Nerve injuries in Lower Limb Flashcards
What could the consequences of nerve injuries be?
- Loss of function : motor, sensory and proprioception.
- Neuroma : formation leading to pain.
what are the grades of nerve injury?
- Neurapraxia : a conduction block.
- Axonotmesis : axons divided but myelin sheath intact so chance for recovery.
- Neurotmesis : axons and myelin sheath disrupted hence most severe form of injury.
which nerves supply to the lower limbs?
- femoral nerve and branches.
- sciatic nerve and branches.
- obtrurator nerve.
- superior gluteal nerve.
what would the result of a nerve lesion to psaos and iliacus cause?
- no pelvic swing upon walking.
what would the result of a nerve lesion to femoral nerve cause?
- loss of hip flexion, knee extension.
- loss of sensation anterior thigh and medial calf.
what would the result of a nerve lesion to obturator nerve cause?
- loss of thigh adduction.
- loss of inner thigh sensation.
what would the result of a nerve lesion in superior gluteal cause?
- pelvic dip, loss of abduction thigh.
what would the result of a nerve lesion in inferior gluteal cause?
- loss of extension at hip, buttock wasting.
what would the result of a nerve lesion in sciatic cause?
- loss of all motor except adduction and flexion of thigh and extension of knee, loss of sensation in lower leg and foot.
what would the result of a nerve lesion in tibial cause?
- loss of flexion of toes and inversion of foot, loss os sensation of sole of foot, inferior aspect of toes and nail bed.
what would the result of a nerve lesion in common fibular cause?
- loss of toe extension and foot (drops), loss of sensation lateral lower leg and upper foot.
what would the result of a root compression be?
- prolapsed disc catches nerve at next intervertebral foramen and not same level.
eg: L4/5 disc catches L5 nerve root.
what causes neuropathy?
- injury-stretch of nerve, complete division.
- extrinsic pressures like tumours, abscesses.
- medical conditions like diabetes, drugs, alcohol.
- rare causes like nerve tumours.
what are the steps involved in the repair processes of nerves?
- Wallerian degeneration 2 weeks after injury.
- Schwann cells proliferate and axon sprout penetrating bands of bungner.
- successfully regenerate in like 3 months or not if proliferated ends fail to meet.
what are the myotomes of the lower limb?
L2, L3, L4, L5, S1, S2
- L2 : hip flexion.
- L3 : knee extension.
- L4 : ankle dorsiflexion.
- L5 : great toe extension.
- S1 : ankle plantarflexion.
- S2 : great toe flexion.
describe the location and the bifurcation of the sciatic nerve.
- largest nerve in body + supplies most of lower limb.
- exits sciatic notch anterior to piriformis, but posterior to short external rotators.
- then between adductor Magnus and long head biceps femoris.
- bifurcates into tibial and common peroneal ( fibular) branch at popliteal fossa ( variants there ).
what is piriformis syndrome?
- sciatica symptoms not originating from spinal roots/ spinal disc compression but involving piriformis muscle. V RARE!
- overuse of muscle = spasm.
- diagnosis of exclusion and treatment is mostly about activity modification.
describe the location of the lateral cutaneous nerve of the thigh.
- passes from lateral border of psoas major across iliac fossa to pierce inguinal ligament.
- travels into fibrous tunnel medial to ASIS.
- enters thigh deep into fascia before becoming superficial 10cm below inguinal ligament.
- supplies anterolateral of thigh.
what is meralgia paraesthetica?
- compression of the lateral femoral cutaneous nerve as it passes through inguinal ligament or pierces fascia lata.
- causes pregnancy, tight clothes, tool belt.
- leads to burning or tingling in distribution of nerve over anterolateral thigh aggravated by walking and relieved by lying down.
how is meralgia paraesthetica diagnosed?
- absence of motor signs and by excluding pelvic and intra-adominal causes of irritation like tumours.
- no tool belts etc, local nerve blocks, surgical interventions to free nerve.
what are the consequences of femoral nerve injury?
- paralysis of iliacus : hip flexion affected.
- paralysis of sartorious : flexion and hip abduction affected.
- paralysis of pectineus : flexion and adduction of hip affected.
- paralysis of quads : extension of knee affected.
describe the superior gluteal nerve.
- originates from L5-S1.
- supplies hip abductors like glutes, tensor fascia lata.
- can be injured with lateral approach to hip.
what is the trendelenberg gait?
- compensatory use of trunk muscle to raise pelvis.
- ## caused by injury to superior gluteal affecting abduction, could be L5 radiculopathy, surgical trauma in hip replacing, deformed hip joint, myopathy = waddling.
describe location of the tibial nerve
- larger terminal branch of sciatic.
- crosses popliteal fossa, passes deep to soleus in posterior compartment between digitorum and hallucis.
- gives off calcaneal nerve, divides into medial and lateral plantar nerves.
what are the consequences of tibial nerve injury?
- loss of posterior leg compartment flexors, loss of plantar flexion, loss of plantar sensations except medial and lateral sides.
what are the consequences of common peroneal (fibular) nerve injury?
- paralysis of ankle everters and dorsiflexors.
- loss of sensation in lateral leg and dorsum of foot.
what are the consequences of superficial peroneal nerve injury?
- loss of active eversion.
- sensory loss of most of dorsum of foot and anterolateral led sparing 1st dorsal web space.
- causes : ankle surgery via lateral approach, ankle arthroscopy portal placement.
what are the consequences of deep Peroneal nerve injury?
- paralysis of anterior muscle compartments.
- loss of active ankle dorsiflexion so foot drop.
- sensory loss in 1st dorsal web space.
what are the consequences of saphneous nerve injury?
- loss of sensation to medial leg, ankle and medial border of foot.
- injured during vein harvest for bypass, vericose vein surgery.
what are the consequences of sural nerve injury?
- loss of sensation to sole of foot.
- surgical injury during posterior approach to ankle. Achilles.
- useful nerve graft.
