Anatomy - Nerves Of Lower Limb Flashcards
Dermatome
Areas of skin innervated by a single spinal neve root
Myotome
Group of muscles, or parts there of, that is innervated by a single spinal nerve root
Nerve root
Connects PNS to CNS
How do rami link to spinal cord
Via rootlets
Ventral ramus
Connects anteriorly
Usually forms peripheral nerves
Dorsal ramus
Connects posteriorly
Lumborsacral plexus
Nerves supplying lower limb
Combination of lumbar plexus and sacral plexus
Lumbar plexus
Ventral rami of L1-5
Sacral plexus
Lumbar sacral trunk (L4 & 5)
Ventral rami of S1-3
Nerve roots of femoral nerve
L2,3,4
Which compartment does the femoral nerve innovate
Anterior compartment of the thigh
Muscles innervated by the femoral nerve
Quadriceps
Sartorius
Pectineus
Skin innervated by the femoral nerve
Anterior thigh
Medial aspect of leg and foot (branches into saphenous nerve)
Nerve roots of obturator nerve
L2,3
Which compartment does the obturator nerve innervate
Medial compartment of the thigh
Muscles innervated by the obturator nerve
Adductors - except pectineus and posterior part of adductor magnus
Skin innervated by obturator nerve
Medial thigh
Biggest nerve in the body
Sciatic nerve
Nerve roots attached to sciatic nerve
L4,5, S1,2,3
Components of the sciatic nerve
Tibial
Common peroneal
Nerve roots attached to tibial nerve
L4,5, S1, 2,3
Muscles innervated by sciatic nerve
Hamstrings
Posterior portion of adductor magnus
Skin innervated by sciatic nerve
Everything below the knee except the skin on the medial leg
Muscles innervated by the tibial nerve
Muscles found in posterior thigh and posterior leg compartment
Skin innervated by tibial nerve
Posterior leg
Sole of foot (sural nerve)
Nerve roots attached to common peroneal nerve
L4,5, S1, 2
Divisions of common peroneal nerve
Deep
Superficial
Which compartment is innervated by the superficial branch of the common peroneal nerve
Lateral leg
Carries L5 nerve root
Which muscles are innervated by the superficial branch of the common peroneal nerve
Peroneal muscles
Which skin is innervated by the superficial branch of the common peroneal nerve
Skin on lateral leg
Dorsum of foot
Which compartment (and muscles) is innervated by the deep branch of the common peroneal nerve
Anterior leg
Which skin is innervated by the deep branch of the common peroneal nerve
1st web space
Gluteal nerves
Only involved in motor
Superior + inferior
Innervation by superior gluteal nerve
Abductors - gluteus medius, gluteus minimus, tensor fascia latae
Causes +ve trendelenburg sign if damaged
Nerve roots attached to superior gluteal nerve
L4,5, S1, 2
Innervation by inferior gluteal nerve
Gluteus maximus
Carries S1 nerve root and is used when extending the hip from a flexed position eg raising from a chair
Nerve roots attached to inferior gluteal nerve
L5, S1, 2
Commonest nerve root injuries
L4, 5 as they pass through areas allowing greatest level of flexion, pressure put on intervertebral disc ——-> prolapse
Loss of function if sciatic nerve was compressed
Innervation to posterior thigh and all muscles of the leg
Weakened hip extension
Absent knee flexion
Unable to move ankle and foot
How do you test which nerve root is damaged
Testing sensory innervation of skin
Cervical vertebrae
7 but 8 nerves
Thoracic vertebrae
12
Lumbar vertebrae
5
Sacral vertebrae
5 - all fused together
Caudal (cocageal) vertebrae
4-all fused together
Nerve roots supplying hip extension
L2, 3
Nerve roots supplying hip flexion
L4, 5
Nerve roots supplying knee extension
L3, 4
Nerve roots supplying knee flexion
L5, S1
Nerve roots supplying ankle flexion
L4,5
Nerve roots supplying ankle extension
S1,2
Nerve roots supplying ankle inversion
L4,5
Nerve roots supplying ankle eversion
L5, S1
Nerve roots supplying lateral rotation
L5,S1
Nerve roots supplying medial rotation
L1,2,3
Nerve roots supplying adduction
L1,2,3
Nerve roots supplying abduction
L5,S1
Nerve roots supplying toe extension/ flexion
L5
Plexus
Network of nerves derived from nerve roots
Why do we have plexuses
Allows multiple nerve roots to enter a single peripheral nerve
Anterior nerves
Nerve to psoas
Femoral nerve
Obturator nerve
Nerve to psoas
Small branch passing directly from lumbar plexus to psoas major
Posterior nerves
Pass posteriorly through greater sciatic foramen
Superior gluteal nerve
Inferior gluteal nerve
Sciatic nerve
Which nerve is responsible for the ankle jerk reflex
Tibial nerve - carries nerve root S1
Typical mechanism of injury for femoral nerve
Hip and pelvic fractures
Stab/gunshot wounds
Typical mechanism of injury for obturator nerve
Anterior hip dislocation
Loss of adduction
Typical mechanism of injury for tibial nerve
Not commonly injured
Popliteal lacerations
Posterior knee dislocation
Typical mechanism of injury for common peroneal nerve
Neck of fibula injury
Tightly applied lower limb plaster cast
Injury causes foot drop
Typical mechanism of injury for superior gluteal nerve
Misplaced intramuscular injection
Hip surgery
Pelvic fracture
Posterior hip dislocation
What does injury of superior gluteal muscle cause
+ve Trendelendburg sign
Typical mechanism of injury for inferior gluteal nerve
Usually injured with sciatic nerve
What does an injury of the inferior gluteal nerve result in
Difficulty rising from seated position
Can’t jump
Can’t climb stairs
Loss of function due to tibial nerve injury
Plantarflexion
Foot inversion
Typical presentation of upper trunk of the brachial plexus (C5, C6) injury
The arm is adducted and internally rotated, elbow extended
Usually seen in babies through forceps delivery
Meralgia paraesthetica
Lateral cutaneous nerve of the thigh is trapped beneath the inguinal ligament
Obesity is a risk factor
A numb, burning area on the anterolateral aspect of thigh and on examination there is increased sensitivity to touch
