Lumbosacral Plexus Flashcards
(12 cards)
What spinal nerve roots form the lumbosacral plexus?
The anterior rami of L2 to S2.
How do anterior rami behave in both the brachial and lumbosacral plexuses?
They split into anterior and posterior divisions.
Which spinal levels form the lumbar plexus?
L2 to L4.
What nerves does the lumbar plexus form?
The obturator nerve (from the anterior division) and the femoral nerve (from the posterior division).
What is the motor function of the obturator nerve?
It supplies muscles of the medial thigh:
• Obturator externus
• ½ of adductor magnus (anterior fibres)
• Adductor brevis
• Adductor longus
• Gracilis
What is the sensory function of the obturator nerve?
Provides sensation to the medial inferior thigh.
What are causes of obturator nerve lesions?
• Pelvic, abdominal, or hip replacement surgeries
• Pelvic neoplasm
• Pelvic and acetabular fractures
• Pregnancy
• Entrapment
What is the motor function of the femoral nerve?
It supplies muscles of the anterior thigh, including:
• Psoas major
• Iliacus
• Sartorius
• Pectineus
• Rectus femoris
• Vastus medialis
• Vastus lateralis
• Vastus intermedius
What reflex is associated with the femoral nerve?
The knee jerk reflex.
What sensory branches arise from the femoral nerve, and what areas do they innervate?
• Anterior femoral cutaneous nerve: anterior thigh and anterior knee
• Lateral femoral cutaneous nerve: lateral thigh
• Posterior femoral cutaneous nerve: posterior thigh
• Saphenous nerve: medial lower leg and foot
What are common causes of femoral nerve injury?
• Seat belt injuries
•Tight clothing, obesity, or pregnancy (can cause meralgia paraesthetica)
• Pelvic or femoral fractures
• Iatrogenic injury (e.g. during pelvic surgery)
• Diabetic neuropathy
• Femoral hernia
What is meralgia paraesthetica?
A condition caused by compression of the lateral femoral cutaneous nerve, leading to burning, pain, numbness, and tingling along the lateral aspect of the thigh.
