Anatomy of the Limbs 8 - Lower Limb Nerves, Arteries and Vessels Flashcards
How is nerve function assessed?
- Motor function
- Sensory function
- Reflex function
- Autonomic function
- Trophic function
Describe the knee jerk. Which spinal nerve is involved?
- Tap
- Stretch patellar tendon
- Stimulation of afferent (1a) fibres in quadriceps
- Passes to spinal cord via posterior nerve root
- Synapse with alpha motor neurone in the anterior horn of the spinal cord
- Efferent signal to quadriceps
- Quadriceps extends the knee joint
- L3
What supplies the ankle jerk reflex?
S1
Describe autonomic segmental supply to the lower limbs.
- Sympathetic via T11-L2 portion of thoraco-lumbar outflow
- No significant parasympathetic outflow to the lower limbs
Where is the lumbosacral plexus derived from?
- Anterior rami of the lumbar and sacral spinal nerves
- Lumbar plexus L1-4
- Sacral plexus S1-4 and L4,5
List the branches of the lumbar plexus
- Illiohypogastric and ilio-inguinal nerves (L1)
- Genitofemoral nerve (L1,2)
- Lateral cutaneous nerve of the thigh (L2,3)
- Femoral nerve (L2-4 posterior divisions due to torsion during development)
- Obturator nerve (L2-4 anterior divisions)
- Lumbosacral trunk (L4,5 - feeds the sacral plexus)
List the branches of the sacral plexus
- Sciatic nerve (L4,5, S1-3)
- Nerve to piriformis (S1,2)
- Posterior cutaneous nerve of the thigh (S1-3)
- Pelvic splanchnic nerve (S2-4, parasympathetic)
- Pudendal nerve (S2-4)
- Nerve to obturator internus (L2, S1,2)
- Superior gluteal nerve (L4,5, S1)
- Inferior gluteal nerve (L5, S1,2)
Where is the femoral nerve formed, what does it supply and what is its terminal branch?
- Formed from the lumbar plexus (L2-4 posterior divisions)
- Supplies the ilio-psoas and anterior thigh muscles
- Sensory to the front of the thigh
- Terminal branch is the saphenous nerve, sensory to the medial aspect of the leg
Where is the obturator nerve formed, and what does it supply?
- Formed from the lumbar plexus (L2-4 anterior divisions)
- Passes through the obturator foramen
- Supplies the adductor (medial) compartment of the thigh
- Sensory to the pelvis and medial aspect of the thigh
Where is the sciatic nerve formed, what are its terminal branches and what does it supply?
- Formed from the tibial nerve and common peroneal nerve (L4,5 and S1-3 both posterior and anterior divisions)
- Passes through the greater sciatic foramen, behind the hip joint and in the posterior compartment of the thigh divides into the tibial and common peroneal nerve
- Sciatic nerve proper supplies the hamstring muscles in the posterior compartment of the thigh
- Has some sensory branches to the back of the thigh
Describe the pathway of the common peroneal nerve, what does it supply and what are its terminal branches?
- Passes around the neck of the fibula where it is easily damaged
- Supplies anterior and lateral compartments of the leg
- Sensory innervation to anterior and lateral aspects of the leg and the dorsum of the foot
- Terminal branches are the superficial peroneal nerve and the deep peroneal nerve
- Important sensory branch: sural nerve
What is supplied by the tibial nerve?
- Posterior compartment of the leg
- Most of the intrinsic muscles of the foot
- Sensory to the back of the leg and sole of the foot
List the muscles supplied by the femoral nerve
- Psoas and illiacus
- Pectineus
- Sartorius
- Rectus femoris
- Vastus medialis
- Vastus intermedius
- Vastus lateralis
(anterior compartment of thigh)
List the muscles supplied by the obturator nerve
- Obturator externus
- Adductor brevis
- Adductor longus
- Part of adductor magnus
- Gracilis
(medial compartment of thigh)
List the muscles supplied by the sciatic nerve
- Biceps femoris
- Semimembranosus
- Semitendinosus
- Part of adductor magnus
(posterior compartment of the thigh)
List the muscles supplied by the common peroneal nerve
DEEP PERONEAL NERVE
- Extensor digitorum longus
- Extensor hallucis longus
- Tibialis anterior
- Peroneus tertius
- Extensor digitorum brevis
(anterior compartment of leg)
SUPERFICIAL PERONEAL NERVE
- Peroneus longus
- Peroneus brevis
(lateral compartment of leg)
List the muscles supplied by the tibial nerve
- Gastrocnemius and soleus
- Plantaris
- Popliteus
- Tibialis posterior
- Flexor hallucis longus
- Flexor digitorum brevis
- Abductor hallucis
- Flexor hallucis brevis
- All interossei and lumbricals
(posterior compartment of leg and most intrinsic foot muscles)
When is the femoral nerve injured?
- Superficial in the groin, but rarely damaged except by doctors
- Most commonly damaged during hip replacements and laparoscopic repair of inguinal nernias
- Can be damaged during erroneus attempted cannulations of the femoral artery or vein
When is the lateral contaneous nerve of the thigh injured?
- Passes 2cm medial to the ASIS at the level of the inguinal ligament
- Can be compressed, causing meralgia parasthetica
What is pain in the distribution of the obturator nerve indicative of?
Malignant disease of the pelvis - rarely damaged
What is the consequence of injury to the superior gluteal nerve?
- Supplies gluteus medius and minimus
- When damaged, there is trendelenberg gait, where the pelvis lurches during gait
When is the superior gluteal nerve commonly injured?
- Hip replacement
- Nerve lies 5cm proximal to the tip of the greater trochanter. It approaches the hip joint.
What causes injury to the sciatic nerve?
- Hip replacement
- Common peroneal division is more vulnerable than tibial
- To avoid damage, IM injections should be given to the upper outer quadrant of the buttock
- Also damaged in trama (eg. hip dislocations or acetabular fractures) and pelvic disease
When is the common peroneal nerve vulnerable?
- Hip
- At the level of the fibular neck (where the nerve winds around)
- Damaged by trauma, knee replacement and external pressure (eg. plasters or during surgical procedure
When is the saphenous nerve damaged?
- Damaged at the medial malleolus (after varicose vein surgery or cut down)
- At the level of the knee (eg. anterior cruciate ligament surgery)
Describe briefly arterial anatomy of the lower limb
- Aortia to common iliac
- Common iliac to external and internal iliac
- External iliac becomes femoral (inguinal ligament)
- Femoral becomes popliteal (adductor canal)
- Popliteal trifurcates into posterior tibial artery, peroneal artery and anterior tibial artery
- Posterior tibial artery enters posterior compartment with the tibialis posterior and passes behind the medial malleolus. In the foot forms medial and lateral plantar arteries
- Anterior tibial artery passes into the anterior compartment of the leg, and becomes the dorsalis pedis artery
Where is the dorsalis pedis artery palpable?
Between the first and second metatarsals, lateral to the extensor hallucis longus
Where is the posterior tibial artery palpable?
Behind the medial malleolus
List the branches of the femoral artery in the thigh
- Superficial circumflex iliac artery
- Superficial epigastric artery
- Superficial external pudendal artery
- Deep external pudendal artery
Where is the profunda femoris artery?
- A branch of the femoral artery
- Arises 4cm distal to the inguinal ligamanet.
- Major branches of the perforating arteries and the medial and lateral femoral circumflex arteries
How do varicose veins occur?
- Perforating veins where blood should flow from the superficial to the deep system
- Perforating veins and the main saphenous veins have valves
- If these valves dont exist, it results in varicose veins
Where does the long saphenous vein join the femoral vein?
Passes through the saphenous opening, 3cm below and lateral to the pubic tubercle (femoral canal)
Where are the valves of the long saphenous vein present?
- About 20 valves
- Mainly present below the knee, some above the knee
Describe the distribution of the deep and superficial veins
- Deep veins lie in the deep fascia
- Run alongside the arteries (2 veins for each artery)
- Have valves to prevent backflow of blood
- Venae comintantes of the anterior and posterior tibial arteries and the popliteal artery form the popliteal vein. Mainly within muscle.
- Popliteal vein also recieves the short saphenous vein at the level of the popliteal fossa
- Femoral vein joined by the profunda femoris veins and the long saphenous vein.
- Femoral vein then forms the external iliac vein once it passes beneath the inguinal ligamanet
When are the femoral artery and vein cannulated?
- For resusitation (vein)
- For cardiac arteriography (artery)
When is cut down of the long saphenous vein performed?
- In a shocked patient, venous cannulation may not be easy or possible
- The long saphenous vein at the ankle, 2cm above and proximal to the tip of the medial malleolus, is a good site for cut down
- A small incision is made at the ankle, and a venous cannula placed under direct vision into the vein for resuscitation
- Now, instead intraosseous administration is used (often in the anterior tibia)
What is the result of arterial embolism in the popliteal artery?
- The leg may become ischaemic and require amputaton if the lesion is not cleared within a few hours
- Intermittent claudication (muscle pain in calf during activity)
What is intermittent claudication?
- A condition where there is gradual occlusion of arteries within the limb, usually atherosclerotic
- The muscles supplied distal to the occlusion become deprived of blood on exercise, so there is limited walking distance before pain occurs (mostly calf, can be thigh or buttock)
What is compartment syndrome?
- Each compartment in the leg is bound by tight fascia, which only let enclosed muscles swell to a certain degree before resisting further expansion and increasing pressure in the muscle itself
- If pressure increases too far, the arterial supply and venous return are cut off, resulting in muscle death, loss of movement an contractures
- Normal pressure is 25mmHg, only need 50-60mmHg to collapse small vessels. The pulse however is still present.
What is acute compartment syndrome?
- After trauma to a limb
- Unless fascia is released urgently, the muscle will die with disastrous consequences
What is chronic compartment syndrome?
- Occurs in athletes
- Muscle swells during exercise and causes activity-related pain
- Elective fasciotomy can relieve the pain in this condition
What do most operations for varicose veins involve?
- Tying off the sapheno-femoral junction
What are varicose veins?
- Dilated and tortuous superficial veins to to non-functional valves in the perforating vein between the superficial and deep veins
- Can be painful, causing aching discomfort on standing
- The increased pressure within superficial venous system can cause skin changes (lipodermatosclerosis or skin thickening) and skin ulcers
What is deep venous thrombosis?
- Blood clotting in the deep vains of the lower limb
- Often silent, may pesent with pain and swelling in the caf or proximal thigh
- Proximal DVT (thigh) is very dangerous, as there is high risk of propagation to the lungs
- Associated with immobility, trauma, surgery, malignancy, obesity, pregnancy, oral contraceptive pill
What are the two main consequences of DVT?
- Pulmonary embolus (propagate into the pulmonary circulation, can be fatal)
- May cause increased back pressure in the deep veins, causing venous insufficiency and leg ulcers (post-phlebotic syndrome)
What is superficial thrombophelbitis?
- Superficial veins clotting, or becoming inflamed/infected
- Not as serious as DVT but can be painful
- Symptomatic treatment (analgesia and rest) rather than anticoagulation
How are superifical veins used in elective surgery?
- Used in cardiac and vascular surgery as grafts to replace arteries
- Arterial by-pass surgery
- Need to be orientated correctly due to valves
Describe organisation of spinal nerves
C1-4 : neck C5-T1 : upper limb T2-L1 : trunk L2-S3 : lower limb S2-C1 : perineum
What is a nerve plexus?
A nerve plexus is formed when peripheral spinal nerve roots merge and split to produce a network of nerves from which new multi-segmental (containing fibres from more than one spinal root) peripheral nerves emerge.
How is the piriformis used as a landmark?
- Superior gluteal arteries and nerves superior to piriformis
- Inferior gluteal arteries and nerves inferior to piriformis
- Sciatic nerve emerges inferior to piriformis
What is the sural nerve?
- Formed by branches from the common peroneal nerve and fibular nerve after they divide.
- Important cutaneous nerve to the lateral leg and foot
Describe segmental somatic motor supply to the limbs
- C5-T1 upper limb
- L2-S3 lower limb
- Plexi for each limb
- Anterior divisions are flexor muscles, posterior divisions are extensor muscles
- Muscles supplied by two adjacent segments
- Same action on joint = same nerve supply
- Opposing muscles 1-2 segments above or below
- More distal in limb = more caudal in spine
What are autonomous sensory zones?
- Areas of skin supplied by nerves from only one spinal segment, so loss of sensation will determine the damage of that spinal root
- L3 upper thigh
- L4 Knee and thigh
- S1 posterior lateral region of the leg
- Obturator nerve supplied the medial thigh
Why is peripheral cutaneous supply different to segmental supply?
Due to the mixing up of nerve fibres in the lumbosacral plexus
Describe cutaneous innervation of the foot
- Dorsal digital nerve dorsal surface between toes 1 and 2
- Saphenous nerve supplies the medial side
- Dorsal lateral cutaneous nerve lateral
- Superficial fibular nerve most of the dorsal surface
- Common plantar digital nerves lateral side of plantar surface
- Proper plantar digital nerves and medial plantar nerve the medial foot plantar surface, to 4th half toe
- Medial calcaneal branch supplies the calcaneus
What would be seen in prolapsed intervertebral disc prolapse at L5/S1
Motor – loss of eversion
Sensory – loss of sensation outer border of foot
Reflex – loss of ankle jerk (S1)
Autonomic – minimal
What would be seen in a lesion of common peroneal nerve at fibular neck?
Motor – foot drop
Sensory – dorsum of foot at least
Reflex – none
Autonomic – minimal
Describe the pathway of the long saphenous vein
- Anterior to medial malleolus from the dorsal venous arch
- Medially travels up the leg
- Just medial to the knee
- Joins the femoral vein at the saphenous opening
Describe the pathway of the short saphenous vein
- Posterior of the leg, from the plantar venous network
- Joins the popliteal vein in the popliteal fossa
What are the functions of venous comitantes
- Artery pulse promotes venous flow
- Allow heat exchange between the artery and veins
Why can inactivity cause DVT? How can this be avoided?
- One of the ways of returing blood to the heart from the leg is by the calf pump
- Deep veins are sandwiches between the layers of calf muscles, so when these muscles contract there is more efficient venous return to the heart
- Surgical socks compress superficial veins to promote more vigorous deep venous return
Describe the motor effects of femoral nerve injury
Quadriceps paralysis. Weakness of knee, difficulty in climbing up or down the stairs.
Describe the sensory effects of femoral nerve injury
Sensory loss to anterior & medial thigh, medial side of leg, and medial border of foot (not the big toe)
Describe the motor signs of obturator nerve injry
- Paralysis of all adductors (except hamstring part of adductor magnus)
- “Cross legging” affected
Describe the sensory effects of obturator nerve injury
Insignificant sensory loss on the medial side of thigh.
Describe the motor effects of common peroneal nerve injury
- Foot extensors & evertors paralysed
- Foot in plantar flexed (foot drop) and inverted (tibialis post active)
Describe the sensory effecs of damage to the common peroneal nerve
Loss in the anterior and lateral side of leg and dorsum of foot
Describe the motor effects of tibial nerve injury
- Hamstrings and all muscles of back of leg & sole of foot affected
- Foot in dorsiflexed and everted position
Describe the sensory effects of tibial nerve injury
Loss in the sole of the foot
Describe the motor effects of sciatic nerve injury
- Hamstrings, and all muscles below the knee are paralysed.
- Foot in plantar flexed position (foot drop) due to its own weight.
Describe the sensory effects of sciatic nerve injury
Loss below the knee except on a narrow area on the medial side of leg and foot (saphenous nerve area), not the big toe
What is sciatica?
- Pain radiating from lower back into buttock, posterior /lateral thigh and into the leg.
- Caused by herniated lumbar intervertebral disc (L4/L5 or L5/S1) which compresses the L5-S1 component of the sciatic nerve.
- Pelvic girdle pain during pregnancy is often misdiagnosed as sciatica
Compare the effect of damage to the anterior collateral and posterior collateral ligament of the leg
- ACL damage results in limited walking upstairs
- PCL damage results in limited walking downstairs
