Nerve Injuries in the Lower Limb Flashcards
What is a neuroma?
Swelling of nerve, healing
To be able to classify nerve injuries using the Seddon classification
1st degree = conduction block
2nd degree = axon divided
3rd degree = nerve divided
What are the main nerves suppling the lower limb?
Femoral n and branches (front)
Sciatic n and branches (back)
Obturator n, superior gluteal n (observing thigh)
In general what are the causes of neuropathy?
Injury = stretch, division
Extrinsic pressure = tumour, abscess
Medical = DM, alcohol excess
Very briefly outline the repair process of nerves
Distal end degeneration
Proliferating schwann cells in proximal direction
Result = successful regeneration OR severed disorganised axonal sprouts
What are the myotomes of the lower limb?
- 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
What makes up the sciatic n?
Common fibular n + tibia n in the same CT sheath
Largest nerve in the body
What is the path of the sciatic n?
- 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
Outline nerve root injury due to prolapsed intervertebral disc
- 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
What is piriformis syndrome
Cause = piriformis over-use leading to spasm
Compression of the sciatic n by the piriformis muscle = sciatica symptoms
What is meralgia paraesthetica
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
Outline femoral nerve injury
Loss of = flexion of hip, ABduc hip, ADduc hip, extention of knee
Describe tibial nerve injury in the popliteal fossa
- Loss of posterior leg compartments
- Weakness of plantar flexion, inversion
- Unopposed pull of dorsiflexion
Outline injuries to the superficial peroneal n
Broken ankle – fracture fibular
Ankle surgery
= weakness in eversion
Describe injuries to the deep peroneal n
Loss of anterior muscle compartment
Weakness in ankle dorsiflexion
= foot drop
Outline injury to the saphenous nerve during surgery to the long (greater) saphenous vein
Stripping of long saphenous vein varicosities
Injury to nerve during vein graft
Outline injury to the sural nerve during surgery to the short (lesser) saphenous vein
Loss of sensation to sole of foot
