronary angiography and angioplasty
access to fem v allows catheters to be manovered in renal and gonadal veins, the R atrium, R side of heart - pulmonary artery and distal vessels of the pulmonary tree
access to superior vena cava and great veins is also possible
describe the lymphatic drainage of the lower limb *
most drain into superficial and deep inguinal lymph nodes located in the fascia just below the inguinal ligament
superficial inguinal nodes - approx 10 are in the superficial fascia and follow course of inguinal ligament; medially they extend inferiorly along terminal part of the great saphenous vein
superficial recieve lymph from gluteal region, lower abdo wall, perineum, and superficial regions of lower limb
superficial drain via vessels that accompany femoral vessels into external iliac nodes, associated with external iliac artery
deep inguinal - up to 3 in number, medial to femoral vein, recieve lymph from deep lymphatics associated with femoral vessels and glans penis/clitoris
deep interconnect with superficial and drain into external iliac nodes via vessels medial to femoral vein
popliteal nodes - deep nodes close to popliteal vessels - they recieve lymph from superficial vessels which accompany superficial saphenous vein, and deep areas of leg and foot
popliteal drain into superficial and deep inguinal
describe how lymph drainage is related to tumour/infection spread *
lymph drains areas in the leg
if these areas are affected or have cancer - these cells will be drained to the nodes
this causes the node to be active - the rapid cell turnover and production of local inflammatory mediators cause node to enlarge and become tender
because the flow through the nodes is slow, cells metastisise away from primary tumours and enter lymphatic vessels - lodge and grow as secondary tumours in lymph nodes
