Nerve Injuries in Lower Limb Flashcards
Classify nerve injuries using the Seddon classification
- Neurapraxia - conduction block, no damage
- Axonotmesis - inner part of nerve (axon) disrupted, still potential for nerve to grow
- Neurotmesis - nerve potential for growth stopped
Describe the nerve sensory function of the lower limb
- Femoral nerve - anteromedial
- Obturator nerve - medial thigh
- Lateral cutaneous nerve of thigh - lateral thigh
- Posterior cutaneous nerve of thigh - posterior thigh and upper leg
- Saphenous nerve (from femoral nerve) - medial aspect of leg
- Common fibular nerve - lateral aspect of thigh
- Tibial nerve - sole of foot
- Sural nerve (from tibial nerve) - lateral side of foot
What are the causes of neuropathy
- Injury stretch of nerve, complete division
- Extrinsic pressure - tumour, abscess
- Medical conditions - diabetes, alcohol, drugs
Explain how nerves repair after injury
- Inflammatory cells migrate to area
- Proximal stumps of degenerated axons sprout and elongate
- Proliferating schwaan cells guide axons to distal end target (eg. Muscle)
- For severe, proliferation of axons sprouts form neuroma and do not join to distal end
Explain the myotomes of the lower limb
- L2 - hip flexion
- L3 - knee extension
- L4 - ankle dorsiflexion
- L5 - great toe extension
- S1 - ankle plantarflexion
- S2 - knee flexion
Describe the dermatomes of the lower limb
- L1 - groin area
- L2 - upper leg (hands in pocket)
- L3 - knee
- L4 - medial leg
- L5 - lateral leg, dorsal foot, medial foot
- S1 - lateral foot, sole of foot
- S2 - posterior leg and thigh
Explain the effects in prolapsed intervertebral disc when L4, L5 or S1 is compressed
- L4 - motor loss in dorsiflexion, reflex loss in patellar tendon, sensory loss in medial leg
- L5 - motor loss in big toe extension, sensory loss in lateral leg and medial foot
- S1 - motor loss in plantarflexion, reflex loss in achilles tendon, sensory loss in sole of foot
Describe the pathway of sciatic nerve
- Exists sciatic notch anterior to piriformis, but posterior to external rotators
- Between adductor magnus and long head biceps femoris
- Bifurcates into tibial and common peroneal nerve in popliteal fossa
Explain the presentation of piriformis syndrome
- Compression of sciatic nerve by piriformis muscle
- Sciatica symptoms not originating from spinal roots
- Overuse of piriformis muscle
- Buttock pain, pain down leg
- Loss of all motor except adduction and flexion of thigh, and extension of knee
- Loss of sensation in lower leg and foot
- Treatment - activity modification
Explain the presentation of meralgia paraesthetica
- Entrapment of the lateral cutaneous nerve of the thigh
- Occurs when it passes through inguinal ligament or pieces fascia lata
- Causes - pressured by belt, tight clothes, abdominal fat if obese, pregnancy
- Burning or stinging sensation over anterolateral aspect of thigh
- Aggravated by walking or standing
- Relieved by lying down or hip flexed
Explain the presentation of femoral nerve injury
- Weakness of quadriceps, hip flexors
- Loss of hip flexion and knee extension
- Loss of saphenous nerve, medial cutaneous nerve of thigh
- Loss of sensation in anterior thigh and medial leg
Explain the effects of common peroneal nerve injury
- Loss of ankle everters and dorsiflexors (foot drop)
- Loss of sensation of lateral calf and dorsal aspect of foot
What are the causes and effects of superficial peroneal nerve injury
- Weakness in evertion
- Sensory loss over most of skin in dorsum of foot and anterolateral calf
- Fracture of fibula, ankle surgery via lateral approach and ankle arthroscopy
What are the effects of deep peroneal nerve injury
- Weakness in dorsiflexion - foot drop
- Sensory loss between 1st and 2nd toes
What are the effects of saphenous nerve injury
- Runs beside great saphenous vein
- Stripping of long saphenous vein varicosities
- Loss of sensation over medial leg
