Nerve Injuries in the Lower Limb

Question 1

What is a neuroma?

Answer 1

Swelling of nerve, healing

Question 2

To be able to classify nerve injuries using the Seddon classification

Answer 2

1st degree = conduction block

2nd degree = axon divided

3rd degree = nerve divided

Question 3

What are the main nerves suppling the lower limb?

Answer 3

Femoral n and branches (front)

Sciatic n and branches (back)

Obturator n, superior gluteal n (observing thigh)

Question 4

In general what are the causes of neuropathy?

Answer 4

Injury = stretch, division

Extrinsic pressure = tumour, abscess

Medical = DM, alcohol excess

Question 5

Very briefly outline the repair process of nerves

Answer 5

Distal end degeneration

Proliferating schwann cells in proximal direction

Result = successful regeneration OR severed disorganised axonal sprouts

Question 6

What are the myotomes of the lower limb?

Answer 6

• L2: hip flexion
• L3: knee extension and hip adduction
• L4: ankle dorsiflexion
• L5: great toe extension /ankle inversion / hip abduction
• S1: ankle plantar-flexion/ankle eversion/ hip extension (or L5)
• S2: knee flexion /great toe flexion

Question 7

What makes up the sciatic n?

Answer 7

Common fibular n + tibia n in the same CT sheath

Largest nerve in the body

Question 8

What is the path of the sciatic n?

Answer 8

• Emerges from lumbosacral plexus
• Enters gluteal region
• Merges inferior to piriformis
• Enters posterior thigh
• Descends inferolateral direction
• At apex of popliteal fossa = bifurcates into tibial and common fibular n

Question 9

Outline nerve root injury due to prolapsed intervertebral disc

Answer 9

• Prolapsed disk pressing on spinal nerve root
• Para-central prolapse = most common type
• Effects transversing nerve not the exiting nerve
• L4/L5 prolapse = L5 compression

Question 10

What is piriformis syndrome

Answer 10

Cause = piriformis over-use leading to spasm

Compression of the sciatic n by the piriformis muscle = sciatica symptoms

Question 11

What is meralgia paraesthetica

Answer 11

entrapment of the lateral cutaneous nerve of the thigh as it passes inguinal lig OR passes fascia lata

Burning/stinging sensation, aggravated by walking/standing

Question 12

Outline femoral nerve injury

Answer 12

Loss of = flexion of hip, ABduc hip, ADduc hip, extention of knee

Question 13

Describe tibial nerve injury in the popliteal fossa

Answer 13

• Loss of posterior leg compartments
• Weakness of plantar flexion, inversion
• Unopposed pull of dorsiflexion

Question 14

Outline injuries to the superficial peroneal n

Answer 14

Broken ankle – fracture fibular

Ankle surgery

= weakness in eversion

Question 15

Describe injuries to the deep peroneal n

Answer 15

Loss of anterior muscle compartment

Weakness in ankle dorsiflexion

= foot drop

Question 16

Outline injury to the saphenous nerve during surgery to the long (greater) saphenous vein

Answer 16

Stripping of long saphenous vein varicosities

Injury to nerve during vein graft

Question 17

Outline injury to the sural nerve during surgery to the short (lesser) saphenous vein

Answer 17

Loss of sensation to sole of foot