Nerve injuries to lower limb Flashcards
What is spinal cord injury known as?
Myelopathy (affects spinal levels resulting in neural level)
What is spinal nerve root injury known as?
Radiculopathy (affects dermatomes and myotomes specific to root)
What is peripheral nerve injury known as?
Peripheral Neuropathy (loss of specific peripheral nerve function)
Types of injury (4S’s)
Stretched (traction)
Squashed (compression)
Severed (laceration)
Stressed (by medical conditions eg diabetes)
How do we class nerve injuries in terms of their severity?
Seddon Classification
Class 1 seddon
Neuropraxia
What occurs in Neuropraxia?
Temporary block of conduction
No disruption/degeneration of nerve structure
Full recovery in days/weeks
Class 2 seddon
Axonotmesis (axons divided)
What occurs in axonotmesis?
Disruption to axon and myelin sheath
Epineurium, perineurium and endoneurium still INTACT
Degeneration distal to injury
Outcomes axonotmesis?
Axonal regeneration (1-3mm per day) No surgical intervention Variable recovery (depending on length apart of axons)
Class 3 seddon
Neurotmesis (nerve divided)
What occurs in neurotmesis?
Partial/full disruption of nerve structure
Epi/peri/endoneurium not intact
Degeneration distal to site
Outcomes neurotmesis?
Scar tissue forms
Surgery needed ALWAYS
Variable prognosis (full loss/recovery)
Femoral nerve damage causes
Uncommon
Direct trauma from hip fracture?
Iatrogenic (hip replacement)
Nerve blocks (treatment)
Sensory function femoral nerve
Anteriomedial thigh (anterior femoral cutaneous nerve) Medial leg (saphenous nerve)
Motor function femoral nerve
Supplies anterior muscles of thigh
Hip flexion weakened (psoas major still can work)
Knee extension absent (quadriceps gone)
How can damage to sciatic nerve occur?
Compression in gluteal region (piriformis syndrome)
Iatrogenic (IM injections)
Direct trauma (posterior hip dislocation)
Sensory function sciatic nerve
Branches into common fibular (then superficial and deep) and tibial nerve
Motor function sciatic nerve
Posterior thigh
Knee flexion absent (sartorius and gracilis not strong enough alone)
Loss of ankle dorsiflexion/plantarflexion, eversion and inversion of foot, flexion and extension of toes
Hip extension intact (gluteus maximus intact)
Superior gluteal nerve injury sign
Trendelenburg sign
SOUND SIDE SAGS
(loss of innervation to gluteus medius and minimus)
How can tibial nerve be damaged?
Popliteal fossa location: Aneurysm of popliteal artery Popliteal (baker's) cyst Iatrogenic (knee surgery) Direct trauma behind knee
Medial malleolar fracture
Compression of tarsal tunnel
Sensory function tibial nerve
Sole of foot (medial and lateral plantar nerve)
Heel (medial calcaneal)
Motor function of tibial nerve
Posterior compartment of leg
No plantarflexion/toe flexion
Inversion weakened (but still works as tibialis anterior)
Proximal vs distal tibial injury
If proximal posterior leg affected
If distal eg medial malleolus only toe flexion really weakened (muscle already have supply)
Common fibular nerve how can it be damaged?
Close proximity to fibula neck (fibula fracture)
Compression from plaster cast
Sensory function common fibular
Proximal lateral
Then divides to deep and superficial
Motor function of common fibular (and if damaged)
Superficial and deep fibular nerve affected
No dorsiflexion (from anterior compartment)
= foot drop
How can superficial fibular nerve be damaged?
Direct trauma (fracture/penetration injury)
Iatrogenic (ankle surgery laterally)
Deficit from common fibular
Sensory function superficial fibular nerve
Anterolateral leg
Dorsum of foot (not first webbed space or medial and lateral borders)
Motor function superficial fibular (and if damaged)
Lateral leg compartment
= No eversion
How can deep fibular nerve be damaged?
Mononeuropathy from medical conditions
eg diabetes, motor neurone disease, vasculitis
Deficit from common fibular
Sensory function deep fibular nerve
1st webbed space on dorsum of foot
Motor function deep fibular nerve (and if damaged)
Anterior leg
No dorsiflexion (foot drop)
No toe extension
Sensory nerves (JUST sensory)
Lateral femoral cutaneous
Sural
Saphenous
Lateral femoral cutaneous supplies (sensory)
Anterolateral thigh (worse when walking if injured)
How can lateral femoral cutaneous be injured?
Compression (meralgia paraesthetica)
tight clothing, belts, pregnancy, obesity
Sural nerve supplies (sensory only)
From tibial and common fibular branches
Lateral ankle/foot
Posterior leg
Key features sural nerve
Close proximity to small saphenous vein
Can be used for nerve grafts
Saphenous nerve supplies (sensory only)
Branch of femoral nerve
Medial leg
Medial border of foot
How can saphenous nerve be damaged?
Iatrogenic:
Close proximity to great saphenous vein (bypass)
Surgery (distal tibia/medial malleolus)
Wallerian degeneration
axons distal to injury degenerate
macrophages and schwann cells phagocytose debris
What do schwann cells do during wallerian degenration
Proliferate
Form lines of cells: Bands of Bunger
(muscle is denervated currently and undergos atrophy)
What happens if severed ends are not surgically apposed?
Sprouting of axons from severed end
Form traumatic neuroma
= Painful
