Week 4 - Lower limb + nerves

Question 1

What are the roots of the lumbosacral plexus made of?

Answer 1

Ventral rami of the spinal nerve:
Lumbar - L2, L3 and 1/2 L4
Sacral - 1/2 L4, L5, S1, S2, S3

Question 2

Where is the lumbar plexus?

Answer 2

Within the psoas muscle

Question 3

Where do branches of the lumbar plexus emerge? What are the nerves that emerge?

Answer 3

From psoas major
Femoral nerve
Obturator nerve
Lateral cutaneous nerve

Question 4

Which roots supply fibres to femoral?

Answer 4

Anterior compartment of the thigh

L2-4

Question 5

Which roots supply fibres to obturator?

Answer 5

The medial compartment i.e. adductors

L2-3

Question 6

What does the femoral nerve supply?

Answer 6

The whole anterior compartment of the leg:
Emerges lateral to psoas, supplies:
iliacus, then passes under inguinal ligament and supplies the quadriceps muscles and the sartorius.
Also supplies the cutaneous area

Question 7

What does the obturator nerve supply?

Answer 7

Medial compartment of thigh:
After emerging medial to psoas, moves along pelvic wall and supplies the three adductors, gracilis and obturator externus

Question 8

Where is the cutaneous area supplied by the femoral nerve?

Answer 8

Along the front of the thigh - the cutaneous femoral nerve splits into the intermediate and medial cuteneous nerves
Also has the saphenous nerve as one of the femoral nerves cutaneous branches

Question 9

What does the saphenous nerve supply?

Answer 9

The area medial to the knee, leg and ankle, right down to the instep

Question 10

Where do all nerves of the sacral plexus exit from?

Answer 10

The greater sciatic foramen

Question 11

What are the four main nerves from the sacral plexus?

Answer 11

Inferior and superior gluteal nerves
Sciatic nerve
Posterior cutaneous nerve of the thigh

Question 12

Describe the sciatic nerve

Answer 12

Emerges below the piriformis, and is essentially two nerves covered by a sheath
Branches into the tibial nerve (L4-S3) and the common fibular nerve (L4-S2)
This branching usually occurs 2/3 down the thigh

Question 13

What general areas does the tibial nerve innervate?

Answer 13

Posterior compartment of the leg, and the foot –> plantar aspect

Question 14

What general area does the common fibular nerve innervate?

Answer 14

The anterior and lateral compartments of the leg, and the extensors Digitorum/hallucis brevis

Question 15

Describe the tibial nerves route through the thigh/leg

Answer 15

Midline course through the thigh, passes through the popliteal fossa
Runs deep to soleus
Crosses ankle medially

Question 16

What are the specific muscles/areas the tibial nerve innervates?

Answer 16

The flexor compartments of the thigh and leg:

• Hamstrings
• Gastrocnemius-soleus, the long flexors of the toes, tibialis posterior and popliteus
• Muscles and skin of the medial and lateral plantar of the sole of the foot

Question 17

Where does the inferior gluteal nerve go?

Answer 17

To gluteus maximus

Question 18

WHat is the course of the fibular nerve down the thigh/leg?

Answer 18

Has a variable beginning
Courses laterally and then crosses the neck of the fibula
Then divides into superficial and deep ficular nerve

Question 19

What does the superficial fibular nerve innervate?

Answer 19

• The lateral compartment of the leg (fibularis longus & fibularis brevis)
• Skin of the anterolateral aspect of the leg
• Dorsum of the foot - except web of big toe

Question 20

What does the deep fibular nerve innervate?

Answer 20

• The anterior compartment of the leg, and the extensor breves of the foot
• The skin of the first web of the toes

Question 21

What are the four arteries of the lower limbs?

Answer 21

Femoral (main)
Gluteal arteries
Obturator arteries
Profunda femoris artery

Question 22

What is the course of the femoral artery?

Answer 22

• Down the front of the thigh, through the adductor magnus
• Turns into popliteal artery, which divides into anterior and posterior tibial arteries
• The anterior tibial artery turns into dorsalis pedis, the dorsal artery of the foot
• Posterior tibial artery goes to the sole of the foot

Question 23

What is femoris profunda and what does it do?

Answer 23

It is the deep artery of the thigh, found high in the thigh

Supplies the hamstring muscles

Question 24

What supplies blood to the head of the femur?

Answer 24

The trochanteric anastomosis

Question 25

Describe the trochanteric anastomosis

Answer 25

This supplies blood to the head of the femur along the reflected part of the capsule

Question 26

Why are fractures of the femur so detrimental?

Answer 26

Disrupts the anastomosis aka blood supply to the femoral head –> avascular necrosis

Question 27

In which joints of the lower limb do you find anastomoses?

Answer 27

Hip, Knee and Ankle

Question 28

Where are the three palpable arterial pulses in the lower limb?

Answer 28

Popliteal
Posterior tibial - half way between medial malleolus and the heel
Anterior tibial/dorsalis pedis - lateral to the FHL tendon, between bases of M1 and M2

Question 29

Where does the lateral cutaneous nerve of the thigh get entrapped? What would this feel like?

Answer 29

By the inguinal ligament

Pain radiates down the lateral side

Question 30

Where does the fibular nerve/s get trapped?

Answer 30

Around the neck of the fibula. Can be a result of a blow to the bony prominence, or by a plaster after broken leg

Question 31

What is the main symptom of an entrapped fibular nerve/s?

Answer 31

Paralyzed dorsiflexors –> foot drop

Question 32

What is compartment syndrome?

Answer 32

Injury/bleeding into spaces with tight fascia causes an increase in pressure that can affect both nerves and blood vessels
This causes compartment syndrome –> sensory features + motor loss
Vascular disturbance is more serious

Question 33

What are the two main movements that cycle through walking?

Answer 33

• Stance - limb stationary and bearing weight

- Swing - limb moves forwards

Question 34

Describe ‘mid-stance’

Answer 34

Knee joint is locked out for stability, while the other limb is off the ground
There is pelvic tilt towards the unsupported side, while the gluteus medius holds the pelvis

Question 35

Describe ‘take-off’

Answer 35

The swinging leg makes contact with the ground in ‘heel-strike’
The gastrocnemius-soleus, tibialis posterior and FHL propel you forwards,, off the supporting leg
The hip joint carries the whole limb forwards - hip flexors have a role

Question 36

Describe the ‘swing’ phase of walking

Answer 36

There is hip flexion, knee flexion and ankle dorsiflexion - these carry the leg forwards, and ensure the foot isn’t caught on the ground

Question 37

Describe the ‘end-of-swing’ phase of walking

Answer 37

There’s knee extension, and hamstrings counteract hip flexion, ‘braking’ the swing

Question 38

How does the leg prepare for heel strike?

Answer 38

Foot dorsiflexors contract, preventing the foot from flapping

Question 39

What happens after heel strike?

Answer 39

The dorsiflexors straighten the limb at the ankle, acting as a fixed distal attachment

Question 40

What happens to the stance phase of walking if gluteus medius is lost?

Answer 40

The pelvis sags to the opposite side in stance phase, and the patient may compensate by tilting to the normal side during walking

Question 41

WHat would happen to someone’s walk if dorsiflexors are lost?

Answer 41

There would be difficulty clearing the ground –> high step to compensate, and the toes would hit the ground with a ‘flap’ on heel strike

Question 42

What would happen to walking if hamstrings were lost?

Answer 42

The swing phase would not be arrested, causing the leg to overshoot, and gravity would bring the heel sharply down at the heel strike